MB39A125 Datasheet, PDF (33/64 Pages) Fujitsu Component Limited. – DC/DC Converter IC for Charging Li-ion Battery

MB39A125/126
■ TRANSIENT RESPONSE AT LOAD-STEP
The constant voltage control loop and the constant current control loop are independent. With the load-step,
these two control loops change.
The battery voltage and current overshoot are generated by the delay time of the control loop when the mode
changes. The delay time is determined by phase compensation constant. When the battery is removed if the
charge control is switched from the constant current control to the constant voltage control, and the charging
voltage does overshoot by generating the period controlled with high duty by output setting voltage. The excessive
voltage is not applied to the battery because the battery is not connected.
When the battery is connected if the charge control is switched from the constant voltage control to the constant
current control, and the charging current does overshoot by generating the period controlled with high duty by
charge current setting.
The battery pack manufacturer in Japan thinks it is not the problem the current overshoot of 10 ms or less.
• Timing chart at load-step
Error Amp3 Output
Error Amp1 Output
Error Amp1 Output
Constant Current
Error Amp3 Output
Constant Voltage
Constant Current
Battery Voltage
Battery Current
When charge control switches
from the constant current control to
the constant voltage control, the
voltage does overshoot by gener-
ating the period controlled with
high duty by output setting voltage.
10 ms
The battery pack manufac-
turer in Japan thinks it is
not the problem the current
overshoot of 10 ms or less.
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