Adaptive pre-biasing of a diode

A time-of-flight module comprising:

• a capacitor circuit connected between a common node and a ground;
• a laser diode circuit connected in parallel with the capacitor circuit between the common node and the ground;
• a derivative circuit having an input and an output, the input being connected to the common node;
• a summing circuit having a first input, a second input, and an output, the first input being connected to the output of the derivative circuit;
• a pre-biasing current source with an input connected to the output of the summing circuit and an output connected to the common node;
• and
• a test voltage source having an output connected to the second input of the summing circuit;
• wherein the test voltage source is configured to output a predetermined test voltage for a predetermined amount of time to the second input of the summing circuit, which in turn causes the pre-biasing current source to inject a test current into the common node;
• wherein, if a voltage at the common node is less than a forward voltage of the laser diode circuit, the injected test current causes the voltage at the common node to increase, which in turn causes the derivative circuit to output a voltage corresponding to a rate of increase of the voltage at the common node to the first input of the summing circuit, which in turn causes the pre-biasing current source to inject a pre-biasing current into the common node;
• and
• wherein, if the voltage at the common node is equal to or greater than the forward voltage of the laser diode circuit, the voltage at the common node will not increase, which in turn causes the derivative circuit to not output a voltage to the first input of the summing circuit, which in turn causes the pre-biasing current source to not inject a pre-biasing current into the common node.

A method of pre-biasing a diode, the method comprising:

• providing a pre-biasing circuit comprising:
• a capacitor circuit connected between a common node and a ground;
• a diode connected in parallel with the capacitor circuit between the common node and the ground;
• a derivative circuit having an input and an output, the input being connected to the common node;
• a summing circuit having a first input, a second input, and an output, the first input being connected to the output of the derivative circuit;
• a pre-biasing current source with an input connected to the output of the summing circuit and an output connected to the common node;
• and
• a test voltage source having an output connected to the second input of the summing circuit;
• and
• outputting a predetermined test voltage for a predetermined amount of time from the test voltage source to the second input of the summing circuit, which causes the pre-biasing current source to inject a test current into the common node;
• wherein, if a voltage at the common node is less than a forward voltage of the diode, the injected test current causes the voltage at the common node to increase, which in turn causes the derivative circuit to output a voltage corresponding to a rate of increase of the voltage at the common node to the first input of the summing circuit, which in turn causes the pre-biasing current source to inject a pre-biasing current into the common node;
• and
• wherein, if the voltage at the common node is equal to or greater than the forward voltage of the diode, the voltage at the common node will not increase, which in turn causes the derivative circuit to not output a voltage to the first input of the summing circuit, which in turn causes the pre-biasing current source to not inject a pre-biasing current into the common node.