Forward-flyback topology switched mode power supply

摘要

A switched mode power supply (400), comprising a transformer (410) having a primary winding (410-1), a transformer core (410-3) configured to store energy transferred thereto from the primary winding (410-1) during operation, and a secondary winding (410-2) having a first terminal (T1) and a second terminal (T2). The switched mode power supply also has a primary side circuit (Q1, Q2, C1) arranged to generate voltage pulses and thereby to drive the primary winding (410-1) of the transformer (410), and a secondary side circuit comprising a rectification circuit connected to the secondary winding (410-2) at the first and second terminals (T1, T2). The rectification circuit is arranged such that during a forward phase of operation of the switched mode power supply, in which the primary winding (410-1) is driven by the primary side circuit to magnetize, and store energy in, the transformer core (410-3), a current induced to flow in the secondary winding (410-2) from the second terminal (T2) to the first terminal (T1) is output by the rectification circuit. The rectification circuit is further arranged such that during a fly-back phase of operation of the switched mode power supply, in which the magnetization of the transformer core (410-3) is reset, a current induced to flow in the secondary winding from the first terminal (T1) to the second terminal (T2) of the secondary winding (410-2) is output by the rectification circuit so that energy stored in the transformer (410) during the forward phase of operation is output by the rectification circuit.

主权项

1. A switched mode power supply, comprising:
a transformer comprising a primary winding, a transformer core configured to store energy transferred thereto from the primary winding during operation, and a single, non-tapped secondary winding having a first terminal and a second terminal; a primary side circuit arranged to generate voltage pulses and thereby to drive the primary winding of the transformer; and a secondary side circuit comprising a rectification circuit connected to the secondary winding at the first and second terminals, wherein the rectification circuit is semi-synchronous, comprises one or more transistors and one or more diodes, and is arranged such that:
during a forward phase of operation of the switched mode power supply, in which the primary winding is driven by the primary side circuit to magnetize, and store energy in, the transformer core, a current induced to flow in the secondary winding from the second terminal to the first terminal is output by the rectification circuit; andduring a fly-back phase of operation of the switched mode power supply, in which the magnetization of the transformer core is reset, a current induced to flow in the secondary winding from the first terminal to the second terminal of the secondary winding is output by the rectification circuit so that energy stored in the transformer during the forward phase of operation is output by the rectification circuit; and wherein the secondary side circuit further comprises a voltage limiter circuit configured to provide signals from the secondary winding to one or more gate terminals of the one or more transistors.