WO2017156891A1

WO2017156891A1 - Alternating current driving mixed dimming circuit and television

Info

Publication number: WO2017156891A1
Application number: PCT/CN2016/084866
Authority: WO
Inventors: 王坚
Original assignee: 深圳Tcl数字技术有限公司
Priority date: 2016-03-18
Filing date: 2016-06-04
Publication date: 2017-09-21
Also published as: CN105764185B; WO2017156893A1; CN105764185A

Abstract

An alternating current driving mixed dimming circuit and a television. The alternating current driving mixed 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), a voltage and current monitoring module (60), a signal isolation module (70), an analogue dimming control module (80) and a digital dimming control module (90). A primary side and a secondary side of the transformer (10) are isolated by the signal isolation module (70), and a light bar driving voltage and a light bar current are monitored by the voltage and current monitoring module (60), so as to achieve constant current output and overvoltage protection; analogue dimming is achieved by means of the analogue dimming control module (80) and the current sampling module (40); and digital dimming is achieved by means of the digital dimming control module (90), the current sampling module (40) and the PWM control module (20). In this way, analogue and digital mixed dimming of a light bar is achieved, and the alternating current driving efficiency is improved.

Description

AC driven hybrid dimming circuit and TV

Technical field

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.

Background technique

Due to the current light bar, LED has a long life, energy saving, and convenient driving. Therefore, most of the current television sets use LED backlight technology to drive the LED light bar through the driving circuit. 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.

Summary of the invention

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.

To achieve the above object, 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. 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 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. Adjusting the current of the light bar to achieve the purpose of analog dimming; 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. Thereby, the light bar analog and digital mixed dimming are realized, and the AC driving efficiency is improved.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and those skilled in the art can obtain other drawings according to the structures shown in the drawings without any creative work.

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;

2 is a schematic structural diagram of a circuit of an AC drive hybrid dimming circuit according to an embodiment of the present invention;

3 is a schematic structural diagram of a circuit of another embodiment of an AC-driven hybrid dimming circuit according to the present invention;

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 implementation, functional features, and advantages of the present invention will be further described in conjunction with the embodiments.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope 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. In the present invention, the light bar is an LED light bar, and the AC drive hybrid dimming circuit is an LED AC drive hybrid dimming circuit. For example, the type of the light bar may be other types, which is not specifically limited herein.

1 is a block diagram of a preferred embodiment of an LED AC drive hybrid dimming circuit of the present invention. In a preferred embodiment of the present invention, as shown in FIG. 1, 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 monitoring module 60, the signal isolation module 70, the analog dimming control module 80, and the digital dimming control module 90.

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. 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. At the same time, 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. Thereby, 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.

Referring to FIG. 1 and FIG. 2, 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. As shown in FIG. 2, 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.

As shown in FIG. 2, 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.

As shown in FIG. 2, 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, and 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.

As shown in FIG. 2, 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.

As shown in FIG. 2, 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.

As shown in FIG. 2, 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.

In the first photocoupler OP1, 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 enable pin EN of the PWM controller U1, and the emitter of the phototransistor is connected to the primary ground.

As shown in FIG. 2, 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. Connected to the cathode of the light-emitting diode in the first photocoupler OP1, 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.

As shown in FIG. 2, 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 ninth resistor R9, the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14, the fifteenth resistor R15, and the sixth capacitor C6.

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.

As shown in FIG. 2, 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.

Of course, in a modified embodiment, 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). As shown in FIG. 2, the working principle of the LED AC drive hybrid dimming circuit of the present invention is specifically described as follows:

In the normal operation of the LED AC drive hybrid dimming circuit, 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. When the switch M1 is turned on, the primary winding of the transformer 10 stores energy. 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.

In the current sampling module 40, 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. Comparing with another internal reference voltage, 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.

In the analog dimming control module 80, 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. Since the third transistor Q3 and the fourth transistor Q4 form a voltage follower without voltage displacement, 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.

In the digital dimming control module 90, 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. Meanwhile, in the case where the first transistor Q1 is turned on, if the backlight switch control signal input from the backlight switch control signal input terminal BL_ON is a high level signal, 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. At this time, 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. At this time, the enable pin EN of the PWM controller U1 is at a low level, so the PWM controller U1 stops working. Thus, 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.

Referring to FIG. 1, FIG. 2 and FIG. 3, 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. In another embodiment of the LED AC drive hybrid dimming circuit of the present invention as shown in FIG. 3, unlike the LED AC drive hybrid dimming circuit shown in FIG. 2, the signal isolation module 70 of FIG. 3 includes the first optoelectronic device. The coupler OP1, the second photocoupler OP2, the fourth resistor R4, the fifth resistor R5, and the first Zener diode DZ1. In the first photocoupler OP1, 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. At this time, the PWM controller U1 can be used as an enable pin on the feedback input pin FB.

