Switching power supply
AssigneeDensei-Lambda Kabushiki Kaisha
InventorSatoshi Tomioka
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Abstract
A switching power supply which feeds energy stored in a choke coil 7 to a load 11 through a freewheeling element when a switching element 2 turns off. The switching power supply includes a freewheeling MOSFET 6 serving as the freewheeling switch element which operates synchronously with the switching element 2 and a surge voltage prevention circuit 32. The surge voltage prevention circuit 32 detects a timing for a current to flow in the direction that a body diode 16 of the freewheeling MOSFET 6 conducts when an operation stoppage signal to the switching element 2 is outputted, and then turns off the freewheeling MOSFET 6 at the timing.
Claims12
A switching power supply in which energy is supplied to a smoothing choke coil from a secondary winding of a transformer via a rectifier element when a switching element turns on, while the energy stored in the choke coil is fed to a load through a freewheeling element when the switching element turns off, in which at least said freewheeling element includes a freewheeling switch element which operates synchronously with said switching element, said the switching power supply comprising:
- an unidirectional conductible element which is connected in parallel with reverse polarity across said freewheeling switch element;
- and
- a surge voltage prevention circuit which detects a timing for a current to flow in a direction in which said unidirectional conductible element conducts by detecting a falling edge of a pulse drive signal fed to said switching element when an operation stoppage signal to said switching element is outputted, and then turns off the freewheeling switch element at this timing.
Dependencies are inferred from the claim text.