JP2009232484A - Rush current suppression circuit and capacitor input type power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rush current suppression circuit which can arrange a resistor for current suppression at the front stage side (AC side) of a rectifier. <P>SOLUTION: The rush current suppression circuit comprises: a suppression resistor 2 which suppresses a current to a smoothing capacitor 17 in a capacitor input type power supply device 11; a connecting part 3a of a relay 3 connected to the suppression resistor 2 in parallel therewith; an AC input type photocoupler 4 in which a light emitting diode 4a is connected to the suppression resistor 2 in parallel therewith, and a phototransistor 4b is shifted to an on-state when a current flows to the light emitting diode 4a; and a control circuit 7 which short-circuits the suppression resistor 2 by controlling the connecting point 3a of the relay 3 into an on-state when the phototransistor 4b is continued in an off-state for a preset reference time or longer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inrush current suppression circuit that suppresses a charging current to a smoothing capacitor in a capacitor input type power supply device, and a capacitor input type power supply device having the inrush current suppression circuit.

  As this type of inrush current suppression circuit, an inrush current suppression circuit disclosed in Patent Document 1 below is known. This inrush current suppression circuit includes a current limiting resistor inserted in series in a charging main circuit to a smoothing capacitor in a capacitor input type rectifier circuit including a rectifier that rectifies an AC voltage and a smoothing capacitor that smoothes the rectified voltage. A current-limiting resistor short-circuit means connected in parallel to the current-limiting resistor and closed under a predetermined condition, and a reference voltage that is always reduced by a predetermined constant voltage compared to the output voltage of the rectifier A voltage forming means and a voltage comparing means for comparing the reference voltage with the terminal voltage of the smoothing capacitor, and a short-circuit means using the output signal of the voltage comparing means when the terminal voltage of the smoothing capacitor becomes equal to or higher than the reference voltage. It is comprised so that it may become a closed circuit command signal.

Specifically, the inrush current suppression circuit 51 utilizes the fact that the terminal voltage Vca of the smoothing capacitor 52 approaches the output voltage Vre of the rectifier 56 as the charging of the smoothing capacitor 52 proceeds as shown in FIG. The voltage Vc obtained by dividing the terminal voltage Vca by the resistors R3 and R4 is larger than the reference voltage Vb obtained from the output voltage Vre by the series connection of the resistors R1 and R2 and the constant voltage diode ZD in the illustrated order. The relay 54 is excited by the output signal of the comparator 53 that detects that the contact has been established, and the contact 54a is closed, thereby short-circuiting the current limiting resistor 55. Thus, according to the inrush current suppression circuit 51, the voltage difference between the output voltage Vre of the rectifier 56 and the terminal voltage Vca of the smoothing capacitor 52 when the resistance is short-circuited is always a constant value designated by the constant voltage diode ZD. Therefore, the amount of fluctuation in the charging current of the smoothing capacitor due to the short circuit of the current limiting resistor 55 is made constant.
JP-A-6-141548 (page 2-4, FIG. 1)

  By the way, for example, due to the structure of a power supply device using an inrush current suppression circuit, there is a demand to arrange a current limiting resistor 55 on the front side (AC side) of the rectifier 56. However, in this inrush current suppression circuit, as described above, the current limiting resistor 55 is arranged on the output line of the rectifier 56, and the terminal voltage Vca of the smoothing capacitor 52, which is the voltage at one end of the current limiting resistor 55, is obtained. The operation of the relay 54 that short-circuits the current limiting resistor 55 is controlled by utilizing the approach to the output voltage Vre of the rectifier 56 that is the voltage on the other end side. Therefore, in this inrush current suppression circuit, since it is essential to arrange the current limiting resistor 55 in the output line of the rectifier 56, this inrush current suppression circuit has a problem that it cannot respond to the above request. Existing.

  The present invention has been made to solve such problems, and provides an inrush current suppression circuit and a capacitor input type power supply device in which a current suppression resistor can be arranged on the front stage side (AC side) of the rectifier. Main purpose.

