Single touch flash charger circuit with timer control
US5781804A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 19, 1996 |
| Grant date | Jul 14, 1998 |
| Priority date | — |
| Expiry date | Nov 19, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/32
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A single touch flash capacitor charging circuit particularly useful in low cost cameras incorporating an oscillation timeout circuit to arrest self-sustaining oscillations for conserving battery consumption. The timeout circuit includes a reference voltage integration circuit coupled to the secondary of the oscillation transformer to develop a reference voltage that is independent of battery voltage. A timer charging circuit is coupled to the voltage reference circuit and determines the timeout period. Closing of a start charge switch resets the timer charging circuit to a fixed voltage differential from the integration circuit reference voltage. When the start charge switch is opened, the timer circuit begins charging to the voltage reference. Once initiated, the flash capacitor charger circuit continues charging the flash capacitor for the duration of the timeout period set by the timer circuit. At the end of the timeout period, the timer charging circuit turns on a pair of switching transistors which operate to shunt off the oscillation transistor in the flash capacitor charger circuit. The start switch resets the timer circuit either through the emitter-base coupled transistors…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.