A Buck converter synchronous rectifier tube junction temperature online monitoring device and method

Abstract

The present invention discloses an online monitoring device and method for the junction temperature of a synchronous rectifier tube in a Buck converter. The device includes a Buck converter main circuit, an isolation circuit, a positive circuit, and a DSP device. The method comprises the following steps: first, a DAC interface of the DSP device issues an instruction to control the synchronous rectifier tube S2 to operate in an intermittent operating mode; second, an ADC interface of the DSP device samples the source-drain voltage of the synchronous rectifier tube S2 after passing through the isolation circuit and being positively sensed; third, a thermal parameter is calculated based on the sampled voltage; fourth, the junction temperature is estimated based on the calculated thermal parameter; and fifth, the DAC interface of the DSP device issues an instruction to control the synchronous rectifier tube S2 to return to normal operating mode. The device and method provided by the present invention can eliminate the effects of device degradation and simultaneously improve temperature sensitivity, offering the advantages of simple measurement, high measurement accuracy, and no need for correction.

Description

Technical Field

[0001] The present invention belongs to the technical field of monitoring in electric energy conversion devices, and in particular to an online monitoring device and method for the junction temperature of a synchronous rectifier tube of a Buck converter. Background Art

[0002] Prognostics and Health Management (PHM) is a comprehensive fault detection, isolation, prediction, and health management technology. By monitoring the system's fault signature parameters and leveraging various inference algorithms to estimate the system's health, PHM can detect and effectively predict system failures before they occur, accurately locate degradation or fault locations, and develop maintenance plans based on various information resources. This enables condition-based maintenance and autonomous support for the system, significantly reducing maintenance costs, ensuring system reliability and safety, and improving operational readiness and mission success rates.

[0003] Buck converters with synchronous rectification are widely used in renewable energy generation, computer power supplies, and communications power supplies. The power switch is a crucial component of the Buck converter and also suffers from a high failure rate. Therefore, research on pH measurement (PHM) of the Buck converter's power switches is crucial. Junction temperature is not only a key parameter for the operating status of the power switch, but also a key indicator of its degradation. Therefore, monitoring the junction temperature of the synchronous rectifiers in Buck converters is crucial for assessing their health. However, existing junction temperature estimation methods cannot eliminate the impact of device degradation and have low temperature sensitivity, making accurate monitoring difficult. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the defects involved in the background technology and provide an online monitoring device and method for the junction temperature of the synchronous rectifier tube of the Buck converter, which can monitor the working junction temperature of the synchronous rectifier tube online and monitor the health status of the power switch tube, thereby providing a research basis for fault prediction of power electronic circuits.

[0005] The technical solutions provided by the present invention are as follows:

[0006] A Buck converter synchronous rectifier junction temperature online monitoring device, characterized by: comprising a Buck converter main circuit, an isolation circuit, a positive circuit and a DSP device; wherein the Buck converter main circuit includes an input voltage source V in , filter inductor L f , filter capacitor C f , power switch tube S1, synchronous rectifier tube S2; input voltage source V inThe positive electrode is connected to the drain of the power switch tube S1; the source of the power switch tube S1 is also connected to the drain of the synchronous rectifier tube S2 and the filter inductor L f One end and the input negative electrode of the isolation circuit; the source of the synchronous rectifier S2 is also connected to the input voltage source V in The negative pole of the filter inductor L f The other end is connected to the output filter capacitor C f The positive terminal and the load resistor R L One end of the output filter capacitor C f The negative pole is connected to the input voltage source V in The negative pole of the load resistor R L The other end is connected to the input voltage source V in the negative electrode of the output of the isolation circuit; the positive output electrode and the negative output electrode are respectively connected to the positive input electrode and the negative input electrode of the positive circuit; the positive output electrode and the negative output electrode of the positive circuit are respectively connected to the DAC port and the gnd port of the DSP; the gate of the synchronous rectifier tube S2 is connected to the ADC port of the DSP; wherein the power switch tube can be a MOSFET or an IGBT, and the synchronous rectifier tube is a MOSFET.