Referring to FIG. 1 to FIG. 4, 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. In another embodiment of the LED AC drive hybrid dimming circuit of the present invention as shown in FIG. 4, unlike the LED AC drive hybrid dimming circuit shown in FIG. 2 or FIG. 3, the signal isolation module 70 of FIG. A photocoupler OP1 and a fourth resistor R4.

In the first photocoupler OP1, 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.

Moreover, 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 eighth triode Q8, the ninth triode Q9, the third Zener diode DZ3, 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, the twenty-third resistor R23, the twenty-fourth resistor R24, and the twenty-fifth resistor R25.

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. When 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.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention, and the equivalent structural transformation, or direct/indirect use, of the present invention and the contents of the drawings are used in the inventive concept of the present invention. It is included in the scope of the patent protection of the present invention in other related technical fields.

Claims

An AC-driven hybrid dimming circuit comprising a transformer, a PWM control module for controlling a 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, the characteristics thereof The utility model 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. After isolation, output to the PWM control module to adjust the driving voltage and the light bar current; the analog dimming control module converts the analog dimming PWM signal into a current signal output to the current sampling module, and the current sampling module according to the current signal Generating 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 on and off of the current sampling module, and generates a synchronous enable switch signal To the signal isolation module to synchronize operation by controlling the PWM control module or Stop lamp of current work is adjusted.
The AC-driven hybrid dimming circuit of claim 1 wherein said driving voltage output module comprises a first diode and a first capacitor;

An anode of the first diode is connected to a different end of the first secondary winding of the transformer, a cathode of the first diode is connected to a positive pole of the first capacitor, and a cathode of the first capacitor Receiving the secondary ground, the positive pole of the first capacitor is connected to the anode of the light bar.
The AC-driven hybrid dimming circuit of claim 1 wherein said auxiliary voltage output module comprises a second diode and a second capacitor;

An anode of the second diode is connected to a second end of the transformer, a cathode of the second diode is connected to a cathode of the second capacitor, and a cathode of the second capacitor Receiving the secondary ground, the anode of the second capacitor is connected to the signal isolation module.
The AC-driven hybrid dimming circuit of claim 1 , wherein the PWM control module comprises a PWM controller, a switching transistor and a first resistor; and an enable pin and a feedback pin of the PWM controller are both Connected to the signal isolation module, a driving output pin of the PWM controller is connected to a gate of the switch tube; a drain of the switch tube is connected to an input power source via a primary winding of the transformer, the switch tube The source is connected to the primary ground via the first resistor and is connected to the current detecting pin of the PWM controller.
The AC-driven hybrid dimming circuit of claim 4, wherein the current sampling module comprises a first triode, a second resistor, and a third resistor; a base of the first triode The digital dimming control module is connected, the collector of the first triode is connected to the negative pole of the light bar, and the emitter of the first triode is connected to the secondary ground via the second resistor. And connecting to the current detecting end of the analog dimming control module via the third resistor.
The AC-driven hybrid dimming circuit according to claim 5, wherein the signal isolation module comprises a first photocoupler, a second photocoupler, a fourth resistor, a fifth resistor, and a first Zener diode; In the first photocoupler, an anode of the light emitting diode is connected to a voltage output end of the auxiliary voltage output module via the fourth resistor, and a cathode of the light emitting diode is connected to a feedback output end of the voltage current monitoring module, and the phototransistor a collector is connected to a feedback input pin of the PWM controller, and an emitter of the phototransistor is connected to the primary ground; a cathode of the first Zener diode is connected to a voltage of the auxiliary voltage output module via the fifth resistor An output, an anode of the first Zener diode is connected to an anode of the LED in the second photocoupler; in the second optocoupler, a cathode of the LED is connected to a secondary ground, and a collector of the phototransistor Connected to the enable pin of the PWM controller, the emitter of the phototransistor is connected to the primary ground.
The AC-driven hybrid dimming circuit according to claim 6, wherein the voltage current monitoring module comprises a voltage current constant controller, a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, and a fourth capacitor. And a fifth capacitor;

The power pin of the voltage current constant controller is connected to the secondary ground via the fifth capacitor, the ground pin of the voltage current constant controller is connected to the secondary ground, and the voltage current constant controller is fed back a pin is connected to a cathode of the light emitting diode in the first photocoupler, and a current detecting pin of the voltage current constant controller is connected to an emitter of the first transistor via the third resistor;

