Switching converter and control circuit and control method thereof

Abstract

The invention provides a switching converter and a control circuit and a control method thereof. The control circuit comprises a feedback compensation unit used for generating a compensation signal according to an output feedback signal of the switching converter; the control unit is used for generating a first current reference signal according to the compensation signal, setting a first current reference adjustment value according to the expected output power, adjusting the first current reference signal according to the first current reference adjustment value to obtain a second current reference signal, and outputting the second current reference signal. According to the second current reference signal and the inductive current sampling signal, a control signal for controlling the on-off of the main switching tube is generated; and the driver is used for outputting a driving signal to the control end of the main switching tube according to the control signal. According to the invention, for a wide-range input voltage occasion, the output power adjustment efficiency and flexibility of the switching converter are improved.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of switching power supplies, and in particular relates to a switching converter and a control circuit and a control method thereof. Background Art

[0002] Switching converters are widely used in low-power power supplies and various power adapters due to their simple circuit structure and low cost. Common switching converters include Buck converters, Boost converters, Buck-Boost converters, and flyback converters. The typical structure of a switching converter includes a transformer including a primary winding, a secondary winding, and an auxiliary winding, a main switch tube, and a primary controller. The excitation inductance and leakage inductance of the primary winding are equivalent to inductance Lm and inductance Lk, respectively. During the driving process, the existing switching converter can generate a current reference signal according to a compensation signal that characterizes the load severity of the switching converter, and obtain an inductor current sampling signal by sampling on a sampling resistor, thereby controlling the on and off of the primary main switch tube according to the current reference signal and the inductor current sampling signal. When the output power of the switching converter needs to be reduced, the inductance peak current of the excitation inductance of the switching converter is reduced by reducing the on time of the main switch tube, thereby reducing the output power of the switching converter. However, for a wide range of input voltages, the output power gap between the low-voltage input and the high-voltage input of the switching converter is large. As the input voltage (Vin) of the switching converter increases, the slope Vin / Lm of the excitation inductor current will increase accordingly. Under the high-voltage input of the switching converter, the on-time of the main switch tube becomes shorter, the peak inductor current decreases as the on-time decreases, and the output power also decreases accordingly. The current common practice is to compensate the on-time as the input voltage increases (by extending the on-time) to maintain the stability of the output power; however, under low-voltage input, as the input voltage decreases, the on-time of the main switch tube becomes longer, and the inductor peak current increases. In order to maintain the stability of the output power, it is difficult to reduce the on-time to reduce more power. In addition, the main switch tube has a certain turn-off delay. During the driving process of the existing switching converter, for different main power tubes and different turn-off delays, it is necessary to adjust the output power of the switching converter by correcting the value of the current reference signal. Obviously, this reduces the output power adjustment efficiency and flexibility of the switching converter. Summary of the invention

[0003] In view of the above problems, the present disclosure provides a switching converter and a control circuit and a control method thereof, aiming to improve the output power adjustment efficiency and flexibility of the switching converter for a wide range of input voltage occasions.

[0004] According to a first aspect of the present disclosure, a control circuit of a switching converter is provided, wherein the switching converter comprises a main switch tube and an inductor connected to each other and a control circuit, wherein the control circuit comprises:

[0005] A feedback compensation unit, configured to generate a compensation signal according to an output feedback signal of the switching converter;

[0006] a control unit, configured to generate a first current reference signal according to the compensation signal, set a first current reference adjustment value according to the expected output power, adjust the first current reference signal according to the first current reference adjustment value to obtain a second current reference signal, and generate a control signal for controlling the on / off of the main switch tube according to the second current reference signal and the inductor current sampling signal;

[0007] A driver is used to output a driving signal to the control end of the main switch tube according to the control signal.

[0008] Optionally, the control unit comprises:

[0009] A first current reference signal generating module, configured to generate the first current reference signal according to the compensation signal;

[0010] The current reference adjustment module sets the first current reference adjustment value according to the expected output power, and the first current reference adjustment value is a positive value or a negative value according to the relationship between the expected output power and the set power.

