Power linearization technique for controlling the luminance of light emitting display devices
AssigneeHoneywell International Inc.
InventorAlan S. Feldman
Life of this patent
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Abstract
A circuit and method for providing a linear power to a load uses pulse modulation technique where the frequency and pulse width of the pulse width modulated waveform driving the load are varied simultaneously. In one aspect of the disclosure, a pulse width modulator circuit is responsive to a command drive signal for producing the pulse width waveform the width of the pulses varying accordingly. In addition, a frequency control circuit that is also responsive to the command drive signal provides a control current to the pulse width modulator circuit wherein the frequency of the waveform is varied as the pulse widths are varied.
Claims9
An apparatus for delivering linear power drive to a light source, comprising:
- a pulse width modulator having an output coupled to the light source, said pulse width modulator configured to be responsive to a command voltage drive signal such that a pulse width modulated signal having a plurality of pulses and a frequency is provided at the output and widths of the plurality of pulses vary as said command voltage drive signal varies;
- a frequency control circuit coupled to the pulse width modulator, said frequency control circuit configured to be responsive to said command voltage drive signal such that a control current is provided to said pulse width modulator that varies the frequency as said command voltage drive signal varies in order to vary the frequency substantially simultaneously with the varying of the widths of the plurality of pulses;
- and
- a feedback loop configured to be responsive to a current flowing in the light source and further configured to provide a logarithmic voltage.
Dependencies are inferred from the claim text.