Check for LM317/LT108x for adjustable solution, or LM7812/LT108x-12 for fixed, 12V version. If you plan to use heavy loads, you probably would want to remove some windings, because linear regulators waste unneeded voltage in heat, but for low current applications small heatsink will do the trick.
With what load current did you measure the output voltage? And what was the AC Mains voltage at the time?
If the load current is to be variable while the voltage needs to stay at about 12 Volts, then a three-terminal regulator might be a good choice, or, a switchmode regulator.
You first need to figure out what the likely range of transformer output voltages would be, with the minimum and maximum likely AC Mains voltage, transformer regulation, and the minimum and maximum load current.
You can calculate the required minimum smoothing capacitance, based on the worst-case combination of the transformer output voltage and load current ranges, to make sure that the bottom of the ripple voltage waveform Never causes the regulator's input minus output voltage to get too close to the regulator's specified dropout voltage (otherwise the output voltage gets really ugly). i.e. Calculate how much smoothing capacitance is required to ensure that the ripple voltage waveform, before the regulator, can never dip down too near to a voltage equal to the regulator's output voltage plus its dropout voltage spec.
All of the basic equations and concepts that you need are at the following link:
Unregulated Power Supply Design
Cheers,
Tom
If the load current is to be variable while the voltage needs to stay at about 12 Volts, then a three-terminal regulator might be a good choice, or, a switchmode regulator.
You first need to figure out what the likely range of transformer output voltages would be, with the minimum and maximum likely AC Mains voltage, transformer regulation, and the minimum and maximum load current.
You can calculate the required minimum smoothing capacitance, based on the worst-case combination of the transformer output voltage and load current ranges, to make sure that the bottom of the ripple voltage waveform Never causes the regulator's input minus output voltage to get too close to the regulator's specified dropout voltage (otherwise the output voltage gets really ugly). i.e. Calculate how much smoothing capacitance is required to ensure that the ripple voltage waveform, before the regulator, can never dip down too near to a voltage equal to the regulator's output voltage plus its dropout voltage spec.
All of the basic equations and concepts that you need are at the following link:
Unregulated Power Supply Design
Cheers,
Tom
Dear All,
I need at least 2A.
I measured the DC voltage directly at the output terminal without any load.
The input voltage was 220V at that time-stepped down to 15V via a toriodal transformer.
There is already a voltage regulator circuit in situ but the DC voltage was 19V instead of 12V. Is there any simple way to step down the voltage without rebuilding the whole circuit? Can I add resistors across the output terminals to bring down the voltage?
Thanks
I need at least 2A.
I measured the DC voltage directly at the output terminal without any load.
The input voltage was 220V at that time-stepped down to 15V via a toriodal transformer.
There is already a voltage regulator circuit in situ but the DC voltage was 19V instead of 12V. Is there any simple way to step down the voltage without rebuilding the whole circuit? Can I add resistors across the output terminals to bring down the voltage?
Thanks
What kind of voltage regulator is in now?
Does it need a minimum load to function properly?
If so, what happens to the voltage when you apply that minimum load?
If that does the trick, the question to you last answer should be "yes", provided you use resistors that can deal with the power they're dissipating.
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