Programmable capacitance coupling amplifier applied to micro fluxgate sensor

Abstract

The invention discloses a programmable capacitance coupling amplifier applied to a micro fluxgate sensor. The programmable capacitance coupling amplifier is composed of a switch 101, a switch 102, a switch 103, a switch 104, a switch 105, a switch 106, a switch 107, a switch 108, a switch 109, a switch 110, a switch 111, a switch 112, a capacitor 201, a capacitor 202, a capacitor 203, a capacitor 204, a capacitor array 301, a capacitor array 302, a resistor 401, a resistor 402, an operational amplifier 501 and a fluxgate probe induction coil 601. According to the invention, common-mode voltage isolation of a micro-fluxgate sensor driving and detection circuit is realized through a capacitive coupling mode, common-mode interference is eliminated, and different amplification factors of a pre-detection circuit can be realized through a capacitor array. The advantages greatly improve the adaptability of the detection circuit to the manufacturing difference of the micro fluxgate probe.

Description

Technical Field

[0001] The invention belongs to the technical field of micro sensor integration, and in particular relates to a programmable capacitive coupling amplifier applied to a micro fluxgate sensor. Background Art

[0002] The micro fluxgate probe made with MEMS technology has a small number of detection coil turns and low output resistance, which requires a common-mode voltage generation circuit with a higher output resistance in the circuit, and supplies it to the drive and detection circuits at the same time, which will inevitably bring common-mode interference to the detection circuit. If the common-mode voltage generation circuits are designed separately for the drive and detection, the sensor will be introduced with a large zero-point offset problem due to the inconsistent common-mode voltages of the drive and detection circuits. In addition, since the processed coil wire is too thin, the resistance consistency of the micro fluxgate detection coil is poor, which needs to be solved by the subsequent detection circuit. Summary of the invention

[0003] The present invention aims to solve the deficiencies of the prior art and provides the following solutions:

[0004] A programmable capacitive coupling amplifier for a micro fluxgate sensor, comprising: a switch 101, a switch 102, a switch 103, a switch 104, a switch 105, a switch 106, a switch 107, a switch 108, a switch 109, a switch 110, a switch 111, a switch 112, a capacitor 201, a capacitor 202, a capacitor 203, a capacitor 204, a capacitor array 301, a capacitor array 302, a resistor 401, a resistor 402, an operational amplifier 501, and a fluxgate probe induction coil 601;

[0005] The center end of the fluxgate probe induction coil 601 is connected to the driving bias voltage Vb1;

[0006] One end of the switch 101 and one end of the switch 102 are connected to the output end V of the fluxgate probe induction coil 601. in- One end of the switch 103 and one end of the switch 104 are connected to the output end V in+ connect;

[0007] The other end of the switch 101 is connected to the other end of the switch 103, one end of the capacitor array 301 and one end of the capacitor 201 respectively, and the other end of the switch 104 is connected to the other end of the switch 102, one end of the capacitor array 302 and one end of the capacitor 202 respectively;

[0008] The other end of the capacitor array 301 is connected to the other end of the capacitor 201, and the other end of the capacitor array 302 is connected to the other end of the capacitor 202;

[0009] The other end of the capacitor 201 is also connected to the inverting input end of the operational amplifier 501, one end of the resistor 401 and one end of the capacitor 203, and the other end of the capacitor 202 is also connected to the non-inverting input end of the operational amplifier 501, one end of the resistor 402 and one end of the capacitor 204;

[0010] The other ends of the resistor 401 and the resistor 402 are both connected to the bias voltage Vb2;

[0011] The other end of the capacitor 203 is connected to the switch 105 and the switch 106 respectively, and the other end of the capacitor 204 is connected to the switch 111 and the switch 112 respectively;

[0012] The in-phase output terminal of the operational amplifier 501 is connected to the switch 107 and the switch 108 respectively, and the inverting output terminal of the operational amplifier 501 is connected to the switch 109 and the switch 110 respectively;

[0013] The other end of the switch 105 is connected to the other end of the switch 110, and the other end of the switch 112 is connected to the other end of the switch 107;

[0014] The other end of the switch 107 is also connected to the other end of the switch 106, the other end of the switch 109 and the output end V outp The other end of the switch 110 is also connected to the other end of the switch 108, the other end of the switch 111 and the output end V outn connect.

