JPH08140344A - Switching power supply apparatus - Google Patents

Abstract

PURPOSE: To provide a switching power supply apparatus by which the release time of a latch operation for a control circuit is shortened for quick restart. CONSTITUTION: A drive power supply generation circuit 14 fr-start is constituted of an auxiliary rectifier circuit 15 connected in parallel with an AC power supply 1 together with a rectifying circuit 11 and of resistors R2, R3 and a capacitor C2 connected in series with the output side of the auxiliary rectifier circuit 15. It is formed in such a way that the capacitor C2 of a small capacitance can be self-discharged in a short time without being affected by the discharging time of a large capacitance smoothing capacitor C1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching system in which a primary DC power supply circuit having a control circuit with a protective latch function and a secondary DC power supply circuit to which a load is connected are coupled and connected via a transformer. Regarding power supply.

[0002]

2. Description of the Related Art In FIG. 2, a primary DC power supply circuit 10 connected to an AC power supply 1 and a secondary DC power supply circuit 30 connected to a load 100 are coupled and connected via a transformer 20. The primary DC power supply circuit 10 is composed of a rectifier (diode bridge) 11, a smoothing capacitor C1, a switching element 12, a control circuit 13, and a startup drive power supply generation circuit 14P. 2 is a power switch, 3 is a noise filter, and R1 is a discharge resistor.

The transformer 20 has a primary winding Np1,
It has an auxiliary winding Np2 and a secondary winding Ns1. The secondary DC power supply circuit 30 includes a diode D2 and smoothing capacitors C3 and C4, generates and outputs a secondary DC power supply (voltage V), and supplies it to the load 100.

Further, the stabilizing circuit 31 outputs a voltage feedback signal fs to the control circuit 13 on the primary side via a photocoupler 32 for electrical insulation when the secondary DC power supply voltage V exceeds a set voltage value. . Then, the control circuit 13
Generates and outputs the control signal S to turn on the switching element 12.
-OFF control. Therefore, the amount of power energy supplied from the primary side (10) to the secondary side (30) can be controlled via the transformer 20, so that the secondary DC power supply voltage V can be stabilized at the set voltage value.

Further, the control circuit 13 controls the protection signal (fi,
Based on fv), it has a latch function capable of continuously outputting the control signal S for keeping the switching element 12 in the OFF state. The protection signal includes an overcurrent protection signal fi detected by an overcurrent detection circuit (resistor R4) on the primary side and a secondary side (3
0) is an overvoltage protection signal fv detected by the overvoltage detection circuit (Zener diode ZD1, resistor R5) 33 and input via the photocoupler 34.

Here, the drive power source of the control circuit 13 (voltage V
d) is the auxiliary winding N of the transformer 20 during continuous operation
It is generated and secured by the cooperation of the diode D1 and the capacitor C2 based on the power (current) energy supplied from p2. Thus, in preparation for so-called start-up up to this point, a start-up drive power supply generation circuit 14P including resistors R2 and R3 and the capacitor C2 is provided.

The protection signals (fi, f) of the control circuit 13
The latch operation due to the input of v) can be canceled by setting the drive power supply voltage Vd to a set voltage value or less. That is, the power switch 2 may be turned off once to shut off the AC power supply 1.

[0008]

By the way, the AC power supply 1
Of the capacitor C2 in order to meet the demand for shortening the start-up time from when the power is turned on until the secondary DC power supply voltage V reaches the set voltage value, that is, in order to early establish the control-enabled state of the control circuit 13. Tends to be smaller. On the other hand, the capacity of the smoothing capacitor C1 tends to increase in order to improve the voltage waveform with respect to the voltage fluctuation of the AC power source 1 and to enhance the stability. For example, the capacity of the capacitor C2 is 20
More than double.

However, in the above-described conventional startup drive power supply generation circuit 14P, if the discharge action through the discharge resistor R1 of the large-capacity smoothing capacitor C1 is not completed while the AC power supply 1 is cut off, The subsequent discharge action of the capacitor C2 cannot be started. That is, the time for releasing the latch operation of the control circuit 13 becomes long. That is, the restarting (startup) of the AC power source is restarted and the speed is delayed.

