CN205987484U - Backlight unit's drive circuit , backlight unit and display device - Google Patents

Abstract

The utility model discloses a backlight unit's drive circuit, backlight unit and display device, include: the output constant current control sub circuit of a constant current source signal is provided at least two way LED source's among the backlight unit positive pole, under the control of the duty cycle of the pulse width modulation signal of control chip output, the colour temperature that provides complemental the 2nd constant current source signal of duty cycle to at least two way LED source's negative pole respectively changes the control sub circuit. Because control chip is through changing control sub circuit output voltage control circuit modulating signal duty cycle to the colour temperature, it provides the duty cycle complemental the 2nd constant current source to each way LED source to control colour temperature change control sub circuit, when guaranteeing to offer each way LED source's total current invariant, can be according to the duty cycle change of control impuls modulated in width signal or invariable relatively, the photochromic temperature of total output of controlling each way LED source is at controllable change of required colour temperature within range or relatively fixed.

Description

Driving circuit of backlight module, backlight module and display device

technical field

The utility model relates to the technical field of driving a backlight module, in particular to a driving circuit of a backlight module, a backlight module and a display device.

Background technique

At present, in the domestic and foreign markets, the advantages of light emitting diodes (Light Emitting Diode, LED) such as small size, long life, high luminous efficiency, no radiation and low power consumption make consumers more and more popular with LED products, especially for LED products. LED products with dimming and color adjustment have been unanimously recognized by consumers. The so-called dimming is to adjust the brightness of the light source; the so-called color temperature is generally considered to be the adjustment of the color of the light source. The color temperature is the temperature of the black body when the color of the light emitted by the light source is the same as that of the black body at a certain temperature. In black body radiation, The color of light varies with temperature. The difference between color temperature and brightness often gives people different feelings. For example, under the illumination of high color temperature light source, low brightness will give people a cold atmosphere; under low color temperature light source, excessive brightness will give people a stuffy feeling. It can be seen that the precise adjustment of the brightness and color temperature of the light source is conducive to improving the market competitiveness of LED lighting products.

At present, the LED circuits with color adjustment function on the market are generally divided into two types, one is a simple three-stage color adjustment circuit, that is, it becomes a low color temperature after the first power-on, and becomes a middle color temperature after a power-off and power-on operation. Then turn it into high color temperature by power off and on, and then turn it into low color temperature by power off and on. The color temperature changes discontinuously, and the color temperature cannot be switched automatically. At the same time, the light is turned off during the color temperature switching process. The other is to change the color temperature of the light source through the color temperature control button on the remote control, but this change in color temperature is generally segment by segment rather than continuous. It is difficult to control the color temperature at the required color temperature point, and it also needs to be manually operated, and automatic changes cannot be achieved. Therefore, it is necessary to provide an LED driving circuit that can control the color temperature of the LED light source within a required color temperature range, so as to overcome the above-mentioned defects.

Utility model content

In view of this, the embodiments of the present invention provide a driving circuit of a backlight module, a backlight module and a display device, so as to control the color temperature of the LED light source within a required color temperature range.

Therefore, the utility model provides a driving circuit of a backlight module, comprising: a rectification and filtering subcircuit connected to an external AC power supply, an output constant current control subcircuit connected to the rectification and filtering subcircuit, and an output constant current control subcircuit connected to the output constant current The color temperature change control sub-circuit connected to the control sub-circuit, the power supply sub-circuit connected to the output constant current control sub-circuit, and the control sub-circuit respectively connected to the output constant current control sub-circuit, the color temperature change control sub-circuit and the power supply sub-circuit chip; among them,

The rectification and filtering sub-circuit is used to convert the AC power provided by the external AC power supply into a DC signal;

The power supply sub-circuit is used to supply power to the output constant current control sub-circuit under the control of the control chip;

The output constant current control sub-circuit is used to provide a first constant current signal to the anodes of at least two LED light sources included in the backlight module under the control of the control chip;

The color temperature change control sub-circuit is used to provide the negative poles of the at least two light-emitting diode light sources with a complementary second constant duty ratio under the control of the duty ratio of the pulse width modulation signal output by the control chip. current signal.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, the control chip is used to set the output duty cycle from 0 to 100% according to the preset cycle time. Then to 0 cyclically changing pulse width modulation signal.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, the backlight module includes two LED light sources; the color temperature change control sub-circuit includes: a first A switch tube, a second switch tube and a voltage dividing resistor; wherein,

The gate of the first switching tube is connected to the pin used to provide the pulse width modulation signal in the control chip, the drain is connected to the negative electrode of one LED light source, and the source is grounded;

The gate of the second switching tube is connected to the anode of each LED light source through the voltage dividing resistor, the drain is connected to the cathode of another LED light source, and the source is grounded.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, the output constant current control sub-circuit includes: a transformer, a third switch tube, a first resistor, a second resistor , the first capacitor, the third resistor, the fourth resistor, the first diode, the second diode and the first polarity capacitor; where,

The gate of the third switching tube is connected to the power supply sub-circuit, the drain is respectively connected to one end of the first winding on the primary side of the transformer and the anode of the first diode, and the source is connected to the control The pins used to provide switching signals in the chip are connected;

The cathode of the first diode is connected to the other end of the first winding on the primary side of the transformer after the third resistor is connected in series; and the other end of the first winding on the primary side of the transformer is connected to the rectifier filter The circuit is connected; the first capacitor is connected in parallel with the third resistor;

The first resistor and the second resistor are connected in parallel to the second winding on the primary side of the transformer after being connected in series, and the conduction point between the first resistor and the second resistor is connected to the control chip The pins for providing feedback signals are connected; one end of the second winding on the primary side of the transformer is connected to the power supply sub-circuit, and the other end is grounded;

The anode of the first polarity capacitor is respectively connected to the cathode of the second diode and the anode of the at least two LED light sources, and the cathode is connected to the other end of the secondary side winding of the transformer and grounded; The anode of the second diode is connected to one end of the secondary side winding of the transformer; the fourth resistor is connected in parallel with the first polarity capacitor.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, the power supply sub-circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a Two polar capacitors, a second capacitor, a third diode and a fourth diode; wherein,

The anode of the second polarity capacitor is connected to the pin used to provide a high-level signal in the control chip, and is connected to the cathode of the fourth diode through the eighth resistor, and the second polarity capacitor The negative pole is grounded; the positive pole of the fourth diode is connected to one end of the second winding on the primary side of the transformer;

One end of the seventh resistor is respectively connected to the other end of the rectifying and filtering sub-circuit and the first winding on the primary side of the transformer, and the other end of the seventh resistor is grounded through the second capacitor; the seventh The conduction point between the resistor and the second capacitor is connected to a pin for providing a gate signal in the control chip;

The cathode of the third diode is connected to the pin for providing gate signal in the control chip through the fifth resistor, and the anode of the third diode is connected to the control chip through the sixth resistor The pin for providing the gate signal is connected, and the anode of the third diode is connected with the gate of the third switch transistor.

In a possible implementation manner, the driving circuit of the above-mentioned backlight module provided in the embodiment of the present utility model further includes: an input connected between the rectification and filtering sub-circuit and the output constant current control sub-circuit A phase detection subcircuit; the input phase detection subcircuit is connected to the control chip, and is used to output a detection signal to the control chip according to the DC signal output by the rectification and filtering subcircuit;

The control chip is further configured to output a pulse width modulation signal with a fixed duty ratio when it is determined that the detection signal is not greater than a preset threshold; and output a pulse width modulation signal with a continuously changing duty ratio when it is determined that the detection signal is greater than a preset threshold.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, the input phase detection sub-circuit includes: a ninth resistor, a tenth resistor and a third capacitor; wherein,

The ninth resistor and the tenth resistor are connected in series between the rectification and filtering sub-circuit and ground;

The conduction point between the ninth resistor and the tenth resistor is connected to a pin of the control chip for receiving the detection signal;

One end of the third capacitor is connected to a pin of the control chip for receiving the detection signal, and the other end is grounded.

In a possible implementation manner, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, the rectification and filtering sub-circuit includes: a rectifier, an inductor, a sixth capacitor and a seventh capacitor; wherein,

The two input ends of the rectifier are connected to the external AC power supply, the first output end is grounded, and the second output end is connected to one end of the inductor;

One end of the inductor is grounded through the sixth capacitor, the other end is grounded through the seventh capacitor, and the other end is the output end of the direct current signal.

