I've been wondering about something for a while now. One of the main advantages about commercial SMPS power supplies is that they will work off a very broad input voltage range, generally about 85-240VAC. When winding a transformer, you'll have to wind the primary with the mimimum expected input voltage in mind, because at that voltage the circuit will be at it's maximum duty cycle. But what I was thinking was that there is potentially another advantage to winding a transformer for a much lower input voltage than what it will generally encounter; you'll need less turns for it's primary, thus saving a fair amount of space.
When building a SMPS yourself for use at home, it won't have to be made to the same kinds of standards as a commercial SMPS such as a laptop or phone charger, as the latter two have to function with every available kind of mains voltage arount the world (anywhere from 90 to 240 VAC), and also still be able to function effectively at wildy fluctuating input voltages. I live in the Netherlands, where we have a very stable 230VAC mains voltage (power outages are extremely rare, and the voltage fluctuates by no more than 3-4 volts). With that in mind, I was thinking that it would be both feasible and much more efficient space wise to wind the primary of my transformers for an input voltage of 80-100 VAC, even though they would never encounter such low voltages. By winding my primaries for 80-100VAC I would need only 40-50% the amount of turns (and thus space) compared to if I would wind them for the actual voltages that it would encounter in a worst case scenario (which would be 180-190VAC). Because I know that in reality the mains would never go below 180VAC, I could also wind the primaries with thinner wire, because for the same amount of power the current drawn at 180VAC is much less than at 80-100VAC. So that would also safe me a fair amount of space.
Unfortunately I also foresee a downside to winding the transformer of my SMPS for a much lower input voltage, and that's regulation. If I would build a SMPS which only needs to output a specific set voltage then I don't foresee much problems, however I'm planning on building a couple of adjustable voltage and current SMPS circuits. If a SMPS circuit has a transformer wound for a minimum input of 80 VAC but in reality get's ~240 VAC nearly all the time, then the circuit will only be on for for a third of it's maximum duty cycle (16,5% for a flyback or forward converter, and 33% for a half or full bridge) in order to adjust for the much higher volts/sec encountered at ~240VAC. I'm afraid that if I try to build an adjustable voltage and current SMPS based on the abovementioned transformer, that it won't have enough regulation to give a very stable and broad range of output voltages and currents. Am I correct in that assumption, and could anyone tell me if anything I wrote above is correct or not, and how well it would work? Thanks in advance!
When building a SMPS yourself for use at home, it won't have to be made to the same kinds of standards as a commercial SMPS such as a laptop or phone charger, as the latter two have to function with every available kind of mains voltage arount the world (anywhere from 90 to 240 VAC), and also still be able to function effectively at wildy fluctuating input voltages. I live in the Netherlands, where we have a very stable 230VAC mains voltage (power outages are extremely rare, and the voltage fluctuates by no more than 3-4 volts). With that in mind, I was thinking that it would be both feasible and much more efficient space wise to wind the primary of my transformers for an input voltage of 80-100 VAC, even though they would never encounter such low voltages. By winding my primaries for 80-100VAC I would need only 40-50% the amount of turns (and thus space) compared to if I would wind them for the actual voltages that it would encounter in a worst case scenario (which would be 180-190VAC). Because I know that in reality the mains would never go below 180VAC, I could also wind the primaries with thinner wire, because for the same amount of power the current drawn at 180VAC is much less than at 80-100VAC. So that would also safe me a fair amount of space.
Unfortunately I also foresee a downside to winding the transformer of my SMPS for a much lower input voltage, and that's regulation. If I would build a SMPS which only needs to output a specific set voltage then I don't foresee much problems, however I'm planning on building a couple of adjustable voltage and current SMPS circuits. If a SMPS circuit has a transformer wound for a minimum input of 80 VAC but in reality get's ~240 VAC nearly all the time, then the circuit will only be on for for a third of it's maximum duty cycle (16,5% for a flyback or forward converter, and 33% for a half or full bridge) in order to adjust for the much higher volts/sec encountered at ~240VAC. I'm afraid that if I try to build an adjustable voltage and current SMPS based on the abovementioned transformer, that it won't have enough regulation to give a very stable and broad range of output voltages and currents. Am I correct in that assumption, and could anyone tell me if anything I wrote above is correct or not, and how well it would work? Thanks in advance!
