USB Power Delivery (USB PD) is the negotiation protocol that lets one charger power a phone, a tablet, a laptop and a workstation at different levels: the charger advertises the voltage and current profiles it can deliver, and the device selects the profile it needs. That negotiation is why a 100W charger is safe for a phone and why a 30W charger may not charge a laptop — the profile list, not the wattage on the box, is the actual specification. This guide explains the negotiation, how to read a profile (PDO) table, what changed between PD versions, and how to match PD to your device stack.
Key takeaways
- USB PD is a negotiation protocol: the device requests a profile, and the charger delivers it.
- The PDO table lists the profiles a charger can deliver; the 20V row is what matters for laptops.
- PD 3.1 added EPR profiles above 100W, with stricter cable requirements.
Content updated: August 2026 — verify current USB-IF specifications and model-specific details before ordering.
How Power Negotiation Works
When a USB-C device is plugged into a PD charger, the two exchange information before power flows. The charger advertises its PDO table — the voltage and current combinations it can deliver. The device compares that table against its own request and selects the profile that matches. The process repeats when devices are added or removed on multi-port chargers, which is why the port behavior can change mid-session.
The consequences for buyers:
- The device controls the load. A phone on a 100W charger takes a phone-level profile; it never receives more than it requests.
- The charger controls the offer. A charger that does not advertise the device's requested profile forces a fallback to a lower profile.
- The cable is in the path. If the cable cannot carry the negotiated current, delivered power caps at the cable's rating.
This is the mechanism behind most "why is it slow?" questions: the profile, the cable or the split, not a broken charger.
The negotiation also explains behavior changes mid-session. When a second device joins a multi-port charger, the charger re-advertises its available profiles, and the first device may be renegotiated down to a lower level. The user sees the phone slow down while the laptop charges, which is the split map working as designed. Understanding the renegotiation makes the split map easier to read: it is not a marketing table but the list of what the charger offers under each combination.
Reading the Profile (PDO) Table
The PDO table is the charger's menu. A typical fixed-profile table lists common voltage steps with their current limits:
| Profile | Current | Delivered power |
|---|---|---|
| 5V | 3A | 15W |
| 9V | 3A | 27W |
| 12V | 3A | 36W |
| 15V | 3A | 45W |
| 20V | 5A | 100W |
The table is an example of the fixed-profile structure, not a specific product's specification — read the actual PDO table from the charger's spec sheet or product page. For most USB-C laptops, the 20V profile is the common request, so a charger that lists 20V at the right current is usually laptop-capable; one that only lists phone-level profiles will slow-charge or fail under load. Confirm the machine's actual input specification before relying on the row.
PPS adds a different kind of entry to the table. Instead of a fixed voltage, a PPS (Programmable Power Supply) entry lets the phone request a precise voltage within a range, which can reduce heat during fast charging. The distinction matters when comparing chargers for phones that support PPS: a charger with only fixed profiles may still charge the phone, but it will not deliver the PPS-optimized behavior the phone is designed for. Read whether the table lists PPS ranges, not just fixed steps.
PD Versions and What Changed
USB PD has evolved in two meaningful steps for buyers. PD 3.0 standardized the fixed-profile structure and added PPS (Programmable Power Supply), which lets a phone request precise voltage steps for faster, cooler charging. PD 3.1 added the Extended Power Range (EPR): profiles above 100W, including 28V, 36V and 48V steps that power high-performance laptops and workstations.
| Range | Power | Typical use |
|---|---|---|
| SPR (standard power range) | Up to 100W | Phones, tablets, most laptops |
| EPR (extended power range) | Above 100W | High-performance laptops, workstations |
EPR charging also requires more of the cable: an e-marked cable rated for the higher current, and sometimes a specific EPR-capable cable. A 140W charger with a basic cable will negotiate lower than its rating.
The cable requirement follows the profile, not the charger's marketing. A 3A-rated cable carries up to 60W at 20V; a 5A e-marked cable is needed for 100W-class profiles, and EPR profiles above that add their own cable expectations. Checking the cable against the top profile is a one-line task that prevents the most common "high-power charger, slow device" complaint. The full cable rules live in the USB-C charging guide on this site; this page keeps only what the PD discussion needs.
Matching PD to Your Device Stack
Match PD by profile, not by headline wattage. List the devices, find the highest request, and check the charger's PDO table against it:
- List the devices and their charging requests.
- Find the highest request — usually the laptop's 20V row.
- Check the profiles — does the charger advertise that request?
- Check the cable — is it rated for the negotiated current?
- Check the split — for multi-port use, does the split map cover the simultaneous combination?
The same method serves a retail line: define the target devices, map the profiles, and stock the charger that covers the widest set without over-promising.
Multi-port devices add a final check to the stack. A single-port PDO table says what the charger can deliver alone; the split map says what each combination delivers together. For a stack that charges a laptop and a phone at the same time, the split row for that combination is the number that matters, not the single-port maximum. Add the split check to the list whenever the stack includes more than one device.
Common PD Misconceptions
- "Higher wattage always charges faster." No — the device requests what it needs; excess capacity only matters for larger devices or multi-device splits.
- "All USB-C chargers support PD." No — a USB-C port can deliver fixed 5V without PD negotiation; check the spec.
- "The total wattage reaches every port." No — multi-port chargers divide power according to the split map.
- "A 100W charger forces 100W into my phone." No — negotiation prevents that.
These misconceptions drive most returns. The profile list and the split map answer the questions before the purchase.
The same discipline applies to any claim on the box. When a charger states a wattage, ask which profile delivers it; when it states a protocol, confirm it is implemented rather than listed as a compatibility badge. Reading the specification this way costs a minute and prevents the return that takes a week.
A verification checklist for buyers: The first document to request is the PDO table and the split map, because they describe what the charger can actually deliver. Read a spec sheet that lists a headline wattage but no profiles as marketing until the table arrives; then check the profile against the device's request and the cable against the profile.
For a PD shortlist, the GaN Charger Category lists platforms with their power ranges, and the WECENT FAQ answers the protocol-level questions that come up during selection. To confirm which configuration fits your device stack, submit the device list to WECENT's project engineering team — the review returns the PDO and split data for the models you shortlist, with a configuration recommendation.
Frequently Asked Questions
What is a PDO?
A PDO (Power Data Object) is a profile the charger advertises: a voltage and current combination it can deliver. The device selects from the PDO table, which is why the table, not the headline wattage, defines compatibility.
What is the difference between PD 3.0 and PD 3.1?
PD 3.0 standardized fixed profiles and added PPS; PD 3.1 added EPR profiles above 100W with higher voltage steps. EPR also raises the cable requirements, so a high-power charger needs an appropriate e-marked cable.
Why does my device charge slowly with a PD charger?
The usual causes are a profile that does not cover the device's request, a cable rated below the negotiated current, or another device sharing the port. Check the PDO table, the cable and the split map in that order.
Can a PD charger charge a device that does not support PD?
It can deliver a fallback 5V in most cases, which charges slowly. Full speed requires the device to request a PD profile; a device without PD support cannot use the higher profiles.
What does PPS add for phones?
PPS lets the phone request precise voltage steps, which can reduce heat during fast charging. Phones that support PPS can charge faster and cooler on a PPS-capable charger; the benefit is phone-dependent.
Which cable do I need for a 100W PD profile?
A 5A e-marked cable is typically required for 100W-class profiles over USB-C; a 3A cable caps delivered power at a lower level. Confirm the cable rating against the charger's top profile and the device's request before testing speed.