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PMP11236: UCC28881

Osman CALISIR
Prodigy 30 points
Part Number: PMP11236
Other Parts Discussed in Thread: UCC28881, PMP20745

Hi dear TI Experts,

I want to use PMP11236 reference design for my project. I need to connect one of both 220V AC or 24V DC in the same plug(only one). Thats why I choose this part(It is okay if you suggest another one). And, here is the problem: I want to use it for powering and Arduino board, relay board and 7-segment board. But the PMP11236 says, it is supply 20mA for 5V. Is the PMP11236's power supply okay for this kind of application?

Here is the board that I have designed so far;

Here, I am not using 24V output, only 5V output.

Best regards;

Osman

  • 0
    TI__Mastermind 31340 points
    Hello Osman,

    Thank you for your interest in the UCC28881 integrated switcher.

    The circuit of PMP11236 is a non-isolated off-line buck topology for a total output power level of ~2.9W (24V *(100mA + 20mA) = 2.88W). The 5V, 20mA portion consists of a linear regulator with dropping resistors (R2-R4), so that load current is added to the 24V output load. If all that you need is a 5V output, then I recommend to redesign for 5V only, and eliminate the 24V output.

    However, much more information is needed to make the correct design decisions.

    1. For your application, you need to add up the total loading that you will apply to the 5V output.
    I am not familiar with an Arduino board, but I imagine that its 5V current level might be much higher than 20mA, plus the relays and 7-segment (LED?) current. Determine the maximum current required from 5V.

    2. The UCC28881 has an integrated MOSFET for small size, but that also limits the maximum power processing capability of the device. The datasheet shows that you can expect to be able to support up to about 4.5W of output power for the normal input line voltage range. At 5Vds output, this is less than 1A. However, the UCC28881 also has a maximum output current limitation of 225mA, so at 5V you can only get 225mA (1.125W). Your total load must sum up to be equal to or less than this.

    3. Your desired input combination of 220Vac and 24Vdc results in an unusually wide input range. This wide range will complicate the inductor design since the duty-cycle variation will be quite wide. Also, you’ll need to determine if the input voltage limits are truly 24Vdc up to 220Vac or some percentage margin for each of those nominal values. For example 24Vdc +/- 15% = 20.4Vdc minimum, and 220Vac +/-15% = 253Vac *1.414 = 358Vpeak. This design may have to operate from 20V to 360V, which is an 18-to-1 variation of input voltage.

    4. The UCC28881 is configured for non-isolated power conversion. Since you wish to power a logic board from a high-voltage AC line (220Vac), you will most likely require safety isolation between the line source and the output to prevent a shock hazard. In fact, if your logic board will connect to some other grounded equipment, it will not be possible to operate from an AC outlet without using an isolation transformer between the line and the converter.

    Since this application appears to be a University project and since safe power conversion design requires significant knowledge in high voltage design and safety agency requirements, I recommend that you follow step 1 above to determine your power needs and then search for and purchase a commercial "off-the-shelf", safety-isolated, wide input-range power converter module from an electronics distributor.

    If your project is actually the power converter design itself, I suggest to look at the PMP20745 reference design.
    www.ti.com/.../PMP20745 It is intended for very wide input range and has an isolated 15V, 0.6A output (9W). The transformer and output stage will have to be redesigned for 5V, and if you require more power the entire converter will have to be upgraded. However, this will give you an idea of what to expect for your application.

    Regards,
    Ulrich