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Time: 2021-08-11 View: 584
The schematic diagram of the production of SMD LED energy-saving lamps is a practical circuit diagram of SMD LED lighting fixtures. The lamp uses 220V power supply. The 220V AC power is reduced by the C1 step-down capacitor, and then the full bridge rectifier is passed through the C2 filter and then passed through the current-limiting resistor. R3 provides a constant current power supply for 10 SMD LEDs connected in series. The rated current of SMD LEDs is 20mA, but when we make energy-saving lamps, we must consider the impact of many factors on SMD LEDs, including light decay and heat generation. The problem is that the temperature of the LED has a great influence on the light attenuation and lifespan. If the heat dissipation is not good, it is easy to cause light attenuation, because the characteristic of the LED is that the current will increase when the temperature rises, so the general heat dissipation problem when doing high-power lighting is The most important thing is that it will affect the stability of the LED. Low power generally adopts self-heating methods, so the current should not be too large during circuit design. In the figure, R1 is the protection resistor, R2 is the discharge resistance of the capacitor C1, and R3 is the limit. The current resistance prevents the voltage rise and the temperature rise from increasing the current of the LED. C2 is a filter capacitor. Actually, the filter circuit can be used in the LED circuit. C2 is used to prevent the impact of the current from damaging the LED when the lamp is turned on. Because of the existence of C1, there will be a large charging current in an instant, and the current flowing through the LED will cause damage to the LED. With the intervention of C2, the charging current of turning on the light is completely absorbed by C2 to protect the light from impact. The circuit is the most practical circuit for low-power lamp cups. It occupies a small size and can be easily installed in a lamp cup with a small space. Now it is widely used by lamp cup products. Advantages: constant current source, low power consumption, small size, Economical and practical. But in the design, the step-down capacitor should be a polyester capacitor or CBB capacitor with a withstand voltage above 400V, and the filter capacitor should use a withstand voltage above 250V. This circuit is suitable for driving 7-12 20mA SMD LEDs.