JP2024098432A - Series Power Supply - Google Patents

Abstract

To provide a series power supply capable of suppressing a large increase in output voltage even if a short circuit occurs in a transistor on the lowest potential side among the transistors.SOLUTION: An emergency power supply 50 as a series power supply includes: a series connection of first and second switches 51 and 52 that connect the positive electrode of a high voltage power supply 10 and a control circuit Dr; a drive circuit that drives each of the switches 51 and 52 so that a source voltage of each of the switches 51 and 52 is equal to or lower than a withstand voltage of the control circuit Dr. The drive circuit includes a resistor 61 and first and second Zener diodes 71 and 72. Each of the switches 51 and 52 has a withstand voltage equal to or higher than the output voltage of the high-voltage power supply 10.SELECTED DRAWING: Figure 2

Description

This disclosure relates to a series power supply.

As described in Patent Document 1, a series power supply is known that steps down the output voltage of a DC power supply and supplies the stepped-down voltage to a power supply target. The series power supply includes a series connection of multiple transistors, a resistor corresponding to each transistor, and a Zener diode. The Zener diode is provided corresponding to the transistor with the lowest potential among the transistors.

Patent No. 5621314

A short circuit failure may occur in the transistor with the lowest potential among the various transistors. In this case, the output voltage of the series power supply will rise significantly, and there is a concern that the output voltage of the series power supply may exceed the withstand voltage of the power supply target. If the output voltage exceeds the withstand voltage of the power supply target, there is a concern that a dependent failure of the power supply target may occur.

The primary objective of this disclosure is to provide a series power supply that can suppress a large increase in output voltage even if a short circuit occurs in the transistor with the lowest potential among the transistors.

The present disclosure relates to a series power supply that steps down the output voltage of a DC power supply and supplies the stepped-down output voltage to a power supply target,
a series connection of a plurality of transistors that connects a positive electrode side of the DC power supply and the power supply target;
a drive circuit that drives each of the transistors so that a voltage of a low potential side terminal of each of the transistors is equal to or lower than a withstand voltage of the power supply target portion;
Equipped with
Each of the transistors has a withstand voltage equal to or higher than the output voltage of the DC power supply.

Each transistor is driven by a drive circuit so that the voltage of the low-potential side terminal of each transistor is equal to or lower than the withstand voltage of the power supply target. Therefore, even if a short circuit occurs in the lowest potential transistor, which is the transistor with the lowest potential among the transistors, the voltage of the low-potential side terminal of the transistor adjacent to the high potential side of the lowest potential transistor can be made equal to or lower than the withstand voltage of the power supply target, and a large increase in the output voltage of the series power supply can be suppressed. This makes it possible to suppress the occurrence of dependent failures in the power supply target.

When a short circuit occurs in some of the transistors, such as the lowest voltage transistor, the remaining transistors that are not short circuited must support the output voltage of the DC power supply. In other words, the voltage between the high-potential terminal and the low-potential terminal of the transistors that are not short circuited rises.

Here, each transistor disclosed herein has a withstand voltage equal to or greater than the output voltage of the DC power supply. Therefore, even if a short circuit occurs in some of the transistors, the voltage between the high potential side terminal and the low potential side terminal of the remaining transistors that are not short circuited can be prevented from exceeding the withstand voltage of the remaining transistors.

FIG. 1 is an overall configuration diagram of a control system according to a first embodiment. Circuit diagram for emergency power supply. FIG. FIG. 11 is a circuit diagram of a second comparative example. FIG. 7 is a circuit diagram of an emergency power supply according to a second embodiment. 13 is a diagram showing current flow paths when a short-circuit fault occurs between the drain and source and a short-circuit fault occurs between the source and gate in the first switch; FIG. FIG. 11 is a circuit diagram of an emergency power supply according to a third embodiment. FIG. 13 is a circuit diagram of an emergency power supply according to a fourth embodiment.

Several embodiments will be described with reference to the drawings. In several embodiments, functionally and/or structurally corresponding and/or associated parts may be given the same reference numerals or reference numerals that differ in the hundredth or higher digit. For corresponding and/or associated parts, the descriptions of other embodiments may be referred to.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a series power supply according to the present disclosure will now be described with reference to the drawings. The series power supply of the present embodiment is applied to an inverter control system.

