CN202210400U - Backlight drive circuit and liquid crystal TV set - Google Patents
Backlight drive circuit and liquid crystal TV set Download PDFInfo
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- CN202210400U CN202210400U CN2011202201789U CN201120220178U CN202210400U CN 202210400 U CN202210400 U CN 202210400U CN 2011202201789 U CN2011202201789 U CN 2011202201789U CN 201120220178 U CN201120220178 U CN 201120220178U CN 202210400 U CN202210400 U CN 202210400U
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Abstract
The utility model discloses a backlight drive circuit and a liquid crystal TV set, which are provided mainly aiming at the problems that the existing backlight drive circuit is provided with more components, and the structure of the existing backlight drive circuit is complicated, etc. The backlight drive circuit comprises a backlight electricity supplying circuit and a control circuit, wherein the backlight electricity supplying circuit supplies voltage needed for work to a backlight load according to received drive pulse signals output by the control circuit; and the control circuit is in response with control voltage signals, takes samples of working current of the backlight load in real time, generates corresponding drive pulse signals according to the current signal and outputs the drive pulse signals. The backlight drive circuit has the advantages that the structure is simple and the drive is stable.
Description
Technical Field
The utility model relates to a LCD backlight technical field especially relates to a backlight drive circuit and LCD TV.
Background
Currently, leds (light Emitting diodes) are widely used as backlight sources of liquid crystal displays. The backlight source of the medium-size and large-size LED liquid crystal display television comprises at least two light bars, and the power supply and driving modes of the light bars are shown in figure 1:
the Power supply unit is composed of a PFC (Power Factor Correction) Power supply 1 and a half-bridge resonance control circuit 2; providing electrical energy to circuitry connected thereto;
a secondary power supply unit comprising: an LLC resonance control and energy transfer circuit 3 and a secondary power supply circuit 4; the input end of the LLC resonant control and energy transfer circuit 3 is connected to the power supply unit, and the output end (i.e. the secondary side coil of the switching transformer T1) generates 12V and 100V voltage outputs via a secondary power supply circuit, so as to provide a working voltage for the driving unit;
a drive unit comprising: the driving circuit comprises a driving chip 5, a boosting circuit 6, a dimming circuit 8 and a current sampling circuit 9 (as shown in fig. 1), wherein only the connection of the driving circuits of two light bars 7 and 10 is shown in fig. 1, and four or more light bars can be driven in the same manner. Each light bar adopts a topology mode of a Boost voltage boosting circuit 6, a voltage boosting MOS tube (V3 or V5) and a dimming MOS tube (V4 or V6) are needed, and each Boost circuit 6 needs an electrolytic capacitor (C5 or C6) to meet the normal work of an LED.
The power supply and drive mode needs more chips and peripheral components, so that the cost is higher and the circuit structure is complex.
SUMMERY OF THE UTILITY MODEL
To the above problem, the utility model provides a simple structure, and drive stable backlight drive circuit and adopt this backlight drive circuit's LCD TV.
In order to achieve the above object, the present invention provides a backlight driving circuit, including: a backlight power supply circuit and a control circuit; wherein,
the backlight power supply circuit is used for providing voltage required by work for a backlight load according to the received driving pulse signal output by the control circuit;
and the control circuit responds to the control voltage signal, samples the working current of the backlight source load in real time, generates and outputs a corresponding driving pulse signal according to the sampled current signal.
Further, the backlight power supply circuit includes: an LLC resonance control and energy transfer circuit and a rectification filter circuit; wherein,
the LLC resonance control and energy transfer circuit outputs a resonance electric signal to the rectification filter circuit connected to the load end of the LLC resonance control and energy transfer circuit according to the received drive pulse signal output by the control circuit;
and the rectification filter circuit is connected to the load end of the LLC resonance control and energy transfer circuit and generates voltage required by the work of the backlight source load after rectifying and filtering the accessed electric signal.
