JP2017011993A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that in a system requiring charging of a battery, when having a charger built in, the volume and weight of the system increase.SOLUTION: A charger comprises a three-phase inverter circuit, a battery supplying a direct current, a step-down converter, and an alternating current motor connected to the output of the three-phase inverter circuit. The input of the step-down converter is connected to a commercial power supply through a rectification circuit. One end of the output of the step-down converter is connected to a winding neutral point of the alternating current motor, and the other end of the output of the step-down converter is connected to the input of the three-phase inverter circuit. A step-up converter is formed of a first transistor and a first diode, which form the three-phase inverter circuit, and the winding of the alternating current motor.SELECTED DRAWING: Figure 5(a)

Description

  The present invention relates to a configuration of a charger.

  Various systems for obtaining an AC power source by converting a DC power source such as a battery have been commercialized. From the viewpoint of protecting the global environment, plug-in hybrid vehicles and electric vehicles have recently been put into practical use.

These are driven by an electric motor that uses a battery power source that has been charged in advance by an external power source as an input, and is characterized by a high greenhouse gas (CO ₂ ) reduction effect.

  A three-phase synchronous motor and a three-phase induction motor, which are excellent in terms of efficiency, are employed exclusively for the electric motor, and a three-phase inverter circuit is also employed as a means for obtaining an AC power source for driving the motor.

  In such a vehicle, the compressor of the air conditioner (air conditioner) also needs to be driven by a battery instead of the conventional engine drive, so an inverter circuit and an electric motor are employed as the drive source.

  The battery power supply can be charged by a quick charging circuit installed outside, but for convenience, a dedicated charger is installed in the vehicle, and if necessary, the battery can be connected to a commercial power supply. It can be charged.

  Such an in-vehicle charger has, for example, a circuit configuration described in Patent Document 1 shown in FIG. This is a diode bridge circuit for rectifying a commercial power supply, a boost converter circuit for boosting the output voltage of the rectifier circuit, expanding the conduction width of the input current, and increasing the power factor, and a step-down converter for adjusting to a predetermined charging voltage Consists of a circuit. This configuration is characterized in that the power supply current can be controlled with low distortion by the control of the boost converter and can be controlled to a predetermined charging voltage according to the battery voltage by the step-down converter.

  Further, Patent Document 2 describes a configuration in which the circuit configuration of transistors and diodes constituting the inverter circuit is switched to the circuit configuration described in Patent Document 1 by a contactor when performing a charging operation. This is characterized in that it is not necessary to add a new transistor and diode for the charger.

  In the configuration described in Patent Document 3, a positive line of a rectifier circuit output connected to a commercial power source is connected to an output of the inverter circuit via a transistor that conducts and cuts off, and a negative line of the inverter circuit and the rectifier circuit output is connected. They are connected to each other. The on-off control of the transistor provided on the positive line of the output of the rectifier circuit together with the prescribed transistor that constitutes the inverter circuit realizes charging of the battery by controlling the coil current of the induction motor connected to the inverter doing. According to this configuration, the charging circuit can be configured by adding one transistor in addition to the rectifier circuit without adding a contactor.

Japanese Unexamined Patent Publication No. 2011-250598 JP 2012-90458 PR Japanese Laid-Open Patent Publication No. 7-87616

  However, in Patent Document 1, there are many parts to be newly added for the charger. On the other hand, according to the invention of Patent Document 2, transistors and diodes are added as compared with the case of adding the configuration of Patent Document 1 as it is. However, it is necessary to add multiple contactors.

  Moreover, in the configuration described in Patent Document 3, the coil current needs to be controlled to a direct current in order not to generate a rotational force in the induction motor. That is, there is a disadvantage that the output current of the rectifier cannot be freely controlled. In addition, when applied to a system in which a magnet motor such as a synchronous motor is connected to the inverter in place of the induction motor, even if the coil current is controlled to a direct current, a rotational force corresponding to the rotor position is generated. Also occurs.

