Abstract: A switch mode power supply and its start-up circuit produce a controlled output voltage from an input voltage. A power supply control circuit is powered by the output voltage and is responsive to the output voltage to control the power supply. The control circuit responds to differences between a fraction of the output voltage and a reference voltage to control the start-up circuit. This control is inhibited at low values of the output voltage to ensure that the power supply starts up correctly despite the reference voltage being indefinite or unstable at such low values of the output voltage.

Abstract: A power supply controller controls power supplies for power-up and/or shut-down in a desired sequence. An input voltage for the power supplies powers, and is monitored by, a first control unit having outputs for enabling the power supplies. A second control unit monitors output voltages of the power supplies, and an isolating signal coupler couples signals in both directions between the first and second control units. The second control unit is powered in an isolated manner from the input voltage, conveniently via a transformer constituting the signal coupler. The control units together respond to the monitored voltages for enabling the power supplies in accordance with the desired sequence, information for which can be stored in a non-volatile store. The second control unit can also include enable outputs isolated from the input voltage, and trim outputs for adjusting the monitored voltages.

Abstract: A switch mode power supply and its start-up circuit produce a controlled output voltage from an input voltage. A power supply control circuit is powered by the output voltage and is responsive to the output voltage to control the power supply. The control circuit responds to differences between a fraction of the output voltage and a reference voltage to control the start-up circuit. This control is inhibited at low values of the output voltage to ensure that the power supply starts up correctly despite the reference voltage being indefinite or unstable at such low values of the output voltage.

Abstract: A power supply controller controls power supplies for power-up and/or shut-down in a desired sequence. An input voltage for the power supplies powers, and is monitored by, a first control unit having outputs for enabling the power supplies. A second control unit monitors output voltages of the power supplies, and an isolating signal coupler couples signals in both directions between the first and second control units. The second control unit is powered in an isolated manner from the input voltage, conveniently via a transformer constituting the signal coupler. The control units together respond to the monitored voltages for enabling the power supplies in accordance with the desired sequence, information for which can be stored in a non-volatile store. The second control unit can also include enable outputs isolated from the input voltage, and trim outputs for adjusting the monitored voltages.

Abstract: A reset circuit produces a composite reset signal, in dependence upon a supply voltage, from reset signals produced by three reset units. A first unit produces its reset signal in dependence upon a precise voltage comparison. A second unit, operable at lower values of the supply voltage than the first unit, produces its reset signal in dependence upon the forward voltage drop of a diode. A third unit produces its reset signal in dependence upon charging of a capacitor from the supply voltage via a resistance, to maintain the composite reset signal for at least a predetermined period.