Intelligent power module（IPM）It is the abbreviation of Intelligent Power Module, which uses power switching device IGBT (insulated gate bipolar transistor), and hasGTR(High power transistor）Highcurrent density, low saturation voltage and high voltage resistance, andMOSFET(Field effect transistor）HighInput impedance, Highswitching frequency And lowDrive powerAdvantages of.IPM integrates logic, control, detection andprotection circuit , easy to use, which not only reduces the volume and development time of the system, but also greatly enhances theSystem reliability, adapting to the development direction of current power devices - modularization, recombination andPower integrated circuit(PIC) has been widely used in the field of power electronics.
IPM consists of high-speed, low-powerIGBTChip and preferred gate driver andprotection circuit As shown in Figure 1.Where IGBT isGTRandMOSFETThe GTR is driven by MOSFET, so IGBT has the advantages of both.
IPM can be divided into four types according to different configurations of internal power circuits: Type H (one IGBT for internal packaging), Type D (two IGBTs for internal packaging), Type C (six IGBTs for internal packaging) and Type R (seven IGBTs for internal packaging).Low power IPM uses multi-layer epoxy insulation system, and medium and high power IPM uses ceramic insulation.
Internal functional mechanism
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IPM built-in drive and protection circuit makes the system hardware circuit simple, reliable, and shortenedsystem developmentTime also improves the self-protection capability under fault.And ordinaryIGBT moduleIn contrast, IPMsystem performance And reliability.
(1) Control voltage undervoltage protection (UV): IPM uses a single+15V power supply, ifSupply voltageBelow 12.5V, and the time exceeds toff=10ms, undervoltage protection occurs, and blocking occursGate poledrive circuit , output fault signal.
(2) Over temperature protection (OT): aTemperature sensor, when IPMTemperature sensorWhen the measured substrate temperature exceeds the temperature value, overtemperature protection occurs, the gate drive circuit is blocked, and fault signals are output.
(3) Overcurrent protection（OC）: If the current flowing through IGBT exceeds the overcurrentAction current, and the time exceeds toff, over-current protection occurs and the gate pole is blockeddrive circuit , output fault signal.To avoid excessive di/dt, most IPMs use two-level shutdown mode.Where, VG is the internal gate poledriving voltage , ISC is the short-circuit current value, IOC is the overcurrent current value,ICbycollectorCurrent, IFO is the fault output current.
(4) Short circuit protection (SC)IGBTCurrent value of exceeds short circuitAction current, the short circuit protection will occur immediately, the gate drive circuit will be blocked, and the fault signal will be output.Like overcurrent protection, most IPMs adopt two-stage shutdown mode to avoid excessive di/dt.To shorten the time between current detection and fault action of overcurrent protectionresponse timeIPM uses real-time current control circuit internally（RTC）The response time is less than 100ns, which effectively suppresses the current and power peak and improves the protection effect.
When the IPM has any fault in UV, OC, OT and SC, its fault outputSignal durationTFO is 1.8ms (SCDurationLonger), the IPM will block the gate drive and turn off the IPM within this time;After the failure output signal duration ends, the IPM automatically resets internally and the gate drive channel is opened.
It can be seen that the fault signal generated by the device itself is non persistent. If the fault source is still not removed after the tFO is completed, the IPM will repeat the process of automatic protection and act repeatedly.Overcurrent, short circuit and overheat protection actions are very bad operating conditions, and their repeated actions should be avoided. Therefore, only the IPM internal protection circuit can not fully realize the device'sSelf protection。To make the system truly safe and reliable, auxiliary peripherals are neededprotection circuit 。
IGBTThe drive design problem ofMOSFETThe following points should be paid attention to during the design: ① IGBT grid withstand voltage is generally about ± 20V, so the output end of the drive circuit should be added to the gridVoltage protection, the common practice is to connect the grid in parallelZener diodeOr resistance.The defect of the former is that it will increase equivalenceInput capacitanceCin，This will affect the switching speed. The disadvantage of the latter is that it will reduceInput impedanceIncrease the driving current, and make a choice when using. ②Although required by IGBTDrive powerVery small, but because MOSFET has input capacitance Cin, the capacitor needs to be charged and discharged during switching, so the output current of the drive circuit should be large enough, which is often ignored by designers.It is assumed that when the drive is turned onrise time If the MOSFET input capacitor Cin is charged linearly within tr, then the driving current is Igt=CinUgs/tr, where tr=2 can be taken.2RChin, R is inputLoop resistance。③For reliable shutdownIGBTTo prevent the phenomenon of holding, add a negative to the gridbias, so it is better to useDual power supply。
IGBT integrated driving circuit
IGBTThere are many discrete components in the separate driving circuit of the, and the discrete circuit with complex structure and perfect protection function is more complex, and its reliability and performance are relatively poor, so most of the practical applications use integrated driving circuits.The EXB series of Fuji Company in JapanIntegrated circuit, FranceThomsonThe company's UA4002 integrated circuits are widely used.
IPM Driver Circuit Design
IPM pairdrive circuit output voltage The requirements are very strict, specifically: ① The driving voltage range is 15V ± 10%?Fumigation voltage lower than 13.5V will occurUnder voltage protection, voltage higher than 16.5V may be damagedInternal components。②The drive voltages are isolated from each other to avoid groundingnoise interference 。③The insulation voltage of the drive power supply shall be at least twice of the IPM pole to pole reverse withstand voltage value (2Vces). ④The driving current can refer to the 20kHz driving current requirements given by the deviceswitching frequency Correct it. ⑤Drive circuit output terminalFilter capacitorCan't be too big, because whenParasitic capacitanceWhen it exceeds 100pF, noise interference will be possibleFalse triggerInternal drive circuit.
