JPH09298876A - Rush current control circuit of power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rush current preventing circuit which effectively suppresses a rush current and does not increase loss or heat generation even if the input voltage is low. SOLUTION: In the case of a double-voltage rectifying system where the input voltage Vin is low and the input current is high, the input current does not flow through a thermister resistor 7. Therefore, loss and heat generation of the thermister resistor 7 can be reduced to zero and a rush current can be effectively suppressed by a choke coil 21. On the contrary, only in the case of the full-wave rectifying system where the input voltage Vin is high and the input current is low, the input current flows through the thermister resistor 7. Therefore, a rush current can be suppressed effectively using a thermister resistor 7 having a large resistance value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device capable of switching a rectification method to full-wave rectification or voltage doubler rectification.

[0002]

Generally, the commercial power supply voltage in each country of the world shows various voltage values from AC80V to AC276V, so that the same power supply device can be used in all the countries of the world, the high and low input voltage. The rectification method is switched to full-wave rectification or voltage doubler rectification according to
For example, it is disclosed in Japanese Patent Application Laid-Open No. 2-84071.

FIG. 2 shows the circuit configuration of a power supply device of this type. In the figure, 1 is an AC power supply, 2 is a diode bridge which is a rectifying unit for rectifying the input voltage Vin from the AC power supply 1, and the rectified output from this diode bridge 2 is smoothed by a pair of smoothing capacitors 3 and 4. A predetermined DC voltage Vout is output between the output terminals 5 and 6. Reference numeral 7 is a thermistor resistor having a negative characteristic, which is inserted and connected to one side of the input voltage line from the AC power source 1 to the diode bridge 2. The thermistor resistance 7 has a resistance value that decreases as the temperature rises. In a state where the resistance value is high immediately after the power is turned on, the rush current to the output side of the rectifying unit 2 is suppressed, and in the steady state, The resistance value is lowered by self-heating due to the input current, and the loss due to the thermistor resistance 7 is reduced as much as possible.

A triac (two-way three-terminal thyristor) 12 as an opening / closing means is connected between one end of the diode bridge 2 on the input side and the middle point of the capacitors 3 and 4. The triac 12 receives a gate control signal from the input voltage detection circuit 13 that detects the level of the input voltage Vin, and opens and closes the main terminals. And
For example, when the input voltage Vin is AC100V, the gate control signal synchronized with the input voltage Vin is input to the input voltage detection circuit.
By outputting from 13 to the gate terminal of TRIAC 12,
Input side end of diode bridge 2 and capacitors 3 and 4
Double voltage rectification is performed by short-circuiting with the middle point. On the other hand, when the input voltage Vin is AC200V, there is no output of the gate control signal from the input voltage detection circuit 13 to the triac 12, and the connection between the input side one end of the diode bridge 2 and the middle points of the capacitors 3 and 4 is opened. And perform full-wave rectification.

In the above structure, since the input current flows through the thermistor resistor 7 regardless of whether the input voltage Vin is high or low, inrush current can be suppressed by the common thermistor resistor 7, but the input voltage Vin is When it is low, the input current increases by that much, so that there is a problem that the thermistor resistance 7 loses a large amount in a steady state and heat generation increases. If the thermistor resistor 7 having a small resistance value is used in order to reduce the loss and heat generation of the thermistor resistor 7, there arises a problem that the inrush current cannot be sufficiently suppressed when the input voltage Vin is high. .

In view of the above problems, the present invention is capable of effectively suppressing the inrush current regardless of the input voltage level, and prevents the loss and heat generation from increasing even when the input voltage is low. The purpose is to provide.

[0007]

In order to achieve the above-mentioned object, a rush current suppressing circuit of a power supply device according to the present invention applies an input voltage from an AC power supply to an input side of a rectifying unit and also In a power supply device that switches a rectification method to full-wave rectification or voltage doubler rectification by opening / closing an opening / closing means connected between one end on the input side and a midpoint of a pair of smoothing capacitors, the AC power supply and the rectification unit A thermistor resistor is connected to one end of the input side, and a connection point between the thermistor resistor and the AC power source is connected to one end of the opening / closing means.

In this case, in the case of the voltage doubler rectification method in which the input voltage is low and the input current is large, simply by changing the connection position of one end of the thermistor resistance, the input current does not pass through the thermistor resistance, so that the thermistor resistance is lost. In addition to eliminating heat generation, it is possible to effectively suppress inrush current by other elements and line impedance. On the contrary, since the input current flows through the thermistor resistance only in the case of the full-wave rectification method in which the input voltage is high and the input current is small, the inrush current can be effectively suppressed by using the thermistor resistance having a large resistance value. Moreover, since the thermistor resistance with low power consumption can be used, miniaturization of the thermistor resistance is also achieved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
The description will be made with reference to FIG. In addition, the same parts as those shown in FIG.
The detailed description of the common part is omitted because it is redundant. In the figure, the harmonic suppression choke coil 21 is connected to each rectified output line from the output side of the diode bridge 2 to the smoothing capacitors 3 and 4, and the AC power supply 1 and the input side of the diode bridge 2 are connected. The thermistor resistor 7 is connected between one end and the connection point between the thermistor resistor 7 and the AC power source 1 is connected to one main terminal which is one end of the triac 12, as shown in FIG. It is different from the configuration. Harmonic suppression choke coil 21
Is a pair of coil parts 22 connected to each rectified output line,
23 is wound around a common core 24. The coil portions 22 and 23 are wound around the core 24 with the same number of turns, and have the same inductance value L.

