Treatment of transient proble照雨ms in the power 理秒stage of integrated circuit

1.The product range of driving IC

IR company provides users with a var相照iety of products from simpl坐年e-phase to three-phase bridge driver IC們化. All types use金票 high integrated elec亮呢trical level conversion techn訊劇ology, simplifies the logic circuits 得問controlling of the power MO小紙S tube. The new product has 她到been extended to have the ability to 音內dirve 1200V power device.

As a cutting edge technolo輛金gy ,it can switch more current at a hig有地h speed. The adve們從rse effects of stray 好對parameters become more an短拿d more evident an知冷d attentive. The main purpos刀城e of this paper is to find the員科ir roots, quantitize the 做子immunity ability of problems possiblly 黃理caused and final山舞ly obtain the greatest 醫地security zone.

2. Stray elements in bridge 生火circuit

Figure 1 shows a白科 typical IC driving bridge 姐歌circuit composed of 制校two MOSFET . In the power circuit, t說藍he device internal connection很大s ,wireless inductance of 鐘離uniform compositi電議on pins and the PCB line are repres事小ented by LS1.2 and LD1.藍著2.

In addition, the stray parame木南ter in the gate circ多對uit should also be considered when 開內wiring.Here we wi光線ll mainly discuss the bridge circui船明t maximum current and the occuren好高ce of di/dt itself. In switchin就習g ,rapidly chaning curren離吧t bridge circuit will兒船 provduce a voltage tr劇去ansients in the st這河ray inductance. The transie區會ntion is coupled with o有光ther circuits,causing noise probl刀聽em and increasing the switching loss, e村費ven in the worst condition damages IC這小.

3.The reason of undershoot

Becuase the problem is caused by區呢 the stray inductan窗木ce, with the devices switching , 坐大as for driving IC ,the main 愛這problem is the VS may undershoot to re畫呢rence ground level. In民分 contrast, forward under靜鐘shoot generally does not cause pr河車oblem. IR company has ver街行ified the IVIC technolog關黑y has the advantage of high voltag愛兵e resistance abillity. 

The bridge circui司資ts inductive load is關懂 perceptual,high en國多d switches can cause the鐵船 fact that sudden load current is conve有熱rted to the low end freewheeling 火木diode .Becuase the di費門odes opening is機慢 delayed , forward voltage drops a外數nd stray inductance LS1 and L舞行D1 makes VS undershoot to th做員e reference ground leve了訊l.As shown in figure 通志1, during the dead time, if腦外 the load circuit生街 can not be fully restored,火長 when the low end devices is hard turne子志d on, VS negative over sho很煙ot or oscillatio影劇n occur.

4. VS undershoots effect 拿妹on driving IC

IR driver IC gurantees tha匠分t compared with COM, V短空S has at least 5V undershoo問內t ability. If the negativ年光e overshoot is above th問答at level, high output 低為will be temporarily locked in微空 its current state.

If VS is kept to 在外an absolute maximum, IC will not be da通你maged. When the undershoot e歌費xceeds 5V, the high end outp白道ut will not respond to the input 器亮control signal. The mode件月l shold be paid attention to畫媽 . But in most applications, t自不hey can be ignored ,because with th兒鄉e switching events, hi可鄉gh end usually do not require the quic為白k changing state.

5. How to avoid locking

Appendix 1 shows the driver ICs 自刀typical internal parasi著花tic diode structure. For any CMO來從S device, the diodes forward condu頻拿ction or the reverse break海明down will cause the controlla那花ble thyristor tube to lock. The locki技明ngs ultimate con算用sequences can be predicate為下d . There may be te快看mporarily the wrong job to comple答農te destruction device.

Driver IC may be indirectly damage市光d by initial over stress reaction那爸 .For example, think that lock will 資員make two outputs hi上數gh and the bridge arm straight,wh亮友ich results in the damage of t請媽he device and the科子n the IC.This failure mode may 黃歌be the main reason of the damage of 高拿the driving IC and power de暗討vice.