DC Power supply types

[alex_bong]

Hi all. just want to ask what is the main different between 'switching' and 'regulated' psu from normal psu. i only know that non regulated psu uotput will more than stated. like say stated 12VDC but measured read 16VDC...something like this....

Just bought HW1288 to replaced my spoiled regulated 12VDC psu.
So now, what's the different and and durabality of this 3 type??

[Super-Hornet]

Normal non switching power supply is using a big transformer (not the robot transformer) to "Step Down" the 240V to 12V (assuming the o/p u want is 12V).

In simple explaination, the steps are:
1. A.C. (Alternative Current) come from power socket and to the "Primary" of the transformer.
2. The transformer has a ratio of 1:20. That mean the o/p of the transformer (or "Secondary") is "Step down" to 12V.... A.C.
3. The 12V A.C. is them go to a bridge of Diode (also known as "rectifier") to convert it to a half wave sinusoidal (half sine wave) o/p. If u connect oscilloscope on it, it will see half sine wave go from 0V to 12V RMS.
4. The half wave is then "smooth" out to close to straight line using capacitors. (some good one also uses inductors also)

Now, because of the o/p from transformer is in Sine Wave, even though it is rated as 12V RMS, the peak voltage (the peak of the sine wave) is more than 12V. That is why after it goes to rectifier and filter (capacitors and inductors), the D.C. voltage is higher than 12V.


For "Regulated", the D.C. voltage is then connected to either "Linear" or "Switching" voltage regulator 1st. The voltage regulator is then convert/step down to the actual 12V as what u want. Normally this type of power supply has transformer o/p of more than 12V in order for the voltage regulator to work properly.

In Switch Mode power supply, it is using "switching on and off rapidly" to "Step down" the voltage to what u want. This design is much much more complicated (or more electronics stuff inside) and the usual transformer type.
In simple explaination:
1. A.C. from power socket is connected to bridge of diode (rectifier) in order to convert 240V AC to 240V D.C. Some uses center taping diode in order to convert 240AC to 480V D.C
2. Either a small simple non regulated or a high voltage, voltage regulator is use to tap 240VAC or from the 240/480V DC to a 5V D.C. This 5V D.C. is required to supply voltage to all electronics inside.
3. The 240/480V DC is connect in series of electronic high speed switch and a high speed transformer (this transformer is much smaller than the conventional transformer). The high speed switch is trigger On and Off rapidly by some electronics (or oscillator)
4. The o/p of the transformer u got is a very high speed PWM like voltage.
5. That o/p PWM like voltage is then fed to a series of filters (capacitors, inductors and sometime even voltage regulator) in order to produce a straight line D.C. voltage for u to use.
6. Most of the Switch Mode power supply also has a feedback circuitry that tap/monitor the o/p D.C. voltage and then control the "oscillator" frequency and thus, controlling the timing of "On-Off" switching. This in term, controlling the o/p of the voltage. Therefore, u have very consistent 12V D.C. supply.


Differences:
Normal non regulated tend to have higher current o/p than regulated (due if using higher current voltage regulator, it will cost more). O/P voltage always higher than it is rated. I/P voltage variation can affect the o/p voltage.

Regulated cost more than non regulated. The voltage regulator is the 1st one to fail. If u get cheapo type, then that regulator tend to fail earlier.

Switch Mode cost more than than the above 2. It is much smaller than non-regulated/regulated due to it do not require huge transformer. Tend to have much higher current than the rest. Has a very good or very straight line D.C. voltage. I/p voltage changes has little or no effect to the o/p voltage (depend on how good the feedback circuitry)

EDIT: One more thing, Switch Mode power supply is much much more efficient than the regulated and non regulated.

SH

[Adrianli]

Too much text for me to digest.

[LittleGiant]

Hi all. just want to ask what is the main different between 'switching' and 'regulated' psu from normal psu. i only know that non regulated psu uotput will more than stated. like say stated 12VDC but measured read 16VDC...something like this....

Just bought HW1288 to replaced my spoiled regulated 12VDC psu.
So now, what's the different and and durabality of this 3 type??

Regulated simply means a constant steady voltage of a certain value. U got it wrong about what measuring 16V of a 12Vdc output.

Get switching regulators. Runs cooler, more efficient and higher current rating.

Efficiency of switching regulators can be more than 80%. Typical linear regulators are very inefficient. let say using a linear regulator to step down from a 20V to a 5V and u are using the output with a 1A current draw, 20-5 x 1 = 15W will wasted as heat. And 15W is alot of heat.

As far as I know, transformers are still bring used to step down the mains voltage to a usable unregulated output for the rectifying diodes. So efficiency of these 2 supplies still aren't very good. But the efficiency of switching regulators beat linear regulators hands down.

[LittleGiant]

Regulated simply means a constant steady voltage of a certain value. U got it wrong about what measuring 16V of a 12Vdc output.

Get switching regulators. Runs cooler, more efficient and higher current rating.

Efficiency of switching regulators can be more than 80%. Typical linear regulators are very inefficient. let say using a linear regulator to step down from a 20V to a 5V and u are using the output with a 1A current draw, 20-5 x 1 = 15W will wasted as heat. And 15W is alot of heat.

As far as I know, transformers are still bring used to step down the mains voltage to a usable unregulated output for the rectifying diodes. So efficiency of these 2 supplies still aren't very good. But the efficiency of switching regulators beat linear regulators hands down.

I need to correct myself. I read wrongly I tot u were talking about regulated power supply having higher output voltage than rated when u were talking about non-regulated power supply.

2nd. As far as I know, transformers are still bring used to step down the mains voltage to a usable unregulated output for the rectifying diodes. So efficiency of these 2 supplies still aren't very good. Only some designs. Not all.

[alex_bong]

old psu

http://www.daddyhobby.com/forum/showthread.php?t=41285

After read urs explaination so, this psu in old thread is linear regulated type psu right?

In simple explaination, the steps are:
1. A.C. (Alternative Current) come from power socket and to the "Primary" of the transformer.
2. The transformer has a ratio of 1:20. That mean the o/p of the transformer (or "Secondary") is "Step down" to 12V.... A.C.
3. The 12V A.C. is them go to a bridge of Diode (also known as "rectifier") to convert it to a half wave sinusoidal (half sine wave) o/p. If u connect oscilloscope on it, it will see half sine wave go from 0V to 12V RMS.
4. The half wave is then "smooth" out to close to straight line using capacitors. (some good one also uses inductors also)

Now, because of the o/p from transformer is in Sine Wave, even though it is rated as 12V RMS, the peak voltage (the peak of the sine wave) is more than 12V. That is why after it goes to rectifier and filter (capacitors and inductors), the D.C. voltage is higher than 12V.


For "Regulated", the D.C. voltage is then connected to either "Linear" or "Switching" voltage regulator 1st. The voltage regulator is then convert/step down to the actual 12V as what u want. Normally this type of power supply has transformer o/p of more than 12V in order for the voltage regulator to work properly.

from this, i can say must be some electronics(rectifier? diode?) cause my old psu problem here....

[Super-Hornet]

http://www.daddyhobby.com/forum/showthread.php?t=41285

After read urs explaination so, this psu in old thread is linear regulated type psu right?




from this, i can say must be some electronics(rectifier? diode?) cause my old psu problem here....

I assume u referring to the one on the left (black color).
Well, size is big. so chances it is non "Switching" type (that is, transformer type).
Then in the picture, there is a word called "Regulated". Thus, it is a voltage regulator type.
Whether is it linear or switching voltage regulator or not...not sure.

If the o/p voltage is still D.C, then very highly chances that the voltage regulator is dead. Some voltage regulator that when they are dead, it is a "open" circuit while some is "closed" circuit. For open circuit, u get not o/p voltage. For "closed" circuit, your o/p voltage is the same as i/p voltage to the voltage regulator.

Normally for voltage regulator, the i/p voltage is higher than o/p voltage in order to work. Thus, when your voltage regulator is dead with "closed" circuit, your total o/p voltage is higher than 12V.

[Super-Hornet]

Too much text for me to digest.

Found some of the diagrams that help u understand

For Transformer, Regulated, it is this:



For Transformer, non regulated, it is similar to above except without regulator.


For Switched Mode Power Supply (or SMPS):




Transformer only:



Transformer + Rectifier:


Because of the

For, transformer of 12Vrms A.C. o/p type,
The peak voltage = 12V x 1.4142
Vpeak = 16V


Transformer + Rectifier + Smoothing


From the above calculation, the Vpeak = 16V. Thus, u always get the o/p voltage of higher than 12V.


Transformer + Rectifier + Smoothing + Regulator




Some designer, use "Center-Tab" transformer instead. By using Center-Tab, you only required 2 diodes and the o/p waveform is the same as full 4 diodes bridge rectifier. This has a good thing because designer can use 2 big diodes (for high current) instead of 4 big diodes. The bad point of using Center-Tab is because the transformer now has double number of copper coil.
{ can't find a better diagram yet }


SH