JPH10174457A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion circuit with improved operation reliability for preventing a phase switch circuit from being short-circuited, regardless of the failure in a power supply part. SOLUTION: A high-side switch 53 and a low-side switch 54 for constituting a phase switch circuit are driven and controlled by driver circuits 61 and 62, respectively, which receive power from power supply parts 63 and 64. To solve the problem that the output impedance of the high-side power supply part 63 and the low-side power supply part 64 increases due to certain causes and hence the output impedance of the driver circuits 61 and 62 increases. Thus the gate electrode potential of the switch 53 or 54 becomes floated and conducts erroneously, and hence a main power supply 1 is short-circuited by the switches 53 and 54, a spare power supply part 300 for feeding a spare power supply voltage to the driver circuit 62 that receives power from the main power supply 1 is provided to feed a spare power supply voltage to the driver circuit 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter such as an inverter for orthogonal transform.

[0002]

[Prior art]

(Drive Circuit of Electric Vehicle) A conventional motor (load) drive circuit for an air-conditioning compressor of an electric vehicle will be described with reference to a circuit diagram shown in FIG. The main battery 1 supplies power to the auxiliary battery 3 through a voltage conversion system (not shown). X-phase phase switch circuit 4a, Y-phase phase switch circuit 4b and Z
A DC-AC inverter 4 composed of a phase switch circuit 4c for a phase supplies power to a three-phase AC motor 5 for driving an air conditioning compressor. The X-phase phase switch circuit 4a is configured by serially connecting a high-side switch 53 and a low-side switch 54 each formed of an N-channel MOSFET.
Power is supplied from the main battery 1. Both switches 53,5
The output terminal of the phase switch circuit 4a consisting of the connection point 4 is connected to the X-phase input terminal of the three-phase AC motor 5. The phase switch circuit 4b of Y phase and the phase switch circuit 4c of Z phase
It has the same circuit configuration as the phase switch circuit 4a of each phase, and applies a drive voltage to the Y-phase input terminal and the Z-phase input terminal of the three-phase AC motor 5, respectively. Reference numerals 25 and 26 denote flywheel diodes for current return, 55 and 56 denote parasitic capacitances of the gate electrode of the high-side switch 53, and 58 and 59 denote parasitic capacitances of the gate electrode of the low-side switch 54.

Reference numeral 61 denotes a high-side driver circuit which amplifies at least the input control signal voltage V1 and applies it to the gate electrode of the high-side switch 53; This is a low-side driver circuit for amplifying and applying the amplified signal to the gate electrode of the low-side switch 54. Reference numeral 63 denotes a high-side power supply of a driver power supply for applying a power supply voltage to the driver circuit 61, and reference numeral 64 denotes a low-side power supply of a driver power supply for applying a power supply voltage to the driver circuit 62. These power supply units 63 and 64 generally comprise a constant voltage power supply or the like, and are supplied with power from the auxiliary battery 3 through a cable (harness) 70. The driver circuit and the power supply unit having the same configuration as the driver circuits 61 and 62 and the power supply units 63 and 64 are a high-side switch and a low-side switch of the Y-phase switch circuit 4b, and a high-side switch of the Z-phase switch circuit 4b. The switch and the low-side switch are provided for driving, but their illustration is omitted. The driver circuits 61 and 62 control the control signal voltages V1 and V2.
It is well known that the high-level ON voltage or the low-level OFF voltage is output to the high-side switch 53 or the low-side switch 54 in accordance with the command (1), and the intermittent control is performed.

In FIG. 15, a high-side power supply section 63 for supplying a power supply voltage to a high-side driver circuit 61 is shown.
And a low-side power supply unit 64 that supplies a power supply voltage to the low-side driver circuit 62. The reason is that the potentials of the lower power supply terminals of the driver circuits 61 and 62 are usually made to coincide with the lower main electrodes S of the MOSFETs 53 and 54. As a result, the lower power supply potentials of both power supply units 63 and 64 are different. This is because these power supply units 63 and 64 cannot be shared. Further, when both power supply units are shared, if a failure occurs in the common power supply unit, the MOSF
This is also to avoid the possibility that the main battery 1 is short-circuited because the ETs 53 and 54 are both conductive.

