Rohm Co., Ltd.

Genki Tsuruyama

Tetsuo Tateishi

Yuhei Yamaguchi

Kiyotaka Umemoto

Yosuke Fukumoto

Hiroto Oshita

Yoju Imamura

A pulse control devicecomprises: a switch output unitwhich generates a pulse output voltage Vo from a direct-current input voltage Vi and supplies the pulse output voltage Vo to a load (such as a relay coilof a mechanical relay); a low-pass filter unitwhich receives a feedback input of the pulse output voltage Vo and generates a feedback voltage Vfb; and an output feedback control unitwhich receives an input of the feedback voltage Vfb and controls the switch output unitso that an average value of the pulse output voltage Vo becomes constant. The low-pass filter unitmay be configured without a coil.

Pulse control device

A sequence circuit () includes a detector () that detects an occurrence of an event based on an input signal, an acceptor () that accepts the event whose occurrence has been detected by the detector, an inhibitor () that inhibits the acceptor from accepting another event for a first period using the acceptance of one event by the acceptor as a trigger, a clock pulse generator () that generates one or more clock pulses during a period after a second period shorter than the first period elapses from the start of the first period until the first period ends, a determiner () that determines a next state based on a current slate and the event accepted by the acceptor, and a latch () that latches the next state using the clock pulse. An output of the latch is the current state.

Logic circuit, sequence circuit, power supply control circuit, switching power supply device

A comparator circuit includes a first comparator arranged to compare an input signal with a reference voltage so as to generate a first comparison signal, a second comparator arranged to compare the input signal with a variable reference voltage so as to generate a second comparison signal, a variable reference voltage generator arranged to generate the variable reference voltage, and a logic unit arranged to output one of the first comparison signal and the second comparison signal as a comparison signal. The logic unit outputs the first comparison signal as the comparison signal while controlling the variable reference voltage generator to sweep the variable reference voltage until the first comparison signal and the second comparison signal exhibit desired response behaviors, and moves to a state capable of outputting the second comparison signal as the comparison signal after the sweep of the variable reference voltage is completed.

Comparator circuit, power supply control IC, and switching power supply device

A constant voltage generating circuit includes an ED-type reference voltage supply that generates a predetermined constant voltage by using a first transistor of depletion-type and a second transistor of enhancement-type that are connected in series between a power supply terminal and a ground terminal, and a third transistor a source of which is connected to an output terminal for the constant voltage, a drain of which is connected to the power supply terminal or the ground terminal, and a gate of which is connected to a connection node between the first transistor and the second transistor.

Constant voltage generating circuit

A comparator circuit includes a first comparator, a second comparator, and a logic portion. The logic portion adjust a variable reference voltage input to the second comparator to become close to a reference voltage input to the first comparator, during a period from a time point when reverse current of current flowing in a coil disposed in a switching power supply device is detected in a state where a first comparison signal is output as a comparison signal while the first comparator and the second comparator are operated, until a first predetermined period of time elapses in a state where switching operation of the switching power supply device is stopped (excluding a period from a time point when the reverse current is detected until a second predetermined period of time shorter than the first predetermined period of time elapses).

An ON-period setting circuit is provided in a fixed-ON-period switching power supply device that produces a desired output voltage from an input voltage by driving a coil by turning ON and OFF an output transistor and a synchronous rectification transistor. The ON-period setting circuit shortens the ON period the more the lighter the load is in a discontinuous-current mode. Or, the ON-period setting circuit transiently shortens the ON period on completion of a transition from a discontinuous-current mode to a continuous-current mode.

On-period setting circuit, power control IC, and switching power supply device

A switching power supply device is a fixed on-time with bottom detection type switching power supply device, including an on-time extending portion, a low-side sensing type overcurrent protection portion using a bottom value threshold value, and a high-side sensing type overcurrent protection portion using a peak value threshold value. The high-side sensing type overcurrent protection portion sets the peak value threshold value to a value larger than the sum of the bottom value threshold value and a ripple component of inductor current during a period from start to end of a fixed on-time, and sets the peak value threshold value to a value equal to or smaller than the sum of the bottom value threshold value and the ripple component of the inductor current during a period after the fixed on-time elapses until at least the upper-side switch is turned off.

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Kyoto, Japan

Genki Tsuruyama