  In order to achieve the above object, an inrush current suppression circuit according to the present invention includes a suppression resistor that suppresses a current to a smoothing capacitor in a capacitor input type power supply device, a switch unit connected in parallel to the suppression resistor, and light emission An AC input type photocoupler in which a diode is connected in parallel to the suppression resistor and a phototransistor is turned on when a current flows through the light emitting diode, and a reference time in which the phototransistor is determined in advance And a control circuit that controls the switch unit to an on state when the off state continues to short-circuit the suppression resistor.

  Further, a capacitor input type power supply device according to the present invention includes an inrush current suppression circuit, a rectifier that converts an AC voltage supplied to an AC line into a pulsating voltage, and a capacitor that smoothes the pulsating voltage. I have.

  The capacitor input type power supply device according to claim 3 is the capacitor input type power supply device according to claim 2, wherein the inrush current suppression circuit is interposed in the AC line.

  In the inrush current suppression circuit and the capacitor input type power supply device according to the present invention, the light-emitting diode is connected in parallel to the suppression resistor, and the phototransistor is turned on when a current flows through the light-emitting diode. A type photocoupler is used. Therefore, according to the inrush current suppression circuit and the capacitor input type power supply device, even in a configuration in which the inrush current suppression circuit is interposed in the AC line, the current flowing in the AC line immediately after the input is suppressed by the suppression resistor. When the current flowing through the AC line is reduced and there is no risk of inrush current generation, the switch part is turned on and the suppression resistor is short-circuited to generate loss at the suppression resistor. Thus, it is possible to continue supplying the current to the capacitor.

  The best mode of an inrush current suppression circuit and a capacitor input type power supply device according to the present invention will be described below with reference to the accompanying drawings.

  First, the configuration of the inrush current suppression circuit 1 will be described with reference to the drawings. As shown in FIG. 1, the inrush current suppression circuit 1 includes a suppression resistor 2, a relay 3, an AC input type photocoupler 4 (hereinafter also referred to as “photocoupler 4”), and a forward current flowing through the light emitting diode 4 a of the photocoupler 4. For example, a resistor 5, a pull-up resistor 6, and a control circuit 7, which are incorporated in a rectifying / smoothing unit 12 of a capacitor input type power supply device 11 (hereinafter also referred to as “power supply device 11”) as an example. ing.

  Next, an outline of the rectifying / smoothing unit 12 of the power supply device 11 will be described. As an example, the rectifying / smoothing unit 12 of the power supply device 11 is connected between the AC lines 13a and 13b (power supply lines) to which the AC voltage Vac is supplied from the AC power supply 21 and the AC lines 13a and 13b, and receives the AC voltage Vac. A rectifier 15 that converts (rectifies) the pulsating current voltage and outputs it to the DC lines 14a and 14b; a switch 16 that is interposed in the AC lines 13a and 13b and turns on / off the supply of the AC voltage Vac to the rectifier 15; And a smoothing capacitor 17 that is connected between the DC lines 14a and 14b and generates the DC voltage Vcc by smoothing the pulsating voltage.

  Next, each component of the inrush current suppression circuit 1 will be described in detail. In order to suppress the current value of the current to the capacitor 17 immediately after the power supply 11 is turned on (to avoid the occurrence of an inrush current), the suppression resistor 2 is connected to the capacitor 17 in the power supply 11 as shown in FIG. It is installed in the power supply line. As an example, the suppression resistor 2 is interposed in an AC line 13a that constitutes a power supply line. The relay 3 includes a contact portion 3 a and a coil portion 3 b, and the contact portion 3 a that is a switch portion in the present invention is connected in parallel to the suppression resistor 2. The relay 3 is a relay in which the contact portion 3a is turned off when the coil portion 3b is not energized, and the contact portion 3a is turned on when the coil portion 3b is energized.

