TWI852490B - LED control chip, method and multi-channel backlight system - Google Patents

Abstract

The present invention discloses a light emitting diode (LED) control chip, method and multi-channel backlight system. The LED control chip provided by the present invention is used to control the turning off and on of each channel in the multi-channel LED, including multiple LED pins corresponding to the multi-channel LED. The LED control chip is configured as follows: after the LED control chip is powered on, each of the multiple LED pins is charged using the internal reference current of the LED control chip; the voltage on each of the multiple LED pins is compared with the preset voltage threshold to obtain multiple comparison results corresponding to each of the multiple LED pins; and according to each of the multiple comparison results, it is determined whether each channel in the multi-channel LED needs to be turned off or on.

Description

LED control chip, method and multi-channel backlight system

The embodiments of the present invention generally relate to the field of integrated circuits, and more particularly to an LED control chip, method, and multi-channel backlight system.

In the application of LED (Light Emitting Diode) backlight of switching power supply, multi-channel constant current backlight drive is a common system architecture. Its advantage is that the backlight distribution is relatively uniform. Compared with the single-string LED backlight system, the multi-string parallel LED backlight system can be evenly distributed under the screen, so that the brightness of each area of the screen remains consistent, and there will be no problem of high brightness in the middle of the screen and low brightness in the four corners in the single-string LED backlight system.

However, in actual use, one or more LED channels need to be disabled to match different screen requirements. The traditional solution is usually to shut down the unused LED channels through LED circuit breakers or LED short circuit protection. The shutdown state is after the chip has started to work normally, which can easily cause a series of problems such as output voltage overshoot and chip misprotection.

In the first aspect, an embodiment of the present invention provides an LED control chip for controlling the turning off and on of each channel in a multi-channel LED, including a plurality of LED pins corresponding to the multi-channel LED, wherein the LED control chip is configured to: after the LED control chip is powered on, charge each of the plurality of LED pins using the internal reference current of the LED control chip; compare the voltage on each of the plurality of LED pins with a preset voltage threshold to obtain a plurality of comparison results corresponding to each of the plurality of LED pins; and determine whether each channel in the multi-channel LED needs to be turned off or on according to each of the plurality of comparison results.

In the second aspect, the embodiment of the present invention further provides an LED control chip and a multi-channel LED as described in the first aspect, wherein each channel in the multi-channel LED is respectively connected to each LED pin in the plurality of LED pins of the LED control chip.

In a third aspect, the embodiment of the present invention also provides a control method executed by an LED control chip, which is used to control the turning off and on of each channel in a multi-channel LED. The LED control chip includes a plurality of LED pins corresponding to the multi-channel LED. The method includes: after the LED control chip is powered on, each of the plurality of LED pins is charged using the internal reference current of the LED control chip; the voltage on each of the plurality of LED pins is compared with a preset voltage threshold to obtain a plurality of comparison results corresponding to each of the plurality of LED pins; and according to each of the plurality of comparison results, it is determined whether each channel in the multi-channel LED needs to be turned off or on.

The LED control chip, method and multi-channel backlight system provided by the embodiment of the present invention can detect whether each channel in the multi-channel LED needs to be turned off or on, and then turn off the channels that are not needed before the LED control chip works normally, thereby preventing a series of problems such as output voltage overshoot and chip misprotection caused by turning off certain channels.

100,200:LED control chip

102: Low voltage dropout linear regulator (LDO)

104: Undervoltage lockout (UVLO) module

106: Reference voltage and reference current generation module

108:Driver

110: Oscillator

112: Comparator

114: Control Logic

116: Amplifier (CS_amp)

118: Error amplifier (EA)

120: Feedback control module

122,OP1: Operational amplifier

124: Constant current unit

126: Channel control module

700:LED control method

C1: Input capacitor

C11: parasitic capacitance

C2: output capacitor

Channel_en1, Channel_en2,....Channel_enx: channel enable signal

CLK,CMP,pg,pg_delay,Ramp:Signal

CMP1: First comparator

CMP1_out: comparator output signal

CS: Current sampling signal

D1: Follow-up diode

DHC: minimum voltage

EA_ref: Error reference voltage

ENA: Chip Enable

Gate: Gate drive signal

GND: Chip ground

Iref, Iref1: internal reference current

ISET: Current setting terminal

L1: Inductor

LED1,...,LEDX: channel

M1: transistor

NM1: The third transistor

NM2: The fourth transistor

pg_delay_b: The third control signal

PM1: The first P-type metal oxide semiconductor (PMOS) transistor

R1: first resistor

Rc: Second resistor

S: Adder

S702, S704, S706: Methods

VCC: Low voltage LDO output inside the chip

VDD: voltage

VIN: Input voltage

Vout: output voltage

Vref: channel reference voltage

Vref1: internal reference voltage

Vth_1: Default voltage threshold

In order to more clearly explain the technical solution of the embodiment of the present invention, the following will briefly introduce the diagrams required for use in the embodiment of the present invention. For ordinary technicians in this field, other diagrams can be obtained based on these diagrams without making any progressive efforts.

