KR101446759B1 - Output specification calibrating apparatus for a capacitance press sensor - Google Patents

Abstract

The present invention relates to an apparatus to adjust an output specification of a capacitive pressure sensor. When shipping a capacitive pressure sensor, an output voltage change, nonlinearity, and an output offset in accordance to the temperature of the capacitive pressure sensor can easily and conveniently be adjusted, thereby satisfying various output specifications demanded by customers.

Description

[0001] The present invention relates to an output specification calibrating apparatus for a capacitive pressure sensor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure measurement technique, and more particularly to an output specification adjustment device of a capacitive pressure sensor.

The pressure sensor converts the mechanical displacement generated by the pressure into an electric signal and outputs the electric signal. The pressure is measured by measuring the intensity of the electric signal outputted. A capacitive pressure sensor as disclosed in Korean Patent Application Laid-Open No. 10-2001-0039983 (2001. 05. 15), etc., converts a mechanical displacement into a capacitance, outputs the capacitance, and the pressure is measured by detecting the capacitance change .

Capacitive pressure sensors have nonlinear characteristics to the applied pressure and are temperature-sensitive. Therefore, in order to satisfy various output specifications required by customers, the output specification of the capacitive pressure sensor at the time of delivery must be adjusted to the customer's requirements . Accordingly, the present inventor has studied a device for adjusting an output specification of a capacitive pressure sensor capable of satisfying various output specifications required by customers.

Korean Patent Publication No. 10-2001-0039983 (May 15, 2001)

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned circumstances and it is an object of the present invention to provide a capacitive pressure sensor which can calibrate the output of a capacitive pressure sensor at the time of shipment to meet various output specifications required by customers, And to provide a control device.

According to an aspect of the present invention, there is provided an apparatus for adjusting the output of a capacitive pressure sensor, including: a capacitance Cp formed by a main electrode of a capacitive pressure sensor; a capacitance Cp formed by a reference electrode; A capacitance-voltage converter for converting a capacitance change into an output voltage and outputting the output voltage; A first compensator for selectively compensating for an output voltage change according to a temperature of the capacitance-voltage converter or an output voltage non-linearity caused by a capacitance Cp and a capacitance Cr of the capacitance-voltage converter; And a compensation controller for selectively adjusting an electrical characteristic value for compensation of an output voltage variation or an output voltage nonlinearity compensation according to a temperature of the first compensation element; And the like.

According to a further aspect of the present invention, the first compensation element is connected in series between the power input and the ground, and is connected to the fixed resistor R _Lin1 and the variable resistor R _Lin2 ; .

According to a further aspect of the present invention, the compensation controller includes a bandgap reference (BGR); A MUX for selectively outputting the BGR output voltage or the output voltage fed back from the capacity-voltage converter according to an applied signal level; An A / D converter for analog-to-digital converting a BGR output voltage selectively output by the mux or an output voltage fed back from the capacitance-to-voltage converter to generate a temperature code or a pressure code; A characteristic value setting unit that selects a resistance value corresponding to a temperature code or a pressure code generated by the AD converter as an electrical characteristic value and sets a resistance value of the variable resistor R _Lin2 to a selected resistance value; .

According to a further aspect of the present invention, there is provided an apparatus for controlling an output of a capacitive pressure sensor, the apparatus comprising: a main control unit for applying an output signal of the capacitive pressure sensor to a low or high level signal; And further comprising:

According to a further aspect of the present invention, there is provided a capacitance-voltage converter comprising: a capacitance Cp formed by the main electrode of the capacitive-pressure sensor; a switch unit for controlling charging and discharging operations of the capacitance Cr formed by the reference electrode; An integrator for receiving the capacitance Cp and the current discharged from the capacitance Cr and outputting it as an output voltage, and integrating the error correction signal in the control loop until the error approaches zero; A capacitance Cp, a power input unit for supplying a constant power to the capacitance Cr; A feedback unit including an amplifier for amplifying the output voltage outputted by the integrator and feeding back the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode and the power input unit; .

