TWI231863B - Detection circuit and method for detecting the saturation status of inductors - Google Patents

Abstract

A detection circuit and method for detecting the saturation status of inductors is provided. As an inductor is an important power storage unit in switching type power converters, it should avoid to operate the inductor in a saturated status during the actual operation. The detection circuit of this invention determines whether the inductor reaches the status of saturation by detecting variance in the slope of current. This invention applies a second order differential operation to the current of the inductor for determining a current slope variance signal, and then uses the gate control signal of a power switch unit in the switching type power converter to eliminate any possible erroneous message which occurs when the power switch unit is turned on or off and fast variance in the slope of current is encountered, thereby correctly determining whether the inductor reaches the saturated state or not.

Description

1231863 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to an inductor saturation state detection circuit and method, and particularly to a saturation state detection circuit for judging an inductor in a switching power converter and method. . The arrival device can sense a small amount of stored electricity. The deficiency ratio can be corrected, but the conversion value of the small and medium-sized devices can be changed. The source inductance and the oligo change are more important. 1 is the energy saving of the electrical technology of the surgical device, which is stored first, and its effect is high. If the temperature is large and the temperature is large, it will be a breeze. The measuring element capacity Aw bb afl The power storage power storage rule > f, the state of the electric state when the current is large and the manipulator of the state energy function under the effect of oversaturation. The actual replacement of the energy converter is based on the electrical inductance of the energy inductor, which makes this possible. The damage caused by the damage to the disaster means one m.l. The brewing rate is lower than the rate of the source, and the & type switching is cut into a built-in device and the electric induction device is full. In order to solve the problem of state factors, it is necessary to measure and measure the current situation and avoid the transmission. The sense of electric current and the current of the telecommunication device should be used for the purpose of measuring. The profit is actually coming. The question-and-answer questions about the protection and loss-protection current transformers are exchanged. The measurement is made by the low extreme resistance of the resistance: the electrical type is large and the quadruple is a string. Divide in France and Party 1 by: The value of the pressure point spans the gap. If the electricity is smaller than the high-level small current and large current bM, the calculation is simple to measure the span: the upper point of the resistance is not good, but the value of the sun is too large. Electricity . If the loss is m}), the resistance to T-I 〇〇 power consumption is more likely to cause

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Page 5 1231863 V. Description of the invention (2) Easy to be interfered by noise. 2. Connect a resistor with very low resistance in series at the source terminal or drain terminal of the power switching element and calculate the current by measuring the voltage across the resistor. The advantages and disadvantages are: Advantages: (1) The measurement is simple, and the current is equal to the voltage across the resistor divided by the resistance. (2) The power consumption is smaller than the measurement method of the series resistance directly in the inductor. Disadvantages: The current signal is discontinuous and must be processed by the filter to obtain the inductor current, which is likely to cause inaccuracies in measurement. 3. A set of RC filters are connected in parallel at both ends of the inductor to measure the inductor current; or in addition to the parallel filter, other auxiliary measuring elements are added to accurately measure the inductor current value. Its advantages and disadvantages are: Advantages: it can measure the current value more accurately, and it is less susceptible to noise. ○ Disadvantages: the circuit is more complicated (more auxiliary measurement components). 4. Use the Hall element to measure the inductor current value. Its advantages and disadvantages are: Advantages: Simple measurement method and high accuracy. Cons: Cost is too high. On the other hand, the overcurrent protection method is to set the maximum current weight. When the measured current value is greater than this set value, the output current or power of the power converter is limited, or the entire power is turned off. Function of converter circuit. Therefore, this inductor saturation state detection method using the overcurrent protection concept is also called the maximum current method.