The utility model also provides a backlight module, including the driving circuit of the above-mentioned backlight module provided by the embodiment of the utility model, and at least two LED light sources.

The utility model also provides a display device, including the above-mentioned backlight module provided by the embodiment of the utility model.

The beneficial effects of the utility model are as follows:

A driving circuit for a backlight module, a backlight module, and a display device provided by an embodiment of the present invention include: a rectification and filtering sub-circuit for converting the AC power provided by an external AC power supply into a DC signal; A power supply sub-circuit for supplying power to the output constant current control sub-circuit under control; under the control of the control chip, the output constant current control for providing the first constant current signal to the anodes of at least two LED light sources included in the backlight module Subcircuit; under the control of the duty ratio of the pulse width modulation signal output by the control chip, the color temperature change control subcircuit is used to provide the negative poles of at least two LED light sources with a second constant current signal with complementary duty ratio. Since the control chip controls the color temperature change control sub-circuit to provide the second constant current with a complementary duty cycle to each light-emitting diode light source by outputting the duty ratio of the pulse width modulation signal to the color temperature change control sub-circuit. While the total current of the diode light source is constant, the total output light color temperature of each LED light source can be controlled to change or be relatively fixed according to the duty cycle of the control pulse width modulation signal. .

Description of drawings

Fig. 1 is the schematic structural diagram of the drive circuit of the backlight module provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of the time sequence of the drive circuit of the backlight module outputting two pulse width modulation signals with complementary duty ratios provided by the embodiment of the utility model;

FIG. 3 is a specific circuit structure diagram of the driving circuit of the backlight module provided by the embodiment of the present invention.

detailed description

The specific implementations of the driving circuit of the backlight module, the backlight module and the display device provided by the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

The embodiment of the utility model provides a driving circuit for a backlight module, as shown in FIG. 1 , comprising: a rectification and filtering sub-circuit 01 connected to an external AC power supply AC, and an output constant current control sub-circuit connected to the rectification and filtering sub-circuit 01 02, the color temperature change control subcircuit 03 connected to the output constant current control subcircuit 02, the power supply subcircuit 04 connected to the output constant current control subcircuit 02, and the output constant current control subcircuit 02 and the color temperature change control subcircuit 03 and the control chip 05 connected to the electronic circuit 04; wherein,

The rectifying and filtering sub-circuit 02 is used to convert the alternating current provided by the external alternating current power supply AC into a direct current signal;

The electronic circuit 04 is used to supply power to the output constant current control sub-circuit 02 under the control of the control chip 05;

The output constant current control sub-circuit 02 is used to provide a first constant current signal to the anodes of at least two LED light sources included in the backlight module under the control of the control chip 05;

The color temperature change control sub-circuit 03 is used to provide second constant current signals with complementary duty ratios to the cathodes of at least two LED light sources under the control of the duty ratio of the pulse width modulation signal output by the control chip 05 .

In the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, the control chip controls the color temperature change control sub-circuit to provide the duty cycle of each light-emitting diode light source by outputting the pulse width modulation signal duty cycle to the color temperature change control sub-circuit. The second constant current with a complementary duty ratio can control the total current of each LED light source according to the change or relatively constant duty cycle of the control pulse width modulation signal while ensuring that the total current supplied to each LED light source is constant. The color temperature of the output light can be controllably changed or relatively fixed within the required color temperature range.

In specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, the control chip is used to output the pulse whose duty cycle changes from 0 to 100% and then to 0 according to the preset cycle time. width modulated signal.

Specifically, the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention can be connected to multiple LED light sources, and by controlling the duty cycle of the current supplied to each LED light source, the total output light of the multiple LED light sources The color temperature is a fixed value or a continuously changing value within the desired color temperature range. The following take the connection of two LED light sources as an example to illustrate.

