CN118711535B

CN118711535B - Backlight driving circuit, backlight driving board and backlight driving method

Info

Publication number: CN118711535B
Application number: CN202410675921.1A
Authority: CN
Inventors: 赵玉成; 杨明明; 栗首; 孟智明; 李文禹; 李耀龙; 万争艳
Original assignee: BOE Technology Group Co Ltd; Hefei BOE Optoelectronics Technology Co Ltd
Current assignee: BOE Technology Group Co Ltd; Hefei BOE Optoelectronics Technology Co Ltd
Priority date: 2024-05-27
Filing date: 2024-05-27
Publication date: 2025-10-28
Anticipated expiration: 2044-05-27
Also published as: CN118711535A

Abstract

The present invention discloses a backlight driving circuit, a backlight driving board and a backlight driving method. The backlight driving circuit includes a boost circuit and a microcontroller. The boost circuit outputs a driving voltage to the backlight module according to a driving voltage output mode. The driving voltage output mode includes a first driving voltage output mode. The first driving voltage output mode outputs a driving voltage to the backlight module in time periods up to a rated driving voltage. The microcontroller is configured to detect the ambient temperature of the backlight module and adjust the driving voltage output mode according to changes in the ambient temperature. It can be seen that the present application can adjust the driving voltage output mode of the boost circuit according to the ambient temperature of the backlight module, so that the boost circuit can work stably, improve the low-temperature startup of the wide-temperature and high-brightness backlight module, and solve the problem of backlight flickering when the backlight module is cold-started in a low-temperature environment, thereby improving the user experience.

Description

Backlight driving circuit, backlight driving plate and backlight driving method

Technical Field

The present invention relates to the field of display technologies, and in particular, to a backlight driving circuit, a backlight driving board, and a backlight driving method.

Background

At present, the demand for large-size wide Wen Gaoliang display products in the market is higher and higher, the brightness of some products is as high as 3500nit, the display products have Local Dimming (LD) function, a Converter board card partition is needed to control backlight LED lamps, and a direct current-direct current (DC-DC) boost driving scheme is needed to be adopted. The Converter board is a control board for driving the backlight LED lamps.

However, width Wen Gaoliang shows that when the product adopts a DC-DC backlight driving scheme, the problem of backlight flickering occurs when the product is cold started in a low-temperature (-30 ℃ and below) environment, and the use is greatly influenced.

Therefore, how to improve the low temperature start-up of the wide Wen Gaoliang display product is a technical problem to be solved in the art.

Disclosure of Invention

In view of the above, the embodiment of the invention provides a backlight driving circuit, a backlight driving board and a backlight driving method, which are used for solving the problem of abnormal low-temperature starting of a display product with a width Wen Gaoliang in the prior art.

The backlight driving circuit provided by the embodiment of the invention is used for driving a backlight module to light and comprises a booster circuit and a microcontroller, wherein the input end of the booster circuit is connected with a power supply, and the output end of the booster circuit is connected with the backlight module;

the step-up circuit is configured to output driving voltage to the backlight module according to a driving voltage output mode, wherein the driving voltage output mode comprises a first driving voltage output mode, and the first driving voltage output mode is used for outputting driving voltage to the backlight module to rated driving voltage in a time-sharing mode;

The microcontroller is configured to detect the ambient temperature of the backlight module and adjust the driving voltage output mode according to the change of the ambient temperature.

In one possible implementation manner, the first driving voltage output mode is that a first driving voltage is output to the backlight module in a first time period, a second driving voltage is output to the backlight module in a second time period, and a rated driving voltage is output to the backlight module in an nth time period, wherein the first driving voltage is smaller than the second driving voltage, and the second driving voltage is smaller than the rated driving voltage.

In one possible implementation manner, the first driving voltage output manner is to output a first driving voltage to the backlight module in a first period of time and output a rated driving voltage to the backlight module in a second period of time;

The ratio of the first driving voltage to the rated driving voltage is a first ratio, the first ratio is more than or equal to 20% and less than or equal to 50%, and/or the ratio of the second time period to the first time period is a second ratio, and the second ratio is more than or equal to 2.

In one possible implementation, the first period of time is greater than or equal to 5 seconds and less than or equal to 15 seconds.

In one possible implementation manner, the microcontroller is configured to adjust the driving voltage output mode of the boost circuit to be a first driving voltage output mode when the ambient temperature is lower than the first temperature, and otherwise adjust the driving voltage output mode of the boost circuit to be a second driving voltage output mode, where the second driving voltage output mode is to directly output the rated driving voltage to the backlight module.

In one possible implementation, the first temperature is equal to or less than-20 ℃.

In one possible implementation, the boost circuit comprises an inductor, a diode, a first triode, a direct current boost chip, a loop and an electrolytic capacitor;

The first end of the first triode is connected with the second end of the inductor, the second end of the first triode is grounded, the gate end of the first triode is connected with the output end of the direct current boost chip, the input end of the direct current boost chip is connected with the first end of the loop, and the second end of the loop is grounded;

the direct current boosting chip outputs a Pulse Width Modulation (PWM) signal to the first triode so as to control the driving voltage output by the output end of the boosting circuit;

the electrolytic capacitor satisfies the following relation:

wherein Wesr denotes a zero frequency of the circuit, ESR denotes an impedance of the electrolytic capacitor, C denotes a capacitance value of the electrolytic capacitor, f1 denotes 1/20 of a switching frequency of the PWM signal, and f2 denotes 1/10 of the switching frequency of the PWM signal.

In one possible implementation, the loop includes a first resistor, a first capacitor, and a second capacitor;

The first end of the first resistor is connected with the first end of the loop, the second end of the first resistor is connected with the first end of the second capacitor, the second end of the second capacitor is connected with the second end of the loop, the first end of the first capacitor is connected with the first end of the loop, and the second end of the first capacitor is connected with the second end of the loop.

In one possible implementation, the backlight driving circuit further includes a temperature detection circuit;

The first resistor comprises a first sub resistor, a second triode and a second sub resistor;

The first end of the first sub resistor is connected with the first end of the first resistor, the second end of the first sub resistor is connected with the second end of the first resistor, the first end of the second triode is connected with the first end of the first resistor, the second end of the second triode is connected with the first end of the second sub resistor, the second end of the second sub resistor is connected with the second end of the first resistor, and the gate end of the second triode is connected with the output end of the microcontroller;

When the temperature is smaller than or equal to the second temperature, the microcontroller controls the second triode to be opened, and the resistor connected in series in the loop is the second sub-resistor.

In one possible implementation, the temperature detection circuit includes a second resistor, a fourth capacitor, and a thermistor;

The first end of the second resistor is connected with the output end of the temperature detection circuit, the second end of the second resistor is grounded, the first end of the fourth capacitor is connected with the output end of the temperature detection circuit, the second end of the fourth capacitor is grounded, the first end of the thermistor is connected with the output end of the temperature detection circuit, and the second end of the thermistor is connected with a power supply.

On the other hand, the embodiment of the invention also provides a backlight driving board, which comprises the backlight driving circuit in the embodiment.

On the other hand, the embodiment of the invention also provides a backlight driving method, which comprises the following steps:

detecting the ambient temperature of the backlight module;

when the ambient temperature is lower than a first temperature, adjusting the output mode of the driving voltage output to the backlight module to be a first driving voltage output mode, wherein the first driving voltage output mode is to output the driving voltage to the backlight module to the rated driving voltage in a time-sharing mode;

When the ambient temperature is not lower than the first temperature, the driving voltage output mode output to the backlight module is adjusted to be a second driving voltage output mode, and the second driving voltage output mode is to directly output rated driving voltage to the backlight module.

In one possible implementation manner, the first driving voltage output manner specifically includes outputting a first driving voltage to the backlight module in a first period of time, outputting a second driving voltage to the backlight module in a second period of time, and outputting a rated driving voltage to the backlight module in an nth period of time, where the first driving voltage is smaller than the second driving voltage, and the second driving voltage is smaller than the rated driving voltage.

The embodiment of the invention has the following beneficial effects:

The backlight driving circuit comprises a boosting circuit and a microcontroller, wherein the boosting circuit outputs driving voltage to the backlight module according to a driving voltage output mode, the driving voltage output mode comprises a first driving voltage output mode, the first driving voltage output mode is used for outputting driving voltage to the backlight module to rated driving voltage in a time-sharing mode, and the microcontroller is used for detecting the ambient temperature of the backlight module and adjusting the driving voltage output mode according to the change of the ambient temperature. Therefore, the application can adjust the driving voltage output mode of the booster circuit according to the ambient temperature of the backlight module, thereby realizing the adjustment of the driving power of the backlight module according to the ambient temperature, reducing the driving power of the backlight module at low temperature, ensuring normal starting, then gradually increasing the driving power to light the backlight module at full power, leading the booster circuit to work stably, improving the low-temperature starting of the wide Wen Gaoliang backlight module, solving the problem that the backlight module can flash when being started at low temperature, and improving the user experience.

