Semtech Corporation

David Paul Keesor

William E Rader, Iii

Karl Richard Volk

Russell Deans

Thomas Joseph Karpus

Paul Edward Hinson

Bill Rader

Calbert Lee Perkins

A system and method is provided for preventing a dropout of an LED current. In one embodiment of the present invention, the system includes a voltage source, a first circuit, a second circuit, a controller, and at least one LED. The first circuit receives a reference voltage from the voltage source, receives set-point current data from the controller, and uses the reference voltage and the set-point current data to produce a threshold voltage. The threshold voltage is then provided to the second circuit, where it is converted into an output current, which is drawn through the LED. The second circuit then compares the threshold voltage to an output voltage corresponding to the output current, and provides an output to the controller. The controller then uses the output to determine whether a dropout has occurred. If a dropout has occurred, then second set-point current data is provided to the first circuit.

Automatic dropout prevention in LED drivers

According to one or more aspects of DC-to-DC voltage conversion as taught herein, a DC-to-DC converter selectively operates in a first mode wherein an included linear pass output circuit supplies the output power from the DC-to-DC converter, in a second mode wherein an included charge pump output circuit supplies the output power, and in a third mode wherein the linear pass and charge pump output circuits operate in parallel to supply the output power. With this third mode, also referred to as a 'dual' mode, wherein the linear pass and charge pump output circuits operate in parallel, the DC-to-DC converter keeps the more efficient output circuit on after it has begun switching to operation with the less efficient output circuit. Such switchover may be performed dynamically in response to changing operating conditions. Detected operating conditions may include input voltages, output voltages, and output load conditions.

Method and apparatus for a charge pump DC-to-DC converter having parallel operating modes

A charge pump power supply includes two or more modes of operation. An input protection circuit is connected between an input of the power supply and a voltage source. The input protection circuit regulates the voltage at the input of the power supply, limits current at the input when switching from a weaker mode to a stronger mode, and prevents current reversal when switching from a stronger mode to a weaker mode. In some modes, the power supply continuously provides current to the load, obviating the need for an output capacitor.

Charge pump with current limiting circuit

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Chapel Hill, NC, United States of America

David Paul Keesor