Solar panel output enhancement circuit

• US 4,847,546 A
• Filed: 03/23/1988
• Issued: 07/11/1989
• Est. Priority Date: 04/07/1987
• Status: Expired due to Term

• Current Assignee: Bobier Electronics Incorporated
• Original Assignee: Bobier Electronics Incorporated
• Inventors: Bobier, Joseph A., Brown, Gerald E.
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): Ault, Anita M.
• Application Number:
  US07/172,294
• Time in Patent Office: 475 Days
• Field of Search: 320/21, 320/39, 320/40, 320/15, 320/19, 323/282, 323/299, 323/303, 323/906, 363/56
• US Class Current: 320/102
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A circuit for operation with solar panels exhibiting constant current and variable voltage characteristics. The power output of the panels is maximized by the circuit through the use of a step-down form of regulator which functions to monitor the peak voltage level of the panel and regulate with a switching type regulator in accordance therewith. Thus, peak voltage levels are maintained while current output to the load driven by the panels is enhanced. When employed for battery charging, the circuit includes a threshold selection network which identifies the nominal voltage rating of the battery under charge and provides appropriate adjustments to carry out a pulse charging technique. For start-up conditions wherein battery voltages may be below levels requisite to evaluate nominal rated voltages, a higher level charging voltage is applied for a predetermined short interval until adequate threshold is achieved to make appropriate determinations of rated voltage values. In one embodiment of the current boosting circuit, the gate capacitance of a field effect transistor type regulator switching component is taken advantage of to simplify circuit structure.

Claims

1. Apparatus for charging a battery exhibiting variable charge state voltage levels from the output of a solar cell energy source exhibiting variable voltage levels and substantially constant current, comprising:

a step-down circuit including solid-state switch means actuable between conducting and non-conducting states, connectable in switching relationship with said source output, inductor means coupled with said switch means and connectable in charging relationship with said battery for conveying current thereto from said source when said switch means is in said conducting state, and unidirectional conducting means connectable in charging relationship with said battery for conveying current from said inductor means when said switch means is in said non-conducting state;

switch control means responsive substantially only to said source variable voltage levels for actuating said switch means, when enabled from a disabled condition, at switching rates controllably varied to substantially maintain a predetermined high value of said voltage levels exhibited by said source so as to optimize energy transfer to said battery; and

charge monitoring means responsive to said battery charge state voltage levels for selectively enabling said switch control means to effect charging of said battery to a fully charged condition.

2. The apparatus of claim 1 in which:

said charge monitoring means includes charge level setting means responsive to said variable charge state voltage levels and having a first set condition selected for effecting a fully charged condition of a said battery having a first nominal voltage rating, and having a second set condition for effecting a fully charged condition of a said battery having a second nominal voltage rating; and

including threshold selection network means responsive to said variable charge state voltage levels for deriving said charge monitoring means first set condition when said variable charge state voltage levels are below a predetermined threshold level and for deriving said charge monitoring means second set condition when said variable charge state voltage levels are above said predetermined threshold level.

3. The apparatus of claim 2 including start-up charge network means for deriving said charge monitoring means second set condition for a predetermined interval at the commencement of said battery charging.

4. The apparatus of claim 1 in which said switch control means includes:

source monitoring means responsive to said source variable voltage levels for deriving a source level signal;

reference means for deriving a reference signal of predetermined value; and

comparison network means responsive to said source level signal and said reference signal for actuating said switch means into said conducting state when the level of said source signal is above the level of said reference signal, and for actuating said switch means into said nonconducting state when the level of said source level signal is below the level of said reference signal.

5. The apparatus of claim 1 in which said charge monitoring means includes:

level setting means responsive to said variable charge state voltage levels for providing a charge state signal;

charge stop means responsive to said state signal and having a charge stop signal when said charge state signal corresponds with a charge state voltage level representing a fully charged condition of said battery;

charge start means responsive to said charge state signal and having a charge start signal when said charge state signal corresponds with a charge state voltage level below a predetermined voltage level for said battery below said charge state voltage level representing said fully charged condition; and

said switch control means is enabled in response to said charge start signal and disabled in response to said charge stop signal.

6. Apparatus for charging a battery exhibiting variable charge state voltage levels from the output of an energy source exhibiting variable voltage levels and substantially constant current, comprising:

a step-down circuit including solid-state switch means actuable between conducting and non-conducting states, connectable in switching relationship with said source output, inductor means coupled with said switch means and connectable in charging relationship with said battery for conveying current thereto from said source when said switch means is in said conducting state, and unidirectional conducting means connectable in charging relationship with said battery for conveying current from said inductor means when said switch means is in said non-conducting state;

switch control means responsive to said source variable voltage levels for actuating said switch means, when enabled in response to a charge start signal from a disabled condition, to substantially maintain a predetermined high value of said voltage levels exhibited by said source, said switch control means being disabled in response to a charge stop signal;

charge monitoring means including;

level setting means responsive to said variable charge state voltage levels for providing a charge state signal;

charge stop means responsive to said charge state signal and having first reference voltage network means for providing a first reference voltage having a value selected to derive a fully charged condition of said battery, and first comparator means responsive to said first reference voltage and to said charge state signal for deriving said charge stop signal; and

charge start means responsive to said charge state signal and including second reference voltage network means for providing a second reference voltage having a predetermined value and second comparator means responsive to said second reference voltage and to said charge state signal for deriving said charge start signal when said charge start signal is at or below the level of said second reference voltage.

7. The apparatus of claim 6 in which said level setting means includes capacitor means chargeable in the absence of adequate said charge state voltage levels between voltage levels corresponding with said first and second reference voltages to derive a start-up signal of predetermined frequency.

8. The apparatus of claim 7 in which:

said charge monitoring means includes charge level setting means responsive to said variable charge state voltage levels and having a first set condition selected for effecting a fully charged condition of a said battery having a first nominal voltage rating, and having a second set condition for effecting a fully charged condition of a said battery having a second nominal voltage rating; and

including threshold selection network means responsive to said variable charge state voltage levels for deriving said charge monitoring means first set condition when said variable charge state voltage levels are below a predetermined threshold level and for deriving said charge monitoring means second set condition when said variable charge state voltage levels are above said predetermined threshold level.

9. The apparatus of claim 8 including start-up charge network means responsive to said start-up signal for deriving said charge monitoring means second set condition for a predetermined interval at the commencement of said battery charging.

10. An output enhancement circuit for driving a load from an energy source having an output exhibiting variable voltage levels including a peak voltage level and substantially constant current, comprising:

a step-down circuit including solid-state switch means actuable between conducting and non-conducting states connectable with said source output, inductor means connectable intermediate said switch means and said load for conveying current thereto from said source when said switch means is in said conducting state, and unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said switch means is in said non-conducting state;

source monitoring means responsive to said source variable voltage levels for providing a source monitoring output;

control means responsive to said source monitoring output for actuating said switch means to derive a pulse width modulation of current from said source into said inductor means selected to substantially maintain said source exhibited peak voltage level so as to optimize energy transfer therefrom to said load.

11. The circuit of claim 10 in which:

said solid-state switch means includes a field effect transistor having a gate exhibiting gate capacitance; and

said control means comprises gate switching means for alternately charging and discharging said gate capacitance to derive said conducting and non-conducting states.

12. The circuit of claim 10 in which said control means includes reference means for deriving a predetermined reference signal and comparison network means responsive to said source monitoring output and said reference signal for actuating said switch means into said conducting state and alternately into said non-conducting state.

13. The circuit of claim 12 in which said comparison network means includes NPN and PNP transistors, the bases of which are coupled in common to receive said source monitoring output and the emitters of which are coupled in common with said reference signal.

14. An output enhancement circuit for driving a load from an energy source having an output exhibiting variable voltage levels including a peak voltage level and substantially constant current, comprising:

a step-down circuit including solid-state switch means having a field effect transistor with a gate exhibiting gate capacitance, said switch means being actuable between conducting and non-conducting states and connectable with said source output, inductor means connectable intermediate said switch means and said load for conveying current thereto from said source when said switch means is in said conducting state, and unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said switch means is in said non-conducting state;

source monitoring means responsive to said source variable voltage levels for providing a source monitoring output;

control means responsive to said source monitoring output for actuating said switch means to derive a pulse width modulation of current from said source into said inductor means selected to substantially maintain said source exhibited peak voltage level so as to optimize energy transfer therefrom to said load; and

said control means comprising reference means for deriving a predetermined reference signal, and comparison network means responsive to said source monitoring output and said reference signal for alternately charging and discharging said gate capacitance to correspondingly derive said conducting and non-conducting states.

15. The circuit of claim 14 in which said comparison network means includes NPN and PNP transistors, the bases of which are coupled in common to receive said source monitoring output and the emitters of which are coupled in common with said reference signal.

16. Apparatus for charging a battery exhibiting variable charge state voltage levels and which is chargeable at one level of select first and second levels of charge from an energy source, comprising:

step-down regulator means having a charging output connectable with said battery and including control means responsive to a charge signal, said charging output and to one of first and second threshold conditions for deriving on respective said first and second select levels of charge;

charge monitoring means responsive to the charge state condition of said battery corresponding with one of third and fourth selected threshold conditions representing a fully charged state of said battery for deriving said charge signal; and

threshold selecting network means responsive to said variable charge state voltage levels for deriving said first threshold condition and deriving said second and fourth threshold conditions when said charge state voltage level exceeds a predetermined maximum charging level determined with respect to said third threshold condition.

17. The apparatus of claim 16 including start-up charge network means for deriving said charge monitoring means fourth selected threshold for a predetermined interval when said charge state voltage level is below a predetermined value at the commencement of charging by said regulator means.

18. The apparatus of claim 16 in which said step-down regulator means comprises solid-state switch means selectively actuable between conducting and non-conducting states and having an input connectable with said source output, inductor means coupled with said switch means and having a charge output connectable with a said battery for conveying current thereto from said source when said switch means is in said conducting state, and unidirectional conducting means connectable with said battery for conveying current from said inductor means when said switch means is in said non-conducting state, said control means actuating said switch means to derive one of said first and second threshold conditions.

19. The apparatus of claim 16 in which said charge monitoring means comprises:

level setting means responsive to said variable charge state voltage levels and one of said third and fourth selected threshold conditions for providing a charge state signal;

charge stop means responsive to said charge state signals and having a charge stop signal when said charge state signal corresponds with a charge state voltage level representing a fully charged condition of said battery;

charge start means responsive to said charge state signal and having a said charge signal when said charge state signal corresponds with a charge state voltage level below a predetermined voltage level; and

said control means is responsive to said charge stop signal to terminate said derivation of battery charge.

20. The apparatus of claim 19 in which said charge start means includes:

first reference voltage network means for providing a first reference voltage having a predetermined value;

first comparator means responsive to said first reference voltage and to said charge state signal for deriving said charge start signal when said charge state signal is below the level of said first reference voltage;

second reference voltage network means for providing a second reference voltage having a value selected to derive a fully charged condition of said battery; and

second comparator means responsive to said second reference voltage and to said charge state signal for deriving said charge stop signal.

21. The apparatus of claim 20 in which said level setting means includes capacitor means chargeable in the absence of said battery between voltage levels corresponding with said first and second reference voltage to derive a start-up signal of predetermined detectable frequency.

22. The apparatus of claim 21 including start-up charge network means for deriving said charge monitoring means fourth selected threshold for a predetermined interval when said charge state voltage level is below a predetermined value at the commencement of charging by said regulator means responsive to said start-up signal.

23. An output enhancement circuit for driving a load from an energy source having an output exhibiting variable voltage levels and having a peak voltage level corresponding with maximum power output, and substantially constant current, comprising:

energy storage means connectable across said output and chargeable at given rates by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage means and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and connectable with said load for conveying current thereto from said source and energy storage means when said solid-state switch means is in said conducting state;

unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state;

switch control network means having a first input responsive to a charge level responsive signal corresponding with the said charge levels of said energy storage means and a second input responsive to a reference level, and a switching output coupled with said solid-state switch means reference network means for deriving said reference level, said switch control network means being responsive to said charge level responsive signal and to said reference level to actuate said solid state switch means at frequencies varying in correspondence with said given rate of charge of said energy storage means to substantially maintain said source peak voltage level.

24. The circuit of claim 23 in which said switch control network includes:

operational amplifier means having a said first input responsive to said charge level signal, a said second input responsive to said reference level, and an amplifier output;

voltage amplification stage means, responsive to said amplifier output of said source for providing a voltage enhanced output; and

emitter-follower stage means being connectable across said output and with said solid-state switch means and responsive to said voltage enhanced output for enhancing the current values assertable therefrom.

25. An output enhancement circuit for driving a load from an energy source having an output exhibiting variable voltage levels including a peak voltage level and substantially constant current, comprising:

energy storage means connectable across said output and chargeable by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage means and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and connectable with said load for conveying current thereto from said source and energy storage means when said solid-state switch means is in said conducting state;

unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state; and

switch control netwsork means having an operational amplifier with a first input responsive to a charge level responsive signal corresponding with the said charge level of said energy storage means and a second input responsive to a reference level, and a switching output coupled with said solid-state switch means reference network means for deriving said reference level, said switch control network means actuating said solid-state switch means into conduction when said storage level responsive signal exceeds a said reference level and actuating said switch means into said non-conducting state when said charge level responsive signal is below said reference level.

26. The circuit of claim 25 in which said switch control network means includes capacitor means coupled with said second input for deriving an assured switching actuation performance of said amplifier.

27. The circuit of claim 25 in which said switch control network means includes feedback network means coupled between said switching output and said second input for enhancing the switching performance of said amplifier.

28. A solar panel assembly comprising;

a panel component having a photovoltaic region mounted upon a supportive substrate, and photovoltaic region having a panel output exhibiting variable voltage levels and substantially constant current and having a peak voltage level corresponding with the maximum power output of said panel component;

electrical junction means mounted with said panel for receiving said panel output and having external output terminal;

an output enhancement circuit mounted with said electrical junction means including;

energy storage means connectable across said panel output and chargeable at given rates by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage means and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and with said external output terminals for conveying current thereto from said source and energy storage means when said solid-state switch means is in said conducting state;

unidirectional conducting means connected with said external output terminals for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state;

switch control network means having a first input responsive to a charge level responsive signal corresponding with said charge levels of said energy storage means and a second input responsive to a reference level, and a switching output coupled with said solid-state switch means, said switch control network means being responsive to said charge level responsive signal and to said reference level to actuate said solid state switch means at frequencies varying in correspondence with said given rate of charge of said energy storage means to substantially maintain said panel peak voltage level.

29. A solar panel assembly comprising:

a panel component having a photovoltaic region mounted upon a supportive substrate, said photovoltaic region having a panel output exhibiting variable voltage levels including a peak voltage level and substantially constant current;

electrical junction means mounted with said panel for receiving said panel output and having an external output terminal;

an output enhancement circuit mounted with said electrical junction means including;

energy storage means connectable across said panel output and chargeable by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage menas and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and with said external output terminals for conveying current thereto from said source and energy storage means when said solid-state switch menas is in said conducting state;

unidirectional conducting means connected with said external output terminals for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state;

switch control network means having an operational amplifier with a first input responsive to a charge level responsive signal corresponding with the said charge levels of said energy storage means and a second input responsive to a reference level, and a switching output coupled with said solid-state switch means, said switch control network means actuating said solid-state switch means into conduction when said storage level responsive signal exceeds a said reference level and actuating said switch means into said non-conducting state when said charge level responsive signal is below said reference level.

30. The assembly of claim 29 in which said switch control network means includes capacitor means coupled with said second input for deriving an assured switching actuation performance of said amplifier.

31. The assembly of claim 29 in which said switch control network means includes feedback network means coupled between said switching output and said second input for enhancing the switching performance of said amplifier.

32. An output enhancement circuit for driving a load of given current demands from an energy source having an output characteristic exhibiting variable voltage levels and a substantially constant current value and having a peak voltage level corresponding with the maximum power output of said source, comprising:

energy storage means connectable across said source and chargeable at given rates by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage means and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and connectable with said load for conveying current thereto from said source and energy storage means when said solid-state switch means is in said conducting state;

unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state;

switch control network means including an operational amplifier exhibiting a given hysteresis characteristic, having first and second inputs, and a switching output coupled with said switch means, means deriving a reference level for assertion at said amplifier second input, means for applying charge levels corresponding with said source voltage levels at said amplifier first input, a feedback network including feedback capacitance means coupled between said switching output and said first input, said switch control network being responsive to said charge level at said first input and to said reference level to actuate said solid-state switch means into conduction when said charge level at said first input exceeds a said reference level and actuating said switch means into said non-conducting state when said charge level is below said reference level, the said switching actuation being developed in accordance with said hysteresis characteristic, and said means for applying charge levels and said reference level being selected for actuating said switch means at frequencies varying in correspondence with said given rate of charge said energy storage means to substantially maintain said source peak voltage level; and

said feedback capacitance means having a capacitance value selected to enhance the rate of said switching actuation during the occurrence of elevated said load current demands.

33. The circuit of claim 32 in which said feedback capacitance means includes a variable capacitor adjustable to minimize the voltage range developed as said hysteresis characteristic effecting the said switch control network actuationg of said solid-state switch means into and out of conduction during said elevated current demands.

34. The circuit of claim 32 in which said feedback network includes resistor means coupled between amplifier first input and switching output and a first capacitor coupled in parallel circuit relationship with said resistor means.

35. The circuit of claim 34 further including second capacitor means coupled with said amplifier first input in divider circuit operative association with said first capacitor for performing therewith to enhance the switching response of said amplifier means ith respect to said given hysteresis characteristic.

36. The circuit of claim 34 in which said first capacitor is a variable capacitor adjusted to enhance said switching response.

37. An output enhancement circuit for driving a load from an energy source having output exhibiting variable voltage levels and substantially constant current, and having a peak voltage corresponding with maximum power output comprising:

energy storage means connectable across said output and chargeable at given rates by said current to variable charge levels;

solid-state switch means connected in energy transfer relationship with said energy storage means and actuable between conducting and non-conducting states;

inductor means connected with said solid-state switch means and connectable with said load for conveying current thereto from said source and energy storage means when said solid-state switch means is in said conducting state;

unidirectional conducting means connectable with said load for conveying current thereto from said inductor means when said solid-state switch means is in said non-conducting state;

switch control network means having a first input responsive to a charge level responsive signal corresponding with the said charge levels of said energy storage means and a second input responsive to a reference level, and a switching output coupled with said solid-state switch means, said switching output including emitter-follower stage means for enhancing the current values assertable therefrom, and said switch control network means being responsive to said charge level responsive signal and to said reference level to actuate said solid state switch means at frequencies varying in correspondence with said given rate of charge of said energy storage means to substantially maintain said source peak voltage level.

38. The output enhancement circuit of claim 37 in which said switch control network includes:

operational amplifier means having a said first input responsive to said charge level signal, a said second input responsive to said reference level, and an amplifier output;

voltage amplification stage means, responsive to said amplifier output for providing a voltage enhanced output; and

said emitter-follower stage means being connectable across said output of said source and with said solid-state switch means and responsive to said voltage enhanced output for enhancing the current values assertable therefrom.

39. The output enhancement circuit of claim 38 in which:

said voltage amplification stage means is a transistor having its base coupled with said amplifier output and a collector connectable with said output;

said solid-state switch means is a field effect transistor having a gate;

said emitter-follower stage means is a transistor pair, the bases of which are coupled in common with said collector and having their emitters coupled in common with said field effect transistor gate.

40. The output enhancement circuit of claim 37 further comprising:

a supplementary power stage including;

supplementary energy storage means connectable across said output;

supplementary solid-state switch means connected in energy transfer relationship with said supplementary energy storage means and actuable between conducting and non-conducting states;

supplementary inductor means connected with supplementary solid-state switch means and connectable with said load for conveying current thereto from said source and supplementary energy storage means when said supplementary solid-state switch means is in said conducting state;

supplementary uni-directional conducting means connectable with said load for conveying current thereto from said supplementary inductor means when said supplementary solid-state switch means is in said non-conducting state; and

means for connecting said switch control network means switching output with said supplementary solid-state switch means, said switch control network means actuating said supplementary solid-state switch means into conduction when said storage level responsive signal exceeds said reference level and actuating said supplementary switch means into said non-conducting state when said charge level responsive signal is below said reference level.

41. An output enhancement circuit for driving a load from an energy source having an output exhibiting variable voltage levels and substantially constant current and having a peak voltage level corresponding with maximum power output, comprising:

first energy storage means connectable across said output and chargeable at given rates by said current to variable charge levels;

first solid-state switch means connected in energy transfer relationship with said first energy storage means and actuable between conducting and non-conducting states;

first inductor means connected with said solid-state switch means and connectable with said load for conveying current thereto from said source and first energy storage means when said solid-state switch means is in said conducting state;

first uni-directional conducting means connectable with said load for conveying current thereto from said inductor means when said first solid-state switch means is in said non-conducting state;

switch control network means having a first input responsive to a charge level responsive signal corresponding with the said charge levels of said first energy storage means and a second input responsive to a reference level, and a switching output coupled with said first solid-state switch means, said switch control network means being responsive to said charge level responsive signal and to said reference level to actuate said solid state switch means at frequencies varying in correspondence with said given rate of charge of said energy storage means to substantially maintain said source peak voltage level;

a supplementary power stage including;

second energy storage means connectable across said output;

second solid-state switch means connected in energy transfer relationship with said second energy storage means and actuable between conducting and non-conducting states;

second inductor means connected with said second solid-state switch means and connectable with said load for conveying current thereto from said source and second energy storage means when said second solid-state switch means is in said conducting state;

second uni-directional conducting means conectable with said load for conveying current thereto from said inductor means when said second solid-state switch means is in said non-conducting state; and

means for connecting said switch control network means switching output with said second solid-state switch means, said control network means actuating said second solid-state switch means into conduction when said storage level responsive signal exceeds said reference level and actuating said second switch means into said non-conducting state when said charge level responsive signal is below said reference level.

42. The output enhancement circuit of claim 41 in which said switch control network means switching output includes emitter-follower stage means for enhancing the current values effecting said actuation of said first and second solid-state switch means.

43. The output enhancement circuit of claim 42 in which said switch control network includes:

operational amplifier means having a said first input responsive to said charge level signal, a said second input responsive to said reference level, and an amplifier output;

voltage amplification stage means responsive to said amplifier output for providing a voltage enhanced output;

said emitter-follow stage means being connectable across said output and with said first and second solid-state switch means and responsive to said voltage enhanced output for selectively simultaneously actuating said first and second solid-state switch means.

44. The output enhancement circuit of claim 43 in which:

said voltage amplification stage means is a transistor having its base coupled with said amplifier output and a collector connectable with said output;

said first and second solid-state switch means respectively include first and second field effect transistors each having a gate;

said emitter-follow stage means is a transistor pair, the bases of which are coupled in common with said collector and having their emitter coupled in common with each said first and second field effect transistor gate.