Drawings

FIG. 1 is a circuit diagram of a boost circuit;

FIG. 2 is a graph showing the actual measurement of 60% of the amplitude of the Gate signal ripple over-voltage at low temperature;

FIG. 3 is a graph showing a specific backlight PWM versus time;

FIG. 4 is a flowchart showing a specific progressive increase in backlight PWM;

FIG. 5A is a diagram showing one of actual current waveforms of the actual Converter board;

FIG. 5B is a diagram showing a second waveform of the actual current of the actual Converter board;

FIG. 6A shows one of the actual test results of the relationship between the PWM and the driving current of the backlight in the stepping stage;

FIG. 6B shows a second actual test result of the relationship between the PWM and the driving current of the backlight in the step stage;

FIG. 7 is a diagram of a loop unstable state Bott;

FIG. 8 shows a loop steady state Bode diagram;

FIG. 9 is a graph showing a low temperature loop stabilized Gate waveform;

fig. 10 is a circuit diagram of a backlight driving circuit.

Detailed Description

For ease of understanding, some technical terms used in the present application are described below.

Converter is a circuit for converting a direct current input voltage into a different direct current output voltage by using the action of a high-frequency switch, and the circuit comprises an inductance filter element and a capacitance filter element. The Converter board is a control board for driving backlight LED lamps, and is also referred to as a backlight driving board in the present application.

Boost IC, namely a direct current Boost chip, wherein a Boost circuit refers to the general name of a Boost part circuit in a Converter board card, and is also called a Boost circuit in the application.

PWM is known as Pulse-width modulation, which is an abbreviation for Pulse width modulation. Pulse width modulation is a digital coding method of analog signal level. The PWM signal is a change in signal, energy, etc. that is adjusted by adjusting a change in duty cycle.

LD, english is called Local Dimming, meaning of Local backlight adjustment. The backlight LEDs can be adjusted according to the brightness of the image, the brightness of the highlight part in the displayed image can be maximized, and the dark part can be reduced in brightness and even turned off, so that the optimal contrast ratio is achieved. Thus, the reduction of the brightness of the dark area reduces the power consumption of the backlight.

ESR, english, is known as Equivalent SERIES RESISTANCE, and refers to the Equivalent series resistance (or impedance) of a capacitor.

MCU is short for microcontroller (Microprogrammed Control Unit), is the main control chip on the Converter board card.

NTC is totally called Negative temperature coefficient, is short for negative temperature coefficient, and means that the resistance value shows a decreasing trend along with the increase of temperature. Are commonly used as temperature sensors.

Specific embodiments of a backlight driving circuit, a backlight driving board and a backlight driving method according to embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Fig. 1 is a circuit diagram of a boost circuit according to an embodiment of the present invention, an input terminal Vin of the boost circuit is connected to a power supply, and an output terminal Vout of the boost circuit is connected to a load. The load may be a backlight module.

The BOOST circuit specifically comprises an inductor L1, a diode D1, a first triode Q1, a direct-current BOOST chip BOOST IC, a loop and an electrolytic capacitor C3, wherein the loop comprises a first resistor R1, a first capacitor C1 and a second capacitor C2.

The first end of the inductor L1 is connected with the input end of the boost circuit, the second end of the inductor L1 is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the output end of the boost circuit, the first end of the first triode Q1 is connected with the second end of the inductor L1, the second end of the first triode Q1 is grounded, the Gate end Gate of the first triode Q1 is connected with the output end of the direct current boost chip, the input end of the direct current boost chip is connected with the first end COMP of the loop, the second end of the loop is grounded, the anode of the electrolytic capacitor C3 is connected with the output end of the boost circuit, and the cathode of the electrolytic capacitor C3 is grounded.

The first end of the first resistor R1 is connected with the first end of the loop, the second end of the first resistor R1 is connected with the first end of the second capacitor C2, the second end of the second capacitor C2 is connected with the second end of the loop, the first end of the first capacitor C1 is connected with the first end of the loop, and the second end of the first capacitor C1 is connected with the second end of the loop.

The direct current boost chip outputs a Pulse Width Modulation (PWM) signal to the first triode Q1 so as to control the voltage of the output end of the boost circuit. The first transistor Q1 may be a MOS transistor.

In the product environment reliability test, the low-temperature start requires the backlight module to be started every 8 hours under the condition that the ambient temperature is minus 30 ℃, the backlight brightness and the power consumption are in the highest product design state during the start, the backlight module is started for 3 times within 24 hours, and the backlight module can normally display and pass without other anomalies. Some product items all exhibited backlight flicker during the test at-30 ℃ start-up.

As shown in fig. 2, it can be seen through waveform testing that abnormal fluctuations exist in the Gate control signal for the BOOST IC output control Q1 in the BOOST circuit at low temperature, and the Gate signal ripple exceeds 60% of the Gate signal voltage amplitude, and is far higher than the 10% ripple upper limit, so that the output Vout of the BOOST circuit is in an unstable state, thereby causing backlight flicker.

The state of the Gate signal is limited by whether a loop is stable in the booster circuit, and when the loop is in an unstable state, the waveform ripple of the Gate signal is large, so that the backlight flicker is caused by the abnormal Q1 switch. The ESR parameter of the electrolytic capacitor C3 participates in loop calculation, and it can be seen from the test data (table 1 below) of the electrolytic capacitor C3 according to the temperature change that the ESR is about 0.682 Ω at 25 ℃ and about 8.208 Ω at-20 ℃, which are about 12 times different from the normal temperature state, and the ESR is not much different from the normal temperature state when the ambient temperature is 60 ℃. Thus, the lower the temperature, the higher the ESR, and the larger the difference from the normal temperature state, the larger the influence on the loop.

The power consumption can be reduced by adjusting the backlight brightness in the initial starting state to effectively improve the defect, and according to the defect characteristics, when the initial power-on driving power is 50% under the condition of not changing hardware, the loop is in a stable state, and the backlight display is normal. After the time of 30S, when the temperature of the electrolytic capacitor C3 is raised to be higher than 0 ℃ due to self-heating of the circuit, the ESR parameter is smaller than 2Ω, and when the driving power is increased to 100%, the loop is still stable. Therefore, the problem can be improved when the driving power is cut to 100% after the components are heated in the low power state.

In view of the above, the embodiment of the invention provides a backlight driving circuit for driving a backlight module to light. The backlight driving circuit specifically comprises a booster circuit and a microcontroller, wherein the booster circuit is shown in fig. 1, the input end of the booster circuit is connected with a power supply, and the output end of the booster circuit is connected with the backlight module.

The step-up circuit is configured to output driving voltage to the backlight module according to a preset driving voltage output mode, wherein the driving voltage output mode comprises a first driving voltage output mode, and the first driving voltage output mode is used for outputting driving voltage to the backlight module to rated driving voltage in a time-sharing mode.

The driving voltage output mode may further include a first driving voltage output mode, and the second driving voltage output mode is to directly output the rated driving voltage to the backlight module.

Specifically, in the first driving voltage output mode, the driving voltage is output to the backlight module to the rated driving voltage in a time-division manner, and various implementation modes are possible.

In one implementation manner, the first driving voltage output manner is to output a first driving voltage to the backlight module in a first time period, output a second driving voltage to the backlight module in a second time period, and output a rated driving voltage to the backlight module in an nth time period, wherein the first driving voltage is smaller than the second driving voltage, and the second driving voltage is smaller than the rated driving voltage.

In another implementation manner, the first driving voltage output mode is to output a first driving voltage to the backlight module in a first time period and output a rated driving voltage to the backlight module in a second time period;

specifically, the ratio of the first driving voltage to the rated driving voltage is a first ratio, the first ratio is greater than or equal to 20% and less than or equal to 50%, and/or the ratio of the second time period to the first time period is a second ratio, and the second ratio is greater than or equal to 2.

That is, in the first driving voltage output mode, the range of the first driving voltage output to the backlight module in the first period may be set to be between 20% and 50% of the rated driving voltage, and the driving voltage output to the backlight module in the second period is 100% of the rated driving voltage. The duration of the second period of time may be set to be twice or more than twice the duration of the first period of time.

Specifically, in some embodiments, the time period of the first period may be set to be 5 seconds or more and 15 seconds or less.

