Magnetic sensor chip, temperature compensated current sensor and preparation method thereof

Abstract

A magnetic sensor chip, a temperature-compensated current sensor and a preparation method thereof, wherein the temperature-compensated current sensor comprises: a magnetic focusing ring, a feedback coil wound on the magnetic focusing ring, a magnetic sensor chip arranged at the gap of the magnetic focusing ring, and a magnetic balance circuit connected to the magnetic sensor chip and the feedback coil; the magnetic sensor chip comprises a tunnel junction magnetoresistance element and a thermistor forming a full-bridge structure, wherein the thermistor is located on the electrode layer of the tunnel junction magnetoresistance element, wherein the electrode layer is a ruthenium metal layer or there is ruthenium metal in the electrode layer, and the thermistor is a ruthenium resistor, wherein the thermistor is connected to a temperature compensation circuit, and the feedback coil outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is used to compensate the detection result according to the signal output by the ruthenium resistor and the feedback coil and then output it. The present invention integrates the thermistor inside the magnetic sensor chip, the temperature acquisition area is closer to the magnetic field detection area, the temperature information fed back is more accurate, and no additional materials and process difficulties are added.

Description

Technical Field

[0001] The present invention belongs to the technical field of current sensing, and in particular relates to a magnetic sensing chip used in a current sensor capable of temperature compensation. Background Art

[0002] Magnetic balance current sensors based on the zero flux principle have been widely used in the field of current measurement due to their high sensitivity and wide measurement range. However, due to the influence of the temperature characteristics of the magnetic field detection part and the feedback coil winding, changes in ambient temperature will affect the sensitivity of the magnetic balance current sensor, and thus affect the measurement accuracy of the current sensor. Therefore, it is necessary to compensate for the temperature drift of the current sensor to ensure its measurement accuracy at different temperatures.

[0003] The magnetic balance current sensor generally installs the magnetic sensor chip in the air gap of the feedback coil winding. The magnetic sensor chip and the feedback coil winding are the main components that cause the temperature drift of the current sensor. In order to obtain accurate temperature information of the detection area, the thermistor (temperature sensor device) used to feedback the temperature information should be as close as possible to the magnetic sensor chip and the feedback coil winding to compensate for the temperature drift of the current sensor. The more commonly used temperature compensation method is to set a thermistor in the current sensor, use the thermistor to collect the ambient temperature, and set a temperature compensation circuit on the circuit board of the current sensor to perform temperature compensation on the output of the current sensor to suppress the temperature drift of the current sensor. In order to simplify the production process of the current sensor, the thermistor is generally installed on the circuit board of the current sensor. Since the thermistor is far away from the magnetic sensor chip and the feedback coil winding, it cannot accurately reflect the temperature of the zero flux detection area of ​​the current sensor, and the effect of improving the measurement accuracy is limited. If the thermistor is integrated into the magnetic sensor chip, the thermistor can be closer to the magnetic sensor chip and the feedback coil, so that it can more accurately reflect the temperature information of the detection area, making the temperature compensation of the current sensor more accurate. However, current thermistors are basically made of metal materials such as platinum, copper, and nickel. Since the material of thermistors is different from that of magnetic sensor chips, integrating thermistors into magnetic sensor chips will undoubtedly increase the complexity of the magnetic sensor chip preparation process and increase the production cost of current sensors. Summary of the invention

[0004] The object of the present invention is to provide a magnetic sensor chip with high temperature compensation accuracy.

[0005] Another object of the present invention is to provide a current sensor that is simple to manufacture and can achieve temperature compensation.

[0006] In order to achieve the above first purpose, the present invention adopts the following technical solutions:

[0007] A magnetic sensor chip includes a tunnel junction magnetoresistance element and a thermistor forming a full-bridge structure. The thermistor is located on an electrode layer of the tunnel junction magnetoresistance element. The electrode layer is a ruthenium metal layer or contains ruthenium metal. The thermistor is a ruthenium resistor.

