WO2007148582A1 - Light emitting diode driving circuit - Google Patents

Light emitting diode driving circuit Download PDF

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Publication number
WO2007148582A1
WO2007148582A1 PCT/JP2007/061923 JP2007061923W WO2007148582A1 WO 2007148582 A1 WO2007148582 A1 WO 2007148582A1 JP 2007061923 W JP2007061923 W JP 2007061923W WO 2007148582 A1 WO2007148582 A1 WO 2007148582A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
current
reference current
circuit
light emitting
emitting diode
Prior art date
Application number
PCT/JP2007/061923
Other languages
French (fr)
Japanese (ja)
Inventor
Koichi Yamaguchi
Daisuke Suzuki
Original Assignee
Mitsumi Electric Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B33/00Electroluminescent light sources
    • H05B33/02Details
    • H05B33/08Circuit arrangements not adapted to a particular application
    • H05B33/0803Circuit arrangements not adapted to a particular application for light emitting diodes [LEDs] comprising only inorganic semiconductor materials
    • H05B33/0842Circuit arrangements not adapted to a particular application for light emitting diodes [LEDs] comprising only inorganic semiconductor materials with control
    • H05B33/0845Circuit arrangements not adapted to a particular application for light emitting diodes [LEDs] comprising only inorganic semiconductor materials with control of the light intensity
    • H05B33/0848Circuit arrangements not adapted to a particular application for light emitting diodes [LEDs] comprising only inorganic semiconductor materials with control of the light intensity involving load characteristic sensing means

Abstract

A light emitting diode driving circuit is provided with a reference current section for generating a reference current, and a current outputting section for generating a driving current based on the reference current by using a current mirror circuit, and supplying the light emitting diode with the driving current. The reference current section is provided with a temperature characteristic element having negative temperature characteristics.

Description

Specification

LED driving circuit

Technical field

[0001] The present invention relates to a light emitting diode driving circuit, a plurality of light emitting diodes arranged about the light emitting diode driving circuit for driving each.

BACKGROUND

As a means for applying light to a photosensitive member in [0002] In a printer or the like, a light emitting diode (hereinafter, referred to as "LED") is one using a LED array in which the linearly. The driving circuit for driving each LED in such an LED array, for example, those described in Patent Document 1, 2 and the like.

[0003] FIG. 1 shows a circuit diagram of an example of a conventional light emitting diode drive circuit. The drive circuitry is being semiconductor integrated circuit, Ru.

[0004] In the figure, the reference voltage Vref from the reference voltage source 11 to the inverting input terminal is applied the operational amplifier 10, Ru. Output terminal of the operational amplifier 10 is a p-channel MOS field effect transistor (hereinafter, simply referred to as "MOS transistor") is connected to the gate of Ml, the gate of the p-channel MOS transistor M2 through the switch 12 such as an analog switch It is connected.

[0005] The source of the MOS transistor Ml is connected to the power supply Vdd, and together with the drain of the MOS transistor Ml is connected to the non-inverting input terminal of the operational amplifier 10 is connected to one end of the resistor R1. The other end of the resistor R1 is connected to ground.

[0006] switch 12 obtain switch the ON Z off in response to switch control signal supplied from the terminal 13. The source of the MOS transistor M2 is connected to the power supply Vdd, and the drain of the MOS transistor M2 is connected to the anode of the LED (light emitting diode) 14, the force Sword LED14 are grounded.

[0007] The operational amplifier 10 and the reference voltage Vref resistor R1, passing a reference current Iref expressed by the equation (1) to the drain of the MOS transistor Ml.

(!) [0008] Iref = Vref / R 1 · ·· when switch 12 is turned on MOS transistors Ml, M2 constitute a current mirror, the gate area ratio of the MOS transistors Ml, M2 is 1: When 1 , a MOS transistor M2 to the LED 14 the reference current Iref flows, LED 14 emits light.

Patent Document 1: Japanese Patent No. 3296882

Patent Document 2: Japanese Patent No. 2516236

Disclosure of the Invention

Problems that the Invention is to you'll solve

[0009] Generally, light emitting diode has a temperature characteristic, a forward descent voltage V decreases when the ambient temperature rises.

F

[0010] In a conventional light emitting diode drive circuit, since a constant I current flowing to LED14 be summer high ambient temperature, the Ru F Shi be reduced forward voltage drop V of the LED14 becomes high ambient temperature, brightness of LED14 is lowered.

[0011] The present invention has been made in view of the above, the light emitting diode drive to compensate for the temperature characteristics of the light-emitting diodes even when temperature changes can hold a light emission luminance of the light emitting diodes substantially constant and to provide a circuit.

