CN101488756A - Digital-to-analog converter and converting method thereof - Google Patents
Digital-to-analog converter and converting method thereof Download PDFInfo
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- CN101488756A CN101488756A CNA2008100032098A CN200810003209A CN101488756A CN 101488756 A CN101488756 A CN 101488756A CN A2008100032098 A CNA2008100032098 A CN A2008100032098A CN 200810003209 A CN200810003209 A CN 200810003209A CN 101488756 A CN101488756 A CN 101488756A
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Abstract
A digital-to-analog converter comprises an X-bit voltage digital-to-analog converting part and a Y-bit current digital-to-analog converting part. The X-bit voltage digital-to-analog converting part can generate intermediate voltage corresponding to X-bit MSB subword. The Y-bit current digital-to-analog converting part can generate reference current corresponding to the intermediate voltage, and current signals obtained by multiplying the reference current with a parameter are outputted, wherein the parameter is corresponding to the X-bit MSB subword. In addition, the invention also discloses a digital-to-analog converting method.
Description
Technical field
The present invention relates to a kind of drive circuit of display, and be particularly related to the digital analog converter in a kind of drive circuit.
Background technology
Prior art person should know that at present existing multiple digital analog converter can be for selecting for use, for example resistor string D/A converter (R-string DAC) etc.Fig. 1 illustrates a kind of traditional resistor string D/A converter.Resistor string D/A converter 100 comprises selector 122 and a plurality of resistance 112.By selector 122, can the tie point of 112 of resistance selectively be switched the node that is connected to output corresponding to digital input signals.Selectedly herein go out and be connected to the tie point voltage of output node, be i.e. the dullness of digital input signals (monotonic) analog representation for this reason.
The drive circuit of Organic Light Emitting Diode (OLED) display, regular meeting uses digital analog converter to adjust brightness, contrast or the GTG value of OLED picture element.For active-matrix Organic Light Emitting Diode (AMOLED) display of current type, the final output of its digital analog converter should be electric current but not voltage so can drive its OLED picture element well.For instance, this digital analog converter may be the framework of pure current type, comes multiplication current to adjust its output by the transistor that uses different length-width ratios.
Yet, when the digital analog converter of this pure current type framework need provide the variation of more kinds of outputs, for example when the bit of digital input signals became more or wants the more GTG value of performance in design, above-mentioned transistor just must take the space of more preciousnesses in drive circuit.Perhaps, convert the magnitude of voltage of selecting earlier to electric current again if use the digital analog converter of pure voltage-type framework instead, then its circuit is not only can be quite complicated but also may be difficult to determine the voltage of each tie point on its resistance string therefore can increase the degree of difficulty in the entire circuit design.
Summary of the invention
A purpose of the present invention provides a kind of digital analog converter, can reduce the shared space of its circuit, and can reduce the complexity of circuit design.
According to one embodiment of the invention, this digital analog converter is in order to convert (X+Y) bit input word to current signal, and wherein (X+Y) bit input word comprises sub-word of X bit highest order (MSB) and the sub-word of Y bit lowest order (LSB).This digital analog converter comprises X bit voltage digital analog-converted part and Y bit current digital analog-converted part.X bit voltage digital analog-converted partly can produce intermediate voltage corresponding to X bit MSB word.Y bit current digital analog-converted partly can produce reference current corresponding to this intermediate voltage, and output reference current be multiply by parameter and current signal, wherein this parameter is corresponding to Y bit LSB word.
Another object of the present invention provides a kind of digital-to-analogue conversion method, can simplify its complexity on the circuit when hypostazation.
According to another embodiment of the present invention, this digital-to-analogue conversion method is in order to convert (X+Y) bit input word to current signal, and wherein (X+Y) bit input word comprises sub-word of X bit highest order (MSB) and the sub-word of Y bit lowest order (LSB).This digital-to-analogue conversion method comprises: produce intermediate voltage corresponding to X bit MSB word; Produce reference current corresponding to intermediate voltage; Reference current be multiply by parameter and draws current signal, and wherein this parameter is corresponding to Y bit LSB word.
Description of drawings
Fig. 1 illustrates a kind of traditional resistor string D/A converter.
Fig. 2 illustrates a kind of digital analog converter according to one embodiment of the invention.
Fig. 3 illustrates its X bit voltage digital analog-converted part according to the foregoing description.
Fig. 4 illustrates its current mirror according to the foregoing description.
Fig. 5 illustrates the flow chart of this digital-to-analogue conversion method according to one embodiment of the invention.
