The charger meets its wattage claim and still charges the laptop slower than the customer expects. The cause is usually not the power stage: it is the negotiated profile. A device requests a voltage and current combination, the charger offers what its firmware supports, and the two settle somewhere below the headline number. That gap – between the number on the box and the number the device actually receives – is decided long before production, in four specification decisions most buyers never see.
This guide is part of our GaN Charger Technology. Read the full topic guide for the decisions that come before and after this step.
PD charger manufacturer: the four decisions behind the number on the box
Four decisions set what your PD charger can actually deliver.
The supported PD profiles, the power-sharing rule between ports, the cable rating shipped with the product, and the thermal design that determines whether the rate holds under sustained load. Get those four right and the wattage on the packaging is honest; leave any of them open and the product under-delivers in exactly the situations customers notice.
From an engineering standpoint the four are coupled. Adding a second port splits the available power, which changes the profile table the controller can offer while both ports are active. A higher delivered rate raises the thermal load in an enclosure whose size was fixed by the industrial design. And a cable that does not carry the correct identification limits what the device will accept regardless of what the charger can supply. The specification is therefore a system decision, not a component choice.
Decision 1: which profiles the platform actually supports
Ask for the profile table before the price.
A PD charger may support fixed voltages only, fixed voltages plus PPS stepping, or fixed voltages plus a manufacturer-specific fast-charge protocol. Which of those matters depends on the devices in your channel: a laptop that negotiates a high fixed voltage can be satisfied by a broad fixed table, while phones that use PPS or a proprietary protocol need the corresponding support. Ask for the tested profile list rather than a marketing summary, and ask what the charger does when a device requests something outside the table – fall back to a lower profile, or fail to negotiate at all. That behaviour is what the customer experiences as “slow charging”.
| Wattage tier | Typical port layout | Profile question that decides the product |
|---|---|---|
| 20W-45W | Single port | Which fast-charge protocols the target phones use |
| 65W-100W | 1A1C to 2A2C | Whether the laptop’s preferred profile holds while a second device charges |
| 140W-240W | 2A3C and above | Extended-range profiles and cable identification |
Decision 2: the power-sharing rule between ports
A multi-port charger distributes a fixed total, and the rule it follows is part of the product specification.
Two chargers with identical total wattage can behave differently: one may hold the primary port at its full rate and reduce the secondary, another may split evenly, and a third may renegotiate both ports when a device is added. Ask for the rule in writing, with the combinations that matter to your customers – laptop plus phone, phone plus earbuds, three devices at once. Then test it on the sample with real devices rather than with a fixed load, because the negotiation is where the behaviour is decided.
Decision 3: cable rating and identification
The cable is part of the power path, not an accessory.
A charger rated above the cable’s capacity will not deliver its rating to a device that asks for more, and the customer attributes the shortfall to the charger. Confirm the rated current, the connector type and whether the cable carries the identification the device expects – particularly at the higher tiers. If the cable is supplied, it belongs in the specification, the certification file and the packaging claim; if it is not supplied, state the required rating clearly so the customer can match it.
Decision 4: thermal design and sustained delivery
The number that matters is the rate the product holds, not the rate it can reach briefly.
PD products concentrate heat in a small enclosure, and the control system reduces power when the temperature reaches its limit. Ask for the temperature rise at full load in the shipping enclosure, at a stated ambient, and ask whether the design derates under sustained charging. A charger that reaches its rated output in a short test and reduces it during a long session will be judged as defective even though it is behaving as designed. The derating conditions should be documented rather than discovered.
What the platform decision buys you
Once the four specification decisions are settled, the commercial route follows from the platform.
On a certified platform, a branded PD charger can open at 200 pieces per model with logo, finish, label and packaging applied; the power stage, the profile firmware and the radio documentation already exist, and samples with branding are typically prepared in two to three days where the platform allows. A new enclosure or a new power stage carries tooling, sample loops and a certification review, which sets a higher minimum and a longer calendar. The engineering work is the same either way; what changes is who has already paid for it.
What to verify on the sample before you approve it
Test with the devices you sell, not with a resistor bank.
Connect the laptop and confirm the negotiated rate; add a phone and confirm the power-sharing rule behaves as specified; measure the enclosure temperature during a sustained session rather than a short one. Then compare the marking and the label content against the certification file. Approving a PD charger from a specification sheet is how a compatibility problem reaches the channel, because the profile behaviour is exactly the characteristic that a datasheet cannot prove.
What to verify on the line
Ask whether the functional test verifies profiles or only the presence of an output.
A production test that checks output voltage confirms the unit works; it does not confirm that the unit negotiates correctly. Ask to see the test screen, how the profile verification is recorded, and whether the result is linked to the batch. Then ask how firmware versions are controlled, because a PD product is partly defined by its firmware, and a version change between orders is a product change even when the hardware is identical.
How to compare two PD quotations
Compare the assumptions, not only the price.
Ask both suppliers to state the platform, the profile table, the power-sharing rule, the cable rating, the certification scope, the MOQ and the lead time from order confirmation. Where one quotation is lower because it excludes a cable, a market or a profile, the difference is scope rather than price. A quotation that does not restate the specification cannot be compared with any other.
FAQ
Why does my PD charger charge a laptop slower than its wattage suggests?
Usually because the charger does not offer the profile the laptop prefers, or because another device is drawing power at the same time and the sharing rule reduces the primary port. Compare the profile table with the laptop’s requirements, then test the combination with both devices connected. Compare the profile table with the laptop’s requirements and test the combination with both devices connected.
Does a PD charger need a special cable?
It needs a cable rated for the current you intend to deliver, with the identification the device expects at the higher tiers. A cable below the charger’s rating limits what the device will accept, and the shortfall appears as a charger problem. A cable below the charger’s rating limits what the device will accept, and the shortfall appears as a charger problem.
What is the difference between PD and PPS?
PD defines the negotiated voltage and current profiles; PPS adds a continuously adjustable voltage range within the protocol, used by devices that vary voltage during charging. A product can support one, both or neither, so the requirement should be stated in the specification. PD defines the negotiated profiles while PPS adds a continuously adjustable voltage range, so the requirement should be stated in the specification.
How many ports should a first PD SKU have?
Start with the port layout your channel actually asks for, then confirm the power-sharing rule for that layout. Adding ports earlier than the demand justifies increases the thermal load and the firmware complexity without adding a customer. Start with the port layout your channel asks for, then confirm the power-sharing rule, because adding ports increases the thermal load and the firmware complexity.
Next step
Send the device list, the port layout and the target markets to Wecent Group through the contact page. The reply states the platform, the tested profile table, the power-sharing rule, the MOQ and the sample timing, so the quotation can be compared with any other supplier line by line. Related reading: GaN charger applications, quality control and OEM/ODM manufacturing. External references: USB-IF documentation, Qualcomm Quick Charge, IEC standards, FCC equipment authorisation, EU CE marking and EU energy-efficient products.