Building a USB Power Delivery Trigger HAT

Overview

This tutorial will walk you through building a USB Power Delivery (PD) trigger HAT for Raspberry Pi. The HAT uses a CH224K controller to negotiate voltage from USB-C PD power supplies, providing configurable 5V to 20V output.

Objectives

A USB PD trigger HAT demonstrates advanced power electronics concepts:

• USB Power Delivery Protocol - Understanding PD negotiation
• Voltage Selection - Configuring output voltage via pins
• Power Distribution - Safe delivery of higher voltages
• HAT Design - Raspberry Pi expansion board conventions

Use Cases

• High Power Projects - Power motors, heaters, or high-brightness LEDs
• Battery Charging - Build chargers for various battery chemistries
• Lab Power Supply - Portable voltage source from USB-C chargers
• Raspberry Pi Clusters - Efficient power for multiple Pis

Bill of Materials

Component	Value	Footprint	Purpose
USB-C Connector	-	16-pin	PD power input
CH224K	-	ESSOP-10	PD controller
LED1	Green	0603	Power good indicator
R1	1kΩ	0402	LED current limit
C1	10µF	0805	Output filtering
C2	100nF	0402	High-freq filtering
J2	2-pin	5.08mm	Terminal block output
J3	40-pin	2.54mm	Raspberry Pi header

Understanding USB Power Delivery

USB PD allows negotiation of higher voltages and currents:

Profile	Voltage	Max Current	Max Power
5V	5V	3A	15W
9V	9V	3A	27W
12V	12V	3A	36W
15V	15V	3A	45W
20V	20V	5A	100W

The CH224K handles all PD communication automatically.

Circuit Design

Step 1: CH224K Voltage Configuration

The CH224K selects output voltage based on CFG pin connections:

CFG3	CFG2	CFG1	Output Voltage
Float	Float	Float	5V
Float	Float	GND	9V
Float	GND	Float	12V
Float	GND	GND	15V
GND	Float	Float	20V

Step 2: USB-C Connection

Connect the USB-C CC pins to the controller for PD communication:

Step 3: Output Filtering

Output capacitors ensure stable voltage delivery:

Step 4: Power Good LED

The PG pin indicates successful voltage negotiation:

Complete Schematic

Testing the HAT

1. Visual Inspection - Check solder joints and component orientation
2. Continuity Test - Verify no shorts between VOUT and GND
3. Power Test - Connect to a USB-C PD charger
4. LED Check - Green LED should illuminate when voltage is negotiated
5. Voltage Verify - Measure output with a multimeter

Safety Considerations

• Always verify voltage before connecting loads
• Use appropriate gauge wires for high current
• Include reverse polarity protection for sensitive loads
• Consider adding a fuse for overcurrent protection

Ordering the PCB

Export the fabrication files and upload to JLCPCB. See Ordering Prototypes for detailed instructions.