Individual LED short circuit detection

Patent metadata

Field	Value
Publication number	US-10178734-B1
Application number	US-201815881891-A
Country	US
Kind code	B1
Filing date	Jan 29, 2018
Priority date	Jan 29, 2018
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

An LED lighting circuit for detecting individual LED failure, including a lighting unit including a plurality of LEDs connected in series, and a plurality of LED sensors each associated with a respective one of the LEDs. Also included is a lighting unit status signal generator coupled to the plurality of LED sensors configured to provide a status signal indicating a fault when any individual LED is short circuited.

First claim

The invention claimed is:

1. A light source failure detection circuit for monitoring a plurality of light sources, comprising at least two circuit paths that are arranged in parallel and in connection with an indicator resistor, each of the at least two circuit paths comprising:
a first transistor that functions as a first switch and is controllable by a voltage on one of the plurality of light sources to be in an on or off state;
a voltage divider circuit connected between the first switch and a ground, receiving a current controlled by the first switch, and providing an input voltage to a second transistor functioning as a second switch;
a resistor connected in series with the second transistor, wherein the resistor and the second transistor connected between a supply voltage and the ground; and
a diode, wherein an anode of the diode receives a current from a node between the resistor and the second transistor, and an cathode of the diode outputs a current to the indicator resistor,
wherein a voltage drop on the indicator resistor above a threshold indicates one of the plurality of light sources is shorted.

2. The light source failure detection circuit of claim 1 , wherein the plurality of light sources are connected in series or in parallel.

3. The light source failure detection circuit of claim 1 , wherein the first or second transistors include a bipolar transistor.

4. The light source failure detection circuit of claim 1 , wherein the plurality of light sources include a light emitting diode (LED).

5. An exterior vehicle lighting device, comprising the light source failure detection circuit of claim 1 .

6. A motor vehicle, comprising the exterior vehicle lighting device of claim 5 .

7. A light source failure detection circuit for monitoring a series of light sources arranged between a current source and a ground, comprising:
a series of transistors each corresponding to one of the series of the light resources, each transistor functioning as a switch controllable by a voltage on the respective light source to be in an on or off state, each transistor followed by a first resistor;
an indicator resistor, wherein the transistors, first resistors, and the indicator resistor are connected in series forming a current path that is connected between the current source and the ground;
a plurality of second resistors each corresponding to one of the series of transistors, each second resistor having a first end and a second end, each second end in connection with a base or a gate of the respective transistor, each first end, except that of the second resistor corresponding to the last transistor, in connection with a first node between the respective light source and the next light resource, the first end of the second resistor corresponding to the last transistor in connection with the ground; and
one or more diodes each corresponding to one of the series of transistors except the last transistor, wherein an anode of each diode receives a current from a second node between the first resistor following the respective transistor and the next transistor, and an cathode of each diode is in connection with the first node between the respective light resource and the next light resource,
wherein a voltage drop on the indicator resistor below a threshold indicating at least one of the series of light sources is shorted.

8. The light source failure detection circuit of claim 7 , further comprising an output stage connected between a supply voltage and the ground, the output stage comprising:
a third resistor and a transistor connected in series, wherein the transistor functions as a switch controlled be the voltage drop on the indicator resistor, and an output voltage of the transistor when the transistor is turned off indicates at least one of the series of light sources is shorted.

9. The light source failure detection circuit of claim 7 , wherein the transistors include a bipolar transistor.

10. The light source failure detection circuit of claim 7 , wherein the series of light sources include a light emitting diode (LED).

11. An exterior vehicle lighting device, comprising the light source failure detection circuit of claim 7 .

12. A motor vehicle, comprising the exterior vehicle lighting device of claim 11 .

Assignees

• Valeo North America Inc

Inventors

• Moumen Monji
• Larribe Sylvain

Classifications

• B60Q11/005 Primary

  for lighting devices, e.g. indicating if lamps are burning or not · CPC title

• H05B45/48

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• H05B45/50

  responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits · CPC title

• H05B33/089 Primary

  Electricity · mapped topic

• H05B33/0845

  Electricity · mapped topic