According to a further aspect of the present invention, there is provided an apparatus for controlling an output of a capacitive pressure sensor, comprising: a second compensating element for adjusting an output voltage offset of the capacitance-voltage converting portion; And further comprising:

According to a further aspect of the present invention, the second compensation element is connected in series between the power input and the ground, and is branched at the series connection connection point to apply a voltage to the non-inverting input terminal of the amplifier of the feedback section, the two variable resistor R and a variable resistor R _{of1 of2} to adjust the conversion unit output voltage offset (offset); .

According to a further aspect of the present invention, the main controller includes a control register in which information to be referred to when setting the electrical property values of the first compensator and the second compensator is recorded.

According to a further aspect of the present invention, the characteristic value setting unit searches for the value recorded in the control bit of the control register and selects the resistance value corresponding to the temperature code or the pressure code as the electrical characteristic value.

According to an additional aspect of the invention, is characterized in that said main control unit is selected, the resistance value of the search for the values recorded in the control bits of the control register two variable resistors R _of1 and the variable resistor R _of2 the electric characteristic value.

The present invention can easily adjust the output voltage change, nonlinearity, and output offset according to the temperature of the capacitive pressure sensor when the capacitive pressure sensor is shipped, thereby satisfying various output specifications required by customers.

1 and 2 are views showing an example of a capacitive pressure sensor.
3 is a block diagram showing a configuration of an embodiment of an output-specification adjusting apparatus for a capacitive pressure sensor according to the present invention.
4 is a timing chart of the main control unit of the output-specification adjusting apparatus of the capacitive pressure sensor according to the present invention.
5 is a switching timing diagram of the capacity-voltage conversion unit of the output-specification adjusting apparatus of the capacitive pressure sensor according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The terms used throughout the specification of the present invention have been defined in consideration of the functions of the embodiments of the present invention and can be sufficiently modified according to the intentions and customs of the user or operator. It should be based on the contents of.

1 and 2 show an example of a capacitive pressure sensor in which a capacitive pressure sensor 100 for converting a mechanical displacement into a capacitance and outputting the capacitive pressure sensor 100 includes a dielectric substrate 110, . ≪ / RTI >

The dielectric substrate 110 is a portion where mechanical deflection occurs due to pressure. The electrode pattern 120 formed on one side of the dielectric substrate 110 includes a main electrode 121 and a reference electrode 122 and is connected to an output specification adjusting device through a lead portion (not shown).

The main electrode 121 and the reference electrode 122 act on a conductor plate formed on the other side of the dielectric substrate 110 to form a capacitance Cp formed by the main electrode and a capacitance Cr formed by the reference electrode.

When a mechanical displacement occurs due to a pressure applied to the dielectric substrate 110, the distance between the main electrode 121 and the reference electrode 122 formed on the dielectric substrate 110 changes, and the capacitance Cp and the capacitance of the capacitance Cr change do.

The output specification adjusting device converts the capacitance change of the capacitance Cp and the capacitance Cr into an electric signal and outputs the electric signal so that the pressure can be measured. 3 is a block diagram showing a configuration of an embodiment of an output-specification adjusting apparatus for a capacitive pressure sensor according to the present invention.

3, the output specification adjustment apparatus includes a capacity-voltage conversion unit 200, a first compensation device 300, and a compensation control unit 400.

The capacitance-to-voltage converter 200 converts the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance change of the capacitance Cr formed by the reference electrode into an output voltage and outputs the output voltage. For example, the capacitance-voltage conversion unit 200 may include a switch unit 210, an integrator 220, a power input unit 230, and a feedback unit 240.

The switch unit 210 controls the charging and discharging operations of the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode.

3, the switch unit 210 includes six switches (two P1 switches that are simultaneously turned on at the start of phase 1 and are off at phase 2, and a phase 2 One P2d switch that is turned on at the start of P2 and is in the off state at phase 1, one P1d switch that is turned on after a specific time delay after P1 switch turn-on at phase 1, And one P2d switch that is turned on after a certain time delay after turning on).

A capacitance Cp formed by the main electrode of the capacitive pressure sensor and a capacitance Cr formed by the reference electrode are connected in series between the two P1-P2 switch connectors. A common terminal Ccom is formed by branching between a capacitance Cp formed by the main electrode connected in series and a capacitance Cr formed by the reference electrode, and a terminal P1d and a switch P2d are connected in parallel at the terminal end of the common terminal Ccom.

The P1 switch of the P1-P2 switch connector to which the capacitance Cr formed by the reference electrode is connected is connected to the output terminal of the power input section 230, and the P2 switch is connected to the ground. The P1 switch of the P1-P2 switch connector to which the capacitance Cp formed by the main electrode is connected is connected to the ground, and the P2 switch is connected to the output terminal of the feedback section 240. [ The P1d switch, which is connected in parallel to the common terminal Ccom, is connected to the inverting input terminal of the integrator 220, and the P2d switch is connected to the ground.

The integrator 220 receives the capacitance Cp and the current discharged from the capacitance Cr and outputs it as an output voltage. The integrator 220 integrates the error correction signal in the control loop until the error approaches zero.

As shown in FIG. 3, the integrator 220 may be implemented to include an operational amplifier and an integral capacitor CF. The noninverting input terminal of the op amp is connected to ground for input bias current compensation. The error of the integration result due to the input bias current can be reduced by connecting the non-inverting terminal to the ground and equalizing the resistance between the two input terminals and the ground.

On the other hand, the inverting input terminal of the operational amplifier receives a capacitance Cp formed by the main electrode of the capacitive pressure sensor and a current discharged by the capacitance Cr formed by the reference electrode through the common terminal Ccom.

On the other hand, an integral capacitor CF is connected between the inverting input terminal and the output terminal of the operational amplifier. The integral error of the integrator 220 is inversely proportional to the open DC gain of the operational amplifier. Compensating only the input offset voltage when an op amp is used can ensure sufficient accuracy.

The power input unit 230 supplies a constant power to the capacitance Cp and the capacitance Cr. For example, the power input unit 230 may be implemented as a buffer used when the output voltage needs to be kept constant regardless of a change in the load.

The buffer outputs the voltage inputted through the input terminal as it is through the output terminal to supply a constant power to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode.

The feedback unit 240 amplifies the output voltage output from the integrator 220 and outputs a capacitance Cp formed by the main electrode of the capacitive pressure sensor, a capacitance Cr formed by the reference electrode, and a power input unit 230, Lt; / RTI >

The voltage outputted by the integrator 220 and amplified by the amplifier is applied to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode by the switching operation of the switch unit 210 . Also, the amplifier applies the output voltage, which is output and fed back by the integrator 220, to the input terminal of the power input unit 230. [

At this time, the fixed resistor ROF may be connected between the inverting input terminal and the output terminal of the amplifier to adjust the gain of the amplifier, and the variable resistor ROI may be connected between the inverting input terminal of the amplifier and the output terminal of the integrator 220 .

The gain of the amplifier indicates how much the output voltage is amplified compared to the input voltage, and the gain (input voltage V _out Output voltage V _bdge ratio) can be expressed as a variable resistance ROI resistance value versus a fixed resistance ROF resistance value ratio (ROI / ROF).

Meanwhile, a second compensator 600 for adjusting an output voltage offset of the capacity-voltage converter 200 to be described later may be connected to the non-inverting input terminal of the amplifier.

Meanwhile, a fixed resistor R _LinF is used between the amplifier output terminal and the input terminal of the power input unit 230 to adjust the output voltage of the amplifier fed back to the power input unit 230.

The first compensator 300 may have an output voltage nonlinearity due to a change in output voltage depending on a temperature of the capacitance-voltage converter 200 or a capacitance Cp and a capacitance Cr of the capacitance-voltage converter 200 Selectively compensate.

For example, the first compensator 300 may include a fixed resistor R _Lin1 and a variable resistor R2, which are connected in series between the power input and the ground and are branched at the series connection connection point and apply a voltage to the capacitive- _Lin2 . &_Lt; / RTI >

The power input can be applied to the non-inverting input terminal of the buffer which is branched from the series connection connection point of the fixed resistor R _Lin1 and the variable resistor R _Lin2 and used as the power input part 230. In addition, the non-inverting input terminal of the buffer is connected to the output terminal of the feedback unit 240, and the inverting input terminal of the buffer can be connected to the output terminal of the buffer.

A power supply input voltage in which the output voltage change depending on the temperature or the output voltage nonlinearity due to the capacitance Cp and the capacitance Cr is selectively compensated by the resistances R _Lin1 and R _Lin2 and the output voltage fed back by the feedback unit 240 are And is applied to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode by the switching operation of the switch unit 210 held at the output voltage of the buffer as it is, The capacitance Cp formed by the main electrode of the positive pressure sensor and the capacitance Cr formed by the reference electrode are charged.

Therefore, the output voltage nonlinearity due to the temperature-dependent output voltage change or the capacitance Cp and the capacitance Cr can be determined by _comparing the resistance values of the two variable resistors R _Lin1 and R _Lin2 included in the first compensation device 300 to the compensation control unit 400, So that it is possible to adjust the output voltage of the capacitive pressure sensor, so that the output specification of the capacitive pressure sensor can be adjusted.

The compensation controller 400 selectively adjusts an electrical characteristic value for compensating an output voltage variation or an output voltage nonlinearity compensation according to a temperature of the first compensator 300. For example, the electrical characteristic value may be a resistance value of a variable resistor for selectively compensating for an output voltage change according to temperature or an output voltage non-linearity.

For example, the compensation controller 400 may be implemented to include a BGR (BandGap Reference) 410, a MUX 420, an AD converter 430, and a characteristic value setting unit 440.

The BGR (BandGap Reference) 410 is a circuit most commonly used in an IC without being influenced by a power supply voltage or temperature, and is a proportional to absolute temperature (PTAT) A CTAT (Complementary To Absolute Temperature) characteristic in which the thermal voltage is constantly changed in inverse proportion to the absolute temperature can be used.

The MUX 420 selectively outputs the output voltage of the BGR 410 or the output voltage fed back from the capacity-voltage converter 200 according to an applied signal level.

For example, when the applied signal level is high, the MUX 420 selects and outputs the output voltage of the BGR 410, and when the applied signal level is low, the MUX 420 May be implemented to select an output voltage that is output from the capacity-voltage converter 200 and is fed back. At this time, the signal level applied to the MUX 420 may be controlled by the main control unit 500 to be described later.

The AD converter 430 converts the output voltage of the BGR 410 selectively output by the mux 420 or the output voltage fed back from the capacity-voltage converter 200 into an analog-digital signal, Generate a pressure code.

When the output voltage of the BGR 410 is selected and output by the MUX 420, the A / D converter 430 converts the output voltage of the BGR 410 into an analog-digital signal to generate a temperature code, The AD converter 430 converts the output voltage of the AD converter 430 into an analog signal and generates a pressure code.

The temperature code is a code referred to when selecting an electrical characteristic value for compensating for an output voltage change according to temperature, and the pressure code is a code referred to when selecting an electrical characteristic value for output voltage nonlinearity compensation.

The characteristic value setting unit 440 selects a resistance value corresponding to a temperature code or a pressure code generated by the AD converter 430 as an electrical characteristic value and sets a resistance value of the variable resistance R _Lin2 to a selected resistance value Setting. The selection of the electrical characteristic value of the characteristic value setting unit 440 will be described later.

Therefore, according to the present invention, the output voltage of the capacitor-voltage converter 200 can be compensated for by changing the output voltage according to the temperature, or by compensating the output voltage nonlinearity caused by the capacitance Cp and the capacitance Cr of the capacitor- The output specifications of the capacitive pressure sensor can be adjusted by adjusting the resistance values of the two variable resistors R _Lin1 and R _Lin2 included in the 1 compensator 300 through the compensation controller 400. [

According to a further aspect of the present invention, the output specification adjusting device of the capacitive pressure sensor may further include a main control part 500. [ The main control unit 500 applies a low or a high level signal to the mux.

Accordingly, when the applied signal level is high, the MUX 420 selects and outputs the output voltage of the BGR 410. When the applied signal level is low, the MUX 420 420 selects and outputs an output voltage that is output from the capacity-voltage converter 200 and is fed back.

For example, as shown in FIG. 4, the main control unit 500 first outputs a signal (MUX_SENSE) level applied to the mux for a specific time period as High, (High), thereby compensating for the output voltage change according to the temperature first, and then compensating the output voltage non-linearity caused by the capacitance Cp and the capacitance Cr.

According to a further aspect of the present invention, the output specification adjustment device of the capacitive pressure sensor may further include a second compensation element 600. [ The second compensator 600 adjusts an output voltage offset of the capacitance-voltage converter 200.

At this time, the second compensator 600 is connected in series between the power input and the ground, and is branched at the series connection connection point to apply a voltage to the non-inverting input terminal of the amplifier of the feedback unit 240, two variable to regulate the output voltage offset (offset) of the voltage conversion unit 200, a resistance R _of1 and the variable resistance can be implemented to include the R _of2.

The output voltage of the voltage converting part 200 - the two variable resistors R _of1 and the variable resistance R is amplified by the amplifier of the feedback unit 240 according to _of2 value because the voltage level is fed back to the power input unit 230 determines the capacity The offset can be adjusted, thereby adjusting the output specification of the capacitive pressure sensor.

According to a further aspect of the present invention, the main controller 500 includes a control register 510 in which information to be referred to when setting the electrical characteristic values of the first compensation element 300 and the second compensation element 600 is recorded, . ≪ / RTI >

At this time, the characteristic value setting unit 440 may search the value written in the control bit of the control register 510 and select the resistance value corresponding to the temperature code or the pressure code as the electrical characteristic value.

The main controller 500 searches the values written in the control bits of the control register 510 to determine the resistance values of the two variable resistors R _of1 and R _of2 included in the second compensator 600 as an electrical characteristic value . ≪ / RTI > Accordingly, the user sets the control bit value of the control register 510 of the main control unit 500 using a PC or the like to set the electrical characteristic values for adjustment of the output specification of the capacitive pressure sensor.

3, a PGA (Programmable Gain Amplifier) 700 is a circuit for amplifying the output voltage of the capacitance-to-voltage converter 200 and a PIA (Polarity Inversion Amplifier) 800 is connected to the PGA 700 And the clamping circuit 900 is a circuit for limiting the output voltage amplified by the PGA 700 to a specific level and the clock generator 920 is a circuit for limiting the output voltage amplified by the output And a POR (Power On Reset) circuit 940 is a circuit for resetting the main control unit.

The operation of adjusting the output specification of the output-specification adjusting device of the capacitive pressure sensor shown in Fig. 3 will be described in detail with reference to Fig. 5 is a switching timing diagram of the capacity-voltage conversion unit of the output-specification adjusting apparatus of the capacitive pressure sensor according to the present invention.

As shown in Fig. 5, six switches (two P1 switches, two P2 switches, one P1d switch, one P2d switch) are turned on at phase 1 and phase 2 that do not overlap each other ) And turn-off.

The two P1 switches are simultaneously turned on at the start of phase 1, and remain simultaneously off at phase 2, and the P1d switch is turned on after a delay of a predetermined time after the P1 switch is turned on.

On the other hand, the two P2 switches are simultaneously turned on at the start of phase 2 and remain off simultaneously in phase 1, and the P2d switch is turned on after a delay of a predetermined time after the P2 switch is turned on.

The two non-overlapping phase control signals for the six switch control are output by an oscillation drive gating circuit (not shown). Six switches are on or off controlled by these two non-overlapping phase control signals.

The output voltage change according to the temperature of the capacitance-voltage converter 200 or the capacitance change of the capacitance-voltage converter 200 according to the electric characteristic value recorded in the control bit of the control register 510 of the main controller 500 And the output voltage non-linearity caused by the capacitance Cr are selectively compensated and the output voltage offset of the capacitance-voltage conversion unit 200 is adjusted.

The output voltage V _out of the integrator 220 and the amplification voltage V _bdge of the amplifier of the feedback unit 240 are given by the following equations.

(Equation 1)

When the power input is V ₊ , the voltage between the variable resistors Rof ₁ and Rof ₂ is:

(Equation 2)

At phase 1, the P1 and P1d switches are turned on, the P2 and P2d switches are turned off, and in phase 2, the P2 and P2d switches are turned on and the P1 and P1d switches are turned off.

Although the P1d switch and P2d are each turned on in phase 1 or phase 2, the on state of both switches is delayed with a specific time interval to the on time of the P1 switch or P2 switch.

During Phase 2 where the P2 switch and the P2d switch are turned on, the capacitance Cp formed by the main electrode is charged to the V _bdge voltage amplified by the amplifier through the P2 switch, and the capacitance Cr formed by the reference electrode is connected to another P2 switch To the ground.

The common terminal Ccom branching between the capacitance Cp formed by the main electrode and the capacitance Cr formed by the reference electrode is discharged to the ground through the switch P2d. The capacitance Cp formed by the main electrode is charged by V _bdge x Cp. The capacitance Cr formed by the reference electrode is not charged at the ground potential. The negative charges are immediately accumulated at the common terminal _Ccom by -V _bdge x Cp.

Then, the P2 switch is turned off after the P2d switch is turned off. No charge transfer occurs at the common terminal Ccom during a period between phase 2 and phase 1.

Then, at the start of phase 1, the capacitance Cp (charged with the V _bdge voltage at phase 2) formed by the main electrode is discharged to ground through the P1 switch, and the capacitance Cr formed by the reference electrode reaches P1 And is charged to the voltage V _L which is the buffer output voltage of the power input unit 230 through the switch.

The common terminal Ccom, which is branched at the phase 1 between the capacitance Cp formed by the main electrode and the capacitance Cr formed by the reference electrode, is connected to the inverting input terminal of the integrator 220 through the switch P1d, The inverting input terminal is connected to ground.

The charge during phase 1 is accumulated by V _L x Cr in the capacitance Cr formed by the reference electrode. This immediate negative charge accumulates at the common terminal Ccom by -V _L x Cr. -V _bdge x Cp = -V _L Cr, the negative charge of the common terminal Ccom is equal between the two phases and there is no charge supply / recovery to the integrator 220. Thus, the output voltage V _out of the integrator 220 is constant during two phase operations. In this condition, the circuit is considered to be in equilibrium.

The voltage V _bdge amplified and outputted by the amplifier of the feedback unit 240 can be obtained by _modifying the charge charged in Cp during phase 1 and the charge charged in Cr during phase 2.

(Equation 3)

However,

(Equation 4)

And V _L x Cr / C p represents the change in capacitance due to the pressure applied to the capacitive pressure sensor.

However, unintended ripple at the output terminal of the integrator 220, capacitance Cp formed by the main electrode and nonlinear characteristics of the capacitance Cr pair formed by the reference electrode and single end power supply operation And it is difficult to use it in the above-mentioned case.

In the control loop, the integrator 220 does not only operate as an error integrator, but also as an output amplifier. This allows the integrator 220 to be input at the ground potential through the common terminal Ccom. In the unbalanced state, Cr × V _L is not equal to Cp × V _bdge . The error charge is integrated by the integrator 220 until it reaches equilibrium through successive periods.

When the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode are connected to the capacitance-to-voltage converter 200 for pressure measurement, the Cr / Cp value relative to the pressure is nonlinear. That is, the decreasing Cr / Cp ratio relative to increasing pressure is not constant.

Also, since the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance-voltage conversion unit 200 for converting the capacitance change of the capacitance Cr formed by the reference electrode into the output voltage are sensitive to temperature, The output voltage varies.

Thus, in the absence of linearity adjustment and correction for temperature-dependent output voltage changes, the output voltage versus the pressure can not, in most cases, meet the tolerances allowed for the production of various pressure sensors.

The present invention is characterized in that the output characteristic of the capacitive pressure sensor is controlled by selectively controlling the electrical characteristic value for the output voltage variation compensation or the output voltage nonlinearity compensation according to the temperature of the first compensator 300 through the compensation controller 400 Adjust.

The voltage V _bdeg amplified by the amplifier of the feedback unit 240 and the power source input V ₊ are inputted to the first input terminal of the power source input unit 230 as the first resistors R _Lin1 and R _Lin2 , the feedback resistor R _LinF , The equation of the buffer output voltage V _L can be derived.

