Power Semiconductors

Description

A Bridge Rectifier is an electronic circuit used to convert alternating current (AC) into direct current (DC). It is typically composed of four diodes in a bridge structure (full bridge) or two diodes (half bridge), and the conversion from AC to DC is achieved through the unidirectional conductivity of the diodes.

Core structure:

1. Full-bridge rectification: Consisting of four diodes, alternating conduction in two groups, suitable for full-wave rectification.

2. Half-bridge rectification: Two diodes are used in conjunction with a center-tap transformer to achieve half-wave rectification (less efficient, less used).

Application of rectifier bridge

Rectifier Bridges are widely used in electronic devices that need to convert AC power to DC power. Typical scenarios include:

1. Power adapter

¢ Mobile phone chargers, laptop power supplies, etc., convert mains power (AC 220V/110V) to low-voltage DC (such as 5V, 12V).

2. Power supply for electronic devices

¢ Dc power modules inside televisions, stereos, home appliance control boards, etc.

3. Industrial equipment

¢ Applications such as motor drives, welding machines, frequency converters, etc. that require a stable DC.

4. LED lighting

¢ Convert alternating current to direct current to drive the LED beads.

5. Automotive electronics

¢ The alternating current output by the on-board charger or generator is rectified into direct current to charge the battery.

The characteristics of rectifier Bridges

l Advantages:

¢ Simple structure, low cost.

¢ Full bridge rectification efficiency is high (utilizing the positive and negative half-cycles of AC).

¢ No transformer required (rectify directly to high voltage AC, but pay attention to the withstand voltage value).

l Disadvantages:

¢ The rectified DC has ripple (which needs to be smoothed by a filter capacitor).

¢ Diode conduction voltage drops can cause power consumption (such as about 0.7V loss per silicon tube).

Common package forms

1. Split type: Four independent diodes soldered into a bridge.

2. Integrated modules: such as GBU, KBU, DB series, etc., marked parameters (withstand voltage, current).

¢ Example: GBU808 (8A current, 800V withstand voltage).

Key parameters for selection

1. Maximum reverse voltage (VRRM) : Needs to be higher than the peak input AC voltage (e.g. 220V AC corresponding VRRM≥600V).

2. Average rectification current (IO) : Select margin based on the load current.

3. Packaging and heat dissipation: Heat sinks are required for high currents.

Expand knowledge

l The difference from half-wave rectification: Full-bridge rectification is more efficient (utilizing the entire waveform).

l Subsequent circuit: After rectification, a regular filter capacitor is connected, and a voltage regulator IC (such as 7805) further smoothed the voltage.

Through the rectifier bridge, the electronic system can efficiently utilize the AC grid power supply to meet the demands of various DC loads.