Overvoltage protection for an integrated circuit
US3970900A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 19, 1974 |
| Grant date | Jul 20, 1976 |
| Priority date | — |
| Expiry date | Dec 19, 1994 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H9/046
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A pass transistor is coupled serially with an integrated circuit across a DC energy source. The DC source includes a battery coupled in parallel with a charging transformer output and a diode, the negative side being connected to ground. A resistor is coupled across the pass transistor collector and base to assure conduction by the pass transistor when the DC source is operative. A string of zener diodes is connected between the pass transistor base and ground to provide voltage limiting by clamping the transistor base during an overvoltage condition arising, for example, when the battery has a defective cell or an open connection to the remainder of the circuit. Such an arrangement allows reliable operation with monolithic transistors having about 27 volts collector to emitter breakdown voltage rating.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.