JP2001025247A - Power supply - Google Patents

Abstract

(57) Abstract: A power supply device that controls the operation of an input-side circuit in accordance with an output current, and an object thereof is to provide a power supply device that can reduce unnecessary power consumption. SOLUTION: A transformer 7 for transmitting electric power from a primary winding L1 to a secondary winding L2, a transistor Q1 for controlling a current supplied to the primary winding L1 of the transformer 7, and a secondary winding of the transformer 7 A detection circuit 9 for detecting the power transmitted to the line L2;
A control circuit 6 for controlling the switching of the
And a voltage doubler circuit 101 for outputting a voltage corresponding to the power transmitted to the secondary winding L2 of the transformer 7 and assisting the power transmitted to the secondary winding L2 of the transformer 7.

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, and more particularly, to a power supply device for controlling an operation of an input side circuit according to an output current.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional power supply device. The conventional power supply device 1 converts an AC voltage supplied from an AC power supply 2 into a predetermined DC voltage and supplies the DC voltage to a load 3. The power supply device 1 includes a fuse 4, an input rectifier circuit 5, a resistor R1, a control circuit 6, a control transistor Q1, a transformer 7, an output rectifier circuit 8, and a detection circuit 9.

[0005] The fuse 4 is connected between the AC power supply 2 and the input side rectifier circuit 5, is cut off when an overcurrent occurs, and cuts off the supply of current. The input side rectifier circuit 5 includes a diode bridge 10 and a capacitor C1. The diode bridge 10 performs full-wave rectification on the AC power supply. Capacitor C
1 absorbs the pulsation of the power supply that has been full-wave rectified by the diode bridge 10.

One end of the power supply rectified by the rectifier circuit 5 is supplied to a primary winding L1 of a transformer 7 and a resistor R1
Is supplied as power to the control circuit 6 via the The primary winding L1 of the transformer 7 is connected to the other end of the power supply via the transistor Q1. Transistor Q1 has power MO
It is composed of an S-FET, and has a gate connected to the control circuit 6. The control circuit 6 supplies a switching pulse to the gate of the transistor Q1. The transistor Q1 is
Switching is performed according to a switching pulse supplied from the control circuit 6.

When the transistor Q1 is switched by the switching pulse, a magnetic field is generated in the primary winding L1 of the transformer 7, and power is transmitted to the secondary winding L2. The power transmitted to the secondary winding L2 is rectified by the rectifier circuit 8 and supplied to the output terminals Tout1 and Tout2. Load 3
Are connected to output terminals Tout1 and Tout2. The detection circuit 9 is connected to the output terminals Tout1 and Tout2.

[0006] The detection circuit 9 comprises resistors R2 to R5, a photocoupler 11, and a shunt regulator 12.
The resistors R2 to R4 divide the voltage between the output terminals Tout1 and Tout2 and supply the voltage at the connection point between the resistors R3 and R4 to the shunt regulator 12. The shunt regulator 12 compares the voltage at the connection point between the resistors R3 and R4 with an internally generated reference voltage and, when the voltage at the connection point between the resistors R3 and R4 is larger than the reference voltage, draws the drawn current. When the voltage at the connection point between the resistors R3 and R4 is smaller than the reference voltage, the drawn current is reduced.

[0007] The shunt regulator 12 is connected in series to the photocoupler 11 and the resistor R5. Photo coupler 1
1 is a light emitting diode D2 and a phototransistor Q2
Consists of The light emitting diode D2 is connected in series with the resistor R5 and the shunt regulator 12, and emits light in accordance with the current drawn by the shunt regulator 12.

The phototransistor Q2 is connected to the control circuit 6, and the light emitting diode D2 supplies a current corresponding to the amount of light emission to the control circuit 6. When the current consumption of the load 3 increases and the current supplied from the photocoupler 11 increases, the control circuit 6 shortens the high-level period of the switching pulse supplied to the gate of the transistor Q1, and
And the current supplied from the photocoupler 11 decreases, the period of the high level of the switching pulse supplied to the gate of the transistor Q1 is lengthened. When the high-level period of the switching pulse supplied from the control circuit 6 to the gate of the transistor Q1 is shortened, the on-period of the transistor Q1 is shortened, and the power from the primary winding L1 of the transformer 7 to the secondary winding L2 is reduced. Transmission is reduced.

When the high-level period of the switching pulse supplied from the control circuit 6 to the gate of the transistor Q1 increases, the on-period of the transistor Q1 increases, and the primary winding L1 to the secondary winding of the transformer 7 change. Power transfer to L2 increases. FIG. 5 shows an operation waveform diagram of an example of the related art. 5A shows a control signal supplied from the detection circuit 9 to the control circuit 6, and FIG. 5B shows a switching pulse supplied from the control circuit 6 to the transistor Q1.

In a state where the load 3 is connected as shown in FIG. 5A, the switching pulse supplied from the control circuit 6 to the gate of the transistor Q1 according to the output voltage as shown in FIG. The on period is defined as Ton1, Ton2, Ton
3 (Ton1 <Ton2 <Ton3), the off-period is Toff1, Ton
By setting ff2 and Toff3 (Toff1>Toff2> Toff3), the output voltage is kept constant.

When there is no load as shown in FIG. 5A, the switching pulse supplied from the control circuit 6 to the gate of the transistor Q1 is set to the minimum ON period Ton3 as shown in FIG. The off period was the longest off period Toff3, and the output was minimized. Transistor Q
1 is an on-period Ton1, Ton2, T shown in FIG.
It turns on at on3 and turns off at off periods Toff1, Toff2, Toff3. That is, the on-period is controlled to be shorter as the load becomes smaller, and the transistor Q1 is continuously switched by the switching pulse even when there is no load, so that power is consumed.

[0012]

However, in the conventional power supply device, even when the output side is not loaded, the control circuit 4 operates according to the detection result of the detection circuit 7, and operates in the same manner as when a load is connected. Therefore, there is a problem that unnecessary operations are performed and unnecessary power consumption is consumed. The present invention has been made in view of the above points, and has as its object to provide a power supply device that can reduce unnecessary power consumption.

[0013]

According to the present invention, there is provided a recording medium comprising:
A transformer for transmitting power from the secondary winding to the secondary winding, a transistor for controlling a current supplied to the primary winding of the transformer, and a detecting means for detecting power transmitted to the secondary winding of the transformer; Control means for controlling the switching of the transistor according to the detection result of the detection means;
Auxiliary power supply means for outputting a voltage corresponding to the power transmitted to the secondary winding and assisting the power transmitted to the secondary winding of the transformer.

According to a second aspect of the present invention, the auxiliary power supply means is a transformer.
It is constituted by a voltage doubler circuit which doubles the voltage transmitted to the next winding. According to a third aspect of the present invention, the auxiliary power supply means includes an auxiliary winding to which power from the primary winding of the transformer is transmitted, and a rectifier circuit for rectifying the power generated by the auxiliary winding. According to the present invention, by supplying the auxiliary power generated by the auxiliary power supply to the detection means, a decrease in the output voltage can be delayed at no load or the like, so that the off period of the transistor can be lengthened. The power supplied from the primary winding of the transformer to the secondary winding can be reduced, and power saving can be realized.

[0015]

FIG. 1 is a block diagram showing a first embodiment of the present invention. 4, the same components as those of FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. The power supply device 100 of the present embodiment includes a secondary winding L2 of the transformer 7 and an output terminal Tou.
The voltage doubler 101 is added between the time t1 and the time t1. The voltage doubler 101 boosts the voltage generated in the secondary winding L2 of the transformer 7 when there is no load, and supplies the boosted voltage to the output terminal Tout1.

The voltage doubler 101 includes capacitors C11 and C11.
12, diodes D11 and D12, and a resistor R11.
One end of the capacitor C11 is connected to one end of the secondary winding L2 of the transformer 7, and the other end is connected to the anode of the diode D11. The capacitor C11 holds the potential at one end of the secondary winding L2 of the transformer 7. The diode D11 has an anode connected to the other end of the capacitor C11 and a cathode connected to one end of the resistor R11. The other end of the resistor R11 is connected to the output terminal Tout1.

