Triac-based, low voltage AC dimmer

• US 7,180,250 B1
• Filed: 01/25/2005
• Issued: 02/20/2007
• Est. Priority Date: 01/25/2005
• Status: Expired due to Fees

• Current Assignee: Henry Michael Gannon
• Original Assignee: Henry Michael Gannon
• Inventors: Gannon, Henry Michael
• Primary Examiner(s): TRAN, THUY V
• Application Number:
  US11/043,298
• Time in Patent Office: 756 Days
• Field of Search: 315/246, 315/276, 315/283, 315/291, 315/307, 315/279, 315/299, 315/362, 315/DIG.4, 307/134, 307/139, 307/140, 307/141
• US Class Current: 315/276
• CPC Class Codes: H05B 39/044 continuously H05B39/042 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A two-wire triac-based low voltage AC dimmer adapted for configuration in series with a typically incandescent lighting load. An external step-down transformer provides a source of low AC voltage, and a separate, electrically isoated loop circuit utilizing a step-up transformer converts a portion of the low AC voltage into a corresponding high AC voltage used to trigger the gate of a triac. An on/off arrangement that serves to lock the triac in its blocking may optionally be provided. A shunting resistor connected across the triac serves to dissipate static charge buildup that may otherwise falsely trigger the triac to its on state. A phi filter provides a smoother and more regulated triggering pulse to the triac, thereby minimizing or eliminating flickering and undesirable extinguishing of the incandescent lighting load at low brightness settings.

Claims

1. A low voltage dimmer circuit, comprising:

a lighting load to be controlled;

a source of low AC voltage for powering the lighting load;

a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage;

a triac coupled in series with the lighting load;

adjustable trigger control circuit means coupled to said step-up transformer and to said triac for triggering said triac into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said lighting load; and

an AC voltage regulator coupled across a secondary winding of said step-up transformer, said AC voltage regulator comprising a bi-directional transient suppressor in series with a resistor.

2. A low voltage AC dimmer circuit as in claim 1, wherein said lighting load comprises an incandescent lighting load.

3. A low voltage AC dimmer circuit as in claim 1, wherein said higher AC voltage comprises AC line voltage.

4. A low voltage AC dimmer circuit, comprising:

a lighting load to be controlled;

a source of low AC voltage for powering the lighting load;

a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage, said step-up transformer comprising a primary winding connected to said source of low AC voltage and a secondary winding for supplying said higher AC voltage;

a triac coupled in series with the lighting load;

adjustable trigger control circuit means coupled to said step-up transformer and to said triac for triggering said triac into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said lighting load; and

switch means connected in series with said primary winding of said step-up transformer for switching said AC dimmer circuit between a normal state of operation and an off state of operation, said triac being locked in a blocking state during said off state of operation of said AC dimmer circuit.

5. A low voltage AC dimmer circuit as in claim 4, wherein said adjustable trigger control circuit means is coupled across said secondary winding of said step-up transformer.

6. A low voltage AC dimmer circuit as in claim 4, further comprising an LC filter coupled to said primary winding of said step-up transformer to provide radio frequency noise attenuation.

7. A low voltage AC dimmer circuit as in claim 4, wherein said lighting load comprises an incandescent lighting load.

8. A low voltage AC dimmer circuit as in claim 4, wherein said higher AC voltage comprises AC line voltage.

9. A low voltage AC dimmer circuit, comprising:

a lighting load to be controlled;

a source of low AC voltage for powering the lighting load;

a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage, said step-up transformer comprising a primary winding connected to said source of low AC voltage and a secondary winding for supplying said higher AC voltage;

a triac coupled in series with the lighting load; and

adjustable trigger control circuit means coupled to said step-up transformer and to said triac for triggering said triac into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said lighting load, said adjustable trigger control circuit means comprising a series combination of a potentiometer and a timing capacitor coupled across said secondary winding of said step-up transformer.

10. A low voltage AC dimmer circuit as in claim 9, wherein said adjustable trigger control circuit means further comprises:

a fixed resistor shunted across said potentiometer; and

a series combination of an auxiliary timing capacitor and a bridge resistor coupled across said timing capacitor.

11. A low voltage AC dimmer circuit as in claim 9, wherein said lighting load comprises an incandescent lighting load.

12. A low voltage AC dimmer circuit as in claim 9, wherein said higher AC voltage comprises AC line voltage.

13. A low voltage AC dimmer circuit, comprising:

a low voltage lighting load to be controlled;

a source of low AC voltage for powering the low voltage lighting load;

a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage;

a triac coupled in series with the low voltage lighting load; and

adjustable trigger control circuit means coupled to said step-up transformer and to said triac said adjustable trigger control circuit means being arranged for receiving said higher AC voltage and for triggering said triac into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said low voltage lighting load, said adjustable trigger control circuit means comprising a phase delay circuit.

14. A low voltage AC dimmer circuit as in claim 13, wherein said low voltage lighting load comprises an incandescent low voltage lighting load.

15. A low voltage AC dimmer circuit as in claim 13, wherein said higher AC voltage comprises AC line voltage.

16. A low voltage dimmer circuit, comprising:

a lighting load to be controlled;

a source of low AC voltage for powering the lighting load;

a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage;

a triac coupled in series with the lighting load;

adjustable trigger control circuit means coupled to said step-up transformer and to said triac for triggering said triac into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said lighting load; and

an AC voltage regulator coupled across a secondary winding of said step-up transformer, said AC voltage regulator comprising a bi-directional transient suppressor.