| The field of power electronics is concerned with the processing of electrical power using electronic devices. Switch-mode power supply (SMPS) is an important part of power electronics technology. The power electronic circuits can be divided into four basic types: AC-DC, DC-AC, AC-AC, DC-DC. The working principle of DC-DC converter is to use the switching signals which is produced by the control circuit and modulated by the error signal to make the power transistor conduction or deadline, as well as the inductance, capacitance, and flowing diode to realize voltage conversion.According to whether the main circuit inductance current drops to zero in a switch cycle, switching power supply has two operational modes, continuous model (CCM) and discontinuous mode (DCM). This paper gives an analysis how to determine the mode switching a power supply should work in. Switching power converter in discontinuous current mode has a higher efficiency than that of discontinuous current mode. But its drawback is the poor ability to load. Lightweight should choose driven converters working in discontinuous current mode.According to feedback control variables, switching power converter can be divided into two kinds: voltage control mode and current control mode; According to whether the pulse frequency is stably, switching power converter can be divided into two other kinds: pulse width modulation mode and pulse frequency modulation mode. Voltage control mode samples the output voltage, as a feedback control signal to achieve closed-loop control, in order to stabilize the output voltage. Current mode control based on the output voltage feedback sampling increases the inductor current as the feedback variable, and the inductor current is no longer a separate volume, so that the closed-loop system changes into an unconditionally stable system. Current-mode control has a greater bandwidth, very good line regulation as well as peak current-limiting function; which make the feedback compensation network,... |
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