[0005]

However, in the above-described configuration of the driver power supply system including the auxiliary battery 3, the cable 70, the high-side power supply 63, and the low-side power supply 64, the high-side The output impedance of the driver circuit 61 or the low-side driver circuit 62 may be extremely high. As described above, when the output impedance of the driver circuits 61 and 62 increases,
Since the gate electrode potentials of the MOSFETs driven by the MOSFETs 1 and 62 float, the gate electrode potentials are increased through the parasitic capacitances 55 and 58 so that the potentials of the high potential side main electrodes of the MOSFETs 53 and 54 sharply increase. There is a problem that the MOSFETs 53 and 54 are erroneously conducted due to the influence of the above.

For example, if a problem occurs in which the output impedance of the driver circuit 62 becomes extremely high with the MOSFET 54 turned off,
Is conducted, and the potential of the connection point C rises sharply, the rapid rise of the potential of the connection point C
4, the potential of the gate electrode 4 is increased, the MOSFET 54 is erroneously turned on, and the main battery 1 is short-circuited by the MOSFETs 53 and 54.

Conversely, if a problem occurs in which the output impedance of the driver circuit 61 becomes extremely high with the MOSFET 53 turned off, the MOSFET 54 conducts and the potential at the connection point C drops sharply. The main electrode 1 is short-circuited by the MOSFETs 53 and 54 because the gate electrode potential of the MOSFET 53 rises through the MOSFET 53 and the MOSFET 53 is erroneously turned on.

Further, when a problem occurs in which the output impedance of the driver circuits 61 and 62 becomes extremely high, if the potential of the battery 1 rises sharply, the MOSFET 53 is erroneously turned on due to the influence of the sudden increase of the potential of the connection point C as described above. This rapid rise in potential at the connection point C raises the potential of the gate electrode of the MOSFET 54 through the parasitic capacitance 58, causing the MOSFET 54 to conduct erroneously, whereby the main battery 1 is short-circuited by the MOSFETs 53 and 54. . That is, when an abnormality occurs in which the output impedance of the driver circuit 61 or 62 increases, M
There is a possibility that the OSFET 61 or 62 is erroneously conducted and the main battery 1 is short-circuited.

[0009] The present applicants have proposed the above-mentioned driver circuit 61 or 6
It has been found that the following cases are the causes of the increase in the output impedance of No. 2. More specifically, for example, when the cable 70 is opened due to disconnection or disconnection of a terminal, the power supply voltage is not supplied from the auxiliary battery 3 to the driver circuits 61 and 62 through the power supply units 63 and 64.
In addition, the high power supply line 200 and the low power supply line 201 on the driver circuit 61 side and the high power supply line 202 on the driver circuit 62 side
Is generally in a floating state. As a result, the output impedance of the driver circuit 61 becomes extremely high, and M
The gate electrode potential of the OSFET 53 becomes a floating potential. Although the lower power supply line 203 on the driver circuit 62 side is grounded to the lower end of the main battery 1, the driver circuit 6
The transistor at the output stage of the driver circuit 62 that connects the output terminal of the driver circuit 2 to the lower power supply line 203 is turned off when power supply to the driver circuit 62 is cut off, and as a result, the output impedance of the driver circuit 62 is reduced. Becomes extremely high, and the gate electrode potential of the MOSFET 54 also becomes the floating potential. That is, by opening the cable 70, the output impedance of the driver circuits 61 and 62 increases, and M
The gate electrode potentials of the OSFETs 53 and 54 float. As a result, as described above, there is a possibility that the MOSFETs 53 and 54 are erroneously turned on due to a sudden rise in the potential of the main battery 1 and the main battery 1 is short-circuited.

[0010] Such a problem is caused not only by the opening of the cable 70 but also by the driver circuit 6 such as a poor connection between the higher output terminals of the power supply units 63 and 64 and the higher power lines 200 and 202.
Power supply unit 6 causing an increase in output impedance of 1, 62
There is a possibility that power supply voltage supply failure from the drivers 3 and 64 to the driver circuits 61 and 62 may occur due to various causes. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and a short-circuit operation of a phase switch circuit is performed despite a malfunction of a power supply unit that supplies a power supply voltage to a driver circuit that drives a voltage-driven switch of the phase switch circuit. It is an object of the present invention to provide a power conversion circuit having an excellent operation reliability for preventing the power conversion circuit from operating.

