JPH02184272A - Power circuit - Google Patents

Abstract

PURPOSE:To constitute a power circuit simply and inexpensively by a method wherein a feedback transformer is provided with a third winding to change the inductance of the feedback transformer by a transistor of a base current control means. CONSTITUTION:A power circuit is constituted of the rectifying circuit of a commercial AC power source 1 and a self-exciting oscillating circuit 14 consisting of a transistor 4, a transformer 6, a feedback transformer 10 and the like to supply an electric power to a load 9 from the secondary winding 8 of the transformer 6. The feedback transformer 10 is provided with a third winding 16 while a rectifying and smoothing means 19, a transistor 20 and the base current control means 22 thereof are connected to the third winding 16. As a result, the power, conducted through the third winding 16, is changed by the transistor 20 to change the inductance of the feedback transformer 10 whereby the frequency and the load output of the title circuit may be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a power supply circuit capable of controlling frequency and load output.

(Prior Art) As a conventional power supply circuit of this camphor, the configuration shown in FIG. 3, for example, is known. The power supply circuit shown in Fig. 3 is
A commercial AC power supply 1 is connected to the input side of a rectifier circuit 2, and the output side of this rectifier circuit 2 is connected to a resonant capacitor 3 from the positive output end.
and is connected to the negative output terminal of the rectifier circuit 2 via the collector and emitter of the transistor 4. Further, the base of the transistor 4 is connected to the positive output terminal of the rectifier circuit 2 via a starting resistor 5. Further, a primary winding 7 of an oscillation transformer 6 is connected in parallel to the capacitor 3, and a load 9 and a saturable reactor 11 of a feedback transformer 10 are connected in series to the secondary winding 8 of the oscillation transformer 6. There is. On the other hand, one end of the secondary winding 8 of the feedback transformer 10 is connected to the emitter of the transistor 4;
! ! The end is connected to the base of the transistor 4 via a coupling capacitor 13. Note that a self-help oscillation circuit 14 is formed by the transistor 4, the feedback winding 12, the resonant capacitor 3, the coupling capacitor 13, the oscillation transformer 6, and the like.

This power supply circuit rectifies AC from a commercial AC power supply 1 in a rectifier circuit 2, supplies a base current to a transistor 4 via a starting resistor 5, turns on the transistor 4, and connects the primary winding of an oscillation transformer 6. 7, the capacitance of the resonant capacitor 3 and the primary winding 8 of the oscillation transformer 6
It oscillates at a frequency determined by the inductance of 7, etc., and induces an alternating current voltage in the secondary winding 8 of the oscillation transformer 6.
Provides power to the load. At this time, the saturable reactor 11
The current flowing through the load 9 side is returned to the power supply side primary winding 12 through the feedback transformer 10, and the base current of the transistor 4 is controlled via the capacitor 13.

(Problem to be solved by the invention) However, in the case of the power supply circuit shown in FIG.
Although the switching characteristics are good in class circuits, etc., the range of frequencies and outputs that can be used is narrow, and it can only be used for circuits with a certain frequency or a certain output. Not suitable for control. Further, there is a problem in that when input/output fluctuations occur, heat is generated in the transistor 4 as a switching element.

The present invention was made in view of the above problems, and an object of the present invention is to provide a power supply circuit that can vary the frequency and load output to any desired value, and further prevents heat generation and destruction of switching elements.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a power supply circuit having a self-help oscillation circuit that induces an output in the secondary winding of an oscillation transformer and switches a switching element according to the output of the feedback winding of a feedback transformer. The feedback transformer is provided with a third winding, and the third winding includes a rectifying and smoothing means for rectifying and smoothing the power induced in the third winding, and the rectifying and smoothing means has an emitter-collector. a connected transistor, a base power source that supplies base current to the transistor,
and base current control means for controlling the base current of the transistor.

A second invention is the invention according to claim 1, in which the base power source is connected to an auxiliary winding provided in the oscillation transformer, and a base rectifying and smoothing means for rectifying and smoothing the power induced in the auxiliary winding. It is equipped with the following.

(Function) The present invention switches the switching element of the self-help oscillation circuit by returning the current flowing through the feedback transformer to the feedback winding. Further, alternating current is induced in a third winding provided in the feedback transformer, and converted to direct current by a rectifying and smoothing means. and,
This rectified and smoothed direct current is supplied to the emitter and collector of the transistor, and a base current is supplied by the base power supply, and the base current is controlled by the base current control means and is supplied to the base of the transistor. By changing the power flowing through the windings, the frequency and load output on the output side of the oscillation transformer can be arbitrarily changed.

A second invention is the invention according to claim 1, in which a voltage is induced in the auxiliary winding of the oscillation transformer, rectified and smoothed by the base rectification and smoothing means, and the base current to be supplied to the transistor by the base current control means is 1 lil III. This supplies a base current to the base of the transistor and controls the current flowing to the third winding of the feedback transformer.

