JP2003235265A - Power control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power control circuit which can reduce the loss of a power transformer itself at waiting for an apparatus and can supply load with waiting power required. <P>SOLUTION: The power control circuit which controls the power to be supplied to the power transformer 10 whose primary winding 11 is connected with an AC power source 20 and whose secondary winding 12 is connected with load is provided with an AC switching element PI1, which switches on or switches off the connection between the primary winding 11 and the AC power source 20, an output voltage detection means 30, which detects the output voltage V1 on the side of the secondary winding 12 and outputs a waiting control signal V2 changing periodically when the load connected to the secondary winding 12 is in waiting state, and a switching control means PI2, which switches on or switches off the AC switching element PI1, according to the waiting control signal, and connects the AC power source 20 intermittently to the power transformer 10 when the load connected to the secondary winding 12 is in waiting state. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control for controlling electric power supplied to a primary winding of a power transformer having a primary winding connected to an AC power source and a predetermined load connected to a secondary winding. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit, and more particularly to control during standby of various devices connected as a load.

[0002]

2. Description of the Related Art Conventionally, it has been desired to reduce power consumption of various devices that consume power. In many cases, unnecessary electric power is consumed when the device is on standby. Therefore, various devices grasp the operating state of themselves and control so as to shift to the energy saving mode in the standby state. Generally, in the energy saving mode, the DC power supply to unnecessary circuits in various standby circuits of the equipment is cut off, or the supplied voltage is switched to the minimum required voltage. .

When the equipment is switched to the energy saving mode, the DC power supplied from the power supply device to the load is reduced, and the power consumption of the entire device is also reduced.

[0004]

By the way, in a general device, AC power supplied from a commercial power source or the like is converted into DC power of a predetermined voltage by a power supply device to supply DC power to a load. An exciting current flows through the windings of the power transformer built in such a power supply device even when power is not supplied to the load.

Therefore, when the device is switched to the energy saving mode, the power consumed by the load is reduced, but the power transformer itself wastes a relatively large amount of power. However, since it is necessary to supply the minimum amount of power to the load even during standby, it is not possible to completely cut off the power supply to the power transformer.

On the other hand, when a trouble such as a power failure occurs in a commercial power supply, AC power of an abnormal voltage is supplied to the power supply device, so that the specified voltage cannot be supplied to the device and the device malfunctions. There is a high possibility that it will lead to a breakdown. An object of the present invention is to provide a power supply control circuit capable of reducing the loss of the power supply transformer itself when the device is on standby and supplying the required standby power to the load.

[0007]

According to a first aspect of the present invention, an electric power supplied to a primary side winding of a power transformer in which a primary side winding is connected to an AC power source and a predetermined load is connected to the secondary side winding is provided. In a power supply control circuit for controlling, an AC switching element for controlling on / off of a connection between a primary side winding of the power supply transformer and an AC power supply, and an output voltage on a secondary side winding side of the power supply transformer are detected, and When the load connected to the secondary winding is in a standby state, output voltage detection means for outputting a standby control signal that changes periodically, and the AC switching element according to the standby control signal output by the output voltage detection means And a switching control means for intermittently connecting an AC power supply to the power transformer when a load connected to the secondary winding is in a standby state.

According to the first aspect of the present invention, when the load connected to the secondary winding of the power transformer enters a standby state and the output voltage on the secondary winding side becomes high, the output voltage detecting means changes periodically. Output a standby control signal. The switching control means controls ON / OFF of the AC switching element according to the standby control signal output by the output voltage detection means.

Therefore, when the load connected to the secondary winding is in the standby state, the AC switching element intermittently connects the AC power supply to the power transformer. That is, in the standby state, a state in which the exciting current flows and a state in which the exciting current does not flow alternately occur in the power transformer. Therefore, the standby loss caused by the exciting current flowing through the power transformer is reduced. However, since the exciting current flows intermittently even during standby, the power transformer can supply the minimum amount of power required during standby to the load.

According to a second aspect of the present invention, in the power supply control circuit according to the first aspect, the voltage of the AC power supply connected to the primary winding of the power supply transformer is detected, and when the detected voltage is less than or equal to an allowable value, the It is characterized in that a power failure detecting means for controlling the AC switching element to be turned off is further provided. In a second aspect of the present invention, when a trouble such as a power failure occurs in a commercial power source and the AC voltage applied to the power transformer falls below an allowable value, the AC switching element is turned off by the control of the power failure detecting means. . That is, when the voltage of the input AC power becomes unstable, the AC power supply to the power transformer is completely cut off. Therefore,
It is possible to prevent malfunction and failure of equipment due to abnormal power supply voltage.

