Power Path, Load Switches, and LED Driver ICs: Building the Power Layer of a Product

Between the power input and the loads sits a layer of small ICs that rarely appears in product photos but decides field-failure rates: protection, switching, routing, and driving. Getting this layer right is mostly about asking four questions in order — and the domestic supplier ecosystem now covers every answer.

Question 1: What Happens When the Input Misbehaves?

Adapters get swapped, cables get miswired, voltage spikes ride the bus. Input protection comes first:

• Overvoltage protection (OVP) ICs clamp or disconnect the input when it exceeds a threshold — a few cents of silicon that saves the board.
• Inrush control: load switches with controlled slew rates keep large downstream capacitors from welding connectors on hot-plug.
• Reverse blocking matters wherever a battery can be back-driven by a charger port.

Question 2: Who Owns the Battery?

Battery products need power-path management, not just a charger. A charger IC with integrated power path (such as the ETA4662 class from ETA Semiconductor / 钰泰半导体, which pairs a 21 V-tolerant input with OVP and separate system/battery paths) lets the system boot instantly from the adapter while the battery charges independently — the difference between a device that powers up dead and one that does not.

Around that core, the same supplier covers the routing and regulation blocks: buck converters specified in the hundreds of nanoamps of quiescent current (the ETA3707 class at ~360 nA Iq) for always-on battery rails, multi-amp bucks (ETA2237, 6 A class) for processor rails, boost converters with integrated FETs for small boost needs, load switches, and ultra-low-noise LDOs — the ETA5220 is specified under 1 µV rms output noise with PSRR near 70 dB, which matters for image sensors and RF front ends. The breadth is deliberate: ETA's design center is wearable and battery devices (its parts ship in large volumes of TWS earbud chargers), where every microamp and every square millimeter is contested.

Question 3: What Drives the Loads?

For LED lighting from mains, the driver topology decision dominates cost and reliability:

• Primary-side regulation (PSR) senses output current from the primary winding, eliminating the optocoupler and secondary-side feedback — fewer parts, higher reliability. The FT833 family from Fremont Micro Devices (远翔 FMD) is a standard-bearer here: high-precision constant-current PSR drivers for LED lighting across a wide power range.
• Isolated PSR with integrated PFC (as in FMD's FT8260 class) extends the same philosophy to higher-power lighting and adapters, meeting power-factor requirements without a secondary feedback network.
• Dimming interface: PWM dimming preserves color; analog dimming is quieter on EMI. Decide before choosing the driver, because not every part supports both cleanly.

Design Checklist for the Power Layer

• Budget Iq like a BOM line item: sum the quiescent currents of every always-on rail; in a 3-year coin-cell product, 10 µA of oversight is a redesign.
• Verify protection thresholds against real adapters, not nominal ones — 21 V-rated inputs exist because 20 V adapters lie.
• Thermal-check the driver at minimum dimming level, where some PSR parts lose regulation stability.
• Keep the power tree shallow: every cascade of regulators multiplies quiescent loss and transient interactions.

Mapping rails to specific regulator, protection, and driver parts — with samples — is routine work for our team: send us your power tree.