LED lamp, linear constant-current driving circuit thereof and driving method of LED lamp
By using a combination of power modules, operational amplifiers, and field-effect transistors in LED lighting fixtures, and utilizing capacitor charging to control the conduction time of the field-effect transistors, a slow-brightness function and power factor correction are achieved. This solves the problem that existing technologies cannot simultaneously meet the requirements of low cost, wide voltage input, and standard requirements, and achieves the effects of slow-brightness, flicker prevention, and low power consumption.
Patent Information
- Application Number
- CN202511019293.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-11-18
AI Technical Summary
Existing linear constant current drive circuits cannot simultaneously meet the requirements of low cost, wide voltage input, soft-light function, and compliance with the new ERP standard and the IEEE 1789 flicker standard.
The system employs a combination of a power supply module, operational amplifier, field-effect transistor (FET), and reference voltage module. By controlling the conduction time of the FET through capacitor charging, a slow-brightness function is achieved. A power factor correction circuit is also included to reduce power consumption and prevent flickering.
It achieves a gradual lighting effect for LED lights, avoids flickering, reduces power consumption, and complies with the new ERP standard and IEEE1789 standard.
Smart Images
Figure CN120980740A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of LED lamp driving, in particular to an LED lamp, a linear constant current driving circuit thereof, and a driving method of the LED lamp. BACKGROUND
[0002] The LED lamp has advantages of energy saving, environmental protection, long service life, and is widely used in home lighting, building decoration and other occasions. The LED lamp has a plurality of LED chips and a driving circuit, and a driving current supplies power to the LED chips. Some existing LED lamps use a linear constant current driving circuit to supply power to the LED chips. The existing linear constant current driving circuit mainly includes a single-stage architecture, a two-stage architecture, and a linear constant current architecture with adjustable dimming time.
[0003] The linear constant current driving circuit of the single-stage architecture has simple structure, fewer peripheral devices, and low cost, but the input voltage range is narrow, and it cannot be applied in an environment with large input voltage fluctuation. The two-stage architecture has more peripheral devices than the single-stage architecture, and the input voltage range is wider due to the two-stage architecture, so it can be applied in an environment with large input voltage fluctuation. The above two architectures meet the new ERP standard and the frequency flash IEEE1789 standard.
[0004] Referring to Figure 1 , the linear constant current architecture with adjustable dimming time has a fuse F1, a rectifier circuit BD1, a diode D1, and a constant current chip U1. The constant current chip U1 is connected with capacitors C1 and C2, and resistors R1 and R2. The LED chip LED1 is connected between the diode D1 and the constant current chip U1. This architecture reduces the inrush current at power-on through the dimming function, avoids damage to the LED chip due to impact current, prolongs the service life of the LED lamp, realizes soft and gradual lightening effect, avoids strong light stimulating the eyes, is suitable for home, hotel and other scenes, and the dimming time is adjustable, which can adapt to different application requirements, such as night light, car welcome light, etc. However, this architecture has high power factor and does not have a circuit to prevent frequency flash, so it cannot meet the new ERP standard and the frequency flash IEEE1789 standard.
[0005] The above three linear constant current circuit architectures have their own advantages and disadvantages, but cannot meet multiple requirements at the same time, such as simple single-stage architecture and low cost, wide voltage input, meeting the new ERP standard and the frequency flash IEEE1789 standard, and having dimming function. SUMMARY
[0006] The first object of the present application is to provide a linear constant current driving circuit of an LED lamp with dimming function and capable of effectively avoiding frequency flash.
[0007] The second object of the present application is to provide an LED lamp with the linear constant current driving circuit.
[0008] The third object of the present application is to provide a driving method of the LED lamp.
[0009] To achieve the first object of the present application, the linear constant current driving circuit of the LED lamp provided by the present application comprises 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 a 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 a second field effect transistor; a first end of the second field effect transistor is connected to an input end of the differential amplifier; a first LED chip is connected between a power supply end and the first end of the second field effect transistor; a first capacitor is connected between a second end of the first field effect transistor and the power supply end; and the second reference voltage module is further grounded through a second capacitor.
