A control method for a switching power supply circuit, a control circuit and a switching power supply

Abstract

The embodiment of the present application discloses a control method, a control circuit and a switching power supply circuit, which generates a first DC compensation signal and a slope compensation signal associated with a duty cycle, and both compensation signals compensate for the sampling current signal of the inductor, so that the output signal of the switching power supply circuit is an expected value. The present application generates a first DC compensation signal based on duty cycle information, and uses it to compensate the inductor current sampling signal of the switching power supply circuit, so that the switching power supply circuit can maintain the expected output power when the input voltage is low.

Description

Technical Field

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

[0002] In different meter applications, it is usually necessary to convert the input voltage through a switching power supply, for example, converting the 220Vac input voltage to 12Vdc to power the various functional modules of the meter. However, due to the different voltage levels of power grids in different countries, in order to be compatible with power grids in different countries, meter manufacturers usually set a wider input voltage range (for example, 40-700Vdc). As a result, for some application scenarios with lower voltage levels, under full load conditions, as the input voltage decreases, the inductor current in the circuit may operate in continuous conduction mode (CCM), resulting in a reduction in the output power of the switching power supply, and in certain cases, the output power may even be too small to carry the load normally.

[0003] [1] Therefore, it is necessary to provide a control method and a control circuit for a switching power supply circuit, which can obtain a DC compensation signal based on duty cycle information, and combine slope compensation to compensate for the peak current of the inductor to increase the output power and solve the problem of too low output power. Summary of the invention

[0004] One of the embodiments of the present application provides a control method for a switching power supply circuit. The method includes: obtaining a first DC compensation signal according to the duty cycle information of a main switch tube in the switching power supply circuit; generating a slope compensation signal by using a slope generating circuit; the first DC compensation signal and the slope compensation signal both compensate for the sampled current signal of the inductor in the switching power supply circuit, so that the output signal of the switching power supply circuit is an expected value.

[0005] One of the embodiments of the present application provides a control circuit for a switching power supply circuit. The circuit includes: a first compensation circuit, the first compensation circuit obtains a first DC compensation signal according to the duty cycle information of a main switch tube in the switching power supply circuit; a slope compensation circuit, the slope compensation circuit is used to generate a slope compensation signal; the first DC compensation signal and the slope compensation signal both compensate for the sampled current signal of the inductor in the switching power supply circuit, so that the output signal of the switching power supply circuit is an expected value. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present application will be further described in the form of exemplary embodiments, which will be described in detail by way of the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0007] Figure 1 is a curve diagram showing the variation of the inductor current sampling signal of the switching power supply circuit with the duty cycle according to some embodiments of the present application;

[0008] Figure 2 is a schematic diagram of a flyback conversion circuit according to some embodiments of the present application;

[0009] Figure 3 is a control circuit schematic diagram of a switching power supply circuit according to some embodiments of the present application;

[0010] Figure 4 is a curve diagram of the inductor current sampling signal and the first DC compensation signal of the switching power supply circuit as the duty cycle changes according to some embodiments of the present application; DETAILED DESCRIPTION

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0012] The embodiments of the present application can be applied to situations where a switching power supply circuit is used and power compensation is required under certain circumstances, and are particularly suitable for electric meters that include a switching power supply circuit and have different functions. In some embodiments, the electric meter may include an ammeter, a voltmeter, an electric energy meter, a smart meter, a multimeter, and other instruments that detect various electrical quantities. It should be understood that the application scenarios of the apparatus and method of the present application are only some examples or embodiments of the present application. For ordinary technicians in this field, without paying creative labor, the present application can also be applied to other similar scenarios based on these drawings.

[0013] In some embodiments, the voltage levels of power grids in different countries are different. For example, the voltage of China's power grid is usually 220V / 50Hz, the voltage of the US power grid is usually 110V / 60Hz, and other countries may be even smaller, such as Ghana's power grid level is 40V / 50Hz. In order to be compatible with power grids of different voltage levels in different countries, electric meter manufacturers usually set a wider input voltage range (for example, 40-700Vdc). Under full load conditions, as the input voltage decreases, the inductor current in the circuit may operate in a continuous mode, resulting in a reduction in the output power of the switching power supply. In certain cases, the output power is even too small to be normally loaded. Therefore, some embodiments of the present application provide a control method and a control circuit for output power compensation of a switching power supply circuit, which can obtain a first DC compensation based on duty cycle information and combine slope compensation to compensate for the peak current, thereby increasing the output power when the input voltage is low, and solving the problem of too small output power to be loaded.

[0014] Figure 1 The diagram is a curve diagram showing the variation of the inductor current peak sampling signal with the duty cycle of the switching power supply circuit according to some embodiments of the present application.

[0015] The duty cycle refers to the ratio of the conduction time of the switch tube in the switching power supply circuit to one switching cycle. Figure 1 As shown, when the input voltage Vin=120Vdc, the sampling voltage signal VCS corresponding to the inductor peak current in the switching power supply circuit is the voltage value VCS_H (the corresponding duty cycle D1 is 0.4), and the sampling voltage signal VCS_L corresponding to the minimum inductor current is 0. At this time, the inductor current in the switching power supply circuit works in the critical conduction mode (that is, the inductor current just drops to 0 at the end of a cycle). When the input voltage Vin is reduced to 40Vdc, the sampling voltage signal VCS_H corresponding to the inductor peak current in the switching power supply circuit is 0.7*Vcs (the corresponding duty cycle Dmax is 0.7), and the sampling voltage signal VCS_L corresponding to the minimum inductor current is 0.2*Vcs. At this time, the inductor current in the switching power supply circuit works in the continuous conduction mode (the inductor current has not dropped to 0 at the end of a cycle, that is, the minimum current in a cycle is greater than 0).

[0016] The output power of the switching power supply is calculated as follows:

[0017]

[0018] Where f is the switching frequency, Ipk is the maximum peak current, Imin is the minimum inductor current, and Lm is the inductor value. The maximum peak current and the minimum inductor current can be calculated by the resistance of the sampling resistor Rcs to obtain Ipk = VCS_H / Rcs, Imin = VCS_L / Rcs, Rcs is the sampling resistor. Further deduction based on the above output power calculation formula: It can also be obtained that when the working mode of the switching power supply circuit is switched from the critical conduction mode to the continuous conduction mode, for example, relative to the input voltage of 120Vdc (the sampling voltage signal corresponding to the peak value of the inductor current is VCS_H, and the minimum value of the sampling voltage signal corresponding to the inductor current VCS_L is 0), when the input voltage is 40Vdc (the sampling voltage signal corresponding to the peak value of the inductor current is VCS_H=0.7*Vcs, and the minimum value of the sampling voltage signal corresponding to the inductor current VCS_L is 0.2*Vcs), the output power of the switching power supply It can be seen that the input voltage of 40Vdc is 45% of the output power when the input voltage is 120Vdc. In other words, when the input voltage is less than a certain critical voltage value, the sampling voltage signal VCS_H corresponding to the inductor peak current will decrease accordingly, and its minimum sampling voltage value VCS_L may be greater than 0 due to being in the continuous conduction mode. In this way, the output power of the switching power supply will decrease as the input voltage decreases.

[0019] In addition, in the switching power supply circuit, since the inductor current is continuous, when the duty cycle is too large, subharmonic (low harmonic) oscillation may occur. Therefore, in some embodiments, in order to solve the subharmonic oscillation phenomenon that may be generated when the duty cycle is too large (for example, when the duty cycle is greater than 0.5), it is usually necessary to perform slope compensation on the inductor current sampling signal of the circuit, further reducing the maximum output power.

[0020] It should be noted that the above data are only examples. The corresponding relationship between the above input voltage, output voltage and duty cycle data can be, but is not limited to Figure 1 The specific relationship of the situation shown can be determined according to the actual circuit, and is not limited in this application.

[0021] Therefore, in order to solve the above-mentioned problem of small maximum output power, an embodiment of the present application provides a control method and a control circuit for a switching power supply circuit. According to the duty cycle information of the switch tube control signal in the switching power supply circuit, when the duty cycle information is greater than a certain threshold, the inductor current sampling signal of the switching power supply circuit is compensated based on the corresponding duty cycle information, thereby compensating the output current, thereby increasing its output power while avoiding other negative problems.

[0022] The output power compensation method of the switching power supply circuit provided in the embodiment of the present application is described in detail below.

[0023] Step 1: Obtain a first DC compensation signal Isink based on the duty cycle information of the main switch tube in the switching power supply circuit. Specifically, the step of generating the first DC compensation signal includes: obtaining the duty cycle information after low-pass filtering the logic control signal of the main switch tube, and generating the first DC compensation signal based on the comparison between the duty cycle information and the first threshold.

[0024] The switching power supply circuit is a power conversion circuit that converts the input power through the internal circuit architecture into the required output voltage or current. In some embodiments, the electronic devices used in the switching power supply circuit may include a switch tube, a transformer, an inductor, a capacitor, a resistor, etc. In some embodiments, the switch tube may include a diode, an IGBT, and a MOSFET, etc.

[0025] The duty cycle refers to the ratio of the conduction time of the switch tube in the switching power supply circuit to one switching cycle. In some embodiments, the duty cycle information is a specific voltage value corresponding to the duty cycle value of the main switch tube in the switching power supply circuit. In some embodiments, the duty cycle information can be a voltage value obtained after the logic control signal of the main switch tube control signal is low-pass filtered. In some embodiments, the main power switch tube in the switching power supply circuit can be controlled by generating a switch control signal after the logic control signal is converted by the driving circuit. In some embodiments, the output power of the main switch tube can be controlled by controlling the ratio of the length of time the main switch tube is turned on and / or off to the switching cycle by the logic control signal.

[0026] In some embodiments, the first DC compensation signal is obtained by a first compensation circuit, the first compensation circuit includes a duty cycle signal acquisition circuit and a current generation circuit, and the duty cycle information acquisition circuit extracts the duty cycle information of the switch tube control signal. In some embodiments, the duty cycle information acquisition circuit can generate a specific voltage value that can reflect the duty cycle value of the main switch tube according to the logic control signal, that is, the duty cycle information corresponding to the duty cycle. In some embodiments, logic control signals with different duty cycle values ​​can correspond to different filtered specific voltage values, so the duty cycle information can reflect the duty cycle of the control signal.

[0027] Further, when the duty cycle information is greater than a first threshold, a first DC compensation signal is generated based on the duty cycle information.

[0028] In some embodiments, the first DC compensation signal may include a first compensation current or a first compensation voltage. In some embodiments, the corresponding relationship between the input voltage and the output voltage and the duty cycle in the switching power supply circuit can be predetermined, and then the inductor peak current of the switching power supply circuit is compensated based on the current duty cycle. In some embodiments, when the duty cycle information corresponding to the extracted current duty cycle is greater than the first threshold, a first compensation current corresponding to the current duty cycle can be generated, and the inductor peak current of the switching power supply circuit is compensated according to the first compensation current, thereby increasing its maximum output power, ensuring that it can obtain the desired output power under the current input voltage and thus stabilize the load.

[0029] The first threshold value is a value corresponding to the duty cycle information corresponding to the logic control signal that needs to generate the first compensation current. In some embodiments, the first threshold value can be determined according to the duty cycle corresponding to when the switching power supply circuit is in the critical conduction mode (that is, the inductor current in the circuit just drops to 0 at the end of a switching cycle). For example, when the duty cycle is 0.4, the switching power supply circuit is in the critical conduction mode, and the first threshold value can be set to the voltage value corresponding to the duty cycle of 0.4, that is, the duty cycle information when the duty cycle is 0.4.

[0030] The first compensation current is a current generated in the switching power supply circuit corresponding to the duty cycle information and can compensate the switching power supply circuit. The specific method for generating the first compensation current is described in detail below.

[0031] In some embodiments, it is considered that as the input voltage decreases, the maximum inductor current Ipk passing through the switching power supply circuit will also decrease. As an example only, when the input voltage is 120V, the maximum inductor current Ipk1 in the circuit is Vcs / Rcs, and when the input voltage is 40V, the maximum inductor current Ipk2 in the circuit is 0.7*Vcs / Rcs (where Rcs is the resistance of the sampling resistor). Therefore, in some embodiments, in order to make the output power corresponding to different input voltages meet the load requirements as much as possible, first compensation currents of different sizes can be generated for different duty cycles. Specifically, compensation can be performed based on the maximum current in the circuit under the current duty cycle and the target current value expected to be achieved. For example, in some embodiments, the maximum inductor current of the switching power supply circuit in the continuous conduction mode can be set to be equal to the maximum inductor current in the discontinuous conduction mode, where the maximum inductor current Ipk in the discontinuous conduction mode is Vcs / Rcs. According to the above situation, when the input voltage is 40V, the first compensation current to be compensated should be 0.3*Vcs / Rcs, and when the input voltage is greater than 40V, since its corresponding maximum inductor current is greater than 0.7*Vcs / Rcs, its corresponding first compensation current can be less than 0.3*Vcs / Rcs.

[0032] In some embodiments, when the duty cycle information is greater than the first threshold and less than or equal to a second threshold, the first DC compensation signal generated based on the duty cycle information changes with the change of the duty cycle information. In some embodiments, when the duty cycle information is greater than the second threshold, the first DC compensation signal generated based on the duty cycle information is fixed to the first DC compensation signal when the duty cycle information is equal to the second threshold.

[0033] In some embodiments, under the condition of the same input voltage, as the duty cycle increases, the first compensation current required to compensate the switching power supply circuit will also increase, and when the duty cycle reaches a certain value, the first compensation current will no longer increase. In some embodiments, the duty cycle information corresponding to the duty cycle at this time can be set as the second threshold. In some embodiments, the second threshold can be set to the duty cycle information corresponding to the duty cycle of 0.7, and when the duty cycle information corresponding to the current duty cycle obtained is greater than the second threshold, the first compensation current will no longer continue to increase. In other words, the size of the first compensation current is no longer adjusted by the duty cycle at this time.

[0034] In some embodiments, the first threshold value may be set to be not less than a voltage value corresponding to a duty cycle of 0.3, and the second threshold value may be set to be not less than a voltage value corresponding to a duty cycle of 0.6.

[0035] Step 120: Generate a slope compensation signal Islope using a slope generating circuit; here, the slope generating circuit may be an existing conventional solution, such as a slope generating circuit composed of a current source and a capacitor, and the slope generating circuit generates a triangular wave signal according to the switching signal of the main switch tube to compensate the sampling current signal of the inductor. Figure 1 Not shown in FIG.

[0036] Step 130: The first DC compensation signal Isink and the slope compensation signal Islope both compensate for the sampled current signal of the inductor in the switching power supply circuit, so that the output signal of the switching power supply circuit is an expected value.

[0037] In some embodiments, a corresponding first compensation current Isink and a corresponding slope compensation signal Islope can be generated for different duty cycle information. The generated first compensation current and the slope compensation signal Islope are superimposed on the inductor current in the switching power supply circuit, thereby increasing the inductor peak current of the switching power supply circuit, so that the output current increases accordingly, thereby increasing its output power, and reducing the subharmonic oscillation of the circuit, ensuring that it can still stably carry the load when the input voltage is low.

[0038] In addition, in some embodiments, considering the margin problem, the output current of the switching power supply circuit can also be overcompensated, that is, the actual compensation value can be slightly larger than the value to be compensated. For example, when the current value to be compensated (that is, the difference between the maximum current and the target current under the current duty cycle) is 0.3*Vcs / Rcs, a first compensation current value of 0.4*Vcs / Rcs or other first compensation current slightly larger than 0.3*Vcs / Rcs can be generated to compensate the output current of the switching power supply circuit to ensure that its output power can be stably loaded.

[0039] In some embodiments, it can be set that when the duty cycle of the control signal of the main switch tube is greater than or equal to the third threshold, slope compensation is performed based on the current inductor current in the switching power supply circuit. The third threshold is the duty cycle value of the control signal of the main switch tube, which can be any value greater than or equal to 0.5 and less than or equal to 1. For example, when the third threshold is set to 0.5, if the duty cycle of the switch tube under the current input voltage is greater than or equal to 0.5, a compensation signal with a fixed slope can be superimposed on the signal sampled by the inductor current by means of slope compensation, so that the effective current in the circuit will not oscillate with the fluctuation of the duty cycle, so that its output current reaches a stable state.

[0040] In some embodiments, in order to ensure that the amplitude of the slope compensation can eliminate the problem of subharmonic oscillation, the slope of the slope compensation can be determined based on the falling slope of the inductor current. In some embodiments, the slope of the slope compensation can be set to be no less than half of the falling slope of the inductor current. As an example only, when the slope of the inductor current falling k1 = Vcs / (0.6*T), where T is the switching period of the switch tube, the slope of the slope compensation can be set to: k2 = 0.3*Vcs / (0.3*T) = 0.6*Vcs / (0.6*T)>1 / 2*k1, the falling slope k1 of the inductor current represents the ratio of the falling value of the inductor current to the falling time when the inductor current is in the falling stage (i.e., the time period when the switch tube is in the off state), and the slope k2 of the slope compensation represents the rate of change of the compensation value over time.

[0041] In some embodiments, the third threshold value can be the same as the duty cycle corresponding to the first threshold value. For example, the third threshold value can be set to 0.4, and the first threshold value can be set to the voltage value corresponding to the duty cycle of 0.4, that is, while performing slope compensation on the inductance sampling signal of the switching power supply circuit, the inductance current of the switching power supply circuit is compensated twice by generating the first compensation current, thereby eliminating subharmonic oscillations and improving the output power of the switching power supply circuit.

[0042] In some embodiments, the third threshold value may also be different from the duty cycle corresponding to the first threshold value. For example, the first threshold value may be set to a voltage value corresponding to a duty cycle of 0.4, and the third threshold value may be set to 0.5. That is, when the duty cycle corresponding to the input voltage is greater than or equal to 0.4, a first compensation current is generated to compensate for the output current of the switching power supply circuit to avoid the output current from being reduced due to the input voltage being too low. When the duty cycle corresponding to the input voltage is greater than or equal to 0.5, a slope compensation current is generated to compensate for the output current of the switching power supply circuit to avoid the problem of subharmonic oscillation caused by a duty cycle greater than 0.5.

[0043] It should be noted that the above description of the control method for output power compensation of the switching power supply circuit is only for example and illustration, and does not limit the scope of application of the present application. For those skilled in the art, various modifications and changes can be made to the above under the guidance of the present application. However, these modifications and changes are still within the scope of the present application.

[0044] Figure 3 Schematic diagram of an output power compensation circuit of a switching power supply circuit according to some embodiments of the present application. Figure 4 It is a curve diagram showing the output voltage of a switching power supply circuit and the voltage to be compensated as the duty cycle changes according to some embodiments of the present application.

[0045] like Figure 3 As shown, in some embodiments, the first compensation circuit may include a duty cycle information acquisition circuit and a current generation circuit. The duty cycle information acquisition circuit may be used to extract the duty cycle information based on the logic control signal used to control the switch tube in the switching power supply circuit; the current generation circuit may be used to compare the duty cycle information with the first threshold value, and generate a first compensation current based on the comparison result, so as to compensate the inductor current of the switching power supply circuit through the first compensation current.

[0046] Specifically, continue to refer to Figure 3 In some embodiments, the duty cycle information acquisition circuit may include a low-pass filter circuit composed of a resistor R1 and a capacitor C1. In some embodiments, the low-pass filter circuit may be used to perform low-pass filtering on the logic control signal Gon to obtain the duty cycle information. The logic control signal Gon is a high or low level signal that controls the main switch tube to be turned on or off. The logic control signal Gon can be converted into a corresponding voltage value V1 after passing through the low-pass filter circuit composed of R1 and C1, which is the duty cycle information of the switch tube control signal duty cycle. The voltage level of the voltage value V1 is determined by the resistor R1, the capacitor C1 and the voltage level of the logic control signal.

[0047] Continue to refer to Figure 3In some embodiments, the current generating circuit may include an operational amplifier OA, a first resistor R2, a current mirror circuit, and a first switch tube Q1. In some embodiments, the output end of the low-pass filter circuit in the duty cycle information acquisition circuit is connected to the non-inverting input end of the operational amplifier OA in the current generating circuit. The logic control signal Gon is converted by the low-pass filter circuit to obtain a voltage value V1, which can be input into the first input end (non-inverting input end) of the operational amplifier OA. The second input end (reverse input end) of the operational amplifier receives the first threshold value, and compares the duty cycle information with the first threshold value, and controls whether the first switch tube is turned on based on the comparison result; the two power ends of the first switch tube are respectively connected to the current mirror circuit and the first resistor; when the operational amplifier controls the first switch tube to be turned on, the current generated on the first resistor and the first switch tube series branch flows into the current mirror circuit, and when there is current flowing into the current mirror circuit, the current mirror circuit generates a first compensation current Isink.

[0048] Continue to refer to Figure 3 In some embodiments, the current generating circuit may further include a current source I0, which is connected to the ground through a resistor R2, and the first threshold value is determined based on the current I0 output by the current source and the resistance value of the resistor R2. Specifically, when the logic control signal Gon is converted by the low-pass filter circuit to obtain a voltage value V1 greater than or equal to I0*R2, the first switch tube Q1 is turned on, and a current is generated in the series branch between the resistor R2 and the first switch tube Q1, and the generated current flows into the current mirror circuit; conversely, when the logic control signal Gon is converted by the low-pass filter circuit to obtain a voltage value V1 less than I0*R2, the first switch tube Q1 is turned off, and no current flows into the current mirror, and the first compensation current Isink is not generated. Specifically, refer to Figure 3 The current mirror circuit includes a first current mirror and a second current mirror. The first current mirror receives a power supply voltage Vcc and is connected to the ground through a series structure in which a first switch tube Q1 and a resistor R2 are connected in series. When the first switch tube Q1 is turned on, the current on the first switch tube Q1 generates a first current Iout through the first current mirror; the second current mirror is connected between the first current mirror and the ground, and the second current mirror receives the first current Iout and outputs the first compensation current Isink at the output end of the second current mirror. Here, the proportional coefficients of the first current mirror and the second current mirror can be the same or different, and the first compensation current Isink can be the same as the first current Iout or have a certain proportional coefficient relationship.

[0049] In some embodiments, as the duty cycle of the main switch control signal gradually increases, the output power in the switch power circuit will also continue to decrease, so the first compensation current that needs to compensate the switch power circuit also needs to increase accordingly. In some embodiments, when the logic control signal Gon is converted by the low-pass filter circuit to obtain a voltage value V1 greater than the first threshold, the operational amplifier OA controls the switch tube Q1 to turn on, and the current generating circuit thereby generates a first compensation current Isink, and the first compensation current Isink will follow the current flowing through the resistor R2. As the duty cycle increases, the voltage value V1 obtained by the logic control signal Gon after the low-pass filter circuit conversion will increase accordingly. According to the virtual short principle of the operational amplifier, the voltage value across the resistor R2 will also increase as V1 increases, thereby increasing the current on the first switch tube Q1 connected in series with the resistor R2, thereby increasing the generated first compensation current Isink as the duty cycle increases. In some embodiments, when the voltage value across the resistor R2 reaches the second threshold value, that is, the reference voltage Vref, due to the clamping of the reference voltage Vref, the first compensation current Isink will no longer continue to increase with the increase of the duty cycle, and the first compensation current Isink will be fixed at the first compensation current corresponding to the second threshold value, which is the maximum first compensation current. In some embodiments, the reference voltage Vref is a preset voltage applied to the other non-inverting input terminal of the operational amplifier OA, which can be set by the size of the set second threshold value. In other words, when the duty cycle reaches the set maximum value, for example, when the maximum duty cycle is 0.7, the size of the first compensation current will no longer be adjusted by the duty cycle to avoid excessive compensation current.

[0050] As an example only, the curve of the output voltage of the switching power supply circuit as the duty cycle changes is as follows Figure 4 As shown in the upper part. When the duty cycle D1 is 0.4 when the switching power supply circuit is in the critical conduction mode, the sampling voltage value corresponding to the peak current of the inductor is Vcs. As the duty cycle increases, the sampling voltage decreases at a fixed slope. When the duty cycle Dmax is 0.7, the sampling voltage value is 0.7*Vcs. In some embodiments, when the duty cycle Dmax is 0.7, the voltage value to be compensated is 0.3*Vcs. Taking into account the margin issue, over-compensation can be performed. For example, the compensated voltage value can be set to 0.4*Vcs or other values ​​slightly larger than 0.3*Vcs. In some embodiments, the compensation value of the sampling voltage can be obtained by adjusting the voltage on the resistor through which the first compensation current Isink flows, such as Figure 2 The resistance value of resistor R3 in is determined.

[0051] It can be understood that in the embodiment of the present application, the duty cycle information is used to determine whether to generate a compensation current to compensate the switching power supply circuit. In some embodiments, when the duty cycle information is greater than or equal to the first threshold, a first compensation current Isink is generated to compensate for the inductor current of the switching power supply circuit, and when the duty cycle information is less than the first threshold, the first compensation current Isink is not generated, which can increase the output current of the switching power supply circuit when the input voltage is low so that it can be stably loaded, and can also avoid the output current of the switching power supply circuit being too large due to the presence of the compensation current when the input voltage is high. In some embodiments, when the duty cycle information is greater than the second threshold, the first compensation current is fixed to the first compensation current generated when the duty cycle information is equal to the second threshold, and the size of the first compensation current is no longer adjusted by the duty cycle to avoid the generation of too large a compensation current.

[0052] Figure 2 is a schematic diagram of a flyback conversion circuit according to some embodiments of the present application.

[0053] In some embodiments, the control circuit for output power compensation of the switching power supply circuit can be combined with a flyback conversion circuit to compensate the output current of the switching power supply circuit. In some embodiments, the compensation of the switching power supply circuit can also be combined with slope compensation to eliminate possible subharmonic oscillation. Figure 4 As shown, the flyback conversion circuit may include a main switch tube Gate, and the above-mentioned duty cycle information acquisition circuit can extract the corresponding duty cycle information according to the control signal of the main switch tube Gate, and then the above-mentioned current generation circuit generates the corresponding first compensation current Isink based on the duty cycle information.

[0054] Similarly, when the input voltage Vin is 80V and the duty cycle is 0.55, the peak current in the circuit can only reach 85% of the rated peak current Ipk. At this time, a first compensation current Isink with a current value slightly greater than 15%*Ipk can be generated based on the duty cycle information, and the first compensation current Isink can be superimposed on the current in the circuit.

[0055] It should be noted that the compensation value of the above first compensation current is only for example. In some embodiments, the compensation value can be determined according to a pre-set compensation requirement. For example, when the maximum current of the switching power supply circuit in the continuous conduction mode is set to 90% of the maximum current in the discontinuous conduction mode, if the maximum current Ipk in the discontinuous conduction mode is Ipk=Vcs / Rcs, and the maximum inductor current Ipk2 in the circuit is Ipk2=0.7*Vcs / Rcs when the input voltage is 40V, then the first compensation current Isink that needs to be compensated is approximately 0.2*Vcs / Rcs. Specifically, considering that the effect of the slope compensation current Islope will further reduce the maximum current Ipk2 under the input voltage, therefore, in order to make the compensated peak current closer to 90% of the maximum current in the discontinuous conduction mode, when the input voltage is 40V, the corresponding first compensation current Isink can be slightly greater than 0.2*Vcs / Rcs.

[0056] In some embodiments, the control circuit of the switching power supply circuit can also be applied to a buck-boost power stage circuit, and the output current is compensated by the magnitude of the inductor current in the compensation topology circuit to obtain a stable output power.

[0057] It should be noted that in the embodiments of the present application, the switch tube Q1, switch tube Q2 and switch tube Gate involved can be MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), etc., and no limitation is imposed on them in the present application.

[0058] The beneficial effects that may be brought about by the embodiments of the present application include but are not limited to: (1) by generating a first compensation current based on duty cycle information and superimposing it with the inductor current of the switching power supply circuit, the magnitude of the inductor peak current is increased, thereby increasing the output current, so that the output power of the switching power supply circuit can be kept stable when the input voltage is low, while avoiding increasing the output power when the input voltage is high; (2) by generating a first compensation current based on duty cycle information, first compensation currents of different magnitudes can be generated for different duty cycles, so that the output power corresponding to different input voltages remains stable, thereby ensuring that the switching power supply circuit is stably loaded; (3) when the duty cycle information is greater than the second threshold, the magnitude of the first compensation current is no longer adjusted by the duty cycle, thereby avoiding excessive compensation current; (4) when the duty cycle is greater than the third threshold, slope compensation is performed based on the inductor current in the switching power supply circuit, which can avoid subharmonic oscillation caused by excessive duty cycle.

[0059] In some embodiments, the switching power supply circuit may include a DC switching power supply circuit and an AC switching power supply circuit. In some embodiments, the DC switching power supply circuit may be divided into two categories, namely, isolated and non-isolated, according to the internal DC / DC converter, wherein the isolated DC / DC conversion circuit may include a forward conversion circuit, a flyback conversion circuit, a double-transistor forward conversion circuit, a double-transistor flyback conversion circuit, a push-pull conversion circuit, and a half-bridge conversion circuit, and the non-isolated DC / DC conversion circuit may include a buck DC / DC conversion circuit, a boost DC / DC conversion circuit, a buck boost DC / DC conversion circuit, a Cuk DC / DC conversion circuit, a Zeta DC / DC conversion circuit, and a SEPIC DC / DC conversion circuit.

[0060] It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other beneficial effects that may be obtained.

