CN101968944A - Operating temperature detection circuit for liquid crystal display driving chip - Google Patents

Abstract

The invention discloses an operating temperature detection circuit for a liquid crystal display driving chip, which is used for solving the technical problem of low working stability of the temperature detection circuit in the prior art. A technical scheme is that: the circuit consists of a reference current generating circuit and a voltage output circuit, wherein a metal oxide semiconductor (MOS) pipe MR1 of the reference current generating circuit works in a linear area and has properties of a linear resistor; the area of an emitter area of an audion Q2 is n times that of an audion Q1; the voltage output circuit consists of an MOS pipe M5 and an MOS pipe MR2; the MOS pipe MR2 works in the linear area and has the properties of a linear resistor; an MOS pipe M5 image reference current generating circuit generates constant current; and the constant current flows through a linear resistor formed by the MOS pipe MR2 to generate an output voltage. The MOS pipes working in the linear area substitute for passive resistors of the prior art, so that nonlinear temperature detection is realized, the data operation load of a host is reduced and the working stability of the temperature detection circuit is improved.

Description

Liquid crystal display drive chip working temperature testing circuit

Technical field

The present invention relates to a kind of temperature sensing circuit, particularly liquid crystal display drive chip working temperature testing circuit.

Background technology

For LCD, because the physical characteristics of liquid crystal panel, the temperature variation of environment temperature and display panels itself can have influence on the photoelectric characteristic of LCD.For example when environment temperature rose, the phase shift meeting of display panels diminished, and this phenomenon can influence optical characteristics such as the brightness, transport property, gamma curve of display panels.In order to overcome this problem, need carry out the dynamic real-time monitoring to the temperature of large-screen lc display system, and the Adjustment System parameter is to eliminate temperature variation to showing the influence of image quality at any time, and this just requires to be provided with the automatic testing circuit of temperature in liquid crystal display drive chip.

With reference to Fig. 5, document " A.Golda; A.Kos; " ANALYSIS AND DESIGN OF PTAT TEMPREATURE SENSOR IN DIGITAL CMOS VLSI CIRCUIT "; MIXDES 2006international conference " discloses a kind of temperature sensing circuit of digital integrated circuit chip, comprises triode Q1, triode Q2, metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor M5, resistance R ₁And resistance R ₂I wherein ₁And I ₂Branch road constitutes reference current generating circuit, and this reference current is directly proportional with temperature, so be called PTAT (Proportional To Absolute Temperature) reference current.Because triode Q1 and triode Q2's | V _BE| difference equal resistance R ₁On pressure drop, therefore

$I_1=I_2=\frac{{\mathrm{\ΔV}}_{\mathrm{BE}}}{R_1}=\frac{V_{T}1n\left(n\right)}{R_1}---\left(1\right)$

In the formula, V _TBe thermal voltage, V _T=kT/q; K is a Boltzmann constant (1.38 * 10 ^-23J/K); Q is the quantity of electric charge (1.60 * 10 of electronics ^-19C); N is a triode Q1 emitter and the ratio of the area of triode Q2 emitter; T is a thermodynamic temperature.Therefore

$I_1=I_2=\frac{{\mathrm{\ΔV}}_{\mathrm{BE}}}{R_1}=\frac{V_T\ln \left(n\right)}{R_1}=-\frac{\mathrm{kT}\ln \left(n\right)}{{\mathrm{qR}}_1}---\left(2\right)$

By (2) formula as can be known, electric current I ₁And I ₂Be directly proportional with temperature T.

Metal-oxide-semiconductor M5 mirror image I ₁Or I ₂Electric current obtains output current I ₅, and act on resistance R ₂On obtain the output voltage V that is directly proportional with temperature _POutput current I ₅Be expressed as

$I_5=\frac{W_5}{W_4}\&times;{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000304192500021.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\frac{\mathrm{kT}\ln \left(n\right)}{{\mathrm{qR}}_1}---\left(3\right)$

In the formula, W ₅Be the grid width of metal-oxide-semiconductor M5, W ₄Be the grid width of metal-oxide-semiconductor M4, the grid appearance of metal-oxide-semiconductor M5 and metal-oxide-semiconductor M4 etc.So output voltage V _PBe expressed as

$V_P=I_5\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000304192500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\frac{\mathrm{kT}\ln \left(n\right)\&times;R_2}{q\&times;R_1}---\left(4\right)$

By (4) formula as can be known, if resistance R ₁And resistance R ₂Temperature characterisitic mate output voltage V so fully _PJust be directly proportional, therefore by detecting V with temperature T _PThe size of voltage just can be extrapolated the height of temperature T, thereby realizes the automatic detection to temperature.Because output voltage V _PBe directly proportional with temperature T, therefore existing temperature sensing circuit is the linearity test system that a kind of output voltage is directly proportional with temperature.

Summary of the invention

In order to overcome operation the burden heavier and chip occupying area bigger deficiency of existing temperature sensing circuit, the invention provides a kind of liquid crystal display drive chip working temperature testing circuit to system host.This circuit is made up of reference current generating circuit and voltage follower circuit two parts, reference current generating circuit is made of metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor MR1 and triode Q1 and Q2, wherein metal-oxide-semiconductor MR1 is operated in linear zone, character with linear resistance, the emitter area of triode Q2 are n times of triode Q1.Voltage follower circuit is made of metal-oxide-semiconductor M5 and metal-oxide-semiconductor MR2, and wherein metal-oxide-semiconductor MR2 is operated in linear zone, has the character of linear resistance.Steady current in the metal-oxide-semiconductor M5 mirror image reference current generating circuit, and flow through the linear resistance that metal-oxide-semiconductor MR2 forms, produce output voltage.Owing to utilize the metal-oxide-semiconductor that is operated in linear zone to substitute the passive resistance in the background technology, can realize that nonlinear temperature detects, thereby alleviate the data manipulation burden of main frame, improve the stability of liquid crystal display systems self work.Adopt metal-oxide-semiconductor resistance can save chip area simultaneously, thereby reduce chip cost.

The technical solution adopted for the present invention to solve the technical problems: a kind of liquid crystal display drive chip working temperature testing circuit, comprise metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor M5, triode Q1 and triode Q2, be characterized in also comprising metal-oxide-semiconductor MR1 and metal-oxide-semiconductor MR2.Metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor MR1 and triode Q1 and triode Q2 constitute reference current generating circuit, and metal-oxide-semiconductor M2 connects with metal-oxide-semiconductor MR1, and metal-oxide-semiconductor MR1 plays linear resistance effect; Metal-oxide-semiconductor M5 connects with metal-oxide-semiconductor MR2 and constitutes voltage follower circuit, and metal-oxide-semiconductor MR2 plays linear resistance effect; Steady current in the metal-oxide-semiconductor M5 mirror image reference current generating circuit, and flow through the linear resistance that metal-oxide-semiconductor MR2 forms.

The invention has the beneficial effects as follows: temperature sensing circuit is made up of reference current generating circuit and voltage follower circuit two parts, metal-oxide-semiconductor MR1 in the reference current generating circuit is operated in linear zone, character with linear resistance, the launch site area of triode Q2 are n times of triode Q1.Voltage follower circuit is made of metal-oxide-semiconductor M5 and metal-oxide-semiconductor MR2, and wherein metal-oxide-semiconductor MR2 is operated in linear zone, has the character of linear resistance.Steady current in the metal-oxide-semiconductor M5 mirror image reference current generating circuit, and flow through the linear resistance that metal-oxide-semiconductor MR2 forms, produce output voltage.Owing to utilize the metal-oxide-semiconductor that is operated in linear zone to substitute the passive resistance in the background technology, realize the nonlinear temperature detection, thereby alleviated the data manipulation burden of main frame, improved the stability of liquid crystal display systems self work.Adopt metal-oxide-semiconductor resistance to save chip area simultaneously, thereby reduced the cost of chip.

Below in conjunction with the drawings and specific embodiments the present invention is elaborated.

Description of drawings

Fig. 1 is a liquid crystal display drive chip working temperature testing circuit synoptic diagram of the present invention.

Fig. 2 is the synoptic diagram of metal-oxide-semiconductor resistance among Fig. 1.

Fig. 3 is liquid crystal display drive chip working temperature testing circuit output voltage of the present invention-temperature relation curve.

Fig. 4 is the liquid crystal display drive chip working temperature testing circuit synoptic diagram that adds enable signal and start-up circuit.

Fig. 5 is a background technology temperature sensing circuit synoptic diagram.

Embodiment

With reference to Fig. 1～4.Liquid crystal display drive chip working temperature testing circuit of the present invention is made up of reference current generating circuit and voltage follower circuit two parts.Reference current generating circuit is made of metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor MR1 and triode Q1 and triode Q2, wherein metal-oxide-semiconductor MR1 is operated in linear zone, character with linear resistance, the emitter area of triode Q2 are n times of triode Q1.Voltage follower circuit is made of metal-oxide-semiconductor M5 and metal-oxide-semiconductor MR2, and wherein metal-oxide-semiconductor MR2 is operated in linear zone, has the character of linear resistance.Steady current in the metal-oxide-semiconductor M5 mirror image reference current generating circuit, and flow through the linear resistance that metal-oxide-semiconductor MR2 forms, produce output voltage.The core of this temperature sensing circuit is to utilize the metal-oxide-semiconductor that is operated in linear zone to substitute passive resistance of the prior art.

Temperature sensing circuit output voltage V of the present invention _PExpression formula be:

$V_P=I_5\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000304192500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\left(\frac{\mathrm{kT}}{q}\ln n\right)\&times;\frac{R_{\mathrm{ON}2}}{R_{\mathrm{ON}1}}---\left(5\right)$

In the formula, R _ON1And R _ON2The conducting resistance of representing metal-oxide-semiconductor MR1 and metal-oxide-semiconductor MR2 respectively.Because the conducting resistance R of metal-oxide-semiconductor _ONBe expressed as

$R_{\mathrm{ON}}=\frac{1}{{\mathrm{\&mu;}}_n{C}_{\mathrm{OX}}\frac{W}{L}(V_{\mathrm{GS}}-V_{\mathrm{TH}})}---\left(6\right)$

In the formula, μ _nBe the mobility of electronics, C _OxBe the gate oxide electric capacity of unit area, W/L is the breadth length ratio of pipe, V _GSBe the gate source voltage of pipe, V _THIt is the threshold voltage of pipe.Therefore, output voltage V _PBe expressed as

$V_P=\frac{W_5}{W_4}\&times;\left(\frac{\mathrm{kT}}{q}\ln n\right)\&times;\frac{{\mathrm{\&mu;}}_n{C}_{\mathrm{OX}}{\left(\frac{W}{L}\right)}_{\mathrm{MR}1}(V_{\mathrm{GSMR}1}-V_{\mathrm{THMR}1})}{{\mathrm{\&mu;}}_n{C}_{\mathrm{OX}}{\left(\frac{W}{L}\right)}_{\mathrm{MR}2}(V_{\mathrm{GSMR}2}-V_{\mathrm{THMR}2})}---\left(7\right)$

Learn by (7) formula, because the threshold voltage V of metal-oxide-semiconductor MR1 and metal-oxide-semiconductor MR2 _THMR1And V _THMR2All relevant with temperature T, so output voltage V _PAnd be nonlinear relationship between the temperature T, can realize that therefore nonlinear temperature detects.

Because metal-oxide-semiconductor M2 and metal-oxide-semiconductor MR1 series connection, so their grid voltage equates that this moment, metal-oxide-semiconductor M2 and metal-oxide-semiconductor MR1 just can not be operated in the saturation region simultaneously, make metal-oxide-semiconductor M2 be operated in the saturation region, metal-oxide-semiconductor MR1 just must operate at linear zone.Its reason is as follows:

Because metal-oxide-semiconductor M2 is operated in the saturation region, then

V _G-V _D2-V _TH≤V _D1-V _D2 (8)

Promptly

V _G-V _TH≤V _D1 (9)

Simultaneously, the condition of metal-oxide-semiconductor M2 conducting is

V _G-V _TH≥V _D2 (10)

(10) the formula both sides deduct V simultaneously _S2, promptly obtain

V _G-V _S2-V _TH≥V _D2-V _S2 (11)

Learn that by (11) formula metal-oxide-semiconductor MR1 is operated in linear zone, so metal-oxide-semiconductor MR1 shows as metal-oxide-semiconductor resistance.

For metal-oxide-semiconductor MR2, because the output current I of metal-oxide-semiconductor M5 mirror image ₅Less than the output current of metal-oxide-semiconductor MR2,, show as metal-oxide-semiconductor resistance so metal-oxide-semiconductor MR2 also is operated in linear zone.This is owing to the metal-oxide-semiconductor for two series connection, and the size of branch current is determined that by the less pipe of output current ability the bigger pipe of output current ability this moment is forced to be operated in linear zone.

The present invention adopts the output voltage of the temperature sensing circuit that metal-oxide-semiconductor resistance forms and the relation curve between the temperature, can satisfy the temperature data acquisition and the real-time monitoring requirement of large-screen lc display driving system, adopt metal-oxide-semiconductor resistance can save chip area simultaneously, thereby reduce chip cost.

From Fig. 4 add behind enable signal and the start-up circuit temperature sensing circuit as can be seen, EN is an enable signal, XEN is the reverse signal of enable signal.Circuit operate as normal when EN is low level, circuit quit work when EN was high level.The principle of work of enable signal and start-up circuit is as follows.

1) start-up course is: when powering on, enable signal EN is a low level, PMOS pipe MP1, PMOS pipe MP2, PMOS pipe MP3, PMOS pipe MP4 conducting this moment, because the grid of NMOS pipe MN4 is a high level, the conducting of NMOS pipe MN4 pipe, the grid voltage of PMOS pipe M3, PMOS pipe M4 is pulled to low level, and the PTAT reference current produces the loop, be that metal-oxide-semiconductor M4, metal-oxide-semiconductor M3, metal-oxide-semiconductor M2, metal-oxide-semiconductor M1, metal-oxide-semiconductor MR1, triode Q1 and triode Q2 begin startup work, current in loop increases gradually.When the PTAT electric current reached stationary value, the grid potential of metal-oxide-semiconductor M2, metal-oxide-semiconductor MR1 raise, NMOS pipe MN2 conducting, the grid voltage of NMOS pipe MN4 is pulled to low level, cause NMOS pipe MN4 pipe to end, this moment, start-up circuit and PTAT reference current produced the loop disconnection, and start-up course finishes.

2) off state is: during breaking circuit, enable signal EN is a high level, PMOS pipe MP1, PMOS pipe MP2, PMOS pipe MP3, PMOS pipe MP4 pipe in the start-up circuit ends, NMOS pipe MN1 conducting, thereby NMOS pipe MN4 ends, NMOS pipe MN3 conducting is simultaneously moved the grid voltage of metal-oxide-semiconductor M1 and metal-oxide-semiconductor M2 to low level.When EN was high level, XEN was a low level simultaneously, PMOS pipe MP5 conducting this moment, thus metal-oxide-semiconductor M3, metal-oxide-semiconductor M4 are turn-offed.Therefore, start-up circuit and PTAT reference current generation loop all is closed.

Claims (1)

1. liquid crystal display drive chip working temperature testing circuit, comprise metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor M5, triode Q1 and triode Q2, it is characterized in that: also comprise metal-oxide-semiconductor MR1 and metal-oxide-semiconductor MR2, metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, metal-oxide-semiconductor M4, metal-oxide-semiconductor MR1 and triode Q1 and triode Q2 constitute reference current generating circuit, metal-oxide-semiconductor M2 connects with metal-oxide-semiconductor MR1, and metal-oxide-semiconductor MR1 plays linear resistance effect; Metal-oxide-semiconductor M5 connects with metal-oxide-semiconductor MR2 and constitutes voltage follower circuit, and metal-oxide-semiconductor MR2 plays linear resistance effect; Steady current in the metal-oxide-semiconductor M5 mirror image reference current generating circuit, and flow through the linear resistance that metal-oxide-semiconductor MR2 forms.

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