An object of the present invention is to provide a switching power supply device capable of shortening the release time of the latch operation of the control circuit and rapidly restarting.

[0011]

A switching power supply device according to the present invention is formed by including a rectifier circuit, a smoothing capacitor, a switching element, a control circuit, and a startup drive power supply generation circuit, and a protection input to the control circuit. In a switching power supply device, a primary DC power supply circuit provided with a latch function for holding a switching element in an OFF state based on a signal and a secondary DC power supply circuit to which a load is connected are coupled and connected via a transformer, The startup drive power supply generation circuit,
The auxiliary rectifier circuit is connected in parallel with the rectifier circuit to an AC power source, and a resistor and a capacitor are connected in series to the output side of the auxiliary rectifier circuit.

[0012]

In the present invention having the above structure, when the protection signal is input, the control circuit forcibly turns off the switching element.
The latch function keeps the OFF state continuously. Therefore, it is possible to protect components and loads from overcurrent and overvoltage.

When the cause of the overcurrent disappears, the AC power supply is once turned off to stop the auxiliary rectifier circuit, and then the auxiliary rectifier circuit is turned on (ON) to restart. During a power failure until the AC power is turned on again, the small-capacity capacitor forming the startup drive power generation circuit can self-discharge in a short time. That is, the latch operation of the control circuit can be released quickly.

Therefore, even if the capacity of the smoothing capacitor forming the primary DC power supply circuit is large, it is not affected by this discharge time, so that a quick restart can be performed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, this switching power supply device has the same basic structure (10, 20, 30, etc.) as that of the conventional example (FIG. 2).
Is a new one including the sub rectifier circuit 15, and is configured to be capable of rapid restart.

The same components as those in the conventional example (FIG. 2) are designated by the same reference numerals, and the description thereof will be simplified or omitted.

In FIG. 1, the drive power supply generation circuit 1 at the time of start-up
Reference numeral 4 denotes a sub-rectifier circuit 15 connected in parallel with a rectifier circuit 11 forming a primary DC power supply circuit 10 in the AC power supply 1, and a resistor R.
2 · R3 and a capacitor C2. The capacitor C2 also serves as the capacitor (C2) for the generation circuit of the driving power supply (voltage Vd) during continuous operation.

In the case of this embodiment, the sub rectifier circuit 15 is
It is a half-wave rectification system composed of two diodes D11 and D12. A full-wave rectification method may be used as in the rectification circuit 11.

In the embodiment having such a configuration, when the AC power source (AC) 1 is first turned on, the sub rectifier circuit 15 (D11, D)
12) and the current flows through the capacitor C2 through the resistors R2 and R3, and the drive power (voltage Vd) of the control circuit 13 is generated and secured.

Then, the control circuit 13 outputs the control signal S to ON-OFF control the switching element 12,
The next DC power supply voltage V is supplied to the load 100. The secondary DC power supply voltage V is stabilized by inputting the voltage feedback signal fs based on the stabilizing circuit 31 to the control circuit 13.

During such continuous operation, the diode D1 and the capacitor C are supplied by the current supplied from the auxiliary winding Np2.
The driving power source (Vd) is secured by the cooperation with 2.

When the overcurrent protection signal fi detected by the overcurrent detection circuit (resistor R4) or the overvoltage protection signal fv detected by the overvoltage detection circuit 33 (ZD1, R5) on the secondary side is input here. , The control circuit 13 causes the control signal S to disappear (L level) and turns off the switching element 12,
The power supply energy to the secondary side (30) is cut off. That is, the components and the load 100 are protected, and the OFF state is held by the latch function.

When restarting after confirming that the factors of overcurrent and overvoltage have disappeared, the power switch 2 is operated to turn off the AC power supply 1 once. Then, the sub rectifier circuit 15 is stopped, so that the capacitor C2 starts self-discharge. At this time, the large-capacity smoothing capacitor C1 also discharges through the discharge resistor R1.

