Backlight driving circuit, backlight driving board and backlight driving method

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, and 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

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a backlight driving circuit, a backlight driving board, and a backlight driving method. Background Technology

[0002] The market demand for large-size, wide-temperature, high-brightness display products is increasing, with some products boasting brightness levels up to 3500 nits and featuring local dimming (LD) functionality. These require a converter board to control the backlight LEDs in zones, necessitating a DC-DC boost converter drive solution. The converter board is the control board used to drive the backlight LEDs.

[0003] However, when using a DC-DC backlight drive solution, wide-temperature, high-brightness display products may experience backlight flickering during cold starts in low-temperature environments (-30°C and below), which significantly impacts usability.

[0004] Therefore, how to improve the low-temperature start-up of wide-temperature, high-brightness display products is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a backlight driving circuit, a backlight driving board, and a backlight driving method to solve the problem of abnormal low-temperature startup in existing wide-temperature high-brightness display products.

[0006] Therefore, the present invention provides a backlight driving circuit for driving a backlight module to light up, comprising: a boost circuit and a microcontroller; the input terminal of the boost circuit is connected to a power supply, and the output terminal of the boost circuit is connected to the backlight module;

[0007] The boost circuit is configured to output a driving voltage to the backlight module according to a driving voltage output mode, the driving voltage output mode including a first driving voltage output mode, the first driving voltage output mode being to output a driving voltage to the backlight module up to the rated driving voltage in time periods;

[0008] The microcontroller is configured to detect the ambient temperature of the backlight module and adjust the drive voltage output mode according to the change in the ambient temperature.

[0009] In one possible implementation, the first driving voltage output method is to output a first driving voltage to the backlight module during a first time period, output a second driving voltage to the backlight module during a second time period, and output a rated driving voltage to the backlight module during an nth time period; the first driving voltage is less than the second driving voltage, and the second driving voltage is less than the rated driving voltage.

[0010] In one possible implementation, the first driving voltage output method is to output a first driving voltage to the backlight module during a first time period and to output a rated driving voltage to the backlight module during a second time period.

[0011] The ratio of the first driving voltage to the rated driving voltage is a first ratio, which 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, which is greater than or equal to 2.

[0012] In one possible implementation, the first time period is greater than or equal to 5 seconds and less than or equal to 15 seconds.

[0013] In one possible implementation, the microcontroller is configured to adjust the drive voltage output mode of the boost circuit to a first drive voltage output mode when the ambient temperature is lower than a first temperature, and conversely, adjust the drive voltage output mode of the boost circuit to a second drive voltage output mode when the ambient temperature is higher than a first temperature. The second drive voltage output mode is to directly output the rated drive voltage to the backlight module.

[0014] In one possible implementation, the first temperature is less than or equal to -20°C.

[0015] In one possible implementation, the boost circuit includes: an inductor, a diode, a first transistor, a DC boost chip, a loop, and an electrolytic capacitor;

[0016] The first end of the inductor is connected to the input terminal of the boost circuit, the second end of the inductor is connected to the anode of the diode, and the cathode of the diode is connected to the output terminal of the boost circuit; the first end of the first transistor is connected to the second end of the inductor, the second end of the first transistor is grounded, the gate of the first transistor is connected to the output terminal of the DC-DC boost chip, the input terminal of the DC-DC boost chip is connected to the first terminal of the loop, and the second terminal of the loop is grounded; the positive terminal of the electrolytic capacitor is connected to the output terminal of the boost circuit, and the negative terminal of the electrolytic capacitor is grounded;

[0017] The DC boost chip outputs a pulse width modulation (PWM) signal to the first transistor to control the drive voltage output from the boost circuit.

[0018] The electrolytic capacitor satisfies the following relationship:

[0019]

[0020] Where Wesr represents the zero-point frequency of the circuit, ESR represents the impedance of the electrolytic capacitor, C represents 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.

[0021] In one possible implementation, the loop includes: a first resistor, a first capacitor, and a second capacitor;

[0022] The first end of the first resistor is connected to the first end of the loop, the second end of the first resistor is connected to the first end of the second capacitor, the second end of the second capacitor is connected to the second end of the loop, and the first end of the first capacitor is connected to the first end of the loop, and the second end of the first capacitor is connected to the second end of the loop.

[0023] In one possible implementation, the backlight driving circuit further includes a temperature detection circuit;

[0024] The first resistor includes: a first resistor, a second transistor, and a second resistor;

[0025] The first terminal of the first resistor is connected to the first terminal of the first resistor, and the second terminal of the first resistor is connected to the second terminal of the first resistor; the first terminal of the second transistor is connected to the first terminal of the first resistor, the second terminal of the second transistor is connected to the first terminal of the second resistor, the second terminal of the second resistor is connected to the second terminal of the first resistor, and the gate terminal of the second transistor is connected to the output terminal of the microcontroller; the input terminal of the microcontroller is connected to the output terminal of the temperature detection circuit.

[0026] When the ambient temperature is greater than the second temperature, the microcontroller controls the second transistor to turn off, and the resistor connected in series in the loop at this time is the first sub-resistor; when the temperature is less than or equal to the second temperature, the microcontroller controls the second transistor to turn on, and the resistor connected in series in the loop at this time is the second sub-resistor.

[0027] In one possible implementation, the temperature detection circuit includes: a second resistor, a fourth capacitor, and a thermistor;

[0028] The first end of the second resistor is connected to the output terminal of the temperature detection circuit, and the second end of the second resistor is grounded; the first end of the fourth capacitor is connected to the output terminal of the temperature detection circuit, and the second end of the fourth capacitor is grounded; the first end of the thermistor is connected to the output terminal of the temperature detection circuit, and the second end of the thermistor is connected to the power supply.

[0029] On the other hand, embodiments of the present invention also provide a backlight driving board, including the backlight driving circuit described in the above embodiments.

[0030] On the other hand, embodiments of the present invention also provide a backlight driving method, including:

[0031] Detect the ambient temperature of the backlight module;

[0032] When the ambient temperature is lower than the first temperature, the driving voltage output mode to the backlight module is adjusted to the first driving voltage output mode; the first driving voltage output mode is to output the driving voltage to the backlight module to the rated driving voltage in time periods;

[0033] When the ambient temperature is not lower than the first temperature, the driving voltage output mode to the backlight module is adjusted to the second driving voltage output mode; the second driving voltage output mode is to directly output the rated driving voltage to the backlight module.

[0034] In one possible implementation, the first driving voltage output method specifically involves outputting a first driving voltage to the backlight module during a first time period, outputting a second driving voltage to the backlight module during a second time period, and outputting a rated driving voltage to the backlight module during an nth time period; wherein the first driving voltage is less than the second driving voltage, and the second driving voltage is less than the rated driving voltage.

[0035] In one possible implementation, the first driving voltage output method is to output a first driving voltage to the backlight module during a first time period and to output a rated driving voltage to the backlight module during a second time period.

[0036] The ratio of the first driving voltage to the rated driving voltage is a first ratio, which 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, which is greater than or equal to 2.

[0037] In one possible implementation, the first time period is greater than or equal to 5 seconds and less than or equal to 15 seconds.

[0038] The beneficial effects of the embodiments of the present invention are as follows:

[0039] This invention provides 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, which includes a first driving voltage output mode, where the driving voltage is output to the backlight module in time-segmented manner 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. Therefore, this application can adjust the driving voltage output mode of the boost circuit according to the ambient temperature of the backlight module, thereby adjusting the driving power of the backlight module based on the ambient temperature. This allows for a reduction in the driving power of the backlight module at low temperatures to ensure normal startup, followed by a gradual increase in driving power to reach full power for backlight module illumination. This ensures stable operation of the boost circuit, improves the low-temperature startup of wide-temperature, high-brightness backlight modules, and solves the problem of backlight flickering during cold starts in low-temperature environments, thus enhancing the user experience. Attached Figure Description

[0040] Figure 1 The diagram shown is a circuit diagram of a boost circuit.

[0041] Figure 2 The figure shown is a measured graph of the Gate signal ripple amplitude exceeding the voltage amplitude by 60% under low temperature conditions.

[0042] Figure 3 The figure shown is a curve of the backlight PWM changing over time.

[0043] Figure 4 The diagram shows a specific flowchart of a backlight PWM progressive increase.

[0044] Figure 5A The image shown is one of the actual current waveforms of the Converter board.

[0045] Figure 5B The image shown is the second actual current waveform of the Converter board.

[0046] Figure 6A The image shows one of the actual test results regarding the relationship between backlight PWM and drive current during the stepping stage;

[0047] Figure 6B The image shows the second actual test result of the relationship between backlight PWM and drive current during the stepping stage;

[0048] Figure 7 The diagram shows the Bode plot for an unstable loop.

[0049] Figure 8The diagram shows the Bode plot of the loop in its steady state.

[0050] Figure 9 The diagram shown is a stable gate waveform for the low-temperature loop.

[0051] Figure 10 The diagram shown is a circuit diagram of a backlight driving circuit. Detailed Implementation

[0052] For ease of understanding, some technical terms used in this application are explained below.

[0053] Converter: A circuit that uses high-frequency switching to convert a DC input voltage into different DC output voltages. This circuit contains inductors and capacitors for filtering. The converter board is a control board used to drive backlight LEDs; in this application, it is also referred to as a backlight driver board.

[0054] Boost IC: DC boost chip. Boost circuit refers to the general term for the boost section circuit in the Converter board, and is also referred to as boost circuit in this application.

[0055] PWM stands for Pulse-width modulation. It's a method of digitally encoding analog signal levels. PWM signals regulate changes in signal strength and energy by adjusting the duty cycle.

[0056] LD stands for Local Dimming, which refers to the adjustment of backlight LEDs according to the brightness of the image. The brightness of bright areas in the displayed image can be maximized, while the brightness of dark areas can be reduced or even turned off to achieve optimal contrast. This reduction in the brightness of dark areas reduces the power consumption of the backlight.

[0057] ESR stands for Equivalent Series Resistance, which refers to the equivalent series resistance (or impedance) of a capacitor.

[0058] MCU: Short for Microprogrammed Control Unit, it is the main control chip on the Converter board.

[0059] NTC stands for Negative temperature coefficient, meaning that the resistance decreases as the temperature increases. It is commonly used as a temperature sensor.

[0060] The specific implementation methods of the backlight driving circuit, backlight driving board, and backlight driving method provided in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0061] Figure 1 The diagram shown is a circuit diagram of a boost circuit according to an embodiment of the present invention. The input terminal Vin of the boost circuit is connected to a power supply, and the output terminal Vout of the boost circuit is connected to a load. The load can be a backlight module.

[0062] The boost circuit specifically includes: inductor L1, diode D1, first transistor Q1, DC boost chip BOOSTIC, loop, and electrolytic capacitor C3; the loop includes: first resistor R1, first capacitor C1, and second capacitor C2.

[0063] The first end of the inductor L1 is connected to the input terminal of the boost circuit, the second end of the inductor L1 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the output terminal of the boost circuit. The first end of the first transistor Q1 is connected to the second end of the inductor L1, the second end of the first transistor Q1 is grounded, the gate of the first transistor Q1 is connected to the output terminal of the DC boost chip, the input terminal of the DC boost chip is connected to the first terminal COMP of the loop, and the second terminal of the loop is grounded. The positive terminal of the electrolytic capacitor C3 is connected to the output terminal of the boost circuit, and the negative terminal of the electrolytic capacitor C3 is grounded.

[0064] The first end of the first resistor R1 is connected to the first end of the loop, the second end of the first resistor R1 is connected to the first end of the second capacitor C2, the second end of the second capacitor C2 is connected to the second end of the loop, the first end of the first capacitor C1 is connected to the first end of the loop, and the second end of the first capacitor C1 is connected to the second end of the loop.

[0065] The DC boost converter chip outputs a pulse width modulation (PWM) signal to the first transistor Q1 to control the voltage at the output terminal of the boost circuit. The first transistor Q1 can be a MOSFET.

[0066] In the product environmental reliability test, the low-temperature start-up requirement stipulates that the backlight module must be started every 8 hours at an ambient temperature of -30℃. During start-up, the backlight brightness and power consumption must be at the product's maximum design level. The module must be started three times within 24 hours, and all startups must display normally without any other abnormalities to pass the test. Some products exhibited backlight flickering during the -30℃ start-up test.

[0067] like Figure 2As shown in the waveform test, it can be seen that the Gate control signal of the BOOST IC output control Q1 in the boost circuit has abnormal fluctuations under low temperature conditions. The Gate signal ripple exceeds 60% of the Gate signal voltage amplitude, which is far higher than the 10% ripple limit, causing the output Vout of the boost circuit to be in an unstable state, thus causing the backlight to flicker.

[0068] The state of the Gate signal is limited by the stability of the loop in the boost circuit. When the loop is unstable, the Gate signal waveform has large ripple, causing abnormal Q1 switching and resulting in backlight flickering. The ESR parameter of electrolytic capacitor C3 is involved in the loop calculation. Test data of electrolytic capacitor C3 as a function of temperature (see Table 1 below) shows that the ESR is approximately 0.682Ω at 25℃, while it is approximately 8.208Ω at -20℃, nearly 12 times higher than at room temperature. When the ambient temperature is 60℃, the ESR is not significantly different from that at room temperature. Therefore, the lower the temperature, the higher the ESR, and the greater the difference from room temperature, the greater the impact on the loop.

[0069]

[0070] This defect can be effectively mitigated by adjusting the backlight brightness at the initial startup state to reduce power consumption. Based on the defect's characteristics, without changing the hardware, when the initial power-on drive power is 50%, the loop is stable and the backlight display is normal. After 30 seconds, due to the circuit's own heat generation, the temperature of electrolytic capacitor C3 rises above 0°C, and the ESR parameter is less than 2Ω. At this point, increasing the drive power to 100% still results in a stable loop. Therefore, switching to 100% drive power after the components heat up at low power levels can improve this problem.

[0071] In view of this, embodiments of the present invention propose a backlight driving circuit for driving a backlight module to illuminate. Specifically, the backlight driving circuit includes a boost circuit and a microcontroller, wherein the boost circuit is... Figure 1 The boost circuit shown has its input connected to a power supply and its output connected to a backlight module.

[0072] The boost circuit is configured to output a driving voltage to the backlight module according to a preset driving voltage output mode. The driving voltage output mode includes a first driving voltage output mode, which is to output a driving voltage to the backlight module up to the rated driving voltage in time periods.

[0073] The driving voltage output method may further include a first driving voltage output method, wherein the second driving voltage output method is to directly output the rated driving voltage to the backlight module.

[0074] Specifically, the time-segmented output of the driving voltage to the backlight module to the rated driving voltage in the first driving voltage output method mentioned above can be implemented in various ways.

[0075] In one implementation, the first driving voltage output method 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; the first driving voltage is less than the second driving voltage, and the second driving voltage is less than the rated driving voltage.

[0076] In another implementation, the first driving voltage output method is to output a first driving voltage to the backlight module in a first time period and to output a rated driving voltage to the backlight module in a second time period.

[0077] Specifically, the ratio of the first driving voltage to the rated driving voltage is a first ratio, which 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, which is greater than or equal to 2.

[0078] In other words, in the first driving voltage output method, the range of the first driving voltage output to the backlight module during the first time period can be set to be between 20% and 50% of the rated driving voltage, and the driving voltage output to the backlight module during the second time period is 100% of the rated driving voltage. The duration of the second time period can be set to twice or more than twice the duration of the first time period.

[0079] Specifically, in some embodiments, the duration of the first time period can be set to be greater than or equal to 5 seconds and less than or equal to 15 seconds.

[0080] The microcontroller is configured to detect the ambient temperature of the backlight module and adjust the drive voltage output mode according to the change in the ambient temperature.

[0081] Specifically, when the ambient temperature is lower than the first temperature, the microcontroller adjusts the driving voltage output mode of the boost circuit to the first driving voltage output mode, and vice versa.

[0082] In practical applications, the first temperature can be set to less than or equal to -20℃, or it can be set according to the actual situation. This application does not limit this setting.

[0083] For example:

[0084] When the ambient temperature is detected to be below -20℃, the microcontroller can adjust the backlight PWM signal of the control drive voltage of the boost circuit as follows:

[0085] 1. Upon initial power-on, the backlight PWM output duty cycle range is ≥20% and ≤50% for 5-15 seconds to initially stabilize the lighting.

[0086] 2. Then, the PWM output is reached in steps between 45 and 60 seconds. The total time from power-on to PWM 100% output should not exceed 60 seconds and should not be less than 45 seconds.

[0087] Figure 3 The figure shown is a curve illustrating the variation of backlight PWM over time. Figure 4 The diagram shows a specific flowchart of a backlight PWM progressive increase.

[0088] like Figure 3 , 4 As shown, in the product environmental reliability test, the initial PWM duty cycle was set to 30% upon power-on, and the device was continuously lit for 10 seconds. Then, the step size was set to increase by 0.5% every 250ms, and finally, 100% power output was reached in 45 seconds. Figure 5A The image shown is one of the actual current waveforms measured on the Converter board. Figure 5B The second image shows the actual current waveform of the Converter board.

[0089] like Figure 5A As shown, after power-on, as the drive voltage increases to V2 (V2 is 30% of the rated drive voltage), the drive current rises to 3.497A for 10 seconds, which is consistent with... Figure 3 , 4 The parameters were set consistently; then, as the drive voltage increased to V1 (V1 being 100% of the rated drive voltage), the drive current slowly increased, finally stabilizing at 11.66A. Calculations showed 11.66A * 30% = 3.498A, consistent with the measured result of 3.497A, and also consistent with the set parameter of 30%. Figure 5B As shown, the measured drive current increased from 30% to 100% in 35 seconds, which is consistent with the set parameter of increasing by 0.5% every 250ms for a duration of 35 seconds.

[0090] To verify the relationship between the backlight PWM and the drive current during the stepping stage, the actual test results are as follows: Figure 6A and 6B As shown. Figure 6A As shown, when the PWM duty cycle test is 56.55%, the measured current is 6.563A. Substituting into the formula for comparison, 11.66A * 56.55% = 6.59A, which is consistent with the actual test result. Figure 6B As shown, when the measured current reaches 11.658A, the measured PWM duty cycle is 99.96%, which meets the parameter settings. Therefore, from Figures 5A-6B As can be seen, through parameter settings, the boost circuit's drive voltage and current output are stable in the product environmental reliability test, and the backlight module does not flicker.

[0091] The above methods improve the low-temperature startup of wide-temperature, high-brightness display products by modifying the software without improving the backlight driver circuit hardware, thus solving the problem of backlight flickering during cold startup in low-temperature environments.

[0092] The first embodiment described above addresses the low-temperature startup flicker problem by setting the initial power-on power based on the display module's usage characteristics. However, it fails to resolve the issue of significant variations in the ESR parameters of the electrolytic capacitor at low temperatures. Embodiment two of this invention proposes a solution that eliminates the need for a stepping algorithm, achieving 100% power output from startup. Since the root cause is the significant variation in ESR parameters at low temperatures, this embodiment calculates the range within which the Wesr zero-point parameter of the electrolytic capacitor satisfies loop stability, based on the characteristics of loop stability. Based on this defined parameter range, it selects an electrolytic capacitor C3 that meets the conditions, thus resolving the startup backlight flicker problem.

[0093] like Figure 1 As shown, the stability of the boost circuit is regulated by the state of the COMP pin of the BOOST IC. Capacitors C1 and C2 and resistor R1 together form the system loop, while electrolytic capacitor C3 participates in the loop stability regulation.

[0094] In this embodiment, Figure 1 The electrolytic capacitor C3 shown satisfies the following relationship:

[0095]

[0096] Where Wesr represents the zero-point frequency of the circuit, ESR represents the impedance of the electrolytic capacitor C3, C represents the capacitance value of the electrolytic capacitor C3, 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.

[0097] In engineering practice, it is generally accepted that under room temperature, standard input, and normal load conditions, the loop phase margin should be greater than 45° to ensure system stability under various error and parameter variations. When load characteristics and input voltage variations are significant, the loop phase margin should be greater than 30° under all load conditions and within the input voltage range.

[0098] Crossover frequency, also known as bandwidth, reflects the speed of control loop response. Generally, a wider bandwidth is considered to provide better suppression of load dynamic response, resulting in less overshoot and undershoot, faster recovery time, and thus greater system stability. However, due to limitations imposed by raw materials and the fact that operational amplifier bandwidth cannot be infinitely large, power supply bandwidth cannot be increased indefinitely; it is typically taken as 1 / 20 to 1 / 10 of the switching frequency. For example, if the switching frequency of a project is 150kHz, a value of 7.5kHz to 15kHz would be used.

[0099] The metrics for measuring power supply stability are phase margin and gain margin. Crossover frequency is also used as a reference metric.

[0100] (1) Phase margin refers to the phase corresponding to when the gain drops to 0dB.

[0101] (2) Gain margin refers to the gain magnitude (actually attenuation) when the phase is 0deg.

[0102] (3) Crossover frequency refers to the frequency value corresponding to a gain of 0dB.

[0103] The criteria for judging loop stability are shown in Table 2 below. Table 2:

[0104] Phase margin [degrees] Gain margin [dB] Evaluation indicators 20 3 Severe oscillations with decreasing amplitude, extremely poor data 30 5 Slightly decreasing oscillations, poor data. 45 7 Critical damping, optimal response time for reduced amplitude oscillations 60 10 Suitable data 72 12 The desired baseline value should have no peak value in the closed-loop response.

[0105] When low-temperature start-up flicker occurs, the ESR of the electrolytic capacitor is 8.2Ω. Based on the capacitor's ESR and capacitance value, the zero-point frequency of the circuit is determined using the following calculation formula:

[0106]

[0107] At this point, the corresponding phase margin, gain margin, and crossover frequency are as follows: Figure 7 As shown, Figure 7 The diagram shows the Bode plot for an unstable loop.

[0108] Depend on Figure 7 It can be seen that when the gain (solid line) is 0dB, the corresponding phase margin is -152°; when the phase is 0deg, the corresponding gain is 20dB and the crossover frequency is 199.5kHz. According to the loop stability judgment standard, it is judged to be a severe damped oscillation with poor data.

[0109] When replacing the electrolytic capacitor with one that exhibits minimal ESR change at low temperatures, and ensuring normal screen operation without flickering, the loop stability diagram is calculated as follows. Figure 8 As shown, Figure 8 The diagram shows the Bode plot of the loop in its steady state.

[0110] Depend on Figure 8 It can be seen that when the gain (solid line) is 0dB, the corresponding phase margin is 52°; the gain corresponding to the phase of 0deg is -5dB, usually taken as an absolute value of 5dB, with a crossover frequency of 8.1kHz. According to the loop stability judgment criteria, this is considered suitable data. Simultaneously, the waveform of the Gate signal at low temperature is measured as follows... Figure 9 As shown, it is stable and the basic ripple is less than 5%. Figure 9 The waveform shown is the stable gate waveform of the low-temperature loop.

[0111] Therefore, once the parameters C1, C2, and R1 are determined, the stability of the system loop is determined by the electrolytic capacitor C3. From the above, it can be seen that when the switching frequency of the backlight drive PWM signal is 150kHz, the ESR parameter should satisfy the formula:

[0112] The above method ensures that the ESR variation remains within the appropriate range under any temperature conditions, even when the backlight driving circuit does not use the first driving voltage output mode and the power is output at 100% upon startup. This ensures system loop stability and avoids low-temperature startup flicker. Of course, it can also be used when the backlight driving circuit uses the first driving voltage output mode; this application does not limit this.

[0113] As shown in Example 2 above, the electrolytic capacitor parameters calculated based on loop stability are a range of values. These parameters place high demands on the electrolytic capacitor, limiting its selection. According to the relevant formulas for loop stability, when the electrolytic capacitor C3 parameter remains constant, loop adjustment can be achieved simply by adjusting resistor R1. Furthermore, to enable the product to adapt to a wider temperature range, the loop can be dynamically and automatically adjusted to ensure system stability.

[0114] Since the Converter board contains a microcontroller (MCU) to receive local dimming data and drive the LED, an NTC thermistor can be added to detect the ambient temperature and dynamically adjust the resistance value of R1 based on the temperature data.

[0115] Based on the above analysis, embodiments of the present invention also provide a backlight driving circuit, such as... Figure 10 As shown, the backlight driving circuit includes: a boost circuit, a microcontroller (MCU), and a temperature detection circuit;

[0116] The boost circuit includes: inductor L1, diode D1, first transistor Q1, DC boost chip BOOST IC, loop, and electrolytic capacitor C3; the loop includes: first resistor R1, first capacitor C1, and second capacitor C2.

[0117] The first end of the inductor L1 is connected to the input terminal of the boost circuit, the second end of the inductor L1 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the output terminal of the boost circuit. The first end of the first transistor Q1 is connected to the second end of the inductor L1, the second end of the first transistor Q1 is grounded, the gate of the first transistor Q1 is connected to the output terminal of the DC boost chip, the input terminal of the DC boost chip is connected to the first terminal COMP of the loop, and the second terminal of the loop is grounded. The positive terminal of the electrolytic capacitor C3 is connected to the output terminal of the boost circuit, and the negative terminal of the electrolytic capacitor C3 is grounded.

[0118] The first end of the first resistor R1 is connected to the first end of the loop, the second end of the first resistor R1 is connected to the first end of the second capacitor C2, the second end of the second capacitor C2 is connected to the second end of the loop, the first end of the first capacitor C1 is connected to the first end of the loop, and the second end of the first capacitor C1 is connected to the second end of the loop.

[0119] The first resistor R1 includes: a first resistor R1', a second transistor Q2, and a second resistor R1”;

[0120] The first end of the first resistor R1' is connected to the first end of the first resistor, and the second end of the first resistor R1' is connected to the second end of the first resistor; the first end of the second transistor Q2 is connected to the first end of the first resistor, the second end of the second transistor Q2 is connected to the first end of the second resistor R1'", the second end of the second resistor R1' is connected to the second end of the first resistor, and the gate of the second transistor Q2 is connected to the output of the MCU; the input of the MCU is connected to the output of the temperature detection circuit.

[0121] When the ambient temperature is higher than the second temperature, the MCU controls the second transistor Q2 to turn off, and the resistor connected in series in the loop at this time is the first sub-resistor R1'; when the ambient temperature is less than or equal to the second temperature, the MCU controls the second transistor Q2 to turn on, and the resistor connected in series in the loop at this time is the second sub-resistor R1'. The second temperature can be set to less than or equal to 0°C.

[0122] The temperature detection circuit includes: a second resistor R2, a fourth capacitor C4, and a thermistor Rntc;

[0123] The first end of the second resistor R2 is connected to the output terminal of the temperature detection circuit, and the second end of the second resistor R2 is grounded; the first end of the fourth capacitor C4 is connected to the output terminal of the temperature detection circuit, and the second end of the fourth capacitor C4 is grounded; the first end of the thermistor Rntc is connected to the output terminal of the temperature detection circuit, and the second end of the thermistor Rntc is connected to the power supply.

