A rectifier is an electrical device that converts Alternating Current (AC) into Direct Current (DC).
AC current periodically reverses its direction, while DC flows in only one fixed direction. Rectifiers block current in one direction and allow it to pass in the other, achieving AC-to-DC conversion.
It mainly uses the unidirectional conduction characteristic of diodes (semiconductor devices).
When the AC voltage is in the forward direction: diode conducts, current passes through.
When AC reverses polarity: diode cuts off, no current flows.
- Half-wave rectifier
Uses only one diode. Only one half-cycle of AC passes, low efficiency, simple structure. - Full-wave rectifier
Uses two diodes plus a center-tapped transformer. Both positive and negative half-cycles are converted into unidirectional current. - Bridge rectifier (most widely used)
Made of 4 diodes arranged in a bridge circuit. No need for center-tapped transformer, high efficiency, commonly used in power supplies, telecom rectifier modules.
- Unregulated rectifier output: Pulsating DC, still contains AC ripple.
- Filter capacitor/inductor: Added after rectifier to smooth pulsating DC into steady DC.
- Regulated rectifier: Combine rectifier + filter + voltage regulator, output stable constant DC voltage (like telecom power rectifier modules).
High-frequency rectifier modules are widely adopted in communication base stations, computer room servers and power supply systems of intelligent computing centers. They convert mains alternating current into stable direct current to power communication devices, server motherboards and storage equipment. Meanwhile, they provide floating charge for the supporting battery packs. In case of power failure, the batteries can supply power seamlessly to ensure uninterrupted operation of network and computing equipment. Rectifiers serve as the core components of 48V telecom power supplies and HVDC power supply systems.
Rectifier circuits are built into all types of battery charging equipment. They convert household or industrial AC power into DC power to meet the charging requirements of lead-acid batteries, lithium batteries and Ni-MH batteries. From small phone adapters and EV chargers to high-power chargers for forklifts and energy storage power stations, all rely on rectifiers to realize AC-to-DC conversion, and cooperate with control circuits to achieve constant-current and constant-voltage charging.
High-power rectifiers are integrated inside DC welding machines. After the power frequency AC is stepped down by a transformer, it is converted into high-current DC via the rectifier to generate a stable welding arc. The DC arc features less spatter and easier arc ignition, suitable for welding stainless steel, alloy steel and other materials. It is widely used in factory steel structure fabrication, pipeline construction and sheet metal maintenance.
High-power thyristor rectifiers are used in converter stations for long-distance HVDC transmission. They convert AC power from the power grid into high-voltage DC for transmission. DC transmission lines have lower power loss, which is suitable for large-capacity power transmission across regions and seas. Inside factories, rectifiers are also used in processes such as electrolysis and electroplating. Production lines for aluminum electrolysis, hydrogen production from water electrolysis and metal electroplating require stable DC current, which is supplied by rectifiers to deliver continuous and controllable DC power.
Rectifier units are also equipped in various home appliances (TVs, desktop PC power supplies), rail transit locomotives and marine power systems. When locomotives run, they convert grid AC into DC to drive traction motors. On ships, rectifiers convert marine AC to DC for instruments, control systems and emergency equipment.
