Rectifier diode

How Rectifier Diode works? – Definition and conctruction

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Rectifier diode definition – diode designed for rectifying alternating current (mostly with low power frequency – 50 Hz at high power emitted during load). Silicon diodes are mainly used, they have large junction surface. The possibility of conducting high value of current can be classified as its basic feature. Germanium diodes have much lower permissible reversed voltage and a smaller permissible junction temperature (Tj = 75 ° C for germanium diodes and Tj = 150 ° C for a silicon diode). The only advantage that germanium diode has over silicon one is lower voltage value during working in a forward-bias (VF (IO) = 0.3 ÷ 0.5V for germanium and 0.7 ÷ 1.4V for silicon).

Rectifier diode

Rectifier diode construction is produced for working on current values from several mA to few kA and voltages up to few kV. The variant of rectifier diode with Schottky barrier (VF = 0.5 ÷ 0.6 is the advantage, whereas the downside is small voltage in the reverse bias) is particularly valued in digital electronics where switching speed of the diode plays a significant role.

Rectifier diode

Rectifier diode symbol

We distinguish two groups of technical parameters of the rectifier diode (as well as other diodes):

  • permissible limit parameters,
  • characteristic parameters.

A rectifier diode is characterized by following permissible limit parameters:

  • IFN – rated current in the forward bias (also known as a maximum average current of the IO diode),
  • IFRM – peak, repeatable current diode conduction (for example, for the pulses with duration of no more than 3.5 ms and a frequency of 50 Hz),
  • IFSM – peak, non-repeatable current conduction (eg. for a single pulse with a duration of less than 10 ms),
  • VRWM – peak, reverse voltage operation (or average, reverse voltage during diode operation in wave rectifier with resistive load),
  • VRRM – peak, repetitive reverse voltage,
  • VRSM – peak, non-repeatable reverse voltage,
  • PTOT – the maximum value of the power dissipated on the item,
  • maximum Tj junction temperature,
  • thermal resistance under Rth operating conditions,
  • a maximum instantaneous current of the diode (it determines resistance for overloads)

High current rectifier diode

An example of a high-performance diode is a double high current rectifier diode with a current of 2x 30A.

STM offers a double high voltage rectifier diode called STPS60SM200C. The diode is best suited for base stations, welders, AC / DC power supplies and industrial applications.

High current rectifier diode

High current rectifier diode STPS60SM200CW

The value of VRRM breakdown voltage is 200V, conduction voltage 640mV, and its current memory is 2x30A. An additional safeguard is from a discharge called ESD to 2kV.

The operating temperature range is -40 degrees Celsius to 175 degrees Celsius. Such temperature values allow the diodes to be used under all conditions in the base stations.

Characteristic parameters of rectifier diode:

  • VF forward voltage with determined IF forwarding current (usually with a maximum average IO rectified current, also known as rated current IFN),
  • IR reverse current at VRWM peak reverse voltage work.

 

rectifier diode characteristics

Current-Voltage characteristics of rectifier diode

Two examples of rectifier diode circuits:

rectifier diode

Wave rectifier diode circuit (U stands for V, as used in some countries)

rectifier diode

Full-wave rectifier diode circuit (U stands for V, as used in some countries)

Bridge rectifier and full wave rectifier

Bridge rectifiers are divided into different types. The following is a breakdown of the bridge rectifiers due to:

  • Structure and number of phases of supply voltage: single phase bridge rectifier, the multi phase bridge rectifier (three phase rectifier bridge, two phase rectifier bridge).
  • A number of half wave rectification voltage: single bridge (half wave rectifier), double bridge (full wave diode rectifier). We can create combined circuit like single phase full wave bridge rectifier or 3 phase full wave rectifier. You can combine the number of phases with full or half wave rectifiers.
  • Load type: resistive, capacitive, inductive.

Characteristics of bridge rectifiers:

  • Supply voltage U
  • Component constant output voltage U0s, I0s
  • Maximum output current I0smax
  • Energy efficiency Nip
  • Circuit ripple factor
  • Maximum back voltage Urm

Half wave rectifier bridge

Single-wave rectifier or half wave rectifier is the simplest alternating current circuits. The system is built on the basis of the voltage reduction transformer, the rectifier diode acting as a current rectifier and the load voltage.

The circuit output is sinusoidal. The current path in the positive half-wave of the voltage flows through the secondary winding of the transformer, the rectifier diode and the load on the circuit. In the event that the voltage half wave is negative, the current does not flow at all because of a diode connected diode that does not conduct in the blocking state. The current flowing through the resistive load is unidirectional and pulsating.

Characteristics of a single phase full wave bridge rectifier with a secondary winding:

half wave rectifier bridge

Time characteristics of half wave rectifier bridge

Full wave diode rectifier

The full wave diode rectifier is created in a two bridge rectifier system and in a four bridge rectifier system also called the Graetz system.

full wave diode rectifier

Time characteristics of the full wave diode rectifier

Profile of the operation of the two bridge rectifier system with the applied transformer and the output of the secondary winding. The first period is the conduction of the diode D1, the diode D2 is in the blocking state. The resistor R is loaded with current i1. The supply voltage changes polarity, at which time the diode D1 changes to a blocking state and the diode D2 conducts. At the same time, the resistor R is loaded with current i2.

Gretz bridge rectifier

Gretz bridge rectifier

Three phase rectifier bridge

The use of a three phase diode rectifier bridge (full wave rectifier bridge) is possible in any three phase voltage circuits. In this case, the output voltage has a minimum ripple. Power sources use the power of the circuit in its greatest extent. Three phase bridge rectifiers often have the ability to control the output current.

Below you can check three phase rectifier circuit schematic which shows you how it can be built.

Three phase rectifier bridge

Three phase rectifier bridge schematic and characteristic

Three phase bridge rectifier calculations

The following is an example of three phase bridge rectifier calculations with patterns and values for the given scheme. Results are shown in the table.

Pd – Power output

Ud – Average value of rectified voltage

Id = Pd / Ud – Average value of rectified current

R = Ud / Id – System resistance

three phase bridge rectifier calculations

Three phase rectilinear bridge rectifier

 

Formulas

Three phase bridge rectifier results Notes
Ud/Uf 2,34 Uf – transformer phase voltage
Ud/U12 1,35 U12 – phase-to-phase transformer voltage
I/Id 0,82 I – effective value on the secondary side of the transformer
URRM/Ud 1,05 URRM – Peak back voltage, repetitive
IF(AV)/Id 0,333 IF (AV) – average conduction current
IFRMS/Id 0,58 IFRMS – effective value of conduction current
Pu=Pd R* Id2 Output power
S2/Pd Processing power of the secondary winding of the transformer
S1/Pd The computing power of the primary transformer winding
St/Pd 1,05 Typical transformer power

 

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I'm Michael. Me and my friend John are students of electronics. We are creating this site to help students and any interested people understand electronics.

3 thoughts on “How Rectifier Diode works? – Definition and conctruction

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