Technical Article

Optimizing Design Efficiency: Shrinking PSUs in Auto and Industrial Applications

April 16, 2024 by Bethlehem Defar

One way to optimize automotive and industrial designs is to reduce the size of the power supply unit, resulting in less physical material, fewer discrete components, and system-level cost savings.

This article is published by EEPower as part of an exclusive digital content partnership with Bodo’s Power Systems.


Isolated bias-supply solutions like push-pull and flyback converters traditionally require heavy, bulky transformers prone to vibrations, necessitating a complicated design layout. The design of isolated bias-supply solutions with external transformers also affects performance efficiency and can lead to high radiated electromagnetic interference (EMI).

Breakthroughs in transformer design have allowed integrated circuit designers to fully integrate a transformer and silicon into one package, significantly reducing the isolated DC/DC power supply unit (PSU) height and size. The end user obtains a tiny, lightweight, isolated power module, enabling high power density without designing a transformer or compromising system performance.

In this article, we’ll describe the basic functionality of three automotive and industrial applications, the importance of the isolated DC/ DC power supply to this functionality, and how Texas Instruments’ UCC33420- Q1 power module can help you design an effective isolated DC/DC power supply.


Image used courtesy of Adobe Stock


Isolated DC/DC Power Supply Units in Battery Management Systems

The main function of a battery management system (BMS) is to monitor pack voltage, pack current, and cell voltage. Monitoring high-voltage battery (> 60 V) leakage current and isolation resistance between the bus and chassis ground is required to comply with safety standards. An isolated DC/DC power supply is present in the high-voltage and isolation diagnosis subsystem within the BMS, providing isolated power to digital isolators and current sensors.

The isolated DC/DC power-supply input gets a 5 V supply from the safety power-management integrated circuit and provides 5 V of output power to digital isolators, voltage/current sensors, or analog-to-digital converters on the high-voltage side in a battery disconnect unit application, as illustrated in Figure 1.

In an intelligent battery junction box using a single voltage, current, and insulation resistance monitor, the isolated DC/DC power supply provides an output voltage of 5 V to the battery monitor. Advancements in integrated transformer technology occupy less printed circuit board area than other push-pull discrete solutions, optimizing power density, reducing system bill-of-materials (BOM) count, and accelerating time to market.


Figure 1. Battery disconnect unit system block diagram. Image used courtesy of Bodo’s Power Systems [PDF]


Figure 2. EV charging station system block diagram. Image used courtesy of Bodo’s Power Systems [PDF]


EV Charging

As the move toward vehicle electrification grows, the need for affordability and reduced charging time increases. Reducing the size of electric vehicle (EV) charging power modules can provide efficiency and reduce overall system cost.

As shown in Figure 2, an EV charging station includes data communication interfaces such as Controller Area Network, RS-485, and isolated amplifiers for voltage and current sensing, all requiring isolated DC/DC power. To decrease charging times, there has to be an increase in power output, which can increase the overall system size. The UCC33420-Q1’s small footprint and high efficiency can help you design a more efficient isolated power-supply system while reducing board space. It is possible to eliminate the number of external components by as much as 50% while supporting the high voltages from AC input lines.


Figure 3. PLC voltage and current output module block diagram. Image used courtesy of Bodo’s Power Systems [PDF]


PLC I/O Modules

As shown in Figure 3, high-performance programmable logic controller (PLC) systems include several modules in a small space. These PLC systems use centralized input/output (I/O) modules to communicate with sensors, solenoids, and valves. The isolated bias supply in a PLC system must be small, have tight output voltage regulation, and be able to mitigate EMI and electromagnetic compatibility. High power density and output-voltage accuracy are also typical requirements.

The UCC33420-Q1’s ability to deliver 1.5 W of output power in a 4 mm by 5 mm very small outline no-lead package enables this device to power multiple integrated circuits. The UCC33420-Q1 can provide 5 V and 3.3 V output voltages with accuracy <± 3% at VIN 3 V to 3.6 V and 4.5 V to 5.5 V without a post regulator or low-dropout regulator.

Within the realm of transformer design, the UCC33420-Q1 delivers over 8.5 times higher power density than discrete transformer solutions with the same output power levels. Other innovations over discrete transformer solutions include a reduction in solution size by > 89%, a reduction in height by > 75%, and a reduction in BOM count by half. Figure 4 compares the size of the UCC33420-Q1 to a push-pull converter.


Figure 4. UCC33420-Q1 isolated DC/DC module vs. a traditional push-pull converter. Image used courtesy of Bodo’s Power Systems [PDF]


The UCC33420-Q1 integrates an isolation power transformer, primary- and secondary-side bridges, and control logic into one package, enabling you to meet the demand for smaller, lighter automotive and industrial applications.

The UCC33420-Q1 is designed with an EMI-optimized transformer with 3pF of primary-to-secondary capacitance that can meet Comité International Spécial des Perturbations Radioélectriques (CISPR) 32 compliance without the use of an EMI filter. The device can also meet the CISPR 25 standard with fewer components and a simpler filter design.


This article originally appeared in Bodo’s Power Systems [PDF] magazine and is co-authored by Bethlehem Defar and German Aguirre Product Marketing Engineers with Texas Instruments.