[0007] A method for online monitoring of the junction temperature of a synchronous rectifier tube of a Buck converter is characterized by:

[0008] In step A), the DAC interface of the DSP device sends a command to make the synchronous rectifier S2 work in the intermittent working mode, that is, it works normally for one switching cycle and then stops working for one switching cycle, and so on.

[0009] Step B), the ADC interface of the DSP device takes the output voltage v of the positive circuit on Sampling to get v on_f , where the input-output relationship of the positive circuit is:

[0010]

[0011] Step C), based on the sampled voltage v on_f Calculate the thermal parameter v T , the calculation formula is:

[0012] v T =v on_f (off)-v on_f (on)

[0013] where v on_f (off) and v on_f (on) are the output voltage v of the positive circuit measured when the synchronous rectifier S2 is turned off and turned on under the same current. on Peak or average value;

[0014] Step D), according to the obtained thermal parameter v T Calculate the junction temperature using:

[0015] T=f T (v T )

[0016] where the function f T Through offline v T The relationship with T is obtained by fitting data;

[0017] In step E), the DAC interface of the DSP device sends an instruction to control the synchronous rectifier S2 to return to the normal working mode.

[0018] The advantages of this approach are explained as follows:

[0019] Because v on_f (off) and v on_f (on) are the output voltage v of the positive circuit measured when the synchronous rectifier S2 is turned off and turned on under the same current. on , so v on_f (off) and v on_f (on) are the forward voltage drop of the parasitic diode of the synchronous rectifier S2 and the forward voltage drop of the channel under the same current.

[0020] When the synchronous rectifier S2 is turned off, the current flows through the parasitic diode of the synchronous rectifier S2, so v on_f (off) is actually the conduction voltage drop of the diode, which can be expressed as:

[0021] v on_f (off)=v pn +R j I j

[0022] where v pn For I j The voltage drop across the pn junction under current has a negative temperature coefficient, R j is the resistance caused by the bonding wire and pins, I j is the current flowing through the synchronous rectifier.

[0023] When the synchronous rectifier S2 is turned on, the current flows through the conductive channel of the synchronous rectifier S2, so v on_f (on) is caused by the on-resistance of the synchronous rectifier and can be expressed as:

[0024] v on_f (on)=R g I j +R j I j

[0025] where R g is the channel resistance of the synchronous rectifier, which is a positive temperature coefficient, R j is the resistance caused by the bonding wire and pins, I j is the current flowing through the synchronous rectifier.

[0026] For synchronous rectifiers, a common degradation is the breakage of the bonding wire, which will cause R j The increase of v on_f (off) or v on_f (on) to monitor the change of junction temperature will be affected by degradation, resulting in inaccurate monitoring results. on_f (off) and v on_f (on) to construct new thermal parameters:

[0027]

[0028] On the one hand, it eliminates the bonding wire and pin resistance R j The interference of degradation on the monitoring results is reduced. On the other hand, the temperature sensitivity of the parameters is improved by making a difference between the positive and negative temperature coefficient parameters, thereby improving the accuracy and anti-interference of the junction temperature monitoring results.

[0029] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0030] 1. Since the current can flow through the parasitic diode even when the synchronous rectifier is turned off, it does not affect the normal operation of the converter;

[0031] 2. The monitoring results are not affected by the degradation of the synchronous rectifier tube;

[0032] 3. The new thermal parameters constructed have higher temperature sensitivity and higher junction temperature estimation accuracy;

[0033] 4. Simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the online monitoring device for the junction temperature of the synchronous rectifier tube of the Buck converter in the present invention;

[0035] Figure 2 This is a simulation waveform diagram of the online monitoring device for the junction temperature of the synchronous rectifier tube of the Buck converter in the present invention; DETAILED DESCRIPTION

[0036] The present invention provides an online monitoring device and method for the junction temperature of a synchronous rectifier tube in a Buck converter. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0037] 1. Theoretical derivation of the Buck converter synchronous rectifier junction temperature online monitoring device and method of the present invention:

