WO2017156891A1 - Circuit de gradation mixte à commande par courant alternatif et télévision - Google Patents

Circuit de gradation mixte à commande par courant alternatif et télévision Download PDF

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Publication number
WO2017156891A1
WO2017156891A1 PCT/CN2016/084866 CN2016084866W WO2017156891A1 WO 2017156891 A1 WO2017156891 A1 WO 2017156891A1 CN 2016084866 W CN2016084866 W CN 2016084866W WO 2017156891 A1 WO2017156891 A1 WO 2017156891A1
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Prior art keywords
resistor
transistor
module
voltage
current
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PCT/CN2016/084866
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English (en)
Chinese (zh)
Inventor
王坚
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深圳Tcl数字技术有限公司
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Publication of WO2017156891A1 publication Critical patent/WO2017156891A1/fr

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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
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • 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]
    • 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
    • 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 backlight driving technologies, and in particular, to an AC driven hybrid dimming circuit and a television set.
  • the drive is divided into AC drive and DC drive.
  • AC drive refers to the AC power supply after the AC power is rectified and filtered.
  • the DC drive is AC-rectified and filtered to obtain an isolated low-voltage DC voltage after AC-DC conversion.
  • the LED strip is then powered by DC-DC conversion. Since the AC drive mode is one level less than the DC drive mode, the drive efficiency is high and the cost is low.
  • the AC drive is divided into constant current drive and constant power drive.
  • the existing LED light bar constant current drive circuit is used to control the output current of the switching power supply.
  • the existing LED light bar constant power drive circuit is In the primary switching current signal of the switching power supply, the output constant power control is performed.
  • the characteristics of the above two AC driving circuits are controlled by the switching current signal of the switching power supply, and the control side thereof is at the primary of the switching power supply.
  • the above two AC drive circuits can be applied to illumination devices that do not require current control dimming, but for backlighting of LCD TVs, analog and digital mixed dimming functions are required to achieve the purpose of LED lamp bar brightness adjustment and to meet energy saving. Environmentally friendly requirements.
  • the main object of the present invention is to provide an LED AC drive hybrid dimming circuit, which aims to realize LED light bar analog and digital mixed dimming, and improve AC driving efficiency.
  • the LED AC drive hybrid dimming circuit proposed by the present invention comprises a transformer, a PWM control module for controlling a transformer boost ratio, a driving voltage output module for supplying power to the LED strip, and a sampling light strip.
  • the current sampling module of the current further comprises an auxiliary voltage output module, a voltage current monitoring module, a signal isolation module, an analog dimming control module and a digital dimming control module;
  • the driving voltage output module and the auxiliary voltage output module are respectively connected to two secondary windings of the transformer, and the driving voltage output module outputs an auxiliary voltage to the signal isolation module, the voltage current monitoring module, the analog dimming control module, and The digital dimming control module supplies power; the voltage current monitoring module monitors a driving voltage output by the driving voltage output module and a light bar current sampled by the current sampling module, and outputs a feedback signal, and the feedback signal passes through the signal isolation module.
  • the analog dimming control module After being isolated, outputting to the PWM control module to adjust the driving voltage and the light bar current; the analog dimming control module converting the analog dimming PWM signal into a controllable current signal output to the current sampling module, the current sampling module according to The current signal generates a voltage signal to adjust the light bar current; the digital dimming control module performs level conversion on the digital dimming PWM signal, and outputs a dimming driving signal to control the on/off of the current sampling module, and generates a synchronization Switching the signal to the signal isolation module to synchronize by controlling the PWM control module Or stop working for adjusting the light of current.
  • the present invention also provides a television set comprising a light bar and an AC driven hybrid dimming circuit, the AC drive hybrid dimming circuit connecting the positive and negative poles of the light bar for driving the light bar;
  • the AC-driven hybrid dimming circuit includes a transformer, a PWM control module for controlling a voltage boost ratio of the transformer, a driving voltage output module for supplying power to the light bar, and a current sampling module for sampling the current of the light bar, wherein
  • the utility model also includes an auxiliary voltage output module, a voltage current monitoring module, a signal isolation module, an analog dimming control module and a digital dimming control module;
  • the driving voltage output module and the auxiliary voltage output module are respectively connected to two secondary windings of the transformer, and the driving voltage output module outputs an auxiliary voltage to the signal isolation module, the voltage current monitoring module, the analog dimming control module, and The digital dimming control module supplies power; the voltage current monitoring module monitors a driving voltage output by the driving voltage output module and a light bar current sampled by the current sampling module, and outputs a feedback signal, and the feedback signal passes through the signal isolation module.
