In this paper, a rule-base fuzzy logic controller (FLC) used for controlling the output power of a series resonant parallel loaded (SRPL) inverter which is applied for dimmable electronic ballasts is presented. A plasma model of a fluorescent lamp is introduced as the load of the SRPL inverter. The component values of the power stage as well as two switching frequencies according to desired two distinct power levels can be, therefore, determined. The output power of the lamp is controlled by varying the ratio of two time intervals for which the two frequencies last respectively. This mechanism is achieved by using a 25-rule fuzzy FLC. A prototype with the FLC which is implemented on an 8-bit microprocessor with a reduced instruction set computer (RISC) architecture is built. The experimental measurements are used to verify the analyses.
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