Page 6 1231863 V. Description of the invention (3) But using the maximum current method to detect whether the inductor has reached saturation state has the following problems: 1. When using the maximum current method to detect whether the inductor current has reached the saturation state, If it is encountered that the inductor current changes too much during one week of power switch switching, although the average current has not reached the rated current of the inductor saturation state, the highest peak current may have already exceeded the limit of the inductor saturation state current. Therefore, in order to meet the convenience of use, it is necessary to use a large-sized inductor with a large saturation current. Therefore, the use efficiency of the inductor is generally reduced, and the overall weight and volume of the switching power converter are increased. 2. After the inductor is operated continuously for a period of time, the temperature of the core and the coil will rise. At this time, the maximum current required for the inductor to reach saturation will be smaller than the maximum saturation current of the original inductor at room temperature. In other words, the maximum current for the inductor to reach saturation at this time will be lower than the maximum current originally set. This situation will allow the inductor to reach the saturation state earlier than the originally set maximum saturation current. Therefore, the state of the inductor under actual operation cannot be detected correctly. 3. If the inductor's own inductance decreases due to winding damage, it will cause the inductor current to enter the saturation state earlier than the original maximum current amount, but it will not be detected correctly. . 4. The noise or surge of the inductor current signal can easily cause the detection circuit to mistakenly think that the maximum current value has been reached, and produce incorrect results.

1231863 V. Description of the invention (4) 5. The actual manufactured inductor will have some differences from the original design. Therefore, it will be difficult to set an accurate value for the setting of the maximum saturation current of the inductor. If the value of the maximum saturation current is set higher, a larger inductor must be used together, which not only causes an increase in volume and weight, but also makes it difficult to detect the early saturation of the inductor due to temperature or winding damage. If the value of the maximum saturation current is set too low, when the change of the inductor current during the power switch switching cycle is too large, it is easy to mistakenly think that the inductor has reached the saturation state, which will cause the test error. Based on the above problems caused by using the maximum current method to detect whether the inductor has reached a saturation state, the inventor has devoted himself to research and cooperated with scientific applications, and finally proposed a reasonable design of the present invention "inductor saturation state detection circuit and method". SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit and method for detecting a saturation state of an inductor, which detect whether the inductor reaches a saturation state by using a second-order differential calculation method for a current signal of the inductor. An object of the present invention is to provide an inductor saturation state detection circuit and method, which can remove the error message of the inductor current slope change caused by the power switching element in the switching power converter when it is turned on or off, so as to provide More accurate test results of inductor saturation. In order to achieve the above object, the present invention provides an inductor saturation state detection circuit, including: an inductor current input unit for inputting an inductor current signal; and a differential unit for inputting an inductor current signal

1231863 V. Description of the invention (5) An inductor current slope change signal is obtained by a second-order differential operation; therefore, it can be known whether the inductor is saturated by judging the voltage of the inductor current slope change signal. In order to achieve the above object, the present invention further provides an inductor saturation state detection circuit for detecting the saturation state of an inductor in a switching power converter. The detection circuit includes an inductor current input unit, Detect the inductor to obtain an inductor current signal; a differentiation unit to obtain an inductor current slope change signal by a second order differential operation on the inductor current signal; and a judgment signal input unit to obtain a switching power converter A gate signal and a delayed gate signal of one of the power switching elements; and a gate unit, which performs an AND operation on the inductor current slope change signal, the gate signal, and the delayed gate signal to obtain an inductor The current slope increases and changes the signal; therefore, by determining the voltage of the inductor current slope increases and changes the voltage, you can know whether the inductor has reached saturation, and the power switching element in the switching power converter can be removed when it is turned on or off. Error message caused by the inductor current slope change. In order to achieve the above object, the present invention provides a method for detecting a saturation state of an inductor, which includes the following steps: measuring a current signal of an inductor; obtaining a current slope change signal of the inductor by a second-order differential operation on the current signal of the inductor; The voltage of the inductor current slope variation signal is judged to determine whether the inductor has reached saturation. To achieve the above object, the present invention further provides an inductor saturation state detection method for detecting a saturation state of an inductor in a switching power converter. The detection method includes the following steps: measuring an inductance

