CN111355458A

CN111355458A - Isolation amplifier structure based on magnetic field coupling

Info

Publication number: CN111355458A
Application number: CN202010311751.0A
Authority: CN
Inventors: 黄海滨; 马辉; 蒋赛尖
Original assignee: STEADICHIPS Inc
Current assignee: Hangzhou Sitai Microelectronics Co ltd
Priority date: 2020-04-20
Filing date: 2020-04-20
Publication date: 2020-06-30

Abstract

The invention relates to the technical field of isolation amplifiers, in particular to an isolation amplifier structure based on magnetic field coupling, which can realize that a sending end, a receiving end and a coupling device are integrated on one chip and comprises a sending end module, a receiving end module and a coupling device.

Description

Isolation amplifier structure based on magnetic field coupling

Technical Field

The invention relates to the technical field of isolation amplifiers, in particular to an isolation amplifier structure based on magnetic field coupling.

Background

In the field of chip applications, it often occurs that the chip is required to perform signal transmission between two voltage domains, which transmission must be performed in different power supply systems, and is therefore referred to as an isolation amplifier.

As shown in fig. 1, a transmission path different from a normal coupling method is adopted between a transmitting end 101 and a receiving end 102 of a conventional isolation amplifier, and the transmission path is usually performed by using an optical coupling 103, an electric field coupling 104, and the like. However, these coupling methods have problems to different degrees: such as: the integration (optical coupling) on a common chip, the large area of a coupling device (electric field coupling), and the like cannot be realized.

Disclosure of Invention

In order to solve the problem of difficult coupling integration in the existing isolation amplifier, the invention provides an isolation amplifier structure based on magnetic field coupling, which can realize the integration of a transmitting end, a receiving end and a coupling device on one chip.

The technical scheme is as follows: the magnetic field coupling-based isolation amplifier structure comprises a sending end module, a receiving end module and a coupling device, and is characterized in that the sending end module comprises a preamplifier/filter, a pulse width modulator and a current source switch group which are sequentially connected, the receiving end module comprises an amplifying and shaping circuit and a low-pass filter which are sequentially connected, the coupling device comprises a coil and a magnetic sensor, and an insulating layer is arranged between the coil and the magnetic sensor.

The current source switch group is further characterized by comprising a current source and four switches, wherein one end of the current source is connected with a power supply, the other end of the current source is respectively connected with the two ends of the coil through two of the switches, and the two ends of the coil are respectively grounded through the rest two switches;

the coupling device comprises two symmetrically arranged coils and two symmetrically arranged magnetic sensors, one end of each of the two coils is connected, and the insulating layer is arranged between one of the magnetic sensors and one of the coils.

After the invention is adopted, the transmitting end module, the receiving end module and the coupling device have simple structures, and the insulating layer is arranged between the coil and the magnetic sensor to realize electric isolation, so that the transmitting end module, the receiving end module and the coupling device can be conveniently integrated on the same chip.

Drawings

FIG. 1 is a schematic diagram of a prior art isolation amplifier;

FIG. 2 is a schematic diagram of the present invention;

FIG. 3 is a schematic diagram of a magnetic coupling device;

FIG. 4 is a schematic diagram of the connection of a current source switch set to a coil;

FIG. 5 is a schematic diagram of two coil connections;

fig. 6 is an illustration of a hall device profile.

Detailed Description

Referring to fig. 2, the magnetic field coupling-based isolation amplifier structure includes a transmitting end module 210, a receiving end module 211 and a coupling device, where the transmitting end module 210 includes a preamplifier/filter 201, a pulse width modulator 202 and a current source switch set 203, which are connected in sequence, the receiving end module 211 includes an amplifying and shaping circuit 204 and a low-pass filter 205, which are connected in sequence, and the coupling device includes a coil 207 and a magnetic sensor 208.

The transmitted signal 212 passes through the preamplifier/filter 201 and enters the pulse width modulator 202 where the analog signal is modulated into a high frequency pulse width modulated discrete signal 206 having a pulse width representative of the signal amplitude. The signal passes through a current source switch group 203, and the voltage signal is converted into a signal in a current form; the current flows through the coil 207 of a specific shape to form a corresponding magnetic field signal; the module completes the conversion from the signal to be transmitted to the magnetic field signal, and the part belongs to the same set of power supply (the same voltage domain). This portion may be referred to as a sender-side module 210;

in general, the specific shape of the coil 207 is determined according to the shape of the hall device. Such as: the hall device shapes shown in fig. 6 are the coil shapes that respond when they are square, hexagonal, and octagonal, respectively.

In another circuit structure powered by a power supply, a magnetic sensor 208 integrated on a chip, such as a hall device, converts a magnetic field signal generated at a transmitting end into an electrical signal, the electrical signal is amplified and shaped by an amplifying and shaping circuit and then restored into a pulse width modulation signal, the signal is filtered by a low-pass filter 205 to remove unnecessary high-frequency signals, and finally, a low-frequency signal 213 to be transmitted is restored and output to a chip pin. This portion may be referred to as a receive side module 211.