  • the analog dimming control module After being isolated, outputting to the PWM control module to adjust the driving voltage and the light bar current; the analog dimming control module converting the analog dimming PWM signal into a controllable current signal output to the current sampling module, the current sampling module according to The current signal generates a voltage signal to adjust the light bar current; the digital dimming control module performs level conversion on the digital dimming PWM signal, and outputs a dimming driving signal to control the on/off of the current sampling module, and generates a synchronization Switching the signal to the signal isolation module to synchronize by controlling the PWM control module Or stop working for adjusting the light of current.
  • the technical scheme of the invention monitors the driving voltage of the light bar and the current of the light bar through the voltage and current monitoring module, and outputs the feedback signal to the PWM control module after being isolated by the signal isolation module, and controls the driving voltage and the flowing light of the output of the driving voltage output module through the PWM control module.
  • the current of the strip reaches the purpose of output constant current and overvoltage protection; the analog dimming control module converts the analog dimming PWM signal into a controllable current signal output to the current sampling module, and the current sampling module generates a voltage signal according to the current signal.
  • the digital dimming control module performs level conversion of the digital dimming PWM signal, and outputs a dimming driving signal to control the on/off of the current sampling module to adjust the current of the light bar, and simultaneously generate one
  • the synchronous enable switch signal is sent to the signal isolation module, and the signal isolation module adjusts the light bar current by enabling the PWM control module to work synchronously or stop working to achieve the purpose of digital dimming.
  • FIG. 1 is a schematic structural diagram of a module of a preferred embodiment of an AC-driven hybrid dimming circuit according to the present invention
  • FIG. 2 is a schematic structural diagram of a circuit of an AC drive hybrid dimming circuit according to an embodiment of the present invention
  • FIG. 3 is a schematic structural diagram of a circuit of another embodiment of an AC-driven hybrid dimming circuit according to the present invention.
  • FIG. 4 is a schematic diagram showing the circuit structure of still another embodiment of the AC-driven hybrid dimming circuit of the present invention.
  • the invention provides an AC drive hybrid dimming circuit for driving a light bar in a display device (such as a television) and a lighting device.
  • the light bar is an LED light bar
  • the AC drive hybrid dimming circuit is an LED AC drive hybrid dimming circuit.
  • the type of the light bar may be other types, which is not specifically limited herein.
  • the LED AC drive hybrid dimming circuit comprises a transformer 10, a PWM control module 20, a driving voltage output module 30, a current sampling module 40, an auxiliary voltage output module 50, and a voltage current.
  • the PWM control module 20 is connected to the primary winding of the transformer 10 for controlling the boosting ratio of the transformer 10; the input end of the driving voltage output module 30 is connected to the first secondary winding of the transformer 10, and the driving voltage output terminal of the driving voltage output module 30 is connected.
  • the anode of the LED strip LB, the driving voltage output module 30 outputs a constant current driving voltage VH to supply power to the LED strip LB.
  • the input end of the auxiliary voltage output module 50 is connected to the second secondary winding of the transformer 10.
  • the auxiliary voltage output terminals of the auxiliary voltage output module 50 are respectively connected to the signal isolation module 70, the voltage current monitoring module 60, the analog dimming control module 80, and the digital tone.
  • the power supply terminal of the light control module 90 is connected, and the auxiliary voltage output module 50 outputs the auxiliary voltage VAUX to the signal isolation module 70, the voltage current monitoring module 60, the analog dimming control module 80, and the digital dimming control module 90.
  • the input end of the current sampling module 40 is connected to the negative pole of the LED strip LB, the current sampling end of the current sampling module 40 is connected to the current detecting end of the voltage current monitoring module 60, and the feedback output end of the voltage current monitoring module 60 is connected to the feedback module 70 through the signal isolation module 70.
  • the feedback input terminal of the PWM control module 20 monitors the driving voltage outputted by the driving voltage output module 30 and the light bar current sampled by the current sampling module 40 and outputs a feedback signal, which is sent to the signal through the signal isolation module 70.
