The half-wave diode rectifier is not only used with a resistive load. In this applet you will see how the voltages and currents for the load and diode changes when different passive elements are connected.

Circuit 1: This shows that the diode only allows current to flow in one direction and that the load (output) voltage only has a positive value. When the input voltage goes negative, the output voltage is zero. Adjust the resistor value to see how the current changes.

Circuit 2: In this case there is an inductor in series with the load resistance. The inductor limits the rate of rise of current compared to the resistor-only circuit. The current continues to increase while the input voltage is greater than the load voltage. The current decreases to zero (it can not go negative) when the input voltage is less than output voltage. The inductor causes the current to flow in the positive direction through the diode even though the input voltage is negative (in the resistive example there was no current flow for negative input voltages). The voltage across the diode is zero when the diode is conducting and when the current reaches zero the diode voltage suddenly jumps to the input voltage. By making the inductor value larger the peak current is reduced and the conducting time of the diode is increased.

Circuit 3: A capacitor is now added in parallel with the load resistor. The role of the capacitor is to act as energy store when the diode is not conducting. This way the load now receives a more constant voltage than for the two previous circuit configurations. The capacitor is sometimes called a “smoothing” capacitor. The diode now only conducts when the input voltage is greater than the capacitor voltage. This means that the diode only conducts for a relatively short time and the current peak is now much larger than before. The inductor helps smooth out the input current, making it less peaky. The output voltage now has a DC component and a voltage ripple on top of it. Notice that by making the capacitor value smaller, the ripple gets larger.

Circuit 4: In this case there is a DC source connected to the output. This circuit can be viewed as the case where an extremely larger capacitor has been connected to the output and that the ripple has reduced almost to zero. The DC voltage value changes the peak value of current and the conduction time if the diode. An application for this circuit could be an automotive battery charger since the battery looks like a constant voltage source.

• In all the circuits you can shift the time point by dragging the red line. As the time changes so will the current path in the circuit.
• Circuit 1: Adjust the load resistance. As the resistance is decreased, the current in the diode and load increases. The conduction time of the diode does not change.
• Circuit 2: Adjust both the resistance and inductor value. Notice how the length of time the diode is conducting for changes with both the inductor and resistor value.
• Circuit 3: Adjust the inductor, capacitor and load resistor value. Notice the difference in the voltage across the load, it is now continuous. This also has shortened the time the diode is conducting current for, what is the impact on the current waveform shape?
• Circuit 4: Change the level of the output DC voltage source and the inductor value. Notice that the current waveform shape is more like the Circuit 3 rather than Circuits 1 & 2.