Micrel, Incorporated

Thruston Awalt

Peter Chambers

Qi Deng

Hardik Dineshchandra Patel

David Andersen

A LED driver circuit avoids undesirable light generated by a LED due to leakage current by shunting the output terminal to the feedback terminal during periods when it is desired that the LED remain turned off. The shunting operation is achieved by providing a switch (e.g., a FET) that is connected between the output and feedback terminals of the LED, and is controlled by the user supplied reference signal. During active operation (i.e., when the user supplied reference signal is 'enabled' and the LED is lit), the switch remains open, allowing the driver circuit to generate the desired driving voltage across the LED. During inactive periods (i.e., when the user supplied reference signal is 'disabled' and the LED is intended to be off), the switch is closed, which couples the output and feedback terminals to generate an essentially zero voltage drop across the LED.

Light emitting diode driver circuit with shunt switch

A Light-Emitting Diode (LED) driver circuit is disclosed that controls the brightness of light generated by a LED that is coupled between a first terminal and a second terminal in response to a user supplied brightness control signal. A constant current source generates a constant current that is supplied to the LED and to a shunt circuit, which his connected in parallel with the LED. A brightness control circuit generates a pulse signal having a duty cycle that is proportional to the brightness control signal, and controls the shunt circuit such that, when said pulse signal is high, the constant current is passed through the shunt circuit and the LED is turned off, and when the pulse signal is low, the constant current is passed through the LED. The duty cycle of the brightness control signal is adjusted to adjust the LED's brightness, while the LED color remains constant.

Light emitting diode driver circuit with high-speed pulse width modulated current control

A circuit in an integrated circuit having an input terminal to be coupled to a resistor network for selecting one of multiple digital states in the integrated circuit includes a voltage decode circuit, a control circuit and a power-up control circuit. The first input terminal receives an input voltage having a voltage value associated with the multiple digital states. The voltage decode circuit receives the input voltage and generates a voltage decode signal indicative of the voltage value of the input voltage. The control circuit receives the voltage decode signal and generates an output control signal accordingly where the output control signal selects one of the multiple digital states. The power-up control circuit provides power to the resistor network, the voltage decode circuit and the control circuit for determining the selected digital state and disconnects power to those circuits after the selected digital state is determined.

Power saving method in an integrated circuit programming and control circuit

A surge current delay time period is added to a current limit delay time period in order to permit a longer time for a possibly temporary larger-than-steady-state electrical current, such as for a start-up power requirement. A system is described for permitting a legitimate surge current by distinguishing true over-current fault conditions from temporary surges in terms of high current duration time.

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Los Gatos, CA, United States of America

Thruston Awalt