Several questions about 7S3P battery pack circuit

QWE4562009

Several questions about 7S3P battery pack circuit [Copy link]

 

Several questions about 7S3P battery pack circuit

1. Figure 1 shows the activation circuit of the short-circuit B+ and P+ of the electronic group. Why should the positive control method be used for the battery group B+ (7 batteries in series 25.9V)? The previous methods all controlled the negative pole. What are the advantages and disadvantages of positive control and negative control? In addition, the common method is to use a triode to control the MOS tube, but here it is just the opposite. Why?

2. I never understood why U4 is used as an over-current detector. And why did the designer use Q5 transistor as the tube to control the battery output? Generally, MOS tubes are used. What is the purpose of this?

3. Here, Q10, Q9, and Q7 are used to control the pre-charging circuit. What is the significance?

chunyang

Regarding the positive and negative control of electronic switches, from a control perspective, the two are equivalent. The difference lies in the control elements and control levels and the different characteristics brought about by them. Positive control requires the use of PNP/P channel tubes, which are turned on at a low level (relative to the controlled input voltage). Negative control requires the use of NPN/N channel tubes, which are turned on at a high level (relative to the ground). Because of the difference in turn-on voltage, if the load itself shares the same ground with the power supply, negative control is obviously not feasible, so for loads that share the same ground with the power supply, it is more convenient to use positive control. However, when the control level is high and is still lower than the controlled power supply voltage, level conversion is required, and the circuit will become correspondingly complicated.

chunyang

In positive-controlled level conversion circuits, bipolar transistors are more commonly used. This is because bipolar transistors are cheaper, current-driven, have a lower threshold voltage (0.7V), and are more convenient to use in low-voltage systems.

qwqwqw2088

The protection board solution determines which control is used.

Positive control has the same effect as negative control

If positive control is used, that is, P+ and B+, the switch is PMOS, that is, Q7 is PMOS

If NMOS is needed for negative control

chunyang

Regarding overcurrent detection, the figure does not show where the detection circuit is. U4 is used for battery voltage detection. Q5 is not a "tube for controlling battery output", but an adjustment tube for the intermediate voltage regulator circuit. The post-stage LDO does not allow excessively high input voltage, so a series voltage regulator circuit is inserted in the middle.

chunyang

The purpose of the pre-charging circuit is to charge the battery with a small current when the voltage at the battery pack terminal is too low. Charging with a large current right away is not good for the battery life.

qwqwqw2088

Generally, battery overcurrent protection should be implemented in the control chip of the battery protection board.

U4 can delay the detection signal and release signal through an external capacitor, and protect the delay according to the voltage control signal.

QWE4562009

I'm still posting analog electronics. Everyone is interested. Few people reply to the code.

QWE4562009

chunyang posted on 2020-7-29 16:14 Regarding the positive and negative control of electronic switches, from a control perspective, the two are equivalent. The difference lies in the control element and control level, as well as the resulting...

I consulted an industry expert and he said that positive control may cause sparks and negative control may damage the sampling IC or other small signal circuit ICs due to lack of common ground during sampling.

QWE4562009

qwqwqw2088 posted on 2020-7-29 16:22 The protection board solution determines which control is used. The positive control and negative control have the same effect. If positive control is used, that is, P+ and B+, then the switch is PM ...

I consulted an industry expert and he said that positive control may cause sparks and negative control may damage the sampling IC or other small signal circuit ICs due to lack of common ground during sampling.

QWE4562009

qwqwqw2088 posted on 2020-7-29 16:22 The protection board solution determines which control is used. The positive control and negative control have the same effect. If positive control is used, that is, P+ and B+, then the switch is PM ...

I consulted an industry expert and he said that positive control may cause sparks and negative control may damage the sampling IC or other small signal circuit ICs due to lack of common ground during sampling.

QWE4562009

chunyang posted on 2020-7-29 16:28 The purpose of the pre-charge circuit is to charge with a small current when the voltage at the battery pack end is too low. Charging with a large current right from the start is not good for the battery life.

Your reply is irrelevant.

chunyang

QWE4562009 posted on 2020-7-29 16:51 I consulted an industry expert and he said that the positive control may cause a spark and the negative control may cause the sampling IC to be disconnected during sampling due to lack of common ground ...

It is meaningless to talk about these without considering the specific circuit.

chunyang

QWE4562009 posted on 2020-7-29 17:00 This reply is irrelevant to the question.

It is just to achieve the aforementioned purpose, there is no "deeper meaning" to speak of.

QWE4562009

qwqwqw2088 posted on 2020-7-29 16:22 The protection board solution determines which control is used. The positive control and negative control have the same effect. If positive control is used, that is, P+ and B+, then the switch is PM ...

In addition to charging detection, what other functions does this have?

qwqwqw2088

QWE4562009 posted on 2020-7-29 17:07 In addition to charging detection, what other functions does this have?

The charging equalization function belongs to the voltage equalization circuit.