Methods and apparatus for voltage and current calibration

A calibration circuit according to various aspects of the present invention comprises a battery pack, a protection IC, and a power source. The power source may have a predetermined voltage and may be selectively coupled to the protection IC. The power source may be capable of providing a current to the protection IC through one of a first current loop and a second current loop, wherein the current through the first current loop generates a first voltage across a first and second terminal of the protection IC, and the current through the second current loop generates a second voltage across the first and second terminals that is substantially equal to the voltage of the power source.

BACKGROUND OF THE TECHNOLOGY

The rise in capacity of batteries requires new protection circuits to protect the battery from over-voltage or over-current situations. As the transistors operating the protection circuit become more sensitive over time, so must the calibration equipment used to calibrate the protection circuits.

SUMMARY OF THE INVENTION

A calibration circuit according to various aspects of the present invention may operate in conjunction with a power source and a battery pack including a protection IC. The power source may have a predetermined voltage and may be selectively coupled to the protection IC. The power source may be capable of providing a current to the protection IC through one of a first current loop and a second current loop, wherein the current through the first current loop generates a first voltage across a first and second terminal of the protection IC, and the current through the second current loop generates a second voltage across the first and second terminals that is substantially equal to the voltage of the power source.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present technology may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions and achieve the various results. For example, the present technology may employ various voltage sensors, current sensors, current sources, voltage sources, semiconductor devices such as transistors and capacitors, and the like, which may carry out a variety of functions. In addition, the present technology may be practiced in conjunction with any number of electrical systems and the systems described are merely exemplary applications for the technology. Further, the present technology may employ any number of conventional techniques for measuring current and voltage levels as well as data trimming processes.

Referring toFIGS. 1A-E, in one embodiment, a calibration circuit100for calibrating the voltage and/or current of a protection IC102of a battery pack105may comprise a power source101, a pulse generator103, and a current source104. The battery pack105may include a battery (not shown), and the protection IC102may comprise an internal storage unit (not shown) configured to receive and store a plurality of data related to the calibration circuit100.

The power source101may provide a predetermined voltage (VSET). For example, the power source101may provide an initial VSETwhich may be utilized by the calibration circuit100when calibrating the voltage and/or current for the protection circuit102. The power source101may provide the desired signal in any appropriate manner, such from a battery, a voltage regulator, or other suitable source. In the present embodiment, the power source101comprises a conventional voltage regulator for providing a selected voltage to a load.

Now referring toFIGS. 1A-C, in one embodiment, the power source101may be selectively coupled to the protection IC102and provide a current to the protection IC102through either a first current loop118or a second current loop119. The first switching device112may be configured to select between the first current loop118or the second current loop119.

The calibration circuit100may utilize either the first current loop118or the second current loop119, depending on various characteristics the calibration circuit100is attempting to calibrate. For example, the first current loop118may be utilized when the calibration circuit100calibrates the voltage of the protection IC102, and the second current loop119may be utilized when the calibration circuit100calibrates the current of the protection IC102.

In one embodiment, the calibration circuit100may operate in conjunction with a plurality of resistors106-110to assist in directing either the first current loop118and/or the second current loop119. A subset of the resistors106,107, and108may not be applicable until another electrical component is coupled to the calibration circuit100(contact resistance). For example, when an electrical component is electrically coupled to resistor R1106, R2107, and/or R3108, the electrical connection creates impedance in the electrical flow of the calibration circuit100. In contrast, when no other electrical components are coupled to resistors106,107, and108, no additional impedance is created in the electrical flow. Resistor RS110may comprise a sense resistor coupled between the power source101and a second terminal116of the protection IC102.

In one embodiment, the battery pack105may comprise transistors117electrically coupled to the IC102. The transistors117may comprise any suitable transistor(s), for example, a FET transistor. The transistors117may operate as switches having a plurality of operating states such as an “on” (activated) state, “off” (deactivated) state, and/or the like. The calibration circuit100may determine the operating state of the transistors117. For example, the calibration circuit100may determine whether the transistors117are on/activated or off/deactivated.

In one embodiment, the battery pack105may comprise any suitable system or device configured to operate as a battery. The battery pack105may comprise a positive battery terminal (BAT+)121and a negative battery terminal (BAT−)122. The battery pack105may further comprise a positive battery pack terminal (PAC+)123and a negative battery pack terminal (PAC−)124.

