LED drive circuit with constant current
By introducing the circuit structure of capacitor C2 and transistor Q2 into the Buck circuit, the flickering problem caused by current fluctuations in the LED lamp is solved, and the constant current and cost reduction are achieved.
Patent Information
- Application Number
- CN202422058900.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2025-07-01
- Estimated Expiration
- 2034-08-23
AI Technical Summary
The LED lamps driven by existing Buck circuits have the problem of current fluctuations causing flickering, and the existing methods cannot be effectively solved due to cost and space limitations.
The circuit structure consisting of capacitor C1, capacitor C2, resistor R1, diode D1, transistor Q2 and switch S1 is adopted. Through the coordination of capacitor C2 and transistor Q2, the current is kept constant and the current fluctuation is reduced.
The LED lamp current is achieved, the circuit cost is reduced, and the flickering phenomenon is reduced, which improves the user experience.
Smart Images
Figure CN223053144U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of LED driving, and particularly relates to an LED driving circuit with constant current. Background Art
[0002] Light-emitting LEDs are more and more widely used in the lighting industry. LEDs have the characteristics of low power consumption and high brightness. Most of the LEDs adopt constant-current drive, which can ensure constant light emission of the LEDs, is independent of the voltage drop of each lamp bead, and is convenient for engineering implementation. The constant-current drive power supply V1 of the LEDs is roughly divided into a linear circuit and a Buck circuit. The linear circuit has large power consumption and a small application range. The Buck circuit has high efficiency and less heat generation, and is the first choice for the drive power supply V1 of LED lamps.
[0003] In the prior art, the LED lamps driven by Buck all have the inherent stroboscopic effect of the Bulk circuit. The basic principle of Buck is intermittent on and off. By controlling the current flowing through the circuit, that is, controlling the average current flowing through the circuit, it is independent of the voltage applied to the circuit. The current generated by the Buck circuit is a sawtooth wave, and the current magnitude is variable. By increasing the output capacitor, the variation of the current can be reduced, but limited by cost and space, the capacitor cannot be increased without limit. Therefore, most of the LED lamps in the existing market have varying degrees of flicker, which makes the human eye more prone to fatigue. Summary of the Utility Model
[0004] In order to overcome the technical problem that the LED driving circuit in the prior art is prone to cause flicker, the technical problem to be solved by the utility model is: to provide an LED driving circuit with constant current, which is used for constant-current processing of the current of the common Buck circuit at the end of the LED driving power supply, reducing the influence of the inherent current fluctuation of the Buck circuit on the current flowing through the LED, keeping the current flowing through the LED lamp constant, and reducing the circuit cost.
[0005] In order to solve the above technical problem, the technical solution adopted by the utility model is: 1. An LED driving circuit with constant current, characterized in that it includes a capacitor C1, a capacitor C2, a resistor R1, a diode D1, a triode Q2, and a switch S1;
[0006] One end of the capacitor C1 is connected to the positive electrode of the lamp LED1, and the other end is sequentially connected to the negative electrode of the power supply V1 through the diode D1, the inductor L1, and the switch S1; the positive electrode of the lamp LED1 is connected to the positive electrode of the power supply V1, and the negative electrode is connected to the emitter of the triode Q2 through the resistor R1; the base of the triode Q2 is connected to the other end of the capacitor C1, and the collector of the triode Q2 is connected between the diode D1 and the inductor L1; one end of the capacitor C2 is connected to the positive electrode of the power supply V, and the other end is connected to the collector of the triode Q2.
[0007] The described LED driving circuit with constant current further includes a diode D2. One end of the diode D2 is connected to the positive pole of the power supply V1, and the other end is connected between the inductor L1 and the switch S1. The negative pole of the power supply V1 is grounded.
[0008] The described LED driving circuit with constant current further includes a cut-off resistor R5. One end of the cut-off resistor R5 is connected to the negative pole of the lamp LED1, and the other end is connected between the capacitor C1 and the diode D1.
[0009] The described LED driving circuit with constant current further includes a resistor R4. One end of the resistor R4 is connected to the base of the triode Q1, and the other end is connected between the capacitor C1 and the diode D1.
[0010] The described LED driving circuit with constant current further includes a triode Q1 and a resistor R2. The emitter of the triode Q1 is connected to the negative pole of the lamp LED1 through the resistor R2, the base is connected to the base of the triode Q2, and the emitter is connected to the emitter of the triode Q2.
[0011] The triode Q2 and the triode Q1 are PNP type triodes.
[0012] The described LED driving circuit with constant current further includes a plurality of current-sharing triodes and a plurality of current-limiting resistors. The emitters of the respective current-sharing triodes are respectively connected to the negative pole of the lamp LED1 through their respective current-limiting resistors, the bases are all connected to the base of the triode Q2, and the emitters are all connected to the emitter of the triode Q2.
[0013] The triode Q2 and the respective current-sharing triodes are all PNP type triodes.
[0014] The capacitor C2 satisfies the following conditions:
[0015] C2>Iled*t / Vbe;
[0016] Wherein, C2 represents the capacitance value of the capacitor C2, Iled represents the working current value of the LED, t represents the off time of the Buck circuit switch, and Vbe represents the voltage between the base and the emitter of the triode Q2.
[0017] The positive pole of the diode D1 is connected to the capacitor C1, and the negative pole is connected to the inductor L1.
[0018] The utility model has the following beneficial effects compared with the prior art:
[0019] The utility model provides an LED driving circuit with constant current, which uses simple passive devices to perform constant-current processing on the current of the commonly used Buck circuit at the end of the LED driving power supply, reduces the influence of the inherent current fluctuation of the Buck circuit on the current flowing through the LED, can achieve constant current flowing through the LED lamp, and can reduce the parallel capacitance value of the LED according to needs. In addition, its circuit structure is simple and the cost can be reduced. Brief Description of the Drawings
[0020] Figure 1 It is a schematic diagram of the circuit principle of an LED driving circuit with constant current provided by Embodiment 1 of the utility model;
[0021] Figure 2 It is a block diagram of a typical Buck circuit in the prior art;
[0022] Figure 3 It is a schematic diagram of the circuit principle of an LED driving circuit with constant current provided by Embodiment 2 of the utility model. Detailed Embodiments
[0023] To make the objectives, technical solutions and advantages of the embodiments of the utility model clearer, the technical solutions in the embodiments of the utility model will be clearly and completely described below. Obviously, the described embodiments are some but not all of the embodiments of the utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the utility model without creative efforts shall fall within the protection scope of the utility model.
[0024] Embodiment 1
[0025] As Figure 1 shown, the embodiment of the invention provides an LED driving circuit with constant current, including capacitor C1, capacitor C2, resistor R1, diode D1, triode Q2 and switch S1.
[0026] Wherein, one end of the capacitor C1 is connected to the positive electrode of the lamp LED1, and the other end is sequentially connected to the negative electrode of the power supply V1 through the diode D1, inductor L1 and switch S1; the positive electrode of the lamp LED1 is connected to the positive electrode of the power supply V1, and the negative electrode is connected to the emitter of the triode Q2 through the resistor R1; the base of the triode Q2 is connected to the other end of the capacitor C1, and the collector of the triode Q2 is connected between the diode D1 and the inductor L1; one end of the capacitor C2 is connected to the positive electrode of the power supply V1, and the other end is connected to the collector of the triode Q2.
[0027] Further, a current-constant LED driving circuit according to this embodiment further includes a diode D2. One end of the diode D2 is connected to the positive electrode of the power supply V1, and the other end is connected between the inductor L1 and the switch S1. Further, in this embodiment, the negative electrode of the power supply V1 is grounded. One end of the capacitor C1 is connected to the positive electrode of the lamp LED1, and the other end is grounded through the diode D1, the inductor L1, and the switch S1 in sequence.
[0028] Further, a current-constant LED driving circuit according to this embodiment further includes a cut-off resistor R5. One end of the cut-off resistor R5 is connected to the negative electrode of the lamp LED1, and the other end is connected between the capacitor C1 and the diode D1.
[0029] Further, a current-constant LED driving circuit according to this embodiment further includes a resistor R4. One end of the resistor R4 is connected to the base of the triode Q1, and the other end is connected between the capacitor C1 and the diode D1.
[0030] Further, in this embodiment, the triode Q2 is a PNP type triode.
[0031] Further, in this embodiment, the positive electrode of the diode D1 is connected to the capacitor C1, and the negative electrode is connected to the inductor L1.
[0032] Specifically, in this embodiment, the triode Q2 serves as a current-sharing triode, and the resistor R1 connected to its emitter is a current-sharing resistor. The other end of the current-sharing resistor R1 is connected to the negative electrode of the lamp LED1. The capacitor C1 serves as a constant-voltage capacitor. One end of it is connected to the positive electrode of the LED lamp, and the other end is connected to the base of the triode Q2.
[0033] A typical Buck circuit is as Figure 2 . When the switch of the Buck circuit is closed, a current loop is formed in the whole circuit, and the current flowing through the inductor gradually increases. The capacitor C2 in parallel with the lamp LED1 is charged, and the current flowing through the lamp LED1 also gradually increases. The current reaches the maximum before the switch of the Buck circuit is disconnected. When the switch of the Buck circuit is disconnected, the current of the inductor will not mutate, and the current flows from the diode D2 to the positive end of the LED. During this process, the capacitor C2 discharges to maintain the current of the lamp LED1 from dropping to 0.
[0034] In this embodiment, when the switch S1 of the Buck circuit is closed, a current loop is formed in the entire circuit, and the current flowing through the inductor L1 gradually increases. The capacitor C1 connected in parallel with the lamp LED1 is charged, and the current flowing through the lamp LED1 also gradually increases, reaching the maximum before the switch of the Buck circuit is turned off. When the switch of the Buck circuit is turned off, the capacitor C1 discharges through the base of the triode, and the outflowing current is very small. The voltage of the capacitor C1 is basically constant during the entire discharge process. The voltage across the lamp LED1 is equal to the voltage across the capacitor C1 minus the voltage between the base B and the emitter E of the triode and the voltage across the current-sharing resistor. Therefore, it can be known that as long as the capacitors C1 and C2 are large enough, the voltage across the LED lamp can be ensured to remain unchanged when the Buck circuit is turned off, that is, the current flowing through the lamp LED1 remains unchanged. To keep the current of the lamp LED1 unchanged, the minimum value of the capacitor C2 can be calculated. Assuming that the off time of the Buck circuit switch is t, the LED lamp current is Iled, and the voltage between the B and E of the triode is Vbe, the electric charge released by the capacitor C2 and the voltage drop Vbe should meet the power consumption requirement of the lamp LED1 in time t, that is:
[0035] Vbe*C2 > Iled * t; (1)
[0036] Therefore, the capacitor C2 satisfies the following condition:
[0037] C2>Iled*t / Vbe; (2)
[0038] Among them, C2 represents the capacitance value of the capacitor C2, Iled represents the operating current value of the LED, t represents the off time of the Buck circuit switch, and Vbe represents the voltage between the base and the emitter of the triode Q2.
[0039] Embodiment 2
[0040] As Figure 3 shown, Embodiment 2 of the present invention provides an LED driving circuit with a constant current. The same as Embodiment 1, it includes a capacitor C1, a capacitor C2, a resistor R1, a resistor R4, a resistor R5, a diode D1, a triode Q2, and a switch S1. Different from Embodiment 1, in this embodiment, a triode Q1 and a resistor R2 are further included; the triode Q1 is connected in parallel with the triode Q2. Specifically, the emitter of the triode Q1 is connected to the negative electrode of the lamp LED1 through the resistor R2, the base is connected to the base of the triode Q2, and the emitter is connected to the emitter of the triode Q2.
[0041] Specifically, in this embodiment, the triode Q2 and the triode Q1 are PNP type triodes.
[0042] Further, a constant-current LED driving circuit according to this embodiment may further include a plurality of current-sharing triodes and a plurality of current-limiting resistors; the emitters of the respective current-sharing triodes are respectively connected to the negative electrode of the lamp LED1 through their respective current-limiting resistors, the bases are all connected to the base of the triode Q2, and the emitters are all connected to the emitter of the triode Q2. Each of the current-sharing triodes is a PNP-type triode.
[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A constant current LED driving circuit, characterized in that: It includes capacitor C1, capacitor C2, resistor R1, diode D1, transistor Q2 and switch S1; One end of the capacitor C1 is connected to the positive electrode of the lamp LED1, and the other end is connected to the negative electrode of the power supply V1 via the diode D1, the inductor L1, and the switch S1 in sequence; the positive electrode of the lamp LED1 is connected to the positive electrode of the power supply V1, and the negative electrode is connected to the emitter of the transistor Q2 via the resistor R1; the base of the transistor Q2 is connected to the other end of the capacitor C1, and the collector of the transistor Q2 is connected between the diode D1 and the inductor L1; one end of the capacitor C2 is connected to the positive electrode of the power supply V, and the other end is connected to the collector of the transistor Q2.
2. The constant current LED driving circuit according to claim 1, characterized in that: It also includes a diode D2, one end of the diode D2 is connected to the positive electrode of the power source V1, and the other end of the diode D2 is connected between the inductor L1 and the switch S1, and the negative electrode of the power source V1 is grounded.
3. The constant current LED driving circuit according to claim 1, characterized in that: The cut-off resistor R5 is also included. One end of the cut-off resistor R5 is connected to the cathode of the lamp LED1, and the other end is connected between the capacitor C1 and the diode D1.
4. The constant current LED driving circuit according to claim 1, characterized in that: The device further comprises a resistor R4 , one end of which is connected to the base of the transistor Q1 , and the other end of which is connected between the capacitor C1 and the diode D1 .
5. The constant current LED driving circuit according to claim 1, characterized in that: It also includes a transistor Q1 and a resistor R2; the emitter of the transistor Q1 is connected to the cathode of the lamp LED1 through the resistor R2, the base is connected to the base of the transistor Q2, and the emitter is connected to the emitter of the transistor Q2.
6. The constant current LED driving circuit according to claim 5, characterized in that: The transistor Q2 and the transistor Q1 are PNP transistors.
7. The constant current LED driving circuit according to claim 1, characterized in that: It also includes multiple current-sharing transistors and multiple current-limiting resistors; the emitter of each current-sharing transistor is connected to the negative electrode of the lamp LED1 through its own current-limiting resistor, the base is connected to the base of the transistor Q2, and the emitter is connected to the emitter of the transistor Q2.
8. The constant current LED driving circuit according to claim 7, characterized in that: The transistor Q2 and each current-sharing transistor are all PNP transistors.
9. The constant current LED driving circuit according to claim 1, characterized in that: The capacitor C2 satisfies the following conditions: C2>Iled*t / Vbe; Wherein, C2 represents the capacitance value of capacitor C2, Iled represents the operating current value of the LED, t represents the off time of the Buck circuit switch, and Vbe represents the voltage between the base and the emitter of the transistor Q2.
10. The constant current LED driving circuit according to claim 1, characterized in that: The anode of the diode D1 is connected to the capacitor C1 , and the cathode of the diode D1 is connected to the inductor L1 .