Specifically, when the ambient temperature is lower than the first temperature, the microcontroller adjusts the driving voltage output mode of the booster circuit to be a first driving voltage output mode, and otherwise adjusts the driving voltage output mode of the booster circuit to be a second driving voltage output mode.

In practical application, the first temperature may be set to be less than or equal to-20 ℃, or may be set according to practical situations, which is not limited in the present application.

For example:

when the ambient temperature is detected to be lower than-20 ℃, the microcontroller can adjust the backlight PWM signal of the control driving voltage of the boost circuit as follows:

1. At the beginning of power-on, the PWM output duty ratio range of the backlight is more than or equal to 20 percent, and is continuously lightened for 5-15 s less than or equal to 50 percent, and the backlight is firstly and initially stabilized and lightened;

2. Then, stepping to reach PWM 100% output within 45-60 s, wherein the total time from power-on to PWM 100% output is required to be not more than 60s and not less than 45s;

fig. 3 is a graph showing a specific backlight PWM versus time, and fig. 4 is a flowchart showing a specific progressive increase of backlight PWM.

As shown in fig. 3 and 4, in the product environment reliability test, the initial PWM duty cycle was set to be 30% at power-up, and the lighting was continued for 10s, then the stepping was set to be increased by 0.5% every 250ms, and finally 100% power output was reached at 45 s. Fig. 5A shows one of the actual current waveforms of the actual Converter board, and fig. 5B shows the second of the actual current waveforms of the actual Converter board.

As shown in fig. 5A, after the power is turned on, as the driving voltage increases to V2 (V2 is 30% of the rated driving voltage), the driving current increases to 3.497a for 10s, which is consistent with the setting parameters of fig. 3 and 4, then as the driving voltage increases to V1 (V1 is 100% of the rated driving voltage), the driving current slowly increases, and finally increases to 11.66A, and then stabilizes, 11.66A is calculated to be 30% =3.498A, which is consistent with the actual measurement result 3.497a, and simultaneously consistent with the setting parameter of 30%. As shown in fig. 5B, the measured drive current rises from 30% to 100% for 35s, consistent with the set parameter increasing by 0.5% every 250ms for 35 s.

To verify the relationship between the backlight PWM and the driving current in the step stage, the actual test results are shown in fig. 6A and 6B. As shown in fig. 6A, when the PWM duty cycle test is 56.55%, the measured current is 6.563a. The carry-over formula contrast verifies that 11.66a x 56.55% = 6.59A, consistent with the actual test results. As shown in fig. 6B, when the measured current reaches 11.658a, the measured PWM duty cycle is 99.96%, which corresponds to the parameter setting. Therefore, as can be seen from fig. 5A-6B, the driving voltage and current output of the boost circuit are stable in the product environment reliability test through parameter setting, and the backlight module does not flicker.

The method improves the low-temperature starting of the wide Wen Gaoliang display product by improving a software method under the condition that the hardware of the backlight driving circuit is not improved, and solves the problem that backlight flicker can occur when the product is started in a cold state in a low-temperature environment.

The first embodiment of the invention sets the initial power according to the usage characteristics of the display module to solve the problem of flicker when the display module is started at low temperature, but fails to solve the problem of larger variation of the ESR parameter of the electrolytic capacitor itself in low temperature environment. The second embodiment of the invention provides a scheme that the power-on is 100% power output without adopting a stepping algorithm. Because the root cause of the method is that the ESR parameter has larger change at low temperature, the embodiment of the invention calculates the range that the zero point parameter of the electrolytic capacitor Wesr meets the loop stability according to the characteristic of loop stability, and selects the electrolytic capacitor C3 meeting the condition according to the defined parameter range, thereby solving the problem of starting up backlight flickering.

As shown in fig. 1, the stability of the BOOST circuit is regulated by the state of BOOST IC pin COMP, capacitors C1, C2 and resistor R1 together form a system loop, while electrolytic capacitor C3 participates in the loop stability regulation.

In this embodiment, the electrolytic capacitor C3 shown in fig. 1 satisfies the following relation:

Wherein Wesr denotes a zero frequency of the circuit, ESR denotes an impedance of the electrolytic capacitor C3, C denotes a capacitance value of the electrolytic capacitor C3, f1 denotes 1/20 of a switching frequency of the PWM signal, and f2 denotes 1/10 of the switching frequency of the PWM signal.

