Average-power control loops and methods through laser supply voltage closed-loop control

An average laser power control loop comprising:

• a laser diode drive circuit coupled to a laser diode circuit for coupling to first and second terminals of a laser diode;
• a switching converter having an output voltage coupled to power the laser diode circuit when the first and second terminals of the laser diode are connected to the laser diode circuit;
• a programmable current source in the laser diode circuit coupled to control a current through the laser diode from the switching converter;
• an average power control for coupling to monitor an output of a monitor diode and to provide a target voltage to a target control;
• the target control also being coupled to a first output of the programmable current source, the target control controlling the output voltage of the switching converter to provide a voltage to the laser diode circuit that causes a voltage output of the current source to be equal to the target voltage;
• the average power control also being coupled to a second output of the programmable current source that is responsive to a headroom of the programmable current source to adjust the target voltage to maintain an adequate headroom for the programmable current source.