Abstract: A method of controlling a six pulse bridge phase controlled rectifier using a microprocessor is provided by the invention herein. The method involves synchronizing an oscillator to the frequency of an ac power source and driving first and second counters with the oscillator. The first counter is used in conjunction with a phase locked loop to monitor and adjust the oscillator frequency. The count of the second counter generates an .alpha. value used in a firing angle match routine. The match routine compares the desired output voltage to the cosine of .alpha. minus an inductance factor. The match routine takes less than 20 microseconds to run allowing a new .alpha. value to be checked every 0.5 degrees for a 60 hertz power source. When a match is found, the thyristors are fired and a reload value projecting a subsequent firing in 60.degree. is calculated for the second counter.