[0011]

According to the first aspect of the present invention, a high side switch constituting a phase switch circuit is provided.
The low-side switches are driven and controlled by a driver circuit, and are supplied with power from high-side and low-side power supply units. The output impedance of the high-side power supply unit and the low-side power supply unit is increased for some reason, so that the output impedance of the high-side driver circuit or the low-side driver circuit is increased. Alternatively, in order to solve the above-described problem that the gate electrode potential of the low-side switch becomes a floating potential and becomes erroneously conductive, as a result, the main power supply is short-circuited by the high-side switch and the low-side switch, power is supplied from the main power supply. A backup power supply unit for supplying a backup power supply voltage to at least one of the driver circuits is provided.

This spare power supply supplies a spare power supply voltage to these driver circuits only when the high-side power supply or the low-side power supply does not reach a sufficient power supply voltage. As a result, even if the normal power supply voltage is not supplied from the high-side power supply unit or the low-side power supply unit, the spare power supply voltage is supplied to the driver circuit. , And as a result, the gate of the voltage-driven high-side switch or low-side switch is not
When the main electrode voltage is fixed to the high or low end of the main power supply and the potential does not float, the high-side switch or low-side switch is erroneously turned on even if the main power supply voltage rises sharply. Are not short-circuited.

According to the power converter of the second aspect, the high-side power supply unit and the low-side power supply unit are supplied with power from a common power supply. In this way, it is possible to prevent the short-circuit problem of the main power supply and to simplify the power supply circuit to the high-side power supply unit and the low-side power supply unit. According to the third aspect, the spare power supply unit outputs the spare power supply voltage to the low-side driver circuit only when the power supply voltage applied to the low-side driver circuit is insufficient. With this configuration, it is possible to compensate for the output shortage of the low-side power supply unit and prevent erroneous conduction of the low-side switch due to the shortage.

According to the fourth aspect, the spare power supply unit outputs the spare power supply voltage to the high-side driver circuit only when the power supply voltage applied to the high-side driver circuit is insufficient. With this configuration, it is possible to compensate for the output shortage of the high-side power supply unit and prevent erroneous conduction of the high-side switch. According to claim 5, the spare power supply unit outputs the spare power supply voltage to the low-side driver circuit only when the power supply voltage applied to the low-side driver circuit is insufficient, and applies the spare power supply voltage to the high-side driver circuit. A spare power supply voltage is output to the high-side high-side driver circuit only when the power supply voltage is insufficient. With this configuration, it is possible to compensate for the output shortage of the high-side power supply unit and the low-side power supply unit and prevent erroneous conduction of the high-side switch and the low-side switch.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the following examples.

[0016]

Embodiment 1 An embodiment in which the power converter of the present invention is applied to a drive circuit of an electric vehicle will be described with reference to FIGS. In the following drawings, common components are given the same reference numerals as much as possible to facilitate understanding. (Electric Vehicle System) The electric vehicle system of this embodiment will be described with reference to the block diagram shown in FIG.

The main battery 1 supplies power to the DC-DC converter 2 and the DC-AC inverters 4 and 6, and
The C-DC converter 2 supplies a low-voltage DC power supply voltage to the auxiliary battery 3 and the various auxiliary machines 100 for a vehicle,
Inverter 4 is a three-phase AC motor 5 for driving a compressor for air conditioning.
, And the DC-AC inverter 6 supplies power to the three-phase AC motor 7 for running the vehicle.

(DC-DC Converter 2) The DC-DC converter 2 will be described with reference to a circuit diagram shown in FIG. 8, 9
Is a high side switch composed of an N-channel MOSFET, and 10 and 11 are low side switches composed of an N-channel MOSFET. The high-side switch 8 and the low-side switch 10 connected in series constitute a first phase switch circuit, the high-side switch 9 and the low-side switch 11 connected in series constitute a second phase switch circuit, These two-phase switch circuits constitute an inverter circuit that converts DC power supplied from the main battery 1 into single-phase AC power. A first connection point between the high-side switch 8 and the low-side switch 10
And the output terminal of the second phase switch circuit, which is the connection point between the high-side switch 9 and the low-side switch 11, is connected to the primary coil of the step-down transformer 12. Is rectified by diodes 13 and 14, and then smoothed by a smoothing circuit including a reactor 15 and a capacitor 16 to charge the auxiliary battery 3. The control circuit 17 detects the voltage of the auxiliary battery 3 and intermittently controls the MOSFETs 8 to 11 so that the voltage becomes a predetermined value.

