Charger Technology Overview

I. Charger Architecture and Fundamentals

In electronic systems, the charger serves as a critical interface component, tasked with converting alternating current (AC) from the mains grid into regulated direct current (DC) tailored to device specifications. A typical charger comprises four primary subsystems:

• Transformer: Steps down high-voltage AC (e.g., 220V) to lower voltages
• Rectifier: Converts AC to pulsating DC
• Filter: Smoothes DC output by reducing voltage ripple
• Voltage Regulator: Maintains precise output voltage within tight tolerances

AC-to-DC Conversion Principle:
Mains power exhibits sinusoidal voltage characteristics (e.g., 220V/50Hz), with periodic amplitude and polarity reversals. In contrast, semiconductor devices (e.g., microprocessors, RF modules) require stable DC power with minimal voltage deviation. This necessitates the sequential conversion processes executed by the charger.

II. Operational Mechanics

Transformer Stage:

• Implements electromagnetic induction via laminated cores and copper windings
• Step-down ratio determined by turns ratio (e.g., 220V→5V requires 44:1 ratio)
• Insulation materials (e.g., Mylar, enamel) mitigate eddy current losses

Rectification Circuit:

• Full-wave bridge configuration using Schottky diodes for low forward voltage drop
• Converts bidirectional AC to unidirectional pulsating DC
• Peak inverse voltage (PIV) ratings selected based on transformer output

Output Filtering:

• Passive RC/LC networks reduce ripple frequency components
• Electrolytic capacitors (100-1000μF) for bulk energy storage
• Ceramic capacitors (<1μF) for high-frequency noise attenuation

Voltage Regulation:

• Linear regulators (e.g., LM7805) for low-noise applications
• Switch-mode regulators (SMPS) for high-efficiency (>85%) power conversion
• Feedback control loops maintain ±5% voltage accuracy

Technical Summary (Mobile Charger Example):

1. Transformer: Steps down mains voltage (e.g., 220V AC) to a lower AC voltage (e.g., 12V AC)
2. Rectifier: Converts AC to pulsating DC via a diode bridge
3. Voltage Regulator: Stabilizes output to precise DC specifications (e.g., 5V/2A)
   This ensures compliant power delivery for USB-C/PD charging protocols.