JP2010283931A - DC voltage converter - Google Patents

Abstract

In order to reduce switching loss of a main switching element, a variable range of a duty ratio is expanded in a DC voltage converter including an auxiliary switching element that generates an auxiliary current that does not directly contribute to DC voltage conversion.
Auxiliary switching elements Q3 and Q4 for generating auxiliary currents Irp and Irp # are provided to reduce switching loss of main switching elements Q1 and Q2. In the normal operation mode, the switching loss is reduced by turning on and off the main switching element in accordance with the set duty ratio with the on / off of the auxiliary switching element. On the other hand, when the duty ratio becomes higher than a predetermined value, an operation mode is applied in which the auxiliary switching element and / or the main switching element are fixed to OFF by one arm and the other main switching element is turned ON / OFF according to the duty ratio. .
[Selection] Figure 1

Description

  The present invention relates to a DC voltage converter, and more particularly, to a DC voltage converter including a partial resonance circuit for reducing switching loss of a power semiconductor switching element.

  A so-called booster that boosts the output voltage of a low-voltage power supply by combining the operation of storing electromagnetic energy in the inductor and the operation of releasing electromagnetic energy stored in the inductor by repeatedly turning on and off the power semiconductor switching element. A circuit configuration of a chopper type DC-DC converter is known.

  In such a type of DC-DC converter, an inductor is required as a circuit element. However, there is a trade-off relationship between an increase in switching frequency for downsizing the inductor and an increase in switching loss due to the increase in frequency. . For this reason, so-called soft switching such as zero current switching (ZCS) or zero voltage switching (ZVS) is possible so that switching loss can be suppressed even if the power semiconductor switching element is turned on and off at a high frequency. Application is in progress.

  For example, Japanese Patent Laying-Open No. 2005-261059 (Patent Literature 1) and Japanese Patent Laying-Open No. 2007-043852 (Patent Literature 2) disclose a configuration of a current bidirectional converter having a boosting function for realizing soft switching. A circuit configuration for providing an auxiliary circuit and a control method thereof are described. This auxiliary circuit is configured to have a circuit element group for generating an auxiliary current that does not directly contribute to DC voltage conversion for realizing soft switching.

  Furthermore, International Publication No. WO2003 / 015254 (Patent Document 3) describes an input target value of an inverter, that is, an output voltage target value of the converter, in the boost converter in which the arrangement of the auxiliary circuit is omitted from the configurations of Patent Documents 1 and 2. Is lower than the voltage of the DC power supply, it is described that the upper arm element of the converter is fixed on and the lower arm element is fixed off.

JP 2005-261559 A JP 2007-038552 A International Publication WO2003 / 015254 (Claim 3)

  In the circuit configuration of the DC-DC converter described in Patent Documents 1 and 2, the voltage conversion ratio is controlled by performing on / off control of the main switching elements (Q1, Q2) in a complementary manner according to the set duty ratio. When such main transistor is switched on and off, a dead time is required.

  Further, in the DC-DC converters described in Patent Documents 1 and 2, the auxiliary transistors (Q3 and Q4) of the auxiliary circuit (partial resonance circuit) are turned on / off in order to perform soft switching of the main main switching elements (Q1 and Q2). Be controlled. At this time, it is necessary to wait for the main switching element to be on / off during a predetermined period from the on / off timing of the auxiliary switching element.

  Therefore, in a DC-DC converter including a partial resonance circuit, there is a concern that the variable range of the duty ratio of the main switching element may be narrowed due to the occurrence of a standby period accompanying the on / off of the auxiliary switching element in addition to the normal dead time. The When the variable range of the duty ratio is narrowed, the control range of the output voltage of the DC-DC converter is also narrowed.

  The present invention has been made to solve such problems, and the object of the present invention is to contribute directly to DC voltage conversion in order to reduce the switching loss of the main switching element for DC voltage conversion. In a DC voltage converter having an auxiliary switching element that generates an auxiliary current that is not generated, the variable range of the duty ratio of the main switching element is expanded to ensure a control range of the output voltage.