One end of the sixth resistor is connected to the driving voltage output end of the driving voltage output module, and the other end is connected to the secondary ground via the seventh resistor; a common connection point of the sixth resistor and the seventh resistor The voltage detection pin connection of the voltage and current constant controller;

One end of the eighth resistor is connected to the current detecting pin of the voltage current constant controller, and the other end is connected to the feedback pin of the voltage current constant controller via the third capacitor, the fourth capacitor The current detecting pin and the feedback pin of the voltage and current constant controller are respectively connected at both ends.
The AC-driven hybrid dimming circuit according to claim 6, wherein the analog dimming control module comprises an analog dimming PWM signal input terminal, a second triode, a third triode, and a fourth triode. a tube, a second voltage regulator, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor and a sixth capacitor;

a base of the second transistor is connected to the analog dimming PWM signal input terminal via the ninth resistor, and is connected to a secondary ground via the tenth resistor, the set of the second triode The electrode is connected to the secondary ground via the eleventh resistor and the sixth capacitor, and is connected to the cathode of the second voltage regulator via the twelfth resistor, and the emitter of the second transistor is connected Secondary land

The base of the third transistor is connected to the eleventh resistor and the sixth capacitor common connection point, the collector of the third transistor is connected to the secondary ground, and the third transistor is emitted a pole and a base of the fourth transistor are connected to a cathode of the second Zener tube via the thirteenth resistor, a collector of the fourth transistor and the second Zener a cathode connection, the emitter of the fourth transistor being connected to the emitter of the first transistor via the fourteenth resistor and the third resistor;

The cathode of the second Zener diode is connected to the auxiliary voltage output terminal of the auxiliary voltage output module via the fifteenth resistor, and the anode of the second voltage regulator tube is connected to the secondary ground.
The AC-driven hybrid dimming circuit according to claim 6, wherein the digital dimming control module comprises a digital dimming PWM signal input terminal, a backlight switch control signal input terminal, a fifth triode, and a sixth three. Polar tube, seventh transistor, eighth transistor, sixteenth resistor, seventeenth resistor, eighteenth resistor, nineteenth resistor, twentieth resistor, twenty-first resistor, twenty-second Resistance and twenty-third resistance;

a base of the fifth transistor connected to the digital dimming PWM signal input terminal via the sixteenth resistor, and to a secondary ground via the seventeenth resistor, the fifth triode a collector connected to a base of the sixth transistor via the eighteenth resistor;

An emitter of the sixth transistor is connected to an auxiliary voltage output end of the auxiliary voltage output module, and a collector of the sixth triode is connected to the second via the nineteenth resistor and the twentieth resistor And connected to the base of the first transistor via the twenty-first resistor;

a base of the seventh transistor is connected to a common connection point of the nineteenth resistor and a tens resistor, and a collector of the seventh transistor is connected to an anode of the first voltage regulator, and Connected to the anode of the light emitting diode in the second photocoupler, the emitter of the seventh transistor is connected to the collector of the eighth transistor;

a base of the eighth transistor is connected to the backlight switch control signal input terminal via the second twelve resistor, and is connected to the secondary ground via the second thirteen resistor, the eighth three pole The emitter of the tube is connected to the secondary ground.
The AC-driven hybrid dimming circuit according to claim 5, wherein the signal isolation module comprises a first photocoupler, a second photocoupler, a fourth resistor, a fifth resistor, and a first Zener diode;

In the first photocoupler, an anode of the light emitting diode is connected to a voltage output end of the auxiliary voltage output module via the fourth resistor, and a cathode of the light emitting diode is connected to a feedback output end of the voltage current monitoring module, and the phototransistor a collector is connected to a feedback input pin of the PWM controller, and an emitter of the phototransistor is connected to the primary ground;

The cathode of the first voltage regulator is connected to the voltage output end of the auxiliary voltage output module via the fifth resistor, and the anode of the first voltage regulator is connected to the anode of the light emitting diode in the second photocoupler;

In the second photocoupler, 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 of the PWM controller, and the emitter of the phototransistor is connected to the primary ground.
The AC-driven hybrid dimming circuit according to claim 10, wherein the voltage current monitoring module comprises a voltage current constant controller, a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, and a fourth capacitor. And a fifth capacitor;

The power pin of the voltage current constant controller is connected to the secondary ground via the fifth capacitor, the ground pin of the voltage current constant controller is connected to the secondary ground, and the voltage current constant controller is fed back a pin is connected to a cathode of the light emitting diode in the first photocoupler, and a current detecting pin of the voltage current constant controller is connected to an emitter of the first transistor via the third resistor;

