LED driving control circuit, driving control method thereof, and LED driving circuit

Abstract

The application provides an LED driving control circuit, a driving control method thereof and an LED driving circuit. The LED driving control circuit comprises a current regulating circuit and an output control circuit. The current regulating circuit comprises a current regulating unit and a first transistor. The output control circuit comprises a third transistor, a fourth transistor and a fast start circuit. The fast start circuit is coupled to the control end of the first transistor and the control end of the third transistor respectively. The fast start circuit is used to turn off the first transistor or control the current flowing through the first transistor within a preset threshold and control the end voltage of the control end of the first transistor to a preset voltage when the chopping signal is at a second level. The fast start circuit is also used to turn off the third transistor when the chopping signal is at the second level. The LED driving control circuit, the driving control method thereof and the LED driving circuit effectively accelerate the start speed in low-depth dimming and ensure stable operation of the driving circuit.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, and relates to LED driving technology, particularly to an LED driving control circuit and its driving control method and LED driving circuit. Background Technology

[0002] A linear LED driver circuit includes a rectifier circuit, a linear regulator transistor, and a control circuit for controlling the linear regulator transistor. Compared to switching LED driver circuits, linear LED driver circuits have a relatively simpler circuit structure, fewer components, and lower cost. Therefore, linear LED driver circuits are widely used in the LED driving field.

[0003] With increasing user demands, the industry is placing higher requirements on the dimming depth of LED driver circuits. In applications where the dimming depth is less than 1%, the traditional circuit architecture of linear LED drivers often cannot meet these requirements. To achieve a dimming depth of 0.1%, further improvements to the control circuitry of the linear LED driver are necessary. Figure 1 The illustrated linear LED driver control circuit can be used in applications requiring low dimming depth. The linear LED driver control circuit includes a current regulation circuit 10 and an output control circuit 11. The current regulation circuit 10 can be considered as a first loop circuit, and the output control circuit 11 can be considered as a second loop circuit. The current regulation circuit 10 is coupled to the output control circuit 11. The current regulation circuit 10 generates a reference signal for the output current of the LED driver circuit, and the output control circuit 11 controls the output current of the LED driver circuit according to the reference signal, thereby controlling the brightness of the LED lamp. Figure 1As shown, the current regulating circuit includes a first current source I1, a first transistor M1, a second transistor M2 and a first operational amplifier circuit CMP1. The input terminal of the first current source I1 is coupled to the power supply pin VDD, the first terminal of the second transistor M2 is coupled to the output terminal of the first current source I1, the first input terminal of the first operational amplifier circuit CMP1 is coupled to the first voltage V1, the second input terminal of the first operational amplifier circuit CMP1 is coupled to the second terminal of the second transistor M2, and the output terminal of the first operational amplifier circuit CMP1 is coupled to the control terminal of the second transistor M2. The first terminal of the first transistor M1 is coupled to the second terminal of the second transistor M2, the second terminal of the first transistor M1 is coupled to the ground, and the control terminal of the first transistor M1 is coupled to the output terminal of the first current source I1. The output control circuit 11 includes a third transistor M3, a fourth transistor M4 and a second operational amplifier circuit CMP2. The first input terminal of the second operational amplifier circuit CMP2 is coupled to the second terminal of the second transistor M2, the second input terminal of the second operational amplifier circuit CMP2 is coupled to the second terminal of the third transistor M3, and the output terminal of the second operational amplifier circuit CMP2 is coupled to the control terminal of the third transistor M3. The first terminal of the fourth transistor M4 is coupled to the second terminal of the third transistor M3, the second terminal of the fourth transistor M4 is coupled to the ground, the control terminal of the fourth transistor M4 is coupled to the control terminal of the first transistor M1, and the first transistor M1 and the fourth transistor M4 constitute a current mirror. The current flowing through the fourth transistor M4 can be controlled by controlling the current flowing through the first transistor M1.

[0004] As shown in another scheme, Figure 2 the linear LED drive control circuit includes a current regulating circuit 20 and an output control circuit 21. The current regulating circuit 20 includes a first current mirror I1, a resistor R and a first transistor M1. The input terminal of the first current mirror I1 is the power supply pin VDD, and the first terminal of the resistor R is coupled to the output terminal of the first current source I1. The first terminal of the first transistor M1 is coupled to the second terminal of the resistor R, the second terminal of the first transistor M1 is coupled to the ground, and the control terminal of the first transistor M1 is coupled to the output terminal of the first current source I1. The output control circuit 21 includes a third transistor M3, a fourth transistor M4 and a second operational amplifier circuit CMP2. The first input terminal of the second operational amplifier circuit CMP2 is coupled to the second terminal of the resistor R, the second input terminal of the second operational amplifier circuit CMP2 is coupled to the second terminal of the third transistor M3, and the output terminal of the second operational amplifier circuit CMP2 is coupled to the control terminal of the third transistor M3. The first terminal of the fourth transistor M4 is coupled to the second terminal of the third transistor M3, the second terminal of the fourth transistor M4 is coupled to the ground, the control terminal of the fourth transistor M4 is coupled to the control terminal of the first transistor M1, and the first transistor M1 and the fourth transistor M4 constitute a current mirror.

[0005] 0.1% dimming depth poses new challenges to the circuit design of the chopping mode. In combination with Figure 1It can be seen that when the PWM signal is low, the third transistor M3 or the fourth transistor M4 needs to be completely turned off, so as to cut off the current flowing through the LED lamp string. When the PWM signal is high, the third transistor M3 and the fourth transistor M4 need to be turned on to carry the current flowing through the LED lamp string. At a chopping frequency of 4 kHz and a gray scale of 0.1%, the duration of the PWM signal being high is only 250 ns, and only the tail current in the first current source I1 and the second operational amplifier circuit CMP2 is insufficient to turn on the third transistor M3 and the fourth transistor M4 with a large area in this time period, resulting in that the current flowing through the LED lamp string is almost zero in the small gray scale chopping mode, and thus there is a problem of slow starting speed.

[0006] Therefore, it is necessary to provide a new structure or control method to solve at least part of the above problems. SUMMARY

[0007] In view of one or more problems in the prior art, the present application provides an LED driving control circuit, an LED driving control method and an LED driving circuit.