  Furthermore, since the transistor provided in the positive line of the rectifier circuit output is always on / off controlled during the charging operation, there is a problem in that switching loss increases and efficiency decreases.

To solve the above problem,
In a system having a three-phase inverter circuit for driving an AC motor and a battery for supplying DC power to the circuit, a step-up / down converter circuit having a configuration in which a step-up converter is connected after the step-down converter as a charging circuit It was adopted.

  The output of the step-up / down converter circuit is connected to the output of any one phase of the inverter and the input of the inverter, and the step-up / down converter circuit is connected to the step-up converter after the step-down converter. With this configuration, the smoothing capacitor of the boost converter can be shared with the capacitor provided in advance in the inverter circuit, and the number of additional parts for the charger can be reduced. Furthermore, charging control can be performed without flowing current to the motor winding.

  If a buck-boost converter circuit with a boost converter connected after the step-down converter is used as the charging circuit, the step-down converter is connected to the winding neutral point of the motor connected to the inverter and the input of the inverter. By connecting the circuit outputs and using the inverter circuit transistor, smoothing capacitor, and motor winding connected to the inverter to operate the boost converter, a charger can be realized and additional components can be reduced.

  By controlling the average current of each phase motor winding current to be the same, charging control can be performed without generating a rotational force in the motor.

  According to the present invention, when a charger is configured for a system having an inverter circuit, additional parts such as a semiconductor element and a contactor can be reduced.

It is a step-up / down converter circuit diagram constituting the charger of the present invention. It is a step-up / down converter circuit diagram constituting the charger of the present invention. It is a circuit diagram which shows the charger structure of this invention which connected the inverter circuit and the buck-boost converter circuit. It is a circuit diagram which shows the charger structure of this invention which connected the inverter circuit and the buck-boost converter circuit. It is a circuit diagram which shows the charger structure of this invention which connected the inverter circuit and the buck-boost converter circuit. It is a schematic diagram which shows switching of the step-up / step-down operation during the operation of the power supply voltage, the power supply current, the battery voltage, and the charger necessary for the control of the present invention. It is a schematic diagram which shows switching of the step-up / step-down operation during the operation of the power supply voltage, the power supply current, the battery voltage, and the charger necessary for the control of the present invention. It is a figure which shows the structural example for controlling the charger of this invention. It is a circuit diagram which shows the charger structure of this invention which connected the inverter circuit and the buck-boost converter circuit. It is a figure which shows the magnetic flux chain man-hour vector which arises in the gap between a motor stator and a rotor, when the electric current with the same magnitude | size and direction is supplied to a three-phase motor winding. It is a circuit diagram which shows the charger structure of this invention which connected the inverter circuit and the buck-boost converter circuit. It is a figure which shows the structural example for controlling the charger of this invention. The clock signal for controlling the charger of the present invention and the current flowing through the motor neutral point when the T / 3 phase difference is given to each phase switching timing of the three-phase transistor are schematically shown. It is a figure. It is the figure which showed the circuit example for setting each phase switching timing to a predetermined phase difference. It is a step-up / down converter circuit diagram constituting a conventional charger. It is a circuit diagram which shows the conventional charger structure which connected the inverter circuit and the buck-boost converter circuit.

  Hereinafter, the operation and effects of the charger of the present invention will be described in detail with reference to the drawings based on the embodiments.

  The configuration of the charging circuit of the present invention is shown in FIG. The diode full-wave rectifier circuit 1 connected to the power source, and the collector of the transistor 2a for adjusting the voltage by controlling on / off of the rectified output voltage of the diodes 1a1 and 1a2 constituting the diode full-wave rectifier circuit 1 Connected to the cathode, the emitter of the transistor 2a is connected to the inductor 2c. The other connection end of the inductor 2c is connected to the capacitor 2d. The inductor 2c and the capacitor 2d are filters for smoothing the ripple voltage associated with on / off of the transistor 2a. The anodes of the diodes 1b1 and 1b2 constituting the diode full-wave rectifier circuit 1 are connected to the negative line, the anode of the diode 2b different from the rectifier circuit 1 is connected to the negative line, and the cathode is connected to the emitter of the transistor 2a. Connecting. When the transistor 2a is turned off, the current of the inductor 2c is circulated to prevent the surge voltage from being generated and to protect the transistor 2a. The step-down converter 2 is constituted by these 2a to 2d.

  The diode full-wave rectifier circuit 1 has a capacitor 1d connected to the cathodes of the diodes 1a1 and 1a2 and the anodes of the diodes 1b1 and 1b2 constituting the diode full-wave rectifier circuit 1, and a connection point between the anode of the diode 1a1 and the cathode of the diode 1b1 One end of the inductor 1c is connected to the connection point between the anode of the diode 1a2 and the cathode of the diode 1b2, and the other end includes the inductor 1c connected to the remaining connection point of the commercial power source.

  The inductor 1c and the capacitor 1d are filters that absorb current ripple generated when the respective transistors of the converter are switched. Note that the filter effect may be obtained by using the system impedance (inductor of about 100 μH) in the commercial power supply without adding the inductor 1c separately.

  The connection point of the inductor 2c and the capacitor 2d constituting the step-down converter 2 is connected to the inductor 3c, and the connection point of the other end of the inductor 3c is connected to the collector of the transistor 3a. The emitter of the transistor 3a is connected to the negative electrode line, and the current of the inductor 3c is adjusted by ON / OFF control of the transistor 3a. The connection point between the collector of the transistor 3a and the inductor 3c is connected to the capacitor 3d through the diode 3b. The other connection end of the capacitor 3d is connected to the negative electrode line. The diode 3b has a cathode connected to the capacitor 3d and an anode connected to the collector of the transistor 3a. The current of the inductor 3c flows to the capacitor 3d while the transistor 3a is off, and both ends of the capacitor 3d are short-circuited while the transistor 3a is on. It plays a role in preventing the situation from entering. The capacitor 3d can smooth the ripple associated with the on / off of the transistor 3a, thereby obtaining a predetermined output voltage. The step-up converter 3 is constituted by these 3a to 3d.

  Here, in FIG. 1A, the inductor 2c and the capacitor 2d constituting the filter circuit provided in the step-down converter 2 can achieve the same effect by the inductor 3c and the capacitor 3d in the configuration of the step-up converter 3. Therefore, the circuit configuration can be simplified as shown in FIG. Although not shown, the transistor 2a, the inductor 3c, and the diode 3b can be inserted in series with the negative electrode line. For example, the diode 3b may have its cathode connected to the emitter of the transistor 3a and its anode connected to the capacitor. The inductor 3c may be inserted between the emitter of the transistor 3a and the anode of the diode 2b.

  In addition to FIG. 1B, another diode, inductor, and / or transistor can be newly added to the negative electrode line.

  Now, the negative line of the charging circuit configured as shown in FIG. 1B is connected to the negative line of the inverter circuit, and the cathode of the diode 3b of the charging circuit is connected to, for example, the U-phase output terminal of the inverter circuit. The capacitor 3d in FIG. 1B can be expected to have the same smoothing effect by the capacitor 5 connected to the inverter circuit. That is, the charging / discharging operation performed by the capacitor 3d of the boost converter 3 is performed by the capacitor 5 connected to the inverter circuit. Therefore, since the capacitor 3d can be omitted, the number of components can be reduced (one capacitor can be reduced) as shown in FIG.

  Here, the configuration of the inverter circuit 4 connected to the charging circuit and its peripheral parts will be described. The inverter circuit 4 includes six transistors 4a to 4f, and six diodes 4a1 to 4f1 each having a cathode connected to a collector and an anode connected to an emitter of each transistor. The emitter of the transistor 4a and the collector of the transistor 4d are connected, and this connection point becomes the U-phase output. Then, by applying a positive DC voltage to the collector of the transistor 4a and a negative DC voltage to the emitter of the transistor 4d, the transistors 4a and 4d are exclusively turned on / off, thereby making the U-phase output voltage positive, Alternatively, it can be controlled negatively.

