Rohm Co., Ltd.

Manabu Oyama

Daisuke Uchimoto

Yoshinori Sato

Hiroaki Ando

A buck converter includes a switching transistor. A switching line connected to a source of the switching transistor is connected to a ground of a controller. The controller drives the switching transistor and generates a step-up pulse. The step-up circuit receives an output voltage Vof a DC/DC converter and generates a power supply voltage Vof the controller using the step-up pulse.

Non-isolated DC/DC converter

A discharge circuit has a voltage divider arranged to divide an alternating-current input voltage to produce a divided voltage, a high-pass filter arranged to pass a high-frequency component of the divided voltage to produce a monitoring voltage, a comparator arranged to compare the monitoring voltage with a threshold voltage to produce a comparison signal, a timer arranged to generate a timer signal indicating whether or not the comparison signal has been kept at the same logic level for a mask period, a controller arranged to generate a discharge control signal according to the timer signal, and a discharger arranged to discharge, according to the discharge control signal, an X capacitor connected to a node to which the alternating-current input voltage is applied.

Discharge circuit and power supply device therewith

A control circuit is used in a switching converter including at least, a switching transistor and a coil connected to the switching transistor. The control circuit includes: a current comparing circuit that asserts a peak current sensing signal when a current flowing in the coil during the ON period of the switching transistor reaches a threshold current. The current comparing circuit includes: a first comparator that compares a sensed voltage according to the current flowing in the switching transistor and the coil with a threshold voltage defining the threshold current, and generates a comparison signal; and a variable delay circuit that generates the peak current sensing signal by delaying the comparison signal, a delay amount of the variable delay circuit varying according to a period of time from a turn-on of the switching transistor to a transition of the comparison signal.

Switching converter and control circuit thereof, current sensing method, AC/DC converter, and power adaptor and electronic devices

The invention improves the voltage regulation rate of the switching regulator in lag control. A divided output voltage divided by the first resistor and the second resistor is input to a first polarity input terminal of a comparator. A driver is used for controlling a switching transistor and a synchronous rectified transistor according to an output pulse of the comparator. A feedback circuit is used for outputting a switching signal to the reverse input terminal of the comparator according to the output pulse, wherein the switching signal is used for switching two voltage levels between the input voltage and a ground voltage. The error amplifier is used for amplifying an error between the divided output voltage and a first reference voltage and generating a second reference voltage to output to a second polarity input terminal of the comparator.

Control circuit for switching regulator, switching regulator and electronic equipment using the control circuit

The present invention provides a comparator with novel output logic. The comparator makes a comparison between an input voltage and a reference voltage. A differential amplifying circuit includes a first input transistor with a control terminal applied with the reference voltage and a second input transistor with a control terminal applied with the input voltage. An output section receives an export signal of the differential amplifying circuit and outputs an output signal that corresponds to the export signal and denotes a result of the comparison. A feedback circuit receives the output signal of the output section, and if the output signal is changed from a first level to a second level, the output signal feeds back to the differential amplifying circuit or the output section while it is restored to the negated level.

Comparator, control circuit of switching regulator using the same, switching regulator, and electronic equipment

A current source generates a reference current. A first transistor is a depletion-type MOSFET arranged such that one terminal thereof is connected to the current source and its gate is connected to its source. A second transistor is an enhancement-type MOSFET arranged such that one terminal thereof is connected to the other terminal of the first transistor, the other terminal thereof is connected to a fixed voltage terminal, and its gate and drain are connected. A third MOSFET is an enhancement-type P-channel MOSFET arranged such that one terminal thereof is connected to the current source, the other terminal thereof is connected to the fixed voltage terminal, and its gate is connected to a connection node connecting the first and second transistors. A constant voltage circuit outputs at least a voltage that corresponds to the gate voltage of the third transistor or a voltage that corresponds to the gate voltage thereof.

Constant voltage circuit

A first switch group includes switches provided on a path for charging a flying capacitor using an input voltage. A second switch group includes switches provided on a path for charging an output capacitor using charge stored in the flying capacitor. A pulse modulator generates a pulse signal having a duty ratio adjusted so that a feedback voltage corresponding to an output voltage of a charge pump circuit matches a given reference voltage. A driver receives the pulse signal from the pulse modulator, and turns on either one of the first switch group and the second switch group during a period corresponding to a high-time of the pulse signal and turns on the other switch group during a period corresponding to a low-time thereof.

