Power Factor Pre-regulator

- The values of all input fields can be changed.
- If an input field is left empty, a default value is chosen. This value is displayed after leaving the input field in question.
- The switch mode power supply operates within a certain AC voltage-input range i.e. between
*V*_{in_min}and*V*_{in_max}. - The program needs the output values for the DC voltage
*V*_{out}and*I*_{out}. - The switching frequency
*f*is the operating frequency of the transistor (not the mains frequency!). - If the field "proposal" is activated, the choking coil
*L*is proposed as well as a value for the output capacitor*C*. These are chosen such that*I*_{L}= 0.4*Î*_{in_max}for*V*_{in_min}, and such that Δ*V*_{out}= 5% of*V*_{out}. (*I*_{in}=*I*_{out}.*V*_{out}/*V*_{in}) - If you should not be content with the proposed values, you can change
*L*as well as*C*. If this is the case, the field "proposal" is deactivated automatically. - The value
*V*_{in}is the value for the calculation of the current and voltage diagrams on the right side of the display.*V*_{in}must lie between*V*_{in_min}and*V*_{in_max}.

Harmonic- order n |
Input Power 75 to 600W Allowable maximum value of harmonic current per Watt (mA/W) / maximum (A) |
Input power > 600W maximum value of harmonic current (A) |
---|---|---|

3 | 3.4 / 2.30 | 2.30 |

5 | 1.9 / 1.14 | 1.14 |

7 | 1.0 / 0.77 | 0.77 |

9 | 0.5 / 0.4 | 0.40 |

11 | 0.35 / 0.33 | 0.33 |

Illustration 1: Direct half-wave rectification: |

Illustration 2: Boost Converter as Power Factor Pre-regulator |

Illustration 3: The inductor current |

For the output power *P*_{out} this leads to:

and for the input power *P*_{out}(t):

The input power consists of a DC component

and an AC component

The DC component is equal to the output power *P*_{out}:

The PFC is taken to be loss free but actually an efficiency of 95% is realistic.

With this efficiency, the input power emerges to:

The r.m.s. value of the input current has its maximum when the input voltage is at its minimal value, i.e. minimal mains voltage:

This value will be required for the calculation of the inductor current later.

Illustration 4: |

The current ripple amounts to (see Boost Converter):

For *L* it follows that:

Usually, one chooses:

The maximum inductor current then amounts to:

This leads to:

Through integration, for Δ

This implies:

The magnitude of the voltage ripple Δ*V*_{out} caused by Δ*W*, depends on the output voltage.

For the voltage ripple Δ*V*_{out} it follows that:

as well as for the output capacitor *C*:

Usually, one chooses Δ*V*_{out} = 5% of *V*_{out} = 380V. This results in a voltage ripple of +/- 10V. For 50/60Hz - mains it follows that the output capacitor should be: *C* = 0.5µF/W