CN104684223A - Led drive circuit - Google Patents
Led drive circuit Download PDFInfo
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- CN104684223A CN104684223A CN201510117001.9A CN201510117001A CN104684223A CN 104684223 A CN104684223 A CN 104684223A CN 201510117001 A CN201510117001 A CN 201510117001A CN 104684223 A CN104684223 A CN 104684223A
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- transistor
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Abstract
The invention provides an LED drive circuit which comprises a drive transistor, a mirror image transistor, a first current source and a second current source, wherein a source of the drive transistor is connected with a first power supply end and a drain of the drive transistor serves as a drive end and is connected with one end of an LED; a source of the mirror image transistor is connected with that of the drive transistor and a gate of the mirror image transistor is connected with that of the drive transistor; the first current source is used for injecting first current into a drain of the mirror image transistor or extracting the first current from the drain of the mirror image transistor; the second current source is used for injecting second current into the drain of the drive transistor or extracting the second current from the drain of the drive transistor. Therefore, a resistor R1 connected in series with the LED in the prior art can be eliminated and miniaturization and low cost of printed circuit boards are facilitated.
Description
[technical field]
The present invention relates to circuit design field, particularly a kind of LED (Light-Emitting Diode) drive circuit.
[background technology]
Increasing system is all configured with LED light, and LED light is used to refer to various state.Fig. 1 illustrates a kind of LED drive circuit of prior art.A NMOS (N-channel Mental Oxide Semiconductor) transistor MN5 is just simply devised in this LED drive chip.Usually, the conducting resistance of transistor MN5 needs the very little of design, the electric current of such LED sets primarily of non-essential resistance R1, its LED current is approximately equal to (VDD-VF)/R1, wherein VDD is the magnitude of voltage of external power source VDD, VF is the forward bias voltage of LED, and R1 is the resistance value of resistance R1.Its shortcoming has 3 points: the current value of one, LED changes along with vdd voltage change, but general user more wishes that LED luminance remains constant, and the brightness of LED directly depends on its current value; Two, need during applications to add resistance R1, for wishing the system that system bulk is less, more frivolous as bluetooth earphone, if without the need to this resistance, be then conducive to system more miniaturized and more frivolous, such bluetooth earphone hangs on ear more comfortable; Three, in order to design less conducting resistance, chip area shared by usual transistor MN5 is comparatively large, and chip cost is higher.
Therefore, be necessary that the LED drive circuit proposing a kind of improvement is to overcome the problems referred to above.
[summary of the invention]
An object of the present invention is to provide a kind of LED drive circuit, and it is conducive to printed circuit board (PCB) miniaturization and low cost.
In order to solve the problem, the invention provides a kind of LED drive circuit, it comprises: driving transistors, and the source electrode of this driving transistors connects the first power end, drains to be connected with one end of LED as drive end; Mirrored transistor, the source electrode of this mirrored transistor connects the source electrode of driving transistors, and the grid of this mirrored transistor connects the grid of driving transistors; First current source, the drain electrode to described mirrored transistor is injected or extracts the first electric current from the drain electrode of described mirrored transistor; Second current source, the drain electrode to described driving transistors is injected or extracts the second electric current from the drain electrode of described driving transistors.
Further, described LED drive circuit also includes: the first clamp transistor, the source electrode of this first clamp transistor is connected with the drain electrode of mirrored transistor, and the first current source injects to the drain electrode of the first clamp transistor or extracts the first electric current from the drain electrode of the first clamp transistor; Second clamp transistor, the source electrode of this second clamp transistor is connected with the drain electrode of driving transistors, second current source injects to the drain electrode of the second clamp transistor or extracts the second electric current from the drain electrode of the second clamp transistor, and the grid of this second clamp transistor is connected with the grid of this first clamp transistor.
Further, the grid of the second clamp transistor is connected with its drain electrode, and the grid of mirrored transistor is connected with the drain electrode of the first clamp transistor.
Further, driving transistors, mirrored transistor, the first clamp transistor are all connected with the first power end with the lining body of the second clamp transistor, and driving transistors, mirrored transistor, the first clamp transistor are identical with the type of the second clamp transistor.
Further, the first clamp transistor and the second clamp transistor be all operated in saturation region.
Further, the ratio of the breadth length ratio of driving transistors and mirrored transistor is K:1, and the electric current in mirrored transistor is the first electric current I 1, and the electric current on driving transistors is K*I1, and the electric current flowing through LED is K*I1-I2, and wherein I2 represents the second electric current.
