A 48 V/100 a Rectifier, using the Switched-Mode Series-Resonance Principle

The principle of the Series-Resonance Power Supply (SRPS) is completely different from the switched-mode forward converter. Its basis is in fact the early d.c. series regulator. In the SRPS, the series element is a low-loss impedance (a series LC tuned-circuit) driven by an a.c. source. Control of the output voltage is achieved by varying the source frequency, using asymmetric SCRs. The whole circuit is fed from a d.c. voltage; a three-phase bridge rectifier, connected directly to the mains, delivers the d.c. voltage. Because of this high d.c. voltage, the primary side of two series-resonance converters are connected in series; their secondaries are in parallel. As the converters are driven out of phase, the switching ripple on the output is very small. The 50 V/100 A rectifier is provided with several alarm and warning circuits; for ease of access, all controls and voltage/current indications are grouped together on the front panel. Output voltage is applied to the load - a 48 V battery plus exchange - either as a 48 V for floating operation or as a 70 V for full charging. A timer can switch in up to ten rectifiers at different intervals.