  A pair of transistors 4b and 4e provides a V-phase output, and a pair of transistors 4c and 4f provides a W-phase output. The U, V, and W phase outputs are connected to a three-phase motor. Further, in order to control the current of each phase, sensors 7a, 7b, and 7c for detecting a current flowing in a line connecting the output of the inverter circuit 4 and the three-phase motor 6 are provided.

  One end of the capacitor 5 for smoothing the ripple accompanying the on / off of each transistor of the inverter circuit 4 is connected to the collectors of the transistors 4a, 4b, and 4c, and the other end is connected to the emitters of the transistors 4d, 4e, and 4f.

  A battery 9 for supplying a DC voltage to the inverter circuit 4 is connected to both ends of the capacitor 5 via a contactor 8.

  The contactor 8a is connected in series between the positive voltage side of the battery and one end of the capacitor, and the contactor 8b is connected in series between the negative voltage side of the battery and the other end of the capacitor.

  A series circuit of a contactor 8c and a resistor 8d is connected in parallel to both ends of the contactor 8a.

  The contactors 8a and 8b constitute a double system for reliably disconnecting the connection with the battery even when either one fails. The contactor 8c and the resistor 8d are operated before the contactor 8a is turned on, and the capacitor 8 is slowly charged by the resistor 8d to prevent the generation of a large rush current.

  FIG. 8B shows a conventional system in which the conventional charging circuit of FIG. 8A is connected to a system constituted by a battery 9, a contactor 8, a capacitor 5, an inverter circuit 4, and a three-phase motor 6. The capacitor of the step-down converter in FIG. 8A is shared by the capacitor 5 connected to the inverter circuit 4. However, the smoothing capacitor of the boost converter remains, and the number of parts is large as compared with FIG.

  Next, a more preferred embodiment of the present invention will be described with reference to FIG.

  In FIG. 2B, the transistor 3d of FIG. 2A is assigned to the transistor 4d of the inverter circuit 4, and the diode 3b is assigned to the diode 4a1 of the inverter circuit 4, thereby omitting the transistor 3a and the diode 3b. In addition, the number of parts can be further reduced.

  Even if the connection method disclosed in the present invention is applied to the conventional charging circuit shown in FIG. Specifically, since it is necessary to connect the inductors constituting the step-down converter of the charging circuit in series, it is structurally possible to share transistors and diodes in the subsequent stage of the inductor with those of the inverter circuit 4. Can not.

  On the other hand, the output part of the charging circuit employed in the present invention shown in FIG. 1 (a) or FIG. 1 (b) only includes a diode 3b in series, which is connected in series with the diode of the inverter circuit 4. . Therefore, the diode 3b can be omitted. If the diode 3b is omitted, the transistor 3a is connected in parallel to the transistor of the inverter circuit 4, the collector, and the emitter. Therefore, the transistor 3a can be omitted.

  Note that the configuration shown in FIG. 2C can be adopted instead of the configuration shown in FIG.

  In this case, the switching control of the transistor 4d is performed in FIG. 2B, but the function of the transistor 3a in FIG. 2A can be achieved by performing the switching control of the transistor 4a in FIG.

  Further, in the present embodiment, the configuration in which one end of the charging circuit is connected to the U phase among the three-phase output of the inverter is exemplified, but instead of this, any one of the V phase and the W phase may be adopted. it can.

  In this case, the transistor for switching control is assumed to be that of an arm to which one end of the charging circuit is connected.

  By selecting the connection points as described above according to the structural arrangement of the wirings and terminals, it is possible to obtain an effect of reducing the size of the device.

  A preferred method for controlling the configuration of FIG. 2B will be described with reference to FIG. 3 and FIG.

