JP2012120269A - Power inverter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power inverter circuit capable of reducing power loss which accompanies passing through a chopper circuit that is not used, although a multistep chopper circuit is utilized.SOLUTION: The power inverter circuit includes a plurality of chopper circuits between a first end and a second end, for performing a first transmission operation which boosts the power inputted in the first end and then outputs it from the second end, as well as a second transmission operation which steps down the power inputted in the second end and outputs it from the first end. The plurality of chopper circuits include a first circuit which is so formed as to step up/down operation in both directions, and a second circuit formed to perform step-up operation. At the time of first transmission operation, the first circuit and the second circuit perform a step-up operation advancing from the first end to the second end. At the time of second transmission operation, the first circuit and the second circuit perform step-down operation advancing from the second end to the first end. At least one of the second circuits performs substantially no step-down operation by itself.

Description

  The present invention relates to a power conversion circuit that converts a voltage, and more particularly to a circuit that transmits power bidirectionally.

  In recent years, cases in which a load is connected to a storage battery for use are increasing. For example, cases in which loads and systems (lines for supplying commercial power) are connected to storage batteries, and storage batteries used in HEV, PHEV, and EV are connected to electric motors are increasing.

  Moreover, in order to respond | correspond to the difference in the voltage in a storage battery and a load side, the converter (power conversion circuit) which converts a voltage is provided between these. As an example of such a converter, Patent Document 1 discloses a buck-boost chopper device using a buck-boost chopper circuit.

  According to this step-up / step-down chopper device, boosting is performed when power is transmitted from the low voltage side to the high voltage side, and stepping down is performed when power is transmitted from the high voltage side to the low voltage side. Thus, bidirectional power transmission is appropriately performed. According to the step-up / step-down chopper circuit, the step-up ratio and the step-down ratio are determined through the conduction ratio of the switching element (duty ratio = switch (including the switching element) ON time / (switch ON time + switch OFF time)). It is possible to control.

JP 2007-267582 A

In the step-up / step-down chopper circuit, if the step-up ratio is R1 and the step-down ratio is R2, these are expressed by the following equations.
R1 = 1 / (1-α)
R2 = α
However, (alpha) shows the duty ratio of a switching element. FIG. 17 shows a graph representing the relationship between the duty ratio and the step-up ratio during boosting, and a graph representing the relationship between the duty ratio and the step-down ratio during step-down.

  As is apparent from the above equation and FIG. 17, the ratio of the step-up ratio R1 increment to the duty ratio α increment (corresponding to the slope in the graph shown in FIG. 17) increases remarkably as the duty ratio increases. To do. Here, when the potential difference between the high voltage side and the low voltage side is large, it is necessary to increase the step-up ratio when transmitting power from the low voltage side to the high voltage side. However, if the duty ratio is increased too much in order to increase the boost ratio, for example, the fluctuation range of the boost ratio with respect to the duty ratio α increases, so the fluctuation of the boost ratio with respect to the deviation of α increases, and the control accuracy of the boost operation decreases. May be incurred.

  As a measure for ensuring a high step-up ratio, for example, a flyback method using a transformer, a forward method, or a push-pull method may be employed. However, in any case, bi-directional power transmission is not easy from the viewpoint of device breakdown voltage.

  Therefore, as another measure for securing a high step-up ratio, it is considered to use a step-up / step-down chopper circuit in which another step-up chopper circuit is connected in series (referred to as a “multistage chopper circuit” for convenience). It is done. Accordingly, each of the plurality of chopper circuits can be operated in a region where α is small, and as a whole, control accuracy can be improved in control at a high step-up ratio.

  The ratio of the step-down ratio R2 increment to the duty ratio α increment is substantially constant regardless of the duty ratio. Therefore, even when the above-described multistage chopper circuit is used, in many cases, it is possible to maintain good control accuracy of the step-down operation only by causing some chopper circuits to perform step-down.

  However, when using a multi-stage chopper circuit, the power must pass through a chopper circuit that is not used (in this application, it is not allowed to operate substantially as a step-down chopper circuit) when transmitting power from the high voltage side to the low voltage side. As a result, unnecessary power loss occurs. From the viewpoint of power transmission efficiency, it is desirable to reduce such power loss as much as possible.

  In view of the above-described problems, an object of the present invention is to provide a power conversion circuit that can reduce power loss in a bidirectional circuit.

  In order to achieve the above object, a power conversion circuit according to the present invention includes a plurality of chopper circuits between a first end and a second end, and boosts the power input to the first end. A power conversion circuit that performs a first transmission operation output from two ends and a second transmission operation output from the first end after stepping down power input to the second end, the plurality of choppers The circuit includes a first circuit formed to perform a step-up operation in a direction from the first end to the second end, and a step-down operation in a direction from the second end to the first end. And at least one second circuit formed to perform a boost operation in a direction toward the two ends, and when performing the first transmission operation, the first circuit and the second circuit are When performing the step-up operation in the direction from the first end to the second end and performing the second transmission operation The first circuit and the second circuit perform the step-down operation in a direction from the second end toward the first end, and at least one of the second circuits is substantially step-down operation only with the second circuit. It is set as the structure which does not perform.

  According to this configuration, when performing the second transmission operation, it is possible to reduce power loss by not causing the second circuit to substantially operate as a step-down circuit.

  Here, “substantially no step-down operation” means that no output is output when the step-down operation is performed. As this form, for example, (1) Even if a form in which the input / output of the step-down circuit is short-circuited by bypassing the step-down circuit (formal step-down operation (switching operation, etc.)), the step-down circuit (2) a mode in which the switching element of the step-down circuit is always turned on (fixed to a conductive state), and (3) a mode not including a circuit unit that performs the step-down operation. When the output when the circuit performs the step-down operation is not output, power loss due to the switching operation for step-down in the circuit is avoided.

  An example of a chopper circuit formed so as to perform a boosting operation is a boosting chopper circuit. The step-up chopper circuit has a step-up switching element and a coil that stores and discharges energy by chopping the step-up switching element, and can perform step-up operation in at least one direction. It may be a formed chopper circuit. In addition, the “boost operation” is to output the electric power after boosting the input power by causing the coil to repeatedly store and release energy by chopping the boosting switching element. As long as having such a basic configuration, various types of circuits are included in the boost chopper circuit.