According to a third aspect of the present invention, in the power supply control circuit according to the first aspect, a rectifying element and a smoothing element for smoothing rectified power are connected to the secondary winding of the power source transformer, and the output voltage detecting means is connected to the output voltage detecting means. Is provided with a comparison element for comparing the DC voltage smoothed by the smoothing element with a predetermined threshold value. In the third aspect, the output voltage detecting means monitors the DC voltage smoothed by the smoothing element. In other words, when the equipment goes into the standby state and the current flowing through the load becomes smaller, the DC voltage output from the power supply becomes higher than usual, so by comparing the voltage with a predetermined threshold value, the equipment goes into the standby state. You can recognize that

According to a fourth aspect of the present invention, in the power supply control circuit according to the third aspect, a feedback element for feeding back an output signal of the comparison element to an input of the comparison element is provided. By providing the feedback element, the operation of the comparison element can have hysteresis. Therefore, it becomes possible to output a stable standby control signal from the comparison element.

According to a fifth aspect of the present invention, in the power supply control circuit according to the first aspect, a phototriac is provided as the AC switching element. In the fifth aspect, since the phototriac is used, the signal for controlling the on / off of the AC switching element can be easily generated. According to a sixth aspect of the present invention, in the power supply control circuit according to the first aspect, a photocoupler is provided as the switching control means.

According to the sixth aspect of the present invention, since the photocoupler is used, the secondary side winding is kept electrically insulated from the primary side winding side circuit and the secondary side winding side circuit of the power transformer. The AC switching element connected to the primary winding side can be controlled according to the signal from the side circuit.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of a power supply control circuit of the present invention will be described with reference to FIGS. This form corresponds to all the claims.

FIG. 1 is an electric circuit diagram showing the configuration of the power supply control circuit of this embodiment. FIG. 2 is a time chart showing the operation of the circuit during the standby operation. FIG. 3 is a time chart showing the operation of the circuit during normal operation. In this embodiment, the power transformer, the AC switching element, the output voltage detecting means and the switching control means of claim 1 are embodied as a power transformer 10, a photocoupler PI1, a voltage detecting circuit 30 and a photocoupler PI2, respectively.

Further, the power failure detecting means of claim 2 is embodied as a Zener diode D3. The rectifying element, the smoothing element and the comparing element of claim 3 are embodied as a rectifying circuit RC1, a capacitor C3 and an analog comparator M1, respectively. The feedback element of claim 4 is embodied as a resistor R16 and a diode D12.

The power supply control circuit shown in FIG. 1 can be used as a part of a power supply device for various electric devices. That is, this power supply control circuit converts the AC power supplied from the commercial AC power supply 20 connected to the input into a predetermined voltage, further converts it into DC power, and supplies the DC power to the output terminal 21. Therefore, the load of the electric device is connected to the output terminal 21 directly or via a voltage stabilizing circuit (not shown).

As shown in FIG. 1, the power supply control circuit includes a power supply transformer 10 for voltage conversion and circuit insulation.
Is equipped with. Primary winding 11 of power transformer 10
Is connected to the commercial AC power supply 20 via the photocoupler PI1. The photocoupler PI1 contains a phototriac and a light emitting diode for controlling the ON / OFF of the phototriac.

When the phototriac of the photocoupler PI1 is turned on (conducting state), AC power (AC100V) from the commercial AC power supply 20 is supplied to the primary winding 11, and the phototriac of the photocoupler PI1 is turned off (non-conducting state). Then, the primary winding 11 is disconnected from the commercial AC power supply 20. Next, a circuit for controlling the light emitting diode incorporated in the photocoupler PI1 will be described. The AC voltage supplied from the commercial AC power source 20 is the diode D1, D
Since it is rectified by 2, a substantially constant DC voltage V4 appears between the terminals of the capacitor C2.

This DC voltage V4 is the photocoupler PI1.
Is applied to the anode terminal of the light emitting diode. Zener diode D is connected to the cathode terminal of this light emitting diode.
3 are connected in series. Also, Photo Cupla PI1
The photocoupler PI is connected to the anode terminal of the light emitting diode of
2 is connected. The photocoupler PI2 includes a phototransistor and a light emitting diode that controls the phototransistor.

When the photocoupler PI2 is turned on (conducting state), the DC voltage V4 is short-circuited by the phototransistor incorporated in the photocoupler PI2, and the photocoupler P2.
The voltage applied to the light emitting diode of I1 becomes almost 0, and the photocoupler PI1 is turned off. On the other hand, when the regulated AC voltage is supplied from the commercial AC power source 20, the DC voltage V4 becomes sufficiently higher than the Zener voltage of the Zener diode D3. Therefore, unless the photocoupler PI2 is turned on, the light emitting diode of the photocoupler PI1 is turned on. A current flows and the phototriac of photocoupler PI1 is turned on.

