Abstract: Disclosed are methods for charging batteries utilizing a charge balance approach, and charger systems using those methods. In one example, a method for charging a battery includes monitoring an amount of charge released by the battery while in a discharge state, recording the amount of charge released while in the discharge state, applying a voltage which results in current in reverse direction to the battery at a first voltage level for a time sufficient to introduce an amount of charge substantially equal to the recorded amount of charge released by the battery while in the discharge state, and maintaining the battery in a stand-by mode by applying a voltage which results in current in reverse direction to the battery at a second voltage level, the second voltage level being in a range sufficient to prevent self-discharge of the battery and insufficient to induce evaporation of electrolyte in the battery.

Abstract: Aspects of the invention are directed to methods and apparatus to protect an inverter from failure due to neutral lifting. In one aspect, the present invention provides a method of controlling an inverter in a UPS, the inverter being selectively coupled to a power line and comprising an input to receive an input voltage from the power line. The method comprises acts of monitoring the input voltage, detecting based on the act of monitoring, that the input voltage exceeds a predetermined high threshold value, isolating the inverter from the power line responsive to detecting that the input voltage exceeds a predetermined high threshold value, determining whether or not a neutral lifting condition exists on the power line, indicating that the inverter is in a fault state if the neutral lifting condition exists, and reconnecting the inverter to the power line if the neutral lifting condition does not exist.

Abstract: A switch circuit and method for converting a hard switch into a soft switch. In one example, the circuit includes a first switch having a first node and a second node, and a switch control circuit coupled in parallel with the first switch between the first and second nodes. The switch control circuit includes a series resonant circuit including a capacitor and an inductor coupled together in series, a second switch coupled in parallel with the series resonant circuit, a third switch coupled in series between the first node and the series resonant circuit, and a first diode coupled between the series resonant circuit and the second node, an negative terminal of the first diode being coupled to the second node.

Abstract: A switch circuit and method for converting a hard switch into a soft switch. In one example, the circuit includes a first switch having a first node and a second node, and a switch control circuit coupled in parallel with the first switch between the first and second nodes. The switch control circuit includes a series resonant circuit including a capacitor and an inductor coupled together in series, a second switch coupled in parallel with the series resonant circuit, a third switch coupled in series between the first node and the series resonant circuit, and a first diode coupled between the series resonant circuit and the second node, an negative terminal of the first diode being coupled to the second node.

Abstract: Disclosed are methods for charging batteries utilizing a charge balance approach, and charger systems using those methods. In one example, a method for charging a battery includes monitoring an amount of charge released by the battery while in a discharge state, recording the amount of charge released while in the discharge state, applying a voltage which results in current in reverse direction to the battery at a first voltage level for a time sufficient to introduce an amount of charge substantially equal to the recorded amount of charge released by the battery while in the discharge state, and maintaining the battery in a stand-by mode by applying a voltage which results in current in reverse direction to the battery at a second voltage level, the second voltage level being in a range sufficient to prevent self-discharge of the battery and insufficient to induce evaporation of electrolyte in the battery.

Abstract: Aspects of the invention are directed to methods and apparatus to protect an inverter from failure due to neutral lifting. In one aspect, the present invention provides a method of controlling an inverter in a UPS, the inverter being selectively coupled to a power line and comprising an input to receive an input voltage from the power line. The method comprises acts of monitoring the input voltage, detecting based on the act of monitoring, that the input voltage exceeds a predetermined high threshold value, isolating the inverter from the power line responsive to detecting that the input voltage exceeds a predetermined high threshold value, determining whether or not a neutral lifting condition exists on the power line, indicating that the inverter is in a fault state if the neutral lifting condition exists, and reconnecting the inverter to the power line if the neutral lifting condition does not exist.