# US 9,521,720 B2 · System for controlling the supply of power to and for thermal management of light sources

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- Number: US 9,521,720 B2
- Document ID: US9521720B2
- Status: Granted
- Kind: B2
- Application number: 14/794,980
- Filed: 2015-07-09
- Published: 2016-01-14
- Granted: 2016-12-13
- Earliest claimed: 2014-07-11
- Assignees: Valeo Vision
- Applicants: Valeo Vision
- Inventors: Patrick Wacheux
- Web page: https://patentgrep.com/patent/US9521720B2

## CPC

- H02H 5/04: responsive to abnormal temperature {(specially adapted for electric machines H02H7/0852)}
- H05B 45/3725: Switched mode power supply [SMPS]
- H05B 45/48: having LEDs organised in strings and incorporating parallel shunting devices
- H05B 45/56: involving measures to prevent abnormal temperature of the LEDs
- H05B 45/375: using buck topology
- H05B 45/38: using boost topology
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

A device and method for controlling the supply of power to light sources, in which a DC/DC converter is capable of delivering a voltage VMAX to the light sources. The forward voltage of the light sources depends on temperature and may temporarily exceed VMAX at low temperatures. The invention proposes means that allow the required forward voltage to be decreased automatically depending on a measurement of ambient temperature.

## Claims

### Claim 1

A device for controlling the supply of power to light sources, comprising:
a DC/DC converter capable of converting an input electrical voltage into an output electrical voltage;
a circuit mounted to load said converter comprising a plurality of light sources mounted in series;
wherein said device furthermore comprises at least one switching circuit comprising switching means intended to short-circuit at least one of said plurality of light sources depending on a temperature measurement obtained by means for measuring ambient temperature;
wherein said at least one switching circuit comprises:
an electrical circuit comprising a thermistor, said electrical circuit being able to deliver two electrical voltage levels, said two electrical voltage levels being substantially equal when the ambient temperature is above said temperature threshold, and said two electrical voltage levels being different when the ambient temperature is below said temperature threshold.

### Claim 2 (depends on 1)

The device according to claim 1, wherein said converter comprises at least one of a boost type circuit, able to increase the voltage, or a buck type circuit, able to decrease the voltage.

### Claim 3 (depends on 2)

The device according to claim 2, wherein said plurality of light sources are light-emitting diodes (LEDs), characterized, inter-alia, by their voltage drop, or forward voltage, VF.

### Claim 4 (depends on 2)

The device according to claim 2, wherein said at least one switching circuit is able to short-circuit at least one of said plurality of light sources only when said temperature measurement is below a temperature threshold.

### Claim 5 (depends on 1)

The device according to claim 1, wherein said plurality of light sources are light-emitting diodes (LEDs), characterized, inter-alia, by their voltage drop, or forward voltage, VF.

### Claim 6 (depends on 5)

The device according to claim 5, wherein:
said plurality of LEDs comprises a number N of LEDs; and
said at least one or more switching circuits are able to short-circuit a number M<N of LEDs; and in that
at an ambient temperature below said temperature threshold, the overall voltage drop N*VF is larger than the maximum electrical voltage VMAX that said converter is capable of delivering to said load circuit, whereas the voltage drop during a short-circuit (N−M)*VF, is smaller than or equal to VMAX.

### Claim 7 (depends on 5)

The device according to claim 5, wherein said at least one switching circuit is able to short-circuit at least one of said plurality of light sources only when said temperature measurement is below a temperature threshold.

### Claim 8 (depends on 1)

The device according to claim 1, wherein said at least one switching circuit is able to short-circuit at least one of said plurality of light sources only when said temperature measurement is below a temperature threshold.

### Claim 9 (depends on 4)

The device according to claim 4, wherein said temperature threshold is below −10° C. and preferably below −15° C.

### Claim 10 (depends on 1)

The device according to claim 1, wherein said at least one switching circuit furthermore comprises a comparator element arranged so as to compare said two electrical voltage levels delivered, and to control the state of a switching element able to short-circuit at least one light source depending on the result of the comparison.

### Claim 11 (depends on 10)

The device according to claim 10, wherein said comparator element is coupled to said at least one switching element by way of a current mirror.

### Claim 12 (depends on 10)

The device according to claim 10, wherein said electrical circuit and said comparator element are supplied with the forward voltage of at least one of said plurality of light sources, VF, and preferably of at least two of said plurality of light sources, 2*VF.

### Claim 13 (depends on 1)

A luminous device for an automotive vehicle comprising at least one device for controlling the supply of power to light sources, especially providing a luminous signalling function of the automotive vehicle, wherein said control device is in accordance with claim 1.

### Claim 14

A method for controlling the supply of power to light sources, comprising steps of:
providing a DC/DC converter capable of converting an input electrical voltage into an output electrical voltage;
providing a circuit mounted to load said converter comprising a plurality of light sources mounted in series;
selectively short-circuiting at least one of said plurality of light sources via at least one switching circuit depending on a temperature measurement obtained by means for measuring ambient temperature;
providing said at least one switching circuit with an electrical circuit comprising a thermistor; and
delivering two electrical voltage levels by said electrical circuit, said two electrical voltage levels being substantially equal when the ambient temperature is above said temperature threshold, and said two electrical voltage levels being different when the ambient temperature is below said temperature threshold.

### Claim 15

A device for controlling the supply of power to light sources, comprising:
a DC/DC converter capable of converting an input electrical voltage into an output electrical voltage;
a circuit mounted to load said converter comprising a plurality of light sources mounted in series;
wherein said device furthermore comprises at least one switching circuit comprising a switch intended to short-circuit at least one of said plurality of light sources depending on a measurement of an ambient temperature;
wherein said at least one switching circuit comprises:
an electrical circuit comprising a thermistor, said electrical circuit being able to deliver two electrical voltage levels, said two electrical voltage levels being substantially equal when the ambient temperature is above said temperature threshold, and said two electrical voltage levels being different when the ambient temperature is below said temperature threshold.

### Claim 16 (depends on 15)

The device according to claim 15, wherein said converter comprises at least one of a boost type circuit, able to increase the voltage, or a buck type circuit, able to decrease the voltage.

### Claim 17 (depends on 15)

The device according to claim 15, wherein said plurality of light sources are light-emitting diodes (LEDs), characterized, inter-alia, by their voltage drop, or forward voltage, VF.

### Claim 18 (depends on 15)

The device according to claim 15, wherein said at least one switching circuit is able to short-circuit at least one of said plurality of light sources only when said temperature measurement is below a temperature threshold.

### Claim 19 (depends on 15)

The device according to claim 15, wherein:
said plurality of LEDs comprises a number N of LEDs; and
said at least one or more switching circuits are able to short-circuit a number M<N of LEDs; and in that
at an ambient temperature below said temperature threshold, the overall voltage drop N*VF is larger than the maximum electrical voltage VMAX that said converter is capable of delivering to said load circuit, whereas the voltage drop during a short-circuit (N−M)*VF, is smaller than or equal to VMAX.