However, when a trouble such as a power failure occurs and the AC voltage supplied from the commercial AC power source 20 becomes lower than the specified voltage, the DC voltage V4 becomes lower than the Zener voltage of the Zener diode D3, and the photocoupler P
No current flows in the light emitting diode of I1, and the phototriac of the photocoupler PI1 is turned off. When the phototriac of the photocoupler PI1 is on, the AC power from the commercial AC power supply 20 is supplied to the primary winding 11 of the power transformer 10 and the exciting current flows, so that the AC power also appears in the secondary winding 12. .

The AC power appearing in the secondary winding 12 is full-wave rectified by the rectifier circuit RC1 and smoothed by the capacitor C3. Therefore, the DC voltage V1 appears at the output terminal 21.
The voltage detection circuit 30 monitors the DC voltage V1 of the output terminal 21, and identifies whether the load of the electric device connected to the output terminal 21 is in the standby state. That is, when the load is in a normal operating state, a relatively large current flows into the load, so that the DC voltage V1 of the output terminal 21 becomes a substantially regulated voltage. The DC voltage V1 of 21 becomes larger than the specified voltage. By checking such a difference in voltage, it is possible to identify whether or not the load is in the standby state.

The voltage detection circuit 30 shown in FIG. 1 includes an analog comparator M1, resistors R11 to R16, and a capacitor C1.
1, a Zener diode D11 and a diode D12 are provided. The analog comparator M1 compares the monitoring voltage Va with the threshold voltage Vref and outputs a binary signal indicating the comparison result as a DC voltage V2.

The monitoring voltage Va is obtained by dividing the DC voltage V1 at the output terminal 21 with resistors R14 and R15. However, since the capacitor C11 is connected in parallel with the resistor R15, the change of the monitoring voltage Va becomes gentler than the change of the DC voltage V1. On the other hand, the threshold voltage Vref is constant because it is obtained by dividing the constant voltage appearing between the terminals of the Zener diode D11 by the resistors R12 and R13. However, since the output voltage V2 of the analog comparator M1 is fed back to the input via the diode D12 and the resistor R16, when the output voltage V2 becomes low level, the threshold voltage Vref temporarily decreases.

The binary signal (V
2) is applied to the light emitting diode of the photocoupler PI2. That is, the photocoupler PI2 is turned on / off according to the binary signal (V2) output from the voltage detection circuit 30.
Actually, when the binary signal (V2) becomes high level, no current flows in the light emitting diode of the photocoupler PI2, and the phototransistor of the photocoupler PI2 is turned off. When the binary signal (V2) becomes low level, the photocoupler PI2
A current flows through the light emitting diode of, and the phototransistor of the photocoupler PI2 is turned on.

Next, the overall operation of the power supply control circuit shown in FIG. 1 will be described. First, assume that the load is in the normal operation mode. In that case, the power supply control circuit of FIG. 1 operates as shown in FIG.

That is, the photocoupler PI1 is constantly turned on, and the power transformer 10 is continuously supplied with AC power from the commercial AC power supply 20. Therefore, sufficiently large electric power can be supplied also to the secondary winding 12 of the power transformer 10. However, since the current flowing through the load becomes sufficiently large, the DC voltage V1 appearing at the output terminal 21 is maintained below the threshold voltage (VrU).

Therefore, the state of (Vref> Va) is maintained at the input of the analog comparator M1, and the binary signal (V2) is maintained at a high level. Therefore, the photocoupler PI2 maintains the off state, and the photocoupler PI1 maintains the on state. On the other hand, when the load is in the standby state, the power supply control circuit of FIG. 1 operates as shown in FIG. That is, the photocoupler PI1 is intermittently turned on, and the power transformer 10 is intermittently connected to the commercial AC power supply 2
AC power from 0 is supplied.

By intermittently supplying the AC power to the power transformer 10, it is possible to reduce the exciting power and reduce the wasted power consumed in the standby state. However, even in this case, a relatively small amount of power corresponding to standby power can be supplied to the secondary winding 12 of the power transformer 10. During standby, the current flowing through the load becomes very small, so while the exciting current is flowing through the primary winding 11, the output terminal 21
The DC voltage V1 appearing at gradual increase. When this DC voltage V1 exceeds the threshold voltage (VrU), the state of (Vref <Va) is changed at the input of the analog comparator M1, and the binary signal (V2) is switched to the low level.

Further, when the binary signal (V2) becomes low level, a current flows from the input side of the analog comparator M1 to the output of the analog comparator M1 via the resistor R16 and the diode D12, so that the threshold voltage Vref is stepped. Will be reduced. As a result, the threshold value of the analog comparator M1 is switched (Vref <Va) is maintained. That is, the comparison operation of the analog comparator M1 has a hysteresis characteristic.

