Method and circuit for controlling the output characteristics of a switched-mode power supply
US5657211A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 21, 1996 |
| Grant date | Aug 12, 1997 |
| Priority date | — |
| Expiry date | May 21, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M3/33507
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The invention relates to a method and a circuit to control the output voltage and current of a switched-mode power supply. In order to restrict the output current, a voltage value proportional to the primary current of a switched-mode power supply is measured and compared to a variable reference voltage U.sub.ext the value of which is determined by the total effect of the constant charging current of a capacitor C.sub.ext and a discharge circuit operating in step with the secondary diode of the power supply. If the voltage value proportional to the primary current is bigger than said reference voltage, the switching pulses of the primary current switch are shortened. In order to restrict the output voltage, an image voltage is generated for the secondary voltage of the power supply transformer which is filtered and rectified and combined with the aforementioned reference voltage in order to produce pulse-width-modulated switching pulses of the primary current switch.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.