Patent Description:
In recent years, batteries have been widely used in power tools, electric bicycles, electric vehicles, military equipment, aerospace and other fields. A voltage of a battery cell represents a potential difference between an anode and a cathode of the battery cell and is one of the important indicators to measure the charge and discharge performance of the battery.

<FIG> is a circuit diagram of a conventional battery voltage detection system <NUM>. The conversion system <NUM> uses a compensation current IMP1 generated by a current mirror <NUM> to compensate the sampling current I322_3 flowing from a resistor RF3 to a resistor 308_3, uses an operating current I304_4 of the operational amplifier 304_4 to compensate the sampling current I322_2 flowing from a resistor RF2 to a resistor 308_2, and uses an operating current I304_3 of the operational amplifier 304_3 to compensate the sampling current I322_1 flowing from a resistor RF1 to a resistor 308_1. In an ideal state, the currents flowing through the resistors RF3, RF2 and RF1 are all zero due to the compensation. However, since the current flowing through the resistor RF4 is relatively large, the voltage drop generated on the resistor RF4 is also relatively large, resulting in a low accuracy of the detected voltage V302_4 of the battery cell 302_4 which is indicated by the sampling current I322_4. <CIT> discloses an arrangement for measuring voltages of individual cells in a battery, comprising, for each cell, a resistive divider and a voltage to current converter. Each voltage to current converter is connected to a cathode (low side) of a battery cell via an enable switch and a lower resistor of a divider, and further switchably connected to an anode (high side) of the cell via the enable switch, wherein the output or operational current flows to ground. Similar art is known from <CIT>, <CIT>, <CIT>, and <CIT>.

Disclosed are embodiments of methods for detecting voltages of battery cells in a battery pack. The battery cells correspond to respective converters, an anode of each battery cell is coupled to a respective converter through a respective first path, a cathode of each battery cell is coupled to the respective converter through a respective second path, and the converters are coupled to anodes of the battery cells through switching units. The method includes: turning on a switching unit corresponding to a battery cell to enable an anode of the battery cell to provide an operating current and a sampling current through a respective first path to a respective converter, where the operating current flows from the anode of the battery cell through the respective converter to ground; and detecting a voltage of the battery cell by a respective converter. Said method further comprises: duplicating, by a mirroring unit, an operating current and a sampling current of a first converter of said plurality of converters corresponding to a first battery cell of said plurality of battery cells, to reduce a difference between a current through a first path of said plurality of first paths that corresponds to said first converter and a current through a second path of said plurality of second paths that corresponds to said first converter, wherein said mirroring unit is coupled to said second path that corresponds to said first converter.

In other embodiments, a controller for detecting voltages of battery cells in a battery pack includes converters coupled to the battery cells and switching units, where an anode of each battery cell is coupled to a respective converter through a respective first path, a cathode of each battery cell is coupled to the respective converter through a respective second path. The switching units are coupled between the battery cells and the converters. The converters are coupled to anodes of the battery cells through the switching units. When a switching unit corresponding to a battery cell is turned on, an anode of the battery cell provides an operating current and a sampling current through a respective first path to a respective converter, where the operating current flows from the anode of the battery cell through the respective converter to ground. Said controller further comprises: a mirroring unit coupled to a second path of said plurality of second paths that corresponds to a first converter of said plurality of converters that corresponds to a first battery cell of said plurality of battery cells, wherein said mirroring unit is operable for duplicating an operating current and a sampling current of said first converter to reduce a difference between a current through a first path of said plurality of first paths that corresponds to said first converter and a current through said second path that corresponds to said first converter.

Features and advantages of embodiments of the claimed subject matter will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which:.

Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in combination with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims.

Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail to avoid obscuring aspects of the present invention.

<FIG> shows a circuit diagram <NUM> of a controller 210A for detecting voltages of battery cells in a battery pack. The example battery pack in <FIG> includes battery cells CELL1, CELL2, CELL3, and CELL4, and the controller 210A includes converters 211_1-<NUM><NUM> corresponding to the battery cells CELL1-CELL4, respectively. In this example, the battery cell CELL1 is called the top battery cell (i.e., the battery farthest from the reference ground GND), and the battery cell CELL4 is called the bottom battery cell (i.e., the battery closest to the reference ground GND).

The anode of the battery cell CELLj (j=<NUM>, <NUM>, or <NUM>) is coupled to the converter 211_j through a first path, and the cathode of the battery cell CELLj is coupled to the converter 211J through a second path. The controller 210A further includes switching units 212_1-212_4 coupled between the battery cells CELL1-CELL4 and the converters 211_1-211_4, respectively. The converters 211_1-<NUM><NUM> are coupled to anodes of the battery cells CELL1-CELL4 through the switching units 212_1-<NUM><NUM>, respectively. When a corresponding switching unit of each battery cell is turned on, an operating current IOPj and a sampling current I1_j provided by the anode of the battery cell CELLj flow through a first path corresponding to the converter 211_j. The operating current IOPj flows from the anode of the battery cell CELLj through the first path and the corresponding converter 211_j to ground. An operating current IOP(j+<NUM>) and a sampling current I1_(j+<NUM>) provided by the anode of the battery cell CELL(j+<NUM>) flow through a second path corresponding to the converter 211_j. In an example, the first path corresponding to the converter 211_j includes a connecting resistor RFj. The second path corresponding to the converter 211_j includes a connecting resistor RF(j+<NUM>). For the battery cell CELL4, the anode of the battery cell CELL4 is coupled to the converter 211_4 via the connecting resistor RF4 and the switching unit 212_4, and the cathode of the battery cell CELL4 is coupled to the converter 211_4 via the switching unit 212_5. In one example, the resistance of the connecting resistors RF1, RF2, RF3, and RF4 are equal.

The converter 211_j can be enabled or disabled by turning on or turning off the switching unit 212_j (j=<NUM>, <NUM>, or <NUM>). For example, by turning on the switching unit 212_1 (e.g., switches S1 and K1), the converter 211_1 is enabled, and by turning off the switching unit 212_1, the converter 211_1 is disabled. In an example, the switching unit 212_j (j=<NUM>, <NUM>, or <NUM>) includes a switch Sj and a switch Kj. By turning on the switch Kj, the anode of the battery cell CELLj provides the converter 211_j with the operating current IOPj through the first path corresponding to the converter 211_j. By controlling the switch Kj, the operational amplifier OPj in the converter 211_j can be enabled or disabled individually to save power. By turning on the switch Sj, the anode of the battery cell CELLj provides the sampling current I1_j to the converter 211_j through the first path corresponding to the converter 211_j.

In addition, when the switching units 212_4 and 212_5 are on at the same time, the converter 211_4 is enabled, and by turning off any one of the switching units 212_4 and 212_5, the converter 211_4 is disabled. When the switching units 212_4 and 212_5 are on at the same time, the sampling current I1_4 (not shown in the figure) and the operating current IOP4 (not shown in the figure) provided by the anode of the cell CELL4 flow through the converter 211_4.

The converter 211_j detects the voltage of the cell CELLj and generates a sampling signal SAMj (j=<NUM>, <NUM>, <NUM>, or <NUM>). In an example, the sampling signal SAMj can be a sampling current I1_j. Specifically, the converter 211_j converts the voltage of the cell CELLj to the sampling current I1_j, thereby indicating the voltage of the cell CELLj. In another example, the sampling signal SAMj can be a sampling voltage VSAMj. Specifically, the sampling current I1_j (j=<NUM>, <NUM>, <NUM>, or <NUM>) flows through the sampling resistor Rsj and is detected as the sampling voltage VSAMj. In an example, the sampling voltages VSAMj (j = <NUM>, <NUM>, <NUM>, <NUM>) are all based on the same reference voltage (for example, ground).

In an example, the converter 211_j (j=<NUM>, <NUM>, or <NUM>) includes an operational amplifier OPj, a resistor Raj, a transistor MPSj, and a sampling resistor Rsj. The operational amplifier OPj (j=<NUM>, <NUM>, or <NUM>) is coupled to the anode of the battery cell CELLj through the switch Kj, and the operating current IOPj flows from the anode of the battery cell CELLj to the ground via the connecting resistor RFj and the operational amplifier OPj. The resistor Raj is coupled to the anode of the cell CELLj through the switch Sj, and the sampling current I1_j flows from the anode of the cell CELLj to the ground via the connecting resistor RFj, the resistor Raj, and the sampling resistor Rsj. The converter <NUM>-<NUM> includes a sampling resistor Rs4. The operating modes of the controller 210A in <FIG> can include the following two modes.

