Laser diode driver circuit

A driver circuit for defining a controlled current flowing through a device, said driver circuit having one or more raw input signals, said driver circuit comprising:

• an input smoothing circuit that converts said raw input signals into an identical number of smoothed input signals, by rectifying and filtering said raw input signals;
• a reference voltage control circuit for generating a reference signal from one or more smoothed input signals, said reference signal being a function of said smoothed input signals;
• a current detector for producing a sense signal proportional to the amplitude of said controlled current;
• a differential amplifier for comparing said reference signal with said sense signal to produce a control signal proportional to the difference between said reference signal and said sense signal;
• a current amplifier that generates said controlled current from said control signal;
• and
• circuit output terminals at which said controlled current can be applied to said device.

A driver circuit, comprising:

• an input smoothing circuit having a first smoothed output and a second smoothed output;
• a device having an anode input connected to said first smoothed output and having a cathode output;
• a reference voltage control circuit having a source input, a detection input, a reference output, and a return output, with said source input coupled to said second smoothed output and said detection input connected to said cathode output;
• a differential amplifier with a negative input, a positive input connected to said reference output, and an amplifier output;
• a current amplifier with a control input connected to said amplifier output, a source input connected to said cathode output, and a current output;
• and
• a current detector with a current input connected to said current output, a sense output connected to said negative input, and a current return output connected to said return output.

A method of initiating current through a device without current spiking, said method comprising:

• placing a driver circuit in an off state with no current flowing through said device and having a reference voltage at a small value;
• applying an input waveform to said driver circuit;
• holding said reference voltage at said small value until said input waveform reaches a threshold voltage;
• thereafter increasing said reference voltage to a pre-determined level;
• and
• increasing said current in proportion to the increase of said reference voltage.

A method of removing current passing through a device without current spiking, said method comprising:

• placing a driver circuit in an on state with a current flowing through said device with an input waveform present and having a reference voltage at a given value;
• removing said input waveform to said driver circuit;
• detecting said removal of input waveform;
• reducing said reference voltage to a small value in response to said detection;
• and
• thereafter, terminating said current in response to said reference voltage reduction.