JPH11275759A - Rush current restraining circuit in electric circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a rush current avoiding voltage loss at the steady state, power loss and enlarging the components. SOLUTION: A power source E is connected to load 122 via a transistor Tr1 for driving the load 122 by means of driving current controlled by the transistor Tr1 . A microcomputer 120 includes two output terminals 2A, 2B and turns on transistors Tr3 , Tr4 at a fixed time lag. At the start of power supply for work, the transistor Tr3 is first turned on to control the base current of the transistor Tr1 and restrain the rush current. The transistor Tr4 is turned on after a fixed time elapse to increase the base current of the transistor Tr1 with two transistors Tr3 , Tr4 , thus supplying a normal drive current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inrush current suppressing circuit for controlling the current of a power supply line and a load line in an electronic circuit to suppress an inrush current which causes a malfunction or malfunction of the circuit or damage to electronic components. About.

[0002]

2. Description of the Related Art Conventionally, in various electronic circuits, a transient state is most unstable when a current is supplied, and when an inrush current flows through the circuit due to the transient phenomenon or a power supply voltage drops momentarily, the transient state occurs. The circuit may malfunction or the electronic components may be damaged. For example, as shown in FIG. 4, an inrush current i in a closed circuit in which an impedance element (Z) 10 and a load (Z _IN ) 12 are connected in series is determined by an input voltage V and an impedance Z + Z _IN , and an impedance Z + Z _IN
The larger the _IN , the smaller the inrush current.

Next, a specific example in which a circuit malfunctions due to an inrush current will be described with reference to FIG. In the circuit shown in FIG. 5, when the power is turned on, the signal from the output terminal of the microcomputer 20 becomes “High” and the transistors Tr1 and T
The load (Z _IN ) 22 is started by turning on r2. Further, the voltage detector (IC ₁₎ 24 monitors the voltage V ₁ of the input line, when the voltages V ₁ becomes less than a predetermined value (V _2), a detection signal which becomes "Low" to the input terminal of the microcomputer 20 Output. Then, when a “Low” detection signal is input to the input terminal of the microcomputer 20, the microcomputer 20 controls to turn off the power.

In such a circuit, a coupling capacitor C ₁ (which lowers the AC impedance of the power supply with respect to GND and stabilizes the AC operation of the circuit) is inserted in the power supply. Due to the phenomenon, a current of I ≒ E / r instantaneously flows through the circuit, and the power supply voltage E
Are all applied to the resistor r. At this time, the voltage of V ₁ is V
₁ ≒ 0, and when voltage is detected at this point, load 2
Although the power supply voltage E is applied to 2, the correct power supply voltage E cannot be detected until the capacitor C ₁ is charged, and the circuit malfunctions.

Therefore, conventionally, as shown in FIG. 4, a method has been adopted in which an inrush current is suppressed by inserting an impedance element such as a resistor or a choke coil into a power supply line or a load line through which an inrush current flows.

[0006]

However, as described above, if the impedance is increased to such an extent that the inrush current is suppressed, a voltage loss and a power loss occur in a steady state, and the load capacity cannot be fully exhibited at the maximum output. . Also,
If the impedance is increased, components such as the choke coil become large, and the mounting space efficiency is deteriorated.

An object of the present invention is to provide an inrush current suppression circuit in an electronic circuit which can suppress an inrush current while avoiding a steady-state voltage loss, power loss, and increase in size of components. .

[0008]

According to the present invention, in order to achieve the above object, in an electronic circuit for driving a load, power supply means for supplying power to the load, and power from the power supply means are supplied to the load. Power supply means and control means for suppressing inrush current to the load and gradually increasing power supply current when the power supply is turned on.