  A DC voltage converter according to the present invention is a DC voltage converter for performing DC voltage conversion between a low-voltage power supply and a power supply wiring, and includes a main inductor, first and second main switching elements, first and second Main rectifying elements, first and second capacitors, auxiliary inductors, first and second auxiliary switching elements, first and second auxiliary rectifying elements, and a control circuit. The main inductor is connected between the low voltage power source and the first node. The first main switching element is electrically connected between the power supply wiring and the first node. The first main rectifying element is connected in antiparallel with the first switching element. The second main switching element is electrically connected between the reference voltage line and the first node. The second main rectifying element is connected in antiparallel with the second main switching element. The first capacitor is connected in parallel with the first main switching element. The second capacitor is connected in parallel with the second main switching element. The auxiliary inductor is connected between the second node and the first node. The first auxiliary switching element is provided corresponding to the first main switching element, and is electrically connected between the power supply wiring and the second node. The second auxiliary switching element is provided corresponding to the second main switching element, and is electrically connected between the reference voltage line and the second node. The first auxiliary rectifying element is connected in series with the first auxiliary switching element so as to block a current in a direction opposite to the current when the first auxiliary switching element is on. The second auxiliary rectifying element is connected in series with the second auxiliary switching element so as to prevent a current in a direction opposite to the current when the second auxiliary switching element is on. The control circuit is provided for controlling on / off of the first and second main switching elements in accordance with the duty ratio (DTY #, DTY). The control circuit includes a mode selection unit. The mode selection unit includes a first operation mode in which the first and second main switching elements are periodically turned on / off according to the duty ratio, with the first and second auxiliary switching elements being turned on / off, and the first and second auxiliary switching elements. A second operation mode in which one of the auxiliary switching elements is fixed off and the first and second main switching elements are periodically turned on and off according to the duty ratio is defined as an operation of the DC voltage converter. It is configured to select according to the state.

  According to the voltage control converter, in addition to the first operation mode (normal operation mode) in which the first and second main switching elements can be controlled to be turned on / off with low loss accompanying the on / off of the first and second auxiliary switching elements. Thus, it is possible to select the second operation mode in which the first and second main switching elements are turned on / off while the auxiliary switching element of the one-side arm is fixed to be off. Thereby, since the variable range (upper and lower limits) of the duty ratio of the main switching element can be expanded, the control range of the output voltage can be ensured.

  Preferably, the mode selection unit is configured to select one operation mode according to the operation state from the first and second operation modes and the third operation mode. In the third operation mode, the control circuit fixes one auxiliary switching element and one main switching element corresponding to the one auxiliary switching element to off, and sets the other main switching element to duty. It is turned on and off periodically according to the ratio.

  In this case, the third operation mode for controlling the on / off of the main switching element and the auxiliary switching element of the other arm can be selected while the main switching element and the auxiliary switching element are fixed to be off by the one arm. it can. Thereby, the variable range (upper and lower limits) of the duty ratio of the main switching element can be further expanded.

  Alternatively, preferably, the control circuit further includes a duty control unit configured to control the duty ratio based on at least a voltage of the power supply wiring. The mode selection unit selects the first operation mode when both of the duty ratios of the first and second main switching elements are lower than the first determination value, while the first or second main switching element selects the first operation mode. When the duty ratio of the switching element is higher than the first determination value, the second operation mode is selected. Alternatively, the mode selection unit selects the first operation mode when both of the duty ratios of the first and second main switching elements are lower than the first determination value, and the first or second main switching When the duty ratio of the element is higher than the second determination value set higher than the first determination value, the third operation mode is selected, and the duty of the first or second main switching element is selected. The second operation mode is selected when the ratio is between the first determination value and the second determination value.

  In this way, by selecting the operation mode according to the duty ratio reflecting the feedback control of the output voltage, it is possible to smoothly perform the transition between the operation modes while automatically switching between the power running and the regeneration.

  More preferably, the control circuit fixes the second auxiliary switching element off when the duty ratio of the first main switching element is equal to or greater than the first determination value when the second operation mode is selected. In addition, the second main switching element is turned on / off according to the duty ratio, and the first main switching element is periodically turned on / off according to the duty ratio while the first auxiliary switching is turned on / off. When the duty ratio of the element is equal to or higher than the first determination value, the first auxiliary switching element is fixed to OFF and the first main switching element is turned ON / OFF according to the duty ratio. The second main switching element is turned on and off according to the duty ratio. Periodically configured so as to off. Alternatively, the control circuit may select the second main switching element and the second auxiliary switching element when the duty ratio of the first main switching element is higher than the second determination value when the third operation mode is selected. The first main switching element is periodically turned on / off according to the duty ratio with the first auxiliary switching element being turned on / off, while the duty ratio of the second main switching element is the second If it is higher than the determination value, the first main switching element and the first auxiliary switching element are fixed to OFF, and the second main switching element is turned ON / OFF according to the duty ratio. Turn on and off periodically.

  In this way, the variable range (upper and lower limits) of the duty ratio can be appropriately expanded by fixing the main switching element and / or the auxiliary switching element to OFF in the arm on the side where the duty ratio of the main switching element is low. .