(Embodiment) Hereinafter, an embodiment of the power supply circuit of the present invention will be described with reference to the drawings. Note that the same parts as those of the conventional power supply circuit shown in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted.

In the power supply circuit shown in FIG. 1, a third winding 16 is provided in the feedback transformer 10 of the power supply circuit shown in FIG. A rectifying and smoothing means 19 is connected. The collector and emitter of a transistor 20 are connected in parallel with the capacitor 18 of this rectifying and smoothing means 19, a resistor 21 is connected between the base and collector of this transistor 20, and a variable resistor 22 as a base current control means is connected between the base and emitter.
is being followed. Further, the third winding 16 and the rectifying and smoothing means 19 constitute a base power source 23.

The power supply circuit shown in FIG. induce exchange. This alternating current flows through diode 1
7, the current is smoothed by a capacitor 18, and the current is supplied to the collector of the transistor 20.
1 and a variable resistor 22, and a base current is supplied to the base. Then, the base current is varied by the variable resistor 22, and by changing the inductance of the saturable reactor 11, the frequency and load output are changed.

The power supply circuit shown in FIG. 2 is another embodiment in which the base power supply 23 of the power supply circuit shown in FIG. A base rectifying and smoothing means 21 composed of a rectifying diode 25 and a smoothing capacitor 26 is provided in the base rectifying and smoothing means 27 .
One end of the resistor 6 is connected to the resistor 21, and the other end is connected to the connection point between the emitter of the transistor 20 and the variable resistor 22.

This power supply circuit shown in FIG. The base current is adjusted by changing the voltage division ratio with 21, and is supplied to the base of the transistor 20. When input fluctuations, load output fluctuations, or temperature changes occur, the voltage induced in the auxiliary winding 24 fluctuates, and for example, as the input or load output increases, the output of the base power supply 23 increases, By increasing the base current of the transistor 20 and increasing the output of the transistor 20, the load output is suppressed, and conversely, by decreasing the input or load output, the base power supply 2
3 decreases, the base current of the transistor 20 decreases, and the output of the transistor 20 decreases.
Suppress load output.

According to the embodiment shown in FIG. 2, the voltage induced in the auxiliary winding 24 of the oscillation transformer 6 is rectified by the diode 25 and smoothed by the capacitor 26, and the base current of the transistor 20 is controlled. Since the output can be controlled, the load output can be kept constant even if input fluctuations, load output fluctuations, or temperature fluctuations occur.

Furthermore, in any of the above embodiments, the frequency and load output are controlled by controlling the DC current flowing through the third winding 16 provided in the feedback transformer 10. The frequency and load output can be controlled arbitrarily while maintaining oscillation. In addition, by detecting the input/output voltage and current, control can be performed on either the negative side or the secondary side, and furthermore, there is no need for insulation elements such as current transformers and photocouplers, making it simple and inexpensive. Can be configured.

〔Effect of the invention〕

The present invention provides a third winding in the feedback transformer, and the third winding is provided in the feedback transformer.
The power induced in the winding is rectified and smoothed by the rectifying and smoothing means, the output of the transistor is changed by the base current control means, and the inductance of the feedback transformer is changed by the transistor, so the load output can be adjusted to any frequency and load output. can be varied.

Further, the second invention provides an auxiliary winding in the oscillation transformer,
By controlling the transistor with the output induced in the auxiliary winding of the oscillation transformer, the load output can be made constant, thereby preventing heat generation and destruction of the switching element.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power supply circuit according to one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment, and FIG. 3 is a circuit diagram showing a conventional power supply circuit. 4. Transistor as a switching element, 6.
Oscillation transformer, 8. Secondary winding, 10. Feedback transformer, 14. Self-help oscillation circuit, 16. Third winding, 19.
- Rectification and smoothing means, 22... Base current control means, 23.
・Base power supply, 24...Auxiliary winding.

Claims (2)

[Claims] (1) In a power supply circuit having a self-excited oscillation circuit that induces an output in a secondary winding of an oscillation transformer and switches a switching element according to an output of a feedback winding of a feedback transformer, the feedback transformer has a third winding. A rectifying and smoothing means for rectifying and smoothing the power induced in the third winding, a transistor whose emitter and collector are connected to the rectifying and smoothing means, and a transistor connected to the rectifying and smoothing means between the emitter and collector. A power supply circuit comprising: a base power supply supplying a base current; and base current control means controlling the base current of the transistor. (2) The power supply for the base includes an auxiliary winding provided on the oscillation transformer, and a rectifying and smoothing means for the base connected to the auxiliary winding for rectifying and smoothing the power induced in the auxiliary winding. The power supply circuit according to claim 1, characterized in that: