The Study On Power Supply System For Medical X-ray Machine

The discovery of X-ray made a great contribution to the advances in the history ofhuman medicine. the X-ray is widely used in the diagnosis and treatment of disease. Thequality of X-ray determines the image quality and affects human health, however, thequality of X-ray machine power supply system determines the quality of X-ray, soresearching on high performance X-ray machine power supply system has the practicalsignificance. The lack of current X-ray machine power supply system mainly reflects inlow frequency, large volume, low efficiency, the rise time of output voltage is long,large ripple. These will seriously affect the quality of the X-ray, increase the damage ofX-ray on the patient.Aiming at the present situation and the existing problems of X-ray machine powersupply, The paper designed for high voltage DC power supply and filament powersupply respectively which composed the X-ray machine power supply system, carriedon the theoretical analysis and the related formula derivation of power system, made thesimulation verification through the Saber simulation software, built the experimentalplatform for experimental verification. That the simulation and experimental resultsaccorded with theoretical analysis achieved the desired effect.At first, this paper expounds the Current situation of the development and thedeficiencies of the Medical X-ray machine power supply, and the impact of powersupply system on the X-ray quality, and the important significance of the quality ofimaging. In this paper, full-bridge inverter LLC resonant soft switch technology wasapplied to X-ray machine power supply system. The resonant soft switch can improvethe working frequency, reduce the volume of power supply, and is helpful to theminiaturization of power system, and solved the problem of large switch loss whichcaused by high frequency, improve the overall efficiency. The full-bridge inverter LLCresonant converter were analyzed in theory, fundamental equivalent model wasestablished, the gain formula was deduced, and the gain curve was drawn for analyzing.The parameters of the resonant elements were designed in detail.Adopted PFM control method, by adjusting the switching frequency to adjust thegain of the resonant tank, so as to realize the output voltage regulation of between40kV~120kV, it was more simple compared to the traditional control method of Buckconnected to full-bridge inverter circuit. The paper designed the PFM control circuits with MC33067chip as the core, and sampling circuit, protective circuit.Adapted passive lossless soft switching Boost APFC circuit of the one cyclecontrol, analyzed one cycle control principle and passive lossless soft switching circuitin detail, and designed the parameters of the PFC main circuit in detail. Introducedone cycle control chip IR1150and its as the core of control circuit was designed.Calculated the open-loop transfer function of PFC circuit, drawn the bode diagram forstability analysis.According to the characteristics that filament power supply only need to provideenough power for heating filament and is not strictly required for waveform, on thebasis of taking full use of the leakage inductance of the transformer and isolationcapacitance, designed filament power supply based on LC series resonance and usedPFM control.Finally, the theory is verified based on Saber simulation software and theexperiment, the simulation and experimental results shown that this design of medicalX-ray machine power supply system achieved the expected effect, and can meet thedesign requirements.