JPH0284071A - Dc power device - Google Patents

Abstract

PURPOSE:To prevent extremely high voltage from applying to circuit elements even in voltage variations by switching over a switching means to full wave rectification side by a force holding means if the input voltage is identified as high in putting the power supply to work, and after that even if low voltage is detected in operation by power supply fluctuation caused by voltage drop, etc., by forcibly holding full wave rectification. CONSTITUTION:If high voltage is detected by a discrimination means 8 in putting the power supply to work, no trigger circuit 9 will turn ON a TRIAC 7 by a forced holding means 10 even if the voltage is reduced as prescribed temporarily after that in operation, so that application of extremely high voltage to the circuit elements at rear stages will be prevented by the time lag in switching the TRIAC 7 without changing over to voltage doubler rectification.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a DC power supply device that automatically switches the rectification method depending on the level of input voltage to obtain a predetermined DC voltage. .

(Prior art) Generally, the commercial power supply voltage in countries around the world ranges from 80V to 80V.
It shows various voltage values up to C276V. For this reason,
The rectification method is automatically switched depending on the input voltage so that the same DC power supply can be used in different countries around the world. That is, for example, if the input voltage is AC100
In the case of (2), voltage double rectification is performed so that the output voltage is approximately twice the maximum value of the input voltage, and the input voltage is AC2.
When the voltage is 00V, full-wave rectification is performed. In order to automatically switch such an M-current type, voltage doubler rectification can be performed by detecting the high or low level of the input voltage and turning on a switch such as a triac connected to a diode bridge circuit depending on this high or low level. Full-wave rectification is performed by turning them off, and for example, Japanese Patent Laid-Open No. 58-213317 discloses this type of rectification.

(Problem to be Solved by the Invention) In this way, in a device that automatically switches the rectification method by determining whether the input voltage is high or low, when a high voltage is input as shown in FIG. When the TRIAC is off and full-wave rectification is occurring, if a voltage drop or voltage fluctuation occurs that causes the input to be interrupted intermittently, a low voltage will be detected, resulting in an ON signal to the TRIAC. The triac is turned on and switched to voltage doubler rectification. However, when tIt returns and a high voltage is detected again, an off signal is output to turn off the triac, but even if this off signal is given, the triac will not be turned off until the applied voltage drops to Ov. Therefore, even if the input voltage returns from a low voltage to a high voltage, there is some time lag before switching from voltage doubler rectification to full wave rectification. As a result, the high voltage is doubled and rectified, and a very high output voltage is temporarily applied to the capacitor and pond elements connected to the rear stage of the triac, which may cause damage. there were.

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problems, and it is an object of the present invention to provide a DC power supply device that can prevent abnormally high voltage from being applied to circuit elements even when there are voltage fluctuations. be.

[Structure J of the Invention (Means for Solving the Problems) The present invention provides a determining means for determining whether the input voltage is high or low, and changes the rectification method to full-wave rectification or A switch means for switching to voltage doubler rectification is provided, and a forced holding means is provided for holding the switch means on the full-wave m flow side during operation after the power is turned on when the discrimination means determines that the voltage is high when the power is turned on. It is something.

(Function) When the input voltage is determined to be high voltage when the power is turned on, the switch means is switched to the full-wave rectification side by the forced holding means, and during subsequent operation, low voltage is detected due to power fluctuations such as voltage drop. Full-wave rectification is forcibly maintained.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. Figure 1 is a block diagram, in which 1 is an AC power supply, 2 is a rectifier in which diodes are bridge-connected to convert AC input into DC in conjunction with a smoothing capacitor 3.4, and DC voltage is output from output terminal 5. Output from .6. 7 is a triac connected between the input ground terminal of the rectifier 2 and the connection point of the smoothing capacitor 3゜4, and when the triac 7 is on, voltage doubler rectification is configured in the rectifier 2, On the other hand, when it is off, Kinwave rectification is configured.

8 is connected to the AC power supply 1 and the input voltage is low voltage (for example, AC
This is a means of determining whether the voltage is high voltage (AC200V) or high voltage (AC200V).

A trigger circuit 9 turns on the triac 7 when the input voltage is a low voltage, and turns off the triac 7 when the input voltage is a high voltage, according to the determination result of the discriminating means 8. Reference numeral 10 denotes forced holding means that, when the determining means 8 determines that the voltage is high when the input is applied, causes the trigger circuit 9 to *ItlJI to forcibly keep the triac 7 off during operation after the input is applied.

