JP4993510B2 - Power-saving power supply - Google Patents

Description

The present invention relates to a power source and an electronic device that can reduce power consumption in a standby state.

Electronic devices such as LCD TVs and PC monitors operate functions that detect the on signal from the remote control and the touch switch even when the power is turned off with the touch switch on the front of the remote control or device. It is not completely turned off and enters a so-called standby state. In recent years, power consumption in the standby state has become a problem, and various techniques have been developed to bring power consumption in the standby state as close to zero as possible.

In FIG. 4, an output voltage adjustment circuit 11 that can change the output voltage setting value of the output voltage detection circuit by a control signal is provided, and the power consumption of the electronic device is reduced by lowering the output voltage in the standby state. A DC-DC converter that can be used is disclosed.

However, the DC-DC converter of FIG. 4 continues to consume power in the output voltage detection circuit 6 for adjusting the output voltage to be constant even in the standby state. The output voltage detection circuit 6 includes a light emitting portion 7 of a photocoupler, and in order to make the output voltage constant, it is necessary that a current of several mA flows in the light emission portion 7. About 10 mW of power is consumed.
Japanese Patent Laid-Open No. 07-170730

An object of the present invention is to reduce power consumption of an output voltage detection circuit of a switching power supply and a photocoupler in the output voltage detection circuit, and to reduce power consumption of a switching power supply and an electronic device in a standby state.

The invention of claim 1 has an output voltage detection circuit for making the output voltage value constant and a transformer including an auxiliary winding, and in the first state, the output voltage value detected by the output voltage detection circuit is constant. A power source that controls the switching element so that the voltage generated in the auxiliary winding becomes constant by disabling the output voltage detection circuit in the second state.

The invention of claim 2 has an output voltage detection circuit for making the output voltage value constant, and a first switch for cutting off a current to the output voltage detection circuit,
A power supply that turns on the first switch in the first state to supply current to the output voltage detection circuit, and disables the output voltage detection circuit by turning off the first switch in the second state.

According to the first and second aspects of the present invention, the power supply can invalidate the output voltage adjusting circuit in the second state and reduce its power consumption.

The invention of claim 3 is a control circuit for controlling the switch element;
An output voltage detection circuit for making the output voltage value constant;
A first switch for cutting off the current of the output voltage detection circuit;
A control switching circuit for switching a voltage supplied to a control terminal of the control circuit;
In the first state, the first switch is turned on to supply current to the output voltage detection circuit, and in the second state, the output voltage detection circuit is invalidated by turning off the first switch. Is supplied to the control terminal of the control circuit in the first state with a voltage corresponding to the output voltage value detected by the output voltage detection circuit, and in the second state, the voltage generated in the auxiliary winding at the control terminal of the control circuit. The power source is characterized in that switching is performed so that a voltage corresponding to the value is supplied.

According to the present invention, the power supply can invalidate the output voltage adjustment circuit on the secondary side in the second state to reduce its power consumption, and the output voltage can be stabilized to some extent even in the second state.

In the invention of claim 4, in addition to the above-mentioned invention, when a transition from the first state to the second state occurs, a voltage corresponding to a voltage value generated in the auxiliary winding is started to be supplied to the control terminal of the control circuit. In the case where the output voltage detection circuit is invalidated and the second state is shifted to the first state, the invalidation of the output voltage detection circuit is canceled, and then the control terminal of the control circuit is connected with the output voltage detection circuit. A power supply that supplies a voltage corresponding to the detected output voltage value

According to the present invention, the power supply disables the output voltage adjustment circuit on the secondary side in the second state and can reduce its power consumption. Furthermore, in the second state, the output voltage can be stabilized to some extent. Transition from the second state to the first state and the state where the output voltage is not controlled at the time of switching from the first state to the second state can be made.

According to a fifth aspect of the present invention, in addition to any one of the above-mentioned inventions, the first state and the second state are power sources determined in accordance with an input signal from the outside of the power source .

According to the present invention, the power source can perform the state transition between the first state and the second state by an external signal.

According to a sixth aspect of the present invention, there is provided an electronic apparatus comprising the power source according to any one of the above aspects, wherein the first state and the second state are a normal state and a standby state of the electronic apparatus.

According to the present invention, the power consumption of the electronic device in the standby state can be reduced.

First, a conventional switching power supply will be described with reference to FIG.