[0015] Preferably, the capacitor array 301 and the capacitor array 302 have the same structure, and are composed of a number of capacitor units connected in parallel; the capacitor unit is composed of 4 switches and 1 capacitor.

[0016] Preferably, the working process of the capacitive coupling amplifier includes:

[0017] In the first stage, the switches 101, 104, 106, 107, 110 and 111 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is:

[0018]

[0019] Among them, C 203 represents the capacitance value of capacitor 203, C 201Indicates the capacitance value of capacitor 201, C 204 represents the capacitance value of capacitor 204, C 202 represents the capacitance value of capacitor 202, and Vinn1 represents the output terminal V of the fluxgate probe induction coil in the first stage. in- The voltage of Vinp1 is the output terminal V of the fluxgate probe induction coil in the first stage. in+ The voltage of Voutp1 is the output voltage of the first stage. outp The output voltage of Voutn1 is the output voltage of the first stage. outn Output voltage

[0020] In the second stage, the switches 102, 103, 105, 108, 109 and 112 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is:

[0021]

[0022] Among them, Vinn2 represents the output terminal V of the fluxgate probe induction coil in the second stage in- Vinp2 represents the voltage at the output terminal V of the fluxgate probe induction coil in the second stage. in+ The voltage of Voutp2 represents the output terminal V of the second stage. outp The output voltage of Voutn2 is the output voltage of the second stage. outn Output voltage

[0023] In one switching cycle, Vinp and Vinp are approximately considered unchanged, then:

[0024]

[0025] Then during the entire cycle of the switch output, the total output voltage can be:

[0026] Voutp=Voutp1+Voutp2=-kVinn

[0027] Voutn=Voutn1+Voutn2=-kVinp

[0028] Voutp-Voutn=-k(Vinn-Vinp)

[0029] This process repeats itself to amplify the differential voltage on both sides of the fluxgate probe induction coil 601 , and at the same time, the bias voltage Vb1 of the fluxgate probe induction coil 601 is isolated from the bias voltage Vb2 of the back-end detection circuit by capacitors C201 and C202 .

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention realizes common-mode voltage isolation of the micro-fluxgate sensor driving and detection circuits by means of capacitive coupling, eliminates common-mode interference, and can also realize different pre-detection circuit amplification factors through a capacitor array. These advantages greatly improve the adaptability of the detection circuit to the manufacturing differences of the micro-fluxgate probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 is a circuit diagram of a capacitive coupling amplifier according to an embodiment of the present invention;

[0034] Figure 2 FIG. 4 is a circuit diagram of a capacitor array according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] In this embodiment, if Figure 1As shown, a programmable capacitive coupling amplifier applied to a micro fluxgate sensor includes: a switch 101, a switch 102, a switch 103, a switch 104, a switch 105, a switch 106, a switch 107, a switch 108, a switch 109, a switch 110, a switch 111, a switch 112, a capacitor 201, a capacitor 202, a capacitor 203, a capacitor 204, a capacitor array 301, a capacitor array 302, a resistor 401, a resistor 402, an operational amplifier 501, and a fluxgate probe induction coil 601;

[0038] The center end of the fluxgate probe induction coil 601 is connected to the driving bias voltage Vb1;

[0039] One end of the switch 101 and the switch 102 are connected to the output end V in- One end of the switch 103 and one end of the switch 104 are connected to the output end V in+ connect;

[0040] The other end of the switch 101 is connected to the other end of the switch 103, one end of the capacitor array 301 and one end of the capacitor 201 respectively, and the other end of the switch 104 is connected to the other end of the switch 102, one end of the capacitor array 302 and one end of the capacitor 202 respectively;

[0041] The other end of the capacitor array 301 is connected to the other end of the capacitor 201, and the other end of the capacitor array 302 is connected to the other end of the capacitor 202;

[0042] The other end of the capacitor 201 is also connected to the inverting input terminal of the operational amplifier 501, one end of the resistor 401 and one end of the capacitor 203, and the other end of the capacitor 202 is also connected to the non-inverting input terminal of the operational amplifier 501, one end of the resistor 402 and one end of the capacitor 204;

[0043] The other ends of the resistor 401 and the resistor 402 are both connected to the bias voltage Vb2;

