# US 5,349,595 A · Drive circuit for semiconductor light-emitting device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,349,595 A - Document ID: US5349595A - Status: Granted - Kind: A - Application number: 08/023,358 - Filed: 1993-02-26 - Granted: 1994-09-20 - Earliest claimed: 1992-02-28 - Assignees: Canon Kabushiki Kaisha - Inventors: Katsuhisa Ogawa; Takamasa Sakuragi - Web page: https://patentgrep.com/patent/US5349595A ## CPC - H01S 5/042: Electrical excitation {; Circuits therefor (monolithically integrated laser drive components H01S5/0261)} - H05B 45/397: Current mirror circuits - H01S 5/0427: {for applying modulation to the laser} - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A drive circuit for supplying a constant drive current to the anode terminal of a semiconductor light emitting device, includes a current supply source connected to the anode terminal for supplying a bias current to the semiconductor light emitting device. Since the drive circuit is formed so as to supply the bias current to the anode terminal of the semiconductor light emitting device, a charge current for charging a conjunction capacitance can be reduced independently on the time period of turning off the semiconductor light emitting device. As a result, a spike noise can be removed in the laser current waveform at its rise-up part, and a reduction of its rise-up speed can be restricted, both of which are due to a dependent upon the time period of turning off the semiconductor device. ## Claims ### Claim 1 A drive circuit of a driving object for supplying a constant drive current to the driving object, comprising: input means for inputting a control signal; constant driving current generating means for generating the constant driving current; switching means for switching a supply of the constant driving current to the driving object in accordance with the control signal inputted by said input means; and means for supplying a current to said switching means in response to an input of the control signal representing a turn-on before said driving object is actually driven. ### Claim 2 (depends on 1) A drive circuit as claimed in claim 1, wherein said driving object is a semiconductor light emitting device. ### Claim 3 (depends on 2) A drive circuit as claimed in claim 2, wherein said semiconductor light emitting device is a semiconductor laser device. ### Claim 4 (depends on 1) A drive circuit as claimed in claim 1, wherein said switching means comprises a transistor. ### Claim 5 (depends on 1) A drive circuit as claimed in claim 1, wherein said switching means comprises a current mirror circuit having a plurality of transistors. ### Claim 6 (depends on 5) A drive circuit as claimed in claim 5, wherein said switching means further comprises means for switching said current mirror circuit in accordance with the control signal inputted by said input means. ### Claim 7 (depends on 1) A drive circuit as claimed in claim 1, wherein said supplying means is a level shift circuit. ### Claim 8 (depends on 7) A drive circuit as claimed in claim 7, wherein said level shift circuit comprises one or more diodes. ### Claim 9 (depends on 7) A drive circuit as claimed in claim 7, wherein said level shift circuit comprises one or more emitter follower transistors. ### Claim 10 (depends on 7) A drive circuit as claimed in claim 7, wherein said level shift circuit comprises one or more source follower transistors. ### Claim 11 (depends on 1) A drive circuit as claimed in claim 1, wherein the control signal inputted by said input means is supplied to both said supplying means and said switching means; and an inverter is provided between input means and said supplying means, or between said input means and said switching means. ### Claim 12 (depends on 11) A drive circuit as claimed in claim 11, further comprising a delay circuit between said input means and said switching means. ### Claim 13 A driver integrated circuit comprising: means for generating a drive current; means for switching an output of the drive current to an output terminal; and a transistor, one terminal of which is connected to said output terminal, wherein a high level voltage is supplied to another terminal of said transistor so that a bias current is supplied to the output terminal independent of a state of said switching means. ### Claim 14 (depends on 13) A driver integrated circuit as claimed in claim 13, wherein said driver integrated circuit drives a semiconductor light emitting element. ### Claim 15 A driver integrated circuit comprising: means for generating a drive current; means for switching an output of the drive current to an output terminal; and current mirror transistors for generating a bias current, wherein the bias current generated by said current mirror transistors is supplied to the output terminal independent of a state of said switching means. ### Claim 16 (depends on 15) A driver integrated circuit as claimed in claim 15, wherein said driver integrated circuit drives a semiconductor light emitting element.