  According to the present invention, in a DC voltage converter having an auxiliary switching element that generates an auxiliary current that does not directly contribute to DC voltage conversion, the variable range of the duty ratio of the main switching element for DC voltage conversion is expanded. The control range of the output voltage can be ensured.

1 is a circuit diagram showing a circuit configuration of a DC-DC converter 100 according to an embodiment of the present invention. It is an operation waveform diagram explaining circuit operation in the normal operation mode in which the auxiliary resonance circuit operates. It is an operation | movement waveform diagram in the operation mode which fixes off the auxiliary switching element of a one side arm. It is an operation | movement waveform diagram in the operation mode which fixes the main switching element and auxiliary | assistant switching element of a one side arm off. It is a conceptual diagram for demonstrating selection of the operation mode according to a duty ratio. It is a chart explaining the correspondence between duty ratio and operation mode.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

  FIG. 1 is a circuit diagram showing a circuit configuration of a DC-DC converter 100 according to an embodiment of the present invention.

  Referring to FIG. 1, DC-DC converter 100 according to the first embodiment includes a main converter circuit 110 and an auxiliary resonance circuit 120.

  The main converter circuit 110 outputs a voltage Vo obtained by boosting the voltage Vi corresponding to the output voltage of the battery BAT, which is a “low voltage power supply”, between the power supply wiring PL connected to the load 200 and the reference voltage wiring GL. The voltage Vo between the wiring PL and the reference voltage wiring GL is lowered to the voltage Vi to charge the low-voltage power supply, and a so-called non-insulated current bidirectional (buck-boost) converter configuration is provided.

  As load 200, for example, an AC motor driven through an inverter circuit is applied. Application to a hybrid vehicle that travels by engine output and / or motor output, an electric vehicle that travels only by motor output, and the like can be given as typical application examples of the DC-DC converter according to the embodiment of the present invention. In this case, for example, the output voltage (voltage Vi) of the low-voltage power supply (battery BAT) is set to about 200V, while the voltage Vo to be supplied to the load 200 is set to about 500V.

  The main converter circuit 110 includes a capacitor C0, an inductor L1 as a “main inductor”, power semiconductor switching elements Q1 and Q2 as “main switching elements”, and diodes D1 and D2 as “main rectifier elements”. Including.

  Capacitor C0 is connected between the positive terminal and the negative terminal of battery BAT to smooth voltage Vi. Inductor L1 is connected between the positive terminal of battery BAT and node N1 (first node).

  As the power switching elements (hereinafter also simply referred to as “switching elements”) Q1 and Q2, in the present embodiment, an IGBT (Insulated Gate Bipolar Transistor) is illustrated, but by drive control of the control electrode (gate or base), As long as the switching elements can control the turn-on and turn-off, voltage-driven switching elements (MOS-FET, IGBT, etc.), current-driven switching elements (bipolar transistors, etc.), and various switching elements can be applied.

  Main switching element Q1 is connected between power supply line PL and node N1. The collector of main switching element Q1, which is an IGBT, is connected to power supply line PL, while the emitter is connected to node N1. The main switching element Q2 is connected between the reference voltage line GL and the node N1. The collector of main switching element Q2 is connected to node N1, while the emitter is connected to reference voltage line GL. Furthermore, on / off of the main switching elements Q1 and Q2 is controlled by the voltage drive of the control electrode (gate) by the control circuit 150. Diodes D1 and D2 are connected in antiparallel to switching elements Q1 and Q2.

  The auxiliary resonance circuit 120 includes capacitors C1 and C2 connected in parallel to the main switching elements Q1 and Q2, inductors L2 and L3 connected in series between the nodes N1 and N2, and the power supply line PL and the node N2, respectively. Switching element Q3 and diode D3 connected in series, and diode D4 and switching element Q4 connected in series between node N2 and reference voltage line GL are included.

  The switching elements Q3 and Q4 are provided as “auxiliary switching elements”, and on / off of the switching elements Q3 and Q4 is controlled by the voltage drive of the control electrode (gate) by the control circuit 150. Diodes D3 and D4 as "auxiliary rectifying elements" are connected with a polarity that prevents currents in the direction opposite to auxiliary currents Irp # and Irp generated when auxiliary switching elements Q3 and Q4 are turned on, respectively.

  The inductor L2 is electromagnetically coupled to the inductor L1 so that an electromotive force is induced with a reverse polarity at a node N1 side terminal of the inductor L1 and a node N1 side terminal of the inductor L2. The electromagnetic coupling is realized by configuring a transformer with the inductor L1 and the inductor L2, for example.

  As can be understood from FIG. 1, the configurations and operations of the main converter circuit 110 and the auxiliary resonance circuit 120 that constitute the DC-DC converter 100 are the same as those in Patent Documents 1 and 2 described above.

  Therefore, in main converter circuit 110, basically, main switching elements Q1 and Q2 are controlled by control circuit 150 so as to be turned on and off exclusively (that is, in a complementary manner).

  The main converter circuit 110, when boosting the voltage Vi from the battery BAT to the voltage Vo to the power supply line PL, converts the electromagnetic energy accumulated in the main inductor L1 by the conduction of the main switching element Q2 into the main switching element. The power supply line PL is operated to be supplied via Q1 and the antiparallel diode D1. Further, during the step-down operation in which the voltage Vo of the power supply wiring PL is stepped down to the voltage Vi to the battery BAT, the main converter circuit 110 converts the electromagnetic energy accumulated in the main inductor L1 by the conduction of the main switching element Q1 into the main switching element Q2. And operates to supply the low-voltage power supply BAT via the anti-parallel diode D2.

  Control circuit 150 includes a duty control unit 152, a timing control unit 154, a driver 156, and an operation mode selection unit 158. The control circuit 150 comprehensively shows the control elements of the DC-DC converter 100. Regarding the duty control unit 152, the timing control unit 154, and the operation mode selection unit 158 corresponding to each control function part, It can be realized by either software processing by execution of a predetermined program or hardware processing by construction of a dedicated electronic circuit. The driver 156 is usually constructed by an electronic circuit (hardware).

  Duty control unit 152 controls the duty ratio of switching elements Q1 and Q2 based on voltage Vo or voltage command value Vor of voltage Vi and detected values of voltage Vi and voltage Vo. The duty control unit 152 has at least a feedback control function of the voltage Vo. For example, the duty ratio can be determined by a combination of the duty ratio setting corresponding to the voltage conversion ratio (Vo / Vi) according to the voltage command value Vor and the voltage feedback control. The duty ratio is generally indicated by the ratio of the ON period of switching elements Q1, Q2 to a predetermined switching period. The sum of the commanded duty ratio DTY of switching element Q1 and duty ratio DTY # of switching element Q2 is 100 (%).

  Operation mode selection unit 158 selects the operation mode of DC-DC converter 100 according to duty ratios DTY and DTY #, as will be described in detail below. A signal MD indicating the operation mode is supplied from the operation mode selection unit 158 to the timing control unit 154.

  The timing control unit 154 is a control signal S1 that is a pulse signal for controlling on / off of the switching elements Q1 to Q4 according to the operation mode selected by the operation mode selection unit 158 and the command duty from the duty control unit 152. ~ S4 is generated. For example, according to a voltage comparison between a DC voltage corresponding to a command duty from duty control unit 152 and a carrier wave (triangular wave or sawtooth wave) having a predetermined frequency corresponding to the switching frequency of main switching elements Q1, Q2, the main switching element Control signals S1 to S4, which are pulse signals for determining on / off of Q1 and Q2, can be generated.

  For example, the control signals S1 to S4 are set to a logic high level (hereinafter also referred to as H level) in each of the ON periods of the switching elements Q1 to Q4, while they are set to a logic low level (hereinafter referred to as L) in each of the OFF periods. Level).

  Driver 156 drives gate voltages Vg1 to Vg4 of switching elements Q1 to Q4 in accordance with control signals S1 to S4 from timing controller 154.

  Next, the operation of the DC-DC converter, particularly the operation in the normal operation mode in which the auxiliary resonance circuit 120 operates will be described. Here, the step-up operation of the DC-DC converter 100 will be described as an example.

  Referring to FIG. 2, Q1 and Q2 of the main switching elements are complementarily turned on and off according to the set duty ratio.

  In the example of FIG. 2, when the main switching element Q1 is turned off at time t0, the main switching element Q2 is turned on at time t1 after the dead time Td has elapsed. Further, a time t2 when the main switching element Q2 is turned off and a time t3 when the main switching element Q1 is turned on, a time t4 when the main switching element Q1 is turned off, and a time t5 when the main switching element Q2 is turned on. Similarly, a dead time Td is provided between them.

  By providing the dead time Td, both the main switching elements Q1 and Q2 are turned on, and are protected from being short-circuited between the power supply line PL and the reference voltage line GL. The current IL of the main inductor L1 is changed by turning on and off the main switching elements Q1 and Q2 with the dead time Td interposed therebetween.

  In DC-DC converter 100, auxiliary currents Irp, Irp # are generated by turning on / off auxiliary switching elements Q3, Q4, thereby reducing the switching loss when main switching elements Q1, Q2 are turned on. Specifically, prior to turning on the main switching element Q2 at times t1 and t5, the auxiliary switching element Q4 is turned on at times tb and tf. Similarly, the auxiliary switching element Q3 is turned on at time td prior to the main switching element Q1 being turned on at time t3.

  As auxiliary switching elements Q3 and Q4 are turned on, auxiliary currents (partial resonance currents) Irp and Irp # are generated. The auxiliary current decreases toward 0 after reaching a peak value due to a resonance phenomenon between the inductors L2 and L3 and the capacitor C2 or C3. Since the reverse current is blocked by the diodes D3 and D4, the auxiliary current disappears without flowing in the opposite direction.

  Here, when the auxiliary switching elements Q3 and Q4 are turned off until the generated auxiliary currents Irp and Irp # disappear, the energy stored in the inductor L3 causes the terminals of the auxiliary transistor (between collector and emitter). There is a possibility that a large surge voltage is generated due to a sudden rise in voltage. If the voltage between the terminals exceeds the withstand voltage due to this voltage rise, the auxiliary switching element may be damaged.

  Therefore, auxiliary switching elements Q3 and Q4 cannot be turned off until auxiliary currents Irp and Irp # generated by their turn-on disappear. Furthermore, the main switching element Q1 cannot be turned off until the turn-off of the corresponding auxiliary switching element Q3 is completed.

  For this reason, after the auxiliary switching element Q4 is turned on, the turned on main switching element Q2 cannot be turned off at least until the standby period Tr until the auxiliary current Irp disappears. Similarly, after the auxiliary switching element Q3 is turned on, the turned on main switching element Q1 cannot be turned off at least until a standby period Tr until the auxiliary current Irp # disappears.

  Further, even if a turn-off instruction for the auxiliary switching elements Q3 and Q4 is generated as the standby period Tr elapses, the main switching elements Q1 and Q1 are maintained during the standby period Tf until the auxiliary switching elements Q3 and Q4 are completely turned off. Q2 cannot be turned off.

  Consider the case where the duty ratio (DTY #) of the main switching element Q2 is further increased from the state of FIG. 2, that is, the duty ratio (DTY) of the main switching element Q1 is further decreased. When the duty ratio is increased for each of the main switching elements Q1 and Q2, the on / off time of (2 × Td + Tf + Tr) occurs in one cycle as the main switching element of the opposite arm is turned on / off. On the other hand, when the duty ratio is lowered for each of the main switching elements Q1 and Q2, an off-impossible period of (Td + Tr) occurs as the auxiliary switching element of the opposite arm is turned on / off.

  For example, the control signals S1 to S4 are generated by the timing control unit 154 so as to add the dead time Td and the waiting periods Tf and Tr to the ideal on / off timing according to the duty ratio DTY (DTY #). Is done.

  As described above, in the DC-DC converter 100, by operating the auxiliary switching elements Q3 and Q4, the switching loss of the main switching elements Q1 and Q2 can be reduced. There is a concern that the range of duty ratios that can be actually realized becomes narrower relative to the commanded duty ratio DTY (DTY #).

  Specifically, when the duty ratio DTY of the main switching element Q1 is close to 100 (%) (in contrast, the duty ratio DTY # of the main switching element Q2 is close to 0 (%)), and the duty ratio DTY is When it is close to 0 (%) (in contrast, the duty ratio DTY # is close to 100 (%)), the output voltage Vo cannot be matched with the target value, and the control range of the output voltage Vo becomes narrow. There is concern.

  Therefore, in DC-DC converter 100 according to the present embodiment, when the duty ratio of main switching elements Q1, Q2 is increased or decreased, an operation mode is set so as to limit switching of the opposite arm. As a result, a realizable duty ratio range is secured.

  FIG. 3 shows on / off timings of switching elements Q1 to Q4 in an operation mode in which auxiliary switching element Q3 is fixed to be off. Hereinafter, such an operation mode is also referred to as “auxiliary switching stop mode”. The auxiliary switching stop mode corresponds to the “second operation mode”.

  FIG. 3 shows an example in which the on-period of the main switching element Q1 of the opposite arm can be shortened, that is, the duty ratio can be lowered by fixing the auxiliary switching element Q3 to OFF.

  Referring to FIG. 3, as in FIG. 1, switching element Q1 is turned off at time t0 and time t4, and is turned on at time t3. The switching element Q2 is turned on at times t1 and t5, and is turned on at time t2.

