Switching power supply control method and control circuit

Abstract

The present invention proposes a switching power supply control method and control circuit, which compensates for the error between a feedback signal and a reference signal to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply works in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply works in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference. The present invention can still provide sufficient output power when the inductance is reduced.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to a switching power supply control method and a control circuit. Background Art

[0002] The switching power supply can adopt a variety of topologies, including Buck circuit, Boost circuit, Flyback circuit, etc. The output power of the switching power supply can be adjusted by controlling the switching frequency, peak current and other information in the switching circuit.

[0003] In the prior art, the application of switching power supplies may be subject to the problem of strong external magnetic field interference. The external magnetic field interference will make the inductor more easily reach saturation, reduce the inductance of the inductor in the switching power supply, reduce the maximum peak current, and thus reduce the maximum output power of the switching power supply, affecting the normal operation of the switching power supply. In the prior art, when designing magnetic components such as inductors in switching power supplies, considering the problem of magnetic field interference, a large margin is often left, which not only increases the size of the switching power supply, but also increases the cost. In addition, even if there is no magnetic interference, if the scope of application of the inductor can be expanded, it is also conducive to reducing costs. Summary of the invention

[0004] The purpose of the present invention is to provide a switching power supply control method and control circuit that can improve the applicable range of inductance and maintain the maximum output power stability, so as to solve the technical problem of insufficient output power when the inductance is reduced in the prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides a switching power supply control method, which compensates for the error between a feedback signal and a reference signal to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply works in a discontinuous conduction mode, the inductance value of the switching power supply is detected; if the switching power supply works in a continuous conduction mode, the turn-off time of the main power tube is extended to make the switching power supply work in the discontinuous conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference.

[0006] Optionally, when the compensation signal is greater than a first reference, the off time of the main power tube is extended; before and after the off time of the main power tube is extended, the on time of the main power tube is detected respectively, and recorded as the first on time and the second on time; if the first on time is greater than the second on time, it is determined that the switching power supply is operating in a continuous conduction mode; if the first on time is close to the second on time, it is determined that the switching power supply is operating in a discontinuous conduction mode.

[0007] Optionally, when the compensation signal is greater than a first reference, the switching power supply enters a detection cycle after working at a normal switching frequency for every N cycles, and extends the off time of the main power tube during the detection cycle; before and after the off time of the main power tube is extended, the on time of the main power tube is detected respectively, and recorded as the first on time and the second on time; if the first on time is greater than the second on time, it is determined that the switching power supply is operating in a continuous conduction mode; if the first on time is close to the second on time, it is determined that the switching power supply is operating in an intermittent conduction mode.

[0008] Optionally, when the compensation signal is greater than the first reference, the time taken for the inductor current to rise to the second reference is detected and recorded as the first time; if in a switching cycle, the ratio of the conduction time of the main power tube to the first time is greater than the ratio of the inductor current peak value to the second reference, it is determined that the switching power supply is operating in a continuous conduction mode; if in a switching cycle, the ratio of the conduction time of the main power tube to the first time is equal to the ratio of the inductor current peak value to the second reference, it is determined that the switching power supply is operating in a discontinuous conduction mode.

[0009] Optionally, when the compensation signal is greater than the first benchmark, the inductor current corresponding to the second time when the conduction time of the main power tube is detected is recorded as the first detection value; if in a switching cycle, the ratio of the conduction time of the main power tube to the second time is greater than the ratio of the inductor current peak value to the first detection value, it is judged that the switching power supply is operating in a continuous conduction mode; if in a switching cycle, the ratio of the conduction time of the main power tube to the second time is equal to the ratio of the inductor current peak value to the first detection value, it is judged that the switching power supply is operating in a discontinuous conduction mode.

[0010] Optionally, the turn-on time of the main power tube is less than the first threshold time.

[0011] Optionally, the conduction time of the main power tube is greater than the first threshold time.