Figure 1 shows a schematic diagram of the structure of a multi-channel backlight system with a traditional boost architecture;

Figure 2 shows a schematic diagram of the structure of an LED control chip provided in an embodiment of the present invention;

Figure 3 shows a schematic diagram of the structure of the channel control module of the normal use channel;

Figure 4 shows a waveform diagram of the corresponding signal in the channel control module of the normally used channel shown in Figure 3;

Figure 5 shows a schematic diagram of the structure of the channel control module for closing the channel;

FIG6 shows a waveform diagram of the corresponding signal in the channel control module of the channel shut down shown in FIG5;

Figure 7 shows a schematic diagram of the process of the LED control method provided by the embodiment of the present invention.

The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in combination with drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the phrase "includes..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

In order to better understand the technical solution provided by the embodiment of the present invention, the following first introduces the multi-channel backlight system of the traditional boost architecture. Referring to Figure 1, Figure 1 shows a structural schematic diagram of the multi-channel backlight system of the traditional boost architecture.

As shown in FIG1 , the multi-channel backlight system of the boost architecture may include an LED control chip 100, a multi-channel LED (including channels LED1...LEDX), an input capacitor C1, an inductor L1, a transistor M1, a first resistor R1, a freewheeling diode D1, and an output capacitor C2, etc., wherein each channel of the multi-channel LED may include an LED light string.

The LED control chip 100 may include a low dropout regulator (LDO) 102, an under voltage lockout (UVLO) module 104, a reference voltage and reference current generation module 106, a driver 108, an oscillator 110, a comparator 112, a control logic 114, an amplifier (CS_amp) 116, an error amplifier (EA) 118, a feedback control module 120, an operational amplifier 122, and a constant current unit 124, etc.

Among them, VIN is the input voltage of the LED control chip 100 and the entire system. When the gate drive signal Gate is at a high level, the transistor M1 (for example, N-type metal oxide semiconductor (NMOS) transistor) is turned on, and the input voltage VIN is stored through the inductor L1. When the gate drive signal Gate is at a low level, the transistor M1 is turned off, and the energy on the inductor L1 is superimposed on the input voltage VIN and then charged to the output capacitor C2 through the freewheeling diode D1, so that the output voltage Vout of the system gradually increases. When the output voltage Vout increases to a certain voltage, the LED string of the channel is turned on.

As an example, the constant current unit 124 in the LED control chip 100 controls the constant current of the LED string. The feedback control module 120 can collect the lowest voltage DHC in the multi-channel LED1 to LEDX, and input the lowest voltage DHC to the first input terminal of the error amplifier 118. The second input terminal of the error amplifier 118 can receive the reference voltage and reference current generation module. The error amplifier 118 can be used to amplify the error of the error reference voltage EA_ref and the lowest voltage DHC in the multi-channel LED1 to LEDX and generate a compensated CMP signal. The comparator 112 can be used to compare the CMP signal with the internally generated Ramp signal and generate a gate drive signal Gate for controlling the turn-off of the transistor M1. The gate drive signal Gate for controlling the turn-on of the transistor M1 can be generated by the CLK signal. Finally, when the error reference voltage EA_ref and the minimum voltage DHC generated by the feedback control module 120 are equal, a suitable output voltage Vout can be generated, that is, the output voltage required by the LED string output is met (due to the difference between the conduction voltages of each LED string, the output voltage Vout needs to meet the requirements of the LED string with the maximum conduction voltage) and the chip loss is minimized.

In order to solve one or more of the existing technical problems, the present invention provides an LED control chip, method and multi-channel backlight system. The LED control chip provided by the present invention is first introduced below.

FIG2 shows a schematic diagram of the structure of an LED control chip provided by an embodiment of the present invention. The same or similar components in FIG1 and FIG2 are marked with the same diagram. For the sake of simplicity, they will not be described here. The following mainly introduces the differences between the two.