The diode D12 has an anode connected to the other end of the secondary winding L2 of the transformer 7, that is, the output terminal Tout2, and a cathode connected to a connection point between the capacitor C11 and the anode of the diode D11. One end of the capacitor C12 is connected to the other end of the secondary winding L2 of the transformer 7, that is, the output terminal Tout2, and the other end is connected to the diode D11 and the resistor R11.
Is connected to a connection point with one end of the.

The voltage doubler circuit 101 rectifies the voltage generated in the secondary winding L2 of the transformer 7 and rectifies the voltage generated in the secondary winding L2 of the transformer 7 at the connection point between the diode D11 and the capacitor C12 and the resistor R11. To generate a double voltage. At this time, in the voltage doubler 101, the resistance R11 is set to a relatively large resistance value, and the output terminal T
The current supplied to out1 is very small.

For example, an output terminal Tout1 and an output terminal Tout2
When a normal load is connected as the load 3 between the load 3 and the load 3, the load 3 consumes the current rectified by the rectifier circuit 8 and the current generated by the voltage doubler circuit 101, and the current is supplied to the detection circuit 9 by the detection circuit 9. Since almost no power is supplied, the current supplied from the transistor Q1 of the photocoupler 11 of the detection circuit 9 to the control circuit 6 becomes small. Control circuit 6 from photocoupler 11
When the current supplied to the gate of the transistor Q1 decreases, the control circuit 6 lengthens the ON period of the switching pulse supplied to the gate of the transistor Q1. In the transistor Q1, when the ON period of the switching pulse becomes longer, the power supplied from the primary winding L1 side of the transformer 7 to the secondary winding L2 side increases.

The electric power generated in the secondary winding L2 is supplied to the load 3 rectified by the rectifier circuit 8. Further, the capacitors C11 and C12 are charged by the electric power generated in the secondary winding L2, and a voltage doubler is generated in the voltage doubler circuit 101. The voltage doubler 101 supplies a small current to the output terminal Tout1. Next, when a light load is connected as the load 3 between the output terminal Tout1 and the output terminal Tout2, the load 3 consumes the current rectified by the rectifier circuit 8 and the current generated by the voltage doubler circuit 101. Is done. Further, a current that cannot be consumed is supplied to the detection circuit 9. The detection circuit 9 generates a voltage across the resistors R2 to R4 according to the supplied current.

When the current supplied from the secondary winding L2 of the transformer 7 via the rectifier circuit 8 is larger than the current consumed by the load 3, the detection circuit 9 detects the shunt regulator 1
2, the current drawn by the photocoupler 1 increases.
The current flowing through the light-emitting diode D2 constituting 1 increases. When the current flowing through the light emitting diode D2 increases, the light emission amount of the light emitting diode D2 increases. When the light emission amount of the light emitting diode D2 increases, the current supplied from the phototransistor Q2 included in the photocoupler 11 to the control circuit 6 increases.

When the current supplied from the photocoupler 11 increases, the control circuit 6 shortens the ON period of the switching pulse to the gate of the transistor Q1. Control circuit 6
When the on-period of the switching pulse supplied to the gate of the transistor Q1 is shortened, the on-period of the transistor Q1 is shortened. Since the ON period of the transistor Q1 is shortened, two
The power transmitted to the next winding L2 is reduced.

When the output of the secondary winding L2 of the transformer 7 decreases, the output of the output terminal Tout1 decreases. Output terminal T
When the output of out1 decreases, the output of the output terminal Tout1 is consumed by the load 3. The current supplied to the detection circuit 9 also decreases. For this reason, the current supplied from the photocoupler 11 constituting the detection circuit 9 to the control circuit 6 is reduced. When the current supplied from the photocoupler 11 to the control circuit 6 is reduced, the control circuit 6 lengthens the ON period of the switching pulse supplied to the gate of the transistor Q1. By increasing the on-period of the switching pulse supplied to the gate of the transistor Q1, the power transmitted from the primary winding L1 to the secondary winding L2 of the transformer 7 increases.

