Nec Corporation

Nippon Electric Co., Ltd.

Yasuhei Shimada

Nobuaki Honbo

Shingo Kawashima

Eitaro Nishigaki

Shuuji Yamaguchi

Makoto Kouno

A drive circuit for a piezoelectric transformer includes a master block 24 having a drive frequency control circuit for controlling the frequency of a drive voltage for a piezoelectric transformer, at least one slave block 25 receiving an output of the above mentioned drive frequency control circuit and having a drive voltage control circuit for controlling a peak value of a drive voltage for a piezoelectric transformer, a circuit for PWM-modulating the drive voltages applied to the piezoelectric transformers, and driving the drive voltages in the same phase, and a circuit for suppressing a harmonic component of a light adjusting frequency included in the drive voltages for the piezoelectric transformers. With this arrangement, when a plurality of cold cathode tubes are driven by using piezoelectric transformer inverters, it is possible to eliminate the limit in the number of tubes lighted and the inclination of the brightness, and to prevent a flickering and the generation of an audible sound.

Inverter and method for driving a plurality of cold cathode tubes in

In a steady-state operation, a rectified voltage obtained from an output current Io of a piezoelectric transformer 1 is compared in a comparator 10 with Vref. When the voltage is lower than Vref, a signal Vdown is at an 'H' level, and otherwise it is at an 'L' level. A switch SW1 or SW2 is thus turned on to charge or discharge a capacitor Cvco. This has an effect of sweeping the oscillation frequency of a VCO 14 downward or upward to increase or reduce the output voltage Vo of the piezoelectric transformer 1 which is driven at the oscillation frequency. When a load 2 is open-circuited, a voltage VR obtained from an output voltage Vo becomes higher than Vmax to set a flip-flop 13 and turn on a switch SW3. The capacitor voltage Vvco is thus reduced to reduce the oscillation frequency of the VCO 14 and reduce the output voltage Vo. When the voltage VR becomes lower than Vmin, the flip-flop 18 is reset by the output of the comparator 16 to turn off the switch SW3.

Piezoelectric transformer driver

A secondary battery unit which can supply constant power for a longer time with a lower input voltage and which is small, light, and suitable for portable use is provided. The secondary battery unit comprises plural inductors having different inductances, to which the first voltage is input; a rectifier inserted between the plural inductors and the output terminal; plural switches respectively connected to the plural inductors, each switch making current according to the first voltage flow through the connected inductor when the switch is operated; a switching controller for selectively operating one of the plural switches according to variation of the first voltage; and a controller for controlling timing of the above switching between the plural switches so as to stabilize a voltage from the output terminal to the predetermined second voltage.

Secondary battery unit using electric double layer condenser

A piezoelectric transformer is driven with the PWM driving method by means of a driving voltage with a waveform obtained by time-dividing a first frequency with a binary pulse of a second frequency lower than the first frequency. A harmonic component of said second frequency component contained in said first frequency component can be suppressed by decreasing a slope of an envelope of said driving voltage waveform. A parasitic vibration of the piezoelectric transformer in the piezoelectric transformer-inverter controlled with the PWM system can be suppressed by controlling such inverter as described above and construction of the piezoelectric transformer support mechanism can be simplified.

Control circuit and method for driving and controlling parasitic

In a driver of a CCFL for lightening the CCFL by using a piezoelectric transformer, a current supplied from a power source or a power consumption of the CCFL is detected and the piezoelectric transformer is on-off driven at a frequency different from an operating frequency of the piezoelectric trabsformer by a pulse width modulation signal having a duty cycle ratio corresponding to the detected value. The current supplied from the power source does not exceed a predetermined value, so that a capacity of the power source can be small and thus the cost of the power source can be reduced.

Driver of cold-cathode fluorescent lamp

An actuating circuit of a piezoelectric transformer which is small in thickness and size and has a wide input voltage range is developed. In the actuating circuit of the piezoelectric transformer, when a sine wave outputted from a AGC circuit is input to a delta-sigma modulator, the sine wave switches output driver and switches a second output driver through an invertor with a 1-bit quantized bit signal so as to generate a pulse signal having an amplitude of power supply voltage Vdd from the GND potential. Actuating waves output from the output drivers and are applied to 1 piezoelectric transformer extracting resonance frequency of a piezoelectric transformer through a filtering effect provided with an input capacitance of the piezoelectric transformer and coil converting the 1-bit quantized bit signal into a sine wave. Consequently, since the piezoelectric transformer can be operated with the sine wave, the piezoelectric transformer can be actuated efficiently.

Actuating circuit of piezoelectric transformer and actuating method

A piezoelectric transformer driving circuit includes a boosting circuit receiving an input DC voltage to generate an AC voltage for driving a piezoelectric transformer, a frequency control circuit for controlling the frequency of the AC voltage applied to the piezoelectric transformer to control a step-up ratio of the piezoelectric transformer, and a drive voltage control circuit for controlling the voltage of the AC voltage applied to the piezoelectric transformer at a predetermined level, regardless of variation of the input DC voltage.

Piezoelectric transformer driving circuit

A high power source unit employing a piezoelectric transformer detects whether the output of the piezoelectric transformer reaches a predetermined value or not using a comparator. Subsequently, using a frequency scanning circuit, an oscillation frequency of a driving frequency control circuit is scanned across a resonance frequency of the piezoelectric transformer. During this frequency scanning, the efficiency of the piezoelectric transformer is detected by a efficiency calculating circuit to detect the frequency where the efficiency becomes maximum, by a most efficient frequency detecting circuit. By maintaining this frequency, the piezoelectric transformer may operate at the frequency at optimal efficiency.

Power source unit employing piezoelectric transformer

N-channel enhancement type switching transistors complementarily turn on and off in response to pulse signals complementary to each other so as to cause two auto-transformers to alternately supply secondary potentials to primary electrodes of a piezoelectric transformer, and the piezoelectric transformer supplies an alternating current signal to a load; the primary winding portion of each auto-transformer is dually used in the accumulation of current energy and the resonating phenomenon for generating the secondary potential, and, for this reason, the auto-transformers make the driving circuit for the load compact.

Wide input voltage range power supply with auto-transformers and

A display information processing apparatus includes a central processing unit, a dual port memory including a first storage area and a second storage area, a display address generator, a timing signal generator and a control circuit and operates such that operation of the central processing unit is stopped only when data is transferred from the first storage area to the second storage area within the dual port memory. Data to be displayed is transferred only from the second storage area to a display device.

Display information processing apparatus

A display processing apparatus which can simply and easily control the size and display screen location of character patterns. The invention is comprised of a memory for storing character data of a predetermined size, an addressing circuit for reading out predetermined character data from the memory, and a transfer circuit for transferring the read character to a display circuit. The addressing circuit includes a counter, an arithmetic circuit for calculating A=MX+B, where X is the counter output value, M is a multiplication factor, B is a predetermined number and A is an address to be provided to the memory for reading out character data. An output shift register passes the memory output to the display circuitry only when the counter value is within predetermined limits, and a control circuit controls the values of the limits as well as M and B.

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Tokyo, Japan

Yasuhei Shimada