Means for Solving the Problems

[0012] The LED driving circuit of the present invention, a reference current section for generating a reference current, generates and light emitting diode comprising a current output unit force you supplied to the light emitting drive current based on the reference current by using a current mirror circuit a diode drive circuit,

Reference current section, the temperature characteristic element having a negative temperature characteristic

By having compensates the temperature characteristics of the light-emitting diodes even when temperature changes can hold a light emission luminance of the light emitting da Iodo substantially constant.

[0013] In the light emitting diode driving circuit,

Reference current unit, an operational amplifier voltage generated by the reference current flows through the resistor circuit to control the reference current so as to be equal to the constant reference voltage,

Resistance and temperature characteristics element may have a resistance circuit connected in series.

[0014] In the light emitting diode driving circuit,

Temperature characteristic element, the effect of the invention can base and collector are common connected transistors

According to [0015] the present invention, to compensate for the temperature characteristics of the light-emitting diodes even when temperature changes can hold a light emission luminance of the light emitting diodes substantially constant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a circuit diagram of an example of a conventional light emitting diode drive circuit.

FIG. 2 is a block diagram of an embodiment of a LED array device using a light emitting diode driving circuit of the present invention.

3 is a circuit diagram of an embodiment of a light emitting diode drive circuit of the present invention.

DESCRIPTION OF SYMBOLS

[0017] 30 operational amplifier

31 reference voltage source circuit

33 reference current section

34, 35 voltage source

36, 38, 40 switch

44 current output section

45 LED

M11~M28 MOS transistor

Ql ρηρ transistor

R11~R23 resistance

Vddl, Vdd2 power

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0019] Ku configuration of an LED array drive circuit>

Figure 2 shows a block diagram of an embodiment of a LED array device using a light emitting diode driving circuit of the present invention. The LED array device is, for example, 48 channel configuration.

[0020] In the figure, are supplied in a time series for example 6 bits of the light emission time data force S48 channels for one channel to the shift register 20, after being latched by the shift register 20 are sequentially shifted, the pulse width modulation circuit 22 It is supplied to. The pulse width modulation circuit 22 generates a light emission pulse of the pulse width indicated by the emission time data for each channel, and supplies the light emission pulse of 48 channels to the LED array drive circuit 26.

[0021] The shift register 24 is supplied with light emission brightness data force 8 Channel partial time series, for example, 6 bits for one channel, after being latched by the shift register 24 are sequentially shifted, supplied to L ED array driver circuitry 26 It is. LED array drive circuit 26, that determine generates switch control signals n systems decodes the light emission brightness data for each channel, a MOS transistor to be turned on by the light emitting pulse for each channel by a switch control signal of the n lines . LED array drive circuit 26 drives the LED 48-channel constituting the LED array 28 to Chiyane Le units.

[0022] Ku configuration of the LED driving circuit>

Figure 3 shows a circuit diagram of an embodiment of a light emitting diode drive circuit of the present invention. Driving circuit of this is the semiconductor integrated circuit.

[0023] In the figure, the reference voltage Vre f is applied from the reference voltage supply circuit 31 to the inverting input terminal of the operational amplifier 30. Output terminal of the operational amplifier 30 is connected to the p-channel MOS transistor Mi l, M12 of gates. MOS transistors Mi l, M12 each source are resistors Rl l, is connected to the power supply Vddl via respective R12 constitute a current mirror circuit. MOS transistors Mi l, Ml 2 each drain is connected to the p-channel M OS transistor M13, M 14 each source.

[0024] The gate of the MOS transistor M13, M14 constitute a current mirror circuit are commonly connected to the drain of the MOS transistor M13, the drain of the MOS transistor M13 is connected to the non-inverting input terminal of the arithmetic amplifier 30 It is connected to one end of the resistor R13.

[0025] MOS transistor Ml 1~M14 by adopting a configuration in which the current mirror circuit is cascaded, the drain potential of the MOS transistor Mi l, M12 becomes substantially equal, the gate area is the same when MOS transistors M13, M14 of drain current is substantially the same.

[0026] The other end of the resistor R13 is connected to Emitta of the pnp transistor Q1. Base and collector of the transistor Q1 constitutes a commonly connected to the diode, the above collector is grounded. It is connected. The gate of the MOS transistor M15 constitute a current mirror circuit is connected to the gate of n-channel MOS transistor M16.

[0028] MOS transistors M15, M16 each source is connected to the n-channel MOS transistor Ml 7, M18 respective drains. Gate of the MOS transistor M17, M18 are connected in common to the drain of the MOS transistor M15 constitute a current mirror circuit, the source of the MOS transistor M17, M18 is grounded.