Further, the control circuit includes: the current sampling circuit, the control sub-circuit and the driving isolation transformer; wherein,
the current sampling circuit samples and outputs the working current of the backlight source load in real time;
the control sub-circuit responds to a control voltage signal, receives the current signal output by the current sampling circuit, converts the current signal into a voltage signal, compares the value of the voltage signal with a reference voltage signal and outputs a corresponding secondary driving pulse signal according to the comparison result;
the driving isolation transformer includes: a winding core, a first coil and a second coil wound on the winding core as a primary side, and a secondary coil wound on the winding core as a secondary side; the secondary driving pulse signal received by the secondary coil is transmitted to the primary side, and then the first coil and the second coil on the primary side output two driving pulse signals.
Furthermore, the backlight source load is two LED lamp bars, and the first LED lamp bar and the second LED lamp bar are connected in series at the load end of the rectifying and filtering circuit.
In a specific embodiment, the LLC resonance control and energy transfer circuit is composed of a first switching tube, a second switching tube, a capacitor, and a switching transformer;
the grid electrode of the first switching tube is connected to one wiring end of the first coil on the primary side of the driving isolation transformer, the drain electrode of the first switching tube is connected to an external alternating current signal, and the source electrode of the first switching tube is respectively connected to the other wiring end of the first coil on the primary side of the driving isolation transformer and the first access end of the primary side of the switching transformer;
the grid electrode of the second switch tube is connected to one terminal of the second coil on the primary side of the driving isolation transformer, the drain electrode of the second switch tube is connected to the source electrode of the first switch tube, and the source electrode of the second switch tube is respectively connected to the other terminal of the second coil on the primary side of the driving isolation transformer, the ground and one end of the capacitor;
the other end of the capacitor is connected to a second access end of the primary side of the switch transformer;
the secondary side of the switch transformer is connected with the input end of the rectifying and filtering circuit;
the first switching tube and the second switching tube are alternately conducted under the driving of the driving isolation transformer.
In one embodiment, the current sampling circuit includes: sampling a resistor; the sampling resistor is connected between the first LED lamp strip and the second LED lamp strip in series.
In one embodiment, the control sub-circuit includes: the voltage stabilizing integrated circuit and the pulse width modulation control circuit are connected in parallel; wherein,
the reference end of the parallel voltage-stabilizing integrated circuit is connected between the first LED lamp strip and the sampling resistor, the anode of the parallel voltage-stabilizing integrated circuit is grounded, and the cathode of the parallel voltage-stabilizing integrated circuit is connected with the current signal output end of the pulse width modulation control circuit; monitoring the terminal voltage of the sampling resistor in real time, comparing whether the terminal voltage is equal to a reference voltage, and feeding back a comparison result to the pulse width modulation control circuit;
the pulse width modulation control circuit responds to a control voltage signal, provides a current signal required by work for the parallel voltage stabilization integrated circuit according to a comparison result of the parallel voltage stabilization integrated circuit, monitors the current signal output to the parallel voltage stabilization integrated circuit in real time, and adjusts the working frequency of the pulse width modulation control circuit according to the current signal so as to output a secondary driving pulse signal with corresponding frequency to the backlight power supply circuit.
Furthermore, the rectification filter circuit consists of a rectification circuit and a filter circuit; the rectifying circuit is composed of rectifying diodes, and the filter circuit is composed of capacitors.
Further, the first switch tube and the second switch tube are both MOS (Metal-Oxide-Semiconductor) field effect tubes.
In order to achieve the above object, the lcd tv set at least comprises an lcd screen and a backlight module, the backlight module at least comprises a backlight load and a backlight driving circuit, and the backlight driving circuit is any one of the above backlight driving circuit.
The utility model has the advantages that:
the utility model discloses a control circuit real-time supervision backlight load's operating current and according to the current signal feedback drive pulse signal who samples extremely backlight supply circuit to control backlight supply circuit provides required operating voltage for the backlight load, reaches the stable purpose of the electric current of the backlight load of stable control flow through. Compared with the prior art, the backlight source drive circuit and the drive method thereof have the advantages that the stable drive to the backlight source load is realized by changing the closed-loop control, and the circuit is simpler and easier to realize.
Specifically, the utility model discloses the LLC resonance control and the energy transfer circuit of driving transformer primary side are kept apart in the accessible adoption drive isolation transformer secondary side circuit control, then directly give the backlight load power supply after the electric signal of LLC resonance control and energy transfer circuit output through rectification filtering, and this is a brand-new backlight drive circuit framework. The structure utilizes a driving isolation transformer to replace a soft switch half-bridge resonant circuit in the prior art, simplifies a backlight source driving circuit and has a simple circuit structure.
