MOSFET temperature sensing method and circuit for load switch applications

Abstract

This invention discloses a method and apparatus for temperature monitoring of a power transistor formed in a semiconductor chip. One side of a temperature-sensing resistor disposed in the semiconductor chip is coupled to the voltage input side of the power transistor. A controller coupled to a second side of the temperature-sensing resistor is configured to detect the voltage across the resistor and trigger a temperature-related correction action using the detected voltage.

Description

Technical Field

[0001] Various aspects of the present invention relate primarily to temperature monitoring of semiconductor devices, and more specifically, various aspects of the present invention relate to temperature sensing of transistor devices. Background Technology

[0002] In power device applications using semiconductor transistors, soft-start can lead to a significant difference between the input and output voltages of the power transistor. Switching across the power transistor with a large voltage difference can cause it to heat up, and without proper management, this can result in thermal damage. Therefore, temperature monitoring of the power transistor is necessary to ensure that it is not damaged by overheating.

[0003] Previous attempts to monitor the temperature of power transistors have involved using temperature resistors or diode networks physically placed near the semiconductor power transistor but not on the semiconductor chip itself. These temperature sensors were inaccurate due to poor thermal conduction between the temperature sensor and the power transistor package. Some thermal sensors use diode networks formed on the semiconductor chip of the transistor because this provides better thermal conduction. Diode network temperature sensors present additional challenges for temperature sensing because the voltage drop across the diodes is non-linear with respect to temperature. Furthermore, series-connected diode networks increase the error in temperature detection because variations in the manufacturing of each diode contribute to the detection error.

[0004] Pihet et al., in U.S. Patent 6,948,847, attempted to create a temperature-sensing resistor formed in a semiconductor chip connected to the gate contacts of a semiconductor transistor, but this is not applicable in many applications. Specifically, a temperature-sensing resistor connected to the gate input of a semiconductor transistor is unsuitable for load switching applications with gate signals, which have a high dynamic range in voltage and frequency because, due to the nature of switching, the gate voltage may be in a constant and unpredictable flux. Therefore, there is an urgent need in the art for a precise method to determine the temperature of a semiconductor transistor in high-frequency switching applications. Summary of the Invention

[0005] This invention discloses a device for monitoring the temperature of power transistors formed in a first semiconductor chip, comprising:

[0006] A temperature sensing resistor located in the first semiconductor chip, wherein one side of the temperature sensing resistor is coupled to the power transistor on the voltage input side of the power transistor.

[0007] A controller coupled to a second side of the temperature sensing resistor, wherein the controller is configured to detect the voltage across the resistor and trigger a temperature-dependent correction action using the voltage across the temperature sensing resistor, wherein the temperature-dependent correction action regulates the current through the power transistor.

[0008] The controller is configured to trigger a temperature-related correction action when the voltage on the temperature sensing resistor reaches a threshold.

[0009] The controller is configured to trigger a temperature-related correction action based on the voltage from the temperature sensing resistor, wherein the controller correlates the voltage from the temperature resistor with the temperature of the transistor device.

[0010] In addition to being coupled to the transistor via the temperature sensing resistor, the controller is also coupled to the transistor on the voltage input side of the transistor.

[0011] The controller is located on the second semiconductor chip.

[0012] The bonding wires electrically connect the controller to the temperature sensing resistor.

[0013] The controller is located on the first semiconductor chip.

[0014] The controller is further configured to draw a constant current from the voltage input side of the power transistor through the temperature sensing resistor, and to draw a separate current through a parallel coupling connected to the input side of the transistor, wherein the parallel coupling is connected in parallel with the temperature sensing resistor.

[0015] The controller is further configured to compare the voltage across the temperature sensing resistor with a reference voltage. When the voltage across the temperature sensing resistor meets the reference voltage, the controller compares the voltage across the temperature sensing resistor with the voltage across the parallel coupling terminals. This comparison between the voltage across the temperature sensing resistor and the output voltage of the parallel coupling triggers a temperature-related correction action.

[0016] The controller is configured to amplify the voltage across the temperature sensing resistor and compare the amplified voltage across the resistor with a reference voltage.

[0017] The temperature sensing resistor is either a diffused resistor formed in a semiconductor chip or a polycrystalline resistor formed on a semiconductor chip.

