Device for driving light emitting diode for flash of camera

• US 20050265709A1
• Filed: 09/08/2004
• Published: 12/01/2005
• Est. Priority Date: 05/31/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Kim, Hyung Suk, Kim, Yong Chun
• Granted Patent: US 7,236,697 B2
• Time in Patent Office: Days
• US Class Current: 396/205
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0567 Solid-state light source, e.g. LED, laser
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/651 for reducing power consumption by affecting camera operations, e.g. sleep mode, hibernation mode or power off of selective parts of the camera

Abstract

Disclosed herein is a device for driving a LED for a flash of a camera, such as a digital camera or a camera of a mobile phone, which is capable of driving the LED in two modes to reduce power consumption. The LED drive device comprises the LED, a continuous low current driver for continuously supplying current which is lower than or equal to rated current of the LED to the LED, a high-current pulse driver for supplying current which is higher than the rated current of the LED to the LED for a predetermined period of time, and a mode selector for selecting one of the continuous low current driver and the high-current pulse driver to drive the LED. According to the present invention, it is possible to prevent unnecessary power consumption and deterioration of reliability of the LED, and obtain an image of brighter picture quality.

Claims

1. A device for driving a light emitting diode (LED) for a flash of a camera, comprising:

said LED;

a continuous low current driver for continuously supplying current which is lower than or equal to rated current of said LED to said LED;

a high-current pulse driver for supplying current which is higher than the rated current of said LED to said LED for a predetermined period of time; and

a mode selector for selecting one of said continuous low current driver and said high-current pulse driver to drive said LED.

2. The device as set forth in claim 1, wherein said current supplied from said high-current pulse driver is a maximum of four times the rated current of said LED.

3. The device as set forth in claim 1, wherein said predetermined time period is 10 msec at maximum.

4. A device for driving an LED for a flash of a camera, comprising:

said LED having one end connected to a voltage source;

a mode selector having a first terminal and a second terminal, said mode selector selectively connecting any one of said first and second terminals to a ground terminal;

continuous low current drive means having one end connected to said first terminal and the other end connected to the other end of said LED; and

high-current pulse drive means including a switching circuit for connecting said other end of said LED to said ground terminal for a predetermined period of time, and switching circuit control means connected between said second terminal and said switching circuit for providing a signal for control of the time period to said switching circuit.

5. The device as set forth in claim 4, wherein said continuous low current drive means is a resistor having one end connected to said first terminal and the other end connected to said other end of said LED.

6. The device as set forth in claim 4, wherein said switching circuit control means is an RC charging circuit, said RC charging circuit including:

a first resistor having one end connected to said voltage source and the other end connected to said second terminal;

a second resistor having one end connected to said voltage source; and

a capacitor having one end connected to the other end of said second resistor and the other end connected to said second terminal.

7. The device as set forth in claim 6, wherein said switching circuit includes:

a PNP transistor having a collector connected to said voltage source and a base connected to said other end of said second resistor; and

an NPN transistor having a collector connected to said other end of said LED, a base connected to an emitter of said PNP transistor and an emitter connected to said ground terminal.