  An example of a chopper circuit formed so as to perform a step-up / step-down operation in both directions is a step-up / step-down chopper circuit. A step-up / down chopper circuit is a form of a step-up chopper circuit, and includes a step-up switching element, a step-down switching element, and a coil that stores and discharges energy by chopping any of these switching elements, and is unidirectional Is a chopper circuit formed so that a step-up operation is possible and a step-down operation is possible in the opposite direction. The “step-down operation” is to output the electric power after stepping down the input power by causing the coil to repeatedly store and release energy by chopping the step-down switching element. As long as it has such a basic configuration, various types of circuits are included in the step-up / step-down chopper circuit.

  Further, in the above configuration, when the second transmission operation is performed, the power supply includes a bypass provided in parallel with all or a part of a part of all the second circuits in the plurality of chopper circuits. By allowing the second circuit to pass through the bypass, the second circuit may not substantially perform the step-down operation. According to this configuration, all or a part of the circuit portion can be short-circuited by bypass, and the power loss can be greatly reduced. The form of the “circuit portion” described above indicates that when there are a plurality of second circuits, each second circuit is continuous or discontinuous (not the second circuit between the second circuits). It does not matter whether or not a chopper circuit is interposed.

  More specifically, the second circuit may be formed as a step-up / step-down chopper circuit, and the bypass may be provided in parallel with the step-down switching element of the second circuit.

  In the above configuration, the bypass may be configured in series with the coil in the second circuit in which the bypass is provided in parallel with the step-down switching element. According to this configuration, power can be passed through the coil, and the ripple of the output current can be further reduced.

  In the above configuration, the second circuit may be formed as a boost chopper circuit, and the bypass may be provided in parallel with the boost rectifier element of the second circuit.

  In the above configuration, the bypass may be configured in series with the coil in the second circuit in which the bypass is provided in parallel with the boosting rectifier element. According to this configuration, power can be passed through the coil, and the ripple of the output current can be further reduced.

  In the above configuration, the second circuit is formed as a step-up / step-down chopper circuit, and when performing the second transmission operation, by fixing the step-down switching element of the second circuit to a conductive state, The second circuit may be configured not to substantially perform the step-down operation. According to this configuration, there is no need to provide a bypass, and power loss can be reduced with a simple configuration.

  Specifically, as the above configuration, at least the one closest to the first end among the plurality of chopper circuits may be configured as the second circuit. According to this configuration, it is possible to reduce the ripple of the output current by using more coils at the time of step-down.

  Specifically, as the above configuration, at least the one closest to the second end among the plurality of chopper circuits may be configured as the second circuit. According to this configuration, it is possible to prevent a coil having a relatively small rated current from being used and to prevent an upper limit value of power that can be transmitted from being reduced.

  As described above, the power conversion circuit according to the present invention can reduce power loss in the bidirectional circuit.

It is explanatory drawing regarding an example of the type of usage about the bidirectional | two-way DCDC converter which concerns on embodiment of this invention. It is a block diagram of the bidirectional DCDC converter which concerns on 2nd Embodiment of this invention. It is a block diagram of the electric power transmission part which concerns on 2nd Embodiment of this invention. It is a timing chart of each signal concerning a 2nd embodiment of the present invention. It is a block diagram of a pulse signal generation circuit. It is a block diagram of the bidirectional DCDC converter which concerns on 3rd Embodiment of this invention. It is a block diagram of the electric power transmission part which concerns on 3rd Embodiment of this invention. It is a timing chart of each signal concerning a 3rd embodiment of the present invention. It is a block diagram of the electric power transmission part which concerns on 4th Embodiment of this invention. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form in which a bypass line is provided. It is explanatory drawing regarding the form of the switch provided in a bypass line. It is a graph showing the relationship between a duty ratio and a step-up ratio or a step-down ratio in a step-up / step-down chopper circuit.

  Embodiments of the present invention will be described below by taking each of the first to fourth embodiments as an example.

1. First Embodiment First, a first embodiment will be described with reference to a bidirectional DCDC converter (hereinafter sometimes abbreviated as “converter 1”). The converter 1 is provided between devices having different voltages, that is, between a low voltage side and a high voltage side. More specifically, the converter 1 is provided with a terminal T1 (first end) and a terminal T2 (second end), the terminal T1 is connected to the low voltage side, and the terminal T2 is connected to the high voltage side. . As an example, as shown in FIG. 1, the terminal T1 is connected to a storage battery, and the terminal T2 is connected to a bidirectional ACDC converter connected to the system.

  The converter 1 is more specifically described as another embodiment in detail, but has the following configuration. The converter 1 includes a plurality of chopper circuits between the terminal T1 and the terminal T2. The converter 1 boosts the power input to the terminal T1, and then outputs the first transmission operation from the terminal T2, and the input to the terminal T2. The second transmission operation of lowering the generated power and outputting from the terminal T1 is performed.

  Thus, by performing the first transmission operation and the second transmission operation, bidirectional power transmission is appropriately performed between the low voltage side and the high voltage side. Note that the converter 1 (main control unit 12 to be described later) receives information on a period during which power should be transmitted from the low voltage side to the high voltage side (period during which the first transmission operation should be performed) and from the high voltage side to the low voltage side. Information on a period for transmitting power (a period for performing the second transmission operation) is acquired.

  The plurality of chopper circuits include a first circuit formed to perform a step-up operation in a direction from the terminal T1 to the terminal T2, and a step-down operation in a direction from the terminal T2 to the terminal T1, and from the terminal T1 to the terminal And at least one of each of the second circuits formed so as to perform the boosting operation in the direction toward T2. When performing the first transmission operation, the first circuit and the second circuit perform the boosting operation in the direction from the first end toward the second end. Also, when performing the second transmission operation, the first circuit and the second circuit perform the step-down operation in the direction from the second end to the first end, and at least one of the second circuits is not the second circuit alone. Substantially no step-down operation is performed.

