摘要:
There is provided a method for driving a piezoelectric transformer in which a driving efficiency and the reliability in terms of withstand power and distortion can be enhanced by suppressing a higher order vibration mode exited by a harmonic component other than a driving frequency included in a driving signal of the piezoelectric transformer without using an inductive element. The driving signal applied to a primary side electrode of the piezoelectric transformer is a signal in a rectangular waveform having a time period δT in which a level is a maximum potential (2V) or a minimum potential (0), obtained by multiplying a period T of the driving signal by a predetermined time ratio δ. The time ratio δ is set to be smaller than 0.5 and so as to minimize a sum of ratios of amplitudes of respective higher order vibration modes with respect to an amplitude of a vibration mode exciting the piezoelectric transformer.
摘要:
The present invention provides a light emission control device that can drive a plurality of cold cathode fluorescent tubes independently only by connecting a plurality of piezoelectric transformers to only one piezoelectric inverter circuit. A first phase control portion that outputs a signal for changing a phase of the third and the fourth driving control signals with respect to a phase of the first and the second driving control signals to the second driving portion, and a second phase control portion that outputs a signal for changing a phase of the fifth and the sixth driving control signals with respect to a phase of the first and the second driving control signals to the third driving portion are provided in the piezoelectric inverter circuit. Thus, the phase difference of the driving control signals is controlled, so that the output powers to the plurality of cold cathode fluorescent tubes are controlled.
摘要:
A low loss, small scale piezoelectric transformer, suited for a cold cathode tube load, and having a high effective coupling factor, is provided using a piezoelectric plate having a single polarization direction. Controlling the dimensions of the third electrode portion 15a constituting the high impedance portion makes it possible easily to adjust the capacitance of the electrostatic capacitor formed between the first electrode portion 12 and the third electrode portion in accordance with the load. Also, the second electrode portion 13 and the fourth electrode portion 15b constituting the low impedance portion are substantially equal in area and the third electrode portion and the fourth electrode portion are formed in one piece, so that energy propagation efficiency can be increased. Consequently, the effective coupling factor resulting from the electrode structure and the vibration mode can be kept high even if the capacitance is changed freely, and thus high element efficiency and a small amount of generated heat can be maintained and stress can be decreased.
摘要:
A driving circuit for a piezoelectric transformer is provided, which ensures lighting of all the cold-cathode tubes connected to the piezoelectric transformer, and reduces the difference in brightness between the cathode tubes during steady lighting, thereby enhancing reliability and performance. A plurality of cold-cathode tubes connected to a secondary side of the piezoelectric transformer, and a cold-cathode tube output detector circuit connected in series to a plurality of cold-cathode tubes, for detecting an output state of the respective cold-cathode tubes are provided, and the driving of the piezoelectric transformer is controlled based on a detection signal from the cold-cathode tube output detector circuit. Because of this, the piezoelectric transformer performs the same operation as that with respect to one cold-cathode tube.
摘要:
The invention provides a method of driving a piezoelectric transformer and a power source apparatus using the same. For a circuit for driving a piezoelectric transformer which steps up a voltage input from a primary electrode by a piezoelectric effect to output the stepped up voltage from a secondary electrode, the gradient (linear differential value) of a step-up ratio at the piezoelectric transformer is detected, and the detected gradient is used to control the driving frequency for the piezoelectric transformer so that the driving frequency approaches to the resonant frequency of the piezoelectric transformer.
摘要:
A driving method and a driving circuit for a piezoelectric transformer are capable of driving the piezoelectric transformer with high driving efficiency independently of an impedance change of a load such as a cold cathode tube by corresponding to the characteristic variance of the piezoelectric transformer, thereby also suppressing mechanical damage to be imposed on the piezoelectric transformer itself even if the load changes abruptly. The piezoelectric transformer is driven with a predetermined first frequency, and a power supply for a load connected to the secondary side of the piezoelectric transformer is started, and when an impedance of a load changes and reaches a predetermined impedance during the power supply, the driving frequency of the piezoelectric transformer is changed without a sweep from the first frequency to a predetermined second frequency. Furthermore, the second frequency is determined by detecting characteristics of the piezoelectric transformer before supplying the load steadily with electric power.
摘要:
A piezoelectric transformer includes a piezoelectric ceramic disc having one face and the other face opposite to each other in a thickness direction. A pair of low-impedance portions acting as one of a driving portion and a generator portion are disposed in the piezoelectric ceramic disc symmetrically with respect to a central axis of the piezoelectric ceramic disc, while a pair of high-impedance portions acting as the other of the driving portion and the generator portion are disposed in the piezoelectric ceramic disc symmetrically with respect to the central axis so as to be electrically separated from the low-impedance portions such that the piezoelectric transformer is driven in a radial extensional vibration mode of the piezoelectric ceramic disc.
摘要:
A driving circuit for a piezoelectric transformer is provided, which ensures lighting of all the cold-cathode tubes connected to the piezoelectric transformer, and reduces the difference in brightness between the cathode tubes during steady lighting, thereby enhancing reliability and performance. A plurality of cold-cathode tubes connected to a secondary side of the piezoelectric transformer, and a cold-cathode tube output detector circuit connected in series to a plurality of cold-cathode tubes, for detecting an output state of the respective cold-cathode tubes are provided, and the driving of the piezoelectric transformer is controlled based on a detection signal from the cold-cathode tube output detector circuit. Because of this, the piezoelectric transformer performs the same operation as that with respect to one cold-cathode tube.
摘要:
A driving circuit for a piezoelectric transformer is provided, which is capable of driving a piezoelectric transformer at a high efficiency and with low distortion, and being miniaturized. At the commencement of lighting a cold-cathode fluorescent tube, a digital controller fixes frequencies of first and second control signals VC1 and VC2 at a predetermined frequency and controls the phase difference therebetween so that an output power of the piezoelectric transformer becomes from substantially zero to a predetermined output power. After lighting of the cold-cathode fluorescent tube, the digital controller controls the phase difference between the first and second control signals VC1 and VC2 so that current detecting data CD substantially is matched with reference data RD.
摘要:
A compact and high-power piezoelectric transformer is realized by using higher order longitudinal extensional mode vibrations and increasing an effective electromechanical coupling factor by a primary electrode which consists of plural electrodes.