JPS62272866A - Power circuit - Google Patents

Abstract

PURPOSE:To miniaturize and lighten a transformer by supplying an electric power from an auxiliary power transformer, only when a power supply is inputted, so as to start a switching action. CONSTITUTION:A switching control power circuit is composed of a rectifier circuit 2 and a smoothing capacitor 3 of an AC power 1, a switching circuit 4, a spike voltage absorbing circuit 5, a transformer 6, a pulse transformer 7, a rectification smoothing circuit 8, a control circuit 9, an auxiliary power transformer 10 and others. In the rectification smoothing circuit 15 connected with an auxiliary power transformer 10 output side, a diode element 16 connected between the rectifier circuit and the smoothing capacitor 18 and a diode element 17 connected between the capacitor 18 and output terminals 12-13 are connected in series with polarities reverse to each other to form an OR circuit and their common junction (a capacitor 18 voltage) is connected with the control circuit 9. In this manner, electricity is supplied from the auxiliary power transformer 10 only when a power supply is inputted and once the power supply is driven, said transformer 10 discontinues its participation.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a separately excited type of switching power supply and a switching control power supply circuit.

(Conventional technology) FIG. 2 is a circuit diagram showing a conventional power supply circuit.

(1) is an AC power supply, (2) is a rectifier circuit consisting of a bridge circuit of diode elements t2υ, (3) is a smoothing capacitor, (4) is a switching circuit including a transistor element 4υ, and (5) is a diode element (51 ), a spike voltage absorption circuit consisting of a capacitor element (52) and a resistor (53), (the spike voltage absorption circuit (5)
) with a primary winding (61) connected to (7
) is a pulse transformer with a secondary winding (72) connected to the transistor (41) of the switching circuit (4), (
8) is a rectifying and smoothing circuit connected to the secondary winding (62) of the transformer (6), which includes a diode element (811), an inductor element (82), and a capacitor element (83). (9) is a switching transistor element (91
), which is connected to the primary winding (71) and the third winding (73) of the pulse transformer (7). (I (Il is an auxiliary power transformer, whose primary winding (101) is connected to the AC power supply (1), and whose secondary winding (102) includes a diode element (111) and a capacitor element (112). Rectifying and smoothing circuit (11) including
is connected. The control circuit (9) of the switching power supply has the output voltage (VZ) of the rectifying and smoothing circuit (11) and the output terminal α2. The voltage across Qa (vo) or its feedback voltage (Vf) is applied.

In the conventional circuit configured as described above, a rectified output (v2) of the illustrated polarity is generated from the AC power supply (1) through the rectifier circuit (2) to both ends of the smoothing capacitor element (3).

On the other hand, a rectified output (V +
+) outputs the transistor element @υ of the switching circuit (4) via the control circuit (9) and the pulse transformer (7).
Therefore, the rectified output (V, ) at both ends of the smoothing capacitor element (3) passes through the transformer (6) and the rectifying and smoothing circuit (8) to the output voltage (V, ) between the output terminals (S71. ) is sent out.

At the same time, this output voltage (vo) becomes the feedback signal (Vf)
Therefore, the transistor element (
91)'s 0N-OFFal1 production is controlled. Sono ILi
i. The ON/OFF time of the transistor element in the switching circuit (4) is controlled, and the output voltage (V
The magnitude of O) is controlled. In addition, the actual control circuit (9
) The detailed circuit is omitted.

(Problems to be Solved by the Invention) In the above electric τ source circuit, the control circuit (9) is a separately excited switching power supply to which a rectified output (V++) is constantly applied from the auxiliary power transformer OQ. This auxiliary power transformer has a large volume and a heavy electrostriction.

This invention was made in order to solve the above-mentioned problems, and aims to obtain a small and lightweight power supply circuit.

[Means for solving problems]

The power supply circuit according to the present invention introduces the rectified voltage by the auxiliary power transformer, the output voltage of the main power supply circuit, and an OR circuit using a diode element, so that power is supplied from the auxiliary power transformer only when the power supply is connected. When switching is started and the output characteristics of the power supply rise, power is supplied to the control circuit from the output end of the switching power supply, thereby eliminating the use of the auxiliary power transformer.

[Effect]

According to this invention, since the auxiliary power transformer is used only when the power supply is plugged in, the transformer is small.

It is lightweight.

(Embodiment of the invention) FIG. 1 is a circuit diagram of a power supply circuit according to this embodiment,
Since most of them are the same or similar to those of the conventional circuit shown in FIG. 2, their explanation will be omitted. Here, the difference from the conventional part is the rectifier and smoothing circuit (surface) connected to the output side of the auxiliary power transformer, and there is a diode element (151).
A diode element (16) connected between a rectifier circuit including a smoothing capacitor (1st) and a smoothing capacitor (1st) and an output terminal 02. The diode elements (17) connected between α connection point,
That is, the voltage between the terminals of the smoothing capacitor (18) is supplied to the control circuit (9).

According to the above configuration, first, power is supplied from the auxiliary power transformer qQ to the control circuit (9) only when the power is turned on, and the output terminals θ2. When the output voltage (VO) is generated at α, the output voltage (VO) and the feedback voltage (Vf) are supplied to the control circuit (9) via the diode element (I7). Once this separately excited switching power supply is driven, the auxiliary power transformer (10) no longer participates in the operation of the switching circuit.

[Effects of the Invention] As detailed above, according to the present invention, the auxiliary power transformer is used only when the power supply is connected, so it can be used with specifications exceeding the rated value. Therefore, the entire power supply circuit has the advantage of being small in size and having a reduced volume and weight.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power supply circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional power supply circuit. In the figure, (1) is an AC power supply, (2) is a rectifier circuit, (3) is a smoothing capacitor, (4) is a switching circuit, (5) is a spike voltage absorption circuit, (6) is a transformer, and (7 ) is a pulse transformer, (8) is a rectifying and smoothing circuit, (9) is a switching power supply control circuit, θQ is an auxiliary power supply transformer, (o)
, (15) are rectifying and smoothing circuits, a and θ are output terminals, and (16) and (17) are diode elements. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a separately excited switching power supply including switching transistors, the DC voltage step-down rectified by the auxiliary power transformer and the output voltage obtained by switching are introduced into an OR circuit using diode elements, and the output of this OR circuit is A power supply circuit characterized in that the obtained DC voltage is supplied to a control circuit of a switching power supply.