INVERTER WITH IMPROVED OVERCURRENT PROTECTION CIRCUIT, AND POWER SUPPLY AND ELECTRONIC BALLAST THEREFOR

摘要

An inverter (100) comprises first and second input terminals (102,104), an inverter output terminal (106), a series arrangement of a first inverter transistor (110) and a second inverter transistor (120), a driver circuit (130), a primary current sensing circuit (150,154,156), and an auxiliary current sensing circuit (160). Primary current sensing circuit (150,154,156) is coupled between second inverter transistor (120) and a current-sense input (132) of driver circuit (130). Auxiliary current sensing circuit (160) is coupled between second inverter transistor (120) and a frequency control input (134) of driver circuit (130). During operation, if the current flow through inverter transistors (110,120) exceeds a predetermined peak limit, auxiliary current sensing circuit (160) provides an auxiliary signal to frequency control input (134) of driver circuit (130), thereby increasing a drive frequency at which driver circuit (130) commutates inverter transistors (110,120). The increase in the drive frequency reduces the peak current flow through inverter transistors (110,120), thereby protecting inverter transistors (110,120) from excessive power dissipation and potentially destructive heating.