Single comparator exponential-scale pwm dimming
AssigneeAnalog Devices, Inc.
InventorChad D. Kersey
Life of this patent
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Abstract
An exponential scale pulse width modulation (PWM) controller comprises a waveform generator circuit configured to generate a logarithmic waveform signal that has the shape of an increasing logarithm function; and a first comparator circuit including a first input to receive the logarithmic waveform signal, a second input to receive an input signal, and an output that provides a PWM control signal that includes signal pulses having a duty cycle that changes exponentially with respect to the input signal.
Claims20
An exponential-scale pulse width modulation (PWM) controller, the PWM controller comprising:
- a waveform generator circuit configured to generate a logarithmic waveform signal that has the shape of an increasing logarithm function;
- and
- a first comparator circuit including a first input to receive the logarithmic waveform signal, a second input to receive an input signal, and an output that provides a PWM control signal that includes signal pulses having a duty cycle that changes exponentially with respect to the input signal.
A method of operating a pulse width modulation (PWM) circuit, the method comprising:
- generating a logarithmic waveform signal that has the shape of an increasing logarithm function;
- receiving an input signal;
- generating a PWM control signal by applying the logarithmic waveform signal and the input signal to a comparator circuit, wherein the PWM control signal includes pulses having a duty cycle that changes exponentially with respect to a duty cycle of the input signal;
- and
- controlling brightness of at least one light emitting diode using the PWM control signal.
A light emitting diode (LED) driver circuit comprising:
- a switching regulator circuit configured to produce a regulated output according to pulse width modulation (PWM) to drive one or more LEDs;
- and
- an exponential PWM controller operatively coupled to the switching regulator circuit and including:
- a waveform generator circuit configured to generate a logarithmic waveform signal having a shape of a logarithm function that increases from an initial amplitude after an initial delay;
- and
- a first comparator circuit including a first input to receive the logarithmic waveform signal, a second input to receive an input signal, and an output that provides a PWM control signal that includes signal pulses having a duty cycle that changes exponentially.
Dependencies are inferred from the claim text.