Introduction to SMPS (Switched Mode Power Supply)

Description

Contributor: 
D.Mohankumar
 
Voltage converter
This stage has a high frequency transformer and the inverted AC drives its primary windings. This creates the up and down voltage at the output. If DC is required, the output AC is converted to DC using a rectifier circuit using Silicon diodes or Schottky diodes (fast recovery and minimum loss of current and low forward voltage drop) . The rectified output DC is then filtered using the filter section consisting of inductors andcapacitors. Some non isolated SMPS contains an inductor instead of the transformer and the circuit act as boost converter or buck converter. In high voltage SMPS,Capacitor-Diode multiplier is used instead of inductors or transformer.

 

Output regulator
The output stage always monitors the output voltage by comparing with a reference voltage using a feedback system. For safety reasons, the output stage is isolated by an optoisolator as seen in the SMPS of computers. In some SMPS, Open loop regulation is used without feedback circuit and constant voltage is fed to the transformer input.

 
The feedback circuit needs power to run before it can generate power, so an additional non-switching power-supply for stand-by is added.
SMPS Mobile Charger
 SMPS Mobile Charger

 

Added advantages of SMPS over the conventional linear power regulators are:
1.      Light weight since the transformer is too small and it  it operates at high frequency of 50Hz-1MHz.
2.      Output voltage is well regulated and controlled by duty cycle and there is little resistive loss since the transistor fully on or off during switching.
3.    Greater efficiency since the switching transistor dissipates very little heat. The SMPS can fail and can cause very high output voltage that destroys the equipment.
Trouble shooting
Breakdown of SMPS can cause the PC either restarts automatically or shutdown instantly. Confirm the SMPS complaint as follows:
1.      Confirm whether the power cord is tight in the socket of SMPS and is connected well in the UPS.
2.       Remove the 4 pin connector and connect a 10 Ohms 10 Watt resistor across the yellow (+ 12V) and black (Gnd) pins of the connector.
  
1.      Connect the power code to UPS and connect the 24 pin cord to the Mother board 

 

1.      Short the pin 16 (Green) with the adjacent black pin (pin17) using a short wire.
2.      If the Fan runs normally, SMPS is working normally.
3.      If not, unplug the fan and check it with 12 volt supply. If the fan is OK, then the check the voltage at the output pins of the connecter. Voltage levels in the 24 pin connector are shown below.
 

 

Pin No
 

 

Wire Color
 

 

Output
1
Orange
+3.3 V
2
Orange
+3.3 V
3
Black
GND
4
Red
+5 V
5
Black
GND
6
Red
+5 V
7
Black
GND
8
Gray
9
Purple
+5 V Standby
10
Yellow
+12 V
11
Yellow
+12 V
12
Orange
+3.3 V
13
Orange
+3.3 V
14
Blue
-12 V
15
Black
GND
16
Green
17
Black
GND
18
Black
GND
19
Black
GND
20
White
-5 V
21
Red
+5 V
22
Red
+5 V
23
Red
+5 V
24
Black
GND
 

 

 


 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
If the voltage in the pins is not as specified, replace the SMPS before powering the PC again.

 

Comments (4)

I need an circuit diaghram of

I need an circuit diaghram of SMPS ... ANyone can help me in doing this ?

 

I need an circuit diaghram of

I need an circuit diaghram of SMPS...

PLZ help.....

  I need an circuit diaghram

 

I need an circuit diaghram of SMPS...

Hi sir I am designing SMPS

Hi sir

I am designing SMPS based Battery charger(Moblile).

looking for help in terms Good website or if you have material plz snd at purisd08@gmail.com..
Thank you