In PCB copy boards, signal isolation technology is usually used in order to ensure that the components of the circuit board do not interfere with each other. Signal isolation technology allows analog or digital signals to be transmitted without the presence of barriers between the receiving end and the current connection across the transmission. This allows for a difference of up to thousands of volts between ground or reference levels outside the sending and receiving end, and prevents damage to the loop current between the different ground potentials of the signal.
It is mainly used in these situations:
- The noise of the system is large and the signal is easy to be damaged. The isolation technology can separate the signal to another clean signal subsystem ground and power supply, so as to ensure the reliability of the isolated part of the signal, and finally meet the PCB copy board and PCB design requirements of the system.
- The system voltage difference is too large. For example, in the strong current circuit, we need to convert the working voltage to the working range allowed by IC through isolation.
- The electrical connection between the reference level will create a current path that is not safe for the operator. The current can be controlled within a safe range by isolation.
In isolation technology, it is key for PCB designers to select different isolation devices according to the different types of isolated signals and the isolation requirements:
- The first type of isolation devices rely on receivers and optical transmitters to break through the isolation barrier, mainly including the isolation transceiver IC and optocoupler, through the light to block the system currently, capacitance can also avoid electrical interference, such devices are suitable for digital signals.
- Analog transformer is sent and received signals by coupling the electromagnetic sense of the transformer. Transformers are inconvenient to use because they are difficult to make, cannot accurately control their parameters, and are usually impossible to make into ICs, but linearization problems force the use of transformers for analog signal isolation.
- In order to solve the transformer is not convenient to use, engineers adopted the modulated carrier make the analog signal break through the barrier, devised by coupling capacitor circuit to modulation signal in order to break through the barrier, the high conversion rate transient acting in isolation barrier device can be used as a single capacitance-voltage signal, developed the double differential capacitance circuit, thus minimizing the error, now capacitive barrier technology has been widely used in digital and analog isolation devices.