Abstract: A drive circuit controls the on/off state of a switching transistor of a DC/DC converter. A first resistor is provided on a path of current flowing through a primary coil of a transformer connected to the switching transistor, and one end of the first resistor is grounded. A second resistor is provided on a path of current flowing through a secondary coil of the transformer, and one end of the second resistor is grounded. A switching controller turns off the switching transistor when a first detection voltage exceeds a first threshold voltage and, turns on the switching transistor after lapse of predetermined delay time since a second detection voltage exceeds the second threshold voltage.

Abstract: A control circuit of a DC/DC converter is provided for supplying a driving voltage to a light emitting element. A hysteresis comparator compares a detection voltage that corresponds to the output voltage of the DC/DC converter with two threshold voltages. If the detection voltage is smaller than the lower threshold voltage, the hysteresis comparator outputs a comparison signal at the low level. Otherwise, the comparison signal is set to the high level. The switching control unit uses the comparison signal as a reference. The switching control unit instructs the switching transistor of the DC/DC converter to perform the switching operation during a period when the comparison signal is at the low level. Otherwise, the switching operation is suspended. The control circuit inhibits light emission of the light emitting element during a period when the comparison signal is at the low level. Otherwise, the control circuit permits the light emission.

Abstract: A linear regulator is provided which stabilizes an input voltage based on a reference voltage source that generates a reference voltage, and the reference voltage generated by the reference voltage. An output voltage of the linear regulator is supplied as a power supply voltage of a switching controller and the reference voltage source. The linear regulator is configured to enable switching of a regulation mode in which voltage is outputted according to the reference voltage, and a bypass mode in which an input voltage is outputted as it is, with no relation to the reference voltage. When a power supply apparatus is started up, during a time period until the input voltage reaches a predetermined threshold voltage, the linear regulator operates in the bypass mode, and when the input voltage exceeds the threshold voltage, operates in the regulation mode.

Abstract: A first transistor may be provided on a current path of a photo transistor. The bias current path may include a bias switch and a first bias resistor connected in series and is provided in parallel with a main current path including the phototransistor. A second transistor may configure a current mirror circuit with the first transistor, and generates second current formed by multiplying the first current flowing in the first transistor by a predetermined factor. The second current is charged in the charging capacitor and converted into a voltage. The bias current path turns on prior to the start of light reception of the phototransistor and turns off after a predetermined period has elapsed from the start of light reception of the phototransistor.

Abstract: A control circuit for controlling a switching element in a switching power supply by generating a switching signal is disclosed. The control circuit may include a soft start circuit that generates a switching signal so that an output voltage of the switching power supply gradually increases for a period until the output voltage reaches a predetermined reference voltage. The soft start circuit may increase the output voltage at a first limiting speed when the output voltage is lower than a predetermined threshold voltage, and may increase the output voltage at a second limiting speed which is set higher than the first limiting speed when the output voltage is higher than the threshold voltage.

Abstract: A switching transistor is connected to the primary coil of a transformer. A first resistor is provided such that one end thereof is connected to the switching transistor, and the other end thereof is grounded. A first voltage comparator compares a first detection voltage with a first threshold voltage. A second voltage comparator compares a second detection voltage with a second threshold voltage. A switching control unit controls the ON/OFF state of the switching transistor according to the output signals of the first voltage comparator and the second voltage comparator. A first electrode pad through a fourth electrode pad are provided to the respective nodes of the switching transistor and the first resistor.

Abstract: A selector circuit outputs one of a first input voltage or a second input voltage via an output terminal. A first transistor and a second transistor are provided in series between a first input terminal and the output terminal A third transistor and a fourth transistor are provided in series between a second input terminal and the output terminal. A control unit controls the ON/OFF operations of the first transistor through the fourth transistor. The back gates of the first transistor and the second transistor are connected such that at least one body diode of the first transistor M1 and at least one body diode of the second transistor are arranged in opposing directions. The back gates of the third transistor and the fourth transistor are connected in the same way.

Abstract: An input terminal is externally input with an input voltage. An output transistor of N-channel MOSFET is arranged between the input terminal and an output terminal. A charge pump circuit steps up the input voltage. An error amplifier receives a voltage stepped up by the charge pump circuit as a power supply, and outputs an error voltage of a feedback voltage corresponding to an output voltage of the output terminal and a predetermined reference voltage to a gate of the output transistor. A controller compares the input voltage with a predetermined threshold voltage, and forcibly turns OFF the output transistor when the input voltage is higher than the threshold voltage.

Abstract: A control circuit of a DC/DC converter is provided for supplying a driving voltage to a light emitting element. A hysteresis comparator compares a detection voltage that corresponds to the output voltage of the DC/DC converter with two threshold voltages. If the detection voltage is smaller than the lower threshold voltage, the hysteresis comparator outputs a comparison signal at the low level. Otherwise, the comparison signal is set to the high level. The switching control unit uses the comparison signal as a reference. The switching control unit instructs the switching transistor of the DC/DC converter to perform the switching operation during a period when the comparison signal is at the low level. Otherwise, the switching operation is suspended. The control circuit inhibits light emission of the light emitting element during a period when the comparison signal is at the low level. Otherwise, the control circuit permits the light emission.

Abstract: A main transistor and a reverse current prevention transistor are provided in series between an input terminal and an output terminal. An input diode is provided between a connection point of the reverse current prevention transistor and the main transistor and a reference voltage terminal in such a direction that the anode becomes the reference voltage terminal side. A control unit controls the gate voltage of the main transistor according to a DC voltage. The reverse current prevention transistor is arranged in such a direction that the anode of its body diode becomes the input terminal side. The reverse current prevention transistor is biased to be turned on in a normal state that the input terminal becomes high potential and the reference voltage terminal becomes low potential.

Abstract: A control circuit for controlling a switching element in a switching power supply by generating a switching signal is disclosed. The control circuit may include a short start circuit that generates a switching signal so that an output voltage of the switching power supply gradually increases for a period until the output voltage reaches a predetermined reference voltage. The soft start circuit may increase the output voltage at a first limiting speed when the output voltage is lower than a predetermined threshold voltage, and may increase the output voltage at a second limiting speed which is set higher than the first limiting speed when the output voltage is higher than the threshold voltage.

Abstract: A control circuit is provided for a separately excited DC/DC converter which directly monitors output voltage to detect a short-circuit state, and performs overcurrent protection. A switching controller of the control circuit controls a switching operation of a switching transistor of the separately excited DC/DC converter. A voltage comparator compares the output voltage and a threshold voltage, to detect the short-circuit state. After a predetermined start-up time has elapsed after beginning start-up of the separately excited DC/DC converter, when the voltage comparator detects the short-circuit state, the switching controller halts the switching operation of the switching transistor, and makes detection of the short-circuit state by the voltage comparator non-operative before elapse of the start-up time.

Abstract: A control circuit of a DC/DC converter is provided for supplying a driving voltage to a light emitting element. A hysteresis comparator compares a detection voltage that corresponds to the output voltage of the DC/DC converter with two threshold voltages. If the detection voltage is smaller than the lower threshold voltage, the hysteresis comparator outputs a comparison signal at the low level. Otherwise, the comparison signal is set to the high level. The switching control unit uses the comparison signal as a reference. The switching control unit instructs the switching transistor of the DC/DC converter to perform the switching operation during a period when the comparison signal is at the low level. Otherwise, the switching operation is suspended. The control circuit inhibits light emission of the light emitting element during a period when the comparison signal is at the low level. Otherwise, the control circuit permits the light emission.

Abstract: A power supply apparatus switchably operates an LDO regulator and a DC/DC converter connected in parallel so as to control a battery voltage Vbat from a power supply at a constant output voltage VO. A detected voltage Vs at a shared output terminal shared by the LDO regulator and the DC/DC converter is input to a feedback input terminal and fed back to the LDO regulator and the DC/DC converter. In order to suppress an undershoot occurring when switching from the LDO regulator to the DC/DC converter, a timing signal generating unit supplies a capability switching timing signal to a pre-drive circuit and switches the control capability of the DC/DC converter from a low capability mode at startup to a high capability mode.

Abstract: A temperature profile storage unit stores a Vf-Ta table showing a relationship between a forward voltage Vf and am ambient temperature Ta of an LED element, and a Ta-Ifmax table showing a relationship between the ambient temperature Ta and a maximum tolerable current Ifmax. The forward voltage Vf of the LED element driven by a power supply is detected and fed to a feedback point determining unit. A temperature computing unit determines the ambient temperature from the detected forward voltage Vf. A driving current determining unit determines a maximum tolerable current Ifmax from the ambient temperature Ta thus determined, by referring to the Ta-Ifmax table, and supplies a command value defining a current to drive the LED element to a constant current source via a D/A converter. The constant current source adjusts the current to drive the LED element in accordance with the command value.

Abstract: A control circuit of a DC/DC converter is provided for supplying a driving voltage to a light emitting element. A hysteresis comparator compares a detection voltage that corresponds to the output voltage of the DC/DC converter with two threshold voltages. If the detection voltage is smaller than the lower threshold voltage, the hysteresis comparator outputs a comparison signal at the low level. Otherwise, the comparison signal is set to the high level. The switching control unit uses the comparison signal as a reference. The switching control unit instructs the switching transistor of the DC/DC converter to perform the switching operation during a period when the comparison signal is at the low level. Otherwise, the switching operation is suspended. The control circuit inhibits light emission of the light emitting element during a period when the comparison signal is at the low level. Otherwise, the control circuit permits the light emission.

Abstract: An input circuit is provided which prevents malfunctioning of a function circuit during a power source voltage rise without the need of a separate Under Voltage Lock Out (UVLO) circuit.

Abstract: An input circuit is provided which prevents malfunctioning of a function circuit during a power source voltage rise without the need of a separate Under Voltage Lock Out (UVLO) circuit.

Abstract: A power supply apparatus switchably operates an LDO regulator and a DC/DC converter connected in parallel so as to control a battery voltage Vbat from a power supply at a constant output voltage VO. A detected voltage Vs at a shared output terminal shared by the LDO regulator and the DC/DC converter is input to a feedback input terminal and fed back to the LDO regulator and the DC/DC converter. In order to suppress an undershoot occurring when switching from the LDO regulator to the DC/DC converter, a timing signal generating unit supplies a capability switching timing signal to a pre-drive circuit and switches the control capability of the DC/DC converter from a low capability mode at startup to a high capability mode.

Abstract: A temperature profile storage unit stores a Vf-Ta table showing a relationship between a forward voltage Vf and am ambient temperature Ta of an LED element, and a Ta-Ifmax table showing a relationship between the ambient temperature Ta and a maximum tolerable current Ifmax. The forward voltage Vf of the LED element driven by a power supply is detected and fed to a feedback point determining unit. A temperature computing unit determines the ambient temperature from the detected forward voltage Vf. A driving current determining unit determines a maximum tolerable current Ifmax from the ambient temperature Ta thus determined, by referring to the Ta-Ifmax table, and supplies a command value defining a current to drive the LED element to a constant current source via a D/A converter. The constant current source adjusts the current to drive the LED element in accordance with the command value.