On-line conduction voltage drop sampling circuit for junction temperature detection of power device

Abstract

The utility model discloses a conduction voltage drop on-line sampling circuit used for power device junction temperature detection. The conduction voltage drop on-line sampling circuit comprises a clamping circuit and a voltage isolation following module which are connected in sequence. The clamping circuit is used for acquiring a conduction voltage drop VDS (on) on a power device; the voltage isolation following module is used for performing equal-voltage following output on the conduction voltage drop VDS (on) output by the clamping circuit; the clamping circuit provided by the utility model has a new topological structure, can clamp without connecting a power supply, is high in sampling precision, has good adaptability and expandability, is wide in application occasion, and is also suitable for power devices except for MOSFETs; the influence on a main circuit is small, different modules are adopted to carry out voltage blocking and isolation on the circuit, the isolation protection effect is good, meanwhile, the junction temperature change of a device can be fed back in time, the reliability of the device is improved, the service life of the device is prolonged, and the use cost of the device is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the related technical field of power electronic conversion and power device reliability, in particular to a kind of conduction voltage drop online sampling circuit for power device junction temperature detection. BACKGROUND

[0002] Power device is the core device of power electronic conversion system, and is one of the key components of which the reliability of conversion system is relatively weak.Most of the failure of power device is closely related to its internal junction temperature, therefore, it is of great significance and value to carry out power device junction temperature online monitoring.The traditional power module junction temperature measurement method is mainly divided into four categories of physical contact method, model estimation method, optical method and temperature sensitive electrical parameter (TSEP) method.TSEP method takes chip itself as temperature sensor, can realize non-invasive measurement, and is most suitable as junction temperature online monitoring method.

[0003] TSEP method takes the device to be measured itself as temperature sensing component, maps chip temperature information on external electrical variable, not only can obtain the average junction temperature of internal chip of the device to be measured, and its cost is low, response is fast, easy to online monitoring.

[0004] TSEP method is divided into multiple types according to different sensitive parameters.Among them, on-state voltage at high current (OVHC) method for estimating junction temperature (on-state voltage at high current, OVHC) under the condition of applying large current (referred to as conduction voltage drop, V DS(on) ) has low measurement bandwidth requirement, does not affect the original control strategy of converter, and has low hardware invasiveness, so it is an ideal online junction temperature estimation method. UTILITY MODEL CONTENT

[0005] Therefore, the utility model aims at providing a kind of conduction voltage drop online sampling circuit for power device junction temperature detection, which utilizes the temperature sensitive electrical parameter of power device (MOSFET) conduction voltage drop to carry out junction temperature detection.

[0006] To achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0007] The utility model provides a be used for power device junction temperature detection's on -line sampling circuit of conduction voltage drop, including clamping circuit and voltage isolation follow module who connects gradually, the clamping circuit is used for obtaining the conduction voltage drop VDS (on) on power device, voltage isolation follow module is used for carrying out the conduction voltage drop VDS (on) of clamping isolation module output isobaric follow -up output, the clamping circuit includes first voltage division resistance breaking module, second voltage division resistance breaking module and voltage clamping module, one end of first voltage division resistance breaking module, second voltage division resistance breaking module is connected with the both ends of the PN junction to be measured respectively, the other end of second voltage division resistance breaking module is connected with one end of voltage clamping module, the other end of first voltage division resistance breaking module is connected with the other end of voltage clamping module and is connected with the input end of voltage isolation follow module.

[0008] Further, the first voltage division resistance breaking module includes a first MOSFET tube, a first resistor, and a second resistor; the drain of the first MOSFET tube is connected with one end of the power device to be measured; the gate of the first MOSFET tube is connected with the second resistor, and the source of the first MOSFET tube is connected with the first resistor.

[0009] Further, the second voltage division resistance breaking module includes a second MOSFET tube, a third resistor, and a fourth resistor; the drain of the second MOSFET tube is connected with one end of the power device to be measured; the gate of the second MOSFET tube is connected with the fourth resistor, and the source of the second MOSFET tube is connected with the third resistor.

[0010] Further, the first MOSFET tube and the second MOSFET tube are depletion mode MOSFET tubes.

