Module Power Supply: Four Major Precautions

Module power supplies serve a broad role in circuits, providing power for digital or analog loads like DSPs, FPGAs, and microprocessors while significantly saving space on PCBs. Given the widespread use of these power supplies, this article will outline the precautions to consider when utilizing module power supplies in daily applications.

Light Load Operation

In general, module power supplies require a minimum load, which varies by manufacturer but is typically around 10%. This is because when the load is too light, the energy storage components struggle to maintain a continuous current, leading to discontinuous current flow and unstable output voltage. This is inherent to the operational principles of the power supply itself. However, how should users handle light load or even no-load scenarios? The most straightforward and effective solution is to add a nominal dummy load, approximately 2% of the output power. This can either be pre-set by the module manufacturer prior to shipping or installed externally by the user in the form of a suitable resistor. It's important to note that choosing the former option reduces the efficiency of the module. Some power supply topologies, however, do not impose a minimum load requirement, such as the E-series module power supplies from Dinglixin Company, which support operation from no load up to full load.

Multi-Output Power Distribution

When selecting multi-output module power supplies, it is crucial to consider the power distribution across different output channels. Taking dual-output products as an example, there are usually two types: one is a balanced dual-output where the current on both channels is equal; the other is an unbalanced dual-output where the main channel carries a higher current than the auxiliary channel. For such products, it is advisable to select an auxiliary-to-main channel power ratio between 1/5 to 1/2, ensuring that the voltage stability of the auxiliary channel remains within ±5%, otherwise, the voltage could become excessively high or low. Conversely, if the dual-channel loads inherently differ, it is best not to opt for a balanced load type module power supply, as these are specifically designed for symmetrical loads. Using them under unbalanced conditions can result in poor voltage accuracy on the auxiliary channel.

Reducing Temperature Rise of Module Power Supplies

The operating temperature of internal components directly impacts the lifespan of the module power supply; lower component temperatures lead to a longer module life. Under given operating conditions, the loss within the module power supply is fixed, but the temperature rise can be mitigated by enhancing heat dissipation conditions, thus significantly extending its service life. For instance, module power supplies rated over 50W should be equipped with a heatsink, and the larger the surface area of the heatsink, the better the heat dissipation. The orientation of the heatsink should facilitate natural air convection. For powers exceeding 150W, in addition to installing a heatsink, a fan can be added for forced air cooling. Furthermore, in environments with high ambient temperatures or poor air circulation, the module must be de-rated to reduce power consumption and consequently lower the temperature rise, extending its service life.

Reasonable Installation to Reduce Mechanical Stress

The output method of module power supplies involves metal pins, and the connections between the module power supply and external circuits, as well as between the metal pins and the internal circuitry, are made via soldering. In environments with high mechanical vibration, especially when heatsinks are added to high-power module power supplies, the situation becomes more critical. While module power supplies are generally filled with thermally conductive insulating rubber, which provides good cushioning and protection for the components, the solder joints might not withstand intense vibrational stress and could break, leading to failure of the module power supply. In such cases, additional securing and cushioning measures must be implemented alongside soldering. For example, clamps or bolts (for modules with tapped holes) can be used to secure the module to the chassis, large PCBs, or other components with good vibration resistance, and some elastic material can be placed between them to cushion the stress generated by vibration.