Control System Design Of High Voltage Power Supply

X-ray diffractometer plays an indispensable role to solve problems from all aspects, such as physics, medicine, chemistry and so on. And high voltage power supply is the core component of X-ray diffractometer, so there needs to be a high requirement on its stability and control accuracy. In this paper, the research relys on major national special instruments which named as the research and development of “high-end muti-functional X diffration”,and this paper mainly completed the research of main circuit, the design of control circuit and the realization of the software.With the emergence of power devices and the continuous improvement of its performance,high frequency power supply gradually replace the fundamental frequency power supply.Various inverters or resonant networks have been proposed constantly, and in the practical application,usually combine a inverter with a resonant network in order to achieve the design requirement. The full-bridge zero-voltage-switching pulse-width modulation(FB ZVS PWM)converter is most widely used soft-swithed circuit in high-power application. whereas, this circuit has some limitations which exist in two aspects: a loss of duty cycle on the secondary side,and a severe parasitic ringing at the secondary side of the transformer. In this paper, a FB ZVS-PWM converter that employs a coupled inductor is described. This constant-frequency FB ZVS converter achieve ZVS in a wide range of load circuit and input voltage with reduced circulating energy and conduction losses. Because, in the proposed circuit, the energy required to create ZVS conditions does not need to be stored in the leakage inductance. The leakage inductance of the transformer can be minimized, this virtually eliminates the duty cycle loss and also significantly reduces the energy of the secondary-side ringing.On the control strategy, the control used the analog control, digital management mode, so it combines the good stability and dynamic characteristics of analog control with the diversity and multifunction of digital management. In this topology, the output voltage at constant frequency is achieved by the phase-shift technique. Therefore, all the high power devices operations in the duty ratio of 50% under 16 KHz frequency by adjusting the phase-shifting angle of power devices to realize the control of the output voltage. The size of the phase-shifting angle on the high pressure part is accomplished through the pulse modulation controller UC3526. The phase-shifting angle of filament voltage is adjusted by current-mode PWM controller UC3525. In order to achieve high precision and improve the transient response. The compensator of Type ? is added before the controller UC3525.Finally, based on the design of the hardware, the STM32 and CPLD double control scheme of digital management is proposed. This paper also elaborated in detail the whole control process and the realization of each units. STM32 accepts the default from the upper computer and puts the default to the control panel. The CPLD based on the phase-shifting angle of controller UC3526 to generate two PWM signals which is duty ratio of 50%. At the same time, the data on the control panel posed on the upper computer for display. The software design and debugging of programming work also is completed in this paper.