Page 9 1231863 V. Description of the invention (6) is the current signal; an inductor current slope and a power switching element current slope change are calculated to obtain an inductor inductor current slope increase to saturation, and it is also on or off interest. In order to make your content more detailed, please refer to the figure below. Only the current signal of the 0-pair inductor is obtained by the second-order differential operation to obtain the rate change signal. Obtain a gate signal and a delayed gate signal in the switching power converter. ; Make the inductor signal, the gate signal and the delayed gate signal and the gate current slope increase and change the signal; determine whether the inductor can remove the power in the switching power converter by judging the voltage of the voltage signal The erroneous information of the inductor current slope change caused by the switching element can further understand the features and techniques of the present invention. I have detailed descriptions and drawings of the present invention. The limitation is that the inductance value of the sum state is used to detect the change in the state of the source converter and the conduction or change. The resulting inductance is enough to detect the speed drop of the detection circuit. There is no de-current slope. [Embodiment When the present invention has reached the saturation state, the characteristics of rising Saturation switching element slope f # The inductor is created when there is a sharp stop. The main use is to make the inductor that is saturated in the actual operation of the switching electric moment, it will eliminate the rapid change of the power switch. In actual operation, whether the inductor is in a state of rapid saturation change. In addition, during the operation, the source converter should be turned on or an error message will cause

1231863 V. Description of the invention (7) The result of misjudgment when determining whether the inductor has reached saturation. The invention also proposes a corresponding solution to this problem. Please refer to the first figure, the present invention is an inductor saturation state detection circuit, which includes an inductor current input unit 11, a differential unit 1 3, a low-pass filter 1 5, an amplifier 17 and a signal The judging unit 19 and a driving unit 21. Among them: the inductor current input unit 11 includes: a current measuring element 111 capable of measuring an inductor current signal, and this part may be a low-resistance resistor or a current sensor using a Hall effect. The differential amplifier Π 3 provides the correct current amplification signal to meet the input voltage range of the circuit of the subsequent stage. The band-pass filter 115 filters signals having a bandwidth near the switching frequency of the power switching element. Theoretically, the fluctuation frequency of the inductor current signal is the same as the switching frequency of the power switching element. Therefore, in order to eliminate high-frequency or low-frequency harmonics generated by circuit parasitic elements of the switching power converter, the present invention uses a band-pass filter 1 1 5. After the inductor current signal S 11 is obtained by using the inductor current input unit 11, the inductor current signal S 11 is obtained through a second-order differential operation on the inductor current signal S 11 through the differentiation unit 13 to obtain an inductor current slope change signal S 1 5. The differential unit 1 3 includes: a first differentiator 1 3 1 and a second differentiator 1 3 3. The output of the first differentiator 1 3 1 can obtain the inductor current slope signal S 1 3, among which the first differentiator 131 Referring to the second figure, the relationship between the output signal Vdlff (that is, the inductor current slope signal S 1 3) and the input current signal V i (that is, the inductor current signal S 1 1) can be expressed as:

Page 11 1231863 V. Description of the invention (8)

Wf (1) Among them, the resistor R1 and the capacitor C 1 are adjustable variables that determine the signal gain ratio. A proper differentiator can be designed by selecting the value of R1 C1. A negative sign indicates that the inductor current slope signal S 1 3 and the inductor current signal S 11 have a phase shift of 180. The inductor current slope signal S1 3 is then passed through the second differentiator 1 3 3 to obtain the inductor current slope change signal S 1 5. The circuit structure of the second differentiator 1 3 3 is the same as that of the second figure, and will not be repeated here. After two stages of differentiator processing, the inductor current slope change signal S1 5 and the inductor current signal S11 will be in phase. Because the differentiator has the characteristics of a high-pass filter, in order to avoid the inductor current signal S 1 1, the inductor current slope change signal S 1 obtained after passing through the first differentiator 1 3 1 and the second differentiator 1 3 3. 5 will contain high-frequency noise, so the low-pass filter 15 is used to filter high-frequency noise higher than the switching frequency of the circuit switching elements. The signal obtained through the low-pass filter 15 is amplified by the amplifier 17 to obtain the amplified signal S17 of the inductor current slope variation. This signal is used as the main basis for judging whether the inductor has reached the saturation state. According to the variation of the inductor current slope, the voltage of the amplified signal S 1 7 can be appropriately designed to reach the saturation voltage level of the inductor. However, because the power switching element in the switching power converter is turned on and off at the moment, it will cause a sharp change in the inductor current slope, that is, the amount of change in the inductor current slope will suddenly increase. At this point, zooming in

