JPH08168236A - Snubber circuit - Google Patents

Abstract

PURPOSE: To obtain a highly efficient power converting apparatus by so constituting a snubber circuit that a signal that is turned on a predetermined time after a switching means is turned on and turned off when a predetermined time thereafter passes, will be output to a reverse switching means. CONSTITUTION: A composite circuit 5 consists of a parallel circuit composed of a forward diode 51 and a reverse switching means 52; and a capacitor 53 connected in series therewith. It is then connected in parallel with a series circuit composed of a switching means 2 and a load 3. When the switching means 2 is turned on, a reverse switching means control signal generating means 6 produces on-signal output to the reverse switching means 52 after a predetermined time. It turns off the output when a predetermined time thereafter passes. When the switching means 2 interrupts a current to the load 3, energy stored in a wiring inductance Lw moves to the capacitor 53 through the forward diode 51, and is stored there. This prevents surges and obtains a highly efficient power converting apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber circuit for protecting a switching means from a switching surge caused by an inductance of a wiring from a DC power source in a power converter having the switching means. In particular,
The present invention relates to an improvement that enables a power conversion device with high conversion efficiency that does not vibrate or absorb heat during surge absorption.

[0002]

2. Description of the Related Art Conventionally used snubber circuits include a C snubber circuit composed only of capacitance and an RCD snubber circuit composed of a resistor, a capacitance and a diode.

See FIG. 4. FIG. 4 is a block diagram of a power converter using a C snubber circuit. In FIG. 3, 1 is a DC power supply, 2 is a switching means composed of semiconductor elements, and 3 is a load to which ON / OFF-controlled power is supplied from the DC power supply 1 via the switching means 2. Reference numeral 7 denotes a C snubber circuit, which is composed of only the capacitance C. Reference numeral 11 is a load surge diminishing diode.

When the switching means 2 cuts off the current flowing through the load 3 by the inductance of the power supply wiring between the series circuit of the switching means 2 and the load 3 and the DC power supply 1, the wiring (hereinafter referred to as wiring inductance Lw), The current flowing through the wiring inductance Lw also tends to be cut off. Therefore, a surge voltage is generated across the wiring inductance Lw, and in some cases, the surge voltage may destroy the switching means 2. The C snubber circuit 7 suppresses the surge voltage due to the wiring inductance Lw. That is, when the current to the load 3 is cut off, the current flowing from the wiring inductance Lw to the load 3 flows from the wiring inductance Lw to the C snubber circuit 7, and a sudden change in the current flowing through the wiring inductance Lw is prevented. Surge voltage is suppressed.

When the switching means 2 cuts off the current flowing through the load 3, a surge voltage is generated across the load 3 due to the inductance component contained in the load 3. The load surge reduction diode 11 works so that this surge voltage is not applied to the switching means 2.
That is, since the surge voltage generated across the load 3 is in the forward direction to the load surge diminishing diode 11, it flows through the load surge diminishing diode 11 to suppress the surge voltage.

Refer to FIG. 5. FIG. 5 is a block diagram of a power conversion device using an RCD snubber circuit. In FIG. 5, reference numeral 8 is an RCD snubber circuit, and a capacitance C is connected in series to a direct current power source 1 in a parallel circuit of a diode D and a resistor R in the forward direction.

The surge voltage caused by the wiring inductance Lw generated when the switching means 2 cuts off the current flowing through the load 3 is suppressed by the RCD snubber circuit 8. That is, the current flowing from the wiring inductance Lw to the load 3 changes from the wiring inductance Lw to RCD.
The surge voltage is suppressed because a sudden change of the current flowing in the wiring inductance Lw flowing in the series circuit with the electrostatic capacitance C of the snubber circuit 8 is prevented. Then, the electric charge charged in the electrostatic capacitance C is discharged through the resistor R, and this discharge current oscillates between the wiring inductance Lw. The value of this oscillatory discharge current is gradually attenuated, and the high voltage is not applied to the switching means 2 again.

