If be below lowermost input voltage, the power input of power source is Pin, lowest inputs alternating voltage virtual value to be Vinacmin, so we think right now the volts d.c. after rectification is Vinmin=1.2×Vinacmin commonly, because be in,communication charges twice between cycle, right from the back the power supply of transformer is by capacitance store will assure, so it is OK that voltage declines computation comes out:

 

C×ΔV=I×Δt,

 

ΔV is voltage ripple, the 10% ～ that take Vinmin commonly 20% , I is capacitance is opposite from the back the =Pin/Vinmin of discharge electric current of circuit

 

And Δt is charging time-interval two (the discharge time that is the capacitance inside cycle of frequency of a labour) , can consider according to 0.8×1/(2×fac) , spoken parts in an opera, in the half sine cycle after communicating rectification namely, the time of 80% is to rely on to electroanalysis capacitance store will supply the transformer from the back.

 

 

So from this we can be calculated wave of the filter after giving the communication commutate that inputs end electroanalysises capacitance capacity.

 

Those who input side electroanalysis capacitance computation

 

Those who output side electroanalysis capacitance. Those who output end electroanalysis capacitance job is in high frequency below, ripple electric current is very big to its influence, we calculate those who output side to electroanalysis commonly according to the limitative condition of ripple electric current capacitance.

 

Electroanalysis the voltaic virtual value of the virtual value of ripple electric current on capacitance and sub commutate diode and the relation that export electricity are:

 

 

Electroanalysis the manufacturer home of capacitance can give out normally electroanalysis capacitance falls in a certain frequency, the IRCrms of rated ripple electric current when a certain temperature. But in using a process actually, we need to consider temperature effect and frequency effect. The ripple electricity that practical electric capacity can use is coefficient of frequency of × of IRCrms× temperature coefficient. Different manufacturer, offer temperature coefficient and frequency coefficient reference point to may differ, want to notice conversion. If the manufacturer was not offerred, so the numerical value below can offer reference:

 

Temperature coefficient:

 

105 ℃ : 1

85 ℃ : 1.7

65 ℃ : 2.1

 

Frequency coefficient:

 

100KHz: 1

10KHz: 0.9

1KHz: 0.8

120Hz: 0.5

50Hz: 0.32

 

Individual if ripple electric current is insufficient,electroanalysis, can use with many paralell connection. Additional, many paralell connection are used also conduce to reduce output voltage ripple.

 

Actual and final electroanalysis the choice of capacitance is right, besides should make sure enough voltage abundant is measured. Mainer is to electroanalysis the temperature of capacitance and temperature rise. Electroanalysis the temperature of capacitance every are elevatory 10 degrees, so life halve. Electroanalysis so the working temperature of capacitance, the limitation that is designed life by power source.

 

On the other hand, because may ab extra quantity of heat causes the temperature rise of capacitance, the loss that also may be oneself causes. So, there still is requirement of a limitation here, namely, from ℃ of temperature rise <5.