KR101438487B1 - Capacitance inertial sensor improving sensing noise - Google Patents

Abstract

A capacitive inertial sensor improving a sensing noise is disclosed. According to the present invention, the capacitive inertial sensor comprises: an inertia sensing part generating a first inertial capacitance and a second inertial capacitance increasing or decreasing complementarily to each other, and generating mass voltage based on a difference between the first inertial capacitance and the second inertial capacitance; a C-V converter generating the amplified mass voltage into amplification voltage; and a calculation part calculating a first level and a second level of the amplification voltage, and generating a check signal. During this time, a frequency of a first sensing signal and a second sensing signal is 2n (where n is a natural number) times as long as that of a reset signal. The capacitive inertial sensor in accordance to the present invention drastically improves the sensing noise caused by an offset voltage (Voff) effect, and as the result drastically enhances efficiency in sensing inertia application.

Description

[0001] CAPACITANCE INERTIAL SENSOR IMPROVING SENSING NOISE [0002]

The present invention relates to a capacitive inertial sensor, and more particularly, to a capacitive inertial sensor that improves sensing noise due to an offset voltage of a CV conversion unit.

The MEMS technology is to form a specific part of the system in a precise micrometer shape on a silicon substrate by using a silicon process. An inertial sensor (ie, a MEMS element for sensing inertial force) including an acceleration sensor and an angular velocity sensor is a representative device manufactured by MEMS technology, and is a sensor capable of measuring translational motion and rotational motion. In particular, the capacitive inertial sensor is a widely used type because of its simple manufacturing process, insensitivity to temperature change, and low nonlinearity.

1 is a view for explaining a conventional capacitive inertial sensor. The conventional capacitive inertial sensor 10 includes an inertial sensing unit 11 and a C-V conversion unit 13. The first capacitance value 11a and the second capacitance value 11b of the inertial sensing unit 11 are complementarily increased or decreased according to the application of the inertial force. At this time, the mat voltage VMAS is determined by the first capacitance value 11a and the second capacitance value 11b which are increased or decreased.

The C-V conversion unit 13 includes a conversion amplifier 13a, an amplification capacitor 13b, and an amplification connection switch 13c. The conversion amplifier 13a inverts and amplifies the mass voltage VMAS with respect to the common voltage VCOM and outputs it as an acknowledgment signal VFI while the reset signal RST is inactivated to "L ". The reset signal RST is driven at the same cycle as the first sensing signal MOD1 and the second sensing signal MOD2 that cause the first capacitance value 11a and the second capacitance value 11b to be generated .

At this time, for effective sensing of inertia force, it is necessary that the mass voltage VMAS is precharged to the same level as the common voltage VCOM.

However, an offset voltage Voff may be generated between the mat voltage VMAS and the common voltage VCOM due to the difference in the structure of the conversion amplifier 13a and the length of the transmission line.

In this case, in the conventional capacitive inertial sensor, sensing noise is generated due to the influence of the offset voltage (Voff), resulting in a problem that the detection efficiency of inertial force application is lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitive inertial sensor in which sensing noise due to an influence of an offset voltage (Voff) is improved and detection efficiency of inertial force application is improved.

According to an aspect of the present invention, there is provided a capacitive inertial sensor. The capacitive inertial sensor of the present invention generates a first inertial capacitance and a second inertial capacitance which are complementarily increased or decreased in accordance with the application of the inertial force and generates a first inertial capacitance and a second inertial capacitance based on the difference between the first inertial capacitance and the second inertial capacitance, Wherein the first inertial capacitance is formed between the first sensing signal and the Math voltage and the second inertial capacitance is the inertial sensing unit formed between the second sensing signal and the Math voltage, The inertial sensing unit being driven so that the first sensing signal and the second sensing signal have phases opposite to each other; A CV converter for receiving a common voltage, amplifying the Math voltage in response to deactivation of a reset signal, and generating the amplified Math voltage as an amplification voltage, the amplification voltage being a level of the Math voltage for the common voltage The CV conversion unit reflects the reflected light; A first level of the amplification voltage is generated in response to a first deactivation of the reset signal and a second level of the amplification voltage is generated in response to a first deactivation of the reset signal, Level is generated in response to a second deactivation of the reset signal, wherein each of the first sensing signal and the second sensing signal is a complementary signal to each other when the first deactivation of the reset signal and the second deactivation of the reset signal are performed, The phase of which is shifted to a phase that is different from the phase of the output signal. At this time, the period of the first sensing signal and the second sensing signal is 2n times (where n is a natural number) the period of the reset signal.

According to the capacitive inertial sensor of the present invention as described above, the sensing noise due to the influence of the offset voltage (Voff) is greatly improved, and as a result, the detection efficiency of the inertial force application is remarkably improved.

A brief description of each drawing used in the present invention is provided.
1 is a view for explaining a conventional capacitive inertial sensor.
2 illustrates a capacitive inertial sensor according to an embodiment of the present invention.
FIG. 3 is a diagram specifically illustrating the inertial sensing unit of FIG. 2. FIGS. 4A and 4B are views for explaining the action of the inertial sensing unit of FIG. 3 according to application of inertia.
5 is a view for explaining the operation of the main signal of the capacitive inertial sensor of FIG.

For a better understanding of the present invention and its operational advantages, and the objects attained by the practice of the present invention, reference should be made to the accompanying drawings, which illustrate preferred embodiments of the invention, and the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are being provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Also, in understanding each of the figures, it should be noted that like parts are denoted by the same reference numerals whenever possible. Further, detailed descriptions of known functions and configurations that may be unnecessarily obscured by the gist of the present invention are omitted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 illustrates a capacitive inertial sensor according to an embodiment of the present invention. Referring to FIG. 2, the capacitive inertial sensor of the present invention includes an inertial sensing unit 100, a C-V conversion unit 200, and an operation unit 300.

The inertial sensing unit 100 generates a first inertial capacitance CAP1 and a second inertial capacitance CAP2. At this time, the first inertial capacitance CAP1 and the inertial second capacitance CAP2 are complementarily increased or decreased according to the application of the inertial force. The mass voltage VMAS is generated based on the difference between the first inertial capacitance CAP1 and the second inertial capacitance CAP2.

FIG. 3 is a view showing the inertial sensing unit 100 of FIG. 1 in detail. 3, the inertial sensing unit 100 includes a mass body 110, a first fixed electrode member 120, a second fixed electrode member 130, a first moving electrode 112, a second moving electrode 114, a first fixed electrode 122, and a second fixed electrode 134.

The first fixed electrode member 120 and the second fixed electrode member 130 are fixed at a predetermined position with respect to application of an inertial force. That is, the first fixed electrode member 120 and the second fixed electrode member 130 are fixed at a fixed relative position even when an inertial force is applied

The mass body 110 is a movable structure elastically supported by a suspension beam (not shown) having a spring function acting as a mechanical stiffness. The mass structure 110 is a movable structure, The first fixed electrode member 120 and the second fixed electrode member 130 in one direction. The mass body 110 is preferably formed of a conductive material.

The first moving electrode 112 and the second moving electrode 114 are formed by extending a certain length from one side of the mass body 110 and another side (left and right in the drawing).

The first fixed electrode 122 extends a predetermined length from the first fixed electrode member 120 toward the mass body 110 so that the first fixed electrode 122 is overlapped with the first movable electrode 112 by a predetermined distance d1. The second fixed electrode 134 is extended from the second fixed electrode member 130 toward the mass body 110 by a predetermined length d2 such that the second fixed electrode 134 overlaps the second movable electrode 124 by a predetermined distance d2. do.

A first sensing signal MOD1 is applied to the first fixed electrode 122 through the first fixed electrode member 120 and a second sensing signal MOD2 is applied to the second fixed electrode 134 to sense applied inertia. And the second sensing signal MOD2 is applied through the second fixed electrode member 130. [ At this time, the first sensing signal MOD1 and the second sensing signal MOD2 have the same period T_SEN and are repeatedly shifted in opposite phases (refer to FIG. 5).

The first moving electrode 112 and the second moving electrode 114 are connected to the mass voltage VMAS through the mass body 110.

In this case, the first inertial capacitance CAP1 is generated by the first moving electrode 112 and the first fixed electrode 122, and the second moving electrode 114 and the second fixed electrode 134 The second inertial capacitance CAP2 is generated.

In the inertial sensing unit 100 having the above configuration, the first inertial capacitance CAP1 and the second inertial capacitance CAP2 are complementarily increased or decreased in accordance with the direction of inertial force application, Direction can be detected.

For example, assume that acceleration occurs upward in the drawing as shown in FIG. 4A. At this time, inertia is generated downward in the drawing, which is the direction opposite to the acceleration direction. Then, the mass body 100 moves downward in the direction of inertia, and the first and second moving electrodes 112 and 114 fixedly connected to the mass body 100 are also moved downward in the inertial direction.

Accordingly, the distance d1 between the first moving electrode 112 and the first fixed electrode 122 is reduced, and the first inertial capacitance CAP1 is increased. The distance d2 between the second moving electrode 114 and the second fixed electrode 134 is increased and the second inertial capacitance CAP2 is decreased.

When an acceleration is generated downward in the drawing as shown in FIG. 4B, inertia is generated upward in the drawing. Then, the mass body 100 moves upward, and the first and second moving electrodes 112 and 114 fixedly connected to the mass body 100 are also moved upward.

Accordingly, the distance d1 between the first moving electrode 112 and the first fixed electrode 122 increases, and the first inertial capacitance CAP1 decreases. The distance d2 between the second moving electrode 114 and the second fixed electrode 134 is reduced and the second inertial capacitance CAP2 is increased.

Preferably, in the capacitive inertial sensor of the present invention, in order to increase the first inertial capacitance CAP1 and the second inertial capacitance CAP2 so as to easily detect the application of the inertial force, the first movable electrode 112, The first fixed electrode 122, the second movable electrode 114, and the second fixed electrode 134 are provided in plurality.

2, the C-V conversion unit 200 applies a common voltage VCOM and amplifies the mass voltage VMAS to provide an amplification voltage VAMP. At this time, the amplification voltage VAMP reflects the level of the mass voltage VMAS with respect to the common voltage VCOM. That is, during the inactivation of the reset signal RST to "L ", the CV conversion unit 200 converts the first inertial capacitance CAP1 and the inertial second capacitance CAP2, which are complementarily changed according to the input inertial force, The amplification voltage VAMP is amplified to generate the amplification voltage VAMP.

The C-V conversion unit 200 is driven so as to precharge the mat voltage VMAS and the amplification voltage VAMP during the activation of the reset signal RST to "H ".

Preferably, the C-V conversion unit 200 includes a conversion amplifier 221, an amplification capacitor 222, and an amplification connection switch 223.

The conversion amplifier 221 is provided with a minus voltage input terminal VMAS at a negative input terminal thereof and a common input terminal VCOM at a positive input terminal thereof, VAMP). The conversion amplifier 221 inverts and amplifies the mezzanine voltage VMAS based on the common voltage VCOM to generate the amplification voltage VAMP.

The amplification capacitor 222 is formed between the Math voltage VMAS and the Amplification voltage VAMP. The amplification capacitor 222 couples the mat voltage VMAS and the amplification voltage VAMP.

The amplification connection switch 223 electrically connects the mat voltage VMAS and the amplification voltage VAMP in response to activation of the reset signal RST to "H ". At this time, it is preferable that the mass voltage VMAS and the amplification voltage VAMP are controlled to the common voltage VCOM during the activation of the reset signal RST to "H".

However, an offset voltage Voff may be generated between the mat voltage VMAS and the common voltage VCOM due to the difference in the structure of the conversion amplifier 221 and the length of the transmission line, It is possible to reduce the detection efficiency of inertia force application as described above.

In order to reduce the sensing noise due to the offset voltage Voff, the calculation unit 300 is provided by the capacitive inertial sensor of the present invention.

The operation unit 300 calculates a first level VAMP <1> and a second level VAMP <2> of the amplification voltage VAMP to generate an acknowledgment signal VFI. In this embodiment, the operation unit 300 generates the confirmation signal VFI using the difference between the first level VAMP <1> and the second level VAMP <2> of the amplified signal VAMP do.

The first level VAMP < 1 > of the amplification voltage VAMP is generated in response to the first deactivation (see t1 in Fig. 5) of the reset signal RST, The second level (VAMP < 2 >) is generated in response to the second deactivation (see t2 in Fig. 5) of the reset signal RST. Each of the first sensing signal MOD1 and the second sensing signal MOD2 includes a first deactivation (see t1 in FIG. 5) of the reset signal RST and a second deactivation of the reset signal t2 &quot;).

Preferably, the first deactivation of the reset signal RST and the second deactivation of the reset signal are continuous. That is, there is one activation between the first deactivation of the reset signal RST and the second deactivation of the reset signal.

Here, the periods of the first sensing signal MOD1 and the second sensing signal MOD2 are 2n times (where n is a natural number) the period of the reset signal RST. Preferably, the period of the first sensing signal MOD1 and the period of the second sensing signal MOD2 are two times the period of the reset signal RST, as shown in FIG.

Subsequently, the influence of the offset voltage Voff is excluded in the detection of the inertial force application by the operation unit 300. FIG.

First, in the capacitive inertial sensor of the present invention, the first level (VAMP < 1 >) of the amplification voltage (VAMP) is equal to (Equation 1).

(1)

VAMP <1> = VCOM + Voff + (VMOD1 <1> -VMOD2 <1>) * 2ΔCd / Cf

       = VCOM + Voff + (VSS-VDD) * 2? Cd / Cf.

here,

VMOD1 <1>: The voltage of the first sensing signal MOD1 controlled at the time of the first deactivation of the reset signal RST, which is the 'ground voltage VSS' in this embodiment

VMOD2 <1>: The voltage of the second sensing signal MOD2, which is controlled in the first deactivation of the reset signal RST, is the 'power supply voltage VDD'

? Cd: Difference between the first normal capacitance (CAP1) and the first normal capacitance (CAP2)

Cf: the capacitance of the amplifying capacitor 222 of the CV conversion unit 200

In the capacitive inertial sensor of the present invention, the second level (VAMP < 2 >) of the amplification voltage (VAMP) is equal to (Equation 2).

(2)

VAMP <2> = VCOM + Voff + (VMOD1 <2> -VMOD2 <2>) * 2ΔCd / Cf

       = VCOM + Voff + (VDD-VSS) * 2? Cd / Cf.

here,

VMOD1 <2>: The voltage of the first sensing signal MOD1 which is controlled at the time of the second deactivation of the reset signal RST, is the 'power supply voltage VDD'

VMOD2 <2>: The voltage of the second sensing signal MOD2, which is controlled at the time of the second deactivation of the reset signal RST, is the 'ground voltage VSS'

In the capacitive inertial sensor of the present invention, the level of the confirmation signal VFI is equal to (Equation 3).

(3)

VFI = VAMP <2> -VAMP <1>

= 2 * (VDD-VSS) * 2? Cd / Cf.

Therefore, the voltage level of the confirmation signal XFI reflects the difference ΔCd between the first normal capacitance CR1 and the first normal capacitance CR1 in accordance with the application of the inertial force, and the voltage level of the confirmation signal XFI depends on the offset voltage Voff Effects are excluded.

Continuing with FIG. 2, the capacitive inertial sensor of the present invention preferably further includes a periodic expansion unit 400.

The period extension unit 400 expands the period of the reset signal RST by 2n to generate the first sensing signal MOD1 and the second sensing signal MOD2. Since the implementation of the period extension unit 400 is obvious to those skilled in the art, a detailed description thereof is omitted here.

According to the capacitive inertial sensor of the present invention as described above, the sensing noise due to the influence of the offset voltage (Voff) is greatly improved, and as a result, the sensing efficiency of application of the inertial force is remarkably improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (6)

In a capacitive inertial sensor,
An inertial sensing unit for generating a first inertial capacitance and a second inertial capacitance which are complementarily increased or decreased in response to application of an inertial force and generating a mass voltage based on a difference between the first inertial capacitance and the second inertial capacitance, Wherein the first inertial capacitance is formed between the first sensing signal and the Math voltage and the second inertial capacitance is the inertial sensing unit formed between the second sensing signal and the Math voltage, 2 sensing signal is driven to have a phase opposite to that of the inertial sensing unit;
A CV converter for receiving a common voltage, amplifying the Math voltage in response to deactivation of a reset signal, and generating the amplified Math voltage as an amplification voltage, the amplification voltage being a level of the Math voltage for the common voltage The CV conversion unit reflects the reflected light; And
A first level of the amplification voltage is generated in response to a first deactivation of the reset signal and a second level of the amplification voltage is generated in response to a first deactivation of the reset signal, Wherein the first sensing signal and the second sensing signal are generated in response to a second deactivation of the reset signal, wherein each of the first sensing signal and the second sensing signal is opposite to the first deactivation of the reset signal and the second deactivation of the reset signal Phase shifting operation,
The period of the first sensing signal and the second sensing signal is
Wherein the period of the reset signal is 2n times (where n is a natural number) of the period of the reset signal.
2. The apparatus of claim 1, wherein the capacitive inertial sensor
Further comprising a period extending unit for extending the period of the reset signal by 2n times to generate the first sensing signal and the second sensing signal.
2. The method of claim 1,
1 &quot;.&lt; / RTI &gt;
The apparatus according to claim 1, wherein the inertia sensing unit
A first fixed electrode body to which the first sensing signal is applied;
A second fixed electrode body to which the second sensing signal is applied;
A mass that is suspended and elastically movable and electrically connected to the Math voltage, the mass being moved in one direction with respect to the first fixed electrode unit and the second fixed electrode unit according to an applied direction of the inertial force;
A first moving electrode extending from a side of the mass body to a predetermined length;
A second moving electrode extending from the other side of the mass body to a predetermined length;
A first fixed electrode formed by extending a predetermined length from the first fixed electrode unit to the mass body so as to be overlapped with the first moving electrode by a predetermined distance; And
And a second fixed electrode extending from the second fixed electrode unit toward the mass body by a predetermined length so as to be overlapped with the second moving electrode by a predetermined distance,
The first inertia capacitance
A second movable electrode disposed on the first movable electrode,
The second inertia capacitance
Wherein the second movable electrode is generated by the second moving electrode and the second fixed electrode.
The apparatus of claim 1, wherein the CV conversion unit
A conversion amplifier to which the Math voltage is provided at a negative input terminal and the common voltage is provided to a positive input terminal and which is driven to generate the amplified voltage through an output terminal;
An amplification capacitor formed between the Math voltage and the amplification voltage; And
And an amplification connection switch for coupling the Math voltage and the amplification voltage in response to the reset signal.
2. The apparatus of claim 1,
And generates the acknowledgment signal using the difference between the first level and the second level of the amplified signal.

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