You still commonly see the dual diode center tap configuration in outputs of ATX power supplies. They usually have one large dual diode package common cathode per rail.
The reason why the full bridge rectifier had a lower voltage (10.5 instead of 11), was the voltage drop by the diodes. There the current has to flow through two diodes. The other versions only have one diode in their paths.
Usually when explaining circuits i use the term reference (vref specifically) instead of ground unless it is tied to earth ground. Ground tends to throw people off. Just easier especially when dealing with floating or biased voltages.
Thanks for the videos, keeps me thinking. An advantage of a center taped transformer over the full bridge is you only get one diode forward voltage drop which might be a consideration? There is the also the split supply advantage as mentioned by other commenters and a half wave rectifier without any reverse current in the other half cycle increase magnetic losses in the core. Thanks for all the great content, keep it coming pls.
I'd be interested in how to add a current control option to a basic linear power supply. I've googled that but find it hard to understand. Thanks for your channel!
Your scope, if AC powered, will have the returns on the scope referenced to the Earth or safety ground. So if you are measuring something referenced to the earth or safety ground the scope has to have the Ground connection tied to this earth ground.
Now you have me questioning how a scope/meter knows it's looking at a negative voltage or a positive voltage. If all it can see is a difference in potential, how does it know "which way is up"?
One of the leads on a 'scope or multimeter probe will be the "reference" lead. This is the "ground" clip on a 'scope or the black/negative lead on a multimeter. The voltage shown on the 'scope or meter is relative to the reference lead. So if you put the red lead on +12V on a PSU and the black lead on ground, the multimeter will show +12 V; if you reverse the two probes it will show -12 V. _All_ voltages in a system are relative; you just pick some arbitrary point in a circuit to call "ground" and then everything is relative to that. That was the point being made near the end of the video. Actually, you don't even need to pick a particular point in a circuit; I can just arbitrary label something run from a 12 V PSU as having +112 V and +100 V power inputs, and nobody can say I'm wrong (though they may not be able to find any point in the circuit that actually measures 0 V relative to my 0 V reference. But even at "112 V" and "100 V", my two power inputs are still 12 V apart.
@@Curt_Sampson Oh, I totally get that part - earth is just a reference, just like someone standing next to a passing train, or someone on the train. My question was HOW does it(the meter/scope) know it's positive or negative.
@@GeorgeGraves For the multimeter the reference is always the "common" input, into which you usually plug the black lead. for the 'scope the reference is the "ground" pin. The voltage each shows is relative to that reference and that reference only. In other words, the instrument has no idea what _you_ may have chosen as the system reference voltage for your board. If you want to figure out what the "real" voltage is by that reference, you need to subtract the instrument reference from your system reference. E.g., if you put the black lead on your -5 V bus, and measure your +5 V bus, the meter will show 10 V, and you have to subtract -5 V from your 0 V ground reference, to get 5 V, and then subtract that from the 10 V measured at the read lead to see that it's measuring 5 V relative to your system ground. I have the feeling that this explanation may not work very well, since it doesn't seem very different from what I said before, but I hope it helps. The key is to remember that the meter is measuring only _one_ voltage, and that's the voltage difference between the black and red leads, regardless of where you place them on the board.
@@Curt_Sampson Thanks. I guess you're describing how to use a multimeter. I'm asking how it works - specifically how it knows a negative is a negative, and a positive is a positive.
@@GeorgeGraves If the red probe is at a spot higher in potential than the black probe, the voltage is positive; if the red probe is at a spot lower in potential than the black probe, the voltage is negative. Or are you asking how a voltage meter works internally? That differs for analogue and digital meters. An analogue meter has a moving coil through which a little bit of current tapped off the circuit passes; this causes the meter to move right (for positive voltages) or left (for negative voltages) .With an analogue meter you (usually) cannot measure negative voltages because the rest point of the coil is at (nearly) full left deflection of the indicator needle. (In this case, if you see the needle "bump" left, you need to reverse the leads and read the deflection rightwards as a negative voltage.) But some voltmeters have a rest position in the centre, allowing you to read either positive or negative voltage directly off the needle over the scale. A digital meter uses an ADC (analogue to digital converter) to compare the input voltage to a carefully calibrated constant voltage source; these are complex and I won't go into the details here. But the principle is the same. They can either have the "zero voltage difference" point in the middle of the ADC, so that half the resolution is positive and half negative or could, presumably do two reads with the second doing a virtual "swap" of the lead; one reading will be zero or max scale, and the other will be the voltage difference. But it's probably cheaper just to add one more bit of resolution to the ADC than to build the circuitry to do this swap.
You can, if you are expecting a reasonably balanced loading between the positive and negative sides, use the center tap of the transformer as your ground reference. You'd have separate filtering and regulation for each side.
I took the idea of half-wave rectification a step further by splitting a full bridge rectifier into two parts. This is how my NO-NEUTRAL circuit works for smart relays needing a neutral. ua-cam.com/video/oBR5O391m_c/v-deo.html
You still commonly see the dual diode center tap configuration in outputs of ATX power supplies. They usually have one large dual diode package common cathode per rail.
There is a 4th way too. Using the CT and a bridge to provide a split supply.
The reason why the full bridge rectifier had a lower voltage (10.5 instead of 11), was the voltage drop by the diodes. There the current has to flow through two diodes. The other versions only have one diode in their paths.
I hope you plan on discussing the advantages and disadvantages of tying or not tying the two grounds (primary and secondary) together.
Usually when explaining circuits i use the term reference (vref specifically) instead of ground unless it is tied to earth ground. Ground tends to throw people off. Just easier especially when dealing with floating or biased voltages.
Excellent explanation! Reality shown on the osciloscope vs theory, you combined them great! Thank you, looking forward for learning more from you! ☺️
I hope the equipment being powered by your power supply _also_ doesn't mind which way round it's connected!
One more example here could be a split positive/negative supply with a center-tapped winding and a FULL BRIDGE RECTIFIER :)
Thanks for the videos, keeps me thinking. An advantage of a center taped transformer over the full bridge is you only get one diode forward voltage drop which might be a consideration? There is the also the split supply advantage as mentioned by other commenters and a half wave rectifier without any reverse current in the other half cycle increase magnetic losses in the core. Thanks for all the great content, keep it coming pls.
Hii, Can you make a video about switching pre Regulators (Tracking Pre Regs) ?? which are used before linear regulators
Help linear power supply scr..
To control the output voltage
I'd be interested in how to add a current control option to a basic linear power supply. I've googled that but find it hard to understand. Thanks for your channel!
ua-cam.com/video/0cbqbb9PmRY/v-deo.htmlsi=xTyFZMIoK6CDVA42
Nice. A suggestion: Mount your camera up top. Maybe it's me but the hands in full view when writing are not working for my viewing comfort.
Why does an earth ground make the ground connection matter?
if the power supply is earth ground referenced and you connect to a device that is earth ground referenced, good or bad things can happen
@@IMSAIGuy thank you!
Your scope, if AC powered, will have the returns on the scope referenced to the Earth or safety ground. So if you are measuring something referenced to the earth or safety ground the scope has to have the Ground connection tied to this earth ground.
Now you have me questioning how a scope/meter knows it's looking at a negative voltage or a positive voltage. If all it can see is a difference in potential, how does it know "which way is up"?
One of the leads on a 'scope or multimeter probe will be the "reference" lead. This is the "ground" clip on a 'scope or the black/negative lead on a multimeter. The voltage shown on the 'scope or meter is relative to the reference lead. So if you put the red lead on +12V on a PSU and the black lead on ground, the multimeter will show +12 V; if you reverse the two probes it will show -12 V.
_All_ voltages in a system are relative; you just pick some arbitrary point in a circuit to call "ground" and then everything is relative to that. That was the point being made near the end of the video.
Actually, you don't even need to pick a particular point in a circuit; I can just arbitrary label something run from a 12 V PSU as having +112 V and +100 V power inputs, and nobody can say I'm wrong (though they may not be able to find any point in the circuit that actually measures 0 V relative to my 0 V reference. But even at "112 V" and "100 V", my two power inputs are still 12 V apart.
@@Curt_Sampson Oh, I totally get that part - earth is just a reference, just like someone standing next to a passing train, or someone on the train. My question was HOW does it(the meter/scope) know it's positive or negative.
@@GeorgeGraves For the multimeter the reference is always the "common" input, into which you usually plug the black lead. for the 'scope the reference is the "ground" pin. The voltage each shows is relative to that reference and that reference only.
In other words, the instrument has no idea what _you_ may have chosen as the system reference voltage for your board. If you want to figure out what the "real" voltage is by that reference, you need to subtract the instrument reference from your system reference. E.g., if you put the black lead on your -5 V bus, and measure your +5 V bus, the meter will show 10 V, and you have to subtract -5 V from your 0 V ground reference, to get 5 V, and then subtract that from the 10 V measured at the read lead to see that it's measuring 5 V relative to your system ground.
I have the feeling that this explanation may not work very well, since it doesn't seem very different from what I said before, but I hope it helps. The key is to remember that the meter is measuring only _one_ voltage, and that's the voltage difference between the black and red leads, regardless of where you place them on the board.
@@Curt_Sampson Thanks. I guess you're describing how to use a multimeter. I'm asking how it works - specifically how it knows a negative is a negative, and a positive is a positive.
@@GeorgeGraves If the red probe is at a spot higher in potential than the black probe, the voltage is positive; if the red probe is at a spot lower in potential than the black probe, the voltage is negative.
Or are you asking how a voltage meter works internally? That differs for analogue and digital meters.
An analogue meter has a moving coil through which a little bit of current tapped off the circuit passes; this causes the meter to move right (for positive voltages) or left (for negative voltages) .With an analogue meter you (usually) cannot measure negative voltages because the rest point of the coil is at (nearly) full left deflection of the indicator needle. (In this case, if you see the needle "bump" left, you need to reverse the leads and read the deflection rightwards as a negative voltage.) But some voltmeters have a rest position in the centre, allowing you to read either positive or negative voltage directly off the needle over the scale.
A digital meter uses an ADC (analogue to digital converter) to compare the input voltage to a carefully calibrated constant voltage source; these are complex and I won't go into the details here. But the principle is the same. They can either have the "zero voltage difference" point in the middle of the ADC, so that half the resolution is positive and half negative or could, presumably do two reads with the second doing a virtual "swap" of the lead; one reading will be zero or max scale, and the other will be the voltage difference. But it's probably cheaper just to add one more bit of resolution to the ADC than to build the circuitry to do this swap.
How do you get + and - voltage (like for an audio opamp circuit) out of the bridge example?
Google it.
Use the CT transformer and a bridge with two filter capacitors.
You can, if you are expecting a reasonably balanced loading between the positive and negative sides, use the center tap of the transformer as your ground reference. You'd have separate filtering and regulation for each side.
I took the idea of half-wave rectification a step further by splitting a full bridge rectifier into two parts. This is how my NO-NEUTRAL circuit works for smart relays needing a neutral. ua-cam.com/video/oBR5O391m_c/v-deo.html
#711 update?
It's leading somewhere
First😂
Fine I'll be second then. Lol
third
No one cares. These comments scream loser.
Sorry, I am late today.