  During the period from the turn-off of the switching element Q1 to the turn-on of the switching element Q2 (time t0 to t1 and time t4 to t5) and the period from the turn-off of the switching element 2 to the turn-on of the main switching element Q1 (time t2 to t3) Is provided with a normal dead time Td.

  On the other hand, by fixing the auxiliary switching element Q3 to OFF, the auxiliary switching element that restricts the on / off of the main switching elements Q1 and Q2 is only Q4. Since the standby period Tr by the auxiliary switching element Q4 is an elapsed time from the turn-on of the main switching element Q2, it is desired to lower the duty ratio of the main switching element Q1 as shown in FIG. 3 (the duty ratio of the main switching element Q2). In the case where it is desired to increase the duty ratio, the auxiliary switching element Q4 does not narrow the variable range of the duty ratio.

  Thus, when it is desired to reduce the duty ratio of the main switching element Q1 or Q2, by selecting the auxiliary switching stop mode, the operation of the auxiliary switching element Q4 or Q3 of the opposite arm is stopped, so that the duty ratio can be realized. The range can be expanded.

  FIG. 4 shows an operation mode when the duty ratio of the switching element Q2 is further increased as compared with the case of FIG. The operation mode of FIG. 4 is also referred to as “main switching stop mode”. The main switching stop mode corresponds to the “third operation mode”.

  In the main switching stop mode, the main switching element (main switching element Q1 in FIG. 4) on the arm opposite to the main switching element whose duty ratio is to be increased is fixed to OFF. Thereby, in the opposite arm, both the auxiliary switching element and the main switching element are fixed off. On the other hand, for the main switching element whose duty ratio is to be increased, the corresponding auxiliary switching element (auxiliary switching element Q4 in FIG. 4) is basically turned on and off.

  In the main switching stop mode, a duty ratio of 100 (%) can be handled. When the duty ratio is 100 (%), no switching loss occurs in the main switching element, so that both auxiliary switching elements Q3 and Q4 can be fixed off.

  Thus, in the DC-DC converter 100, in addition to the normal operation mode (first operation mode) in which each of the main switching elements Q1, Q2 and the auxiliary switching elements Q3, Q4 shown in FIG. The actual variable range of the duty ratio is expanded by corresponding to the auxiliary switching stop mode (second operation mode) shown in FIG. 3 and applying the main switching stop mode (third operation mode) shown in FIG. be able to.

  However, when the main switching stop mode shown in FIG. 4 is applied, when the main switching element Q1 of the upper arm is fixed to OFF, regeneration from the load 200 to the battery BAT cannot be performed. With the control of the voltage Vo, the power running and regeneration cannot be changed automatically.

  However, when main switching element Q1 of the upper arm is fixed off and regeneration is restricted, the voltage of power supply line PL changes in the direction in which voltage Vo increases. Therefore, the voltage feedback control is expected to act on the side that decreases the voltage conversion ratio (Vo / Vi), that is, the side that increases the duty ratio of the main switching element Q1. As a result, the duty ratio of the main switching element Q2 is reduced. Accordingly, if the operation mode is changed from the main switching stop mode to the auxiliary switching stop mode, and further to the normal operation mode, voltage feedback is performed. Regeneration is automatically possible again by the control function.

  Thus, in DC-DC converter 100 according to the present embodiment, regeneration and power running can be automatically switched by changing the operation mode in accordance with the duty ratio controlled by voltage feedback.

  FIG. 5 is a conceptual diagram for explaining selection of an operation mode according to the duty ratio, and FIG. 6 is a chart for explaining a correspondence relationship between the duty ratio and the operation mode.

  The horizontal axis of FIG. 5 shows the duty ratio DTY (%) of the upper arm main switching element Q1. A duty ratio DTY # (%) of main switching element Q2 of the lower arm is shown. As described above, DTY = 100−DTY # holds.

  Referring to FIG. 5, determination values DT1 (%), DT2 (%), DT1 # (%), and DT2 # (%) are set for stratifying cases where one side main switching element is desired to be controlled with a high duty. Is done. DT2> DT1, and DT1 # = 100-DT1, DT2 # = 100-D2.

  Based on the comparison between the duty ratio DTY # (DTY) set by the duty control unit 152 and the determination value, it is determined which of the areas 201 to 205 the current duty ratio is. The region where the duty ratio of the main switching element Q2 is high is the region 201 where DTY #> D2 (in contrast, DTY <D2 #) and D1 ≦ DTY # ≦ D2 (in contrast, D2 # ≦ DTY ≦ D1 #). It is divided into a certain area 202. The intermediate duty ratio region 203 is defined by D1 # <DTY # <D1 (D1 # <DTY <D1). Similarly, the region where the duty ratio of the main switching element Q2 is low includes the region 205 where DTY # <D2 # (in contrast, DTY> D2), and D2 # ≦ DTY # ≦ D1 # (in contrast, D1 ≦ DTY ≦ D2) and the region 204.

