LED lamp and linear constant current driving circuit thereof

Abstract

This invention provides an LED lamp and its linear constant current driving circuit. The linear constant current driving circuit includes a power supply module; the power supply module supplies power to a first operational amplifier, a differential amplifier supplies power to a first reference voltage module, the first reference voltage module outputs a first reference voltage to the first operational amplifier, and the first operational amplifier outputs a control signal to a first field-effect transistor; a second reference voltage module outputs a second reference voltage to a second operational amplifier, and the second operational amplifier outputs a control signal to a second field-effect transistor; the first terminal of the second field-effect transistor is connected to the input terminal of the differential amplifier, and a first LED chip is connected between the power supply terminal and the first terminal of the second field-effect transistor; a first capacitor is connected between the second terminal of the first field-effect transistor and the power supply terminal, and the second reference voltage module is also grounded through the second capacitor. This invention also provides an LED lamp with the above circuit. This invention can achieve low power consumption of the LED lamp and avoid flickering.

Description

Technical Field

[0001] This utility model relates to the technical field of LED lighting drive, specifically, to an LED lighting fixture and its linear constant current drive circuit. Background Technology

[0002] LED lighting fixtures offer advantages such as energy efficiency, environmental friendliness, and long lifespan, making them widely used in home lighting, architectural decoration, and various other applications. Each LED fixture contains multiple LED chips and a driver circuit, with the driving current supplying power to the LED chips. Some existing LED lighting fixtures utilize linear constant current driver circuits to power the LED chips. Existing linear constant current driver circuits mainly include single-stage architectures, two-stage structures, and linear constant current architectures with adjustable dimming times.

[0003] The single-segment architecture of the linear constant current drive circuit is simple in structure, requires fewer peripheral devices, and is low in cost, but has a narrow input voltage range, making it unsuitable for environments with large input voltage fluctuations. The two-segment architecture is slightly more complex, requiring more peripheral devices than the single-segment architecture. However, the two-segment architecture allows for a wider input voltage range, enabling its application in environments with significant input voltage fluctuations. Both architectures comply with the new ERP standard and the IEEE 1789 flicker standard.

[0004] See Figure 1 The linear constant current architecture with adjustable dimming time includes a fuse F1, a rectifier circuit BD1, a diode D1, and a constant current chip U1. The constant current chip U1 is connected to capacitors C1 and C2, and resistors R1 and R2. The LED chip LED1 is connected between diode D1 and the constant current chip U1. This architecture reduces the inrush current at power-on through the dimming function, preventing damage to the LED chip due to surge current, extending the lifespan of the LED lamp, and achieving a soft, gradual brightening effect, avoiding strong light that irritates the eyes. It is suitable for home, hotel, and other scenarios. The adjustable dimming time can adapt to different application needs, such as night lights and car welcome lights. However, because this architecture has a high power factor and lacks anti-flicker circuitry, it cannot meet the new ERP standard and the IEEE 1789 flicker standard.

[0005] The three linear constant current circuit architectures mentioned above each have their own advantages and disadvantages, but they cannot meet multiple requirements at the same time. For example, they need a simple single-segment architecture and low cost, as well as a soft-light function. Or they need a wide voltage input, compliance with the new ERP standard and the IEEE 1789 flicker standard, and a soft-light function. Summary of the Invention

[0006] The primary objective of this invention is to provide a linear constant current drive circuit for LED lamps that features a slow-brightness function and effectively avoids flickering.

[0007] The second objective of this invention is to provide an LED lamp having the above-mentioned linear constant current drive circuit.

[0008] To achieve the first objective of this utility model, the linear constant current driving circuit for LED lamps provided by this utility model includes a power supply module; the power supply module supplies power to a first operational amplifier, a second operational amplifier, a differential amplifier, and a second reference voltage module; the differential amplifier supplies power to the first reference voltage module; the first reference voltage module outputs a first reference voltage to the first operational amplifier; the first operational amplifier outputs a control signal to a first field-effect transistor; the second reference voltage module outputs a second reference voltage to the second operational amplifier; the second operational amplifier outputs a control signal to the second field-effect transistor; the first terminal of the second field-effect transistor is connected to the input terminal of the differential amplifier; the first LED chip is connected between the power supply terminal and the first terminal of the second field-effect transistor; a first capacitor is connected between the second terminal of the first field-effect transistor and the power supply terminal; and the second reference voltage module is also grounded through the second capacitor.

[0009] As can be seen from the above scheme, the second reference voltage module is also grounded through the second capacitor. When power is first applied, the voltage output by the second reference voltage module will not immediately reach a high value because the second capacitor needs to charge, and the second field-effect transistor will not immediately turn on. As the charge of the second capacitor increases, the voltage output by the second reference voltage module slowly increases, and the second field-effect transistor needs a period of time to turn on, thereby causing the LED chip to emit light, thus achieving a gradual lighting effect.

[0010] In addition, since a first capacitor is connected between the second terminal of the first field-effect transistor and the power supply terminal, the first capacitor is charged after the LED lamp is powered on. When the AC voltage of the LED lamp is at its lowest point, the first capacitor can discharge to maintain the operation of the first LED chip and avoid flickering.

[0011] In a preferred embodiment, the second reference voltage module also outputs a third reference voltage to the third operational amplifier, the third operational amplifier outputs a control signal to the third field-effect transistor, and the second LED chip is connected to one end of the first LED chip and the third field-effect transistor.

[0012] Therefore, it can be seen that LED lamps are equipped with two LED chips, and the second LED chip can be controlled to gradually light up by setting a third field-effect transistor, thus realizing a two-stage architecture connection method.

[0013] A further embodiment involves connecting one input terminal of the second operational amplifier to the second terminal of the second field-effect transistor. Preferably, the second terminal of the second field-effect transistor is also grounded via a current-regulating resistor.

[0014] As can be seen, the second terminal of the second field-effect transistor is also grounded through a current-regulating resistor. A voltage is generated at the grounding terminal of the current-regulating resistor and fed back to the input terminal of the second operational amplifier. This voltage is compared with the other input terminal of the second operational amplifier, thereby controlling the conduction current of the second field-effect transistor and keeping the conduction current of the second field-effect transistor constant.

[0015] A further embodiment is that the linear constant current drive circuit is also equipped with a power factor correction circuit, one end of which is connected to the first terminal of the first field-effect transistor.

[0016] Therefore, by setting up a power factor correction circuit, the power factor of LED lamps can be corrected, thereby reducing the power consumption of LED lamps and enabling them to meet the new ERP standard.

[0017] A further solution is to ground the power factor correction circuit by adjusting the charging current resistor.

[0018] Therefore, it can be seen that the power factor correction circuit can reduce the current amplitude by adjusting the resistor through the charging current, thereby achieving power factor correction.

[0019] A further solution is to ground the first reference voltage module via a loop compensation capacitor.

[0020] To achieve the second objective mentioned above, the LED lamp provided by this utility model has a first LED chip and also includes the linear constant current drive circuit of the LED lamp. The first LED chip is connected between the power supply terminal of the LED lamp and the first terminal of the second field-effect transistor. Attached Figure Description

[0021] Figure 1 This is the electrical schematic diagram of a driving circuit for an existing LED lamp.

[0022] Figure 2 This is the electrical schematic diagram of the first embodiment of the linear constant current drive circuit for LED lamps of this utility model.

[0023] Figure 3 This is the circuit diagram of the second embodiment of the linear constant current drive circuit for LED lamps of this utility model.

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0025] The linear constant current drive circuit of this utility model for LED lamps, when applied to LED lamps, can realize the slow-brightness function of LED lamps, avoid the flickering of LED lamps, and reduce the power consumption of LED lamps, so that LED lamps can meet the new ERP standard and the flicker IEEE1789 standard.

[0026] First embodiment: See Figure 2 The LED lamp in this embodiment is provided with a first LED chip LED11 and a linear constant current driving circuit, which includes... Figure 2 The part within the dashed box.

[0027] The LED lamp receives AC voltage and is equipped with a fuse F11, a rectifier circuit DB11, and a diode D11. The AC voltage is converted into DC voltage by the fuse F11 and the rectifier circuit DB11, and then supplies power to the linear constant current drive circuit. The linear constant current drive circuit is a linear constant current drive chip with multiple pins, including HV, CH, OUT, PF, COMP, GND, CS, and CT.

[0028] The linear constant current drive circuit includes a power supply module U15, a differential amplifier U16, a first reference voltage module U11, a second reference voltage module U12, a power factor correction circuit U17, a first operational amplifier U13, a second operational amplifier U14, a first field-effect transistor Q11, and a second field-effect transistor Q12.

[0029] Power module U15 is connected to pin HV of the linear constant current driver chip to obtain DC voltage. Pin HV is the power supply terminal of the linear constant current driver chip and is used for power input. Power module U15 converts the DC voltage output by diode D11 into a preset DC voltage value and supplies power to the first operational amplifier U13, the second operational amplifier U14, the second reference voltage module U12, and the differential amplifier U16. Differential amplifier U16 supplies power to the first reference voltage module U11. The first reference voltage module U11 outputs a first reference voltage to the positive input terminal of the first operational amplifier U13. The positive input terminal of the first operational amplifier U13 is connected to the source of the first field-effect transistor Q11 through resistor R11. The output terminal of the first operational amplifier U13 is connected to the gate of the first field-effect transistor Q11 and outputs a control signal to the first field-effect transistor Q11 to control the on / off state of the first field-effect transistor Q11. The source of the first field-effect transistor Q11 is also grounded through resistor R12. The first reference voltage module U11 is also connected to pin COMP and grounded through loop compensation capacitor C13. Preferably, the capacitance of the loop compensation capacitor C13 is between 0.22μF and 1μF.

[0030] The power factor correction circuit U17 is connected to pin HV to obtain a DC voltage. One output of the power factor correction circuit U17 is connected to the negative input of the first operational amplifier U13, and the power factor correction circuit U17 is also connected to pin PF and grounded through the charging current adjustment resistor R15. When the LED lamp is working, the charging current is adjusted by the charging current adjustment resistor R15, and the amplitude of the charging current is reduced, which can correct the power factor.

[0031] In addition, a first capacitor C11 is connected between the negative terminal of diode D11 and the first field-effect transistor Q11, and one end of the first capacitor C11 is connected to the pin CH.

[0032] The second reference voltage module U12 outputs a second reference voltage to the positive input terminal of the second operational amplifier U14. The input terminal of the second operational amplifier U14 is connected to the source of the second field-effect transistor Q12, and the output terminal of the second operational amplifier U14 is connected to the gate of the second field-effect transistor Q12 and outputs a control signal to control the on / off state of the second field-effect transistor Q12. The second field-effect transistor Q12 is connected to pin OUT, which is connected to the negative terminal of the first LED chip LED11. The source of the second field-effect transistor Q12 is also connected to pin CS, which is grounded through the current-adjusting resistor R13.

[0033] One end of the second reference voltage module U12 is also connected to pin CT. Pin CT is grounded through the second capacitor C12. The second capacitor C12 is used to adjust the second reference voltage output by the second reference voltage module U12, thereby realizing the slow-on function of the LED lamp. In addition, by setting the capacitance of the second capacitor C12, the start-up slow-on time of the LED lamp can be set.

[0034] After the LED lamp is powered on, the 220V AC voltage passes through fuse F11, rectifier circuit DB11, and diode D11 to supply power to the linear constant current drive circuit. Power module U15 converts the DC voltage output by diode D11 into a preset DC voltage value. The second reference voltage module U12 outputs voltage to the positive input terminal of the second operational amplifier U14. However, initially, due to the presence of the second capacitor C12, the second reference voltage output by the second reference voltage module U12 is low, resulting in a low output voltage from the second operational amplifier U14, and the second field-effect transistor Q12 cannot conduct. As the second capacitor C12 charges, after a period of time, the voltage output by the second reference voltage module U12 becomes higher, allowing the second field-effect transistor Q12 to conduct, and the first LED chip LED11 to light up. This achieves the slow-light function of the LED lamp. Furthermore, by adjusting the capacitance value of the second capacitor C12, the slow-light time of the first LED chip LED11 can be adjusted.

[0035] As the voltage of the second capacitor C12 rises to its maximum value, the second reference voltage output by the second reference voltage module U12 to the second operational amplifier U14 also reaches the preset value and will remain unchanged. Even if the voltage of the second capacitor C12 continues to rise, the second reference voltage output by the second reference voltage module U12 will no longer rise. At this time, the gate current of the second field-effect transistor Q12 will flow through the source and ground through the current regulating resistor R13. Therefore, a feedback voltage will be formed at the CS pin, feeding back to the negative input terminal of the second operational amplifier U14. Under the voltage control of the positive and negative input terminals of the second operational amplifier U14, the current of the second field-effect transistor Q12 remains constant, thereby ensuring that the current flowing through the first LED chip LED11 is constant. By adjusting the resistance value of the current regulating resistor R13, the current flowing through the first LED chip LED11 can be adjusted, thereby adjusting the brightness of the LED lamp.

[0036] Differential amplifier U16 can detect the source voltage of the second field-effect transistor Q12, which is also the voltage at the negative terminal of the first LED chip LED11. Since the drain of the second field-effect transistor Q12 is at a high level when the LED lamp is first powered on, the detected voltage is outside the detection range of differential amplifier U16, and therefore, differential amplifier U16 will not output a signal to the first reference voltage module U11. At this time, the first reference voltage module U11 outputs the first reference voltage to the first operational amplifier U13 according to the set value. Since the first field-effect transistor Q11 is not turned on, the voltage at the negative input terminal of the first operational amplifier U13 is much lower than the voltage at the positive input terminal, causing the first operational amplifier U13 to output a high-level signal to the gate of the first field-effect transistor Q11, turning on Q11 and starting to charge the first capacitor C11. Since the source of the first field-effect transistor Q11 is connected to resistors R11 and R12, and to the negative input terminal of the first operational amplifier U13, the conduction depth of the first field-effect transistor Q11 can be controlled, which means controlling the charging current of the first capacitor C11.

[0037] When the drain voltage of the second field-effect transistor Q12 is within the detection range of the differential amplifier U16, the differential amplifier U16 starts to work and amplifies the voltage signal to adjust the first reference voltage output by the first reference voltage module U11, thereby adjusting the conduction current of the first field-effect transistor Q11 and controlling the charging time of the first capacitor C11.

[0038] Since the LED lamp receives AC voltage, during the lowest point of the AC voltage range, when the input voltage is lower than the LED lamp's turn-on voltage, the differential amplifier U16 detects that the voltage is below a set value. The differential amplifier U16 amplifies the differential signal and sends it to the first reference voltage module U11, which controls the positive input of the first operational amplifier U13, causing the output voltage of the first operational amplifier U13 to decrease. Therefore, during the lowest point of the AC voltage range, the first capacitor C11 continuously discharges into the first LED chip LED11, thus preventing flickering.

[0039] Furthermore, since the differential amplifier U16 compares the output voltage of the differential comparator power supply module U15 with the drain voltage of the second field-effect transistor Q12, when the drain voltage of the second field-effect transistor Q12 is low, the differential difference is large. This leads to an increase in the output voltage of the first reference voltage module U11 and the output voltage of the first operational amplifier U13, thereby increasing the conduction angle of the first field-effect transistor Q11. In this way, increasing the conduction angle of the first field-effect transistor Q11 can improve the power factor of the LED lamp, reduce the charging current when the input peak high voltage is high, and lower the losses of the first field-effect transistor Q11.

[0040] As can be seen, this embodiment can reduce the loss of the first field-effect transistor Q11, resulting in a lower power of the LED lamp, which meets the requirements of the new ERP and the IEEE1789 standard. It also has the function of adjusting the slow-light time by adjusting the capacitance value of C2.

[0041] Second embodiment: See Figure 3 The LED lamp in this embodiment is provided with a first LED chip LED21 and a second LED chip LED22, and also includes a linear constant current driving circuit, which includes... Figure 3 The part within the dashed box.

[0042] The LED lamp receives AC voltage and is equipped with a fuse F21, a rectifier circuit DB21, and a diode D21. The AC voltage is converted into DC voltage by the fuse F21 and the rectifier circuit DB21, and then supplies power to the linear constant current drive circuit. The linear constant current drive circuit is a linear constant current drive chip with multiple pins, including HV, CH, OUT1, OUT2, PF, COMP, GND, CS, and CT.

[0043] The linear constant current drive circuit includes a power supply module U25, a differential amplifier U26, a first reference voltage module U21, a second reference voltage module U22, a power factor correction circuit U27, a first operational amplifier U23, a second operational amplifier U24, a first field-effect transistor Q21, and a second field-effect transistor Q22. Compared to the first embodiment, this embodiment also includes a third operational amplifier U28 and a third field-effect transistor Q23. Therefore, this embodiment is a two-stage linear constant current drive circuit.

[0044] Power module U25 is connected to pin HV of the linear constant current driver chip to obtain DC voltage. Power module U25 converts the DC voltage output by diode D21 into a preset DC voltage value and supplies power to the first operational amplifier U23, the second operational amplifier U24, the second reference voltage module U22, and the differential amplifier U26. Differential amplifier U26 supplies power to the first reference voltage module U21. The first reference voltage module U21 outputs a first reference voltage to the positive input terminal of the first operational amplifier U23. The positive input terminal of the first operational amplifier U23 is connected to the source of the first field-effect transistor Q21 through resistor R21. The output terminal of the first operational amplifier U23 is connected to the gate of the first field-effect transistor Q21 and outputs a control signal to the first field-effect transistor Q21, thereby controlling the on / off state of Q21. The source of the first field-effect transistor Q21 is also grounded through resistor R22. The first reference voltage module U21 is also connected to pin COMP and grounded through loop compensation capacitor C23.

[0045] The power factor correction circuit U27 is connected to pin HV to obtain a DC voltage. One output of the power factor correction circuit U27 is connected to the negative input of the first operational amplifier U23, and the power factor correction circuit U27 is also connected to pin PF and grounded through the charging current adjustment resistor R25. When the LED lamp is working, the charging current is adjusted by the charging current adjustment resistor R25, and the amplitude of the charging current is reduced, which can correct the power factor.

[0046] In addition, a first capacitor C21 is connected between the negative terminal of diode D21 and the first field-effect transistor Q21, and one end of the first capacitor C21 is connected to the pin CH.

[0047] The second reference voltage module U22 outputs a second reference voltage to the positive input terminal of the second operational amplifier U24. The input terminal of the second operational amplifier U24 is connected to the source of the second field-effect transistor Q22, and the output terminal of the second operational amplifier U24 is connected to the gate of the second field-effect transistor Q22 and outputs a control signal to control the on / off state of the second field-effect transistor Q22. The second field-effect transistor Q22 is connected to pin OUT1, which is connected to the negative terminal of the first LED chip LED21. The source of the second field-effect transistor Q22 is also connected to pin CS, which is grounded through the current-adjusting resistor R23.

[0048] The second reference voltage module U22 also outputs a third reference voltage to the positive input terminal of the third operational amplifier U28. The input terminal of the third operational amplifier U28 is connected to the source of the third field-effect transistor Q23, and the output terminal of the third operational amplifier U28 is connected to the gate of the third field-effect transistor Q23 and outputs a control signal to control the on / off state of the third field-effect transistor Q23. The third field-effect transistor Q23 is connected to pin OUT2, and pin OUT2 is connected to the negative terminal of the second LED chip LED22. The source of the third field-effect transistor Q23 is also connected to pin CS.

[0049] One end of the second reference voltage module U22 is also connected to pin CT. Pin CT is grounded through the second capacitor C22. The second capacitor C22 is used to adjust the second reference voltage output by the second reference voltage module U22, thereby realizing the slow-on function of the LED lamp. In addition, by setting the capacitance of the second capacitor C22, the start-up slow-on time of the LED lamp can be set.

[0050] After the LED lamp is powered on, the 220V AC voltage passes through fuse F21, rectifier circuit DB21, and diode D21 to supply power to the linear constant current drive circuit. Power module U25 converts the DC voltage output by diode D21 into a preset DC voltage value. The second reference voltage module U22 outputs voltage to the positive input terminal of the second operational amplifier U24. However, at the moment of power-on, due to the presence of the second capacitor C22, the voltage value of the second reference voltage output by the second reference voltage module U22 is low, resulting in a low output voltage of the second operational amplifier U24, and the second field-effect transistor Q22 cannot conduct. As the second capacitor C22 charges, after a period of time, the voltage output by the second reference voltage module U22 becomes higher, and the second field-effect transistor Q22 can then conduct, allowing the first LED chip LED21 to emit light.

[0051] When the voltage at pin OUT1 gradually rises to a level higher than the reference voltage at the positive input terminal of the second operational amplifier U24, the second operational amplifier U24 outputs a low level, thereby turning off the second field-effect transistor Q22. The current of the first LED chip LED21 flows through the second LED chip LED22 and through the drain of the third field-effect transistor Q23. Since the reference voltage of the third operational amplifier U28 is greater than the reference voltage of the second operational amplifier U24, the voltage at the positive input terminal of the third operational amplifier U28 is higher than that at the negative input terminal. The third operational amplifier U28 outputs a high level, turning on the third field-effect transistor Q23. The current flowing through the first LED chip LED21 and the second LED chip LED22 flows through the third field-effect transistor Q23 to the ground terminal, thus forming a loop. The first LED chip LED21 and the second LED chip LED22 then emit light. As can be seen, in this embodiment, the second operational amplifier U24, the third field-effect transistor Q23, the third operational amplifier U28, and the third field-effect transistor Q23 constitute a two-stage linear constant current architecture. When the input voltage of the LED lamp is low, the second field-effect transistor Q22 and the second operational amplifier U24 operate, while the third field-effect transistor Q23 and the third operational amplifier U28 do not operate, allowing normal operation in a low-voltage environment. If the input voltage of the LED lamp increases, the second operational amplifier U24 and the second field-effect transistor Q22 do not operate, while the third operational amplifier U28 and the third field-effect transistor Q23 operate, achieving normal operation over a wider voltage range.

[0052] As the voltage of the second capacitor C22 increases, the third reference voltage output by the second reference voltage module U22 to the third operational amplifier U28 also gradually increases, eventually turning on the third field-effect transistor Q23, thus achieving the slow-brightening function. As the voltage of the second capacitor C22 rises to its maximum value, reaching the preset value, it will remain unchanged. Even if the voltage of the second capacitor C22 continues to rise, the third reference voltage output by the second reference voltage module U22 will no longer increase. At this time, the gate current of the third field-effect transistor Q23 will flow through the source and to ground via the current regulating resistor R13. Therefore, a feedback voltage will be formed at pin CS, feeding back to the negative input terminal of the second operational amplifier U24. Under the voltage control of the positive and negative input terminals of the second operational amplifier U24, the current of the third field-effect transistor Q23 remains constant, thereby ensuring that the current flowing through the first LED chip LED21 and the second LED chip LED22 remains constant. By adjusting the resistance value of the current regulating resistor R23, the current flowing through the first LED chip LED1 and the second LED chip LED22 can be adjusted, thereby adjusting the brightness of the LED lamp.

[0053] Differential amplifier U26 can detect the voltage at the drain of the second field-effect transistor Q22, which is also the voltage at the negative terminal of the first LED chip LED21. Since the drain of the second field-effect transistor Q22 is at a high level when the LED lamp is first powered on, the detected voltage is outside the detection range of differential amplifier U26, and therefore, differential amplifier U26 will not output a signal to the first reference voltage module U21. At this time, the first reference voltage module U21 outputs the first reference voltage to the first operational amplifier U23 according to the set value. Since the first field-effect transistor Q21 is not turned on, the voltage at the negative input terminal of the first operational amplifier U23 is much lower than the voltage at the positive input terminal, causing the first operational amplifier U23 to output a high-level signal to the gate of the first field-effect transistor Q21, turning on Q21 and starting to charge the first capacitor C21. Since the source of the first field-effect transistor Q21 is connected to resistors R21 and R22, and to the negative input terminal of the first operational amplifier U23, the conduction depth of the first field-effect transistor Q21 can be controlled, which means controlling the charging current of the first capacitor C21.

[0054] When the drain voltage of the second field-effect transistor Q22 is within the detection range of the differential amplifier U26, the differential amplifier U26 starts to work and amplifies the voltage signal to adjust the first reference voltage output by the first reference voltage module U21, thereby adjusting the conduction current of the first field-effect transistor Q21 and controlling the charging time of the first capacitor C21.

[0055] Since the LED lamp receives AC voltage, during the lowest point of the AC voltage range, when the input voltage is lower than the LED lamp's turn-on voltage, the differential amplifier U26 detects that the voltage is below a set value. The differential amplifier U26 amplifies the differential signal and sends it to the first reference voltage module U21, which controls the positive input of the first operational amplifier U23, causing the output voltage of the first operational amplifier U23 to decrease. Therefore, during the lowest point of the AC voltage range, the first capacitor C21 continuously discharges into the first LED chip LED21, thus preventing flickering.

[0056] Furthermore, since the differential amplifier U26 compares the output voltage of the differential comparator power supply module U25 with the drain voltage of the second field-effect transistor Q22, when the drain voltage of the second field-effect transistor Q22 is low, the differential difference is large. This leads to an increase in the output voltage of the first reference voltage module U21 and the output voltage of the first operational amplifier U23, thereby increasing the conduction angle of the first field-effect transistor Q21. In this way, increasing the conduction angle of the first field-effect transistor Q21 can improve the power factor of the LED lamp, reduce the charging current when the input peak high voltage is high, and lower the losses of the first field-effect transistor Q21.

[0057] Compared to the first embodiment, this embodiment adopts a two-stage architecture, which can accommodate a wider range of input voltages. Furthermore, this embodiment also has the advantages of low power consumption and effective prevention of flickering.

[0058] Finally, it should be emphasized that the above are only preferred embodiments of the present utility model and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A linear constant current drive circuit for an LED lamp, comprising: Power module; Its features are: The power supply module supplies power to the first operational amplifier, the second operational amplifier, the differential amplifier, and the second reference voltage module. The differential amplifier supplies power to the first reference voltage module. The first reference voltage module outputs a first reference voltage to the first operational amplifier. The first operational amplifier outputs a control signal to the first field-effect transistor. The second reference voltage module outputs a second reference voltage to the second operational amplifier. The second operational amplifier outputs a control signal to the second field-effect transistor. The first terminal of the second field-effect transistor is connected to the input terminal of the differential amplifier. The first LED chip is connected between the power supply terminal and the first terminal of the second field-effect transistor. A first capacitor is connected between the second terminal of the first field-effect transistor and the power supply terminal, and the second reference voltage module is also grounded through a second capacitor.

2. The linear constant current drive circuit for LED lamps according to claim 1, characterized in that: The second reference voltage module also outputs a third reference voltage to the third operational amplifier, which outputs a control signal to the third field-effect transistor. The second LED chip is connected to one end of the first LED chip and the third field-effect transistor.

3. The linear constant current drive circuit for LED lamps according to claim 1 or 2, characterized in that: One input terminal of the second operational amplifier is connected to the second terminal of the second field-effect transistor.

4. The linear constant current drive circuit for LED lamps according to claim 3, characterized in that: The second terminal of the second field-effect transistor is also grounded through a current-regulating resistor.

5. The linear constant current drive circuit for LED lamps according to claim 1 or 2, characterized in that: The linear constant current drive circuit is also provided with a power factor correction circuit, one end of which is connected to the first end of the first field-effect transistor.

6. The linear constant current drive circuit for LED lamps according to claim 5, characterized in that: The power factor correction circuit is also grounded via a charging current adjustment resistor.

7. The linear constant current drive circuit for LED lamps according to claim 5, characterized in that: The first reference voltage module is also grounded through a loop compensation capacitor.

8. An LED lighting fixture, comprising a first LED chip, characterized in that, It also includes a linear constant current drive circuit for an LED lamp as described in any one of claims 1 to 7, wherein the first LED chip is connected between the power supply terminal of the LED lamp and the first terminal of the second field-effect transistor.

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