US-12625191-B2 - DC link capacitor charging and generating excitation currents for battery cell monitoring

US12625191B2US 12625191 B2US12625191 B2US 12625191B2US-12625191-B2

Abstract

A driver circuit is configured to control an ON/OFF state of a semiconductor power switch circuit, wherein the semiconductor power switch circuit is configured to connect a plurality of battery cells to a DC link capacitor associated with an electric motor. The driver circuit is configured to: control the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor; and control the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells, wherein the excitation current is defined for a complex battery impedance measurement operation. The DC link capacitor is positioned in parallel with the electric motor. The excitation current comprises a periodic signal that passes from the semiconductor power switch circuit, through the DC link capacitor, and back to the plurality of battery cells.

Inventors

Guenter Hofer
Guenter Schwarzberger

Assignees

INFINEON TECHNOLOGIES AG

Dates

Publication Date: 20260512
Application Date: 20240410

Claims (20)

1 . A driver circuit configured to control an ON/OFF state of a semiconductor power switch circuit, wherein the semiconductor power switch circuit is configured to connect a plurality of battery cells to a DC link capacitor associated with an electric motor, wherein the driver circuit is configured to: control the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor, wherein the DC link capacitor is positioned on an opposite side of the semiconductor power switch circuit relative to the plurality of battery cells and the DC link capacitor is positioned in parallel with the electric motor; and control the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells, wherein the excitation current is defined for a complex battery cell impedance measurement operation and wherein the excitation current comprises a periodic signal that passes from the semiconductor power switch circuit, through the DC link capacitor, and back to the plurality of battery cells.
2 . The driver circuit of claim 1 , wherein the driver circuit is further configured to control the semiconductor power switch circuit to connect the plurality of battery cells to the electric motor in a presence of a charged DC link capacitor such that the plurality of battery cells deliver power to the electric motor.
3 . The driver circuit of claim 1 , wherein the driver circuit is configured to perform a start-up routine associated with the electric motor and wherein a discharge circuit is configured to perform a shut-down routine associated with the electric motor, wherein the start-up routine comprises: controlling the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor; and controlling the semiconductor power switch circuit to generate and deliver the excitation current from the plurality of battery cells to the plurality of battery cells; and wherein the shut-down routine comprises: discharging the DC link capacitor via the discharge circuit.
4 . The driver circuit of claim 3 , wherein the driver circuit is associated with an electric vehicle and wherein the start-up routine is performed at each start-up of the electric vehicle and wherein the shut-down routine is performed at each shut-down of the electric vehicle.
5 . The driver circuit of claim 1 , wherein the excitation current is defined for the complex battery cell impedance measurement operation to be performed by one or more cell sensor circuits (CSCs) on each of the plurality of battery cells.
6 . The driver circuit of claim 5 , wherein the excitation current includes at least 3 periods.
7 . The driver circuit of claim 6 , wherein the periodic signal includes between 5 and 10 periods inclusive.
8 . The driver circuit of claim 1 , wherein the driver circuit is configured to control the ON/OFF state of the semiconductor power switch circuit according to pulse modulation (PM) signals, wherein the PM signals are configured to define the excitation current.
9 . The driver circuit of claim 1 , wherein a current through the semiconductor power switch circuit simultaneously: charges the DC link capacitor; and defines the excitation current delivered from the plurality of battery cells to the plurality of battery cells.
10 . A method comprising: controlling a semiconductor power switch circuit to connect a plurality of battery cells to a DC link capacitor associated with an electric motor, wherein controlling the semiconductor power switch circuit includes: controlling the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor, wherein the DC link capacitor is positioned on an opposite side of the semiconductor power switch circuit relative to the plurality of battery cells and the DC link capacitor is positioned in parallel with the electric motor; and controlling the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells to the plurality of battery cells, wherein the excitation current is defined for a complex battery cell impedance measurement operation and wherein the excitation current comprises a periodic signal that passes from the semiconductor power switch circuit, through the DC link capacitor, and back to the plurality of battery cells.
11 . The method of claim 10 , further comprising: controlling the semiconductor power switch circuit to connect the plurality of battery cells to the electric motor in a presence of a charged DC link capacitor such that the plurality of battery cells deliver power to the electric motor.
12 . The method of claim 10 , wherein the method includes: performing a start-up routine; and performing a shut-down routine, wherein the start-up routine comprises: controlling the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor; and controlling the semiconductor power switch circuit to generate and deliver the excitation current from the plurality of battery cells to the plurality of battery cells; and wherein the shut-down routine comprises: discharging the DC link capacitor.
13 . The method of claim 12 , wherein the method is associated with an electric vehicle and wherein the start-up routine is performed at each start-up of the electric vehicle and wherein the shut-down routine is performed at each shut-down of the electric vehicle.
14 . The method of claim 10 , wherein the excitation current is defined for the complex battery cell impedance measurement operation by one or more cell sensor circuits (CSCs) on each of the plurality of battery cells.
15 . The method of claim 14 , wherein the excitation current includes at least 3 periods.
16 . The method of claim 15 , wherein the periodic signal includes between 5 and 10 periods inclusive.
17 . The method of claim 10 , further comprising controlling an ON/OFF state of the semiconductor power switch circuit according to pulse modulation (PM) signals, wherein the PM signals are configured to define the excitation current.
18 . The method of claim 10 , wherein current through the semiconductor power switch circuit simultaneously: charges the DC link capacitor; and defines the excitation current delivered to from the plurality of battery cells to the plurality of battery cells.
19 . A system comprising: a semiconductor power switch circuit configured to connect a plurality of battery cells to a DC link capacitor associated with an electric motor; and a driver circuit configured to control an ON/OFF state of the semiconductor power switch circuit, wherein the driver circuit is configured to: control the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor, wherein the DC link capacitor is positioned on an opposite side of the semiconductor power switch circuit relative to the plurality of battery cells and the DC link capacitor is positioned in parallel with the electric motor; and control the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells to the plurality of battery cells, wherein the excitation current is defined for a complex battery impedance measurement operation and wherein the excitation current comprises a periodic signal that passes from the semiconductor power switch circuit, through the DC link capacitor, and back to the plurality of battery cells.
20 . The system of claim 19 , wherein the semiconductor power switch circuit and the driver circuit are positioned on different printed circuit boards.

