Low loss shunt regulator

A shunt regulator for a vehicle, the shunt regulator comprising:

• a first output contact and a second output contact, the first output contact and the second output contact adapted to electrically connect a load to the shunt regulator;
• alternating-current (AC) generator contacts adapted to electrically connect an AC voltage generator to the shunt regulator, wherein the AC generator is operable to generate AC voltages including a nominal AC voltage at a first speed of the vehicle when operating at a peak power point;
• gated power switches electrically coupled between the AC generator contacts and the first output contact and between the AC generator contacts and the second output contact, each of the gated power switches comprising a gate operable to control current flow through the respective gated power switch;
• a shunt controller communicatively coupled to the gates of the gated power switches, the shunt controller configured to:
• operate the gated power switches at duty cycles selected to boost the AC voltages, including the nominal AC voltage, to generate a target DC output voltage in a first mode of operation;
• and
• when the duty cycles in the first mode of operation would be less than minimum duty cycles corresponding to rotational speeds of the AC generator, operate the gated power switches at the minimum duty cycles in a second mode of operation;
• a voltage feedback circuit coupled to the first output contact and the second output contact to determine the actual DC output voltage that is available to the load between the first and second output contacts;
• and
• feedback logic coupled to the voltage feedback circuit configured to compare the actual DC output voltage to the target DC bus voltage to determine an error value and determine a duty cycle of the gated power switches based on the error value,
• wherein the target DC bus voltage is different from the AC voltage generated by the AC generator.

A method of electrical power generation in a vehicle having a combustion engine, the method comprising:

• receiving, by a shunt regulator including a shunt controller, alternating-current (AC) power from an AC generator mechanically coupled to the combustion engine, wherein the AC generator is operable to generate AC voltages including a nominal AC voltage at a first speed of the vehicle when operating at a peak power point;
• by the shunt controller:
• operating, in a first mode of operation, gated power switches at duty cycles selected to boost the nominal AC voltage to an actual DC output voltage corresponding to a target DC bus voltage,
• boosting, in the first mode of operation, the AC voltages to the target DC output voltage in response to changes in a load, and
• limiting, in a second mode of operation, the duty cycles to minimum duty cycles corresponding to rotational speeds of the AC generator when it is determined that the duty cycles of the first mode of operation would be less than the minimum duty cycles;
• and
• determining, by the shunt regulator, a duty cycle based on an error between the actual DC output voltage that is available to the load and the target DC bus voltage,
• wherein the target DC bus voltage is different from the AC voltage generated by the AC generator.