[0012] The present invention also provides a switching power supply control method. When the compensation signal is greater than a first reference, the switching power supply enters a detection cycle after working at a normal switching frequency for N cycles. During the detection cycle, the off time of the main power tube is extended so that the switching power supply enters a discontinuous conduction mode, and the inductance value of the switching power supply is detected. When the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference.

[0013] The off time of the main power tube in the detection period is adjusted according to the on time of the main power tube. The off time of the main power tube in the detection period does not change with the on time, or changes linearly or segmentedly with the on time.

[0014] Optionally, the turn-on time of the main power tube is less than the first threshold time.

[0015] The present invention also provides a switching power supply control circuit, comprising:

[0016] An operational amplifier circuit receives a feedback signal and a reference signal, and compensates for an error between the feedback signal and the reference signal to obtain a compensation signal;

[0017] A mode recognition circuit receives the compensation signal, determines the working mode of the switching power supply when the compensation signal is greater than a first reference, and outputs a mode recognition signal;

[0018] The first control circuit and the detection circuit receive the mode recognition signal respectively; if the mode recognition signal indicates that the switching power supply operates in the intermittent conduction mode, the detection circuit detects the inductance value of the switching power supply; if the mode recognition signal indicates that the switching power supply operates in the continuous conduction mode, the first control circuit controls the main power tube to extend the off time, so that the switching power supply operates in the intermittent conduction mode, and then the detection circuit detects the inductance value of the switching power supply;

[0019] When the inductance value is less than the first threshold, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference.

[0020] Optionally, the mode judgment circuit includes a shutdown delay circuit and a comparison circuit; the shutdown delay circuit receives the compensation signal and outputs a shutdown delay signal; when the compensation signal is greater than a first benchmark, the switching power supply enters a detection cycle after every N cycles of operation at a normal switching frequency, and during the detection cycle, the shutdown delay signal controls the extension of the shutdown time of the main power tube; before and after the shutdown time of the main power tube is extended, the detection circuit detects the on-time of the main power tube respectively, which is recorded as the first on-time and the second on-time; the comparison circuit receives the first on-time and the second on-time, and outputs the mode recognition signal; when the first on-time is greater than the second on-time, the mode recognition signal indicates that the switching power supply operates in a continuous conduction mode; when the first on-time is close to the second on-time, the mode recognition signal indicates that the switching power supply operates in an intermittent conduction mode.

[0021] Optionally, the mode judgment circuit includes a timing circuit and a first operation circuit; the timing circuit receives the compensation signal, and when the compensation signal reaches the first benchmark, the timing circuit starts timing from the moment when the main switch tube is turned on, and when the inductor current rises to the second benchmark, the timing ends and the first time is output; the operation circuit receives the main power tube turn-on time, the first time, the inductor current peak value and the second benchmark, and outputs a mode recognition signal; the operation circuit calculates the ratio of the main power tube turn-on time and the first time, which is recorded as the first ratio; the operation circuit calculates the ratio of the inductor current peak value and the second benchmark, which is recorded as the second ratio; if the first ratio is greater than the second ratio, the mode recognition signal indicates that the switching power supply operates in a continuous conduction mode; if the first ratio is equal to the second ratio, the mode recognition signal indicates that the switching power supply operates in a discontinuous conduction mode.

[0022] Optionally, the mode judgment circuit includes a current detection circuit and a second operation circuit, and the current detection circuit receives the compensation signal; when the compensation signal reaches the first benchmark, the current detection circuit detects the inductor current corresponding to the second time when the main power tube conduction time reaches the second time, and outputs a first detection value; the second operation circuit receives the main power tube conduction time, the second time, the inductor current peak and the first detection value, and outputs a mode recognition signal; the second operation circuit calculates the ratio of the main power tube conduction time and the second time, which is recorded as the first ratio; the second operation circuit calculates the ratio of the inductor current peak and the first detection value, which is recorded as the second ratio; if the first ratio is greater than the second ratio, the mode recognition signal indicates that the switching power supply operates in a continuous conduction mode; if the first ratio is equal to the second ratio, the mode recognition signal indicates that the switching power supply operates in a discontinuous conduction mode.

