Control circuit employing preconditioned feedback amplifier for initializing VCO operating frequency
US6639367B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 2002 |
| Grant date | Oct 28, 2003 |
| Priority date | — |
| Expiry date | Jun 18, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/2827
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A control circuit for a piezo transformer based power supply includes oscillator circuitry, drive circuitry, sense circuitry, and feedback circuitry collectively operating to regulate an operational parameter of the supply, such as the current supplied to a cold cathode fluorescent lamp (CCFL). The feedback circuitry includes initialization circuitry that establishes an initial value of an oscillator control signal corresponding to an initial operating frequency, and thereafter permits the feedback circuitry to gradually drive the oscillator control signal to a normal operating value such that the operating frequency is swept from the initial operating frequency to a normal operating frequency. When controlling the power supplied to a CCFL, the initial operating frequency is preferably a maximum frequency of the oscillator, and the operating frequency is swept downward so as to pass through the frequency at which the lamp “strikes”, or begins conduction, and thereafter into regulation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.