[0011] Further, the voltage clamping module includes a diode D1 and a zener diode Z1 connected in series; the negative electrode of the diode D1 is connected with the negative electrode of the zener diode Z1, the positive electrode of the zener diode Z1 is connected with the other end of the third resistor in the second voltage division resistance breaking module; the positive electrode of the diode D1 is connected with the other end of the first resistor in the first voltage division resistance breaking module.

[0012] Further, the diode D1 is a Schottky diode D1.

[0013] Further, the voltage isolation follow module includes an operational amplifier and a fifth resistor; one end of the fifth resistor is connected as an input end, the fifth resistor is connected with the positive input end of the operational amplifier, the negative input end of the operational amplifier is connected with the output end, and the output end of the operational amplifier is connected as the output end of the voltage isolation follow module.

[0014] Further, the display unit is connected with the on-sampling circuit of the on-voltage drop, and the on-sampling circuit of the on-voltage drop outputs the collected signal to the display unit for display.

[0015] The utility model discloses the beneficial effect lies in:

[0016] The utility model provides a on-sampling circuit of on-voltage drop for power device junction temperature detection, including the clamping circuit and voltage isolation follow module that connect gradually, the clamping circuit is used for obtaining the on-voltage drop VDS (on) on power device, voltage isolation follow module is used for carrying out the isobaric follow output of the on-voltage drop VDS (on) of clamping isolation module output, the utility model provides the clamping circuit has new topological structure, realizes the clamping function by a voltage clamping module, and can clamp without connecting power supply, unlike traditional double diode isolation circuit, sampling precision is high, has good adaptability and expandability, in order to obtain the higher resolution sampling value of ADC converter, still can increase filter circuit, sampling range dynamic self -adaptation circuit etc. behind voltage isolation follow module, application occasion is wide, and sampling circuit is applicable to the power device except MOSFET, and the function effect is good, and the influence to main circuit is little, and voltage is broken and is isolated to the circuit using different module, and the isolation protection effect is good, can feed back device junction temperature change in time simultaneously, improves the reliability of device, increases the service life of device, reduces the use cost of device.

[0017] The other advantages, objects and features of the utility model will be set forth in the subsequent specification in some degree, and in some degree, it will be obvious to those skilled in the art based on the study of the following text or can be taught from the practice of the utility model. The objects and other advantages of the utility model can be realized and obtained by the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the purpose, technical scheme and beneficial effect of the utility model more clear, the utility model provides the following drawings for explanation:

[0019] Figure 1 For on-sampling circuit of on-voltage drop.

[0020] Figure 2 For inverter main circuit diagram.

[0021] Figure 3 For output current I and drain-source voltage VDS schematic diagram.

[0022] Figure 4 For output current I and output sampling voltage Vou schematic diagram.

[0023] Figure 5The cursor is in the on range of the MOSFET, and the VDS and the output voltage Vout are shown in the schematic diagram.

[0024] Figure 6 The cursor is in the on range of the MOSFET, and the VDS and the output voltage Vout are shown in the schematic diagram. Figure 5

[0025] Figure 7 The cursor is in the on range of the MOSFET, and the VDS and the output voltage Vout are shown in the schematic diagram.

[0026] Figure 8 The cursor is in the on range of the MOSFET, and the VDS and the output voltage Vout are shown in the schematic diagram. Figure 7

[0027] In the figure, 1 represents a first voltage division blocking module; 2 represents a second voltage division blocking module; 3 represents a voltage clamping module; and 4 represents a voltage isolation following module. DETAILED DESCRIPTION

[0028] The utility model will be further described below in combination with the drawings and specific embodiments, so that the person skilled in the art can better understand the utility model and can be implemented, but the embodiment is not as the limitation of the utility model.

[0029] As Figure 1 The circuit can detect the on voltage drop of the power device (MOSFET) in real time, and then reflect the change of the junction temperature of the power device in real time, so that the device with excessive junction temperature can be controlled and protected in time.

[0030] The on voltage drop online sampling circuit provided in the embodiment comprises a clamping circuit and a voltage isolation following module 4 connected in sequence; the clamping circuit is used for acquiring the on voltage drop VDS (on) on the power device; and the voltage isolation following module 4 is used for performing isobaric following output on the on voltage drop VDS (on) output by the clamping circuit.

[0031] The power device provided in the embodiment can be a MOSFET power device or other power device; the on voltage drop VDS (on) on the power device refers to the on voltage drop VDS (on) on the PN junction of the power device; and the circuit samples the on voltage drop of the power device (MOSFET).

[0032] ​​The clamping circuit comprises a first voltage division blocking module 1, a second voltage division blocking module 2 and a voltage clamping module 3; one end of the first voltage division blocking module 1 and the second voltage division blocking module 2 is connected with two ends of the PN junction to be measured respectively, the other end of the second voltage division blocking module 2 is connected with one end of the voltage clamping module 3, the other end of the first voltage division blocking module 1 is connected with the other end of the voltage clamping module 3 and then connected with the input end of the voltage isolation follower module 4; the first voltage division blocking module 1 is used for blocking the forward voltage on the PN junction to be measured; the second voltage division blocking module 2 is used for blocking the negative voltage on the PN junction to be measured.

[0033] The first voltage division blocking module 1 comprises a first MOSFET tube, a first resistor and a second resistor; the drain of the first MOSFET tube is connected with one end of the power device to be measured; the gate of the first MOSFET tube is connected with the second resistor, and the source of the first MOSFET tube is connected with the first resistor;

[0034] The second voltage division blocking module 2 comprises a second MOSFET tube, a third resistor and a fourth resistor; the drain of the second MOSFET tube is connected with one end of the power device to be measured; the gate of the second MOSFET tube is connected with the fourth resistor, and the source of the second MOSFET tube is connected with the third resistor;

[0035] The first MOSFET tube Q1 and the second MOSFET tube Q2 in the embodiment are depletion type MOSFET tubes;

[0036] The voltage clamping module 3 comprises a diode D1 and a zener diode Z1 connected in series; the negative electrode of the diode D1 is connected with the negative electrode of the zener diode Z1, the positive electrode of the zener diode Z1 is connected with the other end of the third resistor in the second voltage division blocking module 2; the positive electrode of the diode D1 is connected with the other end of the first resistor in the first voltage division blocking module 1;

[0037] The diode D1 in the embodiment is a Schottky diode D1; the depletion type MOSFT, the Schottky diode and the zener diode are used to constitute the clamping circuit in the embodiment.

[0038] The voltage isolation follower module 4 comprises an operational amplifier and a fifth resistor; one end of the fifth resistor is connected as an input end, the fifth resistor is connected with the positive input end of the operational amplifier, the negative input end of the operational amplifier is connected with the output end, and the output end of the operational amplifier is connected as the output end of the voltage isolation follower module 4; the voltage follower constituted by the operational amplifier is used in the voltage isolation follower module 4 in the embodiment.

[0039] The working principle is that when the switch tube is turned on, the clamping circuit will lead out the on-state voltage drop VDS (on) without affecting the main circuit; the led-out on-state voltage drop VDS (on) is followed by the voltage isolation following module 4 to be followed by the voltage isolation following module 4;

[0040] The online sampling circuit in the embodiment transmits the sampling value to the ADC converter of the control circuit and then feeds back to the control system; the control system compares the sampling value with the fitted on-state voltage drop check curve of the power device to obtain the device junction temperature at this time; when the switch tube is turned off, the clamping circuit clamps the voltage to a threshold value, and continues to feed back the sampling value to the control system, and the control system detects the threshold value to determine that the switch tube is in the off state.

[0041] The on-state voltage drop online sampling circuit in the embodiment mainly samples the on-state voltage drop VDS (on) caused by the on-state resistance of the power device under large current DS(on) . When the power device is turned on, there is a small on-state resistance RDS in the device DS(on) , so under large current, the device has an on-state voltage drop VDS DS(on) . The on-state voltage drop VDS DS(on) has a positive temperature coefficient, good linearity and sensitivity, and the on-state voltage drop under large current is very convenient for online sampling.

[0042] Figure 1 The on-state voltage drop online sampling circuit is divided into four modules, namely the first voltage dividing resistor module 1 and the second voltage dividing resistor module 2, the voltage clamping module 3, and the voltage isolation following module 4; the voltage dividing resistor modules are the first voltage dividing resistor module 1 and the second voltage dividing resistor module 2, and the voltage clamping module 3 forms a clamping circuit;

[0043] The first voltage dividing resistor module 1 and the second voltage dividing resistor module 2 each have a depletion mode MOSFET (Q1 and Q2), which is a normal on-state device of milliamperes, and by controlling the resistance (R1, R2 and R3, R4) connected to the source and gate, different impedances are exhibited during operation, thereby playing a certain voltage dividing and blocking role.

