High efficiency boost LED driver with output
View Patent ↗A current driver for powering a string of LEDs has a boost converter coupled to an input voltage source. A voltage multiplier circuit is coupled to the boost converter and to the string of LEDs. A latch is provided having an output coupled to the boost converter. A current sense element is coupled to the boost converter. A current comparator is provided having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current. A zero-volt detector circuit is provided having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit.
1. A current driver for powering a string of LEDs comprising:
a boost converter coupled to an input voltage source;
a voltage multiplier circuit coupled to the boost converter and to the string of LEDs;
a latch having an output coupled to the boost converter;
a current sense element coupled to the boost converter;
a current comparator having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current; and
a zero-volt detector circuit having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit.
2. A current driver for powering a string of LEDs in accordance with claim 1 , wherein the boost converter and the multiplier circuit have zero-voltage switching transitions.
3. A current driver for powering a string of LEDs in accordance with claim 1 , further comprising a plurality of voltage multiplier circuits.
4. A current driver for powering a string of LEDs in accordance with claim 1 , wherein the boost converter comprises:
an inductive element having a first terminal coupled to the input voltage source;
a switching device having a first terminal coupled to a second terminal of the inductive element, a second terminal coupled to the output of the latch and coupled to the current sense element;
a rectifier diode having a first terminal coupled to the second terminal of the inductive element and the first terminal of the switching device, and a second terminal coupled to the voltage multiplier circuit; and
an output filter capacitive element having a first terminal coupled to the second terminal to the rectifier diode.
5. A current driver for powering a string of LEDs in accordance with claim 1 , wherein the voltage multiplier circuit comprises:
a first diodes having a first terminal coupled to the first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.
6. A current driver for powering a string of LEDs in accordance with claim 3 , wherein each of the plurality of voltage multiplier circuits comprises:
a first diode having a first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.
7. A current driver for powering a string of LEDs in accordance with claim 1 , wherein the second input of the comparator is coupled to a current reference source.
8. A current driver for powering a string of LEDs in accordance with claim 1 , further comprising:
a second current sense element coupled to the string of LEDs;
a second comparator having an output coupled to the second input of the first comparator, a first input coupled to the second current sense element, and a second input coupled to a reference current source.
9. The power supply of claim 1 , wherein the zero-volt detector circuit comprises:
an input current sense element attached to the input voltage source;
a zero-volt detector current comparator having a first input coupled to the input current sense element and a second input coupled to a current reference;
a delay having a first terminal coupled to an output of the zero-volt detector current comparator and a second terminal coupled to the second input of the latch.
10. A current driver for powering a string of LEDs comprising:
a boost converter coupled to an input voltage source;
a voltage multiplier circuit coupled to the boost converter and to the string of LEDs;
a latch having an output coupled to the boost converter;
a current sense element coupled to the boost converter;
a current comparator having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current; and
a zero-volt detector circuit having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit;
wherein the boost converter comprises:
an inductive element having a first terminal coupled to the input voltage source;
a switching device having a first terminal coupled to a second terminal of the inductive element, a second terminal coupled to the output of the latch and coupled to the current sense element;
a rectifier diode having a first terminal coupled to the second terminal of the inductive element and the first terminal of the switching device, and a second terminal coupled to the voltage multiplier circuit; and
an output filter capacitive element having a first terminal coupled to the second terminal to the rectifier;
wherein the boost converter and the multiplier circuit have zero-voltage switching transitions.
11. A current driver for powering a string of LEDs in accordance with claim 10 , further comprising a plurality of voltage multiplier circuits.
12. A current driver for powering a string of LEDs in accordance with claim 10 , wherein the voltage multiplier circuit comprises:
a first diodes having a first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.
13. A current driver for powering a string of LEDs in accordance with claim 11 , wherein each of the plurality of voltage multiplier circuits comprises:
a first diode having a first terminal coupled to the first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.
14. A current driver for powering a string of LEDs in accordance with claim 10 , wherein the second input of the comparator is coupled to a current reference source.
15. A current driver for powering a string of LEDs in accordance with claim 10 , further comprising:
a second current sense element coupled to the string of LEDs;
a second comparator having an output coupled to the second input of the first comparator, a first input coupled to the second current sense element, and a second input coupled to a reference current source.
16. The power supply of claim 10 , wherein the zero-volt detector circuit comprises:
an input current sense element attached to the input voltage source;
a zero-volt detector current comparator having a first input coupled to the input current sense element and a second input coupled to a current reference;
a delay having a first terminal coupled to an output of the zero-volt detector current comparator and a second terminal coupled to the second input of the latch.
17. A current driver for powering a string of LEDs comprising:
a boost converter coupled to an input voltage source;
a voltage multiplier circuit coupled to the boost converter and to the string of LEDs;
a latch having an output coupled to the boost converter;
a current sense element coupled to the boost converter;
a current comparator having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current; and
a zero-volt detector circuit having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit;
wherein the boost converter comprises:
an inductive element having a first terminal coupled to the input voltage source;
a switching device having a first terminal coupled to a second terminal of the inductive element, a second terminal coupled to the output of the latch and coupled to the current sense element;
a rectifier diode having a first terminal coupled to the second terminal of the inductive element and the first terminal of the switching device, and a second terminal coupled to the voltage multiplier circuit; and
an output filter capacitive element having a first terminal coupled to the second terminal to the rectifier diode and a second terminal grounded;
wherein the voltage multiplier circuit comprises:
a first diodes having a first terminal coupled to the first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.
18. A current driver for powering a string of LEDs in accordance with claim 17 wherein the boost converter and the multiplier circuit have zero-voltage switching transitions.
19. A current driver for powering a string of LEDs in accordance with claim 17 , further comprising a plurality of voltage multiplier circuits.
20. A current driver for powering a string of LEDs in accordance with claim 19 , wherein each of the plurality of voltage multiplier circuits comprises:
a first diodes having a first terminal coupled to the boost converter;
a second diode having a first terminal coupled to a second terminal of the first diode and a second terminal coupled to the string of LEDs;
a flying capacitor having a first terminal coupled to the second terminal of the first diode and to the first terminal of the second diode; and
an output filter capacitor having a first terminal coupled to the second terminal of the second diode and to the string of LEDs.