JP6089494B2 - Power converter - Google Patents

Description

  In the present specification, a series circuit of a high potential conductor, a first switching element, a second switching element, and a ground conductor is provided, and the first switching element is turned on and the second switching element is turned off. Disclosed is a technology relating to a device that converts electric power by alternately switching between a state in which the second switching element is turned on and the second switching element is turned on.

For example, as illustrated in FIG. 1, a series circuit of a first switching element SU connected to the high potential side and a second switching element SD grounded is provided, and the first switching element SU is turned on and the first switching element SU is turned on. The voltage of the DC power source 80 is stepped down and applied to the load 2 by alternately switching between the state where the two switching elements SD are turned off and the state where the first switching element SU is turned off and the second switching elements SD are turned on. Step-down converters are known.
Alternatively, as illustrated in FIG. 2, three series circuits of the first switching element SU and the second switching element SD are connected in parallel, and the direct current supplied by the power supply 80 is converted into a three-phase alternating current to convert the three-phase alternating current motor 4 An inverter for applying to (a kind of load) is also known. In the case of an inverter, the switching is alternately performed between a state where the first switching element is turned on and the second switching element is turned off and a state where the first switching element is turned off and the second switching element is turned on. That is, regarding the first phase, SD1 is turned off when SU1 is turned on, and SD1 is turned on when SU1 is turned off. Also for the second phase, SD2 is turned off when SU2 is turned on, and SD2 is turned on when SU2 is turned off. For the third phase, SD3 is turned off when SU3 is turned on, and SD3 is turned on when SU3 is turned off.
1 and 2 exemplify a power conversion device including a series circuit of a high-potential conductor, a first switching element, a second switching element, and a ground conductor, and the scope of application of the technology disclosed in this specification Are not limited to the power converters of FIGS. 1 and 2. The present invention can be generally applied to a power conversion device including a series circuit of a high potential conductor, a first switching element, a second switching element, and a ground conductor.

  As shown in FIG. 3, the power conversion device of the above-described form (in FIG. 3, the first switching element on the high potential side is 40 and the second switching element that is grounded is 70) is the first switching element drive. A circuit (hereinafter referred to as a first drive circuit) 30, a second switching element drive circuit (hereinafter referred to as a second drive circuit) 60, and a control for transmitting control signals to the first drive circuit 30 and the second drive circuit 60. A circuit 10 is provided. 20 shown in the figure is an element (for example, a photocoupler) that transmits a control signal in a state where the control circuit 10 and the first drive circuit 30 are electrically insulated. Similarly, reference numeral 50 denotes an element that transmits a control signal in a state where the control circuit 10 and the second drive circuit 60 are electrically insulated.

  The first drive circuit 30 requires a power source for operating itself, and requires a power source for turning on the first switching element 40. Reference numeral 100 is a power supply circuit for the first drive circuit 30 and is generally composed of a constant voltage circuit. Since power is supplied from the power supply circuit 100, the first drive circuit 30 can operate, and the first switching element 40 is switched on and off. Reference numeral 110 is a power supply circuit for the second drive circuit 60. Since power is supplied from the power supply circuit 110, the second drive circuit 60 can operate and the second switching element 70 is switched on and off. .

  According to the conventional technique shown in FIG. 3, the power supply circuits 100 and 110 are required, and it is necessary to connect the first drive circuit 30 to the power supply circuit 100 and connect the second drive circuit 60 to the power supply circuit 110.

  Non-Patent Document 1 discloses a drive circuit 30 that does not use the power supply circuit 100. In the technique of Non-Patent Document 1, a drive circuit is driven using a voltage difference between a high potential conductor to which a switching element is connected and a ground conductor. According to the technique of Non-Patent Document 1, it is not necessary to provide the power supply circuit 100.

0-7803-9547-6 / 06 / $ 20.00 (c) 2006, IEEE, pp. 183-188, A Self-powered Resonant Gate Driver for High Power MOSFET Modules, Hongfang Wang, Fred Wang

Non-Patent Document 1 proposes a drive circuit in the case where a switching element is used alone, and does not consider the case where the first switching element and the second switching element are connected in series.
When the first switching element and the second switching element are connected in series, if the conductor connecting the first switching element and the second switching element is not connected to the high potential conductor before the start of operation, the first switching element and the second switching element are grounded. It is not connected to a conductor. That is, it is floating. The technique of Non-Patent Document 1 assumes a case where the switching element is used alone, and assumes that the low potential side of the switching element is maintained at the ground voltage. When the first switching element and the second switching element are connected in series, the technique of Non-Patent Document 1 cannot cope with it.

