1. Field of the Invention
The present invention relates to a circuit breaker used in a power semiconductor device, such as an inverter that passes large current, and specifically to a small and low-cost circuit breaker that can reliably break a circuit regardless of operating conditions, and has a small wiring loss.
2. Background Art
There is a case wherein an element of an inverter for driving a motor installed in a hybrid motor vehicle or the like is broken to be a short-circuited state, and regenerative current flows back from a motor rotated by an engine power. In order to prevent the flow of a large current into the circuit in such abnormality, a circuit breaker has been used. As a circuit breaker, a device wherein a fuse is broken by the heat of a heater has been proposed (see, for example, Japanese Patent Laid-Open No. 6-119858).
In a conventional circuit breaker, a heater was serially inserted in a current path, and a fuse was broken when a larger current than in normal operation flows in abnormality. However, in the case of a hybrid vehicle or the like, since there was no significant difference in the current value for driving a motor in normal operation and the regenerative current value from the motor in abnormality, the fuse cannot be reliably broken. In addition, since an electric resistor serially inserted in a current path was used as the heater, there was a problem of large wiring loss. If the fuse was substituted by a relay, although the circuit was reliably broken, there were problems of contact resistance, costs, and a space.