A power converter can include an electrical isolation circuit between input and output nodes. An input signal monitor node can be provided, such as on a converter output side of the isolation circuit. In an example, a peak detection circuit can be coupled to the input signal monitor node. The output node of the power converter can be configured to supply an output power signal that is a function of an input signal at the input node. The power converter can include multiple, independently-switchable switches at one or more of the input and output sides of the isolation circuit. In an example, the power converter with the input signal monitor node can be configured as a bias supply to provide power, at the output node, to a controller circuit for a main stage power converter circuit.