In the process of designing single-power industrial robots, there are always high pressure differences in the system, which brings a lot of inconvenience to my design. So how should we solve it?
1
Current isolation barrier
Galvanic isolation isolates the behavior of a circuit by preventing the generation of a current between the voltage and ground. The following is the current formed from a direct connection between two or more circuits.
In the presence of galvanic isolation, there is no direct conduction path. The advantage of this type of circuit is that it is possible to exchange analog or digital information using a current isolation barrier by using a light field, a magnetic field, or an electric field. These fields opened a lot of doors. Through one of these gates, multiple systems can operate safely and correctly at different ground and voltage potentials. They can also exchange analog or digital information without interfering with or destroying each other in the process.
To solve these problems, designers need to find the right galvanic isolation technology for multi-system circuits. Choice of optical (LED, photodiode), electrical (capacitor) or magnetic (inductor) solutions. In this paper, all isolation gates are implemented in some part of silicon or semiconductor packages.
2 optical isolation
Optical isolation relies on the separation between the light-transmitting LED and the photodetector that receives the light. For galvanic isolation, the LED aligns the photodiode with an isolating material such as transparent polyimide.
The advantage of optical isolation is that it is not affected by electric and magnetic fields. However, LEDs will age over their lifetime.
3
Optical isolation barrier analog signal application
The isolation barrier of optical isolation devices can transmit analog or digital signals. The Vishay Semiconductor Opto Division IL300 linear optocoupler is a linear opto-isolated device with one LED and two photodiodes inside. All components are electrically isolated from each other. In the IL300 chip, the LED light shines uniformly on both photodiodes to produce the same current (IP1 and IP2).
The U1 amplifier (Texas Instruments, TLV9064IDR) drives the IL300 LED to generate feedback photodiode current (IP1). Feedforward photodiode current (IP2) is sent through an isolated R2 resistor in the feedback loop of the isolated U2 amplifier. In this circuit, the gain is equal to R2/R1. In addition, the Vout signal is not affected by the change in VCC1 relative to VCC2 and the two grounds.
LED brightness decreases over time. However, the system in Figure 4 does not depend on the brightness level of the LED; it only requires the LED to turn on. LED light is evenly captured by two photodiodes. To apply the IL300 to the block diagram in Figure 1, the position between the Human Machine Interface (HMI) and the robot controller may be more appropriate.
4
Optical isolation barrier digital signal applications
Another application of optocouplers is to use the device as a digital transmitter. Vishay Semiconductor Opto Division's SFH6750-X007T dual-channel optocoupler and QT Brightek's QTM601T1 single-channel optocoupler are high-speed optocouplers with open-drain NMOS transistor outputs for easy isolation of analog-to-digital converter (ADC) three-channel digital Output.
The serial output code of a 24-bit delta-sigma converter is transmitted from the isolated side of the circuit to the system side. The SFH6750 optically completes this transmission in the digital domain.
The SFH6750 and QTM601T1 configurations offer transmission speeds up to 10 Megabits per second (MBd), making them suitable for high-speed data applications. From the block diagram in Figure 1, it can be seen that the ADC interface may be suitable for placement between the Human Machine Interface (HMI) and the robot controller.
5
Inductive isolation
Inductive isolation uses two coils stacked one above the other, separated by dielectric material. Applying an AC signal produces a magnetic field, which in turn creates an electric field in the secondary coil.
6
Inductive coil isolation barrier power application
Magnetic isolation barriers are suitable for analog and power isolation applications. As a power converter, the inductors and external power FETs of the Analog Devices ADP1621ARMZ-R7 isolated step-up DC-DC controller are T1 and Q3, respectively.
Analog Devices ADUM3190ARQZ-RL7 High-stability linear isolated error amplifier provides analog feedback from the secondary side of T1 to the primary side. The entire circuit operates from 5 V to 24 V and is suitable for standard industrial power supplies.
7
Capacitor isolation
The construction of the capacitive isolation element includes two closely adjacent capacitive plates with a dielectric sandwiched between the two plates. Silicon dioxide (SiO2) materials can be implanted between the capacitor plates to create this isolation capability. In this configuration, the SiO2 breakdown voltage is 500 - 800 V/micrometer (μm). The typical distance for this type of isolator is 27 μm, so the isolation barrier isolation capability is 13.5 kV to 21.6 kV.
Capacitive isolation is best suited for small space applications. However, its peripheral circuits are more complex than optical and magnetic solutions.
8
Capacitive isolation gate simulation applications
A typical capacitive analog isolator, the Texas Instruments AMC1301DWVRQ1 or AMC1311DWV, receives an analog signal, modulates the signal into a digital representation, and then transmits the digitized signal through the isolation barrier.
On the receiver side of the isolation barrier, the signal is demodulated back to the differential output analog signal.
Inductive loads in the motor control environment are susceptible to high switching voltage swings. To ensure proper operation, you need to constantly monitor this changing environment. The use of a resistor divider to reduce the isolation voltage detection of the high common-mode voltage in the motor drive circuit is the corresponding motor control application for the AMC1301 and AMC1311 isolation amplifiers.
Phase current measurement is achieved through shunt resistors RSHUNT and AMC1301 isolated amplifiers. With high-impedance inputs and high common-mode transient immunity, the AMC1311 can sense the bias voltage VBIAS to achieve a stable read of the system configuration. Even in high-noise environments, the AMC1311 ensures reliability and accuracy, such as power level reading of the frequency converter used in motor drives.
The AMC1301 and AMC1311 are both immune to electromagnetic interference and have a galvanic isolation capability of up to 7 kVPEAK. When used with isolated power supplies, the AMC1301 and AMC1311 prevent noise currents from high common-mode voltage lines from entering the local ground to prevent interference with or damage sensitive circuitry.
9 Digital Application of Capacitive Isolation Grids
In preparation for transmitting the DC signal to the output pin, a typical capacitive digital isolator receives the digital signal, modulates the signal to the appropriate AC signal, and sends it to the demodulator.
As long as the transmission signal remains high, high-level digital transmission signals can be generated on the receiver side. The conflict in this logic is that if the charge is dissipated from the capacitor board, or if there is a power interruption at the receiver, the output may go to zero when the input state is high. If this happens, the high state of the receiver digital signal will be lost. To solve this problem, the modulator creates a single low voltage for the digital "0" and a fast ac rail-to-rail signal for the digital "1".
An example of capacitive digital isolation is the use of Silicon Labs SI8422 and SI8423 digital couplers to connect the digital lines between the microcontroller and the ADC.
Capacitive digital devices consume less power while providing high data rates and low propagation delays. Both devices support data rates up to 150 Mbits/s (Mbits/s).
In industrial automation applications, multiple systems have the difficulty of handling analog and digital transmission signals. Optical, magnetic, and capacitive electrical isolation barriers can meet these challenges. By combining these three hardware technologies and the two signal transmission technologies, a suitable industrial automation solution can be realized.
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