Specifically, the light-emitting diode light sources connected to the drive circuit of the above-mentioned backlight module provided by the embodiments of the present utility model can output continuously changing color temperatures as required, that is, can output regularly changing color temperatures, for example, it can be simulated from sunrise to sunset The time interval of is the cycle duration of daylight color temperature change. Taking the time interval from sunrise to sunset as an example of 12 hours, the cycle duration is 12 hours. As shown in FIG. 2 , the duty cycle q of the pulse width modulation signal corresponding to the high color temperature LED light source N is complementary to the duty cycle p of the pulse width modulation signal corresponding to the low color temperature LED light source M. In the half cycle of 6 hours, the control chip changes continuously from 0% to 100% by changing the duty ratio of the pulse width modulation signal, so as to realize the continuous change of the current flowing through the two light-emitting diode light sources with high and low color temperatures respectively, thereby making the two high and low color temperatures The color temperature of the LED light source can be automatically and continuously changed respectively, so that the comprehensive color temperature of the high and low color temperature LED light source can be changed according to the changing law of the color temperature of sunlight from sunrise to noon.

The following table shows the changing law of daylight color temperature from sunrise to sunset and the current ratio of the two LED light sources corresponding to high and low color temperatures:

As shown in the above table, the cycle time is 12 hours, simulating the time interval from sunrise to sunset, and each duty cycle of the pulse width modulation signal corresponds to controlling the color temperature value at each time point. The initial color temperature value of the high color temperature LED light source M is 6500K, the initial color temperature value of the low color temperature LED light source N is 2700K, and the comprehensive color temperature value W of the high and low color temperature LED light sources is the respective initial color temperature value and the corresponding pulse width modulation signal. The sum of the space ratio products, namely (6500q+2700p)K.

Specifically, at sunrise, the duty ratio of the pulse width modulation signal corresponding to the low color temperature light emitting diode light source is 100%, the current flowing through the low color temperature light emitting diode light source is 31mA, and the color temperature value corresponding to the low color temperature light emitting diode is 2700K; The duty cycle of the pulse width modulation signal corresponding to the high color temperature LED light source is 0%, the current flowing through the high color temperature LED light source is 0mA, and the color temperature value corresponding to the high color temperature LED light source is 6500K; the high and low color temperature two-way LED light source The integrated color temperature value is 2700K×100%+6500K×0%=2700K, which matches the daylight color temperature value of 2700K at sunrise. As the sunrise time increases, the color temperature of daylight increases gradually, until at noon, the color temperature of daylight reaches the maximum, which is 6500K; correspondingly, by increasing the duty cycle of the pulse width modulation signal corresponding to the high color temperature light-emitting diode light source, it decreases The duty cycle of the pulse width modulation signal corresponding to the low color temperature LED light source makes the integrated color temperature value of the high and low color temperature LED light sources gradually increase until the duty cycle of the pulse width modulation signal corresponding to the high color temperature LED light source is 100%. , when the duty ratio of the pulse width modulation signal corresponding to the low color temperature LED light source is 0%, the integrated color temperature value of the high and low color temperature LED light sources changes to 6500K, thus simulating the time period from sunrise to noon daylight color temperature.

After noon, the daylight color temperature value gradually decreases until sunset, and the daylight color temperature value gradually decreases to 2700K; correspondingly, by increasing the duty cycle of the pulse width modulation signal corresponding to the low color temperature LED light source, reducing the high color temperature LED light source The duty cycle of the corresponding pulse width modulation signal makes the comprehensive color temperature value of the high and low color temperature LED light source gradually decrease until the duty cycle of the pulse width modulation signal corresponding to the low color temperature LED light source is 100%, and the high color temperature LED light source is 100%. When the duty cycle of the pulse width modulation signal corresponding to the light source is 0%, the integrated color temperature value of the high and low color temperature LED light sources changes to 2700K, thus simulating the daylight color temperature value during the period from noon to sunset.

In this way, the duty ratio of the pulse width modulation signal corresponding to the high and low color temperature two-way LED light source is slowly changed through the way of complementary duty cycle, so that the current flowing through the high and low color temperature two-way light-emitting diode light source can be changed slowly, and then the high and low color temperature can be realized. The comprehensive color temperature of the two light-emitting diode light sources has undergone continuous and slow changes from 2700K to 6500K and then to 2700K, simulating the changing law of daylight color temperature from sunrise to sunset.

