JPH06217448A - Rush current preventer - Google Patents

Abstract

PURPOSE:To reduce heating value by blocking rush current flowing through a rush current preventing resistor upon occurrence of instantaneous power interruption or chattering under low load and to reduce the scale of rush current preventer by reducing power of the rush current preventing resistor. CONSTITUTION:When a voltage obtained by dividing a rectified voltage Va by means of resistors P6, R7 matches the voltage at the joint of a resistor R8 and a capacitor C9, a triac 2 is turned ON to limit rush current by means of a resistor R1 upon turn ON of an AC power supply. The triac 2 is turned OFF after turn ON of AC power supply depending on the heavy and light states of a load circuit 4 at a time when the voltage divided by resistors R13, R14 at the time of instantaneous power interruption drops below a reference voltage V4 produced through a resistor R15 and a Zener diode D16. In case of an instantaneous power interruption under a state where the load is light and the rectified voltage Va is high, AC power supply is turned ON again while sustaining the triac 2 in ON state thus blocking the rush current flowing into the resistor R1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inrush current prevention device for use in a DC power supply device, which prevents an inrush current from flowing into a resistor for preventing inrush current when momentary power failure or chattering occurs when the load is light.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a partial block diagram of the configuration of a conventional inrush current prevention device. In FIG. 3, this inrush current prevention device includes an AC power supply AC and an AC power supply A.
Inrush current limiting resistor R1 connected to one end of C,
It has a triac (two-way three-terminal thyristor) 2 connected in parallel to the resistor R1. Further, this inrush current prevention device includes a resistor R and the other end of the AC power source AC.
1 and the other end of the triac 2 each have a main rectifier circuit 3 and a load circuit 4 such as an electronic circuit to which the DC voltage Va from the main rectifier circuit 3 is supplied.

Further, a sub rectifier circuit 5 connected to the input terminal of the main rectifier circuit 3 is connected in series between the DC voltage output terminal of the sub rectifier circuit 5 and ground, and a voltage V1 divided at the connection point is connected. And resistors R6 and R7 for generating. Furthermore, connect in series between the DC voltage output terminal and ground,
It has a resistor R8 and a capacitor C9 that generate a voltage V2 that is divided with a time constant at the connection point.

A diode D10 connected between the DC voltage output terminal of the sub rectifier circuit 5 and the connection point of the resistor R8 and the capacitor C9, the DC voltage output terminal of the sub rectifier circuit 5 and the resistors R6, R7 and It has a comparison circuit 11 in which the two connection points of the resistor R8 and the capacitor C9 are connected to the input side, and the output side is connected to the gate of the triac 2.

Next, the operation of this conventional structure will be described. 4 (a), (b), (c), and (d) are waveform diagrams showing the voltage of each part and the primary current from the AC power supply AC when the rush current is limited by the resistor R1 when the AC power supply is turned on. When the AC power is turned on, the AC shown in FIG. 4C is supplied to the main rectifier circuit 3. However, at the time limit t1 shown in FIG. 4A in this case, as shown in FIG. 2 is turned off (OFF, non-conduction), and the rush current is limited by the resistor R1.

In this case, when the AC power is turned on, the direct current voltage Va and the voltage V1 divided at the connection point of the resistors R6 and R7, the voltage V at the connection point of the resistor R8, and the capacitor C9 are obtained.
2 stands up. The voltage V2 rises according to the charging time of the capacitor C9, that is, the time constant of the resistor R8 and the capacitor C9, and the rising edge (going edge) is gentler than the voltage V1. The control signal is output from the comparison circuit 11 to the gate of the triac 2 at the point where the voltage V1 and the rising voltage of the voltage V2 coincide. As a result, the triac 2 is turned on (O) as shown in FIG.
As shown in FIG. 4D, AC from the AC power supply is supplied to the main rectifier circuit 3 without passing through the resistor R1.

FIGS. 5A, 5B, and 5C are voltage and current waveform diagrams showing the case of an instantaneous power failure after the AC power is turned off and the AC power is turned on again. As shown in FIG. 5B, the triac 2 does not turn off instantaneously in the case of an instantaneous power failure. Therefore, FIG.
As shown in FIG. 5C, when the DC voltage Va from the main rectifier circuit 3 has a high voltage change (1) when the AC voltage is turned on again due to a momentary power failure, that is, when the load circuit 4 is light in FIG. ), A relatively small inrush current flows through the triac 2 as shown by the primary current fluctuation "1". When the DC voltage Va from the main rectifier circuit 3 is low when the AC power is turned on again when the voltage change is low (2), that is, when the load circuit 4 is heavy, as shown in the primary current fluctuation "2". A large inrush current flows through the triac 2.

