How to Design High-Voltage System Solutions with Higher Reliability, Smaller Size, and Lower Cost

【Introduction】High-voltage industrial and automotive systems such as factory automation equipment, grid infrastructure applications, motor drives, and electric vehicles (EVs) can generate voltages ranging from hundreds to thousands of volts, which not only shorten the life of equipment, but even cause personal safety pose significant risks. This article describes how new isolation techniques can be used to secure these high-voltage systems, thereby increasing reliability while reducing solution size and cost.

isolation method

Integrated circuits (ICs) achieve isolation by blocking DC and low-frequency AC currents while allowing power, analog or high-speed digital signals to pass through the isolation barrier. Figure 1 illustrates three common semiconductor technologies used to achieve isolation: optical (optocouplers), electric field signaling (capacitive), and magnetic field coupling (transformers).

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Figure 1: Semiconductor isolation technology: optocoupler (a); capacitive (b); transformer (c)

TI utilizes capacitive isolation technology and proprietary integrated planar transformers (magnetic isolation), as well as advanced packaging and process technologies, to enhance the reliability, integration and performance of our large and comprehensive line of isolated IC products.

Overcome High Voltage Design Challenges with Reliable Isolation Technology

Read the white paper to learn about common high-voltage electrical isolation problems and methods, and how to reliably achieve high-voltage isolation in industrial and automotive systems while reducing solution size and cost.

Capacitive isolation

Capacitive isolation technology is based on AC signal transmission through a dielectric. TI’s capacitive isolators are constructed using a very high dielectric strength SiO2 dielectric. Because SiO2 is an inorganic material, it is very stable under different humidity and temperature conditions. Additionally, our proprietary multilayer capacitors and multilayer passivation methods reduce the reliance on any single layer for high voltage performance, improving isolator quality and reliability. Our capacitor technology supports a working voltage (VIOWM) of 2kVRMS, a withstand isolation voltage (VISO) of 7.5kVRMS, and can withstand surge voltages of 12.8kVPK.

Magnetic isolation

Magnetic isolation is often used in applications that require high frequency DC/DC power conversion. An advantage of IC transformer-coupled isolation is that power in excess of hundreds of milliwatts can be transferred, often without the need for a secondary-side bias supply. Magnetic isolation can also be used to send high frequency signals. In a system that needs to deliver power and transmit data at the same time, you can use the same transformer winding coils for both power and signal needs, as shown in Figure 2. Combining the signal and power delivery functions on the same integrated transformer coil can substantially reduce the cost and size of the solution. TPSI3050-Q1 and TPSI3052-Q1 combine data transmission and power transmission on the same transformer channel.

Figure 2: Reliable Power and Signal Delivery through Isolation Barriers Using Magnetic Isolation

For magnetic isolation, TI uses a proprietary multi-chip module approach that co-packages high-performance planar transformers with isolated power stages and dedicated controller dies. We can build these transformers using high performance ferrite cores for improved coupling and transformer efficiency, or we can use air cores in applications where power delivery needs are not high, saving cost and reducing complexity.

Reliably meet isolation needs while reducing solution size and cost.

Different applications require different methods of isolation. Let’s look at a few examples of how TI’s ICs can help meet the high-voltage isolation needs of electric vehicle and grid infrastructure applications, and see how SSRs can be used to achieve higher reliability isolation and smaller solution size.

Electric Vehicle Applications

To reduce weight, increase torque, improve efficiency and speed up charging, the level of high-voltage battery packs for electric vehicles has increased from 400V to 800V, and even as high as 1kV. The battery management system (BMS) and traction inverter are two very critical EV subsystems that need to isolate the 800V domain from the chassis to ensure the safety of passengers and their vehicles.

The block diagram shown in Figure 3 is an example of a traction inverter that uses an isolated gate driver to drive a high-voltage insulated gate bipolar transistor (IGBT) or silicon carbide in a three-phase DC-to-AC inverter configuration (SiC) modules. These modules can co-package up to six IGBT or SiC switches, requiring up to six isolation transformers to power six separate gate driver ICs. Our UCC14240-Q1 is a dual output, medium voltage, isolated DC/DC power module that enables higher performance in traction inverter, gate driver biasing applications while reducing the number of external transformers to fully Reduce PCB area.

Figure 3: Typical Traction Inverter System Block Diagram

Additionally, the BMS uses a pre-charge circuit when connecting the high-voltage battery terminals to the subsystem. Our 5kVRMS TPSI3050-Q1 isolating switch driver is designed to replace mechanical precharge contactors, enabling smaller, more reliable solid state solutions. The device provides up to 5kVRMS of reinforced isolation, 10 times the operating life of electromechanical relays, and is not as prone to degradation over time as electromechanical relays. Figure 4 illustrates the area savings of the TPSI3050-Q1 compared to mechanical relays.

Figure 4: Reduced solution size using a magnetic isolation-based solid state relay driver (TPSI3050)

Grid Infrastructure Applications

Isolation is an essential element in grid infrastructure applications, protecting equipment and personnel from high voltage surges, eliminating destructive ground loops involving large ground potential differences (GPD) when interconnecting, and preventing common-mode transients. data integrity during state events.

Solar equipment and EV chargers operate from 200V to 1,500V or higher. Figure 4 shows our AFE reference design for insulation monitoring in high voltage EV charging and solar power. This reference design uses our AMC3330 precision isolation amplifier and TPSI2140-Q1 isolation switch to monitor insulation resistance in grid infrastructure applications. With no moving parts, this solid-state relay solution can perform frequent measurements for decades without performance degradation. Both power and signals can be delivered through the isolation barrier within the TPSI2140-Q1, thus eliminating the need for a secondary-side bias supply. Since the device is housed in a thin small outline IC (SOIC) package, the solution size can be 50% smaller than solutions based on photorelays or mechanical relays.

Figure 5: AFE block diagram for insulation monitoring in high voltage EV charging and solar power

Epilogue

TI is integrating more capabilities into isolation technology to help engineers keep solutions safe while reducing design complexity, solution size and cost in applications such as electric vehicles and grid infrastructure. See ti.com/isolationtechnology to learn how we’re extending capacitive and magnetic isolation technology to add more analog capabilities.

Other references

For more information on the reliability of TI’s high-voltage isolation capacitors, read the white paper “Achieving High-Quality and Reliable High-Voltage Signal Isolation.”

Check out the application note, How to Simplify Designing Isolated 24V PLC Digital Input Modules.

To learn about basic isolation parameters, certification, and how to design and troubleshoot with various types of isolation ICs, watch the TI Precision Labs – Isolation training series.