JPH04372582A - Capacitor rush current preventing circuit for rectifier - Google Patents

Abstract

PURPOSE:To contain a capacitor rush current preventing circuit in a diode module by composing the circuit of an integrator having a series unit of an integrating capacitor and a resistor, and a trigger circuit for detecting the voltage of the capacitor at a predetermined level to supply a gate current to a thyristor. CONSTITUTION:When an AC power source system 2 is connected to a diode rectifying bridge 1, an integrated voltage of an integrating capacitor 22 is low immediately after the connection, and a thyristor 8 maintains an OFF state. And, a smoothing capacitor 3 is charged by an output current of the bridge 1 through a limiting resistor 7. When the integrating voltage of an integrator 21 rises to reach a Zener voltage of a Zener diode 27, the thyristor 8 is triggered to be in a continuity, and a smoothed DC current is supplied to an external load. Thus, a capacitor rush current preventing circuit 20 shows a simple element configuration, and can be contained in a diode module.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a rectifying device used in a DC power source such as an inverter device for variable speed control of an electric motor, and particularly to a rectifier device provided for suppressing inrush current flowing into a smoothing capacitor at the time of starting the device. Related to inrush current prevention circuit.

0002

[Prior Art] In a rectifier that converts AC power to DC power, when a smoothing capacitor is connected directly to the DC output side of a diode rectifier bridge and AC power is turned on, the peak value of the smoothing capacitor is extremely large. Charging current (rush current) flows. Therefore, it is necessary to use a rectifier element with a large surge current rating in the diode rectifier bridge.
Furthermore, if the capacity of the rectifier is large, the charging current may cause problems such as a drop in the voltage of the AC power supply system. Therefore, in order to eliminate the increase in the size of the rectifying element and the adverse effects on the power supply system, it is known that a diode rectifying bridge is provided with a capacitor inrush current prevention circuit on the DC output side.

FIG. 3 is a connection diagram showing a conventional capacitor inrush current prevention circuit for a rectifier. The rectifier converts AC power from the AC power supply system 2 into DC power and supplies it to an external load using a diode rectifier. It is composed of a bridge 1 and a smoothing capacitor 3. In addition, the capacitor inrush current prevention circuit 10
is a main circuit 9 consisting of a parallel circuit of a limiting resistor 7 and a thyristor 8 connected in series between a diode rectifier bridge 1 and a smoothing capacitor 2, and a gate current to the gate G of the thyristor 8. It is composed of a trigger circuit 11 that supplies the trigger circuit. The trigger circuit 11 uses a voltage detector 12 to detect that the voltage of the smoothing capacitor 3 has reached a specified charging voltage, and uses the output as a gate signal for the AND gate 14 to control the oscillation circuit 1.
3 is supplied to the primary winding of an isolation transformer 15, and its secondary winding voltage is supplied as a gate current to the gate G of the thyristor 8 via a diode 16 and a resistor 17. be done.

[0004] Immediately after the power is turned on, the voltage across the smoothing capacitor 3 is low, so the thyristor 8 is in an off state.
The DC output current of the diode rectifier bridge 1 is controlled by the limiting resistor 7.
By charging the smoothing capacitor 3 via the smoothing capacitor 3, it is possible to prevent an excessive charging current from flowing into the smoothing capacitor 3. Furthermore, when the charging voltage of the smoothing capacitor 3 reaches a specified voltage, a gate current flows to the thyristor 8 via the trigger circuit 11, the thyristor 8 is turned on, and the subsequent load current is supplied via the thyristor 8. be done.

[0005]

[Problems to be Solved by the Invention] In the conventional capacitor inrush current prevention circuit as described above, the number of components of the trigger circuit is large and the circuit is complicated, which not only causes an economic disadvantage, but also requires an isolation transformer. Because of this, it is difficult to incorporate it into module products (diode modules) that incorporate power semiconductor elements, and there is a problem that the external circuit of the module becomes complicated and large. Improvement is required.

[0006] An object of the present invention is to have a simple circuit configuration;
An object of the present invention is to obtain a capacitor inrush current prevention circuit for a rectifier having a trigger circuit that can be easily built into a diode module.