Further, driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are nmos pass transistor, and the first power end is earth terminal.The anode of described LED is connected with second source end, and negative electrode is connected with described drive end, and second source end is power voltage terminal.
Further, driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are PMOS transistor, and the first power end is power voltage terminal.The negative electrode of described LED is connected with second source end, and anode is connected with described drive end, and second source end is earth terminal.
Compared with prior art, the resistance R1 joined with LED strip in prior art can be eliminated, be conducive to printed circuit board (PCB) miniaturization and low cost.
[accompanying drawing explanation]
In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.Wherein:
Fig. 1 is the circuit diagram of existing LED drive circuit;
Fig. 2 is the LED drive circuit circuit diagram in one embodiment in the present invention;
Fig. 3 is the LED drive circuit circuit diagram in another embodiment in the present invention.
[embodiment]
For enabling above-mentioned purpose of the present invention, feature and advantage become apparent more, and below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.
Alleged herein " embodiment " or " embodiment " refers to special characteristic, structure or the characteristic that can be contained at least one implementation of the present invention.Different local in this manual " in one embodiment " occurred not all refers to same embodiment, neither be independent or optionally mutually exclusive with other embodiments embodiment.Unless stated otherwise, connection herein, be connected, word that the expression that connects is electrically connected all represents and is directly or indirectly electrical connected.
Fig. 2 is the LED drive circuit circuit diagram in one embodiment in the present invention.As shown in Figure 2, described LED drive circuit 100 comprises driving transistors NM1, mirrored transistor MN2, the first current source I1, the second current source I2, the first clamp transistor MN3 and the second clamp transistor MN4.
The source electrode of driving transistors MN1 connects earth terminal, drains connected as the negative electrode of drive end PAD and LED.The source electrode of mirrored transistor MN2 connects the source electrode of driving transistors MN1, and the grid of this mirrored transistor MN2 connects the grid of driving transistors MN1.The source electrode of the first clamp transistor MN3 is connected with the drain electrode of mirrored transistor MN2, and the first current source I1 injects the first electric current to the drain electrode of the first clamp transistor MN3, and the first electric current flows through the first clamp transistor MN3 and mirrored transistor MN2.The source electrode of the second clamp transistor MN4 is connected with the drain electrode of driving transistors MN1, and the second current source I2 injects the second electric current to the drain electrode of the second clamp transistor MN4.The grid of this second clamp transistor MN4 is connected with the grid of this first clamp transistor MN3, and the grid of the second clamp transistor NM4 is connected with its drain electrode, and the grid of mirrored transistor MN2 is connected with the drain electrode of the first clamp transistor MN3.
Driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are NMOS (N-channel Metal Oxide Semiconductor) transistor.The anode of described LED is connected with power voltage terminal VDD.Driving transistors, mirrored transistor, the first clamp transistor are all connected with earth terminal with the lining body of the second clamp transistor.
Mirrored transistor NM2 and driving transistors NM1 forms current mirror, and the breadth length ratio of design transistor NM1 and NM2 carrys out driving LED more greatly.The electric current of actual driving LED equals the electric current I of transistor NM1
nM1with the electric current I of transistor NM4
nM4difference, i.e. I
nM1-I
nM4.Because the electric current of transistor NM2 equals the electric current of current source I1, the ratio of the breadth length ratio of design transistor NM1 and NM2 is K:1, then the electric current of transistor NM1 is K.I1, and wherein I1 is the current value of current source I1.The electric current of transistor NM4 equals the current value I2 of current source I2.It can thus be appreciated that the current value flowing through LED equals K.I1-I2.In a preferred embodiment, I1 equals I2.In order to save power consumption, I1 and I2 is general, and value is less, such as 1 microampere.I1 can certainly be designed and be not equal to I2, now need the ratio equaling I2 and the I1 breadth length ratio of transistor NM4 and NM3 designed.Because transistor NM3 is the same with NM4 type, its threshold voltage is the same, and their grids are connected in addition, so grid voltage is equal, adjustment makes both source voltages also equal by the connected mode of such transistor NM3 and NM4.The source voltage of transistor NM3 is equal with the source voltage of transistor NM4, and namely the drain voltage of transistor NM2 is equal with the drain voltage of transistor NM1, and the current replication ratio contributing to transistor NM1 and transistor NM2 is like this more accurate.If design constant-current source I1 and I2 does not rely on mains voltage variations, then Fig. 2 implementation driving LED electric current of the present invention is less with mains voltage variations, is better than Fig. 1 prior art.In order to realize good mirror effect, preferably, NM3 and NM4 should be designed and all be operated in saturation region.The present invention, without the need to being series at the current-limiting resistance of LED in Fig. 1, is conducive to printed circuit board (PCB) miniaturization and low cost.Implementation chip occupying area of the present invention is less simultaneously, and cost is lower.Wherein K be more than or equal to 1 positive number.
