JPH044827B2 - - Google Patents

Description

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

[Conventional technology]

Conventionally, this type of power supply circuit, as shown in Figure 2, rectifies and smoothes single-phase AC 200V in a power input rectifier and smoothing circuit 5, supplies it as the input power to the main switching circuit 1, stabilizes the DC current, and outputs the power. In the circuit, a power supply of +15V for an output voltage detection control circuit 6 that controls a main switching circuit 1 is supplied from a control power supply 2.

The power input rectifying and smoothing circuit 5 steps down the single-phase AC 200 V through the power transformer T1, and converts the voltage into the rectifying staff RC.
1 and capacitor C1 to rectify and smooth the main
It is supplied to the switching circuit 1, and is also branched from the rectifying staff RC1 and supplied to the control power supply 2.

In the slow start circuit 3, a Zener diode D1 and a resistor R3 are connected in series from one output line (15V) of the control power supply 2 to the other ground, and a resistor R3 is connected in series to the ground.
4 and the transistor Q1 are connected in series, and the connection point between the Zener diode D1 and the resistor R3 is connected to the base of the transistor Q1. Further, resistors 8, 7, a diode D2 and a transistor Q2 are connected in series from the pin V _R of the switching regulator integrated circuit Z1 in the output voltage detection control circuit 6 to the other output line of the control power supply 2, and a resistor R4 and a transistor Q2 are connected in series. A connection point of the collector of transistor Q1 is connected to the base of transistor Q2. Further, a diode D3 is connected to the input pin NA of the switching regulator integrated circuit Z1, and a resistor R6, a resistor R5 connected in series, and an electrolytic capacitor C3 are provided between the diode D3 and the other output line of the control power supply 2. ,
Transistor Q3 has its base connected to the connection point of resistors R7 and R8, and its emitter connected to pin V _R of switching regulator integrated circuit Z1, and its collector connected to diode D.
3. It is connected to the connection point of resistors R5 and R6.

The output voltage detection control circuit 6 includes a switching regulator integrated circuit Z1, resistors R1 and R2, a variable resistor RV1, and a capacitor C2 provided between the output lines of the main switching circuit 1.

The switching regulator integrated circuit Z1 outputs the built-in reference voltage +5V from pin VR for external control, and this voltage is adjusted by variable resistor RV1, and the voltage applied to input pin IA of integrated circuit Z1 and output The voltage is divided by resistors R1 and R2 and the voltage applied to the input pin NA of the regulator integrated circuit Z1 is compared and detected, and a control pulse signal is sent to the main switching circuit 1 at the output pin C of the regulator integrated circuit Z1. Sends out and stably supplies output voltage +5V. By the way, main breaker CB1
(connected between the single-phase AC 200V and the power transformer T1) and the power is turned on, as the output voltage of the control power supply 2 gradually increases, the reference voltage of the regulator integrated circuit Z1 also increases.

When the output voltage of the control power supply 2 is less than the voltage of the Zener diode D1, the transistor Q1 is turned off.
(blocking), transistor Q2 is connected to resistor R4
turns ON (conducts) through the transistor Q3, and drives the transistor Q3. Transistor Q3 turns on, and electrolytic capacitor C3 starts charging through resistor R5 to the reference voltage of regulator integrated circuit Z1 of 5V.

When the output voltage of control power supply 2 exceeds the voltage of Zener diode D1, transistor Q1 turns on.
The transistor Q2 starts to turn off, turning off the transistor Q3. In this state, since the input pin NA of the regulator integrated circuit Z1 has a higher voltage than the pin IA, the control pulse signal sent to the main switching circuit 1 is a pulse signal so that the output voltage becomes the minimum state. Transistor Q3
When OFF, capacitor C3 discharges through resistor R5 and resistor R6.

The constants of resistors R5 and R6 are set as R5<R6, and the regulator integrated circuit Z1 is connected to the input pin.
Pass diode D3 through NA, capacitor C3
The output voltage is increased according to the detected discharge voltage.

When the voltage of capacitor C3 decreases and the output voltage increases, and the divided voltage of resistors R1 and R2 becomes larger than the voltage of capacitor C3 divided by resistors R5 and R6, the control detects the output voltage side. It operates to supply a stable output voltage.

[Problem that the invention seeks to solve]

In the conventional power supply circuit described above, when the slow start circuit turns on main breaker CB1, if the rise time of the output voltage of control power supply 2 is fast, transistor Q1 turns on quickly, so transistors Q2 and Q3 are turned off. Therefore, capacitor C3 will not be charged.

The input pin NA of the integrated circuit Z1 is 0V, which is smaller than the voltage of the input pin IA, so the integrated circuit Z
1 sends a control pulse signal from the output pin C to the main switching circuit 1 so that the output voltage is maximized.

Since the main switching circuit 1 operates to rapidly raise the output voltage according to the control pulse signal, the inrush current is large, and the input fuse F1 (connected between the power transformer T1 and the rectifier stack RC1)
May lead to amputation. Further, there are drawbacks such as abnormal power cut-off due to overvoltage detection due to overshoot when the output voltage rises.

