National Semiconductor Corporation

Damian Swank

Nathanael Griesert

William James McIntyre

Florence Jacquet

A circuit for monitoring the inductance value of a switching regulator is provided. The circuit includes an inductance sensor circuit that is coupled to a switch node of a switching regulator. The inductor sensor circuit includes a switch, a ramp circuit, and a comparison circuit. The switch is arranged to receive a switch control signal that is based, at least in part, on a switching signal of the switching regulator. When the switch control signal is asserted, the comparison circuit receives a comparison input voltage that is based, at least in part, on the inductance value of the switching regulator. The comparison circuit compares the comparison input voltage to a ramp voltage of the ramp circuit and outputs a signal indicative of whether the inductance value of the switching regulator is at or below a predetermined threshold inductance value.

Apparatus and method for monitoring the inductance value of a switching regulator

A circuit and method for monitoring the forward voltage for a plurality of LEDs in a battery powered device so that the gain in the LED driver circuit can be switched at a point that optimizes the energy provided by the battery. The invention provides for sensing each LED's voltage, V, and determining the maximum forward voltage, V, between the plurality of LEDs. The invention uses the knowledge of Vin conjunction with V, converter output resistance and LED current, and current source/sink minimum headroom to switch from an initial gain to some higher gain just before the current sinks/sources would drop out, or from a higher gain to a lower gain in the event of the battery voltage going back to a voltage close to its initial value after being momentarily pulled down by a heavy load.

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Rocklin, CA, United States of America

Damian Swank