INTEGRATED HETEROGENEOUS THERMISTOR ARRANGEMENT FOR HIGH VOLTAGE PRE-CHARGE CIRCUIT

A pre-charge circuit. The precharge circuit may include a switching device for controlling a voltage to be supplied to a battery; and a heterogeneous thermistor circuit, coupled to the switching device. The heterogeneous thermistor circuit may include a negative temperature coefficient (NTC) component; and a polymer positive temperature coefficient (PPTC) component, arranged in electrical series with the NTC component and the switching device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application serial number 2023105063275, filed May 5, 2023, entitled “INTEGRATED HETEROGENEOUS THERMISTOR ARRANGEMENT FOR HIGH VOLTAGE PRE-CHARGE CIRCUIT,” which is incorporated by reference herein in its entirety.

BACKGROUND

Field

Embodiments relate to the field of resistance current suppressor, and more particularly to the suppressor based upon NTC and PPTC materials.

Discussion of Related Art

In the present day, electric vehicles (EV) and energy storage system (ESS) that are battery powered may include controllers that have high capacitive loads may be used to regulate motors. High voltage (HV) positive and negative contactors are used in an EV and an ESS to act as an emergency disconnect when the motor regulator fails. In present day EVs/ESSs, a pre-charge circuit may be used to avoid contactor damage that would otherwise take place due to high inrush currents. However, such circuitry may include large power resistors that occupy unduly high fraction of the design space for a pre-charge circuit. Using such known pre-charge circuitry, when a circuit problem takes place, such as a short circuit, or main contactor not being properly closed, the large resistor may be burned out quickly.

With respect to this and other considerations the present disclosure is provided.

BRIEF SUMMARY

In one embodiment, a pre-charge circuit is provided. The precharge circuit may include a switching device for controlling a voltage to be supplied to a battery; and a heterogeneous thermistor circuit, coupled to the switching device. The heterogeneous thermistor circuit may include a negative temperature coefficient (NTC) component; and a polymer positive temperature coefficient (PPTC) component, arranged in electrical series with the NTC component and the switching device.

In another embodiment, a battery circuit may include a first terminal line for connecting an external component to a first terminal of a battery. The battery circuit may also include a first main contactor, connected in series along the first terminal line; and a pre-charge circuit, connected along a pre-charge path that extends parallel to the first main contactor, between the first terminal and the external component. The pre-charge circuit may include a silicon-controlled rectifier (SCR); and a heterogeneous thermistor circuit, coupled in electrical series to the SCR. The heterogeneous thermistor circuit may include a negative temperature coefficient (NTC) component; and a polymer positive temperature coefficient (PPTC) component, arranged in electrical series with the negative temperature coefficient (NTC) component and the SCR.

In a further embodiment, a heterogeneous thermistor circuit for use in a pre-charge circuit is provided. The heterogeneous thermistor circuit may include a negative temperature coefficient (NTC) component; at least one polymer positive temperature coefficient (PPTC) component, arranged in electrical series with the negative temperature coefficient (NTC) component; and a thermal coupler, disposed between the at least one PPTC component and the NTC component.

DESCRIPTION OF EMBODIMENTS

The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. The embodiments are not to be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey their scope to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

In the following description and/or claims, the terms “on,” “overlying,” “disposed on” and “over” may be used in the following description and claims. “On,” “overlying,” “disposed on” and “over” may be used to indicate that two or more elements are in direct physical contact with one another. Also, the term “on,”, “overlying,” “disposed on,” and “over”, may mean that two or more elements are not in direct contact with one another. For example, “over” may mean that one element is above another element while not contacting one another and may have another element or elements in between the two elements. Furthermore, the term “and/or” may mean “and”, it may mean “or”, it may mean “exclusive-or”, it may mean “one”, it may mean “some, but not all”, it may mean “neither”, and/or it may mean “both”, although the scope of claimed subject matter is not limited in this respect.

In various embodiments, a novel pre-charge component and pre-charge circuit is provided for protecting a battery circuit. The novel pre-charge circuit of the present embodiments, may be used to manage current flow in an electric circuit that includes a battery circuit. Suitable applications for the pre-charge circuit of the present embodiments includes a battery circuit of an electric vehicle. Batteries may be used to power various loads or components in an electric vehicle, including a motor. In such circuits the pre-charge component is formed of a hybrid or heterogeneous thermistor arrangement, including both a negative temperature coefficient resistance (NTC) component and a polymer positive temperature coefficient resistance (PPTC) component. As such, the cold resistance may be customized to limit peak charging current to less than the limitation of an SCR or similar component in the pre-charge circuit. The novel pre-charge circuit of the present embodiments also provide dynamic resistance change during capacitor charging to withstand a high current, in a small package size. Moreover, as detailed below, the heterogeneous thermistor component, by integrating a PPTC, will protect the NTC component from an overtemperature condition in case of a short circuit fault.

Turning to theFIG.1there is shown an electric circuit100, according to embodiments of the disclosure. The electric circuit100may include a first terminal line126for connecting an external component, such as a motor, to a first terminal120A of a battery120. The electric circuit100may also include a first main contactor122, connected in series along the first terminal line126. In this example, the first terminal line126is connected to a positive terminal of the battery120. The electric circuit100further may include a second terminal line128for connecting the external component to a second terminal120B of the battery120, as well as a second main contactor124, connected in series along the second terminal line128. When closed, the first main contactor122and the second main contactor124will complete a circuit that couples the battery120to drive external component(s), such as a motor(s). Likewise, when closed, the first main contactor122and the second main contactor124will complete a circuit to allow charging of the battery120. The electric circuit100may further include a component that is termed a pre-charge circuit102, connected along a pre-charge path130that extends parallel to the first main contactor122, between the first terminal120A and external component(s) (see, for example, motor controller134and load, as examples of external components.

According to the present embodiments, the pre-charge circuit102may include a silicon-controlled rectifier, shown as SCR104, as well as a heterogeneous thermistor circuit106. The heterogeneous thermistor circuit106may include a negative temperature coefficient resistance (NTC) component108, as well as a polymer positive temperature coefficient resistance (PPTC) component110, arranged in electrical series with the SCR104. The term ‘heterogenous thermistor’ as used herein may refer to a component or circuit that includes an NTC component, arranged in series with a PPTC component. This pre-charge circuit102may be suitable to replace existing pre-charge circuit contactors.

An advantage of this heterogeneous thermistor circuit106, is that the overall pre-charge circuit is simpler, smaller, and more cost efficient than a pre-charge circuit using a simple resistor, for example. The use of the NTC component108, for example, allows the overall resistance of the heterogeneous thermistor circuit106to be customized according to the use temperature of the pre-charge circuit102. The use of the PPTC component110by integrating a PPTC, will protect the NTC component108from an overtemperature condition in case of a short circuit fault.

FIG.2Adepicts a perspective view of a variant of the heterogeneous thermistor circuit106, according to embodiments of the disclosure.FIG.2Bdepicts a plan view of an NTC component108of the heterogeneous thermistor circuit106, according to embodiments of the disclosure.FIG.2Cdepicts a plan view of a PPTC component110of the heterogeneous thermistor circuit106according to embodiments of the disclosure.FIG.2Ddepicts a side view of a variant of the heterogeneous thermistor circuit106according to embodiments of the disclosure. Note that, in various embodiments as illustrated inFIG.2D, the PPTC component110and NTC component108may be thermally coupled to one another using, for example, a thermal coupler112, which coupler is disposed between a main surface of the NTC component108and a main surface of the PPTC component110. The thermal coupler112may also be an electrical conductor that acts to electrically connect the PPTC component110and NTC component108. While shown as a flat structure inFIG.2D, in some embodiments the thermal coupler112may be a wire that is an electrical conductor and a thermally conductive wire that electrically and thermally couples the PPTC component110and NTC component108. Note that the PPTC component110and NTC component108may each be provided with metallized surfaces that act as an electrode. These surfaces are shown as surface108A and surface110A. In addition, the PPTC component110and NTC component108may each be provided with outer metallized surfaces that act as an electrode. These surfaces are shown as surface108B and surface110B. These latter surfaces act as electrodes that may couple to external leads, shown as lead116and lead114.

Note that according to various embodiments, the individual components and overall size of the heterogeneous thermistor circuit106may be relatively compact, as illustrated inFIG.2BandFIG.2C, for example. One non-limiting embodiment may limit the diameter of the NTC component108to 36 mm. As an example, the NTC component108may be a known ceramic NTC that is in the shape of a disc, having a maximum thickness of 8.5 mm. In one non-limiting embodiment the PPTC component110may be a rectangular disc, such as a square disc having a size of 30 mm along one edge and 30 mm along the perpendicular edge.

According to some embodiments, the NTC component108may exhibit a relatively higher resistance (for comparison, this resistance may be a room temperature (RT) resistance), while the PPTC component exhibits a relatively lower (RT) resistance, such as 1 Ohm or less. Returning toFIG.1, during operation of the electric circuit100, when the battery120is to be disconnected from an external load, the first main contactor122and the second main contactor122are maintained in an open position, as shown. During this first state, the first terminal line126and second terminal line are thus disconnected from the external load. In a pre-charge state, the second main contactor124is placed in a closed position, and a current is passed through the pre-charge circuit102. The SCR104or similar component may act as a switch to connect the pre-charge circuit to the battery120. During a charging state, the first main contactor122is closed while maintaining the second main contactor124also in a closed position. In a fault condition, when the first main contactor122fails to close at the appropriate time, excess current may be driven through the pre-charge circuit102, in which circumstance the PPTC component110, by tripping at a predetermined temperature, may protect the NTC component108from overheating.

FIG.3Ashows a side view of a heterogeneous thermistor circuit300according to embodiments of the disclosure. In this embodiment, external leads304are coupled to each of the NTC component108and PPTC component110. The heterogeneous thermistor circuit300includes just one NTC component and just one PPTC component. In this simple design, the overall size of the heterogeneous thermistor circuit300may be minimized.

