| The power that the thesis studies mainly apply to electromagnetic particle detector(ED)in large high altitude air shower observatory(LHAASO).220 V AC in the high and low voltage DC power is used as input voltage,then output +5.5V,-5.5V DC and continuously negative adjustable high voltage which ranges from 0V to 1500 V through internal voltage converter.Core target of LHAASO project is detecting the origin of cosmic ray and studying its accelerating and propagating physical mechanism.For the purpose of detecting more cosmic ray particles,researchers choose plateau section as research site,because of its high altitude(4300m),low pressure(0.6atm)and large temperature differences between day and night.The number of electromagnetic particle detector in LHAASO array is more than 5000,and they distribute within the scope of 1 square kilometers averagely,thus researchers need modular high and low voltage DC power supply and the data collection and analysis system(Electronics).The structure and the function of every ED are the same,which are consisted of closed opaque metal shell,lead plate,scintillant,wave length shift fiber,photomultiplier,electronics and high-low voltage power.+5.5V and-5.5V supply power for the electronics of ED,high direct voltage supply differential pressure for all dynode and anode of photomultiplier so as to realize the transformation of photoelectric signal.To safeguard the fault-free running of the Electronics,the low voltage will be enact to 1%;output ripple wave will be less than 1%;output temperature coefficient will be less than 1?.Although the power consumption of one detector is quiet low,the efficiency of the power supply shall be more than 70% to save the power when 5,000 detectors are worked together.To ensure the accuracy for the gain of photomultiplier,the high voltage will be enact to 0.02%;output ripple wave will be less than 0.01%;output temperature coefficient will be less than 0.01?.The High and low voltage DC power's operation mode is switching mode(namely switching power supply).Compared to traditional linear power supply,switching power supply has many merits,such as small in size,light in weight,low power consumption,high conversion efficiency,low noise,low cost etc.However,there are also many weaknesses,such as high ripple,heavily polluted grid,strong electromagnetic interference,power switch is easy to puncture.We researchers have improved much of its defects by EMI smoothing(mainly used to restrain common code interference and differential-mode interference),soft start,Pulse Width Modulation technology(PWM)and PWM Soft switching circuit.When to research high and low voltage DC power supply,the thesis is divided into two sections—low voltage section and high voltage section.In low voltage section,researchers input 220 V AC grid electricity,then the electricity goes through input protection circuit,EMI filter,rectifier filter,DC-DC converter and feedback,control,stabilivolt four steps.In high voltage section,researchers input continuously adjustable high voltage from 0 to 1,500 V to provide the voltage for all poles of the photomultiplier through inputting 200 V low voltage output,using full bridge inverter to realize high-frequency inversion,using high-frequency transformer to realize voltage boost,low-voltage rectifier filter,and incremental PID feedback control pressure four steps.The part with low voltage in the thesis is conducted the rational protection circuit which is protected by the overcurrent and overvoltage,and the surge in the starting up is restricted;the suitable EMI filter is elected,whose reference is also designed;the single-ended flyback converter is elected as the DC conversion circuit through the research on the strengths and weaknesses of BUCK converter,BOOST converter,push-pull converter,half-bridge converter,full-bridge converter,forward converter,single-ended flyback converter,the leakage inductance for the primary coil of the transformer in the single-ended flyback conversion circuit is restricted by RCD clamping circuit to further improve it.In the high voltage section,it designs the rational reference for the resonant inverter;designs the voltage doubling rectifying circuit to reduce the transformation ratio of the transformer;adopts Atmega16 to be the control core,applies to the incremental PID algorithm to protect the power and the PC communication as well as the voltage adjustment and power.It conducts the test on the accuracy of low voltage output,low voltage temperature coefficient,low voltage ripple coefficient and high voltage output,high voltage temperature coefficient,high voltage ripple coefficient as well as the long-term running and other performances.All performances of the power satisfy the requirements of the detection. |
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