Non-dissipative battery charge circuit

• US 4,371,826 A
• Filed: 01/16/1981
• Issued: 02/01/1983
• Est. Priority Date: 01/16/1981
• Status: Expired due to Term

• Current Assignee: Speery Corporation
• Original Assignee: Sperry Corporation
• Inventors: Shelly, Randolph D. W.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US06/225,768
• Time in Patent Office: 746 Days
• Field of Search: 320/20, 320/21, 320/22-24, 320/32, 320/39, 320/40, 320/DIG. 1
• US Class Current: 320/145
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

A non-dissipative battery charging circuit utilizing pulse width modulated constant current charging signals and having unregulated charging voltage stepped down by the use of a switching transistor and series inductor is described. Charging current is sensed and fed back to cause control of the charging cycle. Battery voltage is sensed and compared to a reference level for terminating charging when the battery is determined to be fully charged. A clocking and control system responsive to the feedback signals and the sensed voltage levels is described for controlling the activation and duration of application of charging current signals.

Claims

1. A battery charging system for charging a battery from an unregulated voltage source by delivering fixed maximum amplitude pulse width modulated constant current charging signals comprising:

input means for coupling to a source of charging voltage;

battery voltage level determining means for determining when the battery is fully charged and for providing a charge disabling signal when the battery is fully charged;

charging current switch means coupled to said input means, and including control means, said charging current switch means for causing conducting of charging current when said control means is activated;

charging current sensing means coupled to said charging current switch means for sensing the levels of said charging current and for providing current level indicating signals in response to said levels;

charging current comparison means coupled to said charging current sensing means for comparing said charging current to a predetermined reference for providing reset signals when a predetermined current level comparison is sensed;

non-dissipative impedance means coupled to said charging current sensing means for providing said charging current to the battery being charged;

charge cycle control means coupled to said battery voltage level determining means and said charging current comparison means for sequentially providing activating signals for successive charge cycles until said battery voltage level determining means indicates the battery is fully charged, wherein said charge cycle control means includes

clock means for providing clocking signals at a predetermined frequency;

flip-flop means having output means for providing signals indicative of its state, set input means coupled to said clock means for causing said flip-flop means to exhibit a first state in response to said clocking signals, and reset input means coupled to said charging current comparison means for causing said flip-flop means to exhibit a second state in response to said reset signals;

logic means responsively coupled to said battery voltage level determining means, said clock means, and said flip-flop means for providing said activating signals to said charging current switch driver means for controlling activation of said charging current switch means to provide said charging current; and

wherein said logic means includes

gating means for controlling termination of the charging of the battery, said gating means having first gate input means coupled to said battery voltage level determining means, second gate input means, and gate output means for providing a disabling signal when the battery is fully charged;

enabling means for controlling activation of said charging current switch driver means, said enabling means having first enable input means coupled to said gate output means, second enable input means coupled to said clock means, third enable input means coupled to said flip-flop means, and enable output means coupled to said second gate input means and to said current switch driver means for providing said activating signals to said charging current switch driver means when signals received on said first, second and third enable input means have a predetermined relationship; and

charging current switch driver means coupled intermediate said charge cycle control means and said charging current switch means for providing drive signals for activating said control means and causing said charging current switch means to provide charging current in response to each of said activating signals.

2. A battery charging system as in claim 1 wherein said battery voltage level determining means includes voltage comparator means for providing charge enabling signals indicative that the battery is not charged to a predetermined voltage level and charge disabling signals when the battery is fully charged, said disabling signals not being effective until the end of an active one of said charging cycles, voltage reference input means coupled to said voltage comparator means for receiving predetermined charge voltage reference signals, and sensed voltage input means coupled to said voltage comparator means for receiving sensed voltage signals indicative of the charge level of the battery both during and at the termination of each of said charging cycles.

3. A battery charging system as in claim 1 wherein said charging circuit switch means comprises switching transistor means having a first electrode coupled to said control means;

a second electrode coupled to said input means;

and a third electrode coupled to said charging current sensing means.

4. A battery charging system as in claim 3 wherein said control means includes pulse transformer means having first drive winding means coupled to said first electrode and said third electrode for biasing said transistor to conduct in response to said drive signals.

5. A battery charging system as in claim 3 wherein said charging current sensing means includes current transformer means having first current winding means coupled in series between said third electrode and said impedance means for sensing the level of said charging current flowing therethrough, and second current winding means;

and

discharge means coupled to said first current winding means for discharging said current transformer means when said charging current is terminated.

6. A battery charging system as in claim 5 wherein said charging current comparison means includes comparator means having reset output terminal means, reference input means for receiving predetermined reference signals, and feedback input means for receiving feedback signals indicative of the level of charging current flow;

and

feedback means coupled to said second current winding means and said feedback input means for providing said feedback signals to said comparator means.

7. A battery charging system as in claim 1 wherein said impedance means includes inductor means having first inductor terminal means coupled to said charging current switch means and second inductor terminal means coupled to the battery being charged for providing charging current signals thereto;

and

inductor discharge means coupled to said inductor means and to the battery being charged for providing a discharge path for said inductor means when said charging current is terminated.

8. A battery charging system as in claim 4 wherein said charging current switch driver means comprises:

second winding means in said control means;

first transistor means coupled to said charge cycle control means for providing pre-drive signals in response to said activating signals;

second transistor means coupled to said first transistor means for providing said drive signals;

means for coupling said second transistor means to said second winding means; and

pulse transformer discharge means coupled to said second winding means for discharging said pulse transformer when said second transistor means does not provide said drive signals.

9. A battery charging system for charging a battery from an unregulated voltage source by delivering pulse width modulated constant current charging signals, said charging system comprising:

input means for coupling to a source of charging voltage;

charging current switch means coupled to said input means for providing charging current when conducting, said charging current switch means including first transformer control means for selectively switching said charging current switch means between a current conducting state and a current non-conducting state in response to control device signals;

charging current sensing means coupled to said charging current switch means for sensing levels of said charging current and for providing current level signals indicative of said levels of said charging current said charging current sensing means including current transformer means having primary winding means connected to said charging current switch means and secondary winding means;

inductor means having an input terminal coupled to said primary winding means and an output terminal for coupling to a battery to be charged, and arranged for charging during conduction of said charging current while minimizing heat generation during said charging;

discharge means coupled across said inductor means and the battery being charged for discharging energy from some inductor means through the battery when conduction of said charging current is terminated;

charging current compare means responsively coupled to said charging current sensing means for converting said current level signals to equivalent voltage signals and comparing said voltage signals to a first predetermined reference voltage and for providing a reset signal when comparison is detected, the time required for generation of said reset signals determined at least in part by the level of the charging voltage applied;

battery voltage level determining means for coupling across the battery to be charged for continously sensing the battery voltage level and comparing it to a second reference voltage for determining when the battery is fully charged and for providing a battery charged signal for use in terminating charging when comparison to said reference voltage is found;

charge cycle control means for controlling successive charge cycles until the battery is fully charged, said charge cycle control means including

clock means for generating clock pulses at a predetermined frequency for use in controlling said charge cycles,

bistable flip-flop means having a set input means coupled to said clock means for causing said flip-flop means to exhibit a set state in response to said clock pulses, reset input means coupled to said charging circuit for causing said flip-flop means to exhibit a reset state in response to said compare means reset signal, and output means for providing pulse width modulated set signals indicative respectively of said set condition for controlling the duration of said charging current,

enabling logic means coupled to said clock means and said flip-flop means for providing drive signals in response to said set state signals;

charge termination logic means coupled to said enabling logic means and said battery voltage level determining means for inhibiting further ones of said drive signals in response to said battery charged signal at the completion of one of said charge cycles for inhibiting further charging as long as said battery charged signal is present; and

charging current switch driver means coupled intermediate said enabling logic means and said first transformer control means for providing said control drive signals to said charging current switch means in response to said drive signals for causing said charging current to be constant amplitude limited until charging is terminated.