[0008] According to one aspect of the present application, an LED driving control circuit is disclosed, which comprises a current regulating circuit and an output control circuit. The current regulating circuit comprises a current regulating unit and a first transistor, the current regulating unit is used to control the current flowing through the first transistor, and the current regulating unit is coupled to the control end and the first end of the first transistor, respectively. The output control circuit comprises a third transistor, a fourth transistor and a fast starting circuit. The first end of the third transistor is used to couple to an LED load, the first end of the fourth transistor is coupled to the second end of the third transistor, and the control end of the fourth transistor is coupled to the control end of the first transistor. The fast starting circuit is coupled to the control end of the first transistor and the control end of the third transistor, respectively. The fast starting circuit is used to turn off the first transistor or control the current flowing through the first transistor within a preset threshold, and control the end voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at a second level. The fast starting circuit is also used to turn off the third transistor when the chopping signal is at the second level. The fast starting circuit comprises a third switch and a third switch control circuit. The first end of the third switch is coupled to a power supply pin, the second end of the third switch is coupled to the control end of the third transistor, and the output end of the third switch control circuit is coupled to the control end of the third switch. The third switch control circuit is used to control the third switch to be turned on when the chopping signal is at a first level and the current flowing through the third switch is lower than a preset current.

[0009] As an embodiment of the present application, the fast starting circuit further comprises:

[0010] a clamping circuit, a first end of which is coupled to the control end of the first transistor, for turning off the first transistor or controlling the current flowing through the first transistor within a preset threshold when the chopping signal is at the second level, and clamping the end voltage of the control end of the first transistor at a preset voltage; and

[0011] a second switch, a first end of which is coupled to the control end of the third transistor, and a second end of which is coupled to the ground, for turning off the third transistor when the chopping signal is at the second level.

[0012] As an embodiment of the present application, the clamping circuit comprises:

[0013] a first switch, a first end of which is coupled to the control end of the first transistor; and

[0014] a fifth transistor, a first end and a control end of which are coupled to the second end of the first switch respectively, and a second end of which is coupled to the ground.

[0015] As an embodiment of the present application, the third switch control circuit comprises:

[0016] a second current source, an input end of which is coupled to the power supply pin;

[0017] a fourth switch, a first end of which is coupled to the input end of the second current source;

[0018] a fifth switch, a first end of which is coupled to the output end of the second current source, and a second end of which is coupled to the second end of the fourth switch;

[0019] a sixth transistor, a control end of which is coupled to the control end of the third transistor, a first end of which is coupled to the second end of the fifth switch, and a second end of which is coupled to the ground; and

[0020] an AND gate, a first input end of which is coupled to the second end of the fifth switch, a second input end of which is coupled to the chopping signal, and an output end of which is coupled to the control end of the third switch.

[0021] As an embodiment of the present application, the output control circuit further comprises a second operational amplifier circuit, a first input end of the second operational amplifier circuit is coupled to the first end of the first transistor, a second input end of the second operational amplifier circuit is coupled to the second end of the third transistor, and an output end of the second operational amplifier circuit is coupled to the control end of the third transistor; the LED driving control circuit further comprises a tail current control circuit, an output end of the tail current control circuit is coupled to a tail current control end of the second operational amplifier circuit, and the tail current control circuit is used for controlling the tail current of the second operational amplifier circuit in a time period when the chopping signal is at the first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

[0022] As an embodiment of the present application, the ratio of the width-length ratio of the first transistor to the width-length ratio of the fifth transistor is 1:m, wherein 1

[0023] As an embodiment of the present application, the current regulating unit comprises a first current source, the first current source has at least two output current levels, and the LED driving control circuit adjusts the output current of the LED driving circuit by adjusting the output current level of the first current source; the output current of the second current source is k1 times of the output current of the first current source, wherein 0.3 < k1 < 1.

[0024] As an embodiment of the present application, the tail current control circuit comprises:

[0025] a third current source;

[0026] a seventh transistor, a first end of which is coupled to the power supply pin, a control end and a second end of which are coupled to the input end of the third current source, respectively;

[0027] an eighth transistor, a first end of which is coupled to the power supply pin, and a control end of which is coupled to the control end of the seventh transistor;

[0028] a sixth switch, a first end of which is coupled to the second end of the eighth transistor, and a second end of which is coupled to the tail current control end of the second operational amplifier circuit; and

[0029] a fourth current source, an input end of which is coupled to the power supply pin, and an output end of which is coupled to the tail current control end of the second operational amplifier circuit.

[0030] As an embodiment of the present application, the current regulating unit comprises a first current source, and the output current of the third current source is k2 times of the output current of the first current source, wherein 0.05 < k2 < 1.

[0031] As an embodiment of the present application, the tail current control circuit further comprises a gradual change control circuit, which is configured to gradually reduce the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal at the first level ends.

[0032] As an embodiment of the present application, the gradual change control circuit comprises:

[0033] a fifth current source, an input end of which is coupled to the power supply pin;

[0034] a seventh switch, a first end of which is coupled to the output end of the fifth current source, and a second end of which is coupled to the ground;

[0035] a first capacitor, a first end of which is coupled to the output end of the fifth current source, and a second end of which is coupled to the ground;

[0036] a ninth transistor, a first end of which is coupled to the power supply pin;

[0037] a tenth transistor, a first end of which is coupled to the power supply pin, a second end of which is coupled to the control end of the seventh transistor, and a control end of which is coupled to the control end of the ninth transistor;

[0038] a first end of the eleventh transistor is coupled to a control end and a second end of the ninth transistor, and a control end of the eleventh transistor is coupled to a first end of the first capacitor; and

[0039] a second end of the second resistor is coupled to the second end of the eleventh transistor.

[0040] According to another aspect of the present application, there is disclosed an LED driving circuit, the LED driving circuit comprising an LED load and an LED driving control circuit as claimed in any one of the preceding claims, the LED driving control circuit being coupled to the LED load, the LED driving control circuit being configured to control an output current of the LED driving circuit.

[0041] According to yet another aspect of the present application, there is disclosed an LED driving control method for controlling an LED driving control circuit, the LED driving control circuit comprising a current regulating circuit and an output control circuit, the current regulating circuit comprising a current regulating unit and a first transistor, the current regulating unit being configured to control a current flowing through the first transistor, the current regulating unit being coupled to a control end and a first end of the first transistor; the output control circuit comprising a third transistor and a fourth transistor, a first end of the third transistor being configured to be coupled to an LED load, a first end of the fourth transistor being coupled to a second end of the third transistor, a control end of the fourth transistor being coupled to the control end of the first transistor; the LED driving control method comprising:

[0042] turning off the first transistor or controlling the current flowing through the first transistor within a preset threshold, and controlling an end voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at the second level; turning off the third transistor when the chopping signal is at the second level; and

[0043] providing a first current to the control end of the third transistor to speed up the start-up of the LED driving control circuit when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current.

