Infineon Technologies Ag

Harald Zoellinger

Marc Fahlenkamp

Martin Feldtkeller

Xiao Wu Gong

Hartmut Jasberg

In a switching mode power supply, an input received from the secondary side of the transformerand indicative of the power being drawn by the loads is used to control the timing of bursts. The input is compared with two threshold different threshold values V, V, and switching is enabled if the input rises above a first higher threshold value V, and disabled if it falls below a second lower threshold value V. A memory device FFcontrols a current limitation circuit which limits currents in the primary of the transformer when the switching mode power supply is operating in the burst mode.

Switching mode power supplies

A switched mode power supply includes a primary coil, a switch element, a secondary circuit, and a control circuit. The switch element is wired in series with the primary coil, for applying a DC voltage to the primary coil according to a control signal. The secondary circuit is coupled to the primary coil with output terminals providing an output voltage. The control circuit prepares the control signal with a feedback signal dependent on the output voltage supplied to the control circuit. The control circuit includes a signal generation circuit to create the control signal and a protection circuit. The protection circuit has the effect that no control signal is delivered to the switch element, if the feedback signal reaches the value of a first reference signal after a first period after starting the control circuit.

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Singapore, Singapore

Harald Zoellinger