Design And Research Of Multi-Channel Synchronous Rectifier DC-DC Converter

With the rapid popularization of portable products, researching and designing power management chips will have been paid more and more attention. Compared to other types of power management chips, DC-DC converters possess many advantages, such as small volume, high efficiency, light weight, which makes it has a good application propect. In terms of the DC-DC converters with high precision, frequency and efficiency, the technology abroad is more advanced than at home. So it is very valuable to do the research on the DC-DC converters with high performance.This dissertation studies the multi-channel synchronous rectifier DC-DC converter. It integrated three channels(two Buck DC-DC converters, a Boost DC-DC converter) in a chip and the switch power transistor and rectifier transistor are installed outside, which greatly saves the chip area and improves the integration of the chip.In the realization of system stability, this paper studies and designs the current loop compensation and the voltage loop compensation. In order to prevent the duty cycle from being greater than 50% and the inductance current oscillation occurring in the current loop, slope compensation technology is put forward to making the system in any duty cycle stable. In the voltage loop, it is necessary to do the analysis of transfer function of the system and find the system zero and pole, using the zero with compensating network to compensate the pole of system and increase the voltage loop phase margin. Over-compensation will reduce system response rate and less-compensation will lead to system oscillation easily. Therefore, selecting the appropriate compensation network of DC-DC converter design is the most important difficulty.Due to the realization of system efficiency, this paper studies the multi-channel synchronous rectifier DC-DC converter by using synchronous of rectifier technology, which reduces the consumption of rectifier diode. Adding the zero crossing detection circuit makes the system work in discontinuous mode and achieve high efficiency. By using PWM and PFM modulation method at the same time, it reduces the switching frequency of system or turns off the oscillator in the light load, it achieves high efficiency. And the circuit of the three channels will be used in the chip-level as much as possible, such as over temperature protection, soft start circuit, bandgap and low dropout regulator. It reduces the loss of static consumption and improves the system efficiency.Finally, the dissertation gives the analysis of the main circuit models and simulation results of the multi-channel synchronous rectifier type DC-DC converter. The simulation results show that Buck DC-DC converter output ripple is less than 10 m V, linear regulation is 0.13%/V and load regulation is 0.52%/A; the Boost DC-DC converter output ripple can be done about 50 m V, linear regulation is 0.24%/V and load regulation is 1.4%/A.System efficiency can reach above 90% and the quiescent current can be less than 1m A. The design of multi-channel synchronous rectifier DC-DC converter in this dissertation can achieve good performance.