The existence need segregation of much voltage n will protect low-pressure circuit to avoid suffer high pressure to affect. Apparent, to the batteries of 400V and above, you need to keep apart, but spend gently in 48V whether to need to keep apart in mixture system? Let us be analysed.

 

The segregation in 48V HEV

 

Although voltage is not as high as 400V or 800V, segregation is very important also to car of 48V mixture motivation, investigate its reason has a lot of kinds, include to increase among them fight the function that fight a confusion of voices and breakdown protection.

 

The graph is shown 1 times start dynamo system for, include H bridge and field effect transistor among them (FET) power level lies 48V side. The switch of these FET can cause voltage twinkling to change (Dv/dt) , this may carry generation in 48V ground connection a few in all modular noise. Below the circumstance that does not have any segregation, this noise will carry side coupling with 12V, affect the signal integrality of low-pressure side circuit. Through segregation increasing between two side, if the graph is shown 1 times, you can rise in all modular very short time changes immunity to interference and signal integrality.

 

Graph 1: The starter in 48 V HEV / dynamo subsystem

 

In the graph 2 in, batteries management system (BMS) group of medium 48 V batteries and small controller (MCU) be located in tall voltage side, and local area network of MCU use controller (CAN) agreement and electronic control unit have communication. If 48 V side appears breakdown, criterion voltage may appear in 12 V side. The circuit component of low voltage side (send and receive for CAN in this exemple implement) the likelihood cannot bear tall voltage, and may damage. Send and receive in the CAN of low-pressure side implement isolator is used to will ensure between the small controller with high-pressured side the security of low-pressure circuit, although there is breakdown happening in high-pressured side

 

Association of German auto industry 320 (VDA320) the standard appointed a car electric check with the fault current of electronic component (E48-20) , check voltage to apply at 48V/12V separator among them, the prospective current between 12V and 48V system must be less than 1 microamper. Deploy isolator to be able to ensure electric current accords with this one standard.

 

Graph 2: 48V BMS block diagram

 

If you are designing 48V HEV system, searching the segregation parts of an apparatus with 48V side interface. Be based on interface standard, a few options can be used at the communication between 48V side and 12V side.

 

Interface of serial to needing to undertake between 12V and 48V side peripheral equipment (SPI) , transmitter of general asynchronous receiver (UART) or general input / output (GPIO) the design of communication, you can use digital isolator, for example ISO7741-Q1 or ISO7721-Q1, specific depend on needs segregation connects number of channels.

 

Fall to using I2C when you when communication will save signal trace to count, keep apart type I2C parts of an apparatus, for example ISO1540-Q1 (two-way data, two-way clock) ISO1541-Q1 (two-way data, two-way clock) can satisfy this utility.

 

If be put when CAN corresponds and need is kept apart between two side, you can add isolator of a number (for example ISO7721-Q1) send and receive with CAN implement series connection, perhaps use parts of an apparatus of compositive segregation type CAN (for example ISO1042-Q1) will save a space.

 

Data communication is the one part of the solution only. You still must keep apart the power source between two side, you can be used stimulate type instead, turn over step-down or push-pull develop to attack realize this one segregation. To local power supply (for example, segregation type CAN is sent and receive implement power source) , can consider can fall with exterior transformer, commutator and low pressure the transformer driver that manostat uses together, for example SN6501-Q1, SN6505A-Q1 or SN6505B-Q1, in order to make simple segregation type power supply, if pursue,3 are shown.

 

Graph 3: Have the simple and easy circuit of the segregation type power source of stable output

 

The output electric current that the main distinction between SN6501-Q1, SN6505A-Q1 or SN6505B-Q1 depends on every driver, whether to exist can reduce radiant enlarge frequency and different switch frequency. These option make you can choose correct parts of an apparatus, in order to satisfy radiation level of the system and power source requirement.

 

Although I had debated these solutions below the setting of 48 V HEV, but the segregation norms of series of these parts of an apparatus and more extensive enclose option to make these series also apply to the EV with batteries taller voltage. The case that can having a few modification to EV design plays the segregation part that duplicates use HEV subsystem, save design and layout time thereby.