Pulsed driver for a diode light source
A powering circuit for a diode light source includes an inductor charged through an on/off switch. The charging occurs during a charging cycle for a controllable amount of time when the on/off switch is closed. The energy of the charged inductor is used to power the semiconductor light source by opening the on/off switch. In such a driving configuration, the ringing is nearly constant and thus may be suppressed using an appropriately configured circuit.
1. A pulsed driver for a diode light source, the pulsed driver comprising:
a first powering terminal for coupling to one of p- and n- terminals of the diode light source;
a second powering terminal for coupling to the other one of the p- and n- terminals of the diode light source;
a powering circuit comprising a power source and an inductor sequentially coupled to the power source, wherein the power source is coupled to the first powering terminal, and the inductor is coupled to the second powering terminal;
an on/off switch coupled to the first and second powering terminals for shunting the diode light source when the on/off switch is in a closed state; and
a control circuit configured to keep the on/off switch in the closed state for charging the inductor before switching to an open state.
2. The pulsed driver of claim 1 , wherein a voltage provided by the power source is lower than a threshold voltage of the diode light source for emitting light.
3. The pulsed driver of claim 1 , wherein the powering circuit lacks a catch diode.
4. The pulsed driver of claim 1 , wherein the pulsed driver lacks a capacitive energy store coupled to the first and second powering terminals.
5. The pulsed driver of claim 1 , wherein the control circuit comprises a programmable delay line configured to receive a first clock signal and to provide a second clock signal delayed relative to the first clock signal by a controllable amount, for keeping the on/off switch in the closed state for a configurable amount of time for charging the inductor by a configurable amount.
6. The pulsed driver of claim 5 , wherein the control circuit further comprises a logic gate comprising first and second input terminals and an output terminal, wherein the first input terminal is configured to receive the first clock signal, the second input terminal is configured to receive the second clock signal, and wherein the output terminal is operably coupled to the on/off switch for controlling the on/off switch.
7. The pulsed driver of claim 6 , wherein the logic gate comprises a pair of inverters coupled by a wired AND connection.
8. The pulsed driver of claim 6 , wherein the control circuit further comprises a level shifter for shifting a level of at least one of the first or second clock signal for coupling to the logic gate.
9. A pulsed light source comprising:
a diode light source comprising p- and n-terminals;
a powering circuit comprising a power source and an inductor sequentially coupled to the power source, wherein the power source is coupled to one of the p- and n-terminals, and the inductor is coupled to the other one of the p- and n-terminals;
an on/off switch coupled to the p- and n-terminals for shunting the diode light source when the on/off switch is in a closed state; and
a control circuit configured to keep the on/off switch in the closed state for charging the inductor before switching to an open state.
10. The pulsed light source of claim 9 wherein, when the on/off switch is opened after the inductor has been charged, a pulsed electrical current flows through the diode light source, causing the diode light source to emit a light pulse having an energy dependent on an amount of time the on/off switch has been in the closed state before opening the on/off switch.
11. The pulsed light source of claim 10 , wherein the diode light source comprises a laser diode.
12. The pulsed light source of claim 11 , wherein the laser diode comprises a side-emitting laser diode.
13. The pulsed light source of claim 11 , wherein the laser diode comprises a vertical cavity surface-emitting laser diode.
14. The pulsed light source of claim 11 , wherein in operation, a voltage provided by the power source is lower than a threshold voltage of the laser diode.
15. The pulsed light source of claim 9 , wherein the powering circuit lacks at least one of: a catch diode; or a capacitive energy store coupled to the p- and n-terminals.
16. A display comprising:
a pulsed light source for providing a light beam including a light pulse, the pulsed light source comprising:
a diode light source comprising p- and n-terminals;
a powering circuit comprising a power source and an inductor sequentially coupled to the power source, wherein the power source is coupled to one of the p- and n-terminals, and the inductor is coupled to the other one of the p- and n-terminals;
an on/off switch coupled to the p- and n-terminals for shunting the diode light source when the on/off switch is in a closed state; and
a control circuit configured to keep the on/off switch in the closed state for charging the inductor before switching to an open state; and
a scanner optically coupled to the pulsed light source for angularly scanning the light beam.
17. The display of claim 16 wherein, when the on/off switch is opened after the inductor has been charged, a pulsed electrical current flows through the diode light source, causing the diode light source to emit the light pulse, wherein the light pulse has an energy dependent on an amount of time the on/off switch has been in the closed state before opening the on/off switch.
18. The display of claim 17 , wherein the diode light source comprises a laser diode, wherein a voltage provided by the power source is lower than a threshold voltage of the diode light source for emitting light.
19. The display of claim 16 , further comprising a display controller operably coupled to the pulsed light source and the scanner and configured to scan the light beam through a succession of directions while causing the pulsed light source to vary pulse energy from pulse to pulse.
20. The display of claim 19 , wherein the display controller is configured to:
use the scanner to scan the light beam;
determine a pointing angle of the scanner;
determine an energy of a light pulse to be emitted in accordance with the determined pointing angle of the scanner; and
cause the diode light source to emit the light pulse having the determined energy.