[0044] The other end of the capacitor 203 is connected to the switch 105 and the switch 106 respectively, and the other end of the capacitor 204 is connected to the switch 111 and the switch 112 respectively;

[0045] The in-phase output terminal of the operational amplifier 501 is connected to the switch 107 and the switch 108 respectively, and the inverting output terminal of the operational amplifier 501 is connected to the switch 109 and the switch 110 respectively;

[0046] The other end of the switch 105 is connected to the other end of the switch 110, and the other end of the switch 112 is connected to the other end of the switch 107;

[0047] The other end of the switch 107 is also connected to the other end of the switch 106, the other end of the switch 109 and the output terminal V outp The other end of the switch 110 is also connected to the other end of the switch 108, the other end of the switch 111 and the output terminal V outn connect.

[0048] The structures of capacitor array 301 and capacitor array 302 are the same, and are composed of a number of capacitor units connected in parallel; the capacitor unit is composed of 4 switches and 1 capacitor. Figure 2 As shown, the capacitor array includes: switch CH101, switch CH102, switch CH103, switch CH104, switch CH201, switch CH202, switch CH203, switch CH204, ..., switch CHn01, switch CHn02, switch CHn03, switch CHn04, capacitor CA1, capacitor CA2, ..., capacitor CAn; wherein, switch CH101, switch CH102, switch CH103, switch CH104 and capacitor CA1 constitute a first capacitor unit, switch CH201, switch CH202, switch CH203, switch CH204 and capacitor CA2 constitute a second capacitor unit, ..., switch CHn01, switch CHn02, switch CHn03, switch CHn04 and capacitor CAn constitute an nth capacitor unit.

[0049] In this embodiment, the working process of the capacitive coupling amplifier includes:

[0050] In the first stage, switches 101, 104, 106, 107, 110 and 111 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is:

[0051]

[0052] Among them, C 203 represents the capacitance value of capacitor 203, C 201 Indicates the capacitance value of capacitor 201, C 204 represents the capacitance value of capacitor 204, C 202 represents the capacitance value of capacitor 202, and Vinn1 represents the output terminal V of the fluxgate probe induction coil in the first stage. in- The voltage of Vinp1 is the output terminal V of the fluxgate probe induction coil in the first stage. in+ The voltage of Voutp1 is the output voltage of the first stage. outp The output voltage of Voutn1 is the output voltage of the first stage.outn Output voltage

[0053] In the second stage, switches 102, 103, 105, 108, 109 and 112 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is:

[0054]

[0055] Among them, Vinn2 represents the output terminal V of the fluxgate probe induction coil in the second stage in- Vinp2 represents the voltage at the output terminal V of the fluxgate probe induction coil in the second stage. in+ The voltage of Voutp2 represents the output terminal V of the second stage. outp The output voltage of Voutn2 is the output voltage of the second stage. outn Output voltage

[0056] The circuit design adopts a fully symmetrical design, that is, C201 = C203 and C202 = C204, and the switching frequency is much higher than the signal frequency. That is to say, within one cycle of the switching action, Vinp and Vinp are approximately considered unchanged, then:

[0057]

[0058] Then during the entire cycle of the switch output, the total output voltage can be:

[0059] Voutp=Voutp1+Voutp2=-kVinn

[0060] Voutn=Voutn1+Voutn2=-kVinp

[0061] Voutp-Voutn=-k(Vinn-Vinp)

[0062] This process repeats itself to amplify the differential voltage on both sides of the fluxgate probe induction coil 601 , and at the same time, the bias voltage Vb1 of the fluxgate probe induction coil 601 is isolated from the bias voltage Vb2 of the back-end detection circuit by capacitors C201 and C202 .

[0063] Therefore, the gain of the circuit is mainly determined by the capacitance in the circuit. In order to control the circuit gain more flexibly, capacitor array 301 and capacitor array 302 are introduced. It can be seen from the formula that as long as the capacitance output by the capacitor array changes, the gain of the circuit will also change accordingly.

