Functional check

AN3105

12/30

Doc ID 16774 Rev 2

is due to a small difference between each half-secondary leakage inductance of the

transformer reflected to the primary side, providing the two slightly different resonant

frequencies. This phenomenon is typically due to a different coupling of transformer

secondary windings and in this case it is not an issue. The slight asymmetry can also be

appreciated in Figure 8 (on the righthand side); the small ringing appearing on both

secondary rectifiers anode voltage indicates that for a short time the rectifiers are not

conducting; it demonstrates that during half cycle the circuit is working below the resonant

frequency while during the following half cycle it is working at resonance frequency.

In Figure 8 it is also possible to appreciate the rectifier operating voltage and its margin with

Figure 8.

EVL130W-SL-EU demonstration board: primary and secondary side resonant stage

waveforms at 230 V - 50 Hz - full load

CH1: HB voltage

CH2: CF pin voltage

CH1: V_D12

CH2: V_D11

CH4: res. tank current