EP0441965A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Light-emitting diode drive circuit

Assignee: Mitsubishi Chemical Corp

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Filing: 1990-06-22

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Granted: —

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Expires: 2010-06-22

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Abstract

Abstract A light-emitting diode drive circuit comprising a current feeding circuit (3) having a first (16) which receives at the base thereof a first drive pulse signal (S3) sent from a signal receiving circuit, and a second transistor (15) of which the collector is connected to a light-emitting diode (2), of which the emitter is connected to a current source (24) together with the emitter of the first transistor (16), and which receives at the base thereof a second drive pulse signal (S2) having a phase opposite to that of the first drive pulse signal (S3); a fall time shortening circuit (6) including a third transistor (13) which is connected in parallel with the light-emitting diode (2) and which, in response to its base input, short-circuits both terminals of the light-emitting diode (2) at the time of turn-off; and a rise time shortening circuit (5) including a circuit (4) that generates a peaking current at the time of turning the light-emitting diode (2) on and a fourth transistor (14) that is connected in series with the third transistor (13) and adds the peaking current to the drive current when the light-emitting diode (2) is turned on. The circuit shortens the rise and fall times of light pulses outputted, improving the response speed of even a light-emitting diode (2) having poor intrinsic response characteristics, for example, a light-emitting diode which emits red light in a short wavelength band.

Inventors

👤 K. Tokyo Res. Lab. Mitsubishi Rayon Co. Ltd Yagi
👤 K. Tokyo Res. Lab. Mitsubishi Rayon Co.Ltd Zenba
👤 Y. Tokyo Re.Lab. Misubishi Rayon Co Sekiguchi
👤 Fumio Sony Coorporation Ishikawa
👤 Tetsuo Sony Corporation Yamamoto
👤 Takayuki Sony Corporation Aoki

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-10-24 19:25

CPC Classifications

H; H03; H03K; H03K17/00; H03K17/04; H03K17/041; H03K17/0412; H03K17/04126; H03K17/51; H03K17/56; H03K17/60; H03K17/603; H05; H05B; H05B45/00; H05B45/30; H05B45/31; H01; H01S; H01S5/00; H01S5/04; H01S5/042; H01S5/0428; Y; Y02; Y02B; Y02B20/00; Y02B20/30

Claims Analysis

Total Claims: 4

Claim 1

Independent Claim 343 words

A light-emitting diode drive circuit characterized by comprising: a signal input circuit for receiving an external input pulse signal and outputting first and second drive pulses in response the input pulse signal; a current supply circuit including a first transistor, a collector of which receives a power source voltage and a base of which receives the first drive pulse signal output from said signal input circuit, and a second transistor, a collector of which connected to said light-emitting diode, an emitter of which is connected to a current source together with an emitter of said first transistor and a base of which receives the second drive pulse signal having a phase opposite to that of the first drive pulse signal, said current supply circuit being arranged to control a drive current supplied to said light-emitting diode on the basis of the first and second drive pulse signals; a fall time shortening circuit including a third transistor, a collector and an emitter of which are respectively connected to both terminals of said light-emitting diode so that said third transistor is connected in parallel with said light-emitting diode, said collector of which receives the power source voltage, and a base of which receives an input for short-circuiting both said terminals of said light-emitting diode during a turn-OFF time, said fall time shortening circuit being arranged to shorten a fall time of the light pulse output during the turn-OFF time; and a rise time shortening circuit including a circuit for generating a peaking current during a turn-ON time of said light-emitting diode, and a fourth transistor, a collector of which is connected to said emitter of said third transistor so that said fourth transistor is connected in series with said third transistor, and a base and an emitter of which are connected to said peaking current generating circuit to add the peaking current to the drive current during the turn-ON time of said light-emitting diode, said rise time shortening circuit being arranged to shorten the rise time of the light pulse output during the turn-ON time.

Claim 2

Dependent Claim 35 words

A light-emitting diode drive circuit according to claim 1, characterized in that at least said fall time shortening circuit, said rise time shortening circuit, and said current supply circuit are monolithically integrated with each other.

Claim 3

Dependent Claim 29 words

A light-emitting diode drive circuit according to claim 1 or 2, characterized in that said rise time shortening circuit comprises a differentiation circuit including a capacitor and a resistor.

Claim 4

Dependent Claim 56 words

A light-emitting diode drive circuit according to claim 1, 2, or 3, characterized in that said rise time shortening circuit is arranged to add the peaking current to the drive current during the turn-ON time and to cause the peaking current to flow in parallel with the drive current after the light pulse output is raised.

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