In addition, the secondary side circuit of the driving isolation transformer can be a circuit formed by a parallel voltage stabilizing integrated circuit and a pulse width modulation control circuit. The utility model discloses the drive pulse signal of parallelly connected steady voltage integrated circuit of accessible and the feedback of pulse width modulation control circuit realizes that simultaneous control establishes ties the electric current of two way lamp strips of backlight supply circuit load end, and then has guaranteed the same of two lamp strip operating characteristic and the invariant of electric current. By the method, the use of an LED drive circuit, a booster circuit, a dimming circuit and a current sampling circuit in the prior art is omitted, and the design of the circuit is further simplified.
Adopt backlight drive circuit's LCD TV, its backlight drive circuit simple structure has reduced the cost of LCD TV on the whole, and the work of its backlight is more stable, and then has improved the display effect of LCD TV.
Drawings
FIG. 1 is a schematic diagram of a prior art backlight driver circuit;
fig. 2 is a schematic diagram of a backlight driving circuit according to the present invention;
fig. 3a is a waveform of a driving pulse signal inputted to the MOS1 in fig. 2;
FIG. 3b is a waveform of a driving pulse signal inputted to the MOS2 of FIG. 2;
FIG. 4a is a current waveform of the first LED light bar of FIG. 2;
FIG. 4b is a current waveform of the second LED light bar of FIG. 2;
fig. 5 is a schematic diagram of a driving flow of the backlight driving circuit of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings.
As shown in fig. 2, the backlight driving circuit of the present invention includes: a backlight power supply circuit and a control circuit; wherein,
the backlight power supply circuit is used for providing voltage required by work for a backlight load according to the received driving pulse signal output by the control circuit;
and the control circuit responds to the control voltage signal, samples the working current of the backlight source load in real time, generates and outputs a corresponding driving pulse signal according to the sampled current signal.
As a further embodiment of the present invention, the backlight power supply circuit includes: an LLC resonance control and energy transfer circuit 14 and a rectification filter circuit 15; wherein,
the LLC resonant control and energy transfer circuit 14, according to the received driving pulse signal output by the control circuit, outputs a resonant electrical signal to the load-side circuit connected to the circuit;
the rectification filter circuit 15 is connected to the load end of the LLC resonance control and energy transfer circuit 14, and rectifies and filters the accessed electrical signal to generate the voltage required by the backlight load.
An isolation transformer is used for replacing a half-bridge resonance control circuit in the prior art, a large number of peripheral devices are omitted, the design of the circuit is simplified, and meanwhile, the performance of the circuit is guaranteed.
As a further embodiment of the present invention, the control circuit includes: a current sampling circuit 18, a control sub-circuit 19 and a drive isolation transformer 20; wherein,
the current sampling circuit 18 samples and outputs the working current of the backlight source load in real time;
the control sub-circuit 19, in response to the control voltage signal, receives the current signal output by the current sampling circuit and converts the current signal into a voltage signal, compares the value of the voltage signal with a reference voltage signal and outputs a corresponding secondary driving pulse signal according to the comparison result;
the driving isolation transformer 20 includes: a winding core, a first coil and a second coil wound on the winding core as a primary side, and a secondary coil wound on the winding core as a secondary side; the secondary driving pulse signal received by the secondary coil is transmitted to the primary side, and then the first coil and the second coil on the primary side output two driving pulse signals.
As a still further embodiment of the present invention, the control sub-circuit 19 includes: a parallel voltage-stabilizing integrated circuit N2 and a pulse width modulation control circuit N1; wherein,
the reference end of the parallel voltage stabilizing integrated circuit N2 is connected between the first LED light bar 16 and the sampling resistor R, the anode is grounded, and the cathode is connected to the current signal output end RT of the pulse width modulation control circuit N1; monitoring the terminal voltage of the sampling resistor in real time, comparing the terminal voltage with a reference voltage, and feeding back a comparison result to the pulse width modulation control circuit N2;
the pwm control circuit N2, in response to a control voltage signal (Vcc), provides a current signal required for operation to the parallel regulator ic N2 according to the comparison result of the parallel regulator ic, monitors the current signal output to the parallel regulator ic N2 in real time and adjusts the operating frequency of the pwm control circuit according to the current signal, so as to output a secondary driving pulse signal of a corresponding frequency to the backlight power supply circuit.