[0029] MOS transistor M15~M18 is by a configuration in which the current mirror circuit is cascaded, MOS transistors M15, the source potential of M16 becomes substantially equal, the drain when the gate surface product are identical MOS transistors M15, M16 current is substantially the same. Incidentally, the MOS transistors M15, MOS transistors M17 to M16 of the gate between this constant voltage Va is applied from the voltage source 34, the drain potential of M18 is Va- VGSL (VGSL gate 'drain voltage of the n-channel MOS transistor ) and a.

[0030] Additional operational amplifier 30, a reference voltage source circuit 31, MOS transistors Ml 1~M15 and M17 constitute a reference current section 33. Operational amplifier 30, and the reference voltage Vref and the differential amplifier from the drain voltage and the reference voltage source circuit 31 of the MOS transistor M13 caused by the drain current of the MOS transistor M13 through the resistor R13, so that both are the same controls drain current of the MOS transistor Mi l supplies a constant reference current Iref to the drain of the MOS transistor M13 and the. Further, a current flows proportional to the reference current Iref to the drain of the MOS transistor M 16 by a current mirror circuit. Are connected, Ru. The source of the MOS transistor M22 is connected to the drain of the p-channel MOS transistor M21. The source of the MOS transistor M21 is connected to and supply Vdd2 through the resistor R15.

[0032] The gate of the MOS transistor M21 are both when connected to the drain of the MOS transistor M22, connected to the gate of the p-channel MOS preparative transistor M23, M25, M27 through a switch 36, 38, 40 respectively, such as an analog switch Te! /, Ru. It switches 36, 38, turns on the MOS transistors M23, M25, M27 and 40 force ^ sign Then MOS transistors M23, M25, the gate potential of the M27 the same as the gate voltage of the MOS transistor M21, switches 36, 38, 40 When off MOS transistors M23, M25, MOS transistors M23 to the gate potential of M27 as the power supply voltage V dd2, M25, turns off the M27.

[0033] MOS transistors M23, M25, M27 are connected to the power supply Vdd2 by each source through the resistor R21, R22, R23 their respective, MOS transistors M23, M25, M27 are switches 36, 38, 40 on constituting the MOS transistor M21 and the current mirror circuit when the.

[0034] The gate of MOS transistor M22 is connected to the gate of p channel MOS transistors M24, M26, M28. MOS transistors M23, M25, M27 are each drain connected to the sources of the MOS transistors M24, M26, M28, MOS transistors M22, M24, M26, M28 constitute a current mirror circuit.

[0035] MOS transistor M21~M28 is by a configuration in which the current mirror circuit is cascaded, MOS transistors M21, M23, M25, substantially the same becomes the drain potential of M27, when the gate area is identical MOS transistors M22, M24, M26, M28 drain current is substantially the same. Here, in order to perform gradation expression, for example, MOS transistors M21, the gate area of ​​M22, the gate area of ​​the MOS transistors M23, M24 is 6 times, the gate areas of the MOS transistors M25, M26 are three times, MOS transistor gate area of ​​M27, M2 8, as referred to twice, and at different gate area, respectively.

[0036] Note that the constant-voltage Vb from voltage source 35 is applied to the gate of the MOS transistor M22, M24, M26, M28, MOS transistors M22, M24, M26, the source potential of M28 is Vb + Vgs2 (Vgs2 is is the gate 'drain voltage) of the p-channel MOS transistor

[0037] switch 36, 38, 40 respectively switches the terminals 37, 39, 41 on Z off in response to a switch control signal lines (n = 3 here) n supplied from each. Here, n 3 two Period should not be produced. The drain of the MOS transistors M24, M26, M28 is connected to the anode of the LED45, force Sword of LED45 is grounded. [0038] Here, switches 36, 38, 40 MOS transistors when off M23, M25, M27 to O off and LED45 current does not flow. When switch 36 is turned on to flow a drain current LED 45 of the MOS transistor M23, the switch 36, 38 is turned sum of MOS transistors M23, M25 of the drain current flows through the LED 45, the MOS transistor when the switch 36, 38, 40 are turned on M23, M25, the sum of the drain current of M27 flows to the LED 45, LED 45 is the light emission luminance as the current that flows is increased becomes larger.

[0039] Additional switches 36, 38, 40, MOS transistors M16, M18~M28 is constitutes the current output section 44 of the one channel, the current output section 44 standards current portion of the same configuration of 48 channels It is connected to the 33. Current output section 44 of each channel are connected to each! Ru LED 45 (part of the LED array 28) to drive.

