WO2017181568A1 - 开关电源和电视机 - Google Patents

开关电源和电视机 Download PDF

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Publication number
WO2017181568A1
WO2017181568A1 PCT/CN2016/096739 CN2016096739W WO2017181568A1 WO 2017181568 A1 WO2017181568 A1 WO 2017181568A1 CN 2016096739 W CN2016096739 W CN 2016096739W WO 2017181568 A1 WO2017181568 A1 WO 2017181568A1
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WO
WIPO (PCT)
Prior art keywords
resistor
circuit
switch
control
twenty
Prior art date
Application number
PCT/CN2016/096739
Other languages
English (en)
French (fr)
Inventor
杨寄桃
陈建忠
Original Assignee
深圳创维－Rgb电子有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 深圳创维－Rgb电子有限公司 filed Critical 深圳创维－Rgb电子有限公司
Priority to AU2016310330A priority Critical patent/AU2016310330B2/en
Priority to US15/495,064 priority patent/US10015434B2/en
Publication of WO2017181568A1 publication Critical patent/WO2017181568A1/zh

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/385—Switched mode power supply [SMPS] using flyback topology
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/63—Generation or supply of power specially adapted for television receivers
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/395—Linear regulators
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to the field of television technology, and in particular, to a switching power supply and a television set.
  • the structure of the traditional switching power supply is shown in Figure 1.
  • the switching power supply can only output the constant voltage source by filtering the rectified voltage through the high voltage electrolytic capacitor.
  • the constant voltage source needs constant current conversion to obtain the constant current source.
  • the high-voltage electrolytic capacitor has a high cost, which leads to an increase in the cost of the switching power supply.
  • the switching power supply comprises a rectifier circuit, a transformer, a constant voltage control circuit, a power management circuit and a constant current control circuit; an output end of the rectifier circuit and a power detection terminal of the power management circuit and the The power input end of the transformer is connected, the controlled end of the transformer is connected to the control end of the power management circuit, and the constant voltage output winding of the transformer is connected to the feedback input of the power management circuit via the constant voltage control circuit
  • the constant current output winding of the transformer is connected to the constant current control circuit via an LED load; wherein the power management circuit is configured to control an operating state of the transformer according to a power supply voltage input to the transformer, And causing the constant voltage output winding to output a constant voltage, the constant current output winding outputs a constant current; the constant voltage control circuit is configured to feed back a magnitude of a voltage output by the constant voltage output winding to the power management circuit So that the power management circuit controls the constant voltage output winding of the transformer to output a constant voltage
  • the power management circuit includes a switch circuit and a switch control circuit; a detection end of the switch control circuit is a power detection end of the power management circuit, and a feedback end of the switch control circuit is a power management circuit a feedback input end, the control end of the switch control circuit is connected to the controlled end of the switch circuit, and the control end of the switch circuit is a control end of the power management circuit.
  • the switch control circuit includes a control chip, a first capacitor, a first resistor, a second resistor, a third resistor, a fifth resistor, a sixth resistor, and a seventh resistor;
  • the first capacitor is grounded, the turn-off trigger end of the control chip is connected to the first end of the fifth resistor, and the second end of the fifth resistor is used to input a turn-off trigger signal;
  • the switch control end is a control end of the switch control circuit;
  • the open duration setting end of the control chip is grounded via the third resistor and connected to the first end of the first resistor via the second resistor, a second end of the first resistor is a detecting end of the switch control circuit;
  • a feedback end of the control chip is grounded through the sixth resistor and the seventh resistor in sequence, the sixth resistor and the seventh resistor
  • the connection node is the feedback end of the switch control circuit.
  • the switch circuit includes a first switch tube and a fourth resistor; a drain of the first switch tube is a control end of the switch circuit, and a gate of the first switch tube is controlled by the switch circuit End, the source of the first switch tube is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded; the connection node of the first switch tube and the fourth resistor Used to output the shutdown trigger signal.
  • the power management circuit further includes an eighth resistor and a ninth resistor; an overvoltage/undervoltage protection terminal of the control chip, a first end of the eighth resistor, and a first end of the ninth resistor Interconnecting, the second end of the ninth resistor is grounded, and the second end of the eighth resistor is connected to the input end of the rectifier circuit.
  • the power management circuit further includes a first diode, a second diode, a first transistor, a second capacitor, a third capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor and a fourteenth resistor; a first end of the tenth resistor is connected to the power detecting end, and a second end of the tenth resistor is connected to the first end of the eleventh resistor a second end of the eleventh resistor, an emitter of the first transistor, a positive pole of the second capacitor, and a power terminal of the control chip, and a cathode of the second capacitor is grounded; a base of the first transistor, a cathode of the first diode, a first end of the fourteenth resistor, and a first end of the thirteenth resistor, the first diode The anode and the second end of the fourteenth resistor are grounded; the collector of the first transistor is connected to the first end of the t
  • the constant voltage control circuit includes a first voltage regulator, a fourth capacitor, an optocoupler, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, and an eighteenth resistor; Extremely grounded, the collector of the optocoupler is a feedback output end of the constant voltage control circuit, the cathode of the optocoupler, the first end of the fourth capacitor and the cathode of the first regulator tube.
  • the second end of the fourth capacitor is connected to the first end of the sixteenth resistor, the second end of the sixteenth resistor, the second end of the seventeenth resistor, and the tenth
  • the first end of the eight resistors and the adjusting pole of the first voltage regulator tube are interconnected, and the anode of the first voltage regulator tube and the second end of the eighteenth resistor are grounded; the seventeenth resistor
  • the first end is connected to the first end of the fifteenth resistor, the second end of the fifteenth resistor is connected to the anode of the optocoupler
  • the constant current control circuit includes a reference voltage output unit, a constant current control unit, a switch unit, and a switch control unit; the controlled end of the switch unit is connected to a control end of the switch control unit, the switch unit The input end is connected to the LED load, the output end of the switch unit is connected to the control end of the constant current control unit, and the power end of the constant current control unit is connected to the output end of the reference voltage output unit.
  • the constant current control unit comprises a twenty-ninth resistor, a thirtieth resistor and n transistors, a base of the n transistors, a first end of the thirtieth resistor, and the twenty-ninth resistor a first end of the interconnection, a second end of the thirtieth resistor is grounded, a second end of the twenty-ninth resistor is used for inputting a reference voltage; a collector of each triode is interconnected, and the connection node is The control terminal of the constant current control unit; the emitter of each of the n triodes is respectively connected to the ground through a current limiting resistor; wherein n is a natural number.
  • the reference voltage output unit has an input terminal for inputting a constant current enable signal for controlling the LED load to be turned off, the reference voltage output unit comprising a second triode, a third triode, and a a nineteenth resistor, a twentieth resistor, a twenty-first resistor, and a twenty-second resistor; the first end of the nineteenth resistor is for inputting a reference voltage, and the second end of the nineteenth resistor is The emitter of the second transistor is connected, the collector of the second transistor is connected to the first end of the twentieth resistor, and the second end of the twentieth resistor is the reference voltage output unit An output end of the second triode connected to the first end of the twenty-first resistor, a second end of the twenty-first resistor and a collector of the third triode Connecting, the emitter of the third transistor is grounded; the base of the third transistor is connected to the first end of the twenty-second resistor, and the second end of the twenty-second resistor is The reference voltage output unit input terminal.
  • the switch unit includes a second switch tube, a drain of the second switch tube is an input end of the switch unit, and a source of the second switch tube is an output end of the switch unit, the first The gate of the two switching tubes is the controlled end of the switching unit.
  • the switch control unit includes a fourth triode, a fifth triode, a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, and a twenty-sixth resistor; a first end of the three resistors for inputting a PWM signal, a second end of the twenty-third resistor is connected to a base of the fourth triode, a collector of the fourth triode, the first a first end of the twenty-four resistor and a base of the fifth triode are interconnected, an emitter of the fourth triode and the fifth triode is grounded; the fifth triode is a collector, a first end of the twenty-fifth resistor, and a first end of the twenty-sixth resistor are interconnected, a second end of the twenty-fourth resistor and a second fifteenth resistor The two ends are connected to the constant voltage output winding, and the second end of the twenty-sixth resistor is a control end of the switch control unit.
  • the switching power supply further comprises a correction circuit, an input end of the correction circuit is connected to a feedback output end of the constant current control circuit, and an input end of the correction circuit is connected to an input end of the constant voltage control unit .
  • the correction circuit comprises a third diode, a fifth capacitor, a twenty-seventh resistor and a twenty-eighth resistor; the first end of the twenty-eighth resistor is an input end of the correction circuit, The second end of the twenty-eighth resistor, the anode of the fifth resistor, and the first end of the twenty-seventh resistor are interconnected, the cathode of the fifth capacitor is grounded, and the twenty-seventh resistor The second end is coupled to the anode of the third diode, and the cathode of the third diode is the output of the correction circuit.
  • the invention also provides a television set comprising the switching power supply as described above; wherein the switching power supply comprises a rectifier circuit, a transformer, a constant voltage control circuit, a power management circuit and a constant current control circuit; The output end is connected to the power detecting end of the power management circuit and the power input end of the transformer, and the controlled end of the transformer is connected to the control end of the power management circuit, and the constant voltage output winding of the transformer is The constant voltage control circuit is connected to a feedback input end of the power management circuit, and the constant current output winding of the transformer is connected to the constant current control circuit via an LED load; the power management circuit is configured to input to the transformer according to the input The power supply voltage magnitude controls an operating state of the transformer such that the constant voltage output winding outputs a stable voltage, the constant current output winding outputs a stable current; and the constant voltage control circuit is configured to apply the constant voltage The magnitude of the voltage output of the output winding is fed back to the power management circuit to cause the power management circuit to control the constant voltage of the transformer A
  • the power management circuit includes a switch circuit and a switch control circuit; a detection end of the switch control circuit is a power detection end of the power management circuit, and a feedback end of the switch control circuit is a power management circuit a feedback input end, the control end of the switch control circuit is connected to the controlled end of the switch circuit, and the control end of the switch circuit is a control end of the power management circuit.
  • the switch control circuit includes a control chip, a first capacitor, a first resistor, a second resistor, a third resistor, a fifth resistor, a sixth resistor, and a seventh resistor;
  • the first capacitor is grounded, the turn-off trigger end of the control chip is connected to the first end of the fifth resistor, and the second end of the fifth resistor is used to input a turn-off trigger signal;
  • the switch control end is a control end of the switch control circuit;
  • the open duration setting end of the control chip is grounded via the third resistor and connected to the first end of the first resistor via the second resistor, a second end of the first resistor is a detecting end of the switch control circuit;
  • a feedback end of the control chip is grounded through the sixth resistor and the seventh resistor in sequence, the sixth resistor and the seventh resistor
  • the connection node is the feedback end of the switch control circuit.
