| 摘要 |
In a zero-current switching forward converter both a unidirectional conducting device and a circuit consisting of a switch in series with a dissipative element are connected across the energy transfer capacitor in the output circuit of the converter. The switch is turned off at the beginning of an energy transfer cycle and is turned on when the voltage across the energy transfer capacitor returns to zero. At relatively high values of load, current flowing in the converter output inductor in the direction of the load will be bypassed around the energy transfer capacitor by the unidirectional conducting device and converter operation will be the same as a prior art zero-current switching forward converter. At low values of load, however, where current reversal may occur in the output inductor, the dissipative element will serve to damp the time varying response of the capacitor to the reverse flow of current in the output inductor and the variation of the voltage across the capacitor will be smooth and predictable. The value of the dissipative element is chosen so that the circuit formed by the dissipative element, capacitor and output inductor is approximately critically damped. In this way the frequency variation of the converter with variations in load is reduced, the output ripple of the converter is reduced and discontinuous operating modes are avoided.
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