🎉 Hope you’ve had a wonderful time with your loved ones during the Holidays period.
🚀 They say “New year, new beginnings”, right?
The goal for this year, as far as the Frenetic Newsletter goes, is to continue exploring the Magnetics and Power Electronics world, providing interesting knowledge and attractive case studies.
💡 We believe that raising awareness over problems and solutions, as well as keeping up with the market needs, has proven to be a good recipe. So, Pablo and I will do our best to keep things light and interesting for this new year!
😅 Alright, alright, the speech is over… Boredom is kicking in…
🔙 USB charging evolution
We all remember the days where we used to see a new USB port almost every year. USB micro, mini, type a, type c, and so on…
At first each device had its thing.
Then the USB evolved from a data cable to a power cable as well, and that’s the interesting part for us.
Then the world shifted to USB-type C, which has a unique feature: no up/down direction, just plug in. But again, many well-known brands were using their proprietary hardware to charge devices. So, you needed a specific charger to rapidly charge your device. Any generic one would recharge your device at a fraction of the original speed.
Then USB-type C/PD was introduced, as a way to make chargers talk to the devices, so a universal cable-charger can be used to charge all devices from 2.5-100W and lately up to 240W with PD 3.1 (released in May 2021).
Figure 1. USB charging evolution
🔎 USB Power Delivery (PD) – What is it exactly?
USB PD is a specification that allows the output voltage of a power supply to be programmed by the load. That’s it, basically. The device that needs to be charged communicates with the charger signalling the appropriate voltage that the charger itself should output.
⚠️ USB-type C is merely the physical specification of the connector. It can either support or not PD functionality.
In a nutshell USB 2.0, USB 3.1, USB-C all output 5V at a current range from 500mA up to 3A. In case we need other voltage than 5V, or higher than 3A, then the USB-type C needs to support the PD functionality.
Figure 2. USB charging protocols
📈 In Figure 2 we can see that USB PD 2.0 and 3.0, released before 2015, had the same fixed voltage current levels. In 2017 PD 3.0 PPS came into market, including the fixed voltage of its predecessor, but also variable output voltage depending on the state of battery charge.
After 2021, PD 3.1 was released and it contained the capabilities of PD 3.0 and also the AVS mode of operation with variable voltages going up to 48V/5A! The difference between PPS and AVS variable voltage modes, although similar in function, is that AVS doesn’t support current limiting operation, and the voltage unit step is set at 100mV (20mV for the PPS).
⚙️ USB PD 3.0 Flyback 60W Design
As experts in Magnetics design, we always try to find new ways to enhance our tools and products in order to reduce the timing. We have also decided to focus on proven transformer and inductor designs that we can get specifications from, in order to create validated and manufacturable designs and building up a library.
With Frenetic, you can start creating your Magnetics by using these proven designs, or even ask directly for samples.
⚡ This week we will design a generic transformer for a PD 3.0 version controller IC. The set of voltages are 5,9,15,20V at 3A. Of course, instead of fixed voltages, the controller can implement the PPS mode, as long as the power output is set at 60W maximum.
Figure 3. Transformer windings arrangement
Key features-specs
👉 Triple insulated flying lead wire secondary (orange coloured)
👉 Primary, Auxiliary 1 are round enamelled wires – no need for more insulation
👉 Insulating the outer transformer core with tape is necessary for isolation purposes.
👉 Pinout can be modified freely
Tab 1. Transformer basic specs
Let’s compare the hardware results for the similar transformer built in RDR-838 app note (Power Integrations) to see how Frenetic simulations compares to it.
Tab 2. Operating conditions at 25°C ambient – free convection
💭 Discussion
In Table 1 we have compared the thermal images of the transformer with our compatible design. You can see that there is a close thermal match for each input voltage/output voltage scenario. The average thermal difference is 5.9% and the maximum in one case is 15%.
Practically speaking in this library design:
✅ Losses are low, between 0.54-1.63W, depending on the input-output voltages
✅ Hotspot temperature is between 48-84°C at a 25°C ambient temperature
✅ Additional windings for EMI shielding can be added, if needed
✅ There is space for other auxiliary windings
✅ Cheap and easy to manufacture
The TempV2 Model™️
✅ 87.5% of the cases listed have a maximum temperature difference of 4°C❗
✅ 12.5% of the cases listed we have a 13°C difference
These percentages match our lab measurements of 20 different magnetic designs that have been tested for their thermal response.
💥 Now you have a starting point to start designing your own USB PD Flyback transformer! Let’s expand and cover more power ranges!
🚀 Discover how to design a USB PD 3.0 Flyback 60W with Frenetic Online!
Apply for a demo and explore all the possibilities that our platform offers.
😎 Hope you liked it, and see you next week!
References
[1] Bruce Rose, 2020, “USB Type-C, Power Delivery and Programmable Power Supply”, Power Blog, May 12, Available at: cui.com/blog/usb-type-c-pd-and-pps
[2] Gines, 2021, “USB PD 2.0 vs 3.0 vs 3.1 Comparison | How Far Have We Come?”, July 31, Available at: thephonetalks.com/usb-pd-2-0-vs-3-0-vs-3-1/
[3] GRL Team, 2021, “Introduction to PD 3.1 – the Latest USB-IF Power Delivery Specification”, September 14, Available at: graniteriverlabs.com/en-us/technical-blog/usb-power-delivery-specification-3-1
[4] Applications Engineering Department, “Reference Design Report for 60 W USB PD 3.0 Power Supply with 3.3 V – 21 V PPS Output Using InnoSwitchTM3-PD PowiGaNTM INN3879C-H801”, Power Integrations
