JPS6126471A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To obtain a stable DC with a simple circuit configuration by producing the primary side exciting voltage of an oscillation transformer, and controlling so that the self-excited oscillation output of the transformer becomes a constant amplitude. CONSTITUTION:The primary side excited voltage of an oscillation transformer 3 is applied through resistors 14, 15 to a transistor 12, the transistor 12 and a reference power source 13 form a voltage comparator, and when the input voltage to the transistor 12 is larger than the voltage of the power source 13, it operates to reduce the base voltage of a transistor 11. Thus, the DC input voltage to the transformer 3 is reduced. On the contrary, when the input voltage to the transistor 12 is smaller than the voltage of the power source 13, it operates to raise the base voltage of the transistor 11 to increase the DC input voltage to the transformer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a DC-DC converter that maintains a constant output voltage even if the voltage of a DC power supply on the input side fluctuates.

(b) Prior Art and Problems A circuit diagram of a conventionally used DC-DC converter/controller is shown in FIG.

In FIG. 2, 1 is a DC power supply, 2 is a power switch, 3 is a power transformer, 4 and 5 are transistors, 6 is a rectifier, and 7 is a DC stabilizing circuit.

The primary side of the oscillation transformer 3 has an intermediate tap, and both ends of the primary winding of the oscillation transformer 3 are connected to the collectors of the transistors 4 and 5, respectively. Further, the transistors 4 and 5 constitute a positive feedback circuit in which the collector and base are connected in a "cross-over" manner through a resistor, and FIG. 2 shows a push-pull type converter.

The transistors 4 and 5 alternately switch to drive the oscillation transformer 3 into saturation.
The oscillating transformer 302 generates a voltage proportional to the primary side excitation voltage.
Output to the next side.

The secondary output of the oscillation transformer 3 is converted into direct current by a rectifier 6.

The DC stabilizing circuit 7 is used when small fluctuations in the DC output voltage are required and when there are large fluctuations in the load.

If the voltage of the DC power supply 1 in Fig. 2 is constant, there is not much problem, but if the voltage of the DC power supply 1 increases or decreases, the switching current of the transistors 4 and 5 will change in proportion to this, and the power loss will increase. It increases exponentially as the voltage of the DC power supply 1 increases. Therefore, there is a problem in that the components constituting the circuit must have sufficient margin in terms of rating.

For example, if you use something like a manganese dry battery with a large difference between the initial voltage and the final discharge voltage for the DC power supply 1,
Most of the power is dissipated inside the converter, significantly reducing battery life.

Therefore, when using a power source with large voltage fluctuations such as a manganese dry battery as the DC power source 1, in order to reduce the loss inside the circuit, the DC stabilizing circuit 8 is used as shown in Figure 3.
It is also necessary to take measures such as turning on the 10th DC power source and keeping the DC voltage to the oscillation transformer 3 constant, resulting in a problem that the circuit configuration becomes complicated.

(C) The object of the invention is to detect the oscillation voltage from the oscillation transformer 3 shown in FIG. It attempts to solve the problems of the prior art by controlling the voltage from the .

(d> Embodiments of the invention First, a circuit diagram of an embodiment according to the present invention is shown in FIG.

1 to 6 in Figure 1 are the same as in Figure 2, 11 and 12
is a transistor, 13 is a reference power supply, 14 and 15 are resistors,
16 is a smoothing capacitor.

Transistor 11 is connected in series between switch 2 and oscillation transformer 3.

The primary side excitation voltage of the oscillation truss 7 truss 3 is the resistor 14 and the resistor 15.
is applied to transistor 12 via.

The transistor 12 and the reference power supply 13 constitute a voltage comparison circuit, and the input voltage to the transistor 12 is equal to the reference power supply 1.
When the voltage is higher than voltage No. 3, it operates to lower the base potential of transistor 11. This reduces the DC input voltage to the oscillation transformer 3.

Conversely, when the input voltage to the transistor 12 is lower than the voltage of the reference power supply 18, the transistor 1 operates to raise the base potential of the transistor 1 and increases the DC input voltage to the oscillation transformer 3.

In this manner, the circuit shown in FIG. 1 is controlled by the transistors 11, 12, and the reference power source 13 so that the primary side excitation voltage of the oscillating truss 7 is constant.

A battery or a Zener diode is used as the reference power source 13.

The circuit shown in FIG. 1 can operate even if one of the resistors 14 and 15 is omitted, and diodes may be used in place of the resistors 14 and 15.

Also, when using both resistor 14 and resistor 15,
There is no problem even if the smoothing capacitor 16 is omitted.

The collector-emitter saturation voltage VCE of the transistors 4 and 5 is set to be sufficiently small, for example, less than 1/0 of the voltage of the reference power supply 13.

This is the collector of transistor 4 and transistor 5.
When the emitter-to-emitter saturation voltage VCE increases and cannot be ignored compared to the voltage of the reference power supply 13, the output load fluctuation becomes large, and there are cases where transistors 4 and 5 cannot be turned on, and the converter output decreases. This is because it decreases.

(e) Effects of the Invention According to the present invention, the primary side excitation voltage of the oscillation transformer 30 is taken out and the self-excited oscillation output transformer 3 of the oscillation transformer 3 is
A stable DC output can be obtained even without the DC stabilizing circuit 7 shown in FIG. 2 on the next side.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment according to the present invention, FIGS.
The figure is a conventional circuit diagram. DESCRIPTION OF SYMBOLS 1...DC power supply, 2...Power switch, 3...Oscillation transformer, 4...Transistor, 5...Transistor, 6...・・・・・・
Rectifier, 7...DC stabilization circuit, 8...
・DC stabilization circuit, 11...Transistor, 1
2...Transistor, 13...Reference power supply, 14...Resistor, 15...Resistor, 16
・・・・・・Smoothing capacitor. Agent Patent Attorney Kin Tsukasa KomataFigure 1Figure 2

Claims (1)

[Claims] 1. Consisting of a DC power supply, an oscillation transformer, a rectifier, and a first transistor and a second transistor connected in a push-pull type to the primary side of the oscillation transformer, the primary side of the oscillation transformer , a DC voltage generator that causes self-oscillation by the first transistor and the second transistor, and rectifies the secondary voltage of the oscillation transformer by the rectifier.
In the DC converter, a third transistor connected in series between the DC power supply and the oscillation transformer, and a fourth transistor receiving the oscillation voltage on the primary side of the oscillation transformer as input.
transistor, and a reference power supply connected to a fourth transistor, the voltage of the third transistor is controlled by the output of the fourth transistor, and the primary side excitation voltage of the oscillation transformer is kept constant. DC-DC converter.