However in reality, during each half cycle the current flows through two diodes instead of just one so the amplitude of the output voltage is two voltage drops ( 2*0.7 = 1.4V ) less than the input V MAX amplitude. The single secondary winding is connected to one side of the diode bridge network and the load to the other side as shown below. The main advantage of this bridge circuit is that it does not require a special centre tapped transformer, thereby reducing its size and cost. This type of single phase rectifier uses four individual rectifying diodes connected in a closed loop “bridge” configuration to produce the desired output. The Full Wave Bridge RectifierĪnother type of circuit that produces the same output waveform as the full wave rectifier circuit above, is that of the Full Wave Bridge Rectifier. The main disadvantage of this type of full wave rectifier circuit is that a larger transformer for a given power output is required with two separate but identical secondary windings making this type of full wave rectifying circuit costly compared to the “Full Wave Bridge Rectifier” circuit equivalent. To obtain a different DC voltage output different transformer ratios can be used. The peak voltage of the output waveform is the same as before for the half-wave rectifier provided each half of the transformer windings have the same rms voltage value. Where: V MAX is the maximum peak value in one half of the secondary winding and V RMS is the rms value. This configuration results in each diode conducting in turn when its anode terminal is positive with respect to the transformer centre point C producing an output during both half-cycles, twice that for the half wave rectifier so it is 100% efficient as shown below.
A multiple winding transformer is used whose secondary winding is split equally into two halves with a common centre tapped connection, (C). In a Full Wave Rectifier circuit two diodes are now used, one for each half of the cycle.
The average (DC) output voltage is higher than for half wave, the output of the full wave rectifier has much less ripple than that of the half wave rectifier producing a smoother output waveform. Full wave rectifiers have some fundamental advantages over their half wave rectifier counterparts. Like the half wave circuit, a full wave rectifier circuit produces an output voltage or current which is purely DC or has some specified DC component. The circuit which allows us to do this is called a Full Wave Rectifier. One method to improve on this is to use every half-cycle of the input voltage instead of every other half-cycle. While this method may be suitable for low power applications it is unsuitable to applications which need a “steady and smooth” DC supply voltage. In the previous Power Diodes tutorial we discussed ways of reducing the ripple or voltage variations on a direct DC voltage by connecting smoothing capacitors across the load resistance.