A switching circuit includes: a drive power supply; a first transistor and a second transistor; a drive signal source; and a drive circuit. Each of the first transistor and the second transistor includes: a drain electrode and a source electrode in which a main current flows when a corresponding one of the first transistor and the second transistor is ON; a first source terminal for passing the main current; and a second source terminal. Here, the first source terminal is connected to the source electrode at an impedance lower than an impedance of the second source terminal.

An operation coil drive device includes a drive control unit to perform control to set, for a semiconductor switching element to switch on and off the source voltage applied to an operation coil of a magnetic contactor, a larger ON/OFF time ratio for a circuit-closing control and a smaller ON/OFF time ratio for a holding control, wherein the drive control unit includes: a circuit-closing-control inductance calculation unit to calculate an inductance of the operation coil immediately after a start of the circuit-closing control; a circuit-closing-control resistance value calculation unit to calculate a direct current resistance value of the operation coil based on the calculation result; and a circuit-closing-control switching correction unit to correct the ON/OFF time ratio of the semiconductor switching element for the circuit-closing control based on the calculation result.

An operation coil drive device includes a drive control unit to perform control to set, for a semiconductor switching element to switch on and off the source voltage applied to an operation coil of a magnetic contactor, a larger ON/OFF time ratio for a circuit-closing control and a smaller ON/OFF time ratio for a holding control, wherein the drive control unit includes: a circuit-closing-control inductance calculation unit to calculate an inductance of the operation coil immediately after a start of the circuit-closing control; a circuit-closing-control resistance value calculation unit to calculate a direct current resistance value of the operation coil based on the calculation result; and a circuit-closing-control switching correction unit to correct the ON/OFF time ratio of the semiconductor switching element for the circuit-closing control based on the calculation result.

A switching circuit includes: a drive power supply; a first transistor and a second transistor; a drive signal source; and a drive circuit. Each of the first transistor and the second transistor includes: a drain electrode and a source electrode in which a main current flows when a corresponding one of the first transistor and the second transistor is ON; a first source terminal for passing the main current; and a second source terminal. Here, the first source terminal is connected to the source electrode at an impedance lower than an impedance of the second source terminal.

A switching circuit includes: a drive power supply; a first transistor and a second transistor; a drive signal source; and a drive circuit. Each of the first transistor and the second transistor includes: a drain electrode and a source electrode in which a main current flows when a corresponding one of the first transistor and the second transistor is ON; a first source terminal for passing the main current; and a second source terminal. Here, the first source terminal is connected to the source electrode at an impedance lower than an impedance of the second source terminal.

An electronic device includes a first substrate, a wiring substrate (second substrate) disposed over the first substrate, and an enclosure (case) in which the first substrate and the wiring substrate are accommodated and that has a first side and a second side. A driver component (semiconductor component) is mounted on the wiring substrate. A gate electrode of a first semiconductor component is electrically connected to the driver component via a lead disposed on a side of the first side and a wiring disposed between the driver component and the first side. A gate electrode of a second semiconductor component is electrically connected to the driver component via a lead disposed on a side of the second side and a wiring disposed between the driver component and the second side.

An electronic device includes a first substrate, a wiring substrate (second substrate) disposed over the first substrate, and an enclosure (case) in which the first substrate and the wiring substrate are accommodated and that has a first side and a second side. A driver component (semiconductor component) is mounted on the wiring substrate. A gate electrode of a first semiconductor component is electrically connected to the driver component via a lead disposed on a side of the first side and a wiring disposed between the driver component and the first side. A gate electrode of a second semiconductor component is electrically connected to the driver component via a lead disposed on a side of the second side and a wiring disposed between the driver component and the second side.

A low-side contactor coil drive circuit can include an input line and a first solid state switch having a first switch base, a first switch collector, and a first switch emitter. The first switch collector can be connected to the input line and the first switch emitter is connected to ground. The circuit can include a second solid state switch having a second switch base, a second switch collector, and a second switch emitter. The second switch emitter can be connected to the input line in parallel with the first switch collector. The second switch collector can be connected to the first switch base. The circuit can include a third solid state switch having a third switch gate, a third switch source, and a third switch drain. The third switch drain can be connected to the second switch base.

A voltage conversion device that includes a switching element; an inductor; a drive circuit, wherein, by turning the switching element on/off with the drive circuit with a PWM signal, an inductor current is generated to transform an input voltage and output a transformed voltage to a load; and a controller that is configured to: switch a switching frequency with the drive circuit according to a size of a current output to the load; and change a waveform of the PWM signal when the switching frequency is switched, wherein the controller is configured to change an on-time of the PWM signal, and to turn the switching element on/off.

A voltage conversion device that includes a switching element; an inductor; a drive circuit, wherein, by turning the switching element on/off with the drive circuit with a PWM signal, an inductor current is generated to transform an input voltage and output a transformed voltage to a load; and a controller that is configured to: switch a switching frequency with the drive circuit according to a size of a current output to the load; and change a waveform of the PWM signal when the switching frequency is switched, wherein the controller is configured to change an on-time of the PWM signal, and to turn the switching element on/off.