[0023] The present invention also provides a switching power supply control circuit, comprising:

[0024] An operational amplifier circuit receives a feedback signal and a reference signal, and compensates for an error between the feedback signal and the reference signal to obtain a compensation signal;

[0025] a first control circuit, when the compensation signal is greater than a first reference, the switching power supply enters a detection cycle after each N cycles of operation at a normal switching frequency, and in the detection cycle, the first control circuit controls the off time of the main power tube to be extended, so that the switching power supply enters a discontinuous conduction mode; the first control circuit adjusts the off time of the main power tube in the detection cycle according to the on time of the main power tube, and the off time of the main power tube in the detection cycle remains unchanged, or changes linearly, or changes in stages;

[0026] The detection circuit detects the inductance value of the switching power supply after the off time of the main power tube is extended; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than a first reference.

[0027] Compared with the prior art, the present invention has the following advantages: the error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply works in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply works in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference. The present invention can still provide sufficient output power when the inductance is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A waveform diagram of Embodiment 1 of the present invention for determining the working mode of a switching power supply;

[0029] Figure 2 A waveform diagram of Embodiment 2 of the present invention for determining the working mode of a switching power supply;

[0030] Figure 3 It is a waveform diagram of the switching power supply of the present invention from continuous to intermittent conduction mode;

[0031] Figure 4 The present invention is a schematic diagram of a first embodiment of a switching power supply control circuit;

[0032] Figure 5 The present invention is a schematic diagram of a second embodiment of a switch power supply control circuit;

[0033] Figure 6 The third schematic diagram of the switching power supply control circuit of the present invention;

[0034] Figure 7 The fourth embodiment of the present invention is a schematic diagram of a switching power supply control circuit;

[0035] Figure 8 This is a schematic diagram of the working waveform of the switching power supply control circuit of the present invention; DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0037] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention. However, those skilled in the art can fully understand the present invention even without the description of these details.

[0038] In the following paragraphs, the present invention will be described more specifically by way of example with reference to the accompanying drawings. It should be noted that the drawings are all in a relatively simplified form and use non-precise scales to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0039] As Figure 1 shown, it schematically shows the waveform diagram of Embodiment 1 for judging the working mode of the switching power supply of the present invention. In the figure, the waveform of iL0 is the inductor current waveform under the normal working condition of the switching power supply; the waveform of iL1 is the inductor current waveform when the switching power supply is overloaded, corresponding to the switching power supply working in the continuous conduction mode (CCM), the current rising slope increases, the falling slope decreases, the conduction time of the main power transistor decreases, and the turn-off time increases; the waveform of iL2 is the inductor current waveform after the inductance L becomes smaller under the influence of magnetic interference, corresponding to the switching power supply working in the discontinuous conduction mode (DCM), the current rising slope and falling slope increase, the conduction time of the main power transistor decreases, and the turn-off time increases. Under abnormal conditions, in the figure, after extending the turn-off time T_delay of the main power transistor, the conduction time of the main power transistor corresponding to iL1 becomes larger, corresponding to Ton1 in the figure; the conduction time of the main power transistor corresponding to iL2 remains unchanged, corresponding to Ton0 in the figure. Thus, the working mode of the switching power supply can be judged according to the change of the conduction time of the main power transistor before and after the turn-off time of the main power transistor is extended.

[0040] As Figure 2 shown, it schematically shows the waveform diagram of Embodiment 2 for judging the working mode of the switching power supply of the present invention. In the figure, the waveform of iL0 is the inductor current waveform under the normal working condition of the switching power supply; the waveform of iL1 is the inductor current waveform when the switching power supply is overloaded; the waveform of iL2 is the inductor current waveform after the inductance L becomes smaller under the influence of magnetic interference. When the inductor current rises to half of the peak current, the conduction time of the main power transistor corresponding to iL1 is less than half of the conduction time of the main power transistor in a switching cycle, and the conduction time of the main power transistor corresponding to iL2 is equal to half of the conduction time of the main power transistor in a switching cycle. Assuming that the inductor current rises to Ix and the corresponding conduction time of the main power switch is, then for iL1, Ipk / Ix < Ton / Tx, and for iL2, Ipk / Ix = Ton / Tx, where Ipk is the peak current and Ton is the conduction time of the main power transistor in a switching cycle. Thus, the working mode of the switching power supply can be judged.