Fig. 3 is the LED drive circuit circuit diagram in another embodiment in the present invention.As shown in Figure 3, described LED drive circuit 100 comprises driving transistors MP1, mirrored transistor MP2, the first current source I1, the second current source I2, the first clamp transistor MP3 and the second clamp transistor MP4.
The source electrode of driving transistors MP1 connects power voltage terminal VDD, drains connected as the anode of drive end PAD and LED.The source electrode of mirrored transistor MP2 connects the source electrode of driving transistors MP1, and the grid of this mirrored transistor MP2 connects the grid of driving transistors MP1.The source electrode of the first clamp transistor MP3 is connected with the drain electrode of mirrored transistor MP2, and the first current source I1 extracts the first electric current from the drain electrode of the first clamp transistor MP3, and the first electric current flows through the first clamp transistor MP3 and mirrored transistor MP2.The source electrode of the second clamp transistor MP4 is connected with the drain electrode of driving transistors MP1, and the second current source I2 extracts the second electric current from the drain electrode of the second clamp transistor MN4.The grid of this second clamp transistor MP4 is connected with the grid of this first clamp transistor MP3, and the grid of the second clamp transistor MP4 is connected with its drain electrode, and the grid of mirrored transistor MP2 is connected with the drain electrode of the first clamp transistor MP3.
Driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are PMOS (P-channel Metal Oxide Semiconductor) transistor.The negative electrode of described LED is connected with earth terminal.Driving transistors, mirrored transistor, the first clamp transistor are all connected with power voltage terminal VDD with the lining body of the second clamp transistor.
Same, mirrored transistor MP2 and driving transistors MP1 forms current mirror.The electric current of actual driving LED equals the electric current I of transistor MP1
mP1with the electric current I of transistor MP4
mP4difference, i.e. I
mP1-I
mP4.Because the electric current of transistor MP2 equals the electric current of current source I1, the ratio of the breadth length ratio of design transistor MP1 and MP2 is K:1, then the electric current of transistor MP1 is K.I1, and wherein I1 is the current value of current source I1.The electric current of transistor MP4 equals the current value I2 of current source I2.It can thus be appreciated that the current value flowing through LED equals K.I1-I2.In a preferred embodiment, I1 equals I2.In order to save power consumption, I1 and I2 is general, and value is less, such as 1 microampere.I1 can certainly be designed and be not equal to I2, now need the ratio equaling I2 and the I1 breadth length ratio of MP4 and MP3 designed.Because transistor MP3 is the same with MP4 type, its threshold voltage is the same, and their grids are connected in addition, so grid voltage is equal, adjustment makes both source voltages also equal by the connected mode of such transistor MP3 and MP4.The source voltage of transistor MP3 is equal with the source voltage of transistor MP4, and namely the drain voltage of transistor MP2 is equal with the drain voltage of transistor MP1, and the current ratio contributing to transistor MP1 and transistor MP2 is like this more accurate.If design constant-current source I1 and I2 does not rely on mains voltage variations, then Fig. 3 implementation driving LED electric current of the present invention is less with mains voltage variations, is better than Fig. 1 prior art.In order to realize good mirror effect, preferably, MP3 and MP4 should be designed and all be operated in saturation region.The present invention, without the need to being series at the current-limiting resistance of LED in Fig. 1, is conducive to printed circuit board (PCB) miniaturization and low cost.Implementation chip occupying area of the present invention is less simultaneously, and cost is lower.
In the present invention, " connection ", " being connected ", " company ", " connecing " etc. represent the word be electrically connected, and if no special instructions, then represent direct or indirect electric connection.
It is pointed out that the scope be familiar with person skilled in art and any change that the specific embodiment of the present invention is done all do not departed to claims of the present invention.Correspondingly, the scope of claim of the present invention is also not limited only to previous embodiment.
Claims (10)
1. a LED drive circuit, is characterized in that, it comprises:
Driving transistors, the source electrode of this driving transistors connects the first power end, drains to be connected with one end of LED as drive end;
Mirrored transistor, the source electrode of this mirrored transistor connects the source electrode of driving transistors, and the grid of this mirrored transistor connects the grid of driving transistors;
First current source, the drain electrode to described mirrored transistor is injected or extracts the first electric current from the drain electrode of described mirrored transistor;
Second current source, the drain electrode to described driving transistors is injected or extracts the second electric current from the drain electrode of described driving transistors.
2. LED drive circuit according to claim 1, is characterized in that, it also includes:
First clamp transistor, the source electrode of this first clamp transistor is connected with the drain electrode of mirrored transistor, and the first current source injects to the drain electrode of the first clamp transistor or extracts the first electric current from the drain electrode of the first clamp transistor,
Second clamp transistor, the source electrode of this second clamp transistor is connected with the drain electrode of driving transistors, and the second current source injects to the drain electrode of the second clamp transistor or extracts the second electric current from the drain electrode of the second clamp transistor,
The grid of this second clamp transistor is connected with the grid of this first clamp transistor.
3. LED drive circuit according to claim 2, is characterized in that, the grid of the second clamp transistor is connected with its drain electrode, and the grid of mirrored transistor is connected with the drain electrode of the first clamp transistor.
4. LED drive circuit according to claim 3, is characterized in that,
Driving transistors, mirrored transistor, the first clamp transistor are all connected with the first power end with the lining body of the second clamp transistor, and driving transistors, mirrored transistor, the first clamp transistor are identical with the type of the second clamp transistor.
5. LED drive circuit according to claim 2, is characterized in that, the first clamp transistor and the second clamp transistor be all operated in saturation region.
6. LED drive circuit according to claim 1, is characterized in that,
The ratio of the breadth length ratio of driving transistors and mirrored transistor is K:1,
Electric current in mirrored transistor is the first electric current I 1,
Electric current on driving transistors is K*I1,
The electric current flowing through LED is K*I1-I2, and wherein I2 represents the second electric current.
7., according to the arbitrary described LED drive circuit of claim 1-6, it is characterized in that,
Driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are nmos pass transistor, and the first power end is earth terminal.
8. LED drive circuit according to claim 7, is characterized in that,
The anode of described LED is connected with second source end, and negative electrode is connected with described drive end, and second source end is power voltage terminal.
9., according to the arbitrary described LED drive circuit of claim 1-6, it is characterized in that,
Driving transistors, mirrored transistor, the first clamp transistor, the second clamp transistor are PMOS transistor, and the first power end is power voltage terminal.
10. LED drive circuit according to claim 9, is characterized in that,
The negative electrode of described LED is connected with second source end, and anode is connected with described drive end, and second source end is earth terminal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510117001.9A CN104684223A (en) | 2015-03-17 | 2015-03-17 | Led drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510117001.9A CN104684223A (en) | 2015-03-17 | 2015-03-17 | Led drive circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN104684223A true CN104684223A (en) | 2015-06-03 |
Family
ID=53318637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510117001.9A Pending CN104684223A (en) | 2015-03-17 | 2015-03-17 | Led drive circuit |
Country Status (1)
| Country | Link |
|---|---|
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5252910A (en) * | 1991-06-27 | 1993-10-12 | Thomson Composants Militaries Et Spatiaux | Current mirror operating under low voltage |
| CN101106855A (en) * | 2007-07-20 | 2008-01-16 | 北京中星微电子有限公司 | LED drive circuit |
| CN104062997A (en) * | 2013-03-20 | 2014-09-24 | 芯原微电子(上海)有限公司 | High-precision high-speed current drive circuit with large output voltage swing |
| CN204442786U (en) * | 2015-03-17 | 2015-07-01 | 无锡中星微电子有限公司 | Led drive circuit |
-
2015
- 2015-03-17 CN CN201510117001.9A patent/CN104684223A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5252910A (en) * | 1991-06-27 | 1993-10-12 | Thomson Composants Militaries Et Spatiaux | Current mirror operating under low voltage |
| CN101106855A (en) * | 2007-07-20 | 2008-01-16 | 北京中星微电子有限公司 | LED drive circuit |
| CN104062997A (en) * | 2013-03-20 | 2014-09-24 | 芯原微电子(上海)有限公司 | High-precision high-speed current drive circuit with large output voltage swing |
| CN204442786U (en) * | 2015-03-17 | 2015-07-01 | 无锡中星微电子有限公司 | Led drive circuit |
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Address after: 214028 Jiangsu Province, Wuxi City District Qingyuan Road No. 18 Taihu International Science Park sensor network university science and Technology Park 530 building A1001 Applicant after: WUXI ZHONGGAN MICROELECTRONIC CO., LTD. Address before: A 530 Taihu international science and Technology Park building 214028 Qingyuan Road in Jiangsu province Wuxi City District 10 layer Applicant before: Wuxi Vimicro Co., Ltd. |
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Application publication date: 20150603 |