  • the switch circuit includes a first switch tube and a fourth resistor; a drain of the first switch tube is a control end of the switch circuit, and a gate of the first switch tube is controlled by the switch circuit End, the source of the first switch tube is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded; the connection node of the first switch tube and the fourth resistor Used to output the shutdown trigger signal.
  • the power management circuit further includes an eighth resistor and a ninth resistor; an overvoltage/undervoltage protection terminal of the control chip, a first end of the eighth resistor, and a first end of the ninth resistor Interconnecting, the second end of the ninth resistor is grounded, and the second end of the eighth resistor is connected to the input end of the rectifier circuit.
  • the power management circuit further includes a first diode, a second diode, a first transistor, a second capacitor, a third capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor and a fourteenth resistor; a first end of the tenth resistor is connected to the power detecting end, and a second end of the tenth resistor is connected to the first end of the eleventh resistor a second end of the eleventh resistor, an emitter of the first transistor, a positive pole of the second capacitor, and a power terminal of the control chip, and a cathode of the second capacitor is grounded; a base of the first transistor, a cathode of the first diode, a first end of the fourteenth resistor, and a first end of the thirteenth resistor, the first diode The anode and the second end of the fourteenth resistor are grounded; the collector of the first transistor is connected to the first end of the t
  • the technical scheme of the invention directly supplies the mains voltage to the transformer after being rectified by the rectifying circuit, and controls the working state of the transformer according to the power supply voltage input to the transformer through the power management circuit, so that the output of the constant voltage output winding of the transformer is stabilized.
  • the voltage, the constant current output winding outputs a steady current. Since the technical solution of the present invention can realize the output function of the switching power supply without a high voltage electrolytic capacitor, the technical solution of the present invention has the characteristics of low cost.
  • the constant voltage output winding output constant voltage is controlled by the constant voltage control circuit
  • the constant current output winding output constant current is controlled by the constant current control circuit
  • FIG. 1 is a schematic structural diagram of a circuit of a switching power supply in the prior art
  • FIG. 2 is a schematic diagram of functional modules of an embodiment of a switching power supply according to the present invention.
  • FIG. 3 is a schematic structural diagram of a circuit of another embodiment of a switching power supply according to the present invention.
  • FIG. 4 is a schematic diagram showing the circuit structure of still another embodiment of the switching power supply of the present invention.
  • the invention provides a switching power supply.
  • FIG. 2 is a schematic diagram of a functional module of a switching power supply according to an embodiment of the present invention
  • FIG. 3 is a circuit diagram of another embodiment of a switching power supply according to the present invention. Schematic.
  • the switching power supply includes a rectifier circuit 10, a transformer 20, a constant voltage control circuit 30, a power management circuit 40, and a constant current control circuit 50; an output end of the rectifier circuit 10 and power management
  • the power detecting end of the circuit 40 is connected to the power input end of the transformer 20, the controlled end of the transformer 20 is connected to the control end of the power management circuit 40, and the constant voltage output winding of the transformer 20 is connected to the power management circuit 40 via the constant voltage control circuit 30.
  • the feedback input terminal, the constant current output winding of the transformer 20 is connected to the constant current control circuit 50 via the LED load 60; wherein the power management circuit 40 is configured to control the working state of the transformer 20 according to the magnitude of the power supply voltage input to the transformer 20 to make the constant The voltage output winding outputs a stable voltage, and the constant current output winding outputs a stable current; the constant voltage control circuit 20 is configured to feed back the voltage output of the constant voltage output winding to the power management circuit 40, so that the power management circuit 40 controls the transformer 20
  • the constant voltage output winding outputs a constant voltage; a constant current control circuit 50 for controlling the current flowing through the LED load 60 to Small constant.
  • the switching power supply is connected to the mains, and the rectifier circuit 10 rectifies the mains voltage and outputs the power supply voltage to the transformer 20 without high voltage electrolytic capacitor filtering.
  • the power management circuit 40 detects the magnitude of the power supply voltage input to the transformer 20 and outputs a corresponding control signal to the transformer 20 such that the constant voltage output winding of the transformer 20 outputs a stable voltage, and the constant current output winding of the transformer 20 outputs a stable current.
  • the power management circuit 40 can realize the stable output of the switching power supply by controlling the output peak current of the transformer 20, the fixed off time, or the switching duty ratio.
  • the specific control manner is not limited herein.
  • the constant current control circuit 50 When the constant current control circuit 50 has a constant current enable signal input, the constant current control circuit 50 is activated.
  • the constant current control circuit 50 controls the current flowing through the LED load 60 to have a constant size.
  • the constant voltage control circuit 30 detects the magnitude of the voltage outputted by the constant voltage output winding of the transformer 20 and feeds it back to the feedback input terminal of the power management circuit 40 to cause the PFC flyback control circuit 40 to respond to the operating state of the transformer 20.
  • the adjustment makes the constant voltage output winding L4 output a constant voltage.
  • the constant current control circuit 50 When the constant current control circuit 50 has no constant current enable signal input, the constant current control circuit 50 is turned off, no current flows through the LED load 60, and the LED load 60 is turned off.
  • the constant voltage control circuit 30 detects the magnitude of the voltage outputted by the constant voltage output winding of the transformer 20 and feeds it back to the feedback input terminal of the power management circuit 40 to cause the power management circuit 40 to adjust the operating state of the transformer 20 accordingly.
  • the constant voltage output winding outputs a constant voltage.
  • the technical solution of the present invention directly supplies the mains voltage to the transformer 20 by using the rectifying circuit 10, and controls the working state of the transformer 20 according to the magnitude of the power supply voltage input to the transformer 20 through the power management circuit 40, so that the transformer 20 is The constant voltage output winding outputs a stable voltage, and the constant current output winding outputs a stable current. Since the technical solution of the present invention can realize the output function of the switching power supply without a high voltage electrolytic capacitor, the technical solution of the present invention has the characteristics of low cost.
  • the constant voltage source outputted by the constant voltage output winding L4 is controlled by the constant voltage control circuit 30, and the constant current source outputted by the constant current output winding is controlled by the constant current control circuit 50, so that the switching power supply eliminates the constant current conversion circuit and can At the same time, the constant voltage source and the constant current source which do not interfere with each other are output, which further reduces the cost of the switching power supply.
  • the power management circuit 40 includes a switch circuit (not shown) and a switch control circuit (not shown); the detection end of the switch control circuit is the power detection terminal of the power management circuit 40, and the feedback end of the switch control circuit is The feedback input end of the power management circuit 40, the control end of the switch control circuit is connected to the controlled end of the switch circuit, and the control end of the switch circuit is the control end of the power management circuit 40.
  • the switch control circuit includes a control chip U4, a first capacitor C1, a first resistor R1, a second resistor R2, a third resistor R3, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; Turning off the timing terminal TIME through the first capacitor C1 to the ground GND, the shutdown trigger terminal CS of the control chip U4 is connected to the first end of the fifth resistor R5, and the second terminal of the fifth resistor R5 is used for inputting the shutdown trigger signal;
  • the switch control terminal GATE of the chip U4 is the control end of the switch control circuit;
  • the open duration setting terminal MULT of the control chip U4 is connected to the ground GND via the third resistor R3 and the first end of the first resistor R1 via the second resistor R2, first The second end of the resistor R1 is the detecting end of the switch control circuit; the feedback end INV of the control chip U4 is grounded to the ground GND via the sixth resistor R6 and the seventh resistor R7, and the
  • the switch circuit includes a first switch tube K1 and a fourth resistor R4; the drain of the first switch tube K1 is the control end of the switch circuit, the gate of the first switch tube K1 is the controlled end of the switch circuit, and the source of the first switch tube K1
  • the pole is connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is grounded to GND; the connection node of the first switch K1 and the fourth resistor R4 is used for outputting the turn-off trigger signal.
  • the control chip U4 When the power supply terminal of the power management circuit 40 has a power supply voltage input, the control chip U4 is turned on.
  • the switch control terminal GATE of the control chip U4 outputs a high level signal to the gate of the first switch K1. Since the drain of the first switch K1 has obtained the power supply voltage input, the first switch K1 is turned on, and the power management circuit is turned on.
  • the control terminal of 40 outputs a control signal that controls the opening of the transformer 20.
  • the sampling circuit formed by the first resistor R1, the second resistor R2 and the third resistor R3 inputs the sampled voltage to the turn-on duration setting terminal MULT of the control chip U4 as the turn-off trigger terminal CS of the control chip U4.
  • the reference voltage is such that the on-time of the first switching transistor K1 varies with the variation of the sine wave half-wave.
  • the on-time of the first switching transistor K1 is long; when the sine wave half-wave voltage is high, the conduction time of the first switching transistor K1 is short.
  • the high voltage electrolytic capacitor is eliminated, which reduces the cost of the switching power supply.
  • the switch control terminal GATE of the control chip U4 When the on-time of the first switch K1 is exactly equal to the time when the switch control terminal GATE outputs a high level, the switch control terminal GATE of the control chip U4 outputs a low-level signal to the gate of the first switch K1, the first switch The tube K1 is turned off, and the control terminal of the power management circuit 40 outputs a control signal for controlling the operation of the transformer 20.
  • the first capacitor C1 is charged by the off timing terminal TIME of the control chip U2.
  • the switch control terminal GATE When the first capacitor C1 is just charged, the switch control terminal GATE outputs a high level signal to the gate of the first switch K1 again.
  • the power management circuit 40 repeats the above operation.
  • the power management circuit 40 implements a fixed off time control of the transformer 20.
  • the sixth resistor R6 and the seventh resistor R7 deliver the changed voltage signal to the feedback terminal INV of the control chip U4, so that the control chip U4 adjusts its switching control.
  • the terminal GATE outputs a high level time, thereby adjusting the time at which the control terminal of the power management circuit 40 outputs a control signal for controlling the opening of the transformer 20.
  • the power management circuit 40 further includes an eighth resistor R8 and a ninth resistor R9; the overvoltage/undervoltage protection terminal BO of the control chip U4, the first end of the eighth resistor R8, and the first end of the ninth resistor R9 are mutually
  • the second end of the ninth resistor R9 is connected to the ground GND, and the second end of the eighth resistor R8 is connected to the input end of the rectifier circuit 10.
  • the eighth resistor R8 and the ninth resistor R9 form a voltage dividing sampling circuit, and the voltage sampled by the ninth resistor R9 is supplied to the overvoltage/undervoltage protection terminal BO of the control chip U4. If the voltage sampled by the ninth resistor R9 is greater than the high pressure threshold value set internally by the overvoltage/undervoltage protection terminal BO or less than the low pressure threshold value set internally by the overvoltage/undervoltage protection terminal BO, the control chip U4 stops working.
  • the eighth resistor R9 and the ninth resistor R9 are added to the power management circuit 40, which can effectively prevent the AC voltage input to the switching power supply from being too large or too small.
  • the adverse effects of the circuit improve the reliability of the switching power supply.
  • the power management circuit 40 further includes a first diode D1, a second diode D2, a first transistor Q1, a second capacitor C2, a third capacitor C3, a tenth resistor R10, and an eleventh resistor R11.
  • the first end is connected, the second end of the eleventh resistor R11, the emitter of the first transistor Q1, the anode of the second capacitor C2, and the power terminal VCC of the control chip U4 are interconnected, and the cathode of the second capacitor C2 is grounded.
  • the first diode D1 is a Zener diode
  • the first transistor Q1 is an NPN type triode.
  • the second capacitor C2 When the power detection terminal of the power management circuit 40 has a power supply voltage input, the second capacitor C2 is charged by the tenth resistor R10 and the eleventh resistor R11. When the voltage charged by the second capacitor C2 reaches a certain level, the control chip U4 is controlled. The power supply terminal VCC obtains the startup voltage, and the control chip U4 is activated. Then, the second diode D2 and the third resistor R3 perform rectification and filtering processing on the voltage output from the auxiliary winding L2 of the transformer 30, and are outputted by the first transistor Q1, the first diode D1, and the twelfth resistor R12.
  • the voltage stabilizing circuit formed by the thirteenth resistor R13 and the fourteenth resistor R14 performs voltage regulation processing on the power supply voltage after the rectification and filtering process, and then supplies the voltage to the power supply terminal VCC of the control chip U4, and the power supply terminal VCC of the control chip U4 is stabilized.
  • the power supply voltage, the control chip U4 works stably. In this way, a power supply for supplying the operating voltage to the control chip U4 is omitted, further reducing the cost of the switching power supply.
  • the constant voltage control circuit 30 includes a first voltage regulator U1, a fourth capacitor C4, an optocoupler U3, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17 and an eighteenth resistor R18;
  • the emitter of the optocoupler U3 is grounded to GND, the collector of the optocoupler U3 is the feedback output of the constant voltage control circuit 30, the cathode of the optocoupler U3, the first end of the fourth capacitor C4, and the cathode of the first regulator U1 Interconnecting, the second end of the fourth capacitor C4 is connected to the first end of the sixteenth resistor R16, the second end of the sixteenth resistor R16, the second end of the seventeenth resistor R17, and the first of the eighteenth resistor R18 One end is connected to the adjusting pole of the first regulator U1, and the anode of the first regulator U1 and the second end of the eighteenth resistor R18 are grounded to GND; the first end and
  • the fifteenth resistor R15 supplies the voltage outputted from the constant voltage output winding L4 to the anode of the optocoupler U3; the seventeenth resistor R17 and the eighteenth resistor R18 form a voltage dividing circuit, eighteenth
  • the resistor R18 sends the voltage outputted by the collected constant voltage output winding L4 to the adjusting pole of the first voltage regulating adjusting tube U1, and the voltage outputted by the sampled and regulated constant voltage output winding L4 is sent to the optocoupler U3. cathode.
  • the constant voltage control circuit 30 supplies the changed current to the power management circuit 40 to make the power supply.
  • the management circuit 40 outputs a corresponding control signal to adjust the operating state of the transformer 20 such that the voltage output from the constant voltage output winding L4 is constant.
  • the constant current control circuit 50 includes a reference voltage output unit 150, a constant current control unit 250, a switch unit 350, and a switch control unit 450; the controlled end of the switch unit 350 is connected to the control end of the switch control unit 350, and the switch unit 350 The input end is connected to the LED load 60, the output end of the switch unit 350 is connected to the control end of the constant current control unit 250, and the power end of the constant current control unit 250 is connected to the output end of the reference voltage output unit 150.
  • the switch control unit 450 controls the switching unit 350 to be turned on, the constant current control circuit 50 is turned on, and the current output from the constant current output winding L3 flows into the constant current control unit 250.
  • the reference voltage output unit 150 outputs the reference voltage value constant current control unit 250 to cause the control terminal of the constant current control unit 250 to output a control signal for controlling the magnitude of the current flowing through the LED load 60 described above.
  • the constant current control circuit 50 correspondingly includes m constant current control units 250.
  • the switching power supply can match the number of any channels of the backlight strip, and has wide versatility. 4 shows the circuit structure of the switching power supply when the LED load 60 includes two sets of LED strips and the constant current control circuit 50 includes two constant current control units 250.
  • the twenty-ninth resistor R29, the thirtieth resistor R30 and the n transistors E1, E2 to En as shown in FIGS. 3 and 4
  • the base of the n transistors and the third resistor R30
  • One end and the first end of the twenty-ninth resistor R29 are interconnected, the second end of the thirtieth resistor R30 is grounded to GND, and the second end of the twenty-ninth resistor R29 is used for inputting a reference voltage
  • the collectors of the respective triodes are mutually Connected, the connection node is the control terminal of the constant current control unit;
  • the emitters of each of the three triodes are respectively connected to the ground through a current limiting resistor (F1, F2 to Fn as shown in Figs. 3 and 4). GND; where n is a natural number.
  • the constant current control unit 250 When the constant current control unit 250 is turned on, the reference voltage is input to the first control transistor E1, the second control transistor E2 to the nth control transistor En through the twenty-ninth resistor R29, to control the flow through the first current limiting control resistor F1.
  • the current of the second current limiting control resistor F2 to the nth current limiting control circuit Fn thereby controlling the collector current of the first control transistor E1, the second control transistor E2 to the nth control transistor En, to achieve control flow through the LED load
  • the reference voltage output unit 150 has an input terminal EN for inputting a constant current enable signal for controlling the LED load 60 to be turned on, and the reference voltage output unit 150 includes a second transistor Q2, a third transistor Q3, and a third 19th resistor R19, twentieth resistor R20, twenty-first resistor R21 and twenty-second resistor R22; the first end of the nineteenth resistor R19 is used for inputting a reference voltage, and the second end of the nineteenth resistor R19 is The emitter of the second transistor Q2 is connected, the collector of the second transistor Q2 is connected to the first end of the tens resistor R20, and the second end of the tens resistor R20 is the output of the reference voltage output unit 150.
  • the base of the second transistor Q2 is connected to the first end of the twenty-first resistor R21, the second end of the twenty-first resistor R21 is connected to the collector of the third transistor Q3, and the third transistor The emitter of Q3 is grounded to GND; the base of the third transistor Q3 is connected to the first end of the twenty-second resistor R22, and the second end of the twenty-second resistor R22 is the input terminal of the reference voltage output unit 150.
  • the PNP type triode of the second triode Q2 and the third triode Q3 are NPN type triodes.
  • the third transistor Q3 is turned off, the second transistor Q2 is turned off, and the reference voltage output unit 150 has no reference voltage output. If the constant current enable signal EN is at a high level, the third transistor Q3 is turned on, the second diode Q2 is turned on, and the reference voltage output unit 150 supplies the input reference voltage to the switch control unit 250.
  • the switch unit 350 includes a second switch tube K2, the drain of the second switch tube K2 is an input end of the switch unit 350, the source of the second switch tube K2 is an output end of the switch unit 350, and the gate of the second switch tube K2 The controlled end of the switch unit 350 is extreme.
  • the switch unit 350 includes p switches. 4 shows a circuit structure in which the LED load 60 includes two sets of LED strips, and the switch unit 350 includes two switch tubes.
  • the switch control unit 450 includes a fourth transistor Q4, a fifth transistor Q5, a twenty-third resistor R23, a twenty-fourth resistor R24, a twenty-fifth resistor R25 and a twenty-sixth resistor R26;
  • the first end of the twenty-third resistor R23 is used for inputting a PWM signal, the second end of the twenty-third resistor R23 is connected to the base of the fourth transistor Q4, and the collector of the fourth transistor Q4 is second.
  • the first end of the fourteen resistor R24 and the base of the fifth triode Q5 are interconnected, the emitters of the fourth triode Q4 and the fifth triode Q5 are grounded to GND; the collector of the fifth triode Q5, The first end of the twenty-fifth resistor R25 and the first end of the twenty-sixth resistor R26 are interconnected, and the second end of the twenty-fourth resistor R24 and the second end of the twenty-fifth resistor R25 are connected to the constant voltage output.
  • the winding L4 is connected, and the second end of the twenty-sixth resistor R26 is the control end of the switch control unit 450.
  • the fourth transistor Q4 and the fifth transistor Q5 are both NPN type transistors.
  • the switch control unit 450 When the PWM signal is at a high level, the fourth transistor Q4 is turned on, the fifth transistor Q5 is turned on, and the switch control unit 450 outputs a control signal that controls the opening of the switch unit 350. When the PWM signal is low, the fourth transistor Q4 is turned off, the fifth transistor Q5 is turned off, and the switch control unit 450 outputs a control signal that controls the switching unit 350 to be turned off.
  • the switching power supply further includes a correction circuit 70.
  • the input terminal of the correction circuit 70 is connected to the feedback output terminal of the constant current control circuit 50, and the input terminal of the correction circuit 70 is connected to the input terminal of the constant voltage control circuit 30.
  • the correction circuit 70 sends the abnormal pressure difference signal to the input end of the constant voltage control circuit 30, so that the constant voltage control circuit 30 transmits the abnormal differential pressure signal.
  • the power management circuit 40 is further adjusted to adjust the operating state of the transformer 20 so that the current of the LED lamp is constant, and at the same time, the voltage output from the constant voltage output winding L4 of the transformer 20 is constant.
  • the correction circuit 70 includes a third diode D3, a fifth capacitor C5, a twenty-seventh resistor R27, and a twenty-eighth resistor R28; the first end of the twenty-eighth resistor R28 is an input end of the correction circuit 70.
  • the second end of the twenty-eighth resistor R28, the anode of the fifth resistor R5, and the first end of the twenty-seventh resistor R27 are interconnected, the cathode of the fifth capacitor C5 is grounded to GND, and the second of the twenty-seventh resistor R27 is second.
  • the terminal is connected to the anode of the third diode D3, and the cathode of the third diode D3 is the output terminal of the correction circuit 70.
  • the power management circuit 40 controls the voltage output from the constant voltage output winding L4 of the transformer 20 to decrease, thereby reducing the temperature rise of the constant current control circuit 50.
  • the EMI filter When the switching power supply proposed by the present invention is connected to the mains, the EMI filter performs the filtering process on the commercial power and then supplies the same to the first end of the eighth resistor R8 and the rectifier circuit 10.
  • the eighth resistor R8 and the ninth resistor R9 form a voltage dividing sampling circuit, and the sampled voltage is input to the overvoltage/undervoltage protection terminal BO of the control chip U4, and if the commercial power voltage is too large or too small, it is not in the preset voltage range.
  • the control chip U4 stops working.
  • the preset voltage range is between 65V and 310V. If the mains voltage is within the preset voltage range, the control chip U4 enters a state to be activated.
  • the rectifier circuit 10 rectifies and outputs the mains voltage, and the second capacitor C2 is charged by the tenth resistor R10 and the eleventh resistor R11.
  • the voltage charged by the second capacitor C2 is sufficient to control the chip U4 to be turned on, Control chip U4 starts working.
  • the switch control terminal GATE of the control chip U4 outputs a high level signal to the gate of the first switch K1, and the drain of the first switch K1 has thus received the rectified processed mains voltage, the first switch K1 When turned on, the transformer 20 starts to work.
  • the output voltage source of the auxiliary winding L2 of the transformer 20 is rectified and filtered by the second diode D2 and the third capacitor C3, and then sent to the second end of the thirteenth resistor R13, and then through the first transistor Q1.
  • the voltage regulator circuit composed of the first diode D1, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14 is regulated and sent to the power supply terminal VCC of the control chip U4, and the control chip U4 is stably operated.
  • control chip U4 controls the on-time of the first switch K1 according to the power supply voltage collected by the third resistor R3, thereby controlling the turn-on time of the transformer 20 so that the voltage of the constant-voltage output winding L4 of the transformer 20 is output.
  • the current output from the constant current output winding L3 is stabilized within a certain range.
  • the fifteenth resistor R15 supplies the changed voltage to the anode of the optocoupler U3, and the current flowing between the anode and the cathode of the optocoupler U3 changes.
  • the collector voltage of the coupling U3 changes, the magnitude of the voltage input to the feedback terminal INV of the control chip U4 changes, and the control chip U4 adjusts the duty ratio of the high-level output of the switch control terminal GATE to change the first switching transistor K1.
  • the duty ratio is turned on, which in turn causes the voltage output from the constant voltage output winding L4 to be constant.
  • the conduction duty ratio of the first switching transistor K1 decreases; when the voltage outputted by the constant voltage output winding L4 becomes smaller, the first switching transistor K1 The on-duty ratio increases.
  • the switching power supply is applied to the television set, the constant voltage outputted by the constant voltage output winding L4 is rectified and filtered to supply power to the television set, and the constant current outputted by the constant current output winding L3 is subjected to rectification and filtering processing.
  • LED load 60 (TV backlight) is powered.
  • a DC-DC circuit such as the DC-DC circuit shown in FIG. 3 or FIG. 4 may be further added to further optimize the constant voltage after the rectification and filtering process. There are no restrictions here.
  • the constant current enable signal EN When in standby, the constant current enable signal EN is at a low level, the third transistor Q3 is turned off, the second transistor Q2 is turned off, a current path cannot be formed between the LED load 60 and the switching power supply, and the LED load 60 is off.
  • the constant voltage control circuit 30 samples the voltage source output from the constant voltage output winding L4 and supplies it to the power source management circuit 40 so that the PFC flyback control circuit 40 controls the voltage output from the constant voltage output winding L4 to be constant.
  • the transformer 20 operates in a skip cycle manner, achieving light load efficiency, meeting low standby requirements, eliminating the need for standby auxiliary power, simplifying the circuit, and reducing the cost.
  • the constant current enable signal EN is at a high level
  • the third transistor Q3 is turned on
  • the second transistor Q2 is turned on
  • the reference voltage is input to the reference voltage output unit 150 (as shown in FIG. 3 or FIG. 4).
  • the illustrated 13V reference voltage provides a resonant source for the constant current control unit 250 through the second transistor Q2, and the constant current control unit 250 starts operating.
  • the PWM signal drives the second switching transistor K2 (and the third switching transistor K3) through the switch control circuit 450, and the LED load 60 switches its light-off state according to the PWM signal.
  • the fourth transistor Q4 When the PWM signal is at a high level, the fourth transistor Q4 is turned on, the fifth transistor Q5 is turned on, the second switch K2 (and the third switch) is turned on, and the current output from the constant voltage output winding is passed through the LED.
  • the load 60 and the second switch tube K2 (and/or the third switch tube K3) flow into the first control transistor E1, the second control transistor E2 to the nth control transistor En (and the first adjustment transistor M1, the second adjustment transistor E2 to The nth adjusts the collector of the transistor Mn), and at the same time, the reference voltage output from the reference voltage output unit 150 controls the base of each of the transistors through the twenty-ninth resistor R29, thereby controlling the current flowing through the LED load 60 to be constant.
  • the first current limiting control resistor F1, the second current limiting control resistor F2 to the nth current limiting control circuit Fn (and the first current limiting adjusting resistor N1, the second current limiting adjusting resistor N2 to the nth limit)
  • the current adjustment resistor Nn is a current limiting resistor of the LED load 60.
  • the constant voltage control circuit 30 samples the voltage source output from the constant voltage output winding L4 and supplies it to the power source management circuit 40 so that the PFC flyback control circuit 40 controls the voltage output from the constant voltage output winding L4 to be constant.
  • the switching power supply proposed by the invention realizes the function of simultaneously outputting the constant voltage source and the constant current source, not only satisfies the constant current requirement of the LED load 60, but also satisfies the constant voltage source requirement of the movement, optimizes the system structure, and reduces The cost.
  • the fourth transistor Q4 When the PWM signal is low, the fourth transistor Q4 is turned off, the fifth transistor Q5 is turned off, the second switching transistor K2 (and the third switching transistor K3) is turned off, and the current loop between the LED load 60 and the switching power supply It is cut off and the LED load 60 is off.
  • the constant voltage control circuit 30 samples the voltage source output from the constant voltage output winding L4 and supplies it to the power source management circuit 40 so that the PFC flyback control circuit 40 controls the voltage output from the constant voltage output winding L4 to be constant.
  • the first control transistor E1, the second control transistor E2 to the nth control transistor En (and the first adjustment transistor M1, the second adjustment transistor E2 to the nth adjustment transistor)
  • the collector voltage of Mn becomes large, causing the temperature rise of each of the triodes and the current limiting resistor in the constant current control unit 50 to be high.
  • the correction circuit 70 composed of the resistor R28 and the fifth capacitor C5 transmits the high temperature rise signal to the power management circuit 40 through the constant voltage control circuit 30, so that the power management circuit 40 controls the output of the constant voltage output winding L4 of the transformer 20.
  • the voltage is reduced, which in turn reduces the temperature rise of the constant current control unit 250. In this way, the problem of large difference in output voltage caused by large voltage deviation of the same screen LED lamp in mass production is solved.
  • the present invention also provides a television set comprising the above-mentioned switching power supply, the specific structure of the switching power supply is referred to the above embodiment, and since the television set adopts all the technical solutions of all the above embodiments, it has at least All the beneficial effects brought about by the technical solutions of the foregoing embodiments are not described herein again.

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Abstract

一种开关电源和电视机，其中，开关电源包括整流电路（10）、变压器（20）、恒压控制电路（30）、电源管理电路（40）及恒流控制电路（50）；整流电路的输出端与电源管理电路的电源检测端及变压器的电源输入端连接，变压器的受控端与电源管理电路的控制端连接，变压器的恒压输出绕组经恒压控制电路连接电源管理电路的反馈输入端，变压器的恒流输出绕组经LED负载连接恒流控制电路。该开关电源和电视机具有成本低的特点。

Description

开关电源和电视机
技术领域
本发明涉及电视机技术领域，特别涉及一种开关电源和电视机。
背景技术
传统开关电源的架构如图1所示，该开关电源只有通过高压电解电容对整流后的电压进行滤波处理才能输出恒压源，恒压源需要经过恒流转换才能得到恒流源。其中的高压电解电容成本较高，导致开关电源的成本增高。
发明内容
本发明的主要目的是提供一种开关电源，旨在降低该开关电源的成本。
为实现上述目的，本发明提出的开关电源包括整流电路、变压器、恒压控制电路、电源管理电路及恒流控制电路；所述整流电路的输出端与所述电源管理电路的电源检测端及所述变压器的电源输入端连接，所述变压器的受控端与所述电源管理电路的控制端连接，所述变压器的恒压输出绕组经所述恒压控制电路连接所述电源管理电路的反馈输入端，所述变压器的恒流输出绕组经LED负载连接所述恒流控制电路；其中，所述电源管理电路，用于根据输入至所述变压器的电源电压大小控制所述变压器的工作状态，以使所述恒压输出绕组输出恒定的电压，所述恒流输出绕组输出恒定的电流；所述恒压控制电路，用于将所述恒压输出绕组输出的电压大小反馈至所述电源管理电路，以使所述电源管理电路控制所述变压器的恒压输出绕组输出恒定的电压；所述恒流控制电路，用于对流经所述LED负载的电流进行控制，以使其大小恒定。
优选地，所述电源管理电路包括开关电路及开关控制电路；所述开关控制电路的检测端为所述电源管理电路的电源检测端，所述开关控制电路的反馈端为所述电源管理电路的反馈输入端，所述开关控制电路的控制端与所述开关电路的受控端连接，所述开关电路的控制端为所述电源管理电路的控制端。
优选地，所述开关控制电路包括控制芯片、第一电容、第一电阻、第二电阻、第三电阻、第五电阻、第六电阻及第七电阻；所述控制芯片的关断计时端通过所述第一电容接地，所述控制芯片的关断触发端与所述第五电阻的第一端连接，所述第五电阻的第二端用于输入关断触发信号；所述控制芯片的开关控制端为所述开关控制电路的控制端；所述控制芯片的开启时长设定端经所述第三电阻接地及经所述第二电阻连接所述第一电阻的第一端，所述第一电阻的第二端为所述开关控制电路的检测端；所述控制芯片的反馈端依次经所述第六电阻及所述第七电阻接地，所述第六电阻及所述第七电阻的连接结点为所述开关控制电路的反馈端。
优选地，所述开关电路包括第一开关管及第四电阻；所述第一开关管的漏极为所述开关电路的控制端，所述第一开关管的栅极为所述开关电路的受控端，所述第一开关管的源极与所述第四电阻的第一端连接，所述第四电阻的第二端接地；所述第一开关管与所述第四电阻的连接结点用于输出关断触发信号。
优选地，所述电源管理电路还包括第八电阻及第九电阻；所述控制芯片的过压/欠压保护端、所述第八电阻的第一端及所述第九电阻的第一端互连，所述第九电阻的第二端接地，所述第八电阻的第二端与所述整流电路的输入端连接。
优选地，所述电源管理电路还包括第一二极管、第二二极管、第一三极管、第二电容、第三电容、第十电阻、第十一电阻、第十二电阻、第十三电阻及第十四电阻；所述第十电阻的第一端与所述电源检测端连接，所述第十电阻的第二端与所述第十一电阻的第一端连接，所述第十一电阻的第二端、所述第一三极管的发射极、所述第二电容的正极及所述控制芯片的电源端互连，所述第二电容的负极接地；所述第一三极管的基极、所述第一二极管的阴极、所述第十四电阻的第一端及所述第十三电阻的第一端互连，所述第一二极管的阳极及所述第十四电阻的第二端接地；所述第一三极管的集电极与所述第十二电阻的第一端连接，所述第十二电阻的第二端、所述第十三电阻的第二端、所述第二二极管的阴极及所述第三电容的正极互连，所述第三电容的负极接地，所述第二二极管的阳极与变压器的辅助绕组连接。
优选地，所述恒压控制电路包括第一稳压调整管、第四电容、光耦、第十五电阻、第十六电阻、第十七电阻及第十八电阻；所述光耦的发射极接地，所述光耦的集电极为所述恒压控制电路的反馈输出端，所述光耦的阴极、所述第四电容的第一端及所述第一稳压调整管的阴极互连，所述第四电容的第二端与所述第十六电阻的第一端连接，所述第十六电阻的第二端、所述第十七电阻的第二端、所述第十八电阻的第一端及所述第一稳压调整管的调整极互连，所述第一稳压调整管的阳极及所述第十八电阻的第二端接地；所述第十七电阻的第一端与所述第十五电阻的第一端连接，所述第十五电阻的第二端与所述光耦的阳极连接，所述第十五电阻及所述第十七电阻的连接结点为所述恒压控制电路的输入端。
优选地，所述恒流控制电路包括基准电压输出单元、恒流控制单元、开关单元及开关控制单元；所述开关单元的受控端与所述开关控制单元的控制端连接，所述开关单元的输入端与所述LED负载连接，所述开关单元的输出端与所述恒流控制单元的控制端连接，所述恒流控制单元的电源端与所述基准电压输出单元的输出端连接。
优选地，所述恒流控制单元包括第二十九电阻、第三十电阻及n个三极管，n个所述三极管的基极、第三十电阻的第一端及所述第二十九电阻的第一端互连，所述第三十电阻的第二端接地，所述第二十九电阻的第二端用于输入基准电压；各个三极管的集电极互连，其连接结点为所述恒流控制单元的控制端；n个三极管中的每一三极管的发射极分别通过一限流电阻连接到地；其中，n为自然数。
优选地，所述基准电压输出单元具有用于输入控制所述LED负载亮灭的恒流使能信号的输入端，所述基准电压输出单元包括第二三极管、第三三极管、第十九电阻、第二十电阻、第二十一电阻及第二十二电阻；所述第十九电阻的第一端用于输入基准电压，所述第十九电阻的第二端与所述第二三极管的发射极连接，所述第二三极管的集电极与所述第二十电阻的第一端连接，所述第二十电阻的第二端为所述基准电压输出单元的输出端；所述第二三极管的基极与所述第二十一电阻的第一端连接，所述第二十一电阻的第二端与所述第三三极管的集电极连接，所述第三三极管的发射极接地；所述第三三极管的基极与所述第二十二电阻的第一端连接，所述第二十二电阻的第二端为所述基准电压输出单元输入端。
优选地，所述开关单元包括第二开关管，所述第二开关管的漏极为所述开关单元的输入端，所述第二开关管的源极为所述开关单元的输出端，所述第二开关管的栅极为所述开关单元的受控端。
优选地，所述开关控制单元包括第四三极管、第五三极管、第二十三电阻、第二十四电阻、第二十五电阻及第二十六电阻；所述第二十三电阻的第一端用于输入PWM信号，所述第二十三电阻的第二端与所述第四三极管的基极连接，所述第四三极管的集电极、所述第二十四电阻的第一端及所述第五三极管的基极互连，所述第四三极管及所述第五三极管的发射极接地；所述第五三极管的集电极、所述第二十五电阻的第一端及所述第二十六电阻的第一端互连，所述第二十四电阻的第二端及所述第二十五电阻的第二端与所述恒压输出绕组连接，所述第二十六电阻的第二端为所述开关控制单元的控制端。
优选地，所述开关电源还包括校正电路，所述校正电路的输入端与所述恒流控制电路的反馈输出端连接，所述校正电路的输入端与所述恒压控制单元的输入端连接。
优选地，所述校正电路包括第三二极管、第五电容、第二十七电阻及第二十八电阻；所述第二十八电阻的第一端为所述校正电路的输入端，所述第二十八电阻的第二端、所述第五电阻的正极及所述第二十七电阻的第一端互连，所述第五电容的负极接地，所述第二十七电阻的第二端与所述第三二极管的阳极连接，所述第三二极管的阴极为所述校正电路的输出端。
本发明还提出一种电视机，该电视机包括如上所述的开关电源；其中，所述开关电源包括整流电路、变压器、恒压控制电路、电源管理电路及恒流控制电路；所述整流电路的输出端与所述电源管理电路的电源检测端及所述变压器的电源输入端连接，所述变压器的受控端与所述电源管理电路的控制端连接，所述变压器的恒压输出绕组经所述恒压控制电路连接所述电源管理电路的反馈输入端，所述变压器的恒流输出绕组经LED负载连接所述恒流控制电路；所述电源管理电路，用于根据输入至所述变压器的电源电压大小控制所述变压器的工作状态，以使所述恒压输出绕组输出稳定的电压，所述恒流输出绕组输出稳定的电流；所述恒压控制电路，用于将所述恒压输出绕组输出的电压大小反馈至所述电源管理电路，以使所述电源管理电路控制所述变压器的恒压输出绕组输出恒定的电压；所述恒流控制电路，用于对流经所述LED负载的电流进行控制，以使其大小恒定。
优选地，所述电源管理电路包括开关电路及开关控制电路；所述开关控制电路的检测端为所述电源管理电路的电源检测端，所述开关控制电路的反馈端为所述电源管理电路的反馈输入端，所述开关控制电路的控制端与所述开关电路的受控端连接，所述开关电路的控制端为所述电源管理电路的控制端。
优选地，所述开关控制电路包括控制芯片、第一电容、第一电阻、第二电阻、第三电阻、第五电阻、第六电阻及第七电阻；所述控制芯片的关断计时端通过所述第一电容接地，所述控制芯片的关断触发端与所述第五电阻的第一端连接，所述第五电阻的第二端用于输入关断触发信号；所述控制芯片的开关控制端为所述开关控制电路的控制端；所述控制芯片的开启时长设定端经所述第三电阻接地及经所述第二电阻连接所述第一电阻的第一端，所述第一电阻的第二端为所述开关控制电路的检测端；所述控制芯片的反馈端依次经所述第六电阻及所述第七电阻接地，所述第六电阻及所述第七电阻的连接结点为所述开关控制电路的反馈端。
优选地，所述开关电路包括第一开关管及第四电阻；所述第一开关管的漏极为所述开关电路的控制端，所述第一开关管的栅极为所述开关电路的受控端，所述第一开关管的源极与所述第四电阻的第一端连接，所述第四电阻的第二端接地；所述第一开关管与所述第四电阻的连接结点用于输出关断触发信号。
优选地，所述电源管理电路还包括第八电阻及第九电阻；所述控制芯片的过压/欠压保护端、所述第八电阻的第一端及所述第九电阻的第一端互连，所述第九电阻的第二端接地，所述第八电阻的第二端与所述整流电路的输入端连接。
优选地，所述电源管理电路还包括第一二极管、第二二极管、第一三极管、第二电容、第三电容、第十电阻、第十一电阻、第十二电阻、第十三电阻及第十四电阻；所述第十电阻的第一端与所述电源检测端连接，所述第十电阻的第二端与所述第十一电阻的第一端连接，所述第十一电阻的第二端、所述第一三极管的发射极、所述第二电容的正极及所述控制芯片的电源端互连，所述第二电容的负极接地；所述第一三极管的基极、所述第一二极管的阴极、所述第十四电阻的第一端及所述第十三电阻的第一端互连，所述第一二极管的阳极及所述第十四电阻的第二端接地；所述第一三极管的集电极与所述第十二电阻的第一端连接，所述第十二电阻的第二端、所述第十三电阻的第二端、所述第二二极管的阴极及所述第三电容的正极互连，所述第三电容的负极接地，所述第二二极管的阳极与变压器的辅助绕组连接。
本发明技术方案通过采用整流电路对市电电压进行整流处理后直接输送至变压器，并通过电源管理电路根据输入至变压器的电源电压大小控制变压器的工作状态，以使变压器的恒压输出绕组输出稳定的电压，恒流输出绕组输出稳定的电流。由于本发明技术方案无需高压电解电容即可实现开关电源的输出功能，因此，本发明技术方案具有成本低的特点。此外，所述恒压输出绕组输出恒定电压受到所述恒压控制电路控制，所述恒流输出绕组输出恒定电流受到所述恒流控制电路控制，使得开关电源既省去了恒流转换电路又能同时输出互不干扰的恒压源和恒流源，进一步降低了开关电源的成本。
附图说明
图1为本现有技术中开关电源的电路结构示意图；
图2为本发明开关电源一实施例的功能模块示意图；
图3为本发明开关电源另一实施例的电路结构示意图；
图4为本发明开关电源又一实施例的电路结构示意图。
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明的一部分实施例，而不是全部的实施例。另外，各个实施例之间的技术方案可以相互结合，但是必须是以本领域普通技术人员能够实现为基础，当技术方案的结合出现相互矛盾或无法实现时应当认为这种技术方案的结合不存在，也不在本发明要求的保护范围之内。
本发明提出一种开关电源。
参照图2至4，图2为本发明开关电源一实施例的功能模块示意图；图3为本发明开关电源另一实施例的电路结构示意图；图4为本发明开关电源又一实施例的电路结构示意图。
如图2所示，在本发明实施例中，该开关电源包括整流电路10、变压器20、恒压控制电路30、电源管理电路40及恒流控制电路50；整流电路10的输出端与电源管理电路40的电源检测端及变压器20的电源输入端连接，变压器20的受控端与电源管理电路40的控制端连接，变压器20的恒压输出绕组经恒压控制电路30连接电源管理电路40的反馈输入端，变压器20的恒流输出绕组经LED负载60连接恒流控制电路50；其中，电源管理电路40，用于根据输入至变压器20的电源电压大小控制变压器20的工作状态，以使恒压输出绕组输出稳定的电压，恒流输出绕组输出稳定的电流；恒压控制电路20，用于将恒压输出绕组输出的电压大小反馈至电源管理电路40，以使电源管理电路40控制变压器20的恒压输出绕组输出恒定的电压；恒流控制电路50，用于对流经LED负载60的电流进行控制，以使其大小恒定。
将开关电源接入市电，整流电路10将市电电压进行整流处理并输出电源电压至变压器20，无需高压电解电容滤波。电源管理电路40检测到输入至变压器20的电源电压大小并向变压器20输出相应的控制信号，使得变压器20的恒压输出绕组输出稳定的电压，变压器20的恒流输出绕组输出稳定的电流。
需要说明的是，电源管理电路40可以通过控制变压器20的输出峰值电流、固定关断时间或者开关占空比等方式来实现开关电源的稳定输出，其具体控制方式此处不做限制。
当恒流控制电路50有恒流使能信号输入时，恒流控制电路50启动。恒流控制电路50对流经LED负载60的电流进行控制，以使其大小恒定。与此同时，恒压控制电路30检测到变压器20的恒压输出绕组输出的电压大小并反馈至电源管理电路40的反馈输入端，以使PFC反激控制电路40对变压器20的工作状态作出相应的调整，使恒压输出绕组L4输出恒定的电压。
当恒流控制电路50无恒流使能信号输入时，恒流控制电路50关断，LED负载60无电流流过，LED负载60灭。与此同时，恒压控制电路30检测到变压器20的恒压输出绕组输出的电压大小并反馈至电源管理电路40的反馈输入端，以使电源管理电路40对变压器20的工作状态作出相应的调整，恒压输出绕组输出恒定的电压。
本发明技术方案通过采用整流电路10对市电电压进行整流处理后直接输送至变压器20，并通过电源管理电路40根据输入至变压器20的电源电压大小控制变压器20的工作状态，以使变压器20的恒压输出绕组输出稳定的电压，恒流输出绕组输出稳定的电流。由于本发明技术方案无需高压电解电容即可实现开关电源的输出功能，因此，本发明技术方案具有成本低的特点。此外，恒压输出绕组L4输出的恒压源受到恒压控制电路30控制，恒流输出绕组输出的恒流源受到恒流控制电路50控制，使得开关电源既省去了恒流转换电路又能同时输出互不干扰的恒压源和恒流源，进一步降低了开关电源的成本。
优选地，电源管理电路40包括开关电路（图未示出）及开关控制电路（图未示出）；开关控制电路的检测端为电源管理电路40的电源检测端，开关控制电路的反馈端为电源管理电路40的反馈输入端，开关控制电路的控制端与开关电路的受控端连接，开关电路的控制端为电源管理电路40的控制端。
具体地，开关控制电路包括控制芯片U4、第一电容C1、第一电阻R1、第二电阻R2、第三电阻R3、第五电阻R5、第六电阻R6及第七电阻R7；控制芯片U的关断计时端TIME通过第一电容C1接地GND，控制芯片U4的关断触发端CS与第五电阻R5的第一端连接，第五电阻R5的第二端用于输入关断触发信号；控制芯片U4的开关控制端GATE为开关控制电路的控制端；控制芯片U4的开启时长设定端MULT经第三电阻R3接地GND及经第二电阻R2连接第一电阻R1的第一端，第一电阻R1的第二端为开关控制电路的检测端；控制芯片U4的反馈端INV依次经第六电阻R6及第七电阻R7接地GND，第六电阻R6及第七电阻R7的连接结点为开关控制电路的反馈端。开关电路包括第一开关管K1及第四电阻R4；第一开关管K1的漏极为开关电路的控制端，第一开关管K1的栅极为开关电路的受控端，第一开关管K1的源极与第四电阻R4的第一端连接，第四电阻R4的第二端接地GND；第一开关管K1与第四电阻R4的连接结点用于输出关断触发信号。
当电源管理电路40的电源检测端有电源电压输入时，控制芯片U4开启。控制芯片U4的开关控制端GATE输出高电平信号至第一开关管K1的栅极，由于此前第一开关管K1的漏极已获得电源电压输入，第一开关管K1导通，电源管理电路40的控制端输出控制变压器20开启的控制信号。与此同时，第一电阻R1、第二电阻R2及第三电阻R3构成的取样电路将取样后的电压输入至控制芯片U4的开启时长设定端MULT以作为控制芯片U4的关断触发端CS的参考电压，使得第一开关管K1的导通时间随正弦波半波的变化而变化。当正弦波半波的电压低时，第一开关管K1的导通时间长；当正弦波半波电压高时，第一开关管K1的导通时间短。省去了高压电解电容，降低了开关电源的成本。
当第一开关管K1的导通时间恰好等于开关控制端GATE输出高电平的时间时，控制芯片U4的开关控制端GATE输出低电平信号至第一开关管K1的栅极，第一开关管K1截止，电源管理电路40的控制端输出控制变压器20停止工作的控制信号。与此同时，第一电容C1通过控制芯片U2的关断计时端TIME充电，在第一电容C1恰好充电完成时，开关控制端GATE再次输出高电平信号至第一开关管K1的栅极，电源管理电路40重复上述运行过程。
可以理解的是，由于控制芯片U4的关断计时端TIME的电压大小固定，第一电容C1的大小也固定，因此，第一电容C1的充电时间固定，开关控制端GATE输出低电平的时间固定，第一开关管K1截止的时间固定，电源管理电路40的控制端输出控制变压器20停止工作的控制信号的时间固定。如此，电源管理电路40实现了对变压器20的固定关断时间控制。
此后，若电源管理电路40的反馈输入端的电压大小发生变化，第六电阻R6及第七电阻R7将该变化的电压信号输送至控制芯片U4的反馈端INV，以使控制芯片U4调整其开关控制端GATE输出高电平的时间，进而调整电源管理电路40的控制端输出控制变压器20开启的控制信号的时间。
优选地，电源管理电路40还包括第八电阻R8及第九电阻R9；控制芯片U4的过压/欠压保护端BO、第八电阻R8的第一端及第九电阻R9的第一端互连，第九电阻R9的第二端接地GND，第八电阻R8的第二端与整流电路10的输入端连接。
当电源管理电路40开启时，第八电阻R8与第九电阻R9构成分压取样电路，第九电阻R9取样得的电压输送至控制芯片U4的过压/欠压保护端BO。若第九电阻R9取样得的电压大于过压/欠压保护端BO内部设定的高压阀值或者小于过压/欠压保护端BO内部设定的低压阀值，则控制芯片U4停止工作。
由于输入至开关电源的交流电压的幅度波动范围比较大，因此，在电源管理电路40中增设第八电阻R9和第九电阻R9，可以有效避免输入至开关电源的交流电压过大或者过小给电路带来的不利影响，提高了开关电源的可靠性。
优选地，电源管理电路40还包括第一二极管D1、第二二极管D2、第一三极管Q1、第二电容C2、第三电容C3、第十电阻R10、第十一电阻R11、第十二电阻R12、第十三电阻R13及第十四电阻R14；第十电阻R10的第一端与整流电路10的输出端连接，第十电阻R10的第二端与第十一电阻R11的第一端连接，第十一电阻R11的第二端、第一三极管Q1的发射极、第二电容C2的正极及控制芯片U4的电源端VCC互连，第二电容C2的负极接地GND；第一三极管Q1的基极、第一二极管D1的阴极、第十四电阻R14的第一端及第十三电阻R13的第一端互连，第一二极管D1的阳极及第十四电阻R14的第二端接地GND；第一三极管Q1的集电极与第十二电阻R12的第一端连接，第十二电阻R12的第二端、第十三电阻R13的第二端、第二二极管D2的阴极及第三电容C3的正极互连，第三电容C3的负极接地GND，第二二极管D2的阳极与变压器20的辅助绕组L2连接。本实施例中，第一二极管D1为稳压二极管，第一三极管Q1为NPN型三极管。
当电源管理电路40的电源检测端有电源电压输入时，第二电容C2通过第十电阻R10及第十一电阻R11充电，当第二电容C2所充得的电压达到一定程度时，控制芯片U4的电源端VCC获得启动电压，控制芯片U4启动。而后，第二二极管D2及第三电阻R3将变压器30的辅助绕组L2输出的电压进行整流滤波处理并输出，由第一三极管Q1、第一二极管D1、第十二电阻R12、第十三电阻R13及第十四电阻R14构成的稳压电路将经整流滤波处理后的电源电压进行稳压处理后输送至控制芯片U4的电源端VCC，控制芯片U4的电源端VCC获得稳定的供电电压，控制芯片U4稳定工作。如此，省去了一个用于为控制芯片U4提供工作电压的电源，进一步降低了开关电源的成本。
优选地，恒压控制电路30包括第一稳压调整管U1、第四电容C4、光耦U3、第十五电阻R15、第十六电阻R16、第十七电阻R17及第十八电阻R18；光耦U3的发射极接地GND，光耦U3的集电极为恒压控制电路30的反馈输出端，光耦U3的阴极、第四电容C4的第一端及第一稳压调整管U1的阴极互连，第四电容C4的第二端与第十六电阻R16的第一端连接，第十六电阻R16的第二端、第十七电阻R17的第二端、第十八电阻R18的第一端及第一稳压调整管U1的调整极互连，第一稳压调整管U1的阳极及第十八电阻R18的第二端接地GND；第十七电阻R17的第一端与第十五电阻R15的第一端连接，第十五电阻R15的第二端与光耦U3的阳极连接，第十五电阻R15及第十七电阻R17的连接结点为恒压控制电路30的输入端。
当恒压控制电路30开启时，第十五电阻R15将恒压输出绕组L4输出的电压输送至光耦U3的阳极；第十七电阻R17与第十八电阻R18构成分压电路，第十八电阻R18将采集得的恒压输出绕组L4输出的电压输送至第一稳压调整管U1的调整极，经采样并稳压处理后的恒压输出绕组L4输出的电压被输送至光耦U3的阴极。当恒压输出绕组L4输出的电压发生变化时，流经光耦U3的阳极与阴极之间的电流发生变化，恒压控制电路30将该变化的电流输送至上述电源管理电路40，以使电源管理电路40输出相应的控制信号以调整变压器20的工作状态，使其恒压输出绕组L4输出的电压大小恒定。
优选地，恒流控制电路50包括基准电压输出单元150、恒流控制单元250、开关单元350及开关控制单元450；开关单元350的受控端与开关控制单元350的控制端连接，开关单元350的输入端与LED负载60连接，开关单元350的输出端与恒流控制单元250的控制端连接，恒流控制单元250的电源端与基准电压输出单元150的输出端连接。
当开关控制单元450控制开关单元350导通时，恒流控制电路50开启，上述恒流输出绕组L3输出的电流流入恒流控制单元250。与此同时，基准电压输出单元150输出基准电压值恒流控制单元250，以使恒流控制单元250的控制端输出控制流经上述LED负载60电流大小的控制信号。
需要说明的是，当LED负载60包括m组LED灯条时，恒流控制电路50对应包括m个恒流控制单元250，如此，可以使开关电源匹配背光灯条任意通道数量，通用性广。其中，图4展示了当LED负载60包括两组LED灯条和恒流控制电路50包括两个恒流控制单元250时，开关电源的电路结构。
优选地，第二十九电阻R29、第三十电阻R30及n个三极管(如图3及图4所示的E1、E2至En)，n个三极管的基极、第三十电阻R30的第一端及第二十九电阻R29的第一端互连，第三十电阻R30的第二端接地GND，第二十九电阻R29的第二端用于输入基准电压；各个三极管的集电极互连，其连接结点为恒流控制单元的控制端；n个三极管中的每一三极管的发射极分别通过一限流电阻(如图3及图4所示F1、F2至Fn)连接到地GND；其中，n为自然数。
本实施例中，取n=3，具体结构参照图3。当恒流控制单元250开启时，基准电压通过第二十九电阻R29输入至第一控制三极管E1、第二控制三极管E2至第n控制三极管En，以控制流经第一限流控制电阻F1、第二限流控制电阻F2至第n限流控制电路Fn的电流大小，进而控制第一控制三极管E1、第二控制三极管E2至第n控制三极管En的集电极电流大小，达到控制流经LED负载60的电流大小的目的。
优选地，基准电压输出单元150具有用于输入控制LED负载60亮灭的恒流使能信号的输入端EN，基准电压输出单元150包括第二三极管Q2、第三三极管Q3、第十九电阻R19、第二十电阻R20、第二十一电阻R21及第二十二电阻R22；第十九电阻R19的第一端用于输入基准电压，第十九电阻R19的第二端与第二三极管Q2的发射极连接，第二三极管Q2的集电极与第二十电阻R20的第一端连接，第二十电阻R20的第二端为基准电压输出单元150的输出端；第二三极管Q2的基极与第二十一电阻R21的第一端连接，第二十一电阻R21的第二端与第三三极管Q3的集电极连接，第三三极管Q3的发射极接地GND；第三三极管Q3的基极与第二十二电阻R22的第一端连接，第二十二电阻R22的第二端为基准电压输出单元150的输入端。需要说明的是，本实施例中，第二三极管Q2的PNP型三极管，第三三极管Q3为NPN型三极管。
若恒流使能信号EN为低电平，则第三三极管Q3截止，第二三极管Q2截止，基准电压输出单元150无基准电压输出。若恒流使能信号EN为高电平，则第三三极管Q3导通，第二二极管Q2导通，基准电压输出单元150将其输入的基准电压输送至上述开关控制单元250。
优选地，开关单元350包括第二开关管K2，第二开关管K2的漏极为开关单元350的输入端，第二开关管K2的源极为开关单元350的输出端，第二开关管K2的栅极为开关单元350的受控端。需要说明的是，当LED负载60包括p组LED灯条时，开关单元350对应的包括p个开关管。其中，图4展示了当LED负载60包括两组LED灯条，开关单元350包括两个开关管的电路结构。
优选地，开关控制单元450包括第四三极管Q4、第五三极管Q5、第二十三电阻R23、第二十四电阻R24、第二十五电阻R25及第二十六电阻R26；第二十三电阻R23的第一端用于输入PWM信号，第二十三电阻R23的第二端与第四三极管Q4的基极连接，第四三极管Q4的集电极、第二十四电阻R24的第一端及第五三极管Q5的基极互连，第四三极管Q4及第五三极管Q5的发射极接地GND；第五三极管Q5的集电极、第二十五电阻R25的第一端及第二十六电阻R26的第一端互连，第二十四电阻R24的第二端及第二十五电阻R25的第二端连接与恒压输出绕组L4连接，第二十六电阻R26的第二端为开关控制单元450的控制端。需要说明的是，本实施例中，第四三极管Q4及第五三极管Q5均为NPN型三极管。
当PWM信号为高电平时，第四三极管Q4导通，第五三极管Q5导通，开关控制单元450输出控制开关单元350开启的控制信号。当PWM信号为低电平时，第四三极管Q4截止，第五三极管Q5截止，开关控制单元450输出控制开关单元350关闭的控制信号。
进一步地，开关电源还包括校正电路70，校正电路70的输入端与恒流控制电路50的反馈输出端连接，校正电路70的输入端与恒压控制电路30的输入端连接。
当LED负载60中LED灯的压差较大时，校正电路70将该异常的压差信号输送至恒压控制电路30的输入端，以使恒压控制电路30将该异常的压差信号传递至上述电源管理电路40，进而使电源管理电路40对变压器20的工作状态作出相应的调整，以使LED灯的电流恒定，与此同时，变压器20的恒压输出绕组L4输出的电压恒定。
优选地，校正电路70包括第三二极管D3、第五电容C5、第二十七电阻R27及第二十八电阻R28；第二十八电阻R28的第一端为校正电路70的输入端，第二十八电阻R28的第二端、第五电阻R5的正极及第二十七电阻R27的第一端互连，第五电容C5的负极接地GND，第二十七电阻R27的第二端与第三二极管D3的阳极连接，第三二极管D3的阴极为校正电路70的输出端。
当流经LED负载60的电压发生变化时，输入至第二十八电阻R28的电压发生变化，第三二极管D3的阴极输出的电压发生变化，校正电路70输出变化了的电压信号。进而使电源管理电路40控制变压器20的恒压输出绕组L4输出的电压降低，达到降低恒流控制电路50温升的目的。解决了在量产中相同屏体LED灯因电压偏差较大导致输出电压差异大问题。
以下，结合图1至图4，说明本发明开关电源的工作原理：
当本发明提出的开关电源接入市电时，EMI滤波器将市电进行滤波处理后分别输送至第八电阻R8的第一端及整流电路10。第八电阻R8及第九电阻R9构成分压取样电路，取样后的电压输入至控制芯片U4的过压/欠压保护端BO，若市电电压因过大或者过小而不在预设电压范围内，则控制芯片U4停止工作。优选地，预设电压范围在65V到310V之间。若市电电压在预设电压范围内，则控制芯片U4进入待启动状态。如此，实现了开关电源的过压/欠压保护功能。与此同时，整流电路10将市电电压进行整流处理后输出，第二电容C2通过第十电阻R10及第十一电阻R11充电，当第二电容C2充得的电压足够控制芯片U4开启时，控制芯片U4开始工作。
控制芯片U4的开关控制端GATE输出高电平信号至第一开关管K1的栅极，第一开关管K1的漏极因此前已经接收到经整流处理后的市电电压，第一开关管K1开启，变压器20开始工作。
而后，一方面，变压器20的辅助绕组L2输出电压源经第二二极管D2及第三电容C3整流滤波处理后输送至第十三电阻R13的第二端，再经由第一三极管Q1、第一二极管D1、第十二电阻R12、第十三电阻R13及第十四电阻R14构成的稳压电路稳压处理后输送至控制芯片U4的电源端VCC，控制芯片U4稳定工作。
另一方面，控制芯片U4根据第三电阻R3采集得的电源电压控制第一开关管K1的导通时间，进而控制变压器20的开启时间，以使变压器20的恒压输出绕组L4输出的电压大小和恒流输出绕组L3输出的电流大小稳定在一定范围内。
此后，若恒压输出绕组L4输出的电压大小发生变化，则第十五电阻R15将变化的电压输送至光耦U3的阳极，流经光耦U3的阳极与阴极之间的电流发生变化，光耦U3的集电极电压发生变化，输入至控制芯片U4的反馈端INV的电压大小发生变化，控制芯片U4调整其开关控制端GATE输出高电平的占空比，以改变第一开关管K1的导通占空比，进而使得恒压输出绕组L4输出的电压大小恒定。需要说明的是，当恒压输出绕组L4输出的电压变大时，第一开关管K1的导通占空比减小；当恒压输出绕组L4输出的电压变小时，第一开关管K1的导通占空比增大。优选地，若将开关电源应用于电视机中，则恒压输出绕组L4输出的恒定电压经整流滤波处理后给电视机机芯供电，恒流输出绕组L3输出的恒定电流经整流滤波处理后给LED负载60（电视机背光）供电。当然，为了减小开关电源输出的恒压源的纹波，还可增设DC-DC电路（如图3或者图4所示的DC-DC电路）对经整流滤波处理后的恒定电压进一步优化处理，此处不做限制。
当待机时，上述恒流使能信号EN为低电平，第三三极管Q3截止，第二三极管Q2截止，LED负载60与开关电源之间无法形成电流通路，LED负载60灭。与此同时，恒压控制电路30将恒压输出绕组L4输出的电压源进行取样后输送至电源管理电路40，以使PFC反激控制电路40控制恒压输出绕组L4输出的电压恒定。此时，变压器20以跳周期方式工作，实现轻载高效，满足低待机需求，无需待机辅助电源，简化了电路，降低了成本。
在开机后，恒流使能信号EN为高电平，第三三极管Q3导通，第二三极管Q2导通，基准电压输出单元150输入的基准电压（如图3或者图4所示的13V基准电压）通过第二三极管Q2为恒流控制单元250提供谐振源，恒流控制单元250开始工作。与此同时，PWM信号通过开关控制电路450驱动第二开关管K2（及第三开关管K3），LED负载60根据PWM信号切换其亮灭状态。
当PWM信号为高电平时，第四三极管Q4导通，第五三极管Q5导通，第二开关管K2（及第三开关管）导通，恒压输出绕组输出的电流经LED负载60及第二开关管K2（和/或第三开关管K3）流入第一控制三极管E1、第二控制三极管E2至第n控制三极管En（及第一调整三极管M1、第二调整三极管E2至第n调整三极管Mn）的集电极，与此同时，基准电压输出单元150输出的基准电压通过第二十九电阻R29控制上述各个三极管的基极，进而控制流经LED负载60的电流恒定。值得一提的是，第一限流控制电阻F1、第二限流控制电阻F2至第n限流控制电路Fn(及第一限流调整电阻N1、第二限流调整电阻N2至第n限流调整电阻Nn)均为LED负载60的限流电阻。与此同时，恒压控制电路30将恒压输出绕组L4输出的电压源进行取样后输送至电源管理电路40，以使PFC反激控制电路40控制恒压输出绕组L4输出的电压恒定。至此，本发明提出的开关电源实现了同时输出恒压源和恒流源的功能，既满足了LED负载60的恒流需求，又满足了机芯的恒压源需求，优化了系统结构，降低了成本。
当PWM信号为低电平时，第四三极管Q4截止，第五三极管Q5截止，第二开关管K2（及第三开关管K3）截止，LED负载60与开关电源之间的电流回路被切断，LED负载60灭。与此同时，恒压控制电路30将恒压输出绕组L4输出的电压源进行取样后输送至电源管理电路40，以使PFC反激控制电路40控制恒压输出绕组L4输出的电压恒定。
若加载在LED灯两端的电压差偏大，则作用在第一控制三极管E1、第二控制三极管E2至第n控制三极管En（及第一调整三极管M1、第二调整三极管E2至第n调整三极管Mn）的集电极电压变大，引起恒流控制单元50中各个三极管和限流电阻的温升偏高，此时，由第三二极管D3、第二十七电阻R27、第二十八电阻R28及第五电容C5构成的校正电路70将该偏高的温升信号通过恒压控制电路30传递到电源管理电路40，以使电源管理电路40控制变压器20的恒压输出绕组L4输出的电压减小，进而降低恒流控制单元250的温升。如此，解决了在量产中相同屏体LED灯的电压偏差较大造成的输出电压差异大的问题。
本发明还提出一种电视机，该电视机包括如上所述的开关电源，该开关电源的具体结构参照上述实施例，由于所述电视机采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
以上所述仅为本发明的优选实施例，并非因此限制本发明的专利范围，凡是在本发明的发明构思下，利用本发明说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本发明的专利保护范围内。

Claims (20)

  1. 一种开关电源，其特征在于，包括整流电路、变压器、恒压控制电路、电源管理电路及恒流控制电路；所述整流电路的输出端与所述电源管理电路的电源检测端及所述变压器的电源输入端连接，所述变压器的受控端与所述电源管理电路的控制端连接，所述变压器的恒压输出绕组经所述恒压控制电路连接所述电源管理电路的反馈输入端，所述变压器的恒流输出绕组经LED负载连接所述恒流控制电路；其中，
    所述电源管理电路，用于根据输入至所述变压器的电源电压大小控制所述变压器的工作状态，以使所述恒压输出绕组输出稳定的电压，所述恒流输出绕组输出稳定的电流；
    所述恒压控制电路，用于将所述恒压输出绕组输出的电压大小反馈至所述电源管理电路，以使所述电源管理电路控制所述变压器的恒压输出绕组输出恒定的电压；
    所述恒流控制电路，用于对流经所述LED负载的电流进行控制，以使其大小恒定。
  2. 如权利要求1所述的开关电源，其特征在于，所述电源管理电路包括开关电路及开关控制电路；所述开关控制电路的检测端为所述电源管理电路的电源检测端，所述开关控制电路的反馈端为所述电源管理电路的反馈输入端，所述开关控制电路的控制端与所述开关电路的受控端连接，所述开关电路的控制端为所述电源管理电路的控制端。
  3. 如权利要求2所述的开关电源，其特征在于，所述开关控制电路包括控制芯片、第一电容、第一电阻、第二电阻、第三电阻、第五电阻、第六电阻及第七电阻；所述控制芯片的关断计时端通过所述第一电容接地，所述控制芯片的关断触发端与所述第五电阻的第一端连接，所述第五电阻的第二端用于输入关断触发信号；所述控制芯片的开关控制端为所述开关控制电路的控制端；所述控制芯片的开启时长设定端经所述第三电阻接地及经所述第二电阻连接所述第一电阻的第一端，所述第一电阻的第二端为所述开关控制电路的检测端；所述控制芯片的反馈端依次经所述第六电阻及所述第七电阻接地，所述第六电阻及所述第七电阻的连接结点为所述开关控制电路的反馈端。
  4. 如权利要求2所述的开关电源，其特征在于，所述开关电路包括第一开关管及第四电阻；所述第一开关管的漏极为所述开关电路的控制端，所述第一开关管的栅极为所述开关电路的受控端，所述第一开关管的源极与所述第四电阻的第一端连接，所述第四电阻的第二端接地；所述第一开关管与所述第四电阻的连接结点用于输出关断触发信号。
  5. 如权利要求2所述的开关电源，其特征在于，所述电源管理电路还包括第八电阻及第九电阻；所述控制芯片的过压/欠压保护端、所述第八电阻的第一端及所述第九电阻的第一端互连，所述第九电阻的第二端接地，所述第八电阻的第二端与所述整流电路的输入端连接。
  6. 如权利要求2所述的开关电源，其特征在于，所述电源管理电路还包括第一二极管、第二二极管、第一三极管、第二电容、第三电容、第十电阻、第十一电阻、第十二电阻、第十三电阻及第十四电阻；所述第十电阻的第一端与所述电源检测端连接，所述第十电阻的第二端与所述第十一电阻的第一端连接，所述第十一电阻的第二端、所述第一三极管的发射极、所述第二电容的正极及所述控制芯片的电源端互连，所述第二电容的负极接地；所述第一三极管的基极、所述第一二极管的阴极、所述第十四电阻的第一端及所述第十三电阻的第一端互连，所述第一二极管的阳极及所述第十四电阻的第二端接地；所述第一三极管的集电极与所述第十二电阻的第一端连接，所述第十二电阻的第二端、所述第十三电阻的第二端、所述第二二极管的阴极及所述第三电容的正极互连，所述第三电容的负极接地，所述第二二极管的阳极与变压器的辅助绕组连接。
  7. 如权利要求1所述的开关电源，其特征在于，所述恒压控制电路包括第一稳压调整管、第四电容、光耦、第十五电阻、第十六电阻、第十七电阻及第十八电阻；所述光耦的发射极接地，所述光耦的集电极为所述恒压控制电路的反馈输出端，所述光耦的阴极、所述第四电容的第一端及所述第一稳压调整管的阴极互连，所述第四电容的第二端与所述第十六电阻的第一端连接，所述第十六电阻的第二端、所述第十七电阻的第二端、所述第十八电阻的第一端及所述第一稳压调整管的调整极互连，所述第一稳压调整管的阳极及所述第十八电阻的第二端接地；所述第十七电阻的第一端与所述第十五电阻的第一端连接，所述第十五电阻的第二端与所述光耦的阳极连接，所述第十五电阻及所述第十七电阻的连接结点为所述恒压控制电路的输入端。
  8. 如权利要求1所述的开关电源，其特征在于，所述恒流控制电路包括基准电压输出单元、恒流控制单元、开关单元及开关控制单元；所述开关单元的受控端与所述开关控制单元的控制端连接，所述开关单元的输入端与所述LED负载连接，所述开关单元的输出端与所述恒流控制单元的控制端连接，所述恒流控制单元的电源端与所述基准电压输出单元的输出端连接。
  9. 如权利要求8所述的开关电源，其特征在于，所述恒流控制单元包括第二十九电阻、第三十电阻及n个三极管，n个所述三极管的基极、第三十电阻的第一端及所述第二十九电阻的第一端互连，所述第三十电阻的第二端接地，所述第二十九电阻的第二端用于输入基准电压；各个三极管的集电极互连，其连接结点为所述恒流控制单元的控制端；n个三极管中的每一三极管的发射极分别通过一限流电阻连接到地；其中，n为自然数。
  10. 如权利要求8所述的开关电源，其特征在于，所述基准电压输出单元具有用于输入控制所述LED负载亮灭的恒流使能信号的输入端，所述基准电压输出单元包括第二三极管、第三三极管、第十九电阻、第二十电阻、第二十一电阻及第二十二电阻；所述第十九电阻的第一端用于输入基准电压，所述第十九电阻的第二端与所述第二三极管的发射极连接，所述第二三极管的集电极与所述第二十电阻的第一端连接，所述第二十电阻的第二端为所述基准电压输出单元的输出端；所述第二三极管的基极与所述第二十一电阻的第一端连接，所述第二十一电阻的第二端与所述第三三极管的集电极连接，所述第三三极管的发射极接地；所述第三三极管的基极与所述第二十二电阻的第一端连接，所述第二十二电阻的第二端为所述基准电压输出单元输入端。
  11. 如权利要求8所述的开关电源，其特征在于，所述开关单元包括第二开关管，所述第二开关管的漏极为所述开关单元的输入端，所述第二开关管的源极为所述开关单元的输出端，所述第二开关管的栅极为所述开关单元的受控端。
  12. 如权利要求8所述的开关电源，其特征在于，所述开关控制单元包括第四三极管、第五三极管、第二十三电阻、第二十四电阻、第二十五电阻及第二十六电阻；所述第二十三电阻的第一端用于输入PWM信号，所述第二十三电阻的第二端与所述第四三极管的基极连接，所述第四三极管的集电极、所述第二十四电阻的第一端及所述第五三极管的基极互连，所述第四三极管及所述第五三极管的发射极接地；所述第五三极管的集电极、所述第二十五电阻的第一端及所述第二十六电阻的第一端互连，所述第二十四电阻的第二端及所述第二十五电阻的第二端与所述恒压输出绕组连接，所述第二十六电阻的第二端为所述开关控制单元的控制端。
  13. 如权利要求1所述的开关电源，其特征在于，所述开关电源还包括校正电路，所述校正电路的输入端与所述恒流控制电路的反馈输出端连接，所述校正电路的输入端与所述恒压控制单元的输入端连接。
  14. 如权利要求13所述的开关电源，其特征在于，所述校正电路包括第三二极管、第五电容、第二十七电阻及第二十八电阻；所述第二十八电阻的第一端为所述校正电路的输入端，所述第二十八电阻的第二端、所述第五电阻的正极及所述第二十七电阻的第一端互连，所述第五电容的负极接地，所述第二十七电阻的第二端与所述第三二极管的阳极连接，所述第三二极管的阴极为所述校正电路的输出端。
  15. 一种电视机，其特征在于，所述电视机包括如权利要求1所述的开关电源。
  16. 如权利要求15所述的电视机，其特征在于，所述电源管理电路包括开关电路及开关控制电路；所述开关控制电路的检测端为所述电源管理电路的电源检测端，所述开关控制电路的反馈端为所述电源管理电路的反馈输入端，所述开关控制电路的控制端与所述开关电路的受控端连接，所述开关电路的控制端为所述电源管理电路的控制端。
  17. 如权利要求16所述的电视机，其特征在于，所述开关控制电路包括控制芯片、第一电容、第一电阻、第二电阻、第三电阻、第五电阻、第六电阻及第七电阻；所述控制芯片的关断计时端通过所述第一电容接地，所述控制芯片的关断触发端与所述第五电阻的第一端连接，所述第五电阻的第二端用于输入关断触发信号；所述控制芯片的开关控制端为所述开关控制电路的控制端；所述控制芯片的开启时长设定端经所述第三电阻接地及经所述第二电阻连接所述第一电阻的第一端，所述第一电阻的第二端为所述开关控制电路的检测端；所述控制芯片的反馈端依次经所述第六电阻及所述第七电阻接地，所述第六电阻及所述第七电阻的连接结点为所述开关控制电路的反馈端。
  18. 如权利要求16所述的电视机，其特征在于，所述开关电路包括第一开关管及第四电阻；所述第一开关管的漏极为所述开关电路的控制端，所述第一开关管的栅极为所述开关电路的受控端，所述第一开关管的源极与所述第四电阻的第一端连接，所述第四电阻的第二端接地；所述第一开关管与所述第四电阻的连接结点用于输出关断触发信号。
  19. 如权利要求16所述的电视机，其特征在于，所述电源管理电路还包括第八电阻及第九电阻；所述控制芯片的过压/欠压保护端、所述第八电阻的第一端及所述第九电阻的第一端互连，所述第九电阻的第二端接地，所述第八电阻的第二端与所述整流电路的输入端连接。
  20. 如权利要求16所述的电视机，其特征在于，所述电源管理电路还包括第一二极管、第二二极管、第一三极管、第二电容、第三电容、第十电阻、第十一电阻、第十二电阻、第十三电阻及第十四电阻；所述第十电阻的第一端与所述电源检测端连接，所述第十电阻的第二端与所述第十一电阻的第一端连接，所述第十一电阻的第二端、所述第一三极管的发射极、所述第二电容的正极及所述控制芯片的电源端互连，所述第二电容的负极接地；所述第一三极管的基极、所述第一二极管的阴极、所述第十四电阻的第一端及所述第十三电阻的第一端互连，所述第一二极管的阳极及所述第十四电阻的第二端接地；所述第一三极管的集电极与所述第十二电阻的第一端连接，所述第十二电阻的第二端、所述第十三电阻的第二端、所述第二二极管的阴极及所述第三电容的正极互连，所述第三电容的负极接地，所述第二二极管的阳极与变压器的辅助绕组连接。
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