The backlight driving circuit of the present invention will be described in detail with reference to a specific embodiment.
As shown in fig. 2, in the present embodiment, the backlight source load is two LED light bars, and the first LED light bar 16 and the second LED light bar 17 are connected in series at a load end of the rectifying and filtering circuit. Namely, the anode of the first LED light bar 16 is connected to the positive voltage output end of the rectifying and filtering circuit 15; the cathode of the second LED light bar 17 is connected to the negative voltage output terminal of the rectifying and filtering circuit 15, and the anode thereof is grounded.
The backlight power supply circuit is composed of an LLC resonance control and energy transfer circuit 14 and a rectification filter circuit 15.
The LLC resonance control and energy transfer circuit 14 consists of a first switching tube MOS1, a second switching tube MOS2, a capacitor C1 and a switching transformer T1; the first switching transistor MOS1 and the second switching transistor MOS2 are both MOS field effect transistors. The gate of the first switching transistor MOS1 is connected to one terminal 203 of the first coil on the primary side of the driving isolation transformer 20, the drain of the first switching transistor MOS1 is connected to an external alternating current signal (as shown in the figure, the alternating current signal is an electrical signal output by a mains supply through a PFC power supply), and the source of the first switching transistor MOS1 is respectively connected to the other terminal 204 of the first coil on the primary side of the driving isolation transformer 20 and the first incoming end on the primary side of the switching transformer T1; the second switching MOS2 has a gate connected to one terminal 201 of the second coil on the primary side of the driving isolation transformer 14, a drain connected to the source of the first switching MOS1, and a source connected to the other terminal 202 of the second coil on the primary side of the driving isolation transformer 20, ground and one end of the capacitor C1, respectively; the other end of the capacitor C1 is connected to the second access end of the primary side of the switch transformer T1; the switching transformer T1 is connected to the input terminal of the rectifying-filtering circuit 15 on the secondary side.
The rectifying/smoothing circuit 15 is composed of a rectifying circuit and a smoothing circuit. The rectifying circuit is composed of rectifying diodes (not shown in the figure), and can adopt a full-bridge rectifying mode or a half-bridge rectifying mode. The filter circuit is constituted by a capacitor (not shown in the figure).
The control circuit is composed of a current sampling circuit 18, a control sub-circuit and a drive isolation transformer 20. Wherein,
the current sampling circuit 18 includes: sampling a resistor R; one end of the sampling resistor R is connected to the cathode of the first LED light bar 16, and the other end of the sampling resistor R is connected to the anode of the second LED light bar 17.
The control sub-circuit comprises: a pulse width modulation control circuit N1 and a parallel voltage-stabilizing integrated circuit N2; in this embodiment, the pwm control circuit N1 selects an existing pwm control chip, and its input/output port mainly includes: a control voltage signal input terminal (i.e., a bias voltage Vin pin), driving pulse signal output pins Drv1 and Drv2, a ground terminal GND, and a current signal output terminal (i.e., an RT pin). In this embodiment, the adjustable precise voltage-stabilizing integrated circuit TL431 is selected as the parallel voltage-stabilizing integrated circuit N2, an anode end of the parallel voltage-stabilizing integrated circuit is grounded, a cathode of the parallel voltage-stabilizing integrated circuit is connected to a current signal output end of the pulse width modulation control circuit, and a reference end of the parallel voltage-stabilizing integrated circuit N2 is connected to a cathode of the first LED light bar 16 and one end of the sampling resistor R.