FIGS. 6A, 6B and 6C are waveform diagrams of voltage and current when the voltage fluctuates due to chattering or the like.
As shown in FIG. 6A, the voltage V1,
If the state where V2 does not rise stably continues, as shown in FIG.
As shown in, the triac 2 remains off,
As shown in FIG. 6C, a large inrush current continuously flows through the resistor R1.

[0009]

In the conventional inrush current prevention device as described above, the inrush current flows through the resistor R1 for preventing the inrush current even when the load circuit 4 is light, and the chattering occurs. Even when the above occurs, a large current flows into the resistor R1 for preventing the inrush current, and the amount of heat generated is large, so that the resistor R1 with a large power is required, and there is a problem that the device scale increases.

The present invention solves the drawbacks of the prior art as described above. When a momentary power failure and chattering occur when the load is light, the inrush current is blocked by the resistor for preventing the inrush current and the amount of heat generated is reduced. It is an object of the present invention to provide an inrush current prevention device that can reduce the power consumption of the inrush current prevention resistor and reduce the device scale.

[0011]

In order to achieve the above object, the inrush current prevention apparatus of the present invention comprises a parallel connection inrush current prevention resistor having one end and one end connected to an AC power supply and an on-current prevention resistor. Rectification in which each of the off switching means, the other end of the inrush current prevention resistor and the on / off switching means, and the other end of the alternating current power supply is connected to the input side, and the load is connected to the output side Means, a first voltage divider connected in series between grounds to divide the rectified voltage obtained by rectifying the AC of the AC power supply, a resistor and a capacitor connected in series, and a voltage divider by the first voltage divider. When the applied voltage and the voltage at the connection point of the resistor and capacitor match, the on / off switching means is set from off to on and the inrush current prevention resistor is used to limit the inrush current when the AC power is turned on. First to output switching signal A comparison / switching signal output means, a second voltage divider connected in series between grounds to obtain a voltage obtained by dividing the rectified voltage from the rectifying means, and a reference voltage generating means for generating a predetermined reference voltage from the rectified voltage. And a voltage divided by each of the second voltage dividers when the load is heavy and light when the AC power supply is cut off, and a predetermined reference voltage or less is compared, and the divided voltage is determined to be a predetermined reference voltage or less. The second comparison that outputs a signal for switching the ON state of the ON / OFF switching means to OFF after the AC power is turned on after
And a switching signal output means.

[0012]

The inrush current prevention device of the present invention having the above-described structure has the ON / OFF switching means when the voltage obtained by dividing the rectified voltage by the two resistors and the voltage at the connection point between the resistor and the capacitor match. Is set from OFF to ON to limit the inrush current when the AC power supply is turned on, and when the load is heavy or light when the AC power supply is cut off, the AC voltage is applied after the time when the divided voltage becomes the specified reference voltage or less. After the power is turned on, the on / off switching means is turned off.

That is, in the case of momentary power interruption or chattering,
When the rectified voltage is higher than a certain voltage, for example, the ON / OFF switching means such as a triac is kept in the ON state, and when the voltage becomes lower than the voltage, the ON / OFF switching means is turned off to cause instantaneous blackout or chattering when the load is light. Inrush current to the inrush current prevention resistor is blocked.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an inrush current prevention device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a partial block diagram of the configuration of an embodiment of the inrush current prevention device of the present invention. It should be noted that in FIG. 1 and subsequent sentences, the same components as those in the previous FIG. In FIG. 1, this example shows an AC power supply AC, a resistor R1 for limiting an inrush current connected to one end of the AC power supply AC, and a triac (two-way three-terminal thyristor connected in parallel with the resistor R1. (Corresponding to the on / off switching means in the claims).

Further, this inrush current prevention device includes a main rectifying circuit 3 (corresponding to the rectifying means in the claims) connected to the other end of the AC power supply AC and the other ends of the resistor R1 and the triac 2, respectively. It has a load circuit 4 such as an electronic circuit to which the DC voltage Va from here is supplied.
Further, a sub rectifier circuit 5 connected to the input terminal of the main rectifier circuit 3 and a DC voltage output terminal of the sub rectifier circuit 5 are connected in series to generate a voltage V1 divided at the connection point. Resistors R6 and R7 (corresponding to the first two resistors in the claims).

Further, a voltage V which is connected in series between the DC voltage output terminal and the ground and is divided with a time constant at the connection point
It has a resistor R8 for generating 2 and a capacitor C9. In addition, the DC voltage output terminal of the sub rectifier circuit 5 and the resistor R
8 and a capacitor C9 (corresponding to a resistor and a capacitor in the claims) and a diode D10 connected to the connection point, and a DC voltage output terminal of the sub rectifier circuit 5 has. Further, a comparison circuit 11 connected to each connection point of the resistors R6 and R7, the resistor R8, and the capacitor C9 and the gate of the triac 2, and an OR circuit 1 connected between the comparison circuit 11 and the triac 2.
7 and 7. The comparison circuit 11 and the OR circuit 1
7 corresponds to the first comparison / switching signal output means in the claims.

