What is an AC to DC Converter?

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Editorial Team - everything PE

Sep 12, 2021


An AC to DC converter is used to convert an AC input voltage level into a DC output voltage level. It utilizes switching devices such as diodes, thyristors, power transistors, MOSFETs, etc. for the conversion of voltage from AC to DC. The AC to DC converters is ideal for televisions, cell phone chargers, computers, medical, military, telecommunications equipment, kitchen appliances, industrial machinery, and commercial products that use DC motors.

AC to DC Converters are broadly classified into two classes:

Uncontrolled Rectifiers: Uncontrolled rectifier provides a fixed DC output voltage for a given AC input. These uncontrolled rectifiers are further divided into three types:

1. Half-wave Rectifier: The half-wave rectifier consists of a single diode connected in series with the load. In half-wave rectification, a single-phase AC supply is fed to a half-wave rectifier circuit. The diode passes only the positive half cycle of the supply and blocks the negative half cycle.

2. Full-wave Rectifier: The full-wave rectifier consists of two diodes connected in such a way that one diode will be forward biased and the other will be reverse biased for a half cycle. In full-wave rectifiers, the output voltage can be obtained during both positive and negative half-cycles.

3. Bridge Rectifier: The bridge rectifier consists of four diodes connected to form a closed loop called “Bridge” across the load. In a full-wave bridge rectifier, two diodes will be conducted for each half cycle and the rest of the diodes will be reverse biased. During both the half cycles the current flowing through the load is unidirectional and hence the voltage developed across the load is also unidirectional. The output voltage containing ripples can be filtered by connecting a capacitor in parallel to the load.

Controlled Rectifiers: Controlled rectifier provides an adjustable DC output voltage with the help of semiconductor devices such as thyristors, BJT, MOSFET, IGBT, etc.

Key Specifications of AC to DC converters:

Phase configuration: It represents the phase of the input AC supply. The phase may be either single-phase or three-phase.

AC Input voltage: It represents the input AC voltage of the AC to DC converter and is expressed in volts (V).

DC Input voltage: It represents the input DC voltage of the AC to DC converter and is expressed in volts (V). Some AC to DC converters can also convert an input DC voltage to a different output DC voltage level. These converters support AC and DC voltage conversion.

DC output voltage: It represents the output DC voltage of the AC-DC converter and is represented in volts (V).

DC output power: This is the amount of power the AC to DC consumes. It is represented in Watts (W).

Isolation Voltage: It refers to the maximum voltage that can be applied across the converter for one second without compromising the isolation in the device. It is expressed in volts (V).

Number of outputs: The AC to DC converter provides multiple DC outputs as required by the application.