The new generation of ignition system IGBTs is tailored to the coils of the spark plug system and is rapidly becoming the mainstream ignition topology. Advances in geometry and doping profiles can miniaturize die and package sizes without sacrificing the most important latching resistance and robustness of avalanche energy capacity. This article refers to the address: http:// Today, IGBT products have high value protection and adaptation features such as active clamping, ESD protection, logic level gate thresholds and gate resistor networks. In the medium term, additional functions can be integrated into the IGBT chip or implemented as a separate controller chip in a multi-chip concept that includes over temperature detection/shutdown, current detection/limitation, watchdog timer , no spark off and ion detection interface. The single-coil (pen-coil) concept of each cylinder takes full advantage of the proven benefits of driving critical performance and reducing costs: mechatronics and modularity. This is a difficult long-term evolution for early mechanical contact breakers and mechanical high-voltage distribution cap ignition by means of no-distributor transistors, and later dual-spark coils (used to date) to the current plug-on coil solution. process. The "passive coil on the plug" only integrates the coil on the spark plug connector, while the switch and pre-driver (one for each cylinder) are located in a separate box between the engine control module (ECU) or the ECU and the coil. The supplier of each ignition system has different internal regulations for whether or not the switch is allowed to be located within the ECU module. Figure 1: Basic circuit for induction ignition Car ignition principle The "active coil on the plug" contains the coils, pre-drivers and switches on the extended spark plug connector, one for each cylinder. They only require four low-voltage connections to the ECU's pen-shaped coil, so the ignition system has more features that provide extremely high modularity, mechatronics and flexibility, enabling the real “plug-in†that automakers expect. point". This principle produces a voltage equal to LdI/dt on the primary side of the transformer and then becomes the spark voltage of the secondary winding. Figure 1 shows a typical pen coil circuit for a cylinder. As long as the rising edge of the trigger pulse from the ECU exceeds the threshold voltage of the IGBT, the circuit is turned on. The current in the primary coil ramps up according to the following equation: dICC/dt=-Vbat/Lcoilexp(t/(), where (=Rcoil/Lcoil In fact, the range of Lcoil is 1~3mH, and the range of Rcoil is 300~700m (the result will be a primary current ramp up of 5-10A/ms. Under normal working conditions, the coil charging time depends on the application - 1~ 3ms, and the primary current peak range before shutdown is 7-15A. When the IGBT is turned off by the falling edge of the trigger signal, the coil axis is released. The induced voltage (-LdI/dt) in the primary coil forces the IGBT into avalanche conduction. When the counter-attack voltage of the gate-collector active clamp diode is reached (VBRR, 350-450V, which is a safe voltage, below the avalanche breakdown voltage of the CE structure), the IGBT is turned on, and the feedback energy is uniformly and reliably distributed in the IGBT. In the entire active area. At the same time, the required spark voltage (about 40 kV) is generated in the secondary coil, the value of which is determined by the transformer turns ratio (generally 1:100 to 1:150). The basic waveform is shown in Figure 3. Primary current switch selection Bipolar Darlington transistors are still used for primary current switching, although usage has been greatly reduced. IGBTs are used in the design of almost all new ignition systems. The IGBT was invented by Frank Wheatly in the former RCA 19 years ago, combining the advantages of bipolar and split-gate transistors and has significant advantages in the specific voltage/switching speed domain. The Darlington tubes and IGBTs in the ignition application concept are compared in detail in Table 1. Main electrical parameters of ignition IGBT IGBTs are well suited for ignition switches and require a large amount of pulse forward current and avalanche energy capability at low switching speeds. For example, according to fmax = nmax / 120, the pen coil for a four-stroke engine must be ignited at a frequency below 100 Hz. Therefore, at least in today's single-cycle single-single systems, switching speed has little effect on the system. Even in the harsh conditions of up to 64 sparks per cycle, IGBTs can be easily used to improve engine-initiated multi-spark systems. The primary switch primarily requires a low Vceon (Iceon) forward characteristic. In normal operation, the energy is mainly dissipated when the primary coil is charged, and the value is Eon(t)=(Ic(t)Vceon(IC)dt. This energy is related to the effective Rthj-a, the maximum local ambient temperature (currently for the pen shape) For coils, approximately 130 ° C) together determine the average junction temperature. Assuming a small temperature ripple, the value is determined by the heat of the die, and is partly determined by the heat of the Rthj-c and the package label. The second driving force of the low Vceon is the low reciprocating voltage of the cold start of the 12V battery at minus 40 ° C, which will drop to 6V at the lowest. Since the peak voltage of the primary coil can be expressed as Ipeak = (Vbat - Vceon) / Rcoil, the lowest Vceon value is determined. Of course, this can be achieved by a steep rise in the active component area, but it is counterproductive for the low-cost plan that is generally promoted by the automotive industry. ON Semiconductor's new third-generation ignition IGBTs, especially the fourth-generation ignition IGBTs, have improved side feature sizes and vertical doping profiles to compensate for significantly reduced die area. In addition, as Ic increases, Vceon's temperature coefficient is optimized from a negative value to a slightly positive value, improving critical low temperature operation. Another major parameter is the threshold voltage. It must be low enough to fully turn on the output voltage provided by the 5V driver MCU (VOUT drops to 3.7V). On the other hand, the gate oxide must be able to withstand the potential failure modes of the 12V network and gate shorts. A new generation of IGBTs has optimized the transmission characteristics of VGE, reducing the same Ic level by approximately 400mV and ensuring full saturation of logic control signal levels. Main reliability parameter The reliability of the ignition application is of the utmost importance, although due to its inherent redundancy, failure of a pen-shaped coil does not endanger life. Since they are in close contact with the cylinder modules, the environment of the pen coil is very strict: the ambient temperature is up to 140 ° C, the power path is limited, and the vibration is sustained. There are also periodic electrical stresses from positive pulse operation and reverse active clamping. Although the data sheet clearly lists the maximum Tj of 175 ° C, it is well known that specific operating conditions have far exceeded this limit. The unspecified short-term temperature offset is as high as 250 ° C, and the temperature shift that can occur during the life of an ignition IGBT is greater. However, the field failure rate must be kept within a few ppm. Robustness can be specified by several SOA (Safe Operating Area) ratings, determined by different parameters in a complex, interactive manner: P-tub doping profile, MOSFET geometry, carriers in the N layer Life expectancy, hfe of NPN/PNP structure, etc., are numerous. The forward-biased SOA is limited by the high current-induced failure mode, where excessive main carriers in the P-tub bias on the NPN structure can cause latch-up of the "parasitic" NPNP thyristor, which can be designed This effect is avoided, but it is still possible to be caused by point defects in the local area. The fundamental way to eliminate this effect is to eliminate defect density in wafer production through continuous improvement projects. Pulse testing at the final test with a continuous current well above the rated value ensures quality. The reverse-biased SOA is limited by the continuity of the N-layer electric field. When switching to the reverse condition, the MOSFET electron current is quickly turned off, so that the N layer is filled with a small number of children, thereby effectively reducing the possibility of avalanche breakdown voltage. Another SOA that is common in ignition applications is the UIS (self-clamping inductive switch). An open secondary (such as an open spark plug connection) will reflect 100% of the secondary energy (minus the coil loss) back to the IGBT. The data sheet specifies "single pulse collector to emitter avalanche energy". ON Semiconductor can guarantee a maximum energy of 500mJ/300mJ at a startup junction temperature of 25/150°C depending on the chip size. The typical value is at least twice as large. Even the smallest die size maintains a UIS energy of 200mJ over all rated temperature ranges up to TJ = 175°C. At present, the actual requirement of the pen coil is 100 to 150 mJ. Figure 5 shows the UIS function of the third-generation IGBT, which has a more gradual temperature dependence and can be obtained through careful optimization and precision design of wafer fabrication parameters. In order to ensure quality, in the final test, each part needs to perform 2 UIS tests with a peak current of 26A to eliminate any potentially damaged parts. And record the fault in the test as reliability monitoring. Robustness also means bearing ESD events that occur primarily in front of the board's pipeline. ESD damage can occur immediately, resulting in a large amount of detectable gate leakage. But more dangerous is the potential damage to the gate dielectric caused by ESD, which can cause field failures at lower overvoltage levels. With gate-to-emitter back-to-back polysilicon, 8kV/800V ESD protection for human/machine models is guaranteed. Enhanced trouble-free operation provides an integrated VGE pull-down resistor to prevent the IGBT from accidentally opening without a control signal connection. The resistors can be customized to protect external components. It is possible to choose to integrate a series gate resistor to limit the occurrence of excessive dVCE/dt, but in some applications it may cause transient current and UIS failure. Moreover, this integrated Rg avoids the negative effects of non-optimal pre-drive designs, providing a low impedance path from gate to ground. Rg ensures that the IGBT can be safely turned on and off under clamping conditions. Development trend of ignition IGBT Plugging the coil will become the mainstream of recent development. High-performance systems turn to miniaturized coils with a turns ratio of around 1:100 and require higher primary currents (up to 18A) and higher clamping voltages (around 400V) to provide high spark energy for fuel-air mixtures . The third-generation device, the NGX19N40, meets these applications with a continuous current of 19A and a clamping voltage rated at 405V. It is available in both TO-220 and D2PAK packages and has a 0.9K/W steady state RTD junction. Recently, the fourth generation (NGX820X series) has been further improved, and the IGBTs in the DPAK package can achieve the required functions and robustness, thus promoting a new degree of freedom in assembly technology while reducing board area (up to 60%) and cost. . The trend of medium-term development has not yet taken shape. For different ignition systems, the difference is great. The common feature is the enhancement of the function "intelligence". But integrating any additional circuitry in the IGBT chip must be compatible with existing components and will not change its optimized IGBT structure: a large number of N-channel FETs and N-layers of IGBTs (in source and ground proximity environments, the only possible The circuit), the diode and the resistor (there are different page impedances and TC's P+ and N+) share the body. Features that can be easily integrated include temperature sensing with two back-to-back diodes that provide the MCU with a voltage drop proportional to the die temperature. Current sensing with the same principle as PowerFET: The precise geometric ratio specifies a small mirror current (0.3 to 1% of the main current) that can be detected almost indefinitely by an integrated sense resistor and then transmitted to the MCU. The disadvantage of these two detection functions is that they require more connections and cannot use the heavy load of a high-capacity, cost-effective 3-terminal power package. It is very challenging or impossible to integrate more complex functions. Here, the features we discuss include over temperature shutdown, overcurrent detection/flag/limitation, optional clamping voltage, dwell time guard, ramp-up shutdown in fault mode, and future ignition soft-on by 42V PowerNet. Some requirements are contradictory, such as hard OTSD and ramp up closure. And it is clear that the application of each type of smart IGBT is limited, thus losing economies of scale. In summary, the best solution is to use an optimized, non-smart IGBT and a linear bipolar or LinCMOS intelligent pre-driver as an interface between the MCU and the IGBT to provide resident protection and control features. Cummins Diesel Generator,Cummins Diesel Generator Set,350Kw Cummins Diesel Generator,Cummins Diesel Generator 1200Kw Jiangsu Lingyu Generator CO.,LTD , https://www.lygenset.com