  In the present specification, a driving circuit for a case where a first switching element and a second switching element are connected in series, and a high potential to which a series circuit of the first switching element and the second switching element is connected. We propose a drive circuit that operates using the voltage difference between the conductor and ground conductor.

The power converter disclosed in this specification includes a series circuit of a high potential conductor, a first switching element, a second switching element, and a ground conductor. Also, a first drive circuit for switching on / off of the first switching element, a second drive circuit for switching on / off of the second switching element, and control for transmitting a control signal to the first drive circuit and the second drive circuit It has a circuit.
The first drive circuit is connected between a conductor connecting the high potential conductor and the first switching element, and a conductor connecting the first switching element and the second switching element. The second drive circuit is connected to a conductor connecting the high potential conductor and the first switching element, a conductor connecting the first switching element and the second switching element, and a conductor connecting the second switching element and the ground conductor. Yes.
The control circuit transmits a control signal for turning off the first switching element and turning on the second switching element at the time of starting, and then turning on the first switching element and turning off the second switching element. A control signal for turning off the element and turning on the second switching element is alternately transmitted.
FIG. 4 illustrates an example of the power conversion device described above, and includes a series circuit of a high potential conductor 82, a first switching element 40, a second switching element 70, and a ground conductor 90. Further, the first driving circuit 30 for switching on / off of the first switching element 40, the second driving circuit 60 for switching on / off of the second switching element 70, the first driving circuit 30 and the second driving circuit 60 are provided. A control circuit 10 for transmitting a control signal is provided.
The first drive circuit 30 is connected between a conductor 84 that connects the high-potential conductor 82 and the first switching element 40, and a conductor 86 that connects the first switching element 40 and the second switching element 70. The second drive circuit 60 includes a conductor 84 that connects the high potential conductor 82 and the first switching element 40, a conductor 86 that connects the first switching element 40 and the second switching element 70, a second switching element 70, and a ground conductor. 90 is connected to a conductor 88 that connects 90.

According to the power conversion circuit, since the second drive circuit is connected between the high potential conductor and the ground conductor, it can operate using the voltage difference. Further, since the second switching element is turned on first, the second switching element can be turned on without providing a separate power supply device. When the second switching element is turned on, the conductor connecting the first switching element and the second switching element is grounded, and power is supplied to the first drive circuit. In this state, the first switching element can be turned on since the first switching element is switched on. When the first switching element is turned on, a high potential is applied to the conductor connecting the first switching element and the second switching element, and power is supplied to the second drive circuit. In this state, the second switching element can be turned on because the second switching element is switched on. Thereafter, the above operation is repeated, and the state where the first switching element is turned on and the second switching element is turned off and the state where the first switching element is turned off and the second switching element is turned on are alternately switched.
The first drive circuit and the second drive circuit operate by obtaining power from the voltage difference between the high potential conductor connected to the first switching element and the ground conductor connected to the second switching element. It is not necessary to connect the first drive circuit and the second drive circuit to a power supply device for that purpose.

  According to the technology described in the present specification, even when the first switching element and the second switching element are connected in series, the first drive circuit and the second drive are utilized using the voltage difference applied to the series circuit. The circuit can be driven. A power supply device for the first drive circuit and the second drive circuit is not required. The circuit configuration of the power converter can be simplified.

1 shows a circuit of a step-down converter (a type of power converter) that uses a series circuit of a first switching element and a second switching element. The circuit of the inverter (a kind of power converter) using the series circuit of the 1st switching element and the 2nd switching element is shown. The conventional connection method of a power supply circuit, a control circuit, and a drive circuit is shown. A novel connection method of the control circuit and the drive circuit is shown. The circuit of the step-down converter of an Example is shown. The control signal which control circuit 10 transmits is illustrated. A phenomenon that occurs immediately after the main switch is turned on will be described. A phenomenon that occurs immediately after the main switch is turned on will be described. A phenomenon that occurs when the second switching element is turned on will be described. A phenomenon that occurs when the second switching element is turned on will be described. A phenomenon that occurs when the first switching element is turned on will be described. A phenomenon that occurs when the second switching element is turned on will be described.

The main features of the embodiments described below are exemplified below.
(Feature 1) The second drive circuit includes an operational amplifier, a complementary transistor, and a capacitor that supplies power to the operational amplifier and the complementary transistor. The capacitor is connected between the high potential conductor and the ground conductor, and is charged even when both the first switching element and the second switching element are off.
(Feature 2) A resistor for reducing the voltage is inserted between the capacitor of Feature 1 and the high potential conductor.
(Feature 3) The control circuit inverts the control signal to turn on the first switching element and turn off the second switching element within a period in which the second switching element can be kept on by the capacitor of feature 1.

FIG. 5 shows a power conversion circuit of the embodiment. In the embodiment of FIG. 5, the first switching element 40 and the second switching element are provided between a high potential conductor 82 to which a high potential is applied by a DC power supply 80 and a ground conductor 90 that is grounded and maintained at the ground potential. A series circuit of the switching elements 70 is connected. The high potential conductor 82 and the first switching element 40 are connected by a conductor 84, the first switching element 40 and the second switching element 70 are connected by a conductor 86, and the second switching element 70 and the ground conductor 90 are a conductor. 88 is connected. The conductor 84 itself may also serve as the high potential conductor 82, and the conductor 88 itself may also serve as the ground conductor 90. A main switch 81 may be inserted between the DC power supply 80 and the high potential conductor 82.
A series circuit of a coil L and a capacitor C is connected between the conductor 86 and the conductor 88. A load 2 is connected in parallel with the capacitor C.
The control circuit 10 alternately transmits a control signal for turning on the first switching element 40 and turning off the second switching element 70 and a control signal for turning off the first switching element 40 and turning on the second switching element 70. .
Specifically, the first drive circuit 30 to be described later controls the first switching element 40 to be turned on and the first switching element 40 to be turned off while the control circuit 10 is transmitting a control signal for turning on the first switching element 40. While the signal is transmitted, the first switching element 40 is turned off. Similarly, the second drive circuit 60 turns on the second switching element 70 and turns off the second switching element 70 while the control circuit 10 transmits a control signal for turning on the second switching element 70. Is transmitted, the second switching element 70 is turned off.
In the circuit of FIG. 5, when the state where the first switching element 40 is turned on and the second switching element 70 is turned off and the state where the first switching element 40 is turned off and the second switching element 70 is turned on are alternately switched. The voltage obtained by stepping down the voltage of the DC power supply 80 is applied to both ends of the load 2. The circuit of FIG. 5 is a DC / DC step-down inverter.
FIG. 5 illustrates a case where the technique disclosed in this specification is applied to a DC / DC step-down inverter. The scope of application of the technology disclosed in this specification is not limited to the DC / DC step-down inverter, and can be applied to, for example, the three-phase AC inverter illustrated in FIG. The technology disclosed in the present specification includes a DC circuit of the first switching element 40 and the second switching element 70, a state in which the first switching element 40 is turned on and the second switching element 70 is turned off; The present invention can be generally applied to a device that converts power by alternately switching a state in which the switching element 40 is turned off and the second switching element 70 is turned on.

  As shown in FIG. 5, the first drive circuit 30 is connected between the conductor 84 and the conductor 86, and does not require a unique power supply circuit. Reference numeral 20 is a photocoupler, and the control circuit 10 and the first drive circuit 30 are electrically insulated. The second drive circuit 60 is connected to the conductor 84, the conductor 86, and the conductor 88, and does not require a unique power supply circuit. Reference numeral 50 is a photocoupler, and the control circuit 10 and the second drive circuit 60 are electrically insulated.

The first drive circuit 30 includes an operational amplifier OP1 that compares whether the control signal transmitted through the photocoupler 20 is high or low, a transistor sa1 that is turned on if the output of the operational amplifier OP1 is high, and an output of the operational amplifier OP1 that is high. If so, a transistor sa2 that is turned off is provided. The transistor sa1 is turned off when the output of the operational amplifier OP1 is low, and the transistor sb1 is turned on when the output of the operational amplifier OP1 is low. The transistors sa1 and sa2 are complementary types. As a result, if the control signal transmitted through the photocoupler 20 is high, the operational amplifier OP1 outputs high, the transistor sa1 is turned on, the transistor sb1 is turned off, and an on-voltage is applied to the gate of the first switching element 40. Applied, the first switching element 40 is turned on. On the other hand, if the control signal transmitted through the photocoupler 20 is low, the operational amplifier OP1 outputs low, the transistor sa1 is turned off, the transistor sb1 is turned on, and the gate of the first switching element 40 is charged. The electric charge is discharged, and the first switching element 40 is turned off.
In order to obtain the above operation, a driving voltage must be applied to the operational amplifier OP1, and a potential difference must be generated between both ends of a series circuit of complementary transistors of the transistor sa1 and the transistor sb1. Before the first switching element 40 is turned on, the potential of the conductor 86 is unstable, and the voltage difference between the conductor 84 and the conductor 86 is unstable. In order to obtain the driving voltage for the first driving circuit 30, special consideration is required.