In FIG. 1, the switching power supply includes an AC input 120, a rectifier diode 121, a smoothing capacitor 123, a switch element 101, a switching control circuit 102, an auxiliary power rectifier circuit 103, a transformer 105, and a secondary side rectifier circuit 104. , An output voltage detection circuit 106, a photocoupler photodiode 107 and a phototransistor 108.

The rectifier diode 121 and the smoothing capacitor 123 rectify and smooth the AC input 120 to generate a DC voltage, which is supplied to the primary winding 111 of the transformer 105. A switch element 101 is connected to the other side of the primary winding 111, and the switch element 101 usually uses a MOSFET or a transistor. The switch element 101 is connected to the switching control circuit 102, and the switching control circuit 102 controls on / off of the switch element 101 and performs control so that the voltage generated at the control terminal 109 is constant.

A method called PWM is generally used by the switching control circuit 102 to control the on / off of the switch element 101. The PWM controls the ratio of the on time and the off time in a certain period. There is a method called PFM as another control method. There is also a multi-stone system that controls a plurality of switch elements. Here, any control method may be used, but the case of PWM control will be described as an example.

The switch element 101 is turned on and off at a constant frequency, and the current intermittently flows in the primary winding 111, whereby the voltage is intermittently applied to the secondary winding 112 and the auxiliary winding 113. Depending on. The voltage generated in the auxiliary winding 113 is rectified by the auxiliary power supply rectifier circuit 103, supplied as the power source of the switching control circuit 102, and connected to the control terminal 109 via the phototransistor 108.

The voltage generated in the secondary winding 112 is rectified by the secondary side rectifier circuit 104 and becomes the output voltage Vout. The output voltage Vout is connected to the output voltage detection circuit 106 and changes the current flowing through the phototransistor 108 via the photodiode 107 in the output voltage detection circuit 106. When the output voltage Vout increases, the light emission of the photodiode increases, and when the output voltage Vout decreases, the light emission decreases. The change in the light emission intensity of the photodiode 107 is detected by the phototransistor 108, and the current flowing through the phototransistor 108 increases as the output voltage Vout increases, and decreases as the output voltage Vout decreases.

Since the phototransistor 108 is connected to the control terminal 109 of the switching control circuit 102, the voltage value of the control terminal 109 changes when the current flowing through the phototransistor 108 changes. The switching control circuit 102 performs control to shorten the switch-on time of the switch element 101 when the voltage at the control terminal 109 increases, and lengthen the switch-on time of the switch element 101 when the voltage at the control terminal 109 decreases, It operates so that the voltage of 109 becomes constant. When the output voltage Vout of the switching power supply as a whole increases, the switch-on time of the switch element 101 decreases, and when the output voltage Vout decreases, the feedback control that the switch-on time of the switch element 101 increases becomes constant. Be controlled.

The primary winding 111, the auxiliary winding 113, and the phototransistor 108 are isolated from the secondary winding 112 and the photodiode 107, which is used to separate dangerous high voltage such as AC input from safe output voltage. This is to ensure the safety of the person. A circuit including the AC input 120, to which the primary winding 111, the auxiliary winding 113, and the phototransistor 108 are connected is called a primary side, and a circuit to which the secondary winding 112 and the photodiode 107 are connected is called a secondary side. In this way, a power source in which the primary side and the secondary side are separated using a transformer, a photocoupler, etc. is called an insulated power source.

In the conventional switching power supply described above, since the control for keeping the output voltage Vout constant is performed even when the electronic device is in a standby state, the power consumption in the output voltage detection circuit 106 is continued. Has been done.

Here, if the output voltage Vout = 18V, the current of the photodiode 107 is 1 mA, and the total resistance value R1 + R2 = 33 kΩ of the resistance R1 and the resistance R2 of the output voltage detection circuit 106,
The power consumption of the resistor R1 and the resistor R2 is Vout ^ 2 / (R1 + R2) = 9.8 mW
The power consumption of the photodiode 107 and the resistor R10 is Vout × 1 mA = 18 mW
Thus, the output voltage circuit 106 consumes 27.8 mW of power.

FIG. 2 shows a switching power supply according to the present invention, which reduces power consumption in an output voltage detection circuit when an electronic device enters a standby state.

