Over-voltage protection circuit

An over-voltage protection circuit for connection to a charging circuit for maintaining a voltage across a plurality of electrical energy storage devices at or below a predetermined voltage during charging, comprising:

• a first electrical energy storage device connected from a top voltage rail to a primary junction;
• a second electrical energy storage device connected from the primary junction to a bottom voltage rail, the first electrical energy storage device and the second electrical energy storage device charged by current flowing from the top rail through the first electrical energy storage device and the second electrical energy storage device to the bottom rail;
• an inductor;
• a first switch and a second switch;
• and
• a dissipation controller to perform a dissipation procedure in which a charge is discharged from the energized inductor upon detection of an over-voltage condition by a voltage sensor;
• the over-voltage protection circuit to perform a first procedure in which a charge is drawn from the first electrical energy storage device through the inductor to energize the inductor, the inductor then to cause a current that charges the second electrical energy storage device, the first procedure beginning when the first switch is closed;
• and
• the over-voltage protection circuit to perform a second procedure in which a charge is drawn from the second electrical energy storage device through the inductor to energize the inductor, the inductor then to cause a current that charges the first electrical energy storage device, the second procedure beginning when the second switch is closed.

A method of operating an over-voltage protection circuit electrical circuit for charging a plurality of electrical energy storage devices that includes a first electrical energy storage device connected from a top voltage rail to a primary junction, a second electrical energy storage device connected from the primary junction to a bottom voltage rail, the first electrical energy storage device and the second electrical energy storage device charged by current flowing from the top rail through the first electrical energy storage device and the second electrical energy storage device to the bottom rail, an inductor, a first diode and a first switch, the first diode and the first switch connected from the top rail to a secondary junction, and a second diode and a second switch, the second diode and the second switch connected from the secondary junction to the bottom rail, with the inductor connected from the primary junction to the secondary junction, the method comprising:

• performing a first procedure in which a charge is drawn from the first electrical energy storage device through the inductor to energize the inductor, the inductor then to cause a current that charges the second electrical energy storage device;
• the first procedure including:
• closing the first switch to conduct current from the top rail, through the first switch and the inductor to the primary junction to energize the inductor;
• and
• opening the first switch to cause the inductor to induce a temporary current to flow from the bottom rail through the second diode and the inductor to the primary junction;
• and
• performing a second procedure in which a charge is drawn from the second electrical energy storage device through the inductor, the inductor then to cause a current that charges the first electrical energy storage device;
• the second procedure including:
• closing the second switch to conduct current from the primary junction, through the inductor and the second switch, to the bottom rail to energize the inductor;
• and
• opening the second switch to cause the inductor to induce a temporary current to flow from the primary junction through the inductor and the first diode to the top rail;
• the over-voltage protection circuit being configured to perform the first procedure in response to the first electrical energy storage device being excessively charged and to perform the second procedure in response to the second electrical energy storage device being excessively charged.