CN101968944B - Operating temperature detection circuit for liquid crystal display driving chip - Google Patents

Abstract

The invention discloses a working temperature detection circuit of a liquid crystal display driving chip, which is used to solve the technical problem of poor working stability of the existing temperature detection circuit. The technical solution is that the circuit is composed of a reference current generating circuit and a voltage output circuit. The MOS transistor MR1 in the reference current generating circuit works in a linear region and has the property of linear resistance. The area of the emitting area of the transistor Q2 is n times that of the transistor Q1. The voltage output circuit is composed of MOS transistor M5 and MOS transistor MR2, wherein MOS transistor MR2 works in the linear region and has the property of linear resistance. The MOS transistor M5 mirrors the reference current to generate a constant current in the circuit, and flows through the linear resistance formed by the MOS transistor MR2 to generate an output voltage. Since the passive resistor in the background technology is replaced by the MOS transistor working in the linear region, the non-linear temperature detection is realized, thereby reducing the data operation burden of the host computer and improving the working stability of the temperature detection circuit.

Description

Operating temperature detection circuit for liquid crystal display driving chip

Technical field

The present invention relates to a kind of temperature sensing circuit, particularly operating temperature detection circuit for liquid crystal display driving chip.

Background technology

For liquid crystal display, due to 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 liquid crystal display.For example when environment temperature rose, the phase shift meeting of display panels diminished, and this phenomenon can affect the optical characteristics such as the brightness, transport property, gamma curve of display panels.In order to overcome this problem, need to carry out 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 impact of image quality at any time, and this just requires set temperature automatic detection circuit 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 consists of reference current generating circuit, and this reference current is directly proportional to temperature, therefore be called PTAT (Proportional To Absolute Temperature) reference current.Due to triode Q1 and triode Q2 | V _BE| difference equal resistance R ₁On pressure drop, therefore

${\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HSA00000304192500011.png"\; state="\{\{state\}\}">I</figure-callout>}}_1=I_2=\frac{{\mathrm{\&Delta;V}}_{\mathrm{BE}}}{R_1}=\frac{V_{T}1n\left(n\right)}{R_1}---\left(1\right)$

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

${\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HSA00000304192500011.png"\; state="\{\{state\}\}">I</figure-callout>}}_1=I_2=\frac{{\mathrm{\&Delta;V}}_{\mathrm{BE}}}{R_1}=\frac{V_T\ln \left(n\right)}{R_1}=-\frac{\mathrm{kT}\ln \left(n\right)}{{\mathrm{qR}}_1}---\left(2\right)$

By (2) formula as can be known, electric current I ₁And I ₂Be directly proportional to 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 to temperature _POutput current I ₅Be expressed as

$I_5=\frac{W_5}{W_4}\&times;{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000304192500012.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\frac{\mathrm{kT}\ln \left(n\right)}{{\mathrm{qR}}_1}---\left(3\right)$

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

$V_P=I_5\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000304192500012.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\frac{\mathrm{kT}\ln \left(n\right)\&times;R_2}{q\&times;R_1}---\left(4\right)$

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

Summary of the invention

In order to overcome existing temperature sensing circuit to the deficiency that the operation burden is heavier and chip occupying area is larger of system host, the invention provides a kind of operating temperature detection circuit for liquid crystal display driving chip.This circuit is comprised 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 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 metal-oxide-semiconductor that is operated in linear zone due to utilization has substituted the passive resistance in the background technology, can realize that nonlinear temperature detects, thereby alleviate the data manipulation burden of main frame, improves the stability of liquid crystal display systems self work.Adopt simultaneously the metal-oxide-semiconductor resistance can saving chip area, thereby reduce chip cost.

The technical solution adopted for the present invention to solve the technical problems: a kind of operating temperature detection circuit for liquid crystal display driving chip, 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 consist of 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 consists of voltage follower circuit, and metal-oxide-semiconductor MR2 plays linear resistance effect; Steady current in 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 comprised of reference current generating circuit and voltage follower circuit two parts, metal-oxide-semiconductor MR1 in 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 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 metal-oxide-semiconductor that is operated in linear zone due to utilization has substituted the passive resistance in the background technology, has realized the nonlinear temperature detection, thereby has alleviated the data manipulation burden of main frame, has improved the stability of liquid crystal display systems self work.Adopt simultaneously metal-oxide-semiconductor resistance to save chip area, 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 operating temperature detection circuit for liquid crystal display driving chip schematic diagram of the present invention.