[0018] The controller is further configured to fine-tune the output voltage of the temperature sensing resistor to compensate for changes in the temperature sensing resistor.

[0019] The present invention also discloses a method for temperature control of a transistor formed in a first semiconductor chip, comprising:

[0020] By drawing input current from the input terminal of the transistor, the temperature sensing resistor formed in the first semiconductor chip is biased.

[0021] A separate current is drawn through parallel coupling connected to the transistor input, where parallel coupling refers to being connected in parallel with the temperature sensing resistor;

[0022] The output voltage of the temperature sensing resistor is compared with the output voltage of the parallel coupling;

[0023] The comparison results are used to trigger temperature-related correction actions.

[0024] The comparison between the output voltage of the temperature sensing resistor and the output voltage of the parallel coupling also includes amplifying the output voltage of the temperature sensing resistor to a threshold voltage.

[0025] The temperature-related correction action triggered by the comparison results also includes comparing the amplified output voltage of the temperature sensing resistor with a threshold voltage, wherein the threshold voltage is related to the voltage of the temperature sensing resistor at the transistor's breakdown temperature.

[0026] The comparison between the output voltage of the temperature sensing resistor and the output voltage of the parallel coupling is the trigger for the temperature-related correction action. Attached Figure Description

[0027] Other features and advantages of the invention will become apparent after reading the following detailed description and referring to the following figures, wherein:

[0028] Figure 1 This diagram illustrates a simplified schematic circuit for a semiconductor transistor temperature sensor, according to one aspect of the present invention.

[0029] Figure 2 This diagram illustrates a detailed schematic circuit for a power transistor temperature sensor configuration, according to one aspect of the present invention.

[0030] Figure 3 According to one aspect of the invention, Figure 2 The circuit shown is a combined graph of the response curves of the power transistor to temperature changes.

[0031] Figure 4 This diagram illustrates a detailed schematic circuit diagram of another configuration for a power transistor temperature sensor, according to one aspect of the present invention.

[0032] Figure 5 According to various aspects of the present invention, Figure 4 The circuit shown is a combined graph of the response curves of the power transistor to temperature changes.

[0033] Figure 6 This diagram illustrates a detailed in-situ arrangement of a power transistor temperature sensor according to various aspects of the present invention.

[0034] Figure 7 This diagram illustrates a detailed in-situ arrangement of a temperature sensor on the same die as a power transistor, according to various aspects of the present invention. Detailed Implementation

[0035] Although the following detailed description contains many specific details for illustrative purposes, those skilled in the art will understand that many variations and modifications to these details are within the scope of the invention. Therefore, the exemplary embodiments of the invention described below do not impose any general limitation or restriction on the claimed invention.

[0036] In the following detailed description, reference is made to the accompanying drawings, which form part of this invention, illustrating by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terms such as “top,” “bottom,” “front,” “rear,” “leading,” “tail,” etc., are used with reference to the orientation of the described figures. Since components of embodiments of the invention can be positioned in multiple different orientations, directional terms are used for illustration and not for limitation in any way. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention. Therefore, the following detailed description should not be considered a limiting description, and the scope of the invention is defined by the appended claims.

[0037] For clarity, not all conventional features of the implementations described herein are shown and described. Those skilled in the art will understand that in any such implementation, numerous embodiment-specific decisions must be made to achieve specific goals of the developer, such as complying with application and business-related constraints, and these specific goals will vary from embodiment to embodiment and from developer to developer. Furthermore, it should be understood that such development work can be complex and time-consuming, but will be a routine engineering task for those of ordinary skill in the art who will benefit from this invention.

[0038] Figure 1This diagram illustrates a simplified schematic circuit of a semiconductor transistor temperature sensor according to one aspect of the present invention. As shown, a power transistor 101 is formed in a semiconductor wafer 103. The temperature sensor includes a temperature sensing resistor 102, which, like the transistor 101, is formed in the same semiconductor wafer 103 and is conductively coupled to the voltage input side 106 of the transistor 101. A controller 104, together with the temperature sensing resistor 102, is connected in parallel to the input side 106 of the transistor via a conductive connection 105.

[0039] It should be understood that the voltage input side of a power transistor refers to the circuitry on one side of the transistor that receives voltage at the transistor, and the transistor's function is to block current from that side in the off state and allow current to flow through the voltage input terminal to the voltage output side in the on state. In an NPN transistor, the circuitry connected to the transistor's drain is on the voltage input side, while in a PNP transistor, the circuitry connected to the source is on the voltage input side. Various aspects of the present invention are contemplated for implementation using either NPN or PNP transistors. Furthermore, embodiments of the present invention are not limited to field-effect transistors (FETs), such as metal-oxide-semiconductor FETs (MOSFETs) or junction FETs (JFETs), and can be applied to other transistors, such as insulated-gate bipolar transistors (IGBTs) or bipolar junction transistors (BJTs).

[0040] At this point, one side of the temperature sensing resistor 102 receives current directly from the voltage input terminal of the power transistor 101. As mentioned above, in high-frequency applications, the gate voltage may fluctuate due to the switching frequency. On the other hand, the voltage input to the transistor may be very stable. Typically, the voltage on the transistor's voltage input side fluctuates only during startup. In the worst case, for this configuration, the voltage may only change by about 20%. This makes the voltage input side a good voltage source for the temperature sensing resistor.

[0041] Controller 104 is coupled to the side of temperature sensing resistor 102 opposite to the transistor voltage input and is configured to detect the voltage across temperature sensing resistor 102. Controller 104 may also be conductively coupled to the gate of transistor 101 to enable temperature-dependent correction action at transistor 102. Controller 104 can be configured to trigger temperature-dependent correction action using the voltage across temperature sensing resistor. Here, it should be understood that the resistance of temperature sensing resistor depends on the local temperature around resistor 102 because resistor 102 is located near transistor 101 on the same semiconductor chip. Temperature sensing resistor 102 is thermally coupled to power transistor 101. Therefore, changes in the resistance of temperature sensing resistor may be related to changes in the temperature of transistor 101. For example, but not limited to, controller 104 may be configured to trigger temperature-dependent correction action when the voltage across temperature sensing resistor meets a threshold. In some implementations, the resistor may have a negative temperature coefficient, so the controller is configured to perform one or more temperature-dependent correction actions when the voltage across temperature sensing resistor 102 drops below the threshold. Alternatively, the resistor may have a positive temperature coefficient, in which case the controller is configured to perform one or more associated temperature correction actions when the voltage across the temperature sensing resistor 102 rises above a threshold. In either case, the controller may take one or more temperature-related correction actions when the voltage reaches the threshold. In some embodiments, the controller 104 may be configured to strongly correlate the voltage across the temperature sensing resistor with the temperature of the transistor, the derivative of the voltage change, or other complex temperature-related calculations.

[0042] Temperature-dependent correction actions can be any action implemented by a controller configured to reduce transistor temperature. For example, but not limited to, temperature-dependent corrections might include turning off the transistor, reducing the current across the transistor, or changing the transistor's switching frequency. Each of these temperature-dependent corrections involves changing the gate voltage. Other temperature-dependent correction actions might also be feasible, such as triggering an over-temperature warning, like a buzzer or displayed message, or triggering another switch to reduce the current flowing to the transistor. This other switch could be located on a different semiconductor chip to ensure that heat is not transferred to the transistor.

[0043] The controller 104 may be located on a second semiconductor chip separate from the semiconductor chip 103 having the transistor 101 and the thermistor 102. Alternatively, the controller 104 may be located on the same die 103 as the power transistor 101 and the thermistor 102. In another configuration, the controller 104 may be located on the opposite side of the same die 103 as the transistor 101 and the temperature-sensing resistor 102. Bonding wires may electrically couple the controller 104 to the voltage input side of the temperature-sensing resistor 102 and the transistor. Additionally, bonding wires may electrically couple the controller to the gate of the transistor 107.