Specifically, the difference between the LED control chip 200 shown in FIG. 2 and the LED control chip 100 shown in FIG. 1 is that, compared with the LED control chip 100 shown in FIG. 1 , the LED control chip 200 shown in FIG. 2 mainly adds a channel control module 126. The main function of the channel control module 126 may include determining the state of the multi-channel LED setting by detecting the voltage of the multi-channel LED1 to LEDX, and determining the state of each channel in the multi-channel LED according to the determined state before the LED control chip 200 works normally. , generating channel enable signals Channel_en1 to Channel_enx corresponding to the multi-channel LED1 to LEDX, and providing the channel enable signals Channel_en1 to Channel_enx to the constant current unit 124 to control the working state of the multi-channel LED1 to LEDX, for example, the channel enable signal Channel_en1 can be used to control the working state of the channel LED1, and the channel enable signal Channel_enx can be used to control the working state of the channel LEDX.

As an example, the LED control chip 200 shown in FIG. 2 can be configured to charge each of the multiple LED pins using the internal reference current Iref of the LED control chip after the LED control chip is powered on; compare the voltage on each of the multiple LED pins with the preset voltage threshold Vth_1 to obtain multiple comparison results corresponding to each of the multiple LED pins; and determine whether each channel of the multi-channel LED needs to be turned off or on according to each of the multiple comparison results.

Specifically, as shown in FIG. 3 and FIG. 5, FIG. 3 and FIG. 5 show the structural schematic diagrams of the channel control module 126 and the constant current unit 124 in the LED control chip 200 provided by the embodiment of the present invention. Specifically, FIG. 3 shows the structural schematic diagram of the channel control module 126 of the normal use channel, and FIG. 5 shows the structural schematic diagram of the channel control module 126 of the closed channel.

As an example, referring to FIG3 and FIG5, after the LED control chip is powered on, the internal reference current Iref1 from the reference voltage and reference current generating module 106 is used to charge the pin of the channel LED1, and the voltage on the pin of the channel LED1 is compared with the preset voltage threshold Vth_1 by the first comparator CMP1. According to the comparison result, it is determined whether the corresponding LED channel needs to be turned off or on.

As an example, the LED control chip 200 can be further configured to charge each of the multiple LED pins using the internal reference current Iref during a preset period of time from the moment the LED control chip is powered on (corresponding to the period when the signal pg is at a high level and the signal pg_delay is at a low level); lock each of the multiple comparison results at the moment when the preset period of time has passed from the moment the LED control chip is powered on (the signal pg_delay changes from a low level to a high level); and determine whether each channel of the multi-channel LED needs to be turned off or on based on each of the locked multiple comparison results.

Specifically, as shown in FIG. 4 and FIG. 6, FIG. 4 shows a waveform diagram of the corresponding signal in the channel control module 126 of the normally used channel shown in FIG. 3, and FIG. 6 shows a waveform diagram of the corresponding signal in the channel control module 126 of the closed channel shown in FIG. 5.

As an example, after a preset period of time (corresponding to the period when the signal pg is high and the signal pg_delay is low) from the moment the LED control chip is powered on, the internal reference current Iref is used to charge the LED pin. For example, in the waveform diagram shown in FIG4 , the voltage on the LED pin is charged to rise to a value greater than the preset voltage threshold Vth_1. At this time, the output signal C of the comparator is MP1_out flips (from low level to high level). When the signal pg_delay changes from low level to high level, the internal reference current Iref is turned off to stop charging the LED pin, causing the voltage on the LED pin to drop below the preset voltage threshold Vth_1. At this time, the comparator output signal CMP1_out flips (from high level to low level). As shown in Figure 6 In the waveform diagram, the voltage on the LED pin is always kept lower than the preset voltage threshold Vth_1 during the charging period, and the comparator output signal CMP1_out remains at a low level without flipping. When the signal pg_delay changes from a low level to a high level, the comparator output signal CMP1_out is locked. According to the locked comparison result, it is determined whether the corresponding channel needs to be turned off or on. For example, in the waveform diagram shown in FIG4, the locked comparison result indicates that the voltage on the LED pin is greater than the preset voltage threshold Vth_1, and it is determined that the LED channel corresponding to the LED pin needs to be turned on, while in the waveform diagram shown in FIG6, the locked comparison result indicates that the voltage on the LED pin is less than the preset voltage threshold Vth_1, and it is determined that the LED channel corresponding to the LED pin needs to be turned off.

As an example, the LED control chip can be further configured to shut down the internal reference current Iref after a preset time period has passed since the LED control chip is powered on (when the signal pg_delay changes from a low level to a high level) to prevent affecting the normal operation of subsequent channels.

As an example, the LED control chip can be further configured to determine that the first LED channel corresponding to the first LED pin in the multi-channel LED needs to be turned on, and control the turning on of the first LED channel, if the voltage on the first LED pin among the multiple LED pins is detected to rise to a value greater than the preset voltage threshold Vth_1 during a preset time period starting from the moment the LED control chip is powered on (corresponding to the period when the signal pg is at a high level and the signal pg_delay is at a low level), wherein the first LED pin may include one or more LED pins.