Page 12 1231863 V. Description of the invention (9) ---- The trigger voltage level signal will not appear at the output end of the inductor 17 due to the saturation state of the inductor. This signal will cause incorrect judgment of the inductor saturation state detection circuit. In order to solve this situation, the present invention uses another ~ stage signal judgment unit 19 to remove the error signal of the inductor current slope variation caused by the power switching element at the moment of on and off. The signal judging unit 19 includes a judging signal input unit 191 and a gate ticket 193. Among them, it is judged that the input of hole 5 tiger early element 1 91 is further composed of gate signal input unit 19; Π and signal delay unit 1 9 1 3. The gate signal input unit 1 9 i 丨 is mainly used to obtain the idle signal S 1 9 of the power switching element in the switching power converter. According to the circuit structure of the switching power converter, the high-voltage level represented by the gate signal S 1 9 is the time period when the power switching element is turned on or off, which causes the inductor current to increase. The gate signal S1 9 obtained by the gate signal input unit 1 9 1 1 is delayed by the signal delay circuit 1 9 1 3—after a short period of time, the gate delay signal S 2 1 can be obtained. As shown in the third figure, the signal delay circuit 1 9 1 3 includes a group of RC filter circuits composed of a resistor R2 and a capacitor C2, a comparison level of a voltage comparator OP2 and a DC 5V voltage. By adjusting the time constant r = R 2 C 2 of the RC filter circuit, the width of the output waveform pulse can be changed. As shown in the fourth figure, it is a waveform diagram of the pulsed square wave VpulS (? V through the RC filter circuit after 0V to 15V). After comparing the voltage comparator 0P2 with the 5V voltage comparison level, the first The V dela noise pulse waveform (ie, gate delay signal S 21) in the four figures. Therefore, by adjusting the time constant r to change the slope of the output voltage of the RC filter circuit from 0V to 5V, we can obtain Pulse square waves with different delay times.

Page 1312863 V. Explanation of the invention (10) Gate signal S 1 9, gate delay signal S 2 1 and inductor current slope change amplification signal S 1 7 are finally input into the gate unit 1 9 3 for logic operation. , 'And n (AND). As shown in the fifth figure, the AND gate unit 193 is also called an analog and gate unit because it uses the analog elements to realize the functions of " and π in digital logic operations. In this way, it can be obtained that the inductor current is in the time zone of continuously increasing state, and does not include the inductor current slope increase and change signal S23 of the power switching element under the on or off instantaneous zone. Referring again to the fifth figure, the gate unit 193 includes an addition amplifier 1 931, a voltage comparator OP4 and a set of 5V DC voltage comparison levels. And the gate unit 193 has three input voltage terminals (respectively the inductor current slope variation amplification signal S17, the gate signal S19, and the gate delay signal S21) and one output voltage terminal (the inductor current slope increase variation signal S twenty three ). Among them, the addition amplifier 1931 is composed of a pre-stage operational amplifier OP3 and resistors R 3 to R 7. The working principle of the AND gate unit 193 is three input voltages (S17, S19, S21) with a voltage level of 0V or 2V. After summing through the addition amplifier 1931, if the three input voltages are not 2V at the same time, the previous stage The sum voltage of OP3 output must not be greater than 5 V. Therefore, after the sum of the output voltage of the previous-stage operational amplifier OP3 and the 5V voltage level passes through the voltage comparator 0p4, the voltage comparator OP4 will output a low level signal of 0V (that is, S23 is a low level signal); otherwise, If the three input voltages are both at the 2V level, the sum of the output voltage of the previous op amp OP3 must be greater than 5 V. Therefore, after comparing with the 5V voltage level, the voltage comparator OP4 will output a high level of 15V Bit signal (that is, S23 is a high level signal).

