Two wire low voltage dimmer

Claim 2

In a two wire AC dimming circuit of the type having electronic bidirectional switch means with control input means for selectively rendering the electronic switch means conductive according to repetitive timed control signals applied to the control input means to control the RMS value of an AC voltage applied to the load, a circuit for regulating the RMS value of the AC voltage applied to the load and for decreasing damaging DC current caused by loads having both resistive and inductive components comprising: (a) first means for providing a signal having a value indicative of a DC current flowing through the load; (b) second means responsive to the signal provided by the first means for adjusting the timing of the control signals during selected half cycles of the waveform of the AC voltage applied to the load to decrease the DC current flowing through the load; and (c) third means in electrical series with the first means for automatically adjusting the timing of the control signals in response to fluctuations in the AC voltage supplied to the dimmer to thereby regulate the RMS value of the AC voltage applied to the load.

Claim 3

Circuit according to claim 1 wherein the first means comprises a first capacitor and means for charging the first capacitor to a DC voltage having a magnitude and polarity indicative of the magnitude and polarity of the DC current flowing through the load.

Claim 4

Circuit acccording to claim 2 wherein the electronic switch means comprises thyristor means and the control input means comprises a gate terminal of the thyristor means and the dimmer includes a second capacitor operatively coupled to the gate terminal for supplying the control signals and rendering the thyristor means conductive when the second capacitor has been charged to a predetermined voltage.

Claim 5

Circuit according to claim 3 wherein the thyristor means comprises first and second thyristors each having a holding current characteristic, the holding current characteristic of the first thyristor being substantially less than the holding current characteristic of the second thyristor.

Claim 6

Circuit according to claim 4 further comprising a resistor connected in series with a main terminal of the first thyristor, the gate of the first thyristor receiving the control signals, the gate of the second thyristor being coupled to a junction of the resistor and the main terminal of the first thyristor, the second thyristor being rendered conductive when a voltage across the resistor exceeds a selected value, the first thyristor being rendered non-conductive after the second thyristor has been rendered conductive.

Claim 7

Circuit according to claim 3 wherein the second means comprises a feedback loop for coupling the DC voltage across the first capacitor to the voltage across the second capacitor to vary the voltage across the second capacitor and thereby alter the timing of the control signals.

Claim 8

Circuit according to claim 3 wherein the third means comprises a diac operatively coupled to the first capacitor, the diac having a breakover voltage thereacross when in its conductive state, at least a portion of the breakover voltage being applied to the second capacitor.

Claim 9

Circuit according to claim 7 wherein the second means comprises means for applying the DC voltage across the first capacitor to the diac to effectively alter the voltage applied to the second capacitor and thereby alter the timing of the control signals.

Claim 10

Circuit according to claim 1 wherein the load is a low voltage transformer.

Claim 11

Circuit according to claim 1 wherein the load is a ballast.

Claim 12

Circuit according to claims 3, 6, 7 or 8 wherein the thyristor means comprises triac means.

Claim 13

Circuit according to claim 4 or 5 wherein the first and second thyristors comprise first and second triacs, respectively.

