CR1225 battery.New AC LED converter topology circuit design

　　Aiming at the fact that the filter capacitor of the traditional LED lamp rectifier circuit causes the AC input current waveform at the rectification front end to become sharp pulses, causing problems such as low power factor and increased harmonic components, a new ACLED converter topology circuit is proposed. The BuckPFC power factor correction circuit and LCC circuit were analyzed in detail respectively. The working principle of the BuckPFC circuit, the operating frequency of the switching tube and the size of the capacitance value are analyzed. At the same time, the working principle of the half-bridge circuit and the selection of parameter values are analyzed theoretically and simulated. Finally, it was verified through experiments that the circuit topology can improve the power factor. This circuit topology can overcome the problems of traditional rectifier circuits such as reduced controller life and harmonic components due to back-end capacitance.

　　The traditional constant current control of LED lights is through AC/DC and then through a DC/DC converter. In the AC/DC converter, a filter capacitor is usually used behind the rectifier circuit to smooth the output voltage, but large capacitors The existence of causes the input current waveform at the AC terminal to become a sharp pulse instead of a sinusoidal function (reducing the power factor). Based on the above shortcomings of LED control, this article adopts ACLED converter control. In DCLED converters, since the input power is pulsating and the output power is constant, an intermediate energy storage capacitor is needed to balance the difference between the two. Therefore, the energy storage capacitor is generally larger in value, and electrolytic capacitors are used. However, electrolytic capacitors with high values are The life of the capacitor is much shorter than the life of the LED, resulting in a reduction in the life of the overall converter.

　　If ACLED is used and both the input and output power are pulsating, the required energy storage capacitor value will be smaller, which will increase the life of the overall converter. The existing ACLED lamp circuit structures include series structure, ladder structure and bridge structure. In the ACLED circuit structure, when the input AC source is the grid voltage of 220V, 50Hz, if the current limiting resistor is not connected in series, a large number of LED lamps need to be connected in series to limit the LED current. At this time, the total turn-on voltage is increased, resulting in a very low power factor. . When a current-limiting resistor is connected in series, the number of LEDs that need to be connected in series is reduced and the power factor is improved. However, the efficiency will be reduced because of the current-limiting resistor. In addition, when the LED operating frequency is 50Hz, the light source will obviously flicker; while when the LED operating frequency is 100Hz, most people will not feel the flickering of the light. In order to solve the low power factor and efficiency of ACLED, and to improve the frequency problem shown by the load structure, this paper proposes a new ACLED converter topology circuit, and analyzes and studies the topology circuit and control method.

　　1ACLED lamp conversion structure

　　Figure 1 shows the structure diagram of the proposed ACLED converter. vdc is the pulsating voltage of 220V AC voltage that has been uncontrolled rectified. In order to improve the power factor, this article uses a BuckPFC circuit to correct the current waveform. The output voltage of the BuckPFC circuit is converted into an AC signal through the half-bridge converter, which is used as the input voltage of the subsequent LCC circuit and is provided to the load LED lamp. Therefore, this topological circuit mainly includes the rectifier circuit, BuckPFC, half-bridge converter and LCC resonant circuit. As can be seen from Figure 1, the values of C1 and C2 are very small to achieve, so the capacitor has no impact on the life of the entire topological circuit; the fundamental frequency of the input and output AC voltage of the LCC resonant circuit is 100Hz, thus loading the LED The voltage frequency is also 100Hz, and no voltage flicker can be seen at this frequency.

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