Linear load circuit to control switching power supplies under minimum load conditions
US5285367A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 7, 1992 |
| Grant date | Feb 8, 1994 |
| Priority date | — |
| Expiry date | Feb 7, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05F1/563
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An embodiment of the present invention is a switching power supply comprising a transformer with a primary and two secondaries, a switching transistor in series with the primary, a rectifier and filter on one secondary to provide regulated output power, a feedback control circuit that monitors the secondary and adjusts the duty cycle of an on-off control signal to the switching transistor to maintain a constant output at the terminals, and a monitor that detects when the power level flowing through the switching regulator has dropped to a predetermined minimum and then linearly turns on a load to the transformer. Transistor is typically a power MOSFET. The monitor tracks a summing junction current before any slope compensation is added. Load is a shunt regulator that is activated when the summing junction current falls below 12% of full scale. Alternatively, the predetermined value of 12% is adjustable. The shunt regulator load increases the load on secondary until the summing junction current returns to 12% of full scale. The feedback control circuit and monitor are preferably fabricated on a single monolithic integrated circuit which increases its power dissipation when the monit…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.