LED drive control chip and LED system circuit

Abstract

The utility model relates to an LED drive control chip and an LED system circuit. A novel LED drive control chip is provided to drive and control light emission of an LED load, a signal indicating a preset LPWM signal conduction width is configured in a PWM dimming control module in the control chip, and the conduction width of an external LPWM signal is compared with the preset LPWM signal conduction width. And a final actual LPWM signal is output to a chip logic control module based on a comparison result, and a power switch tube driving module is controlled to generate a power switch tube driving signal, so that the energy of the driving signal of a main power switch tube in an LED system circuit is ensured to be sufficient under the condition of small duty ratio dimming of the high-frequency PWM signal, and the purposes of ensuring the color accuracy and improving the brightness of the LED system circuit are achieved. And the stroboflash is reduced and the eyesight of the user is protected. In addition, according to some embodiments of the utility model, mixed dimming of high-frequency PWM dimming and analog dimming can be realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to LED backlight technical field generally, more specifically, it relates to a kind of LED drive control chip and LED system circuit. BACKGROUND

[0002] Traditional LED system circuit usually uses low-frequency pulse width modulation (PWM) dimming technology, and using low-frequency PWM signal to dim LED system circuit can cause stroboscopic, thereby causing the problem of affecting vision. Currently, there are also dimming devices that use high-frequency PWM signals to dim LED system circuits. However, when using a PWM signal with a higher frequency and a small duty cycle for dimming, the drive signal energy of the main power switch tube in the LED system circuit may not be sufficient, resulting in a low output voltage and causing the LED load to flicker or even go out, thereby affecting the user experience of the end customer. SUMMARY

[0003] The utility model provides a novel LED drive control chip to drive and control the light emission of LED load.

[0004] According to an aspect of the utility model, an LED drive control chip is provided, which includes a PWM dimming control module, a chip logic control module, a power switch tube driving module, and a logic pulse width modulation (LPWM) signal input pin. The PWM dimming control module is coupled to the LPWM signal input pin to receive an external LPWM signal and is configured with a signal indicating a preset LPWM signal on-width. The PWM dimming control module is configured to compare the on-width of the external LPWM signal with the preset LPWM signal on-width and generate a final actual LPWM signal based on the comparison result and the external LPWM signal to output to the chip logic control module. The preset LPWM signal on-width is set to the duration of N power switch tube driving pulse signals, where N is a preset positive integer. The chip logic control module is coupled to the PWM dimming control module and the power switch tube driving module and is configured to control the power switch tube driving module to generate a power switch tube driving signal based on the final actual LPWM signal to drive the main power switch tube coupled to the LED load.

[0005] In some examples according to an aspect of the utility model, the PWM dimming control module is configured to generate an internal LPWM signal synchronized with the external LPWM signal as the final actual LPWM signal output to the chip logic control module when the on-width of the external LPWM signal is less than the preset LPWM signal on-width. The period of the internal LPWM signal is the same as that of the external LPWM signal, and the on-width of the internal LPWM signal is the preset LPWM signal on-width.

[0006] In some examples according to the aspect of the utility model, the PWM dimming control module is configured to output the external LPWM signal as a final actual LPWM signal to the chip logic control module when the on width of the external LPWM signal is greater than or equal to a preset LPWM signal on width.

[0007] In some examples according to the aspect of the utility model, the PWM dimming control module is configured to adjust the preset LPWM signal on width to the duration of the M power switch tube driving pulse signal when the on width of the external LPWM signal is less than a predetermined threshold, and M is a preset positive integer less than N.

[0008] In some examples according to the aspect of the utility model, the external LPWM signal is a high-frequency LPWM signal with a frequency higher than a predetermined value.

