Apparatus and method for sensing over-temperature of power semiconductor

Abstract

The present invention relates to a device and a method for sensing over-temperature of a power semiconductor. The present invention: provides a current pulse source through a control electrode of the power semiconductor; replicates a current provided by the current pulse source and provides the replicated current to an analog device; compares a voltage across the control electrode with a voltage across the analog device; and notifies a comparison result.

Description

Technical Field

[0001] The present invention generally relates to an apparatus and method for sensing over-temperature of power semiconductors. Background Technology

[0002] Power semiconductor devices are designed to operate below their maximum junction temperature. Operation above the maximum junction temperature can trigger thermal runway conditions, which can lead to irreversible and catastrophic failure of the power semiconductor device. Operation above the maximum junction temperature can be caused by various factors such as cooling system defects, transient operation of the power semiconductor beyond its specifications, aging, etc.

[0003] Today, power semiconductor devices (similar to transistors) use embedded diodes as sensors for chip temperature. The forward voltage drop of the diode depends on the temperature. This solution results in a loss of available active area in the transistor and increases the number of connections to the power semiconductor.

[0004] Given the low bandwidth of sensors and the fact that they cannot be placed close to power semiconductors, directly measuring junction temperature using thermocouples or negative temperature coefficient resistors is not suitable for detecting overtemperature.

[0005] Optical temperature measurements are also slow because they require digital processing and calibration, which increases latency.

[0006] Using thermistor electrical parameters of power semiconductors is promising. For example, the temperature of a power semiconductor can be observed by injecting a measurement current into it to measure the temperature-dependent on-state voltage.

[0007] Therefore, since this measurement needs to be performed with the conduction current known or calibrated for all conduction currents, this increases the complexity of the measurement circuit. In addition, the accuracy associated with this measurement may be insufficient, which may lead to false triggering. Summary of the Invention

[0008] The present invention aims to provide a low-complexity and accurate apparatus and method for sensing over-temperature of power semiconductors.

[0009] Therefore, the present invention relates to a device for sensing over-temperature of a power semiconductor, characterized in that the device comprises:

[0010] - A current pulse source, provided through the control electrodes of a power semiconductor.

[0011] - A current replicator that replicates the current supplied by a current pulse source and provides the replicated current to an analog device.

[0012] - A comparator that compares the voltage across the control electrodes with the voltage across the analog device.

[0013] - A device for notifying comparison results.

[0014] The present invention also relates to a method for sensing over-temperature of power semiconductors, characterized in that the method includes the following steps:

[0015] - Apply current pulses through the control electrodes of the power semiconductor.

[0016] - Copy the current pulse and provide the copied current pulse to the simulation device.

[0017] - Compare the voltage across the control electrode with the voltage across the simulation device.

[0018] - Notify the comparison results.

[0019] Therefore, this invention can detect over-temperature of power semiconductors without complexity and avoid thermal runaway. Because it is an analog device, there is no need to introduce any analog-to-digital converter to read the actual temperature.

[0020] Based on specific characteristics, the device for notifying the comparison result also controls the switching mode of the power semiconductor based on the signal output by the comparator.

[0021] Depending on specific characteristics, the control electrodes to which the current pulse source is applied are the gate and emitter or the gate and source.

[0022] Based on specific characteristics, a current pulse source is provided to the power semiconductor when it is not in a switching or transitional mode.

[0023] Therefore, users can decide to stop or slow down the power semiconductor to protect it from overheating. Furthermore, the voltage at the control electrode changes only according to the current pulse, and electromagnetic and other interferences will not affect the sensing power semiconductor during over-temperature periods.

[0024] According to the present invention, the analog device consists of a resistor and a capacitor connected in series.

[0025] Therefore, the analog device has the same impedance as the internal gate of the power semiconductor at a given temperature (similar to, for example, just below the maximum junction temperature). The analog device is used to create a threshold that changes according to the current pulse source. Then, the comparison between the voltage at the electrodes of the power semiconductor and the voltage at the analog device is independent of the current pulse source value.

[0026] According to the present invention, the capacitor value is equal to or lower than the gate capacitance value of the power semiconductor.

[0027] Therefore, the present invention can prevent false alarms at the output of the comparator.

[0028] According to the present invention, when the power semiconductor is at a temperature that is almost equal to the maximum junction temperature of the power semiconductor, the resistor value is equal to or lower than the internal gate resistance value of the power semiconductor.

