# Emerging Technologies for Advanced Power Electronics and Machine Design in Electric Drives
## 4 Integration of Power Electronics and Electric Machines
### Trends in Integration of the Power Stage  
The components of the power stage range from individual half-bridge modules with IGBTs/MOSFETs to three-phase half-bridge modules and complete inverter modules, comprising a three-phase rectifier, a brake chopper, and a three-phase inverter. Further progress can be seen in the integration of existing power switch technologies, which are integrated into so-called smart power modules. These often contain both the power stage and the gate driver circuits in the same housing [162]. In the case of low-voltage applications, such modules can contain not only the power stage and gate driver circuits, but also all the necessary sensors, control algorithms, and even a microcontroller [163; 164]. Developers are working intensively on optimizing the layout of power components and the associated increase in power density [158]. To optimize the layout, designs with so-called \"sandwich\" or \"tower\" structures [165; 166] are becoming increasingly common due to the low height and the more optimal design of high-current loops (amplitude and slew rate) [167; 168]. In addition to the use of ordinary PCB materials, such as FR4, power stages are often designed on PCBs made of insulated metal substrate (IMS), which enables effective heat dissipation to the aluminium or copper core, and to the converter's housing. This allows for a more compact power stage design with the power switching components closer together [165]. Spatially related characteristics of the PCB, such as resistance, inductance, and capacitance, were less relevant in the past, but are becoming very important in the latest designs of power converters, mainly due to higher switching frequencies, higher voltage slopes (\(dv/dt\)), and higher current slopes (\(di/dt\)) [165; 169; 170]:  
* the resistance of the connections on the PCB, which is becoming comparable to the drain-source on resistance of MOSFETs (e.g., \(R_{DS,on}=2\) m\(\Omega\)) and the equivalent series resistance (\(ESR\)) of capacitors, which leads to non-negligible heat sources; unintentional narrowing of connections can also lead to local overheating;
* the inductance of power switch connections is becoming comparable to the parasitic inductance values of the power switch, which are determined by the size and the form of the power switch housing (e.g., \(L_{d}=1\) nH-3 nH); not taking these values into account can lead to an inadequate estimation of switching losses and overvoltages, as both are directly related to the slew rate of the switched current;
* the capacitance, formed by the large-area connections of the power stage circuit on the IMS PCB with a thin dielectric layer (e.g., \(e_{r}=9\)) to the heat sink, which normally has the same voltage potential as the housing of the electric drive; connections, where the voltage potential changes with a large gradient (\(dv/dt\)) are problematic, as this can lead to capacitive currents that increase the electromagnetic emissions of the device;  
Figure 14: A simplified three-dimensional representation of the concept of integrating power electronics and the electric machine, in which the designers strive to place the power electronics converter closer to the electric machine to make the electric drive as compact as possible. the same capacitance is in some cases being added to the drain-source capacitance (\(C_{DS}\)) of the MOSFET, which further increases the switching losses;
* the mutual inductance between the power and signal (measurement, control) circuit, which can result in incorrectly acquired measurement signals, e.g., in current measurement, position detection with Hall sensors, etc. In power electronics applications today, components are still placed on the PCB at distances less than 10 times the distance of the electromagnetic (EM) wave. Therefore, circuit analysis can usually be simplified by introducing concentrated (lumped) impedance parameter matrices.