Control circuit for progressively varying illumination intensity of lamps

• US 3,991,343 A
• Filed: 01/07/1976
• Issued: 11/09/1976
• Est. Priority Date: 01/07/1976
• Status: Expired due to Term

• Current Assignee: Henry Delpy
• Original Assignee: Henry Delpy
• Inventors: Delpy, Henry
• Primary Examiner(s): La Roche, Eugene
• Application Number:
  US05/646,965
• Time in Patent Office: 307 Days
• Field of Search: 315/194, 315/199, 315/291, 315/296, 315/307, 315/360, 315/DIG. 4, 317/141 R, 317/141 S, 317/142 R, 323/19, 323/41, 307/252 F, 307/252 N, 307/294
• US Class Current: 315/194
• CPC Class Codes: H02M 7/1555 with control circuit
• CPC Class Codes: H05B 39/083 by the variation-rate of light intensity

Abstract

A control circuit for progressively and gradually varying the illumination intensity of incandescent lamps. The circuit comprises a source of alternating current connected in series with an electric lamp load which is also in series with a silicon controlled rectifier. This silicon control rectifier is rendered conductive when its gate is actuated by a gate signal generated by a programmable unijunction transistor (PUT). The conduction of the PUT depends on the voltage applied on its gate by a gate biasing circuit connected thereto and which comprises a charging capacitor. On the other hand, a charging circuit is connected across the silicon control rectifier whereas a second charging circuit is connected between the anode of the PUT and the first-mentioned charging circuit. Thus, progressive and gradual extinction or quenching as well as progressive and gradual ignition or lightening of the electric lamp are effected by making the charging or discharging time of the first-mentioned circuit higher than the charging or discharging time of the gate biasing circuit, whereby the time intervals between which the PUT is made conductive becomes longer and longer due to the reducing difference between the voltage supplied by the biasing circuit to the gate of the PUT and the voltage on the cathode of the PUT supplied by the second-mentioned charging circuit, at each source cycle.

Claims

1. A circuit for progressively and gradually controlling an electric current flowing through incandescent lamp loads, comprising:

a source of alternating current,

a silicon control rectifier having anode, cathode and gate electrodes, said anode electrode being connected in series with at least one of said lamp loads, both being connected across said source,

a programmable unijunction transistor having anode, cathode and gate electrodes for generating, when made conductive, a gate signal through the cathode thereof to the gate of said silicon control rectifier,

a capacitance-resistance biasing circuit connected to the gate of said programmable unijunction transistor, said biasing circuit having a first predetermined charging time,

a charging circuit connected between the anode and cathode of said silicon control rectifier and having a second predetermined charging time,

another charging circuit connected to the anode of the programmable unijunction transistor through a diode and to said charging circuit,

the charging time of said charging circuit being higher than the charging time of said gate biasing circuit so that the current flowing through the lamp load is progressively and gradually decreased at each cycle of said alternating current source till null, and afterwards is increased to its full intensity, such increase and decrease in the current intensity being cyclically and automatically resumed.

2. A control circuit as claimed in claim 1, wherein said gate biasing circuit comprises a capacitor connected across a resistor which is in series with a variable resistor the wiper of which is connected to one terminal of said capacitor and to the cathode of said silicon control rectifier, the other terminal of said capacitor being connected to the gate of the programmable unijunction transistor through a second diode and a second resistor, and wherein the charging circuit comprises a second capacitor in series with a third resistor at the junction point of which is connected said another charging circuit.

3. A control circuit as claimed in claim 2, wherein the anode of the silicon control rectifier is connected to the anode of the programmable unijunction transistor through a third diode and a fourth resistor and, wherein the cathode of the silicon control rectifier is connected to the cathode of the programmable unijunction transistor through a fifth resistor.

4. A control circuit as claimed in claim 2, wherein a fifth resistor is connected between said second diode and said third diode, and wherein said another charging circuit comprises a third capacitor in parallel with a sixth resistor.

5. A circuit for progressively and gradually controlling an electric current flowing through color lamp loads by means of parallely connected circuit units fed by a common source of alternating current, each circuit unit comprising

a silicon control rectifier having anode, cathode and gate electrodes, said anode electrode being connected in series with at least one of said lamp loads, both being connected across said source,

a programmable unijunction transistor having anode, cathode and gate electrodes for generating, when made conductive, a gate signal through the cathode thereof to the gate of said silicon control rectifier,

a capacitance-resistance biasing circuit connected to the gate of said programmable unijunction transistor, said biasing circuit having a first predetermined charging time,

a charging circuit connected between the anode and cathode of said silicon control rectifier and having a second predetermined charging time,

another charging circuit connected to the anode of the programmable unijunction transistor through a diode and to said charging circuit

the charging time of said charging circuit being, in each circuit unit, higher than the charging time of said gate biasing circuit whereas the charging time of each biasing circuit is different from that of the other charging circuits, so that the current flowing through the lamp load in each circuit unit is progressively and gradually decreased at each cycle of said alternating current source till null, and afterwards is increased to its full intensity, such increase and decrease in the current intensity being cyclically different for each circuit unit and automatically resumed for all circuit units.

6. A control circuit as claimed in claim 5, wherein said gate biasing circuit comprises a capacitor connected across a resistor which is in series with a variable resistor of a value which differs in each circuit unit and the wiper of which is connected to the terminal of said capacitor and to the cathode of said silicon control rectifier, the other terminal of said capacitor being connected to the gate of the programmable unijunction transistor through a second diode and a second resistor, and wherein the charging circuit comprises a second capacitor in series with a third resistor at the junction point of which is connected said another charging circuit.

7. A control circuit as claimed in claim 6, wherein the anode of the silicon control rectifier is connected to the anode of the programmable unijunction transistor through a third diode and a fourth resistor and, wherein the cathode of the silicon control rectifier is connected to the cathode of the programmable unijunction transistor through a fifth resistor.

8. A control circuit as claimed in claim 7, wherein a fifth resistor is connected between said second diode and said third diode, and wherein said another charging circuit comprises a third capacitor in parallel with a sixth resistor.