Abstract: A power supply apparatus converts an input voltage (2) into a first (3) and a second output voltage (7). The first (3) and the second output voltage (7) are put into and/or out of operation sequentially. The power supply apparatus comprises a first converter unit (1) which converts the input voltage (2) into the first output voltage (3), and a second converter unit (5) for providing the second output voltage (7). The second converter unit input (6) is coupled to the first converter unit output (3). The second converter unit (5) can only start and provide an output voltage after the first converter unit (1) has started. During power-down, a sequence is created in which the second converter unit remains operational until any capacitance coupled to the first converter unit output has been discharged.

Abstract: A switched mode power supply apparatus is equipped with a start-up device supplying electrical energy to a controller which controls the switching of a switching transistor. The start-up device is bypassed by a bypass device. During start-up of the power supply, the bypass device is open. After a successful start-up, the bypass device is closed, eliminating further dissipation in the start-up device, and, therefore, increasing the overall energy efficiency of the power supply. By connecting the start-up device to a stand-by power supply or to a primary voltage, use of an additional winding on the transformer to supply the controller is obviated. The power supply has an electronic overload protection, and will stop and periodically attempt a restart when an overload condition occurs.

Abstract: A power supply apparatus converts an input voltage (2) into a first (3) and a second output voltage (7). The first (3) and the second output voltage (7) are put into and/or out of operation sequentially. The power supply apparatus comprises a first converter unit (1) which converts the input voltage (2) into the first output voltage (3), and a second converter unit (5) for providing the second output voltage (7). The second converter unit input (6) is coupled to the first converter unit output (3). The second converter unit (5) can only start and provide an output voltage after the first converter unit (1) has started. During power-down, a sequence is created in which the second converter unit remains operational until any capacitance coupled to the first converter unit output has been discharged.

Abstract: In a protection circuit for a plurality of fans, an element is associated with each fan. The impedance or the current value of the element indicates the operation condition of the fan. For example, the impedance or the current value may be low if the fan is operative or functioning normally, and high when the fan is inoperative or functioning abnormally. The elements are arranged in parallel between two conductive lines. A detection circuit determines the total impedance or current value between the two lines. If the total impedance or current is not within a predetermined range which indicates that all fans are operating normally, at least one of the fans functions abnormally. The number of lines required to convey the operation status of the fans to the detection circuit is only two and does not depend on the number of fans involved.

Abstract: A switched mode power supply apparatus is equipped with a start-up device supplying electrical energy to a controller which controls the switching of a switching transistor. The start-up device is bypassed by a bypass-device. During start-up of the power supply, the bypass-device is open. After a successful start-up, the bypass-device will be closed, eliminating further dissipation in the start-up device, and therefore increasing the overall energy efficiency of the power supply. By connecting the start-up device to a stand-by power supply or to a primary voltage, use of an additional winding on the transformer to supply the controller is obviated.

Abstract: In a protection circuit for a plurality of fans, an element is associated with each fan. The impedance or the current value of the element indicates the operation condition of the fan. For example, the impedance or the current value may be low if the fan is operative or functioning normally, and high when the fan is inoperative or functioning abnormally. The elements are arranged in parallel between two conductive lines. A detection circuit determines the total impedance or current value between the two lines. If the total impedance or current is not within a predetermined range which indicates that all fans are operating normally, at least one of the fans functions abnormally. The number of lines required to convey the operation status of the fans to the detection circuit is only two and does not depend on the number of fans involved.