One end of the sixth resistor is connected to the driving voltage output end of the driving voltage output module, and the other end is connected to the secondary ground via the seventh resistor; a common connection point of the sixth resistor and the seventh resistor The voltage detection pin connection of the voltage and current constant controller;

One end of the eighth resistor is connected to the current detecting pin of the voltage current constant controller, and the other end is connected to the feedback pin of the voltage current constant controller via the third capacitor, the fourth capacitor The current detecting pin and the feedback pin of the voltage and current constant controller are respectively connected at both ends.
The AC-driven hybrid dimming circuit according to claim 10, wherein the analog dimming control module comprises an analog dimming PWM signal input terminal, a second triode, a third triode, and a fourth triode. a tube, a second voltage regulator, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor and a sixth capacitor;

a base of the second transistor is connected to the analog dimming PWM signal input terminal via the ninth resistor, and is connected to a secondary ground via the tenth resistor, the set of the second triode The electrode is connected to the secondary ground via the eleventh resistor and the sixth capacitor, and is connected to the cathode of the second voltage regulator via the twelfth resistor, and the emitter of the second transistor is connected Secondary land

The base of the third transistor is connected to the eleventh resistor and the sixth capacitor common connection point, the collector of the third transistor is connected to the secondary ground, and the third transistor is emitted a pole and a base of the fourth transistor are connected to a cathode of the second Zener tube via the thirteenth resistor, a collector of the fourth transistor and the second Zener a cathode connection, the emitter of the fourth transistor being connected to the emitter of the first transistor via the fourteenth resistor and the third resistor;

The cathode of the second Zener diode is connected to the auxiliary voltage output terminal of the auxiliary voltage output module via the fifteenth resistor, and the anode of the second voltage regulator tube is connected to the secondary ground.
The AC-driven hybrid dimming circuit of claim 10, wherein the digital dimming control module comprises a digital dimming PWM signal input terminal, a backlight switch control signal input terminal, a fifth triode, and a sixth three Polar tube, seventh transistor, eighth transistor, sixteenth resistor, seventeenth resistor, eighteenth resistor, nineteenth resistor, twentieth resistor, twenty-first resistor, twenty-second Resistance and twenty-third resistance;

a base of the fifth transistor connected to the digital dimming PWM signal input terminal via the sixteenth resistor, and to a secondary ground via the seventeenth resistor, the fifth triode a collector connected to a base of the sixth transistor via the eighteenth resistor;

An emitter of the sixth transistor is connected to an auxiliary voltage output end of the auxiliary voltage output module, and a collector of the sixth triode is connected to the second via the nineteenth resistor and the twentieth resistor And connected to the base of the first transistor via the twenty-first resistor;

a base of the seventh transistor is connected to a common connection point of the nineteenth resistor and a tens resistor, and a collector of the seventh transistor is connected to an anode of the first voltage regulator, and Connected to the anode of the light emitting diode in the second photocoupler, the emitter of the seventh transistor is connected to the collector of the eighth transistor;

a base of the eighth transistor is connected to the backlight switch control signal input terminal via the second twelve resistor, and is connected to the secondary ground via the second thirteen resistor, the eighth three pole The emitter of the tube is connected to the secondary ground.
The AC-driven hybrid dimming circuit of claim 5, wherein the signal isolation module comprises a first photocoupler and a fourth resistor;

In the first photocoupler, an anode of the light emitting diode is connected to a voltage output end of the auxiliary voltage output module via the fourth resistor, and a cathode of the light emitting diode is connected to a feedback output end of the voltage current monitoring module, and the phototransistor The collector is connected to the feedback input pin of the PWM controller, and the emitter of the phototransistor is connected to the primary ground.
The AC-driven hybrid dimming circuit according to claim 14, wherein the voltage current monitoring module comprises a voltage current constant controller, a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, and a fourth capacitor. And a fifth capacitor;

The power pin of the voltage current constant controller is connected to the secondary ground via the fifth capacitor, the ground pin of the voltage current constant controller is connected to the secondary ground, and the voltage current constant controller is fed back a pin is connected to a cathode of the light emitting diode in the first photocoupler, and a current detecting pin of the voltage current constant controller is connected to an emitter of the first transistor via the third resistor;

One end of the sixth resistor is connected to the driving voltage output end of the driving voltage output module, and the other end is connected to the secondary ground via the seventh resistor; a common connection point of the sixth resistor and the seventh resistor The voltage detection pin connection of the voltage and current constant controller;

