Control and drive circuit and method

The invention provides a control and drive circuit applied to a synchronous rectification switching mode power supply. The circuit comprises a primary switching tube controller, a logic circuit, a switching circuit and a synchronous rectifier tube controller, wherein the primary switching tube controller is used for generating a primary switching tube control signal, the logic circuit is used for generating a first control signal according to received primary switching tube control signal, the switching circuit is used for generating a second control signal according to the received first control signal, and the synchronous rectifier tube controller is used for generating a synchronous rectifier tube control signal according to the received second control signal and guaranteeing phases of the primary switching tube control signal and the synchronous rectifier tube control signal to be the same or inverse according to a topological structure of the synchronous rectification switching mode power supply. The invention further provides a control and drive method, so that the synchronous rectifier tube control signal for controlling on and off of a synchronous rectifier tube is generated according to the primary switching tube control signal, the problem of cross connection of the synchronous rectification power supply is solved, and high frequency, low cost, small size and high efficiency of the synchronous rectification switching mode power supply are achieved.