High fidelity, high power switched amplifier

A gradient amplifier, comprising:

• a gradient amplifier power stage comprising:
• a first bridge amplifier;
• a first direct-current voltage source coupled in parallel to the first bridge amplifier and configured for providing voltage supply at a first voltage to the first bridge amplifier;
• a second bridge amplifier coupled in series with the first bridge amplifier;
• a second direct-current voltage source coupled in parallel to the second bridge amplifier and configured for providing voltage supply at a second voltage to the second bridge amplifier;
• a third bridge amplifier coupled in series with the first bridge amplifer and the second bridge amplifier;
• and
• a third direct-current voltage source coupled in parallel to the third bridge amplifier and configured for providing voltage supply at a third voltage to the third bridge amplifier;
• and
• a first gradient amplifier control stage, wherein the first gradient amplifier control stage comprises a first feedforward control mechanism for the first bridge amplifier and the third bridge amplifier, a second feedforward control mechanism for the second bridge amplifier, and a proportional integral control mechanism for the second bridge amplifier that provides a feedback based on a deviation of a feedback current from a reference current and based on an amount of time the deviation of the feedback current from the reference current is present.

A power amplifier, comprising:

• an amplifier power stage comprising:
• a first bridge amplifier;
• a first direct-current voltage source coupled in parallel to the first bridge amplifier and configured for providing voltage supply at a first voltage to the first bridge amplifier;
• a second bridge amplifier coupled in series with the first bridge amplifier;
• a second direct-current voltage source coupled in parallel to the second bridge amplifier and configured for providing voltage supply at a second voltage to the second bridge amplifier;
• a third bridge amplifier coupled in series with the first bridge amplifer and the second bridge amplifier;
• and
• a third direct-current voltage source coupled in parallel to the third bridge amplifier and configured for providing voltage supply at a third voltage to the third bridge amplifier;
• and
• a gradient amplifier control stage, wherein the first bridge amplifier and the third bridge amplifier are configured to provide an inductive voltage drop in a gradient coil and the second bridge amplifier is configured to provide a resistive voltage drop in the gradient coil.

A method for providing a electrical power to a coil comprising:

• providing a voltage supply at a first voltage to a first bridge amplifier;
• providing a voltage supply at a second voltage to a second bridge amplifier;
• providing a voltage supply at a third voltage to a third bridge amplifier;
• coupling the first bridge amplifier in series with the second bridge amplifier;
• coupling the second bridge amplifier in series with the third bridge amplifier;
• coupling the coil in series with the third bridge amplifier and the first bridge amplifier;
• and
• applying a pulse width modulation scheme to the series combination of the first bridge amplifier, the second bridge amplifier, the third bridge amplifier, wherein the first bridge amplifier and the third bridge amplifier are configured to provide an inductive voltage drop in the coil and the second bridge amplifier is configured to provide a resistive voltage drop in the coil.

A method for providing electrical power to a coil comprising:

• applying reactive power to the coil via a first set of amplifier bridges;
• applying active power to the coil via a second set of amplifier bridges coupled in series with the first set of amplifier bridges;
• and
• controlling the applying of reactive power and applying active power via the first and second sets of amplifier bridges using a first feedforward control mechanism, a second feedforward control mechanism, and a proportional integral control mechanism.

A method for providing electrical power to a coil comprising:

• applying power to the coil at a first voltage level via a first set of switched bridge amplifiers based upon the inductance of the coil, wherein the first set of switched bridge amplifiers is configured to provide an inductive voltage drop in the coil;
• applying power to the coil at a second voltage level lower than the first voltage level via a second set of switched bridge amplifiers in series with the first set of switched bridge amplifiers, wherein the second set of switched bridge amplifiers is configured to provide a resistive voltage drop in the coil;
• and
• controlling the applying of power via the first and second sets of switched bridge amplifiers.

A method for providing electrical power to a coil comprising:

• applying power to the coil via a first set of switched bridge amplifiers;
• applying power to the coil via a second set of switched bridge amplifiers in series with the first set of switched bridge amplifiers;
• and
• controlling the first and second sets of switched bridge amplifiers by using at least a first feedforward control mechanism, a second feedforward control mechanism, and a proportional integral control mechanism, wherein the first set of switched bridge amplifiers is configured to provide an inductive voltage drop in the coil and the second set of switched bridge amplifiers is configured to provide a resistive voltage drop in the coil.

A method for providing electrical power to a coil comprising:

• applying power to the coil via a first set of switched bridge amplifiers;
• applying power to the coil via a second set of switched bridge amplifiers in series with the first set of switched bridge amplifiers;
• and
• controlling the first and second sets of switched bridge amplifiers via a first feedforward control mechanism for the first set of switched bridge amplifiers, a second feedforward control mechanism for the second set of switched bridge amplifiers, and a proportional integral control mechanism for the second set of switched bridge amplifiers that provides a feedback based on a deviation of a feedback current from a reference current and based on an amount of time the deviation of the feedback current from the reference current is present.