[0038] Figure 1 The structure diagram of the online monitoring device for the junction temperature of the synchronous rectifier tube of the Buck converter is shown, which includes the main circuit of the Buck converter, the isolation circuit, the positive circuit and the DSP device; wherein, the main circuit of the Buck converter includes an input voltage source V in , filter inductor L f , filter capacitor C f , power switch tube S1, synchronous rectifier tube S2; input voltage source V in The positive electrode is connected to the drain of the power switch tube S1; the source of the power switch tube S1 is also connected to the drain of the synchronous rectifier tube S2 and the filter inductor L f One end and the input negative electrode of the isolation circuit; the source of the synchronous rectifier S2 is also connected to the input voltage source V in The negative pole of the filter inductor L f The other end is connected to the output filter capacitor C f The positive terminal and the load resistor R L One end of the output filter capacitor C f The negative pole is connected to the input voltage source V in The negative pole of the load resistor R L The other end is connected to the input voltage source V in the negative electrode of the output of the isolation circuit; the positive output electrode and the negative output electrode are respectively connected to the positive input electrode and the negative input electrode of the positive circuit; the positive output electrode and the negative output electrode of the positive circuit are respectively connected to the DAC port and the gnd port of the DSP; the gate of the synchronous rectifier tube S2 is connected to the ADC port of the DSP; wherein the power switch tube can be a MOSFET or an IGBT, and the synchronous rectifier tube is a MOSFET.

[0039] When the synchronous rectifier S2 is turned on, the current flows through the conductive channel of the synchronous rectifier S2, so v on_f (on) is caused by the on-resistance of the synchronous rectifier and can be expressed as:

[0040] v on_f (on)=R g I j +R j I j

[0041] where R g is the channel resistance of the synchronous rectifier, which is a positive temperature coefficient, R j is the resistance caused by the bonding wire and pins, I j is the current flowing through the synchronous rectifier.

[0042] For synchronous rectifiers, a common degradation is the breakage of the bonding wire, which will cause R j The increase of v on_f (off) or v on_f (on) to monitor the change of junction temperature will be affected by degradation, resulting in inaccurate monitoring results. on_f (off) and v on_f (on) to construct new thermal parameters:

[0043]

[0044] On the one hand, it eliminates the bonding wire and pin resistance R j The interference of degradation on the monitoring results is reduced. On the other hand, the temperature sensitivity of the parameters is improved by making a difference between the positive and negative temperature coefficient parameters, thereby improving the accuracy and anti-interference of the junction temperature monitoring results.

[0045] 2. Implementation steps of the threshold voltage monitoring method of the present invention:

[0046] In step A), the DAC interface of the DSP device sends a command to make the synchronous rectifier S2 work in the intermittent working mode, that is, it works normally for one switching cycle and then stops working for one switching cycle, and so on.

[0047] Step B), the ADC interface of the DSP device takes the output voltage v of the positive circuit on Sampling to get v on_f , where the input-output relationship of the positive circuit is:

[0048]

[0049] Step C), based on the sampled voltage v on_f Calculate the thermal parameter v T , the calculation formula is:

[0050] v T =v on_f (off)-v on_f (on)

[0051] where v on_f (off) and v on_f (on) are the output voltage v of the positive circuit measured when the synchronous rectifier S2 is turned off and turned on under the same current.on Peak or average value;

[0052] Step D) estimates the junction temperature using a function calculation method based on the calculated thermal parameters. The calculation method is:

[0053] T=f T (v T )

[0054] where the function f T Through offline v T The relationship with T is obtained by fitting data;

[0055] In step E), the DAC interface of the DSP device sends an instruction to control the synchronous rectifier S2 to return to the normal working mode.

[0056] 3. Simulation verification of the Buck converter synchronous rectifier junction temperature online monitoring device of the present invention:

[0057] Figure 2 The waveform of the Buck converter in intermittent operation mode is given, where v dr is the gate voltage of the synchronous rectifier S2 in this mode. It can be seen that when the gate voltage v dr When the voltage is high, the measured conduction voltage drop v on_f (on) is small, when the gate voltage v dr When it is low, the measured forward voltage drop v on_f (off) is larger. V under different pin resistance conditions T The simulation calculation results are shown in Table 1, which shows that the device and method for monitoring the junction temperature of the synchronous rectifier tube of the Buck converter provided by the present invention can completely avoid the influence of the change of the pin or bonding wire resistance caused by degradation.