  FIG. 3A shows the power supply voltage full-wave rectified by the rectifier circuit 1 and the battery voltage to be charged.

  In Japan, the effective value of commercial power supply voltage is 100V or 200V for a single phase. FIG. 3A shows an example of charging a battery discharged from a single-phase 200V (peak value 282V) and discharged to 240V, taking battery charging of a plug-in hybrid vehicle as an example.

  Referring to the figure, it can be seen that there are periods when the battery voltage is higher and lower than the power supply voltage. In the conventional charging circuit, regardless of the battery voltage, the boost converter is temporarily controlled to obtain a DC voltage higher than the peak value of the commercial power supply at both ends of the smoothing capacitor, and this voltage is suitable for the battery voltage by the step-down converter. I was able to charge by lowering.

  However, as can be seen with reference to the configuration of FIG. 1A as the starting point of the present invention, since the commercial power supply voltage is input to the step-down converter, only a voltage lower than the peak value of the power supply voltage can be obtained.

  Although charging is possible by raising the voltage to a voltage suitable for the battery voltage with a boost converter connected to the output of the buck converter, there are the following two problems.

  First, current does not flow from the power supply in a region where the input power supply voltage of the step-down converter is lower than the output voltage. Therefore, in order to suppress the waveform distortion of the current flowing from the power source, the output voltage needs to be sufficiently reduced compared to the input voltage in order to widen the flow width. Under such circumstances, the energization width cannot be increased to 100% in principle. This is the first inconvenience.

  Although it is possible to obtain a predetermined charging voltage by controlling the voltage of the step-down converter by boosting the voltage, it is preferable to supply as much power as possible to the battery when it is desired to charge the battery in a short time. For example, let us consider a case where a commercial power supply has a power contract of 5 kW, and charging is performed at 5 kW when no other load is used.

  In order to widen the flow width, the output DC voltage of the step-down converter is controlled to 100 V. At this time, the flow width is about 77%. When charging at 5 kW, it is necessary to control the boost converter so that the charging current is 50 A (= 5 [kW] / 100 [V]). With a conventional charger, for example, if the step-up converter is controlled to have a 300 V output, the step-down converter for charging in response to the boost converter may be controlled to 17 A (= 5 [kW] / 300 [V]). . Since the current exemplified here flows through the inductor for constituting the converter, the charging circuit of the present invention requires a large inductor corresponding to a larger current. In addition, the loss due to the current flowing through the inductor and transistor is larger than that of the conventional charging circuit. This is the second disadvantage.

  Therefore, the configuration of FIG. 1B is employed as the charging circuit of the present invention. In this configuration, as described above, the inductor 2c and the capacitor 2b for configuring the step-down converter are omitted, and the inductor 3c and the capacitor 3b for configuring the step-up converter are shared. As a result, the step-down converter and the step-up converter can be selectively operated. Using this feature, control is performed as follows.

  The power supply voltage and the battery voltage are detected, and the respective detected values are compared. In a period when the power supply voltage is lower than the battery voltage, the transistor 3a in FIG. Shed. At this time, the transistor 2a may be always turned on. On the other hand, during a period in which the power supply voltage is higher than the battery voltage, the transistor 2a is controlled to be turned on / off to operate the step-down converter and adjust the current flowing from the power supply. During this period, the transistor 3a is always off.

  By adopting this method, it is possible to control the power supply current to 100% in principle, and assuming that the current flowing through the ripple current absorbing capacitor 1d provided in the rectifier circuit 1 can be ignored. The effective current value flowing through the inductor 3c is the same as the effective power supply current value. That is, in the previous example, the current flowing through the inductor is 25 A (= 5 [kW] / 200 [V]).

  In the above description, the current flowing through the inductor of the step-down converter of the conventional charging circuit is 17 A, but the current flowing through the inductor of the previous boost converter is 25 A (= 5 [kW] / 200 [V]). Become. In the charger of the present invention, the number of inductors through which a current for charging flows is smaller than in the conventional case, and the loss is small.

  Next, the current control method of the charging circuit of the present invention will be described with reference to FIGS. 2B, 3B, and 4. FIG. As described above, the transistor 3a and the diode 3b in FIG. 1B may be read as the transistor 4d and the diode 4a in FIG. 2B, respectively. That is, in FIG. 2B, the transistor of the step-up converter 3 is a transistor 4d, and the transistor of the step-down converter 2 is a transistor 2a.

  FIG. 3B shows a preferable rectified power supply current together with a power supply voltage. If controlled as shown, the power supply current before rectification can be controlled in a sine wave in phase with the power supply voltage. This makes it possible, for example, to clear the European power supply harmonic regulations IEC61000. Furthermore, since the power factor operation of about 100% can be performed, the input current can be minimized, and power saving can be achieved.

  FIG. 4 illustrates a configuration for controlling the circuit of FIG. The battery voltage detection value and the rectified power supply voltage detection value are input to the subtractor 41, and the result (difference) is input to the hysteresis comparator 42. The comparator 42 outputs a logic level “1” when the power supply voltage detection value is smaller than the battery voltage. Otherwise, the logic level “0” is output. This is input to an OR gate 47 and an AND gate 48 that output a signal directed to the gate of the transistor. Therefore, the OR gate output continues to output the logic level “1” while the logic level is “1”, regardless of the remaining input level. Therefore, when the power supply voltage detection value is smaller than the battery voltage, the transistor 2a of the step-down converter to which the OR gate output is also connected is turned on. During this period, the output of the AND gate 48 changes in response to other logic signals.

  The power supply current command value after rectification shown in FIG. 3B and the boost converter current detection value obtained from the sensor provided in the line section shown in FIG. 2B are input to the subtractor 44, and the result (difference) is obtained. , To the hysteresis comparator 46. The comparator 46 outputs a logic output “1” when the command value exceeds the detection value, and outputs “0” otherwise. When this output is input to the AND gate 48 and the power supply voltage detection value is smaller than the battery voltage, the boost converter transistor 4d is on / off controlled in response to the output of the comparator 46.

  Also, the rectified power supply current command value shown in FIG. 3B and the power supply current detection (after rectification) value obtained from the sensor provided in the line section shown in FIG. 2B are input to the subtractor 43. The result (difference) is given to the hysteresis comparator 45. The comparator 45 outputs a logic output “1” when the command value exceeds the detection value, and outputs “0” otherwise. When this output is input to the OR gate 47 and the power supply voltage detection value is larger than the battery voltage, the step-down converter transistor 2a is controlled to be turned on / off in response to the output of the comparator 45.

  From the above, it can be seen that if the configuration of FIG. 4 is adopted, the transistors of the booster or step-down converter can be selectively turned on and off according to the power supply voltage and the battery voltage, and controlled to a predetermined current.

  Here, the hysteresis width set in the comparator is a dead zone where the output does not change. Therefore, when the transistor is on / off controlled by the comparator, the controlled current has a current ripple corresponding to the hysteresis width with the command value as the center. That is, the hysteresis width of the comparators 45 and 46 can be adjusted, and the ripple can be set to an appropriate value.

  On the other hand, the hysteresis width of the comparator 42 may be determined so as to prevent chattering during switching of the step-down and step-up control modes.

  The reason why the current detection sensors are set at two locations is that the influence of the current flowing through the ripple current removing capacitor 1d provided in the rectifier circuit 1 is determined by properly using the detection locations according to the step-up and step-down converter modes. Can be eliminated. When it is not necessary to suppress waveform distortion, control may be performed using either one of the sensor signals.

  Now, when operating as a charging circuit, the transistors 4b, 4c, 4e, 4f of the inverter circuit 4 are always controlled to be off. The transistor 4a may be always off. However, when a MOSFET or the like is employed as the transistor, efficiency improvement can be expected by performing on / off control exclusively with the transistor 4d. In such a case, on / off control is appropriately performed. You may do it.