[0029] Therefore, a threshold temperature can be defined that is equal to or lower than the maximum junction temperature of the power semiconductor.

[0030] According to the present invention, the resistor value is adjusted during the calibration phase.

[0031] Therefore, it can compensate for the variation in the internal gate resistance of each power semiconductor.

[0032] According to the present invention, the duration of the current pulse is equal to:

[0033]

[0034] Where Vth represents the threshold voltage of the semiconductor gate, Vsupply is the negative gate voltage that prevents the power semiconductor from turning on, or Vsupply is the positive gate voltage that prevents the power semiconductor from turning off, Rg is the internal gate resistance of the power semiconductor when the power semiconductor is at a temperature that is almost equal to the maximum junction temperature of the power semiconductor, Cg is the gate capacitance of the power semiconductor, and I is the current pulse value.

[0035] Therefore, the state of the power semiconductor remains the same during the pulse duration.

[0036] According to the invention, the device further includes at least one resistor and at least one comparator, a first terminal of the at least one resistor being connected to a current replicator, a second terminal of the at least one resistor being connected to an analog device, and the at least one comparator comparing the voltage at the electrode of the power semiconductor with the voltage at the second terminal of the at least one resistor.

[0037] According to the present invention, the method further includes the step of adjusting the resistance value of the analog device when the power semiconductor is heated to a predetermined temperature. Attached Figure Description

[0038] The features of the invention will become clearer from the following description of exemplary embodiments, which is made with reference to the accompanying drawings.

[0039] [ Figure 1 ] Figure 1 An example illustrating the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0040] [ Figure 2 ] Figure 2 Examples of power semiconductors.

[0041] [ Figure 3 ] Figure 3This represents the equivalent circuit of the power semiconductor according to the present invention.

[0042] [ Figure 4 ] Figure 4 An example of an analog device for sensing the temperature of a power semiconductor according to the present invention is shown.

[0043] [ Figure 5 ] Figure 5 An example of a current replicator for sensing the temperature of a power semiconductor device according to the present invention is shown.

[0044] [ Figure 6 ] Figure 6 This refers to a signal used for sensing the temperature of a power semiconductor according to the present invention.

[0045] [ Figure 7 ] Figure 7 This indicates a signal that may occur when at least one component value of the analog device is not accurately defined.

[0046] [ Figure 8 ] Figure 8 This indicates the signal that appears when the maximum junction temperature is detected.

[0047] [ Figure 9 ] Figure 9 An example of an algorithm for adjusting the resistor values ​​of a simulated power semiconductor.

[0048] [ Figure 10 ] Figure 10 An example illustrating the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0049] [ Figure 11 ] Figure 11 This is another example of the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0050] [ Figure 12 ] Figure 12 An example of an algorithm for sensing the temperature of a power semiconductor device according to the present invention is shown. Detailed Implementation

[0051] Figure 1 An example illustrating the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0052] The device for sensing the temperature of the power semiconductor includes a current replicator 70 that replicates the current supplied by the current pulse source 60 through the control electrode of the power semiconductor Sc 10 when the power semiconductor is not in a switching or transition mode.

[0053] The control electrodes are the gate and emitter or the gate and source.

[0054] The replicated current is supplied to the simulation device 20.

[0055] The voltage across the gate and emitter or gate and source of the sensed power semiconductor 10 is provided to the voltage comparator 30 of the comparison analog device 20.

[0056] In a variant, instead of sensing the voltage across a control electrode and the voltage across an analog device, the voltage across a control electrode and a reference (e.g., ground) is sensed.

[0057] If the voltage of the analog device is higher than the electrode voltage of the sensed power semiconductor 10, the output of comparator 30 reaches a high level.

[0058] The device for sensing the temperature of power semiconductors includes a controller 50, which notifies comparison results by transmitting predetermined signals or predetermined messages or generates predetermined information through a human-machine interface.

[0059] In a particular implementation mode, the controller further controls the gate-source voltage of the power semiconductor and modifies the gate-source voltage mode applied to the power semiconductor device during operation in order to reduce the junction temperature of the power semiconductor 10.

[0060] The analog device is a simulated impedance that represents the input impedance of the power semiconductor 10 at the desired temperature to be detected (similar to one of the gate / emitter paths).