Description of the parts common to FIG. 1 is omitted. In FIG. 2, the switching power supply includes an AC input 120, a rectifier diode 121, a smoothing capacitor 123, a switch element 101, a switching control circuit 102, an auxiliary power supply rectifier circuit 103, a transformer 105, a secondary side rectifier circuit 104, and an output voltage detection circuit 206. , Photodiode a207 (corresponding to “first photodiode”), phototransistor a208, delay circuit 211, delay circuit 212, photodiode b203 (corresponding to “second photodiode”), phototransistor b204, switch Qa201 (“first photodiode”). A switch Qb202 (corresponding to a “second switch”), a control switching circuit 210, and a switch Qc205. The photodiode a207 and the phototransistor a208 exist in one photocoupler a, and the photodiode b203 and the phototransistor b204 exist in one photocoupler b.

The operation of the switching power supply of the present invention in the normal state of the electronic device will be described.

In a normal state of the electronic device, the control signal Vmain is high (3.3 V). This control signal Vmain is supplied in accordance with the state of the electronic device or in accordance with programmed time control, such as a microcomputer (not shown) of the electronic device detecting and outputting the on-state of the remote controller or the touch switch. Further, the voltage may be supplied by a switch that mechanically holds a state, such as a lock switch.
In this state, the switch Qb202 is turned on, and a current flows through the photodiode b203. The phototransistor b204 of the control switching circuit 210 is turned on and the switch Qc205 is turned off. Further, the switch Qa201 is turned on, a current flows through the output voltage detection circuit 206, and the current of the photodiode a207 also flows.

In this state, the switching power supply of FIG. 2 is equivalent to the conventional switching power supply of FIG. As described above with reference to FIG. 1, the output voltage Vout is connected to the output voltage detection circuit 206, and the light emission of the photodiode a207 in the output voltage detection circuit 206 becomes stronger as the output voltage Vout increases, and the output voltage Vout When it becomes smaller, it becomes weaker. A change in light emission intensity of the photodiode a207 (corresponding to “control information”) is detected by the phototransistor a208, and the current flowing through the phototransistor a208 increases as the output voltage Vout increases, and decreases as the output voltage Vout decreases.

Since the phototransistor a208 is connected to the control terminal 109 of the switching control circuit 102, the voltage value of the control terminal 109 changes when the current flowing through the phototransistor a208 changes. The switching control circuit 102 performs control to shorten the switch-on time of the switch element 101 when the voltage at the control terminal 109 increases, and lengthen the switch-on time of the switch element 101 when the voltage at the control terminal 109 decreases, Since the voltage of the terminal 109 operates to be constant, when the output voltage Vout increases as a whole switching power supply, the switch-on time of the switch element 101 decreases, and when the output voltage Vout decreases, the switch-on time of the switch element 101 increases. Thus, the output voltage Vout is controlled to be constant (VoH).

Here, assuming that the output voltage Vout = VoH = 18V, the current of the photodiode a207 is 1 mA, and the total resistance value R1 + R2 = 33 kΩ of the resistor R1 and the resistor R2 of the output voltage detection circuit 206,
The power consumption of the resistor R1 and the resistor R2 is Vout ^ 2 / (R1 + R2) = 9.8 mW
The power consumption of the photodiode 107 and the resistor R10 is Vout × 1 mA = 18 mW
Thus, the output voltage detection circuit 206 consumes the same 27.8 mW of power as the conventional switching power supply of FIG.

Further, in the switching power supply of the present invention, power is consumed by the resistor R4, the delay circuit 211, the delay circuit 212, the photodiode b203 and the resistor R9.

Control signal Vmain = 3.3V, auxiliary power supply voltage Vcc = 10V, current of photodiode b203 is 2 mA, resistance value of resistor R4 is 30 kΩ, total resistance value R5 + R6 = 80 kΩ of resistor R5 and resistor R6 of delay circuit 211, delay circuit When the total resistance value R7 + R8 = 80 kΩ of the resistor R7 and the resistor R8 of 212,
The power consumption of the resistor R4 is Vcc ^ 2 / R4 = 3.3 mW
The power consumption of the resistors R5 and R6 is Vmain ^ 2 / (R5 + R6) = 0.1 mW
The power consumption of the resistors R7 and R8 is Vmain ^ 2 / (R7 + R8) = 0.1 mW
The power consumption of the photodiode b203 and the resistor R9 is Vmain × 2 mA = 6.6 mW
In the normal state, 10.1 mW of power is consumed in addition to the conventional switching power supply of FIG.

Next, the operation of the switching power supply of the present invention in the standby state of the electronic device will be described.

