Measurement method and measurement device

A measurement method for measuring a reverse recovery charge of a semiconductor element including a diode component, comprising:

• using a measurement device in which a direct-current power supply, a variable inductance, and a switching element are connected in series with a semiconductor element including a diode component, and, at a plurality of conditions in which a parasitic inductance of the measurement device is made mutually different by setting the variable inductance and a current change rate of a current flowing through the semiconductor element is set to an identical value by adjusting a value of a resistance connected to a control electrode of the switching element, acquiring, at each condition, a drain-source current waveform of the semiconductor element and calculating, as a reverse recovery charge, a time integral of a reverse recovery current over an entire duration of current oscillations;
• based on the parasitic inductance and measured values of the reverse recovery charge, determining, at the identical current change rate, a first relationship between the parasitic inductance and the measured values of the reverse recovery charge;
• determining a second relationship between a current change rate and a surge voltage at the plurality of conditions of the measurement device having mutually-different parasitic inductances;
• setting a saturated current change rate as the current change rate corresponding to a reference potential in the second relationship, the reference potential being set between an anode potential and a cathode potential of a power supply;
• determining a third relationship between the saturated current change rate and the parasitic inductance;
• setting a saturated parasitic inductance by determining the parasitic inductance corresponding to an arbitrary value of the saturated current change rate based on the third relationship;
• and
• setting the true value as the charge corresponding to the saturated parasitic inductance based on the first relationship.

A measurement method for measuring a reverse recovery charge of a semiconductor element including a diode component, comprising:

• using a measurement device in which a direct-current power supply, a variable inductance, and a switching element are connected in series with a semiconductor element including a diode component, and, at a plurality of conditions in which a parasitic inductance of the measurement device is made mutually different by setting the variable inductance and a current change rate of a current flowing through the semiconductor element is set to an identical value by adjusting a value of a resistance connected to a control electrode of the switching element, acquiring, at each condition, a drain-source current waveform of the semiconductor element and calculating, as a reverse recovery charge, a time integral of a reverse recovery current over an entire duration of current oscillations;
• based on the parasitic inductance and measured values of the reverse recovery charge, determining, at the identical current change rate, a first relationship between the parasitic inductance and the measured values of the reverse recovery charge;
• determining a second relationship and a third relationship at the plurality of conditions of the measurement device having mutually-different parasitic inductances, the second relationship being between a current change rate and a charge transferred in an initial half period of a current oscillation, the third relationship being between the current change rate and a charge transferred in an entire duration of the current oscillation;
• and
• setting a saturated current change rate as the current change rate at an intersection of the second and third relationships in a graph illustrating a relationship between the current change rate and the charge, and setting the true value as a charge at the intersection.