Controlling charge-balance and transients in a multi-level power converter

A method of setting output level and charge-balancing a set of fly capacitors during a switching cycle of a multi-level converter circuit that includes (1) a set of switches configured to be coupled between a first terminal and a second terminal, and (2) the set of fly capacitors, wherein each fly capacitor of the set of fly capacitors is coupled between a respective inner low-side switch among the set of switches and a respective outer low-side switch among the set of switches and between a respective inner high-side switch among the set of switches and a respective outer high-side switch among the set of switches, the method including:

• (a) selecting an outward-most fly capacitor among the set of fly capacitors that has not previously been selected;
• (b) if a voltage on the selected outward-most fly capacitor is above an associated target voltage and there are remaining high-side switches among the set of switches that are currently closable can be closed, then:
• (1) setting the inner high-side switch of the selected outward-most fly capacitor to a closed state to discharge the selected outward-most fly capacitor, and otherwise (2) setting the inner low-side switch of the selected outward-most fly capacitor to a closed state to charge the selected outward-most fly capacitor;
• (c) repeating steps (a) and (b) until all fly capacitors among the set of fly capacitors have been selected;
• and
• (d) for a remaining pair of left-over outward-most outer switches among the set of switches, setting an associated high-side switch among the set of switches or an associated low-side switch among the set of switches to a closed state based on a set of switch count rules.

A method of setting output level and charge-balancing a set of fly capacitors during a switching cycle of a multi-level converter circuit that includes (1) a set of switches configured to be coupled between a first terminal and a second terminal, and (2) the set of fly capacitors, wherein each fly capacitor of the set of fly capacitors is coupled between a respective inner low-side switch among the set of switches and a respective outer low-side switch among the set of switches and between a respective inner high-side switch among the set of switches and a respective outer high-side switch among the set of switches, the method including:

• (a) selecting an inward-most fly capacitor among the set of fly capacitors that has not previously been selected;
• (b) if a voltage on the selected inward-most fly capacitor is above an associated target voltage and there are remaining high-side switches among the set of switches that are currently closable, then:
• (1) setting the inner high-side switch of the selected inward-most fly capacitor to a closed state to discharge the selected inward-most fly capacitor, and otherwise (2) setting the inner low-side switch of the selected inward-most fly capacitor to a closed state to charge the selected inward-most fly capacitor;
• (c) repeating steps (a) and (b) until all fly capacitors among the set of fly capacitors have been selected;
• and
• (d) for a remaining pair of left-over outward-most outer switches among the set of switches, setting an associated high-side switch among the set of switches or an associated low-side switch among the set of switches to a closed state based on a set of switch count rules.

A method of setting output level and charge-balancing a set of fly capacitors during a switching cycle of a multi-level converter circuit that includes (1) a set of switches configured to be coupled between a first terminal and a second terminal, and (2) the set of fly capacitors, wherein each fly capacitor of the set of fly capacitors is coupled between a respective inner low-side switch among the set of switches and a respective outer low-side switch among the set of switches and between a respective inner high-side switch among the set of switches and a respective outer high-side switch among the set of switches, the method including:

• (a) selecting an inward-most fly capacitor among the set of fly capacitors that has not previously been selected;
• (b) if a voltage on the selected inward-most fly capacitor is above an associated target voltage and there are remaining low-side switches among the set of switches that are currently closable, then:
• (1) setting the outer low-side switch of the selected inward-most fly capacitor to a closed state to discharge the selected inward-most fly capacitor, and otherwise (2) setting the outer high-side switch of the selected inward-most fly capacitor to a closed state to charge the selected inward-most fly capacitor;
• (c) repeating steps (a) and (b) until all fly capacitors among the set of fly capacitors have been selected;
• and
• (d) for a remaining pair of left-over inward-most inner switches among the set of switches, setting an associated high-side switch among the set of switches or an associated low-side switch among the set of switches to a closed state based on a set of switch count rules.