LED retrofit lamp with a strike barrier
A strike barrier for use in an LED retrofit lamp is provided. The present invention provides the strike barrier with two silicon controlled rectifiers (SCRs) whose input is connected to a bridge rectifier and output is connected to a string of LED through a Zener diode. The strike barrier is compatible with UL ANSI requirement for a normal mode and an abnormal mode.
1. A strike barrier for driving an LED retrofit lamp comprising:
a first silicon controlled rectifier having a gate terminal, a cathode terminal and an anode terminal connected to a bridge rectifier;
a first resistor divider having a first resistor between the gate terminal and the anode terminal, and a second resistor placed between the gate terminal and the cathode terminal of the first silicon controlled rectifier;
a second silicon controlled rectifier having a gate terminal, a cathode terminal and an anode terminal, said anode terminal of the second silicon controlled rectifier is connected to a first node present between the cathode terminal of the first silicon controlled rectifier and the second resistor;
a second resistor divider having a third resistor placed between the gate terminal and the cathode terminal of the second silicon controlled rectifier, and a fourth resistor placed between the gate terminal of the second controlled rectifier and a second node present between the first node and the second resistor;
a fifth resistor in parallel to the first silicon controlled rectifier connecting output from the bridge rectifier to the second silicon controlled rectifier, wherein a first end of the fifth resistor is connected to the input to first silicon controlled rectifier and a second end of the fifth resistor is connected to the first node and the second node;
wherein a third node between the cathode terminal and the gate terminal of the second silicon controlled rectifier is an output of the strike barrier.
2. The strike barrier of claim 1 , wherein the fifth resistor transfer the current coming from the bridge rectifier to the second silicon controlled rectifier bypassing the first silicon controlled rectifier.
3. The strike barrier of claim 1 , wherein latching value of the first silicon controlled rectifier and the second silicon controlled rectifier is set using the first resistor divider and the second resistor divider respectively.
4. The strike barrier of claim 3 , wherein the latching value of the first silicon controlled rectifier and second silicon controlled rectifier is set to 400V.
5. The strike barrier of claim 1 , wherein the strike barrier further comprises a first capacitor connected in parallel to the second resistor.
6. The strike barrier of claim 5 , wherein the first silicon controlled rectifier is latched using the first capacitor.
7. The strike barrier of claim 5 , wherein the first capacitor is having a capacitance value of 1 nF to 20 nF.
8. The strike barrier of claim 1 , wherein the strike barrier further comprises a second capacitor connected in parallel to the third resistor.
9. The strike barrier of claim 8 , wherein the second silicon controlled rectifier is latched using the second capacitor.
10. The strike barrier of claim 8 , wherein the second capacitor is having a capacitance value of 1 nF to 20 nF.
11. The strike barrier of claim 1 , wherein the first resistor and fourth resistor are having a resistance value of 1 MΩ to 10 MΩ.
12. The strike barrier of claim 1 , wherein the second resistor and third resistor are having a resistance value of 1 kΩ to 10 kΩ.
13. The strike barrier of claim 1 , wherein the fifth resistor is having a resistance value 50 kΩ to 100 kΩ.
14. The strike barrier of claim 1 , wherein the output of the strike barrier is connected to a Zener diode.
15. The strike barrier of claim 1 , wherein the strike barrier is compatible with UL ANSI requirement for a normal mode and an abnormal mode.
16. The strike barrier of claim 15 , wherein in the normal mode, the first silicon controlled rectifier and second silicon controlled rectifier are open, thereby conducting a small amount of current.
17. The strike barrier of claim 15 , wherein in the abnormal mode, if any of the first silicon controlled rectifier and the second silicon controlled rectifier gets shorted, the other acts as a barrier and if any other components get shorted, a hard short is created to the ballast resulting into opening a fuse.