  With this configuration, in the converter 1, when the second circuit is formed so as to perform a step-up / step-down operation in both directions, when the second transmission operation is performed, the second circuit is substantially Does not perform step-down operation. Therefore, since the second circuit does not output the output when the step-down operation is performed, the power loss due to the switching operation for the step-down in the circuit is avoided, and as a result, the converter 1 can reduce the power loss. ing. In addition, when the second circuit is configured to perform a unidirectional boost operation from the terminal T1 to the terminal T2, efficiency may be improved when performing the first transmission operation.

  An example of a mode in which the step-down operation is not substantially performed in the second circuit will be apparent from the description of the second to fourth embodiments to be described later. In the second and fourth embodiments, the input / output of the step-down circuit is short-circuited by bypassing the step-down circuit (even if a formal step-down operation (switching operation or the like) is performed) Including the case where it does not work). In the third embodiment, a mode in which the switching element of the step-down circuit is always turned on is employed.

2. Second Embodiment Next, a second embodiment of the present invention will be described below.

[Bidirectional DCDC converter configuration]
FIG. 2 is a block diagram regarding the configuration of the converter 1. As shown in the figure, the converter 1 includes a power transmission unit 11, a main control unit 12, a first signal generation unit 13a, and a second signal generation unit 13b. FIG. 3 is a configuration diagram (circuit diagram) of the power transmission unit 11.

  The power transmission unit 11 is provided with a terminal T1 connected to the low voltage side and a terminal T2 connected to the high voltage side, and power can be transmitted bidirectionally between these terminals. . In the power transmission unit 11, a plurality of step-up / step-down chopper circuits (11a, 11b) are connected in series as shown in FIG.

  The step-up / step-down chopper circuit 11a is formed by appropriately connecting a coil L1, a switching element (IGBT) Q1, a switching element (IGBT) Q3, and a capacitor C2.

  More specifically, one end of the coil L1 is connected to the collector of the switching element Q1 and the emitter of the switching element Q3. The collector of the switching element Q3 is connected to one end of the capacitor C2. The emitter of the switching element Q1 and the other end of the capacitor C2 are connected to a ground line GND (usually set to 0V). The emitter and collector of each switching element (Q1, Q3) are connected via a diode (the anode is on the emitter side). The other end of the coil L1 is connected to the terminal T1.

  Further, switching of the switching element Q1 ON / OFF (conduction and non-conduction between collector and emitter) is controlled by a signal S1 described later. The switching of the switching element Q3 is controlled by a signal S2 described later.

  The step-up / step-down chopper circuit 11a stores and releases energy in the coil L1 when the switching element Q3 is turned off and chopping by the switching element Q1 (repetition of power conduction and interruption by high-speed ON / OFF switching) is performed. repeat. As a result, the step-up / step-down chopper circuit 11a performs an operation (step-up operation) of boosting the electric power input to one end (terminal T1 side) and then outputting from the other end (step-up / step-down chopper circuit 11b side). .

  On the other hand, the step-up / step-down chopper circuit 11a repeats accumulation and release of energy in the coil L1 when the switching element Q1 is turned off and chopping is performed by the switching element Q3. As a result, the step-up / step-down chopper circuit 11a performs an operation (step-down operation) in which the power input to one end (step-up / step-down chopper circuit 11b side) is stepped down and then output from the other end (terminal T1 side). .

  As is clear from the above description, the switching element Q1 corresponds to a step-up switching element, and the switching element Q3 corresponds to a step-down switching element. Since it is well known that the step-up / step-down chopper circuit can perform a step-up operation and a step-down operation, a more detailed description on this point is omitted.

  The step-up / step-down chopper circuit 11b is formed by appropriately connecting a coil L2, a switching element (IGBT) Q2, a switching element (IGBT) Q4, and a capacitor C3.

  More specifically, one end of the coil L2 is connected to the collector of the switching element Q2 and the emitter of the switching element Q4. The collector of the switching element Q4 is connected to one end of the capacitor C3. The emitter of the switching element Q2 and the other end of the capacitor C3 are connected to the ground line GND. The emitter and collector of each switching element (Q2, Q4) are connected via a diode (the anode is on the emitter side). The other end of the coil L2 is connected to the collector of the switching element Q3, and the collector of the switching element Q4 is also connected to the terminal T2.

  The ON / OFF switching of the switching element Q2 is controlled by a signal S1 'described later. The switching of the switching element Q4 is controlled by a signal S2 'described later.

  The step-up / step-down chopper circuit 11b repeats accumulation and release of energy in the coil L2 when the switching element Q4 is turned OFF and chopping is performed by the switching element Q2. As a result, the step-up / step-down chopper circuit 11b performs an operation (step-up operation) of boosting the electric power input to one end (step-up / step-down chopper circuit 11a side) and then outputting from the other end (terminal T2 side). . As is apparent from the above description, the switching element Q2 corresponds to a boosting switching element.

  Further, the terminal T1 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is connected to the ground line GND. One end and the other end of the bypass line BYP are connected between the terminal T2 and the switching element Q4 and between the coil L2 and the switching element Q3, respectively.

  That is, the bypass line BYP is provided so as to be in parallel with the step-up / step-down chopper circuit 11b. The bypass line BYP is provided with a switch SW for switching opening and closing of the bypass line BYP. When the switch SW is closed, both ends are in a conductive state.

  Note that the bypass line BYP is designed so that the power loss accompanying the passage of power is minimized. The power loss when power passes through the bypass line BYP is significantly smaller than the power loss when power passes through the step-up / step-down chopper circuit 11b. The opening / closing of the switch SW is controlled by a signal S0 described later.

  Returning to FIG. 2, the main control unit 12 controls each unit of the converter 1 according to which period of the period for performing the first transmission operation and the period for performing the second transmission operation. More specifically, the main control unit 12 controls the first signal generation circuit 13a and the second signal generation circuit 13b to output the signal S0 and control the opening and closing of the switch SW and to generate each signal. To do.