When the output on the secondary winding L2 side increases and becomes larger than the power consumed by the load 3, an extra output is supplied to the detection circuit 9. The supply of power to the detection circuit 9 increases, the current supplied from the photocoupler 11 to the control circuit 6 increases, the on-period of the transistor Q1 becomes shorter again, and the output voltage is kept constant. When the load 3 is disconnected from the output terminals Tout1 and Tout2 and becomes no load, first, the output of the rectifier circuit 8 is supplied to the detection circuit 9. The detection circuit 9 detects the photocoupler 1 based on the output from the rectifier circuit 8.
The current supplied from 1 to the control circuit 6 increases. When the current supplied from the photocoupler 11 to the control circuit 6 increases, the control circuit 6 shortens the ON period of the switching pulse supplied to the gate of the transistor Q1.

When the ON period of the switching pulse supplied to the gate of the transistor Q1 is shortened by the control circuit 6, the power transmitted from the primary winding L1 of the transformer 7 to the secondary winding L2 is reduced. At this time, when the transmission of power from the primary winding L1 to the secondary winding L2 by the transformer 7 is reduced, the output of the rectifier circuit 8 is reduced. When the output of the rectifier circuit 8 decreases, the output of the voltage doubler 101 is supplied to the detection circuit 9. When the output of the detection circuit 9 is increased by the voltage doubler circuit 101, the control circuit 6
Is further increased. When the current supplied from the photocoupler 11 to the control circuit 6 further increases, the control circuit 6 stops supplying the switching pulse to the gate of the transistor Q1.

The transformer 7 has a primary winding L1 to a secondary winding L.
When the supply of electric power to the rectifier circuit 2 is stopped, the electric current accumulated in the capacitor C2 of the rectifier circuit 8 is gradually consumed because the current supplied from the voltage doubler circuit 101 to the detection circuit 9 is very small. When the electric charge accumulated in the capacitor C2 of the rectifier circuit 8 is consumed, the current supplied from the photocoupler 11 of the detection circuit 9 to the control circuit 6 decreases. Photo coupler 11
When the current supplied from the control circuit 6 to the control circuit 6 decreases, the control circuit 6 supplies the switching pulse to the gate of the transistor Q1 again.

The transistor Q1 is switched again by the switching pulse. When the transistor Q1 is switched, the transformer 7 is connected to the primary winding L.
The power is transmitted from the primary winding L2 to the secondary winding L2. The output of the secondary winding L2 charges the capacitor C2 of the rectifier circuit 8, and the output of the rectifier circuit 8 rises. When the output of the rectifier circuit 8 increases, the current supplied from the photocoupler 11 of the detection circuit 9 to the control circuit 6 increases again. When the current supplied from the photocoupler 11 to the control circuit 6 increases, the control circuit 6
Stops the supply of the switching pulse to the gate of the transistor Q1.

When the supply of the switching pulse to the gate of the transistor Q1 is stopped, the transistor Q1 turns off. When the transistor Q1 is turned off, the transformer 7 stops transmitting power from the primary winding L1 to the secondary winding L2. At this time, when the transmission of power from the primary winding L1 to the secondary winding L2 by the transformer 7 is reduced, the output of the rectifier circuit 8 is reduced. When the output of the rectifier circuit 8 decreases, the output of the voltage doubler 101 is supplied to the detection circuit 9. When the output of the detection circuit 9 is increased by the voltage doubler 101, the current supplied from the photocoupler 11 to the control circuit 6 further increases. When the current supplied from the photocoupler 11 to the control circuit 6 further increases, the control circuit 6 stops supplying the switching pulse to the gate of the transistor Q1.

The transformer 7 has a primary winding L1 to a secondary winding L.
When the supply of electric power to the rectifier circuit 2 is stopped, the electric current accumulated in the capacitor C2 of the rectifier circuit 8 is gradually consumed because the current supplied from the voltage doubler circuit 101 to the detection circuit 9 is very small. When the electric charge accumulated in the capacitor C2 of the rectifier circuit 8 is consumed, the current supplied from the photocoupler 11 of the detection circuit 9 to the control circuit 6 decreases. Photo coupler 11
When the current supplied from the control circuit 6 to the control circuit 6 decreases, the control circuit 6 supplies the switching pulse to the gate of the transistor Q1 again.

