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 operating in a forward-bias (VF (IO) = 0.3 ÷ 0.5V for germanium and 0.7 ÷ 1.4V for silicon).
Rectifier diode construction is produced for operating on current values from several mA to few kA and voltages up to few kV. The variant of rectifier diode with the 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.
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.
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.
Two examples of rectifier diode circuits:
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 the 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:
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.
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.
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 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 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|
Full bridge rectifier IC integrated circuits
The full bridge rectifier IC can be seen in integrated circuits. It is built of four rectifier diodes in the Graetz bridge system. The system is built for a THT and SMD housing. Using this solution is the most popular, economical and saves space on the PCB.
The figure above shows the connectors that are in each rectifier bridge circuit integrated circuits. The (+) sign corresponds to the + VDC output, the (-) sign corresponds to the – VDC output, the characters (~) correspond to the VAC connection. The proper voltage connection is made by connecting the VAC input to the + VDC output horizontally, and the VAC output to the – VDC output horizontally.