JPH0614562A - Snubber circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] A high-speed, low-voltage diode is used as a snubber diode in a snubber circuit such as a voltage-source inverter instead of a high-voltage diode that is expensive and has a large loss. Try. [Structure] The snubber circuit 1B provided between the DC input terminals of the switching circuit 2 is composed of a snubber capacitor 31, two snubber diodes 42 and 43 in series, and discharge resistors 52 and 53, and the resistors 52 and 53 are connected to the diodes 42 and 43. Also used as a voltage dividing resistor. The DC terminal bar of the switching circuit 2 is also used as a heat sink for the snubber diodes 42, 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber for an inverter or a chopper as a power conversion circuit for repeatedly opening and closing a high-voltage DC power supply at a high frequency through a switching circuit composed of switching semiconductor elements to convert and output AC or DC power. More particularly, the present invention relates to a snubber circuit in which low withstand voltage diodes are connected in series as a snubber diode.

In the following figures, the same reference numerals indicate the same or corresponding parts.

[0003]

2. Description of the Related Art FIG. 6 shows a configuration example of a conventional snubber circuit in an inverter. In the figure, a switching circuit 2 in which a load 61 is connected between AC output terminals is connected in parallel to a capacitor 11 provided between DC power supply terminals P and N, and a DC terminal of this switching circuit 2 is connected. A snubber circuit 1 including a series circuit of a capacitor 31 and a diode 41 and having a resistor 51 in parallel with the diode 41 (between terminals 81 and 82) is provided therebetween. Reference numeral 71 is the inductance of the wiring of the DC bus in this inverter. Further, in the example of FIG. 6, the switching circuit 2 includes transistors 21, 22, 23 and 24.
It constitutes a bridge inverter.

In such a circuit configuration (operation of turning on transistors 21 and 24 and turning off transistors 22 and 23) → (operation of turning off transistors 21 and 24 and turning off transistors 22 and 23) → (transistor 21 , 24 is turned off and the transistors 22 and 23 are turned on) → (operations of turning off the transistors 21 and 24 and turning off the transistors 22 and 23) are repeated in the order indicated by the arrows to perform switching. The alternating voltage V1 is supplied to the output of the circuit 2.

By the way, the transistors 21 and 22 are turned on,
If the transistors 21 and 24 are turned off and the transistors 22 and 23 are turned off from the transistors 22 and 23 being off, the transistors 21 and 24 are turned off.
4, a wiring inductance 71, a transistor 21,
A voltage determined by di / dt when the transistor 24 is turned off is applied in a direction of increasing the voltage of the transistors 21 and 24. Similarly, the transistors 21 and 24 are turned off, and the transistors 22 and 23 are turned on.
Even when the transistors 1 and 24 are turned off and the transistors 22 and 23 are turned off, the voltage for increasing the voltage of the transistors 22 and 23 is applied. At this time, the transistor 21
In order to suppress the voltage applied to 24 to less than the allowable value, a series circuit of the capacitor 31 and the diode 41 is connected in parallel between the DC terminals of the switching circuit 2, and the resistor 81 is connected to the terminals 81 and 82 of the diode 41. A snubber circuit 1 formed by connecting

The operation of the snubber circuit 1 in FIG. 6 is performed when the transistors 21, 24 are turned on and the transistors 22, 23 are turned off from the transistors 21, 24 turned off and the transistors 22, 23 are turned off. The current flowing through the wiring inductance 71 is the wiring inductance 71 → capacitor 31 → terminal 82 → diode 4
1 → terminal 81 → capacitor 11 → wiring inductance 7
The energy commutated to the path 1 and stored in the wiring inductance 71 is transferred to the capacitor 31. Next, a current flows through the route of capacitor 31 → wiring inductance 71 → capacitor 11 → terminal 81 → resistor 51 → terminal 82 → capacitor 31, and the energy stored in capacitor 31 is consumed by resistor 51. Since the transistors 21 and 24 are off and the transistors 22 and 23 are on, the transistors 21 and 24 are off and the transistors 22 and 24 are off.
The same applies when 23 is turned off.

[0007]

In the snubber circuit 1 of FIG. 6, when the DC voltage of the switching circuit is high, a high breakdown voltage diode must be used as the snubber diode 41. However, a high breakdown voltage diode has a large switching loss, and the snubber circuit becomes large. Further, since the high breakdown voltage diode is expensive, there is a problem that the cost of the device is increased.

