A conversion control circuit for controlling the operation of a power transistor is disclosed. The conversion control circuit includes a voltage-regulating switch and a control unit. One end of the voltage-regulating switch connects to an external voltage input terminal while another end connects to a voltage-regulating capacitor. The conversion control circuit converts an input voltage inputted from the external voltage input terminal into a power voltage. The power voltage is for supplying operating power to the conversion control circuit. The control unit receives a feedback voltage signal to generate a voltage-regulating pulse signal and a turn-on pulse signal, which are used for controlling the operations of the voltage-regulating switch and the power transistor, respectively and for defining a charging period for charging the voltage-regulating capacitor. A converter including the described conversion control circuit is also disclosed.