Power efficient laser diode driver circuit and method
First Claim
1. A voltage mode laser diode driver for selectively turning on and off a laser diode, wherein the laser diode has an anode terminal and a cathode terminal, and wherein the voltage mode laser diode driver is powered by a power supply having a voltage output, the voltage mode laser diode driver comprising:
- an output stage includingan output node configured to be connected to one of the terminals of the laser diode, andan NMOS transistor and a PMOS transistor each including a gate, a source, and a drain, wherein the drains of the NMOS and PMOS transistors are connected together and to the output node of the output stage; and
an active swing controller configured to drive the gates of the NMOS and PMOS transistors of the output stage in dependence on a modulation signal;
wherein the output stage, under control of the active swing controller,selectively pulls a voltage level of the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards a first voltage level, in response to which the laser diode is turned on and emits light, andselectively pulls the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards a second voltage level, in response to which the laser diode is turned off and does not emit light; and
wherein the active swing controller drives the output stage in a manner that substantially prevents inductive kickback, which occurs in response to the laser diode being turned from on to off, from causing the voltage level at the output node of the output stage swinging past the second voltage level.
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Abstract
A voltage mode laser diode driver selectively turns on and off a laser diode. An output stage has an output node configured to be connected to one of the terminals of the laser diode. Depending upon implementation, an active swing controller drives the output stage in a manner that substantially prevents inductive kickback from causing the output node voltage to swinging above the voltage level at the voltage output of the power supply, or swing below ground. The output stage provides a discharge path around the laser diode to shunt current associated with the inductive kickback, and substantially eliminates ringing on the output node of the output stage while the laser diode is off. A power supply controller adjusts the voltage level of the voltage output of the power supply so that current through the laser diode when on and emitting light is substantially equal to a predetermined desired current.
209 Citations
19 Claims
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1. A voltage mode laser diode driver for selectively turning on and off a laser diode, wherein the laser diode has an anode terminal and a cathode terminal, and wherein the voltage mode laser diode driver is powered by a power supply having a voltage output, the voltage mode laser diode driver comprising:
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an output stage including an output node configured to be connected to one of the terminals of the laser diode, and an NMOS transistor and a PMOS transistor each including a gate, a source, and a drain, wherein the drains of the NMOS and PMOS transistors are connected together and to the output node of the output stage; and an active swing controller configured to drive the gates of the NMOS and PMOS transistors of the output stage in dependence on a modulation signal; wherein the output stage, under control of the active swing controller, selectively pulls a voltage level of the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards a first voltage level, in response to which the laser diode is turned on and emits light, and selectively pulls the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards a second voltage level, in response to which the laser diode is turned off and does not emit light; and wherein the active swing controller drives the output stage in a manner that substantially prevents inductive kickback, which occurs in response to the laser diode being turned from on to off, from causing the voltage level at the output node of the output stage swinging past the second voltage level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. For use by a voltage mode laser diode driver powered by a power supply having a voltage output, a method for driving a laser diode having an anode terminal and a cathode terminal,
wherein the voltage mode laser diode driver comprises an output stage including an output node configured to be connected to one of the terminals of the laser diode, and wherein the output stages comprises an NMOS transistor and a PMOS transistor each including a gate, a source, and a drain, with the drains of the NMOS and PMOS transistors connected together and to the output node of the output stage, the method comprising: -
selectively pulling a voltage level at the one of the terminals of the laser diode towards a first voltage level, in response to which a current flows through the laser diode causing the laser diode to turn on and emit light, the current being dependent on a voltage level at the voltage output of the power supply; selectively pulling the voltage level at the one of the terminals of the laser diode towards a second voltage level, response to which current stops flowing through the laser diode causing the laser diode to turn off and not emit light; and adjusting the voltage level of the voltage output of the power supply so that the current that flows through the laser diode when the laser diode is turned on and emitting light is substantially equal to a predetermined desired current; wherein the selectively pulling the voltage level at the one of the terminals of the laser diode towards the first voltage level comprises selectively pulling the voltage level of the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards the first voltage level, in response to which the laser diode is turned on and emits light; and wherein the selectively pulling the voltage level at the one of the terminals of the laser diode towards the second voltage level comprises selectively pulling the output node of the output stage, and thus the drains of the NMOS and PMOS transistors of the output stage, towards the second voltage level, in response to which the laser diode is turned off and does not emit light. - View Dependent Claims (12, 13, 14, 15)
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16. A voltage mode laser diode driver for selectively turning on and off a laser diode, wherein the laser diode has an anode terminal and a cathode terminal, and wherein the voltage mode laser diode driver is powered by a power supply having a voltage output, the voltage mode laser diode driver comprising:
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an output stage including an output node configured to be connected to one of the terminals of the laser diode; an active swing controller configured to drive the output stage in dependence on a modulation signal; and a pre-driver that receives a high frequency periodic differential signal that transitions between ground and a high voltage level that is different than the voltage level of the voltage output of the power supply, and voltage shifts the received high frequency periodic differential signal to a high frequency periodic differential signal that transitions between ground and the voltage level of the voltage output of the power supply; wherein the output stage, under control of the active swing controller, selectively pulls a voltage level of the output node of the output stage towards a first voltage level, in response to which the laser diode is turned on and emits light, and selectively pulls the output node of the output stage towards a second voltage level, in response to which the laser diode is turned off and does not emit light; wherein the active swing controller drives the output stage in a manner that substantially prevents inductive kickback, which occurs in response to the laser diode being turned from on to off, from causing the voltage level at the output node of the output stage swinging past the second voltage level; and wherein the high frequency periodic differential signal that transitions between ground and the voltage level of the voltage output of the power supply comprises the modulation signal in dependence on which the active swing controller drives the output stage. - View Dependent Claims (17, 18, 19)
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Specification