[0064] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A programmable capacitive coupling amplifier for a micro fluxgate sensor, characterized in that: include: Switch 101, switch 102, switch 103, switch 104, switch 105, switch 106, switch 107, switch 108, switch 109, switch 110, switch 111, switch 112, capacitor 201, capacitor 202, capacitor 203, capacitor 204, capacitor array 301, capacitor array 302, resistor 401, resistor 402, operational amplifier 501, and fluxgate probe induction coil 601; The center end of the fluxgate probe induction coil 601 is connected to the driving bias voltage Vb1; One end of the switch 101 and one end of the switch 102 are connected to the output end V of the fluxgate probe induction coil 601. in- One end of the switch 103 and one end of the switch 104 are connected to the output end V in+ connect; The other end of the switch 101 is connected to the other end of the switch 103, one end of the capacitor array 301 and one end of the capacitor 201 respectively, and the other end of the switch 104 is connected to the other end of the switch 102, one end of the capacitor array 302 and one end of the capacitor 202 respectively; The other end of the capacitor array 301 is connected to the other end of the capacitor 201, and the other end of the capacitor array 302 is connected to the other end of the capacitor 202; The other end of the capacitor 201 is also connected to the inverting input end of the operational amplifier 501, one end of the resistor 401 and one end of the capacitor 203, and the other end of the capacitor 202 is also connected to the non-inverting input end of the operational amplifier 501, one end of the resistor 402 and one end of the capacitor 204; The other ends of the resistor 401 and the resistor 402 are both connected to the bias voltage Vb2; The other end of the capacitor 203 is connected to the switch 105 and the switch 106 respectively, and the other end of the capacitor 204 is connected to the switch 111 and the switch 112 respectively; The in-phase output terminal of the operational amplifier 501 is connected to the switch 107 and the switch 108 respectively, and the inverting output terminal of the operational amplifier 501 is connected to the switch 109 and the switch 110 respectively; The other end of the switch 105 is connected to the other end of the switch 110, and the other end of the switch 112 is connected to the other end of the switch 107; The other end of the switch 107 is also connected to the other end of the switch 106, the other end of the switch 109 and the output end V outp The other end of the switch 110 is also connected to the other end of the switch 108, the other end of the switch 111 and the output end V outn connect.

2. A programmable capacitive coupling amplifier for use in a micro fluxgate sensor according to claim 1, characterized in that: The capacitor array 301 and the capacitor array 302 have the same structure, and are composed of a number of capacitor units connected in parallel; the capacitor unit is composed of four switches and one capacitor.

3. A programmable capacitive coupling amplifier for use in a micro fluxgate sensor according to claim 1, characterized in that: The working process of the capacitive coupling amplifier includes: In the first stage, the switches 101, 104, 106, 107, 110 and 111 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is: Among them, C 203 represents the capacitance value of capacitor 203, C 201 Represents the capacitance value of capacitor 201, C 204 represents the capacitance value of capacitor 204, C 202 represents the capacitance value of capacitor 202, and Vinn1 represents the output terminal V of the fluxgate probe induction coil in the first stage. in- The voltage of Vinp1 is the output terminal V of the fluxgate probe induction coil in the first stage. in+ The voltage of Voutp1 is the output voltage of the first stage. outp The output voltage of Voutn1 is the output voltage of the first stage. outn Output voltage In the second stage, the switches 102, 103, 105, 108, 109 and 112 are turned on, and the micro fluxgate probe induction coil 601 outputs a voltage V in- and V in+ are inverted and amplified respectively, then the output terminal V outp and output terminal V outn The output is: Among them, Vinn2 represents the output terminal V of the fluxgate probe induction coil in the second stage in- Vinp2 represents the voltage at the output terminal V of the fluxgate probe induction coil in the second stage. in+ The voltage at the output terminal Voutp2 of the second stage outp The output voltage of Voutn2 is the output voltage of the second stage. outn Output voltage In one switching cycle, Vinp and Vinp are approximately considered unchanged, then: Then during the entire cycle of the switch output, the total output voltage can be: Voutp=Voutp1+Voutp2=-kVinn Voutn=Voutn1+Voutn2=-kVinp Voutp-Voutn=-k(Vinn-Vinp) This process repeats itself to amplify the differential voltage on both sides of the fluxgate probe induction coil 601 , and at the same time, the bias voltage Vb1 of the fluxgate probe induction coil 601 is isolated from the bias voltage Vb2 of the back-end detection circuit by capacitors C201 and C202 .

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