JP2008245444A - Switching power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power loss of output voltage with a simple circuit constitution by controlling connection/disconnection of a bleeder resistance corresponding to an operation state of a load circuit. <P>SOLUTION: The bleeder resistance R13 which constitutes a bleeder resistance connection/disconnection control circuit 402 of a power output control unit 4 is connected/disconnected through operation state signals S1, S3 from the load circuit when insulation between a power input control unit 3 which rectifies/smoothes AC voltage Vin from an AC power supply 2 and a power supply output control unit 4 which generates output voltage Vout to the load circuit 1 is performed through a switching transformer 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply device, and more particularly to a switching power supply device that limits a current flowing through a bleeder resistor to reduce a power loss of an output voltage.

  Conventionally, a DC voltage source circuit has been disclosed in which a bleeder resistor is inserted between the output terminals of a switch circuit so that a predetermined voltage is applied to the output stage even when there is no load (for example, a patent) See reference 1.)

  According to this DC voltage source circuit, the operation of the switching circuit can be stabilized even when there is no load, when the load is extremely light, or when a heavy load is suddenly applied.

JP-A-7-337007 (paragraph numbers “0002” to “0004”, FIG. 3)

  According to the conventional DC voltage source circuit in Patent Document 1 described in the background art, even when the load capacitance is sufficiently large and the switching operation is stable, the bleeder resistor has a current similar to that at the time of no load. Flowed, and there was a difficulty in causing power loss. In particular, this type of DC voltage source circuit is intended to output high voltage and high power, so a capacitor with a large capacity is used as the ripple smoothing capacitor, so the current flowing through the bleeder resistor is also compared. This power loss cannot be ignored.

  Further, in order to solve the above-mentioned difficulties, a DC voltage source circuit according to an embodiment in Patent Document 1 is disclosed. According to this DC voltage source circuit, the current flowing through the bleeder resistance circuit is changed according to the amount of load current. If the load current amount is sufficient to stabilize the operation of the switching circuit, the bleeder resistance circuit is turned off. Thus, there is an effect that a power efficient circuit can be provided with a simple configuration. .

  However, according to the DC voltage source circuit of the embodiment in Patent Document 1, the circuit configuration for limiting the current flowing through the bleeder resistance circuit in accordance with the amount of load current is complicated.

  The present invention has been made to solve this problem, and by controlling the connection or disconnection of the bleeder resistor according to the operating state of the load circuit, the power loss of the output voltage can be reduced with a simple circuit configuration. It aims at providing the switching power supply device which can do.

  In order to achieve the above-described object, a switching power supply apparatus according to the present invention includes a power supply input control unit to which an AC voltage from an AC power supply is applied, a power supply output control unit for generating an output voltage, a power supply input control unit, A switching transformer is provided for insulating between the power supply output control units. The switching transformer includes a primary winding for supplying power from the power input control unit to the power output control unit, and a secondary winding and a primary auxiliary winding for receiving power from the power input control unit. is there. The power input control unit controls an input side rectification / smoothing circuit for rectifying / smoothing AC voltage, a transistor for driving a switching transformer based on an output voltage of the primary auxiliary winding, and a switching operation of the transistor. A switching control circuit. The power supply output control unit detects the voltage from the output side rectification / smoothing circuit for rectifying and smoothing the voltage of the secondary winding, and controls the switching control circuit by detecting the voltage from the output side rectification / smoothing circuit. Constant voltage control circuit to keep constant and bleeder resistor that is provided on the output side of the output side rectification / smoothing circuit and constantly flows current to prevent the output voltage from rising when there is no load. And a bleeder resistance connection / disconnection control circuit for controlling connection / disconnection.

