Dimming circuit for a phase-cut TRIAC dimmer
A dimmer circuit for at least one LED is disclosed. The LED is controlled by a TRIAC dimmer. A leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off. The dimmer circuit include inputs for receiving a source of incoming AC power, a rectifier for receiving the source of incoming AC power and producing a DC voltage, a controller for receiving the DC voltage from the rectifier and providing a switching signal, a first circuit, and a loading circuit. The first circuit receives the switching signal from the controller. The first circuit includes a first switching element that is selectively activated based on the switching signal. The loading circuit receives the switching signal from the controller. The loading circuit includes a second switching element that is activated if the first switching element is deactivated. The loading circuit selectively provides a minimum loading current.
1. A dimmer circuit for at least one LED that is controlled by a TRIAC dimmer, wherein a leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off, comprising:
inputs for receiving a source of incoming AC power;
a rectifier for receiving the source of incoming AC power, the rectifier producing a DC voltage;
a controller for receiving the DC voltage from the rectifier and providing a switching signal;
a first circuit for receiving the switching signal from the controller, the first circuit including a first switching element that is selectively activated based on the switching signal;
a loading circuit for receiving the switching signal from the controller, wherein the loading circuit includes a second switching element that is activated if the first switching element is deactivated, the loading circuit selectively providing a minimum loading current that substantially dissipates the leakage current flowing through the TRIAC dimmer if the second switching element is activated, and wherein the loading circuit further includes a third switching element that inverts the switching signal before being sent to the second switching element.
2. The dimmer circuit as recited in claim 1 , wherein the first circuit is a snubber circuit including a snubber resistor.
3. The dimmer circuit as recited in claim 2 , wherein the snubber resistor is part of the dimming circuit if the first switching element is deactivated.
4. The dimmer circuit as recited in claim 2 , wherein the snubber resistor is activated if the TRIAC dimmer is on.
5. The dimmer circuit as recited in claim 1 , wherein the first switching element and the second switching element are metal-oxide-semiconductor field-effect transistors (MOSFETs).
6. The dimmer circuit as recited in claim 1 , comprising a buck converter that provides current to the LED.
7. The dimmer circuit as recited in claim 6 , wherein the buck converter receives the switching signal from the controller.
8. The dimmer circuit as recited in claim 1 , wherein the loading circuit comprises a resistor, a zener diode, and a capacitor that define gate drive circuitry that conditions the switching signal before being sent to the second switching element.
9. The dimmer circuit as recited in claim 8 , wherein the loading circuit comprises a second resistor that is arranged in series with the second switching element.
10. The dimmer circuit as recited in claim 9 , wherein the minimum loading current is determined by the following equation:
a
voltage
of
the
zener
diode
-
a
gate
to
source
voltage
(
V
GS
)
of
the
second
switching
element
a
resistance
of
the
second
resistor
.
11. The dimmer circuit as recited in claim 1 , wherein the LED is an organic LED (OLED).
12. A dimmer circuit for at least one LED that is controlled by a TRIAC dimmer, wherein a leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off, comprising:
inputs for receiving a source of incoming AC power;
a rectifier for receiving the source of incoming AC power, the rectifier producing a DC voltage;
a controller for receiving the DC voltage from the rectifier and providing a switching signal;
a snubber circuit for receiving the switching signal from the controller, the snubber circuit including a first switching element and a snubber resistor, the first switching element selectively activated based on the switching signal; and
a loading circuit for receiving the switching signal from the controller, wherein the loading circuit comprises:
a second switching element that is activated if the first switching element is deactivated; and
a third switching element that inverts the switching signal before being sent to the second switching element,
wherein the loading circuit selectively provides a minimum loading current that substantially dissipates the leakage current flowing through the TRIAC dimmer if the second switching element is activated.
13. The dimmer circuit as recited in claim 12 , wherein the snubber resistor is part of the dimming circuit if the first switching element is deactivated.
