JPH02299473A - Power source circuit - Google Patents

Abstract

PURPOSE:To prevent an accident by automatically switching a switch in response to voltage system of a utility power source. CONSTITUTION:A power source consists of a rectifying and ripple filter circuit 5 made of a diode bridge DB, etc., and a switching regulator 6 made of a switching transistor Q1, etc., and supplies a predetermined DC voltage to a load. A triac Q2 is provided in the circuit 5, and its gate controller 4 and a utility power source voltage system discriminator 3 are added. As a result, when the utility voltage is determined to be 100V series, the triac Q2 is turned ON to always keep the input power source voltage of the regulator 6 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a power supply circuit that receives commercial power and generates a predetermined DC voltage.

(b) Conventional technology As a power supply circuit that uses a commercial power source as an input power source and supplies a specified DC power to a load such as an electronic circuit, a switching regulator is conventionally used because it has better power exchange efficiency and can be configured in a smaller size. .

Compared to a series dropper or the like, such a switching regulator can generate a predetermined DC voltage more stably even when the input power supply voltage fluctuates. However, in order to construct a power supply circuit that can be used with both AC 100V and AC 200V commercial power sources, it is necessary to be able to control the on-duty ratio of the switching transistor over a wide range, and it is necessary to create an efficient switching regulator. It was difficult to configure.

Therefore, in general, a switch is used as shown below to
By switching between 00V system and AC200V system,
It is designed to be compatible with any voltage system.

In Figure 3, DB is a diode bridge, CI, C2
is a smoothing capacitor. In addition, 1 in the figure is a transformer, and its primary winding N1 is connected to a switching transistor Q1.
is connected, and a rectifying and smoothing circuit 2 is connected to the secondary winding N2. When inputting AC200V as AC input,
Switch the switch SW to the off state. Due to this, DB.

Bridge rectification is performed by C1 and C2, and a DC voltage of approximately ~0° x 200V is applied to the primary winding of the transformer. When inputting a 100v system as an AC input, turn on the switch SW. As a result, voltage doubler rectification is performed by two of the four diodes constituting the diode bridge DB and the capacitors CI and C2, and a DC voltage of EX 200 V is also applied to the primary winding of the transformer.

(C) Problem to be solved by the invention However, by switching the switch in this way, the AC
In the method of switching between the 100V system and the AC 200V system, the switch must be changed manually, and there is a problem in that switching errors can cause failures or abnormal operation of the smoothing capacitor, switching regulator circuit, and even load.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply circuit that can automatically switch the switch according to the commercial power supply voltage system, thereby solving the above-mentioned problems.

(d) Means for Solving the Problems This invention provides a power supply comprising a rectifying and smoothing circuit that rectifies and smoothes a commercial power supply, and a switching regulator that uses the output voltage of this rectifying and smoothing circuit as an input power source to generate a predetermined DC voltage. In the circuit, two capacitors are connected in series between the rectifying output terminals of a diode bridge, and a triac is connected between the connection point of these two capacitors and one AC input terminal of the diode bridge to form a rectifying and smoothing circuit. , a commercial power supply voltage system discrimination circuit that discriminates between 100 V and 200 V series of commercial power supply voltage, and when this commercial power supply voltage system discrimination circuit discriminates between 100 V and 100 V series, the secondary output voltage of the switching regulator transformer The present invention is characterized in that a gate control circuit is provided which generates a gate signal for turning on the triac.

(81 action Figure 1 shows an example of the configuration of the present invention. In the figure, DB is a diode bridge, C1 and C2 are smoothing capacitors,
C2 is a triac, which constitutes a rectifying and smoothing circuit 5. Further, 1 is a transformer, Ql is a switching transistor, and together with the rectifying and smoothing circuit 2, a switching regulator 6 is configured. The commercial power supply voltage system determination circuit 3 determines whether the input commercial power supply is a 100V system or a 200V system. Gate control circuit 4
generates a gate signal that turns on the triac Q2 when the commercial power supply voltage system discrimination circuit 3 discriminates the 100V system.

In the power supply circuit of this invention, a diode bridge D
Two capacitors C1 and C2 are connected in series between the rectifier output terminals of B, and a triac Q2 is connected between the connection point of these two capacitors and one AC input terminal of the diode bridge, thereby forming a rectifier and smoothing circuit. ing.

In other words, this triac corresponds to the above-mentioned switch. The commercial power supply voltage system discrimination circuit 3 uses the commercial power supply voltage of 100V.
/200V system, and the gate control circuit 4 determines that when the commercial power supply voltage system discrimination circuit discriminates the 100V system,
A gate signal for turning on the triac Q2 is generated from the secondary output voltage of the transformer of the switching regulator. Therefore, when a 100-square AC voltage is applied as a commercial power supply, the commercial power supply voltage system discrimination circuit 3 discriminates this and the triac Q2 is turned on by the action of the gate control circuit 4. As a result, the rectifying and smoothing circuit performs double voltage positive rectification. When a 200-inch AC power source voltage is applied as a commercial power source, the triac Q2 remains off, so the rectifying and smoothing circuit performs bridge rectification. In this way, the same DC voltage is input to the switching regulator 6 regardless of whether the 100V/200V commercial power source is input, and the switching regulator 6 efficiently converts power.