FIG.3Bshows a side view of a heterogeneous thermistor circuit310according to embodiments of the disclosure. In this embodiment, a pair of NTC components, each shown as NTC component108, are affixed to opposite sides of the PPTC component110. In this configuration, the width of the heterogeneous thermistor circuit310may be greater than the width of the heterogeneous thermistor circuit300. However, during operation, the advantage of this embodiment is that, when excess current is driven through the heterogeneous thermistor circuit310, both main surfaces (left side vertical and right side vertical) of the PPTC component110will be heated equally by the provision of a NTC component108adjacent each of the main surfaces. In this manner, the PPTC component110is more likely to heat up uniformly an properly trip in a timely fashion.

FIG.3Cshows a side view of a heterogeneous thermistor circuit320according to embodiments of the disclosure. In this embodiment the PPTC component110is arranged on a first side of the NTC component108, while a heating element322, is arranged on a second side of the NTC component108, opposite the first side. In this embodiment, a heater lead may be provided to independently provide current to the heating element322to heat the NTC component108and PPTC component110. The heterogeneous thermistor circuit320may further include sensor circuitry (not separately shown) to determine when to turn on the heating element322. For example, when ambient conditions for a battery circuit are below a certain threshold temperature, such as 0° C., for example, the heterogeneous thermistor circuit320may determine to provide heat to increase the temperature of the NTC component108and PPTC component110. This provision of independent heating may be useful, since at lower temperature, the resistance of the NTC component108may be unduly high, so that the heating element322may bring the resistance of the NTC component108down to a suitable operating range by increasing the temperature locally of the heterogeneous thermistor circuit320.

FIG.3Dshows a side view of a heterogeneous thermistor circuit330according to embodiments of the disclosure. In this embodiment, a first PPTC component, represented by PPTC component110, is arranged on a first side of the NTC component108and a second PPTC component332is arranged on a second side of the NTC component108, opposite the first side. As such, the NTC component108is arranged in electrical parallel fashion with the second PPTC component332via line334, and the NTC component108and second PPTC component332are arranged in electrical series with the first PPTC component110(seeFIG.3E). In operation, the second PPTC component332acts as a resistance balancing PPTC component that balances out the resistance behavior of the NTC component108. In other words, during a temperature range, such as below the trip temperature of the PPTC component110, the overall resistance of the heterogeneous thermistor circuit330will be determined by a combination of the resistance of the second PPTC component332and the NTC component108. As temperature varies over a given range, depending upon the absolute resistance of each of these components, the resistance of the heterogeneous thermistor circuit330will be dominated more by the resistance of the NTC component108of the second PPTC component332. Note that as temperature increases, the resistance of NTC component108will decrease while the resistance of the second PPTC component332will increase. Thus, by suitable choice of NTC and PPTC components, a suitable resistance behavior as a function of temperature may be achieved, in particular, a less variable resistance may be achieved over a desired temperature range.

FIG.4is a composite illustration showing a comparison of a known resistor and a heterogeneous thermistor circuit according to embodiments of the disclosure. A shown, the heterogeneous thermistor circuit of the present embodiments provides short circuit protection, higher power withstanding, and a much smaller overall size.

FIG.5Ais a composite illustration showing an exemplary set of waveforms for a high voltage DC test, and a summary of DC test results for a heterogeneous thermistor circuit according to embodiments of the disclosure. In particular, as shown in the insert, an NTC component and PPTC component are arranged in electrical series with one another under the Test conditions: 400 VDC/20 A, 1 sec on/120 sec OFF for a given cycle, with a total of 10 cycles. The results shown essentially no change in resistance between the NTC component and PPTC component before and after the performance of the test, indicating that the sample can withstand at least 4000 J energy. In contrast, when a prior art resistor (50 W, 20 Ohm; dimensions: 50 mm×30 mm×16 mm) used for pre-charge circuits was subject to a 24V/1 A test, the results after testing indicate fusing of parts of the resistor coil, where a temperature of above 400° C. was generated.

FIG.5Bpresents a summary of NTC component results for high voltage AC test of a heterogeneous thermistor circuit according to embodiments of the disclosure. In particular, as shown in the insert, an NTC component and PPTC component are arranged in electrical series with one another under an applied AC voltage where the test condition is 600 Vac/15A, 30 sec on/120 sec OFF for a given test cycle. The results shown a couple percent decrease in RT resistance of the NTC component after one cycle, and no systematic change thereafter up to 100 cycles. Thus, the NTC component can survive under 600 Vac/15 A conditions.

FIG.5Cis a composite illustration showing an exemplary set of waveforms for a high voltage DC test, simulating short circuit conditions, and a summary of DC test results for a heterogeneous thermistor circuit according to embodiments of the disclosure. The test conditions that apply are the performance of 10 cycles where a given cycle involves the application of 400 V DC/20 A, 15 sec on/120 sec OFF. The results indicate just a small change in room temperature resistance for both NTC and PPTC components of the heterogeneous thermistor, meaning the sample achieves superior self-protection results.

While the present embodiments have been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible while not departing from the sphere and scope of the present disclosure, as defined in the appended claims. Accordingly, the present embodiments are not to be limited to the described embodiments, and may have the full scope defined by the language of the following claims, and equivalents thereof.