One end of the eighth resistor is connected to a current detecting pin of the voltage current constant controller, and the other end is connected to a feedback pin of a voltage current constant controller via the third capacitor, and both ends of the fourth capacitor A current sense pin and a feedback pin of the voltage-current constant controller are respectively connected.
The AC-driven hybrid dimming circuit according to claim 14, wherein the analog dimming control module comprises an analog dimming PWM signal input terminal, a second triode, a third triode, and a fourth triode. a tube, a second voltage regulator, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor and a sixth capacitor;

a base of the second transistor is connected to the analog dimming PWM signal input terminal via the ninth resistor, and is connected to a secondary ground via the tenth resistor, the set of the second triode The electrode is connected to the secondary ground via the eleventh resistor and the sixth capacitor, and is connected to the cathode of the second voltage regulator via the twelfth resistor, and the emitter of the second transistor is connected Secondary land

The base of the third transistor is connected to the eleventh resistor and the sixth capacitor common connection point, the collector of the third transistor is connected to the secondary ground, and the third transistor is emitted a pole and a base of the fourth transistor are connected to a cathode of the second Zener tube via the thirteenth resistor, a collector of the fourth transistor and the second Zener a cathode connection, the emitter of the fourth transistor being connected to the emitter of the first transistor via the fourteenth resistor and the third resistor;

The cathode of the second Zener diode is connected to the auxiliary voltage output terminal of the auxiliary voltage output module via the fifteenth resistor, and the anode of the second voltage regulator tube is connected to the secondary ground.
The AC-driven hybrid dimming circuit according to claim 14, wherein the digital dimming control module comprises a digital dimming PWM signal input terminal, a backlight switch control signal input terminal, a fifth triode, and a sixth three a pole tube, a seventh transistor, an eighth transistor, a ninth transistor, a third voltage regulator, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth a resistor, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, and a twenty-fifth resistor;

a base of the fifth transistor connected to the digital dimming PWM signal input terminal via the sixteenth resistor, and to a secondary ground via the seventeenth resistor, the fifth triode a collector connected to a base of the sixth transistor via the eighteenth resistor;

The emitter of the sixth transistor is connected to the auxiliary voltage output terminal of the auxiliary voltage output module, and the collector of the sixth transistor is connected to the second and second resistors via the nineteenth resistor and the twentieth resistor Levelly connected to the base of the first transistor via the twenty-first resistor;

a base of the seventh transistor is connected to a common connection point of the nineteenth resistor and a tens tenth resistor, and a collector of the seventh transistor is connected to an anode of the third voltage regulator The emitter of the seventh triode is connected to the collector of the eighth triode;

a base of the eighth transistor is connected to the backlight switch control signal input terminal via the second twelve resistor, and is connected to the secondary ground via the second thirteen resistor, the eighth three pole The emitter of the tube is connected to the secondary ground;

a base of the ninth transistor is respectively connected to an anode of the third voltage regulator and a collector of the seventh transistor via the twenty-fourth resistor, the ninth transistor The collector is coupled to the cathode of the light emitting diode in the first photocoupler, and the emitter of the ninth transistor is connected to the secondary ground.
A television set, comprising a light bar, further comprising an AC drive hybrid dimming circuit, the AC drive hybrid dimming circuit comprising a transformer, a PWM control module for controlling a transformer boost ratio, and a light bar Power supply driving voltage output module, current sampling module for sampling light bar current, auxiliary voltage output module, voltage current monitoring module, signal isolation module, analog dimming control module and digital dimming control module; An optical circuit is connected to the positive pole and the negative pole of the light bar for driving the light bar;

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. After isolation, output to the PWM control module to adjust the driving voltage and the light bar current; the analog dimming control module converts the analog dimming PWM signal into a current signal output to the current sampling module, and the current sampling module according to the current signal Generating 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 on and off of the current sampling module, and generates a synchronous enable switch signal To the signal isolation module to synchronize operation by controlling the PWM control module or Stop lamp of current work is adjusted.
The television set according to claim 18, wherein said driving voltage output module comprises a first diode and a first capacitor;

An anode of the first diode is connected to a different end of the first secondary winding of the transformer, a cathode of the first diode is connected to a positive pole of the first capacitor, and a cathode of the first capacitor Receiving the secondary ground, the positive pole of the first capacitor is connected to the anode of the light bar.
The television set according to claim 18, wherein said auxiliary voltage output module comprises a second diode and a second capacitor;

An anode of the second diode is connected to a second end of the transformer, a cathode of the second diode is connected to a cathode of the second capacitor, and a cathode of the second capacitor Receiving the secondary ground, the anode of the second capacitor is connected to the signal isolation module.