For example, in the embodiments shown in FIG. 3 and FIG. 4 , when the signal pg is at a high level and the signal pg_delay is at a low level (corresponding to the internal reference current Iref being at a high level), the first comparator CMP1 can detect that the voltage on the first LED pin is greater than the preset voltage threshold Vth_1, and it can be determined that the first LED channel corresponding to the first LED pin needs to be turned on. It can be understood that the "first" in the first LED pin is only used to distinguish different pins, and is not a restrictive meaning, which may include one or more LED pins that need to be turned on.

As an example, the LED control chip can be further configured to determine that the second LED channel corresponding to the second LED pin in the multi-channel LED needs to be turned off, and control the second LED channel to be turned off, if it is detected that the voltage on the second LED pin among the multiple LED pins remains less than the preset voltage threshold during a preset time period starting from the moment the LED control chip is powered on (corresponding to the period when the signal pg is at a high level and the signal pg_delay is at a low level), wherein the second LED pin may include one or more LED pins.

For example, in the embodiments shown in FIG. 5 and FIG. 6, during a preset period of time (corresponding to a period when the signal pg is high and the signal pg_delay is low) starting from the moment when the LED control chip is powered on, the first comparator CMP1 can detect that the voltage on the second LED pin remains less than the preset voltage threshold Vth_1, and it can be determined that the second LED channel corresponding to the second LED pin needs to be turned off. It can also be understood that the "second" in the second LED pin is only used to distinguish different pins, and is not a restrictive meaning, and it can include one or more LED pins.

The channel control module 126 shown in Figures 3 and 5 is described in detail below. It should be noted that it is provided only as an example and should not be construed as limiting.

As an example, as shown in FIG. 3, when the first channel corresponding to the pin of the channel LED1 needs to be turned on, the channel control module 126 may include a first P-type metal oxide semiconductor (PMOS) transistor PM1, a first comparator CMP1, and a first trigger, wherein the first end of the first PMOS transistor PM1 may receive an internal reference current Iref1, the second end may receive a signal pg_ddlay, and the third end may be connected to the pin of the channel LED1; the first end of the first comparator CMP1 may be connected to the pin of the channel LED1, the second end may receive a preset voltage threshold Vth_1; the first end of the first trigger may be connected to the third end of the first comparator CMP1, the second end may receive a signal pg_delay, and the third end may input The first channel enable signal Channel_en1 for controlling the connection of the first channel corresponding to the pin of the channel LED1 is output; wherein the signal pg_delay can be used to control the conduction of the first PMOS transistor PM1 when the LED control chip is powered on, and is used to control the first trigger to output the first channel enable signal Channel_en1 from a low level to a high level at a preset time period from the moment the LED control chip is powered on (corresponding to the moment when the signal pg_delay changes from a low level to a high level), so as to control the connection of the first channel corresponding to the first LED pin.

FIG3 shows a schematic diagram of the circuit structure of the channel control module 126 of the normal use channel. In combination with FIG3 and FIG4, the pin of the channel LED1 is in a suspended state, C11 is the parasitic capacitance from the pin of the channel LED1 to the ground, and after the LED control chip is powered on, the signal pg_delay is at a low level, the first PMOS transistor PM1 is turned on, the third control signal pg_delay_b (the reverse signal of pg_delay) is at a high level, the fourth transistor NM2 is turned on, and the internal reference current Iref1 is used to charge the pin of the channel LED1 through the first PMOS transistor PM1. Since the parasitic capacitance C11 is relatively small at this time, the channel LED1 is charged within a very short time. The voltage on the pin of D1 is charged to the VDD voltage. When the voltage on the pin of channel LED1 is detected to be greater than the preset voltage threshold Vth_1, the output signal CMP1_out of the first comparator CMP1 is flipped (from low level to high level). When the signal pg_delay changes from low level to high level, the output signal CMP1_out of the first comparator CMP1 is locked and output as a high-level channel enable signal Channel_en1, so that the corresponding channel can work normally. When the signal pg_delay changes from low level to high level, the internal reference current Iref1 is turned off to prevent affecting the normal operation of subsequent channels.

As a further example, each of the multiple channel control modules 126 may also include a delay unit, which may be connected between the first comparator CMP1 and the trigger. The delay unit may be used to mask the interference signal appearing on the LED pin to prevent the problem of erroneously shutting down the channel.

