Zero-current ripple LED linear constant-current driving circuit

Abstract

The utility model relates to the technical field of LED driving, and particularly discloses a zero-current ripple LED linear constant-current driving circuit, which comprises a constant-voltage stabilizing circuit, an auxiliary power supply, an LED string load and a driving circuit, the constant-voltage stabilizing circuit is electrically connected with the auxiliary power supply and the positive electrode of the LED string load, the driving circuit is electrically connected with the auxiliary power supply and the negative electrode of the LED string load, and the driving circuit is electrically connected with the auxiliary power supply and the negative electrode of the LED string load. The driving circuit comprises a dimming MOS tube, an MOS driving module, a switch module, a voltage comparator, a divider resistor, a current detection resistor and an adjustable potentiometer. After the circuit is powered on, the voltage comparator outputs a high level, when the switch module is closed, the brightness of the LED string load is controlled through a PWM signal, the MOS driving module and the dimming MOS tube, the voltage comparator outputs different voltage values by adjusting the resistance value of the adjustable potentiometer, the voltage of the grid electrode of the dimming MOS tube is further adjusted, and the brightness of the LED string load is controlled. The drive current of the LED string load reaches the maximum value, the current drive is linear constant current, and no switch constant current drive current ripple exists.

Description

Technical Field

[0001] The utility model relates to the technical field of LED driving, in particular to a zero-current ripple LED linear constant-current driving circuit. Background Art

[0002] At present, most of the constant current drivers of LEDs adopt the switch drive mode. The disadvantage of this drive circuit is that the drive current ripple is large. The current ripple of some constant current drive circuits can reach 50%. There are three general LED current parameters, namely working current, maximum current, and surge current. Since the LED drive circuit adopts the switch drive mode, its output current will inevitably produce current ripple. Therefore, in order to make the LED operate safely, its current cannot exceed its maximum current. Due to the existence of current ripple, when the LED works at the working current, its maximum current peak may exceed the maximum current of the LED, or even exceed the LED surge current and damage the LED. In order to make the LED work safely, the LED drive current can only be reduced, but this will reduce the normal brightness of the LED. For example, the current parameters of an LED module are working current 5.5A, maximum current 5.7A, and surge current 6A. These three parameters are very close. In order to achieve the normal working current of the LED of 5.5A, and the maximum peak current does not exceed 5.7A, the drive current ripple cannot exceed 400mA, and the current ripple accounts for less than 3.6%. However, most LED drive current ripples on the market are greater than 10%. Therefore, in order to make the LED work safely, the only way is to sacrifice the current and reduce the LED brightness.

[0003] Based on the above problems, how to reduce the ripple of the driving current and make the LED current reach the optimal working state is a problem that needs to be solved urgently. Utility Model Content

[0004] In view of the technical problems in the prior art, the utility model provides a zero-current ripple LED linear constant-current drive circuit.

[0005] The utility model discloses a zero current ripple LED linear constant current driving circuit, comprising a constant voltage stabilizing circuit, an auxiliary power supply, an LED string load and a driving circuit, wherein the constant voltage stabilizing circuit is electrically connected to the positive electrode of the auxiliary power supply and the LED string load, and the driving circuit is electrically connected to the negative electrode of the auxiliary power supply and the LED string load, wherein:

[0006] The driving circuit includes a dimming MOS tube Q2, a MOS driving module U5, a switch module U4, a voltage comparator U10B, a voltage dividing resistor, a current detecting resistor, and an adjustable potentiometer VR2; one end of the voltage dividing resistor is connected to the auxiliary power supply, and the other end is connected to the positive input end of the voltage comparator U10B; one end of the adjustable potentiometer VR2 is grounded, and the other end is connected to the positive input end of the voltage comparator U10B; the negative input end of the voltage comparator U10B is connected to one end of the current detecting resistor and the drain of the dimming MOS tube Q2; the other end of the current detecting resistor is grounded; the input end of the switch module U4 is connected to a PWM signal, and its control end is connected to the output end of the voltage comparator U10B, and the output end is connected to the input end of the MOS driving module U5; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2; the drain of the dimming MOS tube Q2 is connected to the negative electrode of the LED string load.

[0007] Furthermore, the constant voltage stabilizing circuit includes an adjustable potentiometer VR1, one end of the adjustable potentiometer VR1 is connected to the power supply control end of the constant voltage stabilizing circuit, and the other end is grounded.

[0008] Furthermore, the auxiliary power supply includes a buck chip U1, a buck chip U6, a resistor R2, and a resistor R3;

[0009] The VIN pin of the buck chip U1 is connected to the first power supply input terminal, the FB pin of the buck chip U1 is connected to one end of the resistor R2 and one end of the resistor R3; the other end of the resistor R3 is grounded; the other end of the resistor R2 outputs a 12V voltage; the VIN pin of the buck chip U6 is connected to the 12V voltage, and the VOUT end of the buck chip U6 outputs a +5V voltage.

[0010] Furthermore, the constant voltage stabilizing circuit includes a constant voltage control driving chip U2, a MOS tube Q1, a resistor R6, a resistor R8, a resistor R13, a resistor R15, a resistor R21, and a diode D2;

[0011] One end of the adjustable potentiometer VR1 is connected to the FB pin of the constant voltage control driving chip U2 through the resistor R13, and the other end is grounded; the GT pin of the constant voltage control driving chip U2 is connected to the gate of the MOS tube Q1 through the resistor R6, and the VIN pin of the constant voltage control driving chip U2 is connected to the 12V voltage; the drain of the MOS tube Q1 is connected to the second power supply input terminal, and the source of the MOS tube Q1 is grounded through the resistor R21; the resistor R8 and the resistor R15 are connected in series, and one end is connected to the cathode of the diode D2, and the other end is connected to one end of the adjustable potentiometer VR1; the anode of the diode D2 is connected to the drain of the MOS tube Q1;

[0012] The cathode of the diode D2 is the power supply output terminal of the constant voltage stabilizing circuit.

[0013] Furthermore, the driving circuit also includes a resistor R7, a resistor R10, a resistor R16, and a resistor R27;

[0014] The PWM signal is connected to the input end of the switch module U4 through the resistor R27; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2 through the resistor R10; one end of the resistor R16 is connected to the gate of the dimming MOS tube Q2, and the other end is connected to one end of the current detection resistor;

[0015] One end of the voltage-dividing resistor is connected to the 12V voltage output by the auxiliary power supply through the resistor R7, and the other end of the voltage-dividing resistor is connected to the adjustment end of the adjustable potentiometer VR2.

[0016] Furthermore, the current detection resistor includes resistor R22, resistor R23 and resistor R24, which are connected in parallel, one end of which is connected to the negative input end of the voltage comparator U10B and the drain of the dimming MOS tube Q2, and the other end is grounded.

[0017] Furthermore, the auxiliary power supply also includes a resistor R1, an inductor L1, a diode D1, a capacitor C4 and a capacitor C15;

[0018] One end of the resistor R1 is connected to the / SHDN pin of the buck chip U1, and the other end is connected to the 12V voltage output terminal; one end of the inductor L1 is connected to the SW pin of the buck chip U1, and the other end is connected to the other end of the resistor R2; the positive electrode of the diode D1 is grounded, and the negative electrode is connected to the SW pin of the buck chip U1; one end of the capacitor C4 is grounded, and the other end is connected to the 12V voltage output terminal; one end of the capacitor C15 is connected to the +5V voltage output terminal, and the other end is grounded.

[0019] Furthermore, the constant voltage stabilizing circuit further includes an inductor L2, one end of the inductor L2 is connected to the second power supply input end, and the other end of the inductor L2 is connected to the drain of the MOS tube Q1.

[0020] Furthermore, the constant voltage stabilizing circuit further includes a capacitor C8, a capacitor C11, a capacitor C12, a resistor R11, and a resistor R26;

[0021] One end of the capacitor C8 is connected to the power supply output end of the constant voltage stabilizing circuit, and the other end is grounded; one end of the capacitor C11 is grounded, and the other end is connected to the VDD pin of the constant voltage control driving chip U2; one end of the capacitor C12 is grounded, and the other end is connected to the second power supply input end;

[0022] One end of the resistor R11 is connected to the gate of the MOS transistor Q1 , and the other end is connected to the source of the MOS transistor Q1 ; one end of the resistor R26 is connected to the other end of the adjustable potentiometer VR1 , and the other end of the resistor R26 is grounded.

[0023] Furthermore, the LED string load includes n LED lamps and a diode D3; the n LED lamps are connected in series in sequence, the positive end is connected to the power supply output end of the constant voltage stabilizing circuit, and the negative end is connected to the drain of the dimming MOS tube Q2; the positive electrode of the diode D3 is connected to the drain of the dimming MOS tube Q2, and the negative electrode is connected to the power supply output end of the constant voltage stabilizing circuit.

[0024] A zero-current ripple LED linear constant current drive circuit of an embodiment of the utility model includes a constant voltage stabilizing circuit, an auxiliary power supply, an LED string load and a drive circuit, wherein the constant voltage stabilizing circuit is electrically connected to the positive pole of the auxiliary power supply and the LED string load, and the drive circuit is electrically connected to the negative pole of the auxiliary power supply and the LED string load, wherein the drive circuit includes a dimming MOS tube Q2, a MOS drive module U5, a switch module U4, a voltage comparator U10B, a voltage dividing resistor, a current detection resistor, and an adjustable potentiometer VR2; one end of the voltage dividing resistor is connected to the auxiliary power supply, and the other end is connected to the positive input of the voltage comparator U10B. The adjustable potentiometer VR2 is connected to the positive input terminal of the voltage comparator U10B at one end, and the other end is connected to the positive input terminal of the voltage comparator U10B at the other end. The negative input terminal of the voltage comparator U10B is connected to one end of the current detection resistor and the drain of the dimming MOS tube Q2. The other end of the current detection resistor is grounded. The input terminal of the switch module U4 is connected to the PWM signal, and the control terminal thereof is connected to the output terminal of the voltage comparator U10B, and the output terminal thereof is connected to the input terminal of the MOS driving module U5. The output terminal of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2. The drain of the dimming MOS tube Q2 is connected to the negative electrode of the LED string load. After the circuit of the utility model is powered on, the voltage comparator U10B outputs a high level. When the switch module U4 is closed, the brightness of the LED string load is controlled through the PWM signal, the MOS driving module U5 and the dimming MOS tube Q2. When the LED string load is working, by adjusting the resistance value of the adjustable potentiometer VR2, the voltage comparator U10B outputs different voltage values, and then adjusts the voltage of the gate of the dimming MOS tube Q2, so that the driving current of the LED string load reaches the maximum value, and the current drive is a linear constant current, which is not the switch mode constant current used in the prior art, and there is no switch constant current driving current ripple. Compared with the prior art, the driving current can reach 5.7V, which further improves the brightness of the LED string load. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the composition of the zero current ripple LED linear constant current drive circuit of the embodiment of the utility model;

[0027] Figure 2 It is a circuit design diagram of a constant voltage stabilizing circuit in a zero current ripple LED linear constant current driving circuit according to an embodiment of the utility model;

[0028] Figure 3 This is a circuit design diagram of an auxiliary power supply in a zero current ripple LED linear constant current drive circuit according to an embodiment of the utility model;

[0029] Figure 4 This is a circuit design diagram of a driving circuit in a zero current ripple LED linear constant current driving circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the utility model.

[0031] A zero current ripple LED linear constant current drive circuit according to an embodiment of the utility model is as follows: Figure 1 As shown, it includes a constant voltage stabilizing circuit, an auxiliary power supply, an LED string load and a driving circuit. The constant voltage stabilizing circuit is electrically connected to the positive pole of the auxiliary power supply and the LED string load, and the driving circuit is electrically connected to the negative pole of the auxiliary power supply and the LED string load. The constant voltage stabilizing circuit in this embodiment receives voltage input from a DC power supply, and supplies power to the LED string load after constant voltage stabilization, so that the LED string load can work. The auxiliary power supply is used to obtain a working voltage suitable for chips or modules in other circuits to ensure that each circuit is stable and works normally. The driving circuit is used to control the average current of the LED string load, thereby controlling the brightness of the LED string load. The driving circuit includes a dimming MOS tube Q2, a MOS driving module U5, a switch module U4, a voltage comparator U10B, a voltage dividing resistor, a current detecting resistor, and an adjustable potentiometer VR2; one end of the voltage dividing resistor is connected to an auxiliary power supply, and the other end is connected to the positive input end of the voltage comparator U10B; one end of the adjustable potentiometer VR2 is grounded, and the other end is connected to the positive input end of the voltage comparator U10B; the negative input end of the voltage comparator U10B is connected to one end of the current detecting resistor and the drain of the dimming MOS tube Q2; the other end of the current detecting resistor is grounded; the input end of the switch module U4 is connected to a PWM signal, and its control end is connected to the output end of the voltage comparator U10B, and the output end is connected to the input end of the MOS driving module U5; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2; the drain of the dimming MOS tube Q2 is connected to the negative pole of the LED string load. Figure 1As shown, the reference voltage Verf comes from the auxiliary power supply. The reference voltage Verf makes the voltage at the positive input terminal of the voltage comparator U10B greater than 0. Since the switch module U4 is now in the disconnected state, the dimming MOS tube Q2 is not turned on, and the voltage at the negative input terminal of the voltage comparator U10B is 0. At this time, the voltage comparator U10B outputs a high level. When the switch module U4 is closed, the brightness of the LED string load is controlled through the PWM signal, the MOS drive module U5 and the dimming MOS tube Q2. When the LED string load is working, by adjusting the resistance value of the adjustable potentiometer VR2, the voltage comparator U10B outputs different voltage values, and then adjusts the voltage of the gate of the dimming MOS tube Q2, so that the driving current of the LED string load reaches the maximum value, and the current drive is a linear constant current, which is not the switch mode constant current used in the prior art, and there is no switch constant current drive current ripple. Compared with the prior art, the driving current can reach 5.7V, which further improves the brightness of the LED string load.

[0032] Specifically, Figure 1 As shown, the constant voltage stabilizing circuit in this embodiment includes an adjustable potentiometer VR1, one end of the adjustable potentiometer VR1 is connected to the power supply control end of the constant voltage stabilizing circuit, and the other end is grounded. When the resistance value of the adjustable potentiometer VR1 is adjusted, the voltage value required by the LED string load can be adjusted, and the corresponding resistance value can be adjusted according to the different load amounts of the LED string.

[0033] Specifically, Figures 1 to 4 As shown, the auxiliary power supply includes a buck chip U1, a buck chip U6, a resistor R2, and a resistor R3; the VIN pin of the buck chip U1 is connected to the first power supply input terminal, and the FB pin of the buck chip U1 is connected to one end of the resistor R2 and one end of the resistor R3; the other end of the resistor R3 is grounded; the other end of the resistor R2 outputs a 12V voltage; the VIN pin of the buck chip U6 is connected to the 12V voltage, and the VOUT end of the buck chip U6 outputs a +5V voltage. Figure 3 As shown, the first power supply input terminal can be connected to a 52V voltage, and a 12V voltage is output through the step-down chip U1 and the peripheral circuit to power the MOS driver module U5, and then the 12V voltage is output through the step-down chip U6 to obtain a +5V voltage to power the switch module U4. The 12V and 5V voltages can also power other compatible chips, which are not limited here.

[0034] Specifically, the auxiliary power supply in this embodiment also includes a resistor R1, an inductor L1, a diode D1, a capacitor C4 and a capacitor C15; one end of the resistor R1 is connected to the / SHDN pin of the buck chip U1, and the other end is connected to the 12V voltage output terminal; one end of the inductor L1 is connected to the SW pin of the buck chip U1, and the other end is connected to the other end of the resistor R2; the positive electrode of the diode D1 is grounded, and the negative electrode is connected to the SW pin of the buck chip U1; one end of the capacitor C4 is grounded, and the other end is connected to the 12V voltage output terminal; one end of the capacitor C15 is connected to the +5V voltage output terminal, and the other end is grounded. The inductor L1 in this embodiment has the characteristics of passing DC and blocking AC, so after the inductor L1 is connected, the output 12V DC voltage can be more stable. Secondly, the unidirectional conduction characteristic of the diode D1 also protects the circuit. The capacitor C4 and the capacitor C15 can pass AC and block DC, so one end is connected to a high potential and the other end is grounded to play a role in filtering and energy storage.

[0035] Specifically, Figures 1 to 4 As shown, the constant voltage stabilizing circuit includes a constant voltage control driving chip U2, a MOS tube Q1, a resistor R6, a resistor R8, a resistor R13, a resistor R15, a resistor R21, and a diode D2; one end of the adjustable potentiometer VR1 is connected to the FB pin of the constant voltage control driving chip U2 through the resistor R13, and the other end is grounded; the GT pin of the constant voltage control driving chip U2 is connected to the gate of the MOS tube Q1 through the resistor R6, and the VIN pin of the constant voltage control driving chip U2 is connected to a 12V voltage; the drain of the MOS tube Q1 is connected to the second power supply input terminal, and the source of the MOS tube Q1 is grounded through the resistor R21; one end of the resistor R8 and the resistor R15 is connected in series to the cathode of the diode D2, and the other end is connected to one end of the adjustable potentiometer VR1; the anode of the diode D2 is connected to the drain of the MOS tube Q1; the cathode of the diode D2 is the power supply output end of the constant voltage stabilizing circuit. The power supply output end VOUT of the constant voltage stabilizing circuit supplies power to the LED string load.

[0036] Specifically, the constant voltage stabilizing circuit in this embodiment further includes an inductor L2, one end of which is connected to the second power supply input terminal, and the other end of which is connected to the drain of the MOS tube Q1. The function of the inductor L2 is the same as that of the aforementioned inductor L1, which makes the DC voltage outputted from the power supply output terminal more stable.

[0037] Specifically, the constant voltage stabilizing circuit in this embodiment also includes capacitor C8, capacitor C11, capacitor C12, resistor R11, and resistor R26; one end of capacitor C8 is connected to the power supply output end of the constant voltage stabilizing circuit, and the other end is grounded; one end of capacitor C11 is grounded, and the other end is connected to the VDD pin of the constant voltage control driving chip U2; one end of capacitor C12 is grounded, and the other end is connected to the second power supply input end; one end of resistor R11 is connected to the gate of MOS tube Q1, and the other end is connected to the source of MOS tube Q1; one end of resistor R26 is connected to the other end of adjustable potentiometer VR1, and the other end of resistor R26 is grounded. One end of capacitor C8 and capacitor C12 are connected to the high potential, and one end is grounded, both of which play a filtering role. The access of resistor R26 can make the potential of the end connected to the adjustable potentiometer VR1 non-zero, adjust the resistance value of the adjustable potentiometer VR1, and realize the output of the GT pin of the constant voltage control driving chip U2, thereby realizing the adjustment of the voltage value.

[0038] Specifically, Figure 4 As shown, the driving circuit of this embodiment also includes a resistor R7, a resistor R10, a resistor R16, and a resistor R27; the PWM signal is connected to the input end of the switch module U4 through the resistor R27; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2 through the resistor R10; one end of the resistor R16 is connected to the gate of the dimming MOS tube Q2, and the other end is connected to one end of the current detection resistor; one end of the voltage-dividing resistor R30 is connected to the 12V voltage output by the auxiliary power supply through the resistor R7, and the other end of the voltage-dividing resistor is connected to the adjustment end of the adjustable potentiometer VR2. The connection of the resistor R7 reduces the 12V voltage to a 2.5V voltage, and obtains the reference power supply used by the driving circuit. As an example, the current detection resistor in this embodiment includes a resistor R22, a resistor R23, and a resistor R24, and the resistors R22, R23, and R24 are connected in parallel, one end is connected to the negative input end of the voltage comparator U10B and the drain of the dimming MOS tube Q2, and the other end is grounded.

[0039] Resistor R28 and resistor R29 are respectively connected to the negative input terminal and the positive input terminal of the voltage comparator U10B; in this embodiment, resistors, capacitors and electrical components for supporting normal operation of the relevant chip or module can also be connected to the periphery, and the utility model will not list them one by one.

[0040] Specifically, Figure 4As shown, in this embodiment, the LED string load includes n LED lamps and a diode D3; the n LED lamps are connected in series in sequence, the positive terminal is connected to the power supply output terminal of the constant voltage stabilizing circuit, and the negative terminal is connected to the drain of the dimming MOS tube Q2; the positive electrode of the diode D3 is connected to the drain of the dimming MOS tube Q2, and the negative electrode is connected to the power supply output terminal of the constant voltage stabilizing circuit. This embodiment does not limit the value of n, nor does it limit the specific model and parameters of the LED lamp. Those skilled in the art can choose according to the usage.

[0041] The utility model is further described above with the help of specific embodiments, but it should be understood that the specific description here should not be construed as limiting the essence and scope of the utility model. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the utility model.

Claims

1. A zero current ripple LED linear constant current drive circuit, characterized in that: It includes a constant voltage stabilizing circuit, an auxiliary power supply, an LED string load and a driving circuit, wherein the constant voltage stabilizing circuit is electrically connected to the positive electrode of the auxiliary power supply and the LED string load, and the driving circuit is electrically connected to the negative electrode of the auxiliary power supply and the LED string load, wherein: The driving circuit includes a dimming MOS tube Q2, a MOS driving module U5, a switch module U4, a voltage comparator U10B, a voltage dividing resistor, a current detecting resistor, and an adjustable potentiometer VR2; one end of the voltage dividing resistor is connected to the auxiliary power supply, and the other end is connected to the positive input end of the voltage comparator U10B; one end of the adjustable potentiometer VR2 is grounded, and the other end is connected to the positive input end of the voltage comparator U10B; the negative input end of the voltage comparator U10B is connected to one end of the current detecting resistor and the drain of the dimming MOS tube Q2; the other end of the current detecting resistor is grounded; the input end of the switch module U4 is connected to a PWM signal, and its control end is connected to the output end of the voltage comparator U10B, and the output end is connected to the input end of the MOS driving module U5; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2; the drain of the dimming MOS tube Q2 is connected to the negative electrode of the LED string load.

2. A zero current ripple LED linear constant current drive circuit as claimed in claim 1, characterized in that: The constant voltage stabilizing circuit comprises an adjustable potentiometer VR1, one end of the adjustable potentiometer VR1 is connected to the power supply control end of the constant voltage stabilizing circuit, and the other end is grounded.

3. A zero current ripple LED linear constant current drive circuit as claimed in claim 2, characterized in that: The auxiliary power supply includes a buck chip U1, a buck chip U6, a resistor R2, and a resistor R3; The VIN pin of the buck chip U1 is connected to the first power supply input terminal, the FB pin of the buck chip U1 is connected to one end of the resistor R2 and one end of the resistor R3; the other end of the resistor R3 is grounded; the other end of the resistor R2 outputs a 12V voltage; the VIN pin of the buck chip U6 is connected to the 12V voltage, and the VOUT end of the buck chip U6 outputs a +5V voltage.

4. A zero current ripple LED linear constant current drive circuit as claimed in claim 3, characterized in that: The constant voltage stabilizing circuit includes a constant voltage control driving chip U2, a MOS tube Q1, a resistor R6, a resistor R8, a resistor R13, a resistor R15, a resistor R21, and a diode D2; One end of the adjustable potentiometer VR1 is connected to the FB pin of the constant voltage control driving chip U2 through the resistor R13, and the other end is grounded; the GT pin of the constant voltage control driving chip U2 is connected to the gate of the MOS tube Q1 through the resistor R6, and the VIN pin of the constant voltage control driving chip U2 is connected to the 12V voltage; the drain of the MOS tube Q1 is connected to the second power supply input terminal, and the source of the MOS tube Q1 is grounded through the resistor R21; the resistor R8 and the resistor R15 are connected in series, and one end is connected to the cathode of the diode D2, and the other end is connected to one end of the adjustable potentiometer VR1; the anode of the diode D2 is connected to the drain of the MOS tube Q1; The cathode of the diode D2 is the power supply output terminal of the constant voltage stabilizing circuit.

5. A zero current ripple LED linear constant current drive circuit as claimed in claim 4, characterized in that: The driving circuit also includes a resistor R7, a resistor R10, a resistor R16, and a resistor R27; The PWM signal is connected to the input end of the switch module U4 through the resistor R27; the output end of the MOS driving module U5 is connected to the gate of the dimming MOS tube Q2 through the resistor R10; one end of the resistor R16 is connected to the gate of the dimming MOS tube Q2, and the other end is connected to one end of the current detection resistor; One end of the voltage-dividing resistor is connected to the 12V voltage output by the auxiliary power supply through the resistor R7, and the other end of the voltage-dividing resistor is connected to the adjustment end of the adjustable potentiometer VR2.

6. A zero current ripple LED linear constant current drive circuit as claimed in claim 5, characterized in that: The current detection resistor includes a resistor R22, a resistor R23 and a resistor R24. The resistors R22, R23 and R24 are connected in parallel, one end of which is connected to the negative input end of the voltage comparator U10B and the drain of the dimming MOS tube Q2, and the other end is grounded.

7. A zero current ripple LED linear constant current drive circuit as claimed in claim 6, characterized in that: The auxiliary power supply also includes a resistor R1, an inductor L1, a diode D1, a capacitor C4 and a capacitor C15; One end of the resistor R1 is connected to the / SHDN pin of the buck chip U1, and the other end is connected to the 12V voltage output terminal; one end of the inductor L1 is connected to the SW pin of the buck chip U1, and the other end is connected to the other end of the resistor R2; the positive electrode of the diode D1 is grounded, and the negative electrode is connected to the SW pin of the buck chip U1; one end of the capacitor C4 is grounded, and the other end is connected to the 12V voltage output terminal; one end of the capacitor C15 is connected to the +5V voltage output terminal, and the other end is grounded.

8. A zero current ripple LED linear constant current drive circuit as claimed in claim 7, characterized in that: The constant voltage stabilizing circuit further includes an inductor L2, one end of the inductor L2 is connected to the second power supply input end, and the other end of the inductor L2 is connected to the drain of the MOS tube Q1.

9. A zero current ripple LED linear constant current drive circuit as claimed in claim 7, characterized in that: The constant voltage stabilizing circuit also includes a capacitor C8, a capacitor C11, a capacitor C12, a resistor R11, and a resistor R26; One end of the capacitor C8 is connected to the power supply output end of the constant voltage stabilizing circuit, and the other end is grounded; one end of the capacitor C11 is grounded, and the other end is connected to the VDD pin of the constant voltage control driving chip U2; one end of the capacitor C12 is grounded, and the other end is connected to the second power supply input end; One end of the resistor R11 is connected to the gate of the MOS transistor Q1 , and the other end is connected to the source of the MOS transistor Q1 ; one end of the resistor R26 is connected to the other end of the adjustable potentiometer VR1 , and the other end of the resistor R26 is grounded.

10. A zero current ripple LED linear constant current drive circuit as claimed in claim 4, characterized in that: The LED string load includes n LED lamps and a diode D3; the n LED lamps are connected in series in sequence, the positive terminal is connected to the power supply output terminal of the constant voltage stabilizing circuit, and the negative terminal is connected to the drain of the dimming MOS tube Q2; the positive electrode of the diode D3 is connected to the drain of the dimming MOS tube Q2, and the negative electrode is connected to the power supply output terminal of the constant voltage stabilizing circuit.

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