A power electronic drive circuit (10,134,136,142,174,178) on-board of a vehicle comprising: a dc bus (52,176); a first energy storage device coupled to the dc bus (52,176), the first energy storage device configured to output a dc voltage; a first bi-directional dc-to-ac voltage inverter (54,144) coupled to the first energy storage device and to the dc bus (52,176); a first electromechanical device (74,144) coupled to the first bi-directional dc-to-ac voltage inverter (54,144); a charging system coupled to the dc bus (52,176) via a charge bus, the charging system comprising: a receptacle configured to mate with a connector coupled to a voltage source external to the power electronic drive circuit (10,134,136,142,174,178); and an isolation transformer configured to electrically isolate the charge bus from the receptacle; and a controller (34,114) configured to cause the charging system to supply a charging voltage to the dc bus (52,176) based on a voltage received from the voltage source external to the power electronic drive circuit (10,134,136,142,174,178); the charging system further comprising a pair of transistors (106,108); characterized in that the charging system further comprises: a resonance capacitor; and wherein the isolation transformer, the pair of transistors (106,108), and the resonance capacitor form an isolation ac-to-dc inverter; and the controller (34,114) is configured to independently control the transistors (106, 108) in a series resonance mode such that the resonance capacitor and a transformer leakage inductance of the transformer operate substantially at or slightly above resonance in open loop, wherein the controller (34,114) is further configured to cause the isolation ac-to-dc inverter to operate in a series resonance mode. a dc bus (52,176); a first energy storage device coupled to the dc bus (52,176), the first energy storage device configured to output a dc voltage; a first bi-directional dc-to-ac voltage inverter (54,144) coupled to the first energy storage device and to the dc bus (52,176); a first electromechanical device (74,144) coupled to the first bi-directional dc-to-ac voltage inverter (54,144); a charging system coupled to the dc bus (52,176) via a charge bus, the charging system comprising: a receptacle configured to mate with a connector coupled to a voltage source external to the power electronic drive circuit (10,134,136,142,174,178); and an isolation transformer configured to electrically isolate the charge bus from the receptacle; and a receptacle configured to mate with a connector coupled to a voltage source external to the power electronic drive circuit (10,134,136,142,174,178); and an isolation transformer configured to electrically isolate the charge bus from the receptacle; and a controller (34,114) configured to cause the charging system to supply a charging voltage to the dc bus (52,176) based on a voltage received from the voltage source external to the power electronic drive circuit (10,134,136,142,174,178); the charging system further comprising a pair of transistors (106,108); characterized in that the charging system further comprises: a resonance capacitor; and wherein the isolation transformer, the pair of transistors (106,108), and the resonance capacitor form an isolation ac-to-dc inverter; and the controller (34,114) is configured to independently control the transistors (106, 108) in a series resonance mode such that the resonance capacitor and a transformer leakage inductance of the transformer operate substantially at or slightly above resonance in open loop, wherein the controller (34,114) is further configured to cause the isolation ac-to-dc inverter to operate in a series resonance mode. a resonance capacitor; and wherein the isolation transformer, the pair of transistors (106,108), and the resonance capacitor form an isolation ac-to-dc inverter; and the controller (34,114) is configured to independently control the transistors (106, 108) in a series resonance mode such that the resonance capacitor and a transformer leakage inductance of the transformer operate substantially at or slightly above resonance in open loop, wherein the controller (34,114) is further configured to cause the isolation ac-to-dc inverter to operate in a series resonance mode.