[0010] As can be seen from the above scheme, the second reference voltage module is further grounded through the second capacitor; when the power is just turned on, the voltage output by the second reference voltage module will not immediately reach a high voltage value because the second capacitor needs to be charged, and the second field effect transistor will not be immediately turned on. As the amount of electricity of the second capacitor increases, the voltage output by the second reference voltage module slowly increases, and the second field effect transistor needs to be turned on for a period of time, so that the LED chip emits light, thereby achieving the effect of slow lightening.
[0011] In addition, since the first capacitor is connected between the second end of the first field effect transistor and the power supply end, the first capacitor is charged after the power of the LED lamp is turned on, and the first capacitor can be discharged to maintain the operation of the first LED chip during the valley period of the alternating voltage of the LED lamp, thereby avoiding the phenomenon of frequent flashing.
[0012] A preferred scheme is that the second reference voltage module further outputs a third reference voltage to a third operational amplifier; the third operational amplifier outputs a control signal to a third field effect transistor; and a second LED chip is connected between the first LED chip and one end of the third field effect transistor.
[0013] As can be seen from the above scheme, the LED lamp is provided with two LED chips, and the third field effect transistor is arranged to control the slow lightening of the second LED chip, thereby realizing the connection mode of two-stage architecture.
[0014] A further scheme is that one input end of the second operational amplifier is connected to the second end of the second field effect transistor. Preferably, the second end of the second field effect transistor is further grounded through a current adjusting resistor.
[0015] Therefore, the second end of the second field effect tube is grounded through the current adjusting resistor, and a voltage formed at the grounding end of the current adjusting resistor is fed back to the input end of the second operational amplifier, and the voltage is compared with another input end of the second operational amplifier, so as to control the conduction current of the second field effect tube, and the conduction current of the second field effect tube is kept constant.
[0016] Further, the linear constant current driving circuit is further provided with a power factor correction circuit, one end of the power factor correction circuit being connected to the first end of the first field effect tube.
[0017] Therefore, by arranging the power factor correction circuit, the power factor of the LED lamp can be corrected, so as to reduce the power consumption of the LED lamp, and the LED lamp can meet the new ERP standard.
[0018] Further, the power factor correction circuit is grounded through the charging current adjusting resistor.
[0019] Therefore, the power factor correction circuit can reduce the amplitude of the current through the charging current adjusting resistor, so as to correct the power factor.
[0020] Further, the first reference voltage module is grounded through the loop compensation capacitor.
[0021] In order to achieve the second purpose, the LED lamp provided by the present application has a first LED chip, and further comprises the linear constant current driving circuit of the LED lamp, the first LED chip being connected between the power supply end of the LED lamp and the first end of the second field effect tube.
[0022] In order to achieve the third purpose, the present application provides the driving method of the LED lamp, which comprises the following steps: after the LED lamp is powered on, the second reference voltage circuit outputs the second reference voltage to the second field effect tube, and the second capacitor is charged, and after the voltage of the second capacitor is raised, the second field effect tube is turned on, so that the first LED chip emits light.
[0023] From the above-mentioned scheme, since the second field effect tube is not turned on immediately after the LED lamp is powered on, but is turned on after the second capacitor is charged for a period of time, the second LED chip slowly emits light after the LED lamp is powered on, and the slow-light function is realized.
[0024] A preferred scheme is that the voltage output by the power supply end is a direct current voltage obtained by rectifying an alternating voltage; and the first capacitor discharges to the first LED chip during the valley of the alternating voltage.
[0025] From the above scheme, it can be seen that when the input AC voltage of the LED lamp is low, the first capacitor can discharge to the first LED chip, thereby avoiding the flickering phenomenon of the LED lamp. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 is an electric schematic diagram of a driving circuit of an existing LED lamp.
[0027] Figure 2 is an electric schematic diagram of a linear constant current driving circuit of the LED lamp of the present application.
[0028] Figure 3 is an electric schematic diagram of a linear constant current driving circuit of the LED lamp of the present application.
[0029] The present application will be further described below in combination with the drawings and embodiments. DETAILED DESCRIPTION
[0030] The linear constant current driving circuit of the LED lamp of the present application is applied to the LED lamp, which can realize the slow-light function of the LED lamp, avoid the flickering of the LED lamp, and reduce the power consumption of the LED lamp, so that the LED lamp can meet the new ERP standard and the flickering IEEE1789 standard.
