Abstract
In hard-switching applications, insulated gate bipolar transistors (IGBTs) always suffer from harmful turn-off peak voltages. To switch the devices safely, it is a common practice to use large enough drive resistances in conventional gate drives (CGD). This, however, slows down the turn-off transients and increases switching losses. Many other measures have been proposed in the literature to limit the peak voltage but they cannot apply direct or accurate control, making the voltage margin of IGBT in use still large. In this article, a novel self-regulating peak voltage control (SRPVC) method based on active gate drive (AGD) is proposed. The SRPVC method is the first developed and reported method that can control the peak voltage in a direct and accurate way regardless of commutation conditions. The SRPVC has high simplicity. By applying independent control on turn-off $\text{d}i/\text{d}t$ , the SRPVC can produce desired voltage spikes with small drive resistance under different switching conditions. Hence, the SRPVC can reduce the turn-off delays and losses to the utmost without increasing peak voltages. The control ability, accuracy and switching characteristics improvement with SRPVC are validated experimentally on an Infineon IGBT module FF300R12ME4. The experimental results show that under identical peak voltage, the SRPVC can realize up to 53% turn-off delay and 28% loss reduction under various load currents compared with CGD.
Highlights
Due to the rapid hard switching, insulated gate bipolar transistors (IGBTs) can produce large turn-off peak voltage
The verifications will include the evaluation of drive voltage circuit response speed, the whole error of vPK sensing circuit, the proportional-integral factors tuning, the vPK control with the self-regulating peak voltage control (SRPVC) method under different load currents and the corresponding turn-off characteristics in comparison with conventional gate drives (CGD) method
TURN-OFF CHARACTERISTICS IMPROVEMENT WITH THE SRPVC UNDER ALL LOAD CURRENRTS In Fig. 13(b), as analyzed in Section II, under the SRPVC method, vG in delay and dv/dt stages can be maintained at VEE whatever IL is, helping reduce delays and losses
Summary
Due to the rapid hard switching, IGBT can produce large turn-off peak voltage. The control of the peak voltage, denoted as vPK, is critical for safe operating of converters as high overvoltage is destructive. This article is intended to develop a method for the accurate control of vPK together with optimizations of other switching characteristics, e.g., turn-off delays and losses. Miyazaki et al propose a novel integrated circuit (IC) driver, which has numerous drive strengths and this IC driver is verified to be able to reduce vPK [7] It relies on massive offline experiments and iterations to optimize the switching behavior. Based on the analysis above, existing drivers are unable to adapt to different switching conditions for target vpk, denoted as Vref These active drivers fail to control vPK with high accuracy. Both the shortcomings weaken the practical value of vPK control To solve this problem, a self-regulating peak voltage control (SRPVC) method is proposed, described and verified in detail in this article and the SRPVC is the first reported method to achieve direct and accurate vPK control. Afterwards, the control accuracy, control effects and switching characteristics improvement with SRPVC are experimentally validated
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