In a first operating mode, the controller 210A turns on all the switching units 212_1-212_4 in <FIG>, so that the converters 211_1-211_4 are all enabled. The converter 211_j (j=<NUM>, <NUM>, or <NUM>) receives the operating current IOPj and the sampling current I1_j provided by the cell CELLj through the first path corresponding to the converter 211_j. The operating current IOP(j+<NUM>) and the sampling current I1_(j+<NUM>) provided by the lower cell CELL(j+<NUM>) adjacent to the cell CELLj flow through the second path corresponding to the converter 211_j. In an example, in an ideal state, by properly setting the parameters of related components, the sum of the operating current and the sampling current provided by each battery cell can be approximately equal. The converter 211_j detects the voltage of the battery cell CELLj, and generates a sampling signal SAMj (for example, the sampling voltage VSAMj or the sampling current I1_j) indicating the voltage of the battery cell CELLj.

In addition, when detecting the voltage of the battery cell CELL4, the battery cell CELL4, the connecting resistor RF4, and the converter 211_4 constitute a closed loop. The converter <NUM>-<NUM> detects the voltage of the battery cell CELL4 and generates a sampling signal SAM4 (e.g., the current flowing through the converter 211_4 or the voltage on the converter <NUM>-<NUM>) indicating the voltage of the battery cell CELL4.

Compared to <FIG>, the controller 210A in <FIG> changes the power supply method for the operational amplifier in each converter so that the current flowing through the first path and the current flowing through the second path corresponding to each converter both are the sum of the operating current and sampling current provided by the anodes of the two adjacent battery cells. In an ideal state, by properly setting the parameters of the relevant components, the operating current of each operational amplifier can be approximately equal, and each sampling current can be approximately equal. In an embodiment, since the resistances of the connecting resistors are set to be equal, with the above conditions, the voltage drop on each connecting resistor is also approximately equal. Therefore, compared with the system in <FIG>, the controller 210A can detect the voltage of each battery cell more accurately. However, since the anode of each battery cell provides the operating current and sampling current for the corresponding converter, the current flowing through the battery cells CELL1, CELL2, CELL3, and CELL4 increases in sequence. After the controller 210A operates for a relatively long time, the balance between the voltages of the individual cells may be lost (balance means that the voltage differences of the individual cells are within an acceptable range), which would reduce the accuracy of the detected voltage of each cell represented by each sampling signal. To address this, the arrangement includes a second operating mode of the controller 210A.

In the second operating mode, the controller 210A selectively turns on the switching units (for example, the switching units 212_j, 212_(j+<NUM>)) corresponding to two adjacent battery cells (for example, battery cells CELLj, CELL(j+<NUM>), j = <NUM>, <NUM>, <NUM>) to enable two adjacent converters (e.g., converters 211_j, 211_(j+<NUM>)) while other converters remain disabled.

An upper converter (e.g., the converter <NUM>_j) of the two adjacent converters (e.g. converters 211_j, 211_(j+<NUM>), j = <NUM>, <NUM>, <NUM>) receives an operating current IOPj and a sampling current I1_j from an anode of an upper cell (e.g., CELLj) of two adjacent cells through a first path corresponding to the upper converter. An operating current IOP(j+<NUM>) and a sampling current I1_(j+<NUM>) from an anode of a lower cell (e.g., CELL(j+<NUM>)) of the two adjacent cells flows through a second path corresponding to the upper converter (e.g. the converter 211_j). The upper converter (e.g. the converter 211_j) detects a voltage of the upper cell (e.g., CELLj).

To detect the voltage of CELL4, the controller 210A can turn on both switching units 212_4 and 212_5, or can turn on switching unit 212_4 and turn off switching unit 212_5. Both methods can enable the controller 210A to accurately detect a voltage of the battery cell CELL4.

In the second operating mode, by controlling the duty cycle of the on-time of the switching units corresponding to the two adjacent battery cells, an average value of the difference between the currents flowing through each battery cell can be reduced, thereby maintaining balance among battery cells. The duty cycle refers to the ratio of the on-time t of the switching units corresponding to the two adjacent battery cells to the detection period T. The detection period T refers to the total time required to detect the voltages of all the battery cells CELL1, CELL2, CELL3, and CELL4. The details will be described in <FIG>.

<FIG> shows a timing diagram of the switching units in controller 210A operating in the second mode, in accordance with examples of the present invention. In the example shown in <FIG>, during the time period from t0 to t1, only the switching units 212_1 and 212_2 are turned on, and the converter 211_1 detects the voltage of the cell CELL1. During the time period from t2 to t3, only the switching units 212_2 and 212_3 are turned on, and the converter 211_2 detects the voltage of the cell CELL2. In the time period from t4 to t5, only the switching units 212_3, 212_4, and 212_5 are turned on, and the converter 211_3 detects the voltage of the cell CELL3. During the time period from t6 to t7, only the switching unit 212_4 is turned on, and the converter 211_4 detects the voltage of the cell CELL4. In this embodiment, t1-t0 = t3-t2 = t5-t4 = t7-t6. In other examples, t1-t0, t3-t2, t5-t4, and t7-t6 may not be equal.