[0008] Furthermore, the tunnel junction magnetoresistive element may be replaced by a GMR unit.

[0009] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0010] A temperature compensated current sensor, comprising: a magnetic focusing ring, a feedback coil wound on the magnetic focusing ring, a magnetic sensor chip arranged at the gap of the magnetic focusing ring, and a magnetic balance circuit connected to the magnetic sensor chip and the feedback coil; the magnetic sensor chip is the aforementioned magnetic sensor chip, the thermistor is connected to the temperature compensation circuit, the feedback coil outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is used to compensate the detection result according to the signal output by the ruthenium resistor and the feedback coil and then output it.

[0011] It can be seen from the above technical scheme that the present invention adopts ruthenium resistor as the thermistor. Ruthenium is one of the materials for preparing tunnel junction magnetoresistance elements, so that the ruthenium resistor can be integrated into the magnetic sensor chip, and the thermistor is integrated inside the magnetic sensor chip. The area for collecting temperature is closer to the area for magnetic field detection, so that the temperature information fed back by the thermistor is more accurate, and can more accurately reflect the temperature information of the detection area, making the temperature compensation of the current sensor more accurate; and because the ruthenium element itself is used to prepare the tunnel junction magnetoresistance element, it is only necessary to divide the temperature detection area in the magnetic sensor chip and connect it to the temperature compensation circuit. The original preparation process of the magnetic sensor chip remains basically unchanged, and there is no need to add other equipment, which is conducive to controlling production costs.

[0012] Furthermore, the temperature compensation circuit includes a temperature sampling circuit, a multiplication proportional circuit, an addition proportional circuit and a current sampling circuit; the temperature sampling circuit is connected to the ruthenium resistor, the temperature sampling circuit outputs a signal to the multiplication proportional circuit, the multiplication proportional circuit outputs a signal to the addition proportional circuit, the current sampling circuit collects the current signal output by the feedback coil and outputs it to the addition proportional circuit, the addition proportional circuit adds the signal output by the current sampling circuit and the signal output by the multiplication proportional circuit to obtain a temperature compensated output signal finally output by the current sensor, and the temperature compensated output signal is simultaneously output to the multiplication proportional circuit.

[0013] By adopting a closed-loop temperature compensation circuit, the feedback error related to temperature drift is smaller, and the temperature compensation is more stable and accurate.

[0014] Furthermore, the temperature compensation circuit includes a temperature sampling circuit, an addition proportional circuit and a current sampling circuit; the temperature sampling circuit is connected to the ruthenium resistor, the temperature sampling circuit outputs a signal to the addition proportional circuit, the current sampling circuit collects the current signal output by the feedback coil and outputs it to the addition proportional circuit, and the addition proportional circuit adds the signal output by the temperature sampling circuit and the signal output by the current sampling circuit to obtain a temperature compensated output signal finally output by the current sensor.

[0015] An open-loop temperature compensation circuit is adopted, which has a simple circuit structure and low manufacturing cost.

[0016] The present invention also provides a method for preparing a sensor chip, comprising the following steps:

[0017] providing a substrate;

[0018] A lower electrode layer, a pinned layer, a non-magnetic layer and a free layer are deposited on a substrate, wherein the lower electrode layer is made of a ruthenium material;

[0019] According to the layout, the magnetoresistive element area and the thermistor area are etched out;

[0020] Depositing an upper electrode layer, preparing an electrical connection structure, including connection terminals and wiring terminals connected to the magnetoresistive element, thermistor, and the feedback coil, to electrically interconnect the magnetoresistive element and thermistor;

[0021] Package chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 any creative work.

[0023] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of a magnetic sensor chip according to Embodiment 1 of the present invention;

[0025] Figure 3 is a circuit block diagram of embodiment 1 of the present invention;

[0026] Figure 4 Signal block diagram of a temperature compensation circuit according to embodiment 1 of the present invention;

[0027] Figure 5 is a circuit block diagram of embodiment 2 of the present invention;

[0028] Figure 6 This is a signal block diagram of the temperature compensation circuit of embodiment 2 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the above and other purposes, features and advantages of the present invention more obvious, embodiments of the present invention are specifically cited below and described in detail with reference to the accompanying drawings.

[0030] Example 1

[0031] Reference Figure 1 and Figure 3 The current sensor of this embodiment includes a feedback coil 1, a magnetic focusing ring 2, a magnetic sensor chip 3, a magnetic balance circuit 4 and a temperature compensation circuit 5. The feedback coil 1 is wound on the magnetic focusing ring 2 to generate a feedback magnetic field. The magnetic focusing ring 2 can be an annular open-and-closed structure composed of a pair of relatively arranged arc-shaped iron cores, or a fixed structure composed of a C-shaped iron core. The magnetic focusing ring 2 can be made of magnetic materials such as silicon steel sheets, Permalloy, and nanocrystals. A notch 2a is provided on the magnetic focusing ring 2, and the magnetic sensor chip 3 is provided at the notch 2a of the magnetic focusing ring 2, and the magnetic sensor chip 3 is used for magnetic field detection.

[0032] The magnetic sensor chip 3 includes a magnetic sensor unit composed of a tunnel junction magnetoresistive element such as a TMR unit or a GMR unit. Figure 2As shown, four groups of tunnel junction magnetoresistance elements (6, 7, 8, 9) are deposited on the substrate of the magnetic sensor chip 3 by magnetron sputtering technology, and four connecting terminals (12, 13, 14, 15) are provided. The structure of each group of tunnel junction magnetoresistance elements is the same, and they all include at least a pinned layer, a free layer and a non-magnetic layer, and the non-magnetic layer is located between the pinned layer and the free layer. The magnetization direction of the pinned layer in the tunnel junction magnetoresistance element does not change with the change of the external magnetic field, and the magnetization direction of the free layer changes with the change of the external magnetic field. The resistance value of the tunnel junction magnetoresistance element changes with the change of the angle between the magnetization direction of the free layer and the magnetization direction of the pinned layer, thereby realizing the detection of the magnetic field. The four groups of tunnel junction magnetoresistance elements are bridge-connected to form a full-bridge structure, and a differential voltage signal is outputted to the outside. The four groups of tunnel junction magnetoresistance elements are respectively located on the four bridge arms of the full-bridge structure, and each connecting terminal is respectively connected to two adjacent bridge arms. Among the four connection terminals, a pair of connection terminals (14, 15) are input terminals, and an external power supply provides a voltage drop to the magnetic sensor chip 3 through the input terminals, so that the full-bridge circuit is in a working state. Another pair of connection terminals (12, 13) are output terminals, and the magnetic sensor chip 3 outputs a differential voltage signal related to the magnetic field through the output terminals. A ruthenium resistor 16 as a thermistor is also integrated on the substrate of the magnetic sensor chip 3. The ruthenium resistor 16 is used to collect temperature information of the magnetic field detection area. The ruthenium resistor 16 is connected to the temperature compensation circuit 5 through the connection terminals (10, 11). Ruthenium is one of the materials for preparing the electrode layer and the pinning layer of the tunnel junction magnetoresistance element (TMR). Since the pinning layer is thin, it is not suitable for preparing the thermistor. Therefore, it is preferred to set the ruthenium resistor in the electrode layer. Compared with conventional thermistors made of platinum, copper, nickel and other materials, the thermistor is formed by using the electrode layer, so that the thermistor is integrated in the magnetic sensor chip. The tunnel junction magnetoresistance element can also be replaced by GMR, and ruthenium material is added to the material used to prepare the GMR unit, thereby integrating the thermistor into the chip.

[0033] like Figure 2 As shown, the magnetic sensing unit in the magnetic sensing chip 3 is connected to the magnetic balance circuit 4 through the output terminal. The magnetic balance circuit 4 of this embodiment includes a differential voltage sampling circuit 4-1 and a push-pull emitter follower circuit 4-2. The differential voltage sampling circuit 4-1 is used to collect the differential voltage signal V output by the magnetic sensing unit. M The push-pull emitter follower circuit 4-2 generates a current I output to the feedback coil 1 according to the differential voltage signal. s , so that the feedback coil 1 generates a feedback magnetic field, so that the current sensor reaches a magnetic equilibrium state. The feedback coil 1 outputs a current signal to the temperature compensation circuit 5 at the same time.

[0034] The temperature compensation circuit 5 of this embodiment is a closed-loop temperature compensation circuit, which includes a temperature sampling circuit 5-1, a multiplication ratio circuit 5-2, an addition ratio circuit 5-3 and a current sampling circuit 5-4. The temperature sampling circuit 5-1 is connected to the ruthenium resistor 16 to collect the temperature sampling voltage output by the ruthenium resistor 16. The output end of the temperature sampling circuit 5-1 is connected to the multiplication ratio circuit 5-2 to output a temperature sampling signal V to the multiplication ratio circuit 5-2. T The current sampling circuit 5-4 collects the current signal output by the feedback coil 1 and outputs the collected signal to the addition proportional circuit 5-3. The multiplication proportional circuit 5-2 and the addition proportional circuit 5-3 form a closed-loop feedback. Figure 4 As shown, the adding proportional circuit 5-3 obtains the sampling signal V of the feedback coil 1 from the current sampling circuit 5-4. s , and the sampling signal V of feedback coil 1 s The temperature compensation output signal V0 is added to the signal output by the multiplication ratio circuit 5-2 (K1 is the amplification factor of the addition ratio circuit) to obtain the temperature compensation output signal V0 output by the current sensor. The temperature compensation output signal V0 is also output to the multiplication ratio circuit 5-2 for combination with the temperature sampling signal V T After multiplication (K2 is the gain of the addition proportional circuit), it is output to the addition proportional circuit 5-3.

[0035] Combine the following Figure 1 The working principle of this embodiment is described as follows:

[0036] like Figure 1 As shown, when the current sensor is measuring, the conductor 20 to be measured passes through the magnetic ring 2. When current passes through the conductor 20 to be measured, a magnetic field A is generated around the conductor 20 to be measured; the magnetic sensor chip 3 detects the magnitude of the magnetic field at the gap 2a of the magnetic ring 2 and outputs a differential voltage signal V M ; The magnetic balance circuit 4 collects the differential voltage signal V output by the magnetic sensor chip 3 M , and adjust the input current I of feedback coil 1 S ; Feedback coil 1 is at current I S Under the action of , a magnetic field B is generated in the magnetic ring 2; when the differential voltage signal V M When it is zero, the magnetic field A generated by the conductor 20 under test and the magnetic field B generated by the magnetic focusing ring 2 reach a magnetic equilibrium state, and the gap 2a of the magnetic focusing ring 2 is zero magnetic flux.

[0037] The preparation method of the sensor chip integrated with thermistor in this embodiment is as follows:

[0038] providing a substrate;

[0039] A lower electrode layer, a pinned layer, a non-magnetic layer and a free layer are deposited on a substrate, wherein the lower electrode layer is made of a ruthenium material;

[0040] According to the layout, the magnetoresistive element area and the thermistor area are etched out;

[0041] Depositing an upper electrode layer, preparing an electrical connection structure, including connection terminals and wiring terminals connected to the magnetoresistive element, thermistor, and the feedback coil, to electrically interconnect the magnetoresistive element and thermistor;