Preservation of the current at the junction between the fixed resistor R _Lin1 and the variable resistor R _Lin2 follows the following relationship. The amount of current flowing from the amplifier of the feedback unit 240 to the buffer of the power input unit 230 and from the power supply input V ₊ to the buffer of the power supply input unit 230 is the current flowing from the branch point between the fixed resistor R _Lin1 and the variable resistor R _Lin2 .

(Equation 5)

,

,

(Equation 6)

If we transpose this equation,

(Equation 7)

, And by substituting the above equation into this equation,

(Expression 8)

. In the above equation, 1 / R _Lin2 selectively adjusts the output voltage according to the temperature of the capacity-voltage converter 200 and the nonlinearity due to Cr / Cp. That is, by controlling the resistance value, which is the electrical characteristic value of the variable resistor R _Lin2 included in the first compensator 300, through the compensation controller 400, the output voltage change according to the temperature of the capacitance- The output voltage non-linearity caused by the capacitance Cp and the capacitance Cr of the capacity-voltage converter 200 is selectively compensated.

Next, a ripple reduction operation is examined. As shown in Fig. 5, there are switch control waveforms of two phases. The switching operation of the P1 switch and the P2 switch is not overlapped, and the P1d switch is delayed and turned on in the P1 switch on interval, and the P2d switch is delayed and turned on in the P2 switch on interval. At the start of the P2 switch ON period of phase 2, the current is charged from the amplifier of the feedback section 240 to the capacitance Cp formed by the main electrode, and discharged from the capacitance Cr formed by the reference electrode to ground. The P2d switch-on state is delayed until the current transient state (unbalanced state) reaches the steady state (equilibrium state).

The P1 switch is turned on at phase 1 after the P2d switch and P2 switch are turned off and the non-overlapping section has elapsed. At the start of the P1 switch-on period, the current is charged from the buffer, which is the power input part 230, by the capacitance Cr formed by the reference electrode, and discharged from the capacitance Cp formed by the main electrode to the ground. The P1d switch-on state is delayed until the current transient state (unbalanced state) reaches the steady state (equilibrium state).

When the P1d switch is turned on, the unbalanced (error) charge is supplied / recovered to the integrator 220. This unbalance condition continues until the error reaches zero. When reaching equilibrium, no current will flow when the P2d switch or P1d switch is turned on.

As the turn-on is delayed until the P1d switch and the P2d switch respectively reach a steady state, errors or ripples injected into the integrator 220 are prevented or avoided. Without these P1d and P2d switch turn-on delays, not only will the measurement not be accurate, but the output voltage V _out and ripple will be larger.

The integrator 220 has the advantage of using a virtual ground to detect a capacitance change in the capacitive pressure sensor. The electric charge supplied / recovered from the integrator 220 is supplied / recovered only by the common terminal Ccom which is a virtual ground terminal, and is divided into a capacitance Cr formed by the reference electrode or a capacitance Cp formed by the main electrode. Does not affect the output of the integrator 220.

The operation of the common terminal Ccom which is the virtual ground terminal of the integrator 220 is exactly performed at the ground potential. The + input of the integrator 220 is connected to ground to stabilize the bias current or leakage current occurring between the two inputs.

According to Equations 1 and 2, it can be seen that the output voltage V _out of the capacity-voltage converter 200 is related to the variable resistors Rof ₁ and Rof _2, and therefore the output of the capacity-voltage converter 200 The voltage offset can be adjusted according to the resistance values of the variable resistors Rof ₁ and Rof ₂ .

That is, by controlling the resistance values, which are the electrical characteristic values of the variable resistors Rof ₁ and Rof ₂ included in the second compensator 600, through the main control unit 500, the output voltage offset of the capacitance- ) Can be adjusted.

As described above, the present invention can easily adjust the output voltage change, nonlinearity, and output offset according to the temperature of the capacitive pressure sensor when the capacitive pressure sensor is shipped, and satisfy various output specifications required by customers , The object of the present invention can be achieved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. .

The present invention is industrially applicable in the field of pressure measurement technology and its application technology.

