switching power supply

    Question
    Answer
1. What is a conversion efficiency?
Ans:
Power Supply actually is composed by transformer and alter current /direct current the converters and steady voltage " last electric apparatus synthetically " that circuit make up not corresponding . This is " turned into the electric apparatus synthetically " Include two main parts inside - " transformer " and " current converter " ,And these two part itself have consumption of electric energy, the steady voltage circuit that they attach to is no exception naturally, so the power itself is a " power consumptive device " . Input energy of power can not 100% is turned into the effective energy available for every part in the CPU, the question of conversion efficiency has appeared like this.
Conversion efficiency of the power = CPU real-time output power /input real-time power * 100%
A, different power supply products, its conversion efficiency is different.
B, the same power supply product, under different working state, its conversion efficiency changes too.
A is very easy to be understood, because between different power products, their inherent varying voltage circuit, current converter and function circuit will all be different, it was not originally the same to combine with one's own power, so conversion efficiencies were different was natural. But why will conversion efficiency of the same product be changed? This will be talked about from voltage of output of the power firstly:
Ex: Suppose the input voltage is specified 220V, but have such different output demands as +12V, +5V, +3.3V,etc. it show that power has three different kinds transformer at least (" Coil Convolve rated " , " EMF Leakage rated " Difference) , because this three kinds of transformer exhaust are the same, meaning that output +12V, +5V,and +3.3V’s power supply their each corresponding transformer conversion efficiency are not the same also.
The machine at the different working state, frequency of utilization of every part and working load will be different, caused the working load at the outputting return circuit floated, so under different working state, the conversion efficiency of the power supply changes too.
We know through the analysis above, the flows of power supply’s own consumption not too much, but output’s float getting heavy. Usually thinking as that output load more heavy, the power supply unit load share consumption more smaller, at this moment the conversion efficiency is more higher.


2. Standard power supply’s requisition for conversion efficiency?
Ans:
Difference between Conversion efficiency and factors of PFC circuit
Some power recently claim that one's own conversion efficiency up to 98%, after researching what is called conversion efficiency in fact it is a power factor of active PFC circuit, the factor signifies that how much electric energy utilized by power supply ( input actual energy of power / supply energy of power with by electric wire netting) ,To active PFC circuit, the power factor can be up to 98% even 99% levels.
Generally speaking, conversion efficiency should be the power to supply with the energy to others equipment / the energy of inputting power, the target which the two signify is different.


3. Relationship between conversion efficiency and people?
Ans:
Strict with conversion efficiency, we can find it has important meaning. How is conversion efficiency closely related to we?
Ex: As to typical general power supply products, during the working time, the conversion efficiency is probably among 40%-55, mean that there is 45%- 60 of the electric energy that has been turned into heat and wasted. For example, a standard 15W power supply, the loss of power should be about 6.75W- 9W.
If change to a typical exchange type power supply, the conversion efficiency rises to 70%- 85, then the loss of the electric power is only 30%- 15, so long as the input power can reach 6W,the actual output power can reach 5W, from that we can see the consumption of two differ by 9W. If machine work for 10 hours every day, can saved 0.21 degrees (kilowatt hour) electricity one day, saved 77 degrees of electricity a year, has calculated with 0.6RMB for each degree electricity, we can save42RMB a year.
Meanwhile, it means make contributions to environmental protection while economizing on the electricity; On the other hand, the improvement of the conversion efficiency of the power means the reduction of its own caloric value of the power, so it should be good for helping to reduce the temperature of the machine.


4. What is EMI?
Ans:
Any high-frequency electronic product will produce the noise, Electronic noise can be divided into EMI and RFI。 Generally speaking, EMI influencing other electrons or the normal operation of electric equipment products through the cable, RFI influencing other equipments through the air, all make and Most country has issued rules to prevent electric device from EMC, such as European IEC (EN55015) , USA FCC PART 18, Japan JIS, etc. Among them Europe standard is the most sternness.


5. What is safety?
Ans:
It is safe norm, has clear statement and guidance to the device and electronic components, in order to avoid designing badly and improperly using to cause the accident. And then will cause the losses of the life, property. Most countries make one's own security regulation, because of the difference between geographical environment and voltage of various countries, the safety norm are not the same.
General demand for the safety:
Defend by shock of electricity, the fire, radiation, high temperature, chemistry, and dangerous machinery.


6. Safety mark?
Ans:
UL/CUL, FCC Mark (suitable for U.S.A.)
GS Mark (suitable for Germany)
PSE/S-mark (suitable for Japan)
CCC (suitable for China)
CSA (suitable for Canada)
EK-Mark (suitable for S. Korea)
PSB (suitable for Singapore)
ASTA Mark (suitable for Britain)
BSMI (suitable for Taiwan)


7. Why the safety component cannot changed by willing?
Ans:
It is that safety organization is in charge of accusing the safety components, any product which has obtained the safety, it can't be altered by will. Because the changed components don’t checked by the safety organization, it will affect the safety character.
Approved safety components, such as manufacture, material, model, specification if need to change, you must apply to safety organization, and pass their testing, then getting the formal certification means can be produced.

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