Fuji Electric Co., Ltd.

Fuji Electric Systems Co. Ltd.

Mean Well Enterprises Co., Ltd.

Koji Sonobe

Jian Chen

Masaru Saito

Yu-Wei Chung

A controller of a current resonance switching power supply apparatus configured to supply a constant output voltage to a load. The current resonance switching power supply apparatus includes a resonance circuit, and generates a feedback signal indicative of an error between the output voltage and a target voltage. The controller includes a load current detection circuit that receives a part of a resonance current of the resonance circuit, performs averaging and outputs a load current signal, and a standby detection circuit that receives the feedback signal and the load current signal, and determines that the load is in a standby mode upon detecting that the load current signal is lower than a first threshold and the feedback signal is lower than a second threshold, and is in a normal mode upon detecting that the feedback signal continues to be higher than the second threshold for more than a predetermined time.

Controller of switching power supply apparatus

A switching power supply apparatus includes a switching device and a switching power supply control circuit for converting an AC source voltage to a DC voltage. A comparison circuit in the switching power supply control circuit produces an H-level output signal when its non-inverted input voltage exceeds a voltage value during each off-state period of the switching device. A delay circuit outputs a pulse signal after a predetermined delay time from detecting the H-level signal. This pulse signal indicates detection of a bottom point of drain voltage of the switching device. Since the output of the delay circuit is directly connected to the set input terminal S of a flip-flop, the switching device is surely turned on, without bottom skip, upon detection of the bottom point of its drain voltage.

Switching power supply control circuit with bottom point detection

In aspects of the invention, a flyback converter configuration LED drive circuit, by adopting a configuration such that anode voltages of LEDs smoothed by a smoothing capacitor on the secondary side of a transformer and a terminal of a drive IC circuit are used as a node common. Current can be supplied to the primary side of the smoothing capacitor by a start-up circuit when starting, the need for an auxiliary winding, smoothing capacitor, and rectifier diode which have heretofore been necessary to supply a power source to the drive IC circuit is eliminated. Consequently, the number of parts can be reduced, meaning that the configuration of the LED drive circuit becomes simple, thus enabling a reduction in size and cost of the LED drive circuit.

LED drive circuit

A switching power supply device includes a first converter of boost type to which a full-wave rectified AC power supply is input, and a second converter of current resonant type to which an output of the first converter is supplied as an input voltage. The second converter has a normal mode for performing power supply control by continuously outputting an output of an oscillator to a switching element of the second converter and a standby mode for performing power supply control by intermittently outputting the output of the oscillator thereto under light load by comparing a feedback voltage from a secondary side of an isolation transformer with a threshold voltage. The second converter corrects the threshold voltage according to an output voltage of the first converter.

Switching power supply device

A quasi-resonance switching power supply quickly determines the number of bottom skips corresponding to the load condition even in abrupt load change. The quasi-resonance switching power supply is provided with a bottom skipping control function and a capacitor to hold a voltage corresponding to the load condition of the switching element over one switching period of the switching element. The quasi-resonance switching power supply comprises a bottom skipping number determining circuit that compares the voltage held on the capacitor with comparison reference voltages selected from a plurality of reference voltages for determining the number of bottom skips, and revises the comparison reference voltage according to the comparison result. The processing of comparison and revision is executed multiple times in one switching period of the switching element. Thus, the bottom skipping number determining circuit determines the number of bottom skips corresponding to the voltage held on the capacitor.

Quasi-resonant switching power supply

A switching power supply has a start-up circuit that includes a field effect transistor (JFET), which has a gate region (a p-type well region) formed in a surface layer of a p-type substrate and a drift region (a first n-type well region). A plurality of source regions (second n-type well regions) are formed circumferentially around the drift region. A drain region (a third n-type well region) is formed centrally of the source region. The drain region and the source regions can be formed at the same time. A metal wiring of the source electrode wiring connected to source regions is divided into at least two groups to form at least two junction field effect transistors.

Junction field effect transistor, integrated circuit for switching power supply, and switching power supply

A switching power source device IS capable of guaranteeing a normal switching operation even when the input of a coil voltage used for adjusting a dead time is eliminated. The switching power source device includes a dead time adjustment circuit that generates an ON trigger signal that regulates an ON timing of one of the first and second switching elements after elapse of a predetermined dead time from an OFF timing of the other switching element and that adjusts the dead time according to a temporal change of a terminal voltage detected from an auxiliary coil of an inductor; and a disable control circuit that detects a temporal change of the coil voltage during activation and disables a function of the dead time adjustment circuit adjusting the dead time when the coil voltage does not temporally change.

Switching power source device

A switching power source device which has main switch elements which switch a current path of the series resonant circuit, and a transformer which induces a current to a secondary side, controls the main switch elements on a primary side. Synchronous rectification switch elements are turned ON and OFF in response to one of the main switch elements. A synchronous control circuit which turns the synchronous rectification switch element ON in synchronization with an ON timing of the main switch element, or a conduction timing of internal diodes in the synchronous rectification switch elements detected by an inter-terminal voltage signal of the synchronous rectification switch element, whichever timing is later, determines a maximum ON width of the synchronous rectification switch element in accordance with a delay time of the conduction timing of the internal diodes with respect to the ON timing of the main switch element.

Switching power source device and switching power source control circuit

The invention provides a switching power supply device which can detect a light load state on a pulse-by-pulse basis without worsening power efficiency. In a synchronous control circuit, for each timing of the turning-on of main switching elements, the delay time Tdif of the conduction timing of internal diodes Ds determined according to the magnitude of the load LD is detected by a comparator, a reference time pulse Tsrs having a prescribed time width is generated by a load judgment circuit, and the logical product of the two is generated by an AND circuit. By this means, the load is regarded as being a light load when the delay time Tdif is longer than the reference time pulse Tsrs, and the synchronous rectification MOSFETs Qs are not turned on.

Switching power supply device and switching power supply control circuit

A comparator detects whether a feedback signal of an output voltage detecting circuit for a switching power supply circuit reaches a control voltage. A comparator detects an operating state of the switching power supply circuit, which is instructed by a switching instruction signal, by comparing the instruction signal with a reference voltage. The comparators are connected to a decision circuit which outputs to a control circuit a signal instructing a normal state until the feedback signal reaches the control voltage, and thereafter a signal instructing a normal state or a stand-by state that is instructed by the switching instruction signal. Thus, the control circuit makes the switching power supply circuit operate in a normal state until the output voltage reaches the control voltage. After the output voltage reaches the control voltage, the switching power supply circuit operated in an operation state instructed by the switching instruction signal to enable stable startup.

Switching power supply control circuit

A semiconductor device for switching power supply control limits the startup current supplied from a high-voltage input terminal, and prevents heat generation and combustion in case of an anomaly. A high-voltage input terminal is connected to the main winding of a transformer, and is supplied with a startup voltage upon input of a power supply to the switching power supply device. A power supply terminal is connected to a capacitor, and outputs a startup current to charge the capacitor after input of the power supply input. A startup circuit is connected between the high-voltage input terminal and the power supply terminal, and charges the capacitor while increasing the startup current with magnitude proportional to the voltage value of the power supply terminal, and after startup, turns off the startup current and supplies the power supply voltage only from the auxiliary winding of the transformer.

Semiconductor device for switching power supply control, startup circuit, and startup method for switching power supply device

A switching power source device for supplying power to a load includes a series resonant circuit, a plurality of main switch elements or main switch element groups for switching a current path of the series resonant circuit, a transformer for inducing a secondary current from the series resonant circuit, a plurality of synchronous rectification switch elements for rectifying the secondary current, a maximum on width control circuit for ordering a start and a completion of a maximum on width to the synchronous rectification switch element in synchronization with a timing of turning on the main switch elements or the main switch element groups, and a synchronous control circuit. The circuit controls an on period of the synchronous rectification switch element so as to turn on the synchronous rectification switch element in synchronization with a particular timing, and turn off in synchronization with another timing.

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Matsumoto, Japan

Koji Sonobe