Page 14 1231863 V. Description of the invention (11) The sixth figure shows the waveform diagram of the operation of the gate unit. Among them, the possible time section of the inductor current slope variation amplification signal S 1 7 is composed of a dot matrix portion and a diagonal line portion: the dot matrix portion indicates that the inductor current slope variation amplification signal s 1 7 caused by non-inductance saturation is possible. For the interval that appears, the oblique line is the interval that the inductor current slope variation signal S 1 7 may appear due to the inductor saturation. Reuse and gate unit 1 3 3 Amplify the inductor current slope variation signal S1 7, gate signal S 1 9, gate delay signal S2 1 and perform logical operations of "and" to remove the non-inductance saturation The slope change of the inductor current slope amplifies the possible lattice interval of the signal S 1 7, and the slope portion of the interval where the inductor current slope change amplifies the signal S 1 7 which is really caused by the saturation of the inductor is obtained, which is the correct inductance The current gradient of the inductor increases and changes the signal S 2 3. Finally, the AND gate unit 1 9 3 is used to amplify the inductor current slope variation of the signal S 1 7, the gate signal S 1 9, and the gate delay signal S 2 1 to make “and” logic In this way, you can get the positive slope change signal due to the increase of the inductor current, but it does not include a short moment after the power switching element is turned on and off, that is, the inductor current slope change signal caused by the non-inductor saturation state. Therefore The present invention can correctly detect whether the inductor has actually reached the saturation state. Referring to the first figure again, if it is detected that the inductor has reached saturation State, the inductor current slope output change signal S2 3 output by the gate unit 193 can be used as a trigger level signal to a drive unit 21, and the drive unit 2 1 can preferably be a warning light. The light's on and off state can further reflect whether the inductor has reached saturation state, to avoid the power converter

Page 15 1231863 V. Description of the invention (12) Damage caused by saturation of inductor. Alternatively, when it is known that the inductor has reached the saturation state, the gate control signal in the switching power converter can be further appropriately changed to adjust the operating conditions of the switching power converter to achieve the function of the protection circuit. Therefore, the inductor saturation state detection circuit and method of the present invention have the following effects: 1. Directly measuring the actual inductor current can correctly determine whether the inductor has reached the saturation state, and there is no need to set the inductor current The maximum value. 2. It can improve the saturation state offset of the inductor due to temperature changes, and it can still correctly detect the actual saturation state of the inductor. 3. It can detect the situation where the inductor enters the saturation state early due to winding damage. 4. Combined with the gate signal of the power switching element, it can eliminate the influence of noise and surge error signals on the detection circuit, improve accuracy and reliability, and improve the usage rate of the inductor. Under the rated operation of switching power converters, as long as the inductor does not actually reach saturation, a smaller inductor can be used. 6. Switching power converters suitable for a variety of different circuit architectures. However, the above description is only a detailed description and a drawing of one of the best specific embodiments of the present invention. Any embodiment that is within the spirit of the patent application scope of the present invention and similar changes should be included in the scope of the present invention. In the field of the present invention, any changes or modifications that can be easily considered by those skilled in the art can be included in the patent scope of the following case.

Page 1231863 Brief description of the drawings [Simplified description of the drawings]: The first diagram is a circuit block diagram of the inductor saturation state detection circuit of the present invention, and the second diagram is a circuit of a differentiator used in the present invention Schematic diagram; the third diagram is a circuit diagram of the signal delay unit used in the present invention; the fourth diagram is a waveform diagram of the operation of the third diagram; the fifth diagram is a circuit diagram of the sum gate unit used in the present invention; The diagram is a waveform diagram of the fifth diagram operation.

