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AN1673 APPLICATION NOTE

Figure 9. Insulated LCL converter

Resonant circuits.

Any resonant circuit includes capacitors and inductors. Since we deal about applications using the trans-

former, it can be useful to recall the equivalent scheme of the transformer (fig.10), with its simplification

and parameters.

The stray inductance is the one that can be measured from the primary side with the secondary winding

in short circuit connection. The magnetizing inductance is the one that can be measured from the primary

opening the secondary. The parasitic capacitors will not be considered.

The simplified diagram of the transformer is acceptable for the present circuits discussion.

Figure 10. Transformer equivalent circuit

We can now define some basic resonance circuits and their inherent impact on the application, (ref. to

fig.11).

L-SERIES

TRANSFORMER

BOOT

+HV-BUS

HVG

OUT

LVG

C-BOOT

QH

QL

DH

RECT

CFILT

CRES

LOAD

DL

C.M.S.R.C.

DRIVER-H

DRIVER-L

L6598

GND

D03IN1435

L/1-Stray

Primary

L/2-Stray

Secondary

Cstray1

Cstray1-2

D03IN1430

L.Magnetizing

LStray

L.Magnetizing

Transformer equivalent circuit diagram

Simplified Transformer diagram

LOAD

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