Sanken Electric Co., Ltd.

Sanken Electric Korea Co., Ltd.

Shinji Aso

Mamoru Tsuruya

Mitsutomo Yoshinaga

Makoto Sato

Ryuichi Furukoshi

Eunsuk Lee

Hanju Kang

Masaru Nakamura

Masaaki Shimada

Kengo Kimura

Osamu Ohtake

Toshihiro Nakano

Kyusam Choi

Yukihiro Kaminaga

Jianao Yao

Hiroshi Hosoya

Jungyul Kim

Jaekuk Yu

An active clamp flyback converter includes a main switch, a primary winding that is electrically connected in series with the main switch, a clamp switch that is electrically connected to a connection point between the main switch and the primary winding, a clamp capacitor that is connected in series with the clamp switch, and a controller that outputs a first ON signal to control the main switch and a second ON signal to control the clamp switch during a period when the main switch is off. The controller outputs the second ON signal during a half cycle or more of a resonance period, in which the resonance current flowing in a resonance circuit comprising the clamp capacitor and a leakage inductance generated when the clam switch is turned on is limited by an excitation current of an excitation inductance of the primary winding.

Active clamp flyback converter having clamp switch and clamp capacitor and control IC for controlling the clamp switch to limit resonance current

An excitation current detection circuit is disclosed. A transformer comprises a primary winding, an auxiliary winding, and a secondary winding. A first voltage detector detects a positive voltage of an auxiliary winding voltage. A second voltage detector detects a negative voltage of the auxiliary winding voltage. A first voltage controlled oscillator generates a first clock with a frequency proportional to the positive voltage during a period when the auxiliary winding voltage is the positive voltage. A second voltage controlled oscillator generates a second clock with a frequency proportional to the negative voltage during a period when the auxiliary winding voltage is the negative voltage. A counter outputs a counter value, which is added in one of cycles of the first clock and the second clock and subtracted in the other cycle of the first clock and the second clock as a detected value of an excitation current.

Excitation current detection circuit and semiconductor device

A detector compares a drain voltage with a first threshold voltage and outputs a first detection signal. An ON counter detects a period of time during which a current flows in a switching, counts the period of time based on a predetermined clock cycle. An OFF counter detects a period of time during which a current flow through the body diode in a state where no current flows in the switching circuit, counts the period of time. An off-time setting circuit sets the time to turn off the switching circuit. A first comparison circuit compares the cycle count value with turn off time. A second comparison circuit compares a cycle count value output by the ON counter with a comparison result output by the first comparison circuit and outputs a signal to stop transmitting a PWM signal.

Resonant converter with a synchronous rectifier controller having ontime and offtime counting

A DC-DC converter according to one or more embodiments is disclosed that may include: a drive voltage switching circuit of a drive circuit that drives a synchronous rectification MOS transistor. The drive voltage switching circuit may switch a connection so that the drive circuit supplies power from the output voltage to the drive circuit in response to the drive voltage for supplying power to the drive circuit being set to be lower than the output voltage. The drive voltage switching circuit may switch a connection so that the drive circuit supplies power from the drive voltage in response to the drive voltage for supplying power to the drive circuit being set to be higher than the output voltage.

Power supply for driving synchronous rectification elements of SEPIC converter

A detector compares a drain voltage with a first threshold voltage and outputs a first detection signal. An ON-counter detects a period of time during which current flows in a switching circuit based on the first detection signal, counts the period of time based on a predetermined clock cycle, and outputs an ON-count value. A first comparator receives the ON-count value and an ON-threshold value and outputs a first comparison signal when the ON-count value and the ON-threshold value match. A second comparator receives the ON-count value and a decreased ON threshold value, compares the ON-count value and the decreased ON-threshold value, and outputs a second comparison signal. An ON-mask time adjuster receives the second comparison signal and outputs an ON-threshold value for adjusting a mask time and a decreased ON-threshold value that is less than the ON threshold value.

Switching power supply apparatus

An LED driving apparatus comprises a power supply unit that includes a transformer having a primary coil and a plurality of secondary coils and outputs alternating power from the plurality of secondary coils; a current balancing unit and a first rectification smoothing unit connected to a first secondary coil of the plurality of secondary coils; an LED load group that includes a plurality of LEDs connected in series and to which power smoothed from the first rectification smoothing unit is supplied; a power control unit that controls power to be supplied to the first and second LED loads, based on currents flowing in the first and second LED loads; and a direct current load that is connected to both ends of a second secondary coil of the plurality of secondary coils. The power supplying unit controls the alternating power, based on the power supplied to the direct current load.

LED driving apparatus

A DC converter includes: a transformer (T) including a primary winding (P) and a secondary winding (S); a series resonant circuit in which a current resonant reactor (Lr), the primary winding (P) of the transformer, and a current resonant capacitor (Cri) are connected in series; conversion circuits (Q, Q) for converting a DC voltage of a DC power supply (Vin) into a rectangular-wave voltage, so as to output the rectangular-wave voltage to the series resonant circuit; and a rectifier smoothing circuit (D, D, Co) for rectifying and smoothing a voltage generated at the secondary winding (S) of the transformer, so as to output a DC output voltage to a load, wherein a capacitive element (Cr) including a capacitive component corresponding to a floating capacitance (Cp) equivalently present between the primary winding of the transformer was connected to the current resonant reactor (Lr) in parallel.