[0007]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a rectifying device comprising a diode rectifying bridge and a smoothing capacitor connected in parallel to the DC output side of the diode rectifying bridge is provided. - a parallel circuit of a limiting resistor and a thyristor connected in series between a diode rectifying bridge and a smoothing capacitor; when the diode rectifying bridge is started, the thyristor is turned off and the limiting resistor causes a rush to the smoothing capacitor; The current prevention device includes an integrating circuit comprising an integrating capacitor and a series resistor connected in parallel to the DC output side of the diode rectifier bridge, and detecting the voltage of the integrating capacitor at a predetermined level. and a trigger circuit that supplies gate current to the thyristor.

[0008] Also, the trigger circuit
A transistor whose emitter and collector are connected between the gate and the gate with a resistor placed on the gate side, and a Zener diode connected between the base of this transistor and the intermediate connection point of the integrating circuit. The transistor is formed such that a base current begins to flow through the transistor when the integrated voltage of the integrating circuit exceeds the Zener voltage of the Zener diode.

Furthermore, the trigger circuit includes a delay circuit that suppresses the operation of the integrating circuit until the charging voltage of the smoothing capacitor reaches a predetermined level, and the delay circuit includes a resistor connected in parallel to the smoothing capacitor. A voltage divider, a transistor whose emitter and collector are connected in series to an integrating circuit, and a Zener diode connected between the base of this transistor and the voltage dividing terminal of the resistor voltage divider. do.

0010

[Operation] In the configuration of the present invention, in a parallel circuit of a limiting resistor and a thyristor connected in series between a diode rectifier bridge and a smoothing capacitor, an integrating capacitor is connected in parallel to the DC output side of the diode rectifier bridge. By adding an integrating circuit consisting of a resistor and a resistor in series, and a trigger circuit that detects the integrated voltage of this integrating circuit at a predetermined level and supplies a gate current to the thyristor, the integrating circuit By determining the time constant, a function is obtained to delay the time until the thyristor turns on, and during this time, the smoothing capacitor is charged via the limiting resistor, so a function to suppress excessive inrush current is obtained.

[0011] The trigger circuit is also constructed by using a transistor whose emitter and collector are connected between the anode and gate of a thyristor with a resistor placed on the gate side, and the base of this transistor and an integrating circuit. When the integrated voltage of the integrating circuit exceeds the Zener voltage of the Zener diode, base current begins to flow through the transistor. If formed like this,
The trigger circuit including the integrator circuit can be configured simply, and the isolation transformer that would prevent it from being built into the diode module is eliminated, making it possible to create a diode module that integrates the capacitor inrush current prevention circuit and rectifier. − You can obtain the following information.

Furthermore, if the trigger circuit is configured to include a delay circuit that suppresses the operation of the integrating circuit until the charging voltage of the smoothing capacitor reaches a predetermined level, the delay time until the thyristor is turned on can be changed from that of the integrating circuit. Since this function is shared by the delay circuit, the function of reducing the capacitance of the integrating circuit and facilitating modularization can be obtained. In particular, a delay circuit is connected between a resistive voltage divider connected in parallel to a smoothing capacitor, a transistor whose emitter and collector are connected in series with an integrating circuit, and an intermediate connection point between the base of this transistor and the resistive voltage divider. By configuring it with connected Zener diodes, it becomes easy to modularize the delay circuit and the integration circuit.

[0013]

EXAMPLES The present invention will be explained below based on examples. FIG. 1 is a connection diagram showing a capacitor inrush current prevention circuit of a rectifier according to an embodiment of the present invention. Hereinafter, the same components as those in the prior art are given the same reference numerals, and redundant explanation will be omitted. In the figure, smoothing capacitor 3
The inrush current prevention circuit 20 includes a diode rectifier bridge 1
The integrated voltage of the integrating circuit 21 (voltage of the integrating capacitor 22), which is composed of an integrating circuit 21 connected in parallel to the DC output side of the integrator 21 and a series circuit of an integrating capacitor 22 and a resistor 23, is detected and gated to the thyristor 8. It is composed of a trigger circuit 25 that supplies current. The trigger circuit 25 emitter E
is connected to the anode of the thyristor 8, and the collector C is connected to the gate G of the thyristor 8 via the resistor 28. In this case, the midpoint between the pnp transistor 26, its base B, and the integrating circuit 21. and a Zener diode 27 connected between the two.

In the capacitor inrush current prevention circuit of the rectifier constructed as described above, when the AC power supply system 2 is turned on to the diode rectifier bridge 1, immediately after the AC power supply system 2 is turned on, the integrating capacitor 22 is applied between E and B of the pnp transistor 26.
Since the integrated voltage of the transistor 26 is low, the base current of the transistor 26 is blocked by the Zener voltage of the Zener diode 27.
Since no gate current is supplied to the thyristor 8, the thyristor 8 remains off, and the output current of the diode rectifier bridge 1 charges the smoothing capacitor 3 via the limiting resistor 7. Therefore, the peak value of the inrush current having an excessively high peak value flowing into the smoothing capacitor 3 immediately after the diode rectifying bridge is started is suppressed by the limiting resistor 7. When the integrated voltage of the integrating circuit 21 rises at a rising speed determined by its time constant and reaches the Zener voltage of the Zener diode 27, a base current flows through the PNP transistor 26, and the amplified collector current flows into the gate. Since the current is supplied to the gate G of the thyristor 8 as a gate current, the thyristor 8 is triggered and becomes conductive, and the output current of the diode rectifier bridge 1 charges the smoothing capacitor 3 via the thyristor. The smoothed DC current is supplied to an external load.

As a result, the rush current to the smoothing capacitor 3 can be suppressed by determining the time constant of the integrating circuit 21 and the resistance value of the limiting resistor 7, so that the diode used in the diode rectifier bridge 1 can be There is no need to make the current constant particularly large, so the diode rectifier bridge can be made compact and economically advantageous, and the negative effects such as voltage drop in the AC power supply system due to the flow of excessive inrush current are eliminated. Ru. In addition, the capacitor inrush current prevention circuit 20 does not include an isolation transformer and has a simple element configuration that can be integrated into a single chip using a semiconductor process. It can be built-in, and external circuitry can be eliminated or simplified.

Note that in the above embodiment, the trigger circuit has a pn
The explanation was given using a p-transistor as an example, but npn
It is also possible to construct a capacitor inrush current prevention circuit having the same function as the above-described embodiment by using a transistor. In this case, the direction in which the E and C terminals of the transistor are connected to the thyristor and the direction in which the Zener diode is connected are opposite to the direction shown in FIG.

FIG. 2 is a connection diagram showing a different embodiment of the present invention, in which a resistive voltage divider 32 is connected in parallel to a smoothing capacitor 3, and a collector C and an emitter E are connected to an integrating circuit 21.
A delay circuit 31 is added, which consists of a transistor (NPN transistor in the figure) connected in series and a Zener diode 33 connected between its base B and the voltage dividing terminal of the resistor voltage divider 32. This is different from the previous embodiment in that the resistance voltage divider 32 of the delay circuit 31 is replaced by the smoothing capacitor 3.
monitors the charging voltage of the Zener diode 3.
Since the base current of the transistor 34 is blocked until the Zener voltage of No. 3 is reached, the transistor 34 remains off until the charging voltage of the smoothing capacitor reaches the specified voltage value. This prevents the integrating circuit 21 from performing an integrating operation. Therefore, the time during which the thyristor 8 remains off is shared between the integrating circuit 21 and the delay circuit 31, and depending on how the time constants of both are selected, the capacitance of the integrating capacitor 22 can be reduced and the diode module This makes it easier to incorporate a capacitor inrush current prevention circuit into the module.

[0018]

Effects of the Invention As described above, the present invention has a parallel circuit of a limiting resistor and a thyristor connected in series between a diode rectifier bridge and a smoothing capacitor, and a parallel circuit of a limiting resistor and a thyristor connected in parallel to the DC output side of the diode rectifier bridge. The thyristor is provided with an integrating circuit consisting of a series integrated capacitor and a resistor, and a trigger circuit that detects the integrated voltage of the integrating circuit at a predetermined level and supplies a gate current to the thyristor. As a result, by determining the time constant of the integrating circuit, a function is obtained to delay the time until the thyristor turns on, and during this time the smoothing capacitor is charged via the limiting resistor, making it possible to suppress excessive inrush current. , therefore the diode
This eliminates the need to use a power semiconductor element with a large surge current capacity in the double rectifier bridge, and provides an economically advantageous miniaturized rectifier.