Among them, the signal pg, the signal pg_delay and the third control signal pg_delay_b are preset in the LED control chip, wherein the third control signal pg_delay_b is the reverse signal of the signal pg_delay and generates an internal reference current Iref1. As mentioned above, the internal reference current Iref1 is used to charge the pin of the channel LED1. When the signal pg is at a high level and the signal pg_delay is at a low level, If the voltage on the pin of channel LED1 is detected to be greater than the preset voltage threshold Vth_1, the output signal CMP1_out of the first comparator CMP1 flips from low level to high level. When the signal pg_delay changes from low level to high level, the output signal CMP1_out of the first comparator CMP1 is locked and output as a high-level channel enable signal Channel_en1, so that the corresponding channel can work normally.

As an example, as shown in FIG3 , the LED control chip may also include multiple constant current units corresponding to multiple LED pins, and each of the multiple constant current units is turned off when the LED control chip is powered on.

As an example, as shown in FIG3 , the constant current unit 124 may include an operational amplifier OP1, a second resistor Rc, a third transistor NM1, and a fourth transistor NM2, wherein the first end of the operational amplifier OP1 may receive the internal reference voltage Vref1 of the LED control chip; the first end of the third transistor NM1 may be connected to one of the plurality of LED pins, and the second end and the third end may be connected to the second end and the third end of the operational amplifier OP1, respectively; the first end of the second resistor Rc may be connected to the third end of the third transistor NM1, and the second end may be grounded; the first end of the fourth transistor NM2 may be connected to the second end of the third transistor NM1, the second end may receive the third control signal pg_delay_b, and the third end may be grounded, wherein the third control signal pg_delay_b may be used to control the conduction of the fourth transistor NM2 when the LED control chip is powered on, so as to control the shutdown of the third transistor NM1.

Specifically, when the LED control chip is started, the third control signal pg_delay_b is at a high level, the fourth transistor NM2 is turned on, and the gate of the third transistor NM1 is pulled down by the fourth transistor NM2, so that the third transistor NM1 is turned off to turn off the constant current unit 124.

As an example, when the channel corresponding to the pin of the channel LED1 needs to be turned off, as shown in FIG5 , the channel control module 126 may include a first PMOS transistor PM1, a first resistor R1, a first comparator CMP1, and a second trigger, wherein the first end of the first PMOS transistor PM1 may receive an internal reference current Iref1, the second end may receive a signal pg_delay, and the third end may be connected to the pin of the channel LED1; the first end of the first resistor R1 may be connected to the pin of the channel LED1, the second end may be grounded, and the resistance of the first resistor R1 is less than a preset resistance threshold value; the first end of the first comparator CMP1 may be connected to the pin of the channel LED1, the second end may receive a preset voltage threshold value Vth_1; the second end of the first comparator CMP1 may receive a preset voltage threshold value Vth_1; the third ... The first end of the trigger can be connected to the third end of the first comparator CMP1, the second end can receive the signal pg_delay, and the third end can output the channel enable signal Channel_en1 for controlling the shutdown of the first channel corresponding to the pin of the channel LED1; wherein the signal pg_delay can be used to control the conduction of the first PMOS transistor PM1 when the LED control chip is powered on, and is used to control the second trigger to output the channel enable signal Channel_en1 at a low level after a preset time period from the moment the LED control chip is powered on (corresponding to the moment when the signal pg_delay changes from a low level to a high level) to control the shutdown of the first channel corresponding to the pin of the channel LED1.

FIG5 shows a schematic diagram of the circuit structure of the channel control module 126 for closing the channel. Combining FIG5 and FIG6, compared with the circuit shown in FIG3, the circuit shown in FIG5 adds a first resistor R1 between the pin of the channel LED1 and the ground, and the resistance value of the first resistor R1 is set to be less than the preset resistance threshold value, for example, zero ohm. After the LED control chip is powered on, the signal pg changes from low level to high level, the signal pg_delay is low level, the first PMOS transistor PM1 is turned on, the third control signal pg_delay_b (the inverse signal of pg_delay) is high level, the fourth transistor NM2 is turned on, and the internal reference current Iref1 is used to charge the pin of the channel LED1 through the first PMOS transistor PM1. Since the resistance of the first resistor R1 is small at this time, the voltage on the pin of the channel LED1 is very low. During the period when the signal pg is high level and the signal pg_delay is low level, It can be detected that the voltage on the pin of channel LED1 is always less than the preset voltage threshold Vth_1, and the output signal CMP1_out of the first comparator CMP1 does not flip and always remains at a low level. When the signal pg_delay changes from a low level to a high level, the output signal CMP1_out of the first comparator CMP1 is locked and output as a low-level channel enable signal Channel_en1, so that the corresponding channel is turned off, and when the signal pg_delay changes from a low level to a high level, the internal reference current Iref1 is turned off to prevent affecting the normal operation of subsequent channels.

