The present invention relates to an isolated interface circuit for detecting a DC link voltage using a photo coupler in a system for driving a motor. An interface circuit for detecting a DC link voltage in a system for driving an electric motor according to the present invention includes a voltage distribution means for distributing a DC link voltage, and an output voltage detected by detecting a voltage distributed through the voltage distribution means. A first photo coupler for voltage detection for providing, a second photo coupler for compensation for providing an output voltage detected in response to an input voltage, and an error between an output voltage of the first photo coupler and an output voltage of the second photo coupler Error detecting means for detecting a signal, and a proportional integration controller for proportionally integrating the output of the error detecting means. Here, the second photo coupler is fed back as an input of the output voltage of the proportional integral controller. According to the configuration of the present invention, while using a low-cost photo coupler instead of a conventional high-cost photo coupler for the detection of the DC link voltage, compensating for the nonlinearity of the low-cost photo coupler by using a compensation photo coupler, It is possible to provide an isolated interface circuit that can secure a linear section.
展开▼
