Gate driving circuit and switching power supply apparatus

A gate driving circuit that drives a gate of a main switching device, the gate driving circuit comprising:

• a first resistor that is connected between a first potential and the gate of the main switching device;
• a second resistor that is connected between a second potential being lower than the first potential and the gate of the main switching device;
• a first switching device that is connected in series with the first resistor between the first potential and the gate of the main switching device;
• a second switching device that is connected in series with the second resistor between the second potential and the gate of the main switching device;
• a detecting section that detects a magnitude of measurement target current including current that flows through the main switching device during a period during which the main switching device is turned on;
• and
• a control circuit that changes at least one resistance value of a resistance value of the first resistor and a resistance value of the second resistor according to the detected magnitude of the measurement target current, wherein
• the control circuit sets the resistance value of the second resistor to be larger when the detected magnitude of the measurement target current is a first magnitude than when the detected magnitude of the measurement target current is a second magnitude that is smaller than the first magnitude, and
• the control circuit sets the resistance value of the second resistor during a current ON period according to the magnitude of the measurement target current measured during a previous ON period.

A gate driving circuit that drives a gate of a main switching device, the gate driving circuit comprising:

• a first resistor that is connected between a first potential and the gate of the main switching device;
• a second resistor that is connected between a second potential being lower than the first potential and the gate of the main switching device;
• a first switching device that is connected in series with the first resistor between the first potential and the gate of the main switching device;
• a second switching device that is connected in series with the second resistor between the second potential and the gate of the main switching device;
• a detecting section that detects a magnitude of opposite measurement target current including current that flows from a negative-side main terminal side toward a positive-side main terminal side of an opposite switching device connected in series with the main switching device during a period during which the main switching device is turned off;
• and
• a control circuit that changes a resistance value of the first resistor according to the magnitude of the opposite measurement target current.

A gate driving circuit that drives a gate of a main switching device, the gate driving circuit comprising:

• a first resistor that is connected between a first potential and the gate of the main switching device;
• a second resistor that is connected between a second potential being lower than the first potential and the gate of the main switching device;
• a first switching device that is connected in series with the first resistor between the first potential and the gate of the main switching device;
• a second switching device that is connected in series with the second resistor between the second potential and the gate of the main switching device;
• a detecting section that detects a magnitude of measurement target current including current that flows through the main switching device during a period during which the main switching device is turned on;
• and
• a control circuit that changes at least one resistance value of a resistance value of the first resistor and a resistance value of the second resistor according to the detected magnitude of the measurement target current, wherein
• the detecting section samples a magnitude of the measurement target current at a predetermined timing during the period during which the main switching device is turned on, the predetermined timing being set after a lapse of a certain time period from a falling of a control signal to the main switching device.