  That is, the determination value DT1 corresponds to the “first determination value”, and the determination value DT2 corresponds to the “second determination value”.

  Referring to FIG. 6, in region 203 having an intermediate duty ratio, dead time Td (FIG. 2) and standby periods Tf, Tr (FIG. 2) are problematic for both main switching elements Q1, Q2. Until the ON period is not shortened. Therefore, in the region 203, the normal operation mode is selected (for example, MD = 1 is set). That is, main switching elements Q1, Q2 are turned on / off according to duty ratios DTY, DTY #, with auxiliary switching elements Q3, Q4 being turned on / off.

  On the other hand, in the regions 201 and 202 where the duty ratio of the main switching element Q2 is high, the operation mode is selected so as to limit the operation of the main switching element Q1 and / or the auxiliary switching element Q3 on the opposite arm.

  Specifically, in region 202, the auxiliary switching one-side stop mode shown in FIG. 3 is selected (for example, set to MD = 2). Thus, auxiliary switching element Q3 is fixed to OFF, and main switching elements Q1, Q2 are turned on / off according to duty ratios DTY, DTY #. The main switching element Q2 is soft-switched by turning on / off the auxiliary switching element Q4.

  In the area 201, the main switching one-side stop mode shown in FIG. 4 is selected (for example, MD = 3 is set). Thus, in addition to auxiliary switching element Q3, main switching element Q1 is also fixed off, and main switching element Q2 is turned on / off according to duty ratio DTY #. The auxiliary switching element Q4 is basically turned on / off to reduce the switching loss of the main switching element Q2, but may be fixed off when the duty ratio DTY # becomes 100 (%). However, as the operation of the DC-DC converter 100, DTY # = 100 (%) is not usually set.

  On the other hand, in regions 204 and 205 where the duty ratio of main switching element Q1 is high, the operation mode is selected so as to limit the operation of main switching element Q2 and / or auxiliary switching element Q4 on the opposite arm.

  Specifically, in region 204, the auxiliary switching one-side stop mode is selected (for example, set to MD = 2). Thus, auxiliary switching element Q4 is fixed to OFF, and main switching elements Q1, Q2 are turned ON / OFF according to duty ratios DTY, DTY #. The main switching element Q1 is soft-switched by turning on / off the auxiliary switching element Q3.

  In region 205, the main switching one-side stop mode is selected (for example, MD = 3 is set). As a result, in addition to the auxiliary switching element Q4, the main switching element Q2 is also fixed off, and only the main switching element Q1 is turned on / off according to the duty ratio DTY. The auxiliary switching element Q3 is basically turned on / off to reduce the switching loss of the main switching element Q1. However, when the duty ratio DTY becomes 100 (%) (no step-up / down pressure and conduction mode), the auxiliary switching element Q3 is fixed off.

  As described above, in the DC-DC converter 100 according to the embodiment of the present invention, in addition to the normal operation mode, the auxiliary switching one-side stop mode and the main switching one-side stop mode can be selected to change the duty ratio. The range (upper and lower limits) can be expanded. Further, by selecting the operation mode according to the duty ratios DTY and DTY # reflecting the feedback control of the voltage Vo, the operation mode is automatically switched between the DC-DC converter 100 and the load 200 while the power running / regeneration is automatically switched. The transition between them can be performed smoothly.

  In the present embodiment, the AC motor and the inverter circuit mounted on the hybrid vehicle or the electric vehicle are exemplified as the load 200 of the DC-DC converter 100. However, the application of the present invention is not limited to this. Absent. That is, the point that the present invention can be applied without particularly limiting the load 200 will be described in a confirming manner.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  In order to reduce the switching loss of the main power semiconductor switching element, the present invention switches a DC voltage converter having an auxiliary power semiconductor switching element that generates an auxiliary current that does not directly contribute to DC voltage conversion. Can be applied to control.

