Two transistor flyback switching converter with current sensing for discontinuous operation
US4754385A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 30, 1987 |
| Grant date | Jun 28, 1988 |
| Priority date | — |
| Expiry date | Jan 30, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M3/3353
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Disclosed is a dual transistor flyback converter having a pair of synchronously driven switching transistors (20, 36) for switching voltage to a primary (12) of a flyback transformer (10). When driven into a cutoff state, transistor (36) isolates switching transistor (20) from the supply voltage (V1), thereby preventing a transformer reflected voltage from being superimposed on the supply voltage and imposing such voltage across the transistor (20). Clamp diodes (40, 42) maintain the switching transient voltage across the flyback transformer primary (12) between prescribed limits. Capacitor (48) allows the switching transient to pass and be clamped by the diodes (40, 42), but prevents the reflected secondary voltage from being clamped when the input voltage is low. A current sensing circuit (50) in series with the flyback transformer secondary (14) senses current flow during the power conversion cycle, and provides a digital indication to a PWM control circuit (66) to facilitate reliable discontinuous operation of the flyback converter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.