  According to the switching power supply device of the present invention, between the power supply input control unit that rectifies and smoothes the AC voltage from the AC power supply and the power supply output control unit that generates the output voltage to the load circuit, via the switching transformer. In the insulation, the bleeder resistance that constitutes the bleeder resistance connection / disconnection control circuit of the power supply output control unit can be connected or disconnected by the operation state signal from the load circuit, and the power loss of the output voltage can be reduced with a simple circuit configuration. Reduction is possible.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments to which a switching power supply device of the invention is applied will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a specific configuration of a switching power supply device according to an embodiment of the present invention.

  The switching power supply device shown in FIG. 1 includes a load circuit 1 such as home appliances, an AC power supply (commercial power supply) 2, a power input control unit 3 to which an AC voltage Vin from the AC power supply 2 is applied, and a load circuit 1. The power supply output control unit 4 for generating the output voltage Vout for operating the power supply, the switching transformer 5 for insulating between the power supply input control unit 3 and the power supply output control unit 4, and the three connected to the load circuit 1 Terminals (hereinafter referred to as a power supply terminal, a GND terminal, and a signal input terminal) P1, P2, and P3 are provided.

  The switching transformer 5 is induced via a primary winding 500 for supplying power (DC voltage) from the power input controller 3 to the power output controller 4 and from the power input controller 3 via the primary coil 500. A secondary winding 501 and a primary auxiliary winding 502 for receiving the generated power source (DC voltage) are provided.

  The power input control unit 3 includes an input side rectification / smoothing circuit 300 for rectifying and smoothing the AC voltage Vin from the AC power source 2 to generate a DC voltage, and a primary auxiliary winding constituting the switching transformer 5. A transistor 301 (NPN type) for driving the switching transformer based on the output voltage 502, and a switching control circuit 302 for controlling switching operation of the transistor 301, that is, switching between an on state and an off state. Is provided.

  In the power input control unit 3, the input side rectifying / smoothing circuit 300 includes a diode bridge DB and a capacitor C1. The switching control circuit 302 also comprises resistors R1, R2, R3, R4, R5, R6, capacitors C2, C3, C4, diodes D1, D2, Zener diode ZD1, (NPN type) transistor Q1, and photocoupler PC. (NPN type) transistor Q2 (hereinafter referred to as a light receiving transistor).

  The configuration of the power input control unit 3 As a specific connection mode of each part / circuit, the AC power source 2 is connected between one side and the other side of the rectification side of the diode bridge circuit DB constituting the input side rectification / smoothing circuit 300 Has been. Further, a capacitor C1 is connected in parallel between the (+) terminal and the (−) terminal of the diode bridge circuit DB, and a series-connected resistor R3 and transistor Q1 constituting the switching control circuit 302 are connected. Are connected in parallel. The collector of the transistor 301 is connected to the (+) terminal of the diode bridge circuit DB via the primary winding 500 (one end and the other end) constituting the switching transformer 5. Is connected to a reference potential point via a resistor R 1 constituting the switching control circuit 302. Further, the primary auxiliary winding 502 constituting the switching transformer 5 is connected to the base of the transistor 301 through the resistor R4 and the diode D1 constituting the switching control circuit 302 in order. Further, a reference potential point is connected to the (−) terminal of the diode bridge circuit DB.

  The base of the transistor Q1 constituting the switching control circuit 302 is connected between the emitter of the transistor 301 and one end of the resistor R1 via the resistor R2.

  In the switching control circuit 302, the collector of the light receiving transistor Q2 constituting the photocoupler PC is connected between the cathode of the diode D2 and the capacitor C4 via the resistor R6. The emitter of the light receiving transistor Q2 is connected between the emitter of the transistor 301 and the resistor R1 via the capacitor C2. Further, between the emitter of the light receiving transistor Q2 and the capacitor C2, a resistor R5 and a Zener diode ZD1 are sequentially connected between one end of the primary auxiliary winding 502 constituting the switching transformer 5 and the anode of the diode D1. Yes.