[0044] As an embodiment of the present application, the output control circuit further comprises a fast start-up circuit, the fast start-up circuit comprising a third switch, a first end of the third switch being coupled to the supply pin, and a second end of the third switch being coupled to the control end of the third transistor; the LED driving control method further comprising: controlling the third switch to be turned on when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current.

[0045] As an embodiment of the present application, the output control circuit further comprises a second operational amplifier circuit, a first input end of the second operational amplifier circuit is coupled to the first end of the first transistor, a second input end of the second operational amplifier circuit is coupled to the second end of the third transistor, and an output end of the second operational amplifier circuit is coupled to the control end of the third transistor; and the LED driving control method further comprises: controlling the tail current of the second operational amplifier circuit when the chopping signal is at the first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

[0046] As an embodiment of the present application, the LED driving control method further comprises: gradually reducing the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal being at the first level ends.

[0047] The present application provides an LED driving control circuit, a driving control method thereof and an LED driving circuit. The LED driving control circuit comprises a current regulating circuit and an output control circuit. The current regulating circuit comprises a current regulating unit and a first transistor. The current regulating unit is configured to control the current flowing through the first transistor, and is coupled to the control end and the first end of the first transistor respectively. The output control circuit comprises a third transistor, a fourth transistor and a fast start circuit. The first end of the third transistor is configured to be coupled to an LED load. The first end of the fourth transistor is coupled to the second end of the third transistor. The control end of the fourth transistor is coupled to the control end of the first transistor. The fast start circuit is coupled to the control end of the first transistor and the control end of the third transistor respectively. The fast start circuit is configured to turn off the first transistor or control the current flowing through the first transistor within a preset threshold, and control the terminal voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at the second level. The fast start circuit is also configured to turn off the third transistor when the chopping signal is at the second level. The LED driving control circuit, the driving control method thereof and the LED driving circuit provided by the present application can effectively accelerate the start speed in low-depth dimming and ensure the stable operation of the driving circuit. BRIEF DESCRIPTION OF DRAWINGS

[0048] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of the specification. In the drawings:

[0049] Figure 1 FIG. 1 shows a circuit structure schematic diagram of a linear LED driving control circuit of the prior art;

[0050] Figure 2 FIG. 2 shows a circuit structure schematic diagram of another linear LED driving control circuit of the prior art;

[0051] Figure 3 FIG. 3 shows a circuit structure schematic diagram of an LED driving control circuit according to an embodiment of the present application;

[0052] Figure 4 Fig. 1 shows a circuit structure schematic diagram of an LED driving control circuit according to an embodiment of the present application;

[0053] Figure 5 Fig. 2 shows a circuit structure schematic diagram of an LED driving control circuit according to another embodiment of the present application;

[0054] Figure 6 Fig. 3 shows a circuit structure schematic diagram of an LED driving control circuit according to an embodiment of the present application;

[0055] Figure 7 Fig. 4 shows a signal waveform schematic diagram of an LED driving control circuit according to an embodiment of the present application;

[0056] Figure 8 Fig. 5 shows a signal waveform schematic diagram of an LED driving control circuit according to another embodiment of the present application. DETAILED DESCRIPTION

[0057] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the embodiments, but it should be understood that the description is only for further illustrating the features and advantages of the present application, and is not a limitation on the claims of the present application.

[0058] The description of this part is only for several typical embodiments, and the present application is not limited to the scope described in the embodiments. The combination of different embodiments, the mutual replacement of some technical features in different embodiments, and the mutual replacement of some technical features in the same or similar prior art means are also within the description and protection scope of the present application.

[0059] In the specification, "coupling" or "connection" includes both direct connection and indirect connection. Indirect connection is the connection through an intermediate medium, such as the connection through an electrically conductive medium such as a conductor, wherein the electrically conductive medium can contain parasitic inductance or parasitic capacitance, or the connection through the intermediate circuit or component described in the embodiments of the specification; indirect connection can also include the connection through other active devices or passive devices on the basis of achieving the same or similar functions, such as the connection through circuits or components such as switches, signal amplification circuits, follower circuits, etc. "Multiple" or "many" means two or more. In addition, in the present application, words such as first, second, etc. are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply a certain actual relationship or order between the technical features.

[0060] An embodiment of the present application discloses an LED driving control circuit, which comprises a current regulating circuit and an output control circuit, such as Figure 3As shown, the current regulating circuit includes a current regulating unit and a first transistor M1, the current regulating unit is used to control the current flowing through the first transistor M1, a first end of the current regulating unit is coupled to a control end of the first transistor M1, and a second end of the current regulating unit is coupled to a first end of the first transistor M1. In the embodiment as shown, the current regulating unit includes a first current source I1, a first operational amplifier circuit CMP1 and a second transistor M2. An input end of the first current source I1 is coupled to a power supply pin VDD, a first input end of the first operational amplifier circuit CMP1 is coupled to a first voltage V1, a second input end of the first operational amplifier circuit CMP1 is coupled to a second end of the second transistor M2, an output end of the first operational amplifier circuit CMP1 is coupled to a control end of the second transistor M2, and a first end of the second transistor M2 is coupled to an output end of the first current source I1. The current flowing through the first transistor M1 can be regulated by adjusting the output of the first current source I1, etc. In another embodiment, the current regulating unit includes a first current source I1 and a resistor R, an input end of the first current source I1 is coupled to the power supply pin VDD, a first end of the resistor R is coupled to an output end of the first current source I1 and a control end of the first transistor M1 respectively, a second end of the resistor R is used to be coupled to a first end of the first transistor M1, and a second end of the first transistor M1 is coupled to ground. The current flowing through the first transistor can be regulated by adjusting the output of the first current source I1, etc. Figure 3