In the rush current suppressing circuit according to the present invention, when the power is turned on by the power supply means, the power supply current from the power supply means is supplied to the load. Is supplied with a small current. Thereafter, the supply current is gradually increased by the control means, and the current is controlled to a current supply suitable for driving the load. As a result, the load enters the normal drive state, and stable operation can be maintained. Therefore, the rush current immediately after the power is turned on can be suppressed without increasing the impedance of the power supply line, and an efficient driving state can be obtained without causing a loss due to a large impedance in the normal driving state.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inrush current suppressing circuit according to the present invention will be described below. FIG. 1 is a circuit diagram showing a specific example of an electronic circuit provided with an inrush current suppression circuit according to the present invention, and FIG. 2 is a timing chart showing control signals in the inrush current suppression circuit shown in FIG. FIG.
, The power supply E is connected to the load (Z _IN ) 122 via the resistor r and the transistor Tr1, and drives the load (Z _IN ) 122 by the drive current controlled by the transistor Tr1 (first control circuit). I do.

The microcomputer 120 has two output terminals 2A,
2B, the transistors Tr3 and Tr4 (second and third control circuits) are driven by control signals from the output terminals 2A and 2B, and the base current of the transistor Tr1 is controlled by the transistors Tr3 and Tr4. The rush current is suppressed, and the power supply current is gradually increased.

Each transistor Tr3 has a base connected to the output terminal 2A via a resistor r1, a collector connected to the base of the transistor Tr1 via a resistor r2, and an emitter grounded. Each transistor Tr4
Has a base connected to the output terminal 2B via the resistor r3, and a collector connected to the transistor Tr1 via the resistor r4.
And the emitter is grounded.

A voltage detector (IC ₁ ) 124 monitors the voltage V _{1 of the} input line, and when the voltage V ₁ is a constant value (V
₂ ) When the following occurs, a detection signal of "Low" is output to the input terminal 2C of the microcomputer 120. Then, when a “Low” detection signal is input to the input terminal of the microcomputer 20, the microcomputer 20 controls to turn off the power. Also, the coupling capacitor C ₁ is connected in parallel with the load 122.
(Reducing the AC impedance of the power supply to GND and stabilizing the AC operation of the circuit) is inserted.

As shown in FIG. 2, the control signal A output from the output terminal 2A of the microcomputer 120 is a signal that changes from "Low" to "High" at the same time when the power is turned on. The transistor Tr3 is turned on, the control current of the transistor Tr3 is supplied to the base of the transistor Tr1, the transistor Tr1 is turned on, and a small driving current is supplied to the load 122. As a result, the rush current when the power is turned on is suppressed.

The control signal B output from the output terminal 2B of the microcomputer 120 is a signal which changes from "Low" to "High" after a time t from the power-on, and the control signal B causes the other transistor Tr4 Is turned on, and the control current by the transistor Tr4 is supplied to the base of the transistor Tr1. As a result, the base of the transistor Tr1 is connected to the two transistors Tr3 and T3.
The control current by r4 is supplied, and the load 12
2 is supplied with a drive current large enough to drive No. 2 and a normal drive state is set. The time t described above is determined by coupling
With time the capacitor C ₁ is charged to a certain extent, the voltage detector 124 can detect the correct power supply voltage,
A stable operation can be obtained.

FIG. 3 is a circuit diagram showing another example of an electronic circuit provided with an inrush current suppressing circuit according to the present invention. The inrush current suppression circuit of the present example includes one control signal, a capacitor C ₂ , transistors Tr5 and Tr6, and resistors r3 and r1.
The time constant circuit using 0 to r13 turns on the two transistors Tr3 and Tr4 with a time difference, gradually increases the base current of the transistor Tr1, and turns on the load 12
2 is controlled so as to gradually increase the drive current to be supplied to the drive circuit 2.

The configuration shown in FIG. 3 corresponds to the microcomputer 2 shown in FIG.
0, the load 22, the voltage detector 24, a coupling capacitor C _1, is obtained by omitting the power E, the resistor r, 5
Are connected to the output terminals of the microcomputer 20 shown in FIG. The common configuration shown in FIG. 5 will be described using the same reference numerals. When the control signal of the output terminal of the microcomputer 20 becomes “High”, the transistors Tr3, Tr5, Tr6 are turned on at that timing. When the transistor Tr3 is turned on, the control current by the transistor Tr3 is supplied to the base of the transistor Tr1, the transistor Tr1 is turned on, and a small drive current is supplied to the load 22. As a result, the rush current when the power is turned on is suppressed.