  A capacitor C3 is connected in parallel between both ends of the anode and cathode of the diode D1 constituting the switching control circuit 302. A reference potential point is connected between the anode of the diode D1 and the primary auxiliary winding 502 constituting the switching transformer 5 through the diode D2 and the capacitor C4 in this order.

  Further, the power output control unit 4 rectifies and smoothes a DC voltage that is a power source that is induced from the primary winding 500 constituting the switching transformer 5 and then received by the secondary winding 501 to load circuit 1. The output side rectification / smoothing circuit 400 for generating the output voltage Vout to the output and the voltage from the output side rectification / smoothing circuit 400 are detected and the switching control circuit 302 is controlled so that the output voltage Vout is kept at a constant voltage level. The constant voltage control circuit 401 for holding and the output side of the output side rectifying / smoothing circuit 400 and the power supply terminal P1 and the GND terminal P2 are provided to prevent an increase in output voltage when the load circuit 1 is not loaded. In order to control connection / disconnection of the bleeder resistor by an operating state signal transmitted from the load circuit via the signal input terminal P3. Bleeder resistor connecting / disconnecting the control circuit 402 is provided.

  In the power supply output controller 4, the output side rectifying / smoothing circuit 400 includes a diode D4 and a capacitor C7. The constant voltage control circuit 401 includes resistors R9, R10, R11, R12, a diode (hereinafter referred to as a light emitting diode) D5 constituting a photocoupler PC, and a shunt regulator IC. Further, the bleeder resistor connection / disconnection control circuit 402 includes a bleeder resistor R13, resistors R14 and R15, and an (NPN type) transistor Q3.

  As a specific connection mode of each component / circuit of the power supply output control unit 4, one end of a secondary winding 501 (one end of the switching transformer 5) is connected to the anode of the diode D 4 constituting the output side rectification / smoothing circuit 400. And the other end) are connected to the reference potential point. A power supply terminal P1 is connected to the cathode of the diode D4. A capacitor C7 is connected between the cathode of the diode D4 and the GND terminal P2. Further, a reference potential point is connected between the cathode of the diode D4 and the power supply terminal P1 through the resistors R11 and R12 constituting the constant voltage control circuit 401 in order. Further, a reference potential point is connected between the other end of the secondary winding 501 and the GND terminal P2.

  In the constant voltage control circuit 401, the anode of the light emitting diode D5 constituting the photocoupler PC is connected between the cathode of the diode D4 constituting the output side rectifying / smoothing circuit 400 and the power supply terminal P1 via the resistor R9. ing. The cathode of the light emitting diode D5 and the cathode of the shunt regulator IC are connected between the cathode of the diode D4 and the power supply terminal P1 constituting the output side rectifying / smoothing circuit 400 via the resistor R10. The reference of the shunt regulator IC is connected between the resistors R11 and R12 connected in series, and the potential of the power supply terminal P1 is divided and supplied to the reference of the shunt regulator. Further, a reference potential point is connected to the anode of the shunt regulator IC.

  In the bleeder resistance connection / disconnection control circuit 402, one end of the bleeder resistance R13 is connected between the diode D4 and the power supply terminal P1 of the output side rectifying / smoothing circuit 400, and the other end is connected to the transistor Q3 (the collector of the transistor Q3). And the emitter) are connected in sequence via the emitter. A signal input terminal P3 is connected to the base of the transistor Q3 via a resistor R14. Further, a resistor R15 is connected between the base and emitter of the transistor Q3.

  In the switching power supply according to the embodiment of the present invention configured as described above, specific operations will be described below with reference to the drawings.

  In FIG. 1, when the AC voltage Vin from the AC power source 2 is applied between one and the other ends of the rectifying side of the diode bridge circuit DB constituting the input side rectifying / smoothing circuit 300 of the power input control unit 3, The AC voltage Vin is rectified via the diode bridge circuit DB and then smoothed via the capacitor C1.

