Abstract: A fluorescent lamp driving method drives a fluorescent lamp by using an alternating current driving signal generated by an inverter circuit using direct current power as an input. The driving signal is supplied from the inverter circuit to a load including the fluorescent lamp. The method includes the steps of, by using a sum current detecting circuit, detecting a current change in the signal, by using a control circuit, controlling the driving signal generated by the inverter circuit on the basis of the current change detected by the sum current detecting circuit, and controlling a current of the supplied signal to be constant, by using a temperature detecting circuit, detecting the temperature of the fluorescent lamp, and, by using a correction circuit, on the basis of the temperature of the fluorescent lamp detected by the temperature detecting circuit, correcting the controlling the current of the supplied signal to be constant.

Abstract: A fluorescent tube driving method for driving a fluorescent tube on the basis of an alternating current driving signal generated by an inverter circuit that uses a direct current power supply produced by directly rectifying the voltage of a commercial power supply includes the steps of: detecting an input voltage supplied to the inverter circuit by a voltage detector; detecting an output current of the inverter circuit that drives the fluorescent tube on the basis of the alternating current driving signal by using an electric current detector; and controlling an alternating current driving signal generated by the inverter circuit on the basis of the output current of the inverter circuit, which is detected by the electric current detector, and an input voltage supplied to the inverter circuit, the input voltage being detected by the voltage detector, and suppressing a variation in the output current detected by the electric current detector.

Abstract: A power supply unit designed to control a power output and protect an overload easily, economically with little loss. A DC output which is generated by smoothing a rectified current of a rectifier circuit connected to an AC power source is subjected to switching by a switching circuit, creating an AC output which is supplied to a current resonance circuit. A peak detection circuit detects the peak voltage of a resonance voltage of this current resonance circuit. On the basis of a comparison output of the voltage comparator comparing the peak voltage to the reference voltage of a reference voltage source, the switching frequency of the switching circuit is controlled by a switching control circuit so that it is controlled to cause the peak voltage to match the reference voltage. In this manner, the output power is maintained on the constant level.

Abstract: The present invention provides a switching power supply which includes a main rectifying and smoothing circuit (40) and a secondary rectifying and smoothing circuit (50) for rectifying and smoothing an output obtained at a secondary coil (22) of a converter transformer (20) whose primary coil (21) is supplied with a switching output from a switching element (30) which switches a direct input.

Abstract: An object of the present invention is to create the optimum resonating condition to constantly decrease switching losses. A converter transformer capable of varying the leakage inductance is employed as a converter transformer, and a control circuit is arranged to detect an input voltage applied to a switching circuit and a voltage drop brought about in a current detecting resistor which allows a load current to flow. Thus, the leakage inductance of the converter transformer can be controlled.

Abstract: The present invention provides a switching power supply which includes a main rectifying and smoothing circuit (40) and a secondary rectifying and smoothing circuit (50) for rectifying and smoothing an output obtained at a secondary coil (22) of a converter transformer (20) whose primary coil (21) is supplied with a switching output from a switching element (30) which switches a direct input.

Abstract: A power supply unit designed to control a power output and protect an overload easily, economically with little loss. A DC output which is generated by smoothing a rectified current of a rectifier circuit connected to an AC power source is subjected to switching by a switching circuit, creating an AC output which is supplied to a current resonance circuit. A peak detection circuit detects the peak voltage of a resonance voltage of this current resonance circuit. On the basis of a comparison output of the voltage comparator comparing the peak voltage to the reference voltage of a reference voltage source, the switching frequency of the switching circuit is controlled by a switching control circuit so that it is controlled to cause the peak voltage to match the reference voltage. In this manner, the output power is maintained on the constant level.

Abstract: An object of the present invention is to create the optimum resonating condition to constantly decrease switching losses. A converter transformer capable of varying the leakage inductance is employed as a converter transformer, and a control circuit is arranged to detect an input voltage applied to a switching circuit and a voltage drop brought about in a current detecting resistor which allows a load current to flow. Thus, the leakage inductance of the converter transformer can be controlled.

Abstract: A booster type converter (19) wherein a boosting inductor is constituted from a transformer (20) provided with an auxiliary winding (20b), a capacitor (26) is connected to the auxiliary winding, whereby the capacitor is charged by means of resonance of a leakage inductance of the transformer (20) and the capacitor (26), and at the same time, it makes possible to conduct zero voltage switching of the booster type converter (19) on the basis of the electric charge charged in the capacitor, whereby it is intended to attain high efficiency in the booster type converter.

Abstract: In a switching power supply, primary-side MOS transistors are alternately turned on, so that a resonant current flows into the primary winding of a transformer and an alternate power is transferred to the secondary side. The alternate voltage generated at the secondary winding is applied by the voltage generated at the wound-up secondary winding to the gates of secondary-side MOS transistors such that they are turned on respectively in periods when the polarity of the voltage is positive. Rectified currents flow into a capacitor through a choke coil to perform synchronous rectification. If the voltage of a smoothing capacitor becomes higher than the alternate output voltage when the transformer is inverted, reverse currents flow into the secondary-side MOS transistors. With the counterelectromotive force of the choke coil, the reverse currents flowing when the transformer is inverted are suppressed, and the efficiency of the switching power supply is prevented from decreasing.

Abstract: In a switching power source, by alternately turning on first and second MOS transistors, a switching current flows to a primary winding of a transformer, and an alternate current is transferred to a secondary side. The alternate voltage caused in a secondary winding is full-wave rectified by first and second diodes. Resonance elements (capacitor and coil) are connected to a tertiary winding coupled to an isolation transfer, thereby enabling the primary side to be set into a resonated state and to be set to a current resonance type switching power source. Since a leakage inductance of the transformer is not set to a resonance element, an interval between the windings of the isolation transformer can be closely coupled. Since a resonance current is not directly turned on/off, a peak value of the primary current is decreased and switching loss and loss due to an on-resistance can be decreased. The efficiency of a current resonance type switching power source is thus improved.