Power regulation and thermal management circuit
First Claim
1. A circuit for maintaining constant power dissipation in a series element, the circuit comprising:
- a. a power source;
b. a load;
c. at least one series element coupled serially between the power source and the load;
d. a means for sensing a voltage across the series element;
e. a parallel connection of a plurality of current sensing elements, the parallel connection being coupled serially between the power source and the load; and
f. a means of selecting at least one of the plurality of current sensing elements, wherein the selection corresponds to a voltage sensed by the means for sensing voltage across the series element.
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Accused Products
Abstract
This invention provides a means of protecting power dissipating pass elements from exceeding their predetermined thermal limits. In one preferred embodiment, the circuit protects a pass element in a battery charging circuit from exceeding its threshold junction temperature by predicting temperature based upon the voltage across the pass element and the current flowing through it. From this predicted temperature, current is reduced to provide charging of a battery at a constant power. The circuit includes a voltage sensing circuit and a plurality of comparators for selecting a predetermined current based upon the output of the voltage sensing circuit. The circuit provides a piecewise linear approximation of proper pass element voltage and current values to maintain a suitable threshold junction temperature.
31 Citations
16 Claims
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1. A circuit for maintaining constant power dissipation in a series element, the circuit comprising:
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a. a power source;
b. a load;
c. at least one series element coupled serially between the power source and the load;
d. a means for sensing a voltage across the series element;
e. a parallel connection of a plurality of current sensing elements, the parallel connection being coupled serially between the power source and the load; and
f. a means of selecting at least one of the plurality of current sensing elements, wherein the selection corresponds to a voltage sensed by the means for sensing voltage across the series element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A circuit for maintaining constant power dissipation in a series element, the circuit comprising:
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a. a power source;
b. a load;
c. at least one series element coupled serially between the power source and the load, the series element;
i. having at least a maximum operating temperature;
ii. the series element being primarily controlled by a regulator circuit;
d. a means for sensing voltage across the series element;
e. a means for sensing current flowing through the series element; and
f. a power threshold circuit, wherein the power threshold circuit overrides the regulator circuit to keep power constant when the product of sensed voltage and sensed current exceed a threshold corresponding to the maximum operating temperature of the series element. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification