Abstract: A circuit for detecting excessive current flow through a switching element derives an electrical quantity relating to a condition of the switching element and correlated with the current level, and compares the magnitude of that electrical condition quantity with a threshold value corresponding to the maximum allowable level of current. A temperature detection signal indicative of the switching element temperature is converted to a compensation signal having a temperature characteristic which is modified from that of the temperature detection signal, and which is utilized to compensate the magnitude comparison operation against inaccuracy caused by a temperature dependency of the electrical condition quantity.

Abstract: The control device for controlling a power conversion circuit having voltage-controlled type switching elements includes a control unit generating conduction control signals for controlling conduction states of the switching elements in accordance with an external command, and a driver circuit applying a conduction control terminal of each of the switching elements with one of a first voltage having a value to turn on the switching elements and a second voltage having a value to turn off the switching elements in accordance with the conduction control signals. The driver circuit is configured to change at least one of the value of the first voltage and the value of the second voltage so that a voltage difference between the first and second voltages becomes large when the power loss of the switching elements is estimated to exceed a certain value.

Abstract: A circuit for detecting excessive current flow through a switching element derives an electrical quantity relating to a condition of the switching element and correlated with the current level, and compares the magnitude of that electrical condition quantity with a threshold value corresponding to the maximum allowable level of current. A temperature detection signal indicative of the switching element temperature is converted to a compensation signal having a temperature characteristic which is modified from that of the temperature detection signal, and which is utilized to compensate the magnitude comparison operation against inaccuracy caused by a temperature dependency of the electrical condition quantity.

Abstract: A gate driving circuit has a variable current carrying path that switches a current carrying path among a driving target device, a DC power source and a reactor to operate in plural operation modes including at least a hold mode, a preparation mode, and an execution mode. The variable current carrying path includes a backflow path for causing a reactor current flowing through the reactor to flow back to the DC power source when a gate voltage of the driving target device deviates from a preset allowable voltage range. A drive control part sets the operation mode of the variable current carrying path to the hold mode and holds the ON state or the OFF state of the driving target device, and further switches the operation mode in sequence of the preparation mode and the execution mode, and realizes turn-on or turn-off of the driving target device.

Abstract: A DC voltage source, a switch, and an inductor are connected together in series. The inductor is also connected together with a switch, a piezoelectric element in series. Moreover, the switches are connected in parallel with capacitors. By the control circuit, a state in which either of the switches is turned on is repeated through a state in which both of the switches are turned off. Furthermore, in a state in which both switches are turned off, after turning the switch off to enter the state concerned, when the voltage across both terminals of the switch that will be turned on is reduced by the resonance of a resonance circuit composed of the capacitors and the inductor, the switch concerned is turned on.

Abstract: The control device for controlling a power conversion circuit having voltage-controlled type switching elements includes a control unit generating conduction control signals for controlling conduction states of the switching elements in accordance with an external command, and a driver circuit applying a conduction control terminal of each of the switching elements with one of a first voltage having a value to turn on the switching elements and a second voltage having a value to turn off the switching elements in accordance with the conduction control signals. The driver circuit is configured to change at least one of the value of the first voltage and the value of the second voltage so that a voltage difference between the first and second voltages becomes large when the power loss of the switching elements is estimated to exceed a certain value.

Abstract: A gate driving circuit has a variable current carrying path that switches a current carrying path among a driving target device, a DC power source and a reactor to operate in plural operation modes including at least a hold mode, a preparation mode, and an execution mode. The variable current carrying path includes a backflow path for causing a reactor current flowing through the reactor to flow back to the DC power source when a gate voltage of the driving target device deviates from a preset allowable voltage range. A drive control part sets the operation mode of the variable current carrying path to the hold mode and holds the ON state or the OFF state of the driving target device, and further switches the operation mode in sequence of the preparation mode and the execution mode, and realizes turn-on or turn-off of the driving target device.

Abstract: In a gate driving circuit, when a driving target device is turned on, an auxiliary driving element is turned on to form a closed circuit comprising a DC power source, a reactor, an auxiliary driving element and an OFF-driving element, and make reactor current flow in the direction from a power source intermediate point to an output point in advance. Just before the driving target device is turned on, the OFF-driving element is turned off to form a resonance circuit comprising the reactor, the auxiliary driving element and the gate capacitance, and make gate current (reactor current) flow so that the gate capacitance is charged by using resonance phenomenon of the resonance circuit.

Abstract: A DC voltage source, a switch, and an inductor are connected together in series. The inductor is also connected together with a switch, a piezoelectric element in series. Moreover, the switches are connected in parallel with capacitors. By the control circuit, a state in which either of the switches is turned on is repeated through a state in which both of the switches 3, 4 are turned off. Furthermore, in a state in which both switches are turned off, after turning the switch off to enter the state concerned, when the voltage across both terminals of the switch that will be turned on is reduced by the resonance of a resonance circuit composed of the capacitors and the inductor, the switch concerned is turned on.

Abstract: In a gate driving circuit, when a driving target device is turned on, an auxiliary driving element is turned on to form a closed circuit comprising a DC power source, a reactor, an auxiliary driving element and an OFF-driving element, and make reactor current flow in the direction from a power source intermediate point to an output point in advance. Just before the driving target device is turned on, the OFF-driving element is turned off to form a resonance circuit comprising the reactor, the auxiliary driving element and the gate capacitance, and make gate current (reactor current) flow so that the gate capacitance is charged by using resonance phenomenon of the resonance circuit.