Energy Ideas #143: Ideas for protecting the ability converter cool in automotive USB PD purposes

July 31, 2025

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Energy Ideas #143: Ideas for protecting the ability converter cool in automotive USB PD purposes

At present’s automotive consumers, whether or not buying premium or economic system fashions, count on to cost a number of units concurrently by way of in-vehicle USB ports. To fulfill this demand, automakers are changing legacy USB Sort-A ports with a number of USB Sort-C ports that assist the newest USB energy supply (PD) requirements. These requirements allow considerably greater energy ranges—as much as 48 V and 240 W—appropriate for fast-charging laptops, tablets, and telephones.

USB PD controllers function alongside inside or exterior DC/DC converters, which add their very own thermal stress to the system. This problem turns into much more crucial in automotive, industrial, and different space-constrained designs the place airflow is minimal and ambient temperatures are excessive. If left unmanaged, extreme warmth can injury or degrade system reliability. Elevated temperatures speed up the ageing of semiconductors and passive elements, trigger solder joint fatigue, and, within the worst instances, can result in printed circuit board (PCB) delamination or thermal runaway. These dangers make thermal administration a precedence in system-level USB PD designs, particularly when long-term reliability or security are necessities. On this energy tip, I’ll discover totally different strategies to handle warmth and enhance system reliability when implementing automotive USB PD options.

A typical 12-V battery automotive system wants these elements to implement a USB PD charging port:

A DC/DC converter. The converter steps the 12-V battery voltage as much as the specified USB output (generally 5 V to twenty V, as much as 60 W, and even 48 V and 240 W with the newest USB PD specs).
A controller that helps USB PD. This controller is on the coronary heart of contemporary high-power charging methods, negotiating energy roles and voltage ranges with linked units. The TPS26744E-Q1 from Texas Devices (TI) is an instance of a dual-port automotive controller that manages USB PD profiles and controls the related DC/DC converter.

Challenges when designing high-power USB PD from a 12-V rail embrace:

Broad voltage variations: Each enter (automotive battery) and output (USB Sort-C port and linked load) voltages range considerably, requiring a dependable and versatile energy structure.
Excessive present necessities: Delivering 100 W from a 12-V enter can require greater than 10 A of enter present, necessitating giant inductors, low drain-to-source on-resistance MOSFETs, and cautious PCB structure to handle losses on the ability elements.
Thermal bottlenecks: Most designs use buck-boost converters with 4 exterior MOSFETs, which might introduce substantial thermal stress underneath excessive load situations, particularly at low enter voltages and excessive output energy.

The shift to 48-V methods

The automotive business is transitioning towards 48-V energy architectures, which simplifies USB PD designs and improves thermal effectivity. With a better enter voltage, a buck-only topology is ample, changing the extra advanced buck-boost design. You’ll want fewer exterior elements (no four-FET bridge, and with considerably lowered inductor measurement and present ranking necessities).

For instance, TI’s LM72880-Q1 is an built-in automotive-grade buck converter appropriate for 48-V enter USB PD purposes. Determine 1 reveals two USB PD DC/DC converters: a buck-boost converter off a 12-V battery to the left and a buck converter solely off a 48-V battery to the proper. You’ll be able to see that the whole resolution measurement and elements are a lot decrease for the 48-V based mostly system. The 48V-based resolution achieves a 58% discount in PCB space, from 1.75 in² to 0.74 in².

Determine 1 Buck-boost topology for 12-V structure versus a buck-only topology for the 48-V structure. Supply: Texas Devices

Decrease switching frequencies may also help

Switching frequency has a direct impression on energy loss. Increased frequencies cut back the dimensions of passive elements however enhance switching losses in MOSFETs; decrease frequencies cut back switching losses however enhance inductor ripple, and will require bigger output filters.

Determine 2 compares the identical board working at totally different switching frequencies, with 400 kHz to the left and 200 kHz to the proper.

Determine 2 Thermal photos of the identical board working at a switching frequency of 400 kHz (left) versus 200kHz (proper). Supply: Texas Devices

The thermal take a look at evaluating a 400 kHz versus 200 kHz switching frequency (each at a 54-V enter, 5-A output, and with fan cooling) reveals that reducing the frequency reduces converter temperature by 18°C. The inductor temperature does rise barely from 60°C to 63°C, indicating the necessity for output filtering to stability the warmth distribution.

Thicker copper, extra PCB layers

PCB design performs a vital position in thermal administration. Growing copper thickness and including extra layers can considerably cut back temperature rise, particularly when fan cooling will not be accessible.

Determine 3 reveals thermal photos from two equally sized boards. The board on the left is 4 layers, every with 1 oz of copper. The board on the proper is six layers, with 2 oz of copper for the highest and backside layers and 1 oz of copper for the inside layers.

Determine 3 Thermal photos of two PCBs: one with 4 layers with 1 oz of copper every (left) and one with six layers with 2 oz outer layers and 1 oz inside layers (proper). Supply: Texas Devices

Each boards function at a 48-V enter and a 20-V output with 400 kHz switching. The board on the proper carries 5 A versus 4.25 A for the board on the left, but experiences 50% much less temperature rise from improved warmth dissipation. This underscores the significance of investing in copper-heavy PCB stacks for thermally demanding automotive purposes.

Thermal foldback

Conventional safety strategies usually depend on thermal shutdown, fully disabling the system when a temperature threshold is crossed. Whereas thermal shutdown protects {hardware}, this method is abrupt and disruptive. In purposes the place steady operation is preferable to finish shutdown—corresponding to in automotive infotainment, industrial USB charging, or shopper docking stations—thermal shutdown merely doesn’t present a great person expertise.

USB PD controllers at present, together with these from TI, assist firmware-configurable thermal foldback, a extra subtle, dynamic thermal response system that reduces energy supply as temperature rises. As an alternative of slicing energy totally, the controller steps down the V_BUS output energy, permitting the system to chill whereas nonetheless sustaining primary performance. It’s a “fail-soft” method that maintains security and system uptime.

TI’s USB PD controllers monitor system temperature by way of an exterior unfavourable temperature coefficient thermistor linked to an analog-to-digital converter enter. The firmware evaluates this voltage to evaluate temperature situations. Because the temperature rises, the system progresses by way of configurable thermal phases, every with growing ranges of energy discount.

In Determine 4, thermal foldback is split into three thermal phases, every representing a better stage of thermal severity:

Section 1: Delicate temperature rise. Energy is lowered barely to scale back thermal buildup.
Section 2: Intermediate temperature. Energy supply is throttled additional to stabilize the system.
Section 3: Excessive-temperature alert. Energy is considerably lowered or disabled to keep away from harmful overheating.

Determine 4 Thermal thresholds rising and falling with three principal phases of thermal foldback. Supply: Texas Devices

Every part is outlined by two voltage thresholds: a rising (Vth_R) and falling (Vth_F) threshold, creating hysteresis to stop speedy toggling between phases when temperatures hover round a transition level.

In response to part transitions, the USB PD controller will renegotiate the USB PD contract with the linked sink system. The utmost energy allowed in every part is configurable, providing exact management. For instance, if the utmost port energy is 100 W, thermal foldback may cut back the ability to 60 W when getting into part 1, 27 W in part 2, and seven.5 W in part 3.

Thermal foldback is now not a luxurious function; it’s a necessity in high-power USB PD designs. With firmware-configurable habits, TI’s USB PD controllers give engineers the flexibleness to keep up secure, environment friendly operation underneath thermal stress with out sacrificing usability or system availability. By stepping energy down intelligently as a substitute of shutting off totally, thermal foldback improves product reliability, extends element life, and delivers a greater end-user expertise in demanding environments.

USB PD thermal administration

Thermal administration is a crucial design consideration in automotive USB PD purposes. By leveraging higher-voltage methods, optimizing switching frequency, and investing in PCB design, you may considerably cut back heat-related stress and enhance total reliability. TI affords a spread of automotive-grade USB PD controllers and DC/DC converters, such because the TPS26744E-Q1 and LM72880-Q1, that can assist you design compact, environment friendly, and thermally dependable USB Sort-C charging options.

Josh Mandelcorn has been at Texas Instrument’s Energy Design Companies crew for 20 years targeted on designing energy options for automotive and communications / enterprise purposes. He has designed high-current multiphase converters to energy core and reminiscence rails of processors dealing with giant speedy load adjustments with stringent voltage underneath / overshoot necessities. He beforehand designed off-line AC to DC converters within the 250W to 2 kW vary with a give attention to emissions compliance. He’s listed as both an writer or co-author on 17 US patents associated to energy conversion. He acquired a BSEE diploma from the Carnegie-Mellon College, Pittsburgh, Pennsylvania.

Seong Kim is an Functions Engineer at Texas Devices, the place he focuses on automotive USB Energy Supply and DC/DC converter options. With over a decade of expertise at TI, Seong has supported a variety of embedded and energy designs – from Wi-Fi/Bluetooth MCUs for IoT to high-speed USB-C and PD methods in automotive environments. He works carefully with automotive OEMs and Tier-1s to allow dependable fast-charging methods, and is considered a go-to professional on PD integration challenges. Seong has authored technical collateral and coaching supplies used throughout TI’s world buyer base, and is listed as an inventor on a pending U.S. patent associated to USB Energy Supply. He holds a BSEE from the College of Texas at Dallas and is predicated in Dallas, Texas.

Stefano Panaro is a Programs Engineer in Texas Instrument’s Energy Design Companies crew targeted on designing energy resolution for Automotive and Communications purposes. His principal focus is on the design of DCDC converters, with an influence stage starting from mW to kW. He acquired his BS in ECE and his MS in Digital Engineering from Politecnico di Torino, Italy.

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