Therefore, an object of the present invention is to select a snubber circuit which uses a high-speed, low-breakdown voltage diode, reduces switching loss, constructs a cooling structure for the diode at low cost, and makes the device compact and inexpensive. It is in.

[0009]

In order to solve the above-mentioned problems, the snubber circuit according to claim 1 is provided with a first capacitor (11, 301, etc.) between DC terminals on the input side or the output side, In a power conversion circuit (switching circuit 2 or the like) (such as a voltage source inverter or chopper) that repeatedly opens and closes a power supply through a switching semiconductor element to output AC or DC power, the first capacitor and the power conversion circuit A plurality of diodes (42, 43, etc.) that are provided in parallel between the first capacitor and the first capacitor and are connected in series in the forward direction and each have a discharge resistance (52, 53, etc.) in parallel. And a second capacitor (31 or the like) are connected in series.

According to the snubber circuit of claim 2,
In the snubber circuit described in the paragraph [1], one diode is provided at each end of the second capacitor. A snubber circuit according to a third aspect is the snubber circuit according to the second aspect, wherein the first and second capacitors are two series capacitors (12, 13 and 3 respectively).
2, 33, etc.), and a resistor (91, etc.) is connected between the connection points (87, 88, etc.) at the center of the two series capacitors.

According to the snubber circuit of claim 4, claim 2
Alternatively, in the snubber circuit according to claim 3, the diode is a DC terminal (83,
85, etc.) so that heat can be dissipated.

[0012]

[Function] The switching loss is reduced by using a high-speed, low-voltage diode connected in series to the snubber diode. Further, by mounting the two snubber diodes on the DC terminal bars at both ends of the switching circuit, the DC terminal bars serve as a heat sink and cool the snubber diodes. Further, a discharging resistor is connected in parallel to each snubber diode, and this discharging resistor also functions as a voltage dividing resistor of the snubber diode.

[0013]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment (related to claim 3) of the present invention. 6 is different from FIG. 6 in that instead of the capacitor 11, a capacitor 12 and a capacitor 13 are used.
And a point where a series circuit of is connected in parallel with the switching circuit 2, and the capacitor 31, the diode 41 and the resistor 5
In place of the snubber circuit 1 constituted by 1, a series circuit in which a diode 42, a capacitor 32, a capacitor 33 and a diode 43 are serially connected in this order is connected between the DC terminals of the switching circuit 2 and between the terminals 83 and 84 of the diode 42. A resistor 52 to the terminal 8 of the diode 43.
A snubber circuit 1A by connecting a resistor 53 between the capacitors 5 and 86 and a resistor 91 between the mutual connecting terminal 87 of the capacitors 12 and 13 and the mutual connecting terminal 88 of the capacitors 32 and 33, respectively.
Is the point that was configured.

The operation of the snubber circuit 1A shown in FIG. 1 changes from the state where the transistors 21 and 24 are on and the transistors 22 and 23 are off to the state where the transistors 21 and 24 are off and the transistors 22 and 23 are off. The current flowing through the wiring inductance 71 is the wiring inductance 71 → terminal 83 → diode 42 → terminal 84 →
Capacitor 32 → Terminal 88 → Capacitor 33 → Terminal 86
→ diode 43 → terminal 85 → capacitor 13 → terminal 8
The commutation of 7 → capacitor 12 → wiring inductance 71 is performed, and the energy stored in the wiring inductance 71 is transferred to the capacitors 32 and 33. Next capacitor 3
3 → terminal 88 → capacitor 32 → terminal 84 → resistor 52 →
Terminal 83 → wiring inductance 71 → capacitor 12 →
A current flows through the route of terminal 87 → capacitor 13 → terminal 85 → resistor 53 → terminal 86 → capacitor 33, and the energy stored in capacitors 32 and 33 is consumed by resistors 52 and 53.

