Efficient fast pulsed laser or light-emitting diode driver
A capacitor is connected to the output of a multiphase power converter, and a current-driven device (e.g., LED or laser diode) is also connected to the power converter output. A solid state switch (FET or IGBT) is connected in series with the current-driven device. Means are provided for sensing current through the current-driven device. An error amplifier compares sensed current through the current-driven device with a current level demand signal and controls the output of the power converter. Means are provided for turning the switch on and off and may be (i) a fast comparator receiving a voltage reference signal at one input and the current level demand signal at another input, and outputting the switch on/off signal to the switch or (ii) an externally-generated logic signal provided directly to the switch.
1. A pulsed current driver for driving current-driven devices comprising:
a power converter having an output;
a capacitor connected to the power converter output;
a current-driven device connected to the power converter output;
a switch connected in series with the current-driven device;
means for sensing current through the current-driven device and providing a current measurement signal in response thereto;
an error amplifier having two inputs and an output, receiving a current level demand signal at its one input and the current measurement signal at its other input, and providing a control signal at its output for controlling the output of the power converter; and
means for turning the switch on and off by providing a switch on/off signal to the switch in response to an externally-generated pulsed signal.
2. The pulsed current driver of claim 1 , wherein:
the means for turning the switch on and off comprises a fast comparator receiving a voltage reference signal at one input and the current level demand signal at another input, and outputting the switch on/off signal to the switch.
3. The pulsed current driver of claim 1 , wherein:
the means for turning the switch on and off comprises an externally-generated logic signal provided directly to the switch.
4. The pulsed current driver of claim 1 , wherein:
the externally-generated pulsed signal for turning the switch on and off is a part of the current level demand signal.
5. The pulsed current driver of claim 1 , wherein:
the externally-generated pulsed signal for turning the switch on and off is separate from the current level demand signal.
6. The pulsed current driver of claim 1 , wherein:
the power converter comprises a multiphase controller.
7. The pulsed current driver of claim 1 , wherein:
the power converter comprises a single phase converter controller.
8. The pulsed current driver of claim 1 , wherein:
the current-driven device is selected from the group consisting of a light emitting diode (LED), and a laser diode.
9. The pulsed current driver of claim 1 , wherein:
the switch comprises a solid state switching means.
10. The pulsed current driver of claim 9 , wherein:
the solid state switching means is selected from the group consisting of a field effect transistor (FET) and an insulated-gate bipolar transistor (IGBT).
11. The pulsed current driver of claim 1 , wherein:
the means for sensing current is selected from the group consisting of a low-value resistor, a current transformer, a Hall-effect sensor and means for measuring a voltage drop across the switch.
12. The pulsed current driver of claim 1 , wherein:
the switch is turned on and off at a frequency in the range of ten to thousands of Hertz with a duty cycle in the range of 0.001 to 0.5 (0.1-50%/o).
13. Method of driving a current-driven device comprising:
providing a power converter having an output;
providing a reservoir capacitor connected to the power converter output;
connecting a current-driven device to the power converter output;
connecting a switch in series with the current-driven device;
providing an externally-generated pulsed signal for turning the switch on and off; and
controlling the output of the power converter by comparing current flowing through the current-driven device to an externally-provided current level demand voltage signal.
14. The method of claim 13 , wherein:
the current level demand voltage signal is pulsed and includes the externally-generated pulsed signal.
15. The method of claim 13 , wherein:
the current level demand voltage signal is not pulsed and is separate from the externally-generated pulsed signal.
16. The method of claim 14 , further comprising:
providing the current level demand signal to an input of a fast comparator ( 222 ), the other input of which is connected to a voltage reference signal ( 224 ); and
connecting the output of the fast comparator to the switch 212 , to turn the switch ON and OFF.
17. The method of claim 14 , further comprising:
turning the switch ON whenever the Current Level Demand ( 220 ) is above zero.
18. The method of claim 13 , wherein:
the current-driven device is selected from the group consisting of a light emitting diode (LED) and a laser diode.
19. Method of providing fast risetime current pulses for driving a light-emitting current-driven device comprising:
providing a multiphase power converter having an output;
providing a reservoir capacitor connected to the power converter output;
connecting a light-emitting current-driven device directly to the power converter output;
connecting a switch in series with the current-driven device; and
providing an externally-generated pulsed signal for turning the switch on and off.
20. The method of claim 19 , further comprising:
controlling the output of the power converter by comparing current flowing through the current-driven device to an externally-provided current level demand voltage signal.