DIMMER UNIT FOR A LIGHTING CONTROL SYSTEM

• US 3,733,528 A
• Filed: 08/02/1971
• Issued: 05/15/1973
• Est. Priority Date: 08/02/1971
• Status: Expired due to Term

• Current Assignee: Benjamin F. Gilbreath
• Original Assignee: Benjamin F. Gilbreath
• Inventors: Gilbreath, Benjamin F.
• Primary Examiner(s): Brody, Alfred L.
• Application Number:
  US05/168,317
• Time in Patent Office: 652 Days
• Field of Search: 315/201,202,291-295,312-317
• US Class Current: 315/291
• CPC Class Codes: G05F 1/445 being transistors in series with the load
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A plurality of dimmer units are connected between an alternating-current power source and different ones of a plurality of lamp loads for separately controlling the flow of alternating current through such lamp leads. Each dimmer unit includes a switching mechanism for passing the alternating current to the lamp load and a controllable direct-current responsive timing mechanism for controlling the fraction of each alternating-current half cycle during which the switching mechanism is conductive. The direct-current control signal input terminals of each dimmer unit are connected between corresponding output terminals of a pair of multiple output pre-set control units. A fader control unit supplies direct-current voltages to the pre-set control units and includes means for varying such voltages in an inverse manner for shifting control of the system from one pre-set control unit to the other. Each pre-set control unit includes a plurality of adjustable voltage dividers for individually determining the fractions of the pre-set unit input voltage appearing at the different ones of the pre-set unit output terminals.

Claims

1. A dimmer unit for use in a lighting control system and comprising:

circuit means for supplying an alternating-current voltage;

circuit means for supplying a direct-current control voltage;

switching circuit means adapted to be coupled in series between the alternating-current supply circuit means and a lamp load for enabling current flow to the lamp load when such switching circuit means is conductive;

a timing capacitor;

a trigger device coupled to the timing capacitor for discharging same and supplying a trigger pulse to the switching circuit means when the charge on the timing capacitor exceeds a predetermined threshold level; and

controllable charging circuit means responsive to the direct-current control voltage for charging the timing capacitor at a rate dependent on the magnitude of such direct-current control voltage.

2. A dimmer unit in accordance with claim 1 wherein the trigger device is a programmable unijunction transistor.

3. A dimmer unit in accordance with claim 1 and including:

means for controlling the threshold level of the trigger device; and

circuit means responsive to the alternating-current voltage for developing a direct-current bias voltage proportional to the peak amplitude thereof and for supplying such bias voltage to the trigger device threshold control means for compensating for changes in magnitude of the alternating-current voltage.

4. A dimmer unit in accordance with claim 3 wherein the trigger device is a programmable unijunction transistor having anode, cathode and gate electrodes, the anode and cathode electrodes being coupled across the timing capacitor and the gate electrode being coupled to the circuit means for developing the direct-current bias voltage.

5. A dimmer unit for use in a lighting control system and comprising:

circuit means for supplying an alternating-current voltage;

circuit means for supplying a direct-current control voltage;

first switching circuit means adapted to be coupled in series between the alternating-current supply circuit means and a lamp load for enabling current flow to the lamp load when such switching circuit means is conductive;

capacitor means;

second switching circuit means coupled across the capacitor means for discharging same when the voltage thereacross exceeds a predetermined threshold level;

circuit means for sensing the flow of capacitor discharge current and rendering the first switching circuit means conductive at the onset thereof;

rectifier circuit means for rectifying the alternating-current voltage;

first charging circuit means responsive to the rectified alternating-current voltage for charging the capacitor means at a first rate; and

second charging circuit means responsive to the direct-current control voltage for charging the capacitor means at a second rate.

6. A dimmer unit in accordance with claim 5 and including third switching circuit means coupled across the capacitor means and responsive to the rectified alternating-current voltage for completely discharging the capacitor means at the end of each half cycle of the alternating-current voltage.

7. A dimmer unit in accordance with claim 6 and including circuit means responsive to the rectified alternating-current voltage for developing a direct-current bias voltage proportional to the peak amplitude thereof and for supplying such bias voltage to the second switching circuit means for controlling the threshold level thereof for compensating for changes in magnitude of the alternating-current voltage.