[0061] The pulse duration of the pulse current source 60 is controlled to a specific time period (typically a few microseconds) to avoid turning the power semiconductor on or off. Then, the voltage across the real transistor is compared to the voltage across the analog impedance. Therefore, when the measured voltage is higher than the voltage at the analog device, it means that the gate resistance has a higher value than the analog device, the junction temperature of the power semiconductor 10 is higher than the target point, and the comparator 30 outputs a signal indicating that the temperature has exceeded the limit. Finally, the over-temperature signal is fed to the controller 50, which notifies the controller of the comparison result.

[0062] In certain implementation modes, the controller 50 further reduces the switching speed of the power semiconductor or temporarily stops switching.

[0063] This invention allows for the detection of overtemperature during normal operation of power semiconductors without any additional devices near the power semiconductor, has fast bandwidth, and requires no analog-to-digital converters or digital processing.

[0064] Figure 2 Examples of power semiconductors.

[0065] Power semiconductors include, for example, transistor T and diode D, with the anode of diode D connected to the emitter of transistor T and the cathode connected to the collector of transistor T.

[0066] Figure 3 This represents the equivalent circuit of the power semiconductor according to the present invention.

[0067] The equivalent circuit of a power semiconductor consists of a resistor Rg connected in series with a capacitor Cg.

[0068] This invention utilizes the internal gate resistance to infer the junction temperature. The internal gate resistance is created by a polysilicon layer in a field-effect transistor, which is already present in the classic transistor structure. In the case of a typical transistor, the resistance increases with increasing temperature.

[0069] Figure 4 An example of an analog device for sensing the temperature of a power semiconductor according to the present invention is shown.

[0070] The simulation device 20 consists of a resistor Re connected in series with the capacitor Ce.

[0071] The resistor Re has the same value as Rg during maximum safe temperature operation, and the capacitor Ce is, for example, a highly stable (such as C0G) capacitor with the same value as Cg.

[0072] Figure 5 An example is shown of a current replicator for sensing the temperature of a power semiconductor according to the present invention.

[0073] The current replicator 70 is composed, for example, of a gain-matched pair of transistors.

[0074] Figure 6 This refers to a signal used for sensing the temperature of a power semiconductor according to the present invention.

[0075] Figure 6 The waveforms of the power semiconductor 10 voltage 10o, pulse current 60, and analog device 20 voltage and over-temperature signal 50o are shown for the three pulses.

[0076] For the first pulse 60a, the temperature of power semiconductor 10 is equal to the maximum junction temperature. For the second pulse 60b, the temperature of power semiconductor 10 is below the maximum junction temperature. Voltage 10ob is higher than voltage 20ob. For the third pulse 60c, the temperature of power semiconductor 10 is above the temperature threshold, i.e., the maximum junction temperature. Voltage 20oc is higher than voltage 10oc, and the output signal 50o of comparator 30 changes state. Figure 6 In the example, it is assumed that Ce = Cg, and the temperature change is only due to the temperature change of the power semiconductor gate resistance.

[0077] Figure 7This indicates a signal that may occur when at least one component value of the analog device is not accurately defined.

[0078] According to the present invention, the capacitor Ce is strictly less than or equal to Cg, thereby avoiding the generation of false alarms. For example... Figure 7 As shown, for a resistor value Rg lower than the resistor value Re, this condition is necessary and sufficient to maintain a voltage of 10° below 20° at the end of the current pulse. For the first pulse 60a, the capacitor value Ce equals the capacitor value Cg, so even for an infinite pulse duration, a false alarm is impossible. In the second pulse 60b, the capacitor value Ce is higher than the capacitor value Cg, so even for a resistor value Rg lower than the resistor value Re, a false trigger is output. Finally, in the third pulse 60c, the capacitor value Ce is lower than the capacitor value Cg, so even for an infinite pulse duration, a false alarm is impossible.

[0079] The fundamental equations based on power semiconductor 10 and analog device voltage, where I is the current value and t is time:

[0080]

[0081]

[0082] For Rg to be lower than Re, according to t = tmax, the voltage 10° should be lower than 20° at the end of the current pulse. Therefore:

[0083]

[0084] in

[0085]

[0086] Where Vth represents the threshold voltage of the gate of semiconductor 10, and Vsupply is the negative gate voltage that prevents the power semiconductor from turning on, or Vsupply is the positive gate voltage that prevents the power semiconductor from turning off. Considering term R g -R e If it approaches zero, then Ce <Cg。

[0087] In a specific feature, at maximum temperature, resistor Re is set to a value slightly less than or equal to that of resistor Rg.

