Automobile LED driving device

• US 9,148,915 B2
• Filed: 05/07/2014
• Issued: 09/29/2015
• Est. Priority Date: 09/29/2010
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Aoki, Akira, Miyamoto, Koji
• Primary Examiner(s): Le, Tung X
• Application Number:
  US14/271,625
• Publication Number:
  US 20140239851A1
• Time in Patent Office: 510 Days
• Field of Search: 315/77, 315/82, 315/224, 315/225, 315/291, 315/294, 315/297, 315/307, 315/308, 307/10.8
• US Class Current: 1/1
• CPC Class Codes: B60Q 11/005 for lighting devices, e.g. indicating if lamps are burning or not
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 47/24 Circuit arrangements for protecting against overvoltage

Abstract

An automobile LED driving device includes a current setting portion to set multiple reference currents independently from one another for multiple respective current setting resistors connected externally, a current controller to select one of the multiple reference currents based on a control signal provided from outside, and an output transistor to control an output current to an automobile LED connected externally based on the reference current selected by the current controller.

Claims

1. A light emitting device driving device comprising:

a current setting portion to set a reference current for a current setting resistor connected externally to the light emitting device driving device,

an output transistor to control an output current to a light emitting device connected externally to the light emitting device driving device based on the reference current,

a controller to generate an operation control signal according to a detection of an abnormality and to perform an external input/output process for the operation control signal, and

a current controller to control a current supply to the light emitting device based on the operation control signal.

2. The light emitting device driving device according to claim 1 further comprising:

a open circuit detector to detect the open circuit of the light emitting device.

3. The light emitting device driving device according to claim 2, wherein the open circuit detector comprises:

a second comparator to generate a open circuit detection signal based on a comparison between a terminal voltage of an external terminal, to which the light emitting device is connected externally to the light emitting device driving device, and a second threshold voltage, and

an amplifier to generate a current restriction signal by amplifying a difference between the terminal voltage and a clamp voltage lower than the second threshold voltage,

wherein the current controller controls the output current to the light emitting device based on the current restriction signal such that the terminal voltage does not exceed the clamp voltage.

4. The light emitting device driving device according to claim 1, wherein the current setting portion generates the reference current by applying a constant voltage to the current setting resistor.

5. The light emitting device driving device according to claim 1, wherein the current setting portion generates a current setting voltage by flowing a constant current to the current setting resistor, and generates the reference current by applying the current setting voltage to an internal resistor.

6. The light emitting device driving device according to claim 1 further comprising:

a ground short detector to detect the ground short of the light emitting device,

wherein the current controller turns OFF a supply of the output current forcibly when the ground short of the light emitting device occurs.

7. The light emitting device driving device according to claim 6, wherein the ground short detector comprises:

a first comparator to generate a ground short detection signal based on a comparison between a forward drop voltage of the light emitting device or a monitor voltage according to the forward drop voltage and a first threshold voltage, and

a ground short recovery circuit to generate the forward drop voltage by flowing current to the light emitting device when recovering the ground short of the light emitting device.

8. A light emitting device driving device comprising:

a current setting portion to set a reference current for a current setting resistor connected externally to the light emitting device driving device,

an output transistor to control an output current to a light emitting device connected externally to the light emitting device driving device based on the reference current,

a ground short detector to detect the ground short of the light emitting device, and

a current controller to turn OFF a supply of the output current forcibly when the ground short of the light emitting device occurs, wherein the ground short detector comprises;

a first comparator to generate a ground short detection signal based on a comparison between a forward drop voltage of the light emitting device or a monitor voltage based on the forward drop voltage and a first threshold voltage, and

a ground short recovery circuit to generate the forward drop voltage by flowing current to the light emitting device when recovering the ground short of the light emitting device.

9. The light emitting device driving device according to claim 8 further comprising:

a open circuit detector to detect the open circuit of the light emitting device.

10. The light emitting device driving device according to claim 9, wherein the open circuit detector comprises:

a second comparator to generate the open circuit detection signal based on a comparison between a terminal voltage of an external terminal, to which the light emitting device is connected externally to the light emitting device driving device, and a second threshold voltage, and

an amplifier to generate a current restriction signal by amplifying a difference between the terminal voltage and a clamp voltage lower than the second threshold voltage,

wherein the current controller controls the output current to the light emitting device based on the current restriction signal such that the terminal voltage does not exceed the clamp voltage.

11. A light emitting device driving device comprising:

a current setting portion to set a reference current for a current setting resistor connected externally to the light emitting device driving device, and

an output transistor to control an output current to a light emitting device connected externally to the light emitting device driving device based on the reference current,

wherein the current setting portion generates a current setting voltage by flowing a constant current to the current setting resistor, and generates the reference current by applying the current setting voltage to an internal resistor, and

wherein a negative characteristic thermistor is connected in parallel to the current setting resistor.

12. A light emitting device driving device comprising:

a current setting portion to set a reference current for a current setting resistor connected externally to the light emitting device driving device,

an output transistor to control an output current to a light emitting device connected externally to the light emitting device driving device, and

a current controller to control the output transistor based on the reference current,

wherein the current controller comprises;

an input transistor forming a current mirror circuit with the output transistor and generating a mirror current to the output transistor according to the reference current provided to the input transistor.

13. The light emitting device driving device according to claim 12 further comprising:

a bias portion to equalize the source-drain voltages of the input transistor and the output transistor.

14. A light emitting device driving device comprising:

a current setting portion to set a reference current for a current setting resistor connected externally to the light emitting device driving device,

an output transistor to control an output current to a light emitting device connected externally to the light emitting device driving device based on the reference current,

a ground short detector to detect the ground short of the light emitting device,

a current controller to turn OFF a supply of the output current forcibly when the ground short of the light emitting device occurs; and

a open circuit detector to detect the open circuit of the light emitting device, wherein the open circuit detector comprises;

a second comparator to generate the open circuit detection signal based on a comparison between a terminal voltage of an external terminal, to which the light emitting device is connected externally to the light emitting device driving device, and a second threshold voltage, and

an amplifier to generate a current restriction signal by amplifying a difference between the terminal voltage and a clamp voltage lower than the second threshold voltage,

wherein the current controller controls the output current to the light emitting device based on the current restriction signal such that the terminal voltage does not exceed the clamp voltage.