Load driving apparatus

Patent metadata

Field	Value
Publication number	US-10874009-B2
Application number	US-201816207159-A
Country	US
Kind code	B2
Filing date	Dec 2, 2018
Priority date	Jun 13, 2016
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A load driving apparatus receives an input voltage from a power supply, and supplies electric power to a load under processor control. The processor outputs first and second signals via first and second pins in a conjunction such that they are negated when the load is instructed to suspend operation. An output circuit supplies electric power to the load. A protection switch is provided on a driving path that extends from the power supply to the load and returns to the power supply. When the first signal is asserted (negated), a control circuit sets the output circuit to an operation state (suspension state). The control circuit turns on the protection switch on assertion of the second signal, and turns it off on negation of this signal.

First claim

The invention claimed is:

1. A load driving apparatus structured to receive an input voltage from a power supply, and to supply an electric power to a load under a control operation of a processor, wherein the processor outputs a first signal and a second signal in conjunction via a first pin and a second pin such that the first signal and the second signal are negated when the load is instructed to suspend an operation thereof,
and wherein the load driving apparatus comprises:
an output circuit structured to supply an electric power to the load;
a protection switch provided on a driving path that extends from the power supply to the load and returns to the power supply; and
a control circuit structured to be set to an operation state when the first signal is asserted, to be set to a suspension state when the first signal is negated, to turn on the protection switch when the second signal is asserted, and to turn off the protection switch when the second signal is negated.

2. The load driving apparatus according to claim 1 , wherein the output circuit comprises a transistor structured to adjust an electrical state of the load,
wherein the control circuit is structured to control the transistor such that the electrical state of the load approaches a target value when the first signal is asserted, and structured to turn off the transistor when the first signal is negated.

3. The load driving apparatus according to claim 2 , wherein the output circuit is configured as a switching converter, and wherein the transistor is configured as a switching transistor.

4. The load driving apparatus according to claim 1 , wherein the load comprises a light-emitting element structured to emit an excitation light and a fluorescent member structured to be excited by the excitation light and to emit a fluorescence light, and is structured to output a white output light having spectrum of the excitation light and the fluorescence light,
and wherein, when a light leakage abnormality is detected in the light source, the processor negates the first signal and the second signal.

5. The load driving apparatus according to claim 1 , wherein at least one from among the first signal and the second signal is generated as a pulse signal in an asserted state, and is generated as a DC signal in a negated state.

6. An automotive lamp comprising:
a light source;
the load driving apparatus according to claim 1 , structured to drive the light source; and
a processor structured to control the load driving apparatus.

7. A lighting circuit employed in an automotive lamp, the lighting circuit comprising:
a driving circuit structured to supply a driving current to a light-emitting element of a light source; and
an abnormality detector structured to detect an abnormality that can occur in the light source,
wherein the lighting circuit is structured to be switchable between a first mode in which the driving current is raised with a first slope when lighting is started up and a second mode in which the driving current is raised with a second slope that is smaller than the first slope when lighting is started up.

8. The lighting circuit according to claim 7 , wherein a target value of the driving current in the second mode is substantially the same as the target value of the driving current in the first mode.

9. The lighting circuit according to claim 7 , wherein the light source comprises:
a laser diode structured as a light-emitting element; and
a fluorescent member structured to be excited by an excitation light emitted from the laser diode, and to emit a fluorescence light, so as to generate a white output light including the excitation light and a fluorescence spectrum,
and wherein the abnormality detector detects an abnormality which is leakage of the excitation light.

10. The lighting circuit according to claim 7 , wherein, when the automotive lamp is to be tested, the second mode is selected.

11. The lighting circuit according to claim 7 , wherein, when a speed of a vehicle is lower than a predetermined threshold value, the second mode is selected.

12. An automotive lamp comprising:
a light source comprising a light-emitting element; and
the lighting circuit according to claim 7 , structured to supply a driving current to the light-emitting element.

13. A lighting circuit employed in an automotive lamp, the lighting circuit comprising:
a driving circuit structured to supply a driving current to a light-emitting element of a light source; and
an abnormality detector structured to detect an abnormality that can occur in the light source,
wherein the lighting circuit is structured to be switchable between a first mode in which the driving current is raised up to a predetermined value in a first start-up time when lighting is started up and a second mode in which the driving current is raised up to the predetermined value in a second start-up time that is longer than the first start-up time when lighting is started up.

14. The lighting circuit according to claim 13 , wherein the light-emitting element comprises a laser diode,
and wherein the predetermined value is determined to be higher than an oscillation threshold value of the laser diode.

Assignees

• Koito Mfg Co Ltd

Inventors

• Ichikawa Tomoyuki
• Tsuda Toshiaki

Classifications

• H05B47/17

  Operational modes, e.g. switching from manual to automatic mode or prohibiting specific operations · CPC title

• H05B45/50

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

• H05B45/375 Primary

  using buck topology · CPC title

• H05B45/3725

  Switched mode power supply [SMPS] · CPC title

• F21S41/16

  Laser light sources · CPC title