[0041] As Figure 3As shown, a waveform diagram of the switching power supply of the present invention from continuous to discontinuous conduction mode is illustrated. When the switching power supply is in continuous conduction mode, the main power tube shutdown time is extended to make the switching power supply work in discontinuous conduction mode. In the discontinuous conduction mode, the inductance can be calculated according to the peak current Ipk, the main power tube conduction time Ton and the voltage VL on the inductor. Specifically, L = VL*Ton / Ipk. For different switching power supplies, the inductor voltage VL is different. For example, in a buck circuit, the inductor voltage is the difference between the input voltage and the output voltage; in a boost circuit or a buck-boost circuit, the inductor voltage is the input voltage.

[0042] like Figure 4As shown, a schematic diagram of an embodiment of a switch power supply control circuit of the present invention is illustrated, including a mode recognition circuit U01, an operational amplifier circuit U02, a first control circuit U03 and a detection circuit U04. The operational amplifier circuit U02 receives a feedback signal FB and a reference signal VREF, compensates for the error between the feedback signal FB and the reference signal VREF, and outputs a compensation signal COMP. The compensation signal COMP is an inductor current reference signal, and the feedback signal FB is feedback of the output voltage or output current of the switch power supply. The mode recognition circuit U01 receives the compensation signal COMP, and when the compensation signal COMP is greater than the first reference, the switch power supply operation mode is determined, and a mode recognition signal PAT is output. The first control circuit U03 and the detection circuit U04 receive the mode recognition signal PAT respectively; if the mode recognition signal PAT indicates that the switching power supply operates in the discontinuous conduction mode DCM, the detection circuit U05 detects the main power tube conduction time Ton; if the mode recognition signal indicates that the switching power supply operates in the continuous conduction mode CCM, the first control circuit U03 controls the main power tube to extend the off time so that the switching power supply operates in the discontinuous conduction mode, and then the detection circuit detects the main power tube conduction time Ton. The detection circuit U04 calculates the inductance value according to the inductance voltage VL, the main power tube conduction time Ton and the inductance current peak value Ipk. The inductance voltage VL is obtained by the input voltage VIN, or by the input voltage VIN and the output voltage VOUT. When the inductance value L is less than the first threshold value L0, the switching frequency fs of the main power tube is allowed to increase until the compensation signal COMP is less than the first reference COMP1. In this embodiment, the pattern recognition circuit U01 specifically includes: a turn-off delay circuit U101 and a comparison circuit U102. The turn-off delay circuit U101 receives the compensation signal COMP and outputs a turn-off delay signal T_delay. When the compensation signal COMP is greater than the first reference COMP1, a detection cycle is entered after every N switching cycles at a normal switching frequency. During the detection cycle, the turn-off delay signal T_delay controls the turn-off time of the main power tube to be extended. Before and after the turn-off time of the main power tube is extended, the detection circuit U05 respectively The on-time of the main power tube is detected, which is recorded as the first on-time Ton1 and the second on-time Ton2; the comparison circuit receives the first on-time Ton1 and the second on-time Ton2, and outputs the mode recognition signal PAT; when the first on-time Ton1 is greater than the second on-time Ton2, the mode recognition signal PAT indicates that the switching power supply operates in the continuous conduction mode CCM; when the first on-time Ton1 is equal to the second on-time Ton2, the mode recognition signal PAT indicates that the switching power supply operates in the discontinuous conduction mode DCM.

