A protection circuit applied to a convertor including M pieces of driving switch modules each coupled to a power source, a load and one of M sets of driving signals. The ith driving switch module is controlled by the ith set of driving signals to selectively enable current paths between the power source and the load. A first sub protection circuit in the protection circuit includes a first protection switch module and a first detection module coupled to the first protection switch module. When the ith set of driving signals indicates an error event, the first protection switch module selectively couples the ith set of driving signals to a reference voltage according to a first detection signal. M and i are positive integers, and i is not larger than M.