[0061] As shown, the current regulating circuit includes a current regulating unit and a first transistor M1, the current regulating unit is used to control the current flowing through the first transistor M1, a first end of the current regulating unit is coupled to a control end of the first transistor M1, and a second end of the current regulating unit is coupled to a first end of the first transistor M1. In the embodiment as shown, the current regulating unit includes a first current source I1, a first operational amplifier circuit CMP1 and a second transistor M2. An input end of the first current source I1 is coupled to a power supply pin VDD, a first input end of the first operational amplifier circuit CMP1 is coupled to a first voltage V1, a second input end of the first operational amplifier circuit CMP1 is coupled to a second end of the second transistor M2, an output end of the first operational amplifier circuit CMP1 is coupled to a control end of the second transistor M2, and a first end of the second transistor M2 is coupled to an output end of the first current source I1. The current flowing through the first transistor M1 can be regulated by adjusting the output of the first current source I1, etc. In another embodiment, the current regulating unit includes a first current source I1 and a resistor R, an input end of the first current source I1 is coupled to the power supply pin VDD, a first end of the resistor R is coupled to an output end of the first current source I1 and a control end of the first transistor M1 respectively, a second end of the resistor R is used to be coupled to a first end of the first transistor M1, and a second end of the first transistor M1 is coupled to ground. The current flowing through the first transistor can be regulated by adjusting the output of the first current source I1, etc. Figure 3 ​In an embodiment, the output control circuit includes a third transistor M3, a fourth transistor M4, a second operational amplifier circuit CMP2, and a fast start-up circuit. The first terminal of the third transistor M3 is coupled to the second terminal VLED- of the LED load. The first input terminal of the second operational amplifier circuit CMP2 is coupled to the first terminal of the first transistor M1, the second input terminal of the second operational amplifier circuit CMP2 is coupled to the second terminal of the third transistor M3, and the output terminal of the second operational amplifier circuit CMP2 is coupled to the control terminal of the third transistor M3. The first terminal of the fourth transistor M4 is coupled to the second terminal of the third transistor M3, the control terminal of the fourth transistor M4 is coupled to the control terminal of the first transistor M1, and the second terminal of the fourth transistor M4 is coupled to the ground. The fast start-up circuit includes a first start-up module 111 and a second start-up module 112. The first terminal of the first start-up module 111 in the fast start-up circuit is coupled to the control terminal of the first transistor M1, the second terminal of the first start-up module 111 is coupled to the control terminal of the third transistor M3, and the third terminal of the first start-up module 111 is coupled to the ground. The first start-up module 111 in the fast start-up circuit is configured to turn off the first transistor M1 or control the current flowing through the first transistor M1 within a preset threshold and control the voltage at the control terminal of the first transistor M1 to be a preset voltage when the chopping signal is at the second level (e.g., low level). The preset threshold can be a value close to zero. The chopping signal is a PWM signal. The PWM signal is configured to control the third transistor M3 and the fourth transistor M4 to be turned on when the PWM signal is at the first level. The PWM signal is configured to control the third transistor M3 and / or the fourth transistor M4 to be turned off when the PWM signal is at the second level. In an embodiment, the fast start-up circuit is further configured to turn off the third transistor M3 when the chopping signal is at the second level. By adjusting the duty cycle of the chopping signal, the output current of the LED driving circuit can be adjusted. In addition, by selecting the third transistor to be controlled by the fast start-up circuit and not selecting the fourth transistor to be controlled by the start-up circuit, the fast start-up can be achieved while avoiding abnormal circuit function or LED flickering caused by a large overshoot.

[0062] As Figure 3 shown in an embodiment, the second start-up module 112 in the fast start-up circuit includes a third switch S3 and a third switch control circuit. The first terminal of the third switch S3 is coupled to the supply pin VDD, the second terminal of the third switch S3 is coupled to the control terminal of the third transistor M3, and the output terminal of the third switch control circuit is coupled to the control terminal of the third switch S3. The third switch control circuit is configured to control the third switch to be turned on when the chopping signal is at the first level (e.g., high level) and the current flowing through the third transistor M3 is lower than a preset current. The third switch control circuit is configured to control the third switch S3 to be turned off when the chopping signal is at the second level (e.g., low level) or the current flowing through the third transistor M3 is greater than the preset current.

[0063] In Figure 3 one embodiment shown, the fast startup circuit includes a clamping circuit and a second switch S2. The first end of the clamping circuit is coupled to the control terminal of the first transistor M1, the second end of the clamping circuit is coupled to ground, and the clamping circuit is configured to turn off the first transistor M1 when the chopping signal is at the second level or control the current flowing through the first transistor M1 within a preset threshold, and clamp the terminal voltage of the control terminal of the first transistor M1 at a preset voltage. Correspondingly, the terminal voltage of the control terminal of the fourth transistor M4 is also clamped at the preset voltage. The first end of the second switch S2 is coupled to the control terminal of the third transistor M3, and the second end of the second switch S2 is coupled to ground. The second switch S2 is configured to turn off the third transistor M3 when the chopping signal is at the second level. In a specific embodiment, as Figure 3 shown, the clamping circuit includes a first switch S1 and a fifth transistor M5. The first end of the first switch S1 is coupled to the control terminal of the first transistor M1. The first end and the control terminal of the fifth transistor M5 are respectively coupled to the second end of the first switch S1, and the second end of the fifth transistor M5 is coupled to ground. When the chopping signal is at the second level, the control terminal voltages of the first transistor M1 and the fourth transistor M4 are controlled at a voltage Vgs slightly lower than the steady-state value through the fifth transistor M5, and the voltage Vgs is the voltage difference between the control terminal and the second end of the fifth transistor. In one embodiment, the ratio of the width-to-length ratio of the first transistor to the width-to-length ratio of the fifth transistor is 1:m, where 1 < m < 10. In a preferred embodiment, the ratio of the width-to-length ratio of the first transistor to the width-to-length ratio of the fifth transistor is 1:2.

