Voltage controlled light source and image presentation device using the same

A voltage controlled light source having brightness control comprising:

• a field effect transistor (FET) having source, gate, and drain electrodes;
• a current sense network connected to at least one electrode of the FET;
• an operational amplifier, having inverting and non-inverting input terminals, coupled between the source and gate electrodes of the FET;
• a variable voltage signal source coupled to the non-inverting input terminal of the operational amplifier;
• a light source coupled to at least one electrode of the FET;
• a switch disposed between the operational amplifier and the gate electrode of the FET;
• and
• wherein the operational amplifier continuously receives a control signal (VDAC) from the variable voltage signal source, while the switch provides control of gate electrode inputs.

A voltage controlled light emitting diode (LED) having brightness control comprising:

• a field effect transistor (FET) having source, gate, and drain electrodes;
• a light emitting diode (LED) coupled to at least one electrode of the FET;
• a feedback network, coupled to the gate electrode of the FET, and adapted to receive a control signal from a variable voltage signal source;
• a switch, connected between the feedback network and the gate electrode of the FET;
• and
• wherein the switch provides control of gate electrode inputs, and LED brightness is altered as a function of control signal amplitude.

An image presentation device having a light source with brightness control comprising:

• a plurality of differing color light sources, each light source having a control signal input;
• a light sensor positioned to receive light from the plurality of differing color light source and operable to provide an output characterizing the received light;
• a controller coupled to the plurality of color light sources and to the sensor and responsive to output from the sensor to adjust the control signal input to at least one of the plurality of differing color light sources;
• and
• a light source drive circuit, coupled between the controller and the plurality of differing color light sources comprising:
• a field effect transistor (FET) having source, gate, and drain electrodes;
• at least one of the plurality of differing color light source coupled to at least one electrode of the FET;
• a feedback network, coupled to the gate electrode of the FET, and adapted to receive the control signal input from the controller;
• a switch, connected between the feedback network and the gate electrode of the FET;
• and
• wherein the switch provides control of gate electrode inputs, while light source brightness is altered as a function of control signal amplitude.

An image presentation device having a light source with brightness control comprising:

• a plurality of differing color light sources, each light source having a control signal input;
• a reference voltage look-up table providing information characterizing brightness settings for the plurality of differing color light sources;
• a controller coupled to the plurality of color light sources and to the reference voltage look-up table and responsive to output from the reference voltage look-up table to adjust the control signal input to at least one of the plurality of differing color light sources;
• a light source drive circuit, coupled between the controller and the plurality of differing color light sources comprising:
• a field effect transistor (FET) having source, gate, and drain electrodes;
• at least one of the plurality of differing color light source coupled to at least one electrode of the FET;
• a feedback network, coupled to the gate electrode of the FET, and adapted to receive the control signal input from the controller;
• a switch, connected between the feedback network and the gate electrode of the FET;
• and
• wherein the switch provides modulated control of gate electrode inputs, while light source brightness is altered as a function of control signal amplitude.