[0124] In the temperature detection circuit described above, R2 is a voltage divider resistor. Each time the thermistor Rntc detects a temperature change, the output voltage changes accordingly. This can be calculated using the voltage divider formula:

[0125]

[0126] Among them, R NTC V represents the resistance value of the thermistor. ADC This indicates that the MCU has detected the analog voltage value under the current temperature conditions.

[0127] As can be seen from the characteristics of thermistors, the higher the temperature, the lower the resistance. Based on the thermistor specifications, the relationship between temperature and resistance can be obtained. Substituting these values ​​into the formula, the relationship between the MCU detection voltage and the ambient temperature can be obtained.

[0128] In the system loop, an MCU-controlled switching circuit is used to adjust the value of resistor R1, thus affecting the system loop stability. When the temperature is above 0℃, the MCU output is low by default, and MOSFET Q2 is off. At this time, the resistor connected in series in the loop is R1'. When the temperature is below 0℃, the ESR of the electrolytic capacitor increases. According to the loop stability formula, R1 needs to be reduced. The MCU control level is high, turning on MOSFET Q2. At this time, the resistor R1 connected in series in the loop circuit is R1' / / parallel R1', so as to dynamically adjust the loop parameters according to the ambient temperature and ensure loop stability while keeping the electrolytic capacitor constant.

[0129] In this embodiment, by detecting the ambient temperature and switching the matching resistor in the boost circuit to stabilize the loop according to different temperatures, the environmental requirements of the ESR parameter of the electrolytic capacitor are relaxed. This can also improve the low-temperature start-up of wide-temperature high-brightness display products and solve the problem of backlight flickering when the product is cold-started in a low-temperature environment.

[0130] This invention also provides a backlight driver board, including the backlight driver circuit described in the above embodiments. This backlight driver board can be applied to a display module, and this application does not limit its application thereto.

[0131] This invention also provides a backlight driving method, comprising:

[0132] Detect the ambient temperature of the backlight module;

[0133] When the ambient temperature is lower than the first temperature, the driving voltage output mode to the backlight module is adjusted to the first driving voltage output mode; the first driving voltage output mode is to output the driving voltage to the backlight module to the rated driving voltage in time periods;

[0134] When the ambient temperature is not lower than the first temperature, the driving voltage output mode to the backlight module is adjusted to the second driving voltage output mode; the second driving voltage output mode is to directly output the rated driving voltage to the backlight module.

[0135] In one possible implementation, the first driving voltage output method specifically involves outputting a first driving voltage to the backlight module during a first time period, outputting a second driving voltage to the backlight module during a second time period, and outputting a rated driving voltage to the backlight module during an nth time period; wherein the first driving voltage is less than the second driving voltage, and the second driving voltage is less than the rated driving voltage.

[0136] In one possible implementation, the first driving voltage output method is to output a first driving voltage to the backlight module during a first time period and to output a rated driving voltage to the backlight module during a second time period.

[0137] The ratio of the first driving voltage to the rated driving voltage is a first ratio, which 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, which is greater than or equal to 2.

[0138] In one possible implementation, the first time period is greater than or equal to 5 seconds and less than or equal to 15 seconds.

[0139] This invention provides a backlight driving circuit, a backlight driving board, and a backlight driving method. Based on changes in component parameters at low temperatures, the ESR parameter range of the electrolytic capacitor in the boost circuit is quantified. Selection of capacitors within this range ensures stable operation of the boost circuit, achieving full-power normal startup. By detecting ambient temperature, the matching resistor in the boost circuit that stabilizes the loop is switched according to different temperatures, relaxing the environmental requirements for the ESR parameter of the electrolytic capacitor. Without changing the existing hardware solution, the initial power-on power of the backlight driving circuit is reduced to ensure normal startup. Then, the output power is gradually increased to achieve full-power screen illumination, ensuring stable operation of the boost circuit. Through these improvements, the low-temperature startup of wide-temperature, high-brightness display products can be improved, resolving the backlight flickering problem that occurs during cold startup in low-temperature environments, thereby enhancing the user experience.

