Abstract: An apparatus for driving light emitting elements includes a constant-current driver arranged for each of arrays of light emitting elements including a constant-current drive element and a current regulator; a first selector configured to select one having a highest signal level from among control signals of the constant-current drivers and output the selected control signal; a second selector configured to select a lowest one from among output voltages of the constant-current drivers and output a signal representative of the selected output voltage; a differential amplifier configured to output an amplified differential signal that is obtained by amplifying a difference between the signals output from the first and second selectors; and a power source circuit configured to control, according to the amplified differential signal, a voltage supplied to a second end of each of the arrays of light emitting elements.

Abstract: A current resonant DC-DC converter of multi-output type is provided which comprises an output-regulatory MOS-FET 40 connected between a secondary winding 5c of a transformer 5 and a smoothing capacitor 16 in a second rectifying smoother 17, and an output control circuit 41 for controlling the on-off operation of output-regulatory MOS-FET 40 based on voltage VO2 from smoothing capacitor 16 in second rectifying smoother 17. By turning the on-off operation of output-regulatory MOS-FET 40 in synchronization with switching frequency of first or second MOS-FETs 1, 2, an ideal cross regulation among respective DC outputs can be obtained, providing the inexpensive converter with simple circuit alteration capable of producing highly stable DC outputs with high power conversion efficiency, high accuracy and less power conversion loss.

Abstract: A current resonant DC-DC converter of multi-output type is provided which comprises an output-regulatory MOS-FET 40 connected between a secondary winding 5c of a transformer 5 and a smoothing capacitor 16 in a second rectifying smoother 17, and an output control circuit 41 for controlling the on-off operation of output-regulatory MOS-FET 40 based on voltage VO2 from smoothing capacitor 16 in second rectifying smoother 17. By turning the on-off operation of output-regulatory MOS-FET 40 in synchronization with switching frequency of first or second MOS-FETs 1, 2, an ideal cross regulation among respective DC outputs can be obtained, providing the inexpensive converter with simple circuit alteration capable of producing highly stable DC outputs with high power conversion efficiency, high accuracy and less power conversion loss.

Abstract: An apparatus for driving light emitting elements includes a constant-current driver arranged for each of arrays of light emitting elements including a constant-current drive element and a current regulator; a first selector configured to select one having a highest signal level from among control signals of the constant-current drivers and output the selected control signal; a second selector configured to select a lowest one from among output voltages of the constant-current drivers and output a signal representative of the selected output voltage; a differential amplifier configured to output an amplified differential signal that is obtained by amplifying a difference between the signals output from the first and second selectors; and a power source circuit configured to control, according to the amplified differential signal, a voltage supplied to a second end of each of the arrays of light emitting elements.

Abstract: A switching power supply that can accurately detect a period during energy is supplied from a primary side to a secondary side of a transformer with a simple circuit configuration is provided. A first switching element and a second switching element are serially connected to opposite output ends of a full-wave rectifier rectifying an AC voltage from an AC power source. A current resonant capacitor, a resonant reactor, and a primary winding of a resonant transformer are serially connected to opposite ends of the first switching element.

Abstract: A switching power supply that can accurately detect a period during energy is supplied from a primary side to a secondary side of a transformer with a simple circuit configuration is provided. A first switching element and a second switching element are serially connected to opposite output ends of a full-wave rectifier rectifying an AC voltage from an AC power source. A current resonant capacitor, a resonant reactor, and a primary winding of a resonant transformer are serially connected to opposite ends of the first switching element.

Abstract: A switching power device includes a control circuit 20 that inputs output voltage from a voltage detecting terminal a and turns ON/OFF a switching element Q1 on a basis of the output voltage, detection holding means 23, 24 that detect an abnormality when it occurs in a power-factor improvement circuit, stop an operation of the switching element and output a holding signal while holding a stopped condition of the switching element, abnormal operating signal outputting means 30 that outputs an abnormal operating signal in the form of voltage more than a predetermined voltage to the voltage detecting terminal a on the basis of the holding signal from the detection holding means 23, 24, and abnormal signal detecting means 40 that outputs an abnormal signal to a load circuit 10 upon detecting that a potential of the voltage detecting terminal a has reached voltage more than the predetermined voltage on the basis of the abnormal operating signal from the abnormal operating signal outputting means 30.

Abstract: A DC power source device comprises a MOS-FET 5 which performs the intermittent switching operation for converting DC input from a DC power supply 1 into high frequency electric power; a control circuit 9 for turning MOS-FET 5 on and off; and a rectifying smoother 6 for converting the high frequency electric power through MOS-FET 5 into a DC power output supplied to a load 50. Control circuit 9 comprises an output current controller 11 for controlling the on-off term of MOS-FET 5 to make DC output current IO through load 50 settle toward a rated value IOMAX; a shunt regulator 24 for receiving a drive current ISH supplied from rectifying smoother 6 and producing a reference voltage VR1 to regulate the rated value IOMAX of output current controller 11; and a constant current source 32 for keeping drive current ISH on a substantially constant level under the rated output current value condition and reduced output voltage condition.