Assume, for example, that the detection period T in <FIG> is <NUM>, and the on-time t of the switching units corresponding to two adjacent battery cells are both 100ps, in which case the duty cycle is <NUM>/<NUM>. Assume also that the current received by each converter through a corresponding first path is 10µA. In this example, when the controller 210A operates in the first mode, the difference between the current flowing through the battery cell CELL1 and the current flowing through the battery cell CELL3 is 20µA. When the controller 210A operates in the manner shown in <FIG> (second mode), during the detection period T, the average value of the difference between the current flowing through the cell CELL1 and the current flowing through the cell CELL3 is reduced to 20nA in this example. It can be seen that by controlling (for example, reducing) the duty cycle of the on-time t of the switching units corresponding to two adjacent battery cells as in the second mode, the average value of the difference between the currents flowing through the battery cells can be reduced, thereby maintaining balance among battery cells.

<FIG> shows a circuit diagram of a controller 210B, in accordance with embodiments of the present invention.

Compared with the controller 210B in <FIG>, the controller 210B further includes multiple mirroring unit. In the example of <FIG>, the controller 210B includes mirroring unit 410_1, 410_2 and 410_3.

The mirroring unit 410_j (j = <NUM>, <NUM>, or <NUM>) duplicates the operating current IOPj and the sampling current I1_j of the converter 211_j corresponding to the battery cell CELLj, so as to reduce the difference between the current through the first path corresponding to the converter 211_j and the current through the second path corresponding to the converter 211_j. The mirroring unit 410_j is coupled to the second path corresponding to the converter 211J.

Specifically, the mirroring unit 410_j (j=<NUM>, <NUM>, or <NUM>) generates a first duplicated current proportional to the operating current IOPj. In an embodiment, in an ideal state, the first duplicated current can be approximately equal to the operating current IOPj by properly setting parameters of the relevant components. The mirroring unit 410_j (j=<NUM>, <NUM>, or <NUM>) generates a second duplicated current proportional to the sampling current I1_j. In an embodiment, in an ideal state, the second duplicated current can be approximately equal to the sampling current I1_j by properly setting the parameters of the relevant components. The operating current IOPj and the sampling current I1_j flow through the first path corresponding to the converter 211_j. The first duplicated current and the second duplicated current flow through the second path corresponding to the converter 211_j.

In an embodiment, each mirroring unit includes a first branch, a second branch, and a third branch. The sampling current I1_j flows through the first branch coupled to the converter 211_j (j=<NUM>, <NUM>, or <NUM>). The second branch coupled to the first branch generates a first duplicated current proportional to the sampling current I1_j. The first duplicated current flows from the second path corresponding to the converter 211_j to the second branch. The third branch coupled to the converter 211_j generates a second duplicated current proportional to the operating current IOPj. The second duplicated current flows from the second path corresponding to the converter 211_j to the third branch.

In the embodiment shown in <FIG>, the mirroring unit 410_1 includes a first branch, a second branch, and a third branch. The first branch includes a transistor M1, the second branch includes a transistor M2, and the third branch includes a transistor M3. The gate of the transistor M1 is coupled to the gate of the transistor M2 to constitute a current mirror structure, and the gate of the transistor M3 is coupled to components related to the operating current IOP1 inside the operational amplifier OP1 to constitute a current mirror structure. The sampling current I1_1 flows to the ground via the transistor M1. The transistor M2 duplicates the sampling current I1_1 flowing through the transistor M1 to generate a first duplicated current. The first duplicated current flows to the transistor M2 via the second path corresponding to the converter 211_1. The transistor M3 duplicates the operating current IOP1 of the converter 211_1 to generate a second duplicated current. The second duplicated current flows to the transistor M3 via the second path corresponding to the converter 211_1. In the <FIG> embodiments, the structures of the mirroring unit 410_2 and 410_3 are the same as that of the mirroring unit 410_1.

In operation, the controller 210B in <FIG> selectively turns on the switching unit 212J corresponding to the battery cell CELLj (j=<NUM>, <NUM>, or <NUM>), the converter 211_j corresponding to the battery cell CELLj is enabled, and other converters are disabled. The mirroring unit 410_j corresponding to the battery cell CELLj is enabled to duplicate the current flowing through the first path corresponding to the converter 211_j. The voltage of the cell CELLj is detected by the converter 211_j.

