Rectifiers Flashcards
What is the purpose of a rectifier?
A rectifier converts AC to DC power
Draw a single PN junction diode circuit
Single diode in series with load resistor and AC power system
Draw the AC input power waveform for a sinusoidal source
Wave line, with one half cycle (+ve) and one negative (-ve)
Draw the output DC power waveform
One half cycle curved up and down in positive region, with flat line on middle line for the next half cycle
What is the advantage of a single diode half wave rectifier?
Simple, 1 component circuit
What is the disadvantage of a single diode half wave rectifier?
Half of incomin g signal (wave) is wasted, with power being supplied intermittently
Draw the circuit for a two diode FULL WAVE rectifier
AC power system connected to two diodes on either side of load resistor in central branch
Draw the input and output waveforms for a full wave rectifier
Input: standard AC sinusoidal curve
Output: Skipping stone bouncing along neutral line
What are the advantages and disadvantages of a two diode full wave rectifier?
Advantage: provides full wave rectification, so no signal lost
Disadvantage: extra cost of centre tapped transformer
Draw the circuit of a four diode “bridge” full wave rectifier
AC power source connected to four diodes in bridge configuration with load resistor in series
What are the advantages and disadvantages of a bridge full wave rectifier?
Advantages: avoids expense of a cent tapped transformer
Disadvantage: requires more diodes
What are the collective problems with simple power supplies?
Voltage drop: Vout drops as current drawn by load increases, because of the voltage drop inside power supply
Ripple: small, unwanted residual periodic variation of the DC output of a power supply
How would you tackle Ripple in a bridge rectifier?
Add a smoothing capacitor in parallel with load resistor
Waveform with capacitor shows straighter skipping stone waveform, so ripple of original waveform is reduced
What is the equation for ripple?
dV = ____Vpk____
2f x RL x Cs
(Frequency x load resistor x smoothing capacitor)
What is the equation for mean voltage output?
Vmean = Vpk - (0.5 x ripple)