  Further, when a DC voltage is generated through the diode bridge circuit DB and the capacitor C1 constituting the input side rectifying / smoothing circuit 300 of the power input control unit 3, the resistance R3 constituting the switching control circuit 302 is passed through. Thus, when the base current flows into the transistor 301, the transistor 301 is activated and a collector current flows. By this operation, a DC voltage is applied to the primary winding 500 constituting the switching transformer 5, so that the (−) voltage induced from the primary winding 500 is received by the primary auxiliary winding 502, and the switching control circuit 302. The base current flows into the transistor 301 via the diode D1 and the resistor R4 constituting the transistor 301, and the transistor 301 is kept on.

  Further, when the transistor 301 constituting the power input control unit 3 is turned on and a DC voltage is applied to the primary winding 500 constituting the switching transformer 5, the (+) voltage induced from the primary winding 500 is The secondary winding 501 receives power.

  Next, the (+) voltage received by the secondary winding 501 constituting the switching transformer 5 was rectified via the diode D4 constituting the output side rectification / smoothing circuit 400 of the power supply output control unit 4. Then, it is smoothed via the capacitor C7. The DC voltage rectified and smoothed through the diode D4 and the capacitor C7 is output as a constant voltage output voltage Vout from the power supply terminal P1 (and GND terminal P2) to the load circuit 1, and is also constant voltage. The voltage level is divided through resistors R11 and R12 constituting the control circuit 401.

  Further, if the shunt current flowing into the shunt regulator IC by the output voltage Vout divided through the resistors R11 and R12 constituting the constant voltage control circuit 401 of the power supply output control unit 4 is equal to or greater than a predetermined threshold value, this shunt The regulator IC is turned on, and the light emitting diode D5 constituting the photocoupler PC into which the anode current flows through the resistor R9 can be turned on. By this lighting, the light receiving transistor Q2 constituting the photocoupler PC of the switching control circuit 302 (of the power supply input control unit 3) is turned on, and the base is based on the DC voltage stored in the capacitor C4 via the diode D2. Current flows into transistor Q1.

  Further, since the base current flows into the transistor Q1 constituting the switching control circuit 302 of the power input control unit 3, and when the transistor Q1 is turned on, the base current to the transistor 301 is sucked into the reference potential point. 301 switches from an on state to an off state.

  In addition, when the transistor 301 constituting the power input control unit 3 is turned off, the energy of the switching transformer 5 decreases, and no (+) voltage is induced from the primary winding 500 to the secondary winding 501. Will occur. Therefore, when the energy of the switching transformer 5 becomes “0”, the current to the diode D4 discharged from the capacitor C7 constituting the output side rectifying / smoothing circuit 400 of the power supply output control unit 4 is backswing due to residual magnetization, Since a reverse current flows through the secondary winding 501, the primary auxiliary winding 502 receives a (+) voltage.

  Further, when the (+) voltage is received by the primary auxiliary winding 402 constituting the switching transformer 5, the diode D 1, the resistor R 4, and the input side rectifying / smoothing circuit 300 constituting the switching control circuit 302 of the power input control unit 3. The switching operation of the transistor 301, that is, the on state or the off state so that the base current flows into the transistor 301 via the diode bridge circuit DB and the resistor R3 (sequentially) constituting the transistor 301, and the transistor 301 is turned on again. Is repeatedly switched. Thus, by controlling the time during which the transistor 301 is turned off, the constant voltage control of the output voltage Vout becomes possible. At this time, the bleeder resistance connection / disconnection control circuit 402 of the power supply output control unit 4 is configured. A current always flows through the bleeder resistor R13 in order to prevent an increase in the output voltage Vout when the load circuit 1 is not loaded.

  However, since the constant current flowing through the bleeder resistor R13 as described above causes power loss of the output voltage Vout, as in the background art, the load circuit 1 that has received the constant output voltage Vout operates as described above. Different operating state signals S1 and S2 can be generated depending on the state depending on the H (High) level or L (Low) level. The operation state signals S1 and S2 are applied to the base of the transistor Q3 from the load circuit 1 via the signal input terminal P3 and the resistor R14 constituting the bleeder resistance connection / disconnection control circuit 402 of the power supply output control unit 4. .

  Here, in the bleeder resistance connection / disconnection control circuit 402 of the power supply output control unit 4, it is assumed that the load circuit 1 is not operating and the operation state signal S1 of H (High) level is applied to the base of the transistor Q3. Since the transistor Q3 is turned on and a bleeder current is caused to flow through the bleeder resistor R13, the output voltage Vout can be prevented from rising when the load circuit 1 is not loaded.

  On the other hand, when the load circuit 1 is operating in the bleeder resistance connection / disconnection control circuit 402 of the power supply output control unit 4, and an L (Low) level operation state signal S2 is applied to the base of the transistor Q3, Since the transistor Q3 is turned off and the bleeder current flowing through the bleeder resistor R13 is cut off, the power consumed by the bleeder resistor R13 can be suppressed, and the power loss of the output voltage Vout can be reduced.

  As is apparent from the above description, according to the switching power supply device of the present invention, the power supply input control unit 3 for rectifying and smoothing the AC voltage Vin from the AC power supply 2 and the output voltage Vout to the load circuit 1 are generated. When the power supply output control unit 4 is insulated via the switching transformer 5, the bleeder resistor R13 constituting the bleeder resistance connection / disconnection control circuit 402 of the power supply output control unit 4 is operated from the load circuit 1. The state signals S1 and S2 can be connected or disconnected, and the power loss of the output voltage Vout can be reduced with a simple circuit configuration.

  The switching power supply device according to the present invention has been described with a specific embodiment. However, the present invention is not limited to this embodiment, and any switching power supply device having any known configuration can be used as long as the effects of the present invention are achieved. It goes without saying that even if there is, it can be adopted.

The circuit diagram which shows the specific structure of the switching power supply apparatus by the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Load circuit 2 ... AC power supply 3 ... Power source input control part 300 ... Input side rectification / smoothing circuit 301 ... Transistor 302 ... Switching control circuit 4 ... Power supply output control part 400 ... Output side rectification / smoothing circuit Smoothing circuit 401 …… Constant voltage control circuit 402 …… Bleeder resistance connection / disconnection control circuit R13 …… Bleeder resistance 5 …… Switching transformer 500 …… Primary winding 501 …… Secondary winding 502 …… Primary auxiliary winding S1, S2 …… Operation status signal Vin …… AC voltage Vout …… Output voltage

Claims (1)

A power input controller (3) to which an AC voltage (Vin) from an AC power source (2) is applied; a power output controller (4) for generating an output voltage (Vout); the power input controller; A switching transformer (5) for insulating between the power output control units,
The switching transformer includes a primary winding (500) for supplying power from the power input control unit to the power output control unit, a secondary winding (501) for receiving power from the power input control unit, and A primary auxiliary winding (502),
The power input control unit includes an input side rectification / smoothing circuit (300) for rectifying and smoothing the AC voltage, and a transistor (301) for driving the switching transformer based on the output voltage of the primary auxiliary winding. And a switching control circuit (302) for controlling the switching operation of the transistor,
The power supply output control unit detects an output side rectification / smoothing circuit (400) for rectifying / smoothing the voltage of the secondary winding, and detects the voltage from the output side rectification / smoothing circuit, and the switching control circuit A constant voltage control circuit (401) for controlling the output voltage and maintaining the output voltage constant, and is provided on the output side of the output side rectification / smoothing circuit to prevent the output voltage from rising at no load. A bleeder resistance connection / disconnection control circuit (402) for controlling connection / disconnection of the bleeder resistance (R13) through which an electric current flows by an operation state signal (S1, S2) from the load circuit (1) is provided. A switching power supply device.

Images