Claim 14

A circuit for regulating the RMS value of an AC voltage applied to a load and for decreasing damaging DC current caused by loads having both a resistive and an inductive component comprising: (a) only a pair of wires for connection in series with the load and an AC supply voltage; (b) a first thyristor having a gate terminal and first and second main terminals, the first main terminal being operatively coupled to one of the pair of wires, a resistor operatively coupling the second main terminal to the other of the pair of wires; (c) a second thyristor having a pair of main terminals operatively coupled directly across the pair of wires and a gate terminal operatively coupled to a junction between the resistor and the second main terminal of the first thyristor; (d) the first and second thyristors each having a holding current characteristic, the holding current characteristic of the first thyristor being substantially less than the holding characteristic of the second thyristor; (e) a control circuit operatively coupled to the gate terminal of the first thyristor and across the pair of wires and comprising a first capacitor and a potentiometer in R-C series combination for selectively firing and rendering conductive the first and second thyristors at firing angles determined at least in part according to the setting of the potentiometer, the second thyristor being fired and rendered conductive when a voltage across the resistor exceeds a selected value, the first thyristor being rendered nonconductive after the second thyristor has been rendered conductive, the RMS value of the AC voltage applied to the load thereby being variable according to the potentiometer setting; (f) a diac disposed in the circuit and having a breakover voltage, the diac superimposing its breakover voltage upon the R-C series combination of the potentiometer and the first capacitor during periods when the diac is in conduction and adjusting the firing angle to compensate for fluctuations in the AC supply voltage and thereby regulate the RMS value of the AC voltage applied to the load; (g) a second capacitor in electrical series with the diac for charging to a DC voltage indicative of the magnitude and polarity of a DC current flowing through the load; and (h) means responsive to the DC voltage across the second capacitor to alter the firing angle during selected half cycles of the waveform of the AC voltage applied to the load and thereby decrease the DC current flowing through the load.

Claim 15

A circuit for regulating the RMS value of an AC voltage applied to a load and for decreasing damaging DC current caused by loads having both a resistive and an inductive component comprising: (a) only a pair of wires for connection in series with the load and an AC supply voltage; (b) a first thyristor having a gate terminal and first and second main terminals, the first main terminal being operatively coupled to one of the pair of wires, a resistor operatively coupling the second main terminal to the other of the pair of wires; (c) a second thyristor having a pair of main terminals operatively coupled directly across the pair of wires and a gate terminal operatively coupled to a junction between the resistor and the second main terminal of the first thyristor; (d) the first and second thyristors each having a holding current characteristic, the holding current characteristic of the first thyristor being substantially less than the holding characteristic of the second thyristor; (e) a control circuit operatively coupled to the gate terminal of the first thyristor and across the pair of wires and comprising a first capacitor and a potentiometer in R-C series combination for selectively firing and rendering conductive the first and second thyristors at firing angles determined at least in part according to the setting of the potentiometer, the second thyristor being fired and rendered conductive when a voltage across the resistor exceeds a selected value, the first thyristor being rendered nonconductive after the second thyristor has been rendered conductive, the RMS value of the AC voltage applied to the load thereby being variable according to the potentiometer setting; (f) a diac disposed in the circuit and having a breakover voltage, the diac superimposing its breakover voltage upon the R-C series combination of the potentiometer and the first capacitor during periods when the diac is in conduction and adjusting the firing angle to compensate for fluctuations in the AC supply voltage and thereby regulate the RMS value of the AC voltage applied to the load; (g) a second capacitor in electrical series with the diac for charging to a DC voltage indicative of the magnitude and polarity of a DC current flowing through the load; and (h) means responsive to the DC voltage across the second capacitor to alter the firing angle during selected half cycles of the waveform of the AC voltage applied to the load and thereby decrease the DC current flowing through the load.

Claim 16

Circuit according to claim 13 wherein the means responsive to the DC voltage across the second capacitor to alter the firing angle comprises a feedback loop for adding the voltage across the second capacitor to any voltage across the first capacitor.

Claim 17

Circuit according to claim 13 wherein the means responsive to the DC voltage across the second capacitor to alter the firing angle comprises means for adding the voltage across the second capacitor to the voltage across the diac to alter the voltage applied to the R-C series combination of the potentiometer and the first capacitor.

Claim 18

Circuit according to claim 13 wherein the load is a low voltage transformer.

Claim 19

Circuit according to claim 13 wherein the load is a ballast.

Claim 20

Circuit according to claims 13, 14, 15, 16 or 17 wherein the first and second thyristors comprise first and second triacs, respectively.