[0042] Package chip.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the temperature compensation circuit of this embodiment is an open-loop temperature compensation circuit. Figure 5 As shown, the temperature compensation circuit of this embodiment includes a temperature sampling circuit 5-1, an addition ratio circuit 5-3 and a current sampling circuit 5-4. Among them, the temperature sampling circuit 5-1 is connected to the ruthenium resistor 16 to collect the temperature sampling voltage output by the ruthenium resistor 16. The current sampling circuit 5-4 is connected to the feedback coil 1 to collect the current signal output by the feedback coil 1. The output end of the current sampling circuit 5-4 and the output end of the temperature sampling circuit 5-1 are connected to the addition ratio circuit 5-3. Figure 6 As shown, the addition proportional circuit 5-3 adds the temperature sampling signal V output by the temperature sampling circuit 5-1 to T The sampling signal V of the feedback coil 1 output by the current sampling circuit 5-4 s Add (K1 is the amplification factor of the addition proportional circuit) to obtain the temperature compensated output signal V0 of the current sensor. This embodiment uses an open-loop temperature compensation circuit, and the circuit structure is simpler than that of a closed-loop temperature compensation circuit. However, since the closed-loop temperature compensation circuit adds a multiplication proportional circuit, the feedback error related to temperature drift is less, and the compensation is more stable and accurate. The magnetic balance circuit and temperature compensation circuit of the present invention are the same as those of the current sensor using an ordinary thermistor for temperature compensation. They are not the inventive point of the present invention and will not be described here.

[0045] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A magnetic sensor chip, comprising a tunnel junction magnetoresistive element and a thermistor forming a full-bridge structure, characterized in that: The thermistor is located on the electrode layer of the tunnel junction magnetoresistive element, the electrode layer is a ruthenium metal layer or the electrode layer contains ruthenium metal, and the thermistor is a ruthenium resistor.

2. The magnetic sensor chip according to claim 1, characterized in that: The tunnel junction magnetoresistive element may be replaced by a GMR unit.

3. Temperature compensated current sensor, including: A magnetic focusing ring, a feedback coil wound on the magnetic focusing ring, a magnetic sensor chip arranged at the gap of the magnetic focusing ring, and a magnetic balance circuit connected to the magnetic sensor chip and the feedback coil; It is characterized in that: the magnetic sensor chip is the magnetic sensor chip according to claim 1 or 2, the thermistor is connected to the temperature compensation circuit, the feedback coil outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is used to compensate the detection result according to the signal output by the ruthenium resistor and the feedback coil and then output it.

4. The temperature compensated current sensor according to claim 3, characterized in that: The temperature compensation circuit includes a temperature sampling circuit, a multiplication proportional circuit, an addition proportional circuit and a current sampling circuit; the temperature sampling circuit is connected to the ruthenium resistor, the temperature sampling circuit outputs a signal to the multiplication proportional circuit, the multiplication proportional circuit outputs a signal to the addition proportional circuit, the current sampling circuit collects the current signal output by the feedback coil and outputs it to the addition proportional circuit, the addition proportional circuit adds the signal output by the current sampling circuit and the signal output by the multiplication proportional circuit to obtain a temperature compensation output signal finally output by the current sensor, and the temperature compensation output signal is simultaneously output to the multiplication proportional circuit.

5. The temperature compensated current sensor according to claim 3, characterized in that: The temperature compensation circuit includes a temperature sampling circuit, an addition proportional circuit and a current sampling circuit; the temperature sampling circuit is connected to the ruthenium resistor, the temperature sampling circuit outputs a signal to the addition proportional circuit, the current sampling circuit collects the current signal output by the feedback coil and outputs it to the addition proportional circuit, and the addition proportional circuit adds the signal output by the temperature sampling circuit and the signal output by the current sampling circuit to obtain a temperature compensated output signal finally output by the current sensor.

6. The method for preparing a magnetic sensor chip according to claim 1 or 2, characterized in that: The following steps are involved: providing a substrate; A lower electrode layer, a pinned layer, a non-magnetic layer and a free layer are deposited on a substrate, wherein the lower electrode layer is made of a ruthenium material; According to the layout, the magnetoresistive element area and the thermistor area are etched out; Depositing an upper electrode layer, preparing an electrical connection structure, including connection terminals and wiring terminals connected to the magnetoresistive element, thermistor, and the feedback coil, to electrically interconnect the magnetoresistive element and thermistor; Package chip.

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