The Forward Converter

Posted on Feb 5, 2014

Diagram shows the basic construction of a forward converter. Whereas the energy is temporarily stored with the flyback converter before it is transferred to the secondary side, in the forward converter, energy is transferred directly between the primary and secondary sides. As an aid for understanding, the individual switching states in the s

The Forward Converter
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teady state system are examined. With the switch T1 closed, there is the same polarity at both dots of the transformer circuit diagram so that the diode D2 is conducting. In accordance with the function of the transformer (Chapter I/1. 9) the current transformed from the secondary side flows on the primary side and the linearly increasing magnetizing current. The transformed input voltage is applied to the secondary winding. This serves to charge the choke. A linearly increasing current flows through the choke and the load. If the switch T1 is now opened, the current cannot continue to flow on the primary side. The polarity in the magnetic components reverses so that D2 is blocked on the secondary side. The choke L1 now transfers the stored energy to the load (or the output capacitor) via D3. The current through the choke again decreases linearly. The core of the transformer has been magnetized by the magnetization current. The remanence of the core material would cause the core to saturate within a few switching cycles. So it has to be demagnetized after each switching period. Various techniques have been used for this purpose. The simplest option is presented in Figure 3. 179. During the shutdown phase the magnetizing current is fed back via diode D1 through the auxiliary winding. The number of turns used for the auxiliary winding is usually the same as that used for the primary winding. This means that the same time is...

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