Control method and control circuit for voltage switch circuit and usb power delivery

A control circuit, comprising:

• a) a voltage switch circuit having an output voltage to be switched from a first voltage input to a first switch circuit to a second voltage input to a second switch circuit, wherein outputs of said first and second switch circuits are coupled together to provide said output voltage;
• b) a switch control signal generating circuit configured to generate a first switch control signal according to a first reference voltage and said output voltage to control said first switch circuit before said second switch circuit starts conducting, wherein said output voltage is no greater than a second reference voltage, and said second reference voltage equals a smaller one of said first and second voltages;
• c) said switch control signal generating circuit being configured to generate a second switch control signal according to said first reference voltage and said output voltage to control said second switch circuit to switch said voltage switch circuit to said second voltage, and
• d) said switch control signal generating circuit being configured to generate said first switch control signal according to said second reference voltage and said output voltage when said second switch control signal is generated, in order to control said first switch circuit to turn off after said second switch circuit conducts and when said output voltage is no larger than said second reference voltage;
• and
• e) a first reference voltage generating circuit configured to generate said first reference voltage according to said output voltage and said second reference voltage, wherein said first reference voltage is configured as a reference voltage of said output voltage.