Abstract: A control circuit 6 of a resonance type switching power source comprises a drive circuit 21 for supplying drive pulses to each gate terminal of first and second MOS-FETs 2,3; a PWM circuit 9 for causing drive circuit 21 to produce drive pulses; an input voltage detector 7 for detecting input voltage from DC power source 1 and comparing the input voltage and input reference voltage Vref1; and a frequency adjuster 8 for adjusting oscillation frequency of PWM circuit 9 in response to output level from the input voltage detector 7. With adjustment in oscillation frequency of PWM circuit 9 in response to input voltage Vin from DC power source 1, control circuit 6 can modify on-off timing of first and second MOS-FETs 2, 3 to keep good resonating action and prevent off-resonance although DC power source 1 produces fluctuating input voltages.

Abstract: A power factor corrector is connected to an AC power source, to provide a first DC voltage. A DC-DC converter supplies the first DC voltage from the power factor corrector to a primary winding of a transformer. A first rectifying/smoothing circuit rectifies and smoothes a voltage generated by a secondary winding of the transformer and supplies the rectified-and-smoothed voltage to a load. A second rectifying/smoothing circuit rectifies and smoothes a voltage generated by a control winding of the transformer. A light-load detector detects if an output ripple of the second rectifying/smoothing circuit is equal to or greater than a predetermined value, determines upon detection that the switching operation has decreased the frequency thereof or has shifted to an intermittent oscillation, and stops the power factor corrector.

Abstract: A resonant power source apparatus has a series circuit of switching elements QL and QH connected to ends of a DC power source, a series circuit of a current-resonant capacitor, a resonant reactor, and a primary winding of a transformer connected to ends of the switching element QL or QH, a rectifying/smoothing circuit to rectify and smooth a voltage of a secondary winding, a pulse ratio controller to alternately turn on/off the switching elements QL and QH according to an output voltage from the rectifying/smoothing circuit, and a resonant period detector to detect a period during which energy is transmitted from the primary side to the secondary side of the transformer. The pulse ratio controller determines an ON period of the switching element according to a signal from the resonant period detector and an ON period of the switching element QH according to a signal from the rectifying/smoothing circuit.

Abstract: A resonant power source apparatus has a series circuit of switching elements QL and QH connected to ends of a DC power source, a series circuit of a current-resonant capacitor, a resonant reactor, and a primary winding of a transformer connected to ends of the switching element QL or QH, a rectifying/smoothing circuit to rectify and smooth a voltage of a secondary winding, a pulse ratio controller to alternately turn on/off the switching elements QL and QH according to an output voltage from the rectifying/smoothing circuit, and a resonant period detector to detect a period during which energy is transmitted from the primary side to the secondary side of the transformer. The pulse ratio controller determines an ON period of the switching element according to a signal from the resonant period detector and an ON period of the switching element QH according to a signal from the rectifying/smoothing circuit.

Abstract: A DC power source device comprises a MOS-FET 5 which performs the intermittent switching operation for converting DC input from a DC power supply 1 into high frequency electric power; a control circuit 9 for turning MOS-FET 5 on and off; and a rectifying smoother 6 for converting the high frequency electric power through MOS-FET 5 into a DC power output supplied to a load 50. Control circuit 9 comprises an output current controller 11 for controlling the on-off term of MOS-FET 5 to make DC output current IO through load 50 settle toward a rated value IOMAX; a shunt regulator 24 for receiving a drive current ISH supplied from rectifying smoother 6 and producing a reference voltage VR1 to regulate the rated value IOMAX of output current controller 11; and a constant current source 32 for keeping drive current ISH on a substantially constant level under the rated output current value condition and reduced output voltage condition.

Abstract: Mounted on an integrated circuit (41) of a power factor improving circuit are an error amplifier (40A) which outputs a difference voltage between a charged voltage in a capacitor (35) and a predetermined voltage, a timing setting circuit (40B) which sets timings at which a switching element (36) is switched on/off, a comparator (41e) and a switch (41f). When an instantaneous power failure occurs and the charged voltage in the capacitor (35) falls, the comparator (41e) detects the fall and causes the switch (41f) to be switched on. In response to this, a capacitor (42) is discharged and the difference voltage to be input to the timing setting circuit (40B) is reset to 0. When the power is recovered, the period in which the switching element (36) is switched on is shortened thereby suppressing over-rising of the charged voltage in the capacitor (35).

Abstract: A power factor corrector is connected to an AC power source, to provide a first DC voltage. A DC-DC converter supplies the first DC voltage from the power factor corrector to a primary winding of a transformer. A first rectifying/smoothing circuit rectifies and smoothes a voltage generated by a secondary winding of the transformer and supplies the rectified-and-smoothed voltage to a load. A second rectifying/smoothing circuit rectifies and smoothes a voltage generated by a control winding of the transformer. A light-load detector detects if an output ripple of the second rectifying/smoothing circuit is equal to or greater than a predetermined value, determines upon detection that the switching operation has decreased the frequency thereof or has shifted to an intermittent oscillation, and stops the power factor corrector.

Abstract: A control circuit 6 of a resonance type switching power source comprises a drive circuit 21 for supplying drive pulses to each gate terminal of first and second MOS-FETs 2,3; a PWM circuit 9 for causing drive circuit 21 to produce drive pulses; an input voltage detector 7 for detecting input voltage from DC power source 1 and comparing the input voltage and input reference voltage Vref1; and a frequency adjuster 8 for adjusting oscillation frequency of PWM circuit 9 in response to output level from the input voltage detector 7. With adjustment in oscillation frequency of PWM circuit 9 in response to input voltage Vin from DC power source 1, control circuit 6 can modify on-off timing of first and second MOS-FETs 2, 3 to keep good resonating action and prevent off-resonance although DC power source 1 produces fluctuating input voltages.