Fluorescent lamp excitation circuit having a multi-layer piezoelectric acoustic transformer and methods for using the same

• US 6,124,678 A
• Filed: 10/08/1999
• Issued: 09/26/2000
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: Face International Corp.
• Original Assignee: Face International Corp.
• Inventors: Boyd, Clark Davis, Bishop, Richard Patten
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Lee, Wilson
• Application Number:
  US09/415,391
• Time in Patent Office: 354 Days
• Field of Search: 315/209 PZ, 315/209 R, 315/276, 315/277, 315/278, 315/308, 315/224, 315/219
• US Class Current: 315/209.0PZ
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations

Abstract

Fluorescent lamp excitation circuits are provided which use a resonating piezoelectric transformer along with complementary circuit components, to efficiently convert a DC first voltage to a transformer-output AC second voltage. In the preferred embodiment of the invention, A High Displacement Piezoelectric (HDP) transformer achieves sufficiently high voltage output to "cold fire" a gas discharge lamp. The disclosed circuit may be modified using conventional electrical sub-circuitry to pre-heat the cathodes of the lamp.

Claims

1. A gas discharge lamp control circuit comprising:

a DC voltage source;

said DC voltage source having first and second output terminals, a voltage at said first output terminal from said DC voltage source being higher than a voltage at said second output terminal from said DC voltage source;

a piezoelectric transformer;

said piezoelectric transformer comprising a first piezoelectric ceramic layer and a second piezoelectric ceramic layer,

said first piezoelectric ceramic layer having first and second major faces, said first and second major faces of said first piezoelectric ceramic layer being substantially parallel to each other;

said first piezoelectric ceramic layer being polarized such that when a first input voltage is applied across said first and second major faces of said first piezoelectric ceramic layer, said first piezoelectric ceramic layer longitudinally deforms in a direction substantially parallel to said first and second major faces of said first piezoelectric ceramic layer;

said second piezoelectric ceramic layer having first and second major faces, said first and second major faces of said second piezoelectric ceramic layer being substantially parallel to each other;

said second piezoelectric ceramic layer being polarized such that when said second piezoelectric ceramic layer is longitudinally deformed in a direction substantially parallel to said first and second major faces of said second piezoelectric ceramic layer, a first output voltage is generated across said first and second major faces of said second piezoelectric ceramic layer

said first piezoelectric ceramic layer and said second piezoelectric ceramic layer being bonded together such that said first major face of said first piezoelectric ceramic layer and said first major face of said second piezoelectric ceramic layer are facing toward each other, and said second major face of said first piezoelectric ceramic layer and said second major face of said second piezoelectric ceramic layer are facing away from each other;

said first output terminal from said DC voltage source being electrically connected in series to said second major face of said first piezoelectric ceramic layer;

a transformer output terminal electrically connected to said second major face of said second piezoelectric ceramic layer;

said transformer output terminal being adapted to be electrically connected to a first terminal of a gas discharge lamp;

A field effect transistor with a source, a gate and a drain;

a transformer common conductor electrically connected to said first major faces of said first and second piezoelectric ceramic layers;

said transformer common conductor being electrically to the drain of said field effect transistor;

an inductor electrically connected in series between said second major face of said first piezoelectric ceramic layer and said common conductor;

said gate of said field effect transistor being electrically connected in series with said transformer output terminal; and

said source of said field effect transistor being electrically connected in series with said second output terminal of said DC voltage source.