[0011] Optionally, when the expected output power is less than the set power, the first current reference adjustment value is a positive value, and when the expected output power is greater than the set power, the first current reference adjustment value is a negative value.

[0012] Optionally, the current reference adjustment module includes:

[0013] A regulating circuit, which obtains an adjustment voltage according to the expected output power;

[0014] The first operator calculates a preset voltage representing the set power and the adjustment voltage to obtain the first current reference adjustment value.

[0015] Optionally, the current reference adjustment module further includes a second operator, configured to perform an operation on the first current reference signal and the first current reference adjustment value to obtain the second current reference signal.

[0016] Optionally, the current reference adjustment module further includes:

[0017] A first adjustment module, when the first current reference adjustment value is a positive value, is used to obtain the second current reference signal according to the on-time of the main switch tube and the first current reference adjustment value;

[0018] The second adjustment module is configured to obtain the second current reference signal according to the on-time of the main switch tube and the first current reference adjustment value when the first current reference adjustment value is a negative value.

[0019] Optionally, the first adjustment module includes a first capacitor and a first computing device, wherein when the first current reference adjustment value is a positive value, a first current is given during the on-time of the main switch tube to charge the first capacitor to obtain a first voltage; the first computing device obtains the second current reference signal according to the first voltage, the first current reference adjustment value and the first current reference signal;

[0020] The second adjustment module includes a second capacitor and a second computing device, wherein when the first current reference adjustment value is a negative value, a second current is given during the conduction time of the main switch tube to charge the second capacitor to obtain a second voltage; and the second computing device obtains the second current reference signal according to the second voltage, the first current reference adjustment value and the first current reference signal.

[0021] Optionally, when the first current reference adjustment value is a positive value, the longer the on-time of the main switch tube is, the smaller the second current reference signal is;

[0022] When the first current reference adjustment value is a negative value, the longer the on-time of the main switch tube is, the larger the second current reference signal is.

[0023] Optionally, the regulating circuit includes a first electronic device, and the adjustment voltage is obtained by adjusting the magnitude of an electrical signal on the first electronic device according to the expected output power.

[0024] Optionally, the first electronic device is a first resistor, and a first current is given to flow through the first resistor, and the adjustment voltage is obtained by adjusting the size of the first resistor according to the expected output power.

[0025] Optionally, the control circuit is integrated into a chip, and the first electronic device is arranged outside the chip.

[0026] According to a second aspect of the present disclosure, a switching converter is provided, comprising:

[0027] A control circuit as described in any one of the above items.

[0028] According to a third aspect of the present disclosure, a control method for a switching converter is provided, wherein the switching converter comprises a main switch tube and an inductor connected to each other and a control circuit, and the control method comprises:

[0029] generating a compensation signal according to an output feedback signal of the switching converter;

[0030] generating a first current reference signal according to the compensation signal, setting a first current reference adjustment value according to the expected output power, adjusting the first current reference signal according to the first current reference adjustment value to obtain a second current reference signal, and generating a control signal for controlling the on and off of the main switch tube according to the second current reference signal and the inductor current sampling signal;

[0031] A driving signal is output to the control end of the main switch tube according to the control signal.

[0032] The present disclosure brings the following beneficial effects:

[0033] In the control circuit of the switching converter provided by the present disclosure, the first current reference adjustment value can be flexibly set according to the expected output power, and then the first current reference signal can be adjusted according to the first current reference adjustment value to obtain the second current reference signal, and the on and off of the main switch tube can be controlled according to the second current reference signal and the inductor current sampling signal. The first current reference adjustment value can be a positive value or a negative value according to the target to be adjusted, and the peak inductor current can be adjusted in both directions, thereby improving the flexibility and adjustment range of adjusting the output power of the switching converter for a wide range of input voltage occasions. For different input voltages and different shutdown delays, the output power of the switching converter is adjusted by correcting the value of the first current reference signal, which improves the output power adjustment efficiency of the switching converter.