(DC-AC Inverter 4) The DC-AC inverter 4 will be described with reference to a circuit diagram shown in FIG. 19 ~
Reference numeral 24 denotes an IGBT, 19, 21, and 23 are high-side switches, and 20, 22, and 24 are low-side switches. High-side switches 19 connected in series with each other
And the low-side switch 20 constitute a first phase switch circuit, and the high-side switch 2
1 and the low-side switch 22 constitute a second phase switch circuit, and the high-side switch 23 and the low-side switch 24 connected in series constitute a third phase switch circuit. Power is being supplied. Reference numerals 25 to 30 denote flywheel diodes connected in parallel with the IGBTs 19 to 24, for supplying a return current to the three-phase AC motor 5, which is an inductive load.

The output terminal of the first phase switch circuit which is a connection point between the high side switch 19 and the low side switch 20 and the output terminal of the second phase switch circuit which is a connection point between the high side switch 21 and the low side switch 22 ,
The output terminal of the third phase switch circuit, which is the connection point between the high-side switch 23 and the low-side switch 24, is individually connected to each terminal of the three-phase AC motor 5.

Reference numerals 31 and 32 denote current sensors for detecting first and second output currents. A controller 33 controls these output currents and a compressor drive command signal and a rotation speed command received from an external air-conditioner controller 34. The IGBTs 19 to 24 are intermittently controlled based on the signal to rotate the three-phase AC motor 5 at the commanded rotation speed. (DC-AC Inverter 6) The DC-AC inverter 6 will be described with reference to a circuit diagram shown in FIG.

Reference numerals 36 to 41 denote IGBTs;
8, 40 are high-side switches, and 37, 39, 41 are low-side switches. The high-side switch 36 and the low-side switch 37 connected in series with each other
The high-side switch 38 and the low-side switch 39 connected in series with each other form a second phase switch circuit, and the high-side switch 40 and the low-side switch 41 connected in series with each other Each of the phase switch circuits is supplied with power from the main battery 1. 42 to 47 are IGBTs
The flywheel diodes are connected in parallel with 36 to 41 and supply a return current to the three-phase AC motor 7 which is an inductive load.

The output terminal of the first phase switch circuit which is a connection point between the high side switch 36 and the low side switch 37, and the output terminal of the second phase switch circuit which is a connection point between the high side switch 38 and the low side switch 39 ,
The output terminal of the third phase switch circuit, which is a connection point between the high-side switch 40 and the low-side switch 41, is individually connected to each terminal of the three-phase AC motor 7.

Reference numerals 48 and 49 denote current sensors for detecting the first and second output currents. The controller 50 controls the IGBTs 36 to 41 on and off based on these output currents and the motor control signal received from the accelerator sensor 51. Then, the three-phase AC motor 7 is rotated at the commanded rotation speed. The controllers 33 and 50 have IGBTs therein.
It has a driver circuit for independently driving 19 to 24 and 36 to 41.

(Driver system) The above IGBTs 19 to 2
An example of a driver circuit for driving a phase switch circuit composed of voltage-driven high-side switches and low-side switches such as 4, 36 to 41, and a driver power supply for supplying a power supply voltage thereto will be described with reference to the circuit diagram of FIG. . However, in FIG. 5, for the sake of simplicity, the phase switch circuit is composed of a high-side switch 53 and a low-side switch 5 each composed of an N-channel MOSFET.
4 and flywheel diodes D1 and D2 individually and in parallel with each other. The flywheel diodes D1 and D2 are N-channel MOSFs.
Needless to say, it may be constituted by the parasitic diodes of the ETs 53 and 54. The high-side switch 53 has parasitic capacitances 55 to 57, and the low-side switch 54 has parasitic capacitances 58 to 60. The output voltage of the driver circuit 61 is applied to the gate electrode of the high side switch 53,
The output voltage of the driver circuit 62 is applied to the gate electrode of the low side switch 54. Reference numeral 63 denotes a high-side power supply of a driver power supply for applying a power supply voltage to the driver circuit 61, and reference numeral 64 denotes a low-side power supply of a driver power supply for applying a power supply voltage to the driver circuit 62. These power supply units 63 and 64 generally comprise a constant voltage power supply or the like.
Power is supplied from the auxiliary battery 3 through the power supply.

