Two products, one bench. A power bank is a cell plus a power-management IC; a GaN charger is a mains power supply built around a gallium-nitride switch. In both, the reference design is the silicon. The house picks the chips, then wraps a casing, thermals and certification around them, and that chip choice sets capacity, wattage, efficiency and how small the thing can get.
On the power-bank side the platform is the cell (18650 or a li-polymer pouch) plus a power IC, the buck-boost-and-protection brain. Shenzhen's own Injoinic (英集芯) is the classic power-bank SoC vendor; the IC decides input/output protocols, the display, and the safety envelope (BMS, over-current, over-temperature). The cell decides capacity and, bluntly, whether it catches fire, which is why cell grade and UL 2056 matter more than the logo.
On the charger side, GaN (gallium nitride) replaces the silicon MOSFET. It switches faster and wastes less energy as heat, so the transformer shrinks: a 65W GaN brick is roughly half the size of its silicon ancestor. The power devices come from Innoscience, Navitas and Power Integrations; paired with a USB-PD / PPS controller, they let one compact multi-port adapter feed a phone, tablet and laptop at once.
Certification is the gate: CE, FCC, RoHS, PSE (Japan), KC (Korea) and UL, plus UL 2056 specifically for power banks and UN38.3 for shipping lithium cells by air. The houses below are the hireable layer beneath the brands (Anker, UGREEN, Baseus, Belkin). A practical warning from 2025: at least one major power-bank brand faced a large recall over swelling and fire, treat cell sourcing and aging tests as non-negotiable, not a line item.