; n# q" S+ v6 _4 I2 sStandard: IEC60950, 2nd Clause: 4.3.21 Sheet n. P384 . ?7 A" x9 f0 u0 u( V% MPage 1(1) ! Y7 m; ]4 y+ a9 U0 ?. ~1 i6 FSubject: Lithium Cell Protection Key words: * ~* B9 X' U- m5 V \-Lithium Cell 3 R" R. t" p" Y-Clearances % |3 O5 g9 j. H0 g$ w8 S6 N( ^( W. h- failure mode 3 h4 D1 D3 C( J+ k; C5 uProvisional Decision taken by ETF27 Y6 |8 I1 M1 G; r4 G
and to be approved by CTL at its 3 [3 c0 K: h0 L( z8 X0 {4 d38th meeting, in Toronto 0 w+ d$ E# e) `, [Question:1 s( f3 a4 J* Q& S8 i
Clause 4.3.21 requires that two levels of protection are required to prevent forced or reversed charge ' y$ z" I$ b9 q @# lor forced discharge if this would result in a hazard. Conventionally a combination of resistor, diode/ ^# I) K& z' k; g: d+ d$ x
or ic has been considered suitable and is for the series current path. However, a new consideration4 r5 ^" [; ?$ e! J
has been raised in respect of adjacent tracks, separated by no more than operational insulation, which,. C4 f @' L; L( s. K) n
under s/c conditions will bypass the protective series components and provide charging current for & `8 \6 [. a+ y8 Q- E' Beither chargeable or non-rechargeable batteries. Does this mean that there is therefore a requirement, g& v9 i2 B: D2 w, B2 r
for Reinforced separation? 1 w: L9 G3 p8 o0 `# E6 _, _% F: m7 UIf that is the case, then the controlling factor is the clearance of 0.8mm in Table 5 (circuits not subject8 {* a4 L- g8 M. u) C5 ^8 S
to transient over voltage). This is based on the fact that creepage cannot be less than clearance and + Y% g: g' {; g! v. h, l$ |% K0 m6 L: _' ycreepage can be calculated to be, for example at +5V, 0.4mm (based on rounding up 0.12mm to8 m; ?6 @; }. g& b# P( V& e& p
0.2mm for Basic and doubling for reinforced.4 G9 ]8 d% x- Z M
Decision:5 y3 q8 k9 P9 R: @6 T" c) y- {
Operational insulation is suitable taking into account 5.4.4 because there is no risk of electric shock.+ G. z6 G& x8 Q* ?# o
(see 1.2.9.1)% d+ j2 ~) r: c( P; `6 d
Care should be taken by determining clearance and creepage distances which column of the table has9 g6 T! [1 u9 K0 B+ g; J4 U
to be used.(Transients have to be taken into account) + _( U2 C k9 j( J; O8 C3 p 5 ]- ]$ c! M5 t' u h4 h! v( s- c[attach]77175[/attach] ^1 ^( J2 Z0 y& d& I: [) i
DSH 384