[0088] The value of resistor Re is calculated using the following formula:

[0089]

[0090] in It is the resistance value at the maximum junction temperature.

[0091] Therefore, the difference between the two capacitors is compensated, and during the comparator's detection time ( Figure 7 The temperature can be detected within the TCMP (TCMP) port.

[0092] Figure 8 This indicates the signal that appears when the maximum junction temperature is detected.

[0093] When the detection time tcmp is too short and difficult to detect, a setting /

[0094] The latch circuit for the reset function.

[0095] Figure 9 An example of an algorithm for adjusting the resistor values ​​of an analog power semiconductor.

[0096] In step S80, the power semiconductor is heated to a predetermined temperature (e.g., maximum junction temperature - 1 degree).

[0097] In step S81, the over-temperature signal output by comparator 30 is checked. If the signal is high, the algorithm proceeds to step S81. Otherwise, the algorithm is interrupted.

[0098] In step S82, the resistor value Re is adjusted using laser fine-tuning technology or fuse blowing.

[0099] In a specific feature, if the over-temperature signal output by the comparator is high, the resistor value Re is adjusted by an increment. For example, the increment is equal to 1000ppm of the estimated Rg resistor value (e.g., 5mΩ for a nominal Rg of 5Ω).

[0100] The algorithm then returns to step S81.

[0101] Figure 10 An example illustrating the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0102] For example, device 60 has an architecture based on components connected together via bus 901 and a program-controlled processor 900.

[0103] Bus 901 links processor 900 to read-only memory ROM 902, random access memory RAM 903 and input / output interface I / F 905.

[0104] The input / output interface I / F 905 includes a current pulse source, a current replicator 70, an analog device 20, and a comparator 30.

[0105] Memory 903 includes components designed to receive and Figure 12 The program's variables and instruction registers related to the publicly disclosed algorithm.

[0106] Read-only memory or possibly flash memory 902 contains and Figure 12 The instructions for the program related to the algorithm disclosed in the document.

[0107] When the device is powered on, the instructions stored in memory 903 are transferred to random access memory 903.

[0108] The device can be implemented in software by executing an instruction set or program by a programmable computing machine (e.g., a PC (personal computer), a DSP (digital signal processor), or a microcontroller); or in hardware by a machine or a dedicated component (e.g., an FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit)).

[0109] In other words, the device includes circuitry that enables the controller 50 to execute a program.

[0110] Device 60 controls the gate signal of the semiconductor, controls the switching of the power semiconductor, and controls the laser trimmer used to adjust the resistor value of the analog device via the input / output I / O interface I / F 905.

[0111] Figure 11 This is another example of the architecture of a device for sensing the temperature of a power semiconductor device according to the present invention.

[0112] The device for sensing the temperature of the power semiconductor 10 includes a current replicator 70 that replicates the current supplied by the current pulse source 60 through the control electrode of the power semiconductor Sc 10.

[0113] The replicated current is supplied to the first terminal of resistor R1 and the first input of comparator 31.

[0114] The second terminal of resistor R1 is connected to the first terminal of resistor R2 and the first input of comparator 32.

[0115] The second terminal of resistor R2 is connected to analog device 20.

[0116] It is important to note here that... Figure 11 In the example, two resistors and two comparators are added. Figure 1 The device disclosed herein. Only one resistor and one comparator can be added. Figure 1 The device disclosed herein, or more than two resistors and two comparators, can be added. Figure 1 The device disclosed in the document.

[0117] The voltage across the control electrode of the sensed power semiconductor 10 is provided to the voltage comparators 31, 32 and 33 of the comparison analog device 20.

[0118] If the voltage of the analog device 20 is higher than the voltage across the control electrode of the sensed power semiconductor 10, the output of the comparator 30 reaches a high level.

[0119] The device for sensing the temperature of the power semiconductor includes a controller 50 that notifies the comparison results.

[0120] Based on specific characteristics, the controller 50 modifies the mode applied to the power semiconductor device during operation in order to reduce the junction temperature of the power semiconductor 10.

[0121] The analog device is a simulated impedance that represents the input impedance (gate / emitter path) of the power semiconductor 10 at the desired temperature to be detected.

