I haven’t updated my blog recently because I’ve been quite busy working on a DC-DC converter circuit board for my Raspberry Pi 4B. Although the circuit and principles aren’t complex, this isn’t my area of expertise, so it took quite a bit of time. The work is now nearing completion, so in the coming period, I’ll wrap things up and summarize the issues encountered and the insights gained during the process.
The entire circuit is not complex in terms of functional structure: First, there’s the PoE-PD section, which communicates with PoE devices to obtain power. Then, the core DC-DC module converts the 48V input from PoE to a 5V output. Additionally, several Raspberry Pi interfaces are extended on this circuit board for connecting a laser rangefinder, two cooling fans, and a temperature sensor module.
After completing the first version of the circuit design, I soldered and powered it up, only to discover a few issues. Fortunately, identifying and resolving these problems didn’t take much time. Seeing my designed circuit work properly was incredibly satisfying. However, I soon noticed a significant flaw: although the circuit could be correctly mounted onto the Raspberry Pi, the heat-generating components of the Raspberry Pi and the power board were too close and facing each other. This was highly detrimental to heat dissipation. As a result, I spent some additional time redesigning the power board. The new version is theoretically stackable on the Raspberry Pi while fully addressing thermal performance.
To further enhance thermal performance, I designed a dedicated heat sink that not only provides passive cooling for both the Raspberry Pi and the power board but also includes a mounting space for a cooling fan to enable active cooling. Naturally, the cooling fan requires power and a PWM signal to operate. On the power board I designed, I’ve reserved two sets of fan drive interfaces. This means that, in addition to installing an active cooling fan within the heat sink in the middle, an additional cooling fan can be installed in another location based on specific needs.
Work in progress, to be continued…