LED drive control circuit, its drive control method, and LED drive circuit

Abstract

The present invention provides an LED driving control circuit, a driving control method thereof, and an LED driving circuit. The LED driving control circuit includes a current regulation circuit and an output control circuit. The current regulation circuit includes a current regulation unit and a first transistor, and the current regulation unit is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, a second operational amplifier circuit, and a tail current control circuit. The output end of the tail current control circuit is coupled to the tail current control end of the second operational amplifier circuit, and the tail current control circuit is used to control the tail current of the second operational amplifier circuit to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level for a period of time when the chopping signal is at the first level. An LED driving control circuit, a driving control method thereof, and an LED driving circuit provided by the present invention can effectively accelerate the startup speed during low-depth dimming and ensure the stable operation of the driving circuit.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, relates to an LED driving technology, and particularly relates to an LED driving control circuit, a driving control method thereof, and an LED driving circuit. Background Art

[0002] A linear LED driving circuit includes a rectifying circuit, a linear regulating tube, and a control circuit for controlling the linear regulating tube. Compared with a switching-type LED driving circuit, the linear LED driving circuit has a relatively simple circuit structure, fewer components, and lower cost. Therefore, the linear LED driving circuit is widely used in the field of LED driving.

[0003] With the continuous improvement of user requirements, the industry has put forward higher requirements for the dimming depth of LED driving circuits. In application scenarios where the dimming depth is lower than 1%, the circuit architecture of traditional linear LED driving circuits often fails to meet the above requirements for dimming depth. If a dimming depth of 0.1% needs to be achieved, the control circuit of the linear LED driving circuit will need to be further improved. As Figure 1 shown in a linear LED driving control circuit, it can be used in application scenarios with a lower dimming depth. The linear LED driving control circuit includes a current regulating circuit 10 and an output control circuit 11. The current regulating circuit 10 can be regarded as a first loop circuit, and the output control circuit 11 can be regarded as a second loop circuit. The current regulating circuit 10 is coupled to the output control circuit 11. The current regulating circuit 10 is used to generate a reference signal for the output current of the LED driving circuit, and the output control circuit 11 is used to control the output current of the LED driving circuit according to the reference signal, thereby controlling the brightness of the LED lamp. As Figure 1As shown, the current regulation 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. 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 ground. 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. 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 ground. The control terminal of the fourth transistor M4 is coupled to the control terminal of the first transistor M1. The first transistor M1 and the fourth transistor M4 form a current mirror. The magnitude of the current flowing through the fourth transistor M4 can be controlled by controlling the magnitude of the current flowing through the first transistor M1.

[0004] As Figure 2 In another solution as shown, the linear LED driving control circuit includes a current regulation circuit 20 and an output control circuit 21. The current regulation 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. 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 ground. 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. 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 ground. The control terminal of the fourth transistor M4 is coupled to the control terminal of the first transistor M1. The first transistor M1 and the fourth transistor M4 form a current mirror.

[0005] A dimming depth of 0.1% poses new challenges to the circuit design of the chopping mode. Combining Figure 1It can be seen that when the chopping signal PWM is low, the third transistor M3 or the fourth transistor M4 needs to be completely turned off to cut off the current flowing through the LED 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 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. The tail current in the first current source I1 and the second operational amplifier circuit CMP2 alone is not sufficient to turn on the third transistor M3 and the fourth transistor M4 with a large area during this time period, resulting in the current flowing through the LED string being almost zero in the small gray scale chopping mode. Therefore, there is a problem of slow startup speed.

[0006] In view of this, a new structure or control method is needed to solve at least part of the above problems. Summary of the Invention

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

[0008] According to one aspect of the present invention, an LED drive control circuit is disclosed. The LED drive control circuit includes a current regulation circuit and an output control circuit. The current regulation circuit includes a current regulation unit and a first transistor. The current regulation unit is coupled to the first transistor and is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, a second operational amplifier circuit, and a tail current control circuit. The first end of the third transistor is used to be coupled 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 first input terminal of the second operational amplifier circuit is coupled to the first end of the first transistor, the second input terminal of the second operational amplifier circuit is coupled to the second end of the third transistor, and the output terminal of the second operational amplifier circuit is coupled to the control end of the third transistor. The output terminal of the tail current control circuit is coupled to the tail current control end of the second operational amplifier circuit, and the tail current control circuit is used to control the tail current of the second operational amplifier circuit to be greater during a period when the chopping signal is at a first level than when the chopping signal is at a second level.

[0009] As an embodiment of the present invention, the output control circuit further includes a fast startup circuit, and the fast startup circuit includes:

[0010] A third switch, whose first end is coupled to a power supply pin and whose second end is coupled to the control end of the third transistor; and

[0011] A third switch control circuit, whose output terminal is coupled to the control end of the third switch and is used to control the third switch to turn on when the chopping signal is at a first level and the current flowing through the third switch tube is lower than a preset current.

