Thomson Licensing

Harald Grellmann

Jean-Paul Louvel

Daniel Lopez

The switched mode power supply comprises an inductor, a switching transistor, a controller circuit coupled to the switching transistor, a rectifying means and a feedback regulation loop for providing a stabilised output voltage. It comprises further a protection circuit coupled to an output or input of a comparator of the controller circuit for providing an overvoltage protection in case of a failure of the regulation loop. The protection circuit comprises in particular an integrating circuit and a comparating circuit. In a preferred embodiment, an output of the protection circuit is coupled to a sense input of the controller circuit, for switching off the controller circuit immediately in case of a failure. In another aspect of the invention, the protection circuit comprises further a second comparator coupled to the first comparating circuit for the surveillance of the input voltage of the switched mode power supply, and for the detection of a short circuit of the inductor or the rectifying means.

Over-voltage protection circuit for a switched mode power supply

The circuit arrangement comprises a driver stage and a control circuit coupled to the control input of a switching transistor. The driver stage provides a switching voltage for the operation of the switching transistor, and the control circuit provides a shaping of the switching voltage in the sense of delaying the switching through of the switching transistor. The control circuit comprises in particular a control transistor, which is coupled a control input via a high pass filter to the output of the driver stage and with an current input to the control input of the switching transistor. The switching transistor is for example a MOSFET being used for switching on and off a capacitive load.

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Munich, Georgia

Harald Grellmann