  The first signal generator 13a generates a signal S1 and a signal S1 'in response to an instruction from the main controller 12, and outputs a signal S1 to the switching element Q1 and a signal S1' to the switching element Q2. The second signal generator 13b generates a signal S2 and a signal S2 'in response to an instruction from the main controller 12, and outputs a signal S2 to the switching element Q3 and a signal S2' to the switching element Q4. The state of each signal will be described again. The signal S1 'may be the same as the signal S1. Further, the signal S2 'may be the same as the signal S2.

[Bidirectional DCDC converter operation]
Next, the operation of converter 1 will be described in more detail. FIG. 4 shows a timing chart of the signal S0, the signal S1, and the signal S2. In the timing chart (same for FIG. 8), the vertical axis represents voltage, and the horizontal axis represents time. Further, the timing charts of the signal S1 ′ and the signal S2 ′ are the same as those of the signal S1 and the signal S2, respectively (duty ratios and the like may be different), and thus are omitted here. As shown in the figure, the first signal generation unit 13a generates a pulse signal having an H level period as an ON period (a period during which the switching element is turned on) as a signal S1 (duty duty) in the period in which the first transmission operation is to be performed. And a signal S1 ′ (with a duty ratio of α1 ′). In addition, the first signal generation unit 13a generates signals fixed at the L level as the signal S1 and the signal S1 ′ during the period in which the second transmission operation is to be performed.

  On the other hand, the second signal generation unit 13b generates a signal fixed at the L level as the signal S2 and the signal S2 'in the period in which the first transmission operation is to be performed. Further, the second signal generation unit 13b generates a pulse signal having an H level period as an ON period in a period in which the second transmission operation is to be performed, as a signal S2 (with a duty ratio of α2) and a signal S2 ′ (with a duty ratio of α2 ′).

  Further, the main control unit 12 generates the signal S0 so that the switch SW is opened during the period in which the first transmission operation is to be performed and the switch SW is closed during the period in which the second transmission operation is to be performed. Receiving each signal (S0, S1, S1 ', S2, S2') generated in this way, the power transmission unit 11 operates as follows.

  First, in a period in which the first transmission operation is to be performed, the step-up / step-down chopper circuit 11a performs a step-up operation for transmitting the power input to the terminal T1 to the step-up / step-down chopper circuit 11b. The step-up / step-down chopper circuit 11b performs a step-up operation for transmitting the electric power input from the step-up / step-down chopper circuit 11a to the terminal T2. At this time, since the switch SW is open, power does not pass through the bypass line BYP. As a result of these boosting operations being performed in parallel, the first transmission operation is achieved.

  The step-up ratio in the first transmission operation is represented by the product of the step-up ratios in the step-up / step-down chopper circuits (11a, 11b). During the execution of the first transmission operation, the duty ratios α1 and α1 ′ (elements that determine the boost ratio) are adjusted so that the output voltage output from the terminal T2 approaches the target voltage (for example, the standard voltage of the system). Is done.

  Next, in the period in which the second transmission operation is to be performed, the bypass line BYP is in a conductive state, so that the power input to the terminal T2 is transmitted to the step-up / down chopper circuit 11a through the bypass line BYP. As a result, when transmitting power from the terminal T2 to the step-up / step-down chopper circuit 11a, the power loss is significantly reduced as compared with the case where it is assumed that the power passes through the step-up / step-down chopper circuit 11b.

  Further, the step-up / step-down chopper circuit 11a performs a step-down operation for transmitting the electric power input from the bypass line BYP to the terminal T1. As a result, the second transmission operation is achieved. When the second transmission operation is performed, the duty ratio α2 (an element that determines the step-down ratio) is adjusted so that the output voltage output from the terminal T1 approaches the target voltage (for example, the standard voltage of the storage battery).

  Various means can be adopted as means for adjusting the duty ratio so that the output voltage approaches the target voltage. As an example, by providing the pulse signal generation circuit 20 as shown in FIG. 5, the above-described duty ratio can be adjusted.

  As shown in FIG. 5, the pulse signal generation circuit 20 includes a subtraction circuit 21, an amplifier 22, a comparator 23, a triangular wave generation circuit 24, and a driver 25. In the subtracting circuit 21, the output voltage is input to the inverting input terminal, and the target voltage is input to the non-inverting input terminal.

  The signal output from the subtraction circuit 21 is amplified by the amplifier 22 and input to the non-inverting input terminal of the comparator 23. The triangular wave generated by the triangular wave generation circuit 24 is input to the inverting input terminal of the comparator 23. The driver 25 generates and outputs a pulse signal for driving the switching element in accordance with the signal output from the comparator 23.

  According to the pulse signal generation circuit 20, the pulse signal is generated so as to increase the duty ratio when the output voltage is lower than the target voltage, and to decrease the duty ratio when the output voltage is higher than the target voltage. As a result, the duty ratio is adjusted so that the output voltage approaches the target voltage when the first transmission operation is performed (when the step-up operation is performed) and when the second transmission operation is performed (when the step-down operation is performed). It becomes possible to do.

  It should be noted that various other forms can be adopted as the duty ratio adjustment method. For example, a sawtooth wave may be used instead of a triangular wave.

[About the role of each chopper circuit]
As described above, the power transmission unit 11 uses the step-up / step-down chopper circuit 11a and the step-up / step-down chopper circuit 11b as chopper circuits. The step-up / step-down chopper circuit 11a serves as the first circuit referred to in the description of the first embodiment. On the other hand, the step-up / step-down chopper circuit 11b plays a role as the second circuit mentioned in the description of the first embodiment.

  The converter 1 causes both the first circuit and the second circuit to perform a boost operation when the first transmission operation is performed. Therefore, according to the converter 1, it is possible to suppress the increase in the duty ratio of each circuit as much as possible while ensuring a high boosting ratio as a whole, and to maintain good control accuracy of the boosting operation.

  In addition, when the second transmission operation is performed, the converter 1 causes the first circuit to perform a step-down operation while allowing power to pass through the bypass line BYP that is parallel to the second circuit. Therefore, according to the converter 1, it is possible to reduce the power loss by short-circuiting the second circuit.