  • the PWM control module 20 After isolation, feedback to the feedback input end of the PWM control module 20, the PWM control module 20 adjusts the boost ratio of the transformer 10 according to the feedback signal, thereby adjusting the driving voltage output by the driving voltage output module 30 and the current flowing through the LED strip LB.
  • the purpose of output constant current and overvoltage protection is achieved.
  • the current signal output end of the analog dimming control module 80 is connected to the current sampling end of the current sampling module 40, and the analog dimming control module 80 is connected to the analog dimming PWM signal to convert the analog dimming PWM signal into a controllable current signal. And outputting the current signal to the current sampling module 40, the current sampling module 40 generates a voltage signal according to the current signal to adjust the light bar current, thereby realizing the current flowing through the LED light bar LB through the analog dimming PWM signal, Adjust the brightness of the LED strip LB to achieve the purpose of analog dimming.
  • the dimming drive output end of the digital dimming control module 90 is connected to the dimming control end of the current sampling module 40.
  • the switching signal output end of the digital dimming control module 90 is connected to the enable end of the PWM control module 20 through the signal isolation module 70.
  • the digital dimming control module 90 is connected to the digital dimming PWM signal, and the digital dimming PWM signal is level-converted to output a dimming driving signal, and the dimming driving signal is used to control the on/off of the current sampling module 40 to adjust the flow.
  • the current of the LED strip LB is generated.
  • a synchronous enable switch signal is generated to the signal isolation module 70.
  • the enable switch signal is isolated by the signal isolation module 70 and output to the enable end of the PWM control module 20.
  • the enable switch signal controls the synchronous operation or the stop operation of the PWM control module 20, and adjusts the drive voltage outputted by the drive voltage output module 30, that is, regulates the current flowing through the LED strip LB.
  • the on/off of the current sampling module 40 and the PWM control module 20 are synchronously operated or stopped by the digital dimming PWM signal to adjust the current of the light bar, and the brightness of the LED light bar LB is adjusted to achieve the purpose of digital dimming.
  • FIG. 2 is a schematic diagram showing the circuit structure of a specific embodiment of an LED AC-driven hybrid dimming circuit according to the present invention.
  • the LED AC drive hybrid dimming circuit is divided into a primary portion including a primary winding of the transformer 10, and a component connected to the side of the primary winding of the transformer 10, and the secondary portion includes The secondary winding of the transformer 10, and the components connected to the side of the secondary winding of the transformer 10.
  • the driving voltage output module 30 includes a first diode D1 and a first capacitor C1.
  • the anode of the first diode D1 is connected to the first terminal of the transformer 10, the cathode of the first diode D1 is connected to the anode of the first capacitor C1, and the cathode of the first capacitor C1 is connected to the secondary ground.
  • the anode of the first capacitor C1 is connected to the anode of the LED strip LB.
  • the auxiliary voltage output module 50 includes a second diode D2 and a second capacitor C2.
  • the anode of the second diode D2 is connected to the second terminal of the transformer 10
  • the cathode of the second diode D2 is connected to the anode of the second capacitor C2
  • the cathode of the second capacitor C2 is connected to the secondary ground.
  • the anode of the second capacitor C2 is connected to the signal isolation module 70.
  • the PWM control module 20 includes a PWM controller U1, a switch M1 and a first resistor R1, and the switch M1 is an NMOS transistor.
  • the enable pin EN and the feedback pin FB of the PWM controller U1 are both connected to the signal isolation module 70, and the drive output pin DR of the PWM controller U1 is connected to the gate of the switch M1; the drain of the switch M1 is via the transformer
  • the primary winding of 10 is connected to the input power source Vi, and the source of the switching transistor M1 is connected to the primary ground via the first resistor R1 and is connected to the current detecting pin IS of the PWM controller U1.
  • the current sampling module 40 includes a first transistor Q1, a second resistor R2, and a third resistor R3.
  • the base of the first transistor Q1 is connected to the digital dimming control module 90, the collector of the first transistor Q1 is connected to the cathode of the LED strip LB, and the emitter of the first transistor Q1 is connected to the second resistor.
  • R2 is connected to the secondary ground and is connected to the current detecting terminal of the analog dimming control module 80 via the third resistor R3.
  • the signal isolation module 70 includes a first photocoupler OP1, a second photocoupler OP2, a fourth resistor R4, a fifth resistor R5, and a first Zener diode DZ1.
