An OVP system which includes a plurality of OVP circuits coupled to respective parallel-connected switching power supplies. Each OVP circuit comprises a bus voltage overvoltage detection circuit having a first output which toggles when the voltage on the common power bus exceeds a reference voltage, a modulation flag detection circuit which receives a value that varies with a parameter associated with the PWM or PFM drive signals generated for the switching power supply to which the OVP circuit is coupled and has a second output which toggles when the parameter value exceeds a reference parameter value, logic circuitry which toggles an output when both the first and second outputs toggle, and an overvoltage response circuit which initiates a course of action such as latching or shutting down the switching power supply to which the OVP circuit is coupled when the logic circuitry's output toggles.