  By controlling in this way, the V-phase and W-phase outputs of the inverter circuit 4 can maintain the open state (both the transistor and the diode connected in parallel to it are in the off state), so the motor connected to the output of the inverter circuit 4 No current flows through the winding.

  On the contrary, when the inverter is operated, the transistor 2a of the charging circuit is always turned off. The series circuit of the diode 4d1, the inductor 3c, and the diode 2b of the inverter circuit 4 is connected in parallel, but the steeply changing freewheeling current flowing through the diode as the transistors 4a and 4d are turned on and off is blocked because of the inductor 3c. All flows to the diode 4d1 without flowing to the diode 2b. Therefore, an additional circuit that interrupts the charging circuit with a contactor or the like is not necessary in the present invention.

  Here, a modification of the present invention will be described with reference to FIGS. As can be seen by comparing the configurations of FIG. 2B and FIG. 6A, the inductor 3c at the output of the charging circuit is connected to the neutral point of the motor winding. Since the motor winding has an inductance, the inductor 3c (illustrated by a dotted line) is omitted.

During the boost converter operation, the transistors 4d, 4e, and 4f are controlled so that the phase currents are substantially the same. As a result, the number of phase linkage magnetic fluxes λ _U , λ _V , and λ _W generated in the motor by the winding current are 120 ° phase difference and the same magnitude. Since this vector sum is zero, the motor winding is used during charging, but no motor rotational force is generated.

  If the three-phase winding impedance is the same during the step-down converter operation, the current is shunted to the same current. Moreover, although there is a difference in impedance in practice, since it is about several percent, the magnetic flux level due to it is very small, and it does not become a force to sum up motor rotation.

  FIG. 6 shows an example of a circuit for extending the circuit of FIG. 4 to operate the charger of FIG. A subtractor 61, a comparator 63, and an AND gate 65 for controlling the V-phase transistor are added. The power supply current command value and the V-phase current detection value after rectification are input to the subtractor, and in response to the result, the output of the comparator 63 that outputs a logic signal responds to the battery and the power supply voltage in the mode. Are input to the AND gate 65 together with a logic signal for switching. The AND gate 65 outputs a signal toward the gate of the V-phase transistor.

  Also for the W phase, a subtractor 62, a comparator 64, and an AND gate 66 for controlling the transistor are added.

  For the U phase, the current detection value is replaced with U phase current detection, and the rest of the configuration is the same as in FIG.

  In addition to the circuit shown in FIG. 5A, a charger can be connected to the motor neutral point as shown in FIG. 5C.

  FIG. 7 shows an example in which the ripple of the power supply current is reduced at the same switching frequency when performing the control of FIG.

  The outputs of the AND gates 48, 65, and 66 in FIG. 6 are supplied to reset inputs R of the SR flip-flops 71, 72, and 73 through NOT gates 74, 75, and 76, respectively, and PWM periods obtained from a clock source that is not shown. A clock waveform having a T / 3 phase shift with respect to T is obtained as shown in FIG. As a result, each time the clock is input, the flip-flop is set, its output becomes a logic level “1”, and when the outputs of the comparators 48, 65, 66 become “0”, the corresponding flip-flop The output is reset to the logic level “0”.

  As a result, the current of each phase is turned on at the clock input timing as shown in FIG. When the current reaches the command value (the hysteresis width of the comparator is set to 0), the transistor is turned off and the current is attenuated.

  This three-phase waveform is synthesized at a neutral point, and its ripple frequency is 3 / T as shown in the figure, and the ripple width can be reduced.

  As for the control showing the operation and effect of the present invention by showing the embodiment, the control using the comparator and the logic circuit is exemplified, but software-based digital control using a microcomputer can also be adopted. . There are various conventionally known current control methods, and it goes without saying that methods other than the instantaneous value control for comparing the magnitude of the command and the detected current shown in the embodiment can be adopted.