The current signals of the first LED lamp strip 16 and the second LED lamp strip 17 can be sampled in real time through a sampling resistor R, the terminal voltage of the sampling resistor R is obtained, the TL431 compares the voltage value of a reference end (namely the terminal voltage of the sampling resistor) with the reference voltage inside the reference end, the comparison result is fed back to the pulse width modulation control circuit through an RT pin connected with the cathode of the TL431, and if the voltage of the reference end is equal to the reference voltage, the working frequency of the pulse width modulation control chip N1 is unchanged, and a secondary driving pulse signal with unchanged frequency is still output; if the voltage of the reference end is higher than the reference voltage, the current value output by the RT pin is increased, the pulse width modulation control chip correspondingly adjusts the working frequency of the RT pin according to the current signal of the RT pin to output a secondary driving pulse signal after frequency adjustment (wherein, the working frequency of the current signal output by the RT pin and the working frequency of the pulse width modulation control chip are in a linear relationship), the secondary driving pulse signal is fed back to the backlight source power supply circuit through the driving isolation transformer by two driving pulse signals, and the voltage signal output by the backlight source power supply circuit is adjusted under the control of the driving pulse signal to change, so that the voltage values loaded on the first light bar 16 and the second light bar 17 are reduced to ensure that the current values of the first light bar 16 and the second light bar 17 are constant; otherwise, the same principle is applied. By the method, the use of an LED drive circuit, a booster circuit, a dimming circuit and a current sampling circuit in the prior art is omitted, and the design of the circuit is further simplified.
As shown in fig. 6, the driving method of the backlight driving circuit of the present invention includes the following steps:
s1, responding to the control voltage signal to output a driving pulse signal;
s2, controlling the driving pulse signal to output the voltage required by the backlight source load operation;
and S3, sampling the working current flowing through the backlight source load in real time, generating a corresponding driving pulse signal according to the sampled current signal, and returning to the step 2.
As a further embodiment of the present invention, step 1 is specifically implemented as follows:
1.1, responding to a control voltage signal to output a secondary driving pulse signal;
and 1.2, generating a first driving pulse signal and a second driving pulse signal after the secondary driving pulse signal is subjected to isolation and transformation.
As a further embodiment of the present invention, step 2 is specifically implemented as follows:
2.1, cooperatively controlling the first driving pulse signal and the second driving pulse signal to output a resonance electric signal;
and 2.2, rectifying and filtering the resonance electric signal to form the voltage required by the backlight source load to work.
As a further embodiment of the present invention, step 3 is implemented as follows:
3.1, sampling the working current flowing through the backlight source load in real time;
3.2, obtaining the terminal voltage of the current sampling circuit according to the sampled current signal, comparing the terminal voltage with a reference voltage, equaling, and outputting a secondary driving pulse signal with the same frequency as the original output frequency; if so, reducing the frequency of the output secondary driving pulse signal; raising the frequency of the output secondary driving pulse signal less than;
3.3, the secondary driving pulse signal output by the step 3.2 is isolated and transformed to generate a first driving pulse signal and a second driving pulse signal, and the step 2.1 is returned.
In step 3.2, if the terminal voltage of the current sampling circuit is greater than the reference voltage, reducing the frequency of the output secondary drive pulse signal; and if the terminal voltage of the current sampling circuit is smaller than the reference voltage, increasing the frequency of the output secondary driving pulse signal. Here, it should be noted that: in an actual circuit, an adjustable precise voltage-stabilizing integrated circuit TL431 and a pulse width modulation control chip are adopted to realize the step, when the voltage of a reference end of the TL431 (namely the end voltage of a current sampling circuit) is larger than the reference voltage in the TL431, the current (namely the current output from an RT end of the pulse width modulation control chip) flowing through a cathode and an anode of the TL431 can be increased, wherein the current signal output from the RT end and the working frequency of the pulse width modulation control chip are in a linear relation, when the current output from the RT end is increased, the working frequency of the pulse width modulation control chip is reduced in a certain proportion, and then a secondary driving pulse signal with the reduced frequency is output; on the contrary, when the current output by the RT terminal is reduced, the working frequency of the pulse width modulation control chip is increased in a certain proportion, and then the secondary driving pulse signal with the increased frequency is output.
The driving method according to the present invention will be further described with reference to the backlight driving circuit shown in fig. 2.
The PWM control chip N1 starts to operate in response to the control voltage signal Vcc (which provides power for the internal bias and operation of the PWM IC), and outputs a secondary driving pulse signal. The isolation transformer T2 outputs the secondary driving pulse signal as two driving pulse signals, i.e. a first driving pulse signal and a second driving pulse signal (as shown in fig. 3a and 3 b). Wherein, the time sequence of the first driving pulse signal and the second driving pulse signal is opposite, that is, when the first pulse driving signal is at high level (i.e. positive voltage value), the second pulse driving signal is at low level (i.e. negative voltage value); when the first pulse driving signal is at a low level (i.e., a negative voltage value), the second pulse driving signal is at a high level (i.e., a positive voltage value).