[0008]

The C snubber circuit 7 for suppressing the surge voltage applied to the switching means 2 is stored in the wiring inductance Lw when the switching means 2 cuts off the current flowing through the load 3. The energy causes charges to be accumulated in the electrostatic capacitance C of the C snubber circuit 7 and moves to the electrostatic capacitance C. Subsequently, the energy transferred to the electrostatic capacitance C returns to the wiring inductance Lw. Thus, the wiring inductance Lw and the capacitance C vibrate due to series resonance, and an oscillating current continuously flows in the power supply wiring, which may cause a malfunction of the power conversion device.

Further, in the RCD snubber circuit 8, the energy stored in the electrostatic capacity C is the wiring inductance L.
When returning to w, the energy passes through the resistance R and is absorbed by the resistance R, so that it does not vibrate. Therefore, the power converter does not malfunction, but the energy stored in the wiring inductance Lw is converted into heat by the resistor R and is wasted, and the efficiency of the power converter is reduced.

An object of the present invention is to solve these problems. It absorbs a surge caused by the wiring inductance Lw, does not generate vibration, wastes energy, and efficiently converts power. An object is to provide a snubber circuit that can be used as a device.

[0011]

The above object can be achieved by any of the following means.

The first means is connected in parallel to the series circuit of the switching means (2) and the load (3) fed from the DC power source (1), and is forward to the DC power source (1). A composite circuit (5) in which a parallel circuit of a forward diode (51) and a reverse switching means (52) and an electrostatic capacitance (53) are connected in series, and a signal input to the switching means (2). Is being energized, is turned on with a predetermined time delay from the energization, and is turned off after the elapse of a predetermined time, and outputs a signal to the reverse switching means (52), which is a reverse switching means control signal generation. A snubber circuit having means (6).

The second means is fed from the DC power supply (1), is connected in parallel to the input terminal of the DC / AC exchange means (4) having the switching means (2), and is connected to the DC power supply (1) in sequence. Input to the switching means (2) and a composite circuit (5) in which a parallel circuit of a forward direction diode (51) and a reverse switching means (52) and a capacitance (53) are connected in series. The signal is being energized and is turned on with a predetermined time delay from energization,
Further, it is a snubber circuit having a reverse switching means control signal generating means (6) for outputting a signal which turns off after a lapse of a predetermined time to the reverse switching means (52).

[0014]

The snubber circuit according to the present invention has the first means and the second means.
In both of the means, the composite circuit 5 in which the capacitance 53 is connected in series to the parallel circuit of the forward diode 51 in the forward direction when viewed from the DC power supply 1 and the reverse switching means 52 in the reverse direction is seen.
Then, the signal input to the switching means 2 is energized, and is turned on with a predetermined time delay from energization,
Further, it has a reverse switching means control signal generating means 6 for issuing a signal to the reverse switching means 52 to turn off after a predetermined time has elapsed.

In the first means, the composite circuit 5 is connected in parallel to the series circuit of the switching means 2 and the load 3 fed from the DC power supply 1, and in the second means, the composite circuit 5 is connected to the DC power supply. 1 is connected in parallel to the input end of a DC / AC conversion means 4 having a switching means 2 supplied with power from 1.

Therefore, the energy stored in the wiring inductance Lw in the power wiring from the DC power supply 1 passes through the forward diode 51 of the composite circuit 5 when the switching means 2 switches from energization to interruption. Move to the capacitance 53.

FIG. 3 is a time chart showing the operation of the snubber circuit according to the present invention. In FIG. 3, (a) is an energized state of the switching means 2, (b) is an output on / off signal waveform of the reverse direction switching means control signal generating means 6, (c) is an on / off state of the reverse direction switching means 52, (d). Shows the waveform of the current flowing through the capacitance 53, and (e) shows the voltage waveform across the capacitance 53.

At time t1, when the switching means 2 is switched from energization to interruption, a charging current flows through the electrostatic capacity 53 as shown in (d), and a charging current of the electrostatic capacity 53 as shown in (e). The voltage across both ends rises. The voltage across the capacitance 53 is charged to a voltage substantially close to the power supply voltage of the DC power supply 1 immediately before the switching means 2 shuts off. Therefore, when the charging current becomes 0, the voltage across the capacitance 53 is higher than the voltage of the DC power supply 1, and therefore the discharge is attempted.
Remains off and cannot be discharged, and this state continues until the reverse switching means 52 is turned on. That is, neither surge voltage nor vibration occurs.

