a real rectifier
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Rectifier
Rectifier
[1], [3] A rectifier is an electrical device or circuit converting AC direction to DC--using the rectification process, one most useful way to use a diode.
Physically, rectifiers have many forms, like vacuum tube diodes, wet chemical cells, mercury-arc valves, copper stacks and selenium oxide plates, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motor-generator sets have been used. Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector".
Positive and negative half-cycles
Positive and negative half-cycles
[5]
A positive half cycle is the upper part (above zero reference/X-axis) of all AC signals or sine waves, when the anode of the diode(s) becomes positive and the cathode becomes negative--being forward bias.
A negative half cycle is the beneath part (under zero reference/X-axis), when the anode becomes negative and the cathode positive--being reverse bias.
So as an AC source connects to a half-wave rectifier, only half cycle goes through it as shown below.
This rectifier's output is taken across the load resistor (RL). The graph shows the input's pulsating positive half cycle.
The half wave rectifier's output has too many ripples and is unpractical to use this output as DC source. To smooth the output, a capacitor is used across RL, charging during the positive cycle and discharge in negative cycles to release smooth output signals.
Such rectifier types waste AC input’s half cycle's power.
Rectifier circuits types
Rectifier circuits types
[5] A rectifier circuit is the one of most used circuit as many electornics work on DC but DC availability sources are limited, like outlets in homes give AC. Even cellphone chargers use rectifiers to convert the AC from home outlets to DC.
Rectifier types are often categorized by their output.
[5]
Rectifiers are based on the supply type: single (1Φ) and three-phases (3Φ), based on their input type.
Both 1Φ and 3Φ have the same classes based on rectifiers; switching devices and the types are uncontrolled, half controlled and full controlled rectifiers.
Then a rectifier is classified by its waveform type: either half or full-wave.
A bridge rectifier is the most commonly used rectifier, basic bridge rectifier circuit being the most used method for full wave.
Single-phase rectifier
Single-phase rectifier
A single phase (1Φ) rectifier has a single phase input,
Most single-phases are low power rectifiers for domestic equipment.
- Single-phase rectifier
- Single-phase rectifier
-- Single phase half-wave rectifier
-- Single phase half-wave rectifier
[3.6] half-wave rectifier uses rectification by letting half an AC waveform to go through and blocks the other half, via only 1 diode.
Fig. 1
If pt A's voltage is positive via respect to ground and +0.7 V, the diode will conduct.
Any voltage below 0.7 V (negative voltage is considered below 0.7V), the diode won't conduct. If the diode conducts (e.g., pt A is 0.7V or greater wrt ground), 0.7V is dropped across a diode and remaining voltage (Vin –0.7V) is across a load resistor. If a diode doesn't conduct, all used voltage at point A is dropped across a diode and 0 V is dropped across the load resistor.
Fig. 1 shows the diode conducts for the positive half cycle (once Pt A +0.7 V). The output waveform has a ripple frequency identical as input frequency.
The max reverse voltage (PIV) occurs as the diode is reverse bias at the peak of the negative cycle. PIV = Vpk sec
The average DC output voltage of a half wave rectifier = VDC = voltage red on a DC voltmeter.
The voltage across full secondary Vrms (Vsec) is ~0.707 (√2) times the Vpk.
Vpksec = Vsec x 0.707 x 2 (1.414, or √2)
Vpkload= Vpksec - 0.7 V
Vavg = VDC = Vpkload x 1/π (without filter capacitor)
E.g. The secondary voltage is 14 V and there's no filter capacitor. What's the average load voltage?
Vpksec = Vsec x 1.414 = 14x1.414 = 19.8
Vpkload= Vpksec - 0.7 V = (19.8/2) -0.7 V = 19.1
Vavg = VDC = Vpkload x 1/π (no capacitor) = 19.1/π = 6.08 V
If a step-down transformer has a diode on its secondary, it only lets secondary current flow in 1 direction. The diode now gets a pulsating waveform, blocking the wave's negative half.
We can reverse the diode to block the positive half, letting the negative half, making a half wave rectifier and also DC.
A resistor connected to a low voltage AC supply has a usual sine wave.
Via a diode in series, an oscilloscope gives a pulsating pattern in the positive half.
Reversing the diode, the oscilloscope shows a pulsating pattern in the negative part.
Via 2 lamps in parallel (1 with a diode), the one without a diode is brighter as it uses a full waveform, and other one is dimmer and flickering more, using half waves, being blocked by the diode.
So we can use the one with a diode for basic circuits for lighting/charging battery, but not for others as components need constant power.
[5]
--- Positive half wave rectifier
--- Positive half wave rectifier
[5] A positive half wave rectifier converts only the positive half cycle and blocks the positive half cycle.
--- Negative half wave rectifier
--- Negative half wave rectifier
[5] A positive half wave rectifier converts only the positive half cycle and blocks the negative half cycle. It's the simplest of all as rectifiers, using only 1 diode (Fig 3).
[5] Fig. 3
Their current path in the positive and negative half-cycles.
[3.8]
full wave rectifier diagrams
- Full-wave rectifier
- Full-wave rectifier
[3.2], [3.5], [3.7], [3.8] Full-wave rectifier converts a whole AC waveform into a DC waveform, with both positive and negative parts, via 2 diodes and a center-tapped transformer, for more efficient rectification and higher average output voltage.
There are two types of full wave rectifier: bridge rectifier and center-tap rectifier.
a real full wave bridge rectifier
[2]
Fig. 2
[5]
--Bridge rectifier
--Bridge rectifier
A bridge rectifier uses 4 diodes to convert both half cycle of an input AC to DC output.
Fig. 2's circuit uses 4 diodes in a configuration with diode 1 and 2 conducting during the positive half cycle and diode 2 and 4 conducting in the negative half cycle. As there is 2 diodes conducting per half cycle, 2 diode voltage drop must be used in calculations.
Note: The ground of the circuit isn't a secondary lead of the transformer.
Positive half cycle
During input positive half cycle, the diode D1 and D2 becomes forward bias as D3 and D4 becomes reverse bias. The D1 and D2 form a closed loop giving positive output voltage for RL.
Negative half cycle
During the negative half cycle, the diode D3 and D4 becomes forward bias as D1 and D2 becomes reverse bias. But the polarity across RL stays the same and gives a positive output for the load.
The full wave rectifier's output has low ripples unlike half-wave rectifier but it still isn't smooth/steady.
...til a capacitor is used, which charges and discharges to make smooth transitions between the half cycles.
E.g. 1# The full secondary voltage is 14 V and the capacitor is 100 uF. What's the average load voltage?
Vpk = 14x1.414 = 19.8 V
Vpkload = 19.8 - 1.4 = 18.4
Iload = Vavg /Rload = 18.4/1000 = 0.0184 A
Ripple frequency of a full-wave rectifier doubles: secondary frequency (f) = 60x2 = 120 Hz
R = 1k
C = 100 uF = 0.0001 F
Vripple = Iload/2fRC = 0.0184/(2x120x1000x100x10⁻⁶) = 0.000766666667 V
Vavg = 18.4 - (0.000766666667/2) = 18.4 V
t = 1/60 Hz = 0.0166666667 ms
R = 1000
C = 100 uF = 0.0001 F
Vripple = (Vpkload x t)/(R*C) = (18.4x0.0167)/(1000x0.0001) = 3.07
Vavg = Vpkload - (Vripple/2) = 18.4 - (3.07/2) = 16.86
t = 1/60 Hz = 0.0166666667 ms
R = 1000
C = 100 uF = 0.0001 F
Vripple = (Vpkload x t)/(R*C) = (18.4x0.0167)/(1000x0.00047)
Vavg = Vpkload - (Vripple/2) = 18.4 - (0.653787234/2) = 18.07
E.g. 1.2# What's the average load voltage if the capacitor's value changed to 470 uF?
R = 1k Ω
C = 470 uF = 0.00047 F
Vripple = Iload/2fRC = 0.0184/(2x120x1000x470x10⁻⁶) = 0.16 V
Vavg = 18.4 - (0.16/2) = 18.4 V
-- Center-tap rectifier
-- Center-tap rectifier
[5] A center-tap rectifier is a full-wave rectifier using a center-tap transformer and 2 diodes.
A center-tap transformer is a dual-voltage transformer with 2 inputs (I1 and I2) and 3 output terminals (T1, T2, T3). T2 connects to the the output coil's center acting as a reference ground (0 V). The T1 terminal makes positive voltage and the T3 terminal makes negative voltage via respect to T2.
The center-tap rectifier's design:
Positive half cycle
[5] During an input positive half cycle, T1 makes positive and T2 makes negative voltage.
D1 diode becomes forward bias and diode D2 becomes reverse bias, making a close path from T1 to T2 through the RL as shown below.
Negative half cycle
[5] During the input negative half cycle, T1 makes negative cycle and T2 makes a positive cycle, putting D1 into reverse bias and D2 in forward bias. But the polarity across RL is the same as current takes the path from T3 to T1.
A center-tap rectifier's DC output also has ripples, being not smooth or steady DC. A capacitor at the output remove the ripple for a steady DC output.
continue at controlled rectifier https://www.electricaltechnology.org/2019/01/what-is-rectifier-types-of-rectifiers-their-operation.html#controlled-rectifier
continue at controlled rectifier https://www.electricaltechnology.org/2019/01/what-is-rectifier-types-of-rectifiers-their-operation.html#controlled-rectifier
Three-phase rectifiers
Three-phase rectifiers
[4.2] A three phase (3Φ) rectifier has a 3 phase input,
is crucial for industrial applications and energy transmission as DC (HVDC).
[1]
do research via deepseek
- Three-phase, half-wave circuit
- Three-phase, half-wave circuit
- Three-phase, full-wave circuit using center-tapped transformer
- Three-phase, full-wave circuit using center-tapped transformer
- Three-phase bridge rectifier uncontrolled
- Three-phase bridge rectifier uncontrolled
- Three-phase bridge rectifier controlled
- Three-phase bridge rectifier controlled
- Twelve-pulse bridge
- Twelve-pulse bridge
Voltage-multiplying rectifiers
Voltage-multiplying rectifiers
Controlled rectifier
Controlled rectifier
Filtered and unfiltered rectifier
Filtered and unfiltered rectifier
"Filtered" and "unfiltered" don't count as types of rectifiers, but instead depict whether a rectifier's output has been smoothed or not.
A filtered rectifier or smoothed rectifier output has a filter circuit (capacitor, inductor, or LC/RC filters) to smooth the output, making a near-constant DC voltage with reduced ripples.
E.g. Bridge rectifier via a smoothing capacitor (common in power supplies).
An unfiltered rectifier only does rectification (AC to pulsating DC) without smoothing, only using diodes and pulsating DC with ripples (unpure). It's used for simple battery chargers, since ripples don’t matter and some motor drives, when pulsating DC is acceptable.
Related pages
Related pages
[R1] Week 4 ELE8922A 316 Electrical Principles II notes: Rectifier - (Algonquin College) Canva
References
References
[1] Wikipedia
[2] GeeksforGeeks
[3] Youtube
[3.1] What is a Half Wave Rectifier? Circuit, Working and Waveform Representation
[3.3] How AC is turned to DC! EASY! (Rectifiers): Electronics Basics 7
[3.7] Full Wave Bridge Rectifier + Capacitor filters + half wave rectifier
[3.8] How to convert AC to DC | half-wave and full-wave rectifier circuit explained
[3.9]
[3.10]
[3.11]
[3.12]
[3.13]
[4] Full Wave Rectifier - ElectronicsTutorials
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