[0034] Other features and advantages of the present disclosure will be described in the following description, and partly become apparent from the description, or understood by practicing the present disclosure. The purpose and other advantages of the present disclosure are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0035] In order to make the above-mentioned objectives, features and advantages of the present disclosure more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0037] Figure 1 A schematic diagram of the structure of a lighting system provided according to an embodiment of the present disclosure;

[0038] Figure 2 A schematic diagram of the structure of a switching converter provided according to an embodiment of the present disclosure;

[0039] Figure 3 A schematic diagram of the structure of a control unit provided according to an embodiment of the present disclosure;

[0040] Figure 4 A schematic diagram of the structure of a control unit provided according to another embodiment of the present disclosure;

[0041] Figure 5A A curve diagram of a first resistance and a first current reference adjustment value provided according to an embodiment of the present disclosure;

[0042] Figure 5B A waveform diagram of a second current reference signal and an inductor current sampling signal provided according to an embodiment of the present disclosure;

[0043] Figure 5C A waveform diagram of a second current reference signal and an inductor current sampling signal provided according to yet another embodiment of the present disclosure;

[0044] Fig. 6A A working waveform diagram of a switching converter provided according to an embodiment of the present disclosure;

[0045] Figure 6B A working waveform diagram of a switching converter provided according to another embodiment of the present disclosure;

[0046] Figure 7 The present invention is a flow chart of a control method for a switching converter provided according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0047] Various embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0048] Figure 1 FIG. 2 is a schematic diagram showing a structure of a lighting system provided according to an embodiment of the present disclosure. Figure 1 As shown, the lighting system 100 provided by the embodiment of the present disclosure includes: an AC power supply 1, a rectifier circuit 2, a power factor correction circuit 3, a switching converter 4 and a lighting output terminal 5.

[0049] In some embodiments, the rectifier circuit 2 is used to rectify the AC power input by the AC power supply 1 to output a first voltage signal to the power factor correction circuit 3. Optionally, the rectifier circuit 2 can be a full-bridge rectifier circuit or a half-bridge rectifier circuit. The power factor correction circuit 3 is connected to the rectifier circuit 2, and is used to perform power factor correction on the first voltage signal output by the rectifier circuit 2, and output a second voltage signal. The power factor correction circuit 3 generally adopts a BOOST topology structure and serves as a front stage to provide a stable second voltage signal (such as 400V) based on the rectified first voltage signal as an input to a subsequent circuit such as a switching converter 4. The switching converter 4 is connected to the LED load, and is used to provide a driving current to the LED load to drive the LED load.

[0050] In some embodiments, the switching converter 4 includes a transformer TR including a primary winding Np, a secondary winding Ns and an auxiliary winding Na, a main switch tube Q1 and a primary controller 6. In some embodiments, the primary controller 6 generates a compensation signal Vcomp according to an output feedback signal (such as an output voltage Vo or an output current Io) of the switching converter 4, and the compensation signal Vcomp is used to characterize the load severity of the switching converter. In some embodiments, the primary controller 6 generates a current reference signal Vref according to the compensation signal Vcomp, samples the sampling resistor Rs to obtain an inductor current sampling signal Vcs, and controls the on and off of the primary main switch tube Q1 according to the current reference signal Vref and the inductor current sampling signal Vcs. The switching converter 4 stores energy in the primary energy storage element of the transformer TR during the conduction period of the main switch tube Q1, and transfers the energy stored in the primary energy storage element to the secondary part after the main switch tube Q1 is turned off.

[0051] Figure 2 FIG. 1 is a schematic diagram of a switching converter according to an embodiment of the present disclosure. Figure 2 As shown, the switching converter provided by the embodiment of the present disclosure includes: a transformer TR including a primary winding Np, a secondary winding Ns and an auxiliary winding Na, a main switch tube Q1 connected to the primary side of the transformer, and a control circuit 200. The excitation inductance and leakage inductance of the primary winding Np are equivalent to inductances Lm and Lk respectively.

[0052] In some embodiments, one end of the primary winding Np is connected to the input end of the input voltage Vin, and the other end is connected to the first channel end (e.g., drain) of the main switch tube Q1, and the second channel end (e.g., source) of the main switch tube Q1 is connected to the reference ground through the sampling resistor Rcs. The control end (e.g., gate) of the main switch tube Q1 is connected to the control circuit 200, and the capacitor C1 is the parasitic capacitance of the main switch tube Q1. The main switch tube Q1 transfers the energy from the input voltage Vin from the primary part of the switching converter to the secondary part by periodic switching. In some embodiments, the secondary part of the switching converter includes: a diode D1 and an output capacitor Co. The anode of the diode D1 is connected to the secondary winding Ns, and the cathode is connected to the output end of the switching converter. The positive electrode of the output capacitor Co is connected to the output end of the switching converter, and the negative electrode of the output capacitor Co is connected to the reference ground. The same-name end of the secondary winding Ns is also connected to the reference ground. The output end of the switching converter is connected to the load, and the load receives the electric energy converted by the switching converter.

[0053] In some embodiments, the control circuit 200 is coupled to the main switch tube Q1 to control the on and off of the main switch tube Q1 to achieve energy conversion between the input end and the output end of the switching converter. In some embodiments, the control circuit 200 includes a feedback compensation unit 110, a control unit 120 and a driver 130. In some embodiments, the feedback compensation unit 110 is used to generate a compensation signal Vcomp according to the output feedback signal of the switching converter. For example, the feedback compensation unit 110 includes a voltage feedback loop and / or a current feedback loop, the voltage feedback loop is used to sample the output voltage Vo to obtain the compensation signal Vcomp, and the current feedback loop is used to sample the output current Io to obtain the compensation signal Vcomp.

[0054] In some embodiments, the control unit 120 is used to generate a first current reference signal Vref1 according to the compensation signal Vcomp, set the first current reference adjustment value Vt0 according to the expected output power, adjust the first current reference signal Vref1 according to the first current reference adjustment value Vt0 to obtain a second current reference signal Vref, and generate a control signal Scontrol for controlling the on and off of the main switch tube Q1 according to the second current reference signal Vref and the inductor current sampling signal Vcs. In some embodiments, the driver 130 is coupled to the control unit 120, receives the control signal Scontrol, and is used to output a drive signal Vgs1 to the control end of the main switch tube Q1 according to the control signal Scontrol. It should be noted that the first current reference adjustment value can be flexibly set according to the expected output power, and then the peak current of the inductor of the switching converter in the current switching cycle can be adjusted by adjusting the second current reference signal Vref, thereby flexibly adjusting the output power of the switching converter.

[0055] It should be noted that, in the embodiments of the present disclosure, the flyback converter will be taken as an example to explain the technical solution of the present disclosure, but it should be understood that the technical solution disclosed in the embodiments of the present disclosure can also be applied to switching converters such as Buck converters, Boost converters and Buck-Boost converters.

[0056] Figure 3 FIG. 1 is a schematic diagram of the structure of a control unit provided according to an embodiment of the present disclosure. Figure 3 As shown, the control unit 120 provided in the embodiment of the present disclosure includes: a first current reference signal generating module 210 , a current reference adjusting module 220 and a comparator 230 .

[0057] In some embodiments, the first current reference signal generating module 210 generates a first current reference signal Vref1 according to the compensation signal Vcomp. The current reference adjusting module 220 sets a first current reference adjustment value Vt0 according to the expected output power. According to the relationship between the expected output power and the set power, it is determined whether the first current reference adjustment value Vt0 is a positive value or a negative value. In one embodiment, when the expected output power is less than the set power, the first current reference adjustment value Vt0 is a positive value, and when the expected output power is greater than the set power, the first current reference adjustment value Vt0 is a negative value. In some embodiments, the current reference adjusting module 220 includes an adjusting circuit 221, a first operator 222 and a second operator 223. Optionally, the first operator 222 is a first subtractor, and the second operator 223 is a first adder. In some embodiments, the adjusting circuit 221 obtains an adjustment voltage Vset according to the expected output power. In some embodiments, the adjusting circuit 221 includes a first current source Iset1 and a first resistor Rset. The first current source Iset1 and the first resistor Rset are connected in series. The size of the first current source Iset1 and / or the first resistor Rset can be adjusted according to the expected output power. The output current Iset1' of the first current source Iset1 flows through the first resistor Rset to generate an adjustment voltage Vset. Preferably, the first resistor Rset is arranged outside the chip, and the voltage on the first resistor Rset is the adjustment voltage Vset. For different input voltages Vin, the size of the first resistor Rset outside the chip is adjusted according to the expected output power to obtain the adjustment voltage Vset. The first current reference adjustment value Vt0 is obtained according to the adjustment voltage Vset, and then the peak inductor current is adjusted, so that the output power can reach the expected output power even under different input voltages Vin; wherein, the first resistor Rset can also be replaced by other electronic devices, which are arranged outside the chip. For different input voltages, the customer can adjust the size of the electrical signal on the electronic device outside the chip to adjust the inductor peak current, so that the output power remains stable and can reach the expected output power. The adjustment method is flexible and the adjustment range is wide. In some embodiments, the positive input terminal of the first subtractor 222 is connected to the voltage source Uset to receive the preset voltage VT representing the set power, the inverting input terminal is connected to the series connection node of the first current source Iset1 and the first resistor Rset to receive the adjustment voltage Vset, and the output terminal provides the first current reference adjustment value Vt0. The first subtractor 222 subtracts the preset voltage VT representing the set power from the adjustment voltage Vset to obtain the first current reference adjustment value Vt0. The first current reference adjustment value Vt0 can be expressed as follows:

[0058] Vt0=VT-Vset=VT-Iset1'×Rset (1)

[0059] Wherein, Vt0 is the first current reference adjustment value, VT is the preset voltage, Vset is the adjustment voltage, Iset1 ′ is the output current of the first current source Iset1 , and Rset is the first resistor.

[0060] Figure 5A FIG. 1 is a graph of a first resistance and a first current reference adjustment value according to an embodiment of the present disclosure. Figure 5A As shown, the first resistor Rset1 is smaller than the first resistor Rset3, smaller than the preset resistance threshold Rvt, smaller than the first resistor Rset4, and smaller than the first resistor Rset2. The first current reference adjustment value Vt0 decreases as the first resistor Rset increases. The first current reference adjustment value Vt01 corresponding to the first resistor Rset1 and the first current reference adjustment value Vt03 corresponding to the first resistor Rset3 are positive values. The first current reference adjustment value -Vt04 corresponding to the first resistor Rset4 and the first current reference adjustment value -Vt02 corresponding to the first resistor Rset2 are negative values. When the first resistor Rset is equal to the preset resistance threshold Rvt, the first current reference adjustment value Vt01 is 0, that is, when the first resistor Rset is equal to the preset resistance threshold Rvt, the preset voltage VT is equal to the adjustment voltage Vset. The curve diagram shows that by adjusting the size of the first resistor Rset, the size of the adjustment voltage Vset can be adjusted accordingly, thereby adjusting the output power.

[0061] In some embodiments, the first positive phase input terminal of the first adder 223 is connected to the output terminal of the first subtractor 222 to receive the first current reference adjustment value Vt0, the second positive phase input terminal is connected to the first current reference signal generating module 210 to receive the first current reference signal Vref1, and the output terminal provides the second current reference signal Vref. The second current reference signal Vref can be expressed as follows:

[0062] Vref=Vref1+Vt0 (2)

[0063] Wherein, Vref is the second current reference signal, Vref1 is the first current reference signal, and Vt0 is the first current reference adjustment value.

[0064] In some embodiments, the first input terminal of the comparator 230 is connected to the output terminal of the adder 223 to receive the second current reference signal Vref, the second input terminal receives the inductor current sampling signal Vcs, and the output terminal provides a control signal Scontrol. The comparator 230 compares the second current reference signal Vref with the inductor current sampling signal Vcs, and generates a control signal Scontrol for controlling the main switch tube Q1 to turn off when the inductor current sampling signal Vcs is greater than or equal to the second current reference signal Vref, so as to control the main switch tube Q1 to turn off.

[0065] It can be understood that when the output power is less than the expected output power, the first current source Iset1 and / or the first resistor Rset are adjusted to decrease, and the second current reference signal Vref can be increased to improve the output power of the switching converter. When the output power is greater than the expected output power, the first current source Iset1 and / or the first resistor Rset are adjusted to increase, and the second current reference signal Vref can be reduced to reduce the output power of the switching converter.

[0066] Figure 4 FIG. 1 is a schematic diagram of the structure of a control unit provided according to another embodiment of the present disclosure. Figure 4 As shown, the control unit 120 provided in the embodiment of the present disclosure includes: a first current reference signal generating module 310 , a current reference adjusting module 320 and a comparator 330 .

[0067] In some embodiments, the first current reference signal generating module 310 generates a first current reference signal Vref1 according to the compensation signal Vcomp. The current reference adjusting module 320 sets a first current reference adjustment value Vt0 according to the expected output power. Optionally, when the expected output power is less than the set power, the first current reference adjustment value Vt0 is a positive value, and when the expected output power is greater than the set power, the first current reference adjustment value Vt0 is a negative value. In some embodiments, the current reference adjusting module 320 includes a regulating circuit 411, a first subtractor 412, a first adjusting module 420 and a first adjusting module 430. In some embodiments, the regulating circuit 411 obtains an adjustment voltage Vset according to the expected output power. The first subtractor 412 subtracts the preset voltage VT representing the set power from the adjustment voltage Vset to obtain the first current reference adjustment value Vt0. The regulating circuit 411 and Figure 3 The structure of the regulating circuit 221 in FIG. 4 is the same as that of the first subtractor 412. Figure 3 The structure of the first subtractor 222 in the embodiment is the same, so the specific structures of the adjustment circuit 411 and the first subtractor 412 are not described in detail here.

[0068] In some embodiments, when the first current reference adjustment value Vt0 is a positive value, the first adjustment module 420 obtains the second current reference signal Vref according to the on-time of the main switch tube Q1 and the first current reference adjustment value Vt0. In some embodiments, the first adjustment module 420 includes a first capacitor Cset1 and a first computing device 421. When the first current reference adjustment value Vt0 is a positive value, a first current is given to charge the first capacitor Cset1 during the on-time of the main switch tube Q1 to obtain a first voltage Vc1. The first computing device 421 obtains the second current reference signal Vref according to the first voltage Vc1, the first current reference adjustment value Vt0 and the first current reference signal Vref1. In some embodiments, when the first current reference adjustment value Vt0 is a negative value, the second adjustment module 430 obtains the second current reference signal Vref according to the on-time of the main switch tube Q1 and the first current reference adjustment value Vt0. In some embodiments, the second adjustment module 430 includes a second capacitor Cset2 and a second computing device 431. When the first current reference adjustment value Vt0 is negative, a second current is given during the on-time of the main switch tube Q1 to charge the second capacitor Cset2 to obtain a second voltage Vc2. The second operation device 431 obtains a second current reference signal Vref according to the second voltage Vc2, the first current reference adjustment value Vt0 and the first current reference signal Vref1.

[0069] In some embodiments, the current reference adjustment module 320 further includes an enable signal generation module 440. The first adjustment module 420 further includes a second current source Iset2, a first switch S1, and a second switch S2. The first operation device 421 includes a second subtractor 422 and a third subtractor 423. The second adjustment module 430 further includes a third current source Iset3, a third switch S3, and a fourth switch S4. The second operation device 431 includes a second adder 432 and a third adder 433. The second current source Iset2 and the first capacitor Cset1 are connected in series through the first switch S1, and the first capacitor Cset1 is connected in parallel with the second switch S2. The positive input terminal of the second subtractor 422 receives the first voltage Vc1, the inverting input terminal receives the first current reference adjustment value Vt0, and the output terminal provides the second current reference adjustment value VlineA. The positive input terminal of the third subtractor 423 receives the first current reference signal Vref1, the inverting input terminal receives the second current reference adjustment value VlineA, and the output terminal provides the second current reference signal Vref. The third current source Iset3 and the second capacitor Cset2 are connected in series through the third switch S3, and the second capacitor Cset2 is connected in parallel with the fourth switch S4. The first positive phase input terminal of the second adder 432 receives the second voltage Vc2, the second phase input terminal receives the first current reference adjustment value Vt0, and the output terminal provides the second current reference adjustment value VlineB. The first positive phase input terminal of the third adder 433 receives the first current reference signal Vref1, the second positive phase input terminal receives the second current reference adjustment value VlineA, and the output terminal provides the second current reference signal Vref. In some embodiments, the enable signal generation module 420 generates a first enable signal Sen1 when the first current reference adjustment value Vt0 is a positive value and the first enable signal Sen1 is valid when the main switch tube Q1 is in the on state, and generates a second enable signal Sen2 when the first current reference adjustment value Vt0 is a negative value and the second enable signal Sen2 is valid when the main switch tube Q1 is in the on state. In some embodiments, when the first enable signal Sen1 is valid, the first switch S1 is closed and the second switch S2 is opened, so that the first capacitor Cset1 is charged by the second current source Iset2 to obtain the first voltage Vc1. When the first enable signal Sen1 is invalid, the first switch S1 is opened and the second switch S2 is closed to release the charge stored in the first capacitor Cset1. The first voltage Vc1 can be expressed as follows:

[0070] Vc1=Iset2′×Ton / Cset1 (3)

[0071] Wherein, Vc1 is a first voltage, Iset2′ is an output current of the second current source Iset2, Cset1 is a first capacitor, and Ton is the on-time of the main switch tube Q1 in the current switching cycle. In some embodiments, the second current source Iset2 may be related to the first current reference adjustment value Vt0, for example, the output current Iset2′ of the second current source Iset2=Vt0 / Rn, wherein the resistance value of the resistor Rn may be preset. In some embodiments, when the on-time Ton of the main switch tube Q1 is equal to the preset time threshold t1, the first voltage Vc1 is equal to the absolute value of the first current reference adjustment value Vt0. When the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the first capacitor voltage Vc1 is less than the absolute value of the first current reference adjustment value Vt0.

[0072] Fig. 6A FIG. 1 is a working waveform diagram of a switching converter provided according to an embodiment of the present disclosure. Fig. 6A As shown, in some embodiments, the first current reference adjustment value Vt01 corresponding to the first resistor Rset1 is a positive value, and when the on-time Ton of the main switch tube Q1 is equal to the preset time threshold t1, the first voltage Vc1 is equal to the first current reference adjustment value Vt01. When the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the first voltage Vc1 is less than the first current reference adjustment value Vt01.

[0073] The second current reference adjustment value VlineA can be expressed as follows:

[0074] VlineA=Vc1-Vt0 (4)

[0075] Wherein, VlineA is the second current reference adjustment value, Vc1 is the first voltage, and Vt0 is the first current reference adjustment value. Fig. 6A In some embodiments, when the first resistor Rset is equal to the first resistor Rset1, when the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the second current reference adjustment value VlineA is a negative value, and as the on-time Ton of the main switch tube Q1 increases, the second current reference adjustment value VlineA increases from -Vt01 to 0.

[0076] The second current reference signal Vref can be expressed as follows:

[0077] Vref=Vref1-VlineA (5)

[0078] Wherein, Vref is the second current reference signal, Vref1 is the first current reference signal, and VlineA is the second current reference adjustment value. Fig. 6AIn some embodiments, when the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the second current reference signal Vref is greater than the first current reference signal Vref1. As the on-time Ton of the main switch tube Q1 increases, the second current reference signal Vref decreases from Vref1+Vt01 to Vref1.

