TDK patents thermal sensing for modular 800W power supply
TDK has developed a configurable 800W power supply that is half the size of its previous range and quieter for medical and high reliability industrial applications.
“We introduced the concept of a modular power supply back in 1979 with the rectification and the individual DC-DC modules to allow for customisation without all the development costs,” said Chris Maidment, technical marketing manager at TDK-Lambda.
“MU is our four slot device with 800W where we have managed to shrink the size of the supply by half compared to the five slot QM5. It’s a 1U height so it’s significantly smaller height and width, and there is an auxiliary output that gives you a 5th output.”
The MU4 measures MU4 measures 89 x 257.5 x 41mm (W x D x H) and will be manufactured in the UK at the TDK-Lambda plant in Ilfracombe.
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The company has applied for a patent around the communication scheme in the thermal management of the unit, using temperature sensors on each of the modular DC-DC converters as well as the output. These feed back from high side to low side to a controller that varies the speed of the single fan. As the unit is only 1U high, the fan has to be smaller and so has to be faster and more noisy to provide the required airflow at peak usage.
However each of the modules also has a thermal pad that connects to the casing to distribute the heat more evenly, reducing the airflow requirement and allowing the fan to run slower and quieter. This Intelligent Fan Control keeps the temperature down and extends the lifetime of the supply.
“We have applied for a patent on the temperature sensing of the main converter with sensors on each DC-DC module so any one of the modules can call for more airflow,” said Medment. “The patent is for the communication between the high side and low side with sensors reporting back to a microcontroller so we can monitor the fan speed. That data goes back to a PMbus so the user can monitor that as well.”
The MU4 is aimed at medical applications with 1MOPP and 2MOPP isolation but the high reliability and thermal management is also aimed at industrial applications such as test equipment.
“We want to minimise the number of variants that we have, so we have one module for medical but is also released to the industrial market,” said Maidment. “Our customers like the medical certification as it gives the long life and reliability as well as the low current leakage () of 300µA so we don’t distinguish between the two.”
“A pure industrial version of MU would require a different rectifier and case and that would be another design process and materials so we want to optimise for both medical and industrial customers. In that way we can minimise the number of modules and base units. With the problems of sourcing of components having a minimal supply chain is important.”
Initially, nine modules are available, offering a continuous range of voltages from 3.3V to 104V with ratings from 150W to 480W. Options include a 5V / 2A standby voltage, fan fail signal, inhibit and enable (for individual or all outputs), DC good, PMBus communication, and current share for parallel configurations.
The MU4 series has an input to output isolation of 4,000Vac (2 x MoPP), an input to earth isolation of 1,500Vac (1 x MoPP), and an output to earth isolation of 1,500Vac (1 x MoPP) for suitability in B and BF rated medical equipment.
Safety certification is to IEC/EN 60601-1, ES 60601-1. IEC/EN/CSA/UL 62368-1, (IEC/EN 61010-1 designed to meet) and is CE / UKCA marked to the Low Voltage, EMC and RoHS EU Directives and UK regulations. The models meet EN 55011-B, EN 55032-B radiated and conducted emissions and comply with the EN 60601-1-2:2015 (Edition 4) and EN 61000-4 immunity standards.
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