At this time, the current flowing through the resistors 52 and 53 is 10 times or more the leakage current of the diodes 42 and 43. Further, if the resistance values of the resistors 52 and 53 are the same, reverse application of the diodes 42 and 43 is performed. The voltage can be divided evenly. For example, if the leakage current of the diodes 42 and 43 is 10
If it is set to about μA to 100 μA, the resistors 52 and 53 in this circuit are discharge resistors, so the resistance value is selected to be several Ω, and the current flowing through the resistors 52 and 53 is about 10 A.
As a result, the resistors 52 and 53 also serve as voltage dividing resistors for the diodes 42 and 43. Transistors 21, 24
Is off and transistors 22 and 23 are on, transistors 21 and 24 are off, and transistor 2 is on.
The same applies when 2 and 23 are turned off. Further, the resistor 91 plays a role of suppressing an oscillating current caused by the capacitance difference between the capacitors 32 and 33. In this case, assuming that the capacitance of the capacitor 32 is C ₃₂ (F) and the wiring inductance is L (H), the resistance value R ₉₁ of the resistor ₉₁ becomes R ₉₁ > 2.
The oscillating current disappears when (L / C ₃₂ ) ^1/2 is satisfied.

FIG. 5 shows the mechanical structure of the circuit of FIG. 1 and corresponds to an embodiment of the invention according to claim 4. In FIG. 5, 501 is a transistor module in which the transistors 21 and 23 of FIG. 1 are integrated, and 502 is a transistor module in which the transistors 22 and 24 of FIG. 1 are also integrated.
2 is connected to a common DC power supply terminal bar P, N.
Reference numerals 401 and 402 denote snubber modules in which the snubber circuit 1A of FIG. 1 is realized by two parallel circuits having the same configuration. Reference numerals 601 and 602 respectively denote connection terminals for the DC power supply terminal bars P and N of the snubber module. is there.

As shown in FIG. 5, the snubber module 40
1 is installed in the immediate vicinity of the transistor module 501, and the snubber module 402 is installed in the immediate vicinity of the transistor module 502. Then, the anode of the diode 42 is connected to the connection terminal 601 of the snubber module 401,
By attaching the cathode of the diode 43 to the connection terminal 602 of the snubber module 401, the connection terminals 601, 602 of the snubber module 401 and P bar, N
The bar serves as a heat dissipation plate for the diodes 42 and 43.

FIG. 2 shows a second embodiment (related to claims 1 and 2) of the present invention. In the figure, the difference from FIG. 6 is that
Instead of the snubber circuit 1 configured by the capacitor 31, the diode 41 and the resistor 51, a series circuit in which a diode 42, a capacitor 31 and a diode 43 are serially connected in this order is connected between the DC terminals of the switching circuit 2 and the terminal of the diode 42. Resistor 5 between 83 and 84
2 is a resistor 53 between terminals 85 and 86 of diode 43.
Are connected to form a snubber circuit 1B.

The operation of the snubber circuit 1B of FIG. 2 is such that when the transistors 21 and 24 are turned on and the transistors 22 and 23 are turned off, the transistors 21 and 24 are turned off and the transistors 22 and 23 are turned off. The current flowing in the inductance 71 is diverted to the route of the wiring inductance 71 → terminal 83 → diode 42 → terminal 84 → capacitor 31 → terminal 86 → diode 43 → terminal 85 → capacitor 11 → wiring inductance 71,
The energy stored in the wiring inductance 71 is transferred to the capacitor 31. Next, capacitor 31 → terminal 84 →
A current flows through a route of resistor 52 → terminal 83 → wiring inductance 71 → capacitor 11 → terminal 85 → resistor 53 → terminal 86 → capacitor 31, and the energy stored in capacitor 31 is consumed by resistors 52 and 53. At this time, the current flowing through the resistors 52 and 53 is the diode 42,
Is more than 10 times the leakage current of 43, and the resistance 52,
If the resistance value of 53 is the same, the voltages of the diodes 42 and 43 can be equally divided. Diode 42,4
If the leakage current of No. 3 is about 10 μA to 100 μA, the resistors 52 and 53 in this circuit are discharge resistors, so a resistance value of several Ω is selected, and the current flowing through the resistors 52 and 53 is about several tens A. As a result, the resistors 52 and 53 also serve as voltage dividing resistors for the diodes 42 and 43. The transistors 21 and 24 are off, and the transistor 22 and
Transistors 21 and 24 are turned off when 23 is turned on,
The same is true when the transistors 22 and 23 are turned off.

FIG. 3 shows a third embodiment (related to claims 1 and 2) of the present invention. The difference between FIG. 2 and FIG.
As the switching circuit 2, a step-down chopper circuit in which a transistor 201 and a diode 202 are connected in series is used instead of a bridge inverter, and a point in which a series circuit of a DC reactor 101 and a load 61 is connected to the output side of the switching circuit 2. Is.