[0064] In another embodiment, the clamping circuit includes a voltage control circuit, and the first end of the voltage control circuit is coupled to the control terminal of the first transistor M1. When the chopping signal is at the first level, the voltage control circuit may not control the terminal voltage of the control terminal of the first transistor. When the chopping signal is at the second level, the voltage control circuit controls the terminal voltage of the control terminal of the first transistor within a preset voltage, and the preset voltage is a non-zero value. In a specific embodiment, when the chopping signal is at the second level, the voltage control circuit couples the control terminal of the first transistor to a preset voltage terminal so that the terminal voltage of the control terminal of the first transistor is the preset voltage. When the chopping signal is at the second level, by controlling the terminal voltages of the first transistor M1 and the fourth transistor M4 at the preset voltage, the startup speed of the LED driving control circuit can be effectively increased. In addition, when the chopping signal is at the second level, the third transistor is turned off to cut off the current flowing through the LED string. Based on the above circuit control settings, the stable operation of the LED driving circuit can be ensured. <>

[0065] In an embodiment of the present invention, as Figure 4As shown, the fast start-up circuit includes a first start-up module 111 and a second start-up module 112, and the second start-up module 112 includes a third switch S3 and a third switch control circuit. The first end of the third switch S3 is coupled to the power supply pin VDD, and the second end of the third switch S3 is coupled to the control end of the third transistor M3. The output end of the third switch control circuit is coupled to the control end of the third switch S3, and the third switch control circuit is configured to control the third switch S3 to be turned on when the chopping signal is at the first level and the current flowing through the third switch tube M3 is lower than a preset current, so as to quickly raise the voltage at the control end of the third switch tube M3 and speed up the start-up speed of the LED driving control circuit. In a preferred embodiment, the second start-up module 112 includes the third switch S3, a first resistor R1, and the third switch control circuit. The first resistor R1 is coupled in series with the third switch S3, and the resistor R1 is configured to limit the current to avoid excessive charging current. The reason is that the charging current can flow to the gate of the fourth transistor M4 through the parasitic capacitances of the third transistor M3 and the fourth transistor M4, thereby easily causing a large overshoot.

[0066] In a specific embodiment, as shown in Figure 4 As shown, the third switch control circuit includes a second current source k1*I1, a fourth switch S4, a fifth switch S5, a sixth transistor M6, and an AND gate. The input end of the second current source is coupled to the power supply pin VDD. The first end of the fourth switch S4 is coupled to the input end of the second current source. The first end of the fifth switch S5 is coupled to the output end of the second current source, and the second end of the fifth switch S5 is coupled to the second end of the fourth switch S4. The control end of the sixth transistor M6 is coupled to the control end of the third transistor M3, the first end of the sixth transistor M6 is coupled to the second end of the fifth switch S5, and the second end of the sixth transistor M6 is coupled to the ground. The first input end of the AND gate is coupled to the second end of the fifth switch S5, the second input end of the AND gate is coupled to the chopping signal PWM signal, and the output end of the AND gate is coupled to the control end of the third switch S3. In a specific embodiment, within a first preset time (such as 50 ns) after the chopping signal becomes the first level (such as high level), the fourth switch S4 is turned on, and at this time, the current flowing through the sixth transistor M6 is less than the preset current. The fast start-up circuit controls the third switch S3 to be turned on to speed up the voltage at the first end of the sixth transistor M6 Figure 4The end voltage at the middle B point reaches the high level. 50ns after the chopping signal becomes the first level, the current flowing through the sixth transistor M6 is compared with the current output by the second current source, and the third switch is controlled according to the comparison result and turned off in time to avoid a large overshoot of the third transistor. Preferably, the fifth switch S5 is turned on within a second preset time (such as 1us) after the chopping signal becomes the first level, and the fast start of the charging of the third transistor M3 is effective, so as to avoid accidental turning on of the fast start circuit in which the third switch is located due to the fluctuation of the output current flowing through the third transistor M3 and the fourth transistor M4 caused by other reasons. The second preset time is greater than the first preset time.

[0067] In an embodiment of the present application, the output control circuit further comprises a second operational amplifier circuit CMP2, a first input end of the second operational amplifier circuit CMP2 is coupled to the first end of the first transistor M1, a second input end of the second operational amplifier circuit CMP2 is coupled to the second end of the third transistor M3, and an output end of the second operational amplifier circuit CMP2 is coupled to the control end of the third transistor M3. The LED drive control circuit further comprises a tail current control circuit, an output end of the tail current control circuit is coupled to a tail current control end of the second operational amplifier circuit CMP2, and the tail current control circuit is used to control the tail current of the second operational amplifier circuit when the chopping signal is at the first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

[0068] In another embodiment of the present application, as Figure 5As shown, the tail current control circuit 113 includes a third current source k2*I1, a seventh transistor M7, an eighth transistor M8, a sixth switch S6 and a fourth current source I4. The first end of the seventh transistor M7 is coupled to the power supply pin VDD, the control end and the second end of the seventh transistor M7 are coupled to the input end of the third current source respectively, and the output end of the third current source is coupled to the ground. The first end of the eighth transistor M8 is coupled to the power supply pin VDD, and the control end of the eighth transistor M8 is coupled to the control end of the seventh transistor M7. The first end of the sixth switch S6 is coupled to the second end of the eighth transistor M8, and the second end of the sixth switch S6 is coupled to the tail current control end of the second operational amplifier circuit CMP2. The input end of the fourth current source I4 is coupled to the power supply pin VDD, and the output end of the fourth current source I4 is coupled to the tail current control end of the second operational amplifier circuit CMP2. When the chopping signal PWM signal is at the first level (for example, high level), the sixth switch S6 is turned on, the tail current of the second operational amplifier circuit CMP2 is increased, and the voltage at the control end of the third transistor M3 can be quickly pulled up. In a preferred embodiment, the sixth switch S6 is turned on within a second preset time (such as 1us) when the chopping signal PWM signal becomes the first level (for example, high level). The sixth switch S6 is not turned on at other times to reduce the power consumption of the circuit. In an embodiment, the output current of the third current source is k2 times the output current of the first current source, where 0.05<k2<1. By setting the output current of the third current source to be k2 times the output current of the first current source, the LED driving control circuit can be applied to different output current applications, can adaptively achieve fast start, and will not produce a large overshoot, effectively protecting the third transistor and the fourth transistor, so that the LED driving circuit can work stably.

