JP4377893B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device, and more particularly to a technique for reducing power consumption during standby.

  In recent years, there has been an increasing demand for reduction of power consumption during standby of devices due to an energy star program based on a standard for energy saving of OA devices established by the US Environmental Protection Agency. In order to meet such demands, for example, devices such as scanners exhibit large power consumption during operation, but various devices have been made to reduce power consumption during standby.

  FIG. 6 is a diagram showing a configuration of a conventional switching power supply device used in such a device. This switching power supply device includes a main converter 1 and an auxiliary power supply 2, and an output on / off control circuit 3 is connected to the auxiliary power supply 2.

  The main converter 1 includes a main converter switching circuit 11, a transformer 12, a main converter rectification / smoothing circuit 13, a main converter primary side control circuit 14, a photocoupler 15, and a main converter secondary side control circuit 16.

  The main converter switching circuit 11 switches the input DC voltage with a switching element (not shown), and sends it to the transformer 12 as an alternating voltage. The transformer 12 transforms the alternating voltage sent from the main converter switching circuit 11 and sends it to the main converter rectification / smoothing circuit 13. The main converter rectifying / smoothing circuit 13 rectifies and smoothes the transformed alternating voltage output from the transformer 12 and supplies it as an output voltage to an external load circuit (not shown). To supply.

  The main converter secondary side control circuit 16 operates using power supplied from a secondary control power supply rectification / smoothing circuit 28 (details will be described later) of the auxiliary power supply 2 as a power supply, and a control signal sent from the auxiliary power supply 2 The operation starts or stops depending on The main converter secondary side control circuit 16 detects the output voltage of the main converter rectification / smoothing circuit 13, and outputs an error voltage between the detected output voltage and a predetermined reference voltage via the photocoupler 15. To the side control circuit 14.

  The main converter primary-side control circuit 14 operates using power supplied from a primary control power supply rectification / smoothing circuit 27 (details will be described later) of the auxiliary power supply 2 as a power supply, and a control signal sent from the auxiliary power supply 2 The operation starts or stops depending on The main converter primary side control circuit 14 is a PWM (Pulse Wide Modulation) having a pulse width (on period width) corresponding to the error voltage sent from the main converter secondary side control circuit 16 via the photocoupler 15. A control signal is generated and sent to the main converter switching circuit 11. The switching element of the main converter switching circuit 11 performs switching at intervals corresponding to the pulse width of the PWM control signal. Thereby, the output voltage from the main converter rectification / smoothing circuit 13 is kept constant.

  The auxiliary power source 2 includes an auxiliary power source switching circuit 21, a transformer 22, an auxiliary power source output rectifying / smoothing circuit 23, an auxiliary power source primary side control circuit 24, a photocoupler 25, an auxiliary power source secondary side control circuit 26, and a primary control power source rectifier. A smoothing circuit 27 and a secondary control power supply rectification / smoothing circuit 28 are included.

  The auxiliary power supply switching circuit 21 switches the input DC voltage with a switching element (not shown) and sends it to the transformer 22 as an alternating voltage. The transformer 22 transforms the alternating voltage sent from the auxiliary power switching circuit 21 and sends it to the auxiliary power output rectifying / smoothing circuit 23. The auxiliary power output source rectifying / smoothing circuit 23 rectifies and smoothes the transformed alternating voltage output from the transformer 22 and supplies the rectified and alternating voltage to the external output on / off control circuit 3, and the auxiliary power source secondary side control circuit 26. To supply.

  The auxiliary power supply secondary side control circuit 26 detects the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23, and an error voltage between the detected output voltage and a predetermined reference voltage is supplied via the photocoupler 25 to the auxiliary power supply 1. The data is sent to the secondary control circuit 24. The auxiliary power supply secondary side control circuit 26 generates a control signal for controlling start / stop of the main converter 1, and sends it to the main converter primary side control circuit 14 and the main converter secondary side control circuit 16 of the main converter 1. send. This control signal controls whether or not the main converter 1 outputs power.

  The auxiliary power supply primary side control circuit 24 generates a PWM control signal having a pulse width corresponding to the error voltage sent from the auxiliary power supply secondary side control circuit 26 via the photocoupler 25, and the auxiliary power supply switching circuit 21. Send to. The switching element of the auxiliary power switching circuit 21 switches at intervals corresponding to the pulse width of the PWM control signal. As a result, the output voltages of the auxiliary power supply rectification / smoothing circuit 23, the primary control power supply rectification / smoothing circuit 27, and the secondary control power supply rectification / smoothing circuit 28 are kept constant.

  The primary control power supply rectification / smoothing circuit 27 rectifies and smoothes the transformed alternating voltage output from the transformer 22 and supplies it as power to the main converter primary side control circuit 14 of the main converter 1. The secondary control power supply rectifying / smoothing circuit 28 rectifies and smoothes the transformed alternating voltage output from the transformer 22 and supplies it as power to the main converter secondary side control circuit 16 of the main converter 1.

  The output on / off control circuit 3 outputs the output of the auxiliary power supply output rectifying / smoothing circuit 23 according to an on / off control signal sent from an external switch (not shown) to a part of the load circuit described above. Controls whether to supply to a circuit (a circuit that operates even during standby). That is, during standby, the output on / off control circuit 3 supplies power from the auxiliary power supply output rectifying / smoothing circuit 23 to a part of the load circuit in response to an on / off control signal instructing an off state from the outside. This is configured to reduce power consumption during standby.

As a related technique, Patent Document 1 discloses a switching power supply device that can stop the operation of the power factor correction control circuit at the time of low power consumption and further save power. In this switching power supply device, during normal load operation, operating power is supplied to the power factor correction control circuit, whereby the boost chopper circuit is controlled by the power factor correction control circuit, and the power factor of the device is improved. In addition, when the PWM control circuit is in the intermittent oscillation mode during low power consumption operation, the voltage induced in the auxiliary winding during the off period when the operation of the PWM control circuit is stopped decreases. descend. In addition, the operating power supply voltage supplied to the power factor correction control circuit is reduced by the Zener diode, and if the power factor correction control circuit is below the starting voltage, the power factor correction control circuit will not function and power loss will be reduced accordingly. Decrease.
JP 2004-215433 A

  In the conventional switching power supply device described above, in order to reduce power consumption during standby, power supply from the auxiliary power supply 2 to a part of the load circuit is stopped, but the auxiliary power supply 2 itself operates normally. The main converter primary side control circuit 14 and the main converter secondary side control circuit 16 in the main converter 1 are supplied with electric power as usual. Therefore, although the power consumption by a part of the load circuit connected to the output on / off control circuit 3 can be reduced, the power consumption in the auxiliary power source 2 itself, the main converter primary side control circuit 14 in the main converter 1 and the main The power consumption in the converter secondary side control circuit 16 cannot be reduced.

  In a conventional switching power supply device, there are two states, a plug-in off state and a sleep state, as standby states in addition to an on state that is a full load state. The on state refers to a state in which a voltage is output from the main converter 1 and the auxiliary power source 2 (more specifically, from the auxiliary power source 2 via the output on / off control circuit 3).

  The sleep state is a state in which a voltage is output from the auxiliary power supply 2 via the output on / off control circuit 3, but no voltage is output from the main converter 1. The plug-in off state refers to a state in which no voltage is output from both the main converter 1 and the auxiliary power supply 2.

  In the conventional switching power supply device described above, in the plug-in off state, the output of the auxiliary power supply 2 is cut off by the output on / off control circuit 3 to suppress power consumption in a part of the load circuit connected to the output. However, the reduction of power consumption inside the switching power supply device is insufficient, and further reduction of power consumption is desired.

  An object of the present invention is to provide a switching power supply device that can reduce power consumption with a simple configuration.

