[Thermal imaging] Internal view and test of the YSDS-60-5 4.5 A 22.5 W 5 V DIN rail power supply

Join me for a look inside and a practical test, including a thermal imaging analysis, of the Sunny YSDS-60-5 power supply, designed for DIN-rail mounting. The unit supplies 5 VDC at a maximum current output of 4.5 A and a power output of 22.5 W, operating with an input voltage of 90–264 VAC and a frequency of 47–63 Hz. The manufacturer specifies an efficiency exceeding 85 per cent, ripple of 80 mVp-p, a full suite of overload and overvoltage protection features, and operation at temperatures ranging from -20 to +70°C, all housed in a 52x90x58 mm enclosure with an IP20 rating.

The casing is held in place by clips. You don’t even need to unscrew any screws. Inside, we can see a design based on a single-sided circuit board and a large heat sink.

A preliminary visual inspection confirms the presence of the promised components and safety features. There are input filters, a fuse, a varistor and a Y-class capacitor connecting the primary and secondary sides; at the output, next to the capacitor bank, there is a choke.


The underside of the PCB is protected by a layer of varnish:

Despite this, I managed to make out the converter controller’s designation – it appears to be an OB5269.

According to the data sheet, the OB5269 is a PWM controller with a built-in high-voltage start-up circuit. It features a fixed operating frequency of 65 kHz, low EMI and very low no-load current consumption (thanks to Burst Mode). It also features a full suite of protection circuits: from thermal (OTP) and overcurrent (OCP) protection to overvoltage (OVP) protection.

A glance at the data sheet immediately reveals a typical application circuit. This is a classic flyback topology with an external switching transistor. The chip features an integrated start-up circuit powered from the HV pin. Feedback is implemented in the simplest, traditional way – it is based on an optocoupler and, most likely, a TL431 on the secondary side. A cheap, tried-and-tested and widely used configuration.

I then moved on to practical testing. The voltage can be adjusted slightly using a potentiometer within a range of approximately 5 V. The power supply manages to deliver the promised 4.5 A, although the voltage drops slightly as it approaches this limit. Once 4.5 A is exceeded, the voltage drops slightly faster; the power supply limits the power but does not cut off the output immediately.

I loaded the power supply with a current of 4.5 A for 2 hours and immediately noticed that the voltage dropped slightly after a while – probably due to heating. After two hours, I checked the temperatures.

The Schottky rectifier diode at the output gets the hottest. Unfortunately, the electrolytic capacitors inevitably heat up as well. I wonder to what extent this shortens their lifespan?

In addition, the shunt resistor heats up, which, I assume, is used for current limiting.

The highest temperature recorded was just under 70 °C.

To sum up, the power supply seems to deliver what the seller promised, although I am concerned about how long those electrolytic capacitors at the output will maintain their performance. There are indeed filters inside, and it also features protection against overheating and overload. I haven’t tested the ripple, though at the moment I believe this power supply will work well for my purposes, especially as I won’t be running it at full load but will leave a margin of around 1 A. It’s also worth noting the housing, which provides poor cooling in a cramped setup, but this is rather hard to avoid with passive solutions. Of course, apart from the housing, a DIN-rail power supply like this is no different from a standard power supply.
Do you use DIN-rail power supplies, and what factors do you consider when choosing them?