US6331748B1 — Driving circuit of a piezo-ceramic transformer ca…

Claim 1

Independent Claim 264 words

A fixed frequency driving circuit for a piezo-ceramic transformer capable of controlling an input voltage, comprising: a piezo-ceramic transformer driving circuit electrically connected to drive the piezo-ceramic transformer, said piezo-ceramic transformer driving circuit having an input and an output; a voltage doubler rectifier electrically connected to the piezo-ceramic transformer for rectifying an output voltage of the piezo-ceramic transformer, said voltage double having an output; a summing and error amplifier electrically connected to the output of the voltage doubler rectifier for outputting a sum voltage of a dimming voltage and an output voltage of the voltage doubler rectifier; a phase detector electrically connected between the input and output of the piezo-ceramic transformer for detecting a phase between the input and output signals of the piezo-ceramic transformer; a temperature compensated voltage controlled oscillator for compensating temperature characteristics for the piezo-ceramic transformer, the temperature compensated voltage controlled oscillator being electrically connected to the output of the phase detector; a charge pump circuit electrically connected to the input of the piezo-ceramic transformer driving circuit for maintaining zero voltage switching and reducing switching loss of a switching element in combination with a phase-locked loop operation produced by the voltage controlled oscillator and phase detector; and a modulator electrically connected to the input of the piezo-ceramic transformer driving circuit for continuously producing an amplitude of a first harmonic frequency component when the input voltage is changed from a minimum voltage to a maximum voltage by controlling a duty ratio provided to the piezo-ceramic transformer driving circuit according to output signals from the phase detector and the summing and error amplifier.

Claim 2

Dependent Claim 264 words

A fixed frequency driving circuit for a piezo-ceramic transformer capable of controlling an input voltage, comprising: a piezo-ceramic transformer driving circuit electrically connected to drive the piezo-ceramic transformer, said piezo-ceramic transformer driving circuit having an input and an output; a voltage doubler rectifier electrically connected to the piezo-ceramic transformer for rectifying an output voltage of the piezo-ceramic transformer, said voltage double having an output; a summing and error amplifier electrically connected to the output of the voltage doubler rectifier for outputting a sum voltage of a dimming voltage and an output voltage of the voltage doubler rectifier; a phase detector electrically connected between the input and output of the piezo-ceramic transformer for detecting a phase between the input and output signals of the piezo-ceramic transformer; a temperature compensated voltage controlled oscillator for compensating temperature characteristics for the piezo-ceramic transformer, the temperature compensated voltage controlled oscillator being electrically connected to the output of the phase detector; a charge pump circuit electrically connected to the input of the piezo-ceramic transformer driving circuit for maintaining zero voltage switching and reducing switching loss of a switching element in combination with a phase-locked loop operation produced by the voltage controlled oscillator and phase detector; and a modulator electrically connected to the input of the piezo-ceramic transformer driving circuit for continuously producing an amplitude of a first harmonic frequency component when the input voltage is changed from a minimum voltage to a maximum voltage by controlling a duty ratio provided to the piezo-ceramic transformer driving circuit according to output signals from the phase detector and the summing and error amplifier.

Claim 3

Dependent Claim 55 words

A fixed frequency driving circuit in accordance with claim 1 , wherein the piezo-ceramic transformer driving circuit comprises: three transistors, including a first transistor connected in series to a second transistor and a third transistor connected in parallel with the first and second transistors; and an LC filter connected between the second and third transistors.

Claim 4

Dependent Claim 29 words

A fixed frequency driving circuit in accordance with claim 1 , wherein the charge pump circuit reduces switching loss even when the duty ratio is less than approximately 5%.

Claim 5

Dependent Claim 54 words

A fixed frequency driving circuit in accordance with claim 1 , wherein the phase detector controls the phase so that a driving frequency by the voltage controlled oscillator's oscillation frequency is greater than a resonant frequency of the piezo-ceramic transformer, when the resonant frequency of the piezo-ceramic transformer varies due to an environment condition.

Claim 6

Dependent Claim 23 words

A fixed frequency driving circuit in accordance with claim 4 , wherein the environment condition is at least one of temperature and impact.

Claim 7

Dependent Claim 53 words

A method for using the driving circuit in accordance with claim 1 , comprising the step of restricting a driving frequency using the temperature compensated voltage controlled oscillator so that the driving frequency is greater than a resonant frequency when the resonant frequency of the piezo-ceramic transformer is shifted by an environment condition.

Claim 8

Dependent Claim 20 words

A method in accordance with claim 6 , wherein the environment condition is at least one of temperature and impact.

Claim 9

Dependent Claim 96 words

A dimming control method of a driving circuit of a piezo-ceramic transformer comprising the steps of: determining a duty ratio at an input voltage for producing a maximum output current at the input voltage; and providing a current producing a desired brightness by reducing the duty ratio at the input voltage for dimming while substantially maintaining brightness efficiency; wherein the duty ratio is a required ratio of switch turn ON time to a period of the input voltage, and an amplitude of the duty ratio is equivalent to an amplitude of a first harmonic frequency component.

Claim 10

Dependent Claim 96 words

A dimming control method of a driving circuit of a piezo-ceramic transformer comprising the steps of: determining a duty ratio at an input voltage for producing a maximum output current at the input voltage; and providing a current producing a desired brightness by reducing the duty ratio at the input voltage for dimming while substantially maintaining brightness efficiency; wherein the duty ratio is a required ratio of switch turn ON time to a period of the input voltage, and an amplitude of the duty ratio is equivalent to an amplitude of a first harmonic frequency component.

Claim 11

Dependent Claim 32 words

A method in accordance with claim 8 , wherein the amplitude of the duty ratio is determined using a minimum input voltage and the duty ratio value based on the input voltage.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2004-12-17	2005-06-18	2005-12-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2008-12-17	2009-06-18	2009-12-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2012-12-17	2013-06-18	2013-12-18	$7700.00	Window Closed / Lapsed

Driving circuit of a piezo-ceramic transformer capable of controlling an input voltage and a dimming control method thereof

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