JPS6393016A - Rush current limiting circuit - Google Patents

Abstract

PURPOSE:To ensure stable limit of a rush current in simple constitution by controlling a feeder transistor via a constant current source and therefore reducing the using conditions. CONSTITUTION:The voltage of a power supply 1 is applied to a rush current limiting circuit 4 via a rectifier 3 of an AVR 2. The base of a transistor TR Q2 of the circuit 4 is controlled by the constant voltage obtained by a resistance R1 and a constant voltage diode ZD1 and forms a constant voltage source. Then the base of a TR Q1 connected to the single side of a feeder undergoes the control of constant voltage. Thus the rush current to be supplied to a capacitor C and a CAVR internal circuit 5 is limited. The rush current has no fluctuation due to the using conditions with use of a circuit using a transistor instead of a thyristor. Then the limit of the using condition is reduced. Thus it is possible to limit stably a rush current in a simple constitution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an inrush current limiting circuit, and particularly to a circuit that limits inrush current flowing into a DC stabilized power source (hereinafter abbreviated as AVR) when power is turned on. It is.

[Conventional technology]

If the conventional inrush limit circuit collapses, the
As described in No. 4, the operation of an eight-wire circuit in which a thyristor is connected in series to a power supply line, and a resistor and a transistor circuit are connected in parallel with the thyristor is that when the power is turned on, the thyristor is disabled. The inrush current is limited by making the thyristor conductive and supplying current through a parallel-connected resistor, and after the capacitor that is the load is charged, the thyristor is made conductive. However, in this method, an instantaneous increase in current occurs when the thyristor changes from a non-conducting state to a conducting state, and consideration must be given to reducing this current.

FIG. 5 is a diagram showing the configuration of another conventional AVR.

A power supply 1 applies power to the AVR 2 via a switch SW. The power applied at AVR2 is connected to rectifier 3.
is applied to the inrush current limiting circuit 4 via. This inrush current limiting circuit connects a thyristor TH in series to the power supply line,
A resistor R is connected in parallel with the thyristor. In operation, when the power is turned on, the thyristor is rendered non-conductive, and current is supplied to the internal circuit 5 and capacitor C via the parallel-connected resistor R. Therefore, the current when the power is turned on is limited by the resistor R. When the capacitor C is sufficiently charged and the internal circuit 5 is activated, the AVR starts operating by driving the gate terminal G of the thyristor TH and making the thyristor conductive. In this method, the thyristor can be changed from non-conductive to conductive after sufficiently charging the capacitor C, so the increase in current during this change can be made sufficiently small. However, when the power supply experiences a momentary power outage, an inrush current may occur. That is, the power supply is 0FFL,
Furthermore, if the internal circuit 5 of the power supply is in operation when the power supply is turned on, the gate G of the thyristor TH is also driven, so the thyristor TH is in a conductive state. Therefore, when the power is turned from OFF to ON, the thyristor is in a conductive state and cannot limit the current, causing an inrush current several tens of times the normal operating current to flow. For this reason, the external power supply that supplies the AVR, especially the constant voltage power supply, is uneconomical as it requires a large capacity one that can withstand the inrush current.Also, as an internal problem for the AVR, it is difficult to select elements that can withstand the inrush current. It was necessary, and there were design problems.

Conventionally, no consideration was given to the inrush current described above.

[Problem that the invention seeks to solve]

The above conventional technology uses a method of limiting the rush current using a thyristor. Therefore, the current increases when the thyristor changes from non-conducting to conducting, and it is not possible to limit the current increase when the thyristor is conducting.These points were not taken into consideration, and inrush current could become a problem. .

An object of the present invention is to provide an inrush current limiting circuit that can limit inrush current with fewer restrictions on usage conditions.

[Means for solving problems]

The above object is achieved by replacing the thyristor conventionally used as a current limiting element with a transistor and controlling the transistor to perform the current limiting function.

〔Example〕

The present invention will be explained in detail below with reference to one drawing.

FIG. 1 is a diagram showing a connection between an AVR including a circuit according to an embodiment of the present invention and a power supply. 1 is the power supply, 2 is the AVR13
4 is a rectifier, and 4 is an inrush current limiting circuit 5 is an AVR internal circuit. The voltage of power supply 1 is determined by switch SW,'! ii flow vessel 3
A constant current that is applied to the inrush current limiting circuit 4 through the inrush current limiting circuit 4 and limited by the inrush current limiting circuit 4 is applied to the smoothing capacitor C.
and is supplied to the AVR internal circuit 5. The inrush current limiting circuit 4 includes a transistor Q1 which plays a main role in limiting inrush current, a transistor Q2 which constitutes a constant current circuit to control the base current of the transistor Q1, resistors R1 and R2, and a constant voltage diode ZD. It consists of A constant voltage vz is applied to the base terminal of the transistor Q2 by a resistor R1 and a constant voltage diode ZD. Even if the voltage of the power supply 1 fluctuates, the value of the constant voltage vz is kept almost constant due to the action of the constant voltage diode. At this time, the emitter current IE2 of the transistor Q2 is determined by the following equation. Also, from the characteristics of the transistor, the transistor Q
The collector current IC2 of No. 2 is approximately equal to the emitter current IE2.

IE2L: IC2 Cape VZ/R1 In the above equation, constant voltage vZ and resistance value R1 take constant values. Therefore, emitter current IE2 and collector current IC2 also have constant values. That is, a constant current source can be configured by the transistor Q2, the resistors R1 and R2, and the constant voltage diode ZD.

Next, the collector current IC2 of the transistor Q2 becomes the base current IBI of the transistor Q1, and the transistor Q1
limits the collector current ICI of .

If the current amplification factor of the transistor Q1 is β, the collector current ICI can be obtained by the following equation.

IC1=βXIBI Here, the current amplification factor β is a constant constant, and the base current IBI
is a constant as mentioned above. Therefore, the collector current IC
I also becomes constant. A collector-emitter voltage VcEl is added to the base current IBI and collector current ICI of the transistor described above, and this relationship is shown in the transistor characteristic diagram of FIG. As shown in FIG. 2, while the collector current is small, the collector-emitter voltage vcE1 is small. That is, current is supplied to capacitor C1 and AVR internal circuit 5 through the collector and emitter of transistor Q1. Collector current ■C1 is above a certain value, that is, “βX I
It does not flow beyond "B1". As explained above, this circuit can limit the inrush current to a certain value or less.

FIG. 3 is an elliptical diagram of another embodiment of the present invention.

The inrush current limiting circuit shown in FIG. 3 differs from the inrush current limiting circuit shown in FIG. 1 in that a cutoff circuit for transistor Q1 is provided, which includes transistor Q3 and resistors R3 and R4. Collector current ICI of transistor Q1
However, as mentioned above, if the collector-emitter voltage VCEI is smaller than βXIBIJ, the collector-emitter voltage VCEI is small. Therefore, the base current IB3 of the transistor Q3 does not flow, and the collector current IC3 also does not flow. Therefore, functionally, the transistor Q3 Since it is the same as if there is no inrush current, the operation is the same as that of the inrush current circuit shown in Fig. As shown in the transistor characteristics diagram in Figure 2, the collector-emitter voltage VCE'l
increases. This voltage VCE! 1, a base current IB3 flows through the transistor Q3 via the resistor R4, and along with this, a collector current IC3 flows. Therefore, the base current IBI of transistor Q1 decreases and finally reaches zero, and transistor Q1 is cut off. Since the inrush current limiting circuit at this time limits the current only by the resistor R4, the limiting current IL is determined by the following equation.

I L'9VCE1/R4 The maximum value of the collector-emitter voltage VCEI is approximately equal to the voltage of the power supply 1 shown in FIG. 1, and the maximum value of the rush current is determined by the resistance value R4.

The feature of this circuit is that the inrush current is limited by the resistor R4, which has the effect of reducing the capacitance of the transistor Q1. Note that the resistor R3 is connected to the transistor Q along with the resistor R4.
This is necessary to determine the base voltage of No. 3.

FIG. 4 is a circuit configuration diagram of a modified example of the present invention. The four circuits have exactly the same inrush current limiting function as the circuit shown in FIG. 3, but differ in the types of transistors as follows.

Types of Transistors The roles of the transistors Q1 to Q3, the resistors R1 to R4, and the constant voltage diode ZD are the same as in FIG. 3, so their explanations will be omitted.

It is also possible to apply a Darlington transistor with a large current amplification factor to the above-mentioned transistor Q1 of the inrush current limiting circuit invented by Ikemizu.

〔Effect of the invention〕

According to the present invention, the inrush current can be accurately limited, the inrush current does not fluctuate depending on the conditions of use, and a stable and simple inrush current limiting circuit can be realized.

[Brief explanation of the drawing]

FIG. 1 is an AVR and power supply connection diagram including a circuit according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of a transistor, FIG. 3 is a circuit configuration diagram of another embodiment of the present invention, and FIG. FIG. 5 is a circuit diagram of a modified example of an AVR. 61st 5-A Translation Sumimachi

Claims (1)

[Claims] 1. A first transistor is inserted in series with one of the two positive and negative power supply lines, and the power supply line is connected via the emitter terminal and collector terminal of the transistor. , An inrush current limiting circuit characterized in that a constant current source is connected between the base terminal of the transistor and the other power supply line of the power supply line. 2. In claim 1, the constant current source has a second transistor, the collector terminal of the second transistor is connected to the base terminal of the first transistor, and the emitter terminal is connected to a resistor. The base terminal is connected to the anode terminal of the voltage regulator diode, the other terminal of the voltage regulator diode is connected to the other feed line, and the base terminal is connected to the other power supply line through the resistor. Via
An inrush current limiting circuit configured to be connected to the input side of one of the power supply lines. 3. In claim 1, a third transistor circuit is added to the first transistor circuit, the emitter terminal of the third transistor is the emitter terminal of the first transistor, and the collector terminal is: A resistor is connected to the base terminal of the first transistor, and a resistor is connected between the base terminal and the emitter terminal of the third transistor.
An inrush current limiting circuit characterized in that a resistor is connected between the collector terminals of the transistor.