[0044] In actual application, according to the input voltage of the measurement circuit, the voltage dividing and blocking role of the sampling circuit can be improved by connecting two end-symmetric depletion mode MOSFETs in series at the input ends of the sampling circuit to adapt to different sizes of input voltage.

[0045] The first voltage dividing resistor module 1 is used to block the forward voltage, and in order to reduce the influence of the sampling circuit on the measurement circuit and protect the sampling circuit; the second voltage dividing resistor module 2 is used to block the reverse voltage;

[0046] And the first voltage blocking module 1 and the second voltage blocking module 2 and the voltage clamping module 3 are used together to realize the function of voltage blocking; the voltage clamping module 3 is composed of a Schottky diode D1 and a Zener diode Z1. The clamping voltage can be obtained by the Zener diode Z1, instead of the power supply or the self-powered circuit. The Schottky diode D1 is used to protect the Zener diode from forward conduction.

[0047] And the clamping voltage can be changed by using Zener diodes with different Zener voltages to meet the needs of different applications.

[0048] And the first voltage blocking module 1 and the second voltage blocking module 2 and the voltage clamping module 3 can form a clamping circuit for blocking the voltage higher than The specific working principle is as follows.

[0049] When the input voltage is higher than , Z1 works in reverse clamping mode, and its leakage current forms a voltage drop on R1 and R3, so that Q1 and Q2 work in high impedance mode. Then, The voltage is clamped to ;

[0050] When the input voltage is between 0 and , both D1 and Z1 are blocked. At this time, only the reverse leakage current of the Zener diode (microampere level current) flows through the circuit, which is a microampere level current. Therefore, the voltage drop on R1 and R3 is in the millivolt level, which means that Q1 and Q2 are in the on state. Therefore, the voltage drops of the MOSFET and the resistor In this case, it is equal to , that is .

[0051] The voltage isolation and following module 4 in the embodiment uses a voltage follower composed of an operational amplifier for output voltage and voltage isolation. Due to the high gain characteristic of the integrated operational amplifier itself, the voltage follower composed of the integrated operational amplifier has very high input impedance and consumes very little current, which does not interfere with the original circuit and outputs the same voltage signal as the input voltage signal.

[0052] The on-state voltage drop online sampling circuit provided in the embodiment further comprises a display unit, which is used to constitute a test circuit for testing the effect of the circuit provided in the embodiment. The embodiment is specifically described by taking an inverter circuit as an example. Through simulation verification, as shown in Figure 2 , the output voltage of the inverter circuit is Figure 2It is a circuit diagram for testing the on-voltage online sampling circuit effect, the simulation circuit for testing the inverter is provided, the on-voltage online sampling circuit is connected with the main circuit of the inverter, the output end of the main circuit of the inverter is connected with the input end of the on-voltage online sampling circuit, and the on-voltage online sampling circuit outputs collection signals to a simulation display unit for display.

[0053] The main circuit of the inverter in the embodiment is a full-bridge circuit composed of four MOS tubes, and the on-voltage online sampling circuit is connected with the PN junction of the high-power device to be tested in the main circuit of the inverter.

[0054] As shown in Figure 3 , Figure 3 is the output current I of the inverter circuit and the drain-source voltage VDS of the MOSFET.

[0055] As shown in Figure 4 , Figure 4 is the output current I of the inverter circuit and the sampling voltage Vout of the sampling circuit.

[0056] As shown in Figure 5 , Figure 5 is the drain-source voltage VDS of the MOSFET and the sampling voltage Vout of the sampling circuit. The measurement cursors T1 and T2 in the figure are in the range when the MOSFET is turned on, the channel A measures the sampling voltage Vout (the red part), and the channel B measures the drain-source voltage VDS (the gray part).