In one embodiment, the protection circuit102may comprise two electrical terminals configured to provide an electrical contact such that the current and voltage of the calibration circuit100can be monitored or collected. For example, a first terminal115and a second terminal116may provide a testing point for calibrating the voltage of the protection IC102. A third terminal114may be configured to provide a testing point for calibrating the current of the protection IC102.

The pulse generator103provides electrical pulses. The pulse generator may comprise any suitable system or device configured to provide the calibration circuit100with electrical pulses. For example, the pulse generator103may apply a test signal to the protection IC102.

The current source104may comprise any suitable system or device configured to provide the calibration circuit100with a current. The current source104may be coupled between the negative pack terminal and the negative battery terminal to form a third current loop120through the battery pack105as shown inFIGS. 1D and 1E. The current source104may be configured to be disabled or disconnected from the battery pack105, for example with a second switching device113. The second switching device113may be configured to operate as a bypass, wherein the bypass restricts the flow of the third current loop120and prevents the third current loop120from entering the battery pack105.

Still referring toFIGS. 1A-C, in one embodiment, the power source101may operate in conjunction with the first switching device112to generate either a first current loop118or a second current loop119. The first switching device112may select between using one of the first current loop118or the second current loop119.

The first current loop118may originate from the power source101. The first current loop118may flow through at least one resistor (R4)109. The voltage between terminals115and116of the IC102may be designated as VCC111. In an ideal configuration, the value of VCC111should be as close to the value of the VSETproduced by the power source101. For example, if the power source101is configured to produce a 3.7V VSET, then the value of VCCshould be as close to 3.7V as possible. As discussed below, the calibration circuit100may utilize the first switching device112to direct the first current loop118such that the value of Vcc is close to the value produced by the power source101.

In one embodiment, the first switching device112may be configured to be in one of two positions. The calibration circuit100may be configured with any suitable system or device configured to switch the positions of the first switching device112from a first position to a second position. The first position may comprise a “HIGH” position, and the second position may comprise a “LOW” position. When the first switching device112is configured in a “HIGH” position, the path of the current flowing from the power source101may follow that of the second current loop119as shown inFIG. 1C. In this configuration, the second current loop119may originate from the power source101and flow through the sense resistor RS110coupled between the power supply and the second terminal116of the protection IC102.

When the first switching device112is configured in a “LOW” position, the path of the current flowing from the power source101may follow that of the first current loop118as shown inFIG. 1B. In this configuration, the first current loop118may bypass the sense resistor RS110and provide a direct coupling of the power source101to the second terminal116of the protection IC102.

Now referring toFIGS. 1E and 2A to 2E, in one embodiment, the calibration circuit100may be configured to calibrate the protection IC102for either voltage or current. The calibration circuit100may selectively couple the power source101to the protection IC102through either the first current loop118or the second current loop119via the first switching device112depending on the characteristic (voltage or current) being calibrated.

Prior to the calibration phase, the calibration circuit100may first begin an initialization phase (201). After the initialization phase (201), the calibration circuit100may trim the VCCvoltage data111(202). Once the VCCvoltage data111has been trimmed, the calibration circuit100may perform calibration of the IC102(203). Afterwards, the calibration circuit100may begin a finalization phase (204).

In one embodiment, the initialization phase (201) may comprise providing the current source104and power source101with an initial set of settings (205). The initial settings may comprise any suitable settings for utilizing the calibration circuit100. For example, the initial settings may comprise setting the value of VSETfor the power source101as well as configuring the current level produced by the current source104.

Referring now toFIG. 2B, in one embodiment, the initialization phase (201) may include the calibration circuit100setting the first switching device112to a “LOW” position (206). As previously discussed above, when the first switching device112is set in the “LOW” position, a current path resembling the first current loop118can be observed flowing through the calibration circuit100as shown inFIG. 1B. Furthermore, as discussed above, in this configuration, the first current loop118bypasses resistor RS110.

In one embodiment, the calibration circuit100may also set the second switching device113to a “LOW” position (207) during the initialization phase (201). When the second switching device113is set in a “LOW” position, the second switching device113closes and the current path produced by the current source104is bypassed/prevented from flowing into battery pack105.

In one embodiment, the initialization phase may include activating the power source101and/or current source104(208), such as after both the first switching device112and second switching device113have been set into their respective “LOW” positions. The power source101and the current source104may be activated using the initial set of settings. The power source101and current source104may be activated in any order. For example, in one instance, the power source101may be activated prior to activating the current source104. In another example, the current source104may be activated prior to activating the power source101.