[0009] In some examples according to the aspect of the utility model, the LED drive control chip further comprises a hybrid pulse width modulation (HPWM) signal input pin, an output constant current control module, and an analog dimming control module, wherein: the output constant current control module is coupled to the HPWM signal input pin to receive an external HPWM signal, and is configured to convert the external HPWM signal into a direct current voltage reference signal to output to the analog dimming control module; the analog dimming control module is coupled to the output constant current control module and the chip logic control module, and is configured to generate an analog dimming logic control signal based on the direct current voltage reference signal and a channel voltage feedback signal of the LED load to output to the chip logic control module; and the chip logic control module is configured to control the power switch tube driving module to generate an analog power switch tube driving signal based on the analog dimming logic control signal to drive the main power switch tube.

[0010] In some examples according to the aspect of the utility model, the LED drive control chip further comprises an inductance current detection and overvoltage protection detection CS / OVP pin, a current detection module, and an overvoltage protection detection module, wherein the current detection module and the overvoltage protection detection module are coupled to the CS / OVP pin and the chip logic control module, and the LED drive control chip is configured to detect the output voltage value of the LED load received through the CS / OVP pin in real time, and control the power switch tube driving module to stop outputting the power switch tube driving signal when the output voltage value exceeds an internal protection threshold.

[0011] In some examples according to the aspect of the present application, the LED driving control chip further comprises an LED pin, a feedback voltage FB pin, and a built-in power switch tube, wherein the LED pin is coupled with a drain of the built-in power switch tube and an LED load, a source of the built-in power switch tube is coupled to the PWM dimming control module to receive an external LPWM signal as a dimming driving signal of the built-in power switch tube, and the source of the built-in power switch tube is coupled with the FB pin, and the FB pin is used to receive a channel voltage feedback signal of the LED load.

[0012] In some examples according to the aspect of the present application, the LED driving control chip further comprises a chip power supply VDD pin used to receive an external power supply voltage to supply power to internal modules of the chip, and a power switch tube driving GATE pin used to receive a power switch tube driving signal from a power switch tube driving module to drive the main power switch tube.

[0013] According to another aspect of the present application, an LED system circuit is provided, comprising an LED load, a main power switch tube, and an LED driving control chip as described above. BRIEF DESCRIPTION OF DRAWINGS

[0014] The present application can be better understood from the following description of specific embodiments thereof, given by way of example and illustrated in the accompanying drawings in which:

[0015] Figure 1 A schematic diagram of an LED system circuit according to an embodiment of the present application is shown;

[0016] Figure 2 An internal structure block diagram of an LED driving control chip according to an embodiment of the present application is shown;

[0017] Figure 3 A dimming logic timing diagram of an LED system circuit according to an embodiment of the present application is shown;

[0018] Figure 4 A dimming logic timing diagram of an LED system circuit according to another embodiment of the present application is shown;

[0019] Figure 5 A dimming logic timing diagram of an LED system circuit according to yet another embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] The features and exemplary embodiments of various aspects of this utility model will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a comprehensive understanding of this utility model. However, it will be apparent to those skilled in the art that this utility model can be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this utility model by illustrating examples of it. This utility model is by no means limited to any specific configuration set forth below, but covers any modifications, substitutions, and improvements to elements and components without departing from the spirit of this utility model. In the drawings and the following description, some well-known structures and components are not shown to avoid unnecessarily obscuring this utility model.

[0021] As mentioned above, using a low-frequency PWM signal to dim an LED system circuit may cause flicker. Using a higher-frequency PWM signal can make the flicker imperceptible to the human eye. However, when using a higher-frequency PWM signal with a small duty cycle for dimming, the drive signal energy of the main power switch in the LED system circuit may be insufficient, resulting in a low output voltage and causing the LED load to flicker or even turn off, thus affecting the user experience of the end customer.

[0022] In view of these problems, this invention proposes a novel LED driver control chip to drive and control the light emission of an LED load, enabling both color accuracy and reduced flicker to protect the user's eyesight when using a higher frequency (e.g., 20kHz and above) PWM signal to dim the LED load. Furthermore, according to some embodiments of this invention, hybrid dimming combining high-frequency PWM dimming and analog dimming can also be achieved.

[0023] Figure 1 A schematic diagram of an LED system circuit according to an embodiment of this application is shown. Figure 1 As shown, the system circuit may include an LED driver control chip U1, an LED load, a fuse F1, an input filter capacitor C1, an output current setting resistor R4, a VDD bypass capacitor C2, an inductor current sampling resistor R3, overvoltage protection (OVP) voltage setting resistors R1 and R2, a boost inductor L1, a main power switch Q1 controlling the LED load, a freewheeling diode D1, and an output filter capacitor C3. The LED driver control chip U1 can generate a power switch drive signal for driving the main power switch Q1 based on an externally input logic PWM (LPWM) signal and / or mixed PWM (HPWM) signal, and perform dimming control on the LED load.

[0024] According to some embodiments of the present application, the LED drive control chip U1 can include the following pins: a VDD pin, i.e., a chip power supply pin; an LPWM pin, i.e., an LPWM signal input pin; an HPWM pin, i.e., an HPWM signal input pin; an FB pin, i.e., a feedback voltage pin; an LED pin, i.e., a pin through which the control chip U1 is coupled to an LED load, which pin is also coupled to the drain of a built-in power switch tube of the control chip U1; a GND pin, i.e., a reference ground pin of the control chip; a CS / OVP pin, i.e., an inductance current detection and over-voltage protection detection pin; and a GATE pin, i.e., a main power switch tube driving pin. As described above, Figure 1 The example pin setting of the LED drive control chip U1 is shown, for example, the LED drive control chip U1 includes the LPWM pin and the HPWM pin, and mixed dimming of high-frequency PWM dimming and analog dimming can be achieved. However, in actual design or use, the pins of the LED drive control chip U1 can also be set according to actual needs. For example, if only high-frequency LPWM dimming needs to be achieved, the control chip U1 can only need to set the LPWM pin, and does not need to set the HPWM pin.

[0025] The internal structure of the LED drive control chip U1 will be described below in combination with Figure 2 The internal structure of the LED drive control chip U1 will be described below in combination with Figure 2 The internal structure block diagram of the LED drive control chip according to an embodiment of the present application is shown. As Figure 2 shown, the control chip U1 can include a chip power supply module B1, a power switch tube driving module B2, a current detection module B3, an OVP detection module B4, a chip logic control module B5, a PWM dimming control module B6, an output constant current control module B7, an analog dimming control module B8, and a built-in power switch tube Q2.

[0026] Specifically, the chip power supply module B1 receives an external supply voltage through the VDD pin, and provides the required operating voltage for the internal functional modules (e.g., the chip logic control module B5 and the power switch tube driving module B2) of the LED driving control chip U1; the power switch tube driving module B2 receives a logic control signal from the chip logic control module B5, converts it into a suitable power switch tube driving signal to drive the main power switch tube Q1 in the LED system circuit; the current detection module B3 and the OVP detection module B4 detect whether the external voltage signal received through the CS / OVP pin reaches the internal threshold value, and then output a logic signal to the chip logic control module B5 for corresponding logic control according to the detection result; the chip logic control module B5 receives logic signals from each internal functional module in the control chip U1, performs logic algorithm processing, and outputs a logic control signal to the power switch tube driving module B2 to control the switching of the main power switch tube Q1; the PWM dimming control module B6 receives an externally provided LPWM signal through the LPWM pin, processes it, and outputs a logic signal to the chip logic control module B5 for corresponding logic control and outputs an LPWM dimming duty cycle signal; the output constant current control module B7 receives an externally provided HPWM signal through the HPWM pin, converts it into an internal specific form of HPWM signal after processing, and then filters it into a direct current voltage and outputs a direct current voltage reference signal; the analog dimming control module B8 receives a direct current voltage reference signal converted from the external HPWM signal and a channel feedback voltage FB signal from the output constant current control module B7, processes them, and outputs a logic signal to the chip logic control module B5 for corresponding logic control.