The binary signal (V
When 2) becomes a low level, a current flows through the light emitting diode of the photocoupler PI2, so that the phototransistor of the photocoupler PI2 is turned on. Therefore, the DC voltage V4 is short-circuited, the current flowing in the light emitting diode of the photocoupler PI1 is cut off, and the phototriac of the photocoupler PI1 cuts off the current flowing in the primary winding 11. Therefore, the exciting current of the primary winding 11 is temporarily cut off.

When the exciting current of the primary winding 11 is cut off, electric power is not supplied to the secondary winding 12, so that the DC voltage V1 at the output terminal 21 gradually increases according to the standby power consumed by the load. descend. When the DC voltage V1 becomes equal to or lower than the threshold voltage (VrL), the state of (Vref> Va) is changed at the input of the analog comparator M1, and the binary signal (V2) is switched to the high level again.

Therefore, the current of the light emitting diode of the photocoupler PI2 is cut off, the phototransistor of the photocoupler PI2 is turned off, the current flows again to the light emitting diode of the photocoupler PI1, the phototriac of the photocoupler PI1 is turned on, and the primary winding The exciting current flows through the line 11 again. That is, when the load enters the standby state and the current consumption decreases, the exciting current supplied to the primary winding 11 flows intermittently, and the exciting current flowing state and the exciting current not flowing periodically change. To do. Therefore, the exciting current (effective value) of the primary winding 11 can be reduced during standby, and useless power consumption in the power transformer 10 can be suppressed.

On the other hand, when a trouble such as a power failure occurs and the AC voltage supplied from the commercial AC power source 20 becomes lower than the specified voltage, the DC voltage V4 becomes lower than the Zener voltage of the Zener diode D3. Therefore, no current flows through the light emitting diode of the photocoupler PI1,
The photo triac of Photo Cupla PI1 is turned off.
That is, the photocoupler PI1 has a power supply voltage (A
When the C100V) drops abnormally, the power transformer 1
The power supply to 0 is automatically stopped. This allows
It is possible to prevent malfunction and failure of equipment connected as a load.

[0037]

As described above, according to the present invention, when the device connected as the load is in the standby state and the current consumption is reduced, the exciting current of the transformer flows intermittently, so that the standby time is reduced. The power loss of the transformer can be greatly reduced.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a configuration of a power supply control circuit according to an embodiment.

FIG. 2 is a time chart showing the operation of the circuit during a standby operation.

FIG. 3 is a time chart showing the operation of the circuit during normal operation.

[Explanation of symbols]

10 power transformer 11 Primary winding 12 Secondary winding 20 Commercial AC power supply 21 output terminal 30 Voltage detection circuit RC1 rectifier circuit PI1, PI2 Photo coupler Vref threshold voltage Va monitoring voltage D1, D2, D12 diode D3, D11 Zener diode M1 analog comparator C1 to C3 capacitors C11 capacitor R1 to R3 resistors R11 to R16 resistors

Continued front page    F-term (reference) 5G065 AA01 DA06 DA07 EA06 FA05                       GA06 HA01 JA01 KA02 KA05                       LA01 MA03 MA09 MA10 NA09                 5H006 CA06 CA07 CB01 CC01 CC08                       DA04 DB01 DC05                 5H420 CC02 CC04 EA08 EA20 EA27                       EB01 FF03 FF25

Claims (6)

[Claims] 1. A power supply control circuit for controlling the power supplied to the primary winding of a power transformer, the primary winding of which is connected to an AC power supply, and a predetermined load is connected to the secondary winding of the power supply. An AC switching element that controls ON / OFF of the connection between the primary winding of the transformer and the AC power supply, and a load connected to the secondary winding while detecting the output voltage on the secondary winding side of the power transformer. Is in a standby state, output voltage detection means for outputting a standby control signal that changes periodically, and ON / OFF control of the AC switching element according to the standby control signal output by the output voltage detection means, and the secondary side A power supply control circuit comprising: switching control means for intermittently connecting an AC power supply to the power supply transformer when a load connected to the winding is in a standby state. 2. The power supply control circuit according to claim 1, wherein the voltage of an AC power supply connected to the primary winding of the power supply transformer is detected, and when the detected voltage is less than or equal to an allowable value, the AC switching element. A power supply control circuit, further comprising a power failure detection means for controlling the power off. 3. The power supply control circuit according to claim 1, wherein a rectifying element and a smoothing element for smoothing the rectified power are connected to the secondary winding of the power supply transformer, and the output voltage detecting means includes the smoothing element. A power supply control circuit comprising a comparison element for comparing a DC voltage smoothed by a smoothing element with a predetermined threshold value. 4. The power supply control circuit according to claim 3, further comprising a feedback element that feeds back an output signal of the comparison element to an input of the comparison element. 5. The power supply control circuit according to claim 1, wherein a phototriac is provided as the AC switching element. 6. The power supply control circuit according to claim 1, further comprising a photocoupler as the switching control means.