Method and device for controlling load and voltage in voice coils

An apparatus comprising:

• an input configured to receive a detected current flowing through a load of a system, where the load comprises an inductive element;
• an output configured to provide a signal configured to excite the load;
• and
• a controller configured to:
• excite the load with a first known duty cycle having a first polarity for a first time interval following a start time;
• at an end of the first time interval, receive a sensed first end current flowing through the load;
• and
• calculate a lumped term based at least in part on the first time interval and a change in the first load current during the first time interval,
• where the lumped term is representative of the supply voltage and at least one electrical characteristic of the load;
• excite the load with a second known duty cycle having an opposite polarity to the first polarity for a second time interval following the first end time;
• at a second end time at the end of the second time interval, sense a second end load current;
• and
• re-calculate the lumped term based at least in part on the first end load current, the second end load current and the second time interval.

A computer program product embodied on a non-transitory computer-readable medium tangibly encoding a computer program comprising program instructions, wherein execution of the program instructions by a computer results in performing or controlling operations comprising:

• exciting a load in a system comprising the load and a supply voltage with a known first duty cycle having a first polarity for a first time interval following a start time, where the load comprises an inductive element;
• at an end of the first time interval, sensing, at a first end time, a first end load current, where a first load current flows through the load;
• and
• calculating a lumped term based at least in part on the first time interval and a change in the first load current during the first time interval, where the lumped term is representative of the supply voltage and at least one electrical characteristic of the load;
• exciting the load with a second known duty cycle having an opposite polarity to the first polarity for a second time interval following the first end time;
• at the end of the second time interval, sensing, at a second end time, a second end load current in the system;
• and
• re-calculating the lumped term based at least in part on the first end load current, the second end load current and the second time interval.

An apparatus comprising:

• means for exciting a load in a system comprising the load and a supply voltage with a known duty cycle having a first polarity for a first time interval following a start time, where the load comprises an inductive element;
• means for sensing, at an end time of the first time interval, a first end load current, where a load current flows through the load;
• and
• means for calculating a lumped term based at least in part on the first time interval and a change in the first load current during the first time interval,
• where the lumped term is representative of the supply voltage and at least one electrical characteristic of the load,
• where the means for exciting the load is further iteratively exciting the load with a second known duty cycle having an opposite polarity to the first polarity for a second time interval following the first end time, and
• where the means for calculating the lumped term is further re-calculating the lumped term based at least in part on the first end load current, the second end load current and the second time interval.