Circuitry for detecting a short circuit of a load in series with an FET

US5086364A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Ludwig Leipold · Munich, DE
• Rainald Sander · Oberhaching, DE
• Jenoe Tihanyi · Tauberbischofsheim, DE
• Roland Weber · Munich, DE

Key dates

• Filing date: Feb 19, 1991
• Grant date: Feb 4, 1992
• Expiry date: Feb 19, 2011

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R31/52
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The voltage (U.sub.DS) on a power MOSFET (1) is compared with a voltage (U.sub.V) derived from the sum of the voltages of a Zener diode (3) and the threshold voltage (U.sub.T) of a second MOSFET (5) to detect a short circuit in a load (2) in series with the power MOSFET (1). When this total voltage is exceeded, the second MOSFET conducts. Its load current is then evaluated as the short circuit signal.