As shown in FIG. 1, the control system includes a high-voltage power supply 10 as a DC power supply, an inverter 20, and a rotating electric machine 30. The high-voltage power supply 10 is a rechargeable storage battery, for example, a lithium-ion storage battery or a nickel-metal hydride storage battery. The rotating electric machine 30 is connected to the high-voltage power supply 10 via the inverter 20. A smoothing capacitor 11 is provided between the high-voltage power supply 10 and the inverter 20. The rotating electric machine 30 is, for example, a permanent magnet field type or a wound field type synchronous machine.

The inverter 20 is equipped with upper and lower arm switches SW for three phases. A first end of the winding 31 of the rotating electric machine 30 is connected to the connection point of the upper and lower arm switches SW of each phase. A second end of the winding 31 of each phase is connected at the neutral point. The switch SW in this embodiment is an N-channel MOSFET. The switch SW has a body diode. Note that the switch SW of the inverter 20 may be, for example, an IGBT instead of a MOSFET. In this case, it is sufficient that a freewheel diode is connected in reverse parallel to the IGBT. Also, the connection mode of the winding 31 is not limited to star connection, and may be delta connection.

The inverter 20 includes a control circuit Dr. A control circuit Dr is provided for each switch SW. Each switch SW is driven by the control circuit Dr. As a result, the upper arm switch SW and the lower arm switch SW are alternately turned on in each phase of the inverter 20.

The control system includes a low-voltage power supply 12, an insulated power supply 40, and an emergency power supply 50. The low-voltage power supply 12 is a rechargeable storage battery, such as a lead-acid battery, that has a lower output voltage (specifically, a rated voltage) than the high-voltage power supply 10. The output voltage of the low-voltage power supply 12 is, for example, 1/10 or less of the output voltage of the high-voltage power supply 10.

The control system includes a low-voltage area and a high-voltage area that is electrically insulated from the low-voltage area. The low-voltage area includes a low-voltage power supply 12. The high-voltage area includes a high-voltage power supply 10, an inverter 20, a rotating electric machine 30, and an emergency power supply 50. The insulated power supply 40 is provided across the low-voltage area and the high-voltage area.

The insulated power supply 40 supplies each control circuit Dr with power generated using the low-voltage power supply 12 as a power supply source. Figure 1 shows an example in which power is supplied from the insulated power supply 40 to the control circuits Dr corresponding to each lower arm switch SW. Each control circuit Dr is operable by being supplied with power.

Each control circuit Dr is normally supplied with power by an insulated power supply 40. However, if power supply by the insulated power supply 40 becomes impossible, power is supplied to each control circuit Dr by an emergency power supply 50 instead of the insulated power supply 40. For example, if the control system is mounted on a vehicle, a situation in which power supply by the insulated power supply 40 becomes impossible is when the vehicle crashes. Even if power supply by the insulated power supply 40 becomes impossible, the emergency power supply 50 functions as a backup power supply, and each control circuit Dr can continue to operate.

The emergency power supply 50 is a series power supply that steps down the output voltage of the high-voltage power supply 10 and supplies the stepped-down DC voltage to each control circuit Dr. As shown in FIG. 2, the emergency power supply 50 includes a first switch 51, a second switch 52, a resistor 61, a first Zener diode 71, and a second Zener diode 72. The resistor 61, the first Zener diode 71, and the second Zener diode 72 form a drive circuit for the first and second switches 51 and 52. In this embodiment, the first switch 51 and the second switch 52 are voltage-controlled semiconductor switching elements, specifically, N-channel MOSFETs. The first switch 51, the second switch 52, the resistor 61, the first Zener diode 71, and the second Zener diode 72 are provided, for example, on a control board.

The positive electrode of the high-voltage power supply 10 is connected to the drain, which is the high-potential terminal of the first switch 51. The drain of the second switch 52 is connected to the source, which is the low-potential terminal of the first switch 51. The source of the second switch 52 is connected to each control circuit Dr. The source voltage of the second switch 52 is supplied to each control circuit Dr as the output voltage of the emergency power supply 50.