Description

TECHNICAL FIELD This disclosure relates to battery powered devices, such as electric vehicles, power switches and driver circuits for the power switches, and systems and circuits configured to perform battery cell monitoring functions for a plurality of battery cells. BACKGROUND Battery powered devices, such as electric vehicles, often include many battery cells connected in series to form a battery system for the battery powered device. For such battery systems, battery management systems (BMSs) are often used for battery cell monitoring, thermal monitoring, cell balancing of different battery cells or different sets of battery cells, or other battery management functions. The battery cells in the BMS are configured to provide power, e.g., to an electric motor of an electric vehicle. BMSs often use several different battery monitoring circuits (e.g., cell sense circuits “CSCs”) in order to monitor the individual battery cells of a battery powered device. For example, in BMS systems, battery cell impedance measurements are desirable. The so-called “complex impedance” of battery cells, however, can be more difficult to obtain than simple resistance measurements. Battery cell impedance can be affected by many factors, such as the battery cell structure, operational temperature changes, aging, state of charge, atmospheric pressure, environmental exposure, or other factors. It is desirable to utilize a so-called DC link capacitor in the connection of the battery cells to the electric motor. The DC link capacitor may be positioned in parallel to the electric motor. Power delivery form the battery cells to the electric motor can be improved by delivering a pre-charge on the DC-link capacitor prior to connecting the battery cells to the electric motor. The DC-link capacitor can provide several benefits to the system. SUMMARY In general, this disclosure is directed to techniques and driver circuits for controlling a power switch for both the charging of a DC link capacitor and for generating excitation currents for impedance monitoring of battery cells. According to this disclosure, a battery disconnect switch (BDS) may be used as a safety mechanism, e.g., providing the ability to disconnect an electric motor from the battery supply. In addition, the BDS can also be used as a charging mechanism, e.g., used for charging a DC link capacitor associated with the electric motor. Moreover, the current profile used in DC link capacitor charging can be defined in a way to allow that same current to be also used as an excitation current for battery cells, e.g., to facilitate complex impedance measurements on the battery cells. The driver circuits described herein can be used to control the BDS for both the charging of a DC link capacitor and for generating excitation currents for impedance monitoring of battery cells. Several advantages associated with the circuits and techniques of this disclosure are explained in greater detail below. In some examples, this disclosure describes a driver circuit configured to control an ON/OFF state of a semiconductor power switch circuit, wherein the semiconductor power switch circuit is configured to connect a plurality of battery cells to a DC link capacitor associated with an electric motor. The driver circuit may be configured to: control the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor and control the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells, wherein the excitation current is defined for a complex battery impedance measurement operation. In some examples, this disclosure a method that comprises controlling a semiconductor power switch circuit to connect a plurality of battery cells to a DC link capacitor associated with an electric motor. Moreover, according to this disclosure, controlling the semiconductor power switch circuit may include controlling the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor and controlling the semiconductor power switch circuit to generate and deliver an excitation current from the plurality of battery cells to the plurality of battery cells, wherein the excitation current is defined for a complex battery impedance measurement operation. In some examples, this disclosure describes a system that comprises a semiconductor power switch circuit and a driver circuit. The semiconductor power switch circuit may be configured to connect a plurality of battery cells to a DC link capacitor associated with an electric motor. The driver circuit may be configured to control the ON/OFF state of the semiconductor power switch circuit, wherein the driver circuit is configured to: control the semiconductor power switch circuit to cause the plurality of battery cells to charge the DC link capacitor, and control the semiconductor power switch circuit to generate and deliver an exc