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EP0706306A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

A hardware arrangement and method of driving a piezo-electric transformer

Assignee: NEC Corp
•
Filing: 1995-10-05
•
Granted: —
•
Expires: 2015-10-05
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Abstract

Abstract An apparatus for controlling a piezoelectric transformer is disclosed. A transformer driver (12) supplies the transformer with a driving voltage the frequency of which is controlled by a frequency oscillator (18). A load current monitor (20, 22, 24, 26) observes a load current flowing through a load such as a fluorescent which is powered by said transformer. A frequency sweep controller (16) controls the frequency oscillator, when the transformer is initially energized, so as to execute a downward frequency sweep wherein the frequency of the driving voltage is swept from a predetermined upper frequency to a predetermined lower frequency. The frequency sweep controller further controls the frequency oscillator, after the transformer has been brought into stable operation, so as to execute the downward frequency sweep when the load current reduces to a second preset level lower than the first preset level.

Inventors

  • 👤 Shingo c/o NEC Corporation Kawashima

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-10-31 19:07
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/26; H05B41/28; H05B41/282; H05B41/2821; H05B41/2822; H05B41/24; H10; H10N; H10N30/00; H10N30/80; H10N30/802; H10N30/804

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 139 words
An apparatus for controlling a piezoelectric transformer comprising: driver means (12) for applying a driving voltage to said piezoelectric transformer; frequency oscillator means (18) for controlling a frequency of said driving voltage; means (20, 22, 24, 26) for monitoring the load current flowing through a load which is powered by said transformer; and frequency control means (16) for controlling said frequency oscillator means, when said transformer is initially energized, so as to execute a downward frequency sweep wherein the frequency of said driving voltage is swept from a predetermined upper frequency to a predetermined lower frequency, said frequency control means further controlling said frequency oscillator means, after said transformer has been brought into stable operation, so as to execute said downward frequency sweep when the load current reduces to a second preset level lower than said first preset level.
Claim 2
Dependent Claim 36 words
An apparatus as claimed in claim 1, further comprising means (28) for controlling the frequency of said driving voltage so as to converge to a preset frequency when said load current exceeds a first preset level.
Claim 3
Dependent Claim 17 words
An apparatus as claimed in claim 1 or 2, wherein said load is a fluorescent lamp (14).
Claim 4
Dependent Claim 26 words
An apparatus as claimed in claim 1, 2 or 3, wherein said first preset level is above and close to a resonance frequency of said transformer.
Claim 5
Dependent Claim 58 words
An apparatus as claimed in claim 1, 2, 3 or 4, further comprising: means (30) for detecting an output voltage of said transformer; and means (32) for monitoring said output voltage, and wherein said frequency control means reduces the frequency of said driving voltage down to said predetermined lower frequency when said output voltage exceeds a preset voltage.
Claim 6
Dependent Claim 29 words
An apparatus as claimed in claim 5, further comprising means (40) for controlling either said driver means or said frequency oscillator means so as to intermittently drive said transformer.
Claim 7
Dependent Claim 32 words
An apparatus as claimed in claim 6, wherein a frequency for intermittently driving said transformer is not permitted to approach an integer multiple of a vertical synchronization frequency for television and video.

References Cited (Backward Citations)

JPS61152165A Cited
JPH0449846A Cited
JPH04133657A Cited
JPH05219730A Cited

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