  100 DC-DC converter, 110 main converter circuit, 120 auxiliary resonance circuit, 150 control circuit, 152 duty control unit, 154 timing control unit, 156 driver, 158 operation mode selection unit, 200 load, 201-205 region (duty ratio) BAT low voltage power supply, C0, C1, C2 capacitor, D1, D2 antiparallel diode, DT1, DT1 #, DT2, DT2 # judgment value, D3, D4 diode, DTY, DTY # duty ratio, GL reference voltage wiring, Irp, Irp # auxiliary current, L1 main inductor, L2, L3 inductor (auxiliary inductor), MD signal (operation mode), N1, N2 node, PL power supply wiring, Q1, Q2 power semiconductor switching element (main switching element), Q3 Q4 electricity Use semiconductor switching devices (auxiliary switching element), S1 to S4 control signal, Td dead time, Tf, Tr waiting period, Vg1 through Vg4 gate voltage, Vi, Vo voltage, Vor voltage command value.

Claims (6)

A DC voltage converter for performing DC voltage conversion between a low-voltage power supply and a power supply wiring,
A main inductor connected between the low voltage power source and the first node;
A first main switching element electrically connected between the power supply wiring and the first node;
A first main rectifying element connected in anti-parallel with the first main switching element;
A second main switching element electrically connected between a reference voltage line and the first node;
A second main rectifying element connected in anti-parallel with the second main switching element;
A first capacitor connected in parallel with the first main switching element;
A second capacitor connected in parallel with the second main switching element;
An auxiliary inductor connected between a second node and the first node;
A first auxiliary switching element provided corresponding to the first main switching element and electrically connected between the power supply line and the second node;
A second auxiliary switching element provided corresponding to the second main switching element and electrically connected between the reference voltage line and the second node;
A first auxiliary rectifying element connected in series with the first auxiliary switching element so as to block a current in a direction opposite to a current when the first auxiliary switching element is on;
A second auxiliary rectifying element connected in series with the second auxiliary switching element so as to block a current in a direction opposite to the on-state current of the second auxiliary switching element;
A control circuit for controlling complementary on and off of the first and second main switching elements according to a duty ratio;
The control circuit includes:
A first operation mode in which the first and second main switching elements are periodically turned on and off in accordance with the duty ratio, with the first and second auxiliary switching elements being turned on and off; A second operation mode in which one of the two auxiliary switching elements is fixed off, and the first and second main switching elements are periodically turned on and off according to the duty ratio; A DC voltage converter including a mode selection unit configured to select in accordance with an operating state of the DC voltage converter. The mode selection unit is configured to select one operation mode according to the operation state from the first and second operation modes and the third operation mode,
In the third operation mode, the control circuit fixes the one auxiliary switching element and one main switching corresponding to the one auxiliary switching element to be off, and sets the other main switching element to the The DC voltage converter according to claim 1, wherein the DC voltage converter is periodically turned on and off according to a duty ratio. The control circuit further includes a duty control unit configured to control the duty ratio based on at least a voltage of the power supply wiring,
The mode selection unit selects the first operation mode when both of the duty ratios of the first and second main switching elements are lower than a first determination value. The DC voltage converter according to claim 1, wherein the second operation mode is selected when the duty ratio of the second main switching element is higher than the first determination value. The control circuit further includes a duty control unit configured to control the duty ratio based on at least a voltage of the power supply wiring,
The mode selection unit selects the first operation mode when both of the duty ratios of the first and second main switching elements are lower than a first determination value, and the first or the When the duty ratio of the second main switching element is higher than the second determination value set higher than the first determination value, the third operation mode is selected, and the first or The second operation mode according to claim 2, wherein the second operation mode is selected when a duty ratio of the second main switching element is between the first determination value and the second determination value. DC voltage converter.   The control circuit turns off the second auxiliary switching element when the duty ratio of the first main switching element is not less than the first determination value when the second operation mode is selected. While being fixed, the second main switching element is turned on / off in accordance with the duty ratio, and the first main switching element is periodically turned on / off in accordance with the duty ratio while the first auxiliary switching is turned on / off. When the duty ratio of the second main switching element is equal to or greater than the first determination value, the first auxiliary switching element is fixed off and the first main switching element is set to the duty ratio. And turning on and off the second auxiliary switching. It consists of two of the main switching element so as to periodically turned on and off according to the duty ratio, claim 4 DC voltage converter according.   When the duty ratio of the first main switching element is higher than the second determination value when the third operation mode is selected, the control circuit includes the second main switching element and the second main switching element. The auxiliary switching element is fixed off, and the first main switching element is periodically turned on / off according to the duty ratio with the turning on / off of the first auxiliary switching element. When the duty ratio of the element is higher than the second determination value, the first main switching element and the first auxiliary switching element are fixed to OFF, and then the second auxiliary switching element is turned ON / OFF. Accordingly, the second main switching element is periodically turned on / off according to the duty ratio. DC voltage converter to claim 4.

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