In the standby state of the electronic device, the control signal Vmain is low (0 V). The control signal Vmain is supplied by a method in which a microcomputer (not shown) of an electronic device detects that a remote control or a touch switch is off and outputs it. In this state, the switch Qb202 is turned off and no current flows through the photodiode b203. The phototransistor b204 of the control switching circuit 210 is turned off, and the switch Qc205 is turned on. Further, since the switch Qa201 is turned off and no current flows through the output voltage detection circuit 206, no current flows through the photodiode a207. The phototransistor a208 is turned off. Therefore, the voltage Vcc of the auxiliary winding 113 rectified by the auxiliary power supply rectifier circuit 103 is supplied to the control terminal 109 of the switching control circuit 102 via the switch Qc205 and the resistor R11.
The control terminal 109 may be divided and supplied with Vcc.

Since the switching control circuit 102 adjusts the ON time of the switch element 101 so that the voltage of the control terminal 109 is constant, as a result, the auxiliary power supply voltage Vcc is controlled to be constant. At this time, the output voltage Vout is stabilized at a substantially constant voltage VoL if the connected load is constant. However, since the switching control circuit 102 controls the auxiliary power supply voltage Vcc to be constant and not the output voltage Vout, the stability of the output voltage Vout is higher than the stability of the auxiliary power supply voltage Vcc. And low. Further, VoL can be reduced in power consumption in the standby state by setting the voltage lower than the output voltage Vout = VoH in the normal state.

Here, assuming that the control power supply voltage Vcc = 5.5V and the total resistance value R1 + R2 = 500 kΩ of the resistance R3 and the resistance R4 of the control switching circuit 211,
In the output voltage detection circuit 206, the switch Qa201 is off and the power consumption is 0 mW control signal Vmain = 0V.
Power consumption of delay circuit 211, delay circuit 212, photodiode b203 and resistor R9 is 0 mW
In the control switching circuit 210, the phototransistor b204 is off and the switch Qc205 is on, so that power is consumed by the resistors R3 and R4.
The power consumption of the resistors R5 and R6 is Vcc ^ 2 / (R3 + R4) = 0.1 mW
Compared with the conventional switching power supply, 27.8 mW-0.1 mW = 27.7 mW
27.7 mW power consumption is reduced.

Thus, in the switching power supply of the present invention, power consumption in the standby state is reduced. Furthermore, since the increase in power consumption in the normal state is 10.1 mW and the reduction in power consumption in the standby state is 27.7 mW, the standby state time of the day is about 6.4 hours or more. If there is, the amount of electricity per day is also reduced.
-27.7 mW x 6.4 hours + 10.1 mW x (24-6.4 hours) <0

FIG. 3 relates to the control sequence of the switching power supply according to the present invention. The power supply startup S1, the transition from the standby state to the normal state S2, the normal state S3, and the transition from the normal state to the standby state S4 are described below. explain.

S1 is a state related to activation of the switching power supply. The switching power supply is activated and the output voltage Vout starts to rise. The control signal Vmain is still low, and the gate-source voltage Vgs of the switches Qa201 and Qb202 is low. As described above, Vout is constant at VoL. Further, the drain current Id of the switch Qb does not flow.

S2 relates to the transition from the standby state to the normal state. When Vout = VoL is supplied to an electronic device (not shown) and a remote control or touch switch of the electronic device is turned on, the device is activated and the control signal Vmain changes from low to high (3.3 V). When Vmain becomes high, the voltage is supplied to the delay circuit 211 and the delay circuit 212, but the gate-source voltage Vgs of the switch Qa201 becomes high first by setting the constants of the delay circuit (values of the resistors R5 to R8). The switch Qa201 is turned on first. Current is supplied to the output voltage detection circuit 206, and the phototransistor a208 is turned on (not completely turned on due to the light emission intensity of the photodiode a207), but the switch Qb202 is still off, so the photodiode 204 is off. Since the switch Qc205 is on, Vout = VoL.

S3 relates to the normal state. After the state S2, the switch Qb202 is turned on by the voltage supplied to the delay circuit 212. A current flows through the photodiode b203, and the phototransistor b204 is turned on. As a result, the switch Qb is turned off and rises to Vout = VoH.

In the transition from the state S2 to S3, the switch Qa201 is turned on first, and the switch Qb202 is turned on later. This is the reverse order, the switch Qa201 is turned off, the switch Qb202 is turned on, and a current is supplied to the photodiode a207. This is to prevent the phototransistor a208 and the switch Qc205 from being simultaneously turned off and the control terminal 109 to be opened and the output voltage Vout to rise without being controlled if a state where current does not flow and current flows through the photodiode b203 occurs. is there.

