JPH07143748A - Power supply device - Google Patents

Abstract

PURPOSE:To provide a dropper type power supply device corresponding to a world-wide input (AC100/AC200V). CONSTITUTION:An AC input-voltage automatic changeover circuit 2 and voltage chageover switches 3 are mounted so that voltage output from a power transformer 4 is equalized even when AC input voltage I is AC100V or AC200V besides a converter circuit exchanging ACs through the power transformer 4 from AC input voltage 1, rectifying and smoothing the AC output voltage and acquiring DC stabilized voltage. Accordingly, even when AC input voltage 1 is AC100V or AC200V, the loss (heat generation) of a power supply device is equalized, thus providing the small-sized world-wide input corresponding dropper type power supply device having high performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dropper type power supply device used in electronic equipment such as OA equipment and AV equipment.

[0002]

2. Description of the Related Art A power supply device used in a conventional electronic device will be described with reference to FIGS.

FIG. 4 is a block diagram of a conventional dropper type power supply device, and FIG. 5 shows voltage waveforms of respective parts of the power supply device. Here, as components, 1 is an AC input voltage, 4 is a power transformer, 5 is a bridge type rectifying diode in the subsequent stage, 6 is a voltage smoothing capacitor, 7 is a DC voltage stabilizing circuit or stabilizing element, and 8 is stable. It is the converted DC output voltage.

Further, A to E shown in FIG. 4 are voltages indicated by arrows, which coincide with the waveforms A to E shown in FIG. As shown in FIG. 4, the conventional dropper type power supply device AC-exchanges the AC input voltage 1 (voltage A) with the power transformer 4 to obtain the voltage B, and rectifies the voltage of C by the bridge-type rectifying diode 5 to obtain the voltage of C. obtain. Further, it was smoothed by the voltage smoothing capacitor 6 to obtain a voltage of D, which was stabilized by the DC stabilizing circuit or the stabilizing element 7 to obtain the DC output voltage V ₀₈ (voltage E).

[0005]

In such a conventional structure, as shown in FIG. 5, the shaded portion of the voltage D in order to obtain the voltage E from the voltage D causes a loss in the DC stabilizing circuit or the stabilizing element. 7 is absorbed, ie the absorbed loss is
The direct current stabilization circuit or the stabilization element 7 has generated heat.

Therefore, the AC input voltage 1 is AC100V
When changing from AC to 200 V AC, the loss at AC 200 V becomes extremely large as shown by the hatched portion in FIG. 5D, and the shape of the heat dissipation fin for suppressing heat generation of the DC stabilizing circuit or the stabilizing element 7 is huge. It was difficult to use at a practical level.

The above reason is one of the major reasons for the rapid shift of the market from the dropper type power supply device to the switching type power supply device, even though the dropper type power supply device is most suitable for electronic devices that are averse to noise. It is a factor.

An object of the present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide a dropper type power supply device which can be easily put into practical use even when the AC input voltage changes from AC100V to AC200V.

[0009]

In order to solve the above-mentioned problems, the power supply device of the present invention is connected to the center and the end point of the input side (primary side) winding of the power transformer 4 as shown in FIG. The electrical or mechanical switch 3 is provided, and the switch 3 is switched by the AC input voltage automatic switching circuit 2.

[0010]

According to the present invention, when the AC input voltage 1 is AC100V, the AC input voltage automatic switching circuit 2 has the above-mentioned configuration.
When C100V is detected, the switch 3 connected to the middle point of the power transformer 4 is made conductive, and the other switch 3 connected to the end point is made non-conductive. Therefore, when a current flows in the loop of the solid line shown in FIG.
A voltage of 00V × n ′ / n) is generated. When the AC input voltage 1 is AC200V, the AC input voltage automatic switching circuit 2 detects AC200V, the switch 3 connected to the middle point of the power transformer 4 is made non-conductive, and the switch 3 connected to the end point is made conductive. Let Therefore, a current flows through the loop of the broken line shown in FIG.
n) = (AC100V × n ′ / n) voltage is generated and A
It is exactly the same as the voltage value of C100V.

FIG. 2 shows the above operation by the voltage waveforms A to E of the respective parts, and the voltage generated at the point B is the same whether the AC input voltage 1 is AC100V or AC200V. Therefore, the voltage at the point C, which is the input voltage of the DC stabilizing circuit or the stabilizing element 7, and the voltage at the D point are also the same, and the DC stabilizing circuit or the stabilizing element for obtaining the DC stabilized output voltage V ₀ 8 is obtained. The loss (= heat generation) of 7 is the same, and therefore, a dropper type power supply device that can be easily put into practical use from AC100V to AC200V can be configured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a circuit diagram of an embodiment of the present invention. In FIG. 3, 2 is an AC input voltage automatic switching circuit, 9 is two bidirectional thyristors used as voltage changeover switches, and these thyristors 9 are the middle point and the end point of the primary winding of the power transformer 4, respectively. And AC input voltage 1
Is connected in between.

When the AC input voltage 1 is AC100V, the NPN transistor Q2 is turned on by the DC voltage V ₁ generated by the diode D1, the resistor R ₁ and the capacitor C1 in the AC input voltage automatic switching circuit 2, The bidirectional thyristor 9 connected to the midpoint of the power supply transformer 4 where the collector of the transistor Q2 is connected to the gate becomes conductive. At this time, the V ₁ voltage is applied to the resistors R4 and R5.
Between the voltage divided by and the voltage V _BE between the emitters of the constant voltage diode 2D2 and the NPN transistor Q2,
The relationship of (V ₁ × R5 / R4 + R5)> (V _ZD2 + V _BE ) is established. Further, between the voltage obtained by dividing the V ₁ voltage by the resistors R2 and R3 and the base-emitter voltage V _BE of the constant voltage diode ZD1 and the NPN transistor Q1 (V ₁ ×
R3 / R2 + R3) <(V _ZD1 + V _BE ) holds, and V ₁
(V ₁ × R8 / R7 + R8) <between the voltage divided by the resistors R7 and R8 and the base-emitter voltage V _BE of the constant voltage diode ZD3 and the NPN transistor Q3 <
Since (V _ZD3 + V _BE ) is established, the NPN transistors Q1 and Q3 are in the non-conducting state. Since the NPN transistor Q3 is in the non-conducting state, the collector of the NPN transistor Q2 is connected to the gate. Bidirectional thyristor 9 connected to the end of the power transformer 4.
Is in a non-conducting state, a current flows in a loop shown by a solid line in FIG. 3, and if the number of turns from the start point to the middle point of the power transformer 4 is n and the number of output turns is n ', the output of the commercial transformer is (AC10
A voltage of 0V × n ′ / n) is generated.

When the AC input voltage is AC200V,
Between the voltage obtained by dividing the V ₁ voltage by the resistors R2 and R3 and the voltage V _BE between the constant voltage diode ZD1 and the base-emitter of the NPN transistor Q1, (V ₁ × R3 / R2 + R3)>
Since (V _ZD1 + V _BE ) is established and the NPN transistor Q1 becomes conductive, the collector-emitter voltage V _{CE of} the NPN transistor Q1 and the constant-voltage diode ZD2 and the base-emitter voltage V _BE of the NPN transistor Q2. When V _CE <(V _ZD1 + V _BE ) holds,
The NPN transistor Q2 becomes non-conductive, so that the bidirectional thyristor 9 connected to the midpoint of the power transformer 4 becomes non-conductive. Further, between the voltage obtained by dividing V ₁ by the resistors R7 and R8 and the base-emitter voltage V _BE of the constant voltage diode 2D3 and the NPN transistor Q3, (V ₁
× R8 / R7 + R8)> (V _ZD3 + V _BE ), and N
When the PN transistor Q3 becomes conductive, the bidirectional thyristor 9 connected to the end point of the power transformer 4 becomes conductive. Therefore, the current flows in the loop indicated by the broken line in FIG. 3, and the number of turns from the start point to the end point of the power transformer 4 is 2
Assuming n, the output of the power transformer 4 is (AC200V
A voltage of × n ′ / 2n) = (AC100V × n ′ / n) is generated, which is exactly the same as the case of AC100V. Therefore, the voltage after the output of the power transformer 4 and the loss (heat generation) are A even if the AC input voltage 1 is AC100V.
The same is true for C200V.

[0015]

As is apparent from the above description of the embodiments, according to the present invention, the AC input voltage is AC 100V to A.
Even if it changes to C200V, the loss (heat generation) of the power supply can be made the same, so the shape of the radiation fin attached to the DC stabilizing circuit or stabilizing element can be made small, so a compact and high performance world wide input A corresponding dropper type power supply device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a power supply device of the present invention.

FIG. 2 is a voltage waveform diagram of each part of FIG.

FIG. 3 is a circuit diagram of an embodiment of the present invention.

FIG. 4 is a block diagram of a conventional power supply device.

FIG. 5 is a voltage waveform diagram of each part of FIG.

[Explanation of symbols]

 1 AC input voltage 2 AC input voltage automatic switching circuit 3 Electrical or mechanical switch 4 Power transformer 5 Bridge type rectifier diode 6 Voltage smoothing capacitor 7 DC voltage stabilizing circuit or stabilizing element 8 DC stabilizing voltage 9 Bidirectional Thyristor

Claims (1)

[Claims] 1. A converter circuit for performing AC conversion from a commercial AC input voltage via a power transformer, rectifying and smoothing the AC output voltage to obtain a DC voltage, and obtaining a DC stabilized voltage from the DC voltage through a stabilizing circuit. In addition, a changeover switch is provided between the middle point and the terminal of the primary winding of the power transformer and the AC input voltage side, and a voltage automatic changeover circuit for operating the changeover switch is provided so that even if the AC input voltage changes. A power supply device in which the voltage output from the power transformer is the same.