[0027] The following will be described in combination with Figure 1 and Figure 2The working process of the LED system circuit according to the embodiment of the present application is further described. The working process of the LED system circuit can be divided into three stages. The first stage: the external supply voltage supplies power to the internal logic circuit of the control chip U1 through the VDD pin. The supply voltage VDD first charges the capacitor C2, and when the voltage value of the capacitor C2 reaches the starting voltage value of the control chip U1, if the voltage signal exceeding the respective high threshold value is externally provided through the LPWM pin or the HPWM pin, the control chip U1 starts to start. After the control chip U1 starts, the power switch tube driving signal is output through the GATE pin to control the on-off of the main power switch tube Q1. When the main power switch tube Q1 is turned on, the energy is stored in the inductor L1, and the current path of the inductor L1 is VIN->F1->L1->Q1->R3->GND. At this time, the diode D1 is cut off, and the polarity of the inductor voltage UL is positive at the left end and negative at the right end. During the conduction time of the main power switch tube Q1, the control chip U1 limits the inductor current during the conduction of the main power switch tube Q1 by limiting the voltage across the sampling resistor R3. After the conduction time of the main power switch tube Q1 in the current cycle is completed, the control chip U1 controls it to be turned off, and enters the second stage. The second stage: the main power switch tube Q1 enters the off state, at this time, the inductor L1 generates a reverse electromotive force, and the polarity of the inductor voltage UL becomes positive at the right end and negative at the left end. The inductor L1 acts as a temporary power supply and a main power supply VIN in series, at this time, the diode D1 is forward biased, and the inductor L1 starts to discharge energy, and the discharge current path becomes D1->C3->GND->VIN from the right end of the inductor L1, and returns to the left end of the inductor L1. The control chip U1 is a fixed frequency control, which controls the main power switch tube Q1 to enter the first stage of the cycle again, and the control chip U1 transfers energy to the LED load cycle by cycle. During the above-mentioned cycle, the control chip U1 detects the output voltage value in real time through the CS / OVP pin, and when the output voltage value reaches the internal protection threshold value, the control chip U1 stops outputting the power switch tube driving signal to the GATE pin, thereby realizing the output overvoltage protection function. The third stage: during the above-mentioned first or second stage, when the chip supply voltage VDD decreases below the under-voltage protection voltage point of the control chip U1 or the protection function of the control chip U1 is triggered, the control chip U1 will close the GATE pin output, and when the VDD voltage value rises to the chip starting threshold value again, the cycle enters the first stage.

[0028] As mentioned above, when the PWM signal with a higher frequency (for example, 20 kHz and above) and a small duty ratio is used for dimming, the driving signal energy of the main power switch tube in the LED system circuit may be insufficient, resulting in a low output voltage, and the LED load may flicker or even be extinguished. According to the embodiment of the present application, the PWM signal with a higher frequency (for example, 20 kHz and above) and a small duty ratio is used for dimming, and the driving signal energy of the main power switch tube in the LED system circuit is supplemented by the auxiliary power switch tube, so that the output voltage is not too low, and the LED load does not flicker or even be extinguished. Figure 2The LED driving control chip U1 shown compares the on width of the external LPWM signal with the preset LPWM signal on width by configuring a signal indicating the preset LPWM signal on width in the PWM dimming control module B6, and outputs a final actual LPWM signal to the chip logic control module based on the comparison result, controls the power switch tube driving module to generate a power switch tube driving signal, thereby overcoming the problems that may occur when the high-frequency PWM signal is used to dim the LED load.

[0029] The process of high-frequency LPWM signal dimming by the LED driving control chip U1 shown will be described below in combination with Figures 3 to 5 the dimming logic timing diagram of the LED system circuit shown. Figure 2 According to the embodiments of the present application, a signal indicating the preset LPWM signal on width is configured in the PWM dimming control module B6. Specifically, the timing of N power switch tube driving pulse signals (GATE driving pulse signals) is fixedly performed from the rising edge of the LPWM signal, and the duration of the N GATE driving pulse signals is Ton_min, so that the signal obtained is the built-in LPWM signal (denoted as LPWM_min in Figures 3 to 5 ), which has the same period as the external LPWM signal and the on width of which is the preset LPWM signal on width, denoted as Ton_min. Here, N can be a positive integer that is preset according to simulation or experimental data.