[0069] In an embodiment of the present application, in combination with Figure 5 and Figure 7 It can be known that when the chopping signal PWM signal is high, the fast start signal (corresponding to the switching control signal of the third switch S3) is at high level, the third switch S3 is turned on, the third transistor M3 is powered, the fast start circuit provides a large current, and the voltage at the control end of the third transistor M3 can be quickly pulled up to speed up the current response speed. When the current flowing through the sixth transistor M6 reaches the output current of the second current source, the third switch is turned off, and the fast start signal is at low level. When the chopping signal PWM signal is high, the sixth switch S6 is turned on, and the tail current of the second operational amplifier circuit CMP2 is increased, so that the voltage at the control end of the third transistor M3 can be quickly pulled up to speed up the current response speed. Figure 7 As shown, the tail current of the second operational amplifier circuit CMP2 (i.e. Figure 7the third transistor M3. In the phase from t1 to t2, both the fast start-up circuit and the tail current control circuit accelerate the start-up of the LED driving circuit. In the phase from t2 to t3, the third switch S3 in the fast start-up circuit is turned off, and the fast start-up circuit does not function. The LED driving control circuit enters a closed loop working mode, and the output current is accelerated by the increased tail current of the second operational amplifier circuit CMP2. After the output current tends to be stable, the tail current of the second operational amplifier circuit is reduced to a preset value (which can be equal to the tail current when the chopping signal is at the low level). In the phase from t1 to t2, the output current (i.e. the LED current) of the LED driving circuit increases rapidly. In the phase from t2 to t3, the output current of the LED driving circuit increases slowly and gradually increases to the preset output current value. The LED driving circuit of the present application can greatly shorten the start-up time at a low dimming depth and realize fast and stable output at a low dimming depth. Figure 7

[0070] In an embodiment of the present application, the tail current control circuit further comprises a gradual change control circuit, which is configured to gradually reduce the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal at the first level ends. The preset value can be equal to the tail current of the second operational amplifier circuit when the chopping signal is at the second level, or can be a value close to the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

[0071] In an embodiment, as shown in Figure 6 ​As shown, the tail current control circuit 313 further comprises a ramp control circuit, which comprises a fifth current source I5, a seventh switch S7, a first capacitor C1, a ninth transistor M9, a tenth transistor M10, an eleventh transistor M11 and a second resistor R2. The input terminal of the fifth current source I5 is coupled to the power supply pin VDD. The first terminal of the seventh switch S7 is coupled to the output terminal of the fifth current source I5, and the second terminal of the seventh switch S7 is coupled to the ground VSS. The first terminal of the first capacitor C1 is coupled to the output terminal of the fifth current source I5, and the second terminal of the first capacitor C1 is coupled to the ground. The first terminal of the ninth transistor M9 is coupled to the power supply pin VDD. The first terminal of the tenth transistor M10 is coupled to the power supply pin VDD, the second terminal of the tenth transistor M10 is coupled to the control terminal of the seventh transistor M7, and the control terminal of the tenth transistor M10 is coupled to the control terminal of the ninth transistor M9. The first terminal of the eleventh transistor M11 is coupled to the control terminal of the ninth transistor M9 and the second terminal of the ninth transistor M9 respectively, and the control terminal of the eleventh transistor M11 is coupled to the first terminal of the first capacitor C1. The first terminal of the second resistor R2 is coupled to the second terminal of the eleventh transistor M11, and the second terminal of the second resistor R2 is coupled to the ground. When the chopping signal is at the first level, the seventh switch S7 is turned off, the first capacitor C1 is charged by the fifth current source I5, and the terminal voltage of the control terminal of the eleventh transistor M11 continuously increases. When the terminal voltage of the control terminal of the eleventh transistor M11 reaches the driving voltage Vth, the eleventh transistor M11 is turned on, which will cause the current flowing through the eighth transistor M8 to decrease. With the continuous increase of the current flowing through the eleventh transistor M11, the current flowing through the eighth transistor M8 will continuously decrease, so as to gradually reduce the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal at the first level ends. When the chopping signal is at the second level, the seventh switch S7 is turned on, the first capacitor C1 is gradually discharged, and the terminal voltage of the control terminal of the eleventh transistor M11 will decrease. When the terminal voltage of the control terminal of the eleventh transistor M11 decreases to a certain value, the eleventh transistor M11 is turned off.

[0072] In another embodiment of the present application, the ramp control circuit is combined with the tail current control circuit. Figure 6 and Figure 8 It can be known that the ramp control circuit is arranged in the LED drive control circuit. Compared with Figure 7 and Figure 8 It can be known that in the embodiment of Figure 7 at the t3 moment, the LED current curve will have a concave, which will cause the LED lamp string to flicker. In the embodiment of Figure 6In the embodiment, the tail current of the second operational amplifier circuit is gradually changed to the tail current of the second operational amplifier circuit when the chopper signal is at the second level before the state of the chopper signal at the first level ends, the tail current of the second operational amplifier CMP2 slowly decreases, the static power consumption can be reduced, in addition, the output current dip caused by the need for re-stabilization of the loop after the increased tail current disappears, the present application can effectively eliminate the dip of the LED current curve, and stable output of the LED driving circuit is realized.

[0073] In an embodiment of the present application, the first current source is provided with at least two output current levels, and the LED driving control circuit adjusts the output current of the first current source to adjust the output current of the LED driving circuit; the output current of the second current source is k1 times of the output current of the first current source, wherein 0.3 < k1 < 1. In a specific embodiment, the first current source can realize 64-level output current adjustment, thereby realizing 64-level output current control of the LED driving circuit. For example, the current flowing through the LED lamp string can be adjusted and controlled in the range of 1-64 mA. In an embodiment, the output current of the second current source is 2 / 3 times of the output current of the first current source. By setting the output current of the second current source to be k1 times of the output current of the first current source, the LED driving control circuit can be applied to different output current applications, and can adaptively realize fast start without causing large overshoot of the third transistor and the fourth transistor, so that the LED driving circuit can work stably.

[0074] In an embodiment of the present application, the ratio of the width-length ratio of the first transistor to the width-length ratio of the fourth transistor is in the range of 1:100 to 1:6000. In another embodiment, the ratio of the width-length ratio of the first transistor to the width-length ratio of the fourth transistor is in the range of 1:500 to 1:5000, which can better balance the dimming depth and circuit performance. Preferably, the ratio of the width-length ratio of the first transistor to the width-length ratio of the fourth transistor is 1:1000. The ratio of the width-length ratio of the third transistor to the width-length ratio of the sixth transistor is 1000:1.

