Study And Implementation Of Direct Feedback Technology For High Temperature DC Switching Power Supply Based On Isolation Drive

Switching power supply is the source of energy for all kinds of power electronics device.Its stability and reliability are the guarantee of the normal operation of the electrical equipment.Isolation is to achieve the insulation between the high and low voltage of the front and the back levels through the transformer and other related signal isolation transmission components.Isolation is necessary for switching power supply for some applications that have strict requirements for security and anti-jamming.At present,there are three ways of isolation feedback,such as optocoupler isolation feedback,magnetic isolation feedback and transformer original side feedback.However,in some extreme environmental conditions,such as some high temperature environment like aerospace and oil drilling,the three ways of isolation feedback cannot work well due to the limit of operation temperature of the feedback components and that of feedback precision.In order to solve the problem,this thesis proposes the direct feedback method based on isolation drive.The direct feedback method based on isolation drive designed in this thesis use the way of secondary side control.The feedback signal is collected from the output of the power supply and directly transmitted to the PWM controller,to adjust the duty ratio of the PWM waveform to stabilize the output voltage.The isolation transmission of the control signal between PWM controller and MOSFET is realized by the isolation drive module.In order to realize the isolation,the isolation drive module and power supply module are designed in this thesis.The isolation drive module modulates the PWM signal to the higher frequency signal,and transmits by the pulse transformer to the driver to demodulate to the gate drive signal of the MOSFET,thus the isolation between PWM controller and MOSFET can be achieved.Power supply module includes a new designed start-up circuit and auxiliary flyback power supply module,which can cooperate to supply for the isolation drive module on the primary side of the transformer and PWM controller on the secondary side at the same time.The test prototype of half-bridge switching power supply is made in this thesis.The power inverter circuit,rectifier filter circuit and PWM control circuit are new designed on the basis of the previous work.Meanwhile,two test platforms of ordinary temperature and high temperature are set up to test the prototype.Finally,the analysis of the test results confirms that the new feedback method has good performance under high temperature environments,which is of great significance for the application of switching power supply in some extreme environments.