Next, a specific embodiment of the discriminating means 8, the trigger circuit 9, and the forced holding means 10 will be described in detail using the circuit diagram of FIG. and a smoothing capacitor 12, a resistor 13.14 that divides the obtained DC voltage, a transistor 15, a Zener diode 16, etc. that are connected to the voltage division point of these resistors 13.14 and turn on when a high voltage is detected. It consists of

The trigger circuit 9 also includes a transistor 17 that turns on when a low voltage is detected, a light emitting diode 18 that emits light when the transistor 17 turns on, and a phototriac 20 that forms a photocoupler 19 together with the light emitting diode 18. It consists of Further, the forced holding means 10 includes a transistor 21 for performing constant current operation when a high voltage is detected when the power is turned on, and a transistor 21 that is turned on together with the transistor 15 when a high voltage is detected and even if a low voltage is detected thereafter. It is composed of a thyristor 22, etc., through which an on-state holding current continues to flow.

The operation of the present invention constructed as shown below will be explained in detail based on the time chart of FIG. First, when a low voltage is supplied from the AC power source 1, the voltage at the voltage dividing point in the determining means 8 is low, so the transistor 15 is turned off and the transistor 17 is turned on. Therefore, the light emitting diode 18 lights up and the triac 20 is turned on, so the triac 7 is turned on and the NK section 2 is switched to voltage rectification.

On the other hand, when a high voltage is supplied from the AC power source 1, the voltage at the voltage dividing point increases in the determining means 8, the Zener diode 16 and the transistor 15 are turned on, and as a result, the thyristor 22 is turned on and the base of the transistor 17 is turned on. In order to draw current, the transistor 17 is turned off and the light emitting diode 18 is turned off. Therefore, the triac 7 is turned off and the U flow section 2
switches to full-wave rectification. Further, in this case, in the forced holding means 10, the transistor 21 is turned on to perform a constant current operation, and once the thyristor 22 is turned on, the input voltage decreases and even if the transistor 15 is turned off, the thyristor 22 remains on. The holding current continues to flow.

Therefore, when a high voltage is detected by the discriminator 8 and the thyristor 22 is turned on when the power is turned on, as shown in FIG. Since the thyristor 22 continues to be in the ON state due to the constant current action even if the current decreases to Wave rectification is maintained. As a result, even if the high voltage restored from the AC power supply 1 is supplied again, abnormal high voltage will not be supplied to the subsequent circuit elements due to the time lag of the triac 7, unlike in the conventional case, and circuit safety is ensured. However, when the voltage temporarily becomes low as shown in FIG. 3, the output voltage temporarily decreases because the rectifier 2 remains in full-wave rectification.

Further, the thyristor 22 continues to be turned on until the AC power supply 1 is cut off and the smoothing capacitor 12 is no longer charged.

In this way, when a high voltage is detected by the discrimination means 8 when the power is turned on, the trigger circuit 9 is activated by the forced holding means 10 even if the voltage temporarily drops to a predetermined low voltage during subsequent operation. Since triac 7 is not turned on, it is not switched to the voltage doubler wL flow, and a time lag when switching triac 7 prevents an abnormally high voltage from being applied to subsequent circuit elements.

Although one embodiment of the present invention has been described in detail above, it can be modified as appropriate within the scope of the gist of the present invention.

For example, elements other than triacs can be used as the switch means.

[Effects of the Invention] As detailed above, according to the present invention, in a DC power supply device that switches the rectification method depending on the level of input voltage, there is provided a discrimination means for discriminating whether the input voltage is high or low; a switch means for switching the rectification method to full-wave rectification or voltage doubler rectification according to the level of the input voltage; and a switch means for switching the rectification method to full-wave rectification or voltage doubler rectification according to the level of the input voltage; By including the forced holding means for holding on the rectifying side, it is possible to provide a DC power supply device that can prevent abnormally high voltage from being applied to circuit elements even if there is a voltage fluctuation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram thereof, FIG. 3 is a time chart, and FIG. 4 is a time chart showing problems in the conventional technology. 7...Triac (switching means) 8...Discrimination means 10...Forced holding means Patent applicant Utah Power Electric Manufacturing Co., Ltd. Nemic Lambda Co., Ltd. Agent

Claims (1)

[Claims] In a DC power supply device that switches a rectification method depending on the level of input voltage, a determining means for determining whether the input voltage is high or low;
a switch means for switching the rectification method to full-wave rectification or voltage doubler rectification according to the level of the input voltage determined by the determination means; , and forced holding means for holding the switch means on the full-wave rectification side.