For example, to detect the voltage of the cell CELL1, the switches S1 and K1 are turned on, and the converter 211_1 and the mirroring unit 410_1 are enabled. The mirroring unit 410_1 duplicates the current through the first path corresponding to the converter 211_1 to the second path corresponding to the converter 211_1. In an ideal state, with the duplicated current produced by the mirroring unit 410_1 , the current through the first path corresponding to the converter 211_1 is approximately equal to the current through the second path corresponding to the converter 211_1. The converter 211_1 detects the voltage of the cell CELL1 and generates a sampling signal SAM1 indicating the voltage of the cell CELL1.

The process of detecting the voltages of the battery cell CELL2 and CELL3 is similar to that of detecting the voltage of the battery cell CELL1. The process of detecting the voltage of the battery cell CELL4 is similar to that described with <FIG>.

According to the above description, by using the mirroring units, the current through the first path corresponding to the converter 211_i (i=<NUM>, <NUM>, or <NUM>) can be approximately equal to the current through the second path corresponding to the converter 211_i, so that the sampling signal can accurately indicate the voltage of the corresponding cell. Furthermore, by controlling (for example, reducing) the duty cycle of the on-time t of the switching unit corresponding to each battery cell, an average value of the differences between currents flowing through the battery cells can be reduced, thereby maintaining balance among the cells. The duty cycle refers to the ratio of the on-time t of each switching unit to the detection period T.

<FIG> shows a timing diagram of the switching units in the controller 210B in <FIG>. In the embodiment shown in <FIG>, during the time period from t0 to t1, only the switching unit 212_1 is turned on, and the converter 211_1 detects the voltage of the cell CELL1. In the time period from t2 to t3, only the switching unit 212_2 is turned on, and the converter 211_2 detects the voltage of the cell CELL2. In the time period from t4 to t5, only the switching unit 212_3 is turned on, and the converter 211_3 detects the voltage of the cell CELL3. During the time period from t6 to t7, only the switching unit 212_4 is turned on, and the converter 211_4 detects the voltage of the cell CELL4. In this embodiment, t1-t0 = t3-t2 = t5-t4 = t7-t6. In other embodiments, t1-t0, t3-t2, t5-t4, and t7-t6 may not be equal.

By controlling (for example, reducing) the duty cycle of the on-time t of each switching unit, an average value of the difference between the current flowing through each battery cell can be reduced, thereby maintaining balance among the cells.

<FIG> shows a circuit diagram of a controller 210C in accordance with embodiments of the present invention.

Compared with the controller 210A in <FIG>, the controller 210C shown in <FIG> further includes a mirroring unit <NUM> and a compensation circuit <NUM>.

The mirroring unit <NUM> is coupled to the second path corresponding to the top cell CELL1, and is operable for duplicating the operating current IOP1 and the sampling current I1_1 of the converter 211_1 corresponding to the top battery cell, to reduce the difference between the current flowing through the first path corresponding to the converter 211_1 and the current flowing through the second path corresponding to the converter 211_1.

Specifically, to detect the voltage of the cell CELL1, the switching unit 212_1 and the switch SW1 are turned on, and the converter 211_1 and the mirroring unit <NUM> are enabled. The operating current IOP1 and the sampling current I1_1 provided by the anode of the battery cell CELL1 flow through the first path corresponding to the converter 211_1. The mirroring unit <NUM> duplicates the current flowing through the first path corresponding to the converter 211_1 to the second path corresponding to the converter 211_1, thereby reducing the difference between the current flowing through the first path corresponding to the converter 211_1 and the current flowing through the second path corresponding to the converter 211_1. In an embodiment, in an ideal state, by properly setting the parameters of related components and by using the mirroring unit <NUM>, the current flowing through the first path corresponding to the converter 211_1 is approximately equal to the current flowing through the second path corresponding to the converter 211_1. Therefore, the converter 211_1 can accurately detect the voltage of the battery cell CELL1.

The compensation circuit <NUM> is coupled to converters 211_1-<NUM><NUM>, and is operable for generating one or more compensation currents to compensate the currents of the first paths corresponding to one or more cells. The one or more battery cells can be battery cells other than the top battery cell (for example, battery cells CELL2 and CELL3).

Specifically, to detect the voltage of the battery cell CELLj (j=<NUM> or <NUM>), the switching unit 212J and the switch SWj are turned on, and the converter 211_j and the compensation circuit <NUM> are enabled. The converter 211_j receives the operating current IOPj and the sampling current I1_j provided by the cell CELLj through the first path corresponding to the converter 211_j. The compensation circuit <NUM> generates a compensation current ICOMj according to the operating current IOPj and the sampling current I1_j to compensate the current flowing through the first path corresponding to the battery cell CELLj.