[0040] Ku compensation of the temperature characteristic of the light emitting diodes>

Here, the reference current Iref flowing through the drain of the MOS transistor M13 is expressed by equation (1). Incidentally, Vr is the voltage across the resistor R13, V is the forward voltage drop of the transistor Q1

FQ1

[0041] Iref = (Vr ~ V) / R13 · '· (1)

FQl

Here, when partial differentiation at temperature t a (1), the forward voltage drop is negative temperature characteristic α of the transistor Q1 - to have (= 2mVZ ° C), (2) is obtained.

[0042] 3 lref / 3 t = (Vr + a) / R13 ·, · (2)

Thus, reference current Iref is increased when the ambient temperature rises, MOS transistor M23 is proportional to the reference current Iref, M25, M27 drain current, i.e., current collector flowing to LED45 is increased, the luminance of the LED45 increases . Yotsute thereto, decrease in luminance of the LED 14 to the forward voltage drop V of the LED 14 the higher the ambient temperature is caused to drop is canceled

F

It can hold the luminance of LED45 substantially constant.

[0043] Incidentally, a diode instead of the transistor Q1, even if the other end of the resistor R13 is connected to the power cathode grounded and anode, it is possible to obtain the same effect.

[0044] The transistor Q1 corresponds to the temperature characteristic element of claim, resistor R13, transistors Q 1 is equivalent to the resistor circuit.

[0045] The present invention is not limited to the specifically disclosed embodiments described above, various modifications without departing from the scope of the present invention will refinement is performed.

[0046] The present application is based on the priority claiming Japanese Patent Application No. 2006- 171849, filed Jun. 21, 2006, the entire contents of which are incorporated herein.

Industrial Applicability

[0047] The present invention is applicable to a light emitting diode driving circuit for driving the respective arrayed plurality of light emitting diodes.

Claims

The scope of the claims
[1] and a reference current section for generating a reference current, a light-emitting Daio over de drive circuit comprising a current output section for supplying to the light emitting diode to generate a driving current that is based on the reference current using a current mirror circuit ,
The reference current section, the temperature characteristic element having a negative temperature characteristic
LED driving circuit characterized in that it comprises.
[2] In the LED driving circuit according to claim 1,
The reference current section, an operational amplifier the reference current to control the reference current so that the voltage generated by flowing through the resistance circuit becomes equal to a constant reference voltage,
Resistor and the temperature characteristic elements connected in series a resistor circuit
LED driving circuit characterized in that it comprises.
[3] In the light-emitting diode driving circuit according to claim 2,
The temperature characteristic element, the light emitting diode driving circuit, wherein the base and collector are commonly connected transistors.
PCT/JP2007/061923 2006-06-21 2007-06-13 Light emitting diode driving circuit WO2007148582A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2006-171849 2006-06-21
JP2006171849A JP5040185B2 (en) 2006-06-21 2006-06-21 LED driving circuit

Publications (1)

Publication Number Publication Date
WO2007148582A1 true true WO2007148582A1 (en) 2007-12-27

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ID=38833324

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Application Number Title Priority Date Filing Date
PCT/JP2007/061923 WO2007148582A1 (en) 2006-06-21 2007-06-13 Light emitting diode driving circuit

Country Status (3)

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JP (1) JP5040185B2 (en)
CN (1) CN101473455A (en)
WO (1) WO2007148582A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8379583B2 (en) 2009-01-30 2013-02-19 Qualcomm Incorporated Method and apparatus for multiplexing legacy long term evolution user equipment with advanced long term evolution user equipment

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH029182A (en) * 1988-06-28 1990-01-12 Toshiba Corp Light emitting element driving circuit
JP2005116616A (en) * 2003-10-03 2005-04-28 Toshiba Corp Led drive circuit and led drive system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06140700A (en) * 1992-10-27 1994-05-20 Canon Inc Semiconductor light-emitting element driving circuit
JP3613328B2 (en) * 2000-06-26 2005-01-26 サンケン電気株式会社 Semiconductor light-emitting device
JP4763900B2 (en) * 2001-02-16 2011-08-31 キヤノン株式会社 Driving circuit of the light emitting element
JP2005260001A (en) * 2004-03-11 2005-09-22 Seiko Epson Corp Light emitting element driver circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH029182A (en) * 1988-06-28 1990-01-12 Toshiba Corp Light emitting element driving circuit
JP2005116616A (en) * 2003-10-03 2005-04-28 Toshiba Corp Led drive circuit and led drive system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8379583B2 (en) 2009-01-30 2013-02-19 Qualcomm Incorporated Method and apparatus for multiplexing legacy long term evolution user equipment with advanced long term evolution user equipment

Also Published As

Publication number Publication date Type
JP2008004707A (en) 2008-01-10 application
JP5040185B2 (en) 2012-10-03 grant
CN101473455A (en) 2009-07-01 application

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