In the prior art, an analog signal to be transmitted can be directly coupled to a receiving end through a magnetic field, but the magnetic field coupling and related circuit processing are easily interfered by external signals (magnetic interference and electric signal noise interference), so that the pulse width modulator 202 is adopted to modulate the analog signal into a pulse width modulation signal 206 with high-frequency discrete characteristics, so that magnetic coupling and external interference signal resistance are facilitated.

As shown in fig. 3, the coupling device comprises a coil 301 and a magnetic sensor 302. The left side is a top view, and the right side is a cross-sectional view of the chip structure, and it can be seen that, because the insulating layer 303 exists between the coil 301 and the magnetic sensor 302 (e.g., hall device), the two circuit structures (i.e., the transmitting-side module 210 and the receiving-side module 211) powered by different power supplies are electrically isolated from each other.

As shown in fig. 4, since the current flowing through the coil 301 cannot be very large, the magnetic field generated by the coil is relatively weak, and in order to provide a magnetic field which is easier to detect, the current source switch set includes a current source and four switches, one end of the current source is connected to a power supply, the other end of the current source is connected to two ends of the coil through two of the switches, respectively, two ends of the coil are grounded through the remaining two switches, respectively, and the current generated by the current source 401 is introduced into the coil 402 through 4 different switches, respectively. This configuration shows that when the switch control signals are high ("1") and low ("0"), respectively, the current signals passing through the coils 401 are equal in magnitude and opposite in direction, so that magnetic fields with completely opposite directions can be generated and are more easily detected by the receiving end.

In order to keep the cost low, the chip is usually packaged without magnetic isolation, which results in that the magnetic sensor on the chip is interfered by the magnetic field outside the chip to generate a signal completely unrelated to the signal to be transmitted. In order to reduce this interference, the present invention uses two

magnetic sensor structures

502 and 503 as shown in fig. 5, which are arranged at the minimum distance allowed by the process as much as possible, and the induced voltages generated by the

magnetic sensor structures

502 and 503 are subtracted by the subsequent circuit.

Because of different winding modes of the coil, the current of the coil generates magnetic fields with opposite directions on the two magnetic sensors respectively,its magnetic field intensity signal is H_S502And H_S503It shows that, because of the subtraction processing in the chip, the magnetic field strength signals generated by the same current at the two magnetic sensor positions can be processed as follows:

Y_s= H_S502– H_S503（1）

because the two sensors are the same size, the above coil geometry is the same, but the surrounding directions are opposite, and the magnetic field intensity formed by the current on the coil at the two sensor positions is considered to be the same and opposite:

H_S502= - H_S503= H_S（2）

by integrating the formulas (1) and (2), the following can be obtained:

Y_S= 2 * H_S（3）

it can be seen that the signal to be transmitted is enhanced by this structure.

And the interference signal of the external magnetic field can be represented by H_N502、H_N503It shows that, because the two magnetic sensors are very close (several tens of micrometers), the magnetic field intensity of the external magnetic field interference at the two magnetic sensor positions is considered to be the same, and the direction is also the same, and because the chip subtracts the induced voltage, the interference signal of the external magnetic field is:

Y_N= H_N502- H_N503= 0 (5)

as can be seen from equation (5), through the above configuration, the interference of the external magnetic field to the magnetic coupling on the chip can be perfectly removed, so that a better signal coupling characteristic can be obtained;

the method for forming the differential configuration by the two magnetic sensors can also be expanded to a plurality of magnetic sensors, the effect of eliminating the external magnetic field interference is better, and a corresponding processing circuit is more complex.

Claims

1. The magnetic field coupling-based isolation amplifier structure comprises a sending end module, a receiving end module and a coupling device, and is characterized in that the sending end module comprises a preamplifier/filter, a pulse width modulator and a current source switch group which are sequentially connected, the receiving end module comprises an amplifying and shaping circuit and a low-pass filter which are sequentially connected, the coupling device comprises a coil and a magnetic sensor, and an insulating layer is arranged between the coil and the magnetic sensor.

2. The magnetic field coupling-based isolation amplifier structure according to claim 1, wherein the current source switch group comprises a current source and four switches, one end of the current source is connected with a power supply, the other end of the current source is respectively connected with two ends of the coil through two of the switches, and two ends of the coil are respectively grounded through the remaining two switches.

3. The magnetic field coupling-based isolation amplifier structure according to claim 1, wherein the coupling device comprises two symmetrically arranged coils and two symmetrically arranged magnetic sensors, one end of each of the two coils is connected, and the insulating layer is disposed between one of the magnetic sensors and one of the coils.