Two 65 W chargers were compared side by side: one GaN, one silicon, both meeting the same specification. The GaN unit was smaller and slightly more efficient at high line and full load; the silicon unit was cheaper by a margin the brand could not recover in the retail price. The comparison decided the programme, and it was a commercial one rather than a technical one.
GaN versus silicon: the five variables that separate them
Size at the same output, efficiency at defined load points, thermal behaviour, electromagnetic design effort and cost.
The variables are not independent: the switching frequency drives the size, the loss profile drives the efficiency, the power density drives the thermal design, the switching edges drive the electromagnetic effort, and all four drive the cost. Comparing two platforms means comparing the five together rather than the material label.
The useful output of the comparison is a decision rather than a ranking: at which output range and in which size envelope does the difference pay for itself.
Variable 1: size at the same output
The measurable difference, and the one customers notice.
At the same output a GaN design can use smaller magnetic components and bulk capacitance, which shows up as a smaller enclosure or a similar enclosure with more clearance. Where the retail proposition depends on size, that difference is the product. Where the enclosure is determined by the connector layout and the plug mechanism, the advantage may not be visible at all.
Variable 2: efficiency at defined load points
An efficiency figure without its load points is not a comparison.
Efficiency is measured across a load profile, and the difference between the two designs usually appears at high load and high line rather than at half load. A comparison that quotes one figure for each design, without stating the load and the input voltage, describes two different tests. The useful table shows both designs at the same three or four load points with the same input.
Variable 3: thermal behaviour
Lower losses and less room to release them.
The GaN design loses less in the switching stage and occupies a smaller volume, so the temperature rise is a balance rather than a certainty. What matters is the result at full output in the shipping enclosure at a stated ambient, and the derating condition. A smaller charger that reaches its threshold earlier can be a worse product for a market with warm ambient conditions.
Variable 4: electromagnetic design effort
Faster edges, more work in the layout and the pre-scan.
The higher switching frequency and the faster transitions require a layout that keeps the switching loop small and a filter design that manages the emissions. That effort is engineering time and potential schedule risk, and it is the reason a GaN platform usually carries its own pre-scan and, where the enclosure changed, its own thermal investigation.
Variable 5: cost
A material premium that has to be recovered somewhere.
The GaN devices cost more, the magnetics cost less, and the engineering effort is higher. The net effect depends on the output range: at low power the premium is a larger share of the bill of materials, and at higher power the savings in magnetics and the size advantage have more room to pay for it. That is why the same comparison produces opposite conclusions at different wattages.
| Variable | GaN design | Silicon design | How to compare |
|---|---|---|---|
| Size at the same output | Smaller magnetics and capacitance | Baseline | Enclosure volume and clearance |
| Efficiency | Better at high line and high load | Baseline | The same load points and input |
| Thermal | Lower losses, less volume | Baseline | Rise at full output in the enclosure |
| EMC effort | More layout and filter work | Baseline | The pre-scan margin and the board revision |
| Cost | Higher devices, lower magnetics | Baseline | The five cost lines at the target volume |
When silicon is the right answer
Three situations where the baseline wins.
A low-power product where the premium is a large share of the cost; a range where the enclosure is set by the plug mechanism and the size advantage cannot be used; and a programme where the certification budget does not stretch to a new pre-scan and a new test programme. None of the three is a compromise in quality; each is a commercial decision about where the money does the most work.
Running the comparison properly
Four items, measured on the same test bench.
The enclosure volume and the clearance; the efficiency at the same load points and input voltage; the temperature rise at full output in each enclosure at the same ambient; and the five cost lines at the target volume. With those four, the decision can be explained to a channel or an internal stakeholder without appealing to the material.
FAQ
Is GaN worth it at 30 W?
At lower outputs the device premium is a larger share of the cost and the size saving is smaller, so the case is weaker. It becomes stronger as the output rises and the magnetic components and volume have more room to shrink. At lower outputs the device premium is a larger share of the cost and the size saving is smaller, so the case weakens as the output falls.
Which is more reliable?
Reliability follows the design, the thermal margin and the process rather than the material. A GaN design without thermal margin can be less reliable than a silicon design with it, which is why the temperature result is part of the comparison. Reliability follows the design, the thermal margin and the process rather than the material, which is why the temperature result is part of the comparison.
Does the certification cost differ?
A new switching frequency changes the electromagnetic profile, so a new pre-scan and often a new submission follow. Where the enclosure changes too, the construction evidence is re-established. A new switching frequency changes the electromagnetic profile, so a new pre-scan and often a new submission follow, and where the enclosure changes too the construction evidence is re-established from the beginning.
How should the efficiency be stated?
At defined load points and a stated input voltage, with the enclosure and the ambient given. A single figure without those conditions cannot be compared with another design. State the load points, the input voltage, the enclosure and the ambient, because a single figure without those conditions cannot be compared with another design or reproduced by a third party. State it at the defined load points as well.
Next step
Send the output range, the size target and the target volume to Wecent Group through the contact page. The reply compares the two platform options on the four measured items and states which one fits the commercial brief. Related reading: GaN charger applications, OEM and ODM charger manufacturing and charger quality control. External references: USB Power Delivery specification, IEC standards, IEC Webstore, EU energy-efficient products, UL standards and certification and Intertek testing services.
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