[0057] As shown in Figure 6 , Figure 6 is Figure 5 the amplified drain-source voltage VDS and the sampling voltage Vout in the cursor range (MOSFET is turned on) in , that is, the sampling voltage measured by the sampling circuit is equal to the on-voltage V DS(on) of the MOSFET at this time, which indicates that the function of the utility model is better.

[0058] AsFigure 7 As shown, Figure 7 This is a schematic diagram of the drain-source voltage VDS and output voltage Vout when the cursor is in the MOSFET turn-off range. In the figure, the measurement cursors T1 and T2 are in the range when the MOSFET is turned off. Channel A measures the sampled voltage Vout (red part), and Channel B measures the drain-source voltage VDS (gray part).

[0059] like Figure 8 As shown, Figure 8 for Figure 7 A diagram showing the magnified drain-source voltage VDS and sampled voltage Vout, shown in the cursor range (MOSFET on). As shown in the data, Vout is clamped to a fixed value of 10.494 (this fixed value can be adjusted based on actual usage). This means that the output voltage measured by the sampling circuit remains at a fixed value significantly greater than the on-state voltage drop, facilitating subsequent control system processing. This demonstrates that the functionality of the present invention is well implemented.

[0060] pass Figure 5 、 Figure 6 、 Figure 7 and Figure 8 By comparing the drain-source voltage VDS measured in the figure with the sampling voltage Vout, we can know that when the MOSFET is turned on, , that is, the sampled voltage Vout is equal to the drain-source voltage VDS of the MOSFET; when the MOSFET is turned off, the output voltage Vout measured by the sampling circuit is always clamped to a fixed value that is significantly larger than the on-state voltage drop.

[0061] Table 1 Figure 5 Data measurement in the middle blue area

[0062]

[0063]

[0064] In order to further illustrate the sampling accuracy of the sampling circuit, Figure 5 The drain-source voltage V during the middle blue time range (32.36ms to 38.386ms) DS(on) With the sampling voltage V out The measurements were carried out, see Table 1 for details.

[0065] By comparing the data in the table, we can conclude that the sampling voltage V measured by the sampling circuit is out and the forward voltage drop V DS(on) The maximum difference is a few millivolts, indicating that this sampling circuit has high accuracy and small measurement error. It can detect the on-state voltage drop of power devices (MOSFETs) online, thereby reflecting the changes in the junction temperature of power devices in real time. The simulation results prove the feasibility of this circuit.

[0066] The on-line sampling circuit for the on voltage drop of the power device MOSFET junction temperature detection provided by the embodiment can on-line detect the on voltage drop of the power device (MOSFET), and then reflect the change of the power device junction temperature in real time, so that the device with excessive junction temperature can be controlled and protected in time.

[0067] The above-mentioned embodiments are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. The equivalent substitutions or transformations made by the skilled in the art on the basis of the present application are all within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A turn-on voltage drop on-line sampling circuit for power device junction temperature detection, characterized in that: The voltage isolation following module is used for outputting the on-voltage drop output by the voltage isolation module in an equal voltage following manner.

2. The turn-on voltage drop on-line sampling circuit for power device junction temperature detection of claim 1, wherein: The first voltage blocking module comprises a first MOSFET tube, a first resistor and a second resistor.

3. The turn-on voltage drop on-line sampling circuit for power device junction temperature detection of claim 2, wherein: The second voltage blocking module comprises a second MOSFET tube, a third resistor and a fourth resistor.

4. The turn-on voltage drop on-line sampling circuit for power device junction temperature detection of claim 3, wherein: The first MOSFET tube and the second MOSFET tube are depletion mode MOSFET tubes.

5. The on-state voltage drop online sampling circuit for detecting junction temperature of a power device according to claim 1, wherein: The voltage clamping module comprises a diode D1 and a zener diode Z1 connected in series.

6. The on voltage online sampling circuit for power device junction temperature detection of claim 5, wherein: The diode D1 is a Schottky diode D1.

7. The turn-on voltage drop on-line sampling circuit for power device junction temperature detection of claim 1, wherein: The voltage isolation following module comprises an operational amplifier and a fifth resistor.

8. The turn-on voltage drop on-line sampling circuit for power device junction temperature detection of claim 1, wherein: The display unit is connected with the on-voltage drop online sampling circuit. The on-voltage drop online sampling circuit outputs the collected signal to the display unit for display.

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