It is generally accepted in engineering that the phase margin of the loop requires greater than 45 deg. at room temperature and standard input, normal load conditions to ensure stability of the system under various error and parameter variations. When the load characteristics, input voltage, change significantly, it is considered that the loop phase margin should be greater than 30 ° under all load conditions and over the input voltage range.

The cross-over frequency, also known as the frequency bandwidth, may be sized to reflect how fast the control loop responds. It is generally considered that the wider the bandwidth is, the better the suppression capability of the bandwidth to the dynamic response of the load is, the smaller the overshoot and undershoot are, the faster the recovery time is, and the system can be stabilized. However, the bandwidth of the power supply cannot be increased limitlessly due to the limitation of comprehensive factors such as raw materials, the impossible infinity of the bandwidth of the operational amplifier and the like, and the switching frequency is generally 1/20-1/10 of that of the power supply. For example, the switching frequency of the item is 150kHz, so the value is 7.5 kHz-15 kHz.

The indicators measuring the stability of the power supply are a phase margin and a gain margin. And the crossing frequency is also used as a reference index.

(1) The phase margin refers to the phase corresponding to when the gain drops to 0 dB.

(2) The gain margin is the gain magnitude (actually the attenuation) corresponding to a phase of 0 deg.

(3) The crossover frequency is the frequency value corresponding to a gain of 0 dB.

The loop stability determination is based on the following table 2, table 2:

phase margin [ degree ]	Gain margin [ dB ]	Evaluation index
			20	3	Severe ringing and extremely poor data
30	5	Small amount of ringing, poor data
			45	7	Critical damping, optimum response time of ringing
60	10	Appropriate data
			72	12	The value desired as a reference, no peak in the closed loop response

When low-temperature starting flicker occurs, the ESR of the electrolytic capacitor is 8.2 omega, the zero frequency of the circuit is determined according to the ESR and the capacitance value of the capacitor, and the zero frequency is calculated according to the following calculation formula:

At this time, the phase margin (PHASE MARGIN), the gain margin (GAIN MARGIN), the crossover frequency (Crossover Frequency) are corresponding to each other, as shown in fig. 7, and fig. 7 shows a baud diagram of the loop in an unstable state.

As is clear from FIG. 7, when the gain (solid line) is 0db, the corresponding phase margin is-152 DEG, when the phase is 0deg, the corresponding gain is 20db, the crossover frequency is 199.5kHz, and the serious ringing and the data are extremely bad are judged according to the loop stability judgment standard.

When the electrolytic capacitor with smaller ESR change at low temperature is replaced to ensure that the dot screen is normal and has no flicker, a loop stability state diagram is calculated as shown in fig. 8, and a loop stability state baud diagram is shown in fig. 8.

As is clear from fig. 8, when the gain (solid line) is 0db, the corresponding phase margin is 52 °, and when the phase is 0deg, the corresponding gain is-5 db, usually the absolute value is 5db, the crossover frequency is 8.1kHz, and the appropriate data is determined based on the loop stability determination criterion. The waveform of the Gate signal at low temperature was also measured as shown in fig. 9, with a stable and fundamental ripple of less than 5%. Fig. 9 shows a low temperature loop stable Gate waveform.

Thus, after the C1, C2 and R1 parameters are determined, whether the system loop is stable is determined by the electrolytic capacitor C3. From the above, it can be seen that when the switching frequency of the backlight driving PWM signal is 150kHz, the ESR parameter should satisfy the formula:

The method ensures that the ESR change is in a corresponding range under any temperature condition under the condition that the backlight driving circuit does not adopt a first driving voltage output mode and is started to output 100 percent of power, thereby ensuring the stability of a system loop and avoiding the flicker of low-temperature startup. Of course, the present application is not limited to this, and the present application can be used when the backlight driving circuit adopts the first driving voltage output method.

As can be seen from the above embodiment two, the electrolytic capacitor parameter calculated according to the loop stability is a range value, and the parameter has a high requirement on the electrolytic capacitor, which results in limited selection of the electrolytic capacitor. According to a related formula of loop stability, when the parameters of the electrolytic capacitor C3 are kept unchanged, loop adjustment can be realized by only adjusting the resistor R1. In addition, in order to adapt to a wider temperature range, the loop can be dynamically and automatically adjusted, and the stability of the system is ensured.

Because the MCU in the Converter board is used for receiving the Local Dimming data and driving the LEDs, the NTC thermistor can be added to detect the ambient temperature, and the R1 resistance value can be dynamically adjusted according to the temperature data.