In this embodiment, the resistor 61 is a series connection of multiple resistors (e.g., a dozen or so). The resistor 61 is, for example, a chip resistor. Multiple resistors 61 are provided to ensure an insulation distance between both ends of the resistor 61 and to prevent creeping discharge on the control board.

The drain of the first switch 51 and the positive electrode of the high-voltage power supply 10 are connected to a first end of the series connection of the multiple resistors 61. The cathode of the first Zener diode 71 and the gate, which is the control terminal of the first switch 51, are connected to a second end of the series connection of the multiple resistors 61. The gate, which is the control terminal of the second switch 52, and the cathode of the second Zener diode 72 are connected to the anode of the first Zener diode 71. The ground of the high-voltage region is connected to the anode of the second Zener diode 72. The ground of the high-voltage region is also connected to the negative electrode of the high-voltage power supply 10.

The source voltage of the second switch 52 becomes the output voltage of the emergency power supply 50. The source voltage Vs2 of the second switch 52 is controlled to a target voltage of "VD2-Vth2". VD2 is the breakdown voltage of the second Zener diode 72. Vth2 is the threshold voltage of the second switch 52. When the gate voltage of the second switch 52 is equal to or greater than the threshold voltage Vth2, the second switch 52 is turned on, and when the gate voltage of the second switch 52 is less than the threshold voltage Vth2, the second switch 52 is turned off.

The source voltage Vs1 of the first switch 51 is controlled to a target voltage of "VD1 + VD2 - Vth1". VD1 is the breakdown voltage of the first Zener diode 71. Vth1 is the threshold voltage of the first switch 51.

In this embodiment, the breakdown voltages VD1, VD2 of the Zener diodes 71, 72 and the threshold voltage Vth1 of the first switch 51 are set so that the source voltage Vs1 of the first switch 51 is a voltage equal to or lower than the withstand voltage of the control circuit Dr, which is the "power supply target part." The breakdown voltage VD2 of the second Zener diode 72 and the threshold voltage Vth2 of the second switch 52 are set so that the source voltage Vs2 of the second switch 52 is a voltage equal to or lower than the withstand voltage of the control circuit Dr. The reason why each source voltage Vs1, Vs2 is controlled to a voltage equal to or lower than the withstand voltage of the control circuit Dr is to suppress the occurrence of a dependent failure of the control circuit Dr when a short failure of the second switch 52 occurs.

If the second switch 52 experiences a short circuit failure, the output voltage of the emergency power supply 50 becomes the source voltage Vs1 of the first switch 51. The source voltage Vs1 is a voltage that is equal to or lower than the withstand voltage of the control circuit Dr. Therefore, even if a short circuit failure occurs in the second switch 52, the occurrence of a dependent failure in the control circuit Dr can be suppressed.

In this embodiment, the first switch 51 and the second switch 52 have a withstand voltage equal to or higher than the output voltage (specifically, the rated voltage) of the high-voltage power supply 10. This is to prevent the remaining switch that is not short-circuited from failing due to the output voltage of the high-voltage power supply 10 when a short-circuit failure occurs in either of the switches 51 and 52.

In contrast, in the cases of Comparative Examples 1 and 2 described below, the reliability of the emergency power supply decreases when a short circuit occurs.

Figure 3 shows an emergency power supply of Comparative Example 1. The emergency power supply of Comparative Example 1 includes a switch 151, a resistor 161, and a Zener diode 171. For convenience, the resistor 161 is shown in Figure 3 with the circuit symbol for a single resistor.

In Comparative Example 1, the source voltage Vs of the switch 151 is controlled so that Vs ≈ VD - Vth. VD is the breakdown voltage of the Zener diode 171. Vth is the threshold voltage of the switch 151.

In Comparative Example 1, when a short circuit failure occurs in switch 151, the output voltage of high-voltage power supply 10 is applied directly to control circuit Dr. As a result, a dependent failure of control circuit Dr occurs.

