Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
2005-06-02
2009-06-16
Owens, Douglas W (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S224000, C363S098000
Reexamination Certificate
active
07548029
ABSTRACT:
An apparatus and method for determining the output current in a bridge-connected switched transistor output circuit including high-side and low-side transistor switches, typically MOSFETS. The voltage at a common node between the high and low side switches is sensed, and offset in a first circuit by a fixed amount so that the voltage is positive for all positive or negative output currents of interest. The output current is actually determined in a second circuit which receives the offset voltage signal only predetermined times in relation to the on-time of the low side switch. The first circuit includes a current reference source/level shifter and a current mirror circuit formed of a plurality of transistors in a particular circuit configuration. The second circuit is coupled to an output of the first circuit by a gated NMOS transistor at the desired times to provide the current measurement signal. The second circuit includes a second current reference source having substantially the same electrical characteristics as the first current reference source, and a second plurality of transistors respectively matched to the input side circuit transistors, and connected in the same circuit configuration. In the second circuit, the offset signal is compared with high and low reference signals to provide an indication if the output current exceeds an overcurrent limit, either positively or negatively. The sensing circuit is advantageously integrated with the output circuit gate driver in a single IC.
REFERENCES:
patent: 5436581 (1995-07-01), Oberhauser
patent: 6124680 (2000-09-01), Shoji et al.
patent: 6222327 (2001-04-01), Shoji et al.
patent: 6813173 (2004-11-01), Lipcsei
patent: 7049767 (2006-05-01), Wilhelm
Cheng Xiao-Chang
Honda Jun
Wilhelm Dana
International Rectifier Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Owens Douglas W
Vu Jimmy T
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