Meanwhile, the transistor Tr5, Tr6 are turned on, although the charging of the capacitor C ₂ is started, initially has a low potential of the capacitor C _2, the transistor Tr4 is not turned on. After a certain time, is charged capacitor C _2, the transistor Tr4 is turned on, the control current by the transistor Tr4 is a transistor Tr1
Supplied to the base. Thereby, the transistor Tr
A control current by the two transistors Tr3 and Tr4 is supplied to one base, and a driving current large enough to drive the load 22 is supplied, and a normal driving state is set.

[0019] The time until the transistor Tr4 is turned on by the charging of the capacitor C ₂ as described above, by coupling capacitor C ₁ is the time that is charged to a certain extent, the voltage detector 24 can detect the correct power supply voltage,
A stable operation can be obtained. The control means for gradually increasing the drive current to the load is not limited to the above specific example, but may be variously adopted.

[0020]

As described above, in the rush current suppressing circuit of the present invention, the control means for suppressing the rush current to the load and gradually increasing the power supply current when the power is turned on is provided. For this reason, it is possible to suppress the rush current immediately after turning on the power without increasing the impedance of the power supply line, and to obtain an efficient driving state without causing a loss due to a large impedance in the normal driving state. In addition, the circuit elements can be reduced, and the device can be downsized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a specific example of an electronic circuit provided with an inrush current suppression circuit according to the present invention.

FIG. 2 is a timing chart showing control signals in the inrush current suppression circuit shown in FIG.

FIG. 3 is a circuit diagram showing another example of the inrush current suppression circuit according to the present invention.

FIG. 4 is a block diagram illustrating an example of an electronic circuit in which a general impedance element and a load are connected in series.

FIG. 5 is a circuit diagram showing a configuration example of a conventional load drive circuit.

[Explanation of symbols]

120: microcomputer, 122: load, 124: voltage detector, Tr1, Tr3, Tr4, Tr5, Tr6 ...
Transistor, C ₁ ...... Coupling capacitor, C
₂ ... capacitor, E ... power supply, r, r1 to r4, r1
0 to r13: resistance.

Claims (7)

[Claims] 1. An electronic circuit for driving a load, comprising: power supply means for supplying power to the load; power supply means for supplying power from the power supply means to the load; The inrush current of
A rush current suppression circuit in an electronic circuit, comprising: control means for gradually increasing a power supply current. 2. The control means has a first control signal for supplying a smaller power supply current and a second control signal for supplying a larger power supply current than the first control signal. When the power is turned on, the first control current is output to supply a small power supply current, and after a certain period of time, the second control current is output to supply a large power supply current, thereby gradually reducing the power supply current. 2. The inrush current suppression circuit in an electronic circuit according to claim 1, wherein the inrush current is increased. A first control circuit for controlling a power supply amount in the power supply current line; a second control circuit for controlling a control rate of the first control circuit by the first control signal; 3. The rush current suppressing circuit in an electronic circuit according to claim 2, further comprising: a third control circuit that controls a control rate of the first control circuit by the second control signal. 4. The control means according to claim 1, further comprising a control signal for supplying a power supply current, and a time constant means for gradually increasing said power supply current based on said control signal. An inrush current suppression circuit in the electronic circuit described in the above. 5. A first control circuit for controlling a power supply amount in the power supply current line, a second control circuit for controlling a control rate of the first control circuit by the control signal,
5. The inrush current suppression circuit in an electronic circuit according to claim 4, further comprising: a third control circuit for controlling a control rate of said first control circuit by a signal from said time constant means. 6. The inrush current suppression circuit according to claim 5, wherein said time constant means includes a coupling capacitor inserted in parallel with said load. 7. A power supply device comprising: a coupling capacitor inserted in parallel with the load; wherein the control means gradually increases the power supply current in accordance with a charging time of the coupling capacitor. The inrush current suppressing circuit in the electronic circuit according to claim 1.