Bose Lifestyle 28 Manuel de dépannage - Page 7

Parcourez en ligne ou téléchargez le pdf Manuel de dépannage pour {nom_de_la_catégorie} Bose Lifestyle 28. Bose Lifestyle 28 32 pages. Dvd home entertainment systems
Également pour Bose Lifestyle 28 : Manuel d'installation (32 pages), Manuel d'utilisation (44 pages), Manuel du propriétaire (22 pages), Manuel d'utilisation (46 pages), Manuel d'utilisation (44 pages), Manuel d'utilisation (34 pages)

Bose Lifestyle 28 Manuel de dépannage
PS18/28/35 Troubleshooting Guide
Theory of Operation
1.4 High-frequency Resonant Converter
This section describes the theory of operation for a high-frequency half-bridge resonant DC-DC
converter, the heart of the power supply. Figure 5 shows its detailed circuit, where the high-fre-
quency transformer is represented by a leakage inductor Llk, a magnetizing inductor Lm, and an
ideal step-down transformer.
Figure 5. High-frequency half-bridge resonant DC-DC converter
With gate signals from the controller IC, the two power MOSFETs Q101 and Q102 are turned on
and off alternately to invert the DC input voltage to a high-frequency square wave voltage. The
high-frequency square wave voltage is applied to a series resonant circuit made of a resonant
capacitor C115 and leakage inductor Llk of the transformer. The resonant circuit shapes the
current waveform to a quasi sinusoidal waveform. Figure 6 shows oscillograms of the voltage
across MOSFET Q101 and current through capacitor C115. Such a smooth current waveform
lowers electromagnetic interference (EMI) emissions from the power supply.
Figure 6. MOSFET Q101 voltage and C115 current waveforms
The transformer transfers high-frequency power from the primary winding to two secondary
windings. The rectifier diodes D201A, D201B, D203, D204 rectify the high-frequency power and
the two capacitors C201 and C202 filter out high-frequency contents. A low pass L-C filter is
added to each rail to further reduce the high-frequency noise. Two DC voltages, one positive and
one negative, are obtained at the output.
7