During specific implementation, in the drive circuit of the above-mentioned backlight module provided by the embodiment of the present utility model, as shown in FIG. A switch tube Q1, a second switch tube Q2 and a voltage dividing resistor; wherein,

The gate of the first switching tube Q1 is connected to the pin 1 for providing the pulse width modulation signal in the control chip 05, the drain is connected to the negative electrode LED1- of a light-emitting diode light source, and the source is grounded;

The gate of the second switching tube Q2 is connected to the anode LED+ of each LED light source through a voltage dividing resistor, the drain is connected to the negative LED2- of another LED light source, and the source is grounded.

Specifically, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, the pin 1 of the control chip 05 outputs a series of pulse width modulation signals according to a certain frequency to control the first switching tube Q1 and the second switching tube Q2 is turned on and off. When the pin 1 outputs a high level, the first switch tube Q1 is turned on, the gate of the second switch tube Q2 is pulled down, and the second switch tube Q2 is turned off; when the pin 1 outputs a low level, the first switch tube Q1 The gate of the switch is pulled low, the first switching tube Q1 is turned off, and the second switching tube Q2 is turned on. Therefore, the first switching tube Q1 and the second switching tube Q2 are always one on and one off, forming a complementary state.

Further, the pin 1 used to provide the pulse width modulation signal in the control chip 05 can be set according to the number of LED light sources. For example, when there are three or four LED light sources, there are two pins 1; for another example, when there are five or six LED light sources, there are three pins 1. By analogy, when there are 2n-1 or 2n LED light sources, there are n pins 1, where n is an integer greater than or equal to 2.

It is worth noting that because the frequency of the pulse width modulation signal output by pin 1 is very high, there is no change of on and off, but only the increase or decrease of brightness. Since the two groups of LED light sources are connected in parallel to both ends of the first polarity capacitor C1', the total current flowing through the two groups of LED light sources is constant. That is to say, the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention can also realize the effects of avoiding the light-off phenomenon and maintaining a constant total output current during the color temperature change process.

During specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, as shown in FIG. 3 , the output constant current control sub-circuit 02 may include: R1, the second resistor R2, the first capacitor C1, the third resistor R3, the fourth resistor R4, the first diode D1, the second diode D2 and the first polarity capacitor C1'; wherein,

The gate of the third switching tube Q3 is connected to the power supply circuit 04, the drain is respectively connected to one end of the first winding A1 on the primary side of the transformer T and the anode of the first diode D1, and the source is connected to the control chip 05 for The pin 2 that provides the switching signal is connected;

The negative pole of the first diode D1 is connected to the other end of the primary side first winding A1 of the transformer T after the third resistor R3 is connected in series; and the other end of the primary side first winding A1 of the transformer T is connected to the rectifying and filtering sub-circuit 01; The first capacitor C1 is connected in parallel with the third resistor R3;

The first resistor R1 and the second resistor R2 are connected in parallel with the primary side second winding A2 of the transformer T after being connected in series, and the conduction point between the first resistor R1 and the second resistor R2 is used to provide a feedback signal with the control chip 05 The pin 3 of the transformer T is connected; one end of the secondary winding A2 on the primary side of the transformer T is connected to the power supply sub-circuit 04, and the other end is grounded;

The anode of the first polarity capacitor C1' is respectively connected to the cathode of the second diode D2 and the anode LED+ of at least two LED light sources, and the cathode is connected to the other end of the secondary side winding B of the transformer T and grounded; the second The anode of the diode D2 is connected to one end of the secondary winding B of the transformer T; the fourth resistor R4 is connected in parallel with the first polarity capacitor C1 ′.

Specifically, since the color temperature control sub-circuit 03 and the output constant current control sub-circuit 02 need to be controlled by the same control chip 05, they must have a common ground potential. The general step-down transformer topology and buck-boost It is difficult to realize this function with the traditional transformer topology, and even if it is realized, it cannot pass the relevant certification due to the excessive electromagnetic noise. The flyback topology separates the two circuits electrically through the principle of transformer coupling, and only needs to connect the required ground potential point with the ground potential of the control chip. Therefore, the output constant current control sub-circuit 02 adopts a reverse form of excited topology. The flyback topology adopts the source-side feedback mode for constant current control, which simplifies the peripheral control circuit and reduces the overall cost.

During specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, the power supply sub-circuit 04 can supply power to the output constant current control sub-circuit 02 under the control of the control chip 05 . As shown in Figure 3, the power supply circuit 04 specifically includes: a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second polarity capacitor C2', a second capacitor C2, a third diode Tube D3 and fourth diode D4; where,

The anode of the second polarity capacitor C2' is connected to the pin 4 for providing a high-level signal in the control chip 05, and is connected to the cathode of the fourth diode D4 through the eighth resistor R8, and the second polarity capacitor C2 The negative pole of ' is grounded; the positive pole of the fourth diode D4 is connected to one end of the primary side second winding A2 of the transformer T;

One end of the seventh resistor R7 is respectively connected to the other end of the rectifying and filtering sub-circuit 01 and the first winding A1 on the primary side of the transformer T, and the other end of the seventh resistor R7 is grounded through the second capacitor C2; the seventh resistor R7 is connected to the second capacitor The conduction point between C2 is connected with the pin 5 for providing gate signal in the control chip 05;

The cathode of the third diode D3 is connected to the pin 5 used to provide the gate signal in the control chip 05 through the fifth resistor R5, and the anode of the third diode D3 is connected to the pin 5 in the control chip 05 through the sixth resistor R6. The pin 5 providing the gate signal is connected, and the anode of the third diode D3 is connected to the gate of the third switching transistor Q3.

During specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, as shown in FIG. 1 , it may also include: The input phase detection sub-circuit 06; the input phase detection sub-circuit 06 is connected to the control chip 05, and is used to output a detection signal to the control chip 05 according to the DC signal output by the rectification and filtering sub-circuit 01;

The control chip 05 is also used to output a pulse width modulation signal with a fixed duty ratio when it is determined that the detection signal is not greater than a preset threshold; output a pulse width modulation signal with a continuously changing duty ratio when it is determined that the detection signal is greater than a preset threshold.

Specifically, when the input phase detection sub-circuit 06 is powered off, it means that the detection signal output to the control chip 05 is not greater than the preset threshold. At this time, the control chip 05 outputs a pulse width modulation signal with a fixed duty cycle to control the flow The current passing through each LED light source remains unchanged, so that the color temperature of each LED light source stays at the required color temperature point; when the input phase detection sub-circuit 06 is powered on, it means that the detection signal output to the control chip 05 is greater than The threshold is preset. At this time, the control chip 05 outputs a pulse width modulation signal with a continuously changing duty cycle to control the continuous change of the current flowing through each LED light source, so that the color temperature of each LED light source can be automatically continuous. Variety.

In specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, as shown in FIG. 3 , the input phase detection sub-circuit 06 may include: a ninth resistor R9, a tenth resistor R10 and a third capacitor C3; where,

The ninth resistor R9 and the tenth resistor R10 are connected in series between the rectifying and filtering sub-circuit 01 and the ground;

The conduction point between the ninth resistor R9 and the tenth resistor R10 is connected to the pin 6 for receiving the detection signal in the control chip 05;

One end of the third capacitor C3 is connected to the pin 6 of the control chip 05 for receiving the detection signal, and the other end is grounded.

Specifically, the input phase detection sub-circuit 06 senses whether the input exists by detecting whether the voltage of the third capacitor C3 is zero. The input phase detection sub-circuit 06 charges the third capacitor C3 through the ninth resistor R9, and the ninth resistor R9 and the tenth resistor R10 form a voltage divider circuit to control the upper limit of the voltage on the third capacitor C3. The third capacitor C3 is connected to the pin 6 used to receive the detection signal in the control chip 05. The corresponding threshold point is set inside the control chip 05. When the voltage of the third capacitor C3 is greater than the threshold point, it means that the input phase detection sub-circuit 06 After being powered on, when the voltage of the third capacitor C3 is not greater than the threshold point, it means that the input phase detection sub-circuit 06 has been powered off. When the power is off, because the driving circuit of the backlight module has a memory function within a certain period of time, the driving circuit of the backlight module will automatically store the duty cycle at the time of power off, and then restore the duty cycle before power off when the power is on again. configuration, continue to output the duty cycle, and continue all the time, so that the color temperature of the light emitting diode light source is always maintained at the color temperature point corresponding to the duty cycle when the power is turned off.