  In order to solve the above-mentioned problem, the invention described in claim 1 is directed to a main converter that supplies power to a load circuit according to control of the first control circuit, and power to a part of the first control circuit and load circuit of the main converter. In a switching power supply device including an auxiliary power supply for supplying power, a second control circuit that lowers the output voltage of the auxiliary power supply according to an on / off control signal input from the outside, and an auxiliary power supply controlled by the second control circuit And an output on / off control circuit that stops the power supply to the first control circuit of the main converter and a part of the load circuit.

  According to a second aspect of the present invention, in the first aspect of the invention, the output on / off control circuit maintains a constant voltage even when the output voltage of the auxiliary power supply fluctuates, between the first control circuit and the load circuit of the main converter. It has a dropper function for supplying to a part.

  According to the first aspect of the present invention, it is possible to reduce the loss in the auxiliary power supply by reducing the output voltage of the auxiliary power supply, and further reduce the power consumption by not supplying power to unnecessary circuits. can do.

  According to the second aspect of the present invention, the output on / off control circuit has a dropper function so that a constant voltage is supplied to the first control circuit of the main converter and a part of the load circuit. Stabilization of the output voltage can be realized.

  Hereinafter, a switching power supply according to an embodiment of the present invention will be described in detail with reference to the drawings.

  1 is a diagram illustrating a configuration of a switching power supply apparatus according to a first embodiment of the present invention. In this switching power supply device, the output on / off control circuit 3 of the conventional switching power supply device shown in FIG. 6 is replaced with a first output on / off control circuit 3a, and a second output on / off control circuit 3b and The third output on / off control circuit 3c is added, and the auxiliary power supply secondary side control circuit 26 in the auxiliary power supply 2 is replaced with an auxiliary power supply secondary side control circuit 29 whose function is changed. Has been.

  The first output on / off control circuit 3a, the second output on / off control circuit 3b, and the third output on / off control circuit 3c correspond to the output on / off control circuit of the present invention. The main converter primary side control circuit 14 and the main converter secondary side control circuit 16 correspond to the first control circuit of the present invention. Further, the auxiliary power source secondary side control circuit 29 corresponds to the second control circuit of the present invention.

  The auxiliary power supply secondary side control circuit 29 detects the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23, and an error voltage between the detected output voltage and a reference voltage corresponding to an on / off control signal input from the outside. Is sent to the auxiliary power source primary side control circuit 24 via the photocoupler 25. Specifically, the auxiliary power supply secondary side control circuit 29 has an error between the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23 and a predetermined reference voltage when the ON state is instructed by the ON / OFF control signal. The voltage is sent to the auxiliary power source primary side control circuit 24 through the photocoupler 25.

  The auxiliary power supply primary side control circuit 24 generates a PWM control signal having a pulse width corresponding to the received error voltage and sends it to the auxiliary power supply switching circuit 21. The switching elements included in the auxiliary power supply switching circuit 21 are PWM controlled. Switching is performed at intervals according to the signal. As a result, the output voltages of the auxiliary power supply rectification / smoothing circuit 23, the primary control power supply rectification / smoothing circuit 27, and the secondary control power supply rectification / smoothing circuit 28 are kept constant.

  On the other hand, the auxiliary power supply secondary side control circuit 29, when instructed to be in the off state by the on / off control signal, outputs the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23 and a reference voltage lower than a predetermined reference voltage. The error voltage is sent to the auxiliary power source primary side control circuit 24 through the photocoupler 25. The auxiliary power supply primary side control circuit 24 generates a PWM control signal having a pulse width corresponding to the received error voltage and sends it to the auxiliary power supply switching circuit 21. The switching elements included in the auxiliary power supply switching circuit 21 are PWM controlled. Switching is performed at intervals according to the signal. In this case, the pulse width of the PWM control signal is controlled to be shorter than when the on state is instructed by the on / off control signal. As a result, each of the output voltages of the auxiliary power supply output rectification / smoothing circuit 23, the primary control power supply rectification / smoothing circuit 27, and the secondary control power supply rectification / smoothing circuit 28 is instructed to be turned on by the on / off control signal. It is kept constant at a lower voltage than when. Therefore, power consumption in the auxiliary power source 2 can be reduced.

  FIG. 2 is a diagram showing a specific circuit configuration of the auxiliary power source secondary side control circuit 29. The auxiliary power supply secondary side control circuit 29 has a reference terminal at a connection point between the resistor R1 and the resistor R2 connected in series to divide the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23, and the resistor R1 and the resistor R2. Is connected to the shunt regulator SH whose anode is grounded, the cathode of the shunt regulator SH, the resistor R3 provided between the connection points of the resistors R1 and R2, and one end of the cathode of the shunt regulator SH. The resistor R4 is connected between the other end of the resistor R4 and a power source (not shown), and the light-emitting diode of the photocoupler 25 is connected in parallel, and between the anode and cathode of the shunt regulator SH. A transistor Q is connected to a collector and an emitter. An external on / off control signal is input to the base of the transistor Q.

  When the ON state is instructed by the ON / OFF control signal, the transistor Q is turned OFF, and the current according to the error voltage between the voltage obtained by dividing the output voltage by the resistor R1 and the resistor R2 and the reference voltage of the shunt regulator SH. Flows to the resistor R5 via the shunt regulator SH and the resistor R4, and the light emitting diode of the photocoupler 25 emits light and feeds back to the auxiliary power source primary side control circuit 24. As a result, the pulse width of the PWM control signal generated by the auxiliary power primary side control circuit 24 is controlled to be a predetermined width, and the auxiliary power output rectifying / smoothing circuit 23, the primary control power rectifying / smoothing circuit 27, and Each output voltage of the secondary control power supply rectification / smoothing circuit 28 is kept constant.

  On the other hand, when the off state is instructed by the on / off control signal, the transistor Q is turned on, and the potential of the cathode (point A) of the shunt regulator SH is forcibly lowered. Thus, the pulse width of the PWM control signal generated by the auxiliary power source primary side control circuit 24 is controlled to be minimized, and the auxiliary power source output rectifying / smoothing circuit 23, the primary control power source rectifying / smoothing circuits 27 and 2 are controlled. Each output voltage of the next control power supply rectification / smoothing circuit 28 is lowered and kept constant at a low voltage.

  FIG. 3 is a diagram showing another specific circuit configuration of the auxiliary power source secondary side control circuit 29. The auxiliary power supply secondary side control circuit 29 has a reference terminal at a connection point between the resistors R1 and R2 connected in series to divide the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23 and the resistors R1 and R2. The shunt regulator SH connected to the anode, the resistor R4 having one end connected to the cathode of the shunt regulator SH, and the other end of the resistor R4 and a power source (not shown) are connected. The resistor R5 has a light emitting diode connected in parallel, and the transistor Q has an emitter connected to one end of the resistor R2 and a collector connected to the other end via the resistor Rc. An external on / off control signal is input to the base of the transistor Q.

  When the ON state is instructed by the ON / OFF control signal, the transistor Q is turned OFF, and the current according to the error voltage between the output voltage divided by the resistors R1 and R2 and the reference voltage of the shunt regulator SH Flows to the resistor R5 via the shunt regulator SH and the resistor R4, and the light emitting diode of the photocoupler 25 emits light and feeds back to the auxiliary power source primary side control circuit 24. As a result, the pulse width of the PWM control signal generated by the auxiliary power primary side control circuit 24 is controlled to be a predetermined width, and the auxiliary power output rectifying / smoothing circuit 23, the primary control power rectifying / smoothing circuit 27, and Each output voltage of the secondary control power supply rectification / smoothing circuit 28 is kept constant.

