In high-voltage electrical systems in fields such as motor control, photovoltaic energy storage, new energy vehicles and charging piles, digital isolators are an indispensable safety device. They are mainly responsible for converting and transmitting digital signals input from the logic side through isolation mechanisms such as electromagnetic coupling or capacitive coupling, ultimately achieving electrical isolation between the input and output circuits.

Schematic diagram of electrical isolation in high-voltage circuits (HV)

As shown in the figure above, electrical isolation not only prevents signal distortion and loss caused by high-frequency high-voltage transients (dv/dt) in the signal transmission between the input and output circuits, but also prevents current from flowing from the high-voltage circuit into the low-voltage circuit, thereby protecting the safety of the corresponding equipment and operators and making various high-voltage electrical systems more reliable.

How do digital isolators isolate electrical hazards between high-voltage and low-voltage circuits?

Generally speaking, electrical systems that involve transmitting signals between high-voltage and low-voltage circuits generally require the use of digital isolators for electrical isolation to protect sensitive components in low-voltage logic circuits and human-machine interaction links, while also meeting various stringent safety certification requirements.

For example, HOPERF's independently developed digital isolator based on 433MHz radio frequency technology is a domestically produced alternative chip that can effectively improve the stability and safety of high-voltage electrical systems. Its working principle is to modulate the digital signal input from the logic side into a high-frequency pulse signal ( to give it AC characteristics) through OOK modulation technology, and then transmit it to the signal receiving end through capacitive electric field coupling. The signal receiving end then demodulates and outputs it back to the original digital signal , thereby achieving stable signal transmission under electrical isolation conditions .

It is worth mentioning that, based on HOPERF's more than 20 years of expertise in RF chip development, HOPERF digital isolators not only achieve industry-leading levels in traditional safety performance indicators such as isolation voltage (≥5kVrms), common-mode transient immunity (CMTI≥200kV/us), and surge voltage (10kV), but also reach industry-leading levels in key communication indicators related to RF performance, such as transmission rate (150Mbps) and transmission delay (9ns).

HOPERF digital isolators: a cost-effective electrical isolation solution.

With the surge in demand for high-efficiency, high-power-density electrical systems in fields such as new energy vehicles, photovoltaic energy storage, and high-voltage industrial control, wide-bandgap semiconductors (such as silicon carbide SiC and gallium nitride GaN) are gradually replacing traditional silicon-based semiconductors and becoming the mainstream choice for power devices due to their advantages such as high temperature resistance, high voltage resistance, and fast switching speed .

" fast switching characteristics " of wide bandgap semiconductors improve system energy efficiency and power density, they also bring new challenges to signal transmission between strong and weak current circuits. High - frequency and rapid voltage jumps are prone to interference through parasitic capacitance coupling, leading to problems such as signal distortion and false triggering, and even threatening the safety of sensitive components in low-voltage control circuits. This highlights the key role of digital isolators with high common-mode transient immunity.

For example, the HOPERF digital isolator is a high-performance capacitive isolation chip that builds a miniature wireless radio frequency transceiver system inside the chip. It not only has a common-mode transient immunity (CMTI) of up to 200kV/us, which can effectively suppress the interference of high voltage transients (dV/dt) on the signal and ensure that digital signals can still be transmitted accurately and stably in a high-voltage environment, but also effectively blocks adverse electrical phenomena in high-voltage electrical systems. It is a cost-effective electrical isolation solution in modern high-voltage electrical systems.

As shown in the figure above, the CMT812X (2-channel), CMT804X (4-channel), and CMT826X (6-channel) series of standard capacitive isolators use robust and reliable silicon dioxide (SiO2) insulated gates. They not only support isolation voltages up to 5 kVRms, surge capability of 8kV, and expected service life of over 40 years, but also significantly enhance device electromagnetic compatibility (EMC), effectively meeting system-level ESD, EFT, surge, and radiation compliance requirements.