  Further, when using the step-up / step-down chopper circuit for both the first circuit and the second circuit, it is possible to share the parts of the first circuit and the second circuit when manufacturing the converter 1, and from the viewpoint of manufacturing efficiency. It will be advantageous. However, a general step-up chopper circuit that does not have a step-down operation function may be used as the second circuit.

3. Third Embodiment Next, a third embodiment of the present invention will be described. In the description of the third embodiment, emphasis is placed on differences from the second embodiment, and description of points that are equivalent to the second embodiment may be omitted.

  FIG. 6 is a block diagram regarding the configuration of the converter 1. As shown in the figure, the converter 1 includes a power transmission unit 11, a main control unit 12, a first signal generation unit 13a, a second signal generation unit 13b, and a third signal generation unit 13c. FIG. 7 is a configuration diagram of the power transmission unit 11.

  The power transmission unit 11 is provided with a terminal T1 provided on the low voltage side and a terminal T2 provided on the high voltage side, and power can be transmitted bidirectionally between these terminals. . In the power transmission unit 11, a plurality of step-up / step-down chopper circuits (11a, 11b) (here, two as an example) are connected in series. These points are the same as in the case of the second embodiment. However, in this embodiment, the switching of the switching element Q4 is controlled by a signal S3 described later. Further, the bypass line BYP provided in the second embodiment is not provided in the present embodiment.

  The main control unit 12 generates the first signal generation circuit 13a, the first signal generation circuit 13a, and the second signal generation circuit 13a so as to generate each signal according to which period of the first transmission operation is to be performed and which of the second transmission operation is to be performed. The two-signal generation circuit 13b and the third signal generation circuit 13c are controlled.

  The first signal generator 13a generates a signal S1 and a signal S1 'in response to an instruction from the main controller 12, and outputs the signal S1 to the switching element Q1 and the signal S1' to the switching element Q2. The second signal generator 13b generates a signal S2 in response to an instruction from the main controller 12, and outputs the signal S2 to the switching element Q3. The third signal generator 13c generates a signal S3 in response to an instruction from the main controller 12, and outputs the signal S3 to the switching element Q4.

  Next, the operation of converter 1 will be described in more detail. FIG. 8 shows a timing chart of the signal S1 (the same applies to the signal S1 '), the signal S2, and the signal S3. As shown in the figure, the first signal generation unit 13a uses a signal S1 (with a duty ratio α1) and a signal S1 as pulse signals having an H level period as an ON period in a period in which the first transmission operation is to be performed. It is generated as “(the duty ratio is α1”). In addition, the first signal generation unit 13a generates signals fixed at the L level as the signal S1 and the signal S1 'during the period in which the second transmission operation is to be performed.

  The second signal generation unit 13b generates a signal fixed at the L level as the signal S2 during the period in which the first transmission operation is to be performed. Further, the second signal generation unit 13b generates a pulse signal (with a duty ratio α2) having the H level period as the ON period as the signal S2 in the period in which the second transmission operation is to be performed.

  The third signal generation unit 13c generates a signal fixed at the L level as the signal S3 in the period in which the first transmission operation is to be performed. The third signal generator 13c generates a signal fixed at the H level as the signal S3 during the period in which the second transmission operation is to be performed. Receiving each signal (S1, S1 ', S2, S3) generated in this way, the power transmission unit 11 operates as follows.

  First, in a period in which the first transmission operation is to be performed, the step-up / step-down chopper circuit 11a performs a step-up operation for transmitting the power input to the terminal T1 to the step-up / step-down chopper circuit 11b. The step-up / step-down chopper circuit 11b performs a step-up operation for transmitting the electric power input from the step-up / step-down chopper circuit 11a to the terminal T2. As a result of these boosting operations being performed in parallel, the first transmission operation is achieved.

  The step-up ratio in the first transmission operation is represented by the product of the step-up ratios in the step-up / step-down chopper circuits (11a, 11b). During the execution of the first transmission operation, the duty ratios α1 and α1 ′ are adjusted so that the output voltage output from the terminal T2 approaches the target voltage.

  Next, in the period in which the second transmission operation is to be performed, since the signal S3 is fixed at the H level, the switching element Q4 is fixed at ON. In this state, the electric power input to the terminal T2 is transmitted to the step-up / step-down chopper circuit 11a through the switching element Q4 and the coil L2.

  At this time, since the switching element Q4 is fixed to ON, power loss due to switching loss does not occur. Therefore, in transmitting power from the terminal T2 to the step-up / step-down chopper circuit 11a, power loss is reduced compared to the case where the switching element Q4 is assumed to perform switching.

  Further, the step-up / step-down chopper circuit 11a performs a step-down operation of transmitting the electric power input from the step-up / step-down chopper circuit 11b to the terminal T1. As a result, the second transmission operation is achieved. During the execution of the second transmission operation, the duty ratio α2 is adjusted so that the output voltage output from the terminal T1 approaches the target voltage.

  Further, as is clear from the above description, in the present embodiment, the step-up / step-down chopper circuit 11a plays a role as the first circuit, and the step-up / down chopper circuit 11b plays a role as the second circuit. In addition, the converter 1 of the present embodiment causes the first circuit to perform the step-down operation while fixing the step-down switching element of the second circuit to ON during the execution of the second transmission operation. Therefore, it is possible to reduce the power loss accompanying the switching operation of the second circuit.

  Note that the converter 1 according to the present embodiment does not need to be provided with the bypass line BYP as compared with that according to the second embodiment, and thus can have a simpler configuration. Further, by changing the output destination of the signal S2 and the signal S3 as necessary, the step-up / step-down chopper circuit 11a can be changed to the second circuit, or the step-up / step-down chopper circuit 11b can be changed to the first circuit. is there.

4). Fourth Embodiment Next, a fourth embodiment of the present invention will be described. In the description of the fourth embodiment, emphasis is placed on differences from the second embodiment, and description of points that are equivalent to the second embodiment may be omitted.