Description of figure number 11 Inductor current input unit 113 Differential amplifier 13 Differentiating unit 133 Second differentiator 17 Amplifier 191 Judging signal input unit 1 9 1 3 Signal delay unit 1 9 3 1 Adding amplifier 111 Current measuring element 115 Bandpass filtering 131 First differentiator 15 Low-pass filter 19 Signal judgment unit 1 9 1 1 Gate signal input unit 1 9 3 and gate unit 21 drive unit

Page 17

Claims (1)

1231863 VI. Application Patent Scope 1. An inductor saturation state detection circuit, including: an inductor current input unit for inputting an inductor current signal, and a differential unit for the inductor current signal to The second-order differential operation obtains an inductor current slope change signal; by determining the voltage of the inductor current slope change signal to know whether the inductor has reached saturation. 2. The inductor saturation state detection circuit as described in item 1 of the scope of patent application, wherein the inductor current input unit includes: a current measuring element for measuring the current value of the inductor; ^ differential amplification ' Amplify the current value of the inductor Is and a filter to filter the harmonics of the current value of the inductor. 3. The inductor saturation state detection circuit as described in item 2 of the scope of patent application, wherein the current measuring element is one of a resistor and a current sensor using a Hall effect. 4. The inductor saturation state detection circuit as described in item 2 of the scope of patent application, wherein the filter is a band-pass filter. 5. The inductor saturation state detection circuit as described in item 1 of the scope of the patent application, wherein the differential unit comprises: a first differentiator that obtains an inductor current slope signal by performing a differential operation on the inductor current signal; And a second differentiator, the inductor current slope signal is obtained by differentiating the inductor current slope signal. 6. The inductor saturation state detection circuit described in item 1 of the scope of patent application Page 18 1231863 6. Scope of patent application. The circuit also includes a low-pass filter to filter the high-frequency noise of the inductor's current slope change signal. 7. The inductor saturation state detection circuit described in item 1 of the scope of patent application, further comprising an amplifier to amplify the signal of the inductor current slope change. 8. An inductor saturation state detection circuit for detecting the saturation state of an inductor in a switching power converter, the detection circuit includes: an inductor current input unit that detects the inductor to obtain An inductor current signal; a differentiation unit for obtaining an inductor current slope change signal by a second-order differential operation on the inductor current signal; and a judgment signal input unit for obtaining a power in the switching power converter A gate signal and a delayed gate signal of the switching element; and a gate unit, which performs an AND operation on the inductor current slope change signal, the gate signal, and the delayed gate signal to obtain an inductor current The slope increases and changes the signal; it is known whether the inductor has reached saturation by judging the voltage of the inductor when the slope increases and changes the signal. 9. The inductor saturation state detection circuit as described in item 8 of the scope of patent application, wherein the inductor current input unit includes: a current measuring element for measuring the current value of the inductor; a differential amplifier, Amplify the current value of the inductor; and Page 19 1231863 VI. Scope of patent application A filter to filter the harmonics of the current value of the inductor. 10. The inductor saturation state detection circuit according to item 9 of the scope of patent application, wherein the current measuring element is one of a resistor and a current sensor using a Hall effect. 1 1. The inductor saturation state detection circuit according to item 9 of the scope of patent application, wherein the filter is a band-pass filter. 12. The inductor saturation state detection circuit as described in item 8 of the scope of patent application, wherein the differential unit comprises: a first differentiator, which obtains an inductor current slope signal by performing a differential operation on the inductor current signal. And a second differentiator, the inductor current slope signal is obtained by differentiating the inductor current slope signal. 1 3. The inductor saturation state detection circuit as described in item 8 of the scope of patent application, wherein the judgment signal input unit includes: a gate signal input unit that receives the gate signal of a gate terminal of the power switching element ; And a signal delay unit that delays the gate signal for a period of time to obtain the delayed gate signal. 