Tripping preliminary regulator circuit for minimising the power loss of in-phase regulators of multi-voltage switched-mode power supplies

摘要

Switched-mode power supply having a transformer (T) which has a primary winding (LP) and at least two secondary windings (LS1...LS4), a rectifier (D11...D42), a smoothing means (DR1...DR4, C91...C94) and an in-phase regulator (LR1...LR4), at which a regulated output voltage (UA1...UA4) can be picked off, being connected downstream of each secondary winding (LS1...LS4), and the primary winding (LP) having a DC input voltage (UE) across it via a controlled switch (S), which is controlled, via a control circuit (PWM) and one control amplifier (PI1...PI2) each for each in-phase regulator input voltage (U1...U4), as a function of this rectified in-phase regulator input voltage (U1...U4). The actual value inputs of the control amplifiers have the respective in-phase regulator input voltages across them, the desired value inputs of the control amplifiers have a fixed desired value voltage (U1Soll...U4Soll) across them, which desired value voltages correspond to the minimum permissible in-phase regulator input voltage (U1...U4), and the outputs of the control amplifiers are connected to the input of the control circuit via a switching network (D1...D4, R0), which switches through to the control circuit only that control amplifier whose output level has a maximum and minimum value related to the output levels of all the control amplifiers. IMAGE