The driver circuits 61 and 62 are combined with the controller circuits 33 and 50 together with the driver circuits 61 and 62.
A high-level ON voltage or a low-level OFF voltage is output to the high-side switch 53 and the low-side switch 54 by a control signal from a circuit (not shown) configuring
Control them intermittently. In FIG. 5, a high-side power supply unit 63 for supplying a power supply voltage to the high-side driver circuit 61 and a low-side power supply unit 64 for supplying a power supply voltage to the low-side driver circuit 62 are separately configured. . The reason is that the potentials at the lower power supply terminals of the driver circuits 61 and 62 are usually made to match the lower main electrodes (indicated by the symbol S in FIG. 5) of the MOSFETs 53 and 54 as shown in FIG. This is because the lower power supply potentials of the two power supply units 63 and 64 are different, so that the power supply units 63 and 64 cannot be shared. Further, when both power supply units are shared, when a failure such as a short circuit at the output terminal occurs in the common power supply unit, the gate electrodes of the MOSFETs 53 and 54 are affected by the electrostatic coupling through the parasitic capacitances 55, 56 and 58. One of the reasons is that there is a possibility that conduction may occur due to the effect of an increase in the battery voltage.

Further, the driver power supply of this embodiment includes a high-side power supply unit 63 for applying a power supply voltage to the high-side driver circuit 61 and a low-side power supply unit for applying a power supply voltage to the low-side driver circuit 62. In addition to the configuration of the conventional driver power supply shown in FIG. The standby power supply unit 300, which is a feature of the present embodiment, includes a constant voltage diode 7 having a cathode connected to the high end of the battery (main power supply) 1 through the resistor 73 and an anode connected to the low end of the battery 1.
4 and a backflow prevention diode 72 whose anode is connected to the output terminal or cathode of this constant voltage diode 74 and whose cathode is connected to the higher power supply terminal of the low-side driver circuit 62.

Hereinafter, the operation of this circuit will be described.
The driver circuits 61 and 62 include controllers 33 and 50
A high-level ON voltage or a low-level OFF voltage is output to the high-side switch 53 and the low-side switch 54 according to a control signal from a circuit (not shown), and the control signal is intermittently controlled. If the high-side power supply unit 63 and the low-side power supply unit 64 are supplied with power from the auxiliary battery 3 without any problem, the power supply units 63 and 64
1 and 62 are supplied with a suitable power supply voltage, respectively, and the driver circuits 61 and 62 are each supplied with a MOSFE in accordance with an input signal.
T53 and T54 are intermittently controlled without any problem.

In this normal state, the power supply voltage output from the low-side power supply section 64 to the low-side driver circuit 62 is the cathode voltage Vz of the constant voltage diode 74.
Is set to be higher (preferably slightly (eg, about 1 to 3 V)) than the output voltage of the standby power supply unit 300 which is a value obtained by subtracting the forward voltage drop of the diode 72 from the standby power supply unit. Does not supply power to the low-side driver circuit 62. In this way, a large power supply loss from the high-voltage battery 1 to the low-side driver circuit 62 with a low power supply voltage can be avoided.