[0012] As an embodiment of the present invention, the third switch control circuit includes:

[0013] A second current source, whose input terminal is coupled to the power supply pin;

[0014] A fourth switch, whose first terminal is coupled to the input terminal of the second current source;

[0015] A fifth switch, whose first terminal is coupled to the output terminal of the second current source and whose second terminal is coupled to the second terminal of the fourth switch;

[0016] A sixth transistor, whose control terminal is coupled to the control terminal of the third transistor, whose first terminal is coupled to the second terminal of the fifth switch, and whose second terminal is grounded; and

[0017] An AND gate, whose first input terminal is coupled to the second terminal of the fifth switch, whose second input terminal is coupled to the chopping signal, and whose output terminal is coupled to the control terminal of the third switch.

[0018] As an embodiment of the present invention, the tail current control circuit includes:

[0019] A first tail current control circuit, whose output terminal is coupled to the tail current control terminal of the second operational amplifier circuit for providing a first current to the tail current control terminal of the second operational amplifier circuit; and

[0020] A second tail current control circuit, whose output terminal is coupled to the tail current control terminal of the second operational amplifier circuit for providing a second current to the tail current control terminal of the second operational amplifier circuit during a period when the chopping signal is at a first level.

[0021] As an embodiment of the present invention, the first tail current control circuit includes a fourth current source, the input terminal of the fourth current source is coupled to the power supply pin, and the output terminal of the fourth current source is coupled to the tail current control terminal of the second operational amplifier circuit; the second tail current control circuit includes:

[0022] A third current source;

[0023] A seventh transistor, whose first terminal is coupled to the power supply pin, and whose control terminal and second terminal are respectively coupled to the input terminal of the third current source;

[0024] An eighth transistor, whose first terminal is coupled to the power supply pin, and whose control terminal is coupled to the control terminal of the seventh transistor; and

[0025] A sixth switch, whose first terminal is coupled to the second terminal of the eighth transistor, and whose second terminal is coupled to the tail current control terminal of the second operational amplifier circuit.

[0026] As an embodiment of the present invention, the current regulation unit includes 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; the output current of the second current source is k1 times the output current of the first current source, where 0.3 < k1 < 1.

[0027] As an embodiment of the present invention, the second tail current control circuit further includes a slow change control circuit, and the slow change control circuit is used to reduce the second current to a preset value before the state where the chopping signal is at the first level ends.

[0028] As an embodiment of the present invention, the current regulation unit includes a first current source, the output current of the third current source is k2 times the output current of the first current source, where 0.05 < k2 < 1.

[0029] As an embodiment of the present invention, the slow change control circuit includes:

[0030] A fifth current source, whose input terminal is coupled to the power supply pin;

[0031] A seventh switch, whose first terminal is coupled to the output terminal of the fifth current source, and whose second terminal is grounded;

[0032] A first capacitor, whose first terminal is coupled to the output terminal of the fifth current source, and whose second terminal is grounded;

[0033] A ninth transistor, whose first terminal is coupled to the power supply pin;

[0034] A tenth transistor, whose first terminal is coupled to the power supply pin, whose second terminal is coupled to the control terminal of the seventh transistor, and whose control terminal is coupled to the control terminal of the ninth transistor;

[0035] An eleventh transistor, whose first terminal is respectively coupled to the control terminal and the second terminal of the ninth transistor, and whose control terminal is coupled to the first terminal of the first capacitor; and

[0036] A second resistor, whose first terminal is coupled to the second terminal of the eleventh transistor, and whose second terminal is grounded.

[0037] As an embodiment of the present invention, the fast start circuit further includes:

[0038] A clamping circuit, whose first terminal is coupled to the control terminal of the first transistor, and is used to turn off the first transistor or control the current flowing through the first transistor within a preset threshold when the chopping signal is at the second level, and clamp the terminal voltage of the control terminal of the first transistor at a preset voltage; and

[0039] A second switch, whose first terminal is coupled to the control terminal of the third transistor, and whose second terminal is grounded, and is used to turn off the third transistor when the chopping signal is at the second level.

[0040] As an embodiment of the present invention, the clamping circuit includes:

[0041] A first switch, whose first end is coupled to the control end of the first transistor; and

[0042] A fifth transistor, whose first end and control end are respectively coupled to the second end of the first switch, and whose second end is coupled to ground.

[0043] According to another aspect of the present invention, an LED driving circuit is disclosed. The LED driving circuit includes an LED load and the LED driving control circuit as described in any one of the above. The LED driving control circuit is coupled to the LED load, and the LED driving control circuit is used to control the output current of the LED driving circuit.