  • the anode of the light emitting diode is connected to the voltage output end of the auxiliary voltage output module 50 via the fourth resistor R4, and the cathode of the light emitting diode is connected to the feedback output end of the voltage current monitoring module 60, and the set of the phototransistor
  • the electrode is connected to the feedback input pin FB of the PWM controller U1, and the emitter of the phototransistor is connected to the primary ground.
  • the cathode of the first Zener diode DZ1 is connected to the voltage output end of the auxiliary voltage output module 50 via the fifth resistor R5, and the anode of the first Zener diode DZ1 is connected to the second photocoupler OP2.
  • the anode of the light emitting diode is connected to the first Zener diode.
  • the cathode of the light emitting diode is connected to the secondary ground, and the collector of the phototransistor is connected to the enable pin EN of the PWM controller U1, and the emitter of the phototransistor is connected to the primary ground.
  • the voltage current monitoring module 60 includes a voltage and current constant controller U2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5.
  • the third capacitor C3, the fourth capacitor C4 and the eighth resistor R8 form a feedback correction network.
  • the power supply pin VCC of the voltage and current constant controller U2 is connected to the secondary ground via the fifth capacitor C5, the grounding pin GND of the voltage and current constant controller U2 is connected to the secondary ground, and the feedback pin FBC of the voltage and current constant controller U2 is connected.
  • the current detecting pin ISNS of the voltage-current constant controller U2 is connected to the emitter of the first transistor Q1 via the third resistor R3.
  • One end of the sixth resistor R6 is connected to the driving voltage output end of the driving voltage output module 30, that is, one end of the sixth resistor R6 is connected to the anode of the first capacitor C1, and the other end of the sixth resistor R6 is connected to the second resistor R7.
  • the common connection point of the sixth resistor R6 and the seventh resistor R7 is connected to the voltage detecting pin VSNS of the voltage-current constant controller U2.
  • One end of the eighth resistor R8 is connected to the current detecting pin ISNS of the voltage-current constant controller U2, and the other end of the eighth resistor R8 is connected to the feedback pin FBC of the voltage-current constant controller U2 via the third capacitor C3, the fourth capacitor The two ends of C4 are respectively connected to the current detecting pin ISNS and the feedback pin FBC of the voltage-current constant controller U2.
  • the analog dimming control module 80 includes an analog dimming PWM signal input terminal A_DIM, a second triode Q2, a third triode Q3, a fourth triode Q4, and a second Zener diode DZ2.
  • the base of the second transistor Q2 is connected to the analog dimming PWM signal input terminal A_DIM via the ninth resistor R9, and is connected to the secondary ground via the tenth resistor R10, and the collector of the second transistor Q2 is passed through the eleventh
  • the resistor R11 and the sixth capacitor C6 are connected to the secondary ground, and are connected to the cathode of the second Zener diode DZ2 via the twelfth resistor R12, and the emitter of the second transistor Q2 is connected to the secondary ground.
  • the base of the third transistor Q3 is connected to the common connection point of the eleventh resistor R11 and the sixth capacitor C6, the collector of the third transistor Q3 is connected to the secondary ground, and the emitter of the third transistor Q3 is
  • the base of the quadrupole Q4 is connected to the cathode of the second Zener diode DZ2 via the twelfth resistor R13, and the collector of the fourth transistor Q4 is connected to the cathode of the second Zener diode DZ2, the fourth three poles
  • the emitter of the tube Q4 is connected to the emitter of the first transistor Q1 via the fourteenth resistor R14 and the third resistor R3.
  • the cathode of the second Zener diode DZ2 is connected to the auxiliary voltage output terminal of the auxiliary voltage output module 50 via the fifteenth resistor R15, and the anode of the second Zener diode DZ2 is connected to the secondary ground.
  • the digital dimming control module 90 includes a digital dimming PWM signal input terminal P_DIM, a backlight switch control signal input terminal BL_ON, a fifth triode Q5, a sixth triode Q6, and a seventh triode Q7.
  • the eighth transistor Q8 the sixteenth resistor R16, the seventeenth resistor R17, the eighteenth resistor R18, the nineteenth resistor R19, the twentieth resistor R20, the twenty-first resistor R21, the twenty-second resistor R22 and twenty-third resistor R23.
