| 摘要 |
<p>A power supply circuit for generating a stabilized power supply generally comprises a series arrangement of a primary winding (7) of a transformer (T) and a switch (9). The switch is controlled by means of a control circuit (21), an input of which receives a signal (Vfb) related to the output voltage of the power supply circuit. The control circuit (21) determines the duty cycle of the switch (9). Dependent on the power consumption of the load (Rb) connected to the output of the power supply circuit, the duty cycle is either increased or decreased. The duty cycle has a given minimum value which is caused by the inertia of the switch (9) upon switching on and switching off. The minimum duty cycle may be reached, inter alia, when the power supply circuit works in an apparatus using a standby mode. With reference to the power to be supplied to the load and/or with reference to the duty cycle, the power supply circuit according to the invention determines the moment when the frequency of the control signal to be generated by the control circuit is switched to another fixed frequency. <IMAGE></p> |
