A dual-tube flyback LED driving power supply circuit

Abstract

The utility model discloses provide a kind of double-tube flyback LED drive power supply circuit, including auxiliary power supply circuit module, PWM control circuit module, synchronous drive circuit module and double-tube flyback power circuit module, PWM control circuit module, including control chip U2, for sending control signal, double-tube flyback power circuit module, including switching unit, clamping unit, transformer T1, rectifier tube D14 and energy storage capacitor C25, switching unit one end is connected with synchronous drive circuit module, the other end is connected with clamping unit, clamping unit is connected with the primary side of transformer T1, the secondary side of transformer T1 is connected with rectifier tube D14 and energy storage capacitor C25 respectively, the secondary side of transformer T1 is connected with load, and energy storage capacitor C25 is parallelly connected with load;Synchronous drive circuit module, including first synchronous drive unit and second synchronous drive unit, first synchronous drive unit and second synchronous drive unit one end are connected with control chip U2, the other end is connected with switching unit.

Description

Technical Field

[0001] This disclosure relates to the field of LED driver power supply circuit technology, and in particular to a dual-tube flyback LED driver power supply circuit. Background Technology

[0002] LED power supply design (often called LED driver or LED driver power supply) is a conversion device that transforms input power (such as AC mains or DC power) into a constant current suitable for driving LED chips. The outstanding advantages of LED lighting are energy saving and controllability, making it one of the most widely used lighting products. As the core of control, the core design goal of an LED power supply is to provide a stable, efficient, and controllable current (often more critical) to the LED load, enabling it to operate reliably and intelligently at the required brightness with minimal energy consumption and cost.

[0003] Currently, product designs in the industry are mainly based on two topologies: flyback and half-bridge resonant. Flyback converters use pulse width modulation (PWM), which offers advantages such as simple structure, low cost, and a wide output voltage range, enabling full-power dimming. However, their main drawbacks are high switching losses, leading to low efficiency and severe EMI interference. They are commonly used in designs below 150W and are unsuitable for high-efficiency lighting fixtures. Resonant half-bridge converters use pulse frequency modulation (PFM), allowing the power switches to achieve zero-voltage turn-off (ZVS). Their advantages include high efficiency and low EMI interference. However, their disadvantages include complex switching control and high cost. Furthermore, the half-bridge resonant design must balance efficiency and output range, making full-power dimming impossible. Generally, when power drops below 10%, frequency hopping control is necessary, which can easily lead to flickering issues. Utility Model Content

[0004] This disclosure provides a dual-tube flyback LED driver power supply circuit to solve the above-mentioned technical problems.

[0005] This disclosure provides a dual-transistor flyback LED driver power supply circuit, including an auxiliary power supply circuit module, a PWM control circuit module, a synchronous drive circuit module, and a dual-transistor flyback power circuit module, wherein... The auxiliary power supply circuit module is used for auxiliary current input to provide power; The PWM control circuit module includes a control chip U2, which is connected to the auxiliary power supply circuit module, the synchronous drive circuit module, and the dual-transistor flyback power circuit module respectively. The dual-tube flyback power circuit module includes a switching unit, a clamping unit, a transformer T1, a rectifier diode D14, and an energy storage capacitor C25. One end of the switching unit is connected to the synchronous drive circuit module, and the other end is connected to the clamping unit. The clamping unit is connected to the primary side of the transformer T1. The secondary side of the transformer T1 is connected to the rectifier diode D14 and the energy storage capacitor C25, respectively. A load is connected to the secondary side of the transformer T1, and the energy storage capacitor C25 is connected in parallel with the load. The synchronous drive circuit module includes a first synchronous drive unit and a second synchronous drive unit. One end of the first synchronous drive unit and the second synchronous drive unit are connected to the control chip U2, and the other end is connected to the switch unit.

[0006] Preferably, the switching unit includes switching transistors S1 and S2. The gate (G) of switching transistor S1 is connected to the second synchronous drive unit, the drain (D) of switching transistor S1 is connected to the first synchronous drive unit, and the source (S) of switching transistor S1 is connected to the primary side of transformer T1. The gate (G) of switch S2 is connected to both the first synchronous drive unit and the control chip U2. The drain (D) of switch S2 is connected to the primary side of transformer T1. The source (S) of switch S2 and the CS pin of control chip U2 are connected together to a current sensing resistor R43, one end of which is grounded.

[0007] Preferably, the clamping unit includes freewheeling diodes D1 and D2. The negative terminal of the freewheeling diode D1 is connected to the primary side of the transformer T1 and the source terminal of the switching transistor S1, respectively. The positive terminal of the freewheeling diode D1 is connected to a capacitor C3, which is connected to the negative terminal of the freewheeling diode D2. The positive terminal of the freewheeling diode D2 is connected to the primary side of the transformer T1 and the drain terminal of the switching transistor S2, respectively.

[0008] Preferably, the first synchronous drive unit includes transistors Q12 and Q13. The emitters (E) of transistors Q12 and Q13 are connected to each other. Resistors R22 and R23 are connected in series with the emitters of transistors Q12 and Q13. Resistor R23 is connected to the switch S2. Diode D4 is connected in parallel with resistor R23. The collector (C) of transistor Q12 is connected to the tenth pin of the control chip U2. The emitters (E) and collectors (C) of transistors Q12 and Q13 are connected to the second synchronous drive unit. The bases (B) of transistors Q12 and Q13 are connected in series with resistor R28.

[0009] Preferably, the second synchronous drive unit includes a transformer T2, transistors Q14 and Q15. The primary side of the transformer T2 is connected to the emitter (E) and collector (C) terminals of transistors Q12 and Q13. One end of the secondary side of the transformer T2 is connected to diodes D15 and D20 and resistor R49. Resistor R49 is connected to the base (B) terminal of transistors Q14 and Q15. The other end of the secondary side of the transformer T2 is connected to capacitors C35 and C38, resistor R42, and switching transistor S1. The source (S) terminal of the resistor is connected to one end of the resistor R42, which is connected to the resistor R36. The resistors R36 and R42 are connected to the gate (G) terminal of the switch S1, respectively. The resistor R36 is connected to the emitter (E) terminal of transistors Q14 and Q15, respectively. The capacitor C35 is connected to the diode D15, and the capacitor C38 is connected to the diode D20. The collector (C) terminal of the transistor Q14 is connected between the diode D20 and the capacitor C38, and the collector (C) terminal of the transistor Q15 is connected between the diode D15 and the capacitor C35.

[0010] Preferably, it further includes a sampling and filtering circuit module, which includes a resistor Rf1 and a capacitor Cf1. The resistor Rf1 is disposed between the sixth pin of the control chip U2 and the switching transistor S2, and the capacitor Cf1 is disposed between the resistor Rf1 and the sixth pin of the control chip U2.

[0011] Preferably, the auxiliary power supply circuit module includes a first power supply circuit unit, which includes resistors R14, 15, and 16 and capacitors C18 and 36. The tenth pin of the control chip U2 is connected in series with the resistors R14, 15, and 16. The end of the resistor R16 away from the control chip U2 is connected to the drain of the switching transistor S1. One end of the capacitors C18 and C36 is connected to the tenth pin of the control chip U2, and the other end is grounded.

[0012] Preferably, the auxiliary power supply circuit module further includes a second power supply circuit unit, which includes resistors R34, R45, R47, capacitor C6, transistor Q3, diode D7, and diode ZD1. One end of resistor R45 is connected to the sixth pin of the control chip U2 and the first pin of transformer T1, respectively. One end of diode D6 is connected to resistor R45, and the other end is connected to the collector (C) of transistor Q3. The emitter (E) of transistor Q3 is connected to diode D7 and resistor R47, respectively. Resistor R47 is connected to the second pin of transformer T1. The base (B) of transistor Q3 is connected to resistor R34 and diode ZD1, respectively. Diode ZD1 is connected to the second pin of transformer T1.

[0013] Preferably, the device further includes a current compensation circuit module, which includes resistors R58, R59, R19, R52, R46, R60, R63, diode D19, transistor Q8, and diode ZD2. One end of resistor R59 is connected to the first pin of transformer T1, and the other end of resistor R59 is connected to resistor R58 and diode D18. Diode D18 is connected to the base (B) of transistor Q8 and resistor R46. Resistor R46 is connected to resistor R58. The collector (C) of transistor Q8 is connected to resistors R60 and R63. The emitter (E) of transistor Q8 is connected to resistor R52. Resistor R52 is connected to resistor R19 and diode ZD2. Resistor R19 is connected to the emitter (E) of transistor Q3. Diode ZD2, resistors R60, R46, and R58 are grounded.

[0014] Preferably, it also includes an FPC circuit module, which is connected to the first power supply circuit unit.

[0015] The main beneficial effects of this disclosure are: 1. A constant current LED power supply is designed using a dual-tube flyback circuit, and clamping diodes are used to control the voltage stress of the primary-side switching transistor to be no higher than the input voltage. At the same time, the energy of the leakage inductance of the main transformer is fed back to the input energy storage unit, which is more efficient than the single-tube flyback converter in the existing technology. 2. Existing half-bridge resonant converters use PFM control, which limits the output voltage adjustment range and generally achieves a dimming depth of 10%. Below 10%, frequency hopping is required, which introduces flicker issues. In contrast, the dual-transistor flyback converter used in this patent employs PWM control, with no output voltage range limitation, allowing direct dimming from 0-100%, making it more suitable for intelligent LED dimming power supplies.

[0016] It should be understood that both the foregoing general description and the following detailed description are for illustrative purposes and do not necessarily limit the scope of this disclosure. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the subject matter of this disclosure. Furthermore, the specification and drawings serve to explain the principles of this disclosure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1This is a circuit diagram of a dual-tube flyback LED driver power supply according to an embodiment of the present disclosure; Figure 2 A circuit diagram of a dual-tube flyback LED driver power supply according to another disclosed embodiment; Figure 3 This is a schematic diagram illustrating the working principle of an embodiment of this disclosure; Icons: 100 - Auxiliary power supply circuit module; 200 - PWM control circuit module; 300 - Synchronous drive circuit module; 400 - Dual-transistor flyback power circuit module; 410 - Switching unit; 420 - Clamping unit; 500 - Sampling and filtering circuit module. Detailed Implementation

[0019] The technical solutions of this disclosure will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments.

[0020] Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this disclosure.

[0021] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0023] Example like Figure 1-3 As shown, this embodiment provides a dual-tube flyback LED driver power supply circuit, including an auxiliary power supply circuit module 100, a PWM control circuit module 200, a synchronous drive circuit module 300, and a dual-tube flyback power circuit module 400.

[0024] The dual-tube flyback power circuit module 400 includes a switching unit 410, a clamping unit 420, a transformer T1, a rectifier diode D14, and an energy storage capacitor C25. One end of the switching unit 410 is connected to the synchronous drive circuit module 300, and the other end is connected to the clamping unit 420. The clamping unit 420 is connected to the primary side of the transformer T1. The secondary side of the transformer T1 is connected to the rectifier diode D14 and the energy storage capacitor C25, respectively. A load is connected to the secondary side of the transformer T1, and the energy storage capacitor C25 is connected in parallel with the load. Specifically, the switching unit 410 includes switching transistors S1 and S2. The gate (G) of the switching transistor S1 is connected to the second synchronous drive unit, the drain (D) of the switching transistor S1 is connected to the first synchronous drive unit, and the source (S) of the switching transistor S1 is connected to the primary side of the transformer T1. The gate (G) of the switch S2 is connected to both the first synchronous drive unit and the control chip U2. The drain (D) of the switch S2 is connected to the primary side of the transformer T1. The source (S) of the switch S2 and the CS pin of the control chip U2 are connected together to a current sensing resistor R43, one end of which is grounded.

[0025] The clamping unit 420 includes freewheeling diodes D1 and D2. The negative terminal of the freewheeling diode D1 is connected to the primary side of the transformer T1 and the source terminal of the switching transistor S1, respectively. The positive terminal of the freewheeling diode D1 is connected to a capacitor C3, which is connected to the negative terminal of the freewheeling diode D2. The positive terminal of the freewheeling diode D2 is connected to the primary side of the transformer T1 and the drain terminal of the switching transistor S2, respectively.

[0026] In this embodiment, when the driving voltage is high, switches S1 and S2 are turned on simultaneously. The input circuit stores energy for transformer T1 through switches S1 and S2 connected in series. The terminals of freewheeling diodes D1 and D2 are subjected to reverse voltage HV. The output rectifier diode D14 is turned off and is subjected to reverse voltage HV*Ns / Np+Vout. The energy storage capacitor C25 supplies power to the load independently. When the driving voltage is low, switches S1 and S2 are turned off simultaneously. The secondary winding Ns of the transformer stores energy for energy storage capacitor C25 through rectifier diode D14 and supplies power to the load at the same time. At this time, the energy on the leakage inductance of the primary winding Np of transformer T1 is fed back to the energy storage element at the input terminal through freewheeling diodes D1 and D2. Switches S1 and S2 are subjected to reverse voltage HV.

[0027] Furthermore, the input voltage clamping characteristic of the primary-side switch in the two-transistor flyback converter effectively decouples the voltage stress of the primary-side switch from the transformer design parameters. Therefore, during the transformer T1 design optimization stage, only efficiency and the voltage stress of the output rectifier diodes are considered. The voltage stress on rectifier diode D14 is shown in the equation. ,in For the primary side turns of T1, T1 secondary winding turns, transformer turns ratio The larger the diode, the lower the voltage stress on rectifier D14. LED lighting fixtures often use multiple modules connected in series, which requires the LED driver power supply to output high voltage. For example, a 0.7A / 200W LED driver has an output voltage close to 285V, requiring careful design of the transformer turns ratio. Assuming ,but The reliability design requirements can be met by using a 600V rectifier diode. This patent, when applying a dual-transistor forward topology design for LED drivers, significantly reduces the voltage stress on semiconductor devices by increasing the transformer turns ratio, solving the difficulty of device selection under high output voltage conditions, while also reducing costs and improving efficiency.

[0028] The industry-standard designs include two structures: single-transistor flyback and resonant half-bridge. If a traditional single-transistor flyback design is used, assuming the transformer has the same turns ratio, the voltage stress on the primary-side switching transistor will reach [a certain value]. Since MOSFETs cannot be selected, reducing the transformer turns ratio would increase the voltage stress on the output rectifier diodes, requiring the use of higher voltage-rated rectifier diodes or two 600V rectifier diodes in series, resulting in high cost and low efficiency. If a resonant half-bridge design is used, the resonant circuit is relatively complex and costly, and the output voltage range is narrower, resulting in inferior dimming performance compared to a flyback circuit using PWM mode.

[0029] The synchronous drive circuit module 300 includes a first synchronous drive unit and a second synchronous drive unit. One end of the first synchronous drive unit and the second synchronous drive unit are connected to the control chip U2, and the other end is connected to the switch unit 410.

[0030] Specifically, the first synchronous drive unit includes transistors Q12 and Q13. The emitters (E) of transistors Q12 and Q13 are connected to each other. Resistors R22 and R23 are connected in series with the emitters of transistors Q12 and Q13. Resistor R23 is connected to the switch S2. Diode D4 is connected in parallel with resistor R23. The collector (C) of transistor Q12 is connected to the tenth pin of the control chip U2. The emitters (E) and collectors (C) of transistors Q12 and Q13 are connected to the second synchronous drive unit. The bases (B) of transistors Q12 and Q13 are connected in series with resistor R28.

[0031] The second synchronous drive unit includes a transformer T2, transistors Q14 and Q15. The primary winding of the transformer T2 is connected to the emitter (E) and collector (C) terminals of transistors Q12 and Q13. One end of the secondary winding of the transformer T2 is connected to diodes D15 and D20 and resistor R49. Resistor R49 is connected to the base (B) terminal of transistors Q14 and Q15. The other end of the secondary winding of the transformer T2 is connected to capacitors C35 and C38, resistor R42, and the source (S) terminal of switching transistor S1. One end of resistor R42 is connected to resistor R36. Resistors R36 and R42 are respectively connected to the gate (G) terminal of switch S1. Resistor R36 is respectively connected to the emitter (E) terminal of transistors Q14 and Q15. Capacitor C35 is connected to diode D15. Capacitor C38 is connected to diode D20. The collector (C) terminal of transistor Q14 is connected between diode D20 and capacitor C38. The collector (C) terminal of transistor Q15 is connected between diode D15 and capacitor C35.

[0032] In this embodiment, the driving principle of the switch S1 is as follows: the driving signal of the control chip U2 is input to the input terminals of push-pull transistors Q12 and Q13 through resistor R28 for circuit amplification, and drives transformer T2 through resistor R29 and capacitor C27. Resistor R29 acts as a current limiter, and capacitor C27 acts as a DC blocker. When the output of transformer T2 is positive, in addition to charging capacitor C38 through diode D20, it also provides base drive current to transistor Q14 through resistor R49. The energy stored on C38 provides a positive drive voltage to switch S1 through transistor Q14, quickly turning on switch S1. When the output of transformer T2 is negative, in addition to charging capacitor C35 through diode D15, it also provides base drive current to transistor Q15 through resistor R49. The energy stored on capacitor C35 can provide a negative voltage to switch S1 through transistor Q15 for rapid turn-off. The drive circuit stores energy through capacitors C35 and C38, and amplifies it using a push-pull configuration of transistors Q14 and Q15. This makes the drive speed of the switching transistor S1 unaffected by the parameters of the drive transformer, such as inductance and current-limiting resistor, greatly improving the turn-on and turn-off speed and reliability of the switching transistor S1.

[0033] The driving principle of switch S2 is that switch S2 and control chip U2 share a common ground, eliminating the need for complex driving circuitry. Therefore, when the signal output by control chip U2 is high, transistor Q13 conducts, driving switch S2 to turn on; when the signal output by control chip U2 is low, transistor Q12 conducts, driving switch S2 to turn off. Furthermore, switches S1 and S2 are turned on or off simultaneously.

[0034] The PWM control circuit module 200 includes a control chip U2 and related peripheral circuits. The control chip U2 is connected to the auxiliary power supply circuit module 100, the synchronous drive circuit module 300, and the dual-transistor flyback power circuit module 400. It also includes a sampling and filtering circuit module 500, which includes a resistor Rf1 and a capacitor Cf1. The resistor Rf1 is located between the sixth pin of the control chip U2 and the switching transistor S2, and the capacitor Cf1 is located between the resistor Rf1 and the sixth pin of the control chip U2.

[0035] In this embodiment, the sampling and filtering circuit module 500 sends the instantaneous primary-side current to the control chip U2. The control chip U2 performs a series of processes to achieve a constant secondary-side current output. This control is also called primary-side constant current control. Its core is the primary-side constant current algorithm, which measures the primary-side peak current and demagnetization time in each switching cycle and, using preset transformer parameters, calculates the output current in real time and performs closed-loop control. The core formula of the primary-side constant current algorithm is shown in the following equation: ,in This is the primary-side peak current. Demagnetization time during transformer T1 turn-off The switching period is [time period]. It can be seen that, ( (x R43) can be determined by the control chip U2. Different current sensing resistors R43 can be obtained. This changes the output current. However, in the above formula, the demagnetization time of transformer T1 is: ,in The number of turns in the primary winding of T1. This refers to the number of turns in the secondary winding, which is a fixed quantity after the design is completed. After x R43 is determined, It's also confirmed. It is also a constant voltage, and thus belongs to the quantitative category. If the output voltage changes at this time, then... and The amplification ratio also changes accordingly; the higher the output voltage, the lower the output current.

[0036] To reduce the variation in output current, a current compensation circuit module is also included, comprising resistors R58, R59, R19, R52, R46, R60, R63, diode D19, transistor Q8, and diode ZD2. One end of resistor R59 is connected to the first pin of transformer T1, and the other end of resistor R59 is connected to resistor R58 and diode D18. Diode D18 is connected to the base (B) of transistor Q8 and resistor R46. Resistor R46 is connected to resistor R58. The collector (C) of transistor Q8 is connected to resistors R60 and R63. The emitter (E) of transistor Q8 is connected to resistor R52. Resistor R52 is connected to resistor R19 and diode ZD2. Resistor R19 is connected to the emitter (E) of transistor Q3. Diode ZD2, resistors R60, R46, and R58 are grounded.

[0037] The circuit input comes from the auxiliary winding of transformer T1 (at the first and second pins of transformer T1), and its voltage value is directly proportional to the output voltage. Resistor R19 and diode ZD2 form a constant voltage circuit, providing a stable input voltage to the linear amplifier circuit composed of resistor R52, transistor Q8, and resistor R60. The emitter voltage V1 of transistor Q8 is the input voltage. Resistors R58 and R59 form a voltage divider circuit, providing the base voltage V2 of transistor Q8 proportionally. Transistor Q8 operates in the linear amplification region. Diode D18 compensates for the base voltage drop of transistor Q8. Therefore, the collector voltage V3 of transistor Q8 = R60 * (V1 - V2) / R52. It can be seen that V3 changes inversely proportional to the output voltage. This voltage is supplied to the current detection circuit of control chip U2 through resistor R63. When the output voltage is high, it improves the actual control. to compensate The smaller the current, the lower the current.

[0038] The auxiliary power supply circuit module 100 is used to provide power through auxiliary current input.

[0039] Specifically, the auxiliary power supply circuit module 100 includes a first power supply circuit unit, which includes resistors R14, 15, and 16 and capacitors C18 and 36. The tenth pin of the control chip U2 is connected in series with the resistors R14, 15, and 16. The end of the resistor R16 away from the control chip U2 is connected to the drain of the switching transistor S1. One end of the capacitors C18 and C36 is connected to the tenth pin of the control chip U2, and the other end is grounded.

[0040] The auxiliary power supply circuit module 100 further includes a second power supply circuit unit, which includes resistors R34, R45, and R47, capacitor C6, transistor Q3, diode D7, and diode ZD1. One end of resistor R45 is connected to the sixth pin of the control chip U2 and the first pin of transformer T1, respectively. One end of diode D6 is connected to resistor R45, and the other end is connected to the collector (C) of transistor Q3. The emitter (E) of transistor Q3 is connected to diode D7 and resistor R47, respectively. Resistor R47 is connected to the second pin of transformer T1. The base (B) of transistor Q3 is connected to resistor R34 and diode ZD1, respectively. Diode ZD1 is connected to the second pin of transformer T1.

[0041] In this embodiment, the first power supply circuit unit has high energy consumption and only provides power to the PWM control circuit module 200 during the startup phase of the dual-transistor flyback converter. After the dual-transistor flyback converter is working normally, the control chip U2 takes over the power supply of the PWM control circuit module 200 through the branch at the SU pin terminal. At this time, the power supply of the PWM control circuit module 200 is taken over by the second power supply circuit unit, that is, the auxiliary winding of the transformer T1 supplies power to the PWM control circuit module 200 to improve efficiency.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A dual-transistor flyback LED driver power supply circuit, characterized in that, It includes an auxiliary power supply circuit module, a PWM control circuit module, a synchronous drive circuit module, and a dual-transistor flyback power circuit module, among which, The auxiliary power supply circuit module is used for auxiliary current input to provide power; The PWM control circuit module includes a control chip U2, which is connected to the auxiliary power supply circuit module, the synchronous drive circuit module, and the dual-transistor flyback power circuit module respectively. The dual-tube flyback power circuit module includes a switching unit, a clamping unit, a transformer T1, a rectifier diode D14, and an energy storage capacitor C25. One end of the switching unit is connected to the synchronous drive circuit module, and the other end is connected to the clamping unit. The clamping unit is connected to the primary side of the transformer T1. The secondary side of the transformer T1 is connected to the rectifier diode D14 and the energy storage capacitor C25, respectively. A load is connected to the secondary side of the transformer T1, and the energy storage capacitor C25 is connected in parallel with the load. The synchronous drive circuit module includes a first synchronous drive unit and a second synchronous drive unit. One end of the first synchronous drive unit and the second synchronous drive unit are connected to the control chip U2, and the other end is connected to the switch unit.

2. The dual-tube flyback LED driver power supply circuit according to claim 1, characterized in that, The switching unit includes switching transistors S1 and S2. The gate (G) of switching transistor S1 is connected to the second synchronous drive unit, the drain (D) of switching transistor S1 is connected to the first synchronous drive unit, and the source (S) of switching transistor S1 is connected to the primary side of transformer T1. The gate (G) of switch S2 is connected to both the first synchronous drive unit and control chip U2. The drain (D) of switch S2 is connected to the primary side of transformer T1. The source (S) of switch S2 and the CS pin of control chip U2 are connected together to a current sensing resistor R43, one end of which is grounded.

3. The dual-tube flyback LED driver power supply circuit according to claim 2, characterized in that, The clamping unit includes freewheeling diodes D1 and D2. The negative terminal of freewheeling diode D1 is connected to the primary side of transformer T1 and the source terminal of switching transistor S1, respectively. The positive terminal of freewheeling diode D1 is connected to capacitor C3, which is connected to the negative terminal of freewheeling diode D2. The positive terminal of freewheeling diode D2 is connected to the primary side of transformer T1 and the drain terminal of switching transistor S2, respectively.

4. The dual-tube flyback LED driver power supply circuit according to claim 3, characterized in that, The first synchronous drive unit includes transistors Q12 and Q13. The emitters (E) of transistors Q12 and Q13 are connected to each other. Resistors R22 and R23 are connected in series with the emitters of transistors Q12 and Q13. Resistor R23 is connected to the switch S2. Diode D4 is connected in parallel with resistor R23. The collector (C) of transistor Q12 is connected to the tenth pin of the control chip U2. The emitters (E) and collectors (C) of transistors Q12 and Q13 are connected to the second synchronous drive unit. The bases (B) of transistors Q12 and Q13 are connected to resistor R28.

5. The dual-tube flyback LED driver power supply circuit according to claim 4, characterized in that, The second synchronous drive unit includes a transformer T2, transistors Q14 and Q15. The primary winding of the transformer T2 is connected to the emitter (E) and collector (C) terminals of transistors Q12 and Q13. One end of the secondary winding of the transformer T2 is connected to diodes D15 and D20 and resistor R49. Resistor R49 is connected to the base (B) terminal of transistors Q14 and Q15. The other end of the secondary winding of the transformer T2 is connected to capacitors C35 and C38, resistor R42, and the source (S) terminal of switching transistor S1. One end of resistor R42 is connected to resistor R36. Resistors R36 and R42 are respectively connected to the gate (G) terminal of switch S1. Resistor R36 is respectively connected to the emitter (E) terminal of transistors Q14 and Q15. Capacitor C35 is connected to diode D15. Capacitor C38 is connected to diode D20. The collector (C) terminal of transistor Q14 is connected between diode D20 and capacitor C38. The collector (C) terminal of transistor Q15 is connected between diode D15 and capacitor C35.

6. The dual-tube flyback LED driver power supply circuit according to claim 2, characterized in that, It also includes a sampling and filtering circuit module, which includes a resistor Rf1 and a capacitor Cf1. The resistor Rf1 is located between the sixth pin of the control chip U2 and the switching transistor S2, and the capacitor Cf1 is located between the resistor Rf1 and the sixth pin of the control chip U2.

7. The dual-tube flyback LED driver power supply circuit according to claim 6, characterized in that, The auxiliary power supply circuit module includes a first power supply circuit unit, which includes resistors R14, 15, and 16 and capacitors C18 and 36. The tenth pin of the control chip U2 is connected in series with the resistors R14, 15, and 16. The end of the resistor R16 away from the control chip U2 is connected to the drain of the switching transistor S1. One end of the capacitors C18 and C36 is connected to the tenth pin of the control chip U2, and the other end is grounded.

8. The dual-tube flyback LED driver power supply circuit according to claim 7, characterized in that, The auxiliary power supply circuit module further includes a second power supply circuit unit, which includes resistors R34, R45, and R47, capacitor C6, transistor Q3, diode D7, and diode ZD1. One end of resistor R45 is connected to the sixth pin of the control chip U2 and the first pin of transformer T1, respectively. One end of diode D6 is connected to resistor R45, and the other end is connected to the collector (C) of transistor Q3. The emitter (E) of transistor Q3 is connected to diode D7 and resistor R47, respectively. Resistor R47 is connected to the second pin of transformer T1. The base (B) of transistor Q3 is connected to resistor R34 and diode ZD1, respectively. Diode ZD1 is connected to the second pin of transformer T1.

9. A dual-tube flyback LED driver power supply circuit according to claim 8, characterized in that, It also includes a current compensation circuit module, which includes resistors R58, R59, R19, R52, R46, R60, R63, diode D19, transistor Q8, and diode ZD2. One end of resistor R59 is connected to the first pin of transformer T1, and the other end of resistor R59 is connected to resistor R58 and diode D18. Diode D18 is connected to the base (B) of transistor Q8 and resistor R46. Resistor R46 is connected to resistor R58. The collector (C) of transistor Q8 is connected to resistors R60 and R63. The emitter (E) of transistor Q8 is connected to resistor R52. Resistor R52 is connected to resistor R19 and diode ZD2. Resistor R19 is connected to the emitter (E) of transistor Q3. Diode ZD2, resistors R60, R46, and R58 are grounded.

10. A dual-tube flyback LED driver power supply circuit according to claim 7, characterized in that, It also includes an FPC circuit module, which is connected to the first power supply circuit unit.

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