In an embodiment, the compensation circuit <NUM> includes a detection unit <NUM> coupled to the multiple converters, and a compensation unit <NUM> coupled to the detection unit <NUM>. The detection unit <NUM> samples the operating current and the sampling current of the converters, and generates a respective reference current proportional to a sum of the operating current and the sampling current.

Specifically, to detect the voltage of the battery cell CELLj (j = <NUM> or <NUM>), the switching unit 212J is turned on, the converter 211_j is enabled, and the anode of the battery cell CELLj provides the operating current IOPj and sampling current I1_j to the converter 211_j through the corresponding first path. The switch SWj is turned on, and the detection unit <NUM> samples the operating current IOPj and the sampling current I1_j, and generates a reference current IREFj that is proportional to the sum of the operating current IOPj and the sampling current I1_j.

In an embodiment, the detection unit <NUM> includes a selector <NUM>, an operational amplifier OPC, a transistor MC1, a resistor Ra5, and a transistor MC2. The selector <NUM> is operable for selecting one sampling signal VSAMi from among multiple sampling signals. In an embodiment, the sampling signal VSAMi selected by the selector <NUM> is the sampling voltage corresponding to the battery cell CELLj. The transistor MC1 is respectively coupled to components related to the operating current IOPj in the operational amplifier OPj (j = <NUM>, <NUM>, or <NUM>) to constitute a current mirror that is operable for duplicating the operating current IOPj of the operational amplifier OPj. The sampling voltage VSAMi selected by the selector <NUM> is applied to the resistor Ra5 to generate a current ISR. The sum of the operating current IOPj and the current ISR is the reference current IREFi. The reference current IREFi flows through the transistor MC2 to ground. In an ideal state, by properly setting the parameters of related components, the current ISR can be approximately equal to the sampling current I1_i, and the reference current IREFi can be proportional to the sum of the operating current IOPj and the current ISR.

The compensation unit <NUM> generates a compensation current ICOMj that is proportional to the reference current IREFj (j=<NUM> or <NUM>). The compensation current ICOMj compensates the current flowing through the first path corresponding to the battery cell CELLj.

Specifically, the compensation unit <NUM> duplicates the reference current IREFj (j=<NUM> or <NUM>) to generate the compensation current ICOMj. When the switch SWj is turned on, the compensation current ICOMj flows from the compensation unit <NUM> to the first path corresponding to the battery cell CELLj. In an ideal state, by properly setting the parameters of the relevant components, the magnitude of the compensation current ICOMj (j = <NUM> or <NUM>) is approximately equal to the sum of the operating current IOPj and the sampling current I1_j, such that the overall current flowing through the first path corresponding to the converter 211_j is equal to zero. Meanwhile, since the switching unit 212_(j+<NUM>) is turned off, the current flowing through the second path corresponding to the converter 211_j is also zero. Because the current flowing through the first path corresponding to the converter 211_j and the current flowing through the second path corresponding to the converter 211_j are both zero, the converter 211_j can accurately detect the voltage of the battery cell CELLj.

In an embodiment, the compensation unit <NUM> includes transistors MP1, MP2, and MP3. The transistor MP1 and the transistors MP2 and MP3 constitute a current mirror that is operable for duplicating the reference current IREFj flowing through the transistor MP1 to generate a corresponding compensation current ICOMj. When the switch SWj (j=<NUM> or <NUM>) is turned on, the compensation current ICOMj flows from the compensation unit <NUM> to the first path corresponding to the converter 211_j, so that the overall current flowing through the first path corresponding to the converter 211_j is approximately equal to zero.

According to the above description, the converters can accurately detect the voltage of each battery cell. However, when detecting the voltage of the battery cell CELL1, the duplicated current generated by the mirroring unit <NUM> flows from a node between the cathode of the battery cell CELL1 and the anode of the battery cell CELL2 through the resistor RF2, causing the current flowing through the battery cell CELL1 to be less than the current flowing through other battery cells. This will cause the battery pack to lose its balance. To address this, the compensation circuit <NUM> in the controller 210C according to an embodiment of the present invention is further operable for generating a balancing current IBL. When the switch SW2 is turned on, the balancing current IBL flows from the compensation unit <NUM> through the second path corresponding to the converter 211_1 to the cathode of the top battery cell CELL1, and further flows to the anode of the top battery cell CELL1 to reduce the difference between the current flowing through the top battery cell and the current flowing through other battery cells, thereby maintaining balance among each cell.