Based on the above analysis, the embodiment of the invention also provides a backlight driving circuit, as shown in fig. 10, which comprises a boost circuit, a microcontroller MCU and a temperature detection circuit;

The BOOST circuit comprises an inductor L1, a diode D1, a first triode Q1, a direct-current BOOST chip BOOST IC, a loop and an electrolytic capacitor C3, wherein the loop comprises a first resistor R1, a first capacitor C1 and a second capacitor C2;

The first end of the first resistor R1 is connected with the first end of the loop, the second end of the first resistor R1 is connected with the first end of the second capacitor C2, the second end of the second capacitor C2 is connected with the second end of the loop, the first end of the first capacitor C1 is connected with the first end of the loop, and the second end of the first capacitor C1 is connected with the second end of the loop;

the first resistor R1 comprises a first sub resistor R1', a second triode Q2 and a second sub resistor R1';

The first end of the first sub resistor R1 'is connected with the first end of the first resistor, the second end of the first sub resistor R1' is connected with the second end of the first resistor, the first end of the second triode Q2 is connected with the first end of the first resistor, the second end of the second triode Q2 is connected with the first end of the second sub resistor R1', the second end of the second sub resistor R1' is connected with the second end of the first resistor, and the gate end of the second triode Q2 is connected with the output end of the MCU;

When the ambient temperature is lower than or equal to the second temperature, the MCU controls the second triode Q2 to be opened, and when the ambient temperature is lower than or equal to the second temperature, the MCU controls the second triode Q2 to be closed, and the resistor connected in series in the loop is the second branch resistor R1'. The second temperature may be set to 0 ℃ or less.

The temperature detection circuit comprises a second resistor R2, a fourth capacitor C4 and a thermistor Rntc;

The first end of the second resistor R2 is connected with the output end of the temperature detection circuit, the second end of the second resistor R2 is grounded, the first end of the fourth capacitor C4 is connected with the output end of the temperature detection circuit, the second end of the fourth capacitor C4 is grounded, the first end of the thermistor Rntc is connected with the output end of the temperature detection circuit, and the second end of the thermistor Rntc is connected with a power supply.

In the above temperature detection circuit, R2 is a voltage dividing resistor, and when the thermistor Rntc detects a temperature change each time, the output voltage will change accordingly, and the voltage dividing calculation formula can be obtained:

Wherein R _NTC represents the resistance value of the thermistor, and V _ADC represents the analog voltage value detected by the MCU under the current temperature condition.

According to the characteristics of the thermistor, the higher the temperature is, the smaller the resistance is, the corresponding relation between the temperature and the resistance is obtained according to the specification of the thermistor, and the corresponding relation between the MCU detection voltage and the ambient temperature is obtained by substituting the formula.

In the system loop, an MCU controlled switch circuit is adopted to adjust the R1 resistance value, thereby affecting the stability of the system loop. When the temperature is above 0 ℃, the default MCU output is low level, the MOS tube Q2 is closed, the resistor connected in the loop in series is R1', when the temperature is below 0 ℃, the electrolytic capacitor ESR is increased, the R1 needs to be reduced according to a loop stability formula, the MCU control level is high, the MOS tube Q2 is opened, the resistor R1 connected in the loop circuit in series is R1'// R1' in parallel, so that the loop parameter is dynamically adjusted according to the ambient temperature, and the loop stability is ensured under the condition that the electrolytic capacitor is unchanged.

In the embodiment, the environment temperature is detected, the matching resistance which enables the loop to be stable in the boost circuit is switched according to different temperatures, the requirement of the ESR parameter of the electrolytic capacitor on the environment is relaxed, the low-temperature start of a wide Wen Gaoliang display product can be improved, and the problem that backlight flicker can occur when the product is started in a cold mode in a low-temperature environment is solved.

The embodiment of the application also provides a backlight driving board which comprises the backlight driving circuit in each embodiment. The backlight driving plate can be applied to a display module, and the application is not limited to the above.