Figure 4 shows an emergency power supply of Comparative Example 2. The emergency power supply of Comparative Example 2 includes a first switch 151, a second switch 152, a first resistor 161, a second resistor 162, and a Zener diode 171. For convenience, each of the resistors 161 and 162 is shown by the circuit symbol for a single resistor in Figure 4.

The source voltage Vs1 of the first switch 151 is controlled so that Vs1 ≈ VD + R2 / (R1 + R2) × VH. R1 is the resistance value of the first resistor 161, and R2 is the resistance value of the second resistor 162. VH is the output voltage of the high-voltage power supply 10.

In Comparative Example 2, when a short circuit failure occurs in the first switch 151, the source voltage Vs2 of the second switch 152 is controlled to "VD-Vth2". Note that Vth2 is the threshold voltage of the second switch 152. Since the source voltage Vs2 is equal to or lower than the withstand voltage of the control circuit Dr, a dependent failure of the control circuit Dr does not occur.

On the other hand, if a short circuit failure occurs in the second switch 152, the source voltage Vs1 of the first switch 151 becomes approximately half the voltage of the high-voltage power supply 10. In this case, the source voltage Vs1 exceeds the withstand voltage of the control circuit Dr, causing a dependent failure of the control circuit Dr.

As described above, in this embodiment, the switches 51 and 52 are driven so that the source voltage of each switch 51 and 52 is equal to or lower than the withstand voltage of the control circuit Dr. Therefore, even if a short circuit occurs in the second switch 52 (corresponding to the "lowest potential transistor") which is the lowest potential of the switches 51 and 52, the source voltage of the first switch 51 adjacent to the high potential side of the second switch 52 can be set to equal to or lower than the withstand voltage of the control circuit Dr, and a large increase in the output voltage of the emergency power supply 50 can be suppressed. This makes it possible to suppress the occurrence of a dependent failure of the control circuit Dr.

In addition, each switch 51, 52 has a withstand voltage equal to or greater than the output voltage of the high-voltage power supply 10. Therefore, even if a short circuit occurs in, for example, the second switch 52 of the switches 51, 52, the drain-source voltage of the remaining first switch 51, which does not have a short circuit, can be prevented from exceeding the withstand voltage of the drain-source voltage of the first switch 51.

Second Embodiment
The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. As shown in Fig. 5, in an emergency power supply 55 of this embodiment, the gates of a first switch 51 and a second switch 52 are connected to individual reference voltage generating circuits.

The emergency power supply 55 includes a first resistor 61, a first Zener diode 71, and a second Zener diode 72 as a reference voltage generating circuit connected to the gate of the first switch 51. The emergency power supply 55 also includes a second resistor 62 and a third Zener diode 73 as a reference voltage generating circuit connected to the gate of the second switch 52. In this embodiment, the breakdown voltages of the Zener diodes 71 to 73 are the same. The sum of the breakdown voltages of the first Zener diode 71 and the second Zener diode 72 is higher than the breakdown voltage of the third Zener diode 73.

The cathode of the first Zener diode 71 is connected to the gate of the first switch 51. The anode of the first Zener diode 71 is connected to the cathode of the second Zener diode 72. The anode of the second Zener diode 72 is connected to the ground of the high voltage area.

The cathode of the third Zener diode 73 is connected to the gate of the second switch 52. The anode of the third Zener diode 73 is connected to the ground of the high voltage area.

In this embodiment, the first resistor 61 and the second resistor 62 are, as in the first embodiment, a series connection of multiple resistors (e.g., a dozen or so). Each resistor is, for example, a chip resistor.

The first end of the series connection of the first and second resistors 61, 62 is connected to the drain of the first switch 51 and the positive electrode of the high-voltage power supply 10. The second end of the series connection of the first resistors 61 is connected to the cathode of the first Zener diode 71 and the gate of the first switch 51. The second end of the series connection of the second resistors 62 is connected to the cathode of the third Zener diode 73 and the gate of the second switch 52.

The source voltage Vs2 of the second switch 52 is controlled to a target voltage of "VD3-Vth2". VD3 is the breakdown voltage of the third Zener diode 73. The breakdown voltages of the Zener diodes 71 to 73 are set to the same value, for example.

