Dimmer with reduced filtering losses

• US 5,179,324 A
• Filed: 01/21/1992
• Issued: 01/12/1993
• Est. Priority Date: 01/21/1991
• Status: Expired due to Term

• Current Assignee: Legrand France SA (Legrand SA)
• Original Assignee: Legrand (Legrand SA)
• Inventors: Audbert, Jean
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): Shingleton, MIchael B.
• Application Number:
  US07/822,986
• Time in Patent Office: 357 Days
• Field of Search: 315/194, 315/195, 315/283, 315/210, 315/209 R, 315/224, 315/241 R, 315/244, 315/245, 315/199, 315/225, 315/226, 315/DIG. 4, 323/300, 323/324, 323/326, 323/905, 323/239, 307/632
• US Class Current: 315/194
• CPC Class Codes: H02M 5/257 using semiconductor devices only
• CPC Class Codes: H03K 17/16 Modifications for eliminating interference voltages or currents
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps
• CPC Class Codes: Y10S 323/905 Lamp dimmer structure

Abstract

A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Claims

1. Dimmer for a load such as an incandescent lamp connected to an alternating current mains power supply adapted to be inserted into a conductor supplying power to the load via input and output terminals and comprising a triac with two main terminals of which a first is connected to the input terminal and the second is coupled to the output terminal, a control circuit sending to the triac a triggering signal synchronized to the voltage between the terminals with a variable timedelay, a filter inductor with one end connected to the second main terminal of the triac and a second end coupled to the output terminal, a filter capacitor connected between the input and output terminals and a second triac connected between the input terminal and the second end of the inductor, the control circuit sending a second control signal to the second triac with a fixed time-delay relative to the first.

2. Dimmer according to claim 1 wherein said filter capacitor and inductor jointly determine a time constant and said time-delay is greater than said time constant.

3. Dimmer according to claim 1 further comprising a stabilizing circuit for low loads comprising a series resistor-capacitor circuit shunting said filter capacitor.

4. Dimmer according to claim 1 further comprising an auxiliary inductor of substantially lower value than said filter inductor connected between the latter and said output terminal.

5. Dimmer according to claim 1 wherein said triac control circuit comprises a power supply circuit with a reservoir capacitor adapted to be charged via a diode by the voltage between said input and output terminals.