As a further example, as shown in FIG5 , each of the plurality of channel control modules 126 may further include a delay unit, which may be connected between the first comparator CMP1 and the trigger. The delay unit may be used to mask the interference signal appearing on the LED pin to prevent the problem of mistakenly shutting down the channel.

Among them, the signal pg, the signal pg_delay and the third control signal pg_delay_b are pre-set in the LED control chip, wherein the third control signal pg_delay_b is the reverse signal of the signal pg_delay and generates an internal reference current Iref1. As mentioned above, the internal reference current Iref1 is used to charge the pin of the channel LED1. When the signal pg is high and the signal pg_delay is low, During the calibration period, if the voltage on the pin of channel LED1 is always detected to be less than the preset voltage threshold Vth_1, the output signal CMP1_out of the first comparator CMP1 always remains at a low level. When the signal pg_delay changes from a low level to a high level, the output signal CMP1_out of the first comparator CMP1 is locked and output as a low-level channel enable signal Channel_en1, so that the corresponding channel is turned off.

As an example, as shown in FIG5 , the LED control chip may also include a plurality of constant current units corresponding to a plurality of LED pins, and each of the plurality of constant current units is turned off when the LED control chip is powered on.

As an example, as shown in FIG. 5 , the constant current unit 124 may include an operational amplifier OP1, a second resistor Rc, a third transistor NM1, and a fourth transistor NM2. The first end of the operational amplifier OP1 may receive the internal reference voltage Vref1 of the LED control chip; the first end of the third transistor NM1 may be connected to one of the plurality of LED pins (e.g., the pin of the channel LED1), and the second end and the third end may be connected to the second end of the operational amplifier OP1, respectively. The first end of the second resistor Rc can be connected to the third end of the third transistor NM1, and the second end can be grounded; the first end of the fourth transistor NM2 can be connected to the second end of the third transistor NM1, the second end can receive the third control signal pg_delay_b, and the third end can be grounded, wherein the third control signal pg_delay_b can be used to control the conduction of the fourth transistor NM2 when the LED control chip is powered on, so as to control the shutdown of the third transistor NM1.

Specifically, when the LED control chip is started, the third control signal pg_delay_b is at a high level, the fourth transistor NM2 is turned on, and the gate of the third transistor NM1 is pulled down by the fourth transistor NM2, so that the third transistor NM1 is turned off to turn off the constant current unit 124.

It should be noted that the channel control module 126 shown in FIG3 and FIG5 is introduced by taking the pin of channel LED1 as an example, which should not be interpreted as restrictive. Since the multi-channel backlight system includes multiple channels, a channel control module 126 and a constant current unit 124 corresponding to each of the multiple channels are provided, wherein FIG3 and FIG5 only show the channel control module 126 and the constant current unit 124 corresponding to one of the channels, and the channel control module 126 and the constant current unit 124 corresponding to other channels are similar to the circuit structures shown in FIG3 and FIG5, and will not be repeated here for the sake of simplicity.

In addition, the embodiment of the present invention further provides a control method executed by the LED control chip as described above. Referring to FIG. 7 , FIG. 7 shows a flow chart of an LED control method 700 provided by the embodiment of the present invention, which is used to control the turning off and on of each channel in a multi-channel LED. The LED control chip may include a plurality of LED pins corresponding to the multi-channel LED. The method 700 may include: method S702, after the LED control chip is powered on, using L The internal reference current of the ED control chip charges each of the multiple LED pins; Method S704, compares the voltage on each of the multiple LED pins with the preset voltage threshold to obtain multiple comparison results corresponding to each of the multiple LED pins; and method S706, determines whether each channel of the multi-channel LED needs to be turned off or on according to each of the multiple comparison results.

As an example, the method 700 may further include charging each of the multiple LED pins using the internal reference current Iref during a preset time period starting from the moment the LED control chip is powered on; locking each of the multiple comparison results at the moment the preset time period has passed since the LED control chip was powered on; and determining whether each channel of the multi-channel LED needs to be turned off or on based on each of the locked multiple comparison results.

As an example, the method 700 may further include shutting off the internal reference current when a preset time period has passed since the LED control chip is powered on.

As an example, the method 700 may further include determining that a first LED channel corresponding to the first LED pin in the multi-channel LED needs to be turned on and controlling the turning on of the first LED channel if it is detected that the voltage on the first LED pin among the multiple LED pins rises to be greater than a preset voltage threshold during a preset time period starting from the moment the LED control chip is powered on, wherein the first LED pin includes one or more LED pins.