During specific implementation, in the driving circuit of the above-mentioned backlight module provided by the embodiment of the present invention, as shown in FIG. 3 , in order to convert the alternating current provided by the external alternating current power supply AC into a direct current signal, the rectifying and filtering sub-circuit 01 may include: Rectifier DB, inductor L, sixth capacitor C6 and seventh capacitor C7; wherein,

The two input ends of the rectifier DB are connected to an external AC power supply, the first output end is grounded, and the second output end is connected to one end of the inductor L;

One end of the inductor L is grounded through the sixth capacitor C6, the other end is grounded through the seventh capacitor C7, and the other end is the output end of the DC signal.

Based on the same concept of the utility model, an embodiment of the utility model provides a backlight module, including the driving circuit of the above-mentioned backlight module provided by the embodiment of the utility model, and at least two LED light sources. For the implementation of the backlight module, reference may be made to the above-mentioned embodiment of the driving circuit of the backlight module, and repeated descriptions will not be repeated.

Based on the same concept of the utility model, an embodiment of the utility model provides a display device, including the above-mentioned backlight module provided by the embodiment of the utility model. The display device may be any product or component with a display function such as a mobile phone, a tablet computer, a television, a monitor, a notebook computer, a digital photo frame, a navigator, and the like. For the implementation of the display device, reference may be made to the above-mentioned embodiments of the backlight module, and repeated descriptions will not be repeated.

The above-mentioned backlight module drive circuit, backlight module and display device provided by the utility model include: a rectification and filtering sub-circuit for converting the AC power provided by the external AC power supply into a DC signal; A power supply circuit for outputting power to the constant current control sub-circuit; an output constant current control sub-circuit for providing a first constant current signal to the anodes of at least two LED light sources included in the backlight module under the control of the control chip; The color temperature change control sub-circuit is used to provide the negative poles of at least two LED light sources with a second constant current signal with complementary duty ratio under the control of the duty ratio of the pulse width modulation signal output by the control chip. Since the control chip controls the color temperature change control sub-circuit to provide the second constant current with complementary duty ratio to each light-emitting diode light source by outputting the duty cycle of the pulse width modulation signal to the color temperature change control sub-circuit, it ensures that the light-emitting diodes flowing through each path The change of the current of the diode light source relative to the duty ratio of the pulse width modulation signal is constant, therefore, the comprehensive color temperature of each light emitting diode light source can be changed within the required color temperature range.

Obviously, those skilled in the art can make various changes and modifications to the utility model without departing from the spirit and scope of the utility model. In this way, if these modifications and variations of the utility model fall within the scope of the claims of the utility model and equivalent technologies thereof, the utility model is also intended to include these modifications and variations.

Claims (10)