The configuration of this embodiment is designed to suppress the occurrence of a dependent failure in the first switch 51 when a short failure occurs between the gate and source in conjunction with the occurrence of a short failure between the drain and source. The following description will be given with reference to FIG. 6.

Figure 6 shows the configuration of the first embodiment. In the configuration of Figure 6, when a short circuit failure occurs between the drain and source of the first switch 51, the high voltage of the high-voltage power supply 10 is applied between the gate and source of the first switch 51, and a short circuit failure between the gate and source may occur. In this case, a short circuit failure may occur in the first Zener diode 71 and the second Zener diode 72. When a short circuit failure occurs in the first Zener diode 71, a large current flows from the high-voltage power supply 10 to the ground through the first switch 51, the first Zener diode 71, and the second Zener diode 72. After that, when the failure mode of the second Zener diode 72 transitions to an open circuit failure, the source voltage Vs2 of the second switch 52 increases significantly, and the source voltage Vs2 exceeds the withstand voltage of the control circuit Dr, causing a dependent failure of the control circuit Dr.

In contrast, according to the present embodiment shown in FIG. 5, even if a short circuit failure occurs between the drain and source of the first switch 51, followed by a short circuit failure between the gate and source, and an open circuit failure occurs in the first Zener diode 71 or the second Zener diode 72, the operation of the second switch 52 is not affected. Therefore, the source voltage Vs2 of the second switch 52 can be set to be equal to or lower than the withstand voltage of the control circuit Dr. Note that if a short circuit failure occurs in both the first Zener diode 71 and the second Zener diode 72, the output voltage of the emergency power supply 55 becomes 0.

<Modification of the second embodiment>
The Zener diode connected to the gate of the first switch 51 is not limited to two Zener diodes and may be, for example, one Zener diode. In this case, it is sufficient that the breakdown voltage of the Zener diode connected to the gate of the first switch 51 is set to a value higher than the breakdown voltage of the third Zener diode 73.

The reference voltage generating circuit connected to the gate of each switch 51, 52 is not limited to that shown in FIG. 5, and may be, for example, a shunt regulator having a comparator, a bipolar transistor, and a resistor. In this case, a shunt regulator is provided individually corresponding to each switch 51, 52, and the output of the shunt regulator is connected to the gate of the switch.

Third Embodiment
The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. As shown in FIG. 7, the emergency power supply 56 of this embodiment includes a rectifier diode 80 and a discharge resistor 81. The rectifier diode 80 has a withstand voltage equal to or higher than the output voltage (specifically, the rated voltage) of the high-voltage power supply 10. The rectifier diode 80 is provided in an electrical path connecting the gate of the first switch 51 (corresponding to the "highest potential transistor") and the cathode of the first Zener diode 71 (corresponding to the "highest potential diode"). The gate of the first switch 51 is connected to the cathode of the rectifier diode 80.

The gate of the first switch 51 is connected to the source of the first switch 51 via a discharge resistor 81. The discharge resistor 81 is a component that ensures a discharge path for the gate charge of the first switch 51 when the first switch 51 is in a normal state.

According to this embodiment, even if a short circuit failure occurs between the gate and source due to a short circuit failure between the drain and source of the first switch 51, the rectifier diode 80 can prevent the flow of a large current. This prevents a large current from flowing through the first Zener diode 71 and the second Zener diode 72, and protects each of the Zener diodes 71 and 72. As a result, the operation of the second switch 52 can be continued, and the occurrence of a situation in which the source voltage Vs2 of the second switch 52 exceeds the withstand voltage of the control circuit Dr can be suppressed.

Furthermore, according to this embodiment, the number of resistors 61 and the mounting area of the resistors 61 on the control board can be reduced compared to the second embodiment.

<Modification of the third embodiment>
In the configuration shown in FIG. 7, in addition to the rectifier diode 80 and the discharge resistor 81 corresponding to the first switch 51, a rectifier diode 80 and a discharge resistor 81 corresponding to the second switch 52 may be further provided.