[0044] According to still another aspect of the present invention, an LED driving control method is disclosed. The LED driving control method is used to control an LED driving control circuit. The LED driving control circuit includes a current regulating circuit and an output control circuit. The current regulating circuit includes a current regulating unit and a first transistor. The current regulating unit is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, and a second operational amplifier circuit. The first end of the third transistor is used to be coupled 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 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 driving control method includes: controlling that the tail current of the second operational amplifier circuit is greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level for a period of time when the chopping signal is at the first level.

[0045] As an embodiment of the present invention, the output control circuit further includes a fast start circuit. The fast start circuit includes a third switch. 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 LED driving control method further includes: controlling the third switch to conduct when the chopping signal is at the first level and the current flowing through the third switch tube is lower than a preset current.

[0046] As an embodiment of the present invention, the LED driving control method specifically includes: providing a first current to the tail current control end of the second operational amplifier circuit; providing a second current to the tail current control end of the second operational amplifier circuit for a period of time when the chopping signal is at the first level.

[0047] As an embodiment of the present invention, the LED driving control method further includes: reducing the second current to a preset value before the state where the chopping signal is at the first level ends.

[0048] The present invention provides an LED driving control circuit, a driving control method thereof, and an LED driving circuit. The LED driving control circuit includes a current regulating circuit and an output control circuit. The current regulating circuit includes a current regulating unit and a first transistor. The current regulating unit is coupled to the first transistor and is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, a second operational amplifier circuit, and a tail current control circuit. A first end of the third transistor is used to be coupled to an LED load. A first end of the fourth transistor is coupled to a second end of the third transistor, and a control end of the fourth transistor is coupled to a control end of the first transistor. A first input terminal of the second operational amplifier circuit is coupled to a first end of the first transistor, a second input terminal of the second operational amplifier circuit is coupled to a second end of the third transistor, and an output terminal of the second operational amplifier circuit is coupled to a control end of the third transistor. An output terminal of the tail current control circuit is coupled to a tail current control terminal of the second operational amplifier circuit. The tail current control circuit is used to control the tail current of the second operational amplifier circuit in a period when the chopping signal is at a first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at a second level. The LED driving control circuit, the driving control method thereof, and the LED driving circuit provided by the present invention can effectively accelerate the startup speed during low-depth dimming and ensure the stable operation of the driving circuit. Description of the Drawings

[0049] The drawings are used to provide a further understanding of the present invention and, together with the description, are used to explain the embodiments of the present invention and do not constitute a limitation to the present invention. In the drawings:

[0050] Figure 1 The circuit structure schematic diagram of a prior art linear LED driving control circuit is shown;

[0051] Figure 2 The circuit structure schematic diagram of another prior art linear LED driving control circuit is shown;

[0052] Figure 3 The circuit structure schematic diagram of an LED driving control circuit according to an embodiment of the present invention is shown;

[0053] Figure 4 The circuit structure schematic diagram of an LED driving control circuit according to another embodiment of the present invention is shown;

[0054] Figure 5 The circuit structure schematic diagram of an LED driving control circuit according to still another embodiment of the present invention is shown;

[0055] Figure 6 The circuit structure schematic diagram of an LED driving control circuit according to an embodiment of the present invention is shown;

[0056] Figure 7 The figure shows a schematic diagram of the signal waveforms of an LED driving control circuit according to an embodiment of the present invention;

[0057] Figure 8 The figure shows a schematic diagram of the signal waveforms of an LED driving control circuit according to another embodiment of the present invention. Detailed implementation manners

[0058] To further understand the present invention, the preferred implementation manners of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0059] The description of this part only focuses on several typical embodiments, and the present invention is not limited to the scope described in the embodiments. Combinations of different embodiments, mutual substitution of some technical features in different embodiments, and mutual substitution of the same or similar prior art means and some technical features in the embodiments are also within the scope of description and protection of the present invention.

[0060] "Coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrical conduction medium such as a conductor, where the electrical conduction medium may contain parasitic inductance or parasitic capacitance, or may also be a connection through an intermediate circuit or component described in the embodiments of the specification; indirect connection may also include a connection through other active devices or passive devices on the basis of achieving the same or similar functions, such as a connection through circuits or components such as switches, signal amplification circuits, and follower circuits. "Plurality" or "multiple" means two or more. In addition, in the present invention, words such as first and second are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply that there is a certain actual relationship or order between these technical features.

[0061] An embodiment of the present invention discloses an LED driving control circuit. The LED driving control circuit includes a current regulation circuit and an output control circuit. As Figure 3 shown, the current regulation circuit includes a current regulation unit and a first transistor M1. The current regulation unit is coupled to the first transistor, and the current regulation unit is used to control the current flowing through the first transistor M1. The first end of the current regulation unit is coupled to the control end of the first transistor M1, and the second end of the current regulation unit is coupled to the first end of the first transistor M1. In as Figure 3In the illustrated embodiment, the current regulation unit includes a first current source I1, a first operational amplifier circuit CMP1, and a second transistor M2. The input terminal of the first current source I1 is coupled to the power supply pin VDD. 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. 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 second transistor M2 is coupled to the output terminal of the first current source I1. The current flowing through the first transistor M1 can be adjusted by adjusting the output of the first current source I1 or the like. In another embodiment, the current regulation unit includes a first current source I1 and a resistor R. The input terminal of the first current source I1 is coupled to the power supply pin VDD. The first terminal of the resistor R is coupled to the output terminal of the first current source I1 and the control terminal of the first transistor M1 respectively. The second terminal of the resistor R is used to be coupled to the first terminal of the first transistor M1. The second terminal of the first transistor M1 is coupled to the ground. The current flowing through the first transistor can be adjusted by adjusting the output of the first current source I1 or the like.

[0062] As Figure 3 In an embodiment as shown, the output control circuit includes a third transistor M3, a fourth transistor M4, a second operational amplifier circuit CMP2, and a tail current control circuit 111. The first terminal of the third transistor M3 is used to be coupled to one end of the LED load. In one embodiment, the first terminal of the third transistor M3 can be coupled to the second terminal VLED- of the LED load. 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. The second terminal of the fourth transistor M4 is coupled to the ground. 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. The output terminal of the second operational amplifier circuit CMP2 is coupled to the control terminal of the third transistor M3. The output terminal of the tail current control circuit 111 is coupled to the tail current control terminal of the second operational amplifier circuit CMP2. The tail current control circuit 111 is used to control that the tail current of the second operational amplifier circuit CMP2 is greater than the tail current of the second operational amplifier circuit CMP2 when the chopping signal is at the second level (for example, low level) for a period of time when the chopping signal is at the first level (for example, high level). The chopping signal is a PWM signal. When the PWM signal is at the first level, the third transistor M3 and the fourth transistor M4 are controlled to conduct. When the PWM signal is at the second level, the third transistor M3 and / or the fourth transistor M4 are controlled to turn off. By adjusting the duty cycle of the chopping signal, the magnitude of the output current of the LED driving circuit can be adjusted. When the chopping signal PWM signal is at the first level (for example, high level), by increasing the tail current of the second operational amplifier circuit, the terminal voltage of the control terminal of the third transistor can be quickly pulled up, and the quick start of the LED driving circuit can be realized.

[0063] In one embodiment, the tail current control circuit 111 includes a first tail current control circuit and a second tail current control circuit. The output terminal of the first tail current control circuit is coupled to the tail current control terminal of the second operational amplifier circuit. The first tail current control circuit is configured to provide a first current to the tail current control terminal of the second operational amplifier circuit. The output terminal of the second tail current control circuit is coupled to the tail current control terminal of the second operational amplifier circuit. The second tail current control circuit is configured to provide a second current to the tail current control terminal of the second operational amplifier circuit during a period when the chopping signal is at a first level. In one embodiment, as Figure 3 shown, the first tail current control circuit includes a fourth current source I4. The input terminal of the fourth current source I4 is coupled to the power supply pin VDD, and the output terminal of the fourth current source I4 is coupled to the tail current control terminal of the second operational amplifier circuit CMP2.

[0064] In one embodiment, the second tail current control circuit includes a third current source k2*I1, a seventh transistor M7, an eighth transistor M8, and a sixth switch S6. The first terminal of the seventh transistor M7 is coupled to the power supply pin VDD. The control terminal and the second terminal of the seventh transistor M7 are respectively coupled to the input terminal of the third current source, and the output terminal of the third current source is coupled to ground. The first terminal of the eighth transistor M8 is coupled to the power supply pin VDD, and the control terminal of the eighth transistor M8 is coupled to the control terminal of the seventh transistor M7. The first terminal of the sixth switch S6 is coupled to the second terminal of the eighth transistor M8, and the second terminal of the sixth switch S6 is coupled to the tail current control terminal of the second operational amplifier circuit CMP2. When the chopping signal PWM signal is at a second level (e.g., low level), the sixth switch S6 is turned off, and the fourth current source I4 in the first tail current control circuit provides a first current to the tail current control terminal of the second operational amplifier circuit. When the chopping signal PWM signal is at a first level (e.g., high level), the sixth switch S6 is turned on, and the tail current of the second operational amplifier circuit CMP2 is the sum of the first current and the second current. The tail current of the second operational amplifier circuit CMP2 increases, and the terminal voltage of the control terminal of the third transistor M3 can be quickly pulled up. In a preferred embodiment, within a second preset time (e.g., 1 us) when the chopping signal PWM signal becomes the first level (e.g., high level), the sixth switch S6 is turned on. At other times, the sixth switch S6 is not turned on to reduce the circuit power consumption.

[0065] In one 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 applicable to applications with different output currents, can adaptively achieve fast startup, and will not generate a large overshoot, effectively protecting the third transistor and the fourth transistor, and enabling the LED driving circuit to operate stably.

[0066] In another embodiment, asFigure 4 As shown, the output control circuit further includes a fast start circuit. The fast start circuit includes a first start module 112, and the first start module 112 includes a clamping circuit and a second switch S2. The first end of the clamping circuit is coupled to the control end of the first transistor M1, the second end of the clamping circuit is coupled to the ground, and the clamping circuit is used 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 end of the first transistor M1 at a preset voltage. Correspondingly, the terminal voltage of the control end of the fourth transistor M4 is also clamped at a preset voltage. The first end of the second switch S2 is coupled to the control end of the third transistor M3, and the second end of the second switch S2 is coupled to the ground. The second switch S2 is used 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 end of the first transistor I1. The first end and the control end 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 the 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 end and the second end of the fifth transistor. When the chopping signal is at the second level, by controlling the terminal voltages of the control ends of the first transistor M1 and the fourth transistor M4 at a preset voltage, the start-up speed of the LED drive 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. Selecting to control the third transistor through the fast start circuit instead of controlling the start of the fourth transistor can avoid abnormal circuit functions of the LED drive circuit or LED flashing caused by large overshoot while taking into account fast start. Based on the above circuit control settings, the stable operation of the LED drive circuit can be ensured. In an 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.

[0067] In an embodiment, as Figure 5As shown, the output control circuit further includes a fast startup circuit, and the fast startup circuit includes a second startup module 113. The second startup module 113 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. The third switch control circuit is configured to control the third switch S3 to conduct 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 increase the voltage at the control end of the third switch tube M3 and accelerate the startup speed of the LED drive control circuit. In a preferred embodiment, the second startup module 113 includes a third switch S3, a first resistor R1, and a third switch control circuit. The first resistor R1 is serially coupled to the third switch S3. The resistor R1 is provided for current limiting to avoid excessive charging current because 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, thus easily causing a large overshoot.

[0068] In a specific embodiment, as Figure 5 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 grounded. 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) when the chopping signal becomes the first level (such as a high level), the fourth switch S4 conducts. At this time, the current flowing through the sixth transistor M6 is less than the preset current, and the fast startup circuit controls the third switch S3 to conduct to accelerate the voltage at the first end of the sixth transistor M6 ( Figure 5The terminal voltage at point B (in the middle) reaches a high level. 50 ns 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 to turn off in a timely manner according to the comparison result, avoiding a large overshoot in the third transistor. Preferably, the fifth switch S5 is turned on within a second preset time (such as 1 us) after the chopping signal becomes the first level, which is effective for the fast start of charging the third transistor M3, avoiding the accidental conduction of the fast start circuit where the third switch is located due to fluctuations in the output currents 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.

[0069] In an embodiment of the present invention, in combination with Figure 5 and Figure 7 it can be known that when the chopping signal PWM signal is at a high level, the fast start signal (the switch control signal corresponding to the third switch S3) is at a high level, and the third switch S3 is turned on. By supplying power to the third transistor M3, the fast start circuit provides a large current, which can quickly raise the control terminal voltage of the third transistor M3 to accelerate 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 controlled to turn off, and the fast start signal is at a low level. When the chopping signal PWM signal is at a high level, the sixth switch S6 is turned on. As Figure 7 shown, the tail current of the second operational amplifier circuit CMP2 (i.e., Figure 7 the operational amplifier tail current in Figure 7 is lifted, thereby accelerating the start of the third transistor M3. In the stage from t1 to t2, both the fast start circuit and the tail current control circuit play a role in accelerating the start. In the stage from t2 to t3, the third switch S3 in the fast start circuit is turned off, and the fast start circuit does not work. The LED drive control circuit enters a closed-loop working mode, and the tail current increased by the second operational amplifier circuit CMP2 is used to accelerate the stabilization of the output current. After the output tends to be stable, the tail current of the second operational amplifier circuit drops to a preset value (which can be equal to the tail current magnitude when the chopping signal is at a low level). In the stage from t1 to t2, the output current of the LED drive circuit (i.e.,

[0070] the LED current in rapidly increases. In the stage from t2 to t3, the growth rate of the output current of the LED drive circuit slows down and gradually increases to the preset output current value. The LED drive circuit of the present invention can greatly shorten the start time at a low dimming depth, achieving a fast and stable output at a low dimming depth.

[0070] In an embodiment of the present invention, the second tail current control circuit further includes a slow change control circuit, and the slow change control circuit is used to reduce the second current to a preset value before the end of the state where the chopping signal is at the first level. The preset value can be equal to zero or a value close to zero.

[0071] In one embodiment, as Figure 6 shown, the tail current control circuit 211 further includes a slew rate control circuit. The slew rate control circuit includes 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 respectively coupled to the control terminal of the ninth transistor M9 and the second terminal of the ninth transistor M9, 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, and the fifth current source I5 charges the first capacitor C1, 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. As the current flowing through the eleventh transistor M11 continuously increases, 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 end of the state where the chopping signal is at the first level. When the chopping signal is at the second level, the seventh switch S7 is turned on, and 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 invention, in combination with Figure 6 and Figure 8 it can be learned that a slew rate control circuit is provided in the LED driving control circuit. By comparing Figure 7 and Figure 8 it can be learned that in the Figure 7 embodiment, at time t3, there will be a depression in the LED current curve, which will cause the LED string to flicker. In Figure 6In an embodiment of the present invention, before the state where the chopping signal is at the first level ends, the tail current of the second operational amplifier circuit is gradually changed to the tail current of the second operational amplifier circuit when the chopping signal is at the second level. The tail current provided to the second operational amplifier circuit CMP2 slowly decreases, which can reduce the static power consumption. In addition, for the output current depression generated because the loop needs to be stabilized again after the increased tail current disappears, the present invention can effectively eliminate the depression of the LED current curve and achieve the stable output of the LED driving circuit.

[0073] In an embodiment of the present invention, the current regulation unit includes a first current source. The first current source has at least two output current levels. 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 the output current of the first current source, where 0.3 < k1 < 1. In a specific embodiment, the first current source can achieve the adjustment of the output current in 64 levels, so as to achieve the control of the output current of the LED driving circuit in 64 levels. For example, the current flowing through the LED string can be adjusted and controlled in the range of 1 to 64 mA. In an embodiment, the output current of the second current source is 2 / 3 times the output current of the first current source. By setting the output current of the second current source to be k1 times the output current of the first current source, the LED driving control circuit can be applicable to applications with different output currents, can adaptively achieve fast startup, and will not generate a large overshoot of the third transistor and the fourth transistor, enabling the LED driving circuit to work stably.

[0074] In an embodiment of the present invention, the ratio of the aspect ratio of the first transistor to the aspect ratio of the fourth transistor is in the range of 1:100 to 1:6000. In another embodiment, the ratio of the aspect ratio of the first transistor to the aspect 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 aspect ratio of the first transistor to the aspect ratio of the fourth transistor is 1:1000. The ratio of the aspect ratio of the third transistor to the aspect ratio of the sixth transistor is 1000:1.

[0075] In an embodiment of the present invention, the transistors M1 to M12 can be any one of metal oxide semiconductor field effect transistors, junction field effect transistors, insulated gate bipolar transistors, etc. In an embodiment, the transistors M1 to M12 are all metal oxide semiconductor field effect transistors. In an embodiment, such as Figure 3As shown, the first transistor M1, the second transistor M2, the third transistor M3, and the fourth transistor M4 are all metal oxide semiconductor field effect transistors. The first end of the first transistor M1 is the drain, the second end of the first transistor M1 is the source, and the control end of the first transistor M1 is the gate. The first end of the second transistor M2 is the drain, the second end of the second transistor M2 is the source, and the control end of the second transistor M2 is the gate. The third transistor M3 and the fourth transistor M4 can be set with drain and source ends in sequence, which will not be repeated here. In addition, for the embodiments in the accompanying drawings, in the case where there are cross-connected lines, the position of the coupling point is marked to indicate that there is a coupling relationship between the cross-connected lines, otherwise there is no coupling relationship between the cross-connected lines.

[0076] Another embodiment of the present invention discloses an LED driving circuit, which includes an LED load and an LED driving control circuit as described in any one of the above items, wherein the LED driving control circuit is coupled to the LED load, and the LED driving control circuit is used to control the output current of the LED driving circuit.

[0077] Another embodiment of the present invention also discloses an LED drive control method, which is used to control an LED drive control circuit, wherein the LED drive control circuit includes a current regulating circuit and an output control circuit, wherein the current regulating circuit includes a current regulating unit and a first transistor, wherein the current regulating unit is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, and a second operational amplifier circuit, wherein the first end of the third transistor is used to couple 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 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 includes: controlling the tail current of the second operational amplifier circuit for a period of time when the chopping signal is at a first level to be greater than the tail current of the second operational amplifier circuit when the chopping signal is at a second level.

[0078] In one embodiment, the output control circuit further includes a fast start circuit, the fast start circuit includes a third switch, a first end of the third switch is coupled to the power supply pin, and a second end of the third switch is coupled to the control end of the third transistor. By controlling the switching state of the third switch, the terminal voltage of the control end of the third transistor is controlled, thereby improving the startup speed of the LED drive circuit. The LED drive control method also includes: controlling the third switch to turn on when the chopping signal is at the first level and the current flowing through the third switch tube is lower than the preset current.

[0079] In another embodiment, the LED driving control method specifically includes: providing a first current to the tail current control terminal of the second operational amplifier circuit; providing a second current to the tail current control terminal of the second operational amplifier circuit for a period of time when the chopping signal is at a first level.

[0080] In one embodiment, the LED driving control method further includes: reducing the second current to a preset value before the end of the state where the chopping signal is at a first level.

[0081] Those skilled in the art should know that in the logical control involved in the specification or drawings, logical controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input terminal" and "inverting input terminal" can be interchanged or changed with each other, and the same functions or purposes as those in the above embodiments can be achieved by adjusting the subsequent logical control.

[0082] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above embodiments. The related descriptions of effects or advantages in the specification may not be reflected in actual experimental examples due to uncertainties in specific condition parameters or other factors, and the related descriptions of effects or advantages are not used to limit the scope of the invention. It is possible to make deformations and changes to the disclosed embodiments here, and various components of substitution and equivalence for those embodiments are well-known to those of ordinary skill in the art. Those skilled in the art should clearly understand that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the present invention. Other deformations and changes can be made to the disclosed embodiments here without departing from the scope and spirit of the present invention.

Claims

1. An LED driving control circuit, characterized in that, The LED driving control circuit includes a current regulation circuit and an output control circuit. The current regulation circuit includes a current regulation unit and a first transistor. The current regulation unit is coupled to the first transistor, and the current regulation unit is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, a second operational amplifier circuit, and a tail current control circuit. The first end of the third transistor is used to be coupled 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 first input terminal of the second operational amplifier circuit is coupled to the first end of the first transistor, the second input terminal of the second operational amplifier circuit is coupled to the second end of the third transistor, and the output terminal of the second operational amplifier circuit is coupled to the control end of the third transistor. The output terminal of the tail current control circuit is coupled to the tail current control terminal of the second operational amplifier circuit. The tail current control circuit is used to control that the tail current of the second operational amplifier circuit is greater than the tail current of the second operational amplifier circuit when the chopping signal is at the second level for a period of time when the chopping signal is at the first level. The tail current control circuit includes a first tail current control circuit and a second tail current control circuit. The output terminal of the first tail current control circuit is coupled to the tail current control terminal of the second operational amplifier circuit. The first tail current control circuit is used to provide a first current to the tail current control terminal of the second operational amplifier circuit. The output terminal of the second tail current control circuit is coupled to the tail current control terminal of the second operational amplifier circuit. The second tail current control circuit is used to provide a second current to the tail current control terminal of the second operational amplifier circuit for a period of time when the chopping signal is at the first level.

2. The LED driving and controlling circuit according to claim 1, wherein The output control circuit further includes a fast start circuit, and the fast start circuit includes: A third switch, whose first end is coupled to the power supply pin and whose second end is coupled to the control end of the third transistor; and A third switch control circuit, whose output terminal is coupled to the control end of the third switch, and is used to control the third switch to conduct when the chopping signal is at the first level and the current flowing through the third switch tube is lower than a preset current.

3. The LED driving and controlling circuit according to claim 2, wherein The third switch control circuit includes: A second current source, whose input terminal is coupled to the power supply pin; A fourth switch, whose first end is coupled to the input terminal of the second current source; A fifth switch, whose first end is coupled to the output terminal of the second current source and whose second end is coupled to the second end of the fourth switch; A sixth transistor, whose control end is coupled to the control end of the third transistor, whose first end is coupled to the second end of the fifth switch, and whose second end is grounded; and An AND gate, whose first input terminal is coupled to the second end of the fifth switch, whose second input terminal is coupled to the chopping signal, and whose output terminal is coupled to the control end of the third switch.

4. The LED driving control circuit according to claim 1, wherein The first tail current control circuit includes a fourth current source, the input terminal of the fourth current source is coupled to the power supply pin, and the output terminal of the fourth current source is coupled to the tail current control terminal of the second operational amplifier circuit. The second tail current control circuit includes: A third current source; A seventh transistor, whose first end is coupled to the power supply pin, and whose control end and second end are respectively coupled to the input terminal of the third current source; An eighth transistor, whose first end is coupled to the power supply pin, and whose control end is coupled to the control end of the seventh transistor; and The sixth switch, whose first end is coupled to the second end of the eighth transistor and whose second end is coupled to the tail current control end of the second operational amplifier circuit.

5. The LED driving control circuit according to claim 3, wherein The current regulation unit includes a first current source which is provided with 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 the output current of the first current source, where 0.3 < k1 < 1.

6. The LED driving and controlling circuit according to claim 1, wherein, The second tail current control circuit further includes a gradual change control circuit which is configured to reduce the second current to a preset value before the state where the chopping signal is at the first level ends.

7. The LED driving control circuit according to claim 4, wherein The current regulation unit includes a first current source, and the output current of the third current source is k2 times the output current of the first current source, where 0.05 < k2 < 1.

8. The LED driving control circuit according to claim 6, wherein The gradual change control circuit includes: A fifth current source, whose input end is coupled to the power supply pin; A seventh switch, whose first end is coupled to the output end of the fifth current source and whose second end is grounded; A first capacitor, whose first end is coupled to the output end of the fifth current source and whose second end is grounded; A ninth transistor, whose first end is coupled to the power supply pin; A tenth transistor, whose first end is coupled to the power supply pin, whose second end is coupled to the control end of the seventh transistor, and whose control end is coupled to the control end of the ninth transistor; An eleventh transistor, whose first end is respectively coupled to the control end and the second end of the ninth transistor, and whose control end is coupled to the first end of the first capacitor; and A second resistor, whose first end is coupled to the second end of the eleventh transistor and whose second end is grounded.

9. The LED driving control circuit according to claim 2, wherein, The fast startup circuit further includes: A clamping circuit, whose first end is coupled to the control end of the first transistor, and which is configured to turn off the first transistor or control the current flowing through the first transistor within a preset threshold when the chopping signal is at the second level, and clamp the terminal voltage of the control end of the first transistor at a preset voltage; and A second switch, whose first end is coupled to the control end of the third transistor and whose second end is grounded, and which is configured to turn off the third transistor when the chopping signal is at the second level.

10. The LED driving control circuit according to claim 9, wherein, The clamping circuit includes: A first switch, whose first end is coupled to the control end of the first transistor; and A fifth transistor, whose first end and control end are respectively coupled to the second end of the first switch, and whose second end is grounded.

11. An LED driving circuit, characterized in that, The LED driving circuit includes an LED load and the LED driving control circuit according to any one of claims 1-10, the LED driving control circuit is coupled to the LED load, and the LED driving control circuit is used to control the output current of the LED driving circuit.

12. An LED driving control method for controlling an LED driving control circuit, characterized in that, The LED driving control circuit includes a current regulating circuit and an output control circuit. The current regulating circuit includes a current regulating unit and a first transistor. The current regulating unit is used to control the current flowing through the first transistor. The output control circuit includes a third transistor, a fourth transistor, a second operational amplifier circuit, and a tail current control circuit. The first end of the third transistor is used 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 first input terminal of the second operational amplifier circuit is coupled to the first end of the first transistor. The second input terminal of the second operational amplifier circuit is coupled to the second end of the third transistor. The output terminal of the second operational amplifier circuit is coupled to the control end of the third transistor. The tail current control circuit includes a first tail current control circuit and a second tail current control circuit. The output terminal of the first tail current control circuit is coupled to the tail current control end of the second operational amplifier circuit. The first tail current control circuit is used to provide a first current to the tail current control end of the second operational amplifier circuit. The output terminal of the second tail current control circuit is coupled to the tail current control end of the second operational amplifier circuit. The second tail current control circuit is used to provide a second current to the tail current control end of the second operational amplifier circuit during a period when the chopping signal is at a first level. The LED driving control method includes: controlling that the tail current of the second operational amplifier circuit is greater during a period when the chopping signal is at a first level than the tail current of the second operational amplifier circuit when the chopping signal is at a second level.

13. The LED driving control method according to claim 12, wherein The output control circuit further includes a fast start circuit. The fast start circuit includes a third switch. 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. The LED driving control method further includes: controlling the third switch to conduct when the chopping signal is at a first level and the current flowing through the third switch tube is lower than a preset current.

14. The LED driving control method according to claim 12, wherein The LED driving control method specifically includes: providing a first current to the tail current control end of the second operational amplifier circuit; providing a second current to the tail current control end of the second operational amplifier circuit during a period when the chopping signal is at a first level.

15. The LED driving control method according to claim 14, characterized in that, The LED driving control method further includes: reducing the second current to a preset value before the state of the chopping signal at a first level ends.

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