[0044] Figure 2 This diagram illustrates a detailed schematic circuit configuration for a temperature sensing device according to one aspect of the invention. Specifically, the temperature sensing circuit of the controller is shown in detail. In this implementation, the output of a first comparator CMP acts as a trigger for one or more temperature-related correction actions. As shown, input A1 of the comparator receives an output voltage from a parallel coupling connected to the input of a power transistor 201. In this example, the parallel coupling is a constant voltage source V_OT connected in parallel with the temperature sensing resistor RSNS. The controller uses the output of the constant voltage source V_OT as the input of the comparator CMP. The voltage across the temperature sensing resistor RSNS is transferred to the first comparator CMP at input B1. The current through the temperature sensing resistor RSNS flows through the gating transistor 202 and the resistor RSET to ground. The output of a second amplifier V2I controls the control element (e.g., gate or base) of the gating transistor 202, and one input of the second comparator is connected to a reference voltage V. REF The second input terminal is coupled to node 203 between the gating transistor 202 and the resistor RSET in the feedback loop.

[0045] At normal operating temperature, amplifier V2I, gating transistor 202, and resistor RSET set current to bias the temperature sensing resistor RSNS. A temperature rise at RSNS causes a change in the resistance of the temperature sensing resistor, and also changes the voltage drop across the temperature sensing transistor RSNS, as well as the voltage at the input B1 of the first comparator. When the voltage across the temperature sensing diode RSNS exceeds the threshold voltage V_OT, the first comparator CMP switches its output FET_OT. The voltage applied to the gate of power transistor 201 can be changed to turn it off, or the current through the power transistor can be modulated by sequentially turning the gate of power transistor 201 on and off. Alternatively, the correction action may include changing the voltage applied to the gate of power transistor 201 to reduce the current through the power transistor without completely turning it off.

[0046] It should be noted that the polarity of the input terminals of comparator CMP can be switched depending on the type of the temperature sensing resistor RSNS. For example, but not limited to, if resistor RSNS has a positive temperature coefficient, the negative terminal of comparator CMP can be connected to B1, and the positive terminal can be connected to A1. Similarly, if resistor RSNS is a negative temperature coefficient resistor, the positive terminal of comparator CMP can be connected to B1, and the negative terminal to A1. The output of comparator FET_OT can be used as an over-temperature trigger to implement one or more temperature-dependent correction actions. The trigger point of the first comparator CMP can be manipulated by changing the resistance or voltage Vref of Rset, and the threshold voltage V_OT is defined by the following formula: V_OT = (Vref / Rset) * RSNS.

[0047] As described above, the advantage of conductively coupling the temperature sensing resistor to the voltage input side of the transistor is that the voltage received at the temperature sensing resistor RSNS is typically very stable with very small variations, such as about 20%. A low-pass filter (not shown in the figure) can be placed between the connection of the temperature sensing resistor RSNS and the voltage input Vin to filter out any transient voltage spikes. Alternatively, the low-pass filter can be connected to the output of the comparator to filter out transient voltage spikes. In some implementations, voltage spikes occur during device startup, and in those configurations, a blanking period can be added to the comparator output so that the comparator ignores events that are sustained, for example, but not limited to, less than 200 microseconds or less than 300 microseconds.

[0048] Figure 3 Representing various aspects of the present invention Figure 2 The figure shows a graph of the circuit's response to temperature changes in the semiconductor transistor. As shown, the voltage at B1 exhibits a linear temperature dependence, as illustrated in section 302. Meanwhile, the voltage in the parallel branch at A1 remains constant, as shown in section 301. The comparator output OT_FET is low or zero, as shown in section 304. When the voltage at B1 falls below the constant threshold voltage at A1, the CMP output is pulled high, as shown in section 305. Therefore, the output OT_FET can be used as a trigger signal for one or more temperature-dependent correction actions.

[0049] Figure 4This diagram illustrates a detailed schematic circuit of another configuration for a temperature sensing device according to one aspect of the invention. In this configuration, amplifier 402 amplifies the voltage change across resistor RSNS using a first voltage divider resistor R1 between VIN and the first input terminal of amplifier 402, a second voltage divider resistor R2 coupled to the first input terminal of comparator, and coupled between transistor 403 and ground. The output of the comparator is coupled to the base of transistor 403. A constant current is drawn from the biased temperature sensing resistor RSNS and fed into the amplifier. Amplifier 402 compares the voltage across the thermistor RSNS with a voltage connected in parallel to the voltage input side of the transistor and transmits the result to the base of transistor 403. In this implementation, the voltage VTEMP across transistor 403 is controlled by the output of amplifier 402. Due to the nature of the thermistor, as the temperature of power transistor 401 increases, heat causes the resistance of the thermistor RSNS to increase or decrease. The increase or decrease in resistance causes the voltage drop across resistor RSNS to increase or decrease accordingly. The voltage difference generated at the input of amplifier 402 causes a change in the comparator output. This, in turn, leads to a change in the voltage supplied to the base of transistor 403, resulting in a change in the voltage at VTEMP.