Now referring toFIGS. 2A-D, the calibration circuit100may be configured to trim the VCCvoltage data111(202), such as after the initialization phase (201). In one embodiment, the data to be trimmed may comprise an 8-bit value corresponding to a detected VCCvoltage across terminals115and116of the protection IC102. The trimmed data may be configured to be stored within a storage unit (not shown) communicatively coupled to the protection IC102and/or the calibration circuit100.

In one embodiment, all bits within the 8-bit voltage value may be set to “LOW” (00000000). The second switching device113may be selectively set in the “HIGH” position, opening the second switching device113to couple the current source104to the protection IC102through the third current loop120(210).

The calibration circuit100may determine the operating state of the transistors117(211), such as after the third current loop119has been selectively coupled to the current source104. If the transistors117are determined to be on or active, then the current bit of the 8-bit value corresponding to the voltage may be set to “HIGH” (corresponding to a value of 1) (212). If the transistors117are determined to be off or inactive, then the present bit of the 8-bit value corresponding to the voltage may be set to “LOW” (corresponding to a value of 0) (213).

Next, the calibration circuit100determines whether additional iterations are needed or if the trimming process has been completed by determining the binary position of the next data bit in the 8-bit voltage data. In this particular example, because the detected voltage value is represented using an 8-bit value, the process may be repeated up to eight times (once for each bit of the eight possible bits). The calibration circuit100may be configured to check with the least significant bit of the 8-bit detected voltage value that is being trimmed (214). If the calibration circuit100determines that the current bit being trimmed is the least significant bit (214), then the calibration circuit100may be configured to initiate the finalization phase (204).

If the calibration circuit100determines that the bit to be trimmed is not the least significant bit, then the calibration circuit100may change the position of the second switching device113from “LOW” to “HIGH” (215). Changing the position of the second switch to “HIGH” may result in the third current path120being permitted to flow through the calibration circuit100again.

After setting the second switch to a “HIGH” position (215), the calibration circuit100may set the next lower bit in the 8-bit value corresponding to the voltage value to “H” (corresponding to the value of 1) (216). The calibration circuit100may then be configured to repeat the above process. The process may be repeated by the calibration circuit100until all eight bits of the 8-bit value have been trimmed.

In one embodiment, the calibration circuit100may be configured to store the 8-bit value in the internal storage unit (not shown) of the IC102. Other components may access the calibration circuit100and obtain the value from the IC102.

Now referring toFIG. 1E, in one embodiment, the power source101may be configured to facilitate a 3 μA current (ICC), resistors R1106and R3108may comprise 50 mΩ resistors, resistor R4may comprise a 1 kΩ resistor, resistor RS may comprise a 500Ω, and the third current path120may comprise a 10 A current (ICS). The value of VCC111may be measured as 4.39695V. The value of VSETmay be calculated according to Equation 1 below:
VSET=VCC+ICC*R1+ICC*R4+(ICC+ICS)*R3(Equation 1)

Using the values from above to calculate the value of VSET:
VSET=4.39695V+3 μA*50 mΩ+3 μA*1 kΩ+(3 μA+1 mA)*50 mΩ

Thus, the value of VSETis approximately 4.4V.

Now referring toFIG. 1D and 2C, in one embodiment, the calibration circuit100may calibrate the current of the protection circuit102. Calibrating the current may comprise substantially the same process described above, with a few differences. First, to calibrate the current, the calibration circuit100may switch the first switching device112to a “HIGH” position (209). As discussed above, when the first switching device112is configured in the “HIGH” position, the current path may be represented by the second current loop119.

In the foregoing description, the technology has been described with reference to specific exemplary embodiments. The particular implementations shown and described are illustrative of the technology and its best mode and are not intended to otherwise limit the scope of the present technology in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the method and system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or steps between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system.

The technology has been described with reference to specific exemplary embodiments. Various modifications and changes, however, may be made without departing from the scope of the present technology. The description and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present technology. Accordingly, the scope of the technology should be determined by the generic embodiments described and their legal equivalents rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be executed in any order, unless otherwise expressly specified, and are not limited to the explicit order presented in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present technology and are accordingly not limited to the specific configuration recited in the specific examples.

Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments. Any benefit, advantage, solution to problems or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced, however, is not to be construed as a critical, required or essential feature or component.

The present technology has been described above with reference to an exemplary embodiment. However, changes and modifications may be made to the exemplary embodiment without departing from the scope of the present technology. These and other changes or modifications are intended to be included within the scope of the present technology, as expressed in the following claims.