[0043] like Figure 5 FIG. 1 is a schematic diagram of a second embodiment of a switch power supply control circuit according to the present invention. Figure 4 The specific difference between the first embodiment and the second embodiment lies in the difference of the mode recognition circuit U01. In this embodiment, the mode recognition circuit U01 specifically includes: a timing circuit U102 and a first operation circuit U101; the timing circuit U102 receives the compensation signal COMP, and when the compensation signal reaches the first reference COMP1, the timing circuit U102 starts timing from the moment when the main switch tube is turned on, and when the inductor current rises to the second reference CS1, the timing ends and the first time T1 is output; the operation circuit receives the main power tube turn-on time Ton, the first time T1, and the inductor The current peak value Ipk and the second reference CS1, output a mode recognition signal PAT; the operation circuit calculates the ratio of the main power tube conduction time Ton and the first time T1, which is recorded as the first ratio; the operation circuit calculates the ratio of the inductor current peak value Ipk and the second reference CS1, which is recorded as the second ratio; if the first ratio is greater than the second ratio, the mode recognition signal PAT indicates that the switching power supply operates in the continuous conduction mode CCM; if the first ratio is equal to the second ratio, the mode recognition signal PAT indicates that the switching power supply operates in the discontinuous conduction mode DCM.

[0044] like Figure 6 As shown, a schematic diagram of the third embodiment of the switch power supply control circuit of the present invention is shown. Figure 4 The specific difference between the first embodiment and the second embodiment lies in the difference of the mode recognition circuit U01. In this embodiment, the mode recognition circuit U01 specifically includes: a current detection circuit U102 and a second operation circuit U101. The current detection circuit U102 receives the compensation signal COMP. When the compensation signal COMP reaches the first reference COMP1, the current detection circuit U101 detects the inductor current corresponding to the conduction time of the main power tube when the conduction time reaches the second time T1, and outputs a first detection value CS1. The second operation circuit U102 receives the conduction time Ton0 of the main power tube, the second time T1, and the inductor current. The first operation circuit U102 calculates the ratio of the main power tube conduction time Ton0 and the second time T1, which is recorded as the first ratio; the second operation circuit calculates the ratio of the inductor current peak value Ipk and the first detection value CS1, which is recorded as the second ratio; if the first ratio is greater than the second ratio, the mode recognition signal PAT indicates that the switching power supply operates in the continuous conduction mode CCM; if the first ratio is equal to the second ratio, the mode recognition signal PAT indicates that the switching power supply operates in the discontinuous conduction mode DCM.

[0045] like Figure 7As shown, a schematic diagram of a fourth embodiment of the switch power supply control circuit of the present invention is illustrated, comprising a first control circuit U01, an operational amplifier circuit U02 and a detection circuit U03. The operational amplifier circuit U02 receives a feedback signal FB and a reference signal VREF, compensates for the error between the feedback signal FB and the reference signal VREF, and outputs a compensation signal COMP, wherein the compensation signal COMP is an inductor current reference signal, and the feedback signal FB is feedback of the output voltage or output current of the switch power supply. When the compensation signal COMP is greater than the first reference COMP1, the switching power supply enters a detection cycle after working at a normal switching frequency for every N cycles. During the detection cycle, the first control circuit controls the off-time of the main power tube to be extended, so that the switching power supply enters a discontinuous conduction mode; the first control circuit adjusts the off-time of the main power tube during the detection cycle according to the on-time of the main power tube, and according to the change of the on-time of the main power tube, the off-time of the main power tube during the detection cycle remains unchanged, or changes linearly, or changes in segments; after the off-time of the main power tube is extended, the detection circuit detects the inductance value of the switching power supply; when the inductance value is less than the first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference.

[0046] Figure 8 The working waveform of the switching power supply control circuit of the present invention is illustrated. When the compensation signal is greater than the first reference COMP1, the inductance L is detected. When the inductance L is less than the first threshold L0, the switching frequency fs is allowed to increase until the compensation signal COMP is less than the first reference COMP1.

[0047] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0048] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A switching power supply control method, characterized in that: The error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply is working in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply is working in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference; The inductance value is obtained according to the ratio of the product of the inductor voltage and the main power tube conduction time to the inductor peak current; When the compensation signal is greater than the first reference, the off time of the main power tube is extended; before and after the off time of the main power tube is extended, the on time of the main power tube is detected respectively, which are recorded as the first on time and the second on time; if the first on time is greater than the second on time, it is determined that the switching power supply is operating in a continuous conduction mode; if the first on time is close to the second on time, it is determined that the switching power supply is operating in a discontinuous conduction mode.