1. A driving circuit for a backlight module, comprising: a rectifying and filtering subcircuit connected to an external AC power supply, an output constant current control subcircuit connected to the rectifying and filtering subcircuit, and a constant current control subcircuit connected to the output constant current The color temperature change control sub-circuit connected to the control sub-circuit, the power supply sub-circuit connected to the output constant current control sub-circuit, and the control sub-circuit respectively connected to the output constant current control sub-circuit, the color temperature change control sub-circuit and the power supply sub-circuit chip; among them, The rectification and filtering sub-circuit is used to convert the AC power provided by the external AC power supply into a DC signal; The power supply sub-circuit is used to supply power to the output constant current control sub-circuit under the control of the control chip; The output constant current control sub-circuit is used to provide a first constant current signal to the anodes of at least two LED light sources included in the backlight module under the control of the control chip; The color temperature change control sub-circuit is used to provide the negative poles of the at least two light-emitting diode light sources with a complementary second constant duty ratio under the control of the duty ratio of the pulse width modulation signal output by the control chip. current signal. 2. The driving circuit according to claim 1, wherein the control chip is configured to output a pulse width modulation signal whose duty ratio changes cyclically from 0 to 100% and then to 0 according to a preset cycle time. . 3. The drive circuit according to claim 1, wherein the backlight module includes two LED light sources; the color temperature change control sub-circuit includes: a first switch tube, a second switch tube and a voltage divider resistance; among them, The gate of the first switching tube is connected to the pin used to provide the pulse width modulation signal in the control chip, the drain is connected to the negative electrode of one LED light source, and the source is grounded; The gate of the second switching tube is connected to the anode of each LED light source through the voltage dividing resistor, the drain is connected to the cathode of another LED light source, and the source is grounded. 4. The drive circuit according to claim 1, wherein the output constant current control sub-circuit comprises: a transformer, a third switch tube, a first resistor, a second resistor, a first capacitor, a third resistor, a second Four resistors, a first diode, a second diode and a first polarity capacitor; where, The gate of the third switching tube is connected to the power supply sub-circuit, the drain is respectively connected to one end of the first winding on the primary side of the transformer and the anode of the first diode, and the source is connected to the control The pins used to provide switching signals in the chip are connected; The cathode of the first diode is connected to the other end of the first winding on the primary side of the transformer after the third resistor is connected in series; and the other end of the first winding on the primary side of the transformer is connected to the rectifier filter The circuit is connected; the first capacitor is connected in parallel with the third resistor; The first resistor and the second resistor are connected in parallel to the second winding on the primary side of the transformer after being connected in series, and the conduction point between the first resistor and the second resistor is connected to the control chip The pins for providing feedback signals are connected; one end of the second winding on the primary side of the transformer is connected to the power supply sub-circuit, and the other end is grounded; The anode of the first polarity capacitor is respectively connected to the cathode of the second diode and the anode of the at least two LED light sources, and the cathode is connected to the other end of the secondary side winding of the transformer and grounded; The anode of the second diode is connected to one end of the secondary side winding of the transformer; the fourth resistor is connected in parallel with the first polarity capacitor. 5. The drive circuit according to claim 4, wherein the power supply sub-circuit comprises: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second polarity capacitor, a second capacitor, a Three diodes and a fourth diode; where, The anode of the second polarity capacitor is connected to the pin used to provide a high-level signal in the control chip, and is connected to the cathode of the fourth diode through the eighth resistor, and the second polarity capacitor The negative pole is grounded; the positive pole of the fourth diode is connected to one end of the second winding on the primary side of the transformer; One end of the seventh resistor is respectively connected to the other end of the rectifying and filtering sub-circuit and the first winding on the primary side of the transformer, and the other end of the seventh resistor is grounded through the second capacitor; the seventh The conduction point between the resistor and the second capacitor is connected to a pin for providing a gate signal in the control chip; The cathode of the third diode is connected to the pin for providing gate signal in the control chip through the fifth resistor, and the anode of the third diode is connected to the control chip through the sixth resistor The pin for providing the gate signal is connected, and the anode of the third diode is connected with the gate of the third switch transistor. 6. The drive circuit according to any one of claims 1-5, further comprising: an input phase detection subcircuit connected between the rectification and filtering subcircuit and the output constant current control subcircuit; The input phase detection sub-circuit is connected to the control chip, and is used to output a detection signal to the control chip according to the DC signal output by the rectification and filtering sub-circuit; The control chip is further configured to output a pulse width modulation signal with a fixed duty ratio when it is determined that the detection signal is not greater than a preset threshold; and output a pulse width modulation signal with a continuously changing duty ratio when it is determined that the detection signal is greater than a preset threshold. 7. The drive circuit according to claim 6, wherein the input phase detection sub-circuit comprises: a ninth resistor, a tenth resistor and a third capacitor; wherein, The ninth resistor and the tenth resistor are connected in series between the rectification and filtering sub-circuit and ground; The conduction point between the ninth resistor and the tenth resistor is connected to a pin of the control chip for receiving the detection signal; One end of the third capacitor is connected to a pin of the control chip for receiving the detection signal, and the other end is grounded. 8. The driving circuit according to any one of claims 1-5, wherein the rectification and filtering sub-circuit comprises: a rectifier, an inductor, a sixth capacitor and a seventh capacitor; wherein, The two input ends of the rectifier are connected to the external AC power supply, the first output end is grounded, and the second output end is connected to one end of the inductor; One end of the inductor is grounded through the sixth capacitor, the other end is grounded through the seventh capacitor, and the other end is the output end of the direct current signal. 9. A backlight module, characterized by comprising: the driving circuit of the backlight module according to any one of claims 1-8, and at least two LED light sources. 10. A display device, comprising: the backlight module according to claim 9.