Preface
The gate resistance (Rg) directly affects the switching characteristics of IGBT and needs to be reasonably selected to balance the switching speed and system stability. Reducing Rg can lower switching losses, but it may cause oscillations, high di/dt and dv/dt issues; increasing Rg can alleviate these problems, but it will increase switching delay, heat dissipation burden and the risk of false conduction.
Characteristic relationship:
Under a specific driving voltage, the relationship between the gate resistance and the dynamic characteristics of the IGBT is simply expressed in Table 1:
Gate Resistor Characterization Requirements:
1) Low or non-inductive resistance;
2) High precision;
3) Small temperature coefficient;4) Stable mechanical characteristics in different environments.
Resistor power requirements:
P(turn on)= P(turn off )
The power of the selected gate resistor must be more than 2 times of the calculated total power consumption. The power of the selected gate resistor must be more than 2 times the total calculated power consumption.
- P(turn on): the power dissipated in Rg during turn-on;
- P(turn off): the power dissipated in Rg when turning off;
- P(driving): the total power dissipated in Rg; +Vge: forward bias supply voltage;
- Vge: reverse bias supply voltage; -Vge: reverse bias supply voltage;
- F: switching frequency;
- Qg: Charging charge from 0V to +Vge;
- Cies: IGBT input capacitance;
Other considerations:
- Drive leads should be as short as possible, and if longer leads are necessary, they should be twisted together.
- Drive leads and IGBT main circuit wiring should be as far away as possible, and the two are recommended to be orthogonal when wiring.
- Do not tie them together with other signal leads.
- The clamping diode and pull-down resistor should be as close as possible to the gate of the IGBT.
- Ensure that the ESD protection measures are effective when the gate is open.