DC converter

A DC conversion apparatus comprises a first transformer, a second transformer, a parallel circuit having series circuits connected in parallel, one of the series circuits including a reactor and a primary winding of the first transformer, the other series circuit including a reactor and a primary winding of the second transformer, a conversion circuit converting a DC voltage of a DC power source into an AC voltage and outputting it to the parallel circuit, a first rectifying-smoothing circuit rectifying and smoothing a first voltage generated by a first secondary windings of the first transformer into a first DC output, and a second rectifying-smoothing circuit rectifying and smoothing a second voltage generated by a first secondary windings of the second transformer into a second DC output that is different from the first voltage. The second secondary windings of the first transformer are connected in parallel with the first secondary windings of the second transformer.

DC conversion apparatus

A current balancing apparatus includes a first transformer having a first primary winding and a first secondary winding electromagnetically coupled with the first primary winding, the first primary winding having a first end connected to a first load that passes a first current; a second transformer having a second primary winding and a second secondary winding electromagnetically coupled with the second primary winding, the second primary winding having a first end connected to a second load that passes a second current having an AC component substantially having a 180-degree phase difference with respect to the first current; and a series circuit including the first secondary winding, the second secondary winding, and a current smoother, to balance the first current and second current with each other.

Current balancing apparatus, current balancing method, and power supply apparatus

In a DC-DC converter of the present invention, a converting circuit converts a DC-DC voltage outputted from a DC power supply into an AC voltage, and to output to a series circuit in which a primary winding of a first transformer, a first reactor, and a current resonance capacitor are connected to one another in series. A primary winding of a second transformer, a primary winding of a third transformer, and a second reactor constitute a closed loop. A secondary winding of the second transformer and a secondary winding of the third transformer are connected in series to both ends of a secondary winding of the first transformer. A first rectifying/smoothing circuit rectifies and smoothes a voltage of the secondary winding of the second transformer. A second rectifying/smoothing circuit rectifies and smoothes a voltage of the secondary winding of the third transformer.

DC-DC converter

A direct-current converter includes a high-frequency converting circuit converting voltage of a direct-current power source to alternating-current voltage, a transformer having primary and secondary windings P, S and a rectification smoothing circuit rectifying and smoothing voltage induced in the secondary winding. This converting circuit includes other transformer having first and second windings n, n, switching element Qhaving a source connected to a negative pole of the power source and a drain connected to a positive pole thereof through winding n, and switching element Qhaving a source connected to the negative pole of the power source and a drain connected to the positive pole thereof through winding n, element Qbeing turned on/off alternately to element Qbeing turned on/off. Winding P is connected to a point between winding nand the drain of element Qand another point between winding nand the drain of element Q

Direct-current converter

A DC converter has a transformer with loosely coupled primary and secondary windings, a main switch connected in series with the primary winding of the transformer, and a series circuit connected to ends of one of the primary winding and main switch. The series circuit includes a clamp capacitor and an auxiliary switch. The main and auxiliary switches are alternately turned on/off so that a voltage of the secondary winding of the transformer is synchronously rectified with synchronous rectifiers and is smoothed with smoothing elements, to provide a DC output. The DC converter also includes a tertiary winding provided for the transformer, tightly coupled with the primary winding, and configured to generate a voltage that drives the synchronous rectifiers.

DC converter including a tertiary winding for driving synchronous rectifiers

A DC converter includes a time difference detector to detect a time difference between a point around which a main switch provides a minimum voltage after an auxiliary switch turns off and a point at which the main switch turns on, an integrator to integrate the output of the time difference detector, and a first delay circuit to control a turn-on point of the main switch according to the output of the integrator and the output of the time difference detector. The first delay circuit operates to minimize the output of the time difference detector according to the output of the integrator and controls a turn-on point of the main switch in a pulse-by-pulse manner according to a pulse-by-pulse control signal based on the output of the time difference detector.

A DC converter has a transformer with loosely coupled primary and secondary windings, a main switch connected in series with the primary winding of the transformer, and a series circuit connected to ends of one of the primary winding and main switch. The series circuit includes a clamp capacitor and an auxiliary switch. The main and auxiliary switches are alternately turned on/off so that a voltage of the secondary winding of the transformer is synchronously rectified with synchronous rectifiers and is smoothed with smoothing elements, to provide a DC output. The DC converter also includes a tertiary winding tightly coupled with the primary winding of the transformer, a voltage source to supply a voltage lower than a voltage generated by the tertiary winding of the transformer, and clamp diodes to clamp the voltage generated by the tertiary winding with the use of the voltage source. The clamp diodes provide voltage-clamped signals to drive the synchronous rectifiers.

Provided is a direct-current converter which can reduce power consumption at light load by reducing switching losses of a main switch. The direct-current converter is provided with: a first serial circuit which is connected to both ends of a direct current power supply Vdcand in which a primary winding P of a transformer T and a main switch Qare serially connected to each other; a second serial circuit which is connected both ends of the primary winding P of the transformer T and in which an auxiliary switch Qand a snubber capacitor Care serially connected to each other; rectifying/smoothing circuits D, D, Land Cwhich rectify and smooth a voltage generated in a secondary winding S of the transformer T by energy supplied from the primary winding P of the transformer T when the main switch Qis turned on; and a control circuitwhich turns on/off the main switch Qand the auxiliary switch Qalternately using a signal with predetermined switching frequency. The control circuitreduces the switching frequency during light load.

Growing community of inventors

Niiza, Japan

Shinji Aso