(f) Embodiment FIG. 2 shows a circuit diagram of a power supply circuit which is an embodiment of the present invention.

DB is a diode bridge, and two capacitors C1 and C2 are connected in series between its rectified output terminals. Also, the connection point of these two capacitors and the diode bridge D
A rectifying and smoothing circuit 5 is constructed by connecting a triac Q2 between one AC input terminal of B. Further, in the figure, 1 is a transformer, and a switching transistor Q1 is connected in series to the negative winding N1 of the transformer, and supplies the output voltage of the rectifying and smoothing circuit. A rectifying and smoothing circuit 2 is provided in the secondary winding N2 of the transformer. A gate control circuit consisting of resistors R1, R2 and a phototriac Q3 is connected to the other winding N3 on the secondary side of the transformer.

A resistor R3 and a diode D1 are connected between the ACC insert line and ground.
．． A rectifying and smoothing circuit consisting of a capacitor C3 and a resistor R4 is connected. This circuit provides C3 with a DC voltage approximately proportional to the commercial power supply voltage. A Zener diode ZDI is provided between C3 and the base of the transistor Q4, and is cut off when the commercial power supply voltage is 100V.
■For example, AC145V so that it is conductive when the system is
The resistor voltage division ratio by the resistors R3 and R4 and the Zener voltage of ZDl are determined by using this as a threshold value. transistor Q
The LED connected to the collector of 5 constitutes a photocoupler 7 together with the phototriac Q3.

The operation of the circuit shown in FIG. 2 is as follows.

First, when AC200V is input as the input power supply, DB
, bridge rectification is performed by the action of C1 and C2 (
At this time, C2 is in an off state.

), switch control of Ql is started. On the other hand, the charging voltage of C3 rises, ZDl becomes conductive, and C4 turns on. As a result, the base potential of C5 decreases, and C5 remains in the off state, so that the LED does not emit light. Therefore, the phototriac Q3 is not turned on and no gate current flows through the triac Q2, and C2 also remains in the cut-off state.

When AClooV is input as input power 1. DB
, C1 and C2, bridge rectification is also performed at first, and switching is started. On the other hand, the charging voltage of C3 does not rise enough to make ZDI conductive, and C4
The base potential of C4 remains at ground potential due to resistor R5, and C4 remains off. As a result, the base potential of C5 rises in accordance with the partial voltages of R6, R7, and R8, and C5 turns on, causing the LED to emit light. At this time, the phototriac Q3 is turned on by the electromotive voltage of the winding N3 of the transformer, causing a current to flow through the triac Q2. As a result, voltage double rectification is performed by the actions of DB, C1, and C2, and the input voltage to the primary winding N1 of the transformer rises to a specified voltage and maintains that state.

In this way, the input voltage to the switching regulator becomes constant regardless of whether the commercial power supply voltage is 100V or 200V.

(g) Effects of the Invention According to the present invention, it is not necessary to manually switch the switch according to the voltage system of the commercial power supply voltage (it is possible to prevent accidents due to switching errors. Also, the input power supply voltage of the switching regulator is Since it is always substantially constant, the on-duty ratio of the switching transistor does not vary over a wide range and can be operated in an efficient state.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of the present invention. FIG. 2 is a circuit diagram of a power supply circuit according to an embodiment of the present invention. FIG. 3 is a circuit diagram of a conventional power supply circuit. 1-transformer, 3-commercial power supply voltage system discrimination circuit, 4-gate control circuit, 5-rectifier smoothing circuit, 6-switching regulator, DB-diode bridge, C1, C2-capacitor, Q2-triac.

Claims (1)

[Claims] (1) In a power supply circuit consisting of a rectifying and smoothing circuit that rectifies and smoothes commercial power, and a switching regulator that uses the output voltage of this rectifying and smoothing circuit as an input power source to generate a specified DC voltage, a Two capacitors are connected in series, and a triac is connected between the connection point of these two capacitors and one AC input terminal of the diode bridge to configure a rectifying and smoothing circuit, and also to distinguish between 100V and 200V commercial power supply voltage. a commercial power supply voltage system discriminating circuit that performs this, and a gate control that generates a gate signal that turns on the triac from the secondary output voltage of the switching regulator transformer when the commercial power supply voltage system discriminating circuit discriminates the 100V system. A power supply circuit characterized by being provided with a circuit.