[0061] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0062] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0063] Finally, it should be understood that the embodiments described in this application are only used to illustrate the principles of the embodiments of the present application. Other variations may also fall within the scope of the present application. Therefore, as an example and not a limitation, the alternative configurations of the embodiments of the present application may be considered to be consistent with the teachings of the present application. Accordingly, the embodiments of the present application are not limited to the embodiments explicitly introduced and described in the present application.

Claims

1. A control method for a switching power supply circuit, characterized in that: include: Obtaining a first DC compensation signal according to duty cycle information of a main switch tube in a switching power supply circuit; Using a slope generating circuit to generate a slope compensation signal; The first DC compensation signal and the slope compensation signal both compensate for the sampled current signal of the inductor in the switching power supply circuit so that the output signal of the switching power supply circuit is an expected value. Wherein, the step of generating the first DC compensation signal comprises: The logic control signal of the main switch tube is subjected to low-pass filtering to obtain duty cycle information; A first DC compensation signal is generated based on a comparison between the duty cycle information and a first threshold.

2. The control method according to claim 1, characterized in that: Further including: When the duty cycle information is greater than the first threshold and less than or equal to a second threshold, the first DC compensation signal increases as the duty cycle information increases; When the duty cycle information is greater than the second threshold, the first DC compensation signal remains constant.

3. The control method according to claim 2, characterized in that: When the first threshold is greater than the duty cycle of the main switch logic control signal is 0.3, the voltage value of the logic control signal obtained after low-pass filtering; When the second threshold is greater than the duty cycle of the main switch control signal is 0.6, the voltage value obtained after the logic control signal is low-pass filtered.

4. A control circuit for a switching power supply circuit, characterized in that: include: A first compensation circuit, wherein the first compensation circuit obtains a first DC compensation signal according to duty cycle information of a main switch tube in the switching power supply circuit; a second compensation circuit, the second compensation circuit being used to generate a slope compensation signal; The first DC compensation signal and the slope compensation signal both compensate for the sampled current signal of the inductor in the switching power supply circuit so that the output signal of the switching power supply circuit is an expected value. Wherein, the first compensation circuit comprises a duty cycle information acquisition circuit, which is used to extract duty cycle information based on the logic control signal of the main switch tube in the switching power supply circuit; The current generating circuit is used to compare the duty cycle information with a first threshold value and generate the first DC compensation signal based on the comparison result.

5. The control circuit according to claim 4, characterized in that: The duty cycle information acquisition circuit comprises: The low-pass filter circuit receives the logic control signal of the main switch tube and performs low-pass filtering on the logic control signal to obtain the duty cycle information.

6. The control circuit according to claim 4, characterized in that: The current generating circuit comprises an operational amplifier, a first switch tube, a first resistor and a current mirror circuit; The first input end of the operational amplifier is connected to the output end of the duty cycle information acquisition circuit, and the output end of the operational amplifier is connected to the control end of the first switch tube; The second input terminal of the operational amplifier receives the first threshold, compares the duty cycle information with the first threshold, and controls whether the first switch tube is turned on based on the comparison result; Two power ends of the first switch tube are connected to the current mirror circuit and the first resistor respectively; When the first switch tube is turned on, the current of the series branch where the first switch tube and the first resistor are located flows into the current mirror circuit, and the current mirror circuit is used to generate the first DC compensation signal when current flows in.

7. The control circuit according to claim 6, characterized in that: The current generating circuit further includes a current source, one end of the current source is grounded through the first resistor, and the ground end of the first resistor is connected to the second input end of the operational amplifier; The first threshold is determined based on the current output by the current source and the resistance value of the first resistor.

8. The control circuit according to claim 6, characterized in that: The operational amplifier is further configured to control the voltage drop value on the first resistor to remain constant when the duty cycle information is greater than a second threshold value, so that the first DC compensation signal is a maximum first DC compensation signal.

9. The control circuit according to claim 8, characterized in that: A reference voltage is input to the third input terminal of the operational amplifier, and the reference voltage value is equal to the second threshold value.

10. A switching power supply, comprising an inductor current sampling circuit and a logic control circuit, characterized in that: Also includes the control circuit according to any one of claims 4 to 9, The inductor current sampling circuit samples the inductor current information in the switching power supply to obtain the sampling current signal. The logic control circuit receives the sampling current signal and the reference signal, and generates a logic control signal after comparison to control the switching state of the main switch tube. The first DC compensation signal and the slope compensation signal are used to compensate the sampled current signal.

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