[0031] First embodiment: Referring to Figure 2 , the LED lamp of the present embodiment is provided with a first LED chip LED11 and a linear constant current driving circuit. Figure 2 The linear constant current driving circuit includes
[0032] The LED lamp receives an AC voltage and is provided with a fuse F11, a rectifier circuit DB11 and a diode D11. The AC voltage is converted into a DC voltage by the fuse F11 and the rectifier circuit DB11, and is used to supply power to the linear constant current driving circuit. The linear constant current driving circuit is a linear constant current driving chip, which has a plurality of pins, including pins HV, CH, OUT, PF, COMP, GND, CS and CT.
[0033] The linear constant current driving circuit is provided with a power 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.
[0034] The power module U15 is connected to the pin HV of the linear constant current driving chip and obtains the direct current voltage, wherein the pin HV is the power supply end of the linear constant current driving chip and is used for inputting the power supply. The power module U15 converts the direct current voltage output by the diode D11 into a direct current voltage with a preset 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. The differential amplifier U16 supplies power to the first reference voltage module U11. The first reference voltage module U11 outputs the first reference voltage to the positive input end of the first operational amplifier U13. The positive input end of the first operational amplifier U13 is connected to the source of the first field effect transistor Q11 through the resistor R11. The output end of the first operational amplifier U13 is connected to the gate of the first field effect transistor Q11 and outputs the control signal to the first field effect transistor Q11, so as to control the on-off of the first field effect transistor Q11. The source of the first field effect transistor Q11 is also grounded through the resistor R12. The first reference voltage module U11 is also connected to the pin COMP and grounded through the loop compensation capacitor C13. Preferably, the capacitance of the loop compensation capacitor C13 is between 0.22 μF and 1 μF.
[0035] The power factor correction circuit U17 is connected to the pin HV and obtains the direct current voltage. One output end of the power factor correction circuit U17 is connected to the negative input end of the first operational amplifier U13. The power factor correction circuit U17 is also connected to the pin PF and grounded through the charging current adjusting resistor R15. When the LED lamp is working, the charging current is adjusted through the charging current adjusting resistor R15, and the amplitude of the charging current is reduced, so that the power factor can be corrected.
[0036] In addition, the first capacitor C11 is connected between the negative end of the diode D11 and the first field effect transistor Q11. One end of the first capacitor C11 is connected to the pin CH.
[0037] The second reference voltage module U12 outputs the second reference voltage to the positive input end of the second operational amplifier U14. The input end of the second operational amplifier U14 is connected to the source of the second field effect transistor Q12. The output end of the second operational amplifier U14 is connected to the gate of the second field effect transistor Q12 and outputs the control signal, so as to control the on-off of the second field effect transistor Q12. The second field effect transistor Q12 is connected to the pin OUT, and the pin OUT is connected to the negative end of the first LED chip LED11. The source of the second field effect transistor Q12 is also connected to the pin CS, and the pin CS is grounded through the current adjusting resistor R13.
[0038] One end of the second reference voltage module U12 is also connected to pin CT, which is grounded through the second capacitor C12, which is used to adjust the second reference voltage output by the second reference voltage module U12, thereby realizing the slow-light function of the LED lamp. In addition, by setting the capacitance of the second capacitor C12, the boot slow-light time of the LED lamp can be set.
[0039] After the LED lamp is powered on, the 220V alternating voltage is supplied to the linear constant current driving circuit after passing through the fuse F11, the rectifier circuit DB11 and the diode D11, and the power module U15 converts the direct current output by the diode D11 into a direct current with a preset voltage value. The second reference voltage module U12 outputs a voltage to the positive input terminal of the second operational amplifier U14, but at the moment of power-on, due to the presence of the second capacitor C12, the voltage value of the second reference voltage output by the second reference voltage module U12 is low, resulting in a low voltage output by the second operational amplifier U14, and the second field effect transistor Q12 cannot be turned on. With the charging of the second capacitor C12, after a period of time, the voltage output by the second reference voltage module U12 is high, and the second field effect transistor Q12 can be turned on, and the first LED chip LED11 will emit light. In this way, the slow-light function of the LED lamp is realized. And by adjusting the capacitance of the second capacitor C12, the slow-light time of the first LED chip LED11 can be adjusted.
[0040] As the voltage value of the second capacitor C12 rises to the highest value, the second reference voltage output by the second reference voltage module U12 to the second operational amplifier U14 also reaches the preset set 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 be grounded through the current regulating resistor R13, so that a feedback voltage will be formed at pin CS, which is fed back to the negative input terminal of the second operational amplifier U14. Under the voltage control of the positive input terminal and the negative input terminal 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 luminous brightness of the LED lamp.
[0041] The differential amplifier U16 can detect the voltage of the source of the second field effect transistor Q12, that is, the voltage of the negative electrode of the first LED chip LED11. When the LED lamp is powered on, the drain of the second field effect transistor Q12 is at a high level, and the detection voltage is not within the detection range of the differential amplifier U16, so the 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 a first reference voltage to the first operational amplifier U13 according to the set value. At this time, since the first field effect transistor Q11 is not turned on, the voltage at the negative input end of the first operational amplifier U13 is much lower than the voltage at the positive input end, so that the first operational amplifier U13 outputs a high-level signal to the gate of the first field effect transistor Q11, and the first field effect transistor Q11 is turned on, and the first capacitor C11 starts to charge. Since the source of the first field effect transistor Q11 is connected to the resistors R11 and R12 and to the negative input end of the first operational amplifier U13, the conduction depth of the first field effect transistor Q11 can be controlled, that is, the charging current of the first capacitor C11 can be controlled.
[0042] 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 further controlling the charging time of the first capacitor C11.
[0043] Since the LED lamp receives an alternating voltage, during the valley of the alternating voltage, when the input voltage is lower than the turn-on voltage of the LED lamp, the differential amplifier U16 detects that the voltage is lower than the set value, and the differential amplifier U16 amplifies the differential signal and gives it to the first reference voltage module U11 to control the positive input end of the first operational amplifier U13, so that the first operational amplifier U13 outputs a lower voltage. Therefore, during the valley of the alternating voltage, the first capacitor C11 continuously discharges to the first LED chip LED11, thereby avoiding the occurrence of flicker.
[0044] In addition, since the differential amplifier U16 differentially compares the voltage output by the power supply module U15 and 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 value is large, the voltage output by the first reference voltage module U11 is increased, and the voltage output by the first operational amplifier U13 is also increased, thereby increasing the conduction angle of the first field effect transistor Q11. In this way, the power factor of the LED lamp can be improved by increasing the conduction angle of the first field effect transistor Q11, the charging current is reduced when the input peak voltage is high, and the loss of the first field effect transistor Q11 is reduced.
[0045] It can be seen that the embodiment can reduce the loss of the first field effect tube Q11, so that the power of the LED lamp is smaller, meets the requirements of the new ERP and the IEEE1789 standard, and can also adjust the function of the slow light time according to the adjustment of the C2 capacitance value.
[0046] Second embodiment: Referring to Figure 3 The LED lamp of the embodiment is provided with a first LED chip LED21 and a second LED chip LED22, and is also provided with a linear constant current driving circuit, which comprises Figure 3 The part in the dashed box.
[0047] The LED lamp receives an alternating voltage and is provided with a fuse F21, a rectifier circuit DB21 and a diode D21. The alternating voltage is converted into a direct current voltage by the fuse F21 and the rectifier circuit DB21, and is used to power the linear constant current driving circuit. The linear constant current driving circuit is a linear constant current driving chip, which has a plurality of pins, including pins HV, CH, OUT1, OUT2, PF, COMP, GND, CS and CT.
[0048] The linear constant current driving circuit is provided with 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 tube Q21 and a second field effect tube Q22. Compared with the first embodiment, the embodiment is also provided with a third operational amplifier U28 and a third field effect tube Q23, so the embodiment is a two-section linear constant current driving circuit.
[0049] The power supply module U25 is connected to the pin HV of the linear constant current driving chip and obtains a direct current voltage. The power supply module U25 converts the direct current voltage output by the diode D21 into a direct current voltage with a preset 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. The 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 tube Q21 through a resistor R21. The output terminal of the first operational amplifier U23 is connected to the gate of the first field effect tube Q21 and outputs a control signal to the first field effect tube Q21, so as to control the on-off of the first field effect tube Q21. The source of the first field effect tube Q21 is also connected to the ground through a resistor R22. The first reference voltage module U21 is also connected to the pin COMP and connected to the ground through a loop compensation capacitor C23.
[0050] The power factor correction circuit U27 is connected to the pin HV and obtains a direct current voltage, one output end of the power factor correction circuit U27 is connected to the negative input end of the first operational amplifier U23, and the power factor correction circuit U27 is also connected to the pin PF and grounded through the charging current adjusting resistor R25. When the LED lamp is working, the charging current is adjusted through the charging current adjusting resistor R25, and the amplitude of the charging current is reduced, so that the power factor can be corrected.
[0051] In addition, the negative end of the diode D21 is connected to the first field effect transistor Q21, and one end of the first capacitor C21 is connected to the pin CH.
[0052] The second reference voltage module U22 outputs a second reference voltage to the positive input end of the second operational amplifier U24, the input end of the second operational amplifier U24 is connected to the source of the second field effect transistor Q22, the output end of the second operational amplifier U24 is connected to the gate of the second field effect transistor Q22 and outputs a control signal, so as to control the on-off of the second field effect transistor Q22. The second field effect transistor Q22 is connected to the pin OUT1, and the pin OUT1 is connected to the negative end of the first LED chip LED21. The source of the second field effect transistor Q22 is also connected to the pin CS, and the pin CS is grounded through the current adjusting resistor R23.
[0053] The second reference voltage module U22 also outputs a third reference voltage to the positive input end of the third operational amplifier U28, the input end of the third operational amplifier U28 is connected to the source of the third field effect transistor Q23, and the output end of the third operational amplifier U28 is connected to the gate of the third field effect transistor Q23 and outputs a control signal, so as to control the on-off of the third field effect transistor Q23. The third field effect transistor Q23 is connected to the pin OUT2, and the pin OUT2 is connected to the negative end of the second LED chip LED22. The source of the third field effect transistor Q23 is also connected to the pin CS.
[0054] One end of the second reference voltage module U22 is also connected to the pin CT, and the pin CT is grounded through the second capacitor C22, and the second capacitor C22 is used to adjust the second reference voltage output by the second reference voltage module U22, so as to realize the slow light function of the LED lamp. In addition, by setting the capacitance of the second capacitor C22, the boot slow light time of the LED lamp can be set.
[0055] After the LED lamp is powered on, the 220V alternating voltage is supplied to the linear constant current driving circuit after passing through the fuse F21, the rectifier circuit DB21 and the diode D21, and the power module U25 converts the direct current voltage output by the diode D21 into a direct current voltage with a preset voltage value. The second reference voltage module U22 outputs a voltage to the positive input terminal of the second operational amplifier U24, but at the moment of power-on, the voltage value of the second reference voltage output by the second reference voltage module U22 is low due to the presence of the second capacitor C22, resulting in a low voltage output by the second operational amplifier U24, and the second field effect transistor Q22 cannot be turned on. With the charging of the second capacitor C22, after a period of time, the voltage output by the second reference voltage module U22 is high, and the second field effect transistor Q22 can be turned on, and the first LED chip LED21 can emit light.
[0056] When the voltage of the pin OUT1 gradually rises to be higher than the reference voltage of the positive input terminal of the second operational amplifier U24, the second operational amplifier U24 outputs a low level, so that the second field effect transistor Q22 is cut off, and the current of the first LED chip LED21 flows through the drain of the third field effect transistor Q23. Since the reference voltage value of the third operational amplifier U28 is higher than that of the second operational amplifier U24, the voltage of the positive input terminal of the third operational amplifier U28 is higher than that of the negative input terminal, the third operational amplifier U28 outputs a high level, the third field effect transistor Q23 is turned on, and the current flowing through the first LED chip LED21 and the second LED chip LED22 flows to the ground through the third field effect transistor Q23, thereby forming a loop, and the first LED chip LED21 and the second LED chip LED22 emit light. It can be seen that the second operational amplifier U24, the third field effect transistor Q23, the third operational amplifier U28 and the third field effect transistor Q23 of the embodiment constitute a two-section 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 work, and the third field effect transistor Q23 and the third operational amplifier U28 do not work, and the LED lamp can work normally in a low voltage environment. If the input voltage of the LED lamp is increased, the second operational amplifier U24 and the second field effect transistor Q22 do not work, and the third operational amplifier U28 and the third field effect transistor Q23 work, so that the LED lamp can work normally in a wider voltage range.
[0057] When the voltage of the second capacitor C22 increases, the third reference voltage outputted by the second reference voltage module U22 to the third operational amplifier U28 also gradually increases, and eventually makes the third field effect transistor Q23 conduct, thereby realizing the function of slow lightening. When the voltage value of the second capacitor C22 increases to the highest value, reaches the pre-set value, and remains unchanged, even if the voltage of the second capacitor C22 continues to increase, the third reference voltage outputted 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 be grounded through the current regulating resistor R13, so that a feedback voltage is formed at the pin CS, which is fed back to the negative input end of the second operational amplifier U24, and under the voltage control of the positive input end and the negative input end 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 is 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 luminous brightness of the LED lamp.
[0058] The differential amplifier U26 can detect the voltage of the drain of the second field effect transistor Q22, that is, the voltage of the negative electrode 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 powered on, the detection voltage is not within the detection range of the differential amplifier U26, and the 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 a first reference voltage to the first operational amplifier U23 according to the set value. At this time, since the first field effect transistor Q21 is not conductive, the voltage at the negative input end of the first operational amplifier U23 is much lower than the voltage at the positive input end, thereby making the first operational amplifier U23 output a high-level signal to the gate of the first field effect transistor Q21, and making the first field effect transistor Q21 conduct, and the first capacitor C21 begins to charge. Since the source of the first field effect transistor Q21 is connected to the resistors R21 and R22, and is connected to the negative input end of the first operational amplifier U23, the conduction depth of the first field effect transistor Q21 can be controlled, that is, the charging current of the first capacitor C21 can be controlled.
[0059] When the voltage of the drain of the second field effect transistor Q22 is within the detection range of the differential amplifier U26, the differential amplifier U26 begins to work, and amplifies the voltage signal to adjust the first reference voltage outputted by the first reference voltage module U21, thereby adjusting the conduction current of the first field effect transistor Q21, and further controlling the charging time of the first capacitor C21.
[0060] Since the LED lamp receives AC voltage, when the input voltage is lower than the turn-on voltage of the LED lamp during the valley of the AC voltage, the differential amplifier U26 detects that the voltage is lower than the set value, the differential amplifier U26 amplifies the differential signal and gives it to the first reference voltage module U21, controls the positive input end of the first operational amplifier U23, and makes the first operational amplifier U23 output a lower voltage. Therefore, during the valley of the AC voltage, the first capacitor C21 continuously discharges to the first LED chip LED21, thereby avoiding the occurrence of the flicker phenomenon.
[0061] In addition, since the differential amplifier U26 differentially compares the voltage output by the power supply module U25 and the drain voltage of the second field effect tube Q22, when the drain voltage of the second field effect tube Q22 is lower, the differential value is larger, the voltage output by the first reference voltage module U21 is increased, and the voltage output by the first operational amplifier U23 is also increased, thereby increasing the conduction angle of the first field effect tube Q21. In this way, the power factor of the LED lamp can be improved by increasing the conduction angle of the first field effect tube Q21, the charging current is reduced when the input peak voltage is high, and the loss of the first field effect tube Q21 is reduced.
[0062] Compared with the first embodiment, the embodiment adopts a two-stage architecture and can adapt to a wider input voltage. In addition, the embodiment also has the advantages of low power consumption and effective prevention of the flicker phenomenon.
[0063] Finally, it needs to be emphasized that the above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
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.
9. The driving method for an LED lamp as described in claim 8, characterized in that, include: After the LED lamp is powered on, the second reference voltage circuit outputs the second reference voltage to the second field-effect transistor, and the second capacitor is charged. After the voltage of the second capacitor rises, the second field-effect transistor is turned on, causing the first LED chip to emit light.
10. The driving method for an LED lamp according to claim 9, characterized in that: The voltage output from the power supply terminal is the DC voltage obtained after rectifying the AC voltage; During the trough of the AC voltage, the first capacitor discharges to the first LED chip.