Hi Nxp partner
Our Battery junction box is without main pos relay , pre-charge relay, pre-charge R relay.
When we turn off Main_Neg relay and photomos on vsense 3 already turn on , we measured voltage battery out+ & battery - which has 164V voltage. How to avoid the leakage current on our battery junction box.
Br,
Mike Liang
Hi Mike,
1. So from my understanding , you want to use meter to measure the real battery pack voltage between Link+ & Link-, right? I suppose there are 4-wires measurement method include 2 connect point and 2 sense point, you can find in your meter equipment, and this can avoid the current leakage.
2. You can choose high voltage NMOS as back-up plan if there is space issue. But for the performance, the OPT-MOS is the best, there is no current flow back in OPT-MOS since there is ’a pair of back to back diode’, but there might be current flow back if using NMOS since the body-diode.
Best regards,
Tomas
Hi Mike,
In our demo board design, we add two OPT-MOS to avoid current leakage from battery-pack when the load is in off-status. The two OPT-MOS are in position 1 & 2 with circle (you can find it in picture). And there is no OPT-MOS in HV-point_B and point_C since Main_Pos relay must be in close status when system is working.
If I understand it correctly, do you mean there will be current leakage in blue path in picture 2? What is the purpose of point-B in picture 2? It seems it is the same position with point A. It is sure there will be current leakage since there is no OPT-MOS in point_B measure circuit.
Best regards,
Tomas
Hi Tomas
We think leakage current path as below when main negative replay is "open status"(turn off) and optical mos on Vsense 3 is "close status"(Turn on). We measured 164v which dangerous voltage on link +and link-.We need close the main negative relay and optical mos on Vsense 3 to avoid dangerous voltage on link+ and link- when we battery junction is turn off mode, right?
And another question for your mention leakage from A, B,C .
Can we use the non optical mosfet as below because we have the space issue? I saw TI BQ79631 evm use non optical mosfet.thanks
Br,
Mike Liang
Hi Mike,
1. So from my understanding , you want to use meter to measure the real battery pack voltage between Link+ & Link-, right? I suppose there are 4-wires measurement method include 2 connect point and 2 sense point, you can find in your meter equipment, and this can avoid the current leakage.
2. You can choose high voltage NMOS as back-up plan if there is space issue. But for the performance, the OPT-MOS is the best, there is no current flow back in OPT-MOS since there is ’a pair of back to back diode’, but there might be current flow back if using NMOS since the body-diode.
Best regards,
Tomas