Fourth Embodiment
The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. As shown in Fig. 8, the emergency power supply 57 of this embodiment includes a third Zener diode 91, a fourth Zener diode 92, a first rectifier diode 101, and a second rectifier diode 102. Each of the rectifier diodes 101 and 102 has a withstand voltage equal to the output voltage (specifically, the rated voltage) of the high-voltage power supply 10 or a withstand voltage higher than the output voltage (specifically, the rated voltage) of the high-voltage power supply 10.

The gate of the first switch 51 is connected to the anode of the first rectifier diode 101. The cathode of the first rectifier diode 101 is connected to the second end of the series connection of the multiple resistors 61 and to the anode of the second rectifier diode 102. The cathode of the second rectifier diode 102 is connected to the cathode of the third Zener diode 91. The cathode of the third Zener diode 91 is connected to the gate of the second switch 52 and to the cathode of the fourth Zener diode 92. The anode of the fourth Zener diode 92 is connected to the ground of the high voltage area.

In this embodiment, the electrical path from the second end of the series connection of resistors 61 to the ground via the first rectifier diode 101 corresponds to the "first individual electrical path" corresponding to the first switch 51. Also, the electrical path from the second end of the series connection of resistors 61 to the ground via the second rectifier diode 102 corresponds to the "second individual electrical path" corresponding to the second switch 52. The emergency power supply 57 is configured so that the resistance value of the first individual electrical path and the resistance value of the second individual electrical path are the same value. This is to allow current to flow from the high-voltage power supply 10 to both the first and second individual electrical paths via the resistor 61, so that the source voltage of each switch 51, 52 can be controlled to a target voltage. In this embodiment, the total value of the breakdown voltages of the first Zener diode 71 and the second Zener diode 72 and the total value of the third Zener diode 91 and the fourth Zener diode 92 are set to the same value so that the resistance value of the first individual electrical path and the resistance value of the second individual electrical path are the same value, and the forward voltage drop amount of the first rectifier diode 101 and the forward voltage drop amount of the second rectifier diode 102 are set to the same value. In this embodiment, the breakdown voltages of the Zener diodes 71, 72, 91, and 92 are the same.

The configuration of this embodiment is designed to suppress the occurrence of a dependent failure when a short circuit occurs between the gate and source in the first switch 51 or the second switch 52 in conjunction with the occurrence of a short circuit between the drain and source.

Even if a short circuit failure occurs between the drain and source of the first switch 51, followed by a short circuit failure between the gate and source, and an open circuit failure occurs in the first Zener diode 71 or the second Zener diode 72, the large current is blocked by the first rectifier diode 101. This prevents a large current from flowing through the third Zener diode 91 and the fourth Zener diode 92, and does not affect the operation of the second switch 52. As a result, the source voltage Vs2 of the second switch 52 can be made lower than the withstand voltage of the control circuit Dr.

On the other hand, even if a short circuit failure occurs between the drain and source of the second switch 52, followed by a short circuit failure between the gate and source, and an open circuit failure occurs in the third Zener diode 93, the large current is blocked by the second rectifier diode 102. This makes it possible to prevent a large current from flowing through the first Zener diode 71 and the second Zener diode 72, and does not affect the operation of the first switch 51. As a result, the source voltage Vs1 of the first switch 51 can be made equal to or lower than the withstand voltage of the control circuit Dr.

If a short circuit occurs in both the first Zener diode 71 and the second Zener diode 72, or if a short circuit occurs in the fourth Zener diode 92, the output voltage of the emergency power supply 57 becomes 0.

According to the present embodiment described above, it is possible to reduce the number of resistors and the mounting area of the resistors on the control board, while suppressing a decrease in the reliability of the emergency power supply 57 due to a short circuit failure of either of the switches 51 and 52.

<Other embodiments>
Each of the above embodiments may be modified as follows.

- In the fourth embodiment, the third Zener diode 91 may not be provided. In this case, for example, the forward voltage drop of the second rectifier diode 102 may be set to be larger than the forward voltage drop of the first rectifier diode 101 so that the resistance value of the first individual electrical path including the first rectifier diode 101 and the resistance value of the second individual electrical path including the second rectifier diode 102 are the same.

- The switch that constitutes the emergency power supply is not limited to an N-channel MOSFET, but may be, for example, an NPN-type bipolar transistor having a collector that is a high-potential terminal, an emitter that is a low-potential terminal, and a base that is a control terminal.

