Power supply input voltage detection circuit

Abstract

The present invention discloses a power supply input voltage detection circuit. The power supply converts an input voltage to an output voltage by a transformer which includes a primary winding and a secondary winding. The primary winding is coupled to a power switch, which receives a switching signal to adjust the output voltage. The power switch is coupled to a sensing circuit; when the power switch turns ON, the sensing circuit generates a current sense signal according to current through the primary winding. The input voltage detection circuit includes: a rising time detection circuit, which detects a period, of time during which the current sense signal rises from a low reference level to a high reference level to generate a timing signal; and a determination circuit, which generates a determination signal according to the timing signal for determining whether the input signal is a high voltage or a low voltage.

Dependencies are inferred from the claim text.