At time t2, the switching means 2 is switched from the interruption to the energization, and after a lapse of time τ1, the reverse direction switching means control signal generating means 6 issues an ON signal (b) and the reverse direction switching means 52 is turned on. (C). When the reverse switching means 52 is turned on, the electrostatic capacitance 53 is discharged, a discharge current flows as shown in (d), and the voltage across the electrostatic capacitance 53 becomes a voltage close to the power supply voltage as shown in (e). Descend to. This discharge current is
In the means of, the flow from the switching means 2 to the load 3
In this means, the energy flows effectively to the DC / AC conversion means 4 having the switching means 2, so that the efficiency of the power conversion device can be improved. Furthermore, time τ2
After the lapse of time, the backward switching means control signal generating means 6 issues an off signal (b), the backward switching means 52 is turned off (c), and the state returns to the initial state.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A snubber circuit according to an embodiment of the present invention will be described in more detail below with reference to the drawings.

First Embodiment (corresponding to claim 1) See FIG. 1. FIG. 1 is a block diagram when used in a DC power converter. In FIG. 1, 1 is a DC power supply, 2 is a switching means composed of semiconductor elements, and 3 is a load. Electric power controlled to be turned on and off is supplied to the load 3 from the DC power supply 1 via the switching means 2. DC power supply 1
The inductance in the power supply wiring from to the series circuit of the switching means 2 and the load 3 is represented by Lw. 5 is a forward diode 51 in the forward direction when viewed from the DC power supply 1 and a reverse switching means 52 which is in the reverse direction viewed from the DC power supply 1.
Is a composite circuit in which the electrostatic capacitance 53 is connected in series to a parallel circuit of, and is connected in parallel to the series circuit of the switching means 2 and the load 3. Reference numeral 6 denotes a reverse direction switching means control signal generating means, which outputs a turn-on signal to the reverse direction switching means 52 after a predetermined time has elapsed from the time when the switching means 2 is energized and is energized, and is further predetermined. The ON signal is turned off after the elapse of the predetermined time. 1
Reference numeral 1 is a load surge reduction diode.

When the switching means 2 cuts off the current flowing through the load 3, the energy stored in the wiring inductance Lw moves to the electrostatic capacity 53 via the forward diode 51 and is stored in the electrostatic capacity 53. Since the state is maintained, the generation of the surge voltage can be prevented without vibrating unlike the C snubber circuit according to the related art.

The energy stored in the capacitance 53 is
When the reverse switching means control signal generating means 6 outputs an ON signal and the reverse switching means 52 is turned on,
Since it is discharged to the load 3 via the switching means 2 which is energized, energy is not wasted unlike the RCD snubber circuit according to the related art.

Since the function of the load surge reduction diode 11 is completely the same as the explanation of the operation in the block diagram shown in FIG.

Second Embodiment (corresponding to claim 2) See FIG. 2. FIG. 2 is a block diagram when used in a DC / AC power converter. In FIG. 2, reference numeral 1 is a DC power source, and 4 is a bridge connection of four switching means 2 composed of semiconductor elements or the like, and two switching means 2 are turned on at the same time.
(In the figure, two switching means are shown so as to be given the same base signal, that is, two switching means which are diagonally arranged in the arrangement of the figure and are in a so-called side-by-side arrangement) Is a DC / AC converter that outputs a single-phase AC by simultaneously turning on / off the current. An AC load 9 such as a rotating machine is supplied with AC power from the DC / AC converter 4. The inductance in the power supply wiring from the DC power supply 1 to the DC / AC converting means 4 is represented by Lw. Reference numeral 5 denotes a composite circuit in which a capacitance 53 is connected in series to a parallel circuit of a forward diode 51 in the forward direction when viewed from the DC power supply 1 and a reverse switching means 52 which is in the reverse direction viewed from the DC power supply 1. It is connected in parallel to the input side of the AC converting means 4. Reference numeral 6 denotes a reverse direction switching means control signal generating means, the switching means 2 being in the energized state, and the ON signal is supplied to the reverse direction switching means 5 after a lapse of a predetermined time τ1 from the time of energization.
Then, the ON signal is turned off after the elapse of a predetermined time τ2. The starting point of the time when the ON signal is issued may be only when one of the sets of the two switching means 2 which are simultaneously turned on is in the energized state, or when both of them are in the energized state. Capacitance 53 in the former case
The energy charged twice will be discharged once. Reference numeral 41 is an AC load surge reduction diode.

