| 摘要 |
<p>An uninterruptible power supply has a transformer 38 with a first primary winding 60 connected to an AC utility supply, a second primary winding 62 coupled to a rechargeable battery 48 via an H-bridge switch circuit 46 of a switch mode converter, and a secondary winding 64 connected to an AC output 72,74, there being a control circuit 44 which causes the switch circuit 46 to operate as a battery charger when the AC utility supply is within predetermined limits and as an inverter when the AC utility supply is outside such limits. The transformer 38 provides leakage inductance between the primary windings 60, 62, obviating the need for separate inductors during the charging mode. A magnetic shunt 68 is provided between the secondary winding 64 and the primary windings 60, 62. The AC output 72, 74 is connected to a tap on the secondary 64, and a ferroresonant capacitor 70 is connected across the ends of secondary 64. The H-bridge 46 is formed by MOSFETS with integral inverse diodes, all four arms being driven in the inverter mode in response to INV ON, INV A and INV B signals from a microcontroller 58. In the charger mode, the MOSFETS connected to battery positive are held off and those connected to battery negative are turned on and off simultaneously at 50Khz by a pulse width modulated drive signal from a charger controller 40. The charger controller 40 provides charging with power factor correction, current and voltage limiting, and temperature compensation (Fig. 13). If INV ON and CHGR ON signals are simultaneously high, a lock-out circuit (218, Fig.12) in the control circuit 44 holds all four arms of the H-bridge 46 off. The UPS may be used in a cable TV system (Fig.1).</p> |
