How does the UCC33420-Q1 power module help design efficient isolated DC/DC power supplies

Isolated auxiliary power solutions, such as traditional push-pull and flyback converters, utilize bulky, large, and vibration-prone transformers, which complicate the design layout. The design of isolated auxiliary power solutions with external transformers also impacts performance efficiency and can lead to high levels of radiated electromagnetic interference (EMI).

Thanks to breakthroughs in transformer design, IC designers are able to fully integrate the transformer and silicon into a single package, significantly reducing the height and size of isolated DC/DC power supplies. End-users can obtain small, lightweight isolated power modules with high power density without having to design a transformer or degrade system performance.

In this article, the basic functions of three automotive and industrial applications, the importance of isolated DC/DC power supplies to this function, and how Texas Instruments' new UCC33420-Q1 power supply module can help in the design of efficient isolated DC/DC power supplies will be described.

Isolated DC/DC Power Supplies for BMSs
The primary function of a battery management system (BMS) is to monitor pack voltage, pack current and cell voltage. In order to comply with safety standards, it is necessary to monitor high voltage cell (>60V) leakage currents as well as the isolation resistance between the bus and chassis ground. Isolated DC/DC power supplies are used in the high voltage and isolated diagnostic subsystems of the BMS to provide isolated power to digital isolators and current sensors.

As shown in Figure 1, the isolated DC/DC power supply input takes 5V power from the safety power management IC and in turn provides 5V output power to the digital isolators, voltage/current transducers, or analog-to-digital converters on the high-voltage side of the battery disconnect unit application.

In smart battery junction boxes that use a single voltage, current, and insulation resistance monitor, the isolated DC/DC power supply provides 5V output voltage to the battery monitor. Advances in integrated transformer technology enable less printed circuit board area than other push-pull, discrete solutions, optimizing power density, reducing system bill of materials (BOM) quantities, and speeding time to market.

Figure 1 Battery Disconnect Unit System Block Diagram

Electric Vehicle Charging
The trend toward vehicle electrification is on the rise, and with it the need for affordability and shorter charging times. Reducing the size of electric vehicle (EV) charging power modules increases efficiency and reduces overall system cost.

As shown in Figure 2, an EV charging station contains data communication interfaces (e.g., controller LAN RS-485 interface) and isolated amplifiers for voltage and current sensing, both of which require isolated DC/DC power supplies. To reduce charging time, the power output must be increased, which often increases the overall system size. The UCC33420-Q1's compact size and efficiency allow you to design more efficient isolated power systems while saving overall board space. The component supports high voltages from the AC input line while reducing the number of external components by up to 50%.

Figure 2 Electric Vehicle Charging Station System Block Diagram

PLC I/O Module
As shown in Figure 3, high-performance programmable logic controller (PLC) systems contain multiple modules in a small space. These PLC systems use centralized input/output (I/O) modules to communicate with sensors, solenoids, and valves. isolated auxiliary power supplies in the PLC system must be small in size, have excellent output voltage regulation, and be able to minimize EMI and electromagnetic compatibility issues. High power density and output voltage accuracy are also common requirements.

The UCC33420-Q1 provides 1.5W of output power in an ultra-compact 4mm x 5mm leadless package, enabling it to power multiple ICs. The UCC33420-Q1 provides 5V and 3.3V output voltages at VINs of 3V to 3.6V and 4.5V to 5.5V, respectively, with less than ±3% accuracy without the need for a post regulator or low dropout regulator.

Figure 3 PLC Voltage and Current Output Module Block Diagram

Conclusion
In transformer design, the UCC33420-Q1 offers more than 8.5 times the power density of a discrete transformer solution at the same output power level. Other innovations compared to the discrete transformer solution are the reduction of the solution size by more than 89%, the height by more than 75%, and the reduction of the BOM quantity by half. Figure 4 compares the     dimensions of the UCC33420-Q1 to a push-pull converter.

Figure 4 UCC33420-Q1 Isolated DC/DC Module

Comparison to Conventional Push-Pull Converter    
The UCC33420-Q1 is designed to meet the needs of smaller and lighter automotive and industrial applications by integrating an isolated power transformer, primary and secondary side bridges, and control logic into a single package.

The UCC33420-Q1 is an EMI-optimized transformer design with 3pF primary-to-secondary capacitance that meets CISPR 32 without the need for an EMI filter. The device is also CISPR 25 compliant with fewer components and simpler filter design.

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