Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
2000-11-21
2002-07-30
Riley, Shawn (Department: 2838)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C315S307000
Reexamination Certificate
active
06426570
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a power converter configuration for low voltage devices, and more particularly to such a converter configuration employing a pair of complementary switches in a d.c.-to-a.c. converter.
BACKGROUND OF THE INVENTION
The existing standard for supplying power to low voltage devices, such as lamps, motors, radios, fans, or heaters, and in particular, such lamps, motors, radios, fans, or heaters in the automotive industry, is from a single 12 volt d.c. power source. Recently, the automotive industry has been moving from the standard 12 volt d.c. power source to a 42 volt d.c. power source. Use of a single 42 volt d.c. power source allows for smaller cabling to be used within the automobile, which in turn allows the automobile to reduce its overall weight, thereby decreasing its fuel consumption. While the industry standard is switching from a 12 v power source to a 42 v power source it has been determined that existing use of 12 v a.c. powered lamps, motors, radios, fans, or heaters may continue to be used in the automotive lighting system. Such lamps may be incandescent lamps or other low voltage lamps used as headlights, rear lights and interior lamps. Low voltage devices have certain advantages, for example, low voltage (12 v) lamps are desirable as they are efficient and ruggedized, as compared to 42 v or other high voltage lamps. It is also known that powering the low voltage lamps with an a.c. source extends the lamp life as compared to powering these lamps with a d.c. source. In a d.c. lamp, tungsten migration and other chemical debilitating processes will take place which decrease the lamp life.
The present invention provides a converter circuit and controller for low voltage devices, that overcome the foregoing drawbacks.
BRIEF SUMMARY OF THE INVENTION
A power converter circuit and controller supply an a.c. signal to a load circuit incorporating a low voltage incandescent lamp. The converter circuit converts supplied 42 volts d.c. to a regulated 12 volt a.c. signal. Included in the circuit are first and second switches serially connected between a bus conductor and a reference conductor. The switches are connected together at a common node through which the a.c. current flows, and at a control node. Also connected between the control node and the common node is a serially connected circuit including a capacitor and two inductors. The voltage between the control node and the common node are used to determine the conduction state of the associated switches, where the time constant of the serially connected circuit determines the frequency of operation.
Also included are first and second resistors connected serially between the bus conductor and the reference conductor and also connected to the control node. A third resistor is connected between the common node and one of the bus conductor and the reference conductor, to set the initial polarity of the control node with reference to the common node. A controller operates to alter the operational frequency of the converter to maintain signal output within a desired range.
REFERENCES:
patent: 5449973 (1995-09-01), Yamashita et al.
patent: 6088207 (2000-07-01), Sugiura et al.
Fay Sharpe Fagan Minnich & McKee LLP
General Electric Company
Riley Shawn
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