100: capacitive pressure sensor 110: dielectric substrate
120: electrode pattern 121: main electrode
122: reference electrode 200: capacitance-voltage conversion unit
210: switch unit 220: integrator
230: Power input unit 240: Feedback unit
300: first compensation element 400: compensation control part
410: BGR 420: Mux
430: AD converter 440: characteristic value setting section
500: main controller 600: second compensation element

Claims (10)

A capacitance Cp formed by the main electrode of the capacitive pressure sensor, a capacitance-voltage converter for converting the capacitance change of the capacitance Cr formed by the reference electrode into an output voltage, and outputting the output voltage;
A first compensator for selectively compensating for an output voltage change according to a temperature of the capacitance-voltage converter or an output voltage non-linearity caused by a capacitance Cp and a capacitance Cr of the capacitance-voltage converter;
And a compensation controller for selectively adjusting an electrical characteristic value for compensation of an output voltage variation or an output voltage nonlinearity compensation according to a temperature of the first compensation element;
And an output-specification adjusting device for adjusting the output-specification of the capacitive pressure sensor. The method according to claim 1,
Wherein the first compensating element comprises:
A fixed resistor R _Lin1 and a variable resistor R _Lin2 which are connected in series between the power input and the ground and branch from the series connection connection point and apply a voltage to the capacity-voltage converter;
And an output-specification adjusting device for the capacitive pressure sensor. 3. The method of claim 2,
Wherein the compensation control unit comprises:
BGR (BandGap Reference);
A MUX for selectively outputting the BGR output voltage or the output voltage fed back from the capacity-voltage converter according to an applied signal level;
An A / D converter for analog-to-digital converting a BGR output voltage selectively output by the mux or an output voltage fed back from the capacitance-to-voltage converter to generate a temperature code or a pressure code;
A characteristic value setting unit that selects a resistance value corresponding to a temperature code or a pressure code generated by the AD converter as an electrical characteristic value and sets a resistance value of the variable resistor R _Lin2 to a selected resistance value;
And an output-specification adjusting device for the capacitive pressure sensor. The method of claim 3,
Wherein the output specification adjusting device of the capacitive pressure sensor comprises:
A main control unit for applying a low or high level signal to the mux;
Further comprising: an output-specification adjusting device for a capacitive pressure sensor. 5. The method of claim 4,
Wherein the capacitance-voltage converter comprises:
A capacitance Cp formed by the main electrode of the capacitive pressure sensor, a switch unit for controlling charging and discharging operations of the capacitance Cr formed by the reference electrode,
An integrator for receiving the capacitance Cp and the current discharged from the capacitance Cr and outputting it as an output voltage, and integrating the error correction signal in the control loop until the error approaches zero;
A capacitance Cp, a power input unit for supplying a constant power to the capacitance Cr;
A feedback unit including an amplifier for amplifying the output voltage outputted by the integrator and feeding back the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode and the power input unit;
And an output-specification adjusting device for the capacitive pressure sensor. 6. The method of claim 5,
Wherein the output specification adjusting device of the capacitive pressure sensor comprises:
A second compensator for adjusting an output voltage offset of the capacitance-voltage converter;
Further comprising: an output-specification adjusting device for a capacitive pressure sensor. The method according to claim 6,
Wherein the second compensating element comprises:
A variable resistor R connected in series between the power input and the ground and branched at a series connection connection point to apply a voltage to a non-inverting input terminal of the amplifier of the feedback section to adjust an output voltage offset of the capacitance- _of1 and variable resistance R _of2 ;
And an output-specification adjusting device for the capacitive pressure sensor. 8. The method of claim 7,
Wherein the main control unit comprises:
And a control register for recording information to be referred to when setting the electrical characteristic values of the first compensating element and the second compensating element. 9. The method of claim 8,
Wherein the characteristic value setting unit:
And a resistance value corresponding to a temperature code or a pressure code is selected as an electrical characteristic value by searching the value written in the control bit of the control register. 9. The method of claim 8,
Wherein the main control unit comprises:
Output specification adjusting device of a capacitive pressure sensor, characterized in that for selecting the resistance value of both the search for the values recorded in the control bit variable resistor R and a variable resistor R _{of1 of2} of the control register to the electric characteristic value.

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