Murata Manufacturing Co., Ltd.

Yasuyuki Morishima

Takashi Noma

Hidehiko Sugimoto

Kyoji Toshinari

Naoto Sano

Shingo Kunii

Akiyoshi Moriyasu

Ken Takakura

Ichiro Yamawaki

Current flowing through a cold cathode tube is detected and converted to a voltage with a resistor, and is fed to a tube current control circuit. The tube current control circuit drives a drive circuit to control a voltage applied to a piezoelectric transformer. Current from a constant-current source is used to charge a fault protection capacitor. A transistor is allowed to conduct while current flows through the cold cathode tube so that a voltage is developed in a resistor, and thereby, an electric charge is prevented from being stored in the fault protection capacitor, thereby stopping the operation of a fault protection circuit.

High voltage power supply device for lighting discharge tube having protection circuit and fault protection circuit

A part having a large height contained in a module part is placed in a first cut-off portion formed in a part-mounting substrate to be mounted. Moreover, the module part itself is placed in a second cut-off portion formed in a mother board to be mounted.

Module part and electronic device

A switching power supply which is capable of generating several different output voltages and which can be easily miniaturized by using a transformer with a small number of terminals. For example, using a transformer with four terminals and three windings that are connected in series, a rectifying-smoothing circuit having a diode and a capacitor is connected to a connection point of the collector of a switching transistor and the windings. A further pair of rectifying-smoothing circuits having diodes and capacitors is commonly connected to one end of the windings, according to one example. As a result thereof, three voltages are generated.

Switching power supply having a plurality of output voltages and minimal number of terminals

A piezoelectric-transformer inverter includes a piezoelectric transformer for supplying a transformed voltage to a load connected to a secondary electrode thereof. A first coil and a first transistor are connected to one primary electrode of the piezoelectric transformer, and a second coil and a second transistor are connected to the other primary electrode of the piezoelectric transformer. The first and second transistors are alternately turned on and off such that the phase of the voltage applied between the primary electrodes is reversed cyclically. The operation frequency is controlled such that an AC current flowing through the load is maintained at a predetermined level. The piezoelectric transformer has a piezoelectric substrate. In a first half region of the piezoelectric substrate, a plurality of electrode films are layered in order to form the primary electrodes. The secondary electrode is formed on an end surface of the piezoelectric substrate opposite to the primary electrodes. The piezoelectric substrate is polarized in a first direction in the first half region where the primary electrodes exist and is polarized in a second direction different from the first direction in a second half region where the secondary electrode exists. The piezoelectric transformer operates in a half wavelength mode.

Piezoelectric-transformer inverter

A piezoelectric transformer inverter can suppress ripples generated by the oscillations of a transformer, and can reduce the possibility of occurrence of beats in the inverter. In this piezoelectric transformer inverter, a switching element is disposed at a stage before an inverter circuit driving a discharge tube, and the switching element is switched on and off by switching signals from a chopper-duty control unit. Then, an input voltage is converted into a rectangular-wave voltage having a chopper circuit frequency to be supplied to the inverter circuit, and a frequency of n times a driving frequency of the inverter circuit and a chopper frequency of the chopper circuit are set in such a manner that these two frequencies are not close to each other.

Piezoelectric transformer inverter

A piezoelectric transformer inverter can be driven in wide ranges of input voltages and output currents so that a wide range of dimming can be achieved. Furthermore, the piezoelectric transformer inverter can maintain high efficiency in the overall driven ranges thereof so as to yield stable luminance. The above piezoelectric transformer inverter includes a piezoelectric transformer drive unit having conductive elements, switching elements, and a phase drive circuit to convert an inputted AC voltage into an AC voltage having a substantially constant frequency which is lower than the inputted AC voltage and output to a piezoelectric transformer, a phase-difference detecting unit for detecting the phase difference between a drive controlling signal of one of the switching elements and an output current or output voltage of the piezoelectric transformer to output a control voltage corresponding to the phase difference, and a frequency control circuit for outputting a pulse voltage signal of a frequency based on the control voltage to the phase drive circuit of the piezoelectric transformer drive unit.

A piezoelectric inverter is disclosed. In the piezoelectric inverter, an input voltage controller, having a switching transistor and a current circulatingelement, converts an input voltage into a rectangular pulse alternating-current voltage. A piezoelectric transformer driver, having an inductive element, outputs an alternating-current voltage having a substantially constant frequency lower than the frequency of the alternating-current voltage output from the input voltage controller. A load current detect or detects a load current flowing through a discharge tube connected to a piezoelectric transformer. A duty factor controller controls the duty factor of the rectangular pulse of the input voltage controller in response to the output of the load current detector so that the load current coincides with a substantially constant target current value. The piezoelectric inverter thus controls the mean voltage of the alternating-current voltage applied to the piezoelectric transformer.

Piezoelectric inverter

A piezoelectric transformer inverter comprises: a piezoelectric transformer for performing voltage conversion of alternating voltage applied between primary electrodes to supply to a load connected to a secondary electrode; a driving-frequency control unit for controlling load current during driving of the load by changing the driving frequency of the piezoelectric transformer; a chopper unit for chopping input voltage applied into the driving-frequency control unit at a frequency of two or more times as high as the driving frequency and for controlling an average input voltage applied into the driving frequency control unit by changing a duty ratio of the chopping operation; and a dimming unit for intermittently stopping the driving frequency control unit by intermittently stopping the operation of the chopper unit at a frequency smaller than the driving frequency of the piezoelectric transformer, wherein even during a period in which the dimming unit is intermittently stopping the chopper unit, signals having a duty ratio for allowing the chopper unit to perform the chopping operation to be sustained inside the chopper unit.