14. The inductor saturation state detection circuit as described in item 13 of the scope of patent application, wherein the signal delay unit includes: an RC filter circuit that changes the pulse width of the gate signal output waveform; and a first The voltage comparator has a first input terminal and a second input terminal, wherein the first input terminal is electrically coupled to the RC filter circuit. Page 20 1231863 6. Patent application range output terminal, the second input terminal is electrically coupled to a first voltage level 〇 05, the inductor saturation state detection circuit described in item 8 of the patent application scope, The sum gate unit includes: an addition amplifier that sums up the inductor current slope change signal, the gate signal and the delayed gate signal and amplifies them; and a second voltage comparator having a first An input terminal and a second input terminal, wherein the first input terminal is electrically coupled to the output terminal of the addition amplifier, and the second input terminal is electrically coupled to a second voltage level 〇6, such as applying for a patent The inductor saturation state detection circuit according to item 15 of the scope, wherein the addition amplifier includes: a pre-stage operational amplifier having a first input terminal, a second input terminal and an output terminal; a first resistor , One end receives the inductor current slope change signal, the other end is electrically coupled to the second input terminal of the pre-stage operational amplifier, a second resistor, one end receives the gate signal, and the other end is electrically coupled A second input terminal of the pre-stage operational amplifier; a third resistor, one end of which receives the delayed gate signal, and the other end of which is electrically coupled to the second input terminal of the pre-stage operational amplifier; a fourth resistor, one end of which Electrically coupled to a first input terminal of the pre-stage operational amplifier, the other end of which is connected to the ground terminal; and a fifth resistor, one end of which is electrically coupled to the first input terminal of the pre-stage operational amplifier, Page 21 1231863 6. Scope of patent application One input terminal and the other terminal are electrically coupled to the output terminal of the pre-stage operational amplifier. 17. The inductor saturation state detection circuit described in item 8 of the scope of patent application, further includes a low-pass filter to filter high-frequency noise of the inductor current slope change signal. 18. The inductor saturation state detection circuit described in item 8 of the scope of patent application, further comprising an amplifier to amplify the current slope change signal of the inductor. 19. The inductor saturation state detection circuit as described in item 8 of the scope of patent application, further comprising a driving unit electrically coupled to the output terminal of the AND gate unit. 20. The inductor saturation state detection circuit as described in item 19 of the scope of patent application, wherein the driving unit is a warning light. 2 1. A method for detecting the saturation state of an inductor, including the following steps: measuring a current signal of an inductor; and obtaining a current slope change signal of the inductor by a second-order differential operation on the current signal of the inductor; The voltage of the inductor current slope change signal is used to know whether the inductor has reached saturation. 2 2. The method for detecting the saturation state of an inductor as described in item 21 of the scope of patent application, further comprising a step of removing a harmonic of a current signal of the inductor by a band-pass filter. 2 3. The method for detecting the saturation state of an inductor as described in item 21 of the scope of patent application, further comprising the step of removing the inductor power with a low-pass filter. Page 22 1231863 6. Scope of patent application High-frequency noise of signal with fluctuating slope. 24. The method for detecting the saturation state of an inductor as described in item 21 of the scope of patent application, further comprising a step of amplifying the current slope change signal of the inductor with an amplifier. 25. An inductor saturation state detection method for detecting the saturation state of an inductor in a switching power converter. The detection method includes the following steps: measuring the current signal of an inductor; The current signal of the inductor is obtained by a second-order differential operation to obtain an inductor current slope change signal; obtaining a gate signal and a delayed gate signal of a power switching element in the switching power converter; and the current slope of the inductor The change signal, the gate signal and the delayed gate signal are gated and gated to obtain an inductor current slope increase variation signal; determine whether the inductor current slope increases the voltage of the variation signal to determine whether the inductor has reached saturation. 26. The method for detecting the saturation state of an inductor as described in item 25 of the scope of patent application, wherein the delayed gate signal is obtained by delaying the gate signal. 27. The method for detecting the saturation state of an inductor as described in item 25 of the scope of patent application, further comprising a step of filtering the harmonics of the current signal of the inductor by a band-pass filter. 28. Detection of inductor saturation state as described in item 25 of the scope of patent application Page 23 1231863 6. The method of patent application testing method further includes the step of filtering the high-frequency noise of the inductor's current slope change signal with a low-pass filter. 29. The method for detecting the saturation state of an inductor as described in item 25 of the scope of patent application, further comprising a step of amplifying the current slope change signal of the inductor with an amplifier. Page 24