When the energized switching means 2 cuts off the current flowing through the AC load 9, the energy stored in the wiring inductance Lw is transferred to the forward diode 51.
Since it moves to the electrostatic capacity 53 via the and keeps the state of being stored in the electrostatic capacity 53, the generation of the surge voltage can be prevented without vibrating like the C snubber circuit according to the conventional technique.

The energy stored in the capacitance 53 is
When the reverse switching means control signal generating means 6 outputs an ON signal and the reverse switching means 52 is turned on,
AC load 9 via switching means 2 which is energized
Therefore, the energy is not wastefully consumed unlike the conventional RCD snubber circuit.

The AC load surge diminishing diode 41
Prevents the AC load surge due to the inductance component of the AC load 9 from being applied to the switching means 2.

Further, although FIG. 2 illustrates the case where a single-phase alternating current is output, there is no problem even if it is not single-phase alternating current but three-phase alternating current or multi-phase alternating current.
Is connected in parallel to the input terminal of the three-phase alternating current or multi-phase alternating current direct current alternating current converting means, and the above-mentioned reverse switching means control signal generating means 6 is installed, so that a desired result can be obtained.

[0030]

As described above, according to the snubber circuit of the present invention, the capacitance is connected in series to the parallel circuit of the forward diode in the forward direction and the reverse switching means in the reverse direction with respect to the DC power source. The combined circuit is connected in parallel to the series circuit of the switching means fed from the DC power source and the load, or is connected in parallel to the input terminal of the DC / AC conversion means having the switching means fed from the DC power source. However, the reverse direction switching means is configured such that the switching means is energized, and is turned on after a predetermined time has elapsed after the energization and then turned off after a predetermined time has elapsed. Therefore, the energy stored in the wiring inductance in the DC power supply wiring when the switching means is energized is
After moving to the capacitance of the composite circuit and the switching means is energized again, the energy that has moved to the capacitance flows to the load via the switching means. Therefore, it is possible to prevent a surge caused by the wiring inductance, and to enable a power conversion device with high conversion efficiency without vibrating like the conventional snubber circuit and wastefully consuming energy. It is a snubber circuit.

[Brief description of drawings]

FIG. 1 is a block diagram when a snubber circuit according to the present invention is used in a DC power converter.

FIG. 2 is a block diagram when the snubber circuit according to the present invention is used in a DC / AC power converter.

FIG. 3 is a time chart explaining the operation of the snubber circuit according to the present invention.

FIG. 4 is a block diagram of a power conversion device using a C snubber circuit according to a conventional technique.

FIG. 5 is a block diagram of a power conversion device using a conventional RCD snubber circuit.

[Explanation of symbols]

 1 DC power supply 2 Switching means 3 Load 4 DC / AC converting means 5 Composite circuit 6 Reverse direction switching means Control signal generating means 7 C snubber circuit 8 RCD snubber circuit 9 AC load 11 Load surge reducing diode 41 AC load surge reducing diode 51 51 Forward direction Diode 52 Reverse switching means 53 Capacitance Lw Wiring inductance

Claims (2)

[Claims] 1. A forward diode (51) connected in parallel to a series circuit of a switching means (2) and a load (3) fed from a DC power supply (1) and being forward to the DC power supply (1). ) And a reverse switching means (52) in a parallel circuit and a capacitance (53) connected in series, and a signal input to the switching means (2) is energized, Further, there is provided a reverse switching means control signal generating means (6) for outputting to the reverse switching means (52) a signal which is turned on with a predetermined time delay from energization and is turned off after a predetermined time has elapsed. A snubber circuit characterized by that. 2. A forward direction in which power is supplied from a DC power supply (1), is connected in parallel to an input end of a DC / AC exchange means (4) having a switching means (2), and is forward to the DC power supply (1). A composite circuit (5) in which a parallel circuit of a diode (51) and a reverse switching means (52) and a capacitance (53) are connected in series, and a signal input to the switching means (2) are energized. And a reverse switching means control signal generating means (6) for issuing a signal to the reverse switching means (52) which is turned on after a predetermined time delay from energization and is turned off after a predetermined time has elapsed. And a snubber circuit.