By repeating the above operation, the transistor Q1 operates intermittently, and the power consumption can be extremely reduced when there is no load. The load 3 is connected to the output terminals Tout1,
When connected to Tout2, the current is supplied to the load 3 and the current supplied to the detection circuit 9 decreases. As the output of the detection circuit 9 decreases, the current supplied from the photocoupler 11 of the detection circuit 9 to the control circuit 6 decreases.
When the current supplied from the photocoupler 11 to the control circuit 6 decreases, the control circuit 6 lengthens the ON period of the switching pulse supplied to the transistor Q1. When the ON period of the transistor Q1 becomes longer, the power supplied from the primary winding L1 to the secondary winding L2 by the transformer 7 increases, and the power is supplied to the load 3.

FIG. 2 shows an operation waveform diagram of the first embodiment of the present invention. FIG. 2A shows the state of the load 2, and FIG. 2B shows the state of the switching pulse supplied from the control circuit 6 to the gate of the transistor Q1. In a state where the load 3 is connected as shown in FIG.
As shown in (B), the switching pulse supplied from the control circuit 6 to the transistor Q1 has an ON period of Ton11, T1.
on12, Ton13 (Ton11>Ton12> Ton13), and the off period is Toff11, Toff12, Toff13 (Toff11 <Toff12 <
Toff13), and keeps the output voltage constant.

In the no-load state as shown in FIG. 2A, the switching pulse P is intermittently supplied from the control circuit 6 to the gate of the transistor Q1 as shown in FIG. 2B. By intermittently supplying the switching pulse P from the control circuit 6 to the gate of the transistor Q1, power consumption can be minimized.

FIG. 3 is a block diagram showing a second embodiment of the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Power supply device 200 of the present embodiment
Is provided with an auxiliary power supply circuit 201 in place of the voltage doubler circuit 101. The auxiliary power supply circuit 201 includes an auxiliary winding Ls magnetically coupled to the transformer 7, a diode D21, a capacitor C21, and a resistor R21.

The auxiliary winding Ls is magnetically coupled to the transformer 7. Power is supplied to the auxiliary winding Ls from the primary winding L1 of the transformer 7. The power transmitted to the auxiliary winding Ls is
It is rectified by the diode D21 and the capacitor C21 and supplied to the output terminal Tout1 via the resistor R21. The current supplied from the auxiliary power supply circuit 201 to the output terminal Tout1 is limited by the resistor R21 and becomes a very small current.

For example, an output terminal Tout1 and an output terminal Tout2
When a normal load is connected as the load 3 between the load 3 and the load 3, the load 3 consumes the current rectified by the rectifier circuit 8 and the current generated by the auxiliary power supply circuit 201. Since almost no power is supplied, the photocoupler 11 of the detection circuit 9 maintains the off state. Photo coupler 11
Is OFF, the control circuit 6 supplies a switching pulse to the gate of the transistor Q1. Transistor Q1
Are switched in response to a switching pulse supplied from the control circuit 6.

By switching the transistor Q1, the transistor Q1 is connected to the primary winding L1 of the transformer 7.
The current that fluctuates according to the switching of No. 1 flows. A current according to the fluctuation of the current flowing through the primary winding L1 flows through the secondary winding L2 of the transformer 7. The current generated in the secondary winding L2 is supplied to the load 3 rectified by the rectifier circuit 8. Also, the current generated in the secondary winding L2 causes the capacitor C1
1, C12 is charged, and a voltage is generated in the auxiliary power supply circuit 201. The auxiliary power supply circuit 201 supplies a small current to the output terminal Tout1.

Next, when a light load is connected as the load 3 between the output terminal Tout1 and the output terminal Tout2, the load 3 is connected to the current rectified by the rectifier circuit 8 and the auxiliary power supply circuit 20.
The current generated in step 1 is consumed. Further, a current that cannot be consumed is supplied to the detection circuit 9. The detection circuit 9 generates a voltage across the resistors R2 to R4 according to the supplied current.

