JPS6062867A - Power source circuit - Google Patents

Abstract

PURPOSE:To enable to supply a stable voltage to a load with respect to the variation in an input power source of wide range by altering the base current supply value of a switch element by the amplitude of an input voltage. CONSTITUTION:A Zener diode 12 and a transistor 13 are connected in series with a feedback winding 3c of a transformer 3. A feedback resistor is divided into two resistors 5a, 5b, and a resistor 14 and a transistor 13 are connected between the connecting point and an earth. The voltage generated at the feedback winding 3c of the transformer 3 is varied in response to the variation in the input power source 1, the transistor 13 is controlled ON or OFF, thereby stabilizing the output voltage under the control of the current supplied to the base of the transistor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the realization of a self-excited switching regulator that has a wide control range with respect to input power supply voltage.

[Background of the invention]

FIG. 1 shows a commonly used automatic switching regiator circuit.

1 is an uncontrolled DC voltage, 2 is a switching element, 3 is a switching transformer, 4 is a resistor that supplies a starting current for the switching element, and the winding 3c, resistor 5, and capacitor 6 are a positive feedback self-excited switching oscillator circuit. is formed. The switching voltage generated by the transformer 3 for 3 hours is supplied to a rectifying load 9 through a diode 7 and a capacitor 8.

The above voltage fluctuation is amplified by the error detection circuit 10 and the drive circuit 11 to control the base current of the switching element 20. This turns on the switching of switch element 2.
/ OFF duty is a closed loop circuit that suppresses changes in the voltage applied to the load.

In such a circuit, when the input power source 1 changes greatly, trying to keep the voltage applied to the load 9 constant has the following drawbacks.

That is, in order to extend the control range to a low input power supply voltage, it is necessary to sufficiently drive the switching element 2 by the feedback winding 3C. However, as the input power increases, the voltage generated in the feedback winding increases, and an excessive Pesumi current is supplied to the switch element 2, resulting in poor rise and fall times when the switch element 2 turns on and off. and losses will increase. Also, conversely, a high input power supply voltage will cause a problem.

If the feedback winding of the transformer 3 is designed to supply an appropriate pace current to the switch element 2, there is a drawback that the load voltage is not constant when the input power source is low.

[Purpose of the invention]

The object of the present invention is to eliminate the above drawbacks and provide a circuit system that supplies a stable voltage to a load over a wide range of changes in input power.

[Summary of the invention]

The present invention has a switch circuit that changes the pace current supply value of the switch element 2 depending on the level of the input power source.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
Parts that are equivalent to those in the figure are given the same reference numerals as in FIG. 1. The difference is that a Zener diode 12 and a transistor 13 are arranged in series from the feedback winding sC of the transformer 3, and that the feedback resistor 5 is divided.

Connect the two resistors 5α and 5A and connect the resistor 14 to the top from their intersection.

This is where the collector of the transistor 13 is placed.

different.

That is, when the input power supply 1 becomes high, the voltage applied to the feedback winding 5C of the transformer 3 becomes high, and this exceeds the threshold of the Zener diode 12. As a result, the transistor 13 is turned on, and the current supplied to the pace of the transistor 2 is bypassed by the resistor 14. This can prevent an excessive pace current from flowing into the pace of transistor 2. When the input power becomes low, Zener diode 12 is cut off, and transistor 13 is also cut off.
Since the pace current is not bypassed by the resistor 14, the transistor 2 can be sufficiently turned on and off, making it controllable.

〔Effect of the invention〕

According to the present invention, it is possible to realize a switching regulator that is compatible with a wide range of input power sources while reducing transistor loss.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional self-excited switching regulator, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Input power supply, 2... Switching output transformer, 3... Switching transformer, 12... Zener diode for input power supply detection, 13...
・Switch transistor. 1 figure, 2 figures

Claims (1)

[Claims] In a self-excited switching regulator, the primary coil of a transformer and a switching transistor are connected in series to the power supply, and the tertiary coil of the transformer is connected to the base of the transistor of this element. A power supply circuit comprising a switch that detects the current and changes the current flowing from the tertiary coil to the base of the transistor.