Compared with traditional light sources, LEDs are characterized by high efficiency and long service life. Therefore, it has become the first choice for lighting to reduce indoor and outdoor energy consumption. This is especially true for street lighting. Resonant converters improve power efficiency and are one of the most popular power supply topologies. The LLC resonant converter has attracted attention due to the improvement of high power conversion efficiency and low-voltage stress of the secondary rectifier.
However, complex design and high manufacturing costs make it difficult for LLC resonant converters to get to market quickly. One problem with LLC is that it is a large ring current that requires a zero voltage switching power supply. LLC resonant converters cause relatively high power losses at light loads. When the diode performance of the MOSFET is not good, the LLC resonant converter will have many potential failures and problems. The dual-tube flyback converter is designed to solve the problems of LLC resonant converters as an alternative. Efficiency is increased by adding a switch to the high side and then using the leakage inductor energy to the input current. Unbuffered circuits and losses. The dual-tube flyback topology is suitable for a 120W switching power supply. Details of the design specifications and test results are presented below.
Project leader: Won-Seok Kang, who has worked for Fairchild Semiconductor since 2006 and is currently a senior application engineer in the energy conversion department. His research focuses on functional power modules, LED drivers , resonant and soft-switching dc/dc converters, and electronic ballasts. He also holds a bachelor's and master's degree in electrical engineering.
Double switch quasi-resonant flyback topology
The two-switch quasi-resonant flyback topology actually reduces the losses in the clamp circuit. In addition, the quasi-resonant mode of operation of the FL6300A reduces switching losses and ensures high efficiency. Figure 1 is a simplified illustration of the proposed dual switch quasi-resonant flyback converter. The FL7930B is an active power factor correction (PFC) controller, and the FL6300A is a quasi-resonant mode current mode PWM controller for illumination. The FAN7382 can drive two high-side and low-side MOSFETs. The new 600V 385 ohm superjunction, D-PAK packaged MOSFET is used in PFC switches and flyback switches. Conventional single-stage switching flyback converters use RCD clamp circuits to convert leakage inductance energy into heat loss. The dual-switch quasi-resonant anti-excitation uses the leakage inductor energy to the input current to clamp the highest voltage of the MOSFET into the input voltage. Limiting the maximum voltage of the MOSFET, clamping the input voltage is beneficial for reliability. In a single-stage switching flyback converter, it is difficult to control the highest voltage value of the MOSFET, so that a voltage exceeding a value often occurs, causing a short circuit or an overload failure. Limiting the maximum voltage of the MOSFET can increase the low-voltage stress of the secondary rectifier without increasing the power consumption of the clamp circuit. (Laura translation) (to be continued)
Figure 1 Suggested conversion diagram
Material and the process
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