  The operation of turning on / off the second switching element 70 based on the control signal transmitted through the photocoupler 50 by the second drive circuit 60 is the same as that of the first drive circuit 30. By replacing the suffix 1 at the end with 2, the operation of the second drive circuit 60 can be understood. Duplicate explanation is omitted. In order to obtain the driving voltage for the second driving circuit 60, special consideration is required.

  In order to obtain a driving voltage for the first driving circuit 30, a Zener diode dc1, a capacitor ca1, a diode dd1, a coil l1, a diode de1, and a capacitor cb1 are connected to the illustrated positions. One end of the Zener diode dc1, the capacitor ca1, and the diode dd1 is connected to the conductor 84 by a wiring 92. In the wiring 92, a diode de1 and a capacitor cb1 are inserted. The other end of the Zener diode dc1, the capacitor ca1, and the coil 11 is connected to the conductor 86 by a wiring 94. When starting the step-down converter, the conductor 86 is floating, and the voltage difference between the wiring 92 and the wiring 94 is unstable. The capacitors ca1 and cb1 may not be charged.

  In order to obtain a driving voltage for the second driving circuit 60, a Zener diode dc2, a capacitor ca2, a diode dd2, a coil l2, a diode de2, and a capacitor cb2 are connected to the illustrated position. One end of the Zener diode dc2, the capacitor ca2, and the diode dd2 is connected to the conductor 86 by a wiring 96. A diode de2 and a capacitor cb2 are inserted in the wiring 96. The other ends of the Zener diode dc2, the capacitor ca2, and the coil l2 are connected to the conductor 88 by a wiring 98. The capacitor ca2 and the conductor 84 (not the conductor 86) are connected via a resistor rc2. The resistor rc2 is for preventing overcurrent, and the resistor rc2 is set to a resistance value at which a current of about several mA flows.

  It is assumed that the control device 10 transmits a control signal for turning on the first switching element 40 and turning off the second switching element 70 when starting the step-down converter of FIG. In this case, since the capacitor ca1 is not charged, the first drive circuit 30 does not operate. The buck converter does not start.

In this embodiment, when the step-down converter is started, the control device 10 transmits a control signal for turning off the first switching element 40 and turning on the second switching element 70. In this case, the second drive circuit 60 starts operating using the charging power of the capacitor ca2. This will be described in detail below.
At the end of the operation of the step-down converter, the main switch 81 is turned off. When the step-down converter is started, the main switch 81 that has been turned off is turned on. Then, a voltage difference is generated between the conductor 84 and the conductor 88, and the capacitor ca2 is instantaneously charged via the resistor rc2. The capacity of the capacitor ca2 is set to a small capacity that is charged instantly. As a result, when the step-down converter is started, the voltage of the wiring 96 increases instantaneously. In a short time after starting, the voltage of the wiring 96 reaches the breakdown voltage of the Zener diode dc2. The breakdown voltage of the Zener diode dc2 is the driving voltage Vcc of the second drive circuit 60. If the breakdown voltage Vcc of the Zener diode dc2 is applied to the wiring 96, the operational amplifier OP2, the complementary transistors sa2, sb2, etc. are appropriate. Operates on. As a result, the second switching element 70 is turned on. When the second switching element 70 is turned on, the conductor 86 is grounded.
7 and 8 illustrate the above.
(1) The main switch 81 is turned on at start time t1.
(2) When the main switch 81 is turned on, the capacitor ca2 is charged through the path indicated by the thick line in FIG. 7, and the voltage of the wiring 96 rises to Vcc at the timing t2.
(3) Then, the operational amplifier OP2, the transistors sa2, sb2, etc. start to operate properly. Since the control signal for turning on the second switching element 70 is transmitted at the time of starting, the second switching element 70 is turned on.
(4) When the second switching element 70 is turned on, the conductor 86 is grounded.

When the second switching element 70 is turned on and the conductor 86 is grounded, the capacitors cb1 and ca1 are charged through a path indicated by a thick line in FIG. The voltage of the wiring 92 rises to the driving voltage Vcc of the first driving circuit 30. Thereafter, the first drive circuit 30 can operate appropriately.
Timing t3 in FIG. 10 indicates the timing at which the control signal is inverted. The operational amplifier OP1 outputs high, and the first switching element 40 becomes conductive.
When the first switching element 40 is turned on, the electric charge accumulated in the capacitor cb1 is discharged as indicated by an arrow A in FIG. 11, and energy is stored in the coil l1. When the capacitor ca1 is discharged and the potential of the wiring 92 decreases, as indicated by the arrow B, the capacitor c1 is charged from the coil l1, so that the potential of the wiring 92 is maintained at Vcc for a long time. This means that the capacitance of the capacitor ca1 may be small. A time T2 in FIG. 6 indicates a period during which the first switching element 40 is maintained in the ON state. When the capacitor cb1 is used, the capacitance of the capacitor ca1 can be set regardless of the period T2. The capacitor ca1 only needs to have a capacity to turn on the first switching element 40 first, and does not need a capacity to maintain the on state over the period T2. The capacitance of the capacitor ca1 can be set very small. This is advantageous for reducing the power consumption of the first drive circuit 30. When the period T2 is long, it is necessary to increase the capacitance of the capacitor cb1. The capacitance of the capacitor cb1 does not greatly affect the power consumption of the first drive circuit 30.

When the first switching element 40 is turned on and the second switching element 70 is turned off, the capacitors cb2 and ca2 are charged as shown in FIG. The voltage of the wiring 96 increases to the driving voltage Vcc for the second driving circuit 60. The second drive circuit 60 can operate appropriately.
When the control signal is inverted again to turn off the first switching element 40 and turn on the second switching element 70, the operational amplifier OP2 outputs high using the voltage of the capacitor ca2, and the second switching element 70 is turned on. Conduct.
When the second switching element 70 is turned on, the charge accumulated in the capacitor cb2 is discharged as indicated by an arrow C in FIG. 12, and energy is stored in the coil l2. When the capacitor ca2 is discharged and the potential of the wiring 96 decreases, as shown by the arrow D, the capacitor ca2 is charged from the coil l2, so that the potential of the wiring 96 is maintained at Vcc for a long time. This means that the capacitance of the capacitor ca2 may be small. As described above, the second switching element 70 can be kept on using the capacitance of the capacitor cb2.

  When the second switching element 70 is first turned on, the capacitor cb2 is not charged, the second switching element 70 needs to be turned on only by the charge of the capacitor ca2, and the second switching element 70 needs to be kept on. There is. When the capacitance of the capacitor ca2 is increased, the power consumption of the second drive circuit 60 is increased. Further, the timing t2 at which the wiring 96 rises to the operating voltage Vcc is delayed. Therefore, in this embodiment, as shown in FIG. 6, the period T1 during which the second switching element 70 is first turned on is shorter than the subsequent period T2. The period T1 is set to a period in which the ON state can be maintained by the small-capacitance capacitor ca2.

  The above embodiment is applied to a step-down converter. This is just an example, and the application target is not limited to the step-down converter.

The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.
The technical scope of the claims described below is not limited to the examples. The examples are merely illustrative.

SU: 1st switching element SD: 2nd switching element L: Coil C: Capacitor 2: Load 4: Motor (load)
DESCRIPTION OF SYMBOLS 10: Control circuit 20: Photocoupler 30: 1st drive circuit 40: 1st switching element 50: Photocoupler 60: 2nd drive circuit 70: 2nd switching element 80: DC power supply 81: Main switch 82: High potential conductors 84 and 86 88: Conductor 90: Ground conductor OP1, OP2: Operational amplifiers ra1, rb1, ra2, rb2, rc2: Resistors da1, db1, dc1, dd1, de1, da2, db2, dc2, dd2, de2: Diodes sa1, sb1, sa2 , Sb2: transistors ca1, cb1, ca2, cb2: capacitors

Claims (1)

A series circuit of a high potential conductor, a first switching element, a second switching element, and a ground conductor;
A first switching element drive circuit for switching on and off of the first switching element;
A second switching element drive circuit for switching on and off of the second switching element;
A control circuit for transmitting a control signal to the first switching element drive circuit and the second switching element drive circuit;
The drive circuit for the first switching element is connected between a conductor connecting the high potential conductor and the first switching element, and a conductor connecting the first switching element and the second switching element,
The second switching element drive circuit includes a conductor connecting the high potential conductor and the first switching element, a conductor connecting the first switching element and the second switching element, and a conductor connecting the second switching element and the ground conductor. Connected,
The control circuit transmits a control signal for turning off the first switching element and turning on the second switching element at the time of starting, and then turning on the first switching element and turning off the second switching element and the first switching It is configured to alternately transmit a control signal for turning off the element and turning on the second switching element ,
A driving circuit for the second switching element includes an operational amplifier that inputs a control signal, a capacitor that applies driving power to the operational amplifier, a resistor that is inserted between the conductor connecting the high-potential conductor and the first switching element, and the capacitor. power conversion circuit, characterized in that it comprises.

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