The first driving pulse signal and the second driving pulse signal are respectively input to the first switching tube MOS1 and the second switching tube MOS2, when the first driving pulse signal is at a high level, the MOS1 tube is switched on, and the MOS2 tube is switched off; when the second driving pulse signal is at a high level, the MOS2 tube is switched on, and the MOS1 tube is switched off; so as to realize the alternate conduction of MOS1 and MOS2 tubes. MOS1 and MOS2 tubes are conducted alternately, and the LLC resonant circuit starts to work.
The LLC resonant circuit converts the electric energy obtained from the PFC power supply into a resonant electric signal, the resonant electric signal is transmitted to the secondary end through the primary end of the switching transformer T1, and the electric signal output by the switching transformer T1 outputs positive and negative dc voltages after passing through the rectifying and filtering circuit, and directly supplies power to the first LED light bar 16 and the second LED light bar 17 (for example, fig. 4a and 4b show waveforms of the current flowing through the first LED light bar 16 and the second LED light bar 17, respectively).
The current sampling circuit samples the working current flowing through the backlight source load in real time; the parallel voltage-stabilizing integrated circuit N2 is used for monitoring the reference terminal voltage (namely the terminal voltage of the current sampling circuit) in real time, comparing the monitored reference terminal voltage with the internal reference voltage thereof, and when the reference terminal voltage is equal to the reference voltage, the current flowing from the cathode to the anode of the N2 is stable current; when the voltage at the reference terminal is greater than the reference voltage, the current flowing from the cathode to the anode of N2 increases; when the voltage at the reference terminal is smaller than the reference voltage, the current flowing from the cathode to the anode of N2 decreases.
The RT end of the pulse width modulation control chip N1 is connected with the cathode of the parallel voltage-stabilizing integrated circuit N2; the current required for the operation is supplied to the parallel regulator integrated circuit N2 according to the comparison result of the parallel regulator integrated circuit N2. When the current output from the RT terminal is a stable value, the operating frequency of the pwm control chip N1 maintains the secondary driving pulse signal with a constant output frequency. When the current output by the RT terminal is reduced, the pulse width modulation control chip N1 increases the working frequency thereof according to a certain proportional relationship, so that the frequency of the secondary driving pulse signal with high frequency output by the Drv1 and Drv2 pins is fed back to the backlight power supply circuit by the two driving pulse signals through the driving isolation transformer, and further, the voltage output by the backlight power supply circuit is increased, thereby ensuring that the current flowing through the first light bar 16 and the second light bar 17 is constant. On the contrary, similarly, when the current output by the RT terminal increases, the pwm control chip N1 reduces its operating frequency according to a certain proportional relationship, so that the frequency of the secondary driving pulse signal with low frequency output by the Drv1 and Drv2 pins is fed back to the backlight power supply circuit by the two driving pulse signals through the driving isolation transformer, and the voltage output by the backlight power supply circuit is reduced under the cooperative control of the two feedback driving pulse signals, so as to ensure that the current flowing through the first light bar 16 and the second light bar 17 is constant. Backlight drive circuit has realized the stable drive to backlight lamp strip through above-mentioned closed-loop control.
The voltage in the second LED light bar 17 is negative with respect to the ground of the secondary pwm control chip N1, the potential of the secondary ground connected to the anode of the second LED light bar 17 is higher than the lower end potential of the secondary coil of the switching transformer T1 (the lower end potential is negative), and the negative voltage difference generates a current flowing through the second LED light bar 17. The sampling resistor R controls the current flowing to the secondary ground to control the current flowing out of the secondary ground, so that the purpose of simultaneously controlling the currents of the two strings of lamp strips is achieved, and the same working characteristics of the lamp strips are guaranteed. In this way, the LED driving chip and the peripheral circuit thereof as well as the use of electrolysis and inductance are omitted, and the design of the circuit is simplified.
