Secondary output holdover circuit for a switch-mode power supply

摘要

In a switching power supply generating at least a first output voltage and a second output voltage, the second output voltage, being of lower potential is applied to a linear regulator, the power supply further including a storage capacitor on the first output, a holdover circuit includes a comparator circuit for monitoring the first output voltage and for generating an output signal when the first output voltage decreases below predetermined value. A switch is connected to the storage capacitor, the comparator circuit, and the linear regulator. The switch is activated by the comparator output signal and applies the voltage stored in the storage capacitor to the linear regulator. A clamp circuit is connected to the switch for limiting the magnitude of the voltage from the storage capacitor to the linear regulator when the switch is activated.