Renesas Electronics Corporation

Renesas Technology Corp.

Kyoichi Hosokawa

Ryotaro Kudo

Koji Tateno

Toshio Nagasawa

Shin Chiba

Kenichi Onda

Shinichi Yoshida

Yoichi Uehara

In a switching power source which controls a current which flows in an inductor through a switching element which performs a switching operation in response to a PWM signal, and forms an output voltage by a capacitor which is provided in series in the inductor, a booster circuit which is constituted of a bootstrap capacity and a MOSFET is provided between an output node of the switching element and a predetermined voltage terminal. The boosted voltage is used as an operational voltage of a driving circuit of the switching element, another source/drain region and a substrate gate are connected with each other, and a junction diode between one source/drain region and the substrate gate is inversely directed with respect to the boosted voltage which is formed by the bootstrap capacity.

Switching power supply device and a semiconductor integrated circuit

In a switching power source which controls a current which flows in an inductor through a switching element which performs a switching operation in response to a PWM signal, and forms an output voltage by a capacitor which is provided in series in the inductor, a booster circuit which is constituted of a bootstrap capacity and a MOSFET is provided between an output node of the switching element and a predetermined voltage terminal. The boosted voltage is used as an operational voltage of a driving circuit of the switching element, another source/drain region and a substrate gate are connected with each other such that when the MOSFET is made to assume an OFF state, and a junction diode between one source/drain region and the substrate gate is inversely directed with respect to the boosted voltage which is formed by the bootstrap capacity.

The present invention provides a switching power source and a semiconductor integrated circuit which realize an acquisition a sufficient driving voltage of a high-potential side switching element M1 even when a power source voltage VDD is low. In a switching power source which controls a current which flows in an inductor through a switching element which performs a switching operation in response to a PWM signal, and forms an output voltage by a capacitor which is provided in series in the inductor, a booster circuit which is constituted of a bootstrap capacity and a MOSFET is provided between an output node of the switching element and a predetermined voltage terminal, the boosted voltage is used as an operational voltage of a driving circuit of the switching element, another source/drain region and a substrate gate are connected with each other such that when the MOSFET is made to assume an OFF state, and a junction diode between one source/drain region and the substrate gate is inversely directed with respect to the boosted voltage which is formed by the bootstrap capacity.

Switching power supply device and semiconductor integrated circuit

The present invention provides a switching power source and a semiconductor integrated circuit which realize an acquisition a sufficient driving voltage of a high-potential side switching element Meven when a power source voltage VDD is low. In a switching power source which controls a current which flows in an inductor through a switching element which performs a switching operation in response to a PWM signal, and forms an output voltage by a capacitor which is provided in series in the inductor, a booster circuit which is constituted of a bootstrap capacity and a MOSFET is provided between an output node of the switching element and a predetermined voltage terminal, the boosted voltage is used as an operational voltage of a driving circuit of the switching element, another source/drain region and a substrate gate are connected with each other such that when the MOSFET is made to assume an OFF state, and a junction diode between one source/drain region and the substrate gate is inversely directed with respect to the boosted voltage which is formed by the bootstrap capacity.

In a driver circuit constructing a switching power supply device that switches power transistors passing a current through a coil by a PWM mode, a current detection transistor, which is smaller in size than the low-potential side power transistor, and a current detection resistor are provided in parallel to the low-potential side power transistor. The same control voltage as the power transistor is applied to the control terminal of the current detection transistor. An operational amplifier is formed, that has the potential of the connection node between the current detection transistor and the current detection resistor applied to its inverse input terminal and a feedback loop, so as to make a pair of input terminals of the operational amplifier be at the same potential. A signal produced by the current detection resistor is thus outputted as a current detection signal.

Power supply device and switching power supply device

In a driver circuit constructing a switching power supply device that switches power transistors passing a current through a coil by a PWM mode, a current detection transistor, which is smaller in size than the low-potential side power transistor and a current detection resistor are provided in parallel to the low-potential side power transistor. The same control voltage as the power transistor is applied to the control terminal of the current detection transistor. An operational amplifier is formed, that has the potential of the connection node between the current detection transistor and the current detection resistor applied to its inverse input terminal and a feedback loop, so as to make a pair of input terminals of the operational amplifier be at the same potential. A signal produced by the current detection resistor is thus outputted as a current detection signal.

This invention provides a semiconductor integrated circuit for drive and a module for building a synchronous rectifier type switching regulator that is able to correctly detect and prevent a reverse current flowing through a coil (inductance element) during light load using a comparator and has a good power efficiency. In a synchronous rectifier type switching regulator including a reverse current detection circuit that is able to detect a state in which a reverse current flows through the inductance element (coil) and a reverse current prevention function, a switching element for synchronous rectification is formed by a plurality of parallel transistors and the transistors are controlled so that a part of them are not driven during light load.

Electronic component for power supply and a power supply device

It is aimed at decreasing losses not only in a synchronous rectifier circuit provided at a secondary side of a DC-DC converter, but also in a full-bridge switching circuit provided at a primary side thereof. The DC-DC converter comprises a transformer for voltage conversion, a synchronous rectifier circuit at the secondary side, and a full-bridge switching circuit at the primary side. The DC-DC converter performs synchronous rectifier control which uses switch transistors to change paths of currents flowing through the secondary coil in synchronization with switching operations at the primary side. The DC-DC converter detects currents flowing through a load at the secondary side, primary-side currents varying with the load currents, or primary-side input voltages to dynamically control off-timings of a synchronous rectification transistor at the secondary side. In addition, the DC-DC converter detects primary-side input voltages and currents flowing through the secondary-side load to dynamically control on-timings of a transistor in the primary-side switching circuit.

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Tokyo, Japan

Kyoichi Hosokawa