<FIG> and <FIG> show timing diagrams associated with the controller 210C. In an embodiment as shown in <FIG>, in a detection period T, the controller 210C first detects the voltage of each battery cell once (e.g., from CELL1 to CELL4), and then enables the converter 211_1 corresponding to the top battery cell CELL1 again. The compensation circuit <NUM> generates a balancing current IBL proportional to the sum of the operating current IOP1 and the sampling current I1_1 of the converter 211_1. In another embodiment as shown in <FIG>, when detecting the voltage of the cell CELLi, the compensation circuit <NUM> generates a balancing current IBL proportional to the sum of the operating current IOPi and the sampling current I1_i of the converter 211_i corresponding to the cell CELLi. In the example of <FIG>, CELLi is CELL4. In other examples, CELLi may be any battery cell other than the top battery cell CELL1 and the lower battery cell adjacent to the top battery cell (i.e., CELL2). A detailed description is given below.

<FIG> shows a timing diagram of multiple switching units in the controller 210C in <FIG>, in accordance with embodiments of the present invention.

In the time period from t0 to t1, the controller 210C detects the voltage of the battery cell CELL1. The switching unit 212_1 and the switch SW1 are turned on, and the converter 211_1 and the mirroring unit <NUM> are enabled. The mirroring unit <NUM> duplicates the current flowing through the first path corresponding to the converter 211_1 to the second path corresponding to the converter 211_1. The converter 211_1 detects the voltage of the cell CELL1 and generates a sampling signal SAM1 indicating the voltage of the cell CELL1. During this time period, there is current flowing through the second path corresponding to the converter 211_1, and thereby the current flowing through the battery cell CELL1 is less than the current flowing through other battery cells.

During the time period from t2 to t3, the controller 210C detects the voltage of the battery cell CELL2, and during the time period from t4 to t5, the controller 210C detects the voltage of the battery cell CELL3. When the voltage of the cell CELLj (j=<NUM> or <NUM>) is detected, only the switching unit 212_j and the switch SWj are turned on, and the converter 211_j and the compensation circuit <NUM> are enabled. The anode of the battery cell CELLj provides the operating current IOPj and the sampling current I1_j to the converter 211_j through the corresponding first path. The detection unit <NUM> samples the operating current IOPj and the sampling current I1_j, and generates a reference current IREFj proportional to the sum of the operating current IOPj and the sampling current I1_j. The compensation unit <NUM> generates a compensation current ICOMj according to the reference current IREFj. The compensation current ICOMj compensates the current through the first path corresponding to the battery cell CELLj. Due to the effect of the compensation current ICOMj, the current flowing through the first path corresponding to the battery cell CELLj is reduced. In an ideal state, by properly setting the parameters of the relevant components, the compensation current ICOMj (j = <NUM> or <NUM>) is approximately equal to the sum of the operating current IOPj and the sampling current I1_j, so that the overall current flowing through the first path corresponding to the converter 211_j is approximately equal to zero. During this time period, since the switching unit 212_(j+<NUM>) is off, the current flowing through the second path corresponding to the converter 211_j is also zero. Therefore, the converter 211_j can accurately detect the voltage of the battery cell CELLj.

During the time period from t6 to t7, the controller 210C detects the voltage of the battery cell CELL4. The process of detecting the voltage of the battery cell CELL4 is similar to that described with <FIG>.

During the time period from t8 to t9, the controller 210C compensates the current consumed by the cell CELL1. The switching unit 212_1 and the switch SW2 are turned on again, and the converter 211_1 and the compensation circuit <NUM> are enabled. The anode of the battery cell CELL1 provides the converter 211_1 with the operating current IOP1 and the sampling current I1_1. The compensation circuit <NUM> samples the operating current IOP1 and the sampling current I1_1 and generates a balancing current IBL that is proportional to the sum of the operating current IOP1 and the sampling current I1_1. The balancing current IBL flows from the cathode of the battery cell CELL1 to the anode of the battery cell CELL1. In this example, the balancing current IBL only increases the current flowing through the battery cell CELL1. In an ideal state, by properly setting the parameters of related components, the balancing current IBL is approximately equal to the sum of the operating current IOP1 and the sampling current I1_1. This method can accurately compensate the reduced current consumed by the battery cell CELL1.

In this embodiment, t1-t0 = t3-t2 = t5-t4 = t7-t6 = t9-t8. In other embodiments, t1-t0, t3-t2, t5-t4, t7-t6, and t9-t8 may not be equal.