  The photocoupler 4 is connected in parallel to the suppression resistor 2 with the light emitting diode 4 a connected in series with the resistor 5. In the photocoupler 4, for example, the phototransistor 4 b is grounded at the emitter, and the collector terminal is pulled up to the DC voltage Vcc by the pullup resistor 6. With this configuration, in the photocoupler 4, the current value of the current flowing through the AC lines 13a and 13b becomes equal to or greater than a predetermined value (specifically, an inrush current flows), and the voltage Vr across the suppression resistor 2 is the reference. When the value becomes higher than the value (forward voltage of the light emitting diode 4a), a current flows through the light emitting diode 4a. In this state, the light emitting diode 4a is activated, and the phototransistor 4b is turned on. As a result, a low level detection signal S1 is output from the collector terminal of the phototransistor 4b.

  On the other hand, in the photocoupler 4, when the current value of the current flowing through the AC lines 13a and 13b is less than a predetermined value (specifically, when the inrush current is not flowing), the voltage Vr across the suppression resistor 2 is the reference value. Therefore, no current flows through the light emitting diode 4a. In this state, the phototransistor 4b is turned off. As a result, a high level detection signal S1 is output from the collector terminal of the phototransistor 4b.

  The control circuit 7 operates upon receiving the supply of the DC voltage Vcc, and controls the relay 3 based on the level of the detection signal S1. As an example, the control circuit 7 executes control for operating the relay 3 when the phototransistor 4b is kept off for a predetermined reference time Tref or more. In this example, the reference time Tref is defined as a half period (T / 2) of the AC voltage Vac as an example. Further, the control circuit 7 executes control to stop the operation of the relay 3 when the phototransistor 4b is turned on.

  Next, operations of the inrush current suppression circuit 1 and the power supply device 11 will be described.

  When the switch 16 is turned on in the supply state of the AC voltage Vac (transition from the OFF state to the ON state), the supply of the AC voltage Vac to the rectifier 15 is started via the AC lines 13a and 13b. 15 rectifies the AC voltage Vac and outputs it to the DC lines 14a and 14b. Thereby, charging of the capacitor 17 is started, and the DC voltage Vcc gradually rises as shown in FIG. In this case, in the period Ta until the DC voltage Vcc reaches the peak value of the AC voltage Vac, the capacitor 17 passes through the AC lines 13a and 13b and the rectifier 15 and is half the cycle T of the AC voltage Vac. Although current flows at (T / 2), the current value is suppressed by the presence of the suppression resistor 2. Further, due to the flow of this current, the suppression resistor 2 interposed in the AC line 13a has a voltage Vr across the reference voltage exceeding the reference voltage in a half cycle of the cycle T, while reversing the polarity. Generated while gradually decreasing the voltage value.

  In this case, since the photocoupler 4 is an AC input type photocoupler in this example, the light-emitting diode 4a of the photocoupler 4 has a positive voltage Vr between both ends (on the input side of the rectifying / smoothing unit 12 in the suppression resistor 2). When the voltage at the terminal is generated with a polarity higher than the voltage at the terminal on the rectifier 15 side, and the negative polarity (the voltage at the terminal on the rectifier 15 side in the suppression resistor 2 is greater than the voltage at the input side terminal of the rectifying / smoothing unit 12) In both cases, the light is shifted to the on state and emits light. Correspondingly, the phototransistor 4b also shifts to the on state both when the voltage Vr between both ends is generated with a positive polarity and when it is generated with a negative polarity. For this reason, the phototransistor 4b repeats the on / off state at a period (T / 2) that is a half of the period T of the AC voltage Vac. Therefore, although the time period during which the phototransistor 4b is turned off (the high period of the detection signal S1) gradually increases due to the gradual decrease in the voltage value of the voltage Vr between both ends, in the period Ta, The OFF state does not exceed the reference time (one half of the period T (T / 2)), and the operation control for the relay 3 by the control circuit 7 is not performed.

