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USB-C Power Delivery Sink (BCR)

A USB-C PD Sink up to 20V 5A based on the Cypress CYPD3177 USB PD Controller

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USB-C PD offers the option to negotiate power delivery from a compatible power supply. This board plays the role of a sink device, enabling any device to be powered from a USB power supply. Any type of power connector can be attached through a 2-pin screw terminal or directly soldered into the PCB for a lower profile.
The voltage can be set to 5V, 9V, 12V, 15V or 20V and current up to 5A is possible.
BCR stands for Barrel Connector Replacement, the term is invented by Cypress, the manufacturer of the controller chip in use here.
Rev 2 design is on the way. Major change is the switching MOSFET split into 2 single FETs for better temperature management. Details to follow in a separate log.

This board has the goal to replace random power adapters with a standardized way to use a USB-C power delivery (USB PD) adapter instead. For regular operation, no programming or software configuration is involved with this design. All options are set through resistor values. 

If needed an I2C interface to a microcontroller is available, to access status and control registers. This part of the board is separated through a break-off tab (mouse bits) and can be snapped off. 

I made the conscious design decision to not add a USB-A connector option at the output end. I did not want to build a device, that is capable of putting more than 5V on the VBUS pin of a regular USB cable and potentially destroy the device that is plugged in. 

All Features:

  • USB-C PD Power Delivery Sink
  • Selector switch for 5V, 9V, 12V, 15V or 20V
  • Max current 5A, settable in 250mA steps through resistor options
  • Red LED to indicate failed power request
  • I2C telemetry interface to controller chip
  • Snap off option for telemetry interface
  • For fixed voltage, the switch can be replace by wire jumper
  • small form factor to be heat shrinked as part of the power cable
  • Size 48mm x 15mm (without telemetry interface)
  • Height 12mm with screw terminal and switch, 6mm without.
  • 2oz copper to safely handle 5A
  • Lead free RoHS compliant

SC USBC-Sink_ver1.pdf

Schematic Rev1

Adobe Portable Document Format - 70.60 kB - 12/15/2019 at 03:19

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  • 1 × Cypress CYPD3177 USB-C Pwer delivery Controller QFN-24
  • 1 × Nidec Copal SS-10-15SPE 5 pos rotary switch TH
  • 1 × METZ CONNECT 31060102 2pin screw terminal 2.54mm LCSC PN C123214
  • 1 × Jing Extension C168688 USB-C plug mid mount LCSC PN C168688
  • 1 × Infineon IRF9358 Dual P-channel MOSFET SO-8

View all 10 components

  • The heat is on.

    MagicWolfi12/18/2019 at 02:03 0 comments

    I have built a load to test the power draw of the board. It is 2x 2Ohm 50W resistors in series. This gives me a current draw of 5A at 20V. Cooling is not adequate yet, with 3.66A @ 14.6V the heatsink gets up to 92degC, with 3A @ 12V I am measuring 72degC. The fan cannot keep up with 5A @ 20V, the temperature rises to over 100degC in less than 2 minutes.


    I need a bigger heat sink.

  • HPI telemetry

    MagicWolfi12/15/2019 at 18:05 0 comments

    I managed to talk to the BCR over the I2C interface, which is not quite straight forward, as the chip adds a mandatory 3 to5 cycle clock stretch. My solution so far is a bus pirate set to I2C 5 kHz clock speed. With those commands I am able to read out ID and status registers, even though the response does not match the datasheet for the IDs.

    [0x10 0x00 0x00[0x11r]
    [0x10 0x02 0x00[0x11rr]
    [0x10 0x0D 0x10[0x11r]
    [0x10 0x08 0x10[0x11r:4]
    

    No luck using an Arduino Due ( which has 3.3V IOs) so far. :(

  • FET power dissipation

    MagicWolfi12/13/2019 at 18:38 0 comments

    The switching FET in this circuit has to carry up to 5A, which is significant. Thus the drain source resistance Rds-on is important to be minimized and power dissipation through the package needs to be calculated. Here are some test results, in the form of voltage drop over the dual DS junctions.

    U load [V] I load [A]V drain-source x2 [mV]Tjunction [degC]P diss [mW]Rdson [mOhm]
    5.071.2756.529.572
    22
    9.032.26  
    61.633.7139
    14
    11.983.00
    89.541.8268
    15
    14.623.66
    106.549.3389
    15
    19.674.92
    141.068.3693
    14

  • Voltage and Current settings

    MagicWolfi12/11/2019 at 20:19 0 comments

    As a leaflet, I am copying the resistor values for the voltage and current settings here:

  • Reminder to self: it works better when you do it right!

    MagicWolfi12/10/2019 at 23:12 0 comments

    Here is the USB-C PD spec for maximum power:

    VoltageCurrentPower
    5V3A15W
    9V3A27W
    12V3A36W
    15V3A45W
    20V5A100W

    I had the maximum current set to 5A and testing with my power bank failed, because it can only deliver 5V or 9V with 2A max. Reducing the max current to 2A made everything work. Of course if I request higher voltages, negotiation still comes up with a disabled power switch, which makes sense now. I received a USB-C PD wall power supply in the meantime and it can and does deliver 20V at 5A and everything in between. Testing is done in very short cycles because my 100W 4 Ohm test load heats up really fast. I need a bigger heat sink. Also thinking about using light bulbs as load, what a bright idea.

  • Assembly

    MagicWolfi12/08/2019 at 20:54 0 comments

    So.....

    Assembly of the QFN-24 parts were as simple as possible. A tiny bit of solder on the center pad on the PCB. Then hit it with hot air until the solder melts. Place the part, that all other pins line up. Once cooled, the part will not move any more and the external pins can be soldered by applying a liberal amount of flux, then dragging the iron tip with some solder on it, across the pins until all pin accepted some solder. Done!

    All other components are easy to solder.

    And then there was the 5-postion rotary switch. Unfortunately, the datasheet showed the pinout in bottom view. Luckily it is a through hole switch, so I can just solder it from the bottom and it is going to work but a revision 2 will happen very soon.

    The mid mount USB-C connector is a thing of beauty. Through hole tabs make it really sturdy and the VBUS and GND pins are grouped together, which makes it easy to fan out a thick trace for the high current. And the profile height is very low.

  • PCBs arrived

    MagicWolfi12/04/2019 at 19:49 0 comments

    The PCBs arrived from JLC. Optical inspection is a pass and I can clearly see the thicker traces with this 2oz copper layer design. I'll do some testing first before I am going to test the break-off tab feature. 

    All components are here also, so I am off to the workbench.

View all 7 project logs

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Discussions

patrick wrote an hour ago point

Hi,

I just came across these. though they don't provide all voltages, they are a lot smaller. I can't say anything about the quality though. do you have any insight in where your solution trumps this?

https://nl.aliexpress.com/item/4000459863567.html?spm=a2g0s.9042311.0.0.617e4c4d3s6ccU

Patrick

  Are you sure? yes | no

Peter Senna Tschudin wrote 01/12/2020 at 20:16 point

Are you planning to sell it too? I'm definitively interested in buying a few.

  Are you sure? yes | no

patrick wrote 12/10/2019 at 14:56 point

Great. 

If it is resistor value based and the voltages are set, that also means no programming need to set it up?

Looking forwards to it! what is you expected planning?

  Are you sure? yes | no

MagicWolfi wrote 12/11/2019 at 00:53 point

Exactly, this is what I love about this chipset. No programming involved. AWESOME.

And now the pressure is on, to commit to a schedule. If all testing goes well and I don't do any stupid mistakes on the next rev of the layout, I might have hand-assembled units end of January.

  Are you sure? yes | no

patrick wrote 12/09/2019 at 22:45 point

Hi very interesting project and definitely following this! would be interested to buy a couple if they are as affordable as they look ;-)

would it be possible to re-program the voltages to different V/A combinations?

Patrick

  Are you sure? yes | no

MagicWolfi wrote 12/09/2019 at 23:57 point

Hello Patrick,

Thanks for your interest. Yes, the plan is to sell them once everything is working, pricing is not fixed yet.

The voltage settings are limited to 5V, 9V, 12V, 15V or 20V. Current settings are very flexible in steps of 250mA from 0 to 5A, but it depends also on the source, if it can limit the current in those small steps. All settings are through resistor values on the board.

 - W.

  Are you sure? yes | no

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