Digital isolator Si8641 typical circuit and OBC controller system

At present, the pure electric bus technology is very mature, and most of the car manufacturers use the vehicle OBC controller technology to realize the power battery charging management. The OBC controller converts the 220V into a DC through a controllable rectifier bridge, filters it to a high - frequency DC-DC power converter, and then re-filters it to charge the pure electric vehicle power battery according to the DC required by the vehicle and power output. In this process, the design of the controllable rectifier bridge module generally adopts a half bridge topology composed of a driver + MOSFET . Then the driver is not only a low-voltage to high-voltage driving device, that is, it must have an output capability of more than 2.5A , and also has a 5KV isolation function to protect the MOSFET circuit of the latter stage .

Based on these needs, Silicon Labs (also known as " core technology " ) offers the Si8233 driver isolator with a maximum output current of 4A and a safe isolation voltage of 5kvrms . It supports SOIC-8 and SOIC-16 packages and supports up to 1,500 VDC. Peak drive voltage. Compared with other peer products, its advantages are large drive current and high cost performance.

Figure 1 : Si8233 Drive MOSFET Typical Circuit

The OBC controller will have 5V and 3.3V data communication at the same time . For example, the MCU may work at 3.3V , while some other ICs work at 5V . At this time, I2C , SPI , and IO need to be isolated to protect The voltage difference causes the latter IC to be burned. The Silicon Isolator Si8641 from Silicon Labs is recommended here . It is specifically designed for SPI communication isolation. It supports three simultaneous channels and one reverse channel, and the MCU of the OBC controller can be used with pins EN1 and EN2 . Si8641 control output, which is the advantage of improving the reliability of EMC controller OBC, the voltage difference will not result OBC controller crashes.

Figure 2 : Typical circuit of digital isolator Si8641

OBC onboard controller functions to realize there are many ways, but as the core device driver Si8233 and Si8641 digital isolator has been adopted by many companies design. It has been successfully applied to some customers in East China and has passed all tests of the car factory.

For more information on Silicon Labs' digital isolation solutions, please visit: https://cn.silabs.com/products/isolation