Light source driving device, and image processing device, image reading device and image forming apparatus using the light source driving device

• US 8,537,431 B2
• Filed: 03/28/2011
• Issued: 09/17/2013
• Est. Priority Date: 04/12/2010
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Oyama, Tadaaki
• Primary Examiner(s): Worku, Negussie
• Application Number:
  US13/073,200
• Publication Number:
  US 20110249069A1
• Time in Patent Office: 904 Days
• Field of Search: 358/475, 358/509, 358/474, 358/501, 358/488, 358/448, 347/129, 399/220
• US Class Current: 358/474
• CPC Class Codes: B41J 2/45 using light-emitting diode [LED] or laser arrays
• CPC Class Codes: G03G 15/04045 for exposing image information provided otherwise than by directly projecting the original image onto the photoconductive recording material, e.g. digital copiers G03G15/041, G03G15/043 take precedence
• CPC Class Codes: G03G 15/5004 Power supply control, e.g. power-saving mode, automatic power turn-off
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light source driving device for driving plural light sources is provided. The light source driving device includes a voltage booster to boost a voltage from a power source to supply the boosted voltage to each of the plural light sources; a constant current driver to regularly hold driving current of each of the plural light sources constant; a load to consume substantially the same power as the plural light sources; and a switch to selectively connect either the load or the plural light sources with the voltage booster and the constant current driver so that the load or the plural light sources are interposed between the voltage booster and the constant current driver.

Claims

1. A light source driving device for driving plural light sources, comprising:

a voltage booster to perform a voltage boosting operation of boosting a supply voltage from a power source to supply the boosted voltage to each of the plural light sources;

a constant current driver to regularly hold driving current for each of the plural light sources constant;

a load, that is separate from the plural light sources, to consume substantially a same power as all of the plural light sources; and

a switch to perform a switching operation of selectively connecting either the load or the plural light sources with the voltage booster and the constant current driver so that either the load or the plural light sources are connected and positioned in between the voltage booster and the constant current driver.

2. The light source driving device according to claim 1, wherein the switch connects the load with the voltage booster and the constant current driver from start of the voltage boosting operation of the voltage booster to completion of the voltage boosting operation, and connects the plural light sources with the voltage booster and the constant current driver after completion of the voltage boosting operation.

3. The light source driving device according to claim 2, wherein the switch performs the switching operation in synchronization with an external control signal.

4. The light source driving device according to claim 2, wherein the constant current driver is activated by an external start signal, and wherein the constant current driver includes a signal generator generating a signal under the external start signal to allow the switch to perform the switching operation.

5. The light source driving device according to claim 1, further comprising:

a shutoff device to electrically shield the plural light sources from each other.

6. The light source driving device according to claim 5, wherein the shutoff device is a diode.

7. The light source driving device according to claim 1, wherein the load is a resistor.

8. The light source driving device according to claim 1, wherein the light source driving device is a single integrated circuit.

9. An image processing device comprising:

plural light sources to irradiate an object;

the light source driving device according to claim 1 to drive the plural light sources;

an image sensor to receive light reflected from the object while generating analog signals; and

a processor to process the analog signals.

10. The image processing device according to claim 9, wherein the image processing device is an image reading device, and wherein the processor processes the analog signals to obtain image data of the object.

11. An image forming apparatus comprising:

the image processing device according to claim 10 to read image data of an object; and

an image forming device to form an image on a recording material according to the read image data.

12. The image forming apparatus according to claim 11, wherein the image forming device includes:

an image bearing member;

a charger to charge the image bearing member;

an irradiator to irradiate the charged image bearing member with light to form an electrostatic latent image on the image bearing member;

a developing device to develop the electrostatic latent image with a developer to form a toner image on the image bearing member;

a transferring device to transfer the toner image onto a recording material; and

a fixing device to fix the toner image on the recording material.

13. An image forming apparatus comprising:

the light source driving device according to claim 1;

plural light sources to irradiate an object while being driven by the light source driving device; and

an image forming device to form an electrostatic latent image on an image bearing member with light reflected from the object.

14. The image forming apparatus according to claim 13, wherein the image forming device includes:

the image bearing member;

a developing device to develop the electrostatic latent image on the image bearing member with a developer to form a toner image on the image bearing member;

a transferring device to transfer the toner image onto a recording material; and

a fixing device to fix the toner image on the recording material.

15. A light source driving device for driving plural light sources, comprising:

voltage boosting means for performing a voltage boosting operation of boosting a supply voltage from a power source to supply the boosted voltage to each of the plural light sources;

constant current driving means for regularly holding driving current for each of the plural light sources constant;

load means for consuming substantially a same power as all of the plural light sources, the load means is separate from the plural light sources; and

switching means for performing a switching operation of selectively connecting either the load or the plural light sources with the voltage boosting means and the constant current driving means so that either the load or the plural light sources are connected and positioned in between the voltage boosting means and the constant current driving means.