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Simplify Automotive Powertrain Design with Distributed Power Supply

Simplify Automotive Powertrain Design with Distributed Power Supply

The many benefits of a distributed power supply can be realized through a gate-drive optocoupler, ideal for use in automotive powertrain components for electric-vehicle (EV), hybrid electric-vehicle (HEV) and plug-in hybrid electric-vehicle (PHEV) applications.

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Conventionally, a centralized power supply is applied in an automotive powertrain through a multichannel transformer that converts 12-V dc power from the battery to supply six, isolated gate-drive circuits (Fig. 1).

Designers face many challenges in a centralized transformer model, including layout complexity and electromagnetic interference (EMI). There are also challenges associated with larger board space and higher printed-circuit-board (PCB) cost, as more layers are needed to route isolated signal/power lines.

1. Block diagram of centralized power conversion. (Courtesy of Broadcom Limited) (Click image to enlarge)

 A distributed power supply can be easily built using a few discrete components and a small high-efficiency transformer placed next to the IC integrating an automotive-grade smart gate drive with integrated flyback controller (Fig. 2). This reduces the overall footprint and minimizes EMI and noise coupling between insulated-gate bipolar transistor (IGBT) channels.

2. Block diagram of distributed power conversion. (Courtesy of Broadcom Limited) (Click image to enlarge)

Design Simplicity

With a distributed-power-supply architecture, designers have more flexibility in planning the circuit layout; the low-voltage plane can be distinguished and isolated easily from the high-voltage plane. In addition, overall PCB routing becomes more manageable and straightforward.

3. Six-channel IGBT gate-driver board with centralized-power-supply design. (Courtesy of Broadcom Limited)

4. Six-channel IGBT gate-driver board with distributed-power-supply design. (Courtesy of Broadcom Limited)

Figures 3 and 4, respectively, compare a six-channel IGBT gate-driver board based on a centralized power supply versus one based a distributed power supply. It’s obvious that a distributed-power-supply architecture offers a simplified PCB layout and more efficient routing. There are no PCB traces or power planes crossing between low- and high-voltage circuits, enhancing the signal integrity and avoiding unfavorable noise disturbance to the signal lines.


The transformer in a distributed power supply is typically 14 times smaller in volume versus a centralized transformer. Figure 5 shows an individual transformer placed next to a centralized transformer.  The table shows actual dimensions of a centralized transformer and an individual transformer.

5. Size comparison between an individual transformer and a centralized transformer. (Courtesy of Broadcom Limited)

A low-profile single transformer for each driver also improves reliability and robustness, compared to heavier, higher-profile transformers that are more vulnerable to mechanical vibration. While the power-supply capacitors used in a centralized-power-supply architecture tend to be larger and in a radial CAN package with a high profile, designers choose a smaller SMD package capacitor for a distributed power supply. The voltage ratings required for these capacitors is at least 10 to 20 V lower than those required for a conventional centralized-power-supply circuit.

Cost Savings

On top of design simplicity and robustness, another benefit of choosing a distributed power supply is cost savings through the minimization of overall board size and PCB layers. A distributed system of drivers and a single transformer allows these components to be placed closer together, saving critical board space.

Figure 6 shows an example of a well-designed half-bridge gate-driver circuit (top and bottom channel), placed within a 39.7 mm (width) by 52 mm (length) area, that’s less than 50% of a standard card’s size. In this instance, a six-channel gate-driver circuit may only require a PCB area of one and a half that of a standard card’s size.

6. Half-bridge gate-driver board design can be as compact as half a standard card’s size. (Courtesy of Broadcom Limited)

A distributed system also helps reduce the number of PCB layers because there’s no crossing of low-voltage traces/planes between the high-voltage traces/planes. This ensures that no extra layers are needed for passing the crossing signals. Figure 7 shows an example of a compact six-channel gate-driver board designed for the Fuji M651 IGB that uses only four layers of PCB.

7. Compact six-channel gate driver with distributed-power-supply design using only four layers of PCB. (Courtesy of Broadcom Limited and Fuji Electric)

Better EMI Performance

A large six-channel transformer in a centralized power system typically emits a lot more EMI noise than individual small transformers. In a distributed power supply, each smart gate-drive optocoupler drives an individual transformer with an integrated dc-dc controller to provide power to the secondary side for driving the IGBT arm.

Measurements show significantly higher EMI noise from a centralized six-channel transformer (Fig. 8) as compared to small individual transformers (Fig. 9).

8. EMI measurement from a centralized six-channel transformer. (Courtesy of Broadcom Limited)


A distributed power supply further simplifies automotive multichannel IGBT gate-drive design versus that of a gate-drive board using a centralized power supply. Furthermore, it improves robustness, EMI performance, and module cost when compared to a conventional centralized-power-supply architecture.

9. EMI measurement from a small individual transformer. (Courtesy of Broadcom Limited)



 “Automotive R2Coupler Smart Gate Drive Optocoupler,” Broadcom Limited, 2016.

“AV02-4412EN Design of Isolated Flyback Converter for IGBT Gate Driver,” Application Note, Avago Technologies, December 2015

 “IGBT Modules for EV, HEV,” Fuji Electric, 2016.

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