Further, this inrush current prevention device is connected in series between the DC voltage output terminal of the main rectifying circuit 3 and the ground, and resistors R13 and R1 for generating a voltage 3 divided at the connection point.
4 (corresponding to the second two resistors in the claims)
And a resistor R for connecting in series between the DC voltage output terminal of the main rectifier circuit 3 and ground to obtain a reference voltage V4 at the connection point.
15 and a Zener diode D16 (corresponding to the reference voltage generating means in the claims). Further, it has a DC voltage output terminal of the sub rectifier circuit 5, a comparison circuit 12 connected to the connection points of the resistors R13 and R14 and a connection point of the resistor R15 and the Zener diode D16, respectively, and the comparison circuit 12 and the triac. OR circuit 1 between 2 and
7 is connected. The configuration of the comparison circuit 12 and the OR circuit 17 corresponds to the second comparison / switching signal output means in the claims.

Next, the operation of the configuration of this embodiment will be described. 2A, 2B, and 2C are waveform diagrams showing the voltage and current in this embodiment. 2A, AC is supplied to the main rectifier circuit 3 when the AC power is turned on, but at the time limit t1 shown in FIG. 2A, the triac 2 is turned on as shown in FIG. 2C. Off (O
(FF, non-conducting) to limit the inrush current with the resistor R1.

In this case, when the AC power is turned on, the DC voltage Va and the voltage V1 divided at the connection point of the resistors R6 and R7 rise. Furthermore, resistor R8 and capacitor C
The voltage V2 at the connection point of 9 corresponds to the time constant of the resistor R8 and the capacitor C9, and rises more gently than the voltage V1. At a point where the voltage V1 and the rising voltage of the voltage V2 coincide, the comparison circuit 11 outputs a high (H) level signal to the logical sum circuit 17
Then, the OR circuit 17 outputs a control signal to the gate of the triac 2. This control signal is shown in FIG.
As shown in (3), the triac 2 is turned on (ON, conduction), and thereafter is kept on to supply AC from the AC power source to the main rectifier circuit 3 without passing through the resistor R1.

Next, from the ON state of the triac 2, AC
The case where the power is cut off will be described. Depending on the ON state of the triac 2, the DC voltage Va from the main rectifier circuit 3 is applied to the load circuit 4
Is supplied to. In this case, the resistors R13 and R14 that monitor the DC voltage Va rectified by the main rectifier circuit 3.
The comparison circuit 12 compares the voltage V3 at the connection point of the reference voltage V3 with the reference voltage V4 at the connection point of the resistor R15 and the Zener diode D16. Then, when the AC power is cut off, the DC voltage Va and the voltage V4 decrease as shown in FIG. The comparison circuit 12 compares the voltage V3 with the reference voltage V4, and only when the voltage V3 is equal to or lower than the reference voltage V4, the OR circuit 17
A high (H) level signal is output to. A control signal is output from the OR circuit 17 to the gate of the triac 2, and the triac 2 which has been kept in the on state is turned off by this control signal.

In this case, the decrease of the DC voltage Va, that is, the voltage V4 is gradually decreased in a short time as shown at time t2 in FIG. 2C when the load circuit 4 is heavy, and when the load circuit 4 is light. As shown at time t3 in FIG. 2 (c), it gradually decreases in a relatively long time. Therefore, when the load circuit 4 is heavy,
When it is light, the comparison circuit 12 detects the falling and decreasing state of the DC voltage Va.

That is, as in the case where the load circuit 4 shown in FIG. 2 (c) is light, the voltage V3 is equal to the preset reference voltage V.
It takes a relatively long time t4 to become 4 or less, and the triac 2 held on after the relatively long time t4.
Turns off. Further, as in the case where the load circuit 4 shown in FIG. 2 (c) is heavy, the voltage V3 is the preset reference voltage V4.
If the short time t2 is reached below, the triac 2 held on after the short time t2 is turned off.

When the load circuit 4 connected in this manner is heavy, the AC power is cut off and the triac 2 is controlled to be turned off in a short time. Therefore, the AC power is turned on again in a short time such as a momentary power failure. In this case, the inrush current is limited through the resistor R1 for limiting the inrush current as described above when the AC power is turned on. When the load circuit 4 is light, the AC power is cut off and the triac 2 is controlled to be off for a relatively long time.
For example, the AC power is cut off within the time t3 shown in FIG.
At the momentary power failure when the C power is turned on again, the triac 2 remains on, and the inrush current is not limited through the inrush current limiting resistor R1. That is, in the middle of the decrease of the voltage V3 when the AC power supply is cut off, if a certain voltage value is reached,
Since a large current does not flow in the load circuit 4 when the power is re-entered, the midpoint of this drop is judged in advance and the triac 2
You can switch it from the on state to the off state.