[0075] In an embodiment of the present application, the transistors M1 to M12 can be any one of a metal oxide semiconductor field effect transistor, a junction field effect transistor, and an insulated gate bipolar transistor. In an embodiment, the transistors M1 to M12 are all metal oxide semiconductor field effect transistors. In an embodiment, as shown in Figure 3As shown, the first transistor M1, the second transistor M2, the third transistor M3, the fourth transistor M4 and the fifth transistor M5 are all metal oxide semiconductor field effect transistors. The first end of the first transistor M1 is a drain, the second end of the first transistor M1 is a source, and the control end of the first transistor M1 is a gate. The first end of the second transistor M2 is a drain, the second end of the second transistor M2 is a source, and the control end of the second transistor M2 is a gate. The third transistor M3, the fourth transistor M4 and the fifth transistor M5 can be sequentially provided with drain-source ends, which will not be described here. In addition, for the embodiment in the drawing, in the case of crossing of the connection lines, the position of the coupling point is schematically marked as a coupling relationship between the crossing lines, otherwise there is no coupling relationship between the crossing lines.

[0076] Another embodiment of the present application discloses an LED driving circuit, which comprises an LED load and an LED driving control circuit as claimed in any one of the preceding embodiments, the LED driving control circuit being coupled to the LED load, and the LED driving control circuit being configured to control an output current of the LED driving circuit.

[0077] Still another embodiment of the present application further discloses an LED driving control method for controlling an LED driving control circuit, the LED driving control circuit comprising a current regulating circuit and an output control circuit, the current regulating circuit comprising a current regulating unit and a first transistor, the current regulating unit being configured to control a current flowing through the first transistor, and the current regulating unit being coupled to a control end and a first end of the first transistor, respectively. The output control circuit comprises a third transistor and a fourth transistor, a first end of the third transistor being configured to be coupled to an LED load, a first end of the fourth transistor being coupled to a second end of the third transistor, and a control end of the fourth transistor being coupled to the control end of the first transistor. The LED driving control method comprises:

[0078] Step S1: turning off the first transistor or controlling the current flowing through the first transistor within a preset threshold, and controlling the terminal voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at the second level; turning off the third transistor when the chopping signal is at the second level; and

[0079] Step S2: providing a first current to the control end of the third transistor to accelerate the start of the LED driving control circuit when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current.

[0080] In the embodiments of the present application, the order of the step S1 and the step S2 is not limited, that is, the corresponding control process is performed when the corresponding conditions in the step S1 and the step S2 are met. The first current can be a fixed current or a variable current.

[0081] In an embodiment, the LED driving control method comprises: the fast start circuit turns off the first transistor or controls the current flowing through the first transistor within a preset threshold, and controls the terminal voltage of the control terminal of the first transistor at a preset voltage when the chopping signal is at the second level; and the fast start circuit turns off the third transistor when the chopping signal is at the second level.

[0082] In an embodiment, the output control circuit further comprises a fast start circuit, and the fast start circuit comprises a third switch, a first end of the third switch being coupled to the power supply pin, and a second end of the third switch being coupled to the control terminal of the third transistor; and the LED driving control method further comprises: controlling the third switch to be turned on when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current.

[0083] In another embodiment, the output control circuit further comprises a second operational amplifier circuit, a first input end of the second operational amplifier circuit being coupled to the first end of the first transistor, a second input end of the second operational amplifier circuit being coupled to the second end of the third transistor, and an output end of the second operational amplifier circuit being coupled to the control terminal of the third transistor; and the LED driving control method further comprises: controlling the tail current of the second operational amplifier circuit in a time period when the chopping signal is at the first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

[0084] In an embodiment, the LED driving control method further comprises: gradually reducing the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal being at the first level ends.

[0085] Those skilled in the art should know that the "high level" and "low level", "set" and "reset", "and gate" and "or gate", "non-inverting input end" and "inverting input end" and other logic controls in the logical control involved in the description or drawings can be exchanged or changed, and the same functions or purposes as the above embodiments can be achieved by adjusting the subsequent logical control.

[0086] The description and application of the present application herein are illustrative, and are not intended to limit the scope of the present application to the above embodiments. The effects or advantages related descriptions involved in the description may not be embodied in actual experimental examples due to the uncertainty of specific conditions parameters or other factors, and the effects or advantages related descriptions are not used to limit the scope of the application. Variations and changes of the disclosed embodiments are possible, and the replacement and equivalent components of the embodiments are known to those skilled in the art. It should be clear to those skilled in the art that the present application can be realized in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential characteristics of the present application. Other variations and changes of the disclosed embodiments can be made without departing from the scope and spirit of the present application.

Claims

1. An LED drive control circuit, characterized by, The LED driving control circuit comprises a current regulating circuit and an output control circuit. The current regulating circuit comprises a current regulating unit and a first transistor. The current regulating unit is used to control the current flowing through the first transistor, and is coupled to the control end and the first end of the first transistor respectively. The output control circuit comprises a third transistor, a fourth transistor and a fast start circuit. The first end of the third transistor is used to couple to the LED load. The first end of the fourth transistor is coupled to the second end of the third transistor. The control end of the fourth transistor is coupled to the control end of the first transistor. The fast start circuit is coupled to the control end of the first transistor and the control end of the third transistor respectively. The fast start circuit is used to turn off the first transistor or control the current flowing through the first transistor within a preset threshold, and control the end voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at the second level. The fast start circuit is also used to turn off the third transistor when the chopping signal is at the second level. The fast start circuit further comprises a second switch. The first end of the second switch is coupled to the control end of the third transistor. The second end of the second switch is coupled to the ground. The second switch is used to turn off the third transistor when the chopping signal is at the second level. The fast start circuit comprises a third switch and a third switch control circuit. The first end of the third switch is coupled to the power supply pin. The second end of the third switch is coupled to the control end of the third transistor. The output end of the third switch control circuit is coupled to the control end of the third switch. The third switch control circuit is used to control the third switch to be turned on when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current.

2. The LED drive control circuit of claim 1, wherein, The fast start circuit further comprises: a clamping circuit. The first end of the clamping circuit is coupled to the control end of the first transistor. The clamping circuit is used to turn off the first transistor or control the current flowing through the first transistor within a preset threshold, and clamp the end voltage of the control end of the first transistor to be a preset voltage when the chopping signal is at the second level.

3. The LED drive control circuit of claim 2, wherein, The clamping circuit comprises: a first switch. The first end of the first switch is coupled to the control end of the first transistor; and a fifth transistor. The first end and the control end of the fifth transistor are coupled to the second end of the first switch respectively. The second end of the fifth transistor is coupled to the ground.