As an example, the method 700 may further include determining that a second LED channel corresponding to the second LED pin in the multi-channel LED needs to be turned off and controlling the second LED channel to be turned off if it is detected that the voltage on the second LED pin among the multiple LED pins remains less than a preset voltage threshold during a preset period of time starting from the moment the LED control chip is powered on, wherein the second LED pin includes one or more LED pins.

It can be understood that the various steps and details of the LED control method provided in the embodiment of the present invention are consistent with the details described in the above reference LED control chip, so in order to simplify the description, they will not be repeated here.

Furthermore, the embodiment of the present invention also provides a multi-channel backlight system including the LED control chip as described above, which has an arbitrary channel selection function and can be used to control the on and off of any channel in the multi-channel. As an example, the multi-channel backlight system can be a multi-channel backlight system with a boost structure, or a multi-channel backlight system with other suitable structures, and the present invention does not limit this.

In summary, in traditional LED control chips, unused LED channels are usually shut down through LED lamp disconnection or LED lamp short circuit protection. The shutdown state is after the LED control chip has started to work normally, which can easily cause a series of problems such as output voltage overshoot and chip misprotection.

The LED control chip, method and multi-channel backlight system provided by the embodiment of the present invention set the channel status detection mode when the control chip is working normally, configure the channels that need to be turned off through some peripheral settings, and then turn off the channels that are not needed before the control chip works normally to prevent problems such as output voltage overshoot and chip misprotection. At the same time, the embodiment of the present invention can set any unnecessary channels, so that users can conveniently wire when using it.

It should be made clear that the present invention is not limited to the specific configuration and processing described above and shown in the figure. For the sake of simplicity, the detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and technicians in this field can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

The functional blocks shown in the structural block diagram described above can be implemented as hardware, software, firmware or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or program code snippets used to perform the required tasks. The programs or program code snippets can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, read-only memory (ROM), flash memory, erasable ROM (EROM), disks, compact disc read-only memory (CD-ROM), optical discs, hard disks, optical fiber media, radio frequency (RF) links, etc. Code snippets can be downloaded via computer networks such as the Internet and intranets.

It should also be noted that the exemplary embodiments mentioned in the present invention describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above steps, that is, the steps can be executed in the order mentioned in the embodiments, or in a different order from the embodiments, or several steps can be executed simultaneously.

The above is only a specific implementation of the present invention. The technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, the specific working process of the system, module and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited to this. Any technical personnel familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be covered within the protection scope of the present invention.

102: Low voltage dropout linear regulator (LDO)

104: Undervoltage lockout (UVLO) module

106: Reference voltage and reference current generation module

108:Driver

110: Oscillator

112: Comparator

114: Control Logic

116: Amplifier (CS_amp)

118: Error amplifier (EA)

120: Feedback control module

122: Operational amplifier

124: Constant current unit

126: Channel control module

200:LED control chip

Channel_en1, Channel_en2,....Channel_enx: channel enable signal

CLK,CMP,Ramp:Signal

CS: Current sampling signal

DHC: minimum voltage

EA_ref: Error reference voltage

ENA: Chip Enable

Gate: Gate drive signal

GND: Chip ground

Iref: internal reference current

ISET: Current setting terminal

LED1,...,LEDX: channel

S: Adder

VCC: Low voltage LDO output inside the chip

VIN: Input voltage

Vref: channel reference voltage

Claims (12)

An LED control chip is used to control the switching on and off of each channel in a multi-channel LED, and is characterized in that it includes a plurality of LED pins corresponding to the multi-channel LED, and the LED control chip is configured to: after the LED control chip is powered on, use the internal reference current of the LED control chip to charge each of the plurality of LED pins; compare the voltage on each of the plurality of LED pins with a preset voltage threshold to obtain a plurality of comparison results corresponding to each of the plurality of LED pins; and Each comparison result in the plurality of comparison results is used to determine whether each channel in the multi-channel LED needs to be turned off or on; during a preset period of time starting from the moment when the LED control chip is powered on, each LED pin in the plurality of LED pins is charged using the internal reference current; during the moment of the preset period of time starting from the moment when the LED control chip is powered on, each comparison result in the plurality of comparison results is locked; and according to each comparison result in the locked plurality of comparison results, each channel in the multi-channel LED needs to be turned off or on. The LED control chip as described in claim 1, wherein the LED control chip is further configured to: turn off the internal reference current when the preset time period has passed since the LED control chip was powered on. The LED control chip as described in claim 1, wherein the LED control chip is further configured to: during the preset time period starting from the moment when the LED control chip is powered on, if it is detected that the voltage on the first LED pin among the multiple LED pins rises to a value greater than the preset voltage threshold, then it is determined that the first LED channel corresponding to the first LED pin in the multi-channel LED needs to be turned on and the first LED channel is controlled to be turned on, wherein the first LED pin includes one or more LED pins. The LED control chip as described in claim 1, wherein the LED control chip is further configured to: during the preset time period starting from the moment when the LED control chip is powered on, if it is detected that the voltage on the second LED pin among the multiple LED pins remains less than the preset voltage threshold, then determine that the second LED channel corresponding to the second LED pin in the multi-channel LED needs to be turned off and control the turning off of the second LED channel, wherein the second LED pin includes one or more LED pins. An LED control chip as described in claim 3, wherein the LED control chip includes a plurality of channel control modules corresponding to the plurality of LED pins, and each of the plurality of channel control modules includes: a first PMOS transistor, a first end receiving the internal reference current, a second end receiving the first control signal, and a third end connected to the first LED pin; a first comparator, a first end connected to the first LED pin, a second end receiving the preset voltage threshold; and a first trigger, a first The first end is connected to the third end of the first comparator, the second end receives the first control signal, and the third end outputs a first channel enable signal for controlling the first LED channel to be turned on; wherein the first control signal is used to control the conduction of the first PMOS transistor when the LED control chip is powered on, and is used to control the first trigger to output the first channel enable signal from a low level to a high level when the preset time period has passed since the LED control chip is powered on. The LED control chip as described in claim 5, wherein each of the plurality of channel control modules further comprises: a first delay unit connected between the first comparator and the first trigger. The LED control chip as claimed in claim 4, wherein the LED control chip includes a plurality of channel control modules corresponding to the plurality of LED pins, each of the plurality of channel control modules includes: a first PMOS transistor, a first end receiving the internal reference current, a second end receiving the second control signal, and a third end connected to the second LED pin; a first resistor, a first end connected to the second LED pin, a second end grounded, and a resistance value of the first resistor being less than a preset resistance threshold value; a first comparator, a first end connected to the second LED pin , the second end receives the preset voltage threshold; and a second trigger, the first end is connected to the third end of the first comparator, the second end receives the second control signal, and the third end outputs a second channel enable signal for controlling the shutdown of the second LED channel; wherein the second control signal is used to control the conduction of the first PMOS transistor when the LED control chip is powered on, and is used to control the second trigger to output the second channel enable signal at a low level when the preset time period passes from the moment the LED control chip is powered on. The LED control chip as described in claim 7, wherein each of the plurality of channel control modules further comprises: a second delay unit connected between the first comparator and the second trigger. An LED control chip as described in claim 5 or 7, wherein the LED control chip further includes a plurality of constant current units corresponding to the plurality of LED pins, and each of the plurality of constant current units is turned off when the LED control chip is powered on. The LED control chip as described in claim 9, wherein each of the multiple constant current units includes an operational amplifier, a second resistor, a third transistor and a fourth transistor, wherein: the first end of the operational amplifier receives the internal reference voltage of the LED control chip; the first end of the third transistor is connected to one of the multiple LED pins, and the second end and the third end are respectively connected to the second end and the third end of the operational amplifier; The first end of the second resistor is connected to the third end of the third transistor, and the second end is grounded; the first end of the fourth transistor is connected to the second end of the third transistor, the second end receives a third control signal, and the third end is grounded; wherein the third control signal is used to control the conduction of the fourth transistor when the LED control chip is powered on to control the shutdown of the third transistor. A multi-channel backlight system, comprising an LED control chip and a multi-channel LED as described in any one of claims 1 to 10, wherein each channel of the multi-channel LED is respectively connected to each LED pin of a plurality of LED pins of the LED control chip. A control method executed by an LED control chip is used to control the switching on and off of each channel in a multi-channel LED. The method is characterized in that the LED control chip includes a plurality of LED pins corresponding to the multi-channel LED. The control method includes: after the LED control chip is powered on, each of the plurality of LED pins is charged using an internal reference current of the LED control chip; a voltage on each of the plurality of LED pins is compared with a preset voltage threshold to obtain a plurality of comparison results corresponding to each of the plurality of LED pins; Result; and according to each of the multiple comparison results, determine whether each channel in the multi-channel LED needs to be turned off or on; during the preset time period from the moment when the LED control chip is powered on, use the internal reference current to charge each of the multiple LED pins; at the moment when the preset time period has passed since the moment when the LED control chip is powered on, lock each of the multiple comparison results; and according to each of the locked multiple comparison results, determine whether each channel in the multi-channel LED needs to be turned off or on.

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