The main element symbol description
100: resistor string D/A converter
112: resistance
122: selector
200: digital analog converter
202:X bit voltage digital analog-converted part
204:Y bit current digital analog-converted part
214: resistance
216: operational amplifier
224: current mirror
226: transistor
312: resistance
322: selector
324: selection wire
326: switching device
414: transistor
424: switch
502,504,506: step
Embodiment
Fig. 2 illustrates a kind of digital analog converter according to one embodiment of the invention.Digital analog converter 200 is in order to converting (X+Y) bit input word to current signal, and this (X+Y) bit input word comprises sub-word of X bit highest order (MSB) and the sub-word of Y bit lowest order (LSB).This digital analog converter 200 includes X bit voltage digital analog-converted part 202 and Y bit current digital analog-converted part 204.X bit voltage digital analog-converted part 202 can produce middle voltage VM corresponding to X bit MSB word.Y bit current digital analog-converted part 204 can produce reference current IREF corresponding to middle voltage VM, and output reference current IREF be multiply by a parameter and current signal, wherein this parameter is corresponding to Y bit LSB word.
(X+Y) the bit input word can be a digital signal, and for example digital image signal, digital audio signal or other need be converted into the digital signal of current signal.In this embodiment, digital analog converter 200 is used in the drive circuit of Organic Light Emitting Diode (OLED) display, adjusts brightness, contrast or the GTG value of OLED picture element.Therefore, (X+Y) the bit input word is a digital image signal, and current signal then is the GTG electric current.Moreover (X+Y) the bit input word is assumed to be six bit input words at this, and X bit MSB word is assumed to be two bit MSB words, and Y bit LSB word is assumed to be the sub-word of nibble LSB.
Fig. 3 illustrates its X bit voltage digital analog-converted part 202 according to this embodiment.X bit voltage digital analog-converted part 202 includes several resistance 312 and selector 322.Resistance 312 electrically is series between high reference voltage VH and the low reference voltage VL, so that a plurality of voltage levels to be provided.Selector 322 is coupled to the resistance 312 of series connection, and one of them is used as middle voltage VM to select above-mentioned voltage level according to X bit MSB word.
More particularly, selector 322 comprises several selection wires 324, and each bar selection wire 324 is respectively coupled to a tie point of 312 of the resistance of series connection.Have several switching devices 326 on each bar selection wire 324, and control the switch of each switching device 326 respectively by a bit in the X bit MSB word (for example b4 or b5).On real the work, what be used for switching switching device 326 switches may be that a bit (for example b4 or b5) in the X bit MSB word maybe may be the complement (for example b4b or b5b) of this bit.By selector 322, the voltage of 312 tie points of resistance can selectively be switched is connected to the node of output, and becomes dullness (monotonic) analog representation of X bit MSB word.
With reference to Fig. 2, Y bit current digital analog-converted part 204 comprises resistance 214 and current mirror 224.Resistance 214 can convert middle voltage VM to reference current IREF.That is to say that X bit voltage digital analog-converted part 202 can provide middle voltage VM to operational amplifier 216, and middle voltage VM then is applied in an end of resistance 214 by the virtual connection of 216 liang of inputs of operational amplifier.When the output of operational amplifier 216 obtained voltage, promptly when X bit voltage digital analog-converted part 202 produced middle voltage VM, transistor 226 will be switched on.
The electronic component of other types also can be used to reach the conversion between middle voltage VM and reference current IREF, for example use transistor or other change-over circuit as above-mentioned resistance 214.Fig. 4 illustrates its current mirror 224 according to this embodiment.Current mirror 224 can be copied to a plurality of current paths respectively with the reference current IREF of multiple, wherein each current path is respectively according to a bit of Y bit LSB word (b0 for example, b1, b2 or b3) decide its whether conducting, and current signal is the summation of the electric current that those current paths flow through of conducting.
More particularly, each current path includes the transistor 414 and the switch 424 of mutual series connection.Switch 424 control by the bit of Y bit LSB word (for example b0, b1, b2 or b3), and the transistor 414 of two current paths has different length-width ratio (length-to-width ratio) (M).That is to say, the conducting that can rely on switch 424 whether and the different length-width ratios of transistor 414 decide the parameter of the above-mentioned reference current IREF that is used for doubling.
When transistor 414 had different length-width ratio (for example M is respectively 1,2,4,8), current mirror 224 just can provide the selection of more kinds of magnitudes of current to the current signal of last gained.For instance, when the nibble LSB word with four bit b0, b1, b2 and b3 was transfused to Y bit current digital analog-converted part 204, current mirror 224 should select to export the current signal of 16 kinds of different magnitudes of current.
This embodiment combines the digital analog converter of current type and the digital analog converter of voltage-type, and each several part carries out the conversion of part bit in the input word respectively.Therefore, the shared area of whole digital analog converter can be reduced, and the global design mode of the drive circuit of organic light emitting diode display can be improved.
On the other hand, embodiments of the invention also propose a kind of digital-to-analogue conversion method.Fig. 5 illustrates the flow chart of this digital-to-analogue conversion method according to one embodiment of the invention.(X+Y) the bit input word comprises sub-word of X bit highest order (MSB) and the sub-word of Y bit lowest order (LSB).At first, produce middle voltage VM (step 502) corresponding to X bit MSB word.Then, produce reference current IREF (step 504) corresponding to this middle voltage VM.Then, reference current IREF be multiply by parameter and draws current signal, and this parameter is corresponding to Y bit LSB word (step 506).
(X+Y) the bit input word can be a digital signal, and for example digital image signal, digital audio signal or other need be converted into the digital signal of current signal.In this embodiment, (X+Y) the bit input word is a digital image signal, and current signal then is the GTG electric current.Moreover (X+Y) the bit input word is assumed to be six bit input words at this, and X bit MSB word is assumed to be two bit MSB words, and Y bit LSB word is assumed to be the sub-word of nibble LSB.
More particularly, the above-mentioned step that draws current signal can be copied to a plurality of current paths respectively with the reference current IREF of multiple, wherein each current path decides its whether conducting according to a bit of Y bit LSB word respectively, and current signal is the summation of the electric current that those current paths flow through of conducting.Therefore, the conducting that can rely on current path whether and the magnitude of current that current path flow through decide the parameter of the above-mentioned reference current IREF that is used for doubling.
This embodiment reaches conversion between digital input word and the current signal in conjunction with two kinds of digital-to-analogue conversion modes such as current type and voltage-type.Therefore, can improve the performance of transfer process, for example reduce the shared chip area of its entity circuit, alleviate voltage swing (voltage swing), reduce power consumption etc.
Though the present invention discloses as above with a preferred embodiment; right its is not in order to limit the present invention; in the technology of the present invention field, have and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can being used for a variety of modifications and variations, so protection scope of the present invention is as the criterion when looking the accompanying Claim book person of defining.
Claims (9)
1. a digital analog converter converts one (X+Y) bit input word to a current signal, wherein should (X+Y) bit input word comprise a sub-word of X bit highest order (MSB) and the sub-word of a Y bit lowest order (LSB), and this digital analog converter comprises:
One X bit voltage digital analog-converted part produces an intermediate voltage corresponding to this X bit MSB word; And
One Y bit current digital analog-converted part produces a reference current corresponding to this intermediate voltage, and output this reference current be multiply by a parameter and this current signal, wherein this parameter is corresponding to this Y bit LSB word.
2. digital analog converter as claimed in claim 1, wherein this X bit voltage digital analog-converted partly comprises:
A plurality of resistance, electrically series connection is to provide a plurality of voltage levels; And
One selector is coupled to those resistance of series connection, and one of them is used as this intermediate voltage to select those voltage levels according to this X bit MSB word.
3. digital analog converter as claimed in claim 1, wherein this Y bit current digital analog-converted partly comprises:
One resistance converts this intermediate voltage to this reference current; And
One current mirror is copied to a plurality of current paths respectively with this reference current of multiple, and wherein each current path determines whether conducting according to the bit of this Y bit LSB word, and this current signal is the summation of the electric current that those current paths flow through of conducting.
4. digital analog converter as claimed in claim 3, wherein each current path comprises a transistor and a switch is connected mutually, and this switch is controlled by a bit of this Y bit LSB word, and the transistor of two current paths has different length-width ratios.
5. digital analog converter as claimed in claim 1 should (X+Y) bit input word be a digital image signal wherein, and this current signal be a GTG electric current.
6. digital-to-analogue conversion method, convert one (X+Y) bit input word to a current signal, wherein should (X+Y) bit input word comprise a sub-word of X bit highest order (MSB) and the sub-word of a Y bit lowest order (LSB), this digital-to-analogue conversion method comprises following steps:
Produce an intermediate voltage corresponding to this X bit MSB word;
Produce a reference current corresponding to this intermediate voltage; And
This reference current be multiply by a parameter and draws this current signal, and wherein this parameter is corresponding to this Y bit LSB word.
7. digital-to-analogue conversion method as claimed in claim 6 should (X+Y) bit input word be a digital image signal wherein, and this current signal be a GTG electric current.
8. digital-to-analogue conversion method as claimed in claim 6, the step that wherein draws this current signal comprises:
This reference current of multiple is copied to a plurality of current paths respectively, and wherein each current path determines whether conducting according to the bit of this Y bit LSB word, and this current signal is the summation of the electric current that those current paths flow through of conducting.
9. digital-to-analogue conversion method as claimed in claim 8, wherein the magnitude of current that those current paths flow through differs from one another.
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| CN2008100032098A CN101488756B (en) | 2008-01-14 | 2008-01-14 | Digital-to-analog converter and converting method thereof |
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| CN2008100032098A CN101488756B (en) | 2008-01-14 | 2008-01-14 | Digital-to-analog converter and converting method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103095303A (en) * | 2012-10-23 | 2013-05-08 | 深圳先进技术研究院 | Current mode and voltage mode combined digital analog converter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103095303A (en) * | 2012-10-23 | 2013-05-08 | 深圳先进技术研究院 | Current mode and voltage mode combined digital analog converter |
| CN103095303B (en) * | 2012-10-23 | 2018-02-06 | 深圳先进技术研究院 | A kind of current mode and voltage-type compositive mathematical models converter |
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| CN101488756B (en) | 2011-06-15 |
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