[0030] According to the embodiments of the present application, the PWM dimming control module B6 can be configured to compare the on width of the external LPWM signal received through the LPWM pin with the preset LPWM signal on width, and generate and output a final actual LPWM signal to the chip logic control module based on the comparison result and the external LPWM signal. For example, as Figure 3 shown, when the duty cycle of the external LPWM signal is small, that is, when the on width Ton of the external LPWM signal LPWM is less than the preset LPWM signal on width Ton_min, the built-in LPWM signal LPWM_min is output as the final actual LPWM signal LPWM_real to the chip logic control module B5. Further, as Figure 4As shown, when the duty cycle of the external LPWM signal is large, that is, when the on width Ton of the external LPWM signal is greater than or equal to the preset LPWM signal on width Ton_min, the external LPWM signal LPWM is directly output as the final actual LPWM signal LPWM_real to the chip logic control module B5, so that the duration of the GATE drive pulse signal output by the GATE pin is equal to the on width Ton of the external LPWM signal. In this way, in the case of small duty cycle dimming of a high-frequency PWM signal, the GATE pin can output at least N GATE drive pulse signals to drive the main power switch tube Q1, and the internal power switch tube of the control chip U1 at the LED pin still uses the external LPWM signal for dimming, so that in the case of small duty cycle dimming of a high-frequency PWM signal, the driving signal energy of the main power switch tube in the LED system circuit is sufficient.

[0031] In addition, when the duty cycle of the external LPWM signal is extremely small, in order to avoid the occurrence of over-voltage protection due to the output of excessive energy for driving the main power switch tube with N pulse signals, in some embodiments according to the present application, the preset LPWM signal on width Ton_min can be adaptively adjusted according to the change of the duty cycle of the external LPWM signal. For example, a predetermined threshold can be set. When it is detected that the on width Ton of the external LPWM signal is less than the predetermined threshold, the PWM dimming control module B6 can adjust the preset LPWM signal on width Ton_min to the width of M=N-n (1≤n<N) GATE drive pulse signals. In other words, in the case of extremely small duty cycle dimming of a high-frequency PWM signal, the GATE pin outputs at least M (M is less than N) GATE drive pulse signals to drive the main power switch tube Q1, and the specific dimming logic timing diagram is as shown in Figure 5 .

[0032] In summary, according to the embodiments of the present application, the LED drive control chip U1 as shown in Figure 2 can be used to control and adjust the duty cycle of the high-frequency LPWM signal actually used for dimming by configuring a signal indicating the preset LPWM signal on width in the PWM dimming control module B6, so that in the case of small duty cycle dimming of a high-frequency PWM signal, the driving signal energy of the main power switch tube in the LED system circuit is sufficient, achieving the effect of ensuring color accuracy and reducing frequency flicker to protect the user's vision. In addition, according to some embodiments of the present application, hybrid dimming of high-frequency PWM dimming and analog dimming can also be achieved.

[0033] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware components, hardware blocks, and the like, to provide a thorough understanding of embodiments of the subject matter. One skilled in the relevant art will recognize, however, that the subject matter can be practiced without one or more of the

[0034] Those skilled in the art will understand that the embodiments described above are merely exemplary and not limiting. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on the drawings, the specification, and the claims, those skilled in the art should understand and implement other changed embodiments of the disclosed embodiments. The fact that certain technical features appear in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

