Fault diagnosis circuit for LED indicating light

• US 6,888,454 B2
• Filed: 01/28/2003
• Issued: 05/03/2005
• Est. Priority Date: 02/25/2002
• Status: Expired due to Fees

• Current Assignee: PATLITE Corporation. (Inaba Denkisangyo Company Limited)
• Original Assignee: PATLITE Corporation. (Inaba Denkisangyo Company Limited)
• Inventors: Kurose, Takahiro
• Primary Examiner(s): Lieu, Julie B.
• Application Number:
  US10/352,810
• Publication Number:
  US 20030160703A1
• Time in Patent Office: 826 Days
• Field of Search: 340/664, 340/635, 340/652, 324/763, 324/556
• US Class Current: 340/514
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309

Abstract

A fault diagnosis circuit of the present invention includes: LED indicating units 3a, 3b, and so forth; current detecting circuits R1 and Q1 for detecting a flowing current by flowing a short-time pulse of a current through the LED indicating units 3a, 3b, and so forth based on pulses generated by a pulse generating circuit 7; comparing circuits 8 and 9 for comparing a current value detected by the current detecting circuits R1 and Q1 with their respective threshold values to judge a disconnection and a short-circuit; and retaining circuits 10 and 11 for generating a signal and retaining the signal when the current value is judged as being smaller and larger than the respective threshold values as a result of comparisons by the corresponding comparing circuits 8 and 9. Thus, it is possible to indicate a fault in an LED indicating light to the outside while making the turning ON of an LED unperceivable.

Claims

1. A fault diagnosis circuit for an LED indicating light, characterized by:

an LED indicating unit (3a, 3b);

a pulse generating circuit (7);

a current detecting circuit (R1, Q1) for detecting a flowing current by flowing a pulse of a current through said LED indicating unit (3a, 3b) based on pulses generated by said pulse generating circuit (7);

a comparing circuit (8, 22) for comparing a current value detected by said current detecting circuit (R1, Q1) with a threshold value (E1) to judge a disconnection;

a remaining circuit (10, 26) for generating a signal and retaining the signal when the current value is judged as being smaller than the threshold value (E1) as a result of a comparison by said comparing circuit (8,22); and

an output circuit (28) for outputting a disconnection notifying signal based on the signal retained by said retaining circuit (10, 26); and

wherein;

a time width of the pulse of the current flown through said LED indicating unit (3a, 3b) is set too short to perceive light emitted from said LED by sight.

4. The fault diagnosis circuit for an LED indicating light according to claim 1, 2, 3, wherein:

said pulse generating circuit (7) generates pulses respectively; and

said retaining circuit (10, 11, 25, 26, 34) retains and the signal during a pulse repetition cycle.

2. A fault diagnosis circuit for an LED indicating light, characterized by;

an LED indicating unit (3a, 3b);

a pulse generating circuit (7);

a current detecting circuit (R1, Q1) for detecting a flowing current by flowing a pulse of a current through said LED indicating unit (3a, 3b) based on pulses generated by said pulse generating circuit (7);

a comparing circuit (9, 21) for comparing a current value detected by said current detecting circuit (R1, Q1) with a threshold value (E2) to judge a short-circuit;

a retaining circuit (11, 25) for generating a signal and retaining the signal when the current value is judged as being larger than the threshold value (E2) as a result of a comparison by said comparing circuit (9, 21); and

an output circuit (27) for outputting a short-circuit notifying signal based on the signal retained by said retaining circuit (11, 25); and

wherein;

a time width of the pulse of the current flown through said LED indicating unit (3a, 3b) is set too short to perceive light emitted from said LED by sight.

3. A fault diagnosis circuit for an LED indicating light, characterized by:

an LED indicating unit (3a, 3b);

a pulse generating circuit (7);

a current detecting circuit (R1, Q1) for detecting a flowing current by flowing a pulse of a current through said LED indicating unit (3a, 3b) based on pulses generated by said pulse generating circuit (7);

a first comparing circuit (22) for comparing a current value detected by said current detecting circuit (R1, Q1) with a first threshold value (E1) to judge a disconnection;

a second comparing circuit (21) for comparing the current value detected by said current detecting circuit (R1, Q1) with a second threshold value (E2) to judge a short-circuit;

retaining circuit (34) for generating a signal and retaining the signal when the current value is judged as being larger than the first threshold value (E1) to judge the disconnection and smaller than the second threshold value (E2) to judge the short-circuit as a result of comparisons by said first and second comparing circuits (21, 22); and

an output circuit (35) for outputting a normality notifying signal based on the signal retained by said retaining circuit (34); and

wherein;

a time width of the pulse of the current flown through said LED indicating unit (3a, 3b) is set too short to perceive light emitted from said LED by sight.