  On the other hand, after the DC voltage Vcc reaches a value close to the peak value of the AC voltage Vac (after the period Ta has elapsed), the current supply to the capacitor 17 is continued, but the current value becomes small. Therefore, the voltage Vr between both ends generated in the suppression resistor 2 is maintained below the reference voltage. As a result, in the photocoupler 4, no current flows through the light emitting diode 4a. As a result, the phototransistor 4b is continuously maintained in the off state (the level of the detection signal S1 is maintained at the high level). For this reason, the control circuit 7 uses the reference time Tref (= T / 2) as the elapsed time (the duration of the off state) from the last time t1 (end of the period Ta) when the phototransistor 4b transitions from the on state to the off state. ), The relay 3 is actuated to shift the contact portion 3a from the off state to the on state. As a result, supply of current from the AC power source 21 to the capacitor 17 in a state in which generation of loss in the suppression resistor 2 is avoided is started. Further, after the contact portion 3a is turned on, even if the amount of power supplied to the load connected to the power supply device 11 increases and the current flowing through the AC lines 13a and 13b increases, the suppression resistor 2 Is short-circuited by the contact portion 3a, the voltage Vr across the suppression resistor 2 is always maintained below the reference voltage. As a result, the operation control of the relay 3 by the control circuit 7 is continued, and the occurrence of loss in the suppression resistor 2 is continuously avoided.

  Thus, in the inrush current suppression circuit 1 and the power supply device 11, the light-emitting diode 4a is connected in parallel to the suppression resistor 2, and the phototransistor 4b is turned on when a current flows through the light-emitting diode 4a. The shifting AC input type photocoupler 4 is used. Therefore, according to the inrush current suppression circuit 1 and the power supply device 11, even in the configuration in which the suppression resistor 2 is disposed on the upstream side (AC lines 13 a and 13 b) of the rectifier 15 in the power supply device 11, immediately after the switch 16 is turned on. When the current flowing through the AC lines 13a and 13b is suppressed by the suppression resistor 2 to avoid the occurrence of an inrush current, and when the current flowing through the AC lines 13a and 13b becomes smaller and the occurrence of the inrush current is eliminated, the relay 3 By short-circuiting the suppression resistor 2 at the contact portion 3a, the supply of current to the capacitor 17 can be continued while avoiding the generation of loss in the suppression resistor 2.

  In addition, this invention is not limited to said structure. For example, although the example in which the suppression resistor 2 is interposed in the AC line 13a as the power supply line has been described above, it is needless to say that the suppression resistor 2 may be interposed in the other AC line 13b or one of the DC lines 14a and 14b. . Further, the pull-up resistor 6 is connected to the phototransistor 4b to generate the detection signal S1, but any known circuit can be adopted as a circuit for detecting the state (on / off state) of the phototransistor 4b. . The switch unit is not limited to the relay 3 contact unit 3a, and various semiconductor switches such as a thyristor can be used.

2 is a circuit diagram of a power supply device 11. FIG. FIG. 5 is a waveform diagram for explaining the operation of the inrush current suppression circuit 1. It is a circuit diagram of the conventional inrush current suppression circuit 51 and the power supply device incorporating the inrush current suppression circuit 51.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inrush current suppression circuit 2 Suppression resistance 3 Relay 3a Contact part 4 Photocoupler 4a Light emitting diode 4b Phototransistor 11 Power supply device 14a, 14b DC line 17 Capacitor Tref Reference time

Claims (3)

A suppression resistor that suppresses the current to the smoothing capacitor in the capacitor input type power supply device;
A switch unit connected in parallel to the suppression resistor;
An AC input type photocoupler in which a light-emitting diode is connected in parallel to the suppression resistor and a phototransistor is turned on when a current flows through the light-emitting diode;
An inrush current suppression circuit comprising: a control circuit that controls the switch unit to be in an ON state and short-circuits the suppression resistor when the phototransistor is in an OFF state for a predetermined reference time or more.   A capacitor input type power supply device comprising: the inrush current suppressing circuit according to claim 1; a rectifier that converts an AC voltage supplied to an AC line into a pulsating voltage and outputs; and a capacitor that smoothes the pulsating voltage. .   The capacitor input type power supply device according to claim 2, wherein the inrush current suppression circuit is interposed in the AC line.

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