PWM control circuit for a non-symmetrical switching power supply
US4794508A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 23, 1987 |
| Grant date | Dec 27, 1988 |
| Priority date | — |
| Expiry date | Dec 23, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B70/10
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A control circuit is disclosed which provides a pulsewidth modulated, quasi-squarewave control signal to a switching transistor in a non-symmetrical switching power supply. A primary winding of a sense transformer is coupled in series with a switching transistor and a first winding of a magnetic device, such as a power transformer. A load resistor is placed across a secondary winding of the sense transformer so that the voltage across the secondary winding of the sense transformer ramps up with the current through the first winding of the magnetic device. This increasing voltage is compared by a voltage comparator to a feedback signal corresponding to the output voltage of the power supply so that when the voltage across the secondary winding of the sense transformer exceeds that of the feedback signal, the output of the voltage comparator will be low, turning the switching transistor off. The magnetic device now dumps its stored energy into the output load. After the magnetic device has dumped its energy, the switching transistor is once again enabled. Thus, the duty cycle of the switching transistor is being constantly adjusted to keep the power supply output voltage at a predete…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.