ISO 9001 / ISO 14001
01/06/2016
© Productivity Engineering GmbH
Page 11 of 22
EVA4204/4301
User Guide
Evaluation Board for 80W PFC Supply
6,028k
=
220nF
100Hz
2
π
1
=
z
C
z
f
2
π
1
=
SP
R
∗
∗
∗
∗
(34)
R4=5,6kOhm shall be chosen here.
The frequency of the second pole shall be at about 1/7 of the switching frequency. This defines the
capacitance of C
SP
.
4,6nF
=
6k
5,7kHz
2
π
1
=
SP
R
z
f
2
π
1
=
SP
C
∗
∗
∗
∗
(35)
C9=4,7nF shall be chosen here.
4.6 Self Biasing
PE4201/PE4301
Power supply of the PE4201/PE4301 during start up is provided through a high resistance resistor from
the power grid input voltage. The maximum resistance has to be calculated resulting from the minimum
input voltage and the required supply voltage of the PE4301 as well as the minimum required start up
current.
20Meg
Ω
=
5µA
20V
85V
2
=
ST
I
ST
V
in
V
2
=
STUP
R
−
∗
−
∗
(36)
To reduce start up time and account for leakage currents in the external diode the resistor is chosen to
be 4MOhm. This is an experimental trade-off. Make sure the chosen resistor type has the proper power
dissipation. Also, relatively high voltage over the resistor is to be accounted for (245V). It is
recommended to use two 2MOhm resistors is series.
The capacitor on VDD has to provide power until the switching of the power-MOSFET has started and
power will be provided from the help winding on the transformer. That can only happen after start-up
and when the input voltage is at maximum level. At 50Hz this time t
VDD
is about 10ms.
Current consumption calculates from the IC supply current and the loss in the power-MOSFET when
switching.
Power consumption of the IC is <450µA. Power-MOSFET switching consumption consists of an ohmic
part (resistor on ‘G’) and the dynamical part in the MOSFET. This is a charge changing process at the
gate capacitance in the device.
Switching frequency will not be constant over an input frequency period. It can be assumed to be 150
kHz on average. Also the duty cycle factor will not be constant. For simplicity it can be assumed to be
50%.
A simplified but sufficient equation to calculate the dynamic and ohmic portion is given in equation (37)
and (38) respectively.
