Battery balancing circuit balancing voltages between battery units with a fly capacitor

Patent metadata

Field	Value
Publication number	US-2020021118-A1
Application number	US-201816032004-A
Country	US
Kind code	A1
Filing date	Jul 10, 2018
Priority date	Jul 11, 2017
Publication date	Jan 16, 2020
Grant date	—

Abstract

A battery balancing method and circuit for balancing the voltages between battery units with a fly capacitor. In a first time period of a switching cycle, the first battery unit is used to charge the fly capacitor or the first battery unit is used to discharge the fly capacitor, depending on which of the first battery unit and the fly capacitor having a larger voltage value; and in a second time period of the switching cycle, the second battery unit is used to charge the fly capacitor or the second battery unit is used to discharge the fly capacitor, depending on which of the second battery unit and the fly capacitor having a larger voltage value

First claim

What is claimed is:

1 . A battery balancing method for balancing the voltages of a first battery unit and of a second battery unit with a fly capacitor, comprising:
in a first time period of a switching cycle, charging the fly capacitor from the first battery unit or discharging the fly capacitor to the first battery unit, depending on which of the first battery unit and the fly capacitor having a larger voltage value; and in a second time period of the switching cycle, charging the fly capacitor from the second battery unit or discharging the fly capacitor to the second battery unit, depending on which of the second battery unit and the fly capacitor having a larger voltage value.

2 . The battery balancing method of claim 1 , wherein the operation of balancing the voltages of the first battery unit and of the second battery unit with the fly capacitor comprises a starting phase and a non-starting phase, and the battery balancing method comprises:
in the starting phase, charging the fly capacitor from the first battery unit in the first time period of each switching cycle and charging the fly capacitor from the second battery unit in the second time period of each switching cycle; and in the non-starting phase, having the voltage of the first battery unit becoming equal to the voltage of the fly capacitor at the end of the first time period of each switching cycle and having the voltage of the second battery unit becoming equal to the voltage of the fly capacitor at the end of the second time period of each switching cycle.

3 . The battery balancing method of claim 2 , wherein in the non-starting phase,
when the voltage difference between the voltage of the first battery unit and the voltage of the second battery unit is larger than a current limiting threshold, the charging current with which the first battery unit charges the fly capacitor and the discharging current with which the first battery unit discharges the fly capacitor are both preset in the first time period of each switching cycle, and the charging current with which the second battery unit charges the fly capacitor and the discharging current with which the second battery unit discharges the fly capacitor are both preset in the second time period of each switching cycle; and when the voltage difference between the voltage of the first battery unit and the voltage of the second battery unit is lower than the current limiting threshold, the first battery unit is coupled with the fly capacitor in parallel in the first time period of each switching cycle, and the second battery unit is coupled with the fly capacitor in parallel in the second time period of each switching cycle.

4 . The battery balancing method of claim 1 , wherein
in the first time period of each switching cycle, having the first battery unit charging the fly capacitor when the voltage of the first battery unit is larger than the voltage of the fly capacitor or having the first battery unit discharging the fly capacitor when the voltage of the first battery unit is lower than the voltage of the fly capacitor; and in the second time period of each switching cycle, having the second battery unit charging the fly capacitor when the voltage of the second battery unit is larger than the voltage of the fly capacitor or having the second battery unit discharging the fly capacitor when the voltage of the second battery unit is lower than the voltage of the fly capacitor.

5 . The battery balancing method of claim 1 , wherein each switching circuit consists of the first time period and the second time period.

6 . A battery balancing control circuit for balancing the voltages of a first battery unit and of a second battery unit with a fly capacitor, comprising a first switching circuit and a second switching circuit, wherein
in a first time period of a switching cycle, the first switching circuit is switched on and the second switching circuit is switched off so as to charge the fly capacitor from the first battery unit or to discharge the fly capacitor to the first battery unit, depending on which of the first battery unit and the fly capacitor having a larger voltage value; and in a second time period of the switching cycle, the first switching circuit is switched off and the second switching circuit is switched on so as to charge the fly capacitor from the second battery unit or to discharge the fly capacitor to the second battery unit, depending on which of the second battery unit and the fly capacitor having a larger voltage value.

7 . The battery balancing control circuit of claim 6 , wherein
in the first time period of each switching cycle, the first switching circuit is switched on and the second switching circuit is switched off so as to charge the fly capacitor from the first battery unit when the voltage of the first battery unit is larger than the voltage of the fly capacitor or to discharge the fly capacitor to the first battery unit when the voltage of the first battery unit is lower than the voltage of the fly capacitor; and in the second time period of each switching cycle, the first switching circuit is switched off and the second switching circuit is switched on so as to charge the fly capacitor from the second battery unit when the voltage of the second battery unit is larger than the voltage of the fly capacitor or to discharge the fly capacitor to the second battery unit when the voltage of the second battery unit is lower than the voltage of the fly capacitor.

8 . The battery balancing control circuit of claim 6 , wherein
the first battery unit and the second battery unit each comprises a first terminal and a second terminal, the first terminal of the second battery unit is electrically coupled to the second terminal of the first battery unit; the fly capacitor comprises a first terminal and a second terminal; and the first switching circuit comprises a first switch and a second switch, and the second switching circuit comprises a third switch and a fourth switch, wherein
the first switch is electrically coupled between the first terminal of the fly capacitor and the first terminal of the first battery unit;
the second switch is electrically coupled between the second terminal of the fly capacitor and the second terminal of the first battery unit;
the third switch is electrically coupled between the first terminal of the fly capacitor and the first terminal of the second battery unit; and
the fourth switch is electrically coupled between the second terminal of the fly capacitor and the second terminal of the second battery unit.

9 . The battery balancing control circuit of claim 8 , wherein the operation of balancing the voltages of the first battery unit and of the second battery unit with the fly capacitor comprises a starting phase and a non-starting phase, and wherein,
in the starting phase, the fly capacitor is charged by the first battery unit in the first time period of each switching cycle, and the fly capacitor is charged by the second battery unit in the second time period of each switching cycle; and in the non-starting phase, the voltage of the first battery unit is balanced to be equal to the voltage of the fly capacitor at the end of the first time period of each switching cycle, and the voltage of the second battery unit is balanced to be equal to the voltage of the fly capacitor at the end of the second time period of each switching cycle.

10 . The battery balancing control circuit of claim 8 , wherein
the first switching circuit further comprises a first current source, a first controllable switch, a second current source and a second controllable switch; and the second switching circuit further comprises a third current s

Assignees

• Chengdu Monolithic Power Sys

Inventors

• Wang Rui
• Xu Min
• Zhao Qiming

Classifications

• H02J7/575

  Parallel/serial switching of connection of batteries to charge or load circuit · CPC title

• H02J7/52 Primary

  for charge balancing, e.g. equalisation of charge between batteries · CPC title

• H01M2010/4271

  Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing · CPC title

• H01M10/425

  Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing (printed circuits H05K1/00) · CPC title

• H02J7/0014 Primary

  Electricity · mapped topic