Patent ID: 7187567

Claim:
A method of operating a bridge circuit comprising an input that receives a direct current (DC) supply of nominal voltage +V S , an output having an electromagnet connected thereacross, first and second arms having first and second switches, respectively, the first and second arms being connected to opposed ends of the electromagnet, the method comprising the steps of: (a) receiving a voltage demand signal indicative of a desired voltage of an electrical signal to be supplied to the electromagnet in a period; (b) generating first and second switching signals with reference to the voltage demand signal; and (c) applying the first and second switching signals to the first and second switches, respectively, during the period; wherein the switching signals cause the switches to switch between on and off states, switching between various combinations of on and off states of the first and second switches producing an electrical signal across the electromagnet with voltage pulses at levels of nominally +V S , 0V and −V S , the first and second switching signals being generated such that an average voltage of the electrical signal supplied to the electromagnet during the period is substantially equal to the desired voltage.