S4 relates to the transition from the normal state to the standby state. When the remote control or touch switch of the electronic device is turned off, the electronic device enters a standby state, and the control signal Vmain changes from high to low. When the control signal Vmain becomes low, the current to the photodiode b203 is stopped, the phototransistor b204 is turned off, the switch Qc205 is turned on, and the output voltage Vout starts to change toward VoL. The control signal Vmain is supplied to the delay circuit 211 and the delay circuit 212, but the gate-source voltage Vgs of the switch Qa201 becomes low first by setting the constants of the delay circuit (values of the resistor R5 to the resistor R8). Turn off. No current is supplied to the output voltage detection circuit 206, and the phototransistor a208 is turned off. Thereafter, the switch Qb202 is turned off, but the current of the photodiode b203 has already stopped, and there is no change. Vout = VoL is constant.

Even in the transition from the state S3 to S4, no current flows through the photodiode a207 and no current flows through the photodiode b203, the control terminal 109 is opened, and the output voltage Vout is not controlled and does not increase. .

The switching power supply of the present invention can be shifted without going through a state where the output voltage is not controlled when switching from the standby state to the normal state and from the normal state to the standby state.

As described above, in the switching power supply of the present invention, power consumption in the standby state is reduced. Furthermore, compared with an increase in power consumption in the normal state, the power consumption in the standby state is greatly reduced. When the time in the standby state is long, the daily power consumption is also reduced.

It goes without saying that the switching power supply of the present invention can be applied to various electronic devices such as printers in addition to televisions and monitors.

Circuit diagram of conventional switching power supply Circuit diagram of switching power supply of the present invention (Example) Control sequence of switching power supply of the present invention FIG. 1 of Japanese Patent Application Laid-Open No. 07-170730

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Switch element 102: Switching control circuit 103: Auxiliary power supply rectifier circuit 104: Secondary side rectifier circuit 105: Transformer 106: Output voltage detection circuit 107: Photodiode 108: Phototransistor 109: Control terminal 111: Primary winding 112: Secondary winding 113: Auxiliary winding 120: AC input 121: Rectifier diode 123: Smoothing capacitor 201: Switch Qa
202: Switch Qb
203: Photodiode b
204: Phototransistor b
206: Output voltage detection circuit 207: Photodiode a
208: Phototransistor a
210: Control switching circuit 211: Delay circuit 212: Delay circuit

Claims (6)

An output voltage detection circuit for making the output voltage value constant, and a transformer including an auxiliary winding,
In the first state, the switch element is controlled so that the output voltage value detected by the output voltage detection circuit is constant, and in the second state, the output voltage detection circuit is disabled and the voltage generated in the auxiliary winding is constant. power for controlling the switching element so that the. An output voltage detection circuit for making the output voltage value constant, and a first switch for cutting off a current to the output voltage detection circuit;
A power supply that turns on the first switch in a first state to supply current to the output voltage detection circuit, and disables the output voltage detection circuit by turning off the first switch in a second state . A control circuit for controlling the switch element;
An output voltage detection circuit for making the output voltage value constant;
A first switch for cutting off the current of the output voltage detection circuit;
A control switching circuit for switching a voltage supplied to a control terminal of the control circuit;
Turn on the first switch in the first state to supply current to the output voltage detection circuit, and disable the output voltage detection circuit by turning off the first switch in the second state .
The control switching circuit,
The voltage corresponding to the output voltage value detected by the output voltage detection circuit is supplied to the control terminal of the control circuit in the first state, and the voltage value generated in the auxiliary winding at the control terminal of the control circuit in the second state A power source characterized by switching so as to be supplied with a voltage corresponding to . When transitioning from the first state to the second state, after the supply of the voltage corresponding to the voltage value generated in the auxiliary winding to the control terminal of the control circuit, the output voltage detection circuit is invalidated,
When transitioning from the second state to the first state, after canceling the invalidation of the output voltage detection circuit, the voltage corresponding to the output voltage value detected by the output voltage detection circuit at the control terminal of the control circuit The power supply of Claim 3 which supplies . The power supply according to any one of claims 1 to 4, wherein the first state and the second state are determined according to an input signal from outside the power supply. 6. An electronic device comprising the power source according to claim 1, wherein the first state and the second state are a normal state and a standby state of the electronic device.

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