DC to DC Converter adjustable dynamically to battery condition

• US 4,272,806 A
• Filed: 06/08/1979
• Issued: 06/09/1981
• Est. Priority Date: 06/08/1979
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Metzger, Lenard M.
• Primary Examiner(s): PELLINEN, A DAVID
• Application Number:
  US06/047,530
• Time in Patent Office: 732 Days
• Field of Search: 320/1, 320/39, 320/40, 315/219, 315/241 R, 315/241 P, 315/225, 315/239, 315/362, 323/15, 323/17, 323/DIG. 1, 363/18-21, 363/80, 363/97, 363/124
• US Class Current: 363/21.17
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A battery-powered DC to DC converter is operated dynamically in accordance with the condition of the battery so that an optimum compromise is made between the performance of the battery and the performance of the converter in an application such as charging an electronic strobe flash unit capacitor. A transformer has oppositely wound primary and secondary windings. A switching transistor, serially connected between the primary winding and the battery, interrupts battery current through the primary winding, which causes current to flow through the secondary winding to charge the flash unit capacitor. A voltage-sensing circuit senses the battery open-circuit voltage and the battery load voltage, which varies as a function of the open-circuit voltage and battery internal resistance. A bistable control circuit causes the switching transistor to interrupt the primary winding current when the battery load voltage decreases below a predetermined percentage of the battery open-circuit voltage so the load that the converter places on the battery varies dynamically as a function of battery condition.

Claims

1. In a DC to DC converter adapted to be energized by a battery, the battery having a load voltage that varies directly as a function of its open-circuit voltage and inversely as a function of its internal resistance, said converter comprising a transformer including a first winding and a second winding, and a switch for interrupting battery current to said first winding to cause current to flow in said second winding, the improvement comprising:

(a) voltage-sensing means, coupled to the battery, for sensing (1) the battery open-circuit voltage when battery current to said first winding is interrupted, and (2) the battery load voltage when battery current flows to said first winding; and

(b) voltage-comparator means, coupled to said voltage-sensing means and said switch, for comparing the battery open-circuit voltage with the battery load voltage and for causing said switch to interrupt current in said first winding when the battery load voltage is less than a predetermined percentage of the battery open-circuit voltage, whereby the energy drawn from the battery when current flows to said first winding varies in direct proportion to the open-circuit voltage and in inverse proportion to the internal resistance of the battery.

2. In a DC to DC converter adapted to be energized by a battery, the battery having a load voltage that varies with the condition of the battery, directly as a function of its open-circuit voltage and inversely as a function of its internal resistance, said converter comprising transformer means having a first winding and a second winding, and a switch, in series with said first winding and the energizing battery, for periodically interrupting battery current to said first winding to cause current to flow in said second winding, the improvement comprising:

(a) voltage-sensing means, coupled to the energizing battery, for sensing (1) the battery open-circuit voltage when battery current to said first winding is interrupted, and (2) the battery load voltage when battery current flows to said first winding; and

(b) comparator means, having an input coupled to said voltage-sensing means and an output coupled to said switch, and having (1) a first state when the battery load voltage is greater than a predetermined percentage of the battery open-circuit voltage, and (2) a second state when the battery load voltage is less than said predetermined percentage of the battery open-circuit voltage, said output of said comparator means being coupled to said switch so that current is interrupted in said first winding when said comparator means is in its second state whereby the energy drawn from the battery when current flows to said first winding varies with the condition of the battery, in direct proportion to the open-circuit voltage and in inverse proportion to the internal resistance of the battery.

3. In a DC to DC converter adapted to be energized by a battery, the battery having a load voltage that varies with the condition of the battery in direct proportion to its open-circuit voltage and in inverse proportion to its internal resistance, said converter comprising transformer means having a primary winding and a secondary winding, and a switch, in series with said primary winding and the battery, for interrupting battery current in said primary winding to cause current to flow in said secondary winding, the improvement comprising:

(a) voltage-sensing means, coupled to the battery, including (1) first means for sensing the open-circuit voltage of the battery when battery current to said primary winding is interrupted, and (2) second means for sensing the battery load voltage when battery current flows in said primary winding;

(b) comparator means, responsive to said voltage-sensing means, switchable between (1) a first state when said second means senses a battery load voltage that is greater than a predetermined percentage of the battery open-circuit voltage sensed by said first means, and (2) a second state when said second means senses a battery load voltage that is less than said predetermined percentage of the battery open-circuit voltage sensed by said first means; and

(c) bistable means, coupling said comparator means to said switch, for switching said switch, in response to said comparator means switching from its first state into its second state, to interrupt current in said primary winding, whereby the energy drawn from the battery when battery current flows to said primary winding varies with the condition of the battery in direct proportion to battery open-circuit voltage and in inverse proportion to battery internal resistance.

4. In a DC to DC converter adapted to be energized by a battery, the battery having a load voltage that varies with the condition of the battery in direct proportion to its open-circuit voltage and in inverse proportion to its internal resistance, said converter comprising transformer means having a primary winding and a secondary winding, and a switch, in series with said primary winding and the energizing battery, for interrupting battery current to said primary winding to cause current to flow in said secondary winding, the improvement comprising:

(a) voltage-sensing means, coupled to the battery, for sensing (1) the open-circuit voltage of the battery when battery current to said primary winding is interrupted, and (2) the battery load voltage when battery current flows to said primary winding;

(b) comparator means, coupled to said voltage-sensing means, switchable between (1) a first condition when said voltage-sensing means senses a battery load voltage that is greater than a predetermined percentage of the battery open-circuit voltage, and (2) a second condition when said voltage-sensing means senses a battery load voltage that is less than said predetermined percentage of the battery open-circuit voltage;

(c) current-sensing means, coupled to said secondary winding, for sensing current flow in said secondary winding, said current-sensing means having (1) a first condition when the secondary winding current is above a predetermined level, and (2) a second condition when the secondary winding current is below said predetermined level; and

(d) bistable switching means, having an input coupled to (i) said comparator means, and (ii) said current-sensing means, and an output coupled to said switch, and having (1) a first state when said comparator means assumes its second condition, and (2) a second state when said current-sensing means assumes its second condition, said output of said bistable switching means and said switch being coupled together so that battery current is interrupted in said primary winding when said bistable means is in its first state, and battery current flows to said primary winding when said bistable means is in its second state, whereby the energy drawn from the battery when battery current flows to said primary winding varies with battery condition in direct proportion to battery open-circuit voltage and in inverse proportion to battery internal resistance.

5. In a DC to DC converter adapted to be energized by a battery, the battery having a load voltage that changes in direct proportion to the open-circuit voltage of the battery and in inverse proportion to the internal resistance of the battery, said converter comprising transformer means having a primary winding and a secondary winding, and a switch, in series with said primary winding and the battery, for interrupting battery current in said primary winding to cause current to flow in said secondary winding, the improvement comprising:

(a) first voltage-sensing means, coupled to the battery, for producing a reference signal representing the open-circuit voltage of the battery when battery current is interrupted to said primary winding;

(b) second voltage-sensing means, coupled to the energizing battery, for producing a control signal corresponding to the battery load voltage when battery current flows in said primary winding;

(c) voltage-comparator means, coupled to said first voltage-sensing means and said second voltage-sensing means, having (1) a first condition when said control signal is greater than said reference signal, and (2) a second condition when said control signal is less than said reference signal;

(d) current-sensing means, coupled to said secondary winding, for sensing current flow in said secondary winding and having (1) a first condition when the secondary winding current is above a predetermined level, and (2) a second condition when the secondary winding current is below said predetermined level; and

(e) bistable switching means, having an input coupled to (i) said voltage-comparator means, and (ii) said current-sensing means, and an output coupled to said switch, and having (1) a first state in response to said voltage-comparator means assuming its second condition, and (2) a second state in response to said current-sensing means assuming its second condition, said output of said bistable switching means and said switch being coupled together so that battery current is interrupted in said primary winding when said bistable means is in its first state, and battery current flows to said primary winding when said bistable means is in its second state, whereby the energy drawn from the battery varies in direct proportion to the battery open-circuit voltage and in inverse proportion to the battery internal resistance.

6. In a battery-powered DC to DC converter adapted to receive a battery, the battery having a load voltage that varies directly with the open-circuit voltage of the battery and inversely with the internal resistance of the battery, said converter comprising transformer means having a primary winding and a secondary winding, and a switching transistor in series with said primary winding and a received battery for periodically interrupting current through said primary winding to cause current to flow through said secondary winding, the improvement comprising:

(a) voltage-sensing means, coupled to the received battery, for producing (1) a first reference signal corresponding to the battery open-circuit voltage when battery current to said primary winding is interrupted, and (2) a first control signal corresponding to the battery load voltage when battery current flows through said primary winding;

(b) first signal comparator means, coupled to said voltage-sensing means, having (1) a first condition when said first control signal is greater than a predetermined percentage of said first reference signal, and (2) a second condition when said first control signal is less than said predetermined percentage of said first reference signal;

(c) current sensing means, coupled to said secondary winding, for sensing current flow through said secondary winding, said current-sensing means producing (1) a second reference signal corresponding to the maximum current through said secondary winding, and (2) a second control signal corresponding to the instantaneous value of the current through said secondary winding;

(d) second signal comparator means, coupled to said current sensing means, having (1) a first condition when said second control signal is related to said second reference signal by a first predetermined factor, and (2) a second condition when said second control signal is related to said second reference signal by a second predetermined factor; and

(e) bistable switching means, having an input coupled to (i) said first signal comparator means, and (ii) said second signal comparator means, and an output coupled to said switching transistor, and having (1) a first state when said first signal comparator means is in its second condition, and (2) a second state when said second signal comparator means is in its second condition, said output of said bistable switching means being coupled to said switching transistor so that current is interrupted through said primary winding when said bistable means is in its first state, and current flows in said primary winding when said bistable means is in its second state, whereby the energy drawn from the battery when current flows through said primary winding varies in proportion to the battery open-circuit voltage and in inverse proportion to the battery internal resistance.