Research On Active-clamp Forward Converter With Synchronous Rectification

With the rapid development of VLSI, the power supply of computer and communication system has a new trend: supply voltage is getting low and the current increases, the power density is also rising at the same time. Therefore, the study of low voltage, high current, high power density DC/DC power supply is in focus in recent years.Forward converter widely used in small and medium power applications, for its simple circuit and the low ripple voltage. This paper use active clamp reset overcomes the disadvantages of traditional forward converter which transformer core only work in first quadrant lead to not high in core utilization. Active clamp reset also reduces the voltage stress of MOSFET, and recycle the energy of magnetize inductance and leakage inductance which improved the efficiency of the converter. However,In the application of low output voltage and high current, the Schottky diode loss prevents further increase in efficiency. Using the synchronous rectifier technology effectively solved the problem.This paper introduces the work principle of traditional single-ended forward converter, and several commonly reset methods were analyzed and compared. Then in-depth analysis of the working process of the active clamp reset. Discussed the conditional for achieve zero-voltage switching and the impact of the delay from the leakage inductance in this process. Combining the practical application, two kinds of clamping methods are also analyzed in detail.To improve efficiency, synchronous rectification technology has introduced. In the paper discusses and analyses several common synchronous rectifier technology, and then the active clamp forward converter with self-driven synchronous rectification is introduced. Further, to reduce the volume of supply, replaced the traditional by using the planar transformer.Finally, made a detailed process of circuit design and completed prototype production and commissioning. The maximum efficiency of 88% and the power density of 36.53W/ in, the ripple voltage is less than 50 mV, it achieves the design requirements.