S.M.P.S Reference

Summary of S.M.P.S

SMPS(Switching Mode Power Supply) uses semiconductor element like MOSFET which is useful to power
for switch and after transform direct current input voltage to square wave voltage at first, and is tool which
gets direct current output voltage which is controlled via filter.
It uses switching process of semiconductor element and efficiency is high and durability is strong, and is stabilized
power device which is advantageous to be small size and light weight compared with power supply device of
existing linear type by controlling flow of electric power.
S.M.P.S makes switching frequency high and can make small and light weight by being small energy accumulating
element and need development of high- speed semiconductor element for these things.
But if get higher switching frequency , should consider what power loss like switching loss and inductor loss increase,
and surge and noise which happens by switch.
The use of S.M.P.S is divided for communication and industry and civil like PC, OA machinery, home appliances.
Power Supply Division
  The type of Power supply is divided two.
The first is Linear type and the second is Switching type.
Linear Type
  The first is Linear type and the second is Switching type.Linear Type is composed of basic power supplier, electronical adjustment possibility resistance factor, And voltage sensing device and stabilized basic voltage.
When voltage sensing device detects continually DC output voltage and compares it with basic voltage, if changes output voltage and this adjusts adjustment possibility resistance electronically and the movement holds DC output voltage which wants immediately.
Switching Type

Switching Type is composed of basic power supplier and switching element, control circuit and stabilized basic
power .The movement principle is similar with linear, and monitors DC output power in control circuit and
compares with stabilized basic power.And if output power changes and holds output power which wants electronical switch adjustment.Type which control circuit controls switch has two, the one is what adjusts proportion of on-time of and off-time of switch and this is called to PWM (pulse-width modulation).
The other is the type which uses SCR(silicon controlled rectifier) instead of switching transistor which used in
PWM and because makes phase angle changed and so this is called to PCM(phase controlled modulation).

Comparison of Linear and SMPS

The advantage of linear type is available to adjust in very wide range from cutoff (0 volt output) to saturation (maximum output voltage).First of all disadvantage is, efficiency is only 30~40%.
And this needs some high voltage than voltage which needs in the second side of transformer and
this is called to head room.And the other disadvantage is what this is voluminous, heat sinking about one of linear factors, pass transistor has a lot volume and its transformer is 60Hz and volume is big too.
For example, in case of medium-power linear, weight of transformer is 50 pound.
And then this has big disadvantage in the trend which the instrument is miniaturized.

Division of power (stabilization power)
  1) Direct current direct conversion instrument (direct current chopper) +
control instrument (for stabilization)
  2) Direct current indirect conversion instrument (DC/DC converter in a narrow sense) +
control instrument (for stabilization)
B. Series power supply
SMPS and Series power supply
Type item
Series power supply
Low (30~60%) High (70~85%)
Large (Space of converter and radiator) Small (1/4~1/10)
Heavy(converter and radiator is heavy) Light (1/4~1/10)
(transformation, rectification, stabilization)
(rectification, switching, pulse control, transformation, rectification)
High(0.001~0.1%) Normal 0.1%~3%)
Ripple (P.R value)
Small (0.1mV~10mV) Big (10mV~200mV)
Transition response speed
Fast (50Ms~1Ms) Regular (500Ms~10Ms)
Correspondence of input voltage
If input voltage width is wide, efficiency is low.If input voltage width is not narrow, OK Can not correspond to direct current input.
100V/220V public use is available too.
* Cost
Low Regular (The gap is rapidly is decreasing.)
Components number is small and high but decreases for temperature rise. Go down temperature rise and is available same
No explosion
No Yes (filter, it is available to prevent with shield)
Whole Power for instrument assembly Power which needs DC input instrument and minimum size-high efficiency
Connectivity of indoor instrument
PCB installation is not available for
Transformer is heavy.
Small size, light weight component number is by100W and PCB installation is available.

* : Cost per W changes widely with power and circuit number
** : The number of ( ) inside has a lot exception generally.

Basic composition of S.M.P.S

Basic composition of S.M.P.S is composed of DC-DC converter which changes direct current input voltage to direct current output voltage which gets through input rectification 평활 circuit from alternating current input power, 궤환 control circuit which makes output power stabilized, overvoltage, over-electric current prevention circuit.

Orbiting control circuit is composed of error amplifier which amplifies error of output voltage again and comparator
Which compares Amplified error and chopping wave and generates drive pulse, and drive circuit which drives
main switch of DC-DC converter, and DC-DC converter is composed of main switch, reflux diode and LC filter
so called low band frequency filter in the second.
Here DC-DC converter is main part which is responsible for conversion of power and is divided into all kinds of
Converter according to size of input-output conversion proportion and circuit composition.
The circuit type of S.M.P.S can be divided into non-insulation type and insulation type according to high frequency
transformer or not.
Non-insulation type has Buck type, Boost type, Buck-boost type and C’uk type, and insulation has Flyback type,
Forward type, Full-bridge type and Half-bridge type.

