Why do you choose 1200V voltage specification for the working voltage of IGBT in induction cooker?
The fluctuation range of 20 V commercial power is 5%, plus 10% insurance factor, which is 15%. 220 X115%=253V, and 265V AC is generally used. After rectification and filtering, the DC voltage is the formula diagram × 265= 374V。
In induction cooker, the load of IGBT is the coil at the bottom of the pot, which is an inductor. When the IGBT is turned off, an induced voltage will be generated across the coil, which is equal to and superimposed on the power supply voltage. At this time, the withstand voltage of IGBT is 374× 2=748V。
Although the body diode is in IGBT； With the freewheeling effect, the induced voltage will be consumed soon, but it will take time, although this time is very short. Considering the abnormal situation of inductance loop plus 20% insurance coefficient, it is 748× (10 20%)=898V.That is, 809% of VCES is 898V. Then, the VCES value that should be selected is 898÷ 80%=1123V, so it is natural to choose the voltage specification of 1200V.
The above is a single-tube switch. If it is a half-bridge or full-bridge circuit, the IGBT generally only bears half of the peak voltage, so the IGBT with 600V voltage specification can be selected. However, considering that the failure of one bridge arm (one IGBT in half bridge or full bridge is one arm of the bridge) may cause the other bridge arm to bear all the peak voltage, the voltage specification has little influence on the on-off voltage drop of IGBT, and if the cost requirement is not high, it is safer to choose 1200V voltage specification. If VMOS is adopted, the 600V voltage specification will definitely be selected.
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