Fig. 2 is the schematic diagram of metal-oxide-semiconductor resistance in Fig. 1.

Fig. 3 is operating temperature detection circuit for liquid crystal display driving chip output voltage of the present invention-temperature relation curve.

Fig. 4 is the operating temperature detection circuit for liquid crystal display driving chip schematic diagram that adds enable signal and start-up circuit.

Fig. 5 is background technology temperature sensing circuit schematic diagram.

Embodiment

With reference to Fig. 1～4.Operating temperature detection circuit for liquid crystal display driving chip of the present invention is comprised 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 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:

$V_P=I_5\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000304192500012.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{W_5}{W_4}\&times;\left(\frac{\mathrm{kT}}{q}\ln n\right)\&times;\frac{R_{\mathrm{ON}2}}{R_{\mathrm{ON}1}}---\left(5\right)$

In formula, R _ON1And R _ON2The conducting resistance that represents respectively metal-oxide-semiconductor MR1 and metal-oxide-semiconductor MR2.Conducting resistance R due to 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 formula, μ _nThe mobility of electronics, C _oxBe the gate oxide electric capacity of unit area, W/L is the breadth length ratio of pipe, V _GSThe gate source voltage of pipe, V _THIt is the threshold voltage of pipe.Therefore, output voltage V _PBe expressed as

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

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

Due to metal-oxide-semiconductor M2 and metal-oxide-semiconductor MR1 series connection, therefore their grid voltage is equal, 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, and metal-oxide-semiconductor MR1 just must operate at linear zone.Its reason is as follows:

M2 is operated in the saturation region due to metal-oxide-semiconductor,

V _G-V _D2-V _TH≤V _D1-V _D2 (8)

Namely

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, namely obtain

V _G-V _S2-V _TH≥V _D2-V _S2 (11)

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

For metal-oxide-semiconductor MR2, due to the output current I of metal-oxide-semiconductor M5 mirror image ₅Less than the output current of metal-oxide-semiconductor MR2, therefore metal-oxide-semiconductor MR2 also is operated in linear zone, show as metal-oxide-semiconductor resistance.This is due to the metal-oxide-semiconductor for two series connection, and the size of branch current determined by the less pipe of output current ability, and the larger 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 temperature, can satisfy temperature data acquisition and the Real Time Monitoring requirement of large-screen lc display driving system, adopt simultaneously the metal-oxide-semiconductor resistance can saving chip area, thereby reduce chip cost.

Add the temperature sensing circuit after enable signal and start-up circuit to find out from Fig. 4, EN is enable signal, and XEN is the reverse signal of enable signal.Circuit normal operation when EN is low level, when EN is high level, circuit quits work.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 low level, PMOS pipe MP1, PMOS pipe MP2, PMOS pipe MP3, PMOS pipe MP4 conducting this moment, the grid of managing MN4 due to NMOS is high level, the conducting of NMOS pipe MN4 pipe, the grid voltage of PMOS pipe M3, PMOS pipe M4 is pulled to low level, 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, the electric current in the 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 to manage the cut-off of MN4 pipe, 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 high level, PMOS pipe MP1, PMOS pipe MP2, PMOS pipe MP3, PMOS pipe MP4 pipe cut-off in start-up circuit, NMOS pipe MN1 conducting, thereby NMOS pipe MN4 cut-off, 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 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. A liquid crystal display driver chip operating temperature detection circuit, comprising MOS tube M1, MOS tube M2, MOS tube M3, MOS tube M4, MOS tube M5, triode Q1 and triode Q2, is characterized in that: also includes MOS tube MR1 and MOS tube MR2, MOS tube M1, MOS tube M2, MOS tube M3, MOS tube M4, MOS tube MR1, transistor Q1 and transistor Q2 form a reference current generating circuit, MOS tube M2 is connected in series with MOS tube MR1, MOS tube M2 and MOS tube The gate voltages of MR1 connected in series are equal, MOS transistor MR1 works in the linear region, and MOS transistor MR1 acts as a linear resistance; MOS transistor M5 and MOS transistor MR2 are connected in series to form a voltage output circuit, and the output current I ₅ of the mirror image of MOS transistor M5 is smaller than that of MOS transistor MR2 MOS transistor MR2 works in the linear region, and MOS transistor MR2 acts as a linear resistance; MOS transistor M5 mirrors the reference current to generate a constant current in the circuit, and flows through the linear resistance formed by MOS transistor MR2 to generate an output voltage V _p There is a nonlinear relationship with temperature T.

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