When the current supplied from the secondary winding L2 of the transformer 7 via the rectifier circuit 8 is larger than the current consumed by the load 3, the detection circuit 9 detects the shunt regulator 1
2 draws a larger current. When the current drawn from the shunt regulator 12 increases, the current flowing through the light emitting diode D2 constituting the photocoupler 11 increases, and the light emission amount of the light emitting diode D2 increases. As the light emission amount of the light emitting diode D2 increases, the current supplied from the photocoupler 11 to the control circuit 6 increases.

When the current supplied from the photocoupler 11 increases, the control circuit 6 shortens the on-time of the switching pulse supplied to the gate of the transistor Q1. When the supply of the switching pulse from the control circuit 6 to the gate of the transistor Q1 becomes short, the secondary winding L2 of the transformer 7
Side output is reduced and the output voltage is kept constant. Also,
At no load, the output of the output terminal Tout1 increases, and the supply of current to the detection circuit 9 increases. At this time, when no load is applied, the auxiliary power supply circuit 201 is driven in the same manner as the voltage doubler circuit 101, and a current larger than a light load is supplied to the detection circuit 9.

Therefore, the current supplied from the photocoupler 11 constituting the detection circuit 9 to the control circuit 6 increases. When the current supplied from the photocoupler 11 to the control circuit 6 increases, the control circuit 6 stops supplying the switching pulse to the gate of the transistor Q1. When the supply of power from the primary winding L1 to the secondary winding L2 is stopped, the current supplied from the auxiliary power supply circuit 201 to the detection circuit 9 is very small. Is gradually consumed. When the electric charge accumulated in the capacitor C2 of the rectifier circuit 8 is consumed, the detection circuit 9
The current supplied from the photocoupler 11 to the control circuit 6 decreases. When the current supplied from the photocoupler 11 to the control circuit 6 decreases, the control circuit 6 supplies a switching pulse to the gate of the transistor Q1 again.

By repeating the above operation, the transistor Q1 operates intermittently as in the first embodiment, and the power consumption can be extremely reduced when there is no load.

[0042]

As described above, according to the present invention, by supplying the auxiliary power generated by the auxiliary power supply means to the detection means, it is possible to delay the decrease of the output voltage at the time of no load or the like. The off-period of the transistor can be lengthened, so that power supplied from the primary winding of the transformer to the secondary winding can be reduced, and power saving can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the first embodiment of the present invention.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is an operation waveform diagram of an example of the related art.

[Explanation of symbols]

 2 AC power supply 3 Load 4 Fuse 5, 8 Rectifier circuit 6 Control circuit 7 Transformer 9 Detection circuit 10 Diode bridge 11 Photocoupler 12 Shunt regulator 100, 200 Power supply device 101 Voltage doubler circuit 201 Auxiliary power supply circuit

Continued on the front page (72) Inventor Seiji Kono Fukuoka Pref. In-house F-term (reference) 5G065 AA01 DA06 DA07 EA06 HA07 HA09 JA01 LA02 MA01 MA10 NA04 NA09 5H730 AA14 AS01 BB43 BB57 CC01 DD04 EE06 EE07 EE65 FD01 FD24 FF19 FG05 VV06

Claims (3)

[Claims] A transformer for transmitting power from a primary winding to a secondary winding; a transistor for controlling a current supplied to the primary winding of the transformer; Detecting means for detecting the transmitted power; controlling means for controlling switching of the transistor in accordance with a detection result of the detecting means; and a voltage corresponding to the power transmitted to the secondary winding of the transformer. An auxiliary power supply means for outputting power and assisting electric power transmitted to the secondary winding of the transformer. 2. The power supply device according to claim 1, wherein said auxiliary power supply means is a voltage doubler circuit that doubles a voltage transmitted to said secondary winding of said transformer. 3. The auxiliary power supply means includes: an auxiliary winding to which power from the primary winding of the transformer is transmitted; and a rectifier circuit for rectifying power generated in the auxiliary winding. The power supply device according to claim 1, wherein: