Method and apparatus for power control of solar powered display devices
DCFirst Claim
1. A lower power latch circuit for connecting and disconnecting a source of d.c. electric power to and from a load, said source and said load each having first and second means for connections of opposite electric polarity, said source having an output voltage subject to variation, said latch circuit comprising:
- first and second bipolar transistors (Q1, Q2) of opposite polarity types, each having emitter, base and collector connections and each having its base connected to the collector of the other, whereby between the respective emitters of said transistors a regenerative latch unit is constituted;
a substantially resistive voltage divider (D1, D2, D3;
R1, R2, R3, Rt) connected between said first and second connection means of said d.c. power source and having a tap connection, which is connected to the base of said first transistor, the emitter of said first transistor being connected to said first connection means of said d.c. power source, the emitter of said second transistor being connected to said first connection means of said load, and the second connection means of said load being connected to the second connection means of said d.c. power source, with the particular electric polarities of said first and second source and load connections and the particular conductivity types of said first and second transistors being suited to each other for operation of said latch unit as a series latch circuit, whereby the voltage divider provides by said tap connection a control of said latch which avoids unstable operation of said latch during relatively low voltage output of said d.c. source.
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Abstract
An automatic power control device comprising a passive, non-linear voltage detector controlling a series bipolar transistor regenerative latch circuit, acts to connect the load to a power source only when the voltage obtainable from the power source is sufficient to prevent improper ambiguous operation of the load, and further acts to disconnect the load from the power source when its voltage declines to that range which could result in ambiguous and/or erroneous operation. An electronic thermometric digital display instrument is shown, powered solely by a miniature solar panel. The instrument is amply powered, and the display is legible, even in dim light. Operation at lower levels of light is available with an economical auxiliary battery that is cut out of the circuit at when the light is as little as 5 lux.
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Citations
71 Claims
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1. A lower power latch circuit for connecting and disconnecting a source of d.c. electric power to and from a load, said source and said load each having first and second means for connections of opposite electric polarity, said source having an output voltage subject to variation, said latch circuit comprising:
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first and second bipolar transistors (Q1, Q2) of opposite polarity types, each having emitter, base and collector connections and each having its base connected to the collector of the other, whereby between the respective emitters of said transistors a regenerative latch unit is constituted; a substantially resistive voltage divider (D1, D2, D3;
R1, R2, R3, Rt) connected between said first and second connection means of said d.c. power source and having a tap connection, which is connected to the base of said first transistor, the emitter of said first transistor being connected to said first connection means of said d.c. power source, the emitter of said second transistor being connected to said first connection means of said load, and the second connection means of said load being connected to the second connection means of said d.c. power source, with the particular electric polarities of said first and second source and load connections and the particular conductivity types of said first and second transistors being suited to each other for operation of said latch unit as a series latch circuit, whereby the voltage divider provides by said tap connection a control of said latch which avoids unstable operation of said latch during relatively low voltage output of said d.c. source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A d.c. power supply powered at least in part by a solar panel and capable of powering, unattended in varying light conditions, a load which includes a driver unit (U1) which is optimally driven by a voltage which, when present, remains within a limited voltage band, comprising:
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a solar panel having positive and negative output connections; a first capacitor (C1) having a first terminal connected to a first terminal of said solar panel and also directly connected to a first connection means of a load, said capacitor having a second terminal connected to a second output terminal of said solar panel; a first transistor (Q2) having a substantially switchable conduction path connected between said second terminal of said first capacitor and a second means of connection of said load and having a control electrode; voltage detection means (U2, Q1, R, R2, R3, Rt, D1, D2, D3, R4) for detecting a voltage lying above a first lower predetermined voltage value and for producing, at an output connected to said control electrode of said first transistor (Q2), an output signal for turning on said transistor after said voltage exceeds a second higher predetermined voltage value, which voltage to be detected is a voltage that rises and falls with a voltage contemporaneously present between said first and second terminals of said capacitor; voltage limiting means (D4) for defining an upper limit of said limited voltage band, and means interconnecting said transistor (Q2) and said voltage detector (U2, Q1) for accelerating turn-on of said transistor and for keeping said transistor turned on, after being turned on, during continued presence of said output signal of said voltage detector. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 61, 62, 63, 64, 65, 66, 67)
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29. A method of powering by solar energy an electronic instrument having a visual display without the provision of an auxiliary battery, comprising:
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charging a first capacitor, which is permanently connected to a solar panel, by electric current produced by said solar panel; operating a regenerative bipolar transistor latch unit connected in series with power input connections of said instrument and in series with said solar panel, under control of a substantially resistive voltage divider connected in parallel with said first capacitor and having a tap connection to which a control connection of said latch unit is connected, said latch unit comprising first and second bipolar transistors of opposite polarity types, each having a base electrode connected to a collector electrode of the other, said second transistor having an emitter electrode connected to a first polarity power input connection of said instrument and said first transistor having an emitter electrode connected to a corresponding output connection of said solar panel and having a base electrode connected, for operation as a control electrode of said latch unit, to said tap connection of said voltage divider, and limiting the voltage of power supplied to said input connections of said instrument by means of a voltage limiter diode. - View Dependent Claims (30, 31, 32, 33)
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34. A method of charging a storage battery over a wide range of light conditions by means of a solar panel assembly, comprising:
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charging a first capacitor which is permanently connected to a solar panel assembly by electric current produced by said solar panel assembly, and operating a regenerative bipolar transistor latch unit connected in series with said storage battery and with said solar panel, under control of a substantially resistive voltage divider connected in parallel with said first capacitor and having a tap connection to which a control connection of said latch unit is connected, said latch unit comprising first and second bipolar transistors of opposite polarity types, each having a base electrode connected to a collector electrode of the other, said second transistor having an emitter electrode connected to a first polarity power input connection of said instrument and said first transistor having an emitter electrode connected to a corresponding output connection of said solar panel and having a base electrode connected, for operation as a control electrode of said latch unit, to said tap connection of said voltage divider.
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51. A method of powering by solar energy, economically assisted by a battery, an electronic instrument having a visual display, comprising:
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charging a first capacitor (C1) by electric current produced by said solar panel or said battery or both, said capacitor (C1) having a first terminal which is connected to a first terminal of a solar panel through a first auctioneer diode (D6) and is connected to a first terminal of a battery through a second auctioneer diode (D7), said capacitor having a second terminal connected to second terminals respectively of said solar panel and said battery both of the same polarity; operating a regenerative bipolar transistor latch unit connected in series with power input connections of said instrument and in series through said auctioneer diodes respectively with said solar panel and said battery, under control of a substantially resistance voltage divider connected in parallel with said first capacitor and having a tap connection to which a control connection of said latch unit is connected, said latch unit comprising first and second bipolar transistors of opposite polarity types, each having a base electrode connected to a collector electrode of the other, said second transistor having an emitter electrode connected to a first polarity power input connection of said instrument and said first transistor having an emitter electrode connected to a corresponding output connection of said solar panel and having a base electrode connected, for operation as a control electrode of said latch unit, to said tap connection of said voltage divider, and limiting the voltage of power supplied to said input connections of said instrument to a voltage band lying between an upper limit set by means of a voltage limiter diode connected between said first and a second terminal of said instrument and a lower limit set by said voltage divider including any extension thereof connected to said battery (R5). - View Dependent Claims (52, 53, 54, 55)
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56. A low-power latch circuit for connecting and disconnecting a source of d.c. electric power to and from a load, said source and said load each having first and second means respectively for connections of opposite electric polarity said source having an output voltage subject to variation and having a first capacitance (C1) connected between its said first and second connection means, said latch circuit comprising:
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a transistor (Q2) having a switchable conduction path connected between said first connection means of said source and said first connection means of said source and having a control electrode, said second connection means of said source and of said load being connected together; voltage detection means (U2) for detecting a voltage lying above a first lower predetermined voltage and providing an output signal when a second higher predetermined voltage is exceeded, which voltage to be detected is a voltage present between said first and second connection means of said source and having an output for said output signal connected to said control electrode of said transistor for turning on said transistor after said second predetermined voltage is exceeded, a first resistive path (R6) being connected between said control electrode of said transistor and a said connection of said source for providing turn-on bias for said transistor during presence of said output signal of said voltage detection means and a second resistive path (R5, D9) connected between an input of said voltage detection means and said first connection means for setting said second predetermined voltage. - View Dependent Claims (57, 58, 59, 60)
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68. A method of powering by solar energy, with economical assistance of a battery at low light levels, an electronic instruments having a liquid crystal display, comprising:
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charging a first capacitor by said battery during essentially total darkness, by said battery and said solar panel together from a first threshold light level in a band lying between 2 and 8 lux up to a second threshold light level in the band between 30 and 40 lux and exclusively by said solar battery at above said second threshold light level; supplying voltage present across said capacitor to a voltage detector (U2) for providing an output signal to a control electrode of a transistor (Q2) having its switched path connected between a terminal of said capacitor and a terminal of said load, for turning on said transistor when a predetermined voltage is reached in said voltage detector where said voltage is reduced by a diode chain (D8, D9); as soon as said transistor is turned on, keeping said transistor turned on, by means of a resistance path (R6) between said control electrode of said transistor and an electrode of said transistor connected to said capacitor, until a voltage above or near said predetermined voltage no longer is present as aforesaid in said voltage detector; limiting the availability to said load of power from said battery by provision of auctioneer diodes (D6, D7) through which said solar panel and said battery are respectively connected to said first capacitor, and preventing leakage current through said transistor, when said transistor is turned off, from accumulating a charge in said load, by providing a leakage path resistance across said load. - View Dependent Claims (69, 70, 71)
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Specification