[0122] Therefore, different critical temperatures of the power semiconductor 10 can be detected. The value of resistor Re is adjusted for a given temperature using one of the techniques described above. The values ​​of resistors R1 and R2 are selected based on the temperature sensitivity of resistor Rg multiplied by the temperature level. For example, if the temperature level is 5°C and the temperature sensitivity is 5 mΩ / °C, then the values ​​of resistors R1 and R2 are 25 mΩ.

[0123] The pulse duration of the pulse current source 60 is controlled to a specific time period (typically a few microseconds) to avoid turning the power semiconductor on or off. The voltage across the semiconductor electrodes is then compared to the voltage across the analog impedance.

[0124] Figure 12 An example of an algorithm for sensing the temperature of a power semiconductor device according to the present invention is shown.

[0125] In step S110, a current pulse is applied through the control electrode of the power semiconductor.

[0126] In step S111, the current pulse is copied, and the copied current pulse is provided to the simulation device.

[0127] In step S112, the voltage across the control electrode of the power semiconductor is compared with the voltage at the analog device.

[0128] In step S113, the comparison results are notified.

[0129] The switching mode of the power semiconductor can also be controlled based on the comparison results.

Claims

1. A device for sensing over-temperature of a power semiconductor, characterized in that, The device includes: - A current pulse source, which is provided through the control electrode of the power semiconductor. - A current replicator that replicates the current provided by the current pulse source and provides the replicated current to an analog device, wherein the analog device consists of a resistor and a capacitor connected in series, and the value of the resistor is equal to or lower than the gate resistance value of the power semiconductor when the temperature of the power semiconductor is at a temperature equal to the maximum junction temperature of the power semiconductor. - A comparator that compares the voltage across the control electrode with the voltage across the analog device. - A device for notifying comparison results.

2. The apparatus according to claim 1, characterized in that, The device for notifying the comparison result also controls the switching mode of the power semiconductor based on the signal output by the comparator.

3. The apparatus according to claim 1 or 2, characterized in that, The control electrode to which the current pulse source is applied is either the gate and emitter or the gate and source.

4. The apparatus according to claim 2, wherein, When the power semiconductor is not in a switching or transition mode, the current pulse source is provided to the power semiconductor.

5. The apparatus according to claim 1, characterized in that, The value of the capacitor is equal to or lower than the gate capacitance value of the power semiconductor.

6. The apparatus according to claim 1, characterized in that, The value of the resistor is adjusted during the calibration phase.

7. The apparatus according to claim 6, characterized in that, The duration of the current pulse is equal to: Wherein, Vth represents the threshold voltage of the gate of the power semiconductor, Vsupply is the negative gate voltage that prevents the power semiconductor from turning on, or Vsupply is the positive gate voltage that prevents the power semiconductor from turning off, Rg is the gate resistance value of the power semiconductor when the power semiconductor is at a temperature equal to the maximum junction temperature of the power semiconductor, Cg is the gate capacitance value of the power semiconductor, and I is the current pulse value.

8. The apparatus according to any one of claims 1 to 2, 4 to 7, characterized in that, The device further includes at least one resistor and at least one other comparator, a first terminal of the at least one resistor being connected to the current replicator and a second terminal of the at least one resistor being connected to the analog device, and the at least one other comparator comparing the voltage at the electrode of the power semiconductor with the voltage at the second terminal of the at least one resistor.

9. The apparatus according to claim 3, characterized in that, The device further includes at least one resistor and at least one other comparator, a first terminal of the at least one resistor being connected to the current replicator and a second terminal of the at least one resistor being connected to the analog device, and the at least one other comparator comparing the voltage at the electrode of the power semiconductor with the voltage at the second terminal of the at least one resistor.

10. A method for sensing over-temperature of a power semiconductor, characterized in that, The method includes the following steps: - Apply current pulses through the control electrodes of the power semiconductor. - Copy the current pulse and provide the copied current pulse to an analog device, wherein the analog device consists of a resistor and a capacitor connected in series, and the value of the resistor is equal to or lower than the gate resistance value of the power semiconductor when the temperature of the power semiconductor is at a temperature equal to the maximum junction temperature of the power semiconductor; - Compare the voltage across the control electrode with the voltage across the simulation device. - Notify the comparison results.

11. The method according to claim 10, characterized in that, The simulation device consists of a resistor and a capacitor connected in series, and the method further includes the step of adjusting the value of the resistor when the power semiconductor is heated to a predetermined temperature.

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