Patent ID: 6724158
Filing Date: 2004-04-20
Classification: G09G,H03K,H05B,Y02B

Abstract:
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.