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Cypress Semiconductor AN2309, Application Note

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Cypress Semiconductor AN2309 Application Note Download Page 18

AN2309 

 

 

November 25, 2007 

Document No. 001-17394 Rev. *B 

 - 18 - 

Appendix  

Charge/Discharge and Cell-Balancing Profile Examples 

Figure 13. Charge/Discharge Manager Profile 

 

 
 
 

 

 

Constant 
Current Charge 

Constant 
Voltage Charge 

Battery 
Discharge 

Cell Voltages Without 
Charge Interrupt  

Charger State  

Cell-Balancing 
State 

Charge /Discharge 
Current 

Thermistor 
Resistance 

COM #  
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Summary of Contents for AN2309

Page 1: ...cells causes the following problems Reduced overall battery pack capacity to the value of the cell with the least capacity During the charge process this cell reaches the maximum charge level before t...

Page 2: ...e charge is Q I t C V Equation 2 Therefore Equation 1 can be transformed into the following equation 1 1 2 2 C V C V cell cell cell cell Equation 3 The value VcellN is the electrochemical potential of...

Page 3: ...of battery charge discharge Thus it is advisable to perform the balancing routine when the cells are nearly fully charged or nearly fully discharged See also Cell Balancing Algorithm on page 14 The c...

Page 4: ...device family for the same project the overnight conditioning cell balancing algorithm can easily be added see AN2258 Cell Balancing in a Multi Cell Li Ion Li Pol Battery Charger But for most applicat...

Page 5: ...l1 VREF Vref Vref Vref Vbias C1 Q4 C4 R4 R10 Q3 R8 R9 Current Sense The following abbreviations are used in Figure 3 RS_TX RS232 transmitter for debug purposes uses external level translator It monito...

Page 6: ...gnal from the PSoC The resistive network R6 R7 R12 R13 R15 R16 and R18 R22 and the reference voltage Vbias from the divider on R29 and D8 allow transformation of the battery current voltage and temper...

Page 7: ...2 P2 6 23 P0 0 24 P0 2 25 P0 4 26 P0 6 27 Vcc 28 U1 CY8C24423A VCC V1 V2 Vi2 Vbias R24 10K 1 LED_GREEN R16 1M 1 R15 1M 1 R21 200K 1 R20 200K 1 C8 0 1u Vi1 Vi2 Vi1 R14 100 C6 0 01u R17 1M R13 150K 0 1...

Page 8: ...set to 115200 baud The cell balancing MOSFETS Q4 Q5 are controlled directly from the CPU high level close low level open The three opamp topology of the instrumental amplifier INA is used in this imp...

Page 9: ...d down battery charger divider resistors of large nominal resistance are employed To provide higher current measurement accuracy a current sense resistor was put in the pack current path close to the...

Page 10: ...uring process by using external reference For temperature measurement a reference voltage resistive divider is employed based on a thermistor and a precision resistor R6 Thermistor resistance is calcu...

Page 11: ...lgorithms are described Two Cell Battery Charger Algorithm The two cell battery charge algorithm is implemented in the charger firmware as a state machine The following states are used Initialization...

Page 12: ...es jumps to the Wait For Temperature state when the battery temperature is outside the allowed temperature range For the Activation and Rapid states the allowed temperature range is the charge range F...

Page 13: ...t Error State And Error Code Yes No Check Charge Terminate Condition Set Charge Complete State Yes No Set Initialization State No No Send Debug Data Check Cell Balancing Interval Cell Balancing Yes No...

Page 14: ...its voltage has risen above 3 9 volts If the charging current is less than 1C this threshold can be reduced At this charge state the internal resistance drops below 0 2 and the distortion level is wit...

Page 15: ...balancing profile examples are shown in the Appendix Figure 14 on page 19 and Figure 15 on page 20 Figure 11 Cell Balancing Algorithm Start Chagre Off Balancing Reset DoCellBalancing FALSE Wait Start...

Page 16: ...ng Requirements TACT second Time Limit for Battery Activation Period TRAPID second Time Limit for Final Stage of Constant Charge Mode Voltage TCHARGE second Time Limit for Total Charge Period TTERM se...

Page 17: ...arise in a battery pack with two cells in series By altering several configuration parameters the cell balancing algorithm can easily be adapted for various applications and selected batteries A metho...

Page 18: ...ncing Profile Examples Figure 13 Charge Discharge Manager Profile Constant Current Charge Constant Voltage Charge Battery Discharge Cell Voltages Without Charge Interrupt Charger State Cell Balancing...

Page 19: ...AN2309 November 25 2007 Document No 001 17394 Rev B 19 Figure 14 Cell Balancing Activity Profile Voltage Imbalance Value Cell Voltages With Charge Interrupt Feedback...

Page 20: ...About the Author Name Oleksandr Karpin Title Application Engineer Background Oleksandr received a PhD s degree in computer science in 2008 from Lviv Polytechnic National University Ukraine His intere...

Page 21: ...cal control or safety applications unless pursuant to an express written agreement with Cypress Furthermore Cypress does not authorize its products for use as critical components in life support syste...

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