Abstract: A power conversion device includes: a DC/DC converter including a conversion circuit; and a control circuit that detects a first voltage at an output terminal, a first current flowing through the conversion circuit, and a second voltage at an input terminal, obtains information indicating a target output voltage and a predetermined voltage, and performs calculations to emit a PWM signal for operating the conversion circuit. The control circuit performs: a first calculation for calculating a target current for approximating the first voltage to the target output voltage; a second calculation for calculating a first duty ratio for approximating the first current to the target current; a third calculation for calculating a second duty ratio based on the predetermined voltage and the second voltage; and a fourth calculation for calculating a driving duty ratio of the PWM signal using the first and the second duty ratios to control the first voltage.

Abstract: The power conversion device can undergo autonomous search control for ZVS without a larger circuit area or lower reliability. The power conversion device performs, in each switching cycle, an operation of turning the control switch (CTLSW) on and afterward off while the synchronous rectification switch (SRSW) is off, and then turning the synchronous rectification switch on and afterward off while the control switch is off. Whether the inductor current (iL) is positive or negative is detected at the detection timing backed by a predetermined period (Text) from a timing at which the synchronous rectification switch switches from on to off, based on the detection result, the on-period (TOFF) of the synchronous rectification switch is corrected.

Abstract: An in-vehicle power supply system includes a high-voltage direct-current (DC) power supply, a low-voltage storage battery, a DC-DC converter, and a controller. The DC-DC converter includes a conversion circuit including a high-voltage terminal and a low-voltage terminal, an input switch connected between the high-voltage DC power supply and the high-voltage terminal, and an output switch connected between the low-voltage terminal and the low-voltage storage battery. The controller is configured to, after detecting that a current flowing through the conversion circuit exceeds a predetermined current threshold or that a charge voltage of the low-voltage storage battery exceeds a predetermined voltage threshold, execute a failure determination of the DC-DC converter after instructing the conversion circuit to stop a voltage conversion operation, causing the input switch to switch to the disconnected state, and instructing the output switch to switch to the disconnected state.

Abstract: A polyphase power-supply device includes first to N-th DC-DC converters connected in parallel to each other between an input terminal and an output terminal and a switching controller configured to perform interleave control on the first to N-th DC-DC converters by supplying first to N-th pulse width modulation (PWM) signals to the first to N-th DC-DC converters, respectively, where N is any integer equal to or greater than two. A switching frequency of the first PWM signal is changed at a change time point at which a cycle of the first PWM signal starts. A length of a cycle of the k-th PWM signal firstly appearing after the change time point is shorter than lengths of subsequent cycles of the k-th PWM signal appearing the first cycle of the k-th PWM signal. This polyphase power-supply device has high reliability.

Abstract: A polyphase power-supply device includes first to N-th DC-DC converters connected in parallel to each other between an input terminal and an output terminal and a switching controller configured to perform interleave control on the first to N-th DC-DC converters by supplying first to N-th pulse width modulation (PWM) signals to the first to N-th DC-DC converters, respectively, where N is any integer equal to or greater than two. A switching frequency of the first PWM signal is changed at a change time point at which a cycle of the first PWM signal starts. A length of a cycle of the k-th PWM signal firstly appearing after the change time point is shorter than lengths of subsequent cycles of the k-th PWM signal appearing the first cycle of the k-th PWM signal. This polyphase power-supply device has high reliability.

Abstract: An in-vehicle power supply system includes a high-voltage direct-current (DC) power supply, a low-voltage storage battery, a DC-DC converter, and a controller. The DC-DC converter includes a conversion circuit including a high-voltage terminal and a low-voltage terminal, an input switch connected between the high-voltage DC power supply and the high-voltage terminal, and an output switch connected between the low-voltage terminal and the low-voltage storage battery. The controller is configured to, after detecting that a current flowing through the conversion circuit exceeds a predetermined current threshold or that a charge voltage of the low-voltage storage battery exceeds a predetermined voltage threshold, execute a failure determination of the DC-DC converter after instructing the conversion circuit to stop a voltage conversion operation, causing the input switch to switch to the disconnected state, and instructing the output switch to switch to the disconnected state.