14. The dimmer circuit as recited in claim 12 , wherein the snubber resistor is activated if the TRIAC dimmer is on.
15. The dimmer circuit as recited in claim 12 , wherein the first switching element, the second switching element, and the third switching element are metal-oxide-semiconductor field-effect transistors (MOSFETs).
16. The dimmer circuit as recited in claim 12 , comprising a buck converter that provides current to the LED.
17. The dimmer circuit as recited in claim 12 , wherein the loading circuit comprises a resistor, a zener diode, and a capacitor that define gate drive circuitry that conditions the switching signal before being sent to the second switching element.
18. The dimmer circuit as recited in claim 17 , wherein the loading circuit comprises a second resistor that is arranged in series with the second switching element.
19. The dimmer circuit as recited in claim 18 , wherein the minimum loading current is determined by the following equation:
a
voltage
of
the
zener
diode
-
a
gate
to
source
voltage
(
V
GS
)
of
the
second
switching
element
a
resistance
of
the
second
resistor
.
20. A dimmer circuit for at least one LED that is controlled by a TRIAC dimmer, wherein a leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off, comprising:
inputs for receiving a source of incoming AC power;
a rectifier for receiving the source of incoming AC power, the rectifier producing a DC voltage;
a controller for receiving the DC voltage from the rectifier and providing a switching signal;
a first circuit for receiving the switching signal from the controller, the first circuit including a first switching element that is selectively activated based on the switching signal, wherein the first circuit is a snubber circuit including a snubber resistor; and
a loading circuit for receiving the switching signal from the controller, wherein the loading circuit includes a second switching element that is activated if the first switching element is deactivated, the loading circuit selectively provides a minimum loading current that substantially dissipates the leakage current flowing through the TRIAC dimmer if the second switching element is activated.
21. The dimmer circuit as recited in claim 20 , wherein the snubber resistor is part of the dimming circuit if the first switching element is deactivated.
22. The dimmer circuit as recited in claim 20 , wherein the snubber resistor is activated if the TRIAC dimmer is on.
23. A dimmer circuit for at least one LED that is controlled by a TRIAC dimmer, wherein a leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off, comprising:
inputs for receiving a source of incoming AC power;
a rectifier for receiving the source of incoming AC power, the rectifier producing a DC voltage;
a controller for receiving the DC voltage from the rectifier and providing a switching signal;
a first circuit for receiving the switching signal from the controller, the first circuit including a first switching element that is selectively activated based on the switching signal;
a loading circuit for receiving the switching signal from the controller, wherein the loading circuit includes a second switching element that is activated if the first switching element is deactivated, the loading circuit selectively provides a minimum loading current that substantially dissipates the leakage current flowing through the TRIAC dimmer if the second switching element is activated; and
a buck converter that provides current to the LED, wherein the buck converter receives the switching signal from the controller.
24. A dimmer circuit for at least one LED that is controlled by a TRIAC dimmer, wherein a leakage current flows through the TRIAC dimmer if the TRIAC dimmer is off, comprising:
inputs for receiving a source of incoming AC power;
a rectifier for receiving the source of incoming AC power, the rectifier producing a DC voltage;
a controller for receiving the DC voltage from the rectifier and providing a switching signal;
a first circuit for receiving the switching signal from the controller, the first circuit including a first switching element that is selectively activated based on the switching signal;
a loading circuit for receiving the switching signal from the controller, wherein the loading circuit includes a second switching element that is activated if the first switching element is deactivated, the loading circuit selectively provides a minimum loading current that substantially dissipates the leakage current flowing through the TRIAC dimmer if the second switching element is activated, and wherein the loading circuit comprises a resistor, a zener diode, and a capacitor that define gate drive circuitry that conditions the switching signal before being sent to the second switching element.
25. The dimmer circuit as recited in claim 24 , wherein the loading circuit comprises a second resistor that is arranged in series with the second switching element.
26. The dimmer circuit as recited in claim 25 , wherein the minimum loading current is determined by the following equation:
a
voltage
of
the
zener
diode
-
a
gate
to
source
voltage
(
V
GS
)
of
the
second
switching
element
a
resistance
of
the
second
resistor
.