Liquid crystal TV set includes liquid crystal display and backlight module at least, the backlight module includes backlight load and backlight drive circuit at least, backlight drive circuit is above-mentioned arbitrary one backlight drive circuit.
The above is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.
Claims (10)
1. A backlight driving circuit, comprising: a backlight power supply circuit and a control circuit; wherein,
the backlight power supply circuit is used for providing voltage required by work for a backlight load according to the received driving pulse signal output by the control circuit;
and the control circuit responds to the control voltage signal, samples the working current of the backlight source load in real time, generates and outputs a corresponding driving pulse signal according to the sampled current signal.
2. The backlight driver circuit of claim 1, wherein the backlight power supply circuit comprises: an LLC resonance control and energy transfer circuit and a rectification filter circuit; wherein,
the LLC resonance control and energy transfer circuit outputs a resonance electric signal to the rectification filter circuit connected to the load end of the LLC resonance control and energy transfer circuit according to the received drive pulse signal output by the control circuit;
and the rectification filter circuit is connected to the load end of the LLC resonance control and energy transfer circuit and generates voltage required by the work of the backlight source load after rectifying and filtering the accessed electric signal.
3. The backlight driver circuit of claim 2, wherein the control circuit comprises: the current sampling circuit, the control sub-circuit and the driving isolation transformer; wherein,
the current sampling circuit samples and outputs the working current of the backlight source load in real time;
the control sub-circuit responds to a control voltage signal, receives the current signal output by the current sampling circuit, converts the current signal into a voltage signal, compares the value of the voltage signal with a reference voltage signal and outputs a corresponding secondary driving pulse signal according to the comparison result;
the driving isolation transformer includes: a winding core, a first coil and a second coil wound on the winding core as a primary side, and a secondary coil wound on the winding core as a secondary side; the secondary driving pulse signal received by the secondary coil is transmitted to the primary side, and then the first coil and the second coil on the primary side output two driving pulse signals.
4. The backlight driving circuit according to any one of claims 1 to 3, wherein the backlight load comprises two LED light bars, and the first LED light bar and the second LED light bar are connected in series at a load end of the backlight power supply circuit.
5. The backlight source driving circuit according to claim 3, wherein the LLC resonance control and energy transfer circuit is composed of a first switch tube, a second switch tube, a capacitor and a switch transformer;
the grid electrode of the first switching tube is connected to one wiring end of the first coil on the primary side of the driving isolation transformer, the drain electrode of the first switching tube is connected to an external alternating current signal, and the source electrode of the first switching tube is respectively connected to the other wiring end of the first coil on the primary side of the driving isolation transformer and the first access end of the primary side of the switching transformer;
the grid electrode of the second switch tube is connected to one terminal of the second coil on the primary side of the driving isolation transformer, the drain electrode of the second switch tube is connected to the source electrode of the first switch tube, and the source electrode of the second switch tube is respectively connected to the other terminal of the second coil on the primary side of the driving isolation transformer, the ground and one end of the capacitor;
the other end of the capacitor is connected to a second access end of the primary side of the switch transformer;
the secondary side of the switch transformer is connected with the input end of the rectifying and filtering circuit;
the first switching tube and the second switching tube are alternately conducted under the driving of the driving isolation transformer.
6. The backlight driver circuit of claim 3, wherein the current sampling circuit comprises: sampling a resistor; the backlight source load comprises two LED lamp bars, and a first LED lamp bar and a second LED lamp bar are connected in series at the load end of the backlight source power supply circuit; the sampling resistor is connected between the first LED lamp strip and the second LED lamp strip in series.
7. The backlight driver circuit of claim 6, wherein the control sub-circuit comprises: the voltage stabilizing integrated circuit and the pulse width modulation control circuit are connected in parallel; wherein,
the reference end of the parallel voltage-stabilizing integrated circuit is connected between the first LED lamp strip and the sampling resistor, the anode of the parallel voltage-stabilizing integrated circuit is grounded, and the cathode of the parallel voltage-stabilizing integrated circuit is connected with the current signal output end of the pulse width modulation control circuit; monitoring the terminal voltage of the sampling resistor in real time, comparing the terminal voltage with the reference voltage in the parallel voltage-stabilizing integrated circuit, and feeding back the comparison result to the pulse width modulation control circuit;
the pulse width modulation control circuit responds to a control voltage signal, provides a current signal required by work for the parallel voltage stabilization integrated circuit according to a comparison result of the parallel voltage stabilization integrated circuit, monitors the current signal output to the parallel voltage stabilization integrated circuit in real time, and adjusts the working frequency of the pulse width modulation control circuit according to the current signal so as to output a secondary driving pulse signal with corresponding frequency to the backlight power supply circuit.