A piezoelectric transformer inverter includes: a piezoelectric transformer, one of whose primary electrodes is grounded, which performs voltage conversion of alternating voltage or direct current voltage applied between the primary electrodes and supplies the converted voltage to a load connected to a secondary electrode; a drive unit for supplying alternating voltage or direct current voltage between the primary electrodes of the piezoelectric transformer; a low-pass type resonance circuit unit inserted between the output of the drive unit and the primary electrodes of the piezoelectric transformer; a duty control unit for controlling ON-Duty of the drive unit so that a value of current flowing into the load coincides with a targeted current value; a phase-difference detection unit for detecting a phase difference between the input voltage and the output voltage of the piezoelectric transformer; and a frequency control unit for controlling a driving frequency of the drive unit.

A piezoelectric transformer inverter includes an inverter unit and a step-down chopper unit. The inverter unit includes a ceramic piezoelectric transformer whose secondary terminal is to be connected to a fluorescent tube, a drive unit which is connected to a primary terminal of the ceramic piezoelectric transformer, and an inverter control circuit for controlling luminance of the fluorescent tube to a desired value. The step-down chopper unit includes a switching device which is disposed on the side where the voltage of the inverter unit is input, a free wheeling device connected between the switching device and a reference potential, and a PWM feedback control circuit for providing a feedback control to maintain an average voltage of the rectangular-wave voltage of the switching device constant. In the piezoelectric transformer inverter, even when the feedback control by the PWM feedback control circuit is impossible, the on-duty of the chopper unit is restricted so that it is not greater than a given amount.

A piezoelectric transformer-inverter in which a fluorescent light tube is light-modulated when a frequency controller changes the frequency of a drive voltage applied from a piezoelectric transformer drive circuit to a piezoelectric transformer in correspondence with a light-modulating voltage to thereby change the boost ratio of the piezoelectric transformer. A PWM inverter output variable circuit adjusts an average voltage supplied from a PWM inverter to a piezoelectric transformer drive circuit. When tube current is low, the average voltage is low, and when the tube current is high, the average voltage rises. Consequently, fluctuation in the drive frequency of the piezoelectric transformer is restricted even when the light-modulating voltage changes, making it possible to drive the piezoelectric transformer with a good boost ratio. Since the piezoelectric transformer is always driven close to its resonant frequency, there is almost no surge charge flowing to the transistor for driving the piezoelectric transformer.

Piezoelectric transformer-inverter

A boosting drive circuit includes first and second series combinations of a coil and a transistor. The two series combination of a coil and a transistor are connected in parallel. The middle points between the coils and the transistors are connected to respective primary electrodes of a piezoelectric transformer. The transistors are alternately operated with a two-phase drive circuit. Thus, a boosting drive circuit providing for the class 'semi-E' operation is formed. A driving voltage control circuit controls an average voltage applied to the input terminal of the boosting drive circuit to ensure that current on the secondary electrode side of the piezoelectric transformer is controlled at a predetermined value is provided between the input power supply and the boosting drive circuit. A driving frequency control circuit changes the driving frequency of the transistors in the boosting drive circuit in such a manner that the phase difference between an alternating voltage applied to the primary electrodes of the piezoelectric transformer and an alternating current flowing in the load is controlled at a predetermined value.

A high degree of freedom of design and high density mounting are achieved with a laminated electronic part having a structure such that the occurrence of floating capacitance can be restrained. The laminated electronic part is formed of a first layer and a second layer which are joined to each other with a third layer sandwiched therebetween. The first and second layers may be formed of dielectrics having substantially different respective dielectric constants, and the third layer is formed of a dielectric having a dielectric constant lower than that of the first and second layers, or an insulator. Connecting conductors are provided inside the third layer. A through-conductor inside the first layer can be connected to a through-conductor inside the second, for example, layer via the connecting conductor inside the third layer.

Laminated electronic part

A power apparatus includes a compensator which is capable of enabling phase to lead as the frequency increases, even if gain increases, as shown in a Bode diagram, so as to operate stably. The power apparatus includes a power converter for controlling a voltage from a power source and supplying it to a load, a smoothing circuit which is connected between the power converter and the load, and a controller for controlling the power converter, wherein the controller is formed of an amplifier, first to seventh (or eighth) resistors, and first and second capacitors, arranged to provide specific transfer functions.

Power apparatus

A power supply includes a power converter 2 for generating an output voltage to be supplied to a load 3 from a power source 4, a filter 5 connected between power converter 2 and load 3, and a controller 10 for controlling the power converter 2, in which controller 10 applies a voltage instruction value v.sub.r applied as an input to circuitry which implements an operation element A defined as: ##EQU1## subtracts the output voltage from instruction voltage v.sub.r, and applies the difference to power converter 2.

Growing community of inventors

Kyotanabe, Japan

Yasuyuki Morishima