Discrete
Bridge Rectifiers
Four-diode AC-to-DC conversion in one package.
What is it?
A bridge rectifier is four diodes arranged in a full-wave bridge topology, integrated into a single package. It converts AC input to pulsating DC output. Used universally in AC-fed power supplies as the first stage after the EMI filter, turns the mains AC into a rough DC rail that feeds the bulk capacitor and downstream converter.
When do you need it?
- AC-DC power supply primary stage (laptop adapters, server PSUs, LED drivers).
- DC motor controllers fed from AC mains.
- Battery chargers with AC input.
- Low-frequency rectifiers in audio power supplies.
How to pick the right one
- IF (Average forward current)
- Match to peak rectified DC current with thermal margin. 1 A, 2 A, 4 A, 6 A, 10 A common.
- VRRM (Maximum Repetitive Reverse Voltage)
- At least 2× peak AC voltage. For 230 V AC mains, choose 600 V or 800 V VRRM.
- IFSM (Surge current)
- Must survive the initial bulk-cap charging surge at power-on. Higher IFSM = no inrush limiter needed.
- VF (Forward Voltage per diode)
- Two diodes conduct simultaneously, so total drop ≈ 2 × VF.
- Package
- Surface-mount DFS and ABS for compact adapters and chargers; through-hole single-in-line GBU and KBU for higher current.
What Magnias offers
Magnias bridge rectifiers come in four families, all 50 V to 1000 V, halogen-free and RoHS compliant: DF005S thru DF10S (1 A, DFS), ABS205 thru ABS2100 (2 A, ABS), GBU4005 thru GBU410 (4 A, GBU) and KBU8005 thru KBU810 (8 A, KBU).
Common questions
Why not just use four discrete diodes?
Bridge package gives lower thermal resistance, smaller board footprint, and lower cost. Discrete diodes are only better when you need very specific Trr matching.
Do I need a bridge rectifier for DC input?
No, bridges are for AC. For DC input use a single reverse-polarity diode or PMOS-based protection.
Does the bridge add noise?
Yes, pulsating DC has 100 Hz (or 120 Hz) ripple that needs a bulk capacitor to smooth. Most designs use 470-2200 μF after the bridge.