High-precision dimmable LED drive circuit based on PWM

Abstract

The utility model relates to the technical field of LED drive circuits, in particular to a PWM-based high-precision dimmable LED drive circuit, which comprises a chip U1 and a transformer T1, the transformer T1 is connected with a plurality of groups of LEDs through a diode VD1, and the plurality of groups of LEDs are arranged on the diode VD1 in parallel; one end of the diode VD1 is connected with a diode VD3 through an inductor L1, a pin BP of the chip U1 is electrically connected with a diode VD6, and a resistor RF1 is electrically connected between the diode VD3 and the diode VD6. The circuit is provided with an accurate primary-side constant-voltage / constant-current controller, a secondary-side control circuit is omitted, the highest efficiency can be achieved without a current detection resistor, the circuit is automatically restarted for short circuit output and open-loop protection, the full-load efficiency in the whole input voltage range is larger than 80%, and the no-load power consumption is smaller than 150 mW under the condition of 220V alternating current input. And the requirement of low energy consumption is met.

Description

Technical Field

[0001] The utility model relates to an LED driving circuit, in particular to a high-precision dimmable LED driving circuit based on PWM, belonging to the technical field of LED driving circuits. Background Art

[0002] PWM, namely pulse width modulation, is an analog circuit digital control technology. By modulating the widths of a series of pulses, the required waveforms (including shapes and amplitudes) can be equivalently obtained. PWM technology is widely applied in multiple fields such as motor speed regulation, power management, LED lighting control, audio signal processing, etc. A PWM signal is a waveform composed of a series of pulses with variable widths, and its duty cycle (i.e., the ratio of the pulse width to the pulse period) determines the equivalent average voltage or current value. For example, within a fixed period, if the width of the pulse increases, then the average voltage or current will also increase accordingly. By adjusting the duty cycle, precise control of motor speed, LED brightness, audio volume, etc. can be achieved.

[0003] However, the existing high-precision dimmable LED driving circuits based on PWM have a large number of components and high costs, resulting in an increase in the overall volume and size, and the energy consumption of the LED will also increase accordingly.

[0004] Therefore, it is urgent to improve the dimmable LED driving circuit to solve the above existing problems. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a high-precision dimmable LED driving circuit based on PWM. This circuit has a precise primary-side constant voltage / constant current controller, eliminates the optocoupler and all secondary-side control circuits, can achieve the highest efficiency without a current detection resistor, has automatic restart for output short-circuit and open-loop protection, the full-load efficiency is greater than 80% within the entire input voltage range, and the no-load power consumption is less than 150 mW under 220V AC input, meeting the requirement of low energy consumption.

[0006] To achieve the above purpose, the main technical solutions adopted by the utility model include:

[0007] A high-precision dimmable LED driving circuit based on PWM, including a chip U1 and a transformer T1 connected to one side of the chip U1. The pin D of the chip U1 is electrically connected to the pin 4 of the transformer T1. The transformer T1 is connected with a plurality of groups of LEDs through a diode VD1, and the plurality of groups of LEDs are connected in parallel on the diode VD1;

[0008] One end of the diode VD1 is connected to a diode VD3 through an inductor L1. A diode VD6 is electrically connected to the pin BP of the chip U1. A resistor R is electrically connected between the diode VD3 and the diode VD6. F1 。

[0009] Preferably, the model of the chip U1 is LNK605DG. A resistor R1 and a resistor R2 are connected in parallel to the FB terminal of the chip U1. The model of the resistor R1 is 49.9KΩ, and the model of the resistor R2 is 8.25KΩ. The resistor R1 is electrically connected to the pin 6 of the transformer T1, and the resistor R2 is electrically connected to the pin 5 of the transformer T1.

[0010] Preferably, the model of the diode VD1 is SB1100. The diode VD1 is connected between the pin 1 and the pin 8 of the transformer T1.

[0011] Preferably, a capacitor C1 is connected in parallel between the diode VD1 and the pin 7 of the transformer T1. The model of the capacitor C1 is 330µF. A resistor R4 is electrically connected between the capacitor C1 and the LED. The model of the resistor R4 is 3KΩ.

[0012] Preferably, the model of the inductor L1 is 470µF. A capacitor C4 and a capacitor C5 are connected in parallel to one side of the inductor L1. The models of the capacitor C4 and the capacitor C5 are both 4.7µF.

[0013] Preferably, a diode VD4 and a diode VD5 are connected in parallel to one side of the capacitor C4. The diode VD4 and the diode VD5 are connected in series. The models of the diode VD4 and the diode VD5 are both IN4007.

[0014] Preferably, a resistor R is connected between the diode VD4 and the diode VD5. F2 。

[0015] Preferably, the resistor R F1 and the resistor R F2 have a voltage range of 85~220V applied across them.

[0016] The present utility model has at least the following beneficial effects:

[0017] 1. The circuit has an accurate primary side constant voltage / constant current controller, eliminating the optocoupler and all secondary side control circuits. It can achieve the highest efficiency without a current sensing resistor. Automatic restart is used for output short circuit and open loop protection. The full load efficiency is greater than 80% over the entire input voltage range, and the no-load power consumption is less than 150mW at 220V AC input, meeting the requirement of low energy consumption.

[0018] 2. The circuit has the characteristics of few components, wide input voltage range, low cost, small size, light weight, high efficiency, about 70% efficiency when the input is AC85V, meeting the EN55022 B EMI requirements, and an EMI margin greater than SdBIlV, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0020] Figure 1 is the circuit schematic diagram of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following will describe in detail the embodiments of the present application in conjunction with the drawings and embodiments, so as to fully understand the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects and implement accordingly.

[0022] As Figure 1 shown, the PWM-based high-precision adjustable light LED drive circuit provided in this embodiment includes a chip U1 and a transformer T1 connected to one side of the chip U1. The pin D of the chip U1 is electrically connected to the pin 4 of the transformer T1. The transformer T1 is connected with a plurality of groups of LEDs through a diode VD1. The plurality of groups of LEDs are connected in parallel on the diode VD1. The circuit has an accurate primary side constant voltage / constant current controller, eliminating the optocoupler and all secondary side control circuits, achieving the highest efficiency without a current detection resistor, automatic restart for output short circuit and open loop protection, with a full load efficiency greater than 80% throughout the input voltage range, and an idle power consumption less than 150mW under 220V AC input, meeting the requirements of low energy consumption;

[0023] One end of the diode VD1 is connected with a diode VD3 through an inductor L1. A diode VD6 is electrically connected to the pin BP of the chip U1. A resistor R is electrically connected between the diode VD3 and the diode VD6 F1 2. The circuit has the characteristics of few components, wide input voltage range, low cost, small size, light weight, high efficiency, about 70% efficiency when the input is AC85V, meeting the EN55022 B EMI requirements, and an EMI margin greater than SdBIlV, etc.

[0024] The circuit operates in an open-loop manner and has no output feedback. It can be used as a constant current LED driver. The circuit relies on the internal current limiting function of the LNK302PN to ensure a constant current supplied to the load. The resistor RF1 should be of a fusible fireproof type;

[0025] This type of control method has inherent adaptability to any change in the input voltage within the entire operating range. When the current flowing into the feedback pin is greater than 49 μA, the MOSFET will turn off in that cycle. In this application, since no current ever flows into the feedback pin, the device will conduct in each cycle, causing the current to rise to the current limit point. Since the peak current in each cycle is limited and fixed, the output power is only determined by the size of the inductor. If this design operates in a discontinuous manner, in addition to having good 9EMI characteristics, it can also ensure the use of low-cost rectifier diodes with a 75 ns reverse recovery time. For a design operating in a continuous manner, faster rectifier diodes are required.

[0026] Furthermore, as Figure 1 shown, the model of chip U1 is LNK605DG. A resistor R1 and a resistor R2 are connected in parallel on the FB terminal of chip U1. The model of resistor R1 is 49.9 kΩ, and the model of resistor R2 is 8.25 kΩ. Resistor R1 is electrically connected to pin 6 of transformer T1, and resistor R2 is electrically connected to pin 5 of transformer T1. The model of diode VD1 is SB1100. Diode VD1 is connected between pin 1 and pin 8 of transformer T1. A capacitor C1 is connected in parallel between diode VD1 and pin 7 of transformer T1. The model of capacitor C1 is 330 μF. A resistor R4 is electrically connected between capacitor C1 and the LED. The model of resistor R4 is 3 kΩ. The AC input power supply is rectified and filtered by diode VD1, capacitor C1, and capacitor C3. Rectification converts the alternating current into direct current, providing the basis for subsequent circuit processing, while filtering further smooths the fluctuations in the direct current, improving the stability and reliability of the circuit. The two cooperate with each other to jointly achieve the conversion process from alternating current to smooth direct current.

[0027] Even further, as Figure 1As shown, the model of inductor L1 is 470µF. Capacitors C4 and C5 are connected in parallel on one side of inductor L1. The models of both capacitors C4 and C5 are 4.7µF. Diodes VD4 and VD5 are connected in parallel on one side of capacitor C4. Diodes VD4 and VD5 are connected in series, and the models of both diodes VD4 and VD5 are IN4007. When current flows through inductor L1, energy will be stored in the form of a magnetic field. When the current stops, inductor L1 will release this energy, generating a reverse current. This energy storage and release process enables inductor L1 to smooth out current fluctuations in the circuit and prevent current mutations from damaging the circuit. Especially when used in combination with capacitors, an LC filter circuit can be formed to suppress AC interference signals and make the output DC power more pure. By adjusting the values of inductor L1 and the capacitor, the frequency of the oscillator can be changed, which is very useful in fields such as timing applications and signal processing. Inductor L1 has a high impedance to high-frequency signals and can block high-frequency signals from passing through the circuit, thus preventing the generation and propagation of electromagnetic interference. This is very important for protecting sensitive components in the circuit and ensuring the normal operation of the circuit. Inductor L1 can also be used as a transformer using its magnetic coupling principle. A transformer can transfer electrical energy from one circuit to another while changing the voltage and current levels.

[0028] Furthermore, as Figure 1 shown, a resistor R is connected between diodes VD4 and VD5 F2 , resistor R F1 and resistor R F2 have an input voltage range of 85 - 220V connected across them. The full-load efficiency is greater than 80% throughout the entire input voltage range, and the no-load power consumption is less than 200mW under 220V AC input, improving the range of use.

[0029] For example, certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different names to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but rather use the difference in the functions of components as the criterion for distinction. As mentioned throughout the specification and claims, "comprising" is an open-ended term and should be interpreted as "including but not limited to". "Substantially" means within an acceptable error range. Those skilled in the art can solve technical problems within a certain error range and basically achieve the technical effect.

[0030] It should be noted that the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a commodity or system comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such commodity or system. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the commodity or system comprising the element.

[0031] The above description shows and describes several preferred embodiments of the present invention. However, as previously mentioned, it should be understood that the present invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be altered within the scope of the inventive concept described herein through the above teachings or the skills or knowledge in the relevant field. Any alterations and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A PWM-based high-precision adjustable light LED driver circuit, including a chip U1 and a transformer T1 connected to one side of the chip U1, characterized in that, The pin D of the chip U1 is electrically connected to the pin 4 of the transformer T1. The transformer T1 is connected with a plurality of groups of LEDs through a diode VD1, and the plurality of groups of LEDs are connected in parallel on the diode VD1; One end of the diode VD1 is connected to a diode VD3 through an inductor L1. A diode VD6 is electrically connected to the pin BP of the chip U1. A resistor R is electrically connected between the diode VD3 and the diode VD6 F1 .

2. The PWM-based high-precision adjustable LED driving circuit according to claim 1, wherein: The model of the chip U1 is LNK605DG. A resistor R1 and a resistor R2 are connected in parallel on the FB terminal of the chip U1. The model of the resistor R1 is 49.9 KΩ, and the model of the resistor R2 is 8.25 KΩ. The resistor R1 is electrically connected to the pin 6 of the transformer T1, and the resistor R2 is electrically connected to the pin 5 of the transformer T1.

3. The PWM-based high-precision adjustable LED driving circuit according to claim 1, wherein: The model of the diode VD1 is SB1100. The diode VD1 is connected between the pin 1 and the pin 8 of the transformer T1.

4. The PWM-based high-precision adjustable LED driving circuit according to claim 1, characterized in that: A capacitor C1 is connected in parallel between the diode VD1 and the pin 7 of the transformer T1. The model of the capacitor C1 is 330 µF. A resistor R4 is electrically connected between the capacitor C1 and the LED. The model of the resistor R4 is 3 KΩ.

5. The high-precision dimmable LED driver circuit based on PWM according to claim 1, wherein: The model of the inductor L1 is 470 µF. A capacitor C4 and a capacitor C5 are connected in parallel on one side of the inductor L1. The models of the capacitor C4 and the capacitor C5 are both 4.7 µF.

6. The PWM-based high-precision adjustable LED driving circuit according to claim 5, characterized in that: A diode VD4 and a diode VD5 are connected in parallel on one side of the capacitor C4. The diode VD4 and the diode VD5 are connected in series. The models of the diode VD4 and the diode VD5 are both IN4007.

7. The PWM-based high-precision adjustable LED driving circuit according to claim 6, wherein: A resistor R is connected between the diode VD4 and the diode VD5 F2 .

8. The PWM-based high-precision adjustable LED driving circuit according to claim 7, characterized in that: The resistor R F1 and the resistor R F2 have an applied voltage range of 85 to 220V.

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