Abstract: An external resistor is connected to a detection terminal. A pulse modulator is configured to generate a pulse signal SPWM having a duty ratio adjusted such that the output voltage VOUT of a DC/DC converter approaches a target value. A pulse modulator is configured to switch the pulse signal SPWM to a level that corresponds to the off level of the switching transistor according to a detection voltage VS that develops at the detection terminal. A short-circuit detection circuit is configured to generate a short-circuit detection signal which is asserted when the detection voltage VS is higher than a predetermined threshold voltage VTH after a judgment time elapses after the pulse signal SPWM is switched to an on level that corresponds to the on state of the switching transistor. When the short-circuit detection signal is asserted, the pulse modulator is configured to switch the pulse signal SPWM to the off level.

Abstract: A first rectified voltage obtained by rectifying an AC voltage is input to an input detection terminal of a control circuit. A first NMOS transistor configured as a depletion-type high-voltage element, and its drain is connected to the input detection terminal, and its gate is connected to its source. An AC voltage detection circuit detects the amplitude of the AC voltage based on a current that flows through the first NMOS transistor.

Abstract: A power source apparatus comprises: a transformer that insulates a primary system and a secondary system and uses primary/secondary windings to transform an input voltage into an output voltage; a switching control device that is disposed in the primary system to drive the primary winding, and an output monitor device that is disposed in the secondary system to monitor the output voltage. The transformer includes a first auxiliary winding disposed in the primary system and a second auxiliary winding disposed in the secondary system. The output monitor device drives the second auxiliary winding to generate an induced voltage in the first auxiliary winding when the output voltage becomes smaller than a predetermined threshold voltage. The switching control device temporarily stops driving of the first winding upon detecting a light load state and resumes the driving of the first winding upon detecting the induced voltage in the first auxiliary winding.

Abstract: A second control circuit is configured to switch a pulse signal to a level which turns off a second switching transistor when a coil current that flows through a primary winding reaches a predetermined threshold current. The second control circuit is configured to start a switching operation when a power supply for an electronic device is turned on, to set the threshold current to a first value when an intermediate voltage is higher than a predetermined level, and to set the threshold current to a second value that is lower than the first value when the intermediate voltage is lower than a predetermined level. A first control circuit is configured to start a switching operation upon receiving an instruction from a microcontroller to start operating.

Abstract: A first error amplification circuit amplifies a difference between a predetermined reference voltage and a first detection voltage that corresponds to the output voltage of a DC/DC converter, so as to generate a second voltage. A voltage level judgment circuit generates a third voltage having a discrete level that corresponds to the amplitude of a first voltage. A multiplying/dividing circuit multiplies the first voltage by the second voltage, and divides the resulting product by the third voltage, so as to generate a fourth voltage. A comparator compares the fourth voltage with a second detection voltage that corresponds to a current that flows through a switching transistor included in the DC/DC comparator. A driving circuit turns on the switching transistor for each predetermined period, and turns off the switching transistor according to the output of the comparator every time the second detection voltage becomes higher than the fourth voltage.

Abstract: A second control circuit is configured to switch a pulse signal to a level which turns off a second switching transistor when a coil current that flows through a primary winding reaches a predetermined threshold current. The second control circuit is configured to start a switching operation when a power supply for an electronic device is turned on, to set the threshold current to a first value when an intermediate voltage is higher than a predetermined level, and to set the threshold current to a second value that is lower than the first value when the intermediate voltage is lower than a predetermined level. A first control circuit is configured to start a switching operation upon receiving an instruction from a microcontroller to start operating.

Abstract: A first rectified voltage obtained by rectifying an AC voltage is input to an input detection terminal of a control circuit. A first NMOS transistor configured as a depletion-type high-voltage element, and its drain is connected to the input detection terminal, and its gate is connected to its source. An AC voltage detection circuit detects the amplitude of the AC voltage based on a current that flows through the first NMOS transistor.

Abstract: The PD device comprises a primary-side controller configured to control an input current of a DC/DC converter disposed between an input and an output, and a secondary-side controller connected with AC coupling to the output, and configured to feedback electric power information of the output to the primary-side controller. The primary-side controller varies an output voltage value and an available output current capacity of the DC/DC converter by controlling the input current on the basis of the electric power information fed back from the secondary-side controller. The primary-side controller can change an overpower detecting set value in accordance with the target equipments connected to the output, thereby executing the power change of the DC/DC converter.

Abstract: The PD device includes: a DC/DC converter disposed between an input and an output; a primary-side controller configured to start up the DC/DC converter; and a secondary-side controller connected to an output of the DC/DC converter, the secondary-side controller AC-coupled to the output, the secondary-side controller configured to feed back electric power information of the output to the primary-side controller and an input of the DC/DC converter, wherein the secondary-side controller controls an input current of the DC/DC converter, thereby varying an output voltage value and an available output current capacity of the DC/DC converter.

Abstract: The PD device includes: a DC/DC converter disposed between an input and an output; a primary-side controller configured to control an input current of the DC/DC converter; and a secondary-side controller connected with AC coupling to the output, and configured to feed back electric power information of the output to the primary-side controller. The primary-side controller varies an output voltage value and an available output current capacity of the DC/DC converter by controlling the input current on the basis of the electric power information fed back from the secondary-side controller.

Abstract: A current limiting comparator generates a current limiting signal SLIM which is asserted when a detection voltage Vs at a detection terminal CS is higher than a predetermined threshold voltage VTH. A mask signal generating unit generates a mask signal SMSK which is asserted after a predetermined delay time TMSK elapses after a switching transistor is turned on. A pulse signal generating unit has: a function (a) in which, when the set signal SSET is asserted in a period in which the current limiting signal SLIM is negated, a pulse signal SPWM is switched to a first level; and a function (b) in which, when the reset signal SRST is asserted, or when the current limiting signal SLIM is asserted in a period in which the mask signal SMSK is negated, the pulse signal SPWM is switched to a second level.

Abstract: A current limiting comparator generates a current limiting signal SLIM which is asserted when a detection voltage Vs at a detection terminal CS is higher than a predetermined threshold voltage VTH. A mask signal generating unit generates a mask signal SMSK which is asserted after a predetermined delay time TMSK elapses after a switching transistor is turned on. A pulse signal generating unit has: a function (a) in which, when the set signal SSET is asserted in a period in which the current limiting signal SLIM is negated, a pulse signal SPWM is switched to a first level; and a function (b) in which, when the reset signal SRST is asserted, or when the current limiting signal SLIM is asserted in a period in which the mask signal SMSK is negated, the pulse signal SPWM is switched to a second level.

Abstract: An external resistor is connected to a detection terminal. A pulse modulator is configured to generate a pulse signal SPWM having a duty ratio adjusted such that the output voltage VOUT of a DC/DC converter approaches a target value. A pulse modulator is configured to switch the pulse signal SPWM to a level that corresponds to the off level of the switching transistor according to a detection voltage VS that develops at the detection terminal. A short-circuit detection circuit is configured to generate a short-circuit detection signal which is asserted when the detection voltage VS is higher than a predetermined threshold voltage VTH after a judgment time elapses after the pulse signal SPWM is switched to an on level that corresponds to the on state of the switching transistor. When the short-circuit detection signal is asserted, the pulse modulator is configured to switch the pulse signal SPWM to the off level.

Abstract: A DC/DC converter includes a transformer including primary and secondary coils and an auxiliary coil disposed in a primary coil side; a first output capacitor including a first end having a fixed electric potential and a second end; a first diode disposed in a direction where a cathode of the first diode faces the first output capacitor, between the second end of the first output capacitor and one end of the secondary coil; a switching transistor disposed on a path of the primary coil; a second output capacitor including a first end having a fixed electric potential and a second end; a second diode and a switch disposed between the second end of the second output capacitor and the first port of the auxiliary coil; and a control circuit receiving voltage generated in the second output capacitor through a power supply port and controlling turn-on/off of the switching transistor.

Abstract: A direct current (DC)/DC converter capable of lowering power consumption and capable of being started in a short time is provided. A voltage generated at a second output capacitor is input to a power supply terminal. An input voltage is input to a high voltage terminal. A charging transistor is a N-channel Metal Oxide Semiconductor Field Effect Transistor disposed between the high voltage terminal and the power supply terminal and applied with a bias so that the charging transistor is normally on. In a first state, in which the voltage of the power supply terminal is lower than a specified first threshold voltage, a current limiting circuit limits a charging current flowing from the high voltage terminal to the power supply terminal, and in a second state in which the voltage is higher than a second threshold voltage, the current limiting circuit lowers the charging current substantially to zero.

Abstract: A control circuit of a DC/DC converter includes: a pulse modulator configured to generate a pulse signal; and a driver configured to switch a switching transistor based on the pulse signal. The pulse modulator includes an on signal generator to generate an on signal. The on signal generator includes: a bottom detection comparator configured to compare a voltage of one end of an auxiliary winding with a predetermined threshold voltage and generate a bottom detection signal; a first time-out circuit configured to generate a first time-out signal asserted when the bottom detection signal is not asserted; a second time-out circuit configured to generate a second time-out signal asserted when the bottom detection signal is not asserted; and a logic part configured to generate the on signal based on the bottom detection signal, the first time-out signal and the second time-out signal.

Abstract: A pulse modulator generates a pulse modulation signal SPM having a duty ratio which is adjusted according to a feedback voltage Vfb that corresponds to the output voltage VOUT of a DC/DC converter. A second oscillator generates a second cyclic signal which is asserted with each of a predetermined second period. A light load detection circuit generates a light load detection signal which is asserted when the feedback voltage Vfb becomes lower than a first threshold voltage. A driving circuit drives a switching transistor according to the pulse modulation signal SPM, Furthermore, the driving circuit suspends the driving of the switching transistor during a period until the second cyclic signal is next asserted after the light load detection signal is asserted.

Abstract: The present invention provides an Alternating Current/Direct Current (AC/DC) converter employing measures not only against residual voltage but also to reduce power consumption. The AC/DC converter receives an Alternating Current (AC) voltage through a concentric plug and converts the AC voltage into a Direct Current (DC) voltage. A discharge path is disposed on a path from a discharge terminal to a ground terminal. A detection circuit compares a wave detection voltage with a predetermined threshold voltage, and enables the discharge path to be turned on when the wave detection voltage is continuously lower than the threshold voltage for a predetermined detection time.

Abstract: A second control circuit is configured to switch a pulse signal to a level which turns off a second switching transistor when a coil current that flows through a primary winding reaches a predetermined threshold current. The second control circuit is configured to start a switching operation when a power supply for an electronic device is turned on, to set the threshold current to a first value when an intermediate voltage is higher than a predetermined level, and to set the threshold current to a second value that is lower than the first value when the intermediate voltage is lower than a predetermined level. A first control circuit is configured to start a switching operation upon receiving an instruction from a microcontroller to start operating.

Abstract: A power supply adapter receives an AC voltage, converts the AC voltage into a DC voltage, and supplies the DC voltage to an electronic device. A DC/DC converter converts the voltage smoothed by a smoothing capacitor into the DC voltage. A device-side connector is connected to the DC/DC converter via a cable, and is configured to be detachably connected to the electronic device. The device-side connector includes a detection unit detecting whether or not the electronic device is connected, and generates a connection detection signal indicating whether or not the electronic device is connected. A control circuit of the DC/DC converter is connected to the detection unit of the device-side connector via the cable, and is set to an operating state when the connection detection signal indicates that the electronic device is connected, and is set to a non-operating state when the connection detection signal indicates that the electronic device is not connected.