8. The backlight source driving circuit according to claim 2, wherein the rectifying/filtering circuit is composed of a rectifying circuit and a filtering circuit; the rectifying circuit is composed of rectifying diodes, and the filter circuit is composed of capacitors.
9. The backlight driving circuit of claim 5, wherein the first and second switching transistors are both MOSFET devices.
10. A liquid crystal television set at least comprises a liquid crystal display screen and a backlight source module, wherein the backlight source module at least comprises a backlight source load and a backlight source drive circuit, and is characterized in that the backlight source drive circuit is the backlight source drive circuit in any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011202201789U CN202210400U (en) | 2011-06-27 | 2011-06-27 | Backlight drive circuit and liquid crystal TV set |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011202201789U CN202210400U (en) | 2011-06-27 | 2011-06-27 | Backlight drive circuit and liquid crystal TV set |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202210400U true CN202210400U (en) | 2012-05-02 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011202201789U Expired - Lifetime CN202210400U (en) | 2011-06-27 | 2011-06-27 | Backlight drive circuit and liquid crystal TV set |
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| Country | Link |
|---|---|
| CN (1) | CN202210400U (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102243850A (en) * | 2011-06-27 | 2011-11-16 | 青岛海信电器股份有限公司 | Backlight source driving circuit and driving circuit thereof as well as liquid crystal television |
| CN102752918A (en) * | 2012-06-15 | 2012-10-24 | 福建捷联电子有限公司 | Half-bridge-structure LED (light-emitting diode) drive circuit controlled by secondary side |
| CN104918386A (en) * | 2015-06-19 | 2015-09-16 | 青岛海信电器股份有限公司 | LED drive circuit and liquid crystal display device |
| CN106991978A (en) * | 2017-05-16 | 2017-07-28 | 深圳市华星光电技术有限公司 | A kind of backlight drive control circuit based on LLC |
| US10271392B2 (en) | 2017-05-16 | 2019-04-23 | Shenzhen China Star Optoelectronics Technology Co., Ltd. | LLC backlight driving control circuit |
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2011
- 2011-06-27 CN CN2011202201789U patent/CN202210400U/en not_active Expired - Lifetime
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102243850A (en) * | 2011-06-27 | 2011-11-16 | 青岛海信电器股份有限公司 | Backlight source driving circuit and driving circuit thereof as well as liquid crystal television |
| CN102243850B (en) * | 2011-06-27 | 2013-03-06 | 青岛海信电器股份有限公司 | Backlight source driving circuit, driving method thereof as well as liquid crystal television |
| CN102752918A (en) * | 2012-06-15 | 2012-10-24 | 福建捷联电子有限公司 | Half-bridge-structure LED (light-emitting diode) drive circuit controlled by secondary side |
| CN102752918B (en) * | 2012-06-15 | 2015-11-04 | 福建捷联电子有限公司 | A kind of LED drive circuit of half bridge architecture controlled by primary side |
| CN104918386A (en) * | 2015-06-19 | 2015-09-16 | 青岛海信电器股份有限公司 | LED drive circuit and liquid crystal display device |
| CN106991978A (en) * | 2017-05-16 | 2017-07-28 | 深圳市华星光电技术有限公司 | A kind of backlight drive control circuit based on LLC |
| WO2018209823A1 (en) * | 2017-05-16 | 2018-11-22 | 深圳市华星光电技术有限公司 | Llc-based backlight drive control circuit |
| US10271392B2 (en) | 2017-05-16 | 2019-04-23 | Shenzhen China Star Optoelectronics Technology Co., Ltd. | LLC backlight driving control circuit |
| CN106991978B (en) * | 2017-05-16 | 2020-04-10 | 深圳市华星光电技术有限公司 | Backlight drive control circuit based on LLC |
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| RGAV | Abandon patent right to avoid regrant |