| 摘要 |
A switched mode power supply comprising a switched mode converter (12) and a controller (16) for controlling the switched mode converter, the switched mode converter being provided for converting an input voltage (Vin ) to an output voltage (Vout) and including, on a primary side, a primary winding (X1) and a controllable switch based circuitry (31) connecting the input voltage over the primary winding; and, on a secondary side, a secondary winding (X2) coupled to the primary winding, and a capacitive element (C) connected over the secondary winding, wherein the output voltage is obtained as the voltage over the capacitive element: The primary winding comprises a first winding portion (np1) and at least one further winding portion (np2); and the switch based circuitry comprises controllable switches (Q11, Q4, Q12, Q42,Q2, Q31) (i) capable of controlling the duty cycle of the switched mode converter and (ii) capable of switching between a first operation state wherein the input voltage is connected only over the first winding portion and at least a second operation state wherein the input voltage is connected over the first and the at least one further winding portions, thereby enabling switching between two different transformer ratios (n1, n2). The controller comprises a first control arrangement (51, 52) (i) connected to monitor the output voltage (Vout) of the switched mode converter and (ii) operatively connected to the controllable switches to control the controllable switches to switch to thereby control the duty cycle in response to the monitored output voltage and a reference voltage using PID feedback control; and a second control arrangement (16a) (i) connected to monitor the input voltage (Vin) of the switched mode converter and (ii) operatively connected to the controllable switches to control the controllable switches to switch between the first and the at least second operation states in response to the monitored input voltage. |