Circuit type of S,M.P.S

Non-Isolation Type
Buck(Step-Down) Type

The main switch , if Q is on and electric Current from input gets through L and flows to output simultaneously, is accumulated in L, and if Q is off, and energy which is accumulated in L is emitted to output side via reflux diode D.
It is converted to output power which needs input power
and this movement is repeated with doing Ts to one cycle
Buck type shows up in the range which is low than input voltage and this is called “Pressure type converter” for this reason.

Boost(Step-Up) Type

When switch Q flows and if energy is blocked in L by inductor. Electrical current and energy which is accumulated in L is emitted to output side via reflux diode D.Boost(Step-Up) type is value which output voltage is higher than input voltage always and is called to “Boost type converter”.

Buck-Boost(Step-Down) Type
  Pressure- boost type has simultaneously characteristics Which Output voltage is higher or lower than input voltage and characteristics which polarity of output is opposed with input and this is so called to “polar part converter”.
 Isolation Type
Flyback Type

Fly back type is same with Buck-boost type in the basic movement .If switch Q flows and opposite polar voltage with 1st is induced in the 2nd coil of transformer and so diode D
biased conversely and is blocked, and so the electric power doesn’t flow in the 2nd coil and electric current flows in only the 1st coil and energy is accumulated by self inductance.

If the next switch is blocked and voltage which is opposite with the previous condition is induced and makes diode flowed and supplies accumulated energy in 자화 inductance of transfomer to load.
Fly back type is proper to apply to low output below 50W, and circuit is simple and economic, on the other hand Ripple electrical current of output Capacitance is big.

Forward Type

Forward type is applied a lot for heavy electrical use which output capacity is by 500W, and is same with Buck type in the basic movement and stability is distinguished and used widely to general communication which high reliability is needed.

If , the movement principle, main switch Q flows and D1 flows and D2 is blocked and electrical current from input side is transferred via transformer to output side and simultaneously energy is accumulated in inductor L.If Q is blocked in the next and D1 is blocked, and D2 is flowed and supplies energy which is accumulated in L to output side.

Push-Pull Type
  Push-Pull type is type which switch Q1, Q2 is ON, OFF
Alternately and is available to apply for big capacity below 1KW and drive circuit can be available to happen one side condition of transformer simply.
Half-Bridge Type

Half-Bridge type is applied for big capacity of 500W- some KW a lot and drive circuit is complicated.The movement principle, if switch Q1 flows and input electrical current flows via Q1 and transformer 1st coil simultaneously and is transmitted, and makes diode D1 flow and flows via output filter inductor L to output side.
At this time, if energy is accumulated in L and the next switch, both Q1 and Q2 is blocked, and energy which is accumulated in L makes diode D1, D2 pass reflux and is emitted to output side and voltage of transformer is “0”.It makes Q2 flow and flows to output side via L.At this time, energy is accumulated in L again and if the next switch, both Q1 and Q2 is blocked and energy which is accumulated in L makes D1, D2 flow reflux and is emitted to output side, and voltage of transformer is “0”.It moves repeatedly with making this course do one circle.

Full-Bridge Type
  Full-Bridge type is form which adds two of switches to Half-bridge type and uses 4 of switches, and a couple of switches (Q1, Q4 or Q2, Q3) flows and blocks repeatedly
And moves same with Half-bridge type, and drive circuit is very complicated and is applied for over some KW.

Power terms explanation

  1) Input Voltage Range
This is range of input voltage which can insure standard and alternating current is effective value and
Direct current input is net value.

2) Efficiency
This is proportion of output power and input effective power and is marked to
Efficiency = ( output electrical current/ input effective electrical current)*100(%).

3) Inrush Current
This is measurement of electrical current which flows at that time when permit input voltage to Power.

4) Output Voltage
This is value of direct current voltage which flows out in output step.

5) Output Current
This is electrical current value which can supply from power to load continually.

6) Line Regulation
This is regulation maximum value of output voltage when made input voltage changed slow into the
Standard range.

7)Load Regulation
This is regulation maximum value of output voltage when made output electrical current changed slow
Into the standard range.

8) Ripple
This is same recorded component with input frequency and switching frequency which is piled up in output
Voltage and is marked to Peak-to-peak.

9) Ripple Noise
This is noise component except ripple which is piled up in output voltage and marked to Peak-to-peak.

10) Temperature Drift
This is drift value of output voltage into temperature range of standard.

11) Rise Time
This is time until output voltage arrives 90% after permitting input.

12) Holding Time
This is time which output voltage holds voltage range of standard after blocks input and can supply stable output voltage
Momentary power failure too.

13) Isolation Voltage
This is voltage when permit alternating voltage of standard between appointed terminals and
Doesn’t discharge spark and power isn’t destroyed.

14) Isolation Resistance
This is resistance value when permits direct current voltage of standard between appointed terminals. 15) Operating Temp. & Humid
This is surroundings Temp. & Humid which can assure standard of power on moving

16) Storage Temp.& Humid
This is surroundings Temp. & Humid which can charge without raging fire of capacity on not moving.

17) Vibration
This is acceleration of vibration which doesn’t give damage to power as test condition of standard.

18) Impact
This is acceleration of impact which doesn’t give damage to power as test condition of standard
and is marked with acceleration and added time.

19) O.C.P : Over Current Protection
This blocks flowing of output current over standard and is function which protects power and
load if remove over-electrical current condition and output voltage returns automatically to original

20) O.V.P : Over Voltage Protection
This is protection function which blocks output of voltage of over standard in order not to be permitted
For over voltage at load and if protection circuit moves and power is blocked, after blocking input
And leave alone for some minutes and if re-put and output voltage returns to original condition.

21) Remote Sensing
This is used when there is length between power and load and can’t neglect a drop of electric
Pressure of coil and sensing coil holds voltage of point which connects to setting value.

22) Remote Control
This is used when use plural power commonly and set difference of between each power
Rise time and drop time and is function which makes power ON/OFF to outside signal.

Directions for the use

Input voltage
  The sine wave alternating current is effective value and a square wave is expressed to peak value,
And switching power rectifies input voltage and makes direct voltage close to peak value and
Inverter move when permit a square wave and should permit value of some 1.4 times of standard
In the case of alternating input, since there is difference in voltage, frequency according to using district
Should confirm. In the case that Line Filter or Choke Coil which inductance is big is inserted at input side, when input ON/OFF and because give Destruction of power or stress for CEMF(Counter Electromotive Force) generation
and should alert.
In the case of Dual Input Voltage type should adjust 110/220V SELECTOR according to input voltage (AC 110V or AC 220V) and use.

Series operation

In the case that connect plural power to series, there are two circuit types and Fig-10 has any problem.




Fig-11 may not rise because electrical current of one side power is flowed to the other side power for difference of between rise time and drop time of PS1 and PS2.



In the case this if insert output diode D1, D2 like Fig-12 and series operation is available.

Parallel operation

A. Power without function of parallel operation
First of all, if electrical current flows in power of side which voltage is high for difference of output voltage of between PS 1 of Fig-13 and PS2 and O.C.P operates
and voltage is fallen, electrical current flows in power of the other side and one side power is over electrical current condition and makes fault rate of power high or makes life short.




In the case of Fig-14, this is how to insert resistance to output and adjust output electrical current balance of PS2, and resistance value is determined according as how much balance and power loss of resistance is determined.

Fig-15 is how to adjust output electrical current balance of between PS1 and PS2 in the using of slope of electrical current –net direction voltage characteristics of diode, and should consider pressure of diode, loss power and radiant heat and so on.

B. Power with parallel function
Power with CB terminal connects power as it is with parallel and is available,
Parallel operation circuit of power inside moves and adjusts output electrical current balance of each power automatically.
Load without output of power
  In the case of Lamp or static currenr load, output doesn’t show up in power which has over –electrical
current protection circuit of 'ㄱ'.This is condition which V-1 characteristics trace of load happens in over-electrical current protection characteristics coil the after voltage in load is permitted until arrives stability point and need to
consider load characteristics from setting time.
This is solved with power which has over-electrical current protection circuit of most reverse L shape.
Radiant heat

All of the difference of between input effective power of power and output power changes to
Heat and need radiant heat definitely.
If make power operated in free space and is radiated or radiated heat to convection current,
In the case that it is in CASE, make entrance, exit of air in outside and what make exit bigger than entrance
is more effective for radiant heat effectiveness.
Since the power with built-in FAN is cooled compulsively in itself and may treat only surroundings temperature.
The conduction cooling is type which fixed heat components of power in sheet metal like Aluminum board and
Radiate heat to outside.

Counter-plan for SMPS failure

Check items
Used item
Input side Rated voltage is not input. Didn’t you put AC110V in power which input voltage range is converted by hand?
Didn’t you put 110V to 220V use?
Connect voltage selection terminal with 220V in the 220V system and voltage selection terminal with 110V in the 110V
System(except FREE VOLTAGE Item)
The input voltage isn’t permitted to power. Check that wiring of power exactly is set or not. Connect F,G terminal with input voltage coil Setting to slow speed to AC or DC input terminal. All MODEL
Didn’t outside FUSE be cut off? In the case that built-in FUSE in power has drastic measurement, request repair to our Company.
Wrong wiring (lockup condition inferiority) Is wiring correct according to load? (Wrong connection between +V terminal and GDN terminal) Repair wiring
Didn’t output be short? Amend SHORT
Didn’t connection use of SHORT
get loose?
Lock SHORT again
Over voltage protection is working. Wasn’t output voltage setting use V.R turned to clockwise rotation too much?(Output voltage adjustment value has rated failure.) OFF input voltage and turn V.R to counter clockwise rotation and leave it alone for 5min. and ON power again.
Over electrical current protection is working. Wasn’t output electrical current of power had rated electrical current failure? Check rated electrical current of using power and measure real output electrical current.
Over heat protection is working Wasn’t built-in FAN in power or wind of FAN blocked? Remove obstacle, and interrupt
Input and leave it alone in room temperature after and cool it sufficiently after and restart it
WTC 220~1500
Has been Determining. Wasn’t water stained? Water shouldn’t be stained. All MODEL
Hasn’t drastic temperature change had? If possible, make surroundings temperature change a little.