  FIG. 9 is a configuration diagram of the power transmission unit 11. As shown in this figure, in the power transmission unit 11, a plurality of step-up / step-down chopper circuits (11a, 11b, 11c) (three as an example here, but may be two or four or more) may be used. Are connected in series. The configuration of the step-up / step-down chopper circuits (11a, 11b) is the same as that in the second embodiment. However, in this embodiment, the step-up / step-down chopper circuits (11a, 11b) serve as a second circuit.

  The step-up / down chopper circuit 11c is formed by appropriately connecting a coil L3, a switching element (IGBT) Q5, a switching element (IGBT) Q6, and a capacitor C4.

  More specifically, one end of the coil L3 is connected to the collector of the switching element Q5 and the emitter of the switching element Q6. The collector of the switching element Q6 is connected to one end of the capacitor C4. The emitter of the switching element Q5 and the other end of the capacitor C4 are connected to the ground line GND. The emitter and collector of each switching element (Q5, Q6) are connected via a diode (the anode is on the emitter side). The other end of the coil L3 is connected to the collector of the switching element Q4, and the collector of the switching element Q6 is also connected to the terminal T2.

  The ON / OFF switching of the switching element Q5 is controlled by a signal S1 ". The ON / OFF switching of the switching element Q6 is controlled by a signal S2". The signal S1 ″ is a signal generated in the same manner as the signal S1, and the signal S2 ″ is a signal generated in the same manner as the signal S2.

  The step-up / step-down chopper circuit 11c repeats accumulation and release of energy in the coil L3 when the switching element Q6 is turned off and chopping is performed by the switching element Q5. As a result, the step-up / step-down chopper circuit 11c boosts the electric power input to one end (step-up / step-down chopper circuit 11b side), and then performs an operation (step-up operation) for outputting from the other end (terminal T2 side). .

  On the other hand, the step-up / step-down chopper circuit 11c repeats accumulation and release of energy in the coil L3 when the switching element Q5 is turned off and chopping is performed by the switching element Q6. As a result, the step-up / step-down chopper circuit 11c performs an operation (step-down operation) in which the electric power input to one end (terminal T2 side) is stepped down and then output from the other end (step-up / step-down chopper circuit 11b side). .

  As is clear from the above description, the switching element Q5 corresponds to the step-up switching element, and the switching element Q6 corresponds to the step-down switching element.

  Unlike the second embodiment, one end and the other end of the bypass line BYP are connected between the collector of the switching element Q4 and the coil L3, and between the emitter of the switching element Q3 and the coil L1, respectively. . That is, the bypass line BYP is provided so as to be in parallel with the step-up / step-down chopper circuit 11b and the step-up / step-down chopper circuit 11a (excluding the portion of the coil L1). The bypass line BYP is in series with the coil L1.

  The bypass line BYP is provided with a switch SW that switches between opening and closing of the bypass line BYP. When the switch SW is closed, the bypass line BYP is in a conductive state between both ends. Opening and closing of the switch SW is controlled by a signal S0.

  The main control unit 12 generates the signal S0 so that the switch SW is opened during the period in which the first transmission operation is to be performed and the switch SW is closed during the period in which the second transmission operation is to be performed. The first signal generation unit 13a generates a signal S1, a signal S1 ′, and a signal S1 ″ according to an instruction from the main control unit 12, a signal S1 for the switching element Q1, a signal S1 ′ for the switching element Q2, and a switching element A signal S1 ″ is output to Q5. The second signal generator 13b generates a signal S2, a signal S2 ′, and a signal S2 ″ according to an instruction from the main controller 12, and switches the signal S2 to the switching element Q3 and the signal S2 ′ to the switching element Q4. A signal S2 ″ is output to the element Q6. The timing chart of the signal S1 ″ and the signal S2 ″ is the same as that of the signal S1 and the signal S2 shown in FIG. 4 (the duty ratio may be different). Receiving each signal (S0 to S2, S1'S2 ', S1 ", S2") generated in this way, the power transmission unit 11 operates as follows.

  First, in a period in which the first transmission operation is to be performed, the step-up / step-down chopper circuit 11a performs a step-up operation for transmitting the power input to the terminal T1 to the step-up / step-down chopper circuit 11b. The step-up / step-down chopper circuit 11b performs a step-up operation of transmitting the electric power input from the step-up / step-down chopper circuit 11a to the step-up / step-down chopper circuit 11c. Further, the step-up / step-down chopper circuit 11c performs a step-up operation of transmitting the electric power input from the step-up / step-down chopper circuit 11b to the terminal T2. As a result of these boosting operations being performed in parallel, the first transmission operation is achieved.

  The step-up ratio in the first transmission operation is represented by the product of the respective step-up ratios in the step-up / step-down chopper circuits (11a to 11c). During the execution of the first transmission operation, the duty ratios of the signal S1, the signal S1 ', and the signal S1 "are adjusted so that the output voltage output from the terminal T2 approaches the target voltage.

  In the period in which the second transmission operation is to be performed, the step-up / step-down chopper circuit 11c performs a step-down operation of transmitting the power input to the terminal T2 to the step-up / step-down chopper circuit 11b side. At this time, the bypass line BYP is in a conductive state. Therefore, the power that has been stepped down by the step-up / step-down chopper circuit 11c is transmitted between the collector of the switching element Q3 and the coil L1 through the bypass line BYP.

  As a result, in transmitting power from the step-up / step-down chopper circuit 11c to the collector of the switching element Q3 and the coil L1, compared to the case where it is assumed that the power passes through the step-up / down chopper circuit 11b and the switching element Q3, Loss is greatly reduced.

  The electric power that has passed through the bypass line BYP is further transmitted to the terminal T1 through the coil L1. As a result, the second transmission operation is achieved. At the time of execution of the second transmission operation, the duty ratio of the signal S2 ″ is adjusted so that the output voltage output from the terminal T1 approaches the target voltage.

  Further, as is clear from the above description, in the present embodiment, the step-up / step-down chopper circuit 11c serves as the first circuit, and the step-up / step-down chopper circuit 11a and the step-up / down chopper circuit 11b serve as the second circuit. Is fulfilling.