[0058] Table 1

[0059] <![CDATA[v on_f (off)]]> <![CDATA[v on_f (on)]]> <![CDATA[v T ]]> <![CDATA[R j =0.01]]> 0.82 0.12 0.7 <![CDATA[R j =0.02]]> 1.32 1.62 0..7 <![CDATA[R j =0.03]]> 1.82 2.12 0.7

[0060] The device and method for online monitoring of the junction temperature of the synchronous rectifier tube of a Buck converter provided by the present invention can realize online monitoring of the junction temperature of the synchronous rectifier tube without affecting the normal operation of the circuit, providing a basis for predicting the life of the switching tube. It is simple and easy to implement and has important practical application value.

[0061] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0062] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A Buck converter synchronous rectifier junction temperature online monitoring method, characterized in that: The Buck converter synchronous rectifier tube junction temperature online monitoring method adopts a Buck converter synchronous rectifier tube junction temperature online monitoring device for online monitoring, and the Buck converter synchronous rectifier tube junction temperature online monitoring device includes a Buck converter main circuit, an isolation circuit, a positive circuit and a DSP device; wherein, the Buck converter main circuit includes an input voltage source V in , filter inductor L f , filter capacitor C f , power switch tube S1, synchronous rectifier tube S2; input voltage source V in The positive electrode is connected to the drain of the power switch tube S1; the source of the power switch tube S1 is also connected to the drain of the synchronous rectifier tube S2 and the filter inductor L f One end and the input negative electrode of the isolation circuit; the source of the synchronous rectifier S2 is also connected to the input voltage source V in The negative pole of the filter inductor L f The other end is connected to the output filter capacitor C f The positive terminal and the load resistor R L One end of the output filter capacitor C f The negative pole is connected to the input voltage source V in The negative pole of the load resistor R L The other end is connected to the input voltage source V in The output positive electrode and the output negative electrode of the isolation circuit are respectively connected to the input positive electrode and the input negative electrode of the positive circuit; the output positive electrode and the output negative electrode of the positive circuit are respectively connected to the ADC port and the gnd port of the DSP; the gate of the synchronous rectifier tube S2 is connected to the DAC port of the DSP; wherein the power switch tube can be a MOSFET or an IGBT, and the synchronous rectifier tube is a MOSFET; The Buck converter synchronous rectifier tube junction temperature online monitoring method comprises the following steps: In step A), the DAC interface of the DSP device issues a command to make the synchronous rectifier S2 operate in the intermittent working mode; Step B), the ADC interface of the DSP device takes the output voltage v of the positive circuit on Sampling to get v on_f ; Step C), based on the sampled voltage v on_f Calculate the thermal parameter v T , the thermal parameter v T The calculation formula is: v T =v on_f (off)-v on_f (on) where v on_f (off) and v on_f (on) are the output voltage v of the positive circuit measured when the synchronous rectifier S2 is turned off and turned on under the same current. on Peak or average value; Step D), estimating the junction temperature based on the calculated thermal parameters; In step E), the DAC interface of the DSP device sends an instruction to control the synchronous rectifier S2 to return to the normal working mode.

2. The Buck converter synchronous rectifier junction temperature online monitoring method according to claim 1, characterized in that: The isolation circuit can be a magnetic coupling isolation circuit or an optical coupling isolation circuit.

3. The Buck converter synchronous rectifier junction temperature online monitoring method according to claim 1, characterized in that: Take the positive circuit input v a With output v on The relationship is:

4. The Buck converter synchronous rectifier junction temperature online monitoring method according to claim 1, characterized in that: The synchronous rectifier tube S2 works in the intermittent working mode and works normally for one switching cycle and then stops working for one switching cycle, and the cycle repeats.

5. The Buck converter synchronous rectifier junction temperature online monitoring method according to claim 1, characterized in that: The junction temperature estimation method is calculated as follows: T=f T (v T ) where the function f T Through offline v T The relationship with T is obtained by fitting the data.

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