JPS62239861A - Power circuit - Google Patents

Abstract

PURPOSE:To prevent excess current from being generated at the time of throwing-in of a power source, by providing a slow start circuit with the second delay circuit of a large time-constant. CONSTITUTION:So far as a DC stabilizing switching power circuit is concerned, single phase alternating current is stepped down by a power transformer T1, and is rectified and smoothed, and is fed to a main switching circuit 1 as an input power source, and is DC-stabilized to generate the output. The power source of a switching regulator ICZ1 for controlling the switching circuit 1 is fed from a control power source 2, and the voltage is slowly risen by a slow start circuit 3. In this case, the slow start circuit 3 is provided with the second delay circuit 5 of a time constant larger than that of a first delay circuit 4. Then, even if the rise of the output voltage of the control power source 2 on throwing-in of the power source is quick, the slow start circuit 3 is normally worked and rush current on start can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC stabilized switching power supply circuit, and particularly to a circuit for preventing inoperability in a slow start circuit.

[Conventional technology]

Conventionally, this type of power supply circuit, as shown in the circuit diagram of Fig. 2, steps down the single-phase AC 200V with a power transformer '1'1, rectifies and smoothes it with a rectifier stack RCI and a capacitor C1, and then outputs the main power. It is supplied as input power to the switching circuit 1, stabilized as DC, and output. The +15 V power supply for the switching regulator ICZ1 which controls the main switching circuit 1 of this power supply circuit is branched from the rectifier stacks R and CI and supplied from the control power supply s2.

The regulator ICZI converts the IC built-in reference voltage +5V to V.
The voltage is output to the outside for control purposes, and this voltage is adjusted by the variable resistor ratio 1, and the voltage applied to the input bin IA of the switching regulator ICZI and the output voltage are divided by the resistors R1 and 2. Then, the voltage applied to the input bin NA of the regulator ICZI is compared and detected, and a control pulse signal is sent to the output pin C of the regulator ICZI to the main switching circuit 1, thereby stably supplying an output voltage of +5V. By the way, when the main breaker CBl is turned on and the power is turned on, the output voltage of the control power supply 2 is supplied to the slow start circuit 3', and as the output voltage of the slow start circuit 3' gradually increases, the regirator ICZ
The reference voltage of I also increases.

When the output voltage of the control power supply 2 is lower than the voltage of the Zener diode D1 of the slow start circuit 3', the transistor Q1 is turned off, and the transistor Q2 is turned on through the resistor hole 4, driving the transistor Q3. . Transistor Q3 is turned on, and tPs capacitor C3 starts charging through resistor hole 5 to the reference voltage of 5V of regirator 1cZ1.

When the output voltage of the control power supply 2 exceeds the voltage of the Zener diode D1 of the slow start circuit 3', the transistor Q1 starts to turn on, the transistor Q2 turns off, and the transistor Q3 turns off. In this state, regulator I
Since the input bin NA of the CZI has a higher voltage than the IA bin, the control pulse signal sent to the main switching circuit 1 is a pulse signal so that the output voltage is in the minimum state.

When transistor Q3 turns off, capacitor C3 discharges through resistor R5 and resistor hole 6.

The constants of resistor holes 5 and 6 are set as R5<<R6, and switching regulator CZ1 detects the discharge voltage of capacitor C3 through diode D3 to the input bin NA, and lowers the output voltage according to that voltage. To go.

The voltage of capacitor C3 decreases, the output voltage increases,
Previous memory resistance 5. When the divided voltage of about 6 becomes larger than the voltage of the capacitor C3, control is performed by detecting the output voltage side and operates to supply a stable output voltage.

[Problem that the invention seeks to solve]

The conventional slow start circuit described above uses main breaker C.
When B1 is turned on, if the rise time of the output voltage of the control power supply 2 is fast, the transistor Q1 is turned on quickly, so the transistors Q2 and Q3 are in an off state, and the capacitor is not charged.

Input bin NA of switching regulator ICZI is O
v, which is smaller than the voltage of input bin IA, so switching regulator ICZ1 is 1 ul lower than output bin C.
The J control pulse signal is sent to the main switching circuit 1 so that the output voltage is maximized.

The main switching circuit 1 follows the control pulse signal,
Since it operates so as to rapidly raise the output voltage, a rush current is generated, which may lead to disconnection of the input fuse F1. In addition, there is a drawback that when the output voltage rises, overvoltage detection due to the overrun rate may cause abnormal power cut-off.

An object of the present invention is to provide a power supply circuit in which no overcurrent flows when the power is turned on by improving the slow start circuit.

[Means for solving problems]

The configuration of the present invention includes a rectifier circuit that rectifies an AC power source, a main switching circuit that stabilizes the output of the rectifier circuit according to a control pulse signal, and a control circuit that supplies the output of the rectifier circuit and outputs a DC voltage. a slow start circuit that outputs a startup output delayed from the output of the control power supply according to a first delay circuit; and a switching regulator that receives the slow start output and the DC voltage as input and outputs the control pulse signal. A power supply circuit comprising: a second delay circuit having a larger time constant than the first delay circuit in the slow start circuit;
The output is slow and the output is slow.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. When the main breaker CBI is turned on, if the output voltage of the control power supply 2 rises quickly, and the Zener voltage of the Zener diode D1 of the slow start circuit 3 is exceeded, the transistor Q1 is turned on, and the capacitor C4 has a time constant of C4 x 几4. (second delay circuit). When the capacitor C4 is charged to a level higher than the Zener voltage of the Zener diode D4, the transistor Q2 turns on.
During the time when the transistor Q4 is turned on, the transistor Q4 is biased by the drive resistance ratio 10 and turns on, turning on the transistor Q3 and charging the capacitor C3 (first delay circuit).
. At this time, the relationship between the time constants for charging the capacitors C3 and C4 is that they are charged more quickly than the C4XR4 capacitor C4. When the transistor Q2 is turned on, the transistor Q4 is turned off, the capacitor C3 begins to discharge, and the slow start circuit 3 operates normally.

〔Effect of the invention〕

As explained above, the present invention provides circuit breaker CB1.
Even if the output voltage of the control power supply 2 rises quickly when the power is turned on, the slow start circuit 3 operates normally, suppressing the rush current at the time of startup, and smoothly raising the output voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. 1... Main switching circuit, 2...
...control power supply, 3.3'...slow start circuit, 4...group-first delay circuit, 5...second
delay circuit, CBI...circuit breaker,
01~C4...Group/Capacitor, DI, D4...
・Zener diode, D2゜D3...Diode, Q1~Q4...Transistor, 几1~几10...Resistor, C1...Rectifier stack , RVI...variable resistor, Fl...
・Fuse, Tl...Power transformer, Zl/Old...Switching regulator ■C0'-\. Agent Patent Attorney Susumu Uchihara ・、－ノ

Claims (1)

[Claims] A rectifier circuit that rectifies an AC power source, a main switch circuit that stabilizes the output of this rectifier circuit according to a control pulse signal and outputs it, a control power source that supplies the output of the rectifier circuit and outputs a DC voltage, and this control power source. In the power supply circuit, the power supply circuit includes a slow start circuit that takes out a rising output whose output is delayed according to a first delay circuit, and a switching regulator that receives the slow start output and the DC voltage as input and outputs the control pulse signal. A power supply circuit characterized in that a start circuit is provided with a second delay circuit having a larger time constant than the first delay circuit, so that the input voltage of the DC voltage rises later than the rise output of the slow start circuit.