VOLTAGE REGULATIONA LINEAR power supply begins with a power transformer, followed by a rectifier, filter capacitors and some means of voltage and/or current regulation so that the 'load' sees the same voltage regardless of demand. Below are four versions of regulation all using the same rectifier type: half wave (HW), voltage doubler (VD), Bipolar (BP makes two voltages).
FIGURE-1a: A voltage-doubler derives two voltages from a single transformer winding. Keep in mind that the transformer's voltage specification is always RMS. The output of the AC-to-DC conversion - before regulation - will be load dependent, but unloaded could be as high as the AC input (from the secondary) divided by .707 (the square root of 2 = 1.414, which when divided by 2 = .707), quite simply about 70% of the area of the sine wave. The zener diodes will clamp at a specific voltage, this is also known as a shunt regulator. Note that the zener diodes are reverse biased (avalanch mode), while the LEDs are forward biased.
