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Battery charging control system particularly for hand held device

  • US 4,737,702 A
  • Filed: 12/18/1986
  • Issued: 04/12/1988
  • Est. Priority Date: 06/07/1982
  • Status: Expired due to Term
First Claim
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1. In a control system for controlling current flow to a load, a voltage supply input means,controllable current regulator means controlling supply of load current from the voltage supply input means to a load, and controllable between a first mode corresponding to a relatively high current flow and a second mode corresponding to a relatively low current flow,energy storage means providing a load current flow path from the voltage supply input means to a load under the control of said current regulator means and operable to store energy with the regulator means in the first mode and to supply current to a load in the second mode of the regulator means, andcontrol means controlling said regulator means to alternate between the first and second modes so as to supply a selected average current to the load, said control means actuating said regulator means periodically with a maximum time interval between actuations of the regulator means to the first mode of a maximum time duration accommodating a maximum duty cycle of the regulator means in the first mode, the energy storage means reaching a relatively high energy storage condition with the maximum duty cycle of the regulator means and the control means providng a minimum duty cycle of the regulator means such that the energy storage means reaches a substantially reduced energy storage condition, and said control means controlling the duty cycle of the regulator means in the range between said maximum duty cycle and the minimum duty cycle to control the average load current, said control means providing a fixed time interval between actuations of the regulator means to said first mode, and producing a periodically fluctuating load current, said control means having a load current sampling means operating at a sampling rate to define successive potential sampling intervals such that a multiple of the potential sampling interval defines an operating frame interval substantially matched with the time interval between actuations of the regulator means to said first mode, said sampling means reading the load current at asynchronous time intervals asynchronously related to the operating frame interval and effecting an aliased sampling of the periodically fluctuating load current at a sufficient number of asynchronous time intervals to obtain a measure of average load current, and said control means controlling the duty cycle of the regulator means to tend to maintain the measure of average load current obtained from the load current sampling means at a desired value.

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