| The control techniques of switching converters are completely described and analyzed. The advantages and disadvantages of each method , such as PWM, Softswitching ,are analyzed and compared , and where each method is more adapted to is pointed out.PWM ( Pulse Width Modulation ) is the normal control mode in DC/DC converter. Because of its fixed frequency, the efficiency of PWM converter with low loads is lower, In order to solve this problem a novel control mode named SCM (Skip Cycle Modulation) in switching DC/DC converter is developed .The principles .and the control demand of SCM converter is discussed . By using PSPICE tools, the simulations of output voltages and currents of power device with different loads are given and compared with PWM converter.The principles and the characteristics of SCM are described . SCM controller regulates the operation of the power device at the full frequency or skip cycles according to the loads in order to keep the output voltage of converter steadily. The response speed of SCM converter is faster, the efficiency of the system with low loads is higher. The ripple of output voltage is big with the low loads and need to be fixed to get low EMI. All of these indicate that SCM is a better control mode in high frequency switching DC/DC converter.
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