In other words, when there is a momentary power failure and the load circuit 4 is light, the inrush current to the resistor R1 ceases to flow and the triac 2 does not remain in the off state when chattering occurs. A large inrush current does not continuously flow into the resistor R1. That is, the resistor R1 can be used for small electric power. Although the sub rectifier circuit 5 is used in this embodiment, the main rectifier circuit 3 is used instead of the rectified (DC) voltage from the sub rectifier circuit 5.
The same action and effect can be obtained even if the direct current voltage Va from is used after being divided by a resistor or the like. Further, the triac 2 connected in parallel with the resistor R1 for preventing inrush current may be another on / off switch, for example, a thyristor.

[0025]

As is apparent from the above description, the inrush current prevention device of the present invention switches on / off when the voltage obtained by dividing the rectified voltage and the voltage at the connection point of the resistor and the capacitor match. When the means is set from off to on to limit the inrush current when the AC power is turned on, and when the load is heavy or light when the AC power is cut off, the divided voltage becomes less than the specified reference voltage Since the on / off switching means is switched off after the AC power is turned on, the inrush current to the resistor for preventing inrush current is blocked during momentary power failure and chattering when the load is light, and the amount of heat generated is reduced. This has the effect of reducing the power consumption of the inrush current prevention resistor and reducing the device scale.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a partial block diagram of a configuration of an inrush current prevention device according to an embodiment of the present invention.

FIG. 2A is a waveform diagram showing the voltage of each part when the AC power is turned on in the configuration of FIG. (B) is a waveform diagram showing the voltage of each part when the AC power supply is cut off in the configuration of FIG. 1.
(C) is a figure which shows the on / off state of the triac in the structure of FIG.

FIG. 3 is a circuit diagram showing a partial block diagram of a configuration of a conventional inrush current prevention device.

FIG. 4A is a waveform diagram showing the voltage of each part when the AC power is turned on in the configuration of FIG. FIG. 4B is a diagram showing the on / off state of the triac when the AC power is turned on in the configuration of FIG. 3. (C) is an AC input waveform diagram when the AC power is turned on in the configuration of FIG. 3. FIG. 4D is a waveform diagram of the primary current when the AC power is turned on in the configuration of FIG.

5A is a waveform diagram showing the voltage of each part at the momentary power failure in the configuration of FIG. FIG. 4B is a diagram showing an on / off state of the triac at the momentary power failure in the configuration of FIG. 3.
FIG. 4C is a waveform diagram showing the primary current at the momentary blackout in the configuration of FIG. 3.

6 (a) is a waveform diagram showing the voltage of each part when chattering occurs in the configuration of FIG. (B) shows that the triac is turned on when chattering occurs in the configuration of FIG.
It is a figure which shows an off state. FIG. 4C is a waveform diagram showing the primary current when chattering occurs in the configuration of FIG.

[Explanation of symbols]

2 ... Triac 3 ... Main rectifier circuit 4 ... Load circuit 5 ... Sub rectifier circuit 11, 12 ... Comparison circuit 17 ... OR circuit C9 ... Capacitor D10 ... Diodes R1, R6, R7, R8, R13 to R15 ... Resistors

Claims (1)

[Claims] 1. An inrush current preventing resistor and an on / off switching means, which are connected in parallel to each other, and one end of which is connected to one end of an AC power source, and the inrush current preventing resistor and the on / off switching means. A rectifying unit having an end and the other end of the AC power supply connected to the input side and a load connected to the output side, and a rectified voltage obtained by rectifying the AC of the AC power supply. For this reason, when the first voltage divider and the series-connected resistor and capacitor connected in series between the ground and the voltage divided by the first voltage divider and the voltage at the connection point of the resistor and capacitor match And a first comparison / switching signal output means for setting the on / off switching means from off to on and outputting a switching signal for limiting the inrush current when the AC power is turned on by the inrush current preventing resistor. , The above rectifying hand A second voltage divider connected in series between grounds to obtain a voltage obtained by dividing the rectified voltage from the reference voltage generating means for generating a predetermined reference voltage from the rectified voltage, and the load when the AC power supply is cut off. The voltage divided by each of the second voltage dividers when heavy and light is compared with the predetermined reference voltage or less, and after the time when the divided voltage becomes the predetermined reference voltage or less, the AC power supply An inrush current prevention device comprising: a second comparison / switching signal output unit that outputs a signal for switching the ON state of the ON / OFF switching unit after being turned on to OFF.