External characteristics of rectifiers

External characteristics of rectifiers

The external characteristic of a rectifier is the dependence of the voltage on the load device on the current in it (Figure 10).
In the rectifier without a filter (Fig. 7, curve 1) the voltage in the load and the current are interconnected by the relation:

where Unxx is the voltage at the rectifier output at idle, i.e., at Rн = ∞,
RD - the internal resistance of the diode in the open state,
Rтр - resistance of a transformer winding.
In the rectifier (Fig. 7, curve 1), the output voltage at idle will be Unxx, at the rectifier with a filter (Fig. 7, curve 2), the output voltage at idle will be larger and equal to the amplitude of the input voltage, since no load, the capacitor is charged to the amplitude value of the voltage of the secondary winding of the transformer.


Fig.7 External characteristics of rectifiers