2. The switching power supply control method according to claim 1, characterized in that: The conduction time of the main power tube is less than the first threshold time.

3. A switching power supply control method, characterized in that: The error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply is working in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply is working in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference; The inductance value is obtained according to the ratio of the product of the inductor voltage and the main power tube conduction time to the inductor peak current; When the compensation signal is greater than the first reference, the switching power supply enters a detection cycle after working at a normal switching frequency for every N cycles, and extends the off time of the main power tube during the detection cycle; before and after the off time of the main power tube is extended, the on time of the main power tube is detected respectively, which are recorded as the first on time and the second on time; if the first on time is greater than the second on time, it is determined that the switching power supply is working in a continuous conduction mode; if the first on time is close to the second on time, it is determined that the switching power supply is working in a discontinuous conduction mode.

4. The switching power supply control method according to claim 3, characterized in that: The conduction time of the main power tube is less than the first threshold time.

5. A switching power supply control method, characterized in that: The error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply is working in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply is working in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference; The inductance value is obtained according to the ratio of the product of the inductor voltage and the main power tube conduction time to the inductor peak current; When the compensation signal is greater than the first reference, the time taken for the inductor current to rise to the second reference is detected, which is recorded as the first time; If in a switching cycle, the ratio of the conduction time of the main power tube to the first time is greater than the ratio of the inductor current peak value to the second reference, it is determined that the switching power supply operates in a continuous conduction mode; if in a switching cycle, the ratio of the conduction time of the main power tube to the first time is equal to the ratio of the inductor current peak value to the second reference, it is determined that the switching power supply operates in a discontinuous conduction mode.

6. The switching power supply control method according to claim 5, characterized in that: The conduction time of the main power tube is greater than the first threshold time.

7. A switching power supply control method, characterized in that: The error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the working mode of the switching power supply is judged; if the switching power supply is working in the intermittent conduction mode, the inductance value of the switching power supply is detected; if the switching power supply is working in the continuous conduction mode, the off time of the main power tube is extended to make the switching power supply work in the intermittent conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference; The inductance value is obtained according to the ratio of the product of the inductor voltage and the main power tube conduction time to the inductor peak current; When the compensation signal is greater than the first reference, the inductor current corresponding to the second time when the conduction time of the main power tube reaches the detected value is recorded as the first detection value; if in a switching cycle, the ratio of the conduction time of the main power tube to the second time is greater than the ratio of the inductor current peak value to the first detection value, it is determined that the switching power supply operates in a continuous conduction mode; if in a switching cycle, the ratio of the conduction time of the main power tube to the second time is equal to the ratio of the inductor current peak value to the first detection value, it is determined that the switching power supply operates in a discontinuous conduction mode.

8. The switching power supply control method according to claim 7, characterized in that: The conduction time of the main power tube is greater than the first threshold time.

9. A switching power supply control method, characterized in that: The error between the feedback signal and the reference signal is compensated to obtain a compensation signal; when the compensation signal is greater than a first reference, the switching power supply enters a detection cycle after each N cycles of operation at a normal switching frequency, and the off time of the main power tube is extended during the detection cycle, so that the switching power supply enters a discontinuous conduction mode, and the inductance value of the switching power supply is detected; when the inductance value is less than a first threshold value, the switching frequency of the main power tube is allowed to increase until the compensation signal is less than the first reference; The off time of the main power tube in the detection period is adjusted according to the on time of the main power tube, and the off time of the main power tube in the detection period does not change with the change of the on time, or changes linearly or segmentedly with the change of the on time; The inductance value is obtained according to the ratio of the product of the inductance voltage and the main power tube conduction time to the inductance peak current.

10. The switching power supply control method according to claim 9, characterized in that: The conduction time of the main power tube is less than the first threshold time.

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