Claim 21

A circuit for regulating the RMS value of an Ac voltage applied to a load and for decreasing damaging DC current caused by loads having both a resistive and an inductive component comprising: (a) only a pair of wires for connection in series with the load and an AC supply voltage; (b) a first thyristor having a gate terminal and first and second main terminals, the first main terminal being operatively coupled to one of the pair of wires, a resistor operatively coupling the second main terminal to the other of the pair of wires; (c) a second thyristor having a pair of main terminals operatively coupled directly across the pair of wires and a gate terminal operatively coupled to a junction between the resistor and the second main terminal of the first thyristor; (d) the first and second thyristors each having a holding current characteristic, the holding current characteristic of the first thyristor being substantially less than the holding characteristic of the second thyristor; (e) a control circuit operatively coupled to the gate terminal of the first thyristor and across the pair of wires and comprising a first capacitor and a potentiometer in R-C series combination for selectively firing and rendering conductive the first and second thyristors at firing angles determined at least in part according to the setting of the potentiometer, the second thyristor being fired and rendered conductive when a voltage across the resistor exceeds a selected value, the first thyristor being rendered nonconductive after the second thyristor has been rendered conductive, the RMS value of the AC voltage applied to the load thereby being variable according to the potentiometer setting; (f) a diac disposed in the circuit and having a breakover voltage, the diac superimposing its breakover voltage upon the R-C series combination of the potentiometer and the first capacitor during periods when the diac is in conduction and adjusting the firing angle to compensate for fluctuations in the AC supply voltage and thereby regulate the RMS value of the AC voltage applied to the load; (g) a second capacitor operatively coupled to the circuit for charging to a DC voltage indicative of the magnitude and polarity of a DC current flowing through the load; and (h) means responsive to the DC voltage across the second capacitor to alter the firing angle during selected half cycles of the waveform of the AC voltage applied to the load and thereby decrease the DC current flowing through the load, said means including means for adding the voltage across the second capacitor to the voltage across the diac to alter the voltage applied to the R-C series combination of the potentiometer and the first capacitor.

Claim 22

A circuit for regulating the RMS value of an Ac voltage applied to a load and for decreasing damaging DC current caused by loads having both a resistive and an inductive component comprising: (a) only a pair of wires for connection in series with the load and an AC supply voltage; (b) a first thyristor having a gate terminal and first and second main terminals, the first main terminal being operatively coupled to one of the pair of wires, a resistor operatively coupling the second main terminal to the other of the pair of wires; (c) a second thyristor having a pair of main terminals operatively coupled directly across the pair of wires and a gate terminal operatively coupled to a junction between the resistor and the second main terminal of the first thyristor; (d) the first and second thyristors each having a holding current characteristic, the holding current characteristic of the first thyristor being substantially less than the holding characteristic of the second thyristor; (e) a control circuit operatively coupled to the gate terminal of the first thyristor and across the pair of wires and comprising a first capacitor and a potentiometer in R-C series combination for selectively firing and rendering conductive the first and second thyristors at firing angles determined at least in part according to the setting of the potentiometer, the second thyristor being fired and rendered conductive when a voltage across the resistor exceeds a selected value, the first thyristor being rendered nonconductive after the second thyristor has been rendered conductive, the RMS value of the AC voltage applied to the load thereby being variable according to the potentiometer setting; (f) a diac disposed in the circuit and having a breakover voltage, the diac superimposing its breakover voltage upon the R-C series combination of the potentiometer and the first capacitor during periods when the diac is in conduction and adjusting the firing angle to compensate for fluctuations in the AC supply voltage and thereby regulate the RMS value of the AC voltage applied to the load; (g) a second capacitor operatively coupled to the circuit for charging to a DC voltage indicative of the magnitude and polarity of a DC current flowing through the load; and (h) means responsive to the DC voltage across the second capacitor to alter the firing angle during selected half cycles of the waveform of the AC voltage applied to the load and thereby decrease the DC current flowing through the load, said means including means for adding the voltage across the second capacitor to the voltage across the diac to alter the voltage applied to the R-C series combination of the potentiometer and the first capacitor.

Claim 23

Circuit according to claim 19, wherein the first and second thyristors comprise first and second triacs, respectively.