  Further, when executing the second transmission operation, the converter 1 causes the first circuit to perform a step-down operation while allowing power to pass through the bypass line BYP that is in parallel with the second circuit (excluding the portion of the coil L1). . Therefore, according to the converter 1, it is possible to reduce the power loss accompanying the switching operation of the second circuit.

  The bypass line BYP is provided in series with the switching element Q3 (step-down switching element) but in series with the coil L1 in the step-up / step-down chopper circuit 11a. Therefore, the coil L1 is included in the power transmission path when the second transmission operation is performed.

  As a result, according to the converter 1 of the present embodiment, when the second transmission operation is performed, two coils of the coil L1 and the coil L3 are used for the use of the single switching element Q6. Thereby, compared with the case where only one coil is used (refer to the second embodiment), it is possible to suppress the ripple of the output current.

5. Others As described above, the converter 1 of each embodiment includes a plurality of chopper circuits between the terminal T1 (first end) and the terminal T2 (second end), and boosts the power input to the terminal T1. A first transmission operation that is output from the terminal T2 and a second transmission operation that is output from the terminal T1 after stepping down the power input to the terminal T2 are performed.

  The plurality of chopper circuits include a first circuit formed to perform a step-up operation in a direction from the first end to the second end and a step-down operation in a direction from the second end to the first end, And at least one of each of the second circuits formed to perform a boosting operation in a direction from the first end toward the second end. When performing the first transmission operation, the first circuit and the second circuit perform the boosting operation in the direction from the terminal T1 to the terminal T2, and when performing the second transmission operation, the first circuit and the second circuit The circuit performs a step-down operation in a direction from the terminal T2 toward the terminal T1, and at least one of the second circuits is not substantially subjected to the step-down operation only by the second circuit.

  The converter 1 of the second embodiment and the fourth embodiment includes a bypass line BYP (bypass) provided in parallel with all or part of the circuit portion including the second circuit in the plurality of chopper circuits. When the transmission operation is performed, the power is allowed to pass through the bypass line BYP so that the second circuit does not substantially perform the step-down operation.

  As the form in which the bypass line BYP is provided in parallel with all or part of the circuit portion including the second circuit, various forms other than those already shown in FIGS. 3 and 9 are conceivable. For example, the forms include those shown in FIGS.

  In the circuit shown in FIG. 10, in the converter 1 of the second embodiment (see FIG. 3), the step-up / step-down chopper circuit 11b is the first circuit, the step-up / step-down chopper circuit 11a is the second circuit, and the bypass line BYP is the first circuit. It is modified to be in parallel with two circuits. That is, the circuit is equivalent to the circuit shown in FIG. 3 except that the positions of the first circuit and the second circuit are interchanged. Further, the circuit shown in FIG. 11 is modified from the circuit shown in FIG. 10 so that the bypass line BYP is in series with the coil of the second circuit. Further, the circuit shown in FIG. 12 is modified from the circuit shown in FIG. 11 so that the bypass line BYP is in parallel with the coil of the first circuit.

  Further, the circuits shown in FIGS. 13 to 15 are the same as those shown in FIGS. 10 to 12, but the step-up chopper circuit 11d that does not have the step-down function of the second circuit (the switching element Q3 is omitted for the step-up / step-down chopper circuit 11a). Equivalent to the above). In the circuits shown in FIGS. 13 to 15, the bypass line BYP is in parallel with a diode D <b> 1 (a boosting rectifier that performs rectification during the boosting operation) included in the second circuit. 10 to 15, the step-up / step-down chopper circuit 11b is the first circuit, and the step-up / step-down chopper circuit 11a (or the step-up chopper circuit 11d) is the second circuit.

  The circuits shown in FIGS. 3, 10, and 13 can be said to be an example in which the bypass line BYP is provided in parallel with all the circuit portions including all the second circuits. In addition, the circuits shown in FIGS. 9, 11, 12, 14, and 15 can be said to be examples in which the bypass line BYP is provided in parallel with a part of the circuit portion including all the second circuits. 9, 11, 12, 14, and 15, the second circuit (except for the step-up / step-down chopper circuit 11 b in FIG. 9) is the first circuit during the execution of the second transmission operation. Although the step-down operation is performed accompanying the switching operation of the circuit (particularly, the coil contributes to the step-down operation), the step-down operation is not substantially performed only by the second circuit.

  Further, in the converter 1 of the second embodiment and the fourth embodiment (similar to those having the circuits shown in FIGS. 10 to 12), the second circuit is formed as a step-up / step-down chopper circuit, and the bypass line BYP is It is provided in parallel with the step-down switching element of the second circuit. In particular, in the converter of the fourth embodiment (the same applies to those having the circuits shown in FIGS. 11 and 12), the bypass line BYP is a second circuit in which the bypass line BYP is provided in parallel with the step-down switching element. The coil is provided in series.

  Further, any number of second circuits parallel to the bypass line BYP can be provided at any position as a part of a plurality of chopper circuits included in the converter 1. When a plurality of such second circuits are provided, these second circuits may be continuous (adjacent state) or discontinuous. When discontinuous, there are a plurality of bypass lines BYP having the switch SW.

  Further, in the converter of the third embodiment, the second circuit is formed as a step-up / step-down chopper circuit, and when the second transmission operation is performed, by fixing the step-down switching element of the second circuit to a conductive state, The second circuit is substantially prevented from performing the step-down operation.

  In the third embodiment, the switching element Q4 is selected as the step-down switching element that is fixed in the conductive state. However, this is merely an example, and other switching elements can be selected.

  In addition, the second circuit that fixes the step-down switching element to the conductive state can be provided in an arbitrary number at any position as a part of the plurality of chopper circuits included in the converter 1. When a plurality of such second circuits are provided, these second circuits may be continuous (adjacent state) or discontinuous. When a plurality of such second circuits are provided, there are a plurality of step-down switching elements that are fixed in a conductive state.

