To explain the forward drop across a diode suggested by wvmarle
Consider this -
Diode - Wikipedia
In a small silicon diode operating at its rated currents, the voltage drop is about 0.6 to 0.7 volts.
The value is different for other diode types—Schottky diodes can be rated as low as 0.2 V, germanium diodes 0.25 to 0.3 V, and red or blue light-emitting diodes (LEDs) can have values of 1.4 V and 4.0 V respectively.
At higher currents the forward voltage drop of the diode increases.
A drop of 1 V to 1.5 V is typical at full rated current for power diodes.