[0019] The trigger circuit is also constructed by using a transistor whose emitter and collector are connected between the anode and gate of a thyristor with a resistor placed on the gate side, and the base of this transistor and an integrating circuit. It consists of a zener diode connected between the center point and the zener diode, and when the integrated voltage of the integrating circuit exceeds the zener voltage of the zener diode, the base current starts flowing through the transistor. This eliminates the problem of increasing the size of the capacitor inrush current prevention circuit and the isolation transformer that prevents it from being built into the diode module, which was a problem with the conventional technology, and also eliminates the need for a capacitor inrush current prevention circuit that requires a capacitor, a resistor, and a diode module. Consists of small semiconductor elements,
Since it can be easily built into a diode module and has a simple circuit configuration, we have developed a rectifier that has a built-in capacitor inrush current prevention circuit in a rectifier that consists of a diode module that incorporates multiple power semiconductor chips. can be provided.

Furthermore, if the trigger circuit is configured to include a delay circuit that suppresses the operation of the integrating circuit until the charging voltage of the smoothing capacitor reaches a predetermined level, the delay time until the thyristor is turned on can be changed from that of the integrating circuit. Since this is shared by the delay circuit, the capacitance of the integrating circuit can be reduced and modularization can be further facilitated. In particular, the delay circuit is configured with a resistive voltage divider connected in parallel with a smoothing capacitor,
If an integrating circuit is constructed with a transistor whose emitter and collector are connected in series, and a Zener diode connected between the base of this transistor and the midpoint of a resistor voltage divider, a delay circuit and an integrating circuit can be formed. This has the advantage that modularization is even easier.

[Brief explanation of the drawing]

[Fig. 1] A simplified connection diagram showing a capacitor inrush current prevention circuit of a rectifier according to an embodiment of the present invention.

[Fig. 2] Connection diagram showing different embodiments of this invention

[Figure 3] Connection diagram showing a conventional capacitor inrush current prevention circuit for a rectifier

[Explanation of symbols]

1 Diode rectifier bridge 3 Smoothing capacitor 7 Limiting resistor 8 Thyristor 9 Main circuit 10 Capacitor inrush current prevention circuit 11
Trigger circuit 20 Capacitor inrush current prevention circuit 21
Integrating circuit 22 Integrating capacitor 23 Resistor 25 Trigger circuit 26 Transistor 27 Zener diode 28 Resistor 31 Delay circuit 32 Resistor voltage divider 33 Zener diode 34 Transistor

Claims (4)

[Claims] 1. A rectifier comprising a diode rectifier bridge and a smoothing capacitor connected in parallel to the DC output side of the rectifier, comprising a limiting resistor connected in series between the diode rectifier bridge and the smoothing capacitor; A parallel circuit of thyristors is provided, and when the diode rectifier bridge is started, the thyristor is turned off to prevent inrush current to the smoothing capacitor by the limiting resistor, the DC output side of the diode rectifier bridge being It comprises an integrating circuit consisting of a series body of an integrating capacitor and a resistor connected in parallel, and a trigger circuit that detects the integrated voltage of the integrating capacitor at a predetermined level and supplies a gate signal to the thyristor. A capacitor inrush current prevention circuit for a rectifier, characterized by: [Claim 2] The trigger circuit includes a thyristor anode,
A transistor whose emitter and collector are connected between the gates with a resistor placed on the gate side, and a Zener diode connected between the base of this transistor and the intermediate connection point of the integrating circuit. and when the integrated voltage of the integrating circuit exceeds the Zener voltage of the Zener diode,
2. A capacitor inrush current prevention circuit for a rectifier according to claim 1, wherein said transistor is formed so that a base current begins to flow through said transistor. 3. The rectifier according to claim 1 or 2, wherein the trigger circuit includes a delay circuit that suppresses the operation of the integrating circuit until the charging voltage of the smoothing capacitor reaches a predetermined level. Equipment capacitor inrush current prevention circuit. 4. The delay circuit comprises a resistive voltage divider connected in parallel to a smoothing capacitor, a transistor whose emitter and collector are connected in series to an integrating circuit, and a base of the transistor and a voltage dividing terminal of the resistive voltage divider. 4. The capacitor inrush current prevention circuit for a rectifier according to claim 3, further comprising a Zener diode connected between the rectifier and the zener diode.