| A great deal of test instruments will be demanded with home electronic appliances developing in China. The safe test is related to the quality of home electronic appliances directly. So developing a stable and high accurate safe-test instrument is important.The paper analyses the inefficiency in developing instruments and adopts the module method to develop the instrument, which can improve the efficiency. For hardware, the often used parts will be designed in the module board with the standard interface defined. For software, C that is readable and can masks the differents between the different hardware is adopted. The paper also introduces the design of the high-voltage test and leak test instruments and the key unit circuit such as RMS measure, AD conversion, Hardware protect.The paper explores the high-voltage AC power further. The high voltage part of the same kind products in market is composed of bulking transformer which isn't according to the trend to minitype. A switch high-voltage sine out inverter based on SPWM is designed instead of the old transformer. This inverter adopts the double CPU which are communicated with SPI. Master CPU works with user interface and SPWM calculation. Slave CPU receives the SPWM data and output the SPWM wave by query the SPWM table. The dead time is generated by hardware to prevent the H bridge arm from short directly. The power out module is protected for over current, over voltage and over heat. This design is simple and flexible, the parameters of spwm are adjustable, and the sine output is quality. In order to reduce EMI, PFC is designed which eliminate the disturb to power net and itself.The design adopts the normative procedure. First, the SPWM is validated by math tool matlab, which prove the data of SPWM is consistent with the theory. Second, the SPICE circuit model is simulated by protel99SE which is also proved. Finally, the sine in SPWM is output by actual physical circuit. The math is important to the success of the design. |
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