Method and device for remote monitoring of led lamps

• US 20030042914A1
• Filed: 10/02/2002
• Published: 03/06/2003
• Est. Priority Date: 11/19/1999
• Status: Active Grant

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: Gelcore (General Electric Company)
• Inventors: St-Germain, Nicolas
• Granted Patent: US 6,624,638 B2
• Time in Patent Office: Days
• US Class Current: 324/617
• CPC Class Codes: B61L 2207/02 using light-emitting diodes [LEDs]
• CPC Class Codes: B61L 5/1881 Wiring diagrams for power supply, control or testing
• CPC Class Codes: G01R 31/44 Testing lamps
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits

Abstract

LED lamp circuitry that emulates an incandescent lamp'"'"'s behaviour upon remote verification of the LED lamp. The invention presents a fuse blow-out circuit and a cold filament detection circuit permitting the use of LED lamps in applications, such as railway signal light applications, where there is a need for remote monitoring of the lamps, while keeping the advantageous features of lower power consumption and longer life. The invention also provides a control circuit for enabling/disabling the power supply to LED lamps in relation to the level of the line voltage. The advantage of this embodiment is to avoid unwanted functioning of the LED lamp caused by interference from surrounding electrical cables.

Claims

1. A power supply unit responsive to alternating voltage and current from an ac source for supplying a dc voltage and current to a light-emitting load, comprising:

a) a rectifier unit rectifying the alternating voltage and current from the ac source and suppling the rectified voltage and current to first and second voltage and current supply lines;

b) a protection fuse through which the alternating current from the ac source is supplied to the rectifier unit;

c) a converter of the rectified voltage and current into the dc voltage and current supplied to the light-emitting load;

d) a fuse blow-out circuit for establishing a short circuit between the first and second voltage and current supply lines to blow out the protection fuse said fuse blow-out circuit comprising;

a resistor and a capacitor connected in series between the first and second lines, said resistor having a given resistance value, and said capacitor having a given capacitance value and a capacitor charge period dependent on said given resistance value and said given capacitance value;

a trigger circuit connected in parallel with the capacitor, and comprising a fist controllable switch member closed in response to the current supplied to the light-emitting load to discharge said capacitor; and

a second controllable switch member defining a current path between said first and second lines and closed in response to a given voltage amplitude across the capacitor;

whereby, in the absence of current supplied to the light-emitting load for a duration equivalent to said capacitor charge period, said given voltage amplitude across said capacitor is reached to thereby close said second switch member, establish said current path and provide the short circuit between the first and second lines that will blow out the protection fuse and emulate an open circuit of a defective incandescent lamp; and

e) a controller of the converter in response to the recitified voltage on the first and second lines.

2. A power supply unit as in claim 1, wherein said first controllable switch member comprises a first transistor.

3. A power supply unit as in claim 2, wherein said transistor is a first resistor, said capacitor is a first capacitor, and said second controllable switch member comprises:

a) a second resistor connected in series with a second capacitor, said serially interconnected second resistor and second capacitor being connected in parallel with said first capacitor;

b) a semiconductor switch selected from the group consisting of a triac and a silicon bilateral switch, said semiconductor switch connected in parallel with said second capacitor, said semiconductor switch having first and second semiconductor switch electrodes, and a trigger electrode;

c) a Zener diode connected between the trigger electrode and one of the first and second semiconductor switch electrodes, said Zener diode having a breakdown voltage value and being responsive to a voltage across said second capacitor; and

d) a thyristor connected between said first and second lines and having a trigger electrode connected to one of said first and second semiconductor switch electrodes;

whereby, in the absence of current supplied to the light-emitting load for a duration equivalent to said capacitor charge period, said given voltage amplitude across said first capacitor is reached to thereby charge said second capacitor is reached to thereby charge said second capacitor through said second resistor until said breakdown voltage value os the Zener diode is reached and said semiconductor switch is triggered to thereby trigger said thyristor, establish through said tyristor said current path, and provide the short circuit between the first and second lines that will blow the protection frst and emulate an open circuit of a defective incandescent lamp.

4. A power supply unit as in claim 3, further comprising a third resistor connected in series with the first resistor between said first and second lines, wherein said first capacitor is connected in parallel with the third resistor.

5. A power supply unit as in claim 2, wherein said second controllable switch member comprises:

a) a second transistor connected in parallel with said capacitor and having a control electrode;

b) a Zener diode connected between the control electrode of the second transistor and said capacitor, having a breakdown voltage, and being responsive to the voltage across the capacitor, and

c) a third transistor connected between said first and second lines and having a control electrode activated by the second transistor;

whereby, in the absence of current supplied to the light-emitting toad for a duration equivalent to said capacitor charge period, said given voltage amplitude across said capacitor is reached to successively apply said breakdown voltage to the Zener diode, turn on said second transistor, and turn on said third transistor to establish said current path and provide the short circuit between the first and second lines that will blow out the protection fuse and emulate an open circuit of a defective incandescent lamp.

6. A power supply unit as in claim 5, wherein said resistor is a first resistor, and said fuse blow-out circuit further comprises a second resistor connected in series with said first resistor, said capacitor being connected in parallel with said second resistor.