Next, consider a case where the cable 70 is disconnected, for example. In this case, as described above, the power supply units 63 and 64 cannot output the power supply voltage to the driver circuits 61 and 62, and as described above, the output impedance of the driver circuit 61 increases, and the gain of the MOSFET 53 increases.
The electrode potential is in a floating state. On the other hand, MOS
Similarly, the gate electrode potential of the FET 54 also tends to be in a floating state. However, when the voltage supplied from the low-side power supply unit 64 to the high-order power supply terminal of the low-side driver circuit 62 slightly decreases, the auxiliary power supply unit 300 supplies the high-order power supply terminal of the low-side driver circuit 62 with the auxiliary power supply voltage Vp = Vz−pn. A junction forward drop (approximately 0.7 V) is provided immediately. The spare power supply voltage Vp = Vz-approximately 0.7 V is supplied to the low-side driver circuit 62 and the MOSF.
Since the level is set to a level that guarantees sufficient operation of the ET 54, the driver circuit 62 operates normally. Therefore, if the control signal voltage V1 input to the low-side driver circuit 62 is a value that outputs a low-level voltage to the driver circuit 62, the driver circuit 62
Is fixed at a low level. By the way,
The current path to the low-side driver circuit 62 through the standby power supply unit 300 corresponds to the high-order terminal of the battery 1 and the resistor 7.
3, diode 72, low-side driver circuit 62,
The order is the lower end of the battery 1.

Therefore, according to the present embodiment, the cable 70 is disconnected and the
If the potential of the gate electrode of the SFET 53 floats and the potential of the battery 1 rises abnormally and the MOSFET 53 is turned on, the gate electrode of the MOSFET 54 is kept at a low level, so that it is turned on. The battery 1 is not short-circuited by the phase switch circuit 4a.

(Driver Circuit 62) Next, an example of the driver circuit 62 will be described with reference to the block circuit diagram of FIG. The driver circuit 62 includes a pre-stage circuit 65 to which the control signal voltage V2 is input, and a high-side switch 68 and a low-side switch 69 that are driven and controlled by the pre-stage circuit 65. These switches 68 and 69 are used for power amplification. It constitutes an inverting or non-inverting output stage. Of course, it is preferable that the switches 68 and 69 perform reverse (complementary) operations. The driver circuit 62 can be realized by various circuit configurations other than the block circuit shown in FIG. 6, for example, the switch 68 can be replaced with a resistor,
When the input impedance of the low-side switch 69 is large as in the above, the pre-stage circuit 65 may be omitted.

The operation of the driver circuit 62 when the power supply voltage is normally applied from the power supply section 64 will be described. If the control signal voltage V2, which is a binary signal voltage, is a potential for commanding to shut off the MOSFET 54, the pre-stage circuit 65 turns on the low-side switch 69 and shuts off the high-side switch 68 to lower the gate electrode potential of the MOSFET 54. Fix to level and shut it off. Conversely, if the control signal voltage V2, which is a binary signal voltage, is a potential for commanding the conduction of the MOSFET 54, the pre-stage circuit 65 turns off the low-side switch 69 and turns on the high-side switch 68 to turn on the gate electrode of the MOSFET 54. The potential is fixed at a high level to make it conductive.

Now, a case where the cable 70 is opened and the output impedance of the power supply unit 64 becomes extremely high will be described. However, in the following, it is assumed that the low-side switch 69 is a common-emitter bipolar transistor or a common-source FET. In this case, even if the control signal voltage V2 is a potential for instructing the MOSFET 54 to shut off, the power supply voltage is not supplied to the pre-stage circuit 65, so that the pre-stage circuit 65 cannot conduct the low-side switch 69, and Since the high-order power supply terminal 62a of the driver circuit 62 is open, the MOSFET 5
The gate electrode of No. 4 cannot be discharged through the high side element 68 comprising a switch or a resistor, and the output impedance of the driver circuit 62 becomes extremely high. this is,
The same applies to the case where the driver circuit 62 shown in FIG. 6 is used for the high-side driver circuit 61 in FIG.

Next, the gate electrode potential of the MOSFET 54 when the low-side switch 69 at the output stage of the driver circuit 62 is constituted by an emitter follower transistor will be described with reference to FIG. In FIG. 7, the pre-stage circuit 6
Is connected to the base of a common-emitter transistor 652 having a collector resistance 651, and a control voltage is supplied to an output stage of a driver circuit 62 including a complementary emitter follower circuit through an inverter circuit including the collector resistance 651 and the common-emitter transistor 652. It is assumed that it is output.

