JPH0210794Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> This invention is a switch having an input capacitor discharge circuit in which the input capacitor is discharged by an absorber resistor for preventing spikes in the output transformer attached to the switching transistor. It concerns an angular regulator.

<Prior art> As shown in Fig. 1, the input side of a switching regulator includes an input power supply AC, a rectifier 1, a smoothing input capacitor C1, and a capacitor C1 when the input power supply AC is not in operation. The circuit has a resistor R1 for discharging. Note that V1 is an input voltage applied to a series connection circuit between the primary winding of the output transformer of the switching regulator and the switching transistor. In this circuit, when there is some load on the output side of the switching regulator, the power consumed by resistor R1 is small, but when the output side becomes no-load,
The charge stored in the capacitor C1 is not completely discharged. The charge remaining in the capacitor C1 is consumed exclusively by the resistor R1, and since the input capacitor C1 has a large capacity of about 10 μF/W with respect to the output power, the resistor R1 when the output is not loaded is The current flowing through is approximately
The disadvantage is that the power usage efficiency decreases because the current is as high as 10mA.

<Problems to be solved by the invention> The purpose of this invention is to solve the above-mentioned drawbacks of switching regulators. , it is an object of the present invention to provide a switching regulator having an input capacitor discharge circuit.

<Means for solving the problem> This idea focuses on the fact that the switching transistor is equipped with an absorber resistor to prevent spikes in the output transformer, and this absorber resistor is connected to the input capacitor when the input power supply is not operating. It was used for electric discharge. That is, the switching regulator with the discharge circuit for the input capacitor of this invention connects the input capacitor, the series connection circuit of the primary winding of the output transformer, and the switching transistor between the output lines of the input power source. In addition, in a switching regulator formed by connecting this switching transistor and an absorber resistor for preventing spikes in parallel or in series, the electric charge stored in the input capacitor is discharged by the absorber resistor for preventing spikes. The gist of the present invention is to configure a circuit and provide a contact in the circuit that is closed only when the input power source is not in operation.

<Example> The example in Fig. 2 shows the operational state of the input power supply. Between the output lines of the input power supply, there is an input capacitor C1, a relay R, the primary winding of an output transformer T, and a switching circuit. transistor Q1
and series connection circuits, are connected respectively.
Also, between the primary winding of the output transformer T, there is an absorber resistor R2, a capacitor C2, and a diode D.
1, and a spike prevention circuit based on the leakage inductance of the output transformer T is connected thereto. Also, Rb is the b contact of relay R,
When relay R is out of power, it turns ON and works to connect resistor R directly between the output lines of the input power supply. On the other hand, a rectifying and smoothing circuit including diodes D2 and D3, an inductance L, and a capacitor C3 is connected to the secondary winding of the output transformer T. Note that V2 is the output voltage supplied to the load.

The embodiment in FIG. 3 also shows the state when the input side power supply is operating, and the absorber resistor R2 and capacitor C2
A spike prevention circuit consisting of the following is connected between the collector and emitter of the switching transistor Q1. Further, Rb is the b contact of the relay R that is turned on when the relay R is disconnected. The other configurations are the same as those shown in FIG. 2, so explanations will be omitted.

In each of the embodiments of this invention having the above configuration, relay R is energized when the input power supply shown in FIGS. 2 and 3 is in operation, so relay b contact Rb is
It is OFF. Therefore, even if there is no load on the output side in this state, the resistor R2 only functions as its original function of preventing spikes. On the other hand, when the input power supply is not operating, relay b contact Rb is turned on and resistor R2 is connected between the output lines of the input power supply, so the charge stored in the input capacitor C2 is quickly transferred by resistor R2. Discharged.

<Effects> The switching regulator of this invention has a structure in which the charge of the input capacitor is discharged by the spike prevention absorber resistor only when the input side power supply is not operating, so even if the output side is in a no-load state, The charge remaining in the input capacitor is not wasted. Furthermore, since the absorber resistor for preventing spikes is also used for discharging the input capacitor, there is the advantage that the increase in the number of parts can be kept to the minimum necessary.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the input side of a switching regulator having a conventional input capacitor discharge circuit, and Figs. 2 and 3 respectively show a switching regulator having an input capacitor discharge circuit of this invention. FIG. C1 to C3...Capacitor, R2...Absorber resistor, R...Relay.

Claims (1)

[Scope of utility model registration request] Connect an input capacitor, a series connection circuit between the output transformer primary winding and a switching transistor between the output lines of the input power supply, and connect the spike prevention absorber resistor in parallel or series to this switching transistor. In the switching regulator, a circuit is configured to discharge the electric charge stored in the input capacitor by the spike prevention absorber resistor. A switching regulator having a discharge circuit for an input capacitor, characterized in that a contact is provided that only closes.