[Means for solving problems]

The present invention includes a power input rectifying and smoothing circuit 5, a main switching circuit 1 to which a current rectified and smoothed by the power input rectifying and smoothing circuit 5 is supplied,
A control signal is generated depending on the comparison state between a voltage proportional to the output voltage of the main switching circuit 1 inputted from the input terminal NA and a voltage proportional to the reference voltage outputted to the reference voltage terminal VR and inputted from the other input terminal IA. an output voltage detection control circuit 6 for stabilizing the output voltage of the main switching circuit 1 by sending out the output voltage, a control power supply 2 for supplying power to the output voltage detection control circuit, and an output of the main switching path 1. The slow start circuit 3 has a slow start circuit 3 for gradually raising the voltage, and the slow start circuit 3 has one end connected to the ground and the other end connected to the reference voltage terminal VR via the first transistor Q3. Condenser C3
and the first transistor Q, which becomes conductive when the output voltage of the control power supply 2 rises and is connected to the reference voltage terminal VR via the first resistor R8.
By displacing the voltage of the base of No. 3 to the earth side,
conducts the transistor Q3 to charge the first capacitor C3, and after the pre-output voltage of the control power source 2 rises above a certain voltage, shuts off the transistor Q3, and also shuts off the first transistor Q3. a second transistor Q2 for discharging the capacitor C3 through a parallel second resistor R6;
capacitor C3 and the first transistor Q
a diode D3 that transmits a voltage between the reference voltage terminal VR and the earth to the input terminal NA; a second capacitor C4 connected in parallel with the third resistor R9; and a fifth resistor R1 whose base is provided between the base of the first transistor Q3 and the ground.
1 through the third and fourth resistors R9, R10
and a third transistor Q4 connected between the third and fifth resistors R when the reference voltage output from the reference voltage terminal VR rises.
9, R11 and the second capacitor C4, the third transistor Q4 is made conductive, thereby making the first transistor Q3 conductive.

〔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. In FIG. 1, a slow start drive circuit 4 is added to the power supply circuit shown in FIG. The slow start drive circuit 4 includes an integrated circuit Z
Resistors R9 and R10 are connected in series between pin VR of No. 1 and the ground, and the base is connected between the connection point of the resistor R7 and diode D2 in the slow start circuit 3 and the ground through the resistor R11. Resistance R9, R1
A transistor Q4 connected to the node 0 and a capacitor C4 connected in parallel with the resistor R9 are provided. When main breaker CB1 is turned ON, even if the rise time of the output voltage of control power supply 2 is fast, since the slow start drive circuit 4 is added, capacitor C4 is not charged and transistor Q4 is OFF. The transistor Q3 is turned OFF, and when the transistor Q4 is turned ON from the reference voltage power supply of the switching regulator integrated circuit Z1 through the capacitor C4 and resistors R9 and R11, the transistor Q3 of the slow start circuit 3 is driven, and the transistor Q3 is turned on. Turn on and charge capacitor C3. At this time, the constant of the resistor of the slow start drive circuit is R9>>R10=R11, and there is a relationship of R10/R9+R10<0.7/5, capacitor C4 is charged and transistor Q4 is turned off. Then, transistor Q
3 are turned off at the same time, the capacitor C3 starts discharging, and the slow start circuit 1 operates normally.

〔Effect of the invention〕

As explained above, the present invention adds a slow start drive circuit consisting of a second capacitor, second and third resistors, and a third transistor, thereby reducing the power supply to the rectifier circuit by the main breaker, etc. Even if the rise time of the output voltage of the control power supply is fast when the power is turned on, the slow start circuit consisting of the first and second transistors, the first capacitor, etc. is driven to operate normally, and the inrush current at startup is reduced. This has the effect of suppressing the output voltage and allowing the output voltage to rise smoothly.

[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 power supply circuit. CB1...Circuit breaker, T1...Power transformer, F1...Fuse, C1-C4...Capacitor, R1-R11...Resistor, D1...Zener diode, D2, D3...Diode, Q
1 to Q4...Transistor, RV1...Variable resistor, Z1...Switching regulator IC, 1
... Main switching circuit, 2 ... Control power supply, 3 ... Slow start circuit, 4 ... Slow start drive circuit.

Claims (1)

[Claims] 1. A power input rectifying and smoothing circuit 5, a main switching circuit 1 to which a current rectified and smoothed by the power input rectifying and smoothing circuit 5 is supplied, and an input terminal.
The voltage proportional to the output voltage of the main switching circuit 1 input from NA and the reference voltage terminal VR
an output voltage detection control circuit 6 which stabilizes the output voltage of the main switching circuit 1 by sending out a control signal in proportion to the reference voltage outputted from the main switching circuit 1 and according to a comparison state with a voltage inputted from another input terminal IA; ,
It has a control power supply 2 for supplying power to the output voltage detection control circuit, and a slow start circuit 3 for gradually raising the output voltage of the main switching circuit 1, and one end of the slow start circuit is grounded. a first capacitor C3 whose other end is connected to the reference voltage terminal VR via a first transistor Q3;
and the first transistor Q, which becomes conductive when the output voltage of the control power supply 2 rises and is connected to the reference voltage terminal VR via the first resistor R8.
By displacing the voltage of the base of No. 3 to the earth side,
The transistor Q3 is made conductive to charge the first capacitor C3, and after the output voltage of the control power source 2 rises above a certain voltage, the transistor Q3 is cut off, and the first transistor Q3 is also cut off. a second transistor Q2 that discharges a capacitor C3 through a parallel second resistor R6, and a diode D3 that transmits the voltage between the first capacitor C3 and the first transistor Q3 to the input terminal NA. In the power supply circuit, third and fourth resistors R9 and R10 are connected in series between the reference voltage terminal VR and the earth, and a second capacitor C4 is connected in parallel with the third resistor R9. , which is provided between the base of the first transistor Q3 and the ground, and whose base is connected to a fifth resistor R1.
1 through the third and fourth resistors R9, R10
and a third transistor Q4 connected between the third and fifth resistors R when the reference voltage output from the reference voltage terminal VR rises.
9, R11 and the second capacitor C4, the third transistor Q4 is made conductive, thereby making the first transistor Q3 conductive.