Secondary control device and charging system having the same

A charging system, comprising:

• a charging interface, configured to be connected with a load terminal;
• a transformer, having a primary winding, a secondary winding and a feedback winding, wherein the secondary winding is connected with the charging interface and is controlled to generate a mutation voltage;
• a rectifier module, configured to convert an input alternating current into a direct current and to charge the primary winding according to the direct current;
• a secondary control device connected with the transformer, wherein the feedback winding is configured to receive the mutation voltage feedback from the secondary winding, and to generate an output voltage switching signal according to the mutation voltage;
• and
• a primary control device comprising a primary control chip, a detecting resistor and a primary switch connected to ground via the detecting resistor, wherein the primary control chip has a voltage feedback terminal sampling the output voltage switching signal and a feedback voltage of the feedback winding and a voltage detecting terminal sampling a voltage of the detecting sensor, and is configured to generate a selection signal according to the output voltage switching signal, and to control the primary switch according to the selection signal, the voltage of the detecting resistor, and the feedback voltage of the feedback winding, so as to adjust an output voltage and an output current of the charging system.