| 摘要 |
In a standby mode, a switched-mode power supply circuit may be operated in a burst mode with reduced secondary voltages (Vo1, Vo2) for supplying a standby voltage (Vo1) at a very high efficiency. In a normal operating mode of the power supply, a control circuit (1) is maintained in its on-state by a power supply voltage (Vcc) generated by the power supply. The control circuit (1) supplies control pulses (Vd) for switching the power supply. The burst mode is obtained by decreasing the power supply voltage (Vcc) generated for the control circuit (1) to such an extent that, without any further provisions, the control circuit (1) reaches an off-state in which no control pulses (Vd) are generated. In the standby mode, the control circuit (1) is supplied with current by a power supply circuit (4). In the off-state, the control circuit (1) takes up a smaller power supply current (Icc) from the power supply circuit (4) than it is supplying and the power supply voltage (Vcc) increases until the control circuit (1) reaches the on-state and starts generating the control pulses (Vd). In the on-state, the control circuit (1) takes up a larger current from the power supply circuit (4) than it is supplying and the power supply voltage (Vcc) decreases until the control circuit (1) reaches the off-state again. In this way, the power supply, in the standby mode is each time active during first periods and inactive during second periods. To bring the power supply voltage to the standby mode, the power supply voltage (Vcc) generated for the control circuit (1) is decreased in such a way that also the secondary voltage (Vs1, Vs2) are decreased. |
