Patent application number | Description | Published |
20090039844 | POWER SUPPLY UNIT AND PORTABLE DEVICE - A power supply unit, adapted to provide a predetermined output voltage from its output circuit, compares a feedback voltage associated with the output voltage of the output circuit with a reference voltage so as to control the output circuit. The power supply unit is enabled and disabled in response to an externally supplied operation command signal. The reference voltage is generated by a reference voltage generation circuit, which is operable on the voltage of the operation command signal, and is controllably enabled when the voltage of the operation command signal exceeds a predetermined level, but otherwise disabled. Thus, the reference voltage is stabilized to improve the ripple rejection characteristic of the power supply unit without increasing its current consumption. | 02-12-2009 |
20090108822 | POWER SUPPLY UNIT AND PORTABLE DEVICE - A power supply unit is adapted to automatically switch its operational mode between a light load mode and a heavy load mode depending on the level of its output current. The unit has a first error amplification circuit for controlling a first output circuit in the heavy load mode, and a second error amplification circuit for controlling the second output circuit in the light load mode. The first and the second output circuits are controllably enabled and disabled in the opposite manner based on the level of the output current. Thus, the unit can operate on a reduced consumption current with an improved transient response when operating in the light load mode. | 04-30-2009 |
20090212752 | POWER SUPPLY UNIT AND PORTABLE DEVICE - A step-like operation command signal is inputted into a time-constant circuit to generate a gradually rising operation command input voltage, which is supplied to a power supply unit. Enablement and disablement of the power supply unit is controlled on the basis of the operational command input voltage. When the operation command input voltage exceeds a first predetermined voltage level, a detection signal and a reference voltage are generated, and at the same time an error amplification circuit is enabled. On the other hand, when the operation command input voltage exceeds a second predetermined voltage level, a level shift voltage for initiating a soft start is generated, which enables execution of a soft start of the power supply unit without increasing its consumption current and reduction of the number of its terminals. | 08-27-2009 |
20100164858 | CONTROL CIRCUIT FOR LIGHT-EMITTING ELEMENT - A control circuit generates a driving signal for driving a light-emitting element. An external synchronization oscillator receives a synchronization clock signal from an external circuit, and generates an external synchronization cyclic signal synchronously with the clock signal. An internal oscillator generates an internal cyclic signal having a predetermined frequency asynchronously with the synchronization clock signal. When the frequency of the external synchronization cyclic signal is within a predetermined range, the driving signal generating unit generates the driving signal based upon the external synchronization cyclic signal. When the frequency of the external synchronization cyclic signal deviates from the predetermined range, the driving signal generating unit generates the driving signal based upon the internal cyclic signal. | 07-01-2010 |
20120025737 | CURRENT MIRROR CIRCUIT - A current mirror circuit duplicates an input current that flows through an input terminal, and outputs an output current via an output terminal. A first transistor, a second transistor, and a diode are sequentially arranged in series between a power supply terminal to which a fixed voltage is applied and an input terminal. A third transistor and a fourth transistor are sequentially arranged in series between the power supply terminal and the output terminal. The gate of the first transistor and the gate of the third transistor are connected to the drain of the second transistor. The gate of the second transistor and the gate of the fourth transistor are connected to the input terminal. | 02-02-2012 |
20120119724 | CURRENT GENERATING CIRCUIT - A first current source generates a first current having positive temperature characteristics. A second current source generates a second current. A first current mirror circuit generates a third current by multiplying, by a first coefficient, the base current of a compensation transistor configured as an NPN bipolar transistor arranged on a path of the second current. A second current mirror circuit generates a fourth current that is proportional to the difference between the first current and the third current. A current generating circuit outputs the sum total of the fourth current and a fifth current that is proportional to the base current. | 05-17-2012 |
20120120342 | CONTROL CIRCUIT FOR SWITCHING POWER SUPPLY - A control IC controls a switching power supply configured to supply a driving voltage Vout to one terminal of an LED string to be intermittently driven. In the on period of the LED string, a pulse modulator generates a pulse signal having a duty ratio adjusted such that a detection voltage V | 05-17-2012 |
20120229045 | CONTROL CIRCUIT OF SWITCHING POWER SUPPLY FOR DRIVING LIGHT EMITTING ELEMENTS, AND LIGHT EMITTING DEVICE AND ELECTRONIC APPARATUS USING THE SAME - A control circuit of a switching power supply for supplying a drive voltage to a light emitting element is provided. The control circuit includes a pulse width modulator which generates a pulse signal whose duty ratio is adjusted such that a detection voltage corresponding to an output voltage of the switching power supply is equal to a predetermined reference voltage, a driver which drives a switching element of the switching power supply based on the pulse signal, and a standby control unit which stops driving of the switching element once a predetermined time has passed after a standby signal steps down to a level indicating a standby state, and to shut down the control circuit and a current source. | 09-13-2012 |
20140043562 | COMPARATOR, OSCILLATOR USING THE SAME, DC/DC CONVERTER, CONTROL CIRCUIT THEREOF, AND ELECTRONIC APPARATUS - A comparator compares a first input voltage and a second input voltage to generate a comparative output depending on a result of the comparison. The comparator includes a first input terminal configured to receive the first input voltage, a second input terminal configured to receive the second input voltage, a differential pair including a first input transistor whose control terminal is connected with the first input terminal and a second input transistor whose control terminal is connected with the second input terminal, a tail current source configured to supply a tail current to the differential pair, and a load circuit connected to the first input transistor and the second input transistor, and the tail current source increases the tail current, as the first input voltage approaches the second input voltage, depending on the first input voltage. | 02-13-2014 |
20140340615 | DRIVING CIRCUIT OF LIGHT EMITTING ELEMENT, AND LIGHT EMITTING DEVICE AND ELECTRONIC APPARATUS INCLUDING THE LIGHT EMITTING ELEMENT - A driving circuit for a light emitting element is disclosed. The driving circuit includes a DC-DC converter configured to generate a drive voltage between a first line and a second line; a current driver, configured to be connected to the light emitting element in series between the first line and the second line, configured to supply a drive current to the light emitting element; a protection resistor configured to be connected to the light emitting element in series between the first line and the current driver; and a controller configured to control the DC-DC converter such that a first detection voltage, which corresponds to a voltage between both ends of the current driver, approaches a predetermined reference voltage and perform a predetermined protection process if the drive voltage between the first line and the second line exceeds a predetermined first threshold voltage. | 11-20-2014 |