  • the base of the fifth transistor Q5 is connected to the digital dimming PWM signal input terminal P_DIM via the sixteenth resistor R16, and is connected to the secondary ground via the seventeenth resistor R17, and the collector of the fifth transistor Q5 is passed through the first
  • the eighteen resistor R18 is connected to the base of the sixth transistor Q6.
  • the emitter of the sixth transistor Q6 is connected to the auxiliary voltage output terminal of the auxiliary voltage output module 50, and the collector of the sixth transistor Q6 is connected to the secondary ground via the nineteenth resistor R19 and the twentieth resistor R20, and Connected to the base of the first transistor Q1 via the twenty-first resistor R21.
  • the base of the seventh transistor Q7 is connected to a common connection point of the nineteenth resistor R19 and the twentieth resistor R20, and the collector of the seventh transistor Q7 is connected to the anode of the first Zener diode DZ1, and the second The anode of the light emitting diode in the photocoupler OP2 is connected, and the emitter of the seventh transistor Q7 is connected to the collector of the eighth transistor Q8.
  • the base of the eighth transistor Q8 is connected to the backlight switch control signal input terminal BL_ON via the twenty-second resistor R22, and is connected to the secondary ground via the twenty-third resistor R23, and the emitter of the eighth transistor Q8 is connected. To the secondary land.
  • the emitter of the fifth transistor Q5 can be connected to the base of the first transistor Q1, and a resistor is connected between the base and the emitter of the first transistor Q1. That is, the fifth transistor Q5 and the first transistor Q1 are connected in a Darlington mode (not shown).
  • the working principle of the LED AC drive hybrid dimming circuit of the present invention is specifically described as follows:
  • the drive output pin DR of the PWM controller U1 outputs a PWM signal to control the switch M1 to be turned on or off.
  • the switch M1 When the switch M1 is turned on, the primary winding of the transformer 10 stores energy.
  • the switch M1 When the switch M1 is turned off, the primary winding of the transformer 10 is discharged, thereby generating an induced voltage on the first secondary winding and the second secondary winding of the transformer 10, and the induced voltage generated by the first secondary winding of the transformer 10 passes through the first two.
  • the pole tube D1 is rectified, the first capacitor C1 is filtered, and the driving voltage VH is outputted to the anode of the LED strip LB, and the LED strip LB is supplied with the driving voltage; and the induced voltage generated by the second secondary winding of the transformer 10 passes through the second second.
  • the pole tube D2 is rectified, and the second capacitor C2 is filtered to output an auxiliary voltage VAUX, and the auxiliary voltage is respectively given to the first photocoupler OP1, the second photocoupler OP2, the voltage current constant controller U2, the analog dimming control module 80, and the digital The dimming control module 90 supplies power.
  • the second resistor R2 samples the current flowing through the LED strip LB to obtain a strip current signal, and the strip current signal is output to the current detecting pin ISNS of the voltage and current constant controller U2 via the third resistor R3.
  • the voltage and current constant controller U2 compares the input light bar current signal voltage value with an internal reference voltage, and monitors the current flowing through the LED light bar LB according to the comparison result; the sixth resistor R6 and the seventh resistor R7 drive the voltage output
  • the driving voltage outputted from the first capacitor C1 in the module 30 is divided and the divided voltage signal is outputted to the current detecting pin VSNS of the voltage-current constant controller U2, and the voltage-current constant controller U2 inputs the voltage value of the divided voltage signal.
  • the driving voltage outputted by the driving voltage output module 30 is monitored based on the comparison result.
  • the voltage and current constant controller U2 outputs a corresponding feedback signal according to the detected driving voltage and the light bar current.
  • the feedback signal is signal-isolated by the first photocoupler OP1 and fed back to the feedback input pin FB of the PWM controller U1, PWM.
  • the control module 20 adjusts the boosting ratio of the transformer 10 according to the feedback signal, adjusts the driving voltage and the light bar current, and realizes the output constant current and overvoltage protection of the LED AC driven hybrid dimming circuit.
  • the analog dimming PWM signal is input through the analog dimming PWM signal input terminal A_DIM, and the analog dimming PWM signal is divided by the ninth resistor R9 and the tenth resistor R100 and output to the second three poles.
  • the base of the tube Q2 controls the second transistor Q2 to be alternately turned on and off, thereby outputting a square wave signal at the collector of the second transistor Q2.