Control circuit and method for charge pump circuit with pulse modulation

In a switching power supply apparatus, an input voltage Vin applied to an input terminal is output from a first output terminal and a second output terminal after boosting or inverting of the voltage Vin. When a first and a fourth switches are turned on, a flying capacitor is charged. When a second and a fifth switches are turned on, charges charged in the flying capacitor are transferred to a first output capacitor. When a third and a fifth switches are turned on, charges charged in the flying capacitor are transferred to a second output capacitor. A voltage Vin&#xd7;double the input voltage Vin is output from the first output terminal as a first output voltage Vout, and a voltage &#x2212;Vin obtained by inverting the input voltage is output from the second output terminal as a second output voltage.

Switching power supply and electronic apparatus employing the same

A charge pump circuit includes a first switch to a fourth switch, a flying capacitor, and an output capacitor. A driver turns on the first switch and the fourth switch during a predetermined precharge period from the start of activation of the charge pump circuit to charge the output capacitor. Thereafter, on the basis of a pulse signal, the driver alternately turns on and off a first pair and a second pair.

Control circuit and control method for charge pump circuit

A minimum pulse signal generating circuit generates a minimum pulse signal having a predetermined minimum duty ratio, synchronously with a PWM signal. When the duty ratio of the PWM signal is smaller than the minimum duty ratio, a corrected pulse signal generating circuit fixes the logical level of the PWM signal to the level that turns off a switching transistor. A driver circuit drives the switching transistor according to a corrected PWM signal output from the corrected pulse signal generating circuit. In a case in which the level of the PWM signal is fixed by means of the corrected pulse signal generating circuit, a stop signal generating circuit generates a stop signal at a predetermined first level. When the stop signal is at the predetermined first level, at least an oscillator used for pulse modulation is stopped.

Control circuit for switching regulator

A pulse frequency modulator generates a pulse signal having a fixed duty ratio and a frequency which is adjusted such that a feedback voltage corresponding to the output voltage of a charge pump circuit is coincident with a predetermined first reference voltage. A driver, on receiving the pulse signal, turns on a first or second group of switches during the time periods corresponding to the high time periods of the pulse signal and turns on the other ones of the first and second group of switches during the time periods corresponding to the low time periods of the pulse signal.

A switching power supply apparatus generates a first output voltage with a reversed polarity of an input voltage and a second input voltage of double the input voltage with the reversed polarity, and then outputs them from the first output terminal and the second output terminal. A driver circuit includes a control unit and a first switch to a sixth switch. The driver circuit repeats three charging periods in a time-division manner. The three charging periods are a first charging period during which a flying capacitor is charged with the input voltage, a second charging period in which a low-potential-side terminal of the flying capacitor is connected to a ground terminal and a first output capacitor is charged with a voltage appearing at the other end of the flying capacitor, and a third charging period in which a high-potential-side of the flying capacitor is connected with the first output terminal and a second output capacitor is charged with a voltage appearing at the other end of the flying capacitor.

Charge-pump type switching power supply apparatus

A first constant-current source supplies a charging current to a second terminal of a first capacitor in which a first terminal is grounded. A first terminal of a second capacitor is grounded, and a first switch is provided between the second terminal of the first capacitor and a second terminal of the second capacitor. A second constant-current source supplies current to the second capacitor, and a second switch is provided on a current path of the second constant-current source. A third constant-current source draws out current from the first capacitor and the second capacitor. A switch controller turns on the first switch and turns off the second switch when an output voltage appearing in the second terminal of the first capacitor reaches a predetermined upper-limit voltage. The switch controller turns off the first switch and turns on the second switch when the output voltage drops to a predetermined lower-limit voltage.

Triangular wave generation circuit

A first charge pump circuit converts an input voltage (Vin) into a predetermined voltage, to be outputted as a first output voltage (Vout). A second charge pump circuit converts the first output voltage (Vout), outputted from the first charge pump circuit, into a predetermined voltage, to be outputted as a second output voltage (Vout). A control circuit controls charge-discharge states of the first charge pump circuit and the second charge pump circuit. The control circuit synchronously controls a state in which a first output capacitor of the first charge pump circuit is charged, and a state in which a second flying capacitor of the second charge pump circuit is charged.

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Kyoto, Japan

Manabu Oyama