Inverter firing control with error compensation

Claim 1

A pole switch firing control circuit for controlling a pulse width modulated inverter in accordance with a reference pulse signal, said control circuit comprising: means for receiving a clock signal containing voltage pulses; means for generating a control signal having transition points for initiating a pole switch switching sequence in the inverter; a first counter for counting the number of said clock voltage pulses which occur between a selected transition point in said control signal and the switching of an associated pole switch; memory means for storing the number of clock voltage pulses counted by said first counter during each pole switch switching sequence; and a second counter being presettable to start counting at a number equal to the number of clock voltage pulses previously counted by said first counter during the preceeding switching sequence of said associated pole switch, and connected to count said voltage pulses which occur after a preselected transition point of said reference signal until a preselected count has been reached, whereupon said second counter produces a carry output signal pulse which causes said means for producing a control signal to create a second transition point in said control signal.

Claim 9

A method of controlling the switching of a power pole switch in a pulse width modulated inverter in accordance with a reference pulse signal, said method comprising: counting a series of clock pulses, which occur between a preselected transition point in a control signal and the switching point of a power pole switch in response to said transition point, with a first counter; presetting a second counter at a count equal to the number of clock pulses counted by said first counter during a preceding switching cycle of said power pole switch; operating said second counter to count clock pulses, beginning at the preset count, when a preselected transition point occurs in a reference signal; and causing a second transition point in said control signal to occur when said second counter reaches a predetermined count, thereby initiating a second switching cycle of said power pole switch.

Claim 10

A method of controlling the switching of a power pole switch in a pulse width modulated inverter in accordance with a reference pulse signal, said method comprising: counting a series of clock pulses, which occur between a preselected transition point in a control signal and the switching point of a power pole switch in response to said transition point, with a first counter; presetting a second counter at a count equal to the number of clock pulses counted by said first counter during a preceding switching cycle of said power pole switch; operating said second counter to count clock pulses, beginning at the preset count, when a preselected transition point occurs in a reference signal; and causing a second transition point in said control signal to occur when said second counter reaches a predetermined count, thereby initiating a second switching cycle of said power pole switch.