  On the other hand, when the off state is instructed by the on / off control signal, the transistor Q is turned on, the output voltage is divided by the resistor R2 and the parallel circuit of the resistor Rc, and the resistor R1, and the reference terminal of the shunt regulator SH ( The voltage applied to point B) rises and the current flowing through the shunt regulator SH increases. Thereby, the pulse width of the PWM control signal generated by the auxiliary power source primary side control circuit 24 is controlled to be narrowed, and the auxiliary power source output rectifying / smoothing circuit 23, the primary control power source rectifying / smoothing circuit 27 and the secondary power are controlled. Each output voltage of the control power supply rectification / smoothing circuit 28 is lowered and kept constant at a low voltage. The auxiliary power supply secondary side control circuit 29 shown in FIG. 3 can be used when the pulse width of the PWM control signal cannot be minimized.

  Referring to FIG. 1, the first output on / off control circuit 3a detects the output voltage of the auxiliary power supply output rectifying / smoothing circuit 23, and when the detected output voltage is equal to or higher than a predetermined threshold, Power is supplied to a part of a load circuit (not shown). The second output on / off control circuit 3b detects the output voltage of the primary control power supply rectifying / smoothing circuit 27, and when detecting that the detected output voltage is equal to or higher than a predetermined threshold, the main converter primary side Power is supplied to the control circuit 14. The third output on / off control circuit 3c detects the output voltage of the secondary control power supply rectifying / smoothing circuit 28, and when detecting that the detected output voltage is equal to or higher than a predetermined threshold value, Power is supplied to the control circuit 16.

  FIG. 4A is a diagram showing a specific circuit configuration of the first output on / off control circuit 3a. The circuit configurations of the second output on / off control circuit 3b and the third output on / off control circuit 3c are the same as the circuit configuration of the first output on / off control circuit 3a. Only the on / off control circuit 3a will be described.

  The first output on / off control circuit 3a includes a capacitor C1 connected between input terminals, a series circuit including a Zener diode ZD, a resistor R1, and a resistor R2 connected in parallel to the capacitor C1, and a capacitor C1 in parallel. Between the output terminal and a parallel circuit of a resistor R3 and a capacitor C3, a series circuit composed of a resistor R4 and a transistor Q2, and a MOSFET Q1 having a source and a drain connected between the input terminal and the output terminal. And a connected capacitor C2. The base of the transistor Q2 is connected to the connection point between the resistor R1 and the resistor R2. The gate of the MOSFET Q1 is connected to a connection point between the resistor R3 and the resistor R4.

  In the first output on / off control circuit 3a configured as described above, when the input voltage is low during standby (plug-in off state), the MOSFET Q1 is off, so that no voltage is generated on the output side. Therefore, no loss occurs in a part of the load circuit connected to the output side. As shown in FIG. 4B, when the auxiliary power supply 2 returns to the normal operation and the input voltage rises when the standby power is restored from the standby time, the standby voltage <Vzd <the threshold set to the rated voltage is exceeded. MOSFET Q1 is turned on and power is supplied to a part of the load circuit.

  As described above, the first output on / off control circuit 3a is configured to detect the output voltage of the auxiliary power supply 2 and supply power to the load circuit when the detected output voltage is equal to or higher than a certain threshold value. Therefore, power is supplied only to the minimum necessary circuit at the time of OFF. Therefore, in addition to the reduction of power consumption by lowering the voltage of the auxiliary power supply 2, further power saving can be realized.

  Each of the first output on / off control circuit 3a, the second output on / off control circuit 3b, and the third output on / off control circuit 3c detects an input voltage, Since it is determined whether or not power is supplied to the main converter primary side control circuit 14 and the main converter secondary side control circuit 16, it is not necessary to provide each circuit with a control signal for controlling whether or not output is possible. Therefore, the configuration of the switching power supply device can be simplified.

  The switching power supply according to the second embodiment of the present invention has a detailed circuit configuration of the first output on / off control circuit 3a, the second output on / off control circuit 3b, and the third output on / off control circuit 3c. Different from those according to 1. Below, it demonstrates focusing on a different part.

  FIG. 5A is a diagram showing a specific circuit configuration of the first output on / off control circuit 3a. The circuit configurations of the second output on / off control circuit 3b and the third output on / off control circuit 3c are the same as the circuit configuration of the first output on / off control circuit 3a. Only the on / off control circuit 3a will be described.

  The first output on / off control circuit 3a is connected in parallel to a series circuit composed of a resistor R1, a resistor R2, and a Zener diode ZD1, and a series circuit composed of a resistor R1 and a resistor R2, connected between input terminals. A series circuit comprising a transistor Q2, a resistor R3, a backflow preventing diode D and a Zener diode ZD2, a transistor Q1 having a collector and an emitter connected between an input terminal and an output terminal, a diode D, a Zener diode ZD2 and a Zener The capacitor C1 is connected to a series circuit including a diode ZD1, and the capacitor C2 is connected between output terminals. The base of the transistor Q2 is connected to the connection point between the resistor R1 and the resistor R2. The base of the transistor Q1 is connected to the connection point between the resistor R3 and the diode D.

  The first output on / off control circuit 3a configured in this manner also serves as a dropper circuit for stabilizing the output, and is used to turn on / off the output without being controlled from the outside. At the time of standby, similarly to the first output on / off control circuit 3a shown in FIG. 4, the transistor Q1 is off, and as shown in FIG. 5 (b), the standby voltage <Vzd1 <rated voltage is set. By shifting from the standby state to the sleep state by the threshold, the transistor Q1 is turned on, and power is supplied to the load circuit. Furthermore, even if the input voltage fluctuates, the output voltage is stabilized by the voltage set by “Vzd1 + Vzd2”.

  The present invention can be used as a power supply device for various devices that require power consumption, such as OA devices.

It is a figure which shows the structure of the switching power supply apparatus which concerns on Example 1 of this invention. It is a figure which shows the specific circuit structure of the auxiliary power supply secondary side control circuit which comprises the switching power supply which concerns on Example 1 of this invention. It is a figure which shows the other specific circuit structure of the auxiliary power supply secondary side control circuit which comprises the switching power supply which concerns on Example 1 of this invention. It is a figure which shows the specific example of the output on / off control circuit which comprises the switching power supply apparatus which concerns on Example 1 of this invention. It is a figure which shows the specific example of the output on / off control circuit which comprises the switching power supply apparatus which concerns on Example 2 of this invention. It is a figure which shows the structure of the conventional switching power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main converter 2 Auxiliary power supply 3a-3c 1st-3rd output on / off control circuit 11 Main converter switching circuit 12, 15 Transformer 13 Main converter rectification / smoothing circuit 14 Main converter primary side control circuit 16 Main converter secondary side Control circuit 21 Auxiliary power supply switching circuit 22, 25 Transformer 23 Auxiliary power supply output rectification / smoothing circuit 24 Auxiliary power supply primary side control circuit 26, 29 Auxiliary power supply secondary side control circuit 27 Primary control power supply rectification / smoothing circuit 28 Secondary control Power rectification / smoothing circuit

Claims (2)

A main converter for supplying power to the load circuit according to the control of the first control circuit;
In a switching power supply comprising a first control circuit of the main converter and an auxiliary power supply for supplying power to a part of the load circuit,
A second control circuit for lowering the output voltage of the auxiliary power supply in accordance with an on / off control signal input from the outside;
An output on / off control circuit that detects that the output voltage of the auxiliary power supply has dropped due to control by the second control circuit and stops power supply to the first control circuit of the main converter and a part of the load circuit When,
A switching power supply device comprising:   The output on / off control circuit has a dropper function for supplying a constant voltage to the first control circuit of the main converter and a part of the load circuit even if the output voltage of the auxiliary power supply fluctuates. The switching power supply device according to claim 1.

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