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.

Abstract: This invention includes a trickle charging circuit that works with a series charging element to charge battery cells with a low, constant current when the voltage of the cell is below a predetermined operational range. The trickle charging circuit includes a control transistor that is actuated by a current source when both the power supply and undervoltage battery cell are coupled. The trickle charging continues until a minimum operational voltage of the cell is reached. The invention includes a means for rapid charging the cell once the cell voltage is within a preferred operational range. The circuit includes means for charging at other currents, like mid-rate currents, as well.

Abstract: An electronic device (100) includes at least L keys (114) and a processor (506) having at least M inputs (600). Upon actuation, each one of the at least L keys (114) toggles a unique combination of N inputs of the at least M inputs (600), where each unique combination is taken from all possible combinations thereof. The at least M inputs (600) are read by the processor (506) and compared to a plurality of predetermined key patterns (806). Upon a match between the at least M inputs (600) and one of the plurality of predetermined key patterns (806), a key actuation is detected and a predetermined function may be processed in response thereto. The processor (506) may ignore simultaneous key actuations where combinations of inputs greater than N are toggled.

Abstract: A circuit (103) for charging a battery (101) is connected to an input (126) for inputting a signal indicative of a temperature of the battery. A switch (108) selectively supplies power to the battery under the control of a control signal. A microcontroller (140) calculates a rate of change of the temperature signal and stores a peak rate of change during a battery charging interval. The microcontroller is operable to control the switch to disable charging of the battery when the temperature rate of change drops below the peak value by a rate of change threshold amount.