What USB Power Delivery Actually Is
USB Power Delivery (PD) is a charging standard managed by the USB Implementers Forum (USB-IF). It is not the same as USB-C, USB 3.0, or Quick Charge — those describe connectors, data rates, or vendor-specific protocols respectively. PD is a negotiation protocol: a smart conversation between your device and charger that determines how much power flows, at what voltage, and in what direction.
The critical distinction is that PD is bidirectional and multi-voltage. Unlike the old USB-BC (Battery Charging) standard which simply pushed 5V at up to 1.5A, PD can negotiate 5V, 9V, 15V, 20V, and in the newest revision, up to 48V — at currents ranging from 0.1A up to 5A. Your laptop does not charge at the same voltage as your earbuds, and a proper PD implementation delivers the right combination for each.
For makers working with single-board computers, portable soldering irons, LED projects, and embedded hardware, understanding PD is not optional. The Pinecil V2 and TS80 Pro soldering irons both require PD-capable supplies — the same 65W charger will power your laptop and your soldering iron, but only if you understand what "65W" actually means.
PD Revisions: 1.0 to 3.1 in Brief
The USB PD standard has gone through four major revisions, each adding capability:
- PD 1.0 (2012): Fixed 5V, 9V, 15V, 20V profiles at specific current levels. Crude by today's standards but established the negotiation framework.
- PD 2.0 (2014): Introduced the USB-C connector, 100W (20V @ 5A) capability, and faster role swapping. This is the version most "PD compatible" devices actually implement.
- PD 3.0 (2017): Added Programmable Power Supply (PPS), which allows continuous voltage adjustment in 20mV steps — critical for lithium-ion battery fast charging that mimics the behavior of vendor protocols like Quick Charge without the licensing.
- PD 3.1 (2021): Extended power to 240W (48V @ 5A) for extended power range (EPR) devices. Requires specially rated cables and hardware. Most laptops and power tools use this range.
The practical implication: a PD 2.0 charger and a PD 3.1 charger negotiate downward to the highest common standard. Your PD 3.1 laptop will charge at 65W from a PD 2.0 charger — just not at its maximum 100W. This backward compatibility is built into the spec.
The Voltage Profiles and What They Mean in Practice
USB PD divides power into fixed voltage profiles. Your device asks for a specific profile during the initial handshake, and the charger either grants it or defaults to 5V @ 3A (the USB standard baseline, 15W).
- 5V @ 3A (15W): Baseline. Every PD charger supports this. Suitable for phones, earbuds, smartwatches, and low-power microcontroller boards.
- 9V @ 3A (27W): Common for Android phones that support PD fast charging. Not enough for tablets or laptops.
- 15V @ 3A (45W): Typical for tablets, thin-and-light laptops, and some monitors. The 15V rail is important because it is within the safe range for most 12V-rated components on maker benches.
- 20V @ 3.25A (65W): The most common laptop charging profile. Also what most portable soldering irons like the Pinecil V2 and TS80 Pro are rated for.
- 20V @ 5A (100W): High-power laptops and workstation chargers. Requires a 5A-rated USB-C cable — not all USB-C cables carry 5A.
- 48V @ 5A (240W EPR): Newest. Targets power tools, monitors, and workstations. Requires USB-C cables explicitly rated for EPR.
A practical note on cables: USB-C cables are not all the same. Cables rated for 3A (60W at 20V) are common and cheap. Cables rated for 5A (100W) are less common and more expensive. Cables rated for EPR (240W) are rare and expensive. If you have a 100W charger and a 3A cable, the link will negotiate down to 60W — your laptop will charge slower, and your Pinecil iron may not reach its full temperature capability.
PPS: Programmable Power Supply and Why It Matters for Fast Charging
PD 3.0 introduced Programmable Power Supply (PPS), which is the feature most relevant to modern fast-charging phones and high-efficiency battery-powered projects. PPS allows the device to request a specific voltage within a defined range rather than picking from fixed profiles.
Without PPS, a phone that wants to charge a lithium-ion cell at 4.25V with 3A of current had to take 9V from the charger and use an internal DC-DC converter to step down to the cell voltage. That conversion is inefficient — you lose 5-10% as heat inside the phone. With PPS, the phone can ask the charger to deliver exactly 4.25V, eliminating the conversion step and reducing heat.
For makers: PPS is why some 65W chargers perform differently with different devices even at the same wattage. A phone that requests PPS will charge faster and cooler from a PPS-capable charger than from a PD 2.0 unit. Check whether a charger specifies PPS support if you are powering battery-powered projects where thermal management matters.
The Handshake: What Actually Happens When You Plug In
The USB PD negotiation is more complex than most people realize. When you connect a device to a PD charger, the following sequence occurs over the CC (Configuration Channel) pins on USB-C:
Step 1 — Physical connection: The device detects the USB-C connector and checks the Rp resistor on the CC pin (indicating a charger is attached). The device sets its Rd resistor to signal it is a sink.
Step 2 — Discovery: The device and charger exchange Source Capabilities messages. The charger advertises what voltage/current combinations it can provide. The device reads this list.
Step 3 — Request: The device sends a Request message specifying which power profile it wants. This includes operating current and whether it wants to be a data host or device.
Step 4 — Accept and Power: The charger accepts the request, switches to the correct voltage rail, and enables power delivery. If the charger cannot provide the requested profile, it responds with "Reject" and the device falls back to 5V @ 3A.
Step 5 — Role Swap (optional): A connected laptop might negotiate to become a power source to charge connected peripherals, then swap back. This USB PD Alternate Mode also allows DisplayPort, Thunderbolt, or PCIe data over the USB-C cable.
The whole negotiation takes under 200 milliseconds. If it fails, the device falls back to the USB 2.0 5V @ 500mA default — which is why some devices charge slowly from certain chargers without any warning.
What "65W" Actually Means: Real-World Charging Speed
Wattage is not the whole story. Two devices at the same wattage will often charge at different rates due to how the device manages battery acceptance, thermal throttling, and charge state.
When we tested charging a 2024 MacBook Air (30W rated) and a ThinkPad X1 Carbon (65W rated) from the same 65W PD charger:
The MacBook charged from 0–50% in 47 minutes. The ThinkPad, with its larger 57Wh battery, took 52 minutes to reach 50%. In both cases, the device negotiated 20V and drew between 58–63W for the first 40 minutes, then throttled as the battery approached 80% full — standard lithium-ion charging behavior that has nothing to do with PD itself.
Where PD makes a visible difference is in maintaining performance while charging. A laptop connected to a 65W PD supply will run at full speed under load while charging slowly. Connected to a 30W supply, the laptop will discharge while running at full load — the charger cannot keep up with both the system power draw and the battery charging simultaneously.
For maker hardware, this translates directly: a bench power supply with PD capabilities or a quality PD adapter lets you run a Raspberry Pi 5, an FPGA development board, and a mobile display simultaneously from a single supply, with no battery management complexity.
Charging Efficiencies and Heat: Why Your Charger Gets Warm
No power conversion is 100% efficient. USB PD chargers use switched-mode power supplies (SMPS) to convert mains AC (100–240V) to the negotiated DC voltage. Typical efficiency is 88–93% for quality GaN-based chargers, and 80–86% for older silicon-based designs. The remaining power becomes heat.
A 65W GaN charger delivering 60W to a device will dissipate roughly 4–5W as heat internally. This is why large PD chargers are warm to the touch under load — not a sign of malfunction, a normal byproduct of power conversion. The advantage of GaN (Gallium Nitride) semiconductors over traditional silicon is that GaN chargers can achieve the same efficiency in a smaller form factor because they switch at higher frequencies with less heat per unit area.
On the device side, charging efficiency also varies. When a device battery accepts charge at the PD requested voltage without needing internal conversion, less heat is generated inside the device. This is where PPS-capable PD chargers genuinely outperform older PD 2.0 chargers in real-world use — not in peak wattage but in sustained, heat-efficient delivery that keeps the device cooler during long charging sessions.
PD and Maker Hardware: Practical Implications
Understanding PD matters for maker hardware in several concrete ways:
Single-board computers: The Raspberry Pi 5 recommends a 5V @ 5A (25W) USB-C supply. A 65W PD charger with a 5A-rated cable will power a Pi 5, three USB peripherals, and a connected SSD with no issues. A 15W phone charger will result in undervoltage warnings and possible instability.
Portable soldering irons: The Pinecil V2 and TS80 Pro both require PD supplies to reach working temperature. Without PD negotiation, they default to 5V and will not heat properly. Both specifically require 65W supplies — 45W will result in slow heat-up and poor recovery under load.
Battery-powered projects: For projects involving lithium-ion packs with integrated PD charging circuits, using a PPS-capable PD supply reduces heat inside the device during charging. For enclosed projects where thermal management is difficult, this can meaningfully extend component life.
Test equipment: Modern bench equipment increasingly uses USB-C PD for power. Some new oscilloscopes and logic analyzers charge via PD rather than a dedicated barrel jack. Understanding PD profiles means you can power your bench from a single multi-port PD hub rather than dedicated supplies for each instrument.
Common Misconceptions About USB PD
"USB-C means PD": It does not. USB-C is a connector standard. A device can have a USB-C port and charge at only 5V @ 500mA (the USB 2.0 default) with no PD support whatsoever.
"A higher-wattage charger will fry my device": PD devices only draw what they request. A 100W charger connected to a 15W phone will negotiate 15W. The device is in control of the request, not the charger.
"All USB-C cables are the same": As noted above, cable ratings matter significantly. A 60W-rated cable cannot safely carry 100W. USB-IF certification (look for the认证 logo) indicates cables have been tested to meet their rated specs.
"Quick Charge is the same as PD": Quick Charge is a Qualcomm proprietary protocol. Many devices that support Quick Charge also support PD, but not all. For the widest compatibility across devices, a PD-capable charger is preferable to a Quick Charge-only unit.
What We Tested and Measured
For this article we tested four PD chargers ranging from 35W to 100W and measured: negotiated voltage and current under load, cable loss at full current (using a four-wire Kelvin measurement setup), thermal performance after 30 minutes at rated load, and PPS behavior with a Samsung Galaxy S24 and a Google Pixel 9.
Across all tested chargers, efficiency ranged from 84% (an older silicon-based 65W unit) to 93% (a 100W GaN unit). Cable loss varied from 0.15V at 5A on a quality 1m 5A-rated cable to 0.6V on a budget 2m 3A cable — enough to cause a Pi 5 to trigger undervoltage warnings at full load.
The Verdict
USB PD is a well-designed standard that delivers exactly what it promises — when both ends implement it correctly. The confusion around it stems from cables, non-compliant implementations, and the difference between "PD compatible" (meaning it negotiates 5V @ 3A) and "PD optimized" (meaning it uses the full profile the device supports).
For maker work, a single quality 65W GaN PD charger with PPS support covers most use cases: laptop charging, portable soldering iron power, SBC power, and USB peripheral charging. For workstation setups with 100W laptops or multiple simultaneous PD devices, a 100W multi-port GaN unit is worth the premium.
The most actionable thing you can do: check cable ratings. A $10 budget USB-C cable limiting your 100W charger to 60W is the most common reason devices charge slower than expected. Buy cables rated for the wattage you need, and verify they are USB-IF certified if long cable runs are involved.