Power Circuits guides
Power rails, sequencing, charging and VCore circuits explained for repair work.
- Power Circuits
VCore Phases, Inductors and Output Capacitors
Inside a laptop VCore regulator: how phases share the load, smart power stages, phase inductors, output capacitor banks, and comparing phases to find faults.
- Power Circuits
The USB-C Power Path on Laptops: From Port to Charger IC
The USB-C power path on laptops: from VBUS through protection and sink switches to the charger, port OR-ing, the dead-battery start, and where faults usually hide.
- Power Circuits
The RTC Circuit and CMOS Battery in Laptops
How the laptop RTC circuit and CMOS battery work: the RTC rail, its diodes and crystal, RTC reset, symptoms of a flat coin cell, and how to measure and fix them.
- Power Circuits
Power Good Signals and Why They Matter
What power-good signals are, how regulators report a healthy rail, how PG chains drive the laptop power sequence, and how to find a power-good that never goes high.
- Power Circuits
Load Switches and Rail Gating on Laptop Motherboards
Load switches and rail gating on laptop boards: integrated switches and discrete MOSFETs, enables, slew rate and discharge, and how to diagnose a gated rail.
- Power Circuits
LDO Regulators on Laptop Boards
LDO regulators on laptop boards: how linear regulators work, where boards use them, dropout and stability, heat, and how to diagnose a missing or hot LDO rail.
- Power Circuits
Laptop RAM Power Rails: VDDQ, VTT and VPP
The laptop memory power rails explained: VDDQ, VTT, VPP and VREF for DDR3L, DDR4, DDR5 and LPDDR, how they are made, when they turn on and how to diagnose them.
- Power Circuits
Laptop Power Rails Explained: DCIN, B+, 3V/5V and VCore
A map of laptop power rails from the adapter to the CPU: DCIN, the system B+ rail, always-on 3V/5V, suspend and run rails, memory rails and VCore.
- Power Circuits
Laptop GPU Power Circuit Basics
How a laptop's dedicated GPU is powered: core and memory rails, power-gating on switchable graphics, enable sequence, and diagnosing a shorted or missing GPU rail.
- Power Circuits
The Laptop CPU VCore Circuit Explained
How the laptop CPU VCore circuit works: multi-phase controllers, power stages, SVID voltage control, enable and power-good signals, and how to diagnose VCore faults.
- Power Circuits
The Laptop Charging IC: How It Works
How a laptop charging IC works: adapter detection, input MOSFETs, the NVDC system rail, battery charging phases, current sensing, SMBus control and what to measure.
- Power Circuits
MOSFETs on Laptop Motherboards: How to Test Them
Where MOSFETs sit on a laptop board — power stages, load switches, input and battery switches — and how to test each one in circuit, powered and unpowered.
- Power Circuits
How to Measure Voltages on a Laptop Board Safely
How to measure voltages on a powered laptop board without damaging it: setup, current-limited power, ground points, probe tips, where to probe and what to avoid.
- Power Circuits
Enable Signals in Laptop Power Sequencing
How enable signals switch on laptop power rails: where they come from, SLP_S3 and SLP_S4, active-low logic, RC delays, and how to trace an enable that never arrives.
- Power Circuits
The Embedded Controller (EC): What It Does
What a laptop's embedded controller does: power button, power sequencing, charging, keyboard, fans and LEDs, where its firmware lives, and how to check a dead EC.
- Power Circuits
Buck Converters on Laptop Boards: How a Rail Is Made
How buck converters make laptop power rails: switching, inductor and capacitors, synchronous MOSFETs, control modes, light-load behaviour, protection and failures.
- Power Circuits
The Laptop Battery Connector and SMBus Explained
The laptop battery connector and SMBus explained: power, thermistor and presence pins, how the EC talks to the battery's fuel gauge, and diagnosing faults.
- Power Circuits
Always-On Rails (3VALW, 5VALW): What They Do
What the always-on 3VALW and 5VALW rails power, how the controller that makes them starts, the names they use on different boards, and how to diagnose them.