Claims

1. An LED driving control chip, characterized in that Comprising: a pulse width modulation (PWM) dimming control module, a chip logic control module, a power switch tube driving module, and a logic pulse width modulation (LPWM) signal input pin, wherein: the PWM dimming control module is coupled to the LPWM signal input pin to receive an external LPWM signal, and is configured with a signal indicating a preset LPWM signal on-width, the PWM dimming control module is configured to compare an on-width of the external LPWM signal with the preset LPWM signal on-width, and generate a final actual LPWM signal based on a comparison result and the external LPWM signal to output to the chip logic control module, wherein the preset LPWM signal on-width is set to a duration of N power switch tube driving pulse signals, N being a preset positive integer; and the chip logic control module is coupled to the PWM dimming control module and the power switch tube driving module, and is configured to control the power switch tube driving module to generate a power switch tube driving signal based on the final actual LPWM signal to drive a main power switch tube coupled to an LED load.

2. The LED driving control chip according to claim 1, wherein the PWM dimming control module is configured to: when the on-width of the external LPWM signal is less than the preset LPWM signal on-width, generate an internal LPWM signal synchronized with the external LPWM signal as the final actual LPWM signal to output to the chip logic control module, a period of the internal LPWM signal being the same as a period of the external LPWM signal, and an on-width of the internal LPWM signal being the preset LPWM signal on-width.

3. The LED driving control chip according to claim 1, wherein the PWM dimming control module is configured to, when the on-width of the external LPWM signal is greater than or equal to the preset LPWM signal on-width, output the external LPWM signal as the final actual LPWM signal to the chip logic control module.

4. The LED driving control chip according to any one of claims 1 to 3, wherein the PWM dimming control module is configured to, when the on-width of the external LPWM signal is less than a predetermined threshold, adjust the preset LPWM signal on-width to a duration of M power switch tube driving pulse signals, M being a preset positive integer less than N.

5. The LED driving control chip according to any one of claims 1 to 3, wherein the external LPWM signal is a high-frequency LPWM signal with a frequency higher than a predetermined value.

6. The LED drive control chip of any one of claims 1-3, further comprising: a hybrid pulse width modulation (HPWM) signal input pin, an output constant current control module, and an analog dimming control module, wherein: the output constant current control module is coupled to the HPWM signal input pin to receive an external HPWM signal, and is configured to convert the external HPWM signal into a direct current voltage reference signal to output to the analog dimming control module; The analog dimming control module is coupled with the output constant current control module and the chip logic control module, and is configured to generate an analog dimming logic control signal based on the direct current voltage reference signal and a channel voltage feedback signal of the LED load, and output the analog dimming logic control signal to the chip logic control module; and The chip logic control module is configured to control the power switch tube driving module to generate an analog power switch tube driving signal based on the analog dimming logic control signal, so as to drive the main power switch tube.

7. The LED drive control chip of any one of claims 1 to 3, further comprising an inductor current sense and overvoltage protection sense CS / OVP pin, a current sense module, and an overvoltage protection sense module, wherein, The current detection module and the overvoltage protection detection module are coupled with the CS / OVP pin and the chip logic control module, and the LED driving control chip is configured to detect the output voltage value of the LED load received through the CS / OVP pin in real time, and control the power switch tube driving module to stop outputting the power switch tube driving signal when the output voltage value exceeds an internal protection threshold.

8. The LED driving control chip according to any one of claims 1 to 3, further comprising an LED pin, a feedback voltage (FB) pin, and a built-in power switch tube, wherein, The LED pin is coupled with the drain of the built-in power switch tube and the LED load, the source of the built-in power switch tube is coupled to the PWM dimming control module to receive the external LPWM signal as a dimming driving signal of the built-in power switch tube, and the source of the built-in power switch tube is coupled with the FB pin, which is used to receive the channel voltage feedback signal of the LED load.

9. The LED drive control chip of any one of claims 1-3, further comprising: A chip power supply VDD pin for receiving an external power supply voltage to supply power to internal modules of the chip; And a power switch tube driving GATE pin for receiving the power switch tube driving signal from the power switch tube driving module to drive the main power switch tube.

10. An LED system circuit comprising an LED load, a main power switch tube, and an LED driving control chip according to any one of claims 1 to 9.

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