Light-emitting module driving circuit and light-emitting device

Abstract

This application relates to a light-emitting module driving circuit and a light-emitting device. The light-emitting module driving circuit includes: an inner-loop constant current control circuit that receives a pulse width modulation signal and performs constant current regulation on the light-emitting module based on the pulse width modulation signal and the current feedback signal of the light-emitting module; and an outer-loop voltage regulation circuit that controls the voltage drop of the first switching transistor used to drive the light-emitting module to stabilize at a target value through closed-loop regulation. The inner-loop constant current control and outer-loop voltage regulation of the light-emitting module driving circuit in this application constitute a dual-loop control circuit, which can greatly improve the rise and fall speed of the current, thereby allowing the light source to operate under a constant current as much as possible when it is turned on.

Description

Technical Field

[0001] This application belongs to the field of electronic circuit technology, and in particular relates to a light-emitting module driving circuit and a light-emitting device. Background Technology

[0002] In conventional light source dimming schemes, brightness is adjusted by changing the current. However, because changes in current cause changes in the light-emitting characteristics of the light-emitting diode (LED), in some scenarios with strict spectral requirements, this can lead to significant changes in both color temperature and color rendering index.

[0003] For the above reasons, a pulse width modulation (PWM) dimming scheme was adopted. PWM dimming allows the LED light source to operate under a stable current. The brightness of the light source is adjusted by different duty cycles. However, most traditional driver circuits are based on a buck topology. In this structure, the energy storage inductor and the energy storage capacitor on the load side form a second-order filter, which is insufficient for the fast response of PWM. This results in the current waveform having insufficiently steep rise and fall edges, thus affecting the LED's luminous characteristics. Summary of the Invention

[0004] The purpose of this application is to provide a light-emitting module driving circuit and a light-emitting device, which aims to solve the problem of insufficient PWM response affecting the light-emitting characteristics of light-emitting diodes.

[0005] In a first aspect, embodiments of this application provide a light-emitting module driving circuit, including a step-down circuit, a first switching transistor, a sampling resistor, an inner-loop constant current control circuit, and an outer-loop voltage regulation circuit. The step-down circuit includes a main power transistor, a freewheeling transistor, a step-down inductor, and an output capacitor. The first terminal of the main power transistor is connected to the input terminal, and the second terminal of the main power transistor is connected to the first terminal of the freewheeling transistor and the first terminal of the step-down inductor. The second terminal of the freewheeling transistor is grounded. The second terminal of the step-down inductor is connected to the first terminal of the output capacitor and the first terminal of the first switching transistor. The second terminal of the first switching transistor is connected to the anode of the light-emitting module, and the cathode of the light-emitting module is grounded through the sampling resistor. The inner loop constant current control circuit is connected to the control terminal, the dimming input terminal, and the negative terminal of the light-emitting module of the first switching transistor. The inner loop constant current control circuit receives the pulse width modulation signal input from the dimming input terminal and performs constant current adjustment on the light-emitting module according to the pulse width modulation signal and the current feedback signal of the light-emitting module. The outer loop voltage regulation circuit is connected to both ends of the first switching transistor and the dimming input terminal. The outer loop voltage regulation circuit controls the voltage drop of the first switching transistor used to drive the light-emitting module to stabilize at the target value through closed-loop regulation.

[0006] In some embodiments, the inner loop constant current control circuit includes: a first switching transistor and a first operational amplifier; the output terminal of the first operational amplifier is connected to the control terminal of the first switching transistor, the cathode of the light-emitting module is connected to the inverting input terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier is also connected to a dimming input terminal, and the non-inverting input terminal of the first operational amplifier is connected to a first reference voltage.

[0007] In some embodiments, the inner-loop constant current control circuit includes: an adder; the first input terminal of the adder is connected to the cathode of the light-emitting module, the second input terminal of the adder is connected to the dimming input terminal, and the output terminal of the adder is connected to the inverting input terminal of the first operational amplifier.

[0008] In some embodiments, when the pulse width modulation signal is high, the first operational amplifier is controlled to output a low level, the first switching transistor is turned off, and the current of the light-emitting module is zero. When the pulse width modulation signal is low, the first switch is turned on and off according to the current feedback signal of the light-emitting module, thus forming a constant current circuit.

[0009] In some embodiments, the outer loop voltage regulation circuit includes: a BUCK power chip, a second operational amplifier, and a third operational amplifier; the output terminal of the BUCK power chip is connected to the control terminal of the main power transistor, the non-inverting input terminal of the second operational amplifier is connected to the first terminal of the first switching transistor, the inverting input terminal of the second operational amplifier is connected to the second terminal of the first switching transistor, the output terminal of the second operational amplifier is connected to the non-inverting input terminal of the third operational amplifier, the inverting input terminal of the third operational amplifier is connected to a second reference voltage, and the output terminal of the third operational amplifier is connected to the input terminal of the BUCK power chip.

[0010] In some embodiments, the outer loop voltage regulation circuit further includes: a second resistor and a low-pass filter; the output terminal of the third operational amplifier is connected to the input terminal of the low-pass filter through the second resistor, and the output terminal of the low-pass filter is connected to the BUCK power chip.

[0011] In some embodiments, the outer loop voltage regulation circuit further includes: a third resistor and a second switch; the control terminal of the second switch is connected to the dimming input terminal through the third resistor, the first terminal of the second switch is connected to the input terminal of the low-pass filter, and the second terminal of the second switch is grounded.

[0012] In some embodiments, the BUCK power chip includes the main power transistor.

[0013] In some embodiments, the BUCK power chip further includes a fourth operational amplifier, a fifth operational amplifier, and a sawtooth wave generator; the non-inverting input terminal of the fifth operational amplifier is connected to the output terminal of the third operational amplifier, the inverting input terminal of the fifth operational amplifier is connected to a third reference voltage, the output terminal of the fifth operational amplifier is connected to the inverting input terminal of the fourth operational amplifier, the non-inverting input terminal of the fourth operational amplifier is connected to the sawtooth wave generator, and the output terminal of the fourth operational amplifier is connected to the control terminal of the main power transistor.

[0014] Secondly, embodiments of this application also provide a light-emitting device, including the light-emitting module driving circuit described above.

[0015] The advantages of the embodiments in this application compared with related technologies are: The light-emitting module driving circuit of this embodiment includes: a step-down circuit, a first switching transistor, a sampling resistor, an inner-loop constant current control circuit, and an outer-loop voltage regulation circuit. The inner-loop constant current control circuit is connected to the control terminal, the dimming input terminal, and the negative terminal of the light-emitting module of the first switching transistor. It receives the pulse width modulation signal from the dimming input terminal and performs constant current regulation on the light-emitting module based on the pulse width modulation signal and the current feedback signal of the light-emitting module. The outer-loop voltage regulation circuit is connected to both ends of the first switching transistor and the dimming input terminal. The outer-loop voltage regulation circuit controls the voltage drop of the first switching transistor used to drive the light-emitting module to stabilize at a target value through closed-loop regulation. The inner-loop constant current control and outer-loop voltage regulation of the light-emitting module driving circuit of this embodiment constitute a dual-loop control circuit, which can greatly improve the rise and fall speed of the current, thereby allowing the light source to operate under a constant current as much as possible when it is turned on. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a light-emitting module driving circuit provided in one embodiment of this application.

[0017] Figure 2 This is a circuit diagram of a light-emitting module driving circuit provided in an embodiment of this application.

[0018] Figure 3 The current waveform diagram of a light-emitting module provided in an embodiment of this application is shown. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0020] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0021] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] To address the issue of insufficient PWM response affecting the light-emitting characteristics of LEDs, embodiments of this application provide a light-emitting module driving circuit, wherein the light-emitting module includes at least one LED. For example... Figure 1 As shown, the light-emitting module driving circuit includes a step-down circuit, a first switching transistor Q1, a sampling resistor R1, an inner-loop constant current control circuit 11, and an outer-loop voltage regulation circuit 12. The step-down circuit includes a main power transistor Q3, a freewheeling transistor D1, a step-down inductor L1, and an output capacitor C1. The first terminal of the main power transistor Q3 is connected to the input terminal, which is connected to DC power VDD. The second terminal of the main power transistor Q3 is connected to the first terminal of the freewheeling transistor D1 and the first terminal of the step-down inductor L1. The second terminal of the freewheeling transistor D1 is grounded. The second terminal of the step-down inductor L1 is connected to the first terminal of the output capacitor C1 and the first terminal of the first switching transistor Q1. The second terminal of the first switching transistor Q1 is connected to the anode of the light-emitting module LED. The cathode of the light-emitting module LED is grounded through the sampling resistor R1.

[0024] The inner loop constant current control circuit 11 is connected to the control terminal of the first switching transistor Q1, the dimming input terminal PWM, and the negative terminal of the light-emitting module LED. The inner loop constant current control circuit 11 receives the pulse width modulation signal (i.e., dimming signal) input from the dimming input terminal PWM, and performs constant current adjustment on the light-emitting module according to the pulse width modulation signal and the current feedback signal of the light-emitting module. The outer loop voltage regulation circuit 12 is connected to both ends of the first switching transistor Q1 and the dimming input terminal PWM. The outer loop voltage regulation circuit 12 controls the voltage drop of the first switching transistor Q1 used to drive the light-emitting module to stabilize at the target value through closed-loop regulation.

[0025] In this embodiment, the main power transistor Q3, the freewheeling transistor D1, and the first switching transistor Q1 can be, for example, MOSFETs. In other embodiments, the first switching transistor Q1 and the main power transistor Q3 can also be replaced by different types of semiconductor transistors, such as insulated-gate bipolar transistors (IGBTs) or bipolar transistors. In this embodiment, the first switching transistor Q1 and the main power transistor Q3 are MOSFETs, with the control terminal of the first switching transistor Q1 and the main power transistor Q3 being the gate, the first terminal being the drain, and the second terminal being the source. The freewheeling transistor D1 is a diode, with its cathode and anode serving as the first and second terminals, respectively.

[0026] In this embodiment, the inner-loop constant current control circuit 11 uses an analog method for constant current regulation. This loop control is simple and has a rapid response, thereby greatly improving the current response speed. The outer-loop voltage regulation circuit 12 uses a feedback voltage method to allow the inner-loop regulating device to operate at a low voltage drop close to saturation, thereby greatly reducing the heat dissipation of the regulating tube.

[0027] The light-emitting module driving circuit of this application embodiment consists of an inner loop constant current control and an outer loop voltage regulation, forming a dual-loop control circuit. This can greatly improve the rise and fall speed of the current, thereby allowing the light source to operate under a constant current as much as possible when it is turned on.

[0028] In one embodiment, see Figure 2 The inner loop constant current control circuit 11 includes: a first switching transistor Q1 and a first operational amplifier OP1; the output terminal of the first operational amplifier OP1 is connected to the control terminal of the first switching transistor Q1, the cathode of the light-emitting module LED is connected to the inverting input terminal of the first operational amplifier OP1, the inverting input terminal of the first operational amplifier OP1 is also connected to the dimming input terminal PWM, and the non-inverting input terminal of the first operational amplifier OP1 is connected to the first reference voltage Vref1.

[0029] In this circuit, the first switching transistor Q1 can be, for example, a MOSFET. The control terminal of the first switching transistor Q1 is the gate, the first terminal is the drain, and the second terminal is the source. The non-inverting input terminal of the first operational amplifier OP1 can be directly connected to an external first reference voltage Vref1. Alternatively, the non-inverting input terminal of the first operational amplifier OP1 can be connected to a constant voltage source. The positive terminal of the constant voltage source is connected to the non-inverting input terminal of the first operational amplifier OP1, and the negative terminal is grounded to GND. This constant voltage source provides a constant first reference voltage Vref1.

[0030] The sampling voltage of the sampling resistor R1, along with the pulse width modulation signal, is transmitted to the inverting input of the first operational amplifier OP1. After comparison with the first reference voltage Vref1, a control signal is output to the first switching transistor Q1 to control its on / off state, thereby controlling the operation of the LED module. Using the sampling voltage of the sampling resistor R1 as a current feedback signal to control the constant current operation of the LED module is simple, has a rapid response, and significantly improves the current response speed.

[0031] In one embodiment, see Figure 2 The inner-loop constant current control circuit 11 also includes an adder AD1. The first input terminal of adder AD1 is connected to the cathode of the LED light-emitting module, the second input terminal of adder AD1 is connected to the dimming input terminal PWM, and the output terminal of adder AD1 is connected to the inverting input terminal of the first operational amplifier OP1. The waveform of the pulse width modulation signal is added to the sampling voltage obtained by sampling through sampling resistor R1 via adder AD1 to obtain a current feedback signal. This current feedback signal is transmitted to the inverting input terminal of the first operational amplifier OP1, compared and amplified with the first reference voltage Vref1, and then used to control the on / off state of the first switching transistor Q1, thereby controlling the LED light-emitting module.

[0032] In this embodiment, when the pulse width modulation signal is high, the first operational amplifier OP1 is controlled to output a low level, which pulls down the control voltage of the first switching transistor Q1, turns off the first switching transistor Q1, and makes the current of the light-emitting module LED zero; when the pulse width modulation signal is low, the first switching transistor is controlled to turn on and off according to the current feedback signal of the light-emitting module, thus forming a constant current circuit.

[0033] In the inner-loop constant current control circuit 11, the first switching transistor Q1 and the first operational amplifier OP1 together form a transconductance amplifier circuit, with a transconductance gain of gm. When the pulse width modulation signal is high, it pulls down the control voltage of the first switching transistor Q1, making the output current zero, thereby achieving the turn-off effect of the pulse width modulation signal. When the pulse width modulation signal is low, the control voltage of the first switching transistor Q1 is determined by the sampling voltage of the sampling resistor R1, thus forming a constant current circuit and realizing the constant current effect when the pulse width modulation signal is on.

[0034] Based on the inner-loop constant current control circuit 11, the output current Iout of the first switching transistor Q1 is Iout = Vref1·gm / (gm·R1+1). Since the transconductance gain gm is generally much greater than 1, after simplification, we can obtain: Iout = Vref / R1. Since the first reference voltage Vref1 and the sampling resistor R1 are fixed, the output current is constant. The inner-loop constant current control circuit 11 uses an analog method for constant current regulation, which is simple to control and has a fast response, thus greatly improving the current response speed.

[0035] In one embodiment, see Figure 2 The outer loop voltage regulation circuit 12 includes: a BUCK power chip 121, a second operational amplifier OP2, and a third operational amplifier OP3. The output terminal of the BUCK power chip 121 is connected to the control terminal of the main power transistor Q3. The non-inverting input terminal of the second operational amplifier OP2 is connected to the first terminal of the first switching transistor Q1. The inverting input terminal of the second operational amplifier OP2 is connected to the second terminal of the first switching transistor Q1 and the anode of the LED light-emitting module. The output terminal of the second operational amplifier OP2 is connected to the non-inverting input terminal of the third operational amplifier OP3. The inverting input terminal of the third operational amplifier OP3 is connected to the second reference voltage Vref3. The output terminal of the third operational amplifier OP3 is connected to the input terminal of the BUCK power chip 121.

[0036] The inverting input of the third operational amplifier OP3 can be directly connected to the second reference voltage Vref3 from the outside. The inverting input of the third operational amplifier OP3 can also be connected to a constant voltage source. The positive terminal of the constant voltage source is connected to the inverting input of the third operational amplifier OP3, and the negative terminal is grounded to GND. The constant voltage source provides a constant second reference voltage Vref3.

[0037] The second operational amplifier OP2 amplifies the saturation voltage drop of the first switching transistor Q1, obtaining transistor voltage drop feedback. Let the output operating voltage of the BUCK power chip 121 be Vm(s). Since the bandwidth of operational amplifiers is generally much larger than that of the BUCK power chip 121, we can assume that the gain of all operational amplifiers is constant. Let the voltage gain of the second operational amplifier OP2 be K2, and the voltage gain of the third operational amplifier OP3 be K3. Let the operating voltage drop of the LED module be Vled. Let the transfer function of the control terminal of the BUCK power chip 121 be G(s), then the equations are as follows: {(Vm(s)-Vled)·k2-Vref3}·k3·G(s)=Vm(s), where the zero-frequency response of the BUCK power chip 121 is the output operating voltage, and the AC section determines the voltage regulation speed of the entire light-emitting module driving circuit. To obtain the operating output voltage Vm(0) of the BUCK power chip 121, the above equation is expanded to obtain: Vm(0) = (k2·k3·G(0)·Vled-k3·G(0)·Vref3) / (k2·k3·G(0)-1), Expanding and simplifying the above equation, we get Vm(0) = Vled - Vref3 / K2. Therefore, the voltage drop across the first switch Q1 is Vm(0) - Vled = Vref3 / K2. Thus, by adjusting the magnitude of the second reference voltage Vref3 and the gain of the second operational amplifier OP2, the voltage drop across the first switch Q1 can be controlled to the target value.

[0038] The outer loop voltage regulation circuit 12 of this application embodiment uses feedback voltage to allow the first switching transistor Q1 in the inner loop constant current control circuit 11 to operate as close to saturation as possible under a low voltage difference, thereby greatly reducing the heat dissipation of the first switching transistor Q1.

[0039] In some embodiments, see Figure 2 The outer loop voltage regulation circuit 12 further includes a second resistor R2 and a low-pass filter 122. The output of the third operational amplifier OP3 is connected to the input of the low-pass filter through the second resistor R2, and the output of the low-pass filter 122 is connected to the input of the BUCK power chip 121. The second resistor R2 is a current-limiting resistor to prevent current spikes in the outer loop voltage regulation circuit 12. The low-pass filter 122 is used to perform low-pass filtering on the signal input to the BUCK power chip 121.

[0040] In some embodiments, see Figure 2 The outer loop voltage regulation circuit 12 also includes: a third resistor R3 and a second switch Q2. The first control terminal of the second switch Q2 is connected to the dimming input terminal PWM through the third resistor R3, the first terminal of the second switch Q2 is connected to the input terminal of the low-pass filter 122, and the second terminal of the second switch Q2 is grounded to GND.

[0041] The second switch Q2 can be, for example, a transistor. The control terminal of the second switch Q2 is the base, the first terminal is the collector, and the second terminal is the emitter. In other embodiments, the second switch Q2 can also be replaced by different types of semiconductor transistors, such as an insulated-gate bipolar transistor (IGBT) or a MOSFET. The third resistor R3 is a current-limiting resistor. When the pulse width modulation signal is high, the second switch Q2 is turned on. The collector output of the second switch Q2 is superimposed with the output of the third operational amplifier OP3 and then filtered by the low-pass filter 122 to remove high-frequency spurious signals and improve voltage control accuracy.

[0042] In some embodiments, the main power transistor Q3 is integrated into the BUCK power chip 121. In some embodiments, the freewheeling transistor D1 is also integrated into the BUCK power chip 121 to reduce circuit area.

[0043] In some embodiments, the BUCK power chip 121 also includes a fourth operational amplifier OP4, a fifth operational amplifier OP5, and a sawtooth wave generator. The non-inverting input of the fifth operational amplifier OP5 is connected to the output of the third operational amplifier OP3, the inverting input of the fifth operational amplifier OP5 is connected to the third reference voltage Vref5, the output of the fifth operational amplifier OP5 is connected to the inverting input of the fourth operational amplifier OP4, the non-inverting input of the fourth operational amplifier OP4 is connected to the sawtooth wave generator, and the output of the fourth operational amplifier OP4 is connected to the control terminal of the main power transistor Q3.

[0044] In this design, the non-inverting input of the fifth operational amplifier OP5 forms the input of the BUCK power chip 121, and the output of the fourth operational amplifier OP4 forms the output of the BUCK power chip 121. The inverting input of the fifth operational amplifier OP5 can be directly connected to an external third reference voltage Vref5. Alternatively, the inverting input of the fifth operational amplifier OP5 can be connected to a constant voltage source, with its positive terminal connected to the inverting input and its negative terminal grounded (GND). This constant voltage source provides a constant third reference voltage Vref5. The main power transistor Q3 is a switching device in the BUCK power chip 121, used for voltage conversion.

[0045] When the pulse width modulation signal is high, the voltage drop across the first switch Q1 is amplified by the second operational amplifier OP2 and the third operational amplifier OP3, and then superimposed with the pulse width modulation signal (PWM) amplified by the second switch Q2 to obtain a high level. This high level is then transmitted to the fifth operational amplifier OP5 via the low-pass filter 122. After being compared and amplified with the third reference voltage Vrsf5, it is compared with the output of the sawtooth wave generator and outputs a low level to the control terminal of the main power transistor Q3, controlling the main power transistor Q3 to turn off and cutting off the power supply VDD input.

[0046] When the pulse width modulation signal is low, the voltage drop across the first switch Q1 is amplified by the second operational amplifier OP2 and the third operational amplifier OP3, and then superimposed with the pulse width modulation signal (PWM) amplified by the second switch Q2 to obtain a low level. This low level is transmitted to the fifth operational amplifier OP5 through the low-pass filter 122. After being compared and amplified with the third reference voltage Vrsf5, it is compared with the output of the sawtooth wave generator and outputs a high level to the control terminal of the main power transistor Q3, controlling the main power transistor Q3 to conduct and transmitting the power signal to the first switch Q1 to drive the LED module.

[0047] For example, a complete PWM cycle operation is as follows: When the initial input pulse width modulation signal is low, the first operational amplifier OP1 outputs a high level, controlling the first switch Q1 to turn on. The current in the buck inductor L1 begins to rise linearly. As the first switch Q1 remains on, the current flowing through the LED module increases. When the voltage value of the pulse width modulation signal plus the LED current is less than the first reference voltage Vref1, the first operational amplifier OP1 outputs a high level and maintains the high output, while the first switch Q1 remains on. When the current in the buck inductor L1 rises to a certain level, and the voltage value of the pulse width modulation signal plus the LED current is greater than or equal to the first reference voltage Vref1, the output of the first operational amplifier OP1 reverses, outputting a low level, causing the first switch Q1 to turn off, and the inductor current begins to decrease. The output of the first operational amplifier OP1 remains high for the duration of one (pulse width modulation signal) PWM cycle, i.e., the duty cycle. During the period when the first switch Q1 is off, this continues until the next pulse width modulation signal arrives. It is easy to understand that the magnitude of the first reference voltage Vref1 is related to the voltage value of the current of the LED module superimposed on the pulse width modulation (PWM) signal. See the waveform of the LED current output for details. Figure 3The green curve represents the original current waveform of the LED light-emitting module, while the purple curve represents the current waveform of the LED light-emitting module in the light-emitting module driving circuit of this application embodiment. It can be seen that the light-emitting module driving circuit of this application embodiment can greatly improve the rise and fall speed of the current, thereby allowing the light source to work under a constant current as much as possible when it is turned on.

[0048] In summary, the light-emitting module driving circuit of this application embodiment includes: an inner-loop constant current control circuit 11, which receives a pulse width modulation signal and performs constant current regulation on the light-emitting module LED based on the pulse width modulation signal and the current feedback signal of the light-emitting module LED; and an outer-loop voltage regulation circuit 12, which stabilizes the voltage drop of the first switching transistor Q1 used to drive the light-emitting module LED at a target value through closed-loop regulation. The inner-loop constant current control and outer-loop voltage regulation of the light-emitting module driving circuit of this application embodiment constitute a dual-loop control circuit, which can greatly improve the rise and fall speed of the current, thereby allowing the light source to operate under a constant current as much as possible when it is turned on.

[0049] This application also provides a light-emitting device, which includes the aforementioned light-emitting module driving circuit.

[0050] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A light-emitting module driving circuit, characterized in that, The circuit includes a step-down circuit, a first switching transistor, a sampling resistor, an inner-loop constant current control circuit, and an outer-loop voltage regulation circuit. The step-down circuit includes a main power transistor, a freewheeling transistor, a step-down inductor, and an output capacitor. The first terminal of the main power transistor is connected to the input terminal, and the second terminal of the main power transistor is connected to the first terminal of the freewheeling transistor and the first terminal of the step-down inductor. The second terminal of the freewheeling transistor is grounded. The second terminal of the step-down inductor is connected to the first terminal of the output capacitor and the first terminal of the first switching transistor. The second terminal of the first switching transistor is connected to the anode of the light-emitting module, and the cathode of the light-emitting module is grounded through the sampling resistor. The inner loop constant current control circuit is connected to the control terminal, the dimming input terminal, and the negative terminal of the light-emitting module of the first switching transistor. The inner loop constant current control circuit receives the pulse width modulation signal input from the dimming input terminal and performs constant current adjustment on the light-emitting module according to the pulse width modulation signal and the current feedback signal of the light-emitting module. The outer loop voltage regulation circuit is connected to both ends of the first switching transistor and the dimming input terminal. The outer loop voltage regulation circuit controls the voltage drop of the first switching transistor used to drive the light-emitting module to stabilize at the target value through closed-loop regulation.

2. The light-emitting module driving circuit as described in claim 1, characterized in that, The inner loop constant current control circuit includes: a first switching transistor and a first operational amplifier; the output terminal of the first operational amplifier is connected to the control terminal of the first switching transistor, the cathode of the light-emitting module is connected to the inverting input terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier is also connected to a dimming input terminal, and the non-inverting input terminal of the first operational amplifier is connected to a first reference voltage.

3. The light-emitting module driving circuit as described in claim 2, characterized in that, The inner loop constant current control circuit further includes an adder; the first input terminal of the adder is connected to the cathode of the light-emitting module, the second input terminal of the adder is connected to the dimming input terminal, and the output terminal of the adder is connected to the inverting input terminal of the first operational amplifier.

4. The light-emitting module driving circuit as described in claim 3, characterized in that, When the pulse width modulation signal is high, the first operational amplifier is controlled to output a low level, the first switching transistor is turned off, and the current of the light-emitting module is zero. When the pulse width modulation signal is low, the first switch is turned on and off according to the current feedback signal of the light-emitting module, thus forming a constant current circuit.

5. The light-emitting module driving circuit as described in claim 1, characterized in that, The outer loop voltage regulation circuit includes: a BUCK power chip, a second operational amplifier, and a third operational amplifier; the output terminal of the BUCK power chip is connected to the control terminal of the main power transistor; the non-inverting input terminal of the second operational amplifier is connected to the first terminal of the first switching transistor; the inverting input terminal of the second operational amplifier is connected to the second terminal of the first switching transistor; the output terminal of the second operational amplifier is connected to the non-inverting input terminal of the third operational amplifier; the inverting input terminal of the third operational amplifier is connected to a second reference voltage; and the output terminal of the third operational amplifier is connected to the input terminal of the BUCK power chip.

6. The light-emitting module driving circuit as described in claim 5, characterized in that, The outer loop voltage regulation circuit further includes: a second resistor and a low-pass filter; the output terminal of the third operational amplifier is connected to the input terminal of the low-pass filter through the second resistor, and the output terminal of the low-pass filter is connected to the BUCK power chip.

7. The light-emitting module driving circuit as described in claim 6, characterized in that, The outer loop voltage regulation circuit further includes: a third resistor and a second switch; the control terminal of the second switch is connected to the dimming input terminal through the third resistor, the first terminal of the second switch is connected to the input terminal of the low-pass filter, and the second terminal of the second switch is grounded.

8. The light-emitting module driving circuit as described in claim 5, characterized in that, The BUCK power chip includes the main power transistor.

9. The light-emitting module driving circuit according to any one of claims 5 to 8, characterized in that, The BUCK power chip also includes a fourth operational amplifier, a fifth operational amplifier, and a sawtooth wave generator; the non-inverting input of the fifth operational amplifier is connected to the output of the third operational amplifier, the inverting input of the fifth operational amplifier is connected to a third reference voltage, the output of the fifth operational amplifier is connected to the inverting input of the fourth operational amplifier, the non-inverting input of the fourth operational amplifier is connected to the sawtooth wave generator, and the output of the fourth operational amplifier is connected to the control terminal of the main power transistor.

10. A light-emitting device, characterized in that, Includes the light-emitting module driving circuit as described in any one of claims 1-9.

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