The output impedance of the driver circuit 62 when the output impedance of the power supply unit 64 increases and the supply of the power supply voltage is cut off will be described below. However, the standby power supply unit 300 is not considered. When the supply of the power supply voltage is cut off, regardless of the level of the input control signal voltage V2, the transistor 652
Cannot be conducted, and as a result, MOSFET 5
The charge of the gate electrode of the battery 4 is passed through the resistor 66, the emitter follower transistor 69, and the transistor 652.
Can not be discharged to the lower end. The power supply unit 64
Of the MOSFET 54 cannot be discharged to the power supply unit 64 through the resistor 66, the emitter follower transistor 68, and the resistor 651. As a result, also in the driver circuit 62 of FIG. 7, the output impedance of the power
It can be seen that the gate electrode potential of the SFET 54 becomes a floating potential.

8 to 11 show other examples of the low-side driver circuit 62. FIG. Also in these circuit configurations, the output impedance of the low-side power supply unit 64 increases,
When the output voltage decreases, the output impedance of the driver circuit 62 increases and the gate electrode potential of the MOSFET 54 becomes a floating potential. Therefore, the backup power supply unit 300 of the present embodiment
It is understood that the short-circuit prevention of the phase switch circuit 4a can be realized by supplying the spare power supply voltage to the power supply.

(Power Supply Unit 64) Next, an example of the power supply unit 64 will be described with reference to the circuit diagram of FIG. The current of the auxiliary battery 3 is supplied to the transistor 76 through the primary coil of the transformer 75. The control circuit is a transistor 76
Are intermittently performed at a constant cycle, so that an AC voltage is generated in the secondary circuit of the transformer 75. This AC voltage is supplied to a diode 78.
, And is smoothed by the capacitor 71 and output to the driver circuit 62.

The error amplifier 79 rectifies the output voltage of the power supply unit 64, amplifies the error, and drives the photocoupler 80. The output of the photocoupler 80 is the control circuit 7
7, and the control circuit 77 receives the MOSFET 76 based on the feedback signal from the photocoupler 80.
, And the required DC power is supplied to the driver circuit 62.

Referring to FIG. 12, the output voltage and the output impedance when the cable 70 is opened will be described below. As can be easily understood, since the power supply unit 64 cannot output the power supply voltage, the diode 78 is present, and the input impedance of the error amplifier 79 is high, the output impedance of the power supply unit 64 is extremely high. This is the same when this circuit is used for the power supply unit 63.

[0041]

Embodiment 2 Another embodiment of the present invention will be described with reference to FIG. This circuit differs from the circuit of FIG. 5 in that a backup power supply unit 400 is used instead of the backup power supply unit 300, and a P-channel MOSFET is used for the high-side switch 53 of the phase switch circuit 4a.

The standby power supply section 400 uses a reverse voltage prevention diode 85 in which the direction of the reverse current prevention diode 72 is reversed in the standby power supply section 300 and a constant voltage circuit in which the positions of the constant voltage diode 74 and the resistor 73 are reversed. The configuration is the same except that the constant voltage diode 86 and the resistor 87 are used.
When the high-side power supply unit 63 cannot output a predetermined low-level power supply voltage to the low-level power supply line 201, the standby power supply unit 400 supplies a slightly higher low-level power supply voltage. Since the functions are the same,
The detailed description is omitted.

In this way, even if the output voltage of the high-side power supply unit 63 is cut off by opening the cable 70 and the output impedance of the high-side power supply unit 63 becomes high, the spare power supply unit 400 is connected to the high-side driver circuit 61. , The control signal voltage V1 to be input is
Driver circuit 61 can normally output a high-level potential with a small output impedance when MOSFET 53 is turned off.
Irrespective of the rapid rise of the potential, the phase switch circuit 4a is not short-circuited.
That is, even if the output of the power supply unit 63 decreases for some reason and its output impedance increases, the standby power supply unit 400 supplies power to the driver circuit 61, so that the driver circuit 61 does not conduct erroneously.

[0044]

Embodiment 3 Another embodiment of the present invention will be described with reference to FIG. This circuit is an example of a circuit provided with both the backup power supply unit 300 shown in FIG. 5 and the backup power supply unit 400 shown in FIG. 13. In this case, the power supply voltage of both the power supply units 63 and 64 becomes insufficient. , The erroneous conduction of both the high-side switch 53 and the low-side switch 54 can be prevented.

