IGBT gate current slope measure to estimate miller plateau
AssigneeNXP USA, Inc.
InventorThierry Sicard
Life of this patent
Estimating the term…
Abstract
A method and apparatus are provided for controlling a drive terminal of a power transistor by applying a turn-off voltage to the drive terminal at a turn-off time, measuring a gate current at the drive terminal to detect a predetermined gate current slope, determining a first time increment after the turn-off time when the predetermined gate current slope is detected, determining a second time increment which is proportional to the first time increment and which expires within a Miller plateau for the power transistor, and lowering the gate current at the drive terminal to a predetermined current level upon expiration of the second time increment in order to reduce overvoltages at the power transistor.
Claims15
A method for controlling a drive terminal of a power transistor, comprising:
- applying a turn-off voltage to the drive terminal at a turn-off time;
- measuring a gate current at the drive terminal to detect a predetermined gate current slope;
- determining a first time increment after the turn-off time when the predetermined gate current slope is detected;
- determining a second time increment which is an extension of the first time increment;
- and
- lowering the gate current at the drive terminal to a predetermined current level upon expiration of the second time increment in order to reduce overvoltages at the power transistor.
A gate drive circuit for driving a control terminal of a power transistor, the gate drive circuit comprising:
- a drive terminal for electrical coupling to the control terminal;
- an active current gate drive circuit for applying a voltage control signal to the drive terminal at a turn-off time and for lowering a control terminal current supplied to the drive terminal to a predetermined current level upon expiration of a time increment in order to reduce overvoltages at the power transistor;
- and
- a measurement circuit having a measurement input connected to the drive terminal for measuring a gate current slope at the control terminal, and a measurement output connected to a first input of the active current gate drive circuit for supplying the time increment as a control signal to the active current gate drive circuit to initiate the lowering of the control terminal current to the predetermined current level.
Dependencies are inferred from the claim text.