  Moreover, although embodiment of this invention was described as mentioned above, what was mentioned above is only the example. The present invention can be implemented in various forms without departing from the gist thereof. Examples of modifications relating to the embodiment include the following.

  In the plurality of chopper circuits connected in series in the power transmission unit 11, the number of first circuits and second circuits (the number of series) is not particularly limited. The number can be arbitrarily set according to the design policy of the converter 1.

  Further, the switch SW provided in the bypass line BYP can have various forms. For example, as the switch SW, a relay switch may be used, or a semiconductor element such as IGBT or FET may be used. However, when using a semiconductor element, it is necessary to connect a plurality of semiconductor elements in different directions as shown in FIG. 16, for example, so that the first transmission operation is not hindered. For each switching element (Q1 to Q6), an FET or the like may be used instead of the IGBT.

  Further, in the plurality of chopper circuits connected in series in the power transmission unit 11, there is no particular limitation as to where (in what order) the first circuit and the second circuit are arranged. However, depending on the design policy of the converter 1, it is conceivable to adopt the following form.

  First, for each coil (L1 to L3), generally, the closer to the low voltage side, the larger the rated current is used (in other words, the closer to the high voltage side, the smaller the rated current is used). ) Further, for example, in the second embodiment, the coil of the second circuit is bypassed when the second transmission operation is performed, so that it is not necessary to pass power. For this reason, when importance is attached to enabling transmission of large power, it is desirable that at least the one closest to the terminal T2 among the plurality of chopper circuits be the second circuit. As a result, a coil having a relatively small rated current is not used, and the upper limit value of the transmittable power can be prevented from becoming small.

  For example, in the third embodiment, if the step-up / step-down chopper circuit 11a (the one closer to the terminal T1) is the second circuit, both the coil L1 and the coil L2 can be used for the step-down operation. Therefore, compared to the case where the step-up / step-down chopper circuit 11b is the second circuit (only the coil L1 is used for the step-down operation), the ripple of the output current can be reduced. For this reason, when importance is attached to ripple reduction, it is desirable that at least the one closest to the terminal T1 among the plurality of chopper circuits be the second circuit.

  In order to prevent the second circuit from performing a step-down operation, in the embodiment using the bypass line BYP, when the second circuit is at least closest to the terminal T1, the bypass line BYP is at least connected to the terminal T1. It is provided in parallel with the nearest second circuit. In addition, when the second circuit is at least closest to the terminal T2, the bypass line BYP is provided in parallel with at least the second circuit closest to the terminal T2.

  Further, since the step-down operation is not substantially performed in the second circuit, in the embodiment in which the step-down switching element is fixed in the conductive state, when the second circuit is at least closest to the terminal T1, The closest step-down switching element of the second circuit is fixed to the conductive state. When at least the one closest to the terminal T2 is the second circuit, at least the step-down switching element of the second circuit closest to the terminal T2 is fixed in the conductive state.

  Further, the field of use of the present invention is not limited to the embodiments described above. The present invention can be used in various applications that convert voltage and transmit power bidirectionally. In particular, the present invention is suitably used as a circuit for transmitting power bidirectionally between devices and components having different voltages.

  The present invention can be used in a power conversion circuit that converts a voltage.

1 Bidirectional DCDC converter (power conversion circuit)
DESCRIPTION OF SYMBOLS 11 Power transmission part 11a-11c Buck-boost chopper circuit 11d Boost chopper circuit 12 Main control part 13a 1st signal generation part 13b 2nd signal generation part 13c 3rd signal generation part BYP bypass line C1-C4 capacitor | condenser D1 diode (rectification for pressure | voltage rise) element)
GND ground line L1 to L3 Coil Q1 to Q6 Switching element S0 to S2, S1 ′, S2 ′, S1 ″, S2 ″ Signal SW switch T1 First end (terminal)
T2 Second end (terminal)

Claims (9)

A plurality of chopper circuits are provided between the first end and the second end,
A first transmission operation in which the power input to the first end is boosted and then output from the second end, and a second transmission in which the power input to the second end is stepped down and output from the first end A power conversion circuit for performing operation,
The plurality of chopper circuits are:
A first circuit formed to perform a step-up operation in a direction from the first end toward the second end and a step-down operation in a direction from the second end toward the first end;
Each including at least one second circuit formed to perform a boosting operation in a direction from the first end toward the second end,
When performing the first transmission operation,
The first circuit and the second circuit perform the boosting operation in a direction from the first end toward the second end;
When performing the second transmission operation,
The first circuit and the second circuit perform the step-down operation in a direction from the second end toward the first end, and at least one of the second circuits substantially performs the step-down operation only with the second circuit. A power conversion circuit that is not performed. A bypass provided in parallel with all or a part of the circuit portion of all the second circuits in the plurality of chopper circuits;
2. The power conversion circuit according to claim 1, wherein when the second transmission operation is performed, the second circuit does not substantially perform a step-down operation by allowing the power to pass through the bypass. . The second circuit is formed as a buck-boost chopper circuit,
The bypass is
The power conversion circuit according to claim 2, wherein the power conversion circuit is provided in parallel with the step-down switching element of the second circuit. The bypass is
4. The power conversion circuit according to claim 3, wherein the second circuit in which the bypass is provided in parallel with the step-down switching element is provided in series with the coil. 5. The second circuit is formed as a boost chopper circuit,
The bypass is
The power conversion circuit according to claim 2, wherein the power conversion circuit is provided in parallel with the boosting rectifier element of the second circuit. The bypass is
The power conversion circuit according to claim 5, wherein the second circuit in which the bypass is provided in parallel with the boosting rectifier element is provided in series with the coil. The second circuit is formed as a buck-boost chopper circuit,
When the second transmission operation is performed, the step-down switching element of the second circuit is fixed to a conductive state so that the second circuit is not substantially subjected to the step-down operation. The power conversion circuit according to claim 1.   8. The power conversion circuit according to claim 1, wherein at least one of the plurality of chopper circuits that is closest to the first end is the second circuit. 9.   8. The power conversion circuit according to claim 1, wherein at least one of the plurality of chopper circuits that is closest to the second end is the second circuit. 9.