<FIG> shows another timing diagram of multiple switching units in the controller 210C in <FIG>, in accordance with embodiments of the present invention. In the time period from time t0 to t6, the process of detecting the voltages of the battery cells CELL1, CELL2, and CELL3 is similar to that described with <FIG>.

In the time period from t6 to t7, the controller 210C detects the voltage of the battery cell CELL4. The switching unit 212_4 is turned on and the switching unit 212_5 is turned off. The converter 211_4 detects the voltage of the cell CELL4 and generates a sampling voltage VSAM4 indicating the voltage of the cell CELL4. The compensation circuit <NUM> turns on any one of the switching units 212_1-212_3, samples the operating current of the operational amplifier corresponding to the turned-on switching unit, and samples the sampling voltage VSAM4 to generate a balancing current IBL. The balancing current IBL flows from the cathode of the battery cell CELL1 to the anode of the battery cell CELL1. In this example, the balancing current IBL only increases the current flowing through the battery cell CELL1. This method can compensate the reduced current consumed by the battery cell CELL1 while detecting the voltage of the battery cell CELL4, thus saving time and reducing power consumption.

In this embodiment, t1-t0 = t3-t2 = t5-t4 = t7-t6. In other embodiments, t1-t0, t3-t2, t5-t4, and t7-t6 may not be equal. In the example of <FIG>, when the voltage of the battery cell CELL4 is detected, the compensation circuit <NUM> generates a balancing current IBL. In other examples, when detecting other battery cells (e.g., CELL3), the compensation circuit <NUM> generates a balancing current IBL according to the operating current and sampling voltage of the operational amplifier corresponding to the battery cell being detected.

In the embodiments shown in <FIG> and <FIG>, the compensation current generated by the compensation circuit <NUM> makes the overall current through the first path corresponding to the converters <NUM>-<NUM> and <NUM>-<NUM> approximately equal to zero, and the balancing current generated by the compensation circuit <NUM> makes the current flowing through cell CELL1 during detecting period T is approximately equal to the current flowing through other cells. Therefore, while enabling each converter to accurately detect the voltage of each battery cell, it also maintains balance between current flowing through each battery cell so that the life span of the battery pack is not shortened.

<FIG> shows a flowchart <NUM> of a method for detecting battery cell voltages.

In block <NUM>, converters are respectively coupled to anodes of battery cells through switching units.

In block <NUM>, a corresponding switching unit of a battery cell is turned on to enable the anode of a battery cell to provide an operating current and sampling current to a respective converter through a respective first path for the battery cell. The operating current flows from the anode of the battery cell through the respective converter to ground.

In block <NUM>, the respective converter detects a voltage of the battery cell.

As described above, the present invention discloses a controller and a method for detecting battery cell voltages. The embodiments according to the present invention reduce the difference between the current through a first path coupled between a converter and an anode of a corresponding battery cell and the current through a second path coupled between the converter and a cathode of the corresponding battery cell, thereby enabling the converters to accurately detect the voltage of each battery cell.

Claim 1:
A method for detecting voltages of a plurality of battery cells (CELL1, CELL2, CELL3, CELL4) in a battery pack,
wherein each battery cell of said plurality of battery cells is coupled to a respective converter of a plurality of converters (211_1, 211_2, 211_3),
wherein said plurality of converters are coupled to anodes of said plurality of battery cells through a plurality of switching units (212_1, <NUM>-<NUM>, 212_3), wherein an anode of said each battery cell is coupled to said respective converter through a respective first path of a plurality of first paths, and wherein a cathode of said each battery cell is coupled to said respective converter through a respective second path of a plurality of second paths, said method comprising:
turning on a switching unit of said plurality of switching units, said switching unit corresponding to a battery cell of said plurality of battery cells, to enable said anode of said battery cell to provide an operating current and a sampling current through said respective first path for said battery cell to said respective converter for said battery cell, wherein said operating current flows from said anode of said battery cell through said respective converter for said battery cell to ground; and
detecting a voltage of said battery cell by said respective converter for said battery cell, characterized in:
duplicating, by a mirroring unit (410_1, 410_2, 410_3), an operating current and a sampling current of a first converter of said plurality of converters corresponding to a first battery cell of said plurality of battery cells, to reduce a difference between a current through a first path of said plurality of first paths that corresponds to said first converter and a current through a second path of said plurality of second paths that corresponds to said first converter, wherein said mirroring unit is coupled to said second path that corresponds to said first converter.