[0050] Figure 4 The circuit shown typically replicates and amplifies the voltage across the temperature-sensing resistor RSNS according to the ratio of the voltage divider resistors R2 / R1. This amplified voltage can then be compared to a reference voltage, and the comparison result can trigger one or more temperature-dependent correction actions. For example, Figure 4 The circuit shown can typically be configured such that as the temperature of the temperature sensing resistor RSNS increases, the change in the output of comparator 402 causes transistor 403 to shunt the current through voltage divider resistors R1 and R2, thereby reducing the current through power transistor 401.

[0051] To simplify manufacturing, the power transistor 401 and the temperature sensing resistor RSNS can be fabricated on a single die, and controller components such as the current bias IBIA, voltage dividers R1 and R2, comparator 402, and transistor 403 can be formed on separate dies. Figure 4 Another advantage of the illustrated implementation is that process variations in the production of the temperature sensing resistor RSNS can be compensated for by fine-tuning the constant current consumption Ibias.

[0052] Figure 5 According to various aspects of the present invention, Figure 4The figure shows a graph of the circuit's response to temperature changes in the semiconductor transistor. As shown, the output VTEMP 501 (solid line) increases linearly with temperature and replicates the voltage across the temperature-sensing resistor V_RSNS 502 (dashed line) at higher voltages. It should also be noted that the voltage across the reference resistor V_R1 503 (solid line) closely follows that of the temperature-sensing resistor V_RSNS. This close correlation between VTEMP 501 and temperature allows this curve to be used to trigger one or more temperature-dependent correction actions.

[0053] Figure 6 Detailed diagrams illustrating the in-situ configuration of the temperature sensing device according to various aspects of the present invention are shown. As shown, the power transistor 601 and the temperature sensing resistor RSNS share the same die 603. In this implementation, the controller 602 is located on a separate die, and bonding wire 606 connects the temperature sensing resistor RSN to the controller 602. A separate bonding wire 605 conductively couples the transistor gate output of the controller 602 to the gate of the transistor 601. One side of the temperature sensing resistor RSNS is connected to the voltage input of the transistor via a via 604 in the transistor die (as shown) or a bonding wire (not shown here) connected to the voltage input connection VIN. Bond wire 607 can provide parallel coupling to the input of the transistor VIN. The voltage input to the transistor VIN can be connected via the conductive plane 608 of the device package. The voltage output of the transistor can be connected to the voltage output pad VOUT via bonding wire 609, as shown, two bonding wires connect the voltage output to the transistor to increase the carrying capacity.

[0054] Figure 7 This diagram illustrates a detailed in-situ configuration of a temperature sensor on the same die as the power transistor, according to various aspects of the invention. In this single-chip implementation, the controller and transistor 601 share the same chip 702. The input and output of the power FET 601 may be located on the upper part of chip 702. In this implementation, the voltage input (drain) of transistor 601 is connected to VIN via bonding wire 704. The input voltage VIN can be coupled to the temperature sensing resistor RSNS and the controller via metal trace 707 on die 702, as shown. Figure 7 As shown, it can be coupled to the controller via a bonded wire. Furthermore, in Figure 7 In the configuration shown, metal traces 705 and 706 connect the temperature sensing resistor RSN and the gate G of transistor 601 to the controller, rather than using wires. It should be noted that the connection between the parallel coupling to the voltage input of the transistor and the connection between the temperature sensing resistor RSNS and the voltage input of the transistor can be achieved via vias, metal trenches, or bonded wires.

[0055] Various aspects of this invention allow for the precise determination of the temperature of semiconductor transistors in high-frequency switching applications and the implementation of corrective measures when high temperatures affect the operation of such transistors. Temperature sensing utilizes the voltage across a resistor, which exhibits a substantially more linear correlation with temperature compared to a diode network. Various aspects of this invention include implementations using fewer bonding wires than existing solutions.

[0056] While the foregoing is a complete description of preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the scope of the invention should not be determined by reference to the foregoing description, but rather by reference to the appended claims and their full scope of equivalents. Any feature, whether preferred or not, may be combined with any other feature, whether preferred or not. In the following claims, the indefinite article “A” or “An” refers to the number of one or more items following that article, unless expressly stated otherwise. The appended claims should not be construed as including means plus functional limitations unless such limitation is expressly recited in a given claim using the phrase “means.” Any element of “means” not expressly stated in the claims as “for” performing a particular function shall not be construed as a “means” or “step” clause as defined in Section 112, Section 6 of Title 35 of the United States Code.

Claims

1. A device for monitoring the temperature of a power transistor formed in a first semiconductor chip, comprising: A temperature sensing resistor located in the first semiconductor chip, wherein one side of the temperature sensing resistor is coupled to the power transistor on the voltage input side of the power transistor. A controller coupled to a second side of the temperature sensing resistor, wherein the controller is configured to detect the voltage across the resistor and trigger a temperature-dependent correction action using the voltage across the temperature sensing resistor, wherein the temperature-dependent correction action regulates the current through the power transistor.

2. The device of claim 1, wherein the controller is configured to trigger a temperature-related correction action when the voltage on the temperature sensing resistor reaches a threshold.

3. The device of claim 1, wherein a controller is configured to trigger a temperature-dependent correction action based on a voltage from a temperature sensing resistor, wherein the controller is configured to correlate the voltage from the temperature resistor with the temperature of the transistor device.

4. The device of claim 1, wherein the controller is coupled to the transistor not only through the temperature sensing resistor, but also to the transistor on the voltage input side of the transistor.

5. The device of claim 1, wherein the controller is located on the second semiconductor chip.

6. The device of claim 5, wherein the bonding wires electrically connect the controller to the temperature sensing resistor.

7. The device of claim 1, wherein the controller is located on the first semiconductor chip.

8. The device of claim 1, wherein the controller is further configured to draw a constant current from the voltage input side of the power transistor through the temperature sensing resistor, and to draw a separate current through a parallel coupling connected to the input side of the transistor, wherein the parallel coupling is connected in parallel with the temperature sensing resistor.

9. The device of claim 8, wherein the controller is further configured to compare the voltage across the temperature sensing resistor with a reference voltage, and when the voltage across the temperature sensing resistor meets the reference voltage, compare the voltage across the temperature sensing resistor with the voltage across the parallel coupling terminals, thereby triggering a temperature-related correction action by comparing the voltage across the temperature sensing resistor with the output voltage of the parallel coupling.

10. The device of claim 8, wherein a controller is configured to amplify the voltage across the temperature sensing resistor and compare the amplified voltage generated across the resistor with a reference voltage.

11. The device of claim 1, wherein the temperature sensing resistor is a diffused resistor formed in a semiconductor chip, or a polycrystalline resistor formed on a semiconductor chip.

12. The device of claim 1, wherein the controller is further configured to fine-tune the output voltage of the temperature sensing resistor to compensate for variations in the temperature sensing resistor.

13. A method for temperature control of a transistor formed in a first semiconductor chip, comprising: a) By drawing input current from the input terminal of the transistor, a temperature sensing resistor formed in the first semiconductor chip is biased; b) Draw a separate current through parallel coupling connected to the transistor input, where parallel coupling means in parallel with the temperature sensing resistor; c) Compare the output voltage of the temperature sensing resistor with the output voltage of the parallel coupling; d) Use the comparison results to trigger temperature-related correction actions.

14. The method of claim 13, wherein comparing the output voltage of the temperature sensing resistor with the output voltage of the parallel coupling further comprises amplifying the output voltage of the temperature sensing resistor to a threshold voltage.

15. The method of claim 13, wherein d) further comprises comparing the amplified output voltage of the temperature sensing resistor with a threshold voltage, wherein the threshold voltage is related to the voltage of the temperature sensing resistor at the breakdown temperature of the transistor.

16. The method of claim 13, wherein the comparison result between the output voltage of the temperature sensing resistor and the output voltage of the parallel coupling is the trigger for the temperature-related correction action.

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