An electromagnetic valve drive device includes: a state detection unit configured to detect an on-state or an off-state of a first switch and a second switch forming a boosting circuit; a boosting control unit configured to control a boosting operation, by performing a synchronous rectification control on switching of the first switch and the second switch, depending on the state of the first switch or the second switch detected by the state detection unit; and a drive circuit configured to drive an electromagnetic valve by supplying a voltage boosted by the boosting operation to the electromagnetic valve.

A circuit configuration for inductively heating at least one fuel injection valve includes a power-transistor full-bridge circuit which acts as a driver for operating a series resonant circuit at an alternating voltage at or near the resonant frequency. The series resonant circuit includes a heater coil on which the resulting voltage can be significantly higher than the supply voltage. The power that can be fed to the heater coil can be modified or controlled by changing the frequency or the duty factor of the control signals of the switching elements of the bridge circuit. A fuel injection valve and methods for operating the circuit configuration are also provided.

A booster circuit installed in a fuel injection device of an internal combustion engine, wherein malfunctions and characteristic changes of the booster circuit are detected, among which the detection distinguishes between decreases in capacity caused by deterioration or broken wires in a booster capacitor, and failures of a current monitor circuit, coil, externally connected fuel injection valve, and other components. The range of decrease in boost voltage when the fuel injection valve is opened is monitored, as is the range of increase per switch performed in order to restore the boost voltage. This makes it possible to detect malfunctions and characteristic changes of the booster circuit.

To protect a switching element to be used in a boost circuit for an in-cylinder injection type internal combustion engine or the like from damage caused by overheating without using a temperature detection element.

In a control circuit that switches a switching element between a conductive state and a non-conductive state, the switching element is controlled or a temperature of the switching element is estimated based on a potential difference between an input terminal and an output terminal of the switching element and a voltage applied to a control terminal of the switching element in the conductive state.

In voltage boosting circuit for performing rapid power supply to a plurality of electromagnetic coils that drive fuel-injection electromagnetic valves, an overcurrent from vehicle battery is suppressed, and continuous noise is prevented from being produced. Each of rapid-power-supply voltage boosting capacitors that are connected in parallel with each other is charged from corresponding one of a pair of induction devices, which are asynchronously on/off-magnetized by first and second voltage boosting control circuits, by way of corresponding one of charging diodes in a pair; when addition value of exciting currents for induction devices in a pair continuously exceeds predetermined value, driving modes of one of and the other one of voltage boosting control circuits are set to large-current low-frequency mode and to small-current high-frequency mode, respectively, so that on/off timing of exciting current becomes irregular even when respective inductances values of induction devices in a pair are close to each other.

According to the present invention, by providing control whereby a rising slope or a descending slope of step-up current flowing to a step-up coil is detected, and corrections are made to step-up switching control, the step-up upper and lower limit current values of the step-up circuit can be controlled within intended current threshold values regardless of constant modifications or change in characteristics due to fluctuations of the battery power supply voltage or degradation of step-up circuit elements over time; heat emission by step-up circuit elements can be kept to a minimum; and the step-up recovery time can be adjusted to a constant value regardless of the slope of the step-up current.

A control device for a fuel injection system includes a CPU which generates a drive signal for instructing execution of compression by a fuel pump; a fuel pump drive circuit which controls application of electric power to a solenoid of the fuel pump based on the drive signal; a boost circuit provided with a capacitor for storing electric power to be used for driving an injector; a charging circuit which leads a current generated when the application of electric power to the solenoid is stopped to the capacitor; and an excess electric power consumption circuit which consumes excess electric power of the capacitor. While fuel injection from the injector is stopped, the CPU counts the number of times the fuel pump is driven and turns off the drive signal so as to stop driving the fuel pump as soon as the drive count has exceeded a predetermined count value.

In voltage boosting circuit for performing rapid power supply to a plurality of electromagnetic coils that drive fuel-injection electromagnetic valves, an overcurrent from vehicle battery is suppressed, and continuous noise is prevented from being produced. Each of rapid-power-supply voltage boosting capacitors that are connected in parallel with each other is charged from corresponding one of a pair of induction devices, which are asynchronously on/off-magnetized by first and second voltage boosting control circuits, by way of corresponding one of charging diodes in a pair; when addition value of exciting currents for induction devices in a pair continuously exceeds predetermined value, driving modes of one of and the other one of voltage boosting control circuits are set to large-current low-frequency mode and to small-current high-frequency mode, respectively, so that on/off timing of exciting current becomes irregular even when respective inductances values of induction devices in a pair are close to each other.

A device for charging and discharging a capacitive actuator connectable to an output connection has a first capacitor disposed between an input connection and a reference potential. The device has a series connection composed of a first and a second power switching element which is connected in parallel with the first capacitor. The device additionally has a first coil with a first connection connected to the center tap of the series connection, wherein the second connection of the first coil is connected to the reference potential via a third power switching element and to the output connection via a fourth power switching element. Wherein the power switching elements have diodes connected in parallel therewith such that they are reverse-biased from the input connection or the output connection to the reference potential. Wherein a connection of the fourth power switching element is connected to the input connection via a diode.

A booster circuit installed in a fuel injection device of an internal combustion engine, wherein malfunctions and characteristic changes of the booster circuit are detected, among which the detection distinguishes between decreases in capacity caused by deterioration or broken wires in a booster capacitor, and failures of a current monitor circuit, coil, externally connected fuel injection valve, and other components. The range of decrease in boost voltage when the fuel injection valve is opened is monitored, as is the range of increase per switch performed in order to restore the boost voltage. This makes it possible to detect malfunctions and characteristic changes of the booster circuit.