Board description

UM1470

8/19

Doc ID 022241 Rev 1

3.2

Description of the schematic

The input part of converter consists of an input single-wave rectifier, EMI/EMC filter and bulk

capacitor.

The input rectifier is based on two 1 A/1 kV general purpose diodes (D1, D2). The 2 kV

blocking voltage is selected to increase robustness against input surge pulse.

The EMI filter is based on a

π filter (C10, C2, L1) and the possibility to place an input foil

capacitor may also be an option. This capacitor is not mandatory in order to satisfy EMI

limits (see Figure 9), but it can be used in case a wider margin of EMI limits is required.

The input EMC filter is based on the inrush resistor R2 and bulk capacitors C10 and C2.

The buck-boost converter itself uses a standard connection. The VIPer06XS (U1),

containing an active switch and controller, is placed as the high side with floating reference.

After turn-ON of the internal MOSFET the energy is stored in the inductor L3. After U1 is

turned off the energy stored in the L3 is distributed to the output capacitor C5 via diode D4

and in capacitor C3 via diode D3. It can be expected that the voltage drop over capacitor C3

is almost the same as the voltage drop over output capacitor C5. The feedback loop

performs constant voltage regulation and the output voltage is measured across C3 by

a voltage divider (R1 and R3) connected to the FB pin of U1.

3.3

Layout

The layout of the PCB is based on a one-sided FR4 with a 35

μm thickness and is shown in

Figure 4.

The size of the PCB dedicated for the SMPS itself is 39 mm x 19 mm while the size of the

complete PCB is 61 x 38 mm; this extra space (area provided by through-hole connections)

is intended to give the user the possibility of modifying certain board specifications.

It is possible, for example, to apply an output linear regulator generating precisely 3.3 or 5 V

or to realize different types of feedback loop to minimize load regulation.