In such a circuit configuration, when the transistor 201 is on, the DC voltage of the capacitor 11 is applied to the load 6
1 and the DC reactor 101, DC power is supplied to the load 61, and the DC reactor 101 accumulates energy at the same time. Next, when the transistor 201 changes from on to off, the load current is diverted to the diode 202,
The energy accumulated in the DC reactor 101 is applied to the load 61.
Is released to. In this way, the transistor 201 turns on,
By repeating turning off, a DC voltage lower than the DC power supply voltage is supplied to the load 61. When the transistor 201 changes from on to off or the diode 202 changes from on to off, the snubber circuit 1B operates in the same manner as in FIG. 2 and serves to suppress the applied voltage of the transistor 201 and the diode 202 to be equal to or less than the allowable value.

FIG. 4 shows a fourth embodiment (related to claims 1 and 2) of the present invention. The difference between FIG. 2 and FIG.
As the switching circuit 2, a step-up chopper circuit in which a diode 202 and a transistor 201 are connected in series instead of a bridge inverter is used, and a DC reactor 101 is connected to an input terminal 89 of the switching circuit 2, and an output terminal of the switching circuit 2 is connected. Snubber circuit 1B in between
The point is that the capacitor 301 and the load 61 are sequentially connected in parallel.

In such a circuit configuration, when the transistor 201 is on, the input DC voltage is applied to the DC reactor 101, and the reactor 101 accumulates energy. Next, when the transistor 201 changes from on to off, the energy stored in the DC reactor 101 and the energy from the DC input are released to the capacitor 301 via the diode 202. Capacitor 30
1 serves to smooth the electric power and supplies a constant DC electric power to the load 61. Transistor 2 in such a circuit
By repeating ON and OFF of 01, a DC voltage higher than the DC power supply voltage is supplied to the load 61.

Also in FIG. 4, when the transistor 201 changes from on to off or the diode 202 changes from on to off, the input capacitor 11 in FIG. 2 is replaced by the output capacitor 301 in FIG. 1B operates in the same manner as in FIG. 2 and has a function of suppressing the applied voltage of the diode 202 and the transistor 201 to be equal to or lower than an allowable value.

[0025]

According to the present invention, a plurality of snubber diodes are connected in series, and the discharge resistors are connected in parallel to the respective diodes, so that the snubber diodes of high speed and low withstand voltage can be used. In addition, since the discharge resistance can be a voltage dividing resistance, the loss generated in the snubber circuit is reduced, and the device can be made highly efficient and miniaturized. Further, since the snubber diode is attached to the DC terminal bar of the switching circuit, the heat dissipating fin of the snubber diode is unnecessary, and the device structure can be simplified and the device cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram as a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

FIG. 3 is a circuit diagram as a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a fourth embodiment of the present invention.

5 is a mechanical structural diagram of the circuit of FIG.

FIG. 6 is a conventional circuit diagram.

[Explanation of symbols]

 1A snubber circuit 1B snubber circuit 2 switching circuit 11 capacitor 12 capacitor 13 capacitor 21 transistor 22 transistor 23 transistor 24 transistor 31 capacitor 32 capacitor 33 capacitor 42 diode 43 diode 52 resistor 53 resistor 61 load 71 wiring inductance 83 terminal 84 terminal 85 terminal 86 terminal 87 terminals 88 terminals 89 terminals 91 resistance 101 DC reactor 201 transistor 202 diode 301 capacitor 401 snubber module 402 snubber module 501 transistor module 502 transistor module 601 snubber module connection terminal (P side) 602 snubber module connection terminal (N side)

Claims (4)

[Claims] 1. A power conversion circuit comprising a first capacitor between input-side or output-side DC terminals, which repeatedly opens and closes a DC power supply through a switching semiconductor element to convert and output AC or DC power. A snubber circuit provided between the first capacitor and the power conversion circuit and in parallel with the first capacitor, the plurality of diodes being connected in series in a forward direction and each having a discharge resistance in parallel; A snubber circuit characterized by being connected in series with the capacitor of. 2. The snubber circuit according to claim 1, wherein one diode is provided at each end of the second capacitor. 3. The snubber circuit according to claim 2, wherein each of the first and second capacitors is formed in two series, and a resistor is connected between the connection points at the center of the two series capacitors. Snubber circuit characterized by. 4. The snubber circuit according to claim 2 or 3, wherein the diode is mounted so as to dissipate heat to a DC terminal of the power conversion circuit to which the diode is connected. The characteristic snubber circuit.