[0140] It should be noted that:

[0141] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0142] Similarly, it should be understood that, in order to simplify this application and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together into a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0143] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0144] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0145] The various component embodiments of this application can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components in the virtual machine creation apparatus according to embodiments of this application. This application can also be implemented as a device or apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such an implementation of this application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0146] It should be noted that the above embodiments are illustrative of this application and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0147] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A backlight driving circuit for driving a backlight module to light up, characterized in that, include: Boost circuit and microcontroller; The input terminal of the boost circuit is connected to the power supply, and the output terminal of the boost circuit is connected to the backlight module. The boost circuit is configured to output a driving voltage to the backlight module according to a driving voltage output mode, the driving voltage output mode including a first driving voltage output mode, the first driving voltage output mode being to output a driving voltage to the backlight module up to the rated driving voltage in time periods; 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 includes: an inductor, a diode, a first transistor, a DC boost chip, a loop, and an electrolytic capacitor; The first end of the inductor is connected to the input terminal of the boost circuit, the second end of the inductor is connected to the anode of the diode, and the cathode of the diode is connected to the output terminal of the boost circuit; the first end of the first transistor is connected to the second end of the inductor, the second end of the first transistor is grounded, the gate of the first transistor is connected to the output terminal of the DC boost chip, the input terminal of the DC boost chip is connected to the first terminal of the loop, and the second terminal of the loop is grounded; the positive terminal of the electrolytic capacitor is connected to the output terminal of the boost circuit, and the negative terminal of the electrolytic capacitor is grounded; The DC boost chip outputs a pulse width modulation (PWM) signal to the first transistor to control the drive voltage output from the boost circuit. The electrolytic capacitor satisfies the following relationship: f1 ≤ ≤f2; in, Indicates the zero-point frequency of the circuit. This represents the impedance of the electrolytic capacitor. f1 represents the capacitance value of the electrolytic capacitor, f2 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, characterized in that, The first driving voltage output method 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; the first driving voltage is less than the second driving voltage, and the second driving voltage is less than the rated driving voltage.

3. The backlight driving circuit according to claim 1, characterized in that, The first driving voltage output method is to output a first driving voltage to the backlight module during a first time period and to output a rated driving voltage to the backlight module during a second time period. The ratio of the first driving voltage to the rated driving voltage is a first ratio, which 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, which is greater than or equal to 2.

4. The backlight driving circuit according to claim 2 or 3, characterized in that, The first time period is greater than or equal to 5 seconds and less than or equal to 15 seconds.

5. The backlight driving circuit according to claim 1, characterized in that, The microcontroller is configured to adjust the driving voltage output mode of the boost circuit to a first driving voltage output mode when the ambient temperature is lower than a first temperature, and to adjust the driving voltage output mode of the boost circuit to a second driving voltage output mode when the ambient temperature is higher than a first temperature. The second driving voltage output mode is to directly output the rated driving voltage to the backlight module.

6. The backlight driving circuit according to claim 5, characterized in that, The first temperature is less than or equal to -20°C.

7. The backlight driving circuit according to claim 1, characterized in that, The loop includes: a first resistor, a first capacitor, and a second capacitor; The first end of the first resistor is connected to the first end of the loop, the second end of the first resistor is connected to the first end of the second capacitor, the second end of the second capacitor is connected to the second end of the loop, and the first end of the first capacitor is connected to the first end of the loop and the second end of the first capacitor is connected to the second end of the loop.

8. The backlight driving circuit according to claim 7, characterized in that, The backlight driving circuit also includes: a temperature detection circuit; The first resistor includes: a first resistor, a second transistor, and a second resistor; The first terminal of the first resistor is connected to the first terminal of the first resistor, and the second terminal of the first resistor is connected to the second terminal of the first resistor; the first terminal of the second transistor is connected to the first terminal of the first resistor, the second terminal of the second transistor is connected to the first terminal of the second resistor, the second terminal of the second resistor is connected to the second terminal of the first resistor, and the gate terminal of the second transistor is connected to the output terminal of the microcontroller; the input terminal of the microcontroller is connected to the output terminal of the temperature detection circuit. When the ambient temperature is greater than the second temperature, the microcontroller controls the second transistor to turn off, and the resistor connected in series in the loop at this time is the first sub-resistor; when the ambient temperature is less than or equal to the second temperature, the microcontroller controls the second transistor to turn on, and the resistor connected in series in the loop at this time is the second sub-resistor.

9. The backlight driving circuit according to claim 8, characterized in that, The temperature detection circuit includes: a second resistor, a fourth capacitor, and a thermistor; The first end of the second resistor is connected to the output terminal of the temperature detection circuit, and the second end of the second resistor is grounded; the first end of the fourth capacitor is connected to the output terminal of the temperature detection circuit, and the second end of the fourth capacitor is grounded; the first end of the thermistor is connected to the output terminal of the temperature detection circuit, and the second end of the thermistor is connected to the power supply.

10. A backlight driving board, characterized in that, include: The backlight driving circuit according to any one of claims 1 to 9.

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