In each of the above embodiments, an example has been described in which MOSFETs are used as the voltage-driven high-side switch 53 and the low-side switch 54. Instead, another voltage-driven semiconductor element such as an IGBT is employed. In this case, the same operation and effect can be obtained. In addition, for setting the output potential of the standby power supply unit 200, various known circuits other than using a constant voltage diode can be employed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a drive circuit of an electric vehicle according to a first embodiment.

FIG. 2 is a circuit diagram showing the DC-DC converter 2 of FIG.

FIG. 3 is a circuit diagram showing the DC-AC inverter 4 of FIG.

FIG. 4 is a circuit diagram showing the DC-AC inverter 6 of FIG.

FIG. 5 is a circuit diagram showing a driver circuit and a driver power supply for driving and controlling the phase switch circuit 4a of FIG. 3;

FIG. 6 is a block circuit diagram showing an example of a driver circuit 62 of FIG.

FIG. 7 is a circuit diagram showing a specific example of the driver circuit 62 of FIG.

8 is a circuit diagram showing a specific example of the driver circuit 62 in FIG.

9 is a circuit diagram showing a specific example of the driver circuit 62 in FIG.

FIG. 10 is a circuit diagram showing a specific example of a driver circuit 62 of FIG.

11 is a circuit diagram showing a specific example of the driver circuit 62 in FIG.

FIG. 12 is a circuit diagram showing an example of a driver power supply 64 of FIG.

FIG. 13 is a circuit diagram illustrating a driver circuit and a driver power supply according to a second embodiment.

FIG. 14 is a circuit diagram illustrating a driver circuit and a driver power supply according to a third embodiment.

FIG. 15 is a circuit diagram showing a conventional driver circuit and driver power supply.

[Explanation of symbols]

1 is a main battery (main power supply), 5 is a three-phase AC motor (load), 4a, 4b and 4c are phase switch circuits, 53 is a high side switch of the phase switch circuit 4a, 54 is a low side switch of the phase switch circuit 4a, 61 is a high side driver circuit, 62 is a low side driver circuit, 63
Is the high side power supply, 64 is the low side power supply, 3
00 and 400 are spare power supply units, and 3 is an auxiliary battery (common power supply).

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[Procedure amendment]

[Submission date] October 31, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Claims (5)

[Claims] 1. A plurality of phase switch circuits each including a voltage-driven high-side switch and a low-side switch connected in series with each other and connected between both ends of a main power supply, and each of the high-side switches based on an input signal. A high-side driver circuit that outputs a drive voltage to the gate electrode of the switch to turn on and off the high-side switch; and outputs a drive voltage to the gate electrode of each low-side switch based on an input signal to turn on and off the low-side switch. A power conversion device comprising: a low-side driver circuit; and a driver power supply for applying a power supply voltage to both driver circuits, wherein a connection point between the two switches is connected to a load. A high-side power supply that outputs a power supply voltage to the power supply; A low-side power supply unit that is formed to be operable and outputs a power supply voltage to the low-side driver circuit; and a spare unit that can operate the driver circuit by power supply from the main power supply only when the power supply voltage is insufficient. And a standby power supply unit that outputs the power supply voltage to the driver circuit on the power supply voltage shortage side. 2. The power conversion device according to claim 1, wherein the high-side power supply unit and the low-side power supply unit are supplied with power from a common power supply. 3. The power conversion device according to claim 1, wherein the auxiliary power supply unit operates the low-side switch by the low-side driver circuit only when the power supply voltage applied to the low-side driver circuit is insufficient. A power conversion device, wherein the spare power supply voltage that can be driven is output to the low-side driver circuit. 4. The power conversion device according to claim 1, wherein the standby power supply unit is configured to switch the high-side driver circuit to the high-side driver circuit only when the power supply voltage applied to the high-side driver circuit is insufficient. A power converter that outputs the spare power supply voltage capable of driving a side switch to the high-side driver circuit. 5. The power conversion device according to claim 1, wherein the auxiliary power supply unit drives the low-side switch by the low-side driver circuit only when the power supply voltage applied to the low-side driver circuit is insufficient. And driving the high-side switch by the high-side driver circuit only when the power supply voltage applied to the high-side driver circuit is insufficient. And outputting the spare power supply voltage capable of performing the operation to the high-side driver circuit.