  Moreover, the charger of this invention can be employ | adopted also for household appliances, such as a rechargeable vacuum cleaner which employ | adopted the drive source as a three-phase motor and an inverter besides the vehicle-mounted use.

DESCRIPTION OF SYMBOLS 1 Rectifier circuit including a filter 2 Step-down converter circuit 3 Step-up converter circuit 4 Inverter circuit 5 Smoothing capacitor 6 Three-phase motor 7 Three-phase current sensor 8 Contactor unit 9 Battery 1a1, 1a2, 1b1, 1b2, 2b, 3b, 4a1, 4b1, 4c1, 4d1, 4e1, 4f1 Diodes 2a, 3a, 4a, 4b, 4c, 4d, 4e, 4f Transistors 1c, 2c, 3c Inductors 1d, 2d, 3d Capacitors 6a, 6b, 6c Motor windings 7a, 7b for each phase, 7c Current sensor 8a, 8b, 8c Contactor 8d Inrush current prevention resistor 41, 43, 44, 61, 62 Subtractor 42, 45, 46, 63, 64 Hysteresis comparator 47 OR gate 48, 65, 66 AND gate 71, 72, 73 SR flip-flops 74, 75, 76 NOT gate

Claims (7)

A three-phase inverter circuit for driving an AC motor supplied with a DC current from a battery;
A buck converter,
The AC motor connected to the output of the three-phase inverter circuit,
The input of the step-down converter is connected to a commercial power source through a rectifier circuit,
One end of the output of the step-down converter is connected to a winding neutral point of the AC motor,
The other end of the output of the step-down converter is connected to the input of the three-phase inverter circuit,
A battery charger, wherein a step-up converter is constituted by the first transistor and the first diode constituting the three-phase inverter circuit and the winding of the AC motor. The battery charger according to claim 1, wherein
The positive output of the step-down converter is connected to the winding neutral point of the AC motor,
The battery charger, wherein the negative output of the step-down converter is connected to the negative input of the three-phase inverter circuit. The battery charger according to claim 1, wherein
The negative output of the step-down converter is connected to the winding neutral point of the AC motor,
The battery charger, wherein a positive output of the step-down converter is connected to a positive input of the three-phase inverter circuit. The battery charger according to any one of claims 1 to 3,
Power supply voltage detection means for detecting a voltage instantaneous value of the commercial power supply;
Battery voltage detection means for detecting the voltage value of the battery;
Comparing means for comparing the voltage value detected by the power supply voltage detecting means with the voltage value detected by the battery voltage detecting means,
As a result of comparison by the comparison means,
When the voltage value detected by the power supply voltage detection means is higher than the voltage value detected by the battery voltage detection means, the third transistor of the step-down converter is turned on / off,
When the voltage value detected by the power supply voltage detection means is lower than the voltage value detected by the battery voltage detection means, the third transistor of the step-down converter is always turned on, and the transistor of the three-phase inverter circuit is turned on. A battery charger characterized by comprising switching means for on / off control and control so that each phase winding current of the AC motor is substantially the same. The battery charger according to any one of claims 1 to 4,
Power supply current detection means for detecting the current value of the commercial power supply,
A battery charger comprising: means for controlling the current value detected by the power source current detecting means so as to follow a sine wave having the same frequency as the commercial power source and having a predetermined amplitude. The battery charger according to claim 5,
Motor current detection means for detecting a current flowing in each phase motor winding of the AC motor;
During operation of the step-down converter, converter control is performed based on the detection value by the power supply current detection means,
A battery charger characterized in that when the step-down converter is not in operation, transistor control of the three-phase inverter circuit is performed based on a value detected by the motor current detecting means. The battery charger according to any one of claims 1 to 6,
A battery charger characterized by setting a phase difference of approximately 1/3 of a PWM cycle to the switching timing of each phase transistor of the three-phase inverter circuit.

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