4. The LED drive control circuit of claim 1, wherein, The third switch control circuit comprises: a second current source. The input end of the second current source is coupled to the power supply pin; a fourth switch. The first end of the fourth switch is coupled to the input end of the second current source; a fifth switch. The first end of the fifth switch is coupled to the output end of the second current source. The second end of the fifth switch is coupled to the second end of the fourth switch; a sixth transistor. The control end of the sixth transistor is coupled to the control end of the third transistor. The first end of the sixth transistor is coupled to the second end of the fifth switch. The second end of the sixth transistor is coupled to the ground; and an AND gate. The first input end of the AND gate is coupled to the second end of the fifth switch. The second input end of the AND gate is coupled to the chopping signal. The output end of the AND gate is coupled to the control end of the third switch.

5. The LED drive control circuit of claim 1, wherein, The output control circuit further comprises a second operational amplifier circuit. The first input end of the second operational amplifier circuit is coupled to the first end of the first transistor. The second input end of the second operational amplifier circuit is coupled to the second end of the third transistor. The output end of the second operational amplifier circuit is coupled to the control end of the third transistor. The LED drive control circuit further comprises a tail current control circuit, an output end of the tail current control circuit is coupled to a tail current control end of the second operational amplifier circuit, and the tail current control circuit is configured to control the tail current of the second operational amplifier circuit in a time period when the chopping signal is at the first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

6. The LED drive control circuit of claim 3, wherein, A ratio of a width-length ratio of the first transistor to a width-length ratio of the fifth transistor is 1:m, where 1 7. The LED drive control circuit of claim 4, wherein, The current regulation unit comprises a first current source, the first current source is provided with at least two output current levels, and the LED drive control circuit adjusts the output current of the LED drive circuit by adjusting the output current level of the first current source; an output current of a second current source is k1 times of an output current of the first current source, where 0.3 8. The LED drive control circuit of claim 5, wherein, The tail current control circuit comprises: a third current source; a seventh transistor, a first end of the seventh transistor is coupled to the power supply pin, and a control end and a second end of the seventh transistor are coupled to an input end of the third current source, respectively; an eighth transistor, a first end of the eighth transistor is coupled to the power supply pin, and a control end of the eighth transistor is coupled to the control end of the seventh transistor; a sixth switch, a first end of the sixth switch is coupled to a second end of the eighth transistor, and a second end of the sixth switch is coupled to the tail current control end of the second operational amplifier circuit; and a fourth current source, an input end of the fourth current source is coupled to the power supply pin, and an output end of the fourth current source is coupled to the tail current control end of the second operational amplifier circuit.

9. The LED drive control circuit of claim 8, wherein, The current regulation unit comprises a first current source, and an output current of the third current source is k2 times of an output current of the first current source, where 0.05 10. The LED drive control circuit of claim 8, wherein, The tail current control circuit further comprises a gradual change control circuit, and the gradual change control circuit is configured to gradually reduce the tail current of the second operational amplifier circuit to a preset value before a state of the chopping signal at the first level ends.

11. The LED drive control circuit of claim 10, wherein, The gradual change control circuit comprises: a fifth current source, an input end of the fifth current source is coupled to the power supply pin; a seventh switch, a first end of the seventh switch is coupled to an output end of the fifth current source, and a second end of the seventh switch is coupled to the ground; a first capacitor, a first end of the first capacitor is coupled to the output end of the fifth current source, and a second end of the first capacitor is coupled to the ground; a ninth transistor, a first end of the ninth transistor is coupled to the power supply pin; a tenth transistor, a first end of the tenth transistor is coupled to the power supply pin, a second end of the tenth transistor is coupled to the control end of the seventh transistor, and a control end of the tenth transistor is coupled to a control end of the ninth transistor; an eleventh transistor, a first end of the eleventh transistor is coupled to the control end and the second end of the ninth transistor, respectively, and a control end of the eleventh transistor is coupled to the first end of the first capacitor; and a second resistor, a first end of the second resistor is coupled to a second end of the eleventh transistor, and a second end of the second resistor is coupled to the ground.

12. An LED driving circuit, characterized by comprising: The LED drive circuit comprises an LED load and the LED drive control circuit according to any one of claims 1-11, the LED drive control circuit is coupled to the LED load, and the LED drive control circuit is configured to control an output current of the LED drive circuit.

13. An LED drive control method for controlling an LED drive control circuit, characterized by, The LED drive control circuit comprises a current regulating circuit and an output control circuit, the current regulating circuit comprises a current regulating unit and a first transistor, the current regulating unit is used for controlling the current flowing through the first transistor, and the current regulating unit is coupled to the control end and the first end of the first transistor respectively; the output control circuit comprises a third transistor and a fourth transistor, the first end of the third transistor is used for coupling to the LED load, the first end of the fourth transistor is coupled to the second end of the third transistor, and the control end of the fourth transistor is coupled to the control end of the first transistor; the output control circuit further comprises a fast start circuit, the fast start circuit comprises a second switch, the first end of the second switch is coupled to the control end of the third transistor, the second end of the second switch is coupled to the ground, and the second switch is used for turning off the third transistor when the chopping signal is at the second level; The LED drive control method comprises: when the chopping signal is at the second level, turning off the first transistor or controlling the current flowing through the first transistor within a preset threshold, and controlling the end voltage of the control end of the first transistor at a preset voltage; when the chopping signal is at the second level, turning off the third transistor; and when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current, providing a first current to the control end of the third transistor to accelerate the start of the LED drive control circuit.

14. The LED driving control method according to claim 13, wherein The output control circuit further comprises a fast start circuit, the fast start circuit comprises a third switch, the first end of the third switch is coupled to the supply pin, and the second end of the third switch is coupled to the control end of the third transistor; The LED drive control method further comprises: when the chopping signal is at the first level and the current flowing through the third switch is lower than a preset current, controlling the third switch to be turned on.

15. The LED driving control method according to claim 13, wherein The output control circuit further comprises a second operational amplifier circuit, the first input end of the second operational amplifier circuit is coupled to the first end of the first transistor, the second input end of the second operational amplifier circuit is coupled to the second end of the third transistor, and the output end of the second operational amplifier circuit is coupled to the control end of the third transistor; The LED drive control method further comprises: the tail current of the second operational amplifier circuit when the chopping signal is at the first level for a period of time is greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level.

16. The LED driving control method according to claim 15, wherein The LED drive control method further comprises: gradually reducing the tail current of the second operational amplifier circuit to a preset value before the state of the chopping signal being at the first level ends.

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