- The number of switches connected in series that make up the emergency power supply is not limited to two, and may be three or more. In this case, the drive circuit of the emergency power supply should be configured so that the source voltage of each switch decreases from the high-potential switch to the low-potential switch.

- The series power supply disclosed herein is not limited to being embodied as an emergency power supply, but may also be embodied, for example, as a starter circuit for a flyback power supply whose primary side is a high-voltage power supply.

10...High voltage power supply, 50...Emergency power supply, 51...First switch, 52...Second switch, 61...Resistor, 71...First Zener diode, 72...Second Zener diode, Dr...Control circuit.

Claims (6)

In a series power supply (50, 55 to 57) that steps down the output voltage of a DC power supply (10) and supplies the stepped-down output voltage to a power supply target (Dr),
A series connection of a plurality of transistors (51, 52) that connects the positive electrode side of the DC power supply and the power supply target part;
a drive circuit (61, 62, 71 to 73, 80, 81, 91, 92, 101, 102) that drives each of the transistors so that the voltage of the low potential side terminal of each of the transistors is equal to or lower than the withstand voltage of the power supply target part;
Equipped with
A series power supply, wherein each of the transistors has a withstand voltage equal to or higher than the output voltage of the DC power supply. The drive circuit includes:
A resistor (61);
Zener diodes (71, 72) provided individually corresponding to the transistors;
Equipped with
Each of the Zener diodes has a cathode electrically connected to the gate of the transistor;
The Zener diodes are connected in series such that an anode of a Zener diode on a high potential side and a cathode of a Zener diode on a low potential side among adjacent Zener diodes are electrically connected;
The anode of the Zener diode (72) having the lowest potential among the Zener diodes is electrically connected to ground,
a first end of the resistor is electrically connected to a positive electrode side of the DC power supply;
2. The series power supply (50, 56) of claim 1, wherein the second end of the resistor is electrically connected to a cathode of a highest potential diode (71) that is the Zener diode with the highest potential among the Zener diodes. a rectifier diode (80) provided in a path electrically connecting a gate of a highest potential transistor (51) which is the transistor on the highest potential side among the transistors, and a cathode of the highest potential diode;
3. The series power supply (56) of claim 2, wherein the cathode of said rectifier diode is electrically connected to the gate of said highest potential transistor. The drive circuit has reference voltage generating circuits (61, 62, 71 to 73) provided individually corresponding to the respective transistors,
2. The series power supply (55) according to claim 1, wherein each of the reference voltage generating circuits generates a voltage for controlling the voltage of the low potential side terminal of the transistor corresponding thereto to a voltage equal to or lower than a withstand voltage of the power supply target part, and supplies the generated voltage to a gate of the transistor. Each of the reference voltage generating circuits is
Zener diodes (71 to 73),
Resistors (61, 62);
having
In each of the reference voltage generating circuits, a first end of the resistor is electrically connected to a positive electrode side of the DC power supply,
In each of the reference voltage generating circuits, a second end of the resistor is electrically connected to the cathode of the Zener diode;
5. The series power supply according to claim 4, wherein in each of the reference voltage generating circuits, the anode of the Zener diode is electrically connected to ground. The drive circuit includes:
A resistor (61);
individual electrical paths (71, 72, 91, 92, 101, 102) provided individually corresponding to each of the transistors;
having
a first end of the resistor is electrically connected to a positive electrode side of the DC power supply;
Each of the individual electrical paths electrically connects a second end of the resistor to a ground;
Each of the individual electrical paths includes:
Rectifier diodes (101, 102);
a Zener diode (71, 72, 92) that generates a voltage for controlling the voltage of the low potential side terminal of the transistor to a voltage equal to or lower than the withstand voltage of the power supply target portion and supplies the generated voltage to a gate of the transistor;
was established,
In each of the individual electrical paths, a rectifier diode is provided such that an anode of the rectifier diode faces a second end side of the resistor,
The series power supply (57) according to claim 1, wherein the Zener diode is provided on the ground side of the rectifier diode in each of the individual electrical paths.

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