Importance

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Abstract

Current (ip) flowing in the primary of a transformer in a full wave bridge converter is monitored and compared against thresholds (+imax, +imin, -imax, -imin). When the input voltage is adequate, the full wave bridge converter is operated in a normal manner. When the input voltage is insufficient to cause the current ip ramp reach the first threshold before a first predetermined timeout period (t1), the pulse is truncated and a next portion of the cycle is initiated and, providing that the current at the end of the first timeout period exceeds a second, lower threshold current (+imin), continuing to operate the full wave bridge converter in a normal manner. If the current at the end of the first timeout period fails to reach the second (+imin) threshold at the end of the timeout period (t1), then current in the primary winding is reversed and energy is stored in an inductor which is connected in series with the primary winding and said energy is transferred to a holding capacitor until sufficient voltage is stored to allow the converter to operate. The thresholds and cycle frequency are varied to allow a large power throughput variation that is used to modulate the input current for good power factor. The converter is designed to charge a capacitive load.

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First Claim