News Column

Patent Issued for Semiconductor Laser Drive Device and Image Forming Apparatus Incorporating Same

January 29, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- Ricoh Company, Ltd. (Tokyo, JP) has been issued patent number 8630324, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Sumino, Daijiroh (Osaka, JP); Kyogoku, Hiroaki (Hyogo, JP).

This patent was filed on June 30, 2011 and was published online on January 14, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Recently, semiconductor laser diodes (hereinafter, referred to as 'semiconductor laser') have come to be widely used in a variety of image forming apparatuses using electrophotography, for example, laser printers and digital copiers.

"However, the semiconductor laser degrades due to various factors. More specifically, degradation of the semiconductor laser may arise due to crystal defect within several hours. Further, the degradation of the semiconductor laser may arise gradually by being driven at high temperature for a long time.

"Further, the degradation of the semiconductor laser may arise due to catastrophic optical damage (COD) or an electrostatic discharge (ESD) during assembly of the laser printers and the digital copiers.

"When the semiconductor laser degrades, a larger drive current is required to emit light at a predetermined intensity (quantity of light). When the drive current is increased excessively and power consumption exceeds a rated value, the semiconductor laser may degrade due to heat generated by the power and cause trouble. Further, when a large current beyond the assumed value flows from a semiconductor laser drive device, there is also a possibility of a defect arising due to melting of metal wiring.

"JP-2005-32798-A discloses a semiconductor laser drive device that can detect such a degradation of the semiconductor laser. FIGS. 1 and 2 represent a circuit diagram of the semiconductor laser drive device disclosed in JP-2005-32798-A.

"In one example, the semiconductor laser drive device shown in FIG. 1 outputs a current Im attenuated from a drive current Iop at a fixed ratio. This output current Im is converted to a voltage Vm. The voltage Vm is compared with a fixed voltage (half of a power-supply voltage) VCC1/2 by a comparator. When the voltage Vm exceeds the fixed voltage VCC1/2 (Vm>Vcc/2), a signal Serr indicating abnormality of the value of drive current Iop is output to an image controller provided at a previous stage of the semiconductor laser drive device. Accordingly, the image controller can recognize the abnormality based on the signal Serr indicating the abnormality.

"However, when the value of drive current Iop is small and below a predetermined current value, the signal indicating abnormality may not be output in the semiconductor laser drive device shown in FIG. 1.

"In another example, a semiconductor laser drive device shown in FIG. 2 outputs the current Im attenuated from the drive current Iop at a fixed ratio. This current Im is converted to the voltage Vm representing the value of the drive current Iop by a current to a voltage conversion circuit R2, and is output to an image controller provided at the previous stage of the semiconductor laser drive device. Accordingly, the image controller can recognize the abnormality based on the voltage Vm representing the value of the drive current Iop.

"However, the semiconductor laser drive device shown in FIG. 2 outputs an analog value, making it necessary to mount an analog-to-digital (A/D) converter that converts an analog value to a digital value on the circuit board or have a built-in circuit in the image controller because the image controller cannot perform data processing with the analog value directly.

"Accordingly, the number of parts on the circuit board of the image controller increases. Consequently, the configuration of the image controller becomes complicated and the chip area of the image controller expands, resulting in a cost penalty."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In an aspect of this disclosure, there is a provided a semiconductor laser drive device that includes a semiconductor-laser drive element, a control circuit, and a drive current detection circuit. The semiconductor-laser drive element generates a drive current according to an input control signal to supply the drive current to a semiconductor laser. The control circuit controls the drive current by controlling the semiconductor-laser drive element. The drive current detection circuit detects a current value of the drive current supplied to the semiconductor laser and generates a digital control signal representing the detected digital value of the drive current to output.

"In another aspect, there is provided a semiconductor laser drive device that includes a semiconductor-laser drive element, a control circuit, a drive current detection circuit, and a storage circuit. The semiconductor-laser drive element generates a drive current in accordance with an input control signal to supply the drive current to a semiconductor laser. The control circuit controls the supply current by controlling the semiconductor-laser drive element. The drive current detection circuit detects a current value of the drive current supplied to the semiconductor laser and generates a digital control signal representing the detected drive current value to output. The storage circuit stores a digital threshold signal representing an abnormal level of the drive current that is one criterion for detecting degradation of the semiconductor laser. The abnormality detection circuit detects a current value of the drive current supplied to the semiconductor laser to emit light at a predetermined light-emission intensity, and generate and output an abnormality detection signal indicating an abnormal state in which the detected signal corresponding to the digital control signal representing the detected drive current exceeds the digital threshold signal representing the abnormal level.

"In another aspect, there is provided a semiconductor laser drive device that includes a drive circuit, a control circuit, an arithmetic and adder circuit, a register, a storage circuit, and an abnormality detection circuit. The drive circuit, including multiple D/A converters, generates a drive current by adding together currents generated by each D/A converter to supply the drive current to the semiconductor laser. The control circuit generates digital control signals to control the currents output from the respective D/A converters and outputs them to the drive circuit. The arithmetic and adder circuit to generate a digital sum signal obtained by setting a digital reference signal chosen from the digital signals, calculating other digital signal based on the standard signal, and adding the calculated other digital signal to the digital reference signal and outputting the digital sum signal. The register temporarily stores a value of the digital sum signal output from the arithmetic and adder circuit. The storage circuit to store a digital threshold signal representing an abnormal level of the drive signal that is one criterion for determining the degradation of the semiconductor laser. The abnormality detection circuit to generate an abnormality detection signal indicating an abnormal state in which the value of the digital sum signal stored in the register exceeds the value of the digital threshold signal stored in the storage circuit."

For the URL and additional information on this patent, see: Sumino, Daijiroh; Kyogoku, Hiroaki. Semiconductor Laser Drive Device and Image Forming Apparatus Incorporating Same. U.S. Patent Number 8630324, filed June 30, 2011, and published online on January 14, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=33&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1604&f=G&l=50&co1=AND&d=PTXT&s1=20140114.PD.&OS=ISD/20140114&RS=ISD/20140114

Keywords for this news article include: Electronics, Circuit Board, Semiconductor, Digital Control, Ricoh Company Ltd..

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools