Rohm Co., Ltd.

Yoichi Tamegai

Isao Yamamoto

Kyoichiro Araki

Satoru Nate

Masashi Horimoto

Tomoyuki Ito

Ichiro Yokomizo

Takahiro Shimizu

Hironori Nakahara

Koki Tamakawa

Multiple voltage monitoring circuits each detect the voltage across at least one corresponding cell from among multiple cells. A current monitoring circuit detects the current that flows through the multiple cells. When the length of a period during which the current that flows through the multiple cells is substantially zero exceeds a predetermined judgment time, the current monitoring circuit asserts a detection signal. Upon detecting an assertion of the detection signal, each voltage monitoring circuit measures the voltage across at least one corresponding cell.

Current monitoring circuit and coulomb counter circuit

A power supply circuit including a DC/DC converter having switching elements and configured to receive an input voltage in an input line and generate an output voltage in an output line; and a linear regulator configured to receive the output voltage and supply a stabilized voltage to a load. The DC/DC converter switches between a switching mode to switch the switching elements and a bypass mode to put a switching element existing on a path from the input line to the output line, of the switching elements, in a full-on state and stop switching of the other switching element.

Power supply circuit, control circuit thereof, and electronic apparatus

An apparatus for estimating a residual capacity of a storage battery including an electrode whose stage structure is changed based on a state of includes a current monitor configured to monitor a current value flowing in the storage battery; a voltage monitor configured to monitor a voltage value of the storage battery; a Coulomb counter configured to integrate the current value monitored by the current monitor; a differentiation circuit configured to detect a differential value of the voltage value monitored by the voltage monitor; a reset detecting circuit configured to reset an accumulated error due to current integration of the Coulomb counter using an inflection point of the differential value detected by the differentiation circuit; and a residual capacity estimating part configured to estimate a residual capacity of the storage battery based on a value of the Coulomb counter.

Apparatus for estimating residual battery capacity, system for estimating residual battery capacity, battery pack, and method for estimating residual battery capacity

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.

Overvoltage protection circuit

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.

DC/DC converter

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.

Current detection circuit

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 Mand 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.

Selector circuit

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.

Drive circuit of DC/DC converter, light emitting apparatus and electronic device using the same

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.

Power supply device, electronic device using the same, and semiconductor device

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.

Over-voltage protection circuit

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.

Control circuit for self exciting DC/DC converter

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. After detecting the short-circuit state and halting the switching operation of the switching transistor for a predetermined halt time, the switching controller begins start-up of the separately excited DC/DC converter once again.

DC/DC converter control circuit, and power supply apparatus, light emitting apparatus and electronic device using the same

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.

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Kyoto, Japan

Yoichi Tamegai