The embodiment of the invention also provides a backlight driving method, which comprises the following steps:

detecting the ambient temperature of the backlight module;

According to the backlight driving circuit, the backlight driving plate and the backlight driving method provided by the embodiment of the invention, the ESR parameter range of the electrolytic capacitor in the booster circuit is quantized according to the parameter change of the components at low temperature, and the booster circuit is enabled to work stably according to the range selection, so that the full-power normal start is achieved. The matching resistance which stabilizes the loop in the boost circuit is switched according to different temperatures by detecting the ambient temperature, so that the requirement of the ESR parameter of the electrolytic capacitor on the environment is relaxed. The initial power-on power of the backlight driving circuit is reduced on the basis of not changing the existing hardware scheme, normal starting is ensured, and then the booster circuit stably works by gradually increasing the output power to reach the full power point screen. Through the improvement in the aspects, the low-temperature start of the wide Wen Gaoliang display product can be improved, the problem that backlight flicker can occur when the product is started in a cold mode in a low-temperature environment is solved, and therefore user experience is improved.

It should be noted that:

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the above description of exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this application.

Those skilled in the art will appreciate that the modules in the apparatus of the embodiments may be adaptively changed and disposed in one or more apparatuses different from the embodiments. The modules or units or components of the embodiments may be combined into one module or unit or component and, furthermore, they may be divided into a plurality of sub-modules or sub-units or sub-components. Any combination of all features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be used in combination, except insofar as at least some of such features and/or processes or units are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Various component embodiments of the application may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that some or all of the functions of some or all of the components in the creation means of a virtual machine according to an embodiment of the present application may be implemented in practice using a microprocessor or Digital Signal Processor (DSP). The present application can also be implemented as an apparatus or device program (e.g., a computer program and a computer program product) for performing a portion or all of the methods described herein. Such a program embodying the present application may be stored on a computer readable medium, or may have the form of one or more signals. Such signals may be downloaded from an internet website, provided on a carrier signal, or provided in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The application may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third, etc. do not denote any order. These words may be interpreted as names.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the specification and drawings of the present invention or direct/indirect application in other related technical fields are included in the scope of the present invention.

Claims

1. The backlight driving circuit is used for driving a backlight module to light and is characterized by comprising a booster circuit and a microcontroller, wherein the input end of the booster circuit is connected with a power supply, and the output end of the booster circuit is connected with the backlight module;

The microcontroller is configured to detect the ambient temperature of the backlight module and adjust the driving voltage output mode according to the change of the ambient temperature;

The boost circuit comprises an inductor, a diode, a first triode, a direct current boost chip, a loop and an electrolytic capacitor;

the electrolytic capacitor satisfies the following relation:

f1 ≤ ≤f2;

wherein, the Representing the zero frequency of the circuit,Representing the impedance of the electrolytic capacitor,Representing the capacitance value of the electrolytic capacitor, f1 represents 1/20 of the switching frequency of the PWM signal, and f2 represents 1/10 of the switching frequency of the PWM signal.

2. The backlight driving circuit according to claim 1, wherein the first driving voltage output mode is to output a first driving voltage to the backlight module in a first period of time, output a second driving voltage to the backlight module in a second period of time, and output a rated driving voltage to the backlight module in an nth period of time, wherein the first driving voltage is smaller than the second driving voltage, and the second driving voltage is smaller than the rated driving voltage.

3. The backlight driving circuit according to claim 1, wherein the first driving voltage output mode is to output a first driving voltage to the backlight module in a first period of time and output a rated driving voltage to the backlight module in a second period of time;

4. A backlight driving circuit according to claim 2 or 3, wherein the first period of time is 5 seconds or more and 15 seconds or less.

5. A backlight driving circuit according to claim 1, wherein,

And the microcontroller is configured to adjust the driving voltage output mode of the booster circuit to be a first driving voltage output mode when the ambient temperature is lower than the first temperature, otherwise adjust the driving voltage output mode of the booster circuit to be a second driving voltage output mode, and the second driving voltage output mode is to directly output rated driving voltage to the backlight module.

6. The backlight driving circuit according to claim 5, wherein the first temperature is equal to or lower than-20 ℃.

7. The backlight driving circuit according to claim 1, wherein the loop circuit comprises a first resistor, a first capacitor, and a second capacitor;

8. The backlight driving circuit according to claim 7, further comprising a temperature detection circuit;

When the ambient temperature is lower than or equal to the second temperature, the microcontroller controls the second triode to be opened, and the resistor connected in series in the loop is the second sub-resistor.

9. The backlight driving circuit according to claim 8, wherein the temperature detecting circuit comprises a second resistor, a fourth capacitor, and a thermistor;

10. A backlight driving board comprising the backlight driving circuit according to any one of claims 1 to 9.