Adaptive current control
AssigneeDelco Electronics Corporation
InventorsEdward L. Hale, David D. Moller, Robert R. McConnell
Life of this patent
Estimating the term…
Abstract
Closed-loop control of current through a load through pulse-width modulated application of a substantially constant supply voltage across the load, wherein a duty cycle turn-on time is adjusted according to the result of a comparison between a commanded minimum current level and a sensed minimum current through the load during a cycle.
Claims7
A method for controlling electrical current through a load by repeatedly applying a predetermined voltage across the load for a controlled charge time during which the electrical current passes through a current measuring device, and removing the predetermined voltage from the load for a controlled discharge time during which the electrical current by-passes said current measuring device, comprising the steps of:
- establishing a minimum and a maximum commanded current through the load;
- measuring said electrical current during the charge time using said current measuring device;
- sampling the measured current when it is at a minimum current level during the charge time to provide an estimate of minimum current occurring during the discharge time;
- comparing the sampled current to the minimum commanded current;
- and
- adjusting a subsequent controlled discharge time in a direction to drive the sampled current toward the minimum commanded current.
A method for controlling electrical load current through a load, comprising the steps of:
- establishing a maximum current level and a minimum current level having a predetermined relationship to a desired load current level;
- sensing the load current during a voltage control period during which a voltage is applied across the load and the load current passes through a current sensing device;
- repeatedly (a) terminating the voltage control period when the sensed load current becomes greater than the maximum current level so as to circulate the load current through a circuit path that by-passes said current sensing device and initiate a period of decreasing load current, and (b) initiating the voltage control period after expiration of a controlled duration of the period of decreasing load current;
- sampling the sensed load current upon initiation of the voltage control period to provide an estimate of minimum current occurring during the period of decreasing load current;
- and
- adjusting a subsequent controlled duration of the period of decreasing load current in a direction to establish the sampled load current at the minimum current level.
An apparatus for controlling electrical current through a load by repeatedly applying a predetermined voltage across the load for a controlled charge time during which the electrical current passes through a current sensing device, and removing the predetermined voltage from the load for a controlled discharge time during which the electrical current by-passes said current sensing device, comprising:
- maximum current and minimum current command means for commanding a maximum and a minimum current level through the load;
- sampler means for sampling the current passing through said current sensing device when such current is at its minimum level during a controlled charge time, thereby providing an estimate of minimum current occurring during the controlled discharge time;
- comparator means for comparing the sampled current to the commanded minimum current level;
- and
- means for adjusting a subsequent controlled discharge time in a direction to establish the sampled current at the commanded minimum current level.
Dependencies are inferred from the claim text.