The self-discharge time of the small-capacity capacitor C2 is short. Therefore, when the driving power supply (voltage Vd) becomes equal to or lower than the set voltage value, the latch operation of the control circuit 13 is canceled. Thus, when the AC power supply 1 is turned on again, the sub rectifier circuit 15 operates, the capacitor C2 is charged again and in a short time, the drive power supply (Vd) is established, and it can be restarted rapidly.

According to this embodiment, however, the startup drive power supply generation circuit 14 is connected to the AC power supply 1 in parallel with the rectifier circuit 11 and the auxiliary rectifier circuit 15 is connected to the output side of the auxiliary rectifier circuit 15. It is composed of resistors R2 and R3 and a capacitor C2 connected in series, and has a small capacitance C2 without being affected by the discharge time of the large smoothing capacitor C1.
Since it is formed so as to be self-dischargeable in a short time, the latch operation of the control circuit 13 can be released in a short time. Therefore, it is possible to achieve restart by rapid startup.

Further, since the auxiliary rectifier circuit 15 of the startup drive power supply generation circuit 14 is formed by the two diodes D11 and D12, it can be realized with a simple structure and at low cost.

Further, the drive power supply generation circuit (Np2, Np2) during continuous operation of the capacitor C2 of the start-up drive power supply generation circuit 14 is in operation.
Since it is formed to also serve as the capacitor C2 of D1 and C2), it can be realized at low cost also from this point.

Further, the latch operation time of the control circuit 13 is determined by the self-discharge time of the capacitor C2 and is not affected by the discharge time of the smoothing capacitor C1. Therefore, the capacity of the capacitor C2 can be made smaller, and the startup time of the drive power supply (Vd) at startup can be greatly shortened.

Furthermore, since the discharge time of the smoothing capacitor C1 does not affect the time for releasing the latch operation, the capacity of the smoothing capacitor C1 can be increased. Therefore, the voltage quality and the like can be significantly improved, and the power energy efficiency can be improved because the power source can be restarted without being completely discharged.

[0030]

According to the present invention, the startup drive power supply generation circuit has a sub rectifier circuit in which an AC power supply is connected in parallel with the rectifier circuit, and a resistor and a capacitor connected in series to the output side of the sub rectifier circuit. Since the small-capacity capacitor can be self-discharged in a short time without being affected by the discharging time of the large-capacity smoothing capacitor, the latch operation of the control circuit can be canceled in a short time. Therefore, it is possible to achieve restart by rapid startup.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram for explaining a conventional example.

[Explanation of symbols]

 1 AC power supply 10 Primary DC power supply circuit 11 Rectifier circuit 12 Switching element 13 Control circuit 14, 14P Startup drive power supply generation circuit 15 Sub rectifier circuit 20 Transformer 30 Secondary DC power supply circuit 31 Stabilization circuit 32 Photocoupler 33 Overvoltage detection circuit 34 Photocoupler 100 Load C1 Smoothing capacitor C2 Capacitor C3, C4 Smoothing capacitor D2 Diode D11, D12 Diode fi Overcurrent protection signal (protection signal) fs Voltage feedback signal fv Overvoltage protection signal (protection signal) Np1 Primary winding Np2 Auxiliary winding Ns1 secondary winding R2, R3 resistance R4 resistance S control signal Vd drive current

Claims (1)

[Claims] 1. A latch function which includes a rectifying circuit, a smoothing capacitor, a switching element, a control circuit, and a startup drive power supply generation circuit, and which holds the switching element in an OFF state based on a protection signal input to the control circuit. In a switching power supply device comprising a primary DC power supply circuit provided with and a secondary DC power supply circuit to which a load is connected via a transformer, the startup drive power supply generation circuit is used as an AC power supply. A switching power supply device comprising a sub-rectifier circuit connected in parallel with the rectifier circuit, and a resistor and a capacitor serially connected to an output side of the sub-rectifier circuit.