[0079] In some embodiments, when the second enable signal Sen2 is valid, the third switch S3 is closed and the fourth switch S4 is opened, so that the third current source Iset3 is used to charge the second capacitor Cset2 to obtain the second voltage Vc2. When the second enable signal Sen2 is invalid, the third switch S3 is opened and the fourth switch S4 is closed to release the charge stored in the second capacitor Cset2. The second voltage Vc2 can be expressed as follows:

[0080] Vc2=Iset3′×Ton / Cset2 (6)

[0081] Wherein, Vc2 is the second voltage, Iset3′ is the output current of the third current source Iset3, Cset2 is the second capacitor, and Ton is the on-time of the main switch tube Q1 in the current switching cycle. In some embodiments, the third current source Iset3 can be related to the first current reference adjustment value Vt0, for example, the output current Iset3′ of the third current source Iset3=Vt0 / Rn, wherein the resistance value of the resistor Rn can be preset. In some embodiments, when the on-time Ton of the main switch tube Q1 is equal to the preset time threshold t1, the second voltage Vc2 is equal to the absolute value of the first current reference adjustment value Vt0. When the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the second voltage Vc2 is less than the absolute value of the first current reference adjustment value Vt0.

[0082] Figure 6B FIG. 1 is a working waveform diagram of a switching converter according to another embodiment of the present disclosure. Figure 6B As shown, in some embodiments, the first current reference adjustment value -Vt02 corresponding to the first resistor Rset2 is a negative value, and when the on-time Ton of the main switch tube Q1 is equal to the preset time threshold t1, the second voltage Vc2 is equal to the absolute value Vt02 of the first current reference adjustment value. When the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the first voltage Vc1 is less than the absolute value Vt02 of the first current reference adjustment value.

[0083] The second current reference adjustment value VlineB can be expressed as follows:

[0084] VlineB=Vc2+Vt0 (7)

[0085] Wherein, VlineB is the second current reference adjustment value, Vc2 is the second voltage, and Vt0 is the first current reference adjustment value. Figure 6B In some embodiments, when the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the second current reference adjustment value VlineB is a negative value, and as the on-time Ton of the main switch tube Q1 increases, the second current reference adjustment value VlineB increases from -Vt02 to 0.

[0086] The second current reference signal Vref can be expressed as follows:

[0087] Vref=Vref1+VlineB (8)

[0088] Wherein, Vref is the second current reference signal, Vref1 is the first current reference signal, and VlineB is the second current reference adjustment value. Figure 6B In some embodiments, when the on-time Ton of the main switch tube Q1 is less than the preset time threshold t1, the second current reference signal Vref is less than the first current reference signal Vref1. As the on-time Ton of the main switch tube Q1 increases, the second current reference signal Vref increases from Vref1-Vt02 to Vref1.

[0089] In some embodiments, the first input terminal of the comparator 330 is connected to the output terminal of the third subtractor 423 to receive the second current reference signal Vref when the first current reference adjustment value Vt0 is a positive value, the second input terminal is connected to the output terminal of the third adder 433 to receive the second current reference signal Vref when the first current reference adjustment value Vt0 is a negative value, the third input terminal receives the inductor current sampling signal Vcs, and the output terminal provides a control signal Scontrol. In some embodiments, the comparator 330 compares the second current reference signal Vref with the inductor current sampling signal Vcs, and generates a control signal Scontrol for controlling the main switch tube Q1 to turn off when the inductor current sampling signal Vcs is greater than or equal to the second current reference signal Vref, so as to control the main switch tube Q1 to turn off.

[0090] Figure 5B 1 is a waveform diagram of a second current reference signal and an inductor current sampling signal provided according to an embodiment of the present disclosure. Figure 5A and 5BAs shown, the first resistor Rset1 and the first resistor Rset3 are both smaller than the preset resistance threshold Rvt, and the first resistor Rset1 is smaller than the first resistor Rset3. The first current reference adjustment value Vt01 corresponding to the first resistor Rset1 and the first current reference adjustment value Vt03 corresponding to the first resistor Rset3 are both positive values, and the first current reference adjustment value Vt01 is greater than the first current reference adjustment value Vt03. It is easy to understand that at the moment when the on-time Ton of the main switch tube Q1 in the current switching cycle ends, the second current reference signal Vref corresponding to the first resistor Rset1 is greater than the second current reference signal Vref corresponding to the first resistor Rset3, that is, at the moment when the on-time Ton of the main switch tube Q1 in the current switching cycle ends, the inductance peak current Vcs_ipk1 of the primary loop of the switching converter corresponding to the first resistor Rset1 is greater than the inductance peak current Vcs_ipk3 of the primary loