High power factor non-isolated LED driver circuit based on AP3766


As an emerging industrial technology, LED lighting is constantly exploring a wider range of applications. For AC power input applications, switching power supplies based on flyback topologies are currently commonly used. The flyback topology switching power supply includes an input rectification filter circuit, a switch control circuit, an isolation transformer and a secondary side rectification filter circuit. However, flyback power circuits are not efficient, and some LED lighting applications do not necessarily need to be isolated. Therefore, it is necessary to develop a low-cost and cost-effective non-isolated LED driver circuit.

The IEC International Electrotechnical Commission has set clear harmonic requirements for lighting fixtures, namely the IEC61000-3-2 standard. At the same time, the latest EnergyStar standard proposes that for LED lighting products larger than 5W, the power factor specification, PF, must be greater than 0.7.

This paper proposes a new high-power factor non-isolated LED driver circuit, which combines a flow-by-flow power factor correction circuit and a Buck-boost switching power supply circuit with primary side control. The circuit structure is simple and meets the high power of the LED driving power supply . Factor, high efficiency, in line with EMC standards, high current control accuracy, high reliability, small size, low cost and other requirements.

Introduction to AP3766

AP3766 is the latest LED dedicated drive control chip from BCD. It uses the primary side adjustment control (PSR) technology to achieve high precision constant voltage/constant current (CV/CC) output, eliminating the need for secondary side optocouplers and constant voltage constant current. The control circuit also does not require a loop compensation circuit to achieve stable control of the circuit, and the SOT-23-6 small-volume package significantly reduces system size and reduces system cost. The AP3766 features a patented "Asian Micro Startup Current" technology that reduces system power consumption and increases efficiency. Can make the efficiency more than 80%, no-load power consumption is less than 30mW. The AP3766 has built-in external component temperature variation compensation and constant current CC tightening technology to achieve vertical CC characteristics, ensuring ±5% output constant current accuracy in mass production. At the same time, AP3766 has built-in soft start, over voltage protection and short circuit protection to improve system reliability.

AP3766 has strong system adaptability, can be matched with passive PFC flow-by-flow circuit, output totem pole drive circuit and other peripheral lines to meet high power factor requirements and greater power output. Therefore, AP3766 can be applied not only to GU10 spotlights, E27 bulbs, but also to PAR lamps, straight tube lamps, etc.

Figure 1 shows the pin diagram of the AP3766.

Figure 1. Pin diagram of the AP3766


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