Self-contained, self-snubbed, HID dimming module that exhibits non-zero crossing detection switching
View Patent ↗A protection circuit for an HID dimming circuit is provided. A resistive component limits the initial current after a relay closes and current flows from a charged capacitor to a second capacitor. An inductive component limits the rate of change of current through the circuit. A voltage limited device limits voltage across the contacts of a solid state relay. The circuit is preferably formed in a small module that is adapted to be plugged into an HID lighting device.
1. A protective circuit for an HID dimming device comprising:
a relay having two contacts, a resistive device and an inductive device connected in series between a first capacitive device and a second capacitive device, said resistive device adapted to limit an initial current between said capacitive devices when said relay is closed, said inductive device adapted to limit the rate at which said current between said capacitive devices changes; and
a voltage limiting device connected between said relay contacts and adapted to prevent a voltage across said relay contacts from exceeding a predetermined threshold.
2. The protective circuit of claim 1 , wherein said resistive device is a negative temperature coefficient (NTC) thermistor.
3. The protective circuit of claim 1 , comprising a plurality of said resistive devices.
4. The protective circuit of claim 1 , wherein said inductive device is adapted to pass frequencies below a predetermined cut-off frequency that is above the operating frequency of an HID lamp connected to the HID dimming device.
5. The protective circuit of claim 1 , wherein the voltage limiting device is a metal oxide varistor (MOV).
6. The protective circuit of claim 1 , wherein the voltage limiting device is a zener diode.
7. The protective circuit of claim 1 , wherein said voltage limiting device becomes conductive if said voltage between said relay contacts:exceeds said predetermined threshold.
8. The protective circuit of claim 1 , wherein said relay is a solid state relay.
9. A dimming module comprising:
a relay having two input control contacts and two output contacts adapted to be connected to first and second capacitors;
a protection circuit comprising a resistive device adapted to limit an initial current between said capacitors when said relay is closed, an inductive device adapted to limit the rate of change of current between said capacitors, and a voltage limiting device connected between the relay contacts and adapted to prevent a voltage, across said relay contacts from exceeding a predetermined threshold.
10. The dimming module of claim 9 , wherein the predetermined threshold is at or below the rated voltage of the relay.
11. The dimming module of claim 9 , wherein the relay is a solid state relay.
12. The dimming module of claim 9 , wherein the resistive device is a negative temperature coefficient (NTC) thermistor.
13. The dimming module of claim 9 , comprising a plurality of resistive devices.
14. The dimming module of claim 9 , wherein the inductive device is adapted to pass frequencies below a predetermined cut-off frequency that is above the operating frequency of an HID lamp connected to the dimming module.
15. The dimming module of claim 9 , wherein the voltage limiting device is a metal oxide varistor (MOV).
16. The dimming module of claim 9 , wherein the voltage limiting device is a zener diode.
17. The dimming module of claim 9 , wherein said voltage limiting device becomes conductive if said voltage between said relay contacts exceeds said predetermined threshold.
18. The dimming module of claim 9 , wherein said module is adapted to be plugged into a relay socket of a HID lighting device.
19. The dimming module of claim 9 , wherein said resistive device, said inductive device, and said voltage limiting device are mounted on a printed circuit board.
20. The dimming module of claim 19 , wherein said PCB is adapted to be the same or smaller in size than said relay.
21. The dimming module of claim 20 , wherein said PCB comprises a notch corresponding to a mounting hole of said relay.
22. An HID dimming module comprising:
a non-conductive housing containing a dimming control drive for an HID lamp and a snubber circuit;
terminals extending from said housing adapted to connect said dimming module to a relay socket of a HID lighting device;
wherein said snubber circuit comprises a relay having two contacts, a resistive device and an inductive device connected in series between a first capacitive device and a second capacitive device, said resistive device adapted to limit an initial current between said capacitive devices when said relay is closed, said inductive device adapted to limit the rate at which said current between said capacitive devices changes; and a voltage limiting device connected between said relay contacts and adapted to prevent a voltage across said relay contacts from exceeding a predetermined threshold.
23. The dimming module of claim 22 , wherein said resistive device is a negative temperature coefficient (NTC) thermistor.
24. The dimming module of claim 22 , comprising a plurality of said resistive devices.
25. The dimming module of claim 22 , wherein said inductive device is adapted to pass frequencies below a predetermined cut-off frequency that is above the operating frequency of an HID lamp connected to the HID dimming device.
26. The dimming module of claim 22 , wherein the voltage limiting device is a metal oxide varistor (MOV).
27. The dimming module of claim 22 , wherein the voltage limiting device is a zener diode.
28. The dimming module of claim 22 , wherein said voltage limiting device becomes conductive if said voltage between said relay contacts exceeds said predetermined threshold.
29. The dimming module of claim 22 , wherein said relay is a solid state relay.
30. The dimming module of claim 22 , wherein the dimming control drive comprises a first PCB and the snubber circuit comprises a second PCB.
31. The dimming module of claim 30 , wherein the first PCB and the second PCB are mounted within said housing facing each other.