Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Hirohisa Tanabe

Takashi Ryu

Takuya Ishii

Mikio Motomori

Tomoya Shigemi

Hiroki Akashi

Makoto Ishimaru

Naoyuki Nakamura

Masaaki Koto

Tamotsu Yamamoto

Kazuhito Kimura

Masato Yoshida

Richard Oswald

The step-down converter includes: a switch; an inductor; a rectifier; a smoothing unit; and a current bypass circuit, wherein when the current flowing toward the inductor exceeds a predetermined value, the current bypass circuit forms a path through which the current flows from the input terminal to the output terminal while bypassing the inductor.

Step-down converter

A reference voltage is applied from a reference voltage generating circuit to the non-inverting input terminal of an amplifier for supplying a drive voltage to the gate terminal of an NMOS transistor, and the output voltage appearing at the source terminal of the NMOS transistor is divided by a resistor pair and applied to the inverting input terminal of the amplifier. The voltage obtained by adding a voltage equal to or higher than the voltage for sufficiently driving the NMOS transistor to the output voltage appearing at the source terminal of the NMOS transistor is generated by a charge pump circuit and supplied to the amplifier as a power supply voltage. With this configuration, the drive voltage for the NMOS transistor is suppressed to the required minimum voltage while the drive voltage is obtained securely. The power consumption in the amplifier can thus be suppressed.

Output circuit

A switching regulator circuit including a high-side switch and a low-side switch; an inductor having a first terminal coupled to a common terminal between the high-side switch and the low-side switch, and a second terminal coupled to an output terminal of the switching regulator circuit; a low-pass filter coupled to the first terminal of the inductor, where the low-pass filter is operative for generating a ramp signal based on the voltage signal present at the first terminal of the inductor; and a hysteretic comparator coupled to the low pass filter, where the hysteretic comparator receives the ramp signal as an input signal, and generates an output signal which is operative for controlling the operation of the high-side switch and the low-side switch.

Hysteretic switching regulator

A step-up converter includes an inductor which receives input voltage Vi at one end, a first FET of the first conduction type which functions as a switch for determining whether or not energy is accumulated in the inductor, a second FET of the second conduction type which rectifies a current output from the other end of the inductor, an output capacitor having an end connected to the source of the second FET, a current detection circuit, and a feedback control circuit. The current detection circuit detects a current flowing through the first N-channel FET to output current detection signal Vc. The feedback control circuit controls the operations of the first N-channel FET and a P-channel FET based on current detection signal Vc.

Step-up converter

A current detection circuit of the present invention has a switching devicean auxiliary switching devicean offset voltage source comprising an offset resistor deviceand a current source circuita compensation circuit, comprising a differential amplifierand a compensation transistorfor adjusting the output current of the auxiliary switching deviceso that the potential obtained by subtracting the voltage drop across the offset resistor devicefrom the output potential of the switching deviceis equal to the output potential of the auxiliary switching devicebeing configured that the detection level of the current flowing in the switching deviceis shifted by an offset amount.

Current detection circuit and switching power supply

In a DC-DC converter conforming to the current mode control system, in which the valley value of an inductor current is controlled for output control, a current detection circuitis configured to detect the current flowing from a low-side FETto an inductorusing an FET, an NPN transistor, an NPN transistor, a PNP transistor, a PNP transistorand a resistor, to detect the current flowing from the inductorto the low-side FETusing an FET, a differential amplifier, an FETand the resistor, and to output a current detection signal Vc.

DC-DC converter

A current detection circuit of the present invention has a switching device; an auxiliary switching device; an offset voltage source comprising an offset resistor deviceand a current source circuit; a compensation circuit, comprising a differential amplifierand a compensation transistor, for adjusting the output current of the auxiliary switching deviceso that the potential obtained by subtracting the voltage drop across the offset resistor devicefrom the output potential of the switching deviceis equal to the output potential of the auxiliary switching device, being configured that the detection level of the current flowing in the switching deviceis shifted by an offset amount.

Current detection circuit and switching power supply using the same

An output detection feedback section () for controlling the power supply output voltage of a converter unit () in response to an error signal Ve has an error amplifier () for outputting the error signal Ve, a phase compensation circuit (), a state detection circuit (), and a response compensation circuit () for setting the voltage of a capacitor () of the phase compensation circuit () to a predetermined value. When output voltage is switched, the output voltage is fixed at the predetermined value in a DC manner while a transitional response of the error signal (Ve) is accelerated, so that the output voltage is changed at a high speed to a desired value and the overshoot and undershoot are suppressed around the desired value.

Power supply

A DC-DC converter for converting an input DC voltage to an output DC voltage has a switch element which is turned ON/OFF by a drive signal, a reference voltage source for outputting a first reference voltage when the switch element is ON or outputting a second reference voltage when the switch element is OFF, a capacitive element having one terminal connected to the reference voltage source, a charge/discharge circuit for discharging the capacitive element when the switch element is ON and charging the capacitive element when the switch element is OFF, a switch circuit for short-circuiting the capacitive element when the switch element is turned ON and OFF, and a comparison circuit for comparing the output DC voltage or a voltage at which the output DC voltage is detected with a voltage at the other terminal of the capacitive element and generating the drive signal.

For controlling DC-DC converters conforming to voltage mode control system and current mode control system, in multi-output power supply, first converter sectionis configured that first detection circuitoutputs first control signal, that first oscillation circuitoutputs first triangular wave signal and clock signal, and that first pulse-width modulation circuitdrives first switch by comparing first control signal with first triangular wave signal. Second converter sectionis configured that second detection circuitoutputs second control signal, that second oscillation circuitoutputs second triangular wave signal synchronized with clock signal, that current detection circuitoutputs current signal of second inductor, and that second pulse-width modulation circuitturns ON second switch in synchronization with clock signal and turns OFF second switch by calculating or comparing second control signal, the second triangular wave signal and current signal.

Multi-output power supply and electronic device using them

A DC-DC converter has switching means which generates a continuous switching voltage having a specified period from an input voltage and outputs the generated switching voltage, output voltage generating means which receives the switching voltage at an inductor and generates an output voltage obtained by rectifying and smoothing a voltage generated in the inductor, lamp signal generating means which generates a lamp signal and outputs the generated lamp signal, and control means which performs an arithmetic operation using a current signal relative to a current flowing in the inductor, an error signal relative to the output voltage, and the lamp signal to generate a control signal for controlling the operation of the switching means and outputs the generated control signal to the switching means. The lamp signal generating means includes first signal generating means for generating a first output signal based on a frequency divided signal having first and second periods obtained by dividing the time of a clock signal having the specified period and second signal generating means for generating a second output signal having a phase 180 degrees different from the phase of the first output signal based on the frequency divided signal, generates the lamp signal which rises after being held at a constant value for a specified time period in each of the first and second periods, and outputs the generated lamp signal.

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Kyoto, Japan

Hirohisa Tanabe