Interface for USB Type C Chargers with PD/PPS
- mini: 35 mm x 21 mm x 12 mm (length x width x heigth)
- 0.96 color display (160 x 80 px)
- only 3 buttons to operate
- operation through 4 menus
- voltage / current selection
- power profile selection
- setup
- automatic restoration of last settings after power on
- automatic output enable upon succesfull restoration of last settings
- regulation mode off = done by power source or 3 different point of load controll loops
- brightnes controll
- calibration option for current measurement
- RGB LED for output state
- remote UI via VT100 serial terminal
- serial programming interface for intergration in controll applications
- SD Card for future use (eg. data logging)
- all essential data at a glance
- operating mode
- set voltage / current
- output voltage / current
- input voltage
- fixed voltage 5 V / 9 V / 12 V / 15 V / 20 V, up to 3 A / 5 A
- adjustable voltage 3.3 V - 21 V up to 5 A
- adjustable current limit 50 mA to 5 A
- beeper (futer use)
- IMU (futere use)
- temperature sensor (future use)
- audio decoder (future use)
-
the menu
This project originates in a colaboration with embres GmbH.
They did a great job in
- supporting in sourcing of parts
- PCB desgin
- manufacturing PCBs
What the heck is a PD-PPS-Controller?
This is the mini:
click here for details on the mini or continue reading
for more information. There are other versions udner development, see motivation
and hardware for an in depth coverage.
A USB C charger with Power delivery capabilities has some nice and very useful features:
The output voltage as not fixed to 5 V but will be negotiated between source (the charger)
and the sink (your device).
The most common features are the fixed profiles with fixed voltages of 5 V, 9 V, 12 V, 15 V
and 20 V with up to 5 A (100 W chargers).
This covers the most common voltages of wall mount power supplies.
Part of the power delivery standard are the augmented profles or programmable power supply.
These profile offers an adjustable voltage from as low as 3.3 V up to 21 V and 5 A maximum
current. Adjustable in 20 mV steps and programmable current limit from 1 A to 5 A in 50 mA
increments.
This is allmost as good as a lab power supply. All you need ist a device which is capable
of communicating your request to the PD source.
Whit PD 3.1 the Power Rating has even increased to 140 W using up to 28 V with 5 A.
Unfortunatly this is currently out of the scope of this project.
The PD-PPS_Controller does not only request the desired voltage and current from the PD
source, it implements a closed loop controller to keep the output voltage within 20 mV of
the requested voltage with a precise constant current mode when operatet in PPS mode.
The PD-PPS-Controller offers a simple UI for direct control, a
Terminal UI and a serial programming interface
for integration in your own applications.
There are some interesting boards out there to trigger USB Type C power delivery sources. Such as the ZY12PDN.
You can find many details at Manuel Bl.. These modules allow you to
step through the available fixed profiles which include 5 V, 9 V, 12 V, 15 V and 20 V.
There are many others out there, some have selectable voltage through resistors or jumpers.
I managed to get my hands on one the utilises a HUSB238 chip from Hynetek. This one
is programmable either through resistors or a microcontroller using I2C.
Unfortunatly this is well below the capabilities of a PD 3.0 compliant power supply. All these modules use only so called fixed profiles. But there is the PPS Mode (porgrammable power supply). This uses the augmented profile. The Augmented Profiles is specified from 3.3 V to 21 V and up to 5 A. The voltage can be selected in 20 mV steps and the maximum current can be selected in 50 mA steps.
And here is my idea: Have you ever used one of those chunky lab power supplies eating up most space on your desk? These power supplies often range from 0 - 30 V and 0 - 5 A. As far as I am concerned, I mostly use 5 - 15 V at a few amps.
What if we can use this augmented profile to mimic a lab power supply? We would need a chip which is capable of
requesting this profile from a suitable PPS capable USB Type C power supply.
Well there is the easy and the hard way:
The easy way would be to tell some chip to request the desired voltage form the power supply.
Such a chip is the AP33772 available from Diodes Incorporated. You can get a dedicated
evaluation board form Diodes or other manufacturers eg. MICROE. This is the
USB-C sink 2 click form MICROE:
This chip has been marked as NRND and was replaced by the AP33772S. The "S" version is even easier to use but has a huge
downside: It allows only 100 mV and 250 mA steps.
The hard way is to use one of those USB-C PD phys. they provide an OSI 0 + 1 interface to the power supply. Higher levels have to be implemented in SW. The most commonly used chip seems to be the FUSB302 form ON Semiconductor. This chip was used in the original ZY12PDN.
And here it is:
This is the PD-Micro deigned by Ryan Ma. It is Aruduino Pro Micro with
the FUSB302, some LEDs, a power switch and a voltage regulator. Ryan has made it easy to select appropiate
profiles. Kai Clemens Liebich has made some improvements to Ryan's
FUSB302 lib.
The only problem is voltage stability. Even when using 5 A USB C cables the voltage drop is quite significant.
So we might need to measure the output voltage to fine adjust the power supply voltage. The frist idea was to use
the internal ADC with an external 2.048 V voltage eference. The problem is, this is only a 10 bit ADC, but we need
to measure voltages up to 21 V. Assuming we clip at 20.48 V we will have a resolution of 20 mV. This seems to be
just enough but we can easyly do better. When using a dedicated ADC e.g. The INA219
We can improve the precision to 4 mV. This is well below the 20 mV stepsize. An we get an current sensor on top.
Warning on current sensor ACS712
The ACS 712 is an easy to use isolated current sensor. But:
- there are many Fake modules out there using an relabled ACS704. The fake chips can easyly be found by measuring continuity between pin 5 and 6. In the ACS704 those pins are shorted while in the ACS712 they are not. The ACS712 has improved stability and noise reduction.
- the ACS712 is very sensitive to VCC stability.
- the ACS712 is bidirectional and therefore centered aroud 2.5 V for 0 A
- the ACS712 uses magnetic coupling therefore is sensitive to external magnetic fields and may need complex magnetic shielding
- the ACS712 is very sensitive on the VCC side. It need a stable reliable supply voltage. with in the specified range.
Now we can set a voltage, enable the output and measure the output voltage and current. So we can write a few lines of code to implement a constant voltage / current source. Well the reagulator response time will be limited by the speed of the power supply but it is within reasonable limits depenting on your USB power supply. My PS is an outdated Ugreen Nexode 2 with 100W which switches in ~40 .. 50 ms.
But how is the voltage and current slectet? Well we could use a serial interface and a computer to "remote control" the circuit. But what about an LCD a rotary switch as UI?.
And this leads me to my first prototype.
