1. Field of the Invention
The present invention relates to an inverter circuit.
2. Description of the Background Art
An inverter circuit generally includes high-voltage and low-voltage switching elements connected in series between a power supply potential and a GND potential, and high-voltage and low-voltage drive circuits for respectively controlling actuation of the high-voltage and low-voltage switching elements. The inverter circuit conventionally used is introduced in Japanese Patent Application Laid-Open Nos. 2003-178895, 9-219977 (1997), 10-42575 (1998), and in PCT Publication No. WO 01/59918, for example.
The conventional inverter circuit faces the problem below.
At the time when the high-voltage switching element is turned off, the inverter circuit is placed in a free-wheeling mode of an FWD connected in inverse-parallel to the low-voltage switching element (FWD of the lower arm). At this time, a negative surge voltage is generated at an output terminal of the inverter circuit, which voltage is the product of di/dt during turn-off of the high-voltage switching element and an inductance in a free-wheeling loop of the FWD of the lower arm. This surge voltage, when being at a predetermined level or higher, may cause breakdown or malfunction of the high-voltage drive circuit. A higher switching current is likely to generate increase in surge voltage, thus causing difficulty in obtaining a large current-carrying capacity of the inverter circuit.