| US 7,525,821 B2 | ||
| Power supply system and apparatus | ||
| Anders Hansson, Stockholm (Sweden); Thomas Sahlstrom, Huddinge (Sweden); Jun Ma, Farsta (Sweden); and Mattias Andersson, Stockholm (Sweden) | ||
| Assigned to Emerson Energy Systems, AB, Stockholm (Sweden) | ||
| Filed on Mar. 28, 2008, as Appl. No. 12/57,682. | ||
| Application 12/057682 is a division of application No. 11/470521, filed on Sep. 06, 2006, granted, now 7,408,790. | ||
| Application 11/470521 is a continuation of application No. 10/487107, granted, now 7,193,864, filed on Mar. 20, 2007, previously published as PCT/SE03/00700, filed on Apr. 29, 2003. | ||
| Claims priority of application No. 0201290 (SE), filed on Apr. 29, 2002; and application No. 0201432 (SE), filed on May 13, 2002. | ||
| Prior Publication US 2008/0192511 A1, Aug. 14, 2008 | ||
| Int. Cl. H02M 3/335 (2006.01) | ||
| U.S. Cl. 363—16 [363/98; 323/222; 323/269] | 20 Claims |
| 1. A switched mode power supply comprising:
input terminals for receiving electric power and output terminals for delivering an output power having an output voltage
and an output current;
wherein the input terminals are separated from the output terminals by an insulation barrier adapted to electrically insulate
the input terminals from the output terminals so that the input terminals are provided on a primary side of the insulation
barrier and the output terminals are provided on a secondary side of the insulation barrier;
the insulation barrier being provided by a transformer having a primary winding and a secondary winding;
the switched mode power supply further comprising:
a converter stage coupled between the input terminals and the output terminals, the converter stage having at least one controllable
first switching element for generating a converter stage duty cycle so as to cause the converter stage to generate the output
signal, the at least one first switching element being located on the primary side of tile insulation barrier; and
a programmable digital circuit for controlling the at least one first switching element; wherein:
the programmable digital circuit has a memory and means for receiving a signal representing the input current of the converter
stage;
the switched mode power supply being characterized in that the programmable digital circuit is located on the primary side
of the insulation barrier;
the programmable digital circuit is adapted to derive the output current from the signal representing the input current of
the converter stage by means of executable commands stored in the memory; and
the programmable digital circuit is further adapted to use the derived value of the output current in the control of the first
switching element;
wherein the executable commands are operable to generate the derived value of the output current as a value corresponding
to the numerical value of:
 when the value representing the duty cycle is higher than a first threshold value; wherein:
Iint is the input current of the converter stage,
Iintoff is an offset current;
D is the value representing the duty cycle;
Np is the number of turns of the primary winding;
Ns is the number of turns of the secondary winding;
and E is a value representing the efficiency of the switched mode power supply.
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