Next, the operation of the above configuration will be described. When the input voltage is low, for example, about 100 V AC, the input voltage detection circuit 13 detects it and inputs the input voltage Vin to the gate terminal of the triac 12. Outputs a gate control signal synchronized with. Then, the triac 12 short-circuits between the input side end of the diode bridge 2 and the midpoints of the capacitors 3 and 4, and the rectification method of the current device is switched to double voltage rectification. In this case, according to the polarity of the input voltage Vin of the AC power supply, the AC power supply 1 → diode bridge 2 → coil part 22 → smoothing capacitor 3 → triac 12 → AC power supply 1
Closed circuit and AC power supply 1 → triac 12 → smoothing capacitor 4 → coil section 23 → diode bridge 2 → AC power supply 1 closed circuit is formed every half cycle, and the input from the AC power supply 1 follows this closed circuit. The current flows in. Then, the harmonic current contained in the AC power supply 1 is suppressed by one of the coil portions 22 and 23 of the choke coil 21.

On the other hand, the input voltage Vin is AC200V, for example.
If the input voltage detection circuit 13 is
Stop supplying gate control signals to the 12 gate terminals.
Then, with the triac 12, the diode bridge 2
The one end of the input side and the middle point of the capacitors 3 and 4 are opened, and the rectification method of the current device is switched to full-wave rectification. In this case, regardless of the polarity of the AC power supply 1, the AC power supply 1 → diode bridge 2 → coil part 22 → smoothing capacitor 3 → smoothing capacitor 4 → coil part 23 → diode bridge 2 → thermistor resistance 7 → closed circuit of the AC power supply 1 The input current from the AC power supply 1 flows in along. The harmonic current contained in the AC power supply 1 is suppressed by the coil portions 22 and 23 of the choke coil 21.

As described above, when the input voltage Vin is low, the rectification method of the power supply device is switched to the double voltage rectification, but the AC power supply 1
The input current from does not pass through the thermistor resistor 7. Therefore, when the input voltage Vin is low, the input current increases by that much, but there is no loss or heat generation of the thermistor resistor 7 in the steady state. Further, since the inrush current immediately after the power is turned on can be suppressed by the impedance that is small as the input current increases, the inrush current can be effectively suppressed by using the impedance of the choke coil 21, for example, as in the present embodiment. can do. In this case, the line impedance in each closed circuit may be used instead of the element such as the choke coil 21.

On the other hand, in the case of the full-wave rectification method in which the input voltage Vin is high, the input current from the AC power supply 1 is the thermistor resistance 7.
Pass through. However, in this case, since the input current is smaller than when the input voltage Vin is low, the thermistor resistance 7
There is little loss or heat generation. Further, since the input current flows into the thermistor resistor 7 only when the input voltage Vin is high, the inrush current can be effectively suppressed by using the thermistor resistor 7 having a resistance value larger than that of the conventional one. Further, since the thermistor resistor 7 with low power consumption can be used, the thermistor resistor 7 and eventually the power supply device can be downsized.

As described above, in the inrush current suppressing circuit of the power supply device according to this embodiment, the input voltage Vin is low and the input voltage Vin is large and the double voltage rectification method is used only by changing the connection position of one end of the thermistor resistor 7. Since the input current does not pass through the thermistor resistor 7, the loss and heat generation of the thermistor resistor 7 can be eliminated, and the inrush current can be effectively suppressed by other elements and line impedance. On the contrary, since the input current flows through the thermistor resistor 7 only in the case of the full-wave rectification method in which the input voltage Vin is high and the input current is small, the inrush current is effectively suppressed by using the thermistor resistor 7 having a large resistance value. At the same time, the thermistor resistor 7 with low power consumption can be downsized. That is, the thermistor resistor 7 is connected between the AC power supply 1 and one end of the diode bridge 2 on the input side, and the connection point between the thermistor resistor 7 and the AC power supply 1 is connected to one end of the triac 12 for input. Inrush current can be effectively suppressed regardless of whether the voltage Vin is high or low, and loss or heat generation does not increase even when the input voltage Vin is low. In addition, an inrush current prevention circuit that can make the thermistor resistance 7 small can be obtained. .

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. In the embodiment, the switching of the rectification method is performed by using the triac 12 as the opening / closing means, but other than that, for example, a manual switch or the like can be used. Further, a plurality of thermistor resistors 7 in FIG. 1 may be connected in parallel to reduce the power consumption of each thermistor resistor 7.

[0016]

In order to achieve the above-mentioned object, the inrush current suppressing circuit of the power supply device according to the present invention applies the input voltage from the AC power source to the input side of the rectifying section and connects the input side end of the rectifying section to the input side. In a power supply device that switches a rectification method to full-wave rectification or voltage doubler rectification by opening and closing an opening / closing means connected between the middle point of a pair of smoothing capacitors, the AC power supply and one input side end of the rectification unit. A thermistor resistor is connected between the two, and a connection point between the thermistor resistor and the AC power source is connected to one end of the opening / closing means, and the inrush current can be effectively suppressed regardless of the input voltage level. Even if the input voltage is low, the loss and heat generation do not increase, and at the same time, the thermistor resistance can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional power supply device.

[Explanation of Codes] 1 AC power supply 2 Diode bridge (rectifier) 3,4 Smoothing capacitor 7 Thermistor resistance 12 Triac (opening / closing means)

Claims (1)

[Claims] 1. An input voltage from an AC power supply is applied to an input side of a rectifying section, and an opening / closing means connected between one input side end of the rectifying section and a midpoint of a pair of smoothing capacitors is opened / closed. Thus, in a power supply device that switches the rectification method to full-wave rectification or voltage doubler rectification, a thermistor resistor is connected between the AC power supply and one input side end of the rectification unit, and a connection point between the thermistor resistance and the AC power supply. Is connected to one end of the opening / closing means.