Overvoltage protection circuit with internal diagnostic function

Abstract

Provided is an overvoltage protection circuit that is capable of detecting a single internal failure and capable of stably supplying a power supply voltage to a downstream circuit during an internal diagnosis. A calculation unit (10) of an overvoltage protection circuit (100) outputs first and second diagnostic pulse signals (Pd1, Pd2). A voltage monitoring unit (30) outputs a signal (Vmon), and a voltage comparison unit (50) outputs a signal (Vcmp). A discharge unit (70) and a diagnostic signal input unit (90) are connected to a connection point (N1) between first and second switches (M4, M2). A voltage holding unit (80) and a second power supply (Vcc2) are connected to the drain of the second switch (M2). The signal (Vcmp) is input to the first and second switches (M4, M2) and the discharge unit (70). When the first or second diagnostic pulse signal (Pd1, Pd2) is output, a voltage (Vnod) at the connection point (N1) is reduced, and the degree ΔV of reduction in voltage of the second power supply (Vcc2) is less than or equal to a first prescribed value.

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