  • the square wave signal of the collector output of the second transistor Q2 is integrated by the eleventh resistor R11 and the sixth capacitor C6 to obtain a DC voltage signal, and the DC voltage is wider when the pulse width of the input analog dimming PWM signal is wider. The smaller it is.
  • the emitter output voltage of the fourth transistor Q4 is equal to the voltage across the sixth capacitor C6, and the voltage passes through the tenth After the four resistors R14 become a current source, at this time, the current source injects a current into the third resistor R3, thereby realizing the adjustment of the current of the light bar, and achieving the purpose of analog dimming.
  • the digital dimming PWM signal is input through the digital dimming PWM signal input terminal P_DIM, and the digital dimming PWM signal is divided by the sixteenth resistor R16 and the seventeenth resistor R17 and output to the fifth.
  • the base of the transistor Q5. When the digital dimming PWM signal is a low level signal, the fifth triode Q5 and the sixth triode Q6 are both turned off, so that the first triode Q1 is also turned off; when the digital dimming PWM signal is high When the signal is flat, the fifth transistor Q5 and the sixth transistor Q6 are both turned on, so that the first transistor Q1 is also turned on.
  • the eighth transistor Q8 is turned on, and the seventh transistor Q7 is also turned on, the light-emitting diode in the second photocoupler OP2 is short-circuited, and the second photocoupler OP2 is not turned on.
  • the PWM controller U1 operates normally; if the backlight switch control signal is a low-level signal, the first When the seven transistor Q7 and the eighth transistor Q8 are both turned off, the auxiliary voltage outputted from the second capacitor C2 in the auxiliary voltage output module 50 passes through the fifth resistor R5 and the first Zener diode DZ1 as the second photocoupler OP2.
  • the light-emitting diode in the power supply is turned on, so that the phototransistor in the second photocoupler OP2 is turned on.
  • the enable pin EN of the PWM controller U1 is at a low level, so the PWM controller U1 stops working.
  • the digital dimming control module 90 controls the light bar current by controlling the on and off of the first transistor Q1 and the operating state of the PWM controller U1 to achieve the purpose of digital dimming.
  • FIG. 3 is a schematic diagram showing the circuit structure of another embodiment of the LED AC drive hybrid dimming circuit of the present invention.
  • the signal isolation module 70 of FIG. 3 includes the first optoelectronic device.
  • the anode of the light emitting diode is connected to the voltage output end of the auxiliary voltage output module 50 via the fourth resistor R4, and the cathode of the light emitting diode is connected to the feedback output end of the voltage current monitoring module 60, and the set of the phototransistor
  • the electrode is connected to the feedback input pin FB of the PWM controller U1, and the emitter of the phototransistor is connected to the primary ground.
  • the cathode of the first Zener diode DZ1 is connected to the voltage output end of the auxiliary voltage output module 50 via the fifth resistor R5, and the anode of the first Zener diode DZ1 is connected to the second photocoupler OP2.
  • the anode of the light emitting diode In the second photocoupler OP2, the cathode of the light emitting diode is connected to the secondary ground, and the collector of the phototransistor is connected to the feedback input pin FB of the PWM controller U1, and the emitter of the phototransistor is connected to the primary ground.
  • the working principle of the LED AC-driven hybrid dimming circuit shown in FIG. 3 is similar to the working principle of the LED AC-driven hybrid dimming circuit shown in FIG. 2, and is not described here. The only difference is that the seventh triode Q7 in FIG.
  • the enable switch signal of the collector output is also isolated by the second optocoupler OP2 and output to the feedback input pin FB of the PWM controller U1, and the PWM controller U1 detects the low level signal when the feedback input pin FB is detected.
  • the output of the PWM signal can also be turned off.
  • the PWM controller U1 can be used as an enable pin on the feedback input pin FB.
  • FIG. 4 is a schematic diagram showing the circuit structure of still another embodiment of the LED AC drive hybrid dimming circuit of the present invention.
  • the anode of the LED is connected to the voltage output terminal of the auxiliary voltage output module 50 via the fourth resistor R4, and the cathode of the LED is connected to the feedback output of the voltage current monitoring module 60, and the collector of the phototransistor
  • the feedback input pin FB of the PWM controller U1 is connected, and the emitter of the phototransistor is connected to the primary ground.
  • the digital dimming control module 90 of FIG. 4 includes a digital dimming PWM signal input terminal P_DIM, a backlight switch control signal input terminal BL_ON, a fifth triode Q5, a sixth triode Q6, and a seventh triode Q7.
  • the base of the fifth transistor Q5 is connected to the digital dimming PWM signal input terminal P_DIM via the sixteenth resistor R16, and is connected to the secondary ground via the seventeenth resistor R17, and the collector of the fifth transistor Q5 is passed through the first
  • the eighteen resistor R18 is connected to the base of the sixth transistor Q6.
  • the emitter of the sixth transistor Q6 is connected to the auxiliary voltage output terminal of the auxiliary voltage output module 50, and the collector of the sixth transistor Q6 is connected to the secondary ground via the nineteenth resistor R19 and the twentieth resistor R20. And connected to the base of the first transistor Q1 via the twenty-first resistor R21.
  • the base of the seventh transistor Q7 is connected to the common connection point of the nineteenth resistor R19 and the twentieth resistor R20, and the collector of the seventh transistor Q7 is connected to the anode of the third Zener diode DZ3, and the seventh three pole
  • the emitter of the tube Q7 is connected to the collector of the eighth transistor Q8.
  • the base of the eighth transistor Q8 is connected to the backlight switch control signal input terminal BL_ON via the twenty-second resistor R22, and is connected to the secondary ground via the twenty-third resistor R23, and the emitter of the eighth transistor Q8 is connected. To the secondary land.
  • the base of the ninth transistor Q9 is connected to the anode of the third Zener diode DZ3 and the collector of the seventh transistor Q7 via the twenty-fourth resistor R24, and the collector and the first of the ninth transistor Q9
  • the cathode of the light-emitting diode in the photocoupler OP1 is connected, and the emitter of the ninth transistor Q9 is connected to the secondary ground.
  • the working principle of the LED AC-driven hybrid dimming circuit shown in FIG. 4 is similar to the working principle of the LED AC-driven hybrid dimming circuit shown in FIG. 2, and is not described here. The only difference is that the seventh triode in FIG.
  • the enable switch signal of the collector output of Q7 is a high level signal
  • the high level signal controls the ninth transistor Q9 to be turned on, thereby turning on the first photocoupler OP1, and the PWM controller U1 at this time
  • the feedback input pin FB is at a low level, so that the PWM controller U1 stops working; when the enable switch signal of the collector output of the seventh transistor Q7 is a low level signal, the ninth transistor Q9 is turned off, and further
  • the first photocoupler OP1 is also turned off, and the PWM controller U1 operates normally to realize digital dimming.
  • the present invention also provides a television set comprising a light bar and an AC drive hybrid dimming circuit, the AC drive hybrid dimming circuit connecting the positive and negative poles of the light bar for driving the light bar, the alternating current
  • the specific structure of the driving hybrid dimming circuit is referred to the above embodiment. Since the television set of the present invention adopts all the technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are no longer used. One by one.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Dc-Dc Converters (AREA)
  • User Interface Of Digital Computer (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)

Abstract

L'invention concerne un circuit de gradation mixte à commande par courant alternatif et une télévision. Le circuit de gradation mixte à commande par courant alternatif comprend un transformateur (10), un module de commande PWM (20), un module de sortie de tension d'actionnement (30), un module d'échantillonnage de courant (40), un module de sortie de tension auxiliaire (50), un module de contrôle de tension et de courant (60), un module d'isolation de signal (70), un module de commande d'atténuation analogique (80) et un module de commande d'atténuation numérique (90). Un côté primaire et un côté secondaire du transformateur (10) sont isolés par le module d'isolation de signal (70), et une tension d'actionnement de barre lumineuse et un courant de barre lumineuse sont contrôlés par le module de contrôle de tension et de courant (60), de manière à obtenir une sortie de courant constante et une protection contre les surtensions; une atténuation analogique est obtenue au moyen du module de commande d'atténuation analogique (80) et du module d'échantillonnage de courant (40); et une atténuation numérique est obtenue au moyen du module de commande d'atténuation numérique (90), du module d'échantillonnage de courant (40) et du module de commande PWM (20). De cette manière, une atténuation mixte analogique et numérique d'une barre de lumière est obtenue, et l'efficacité d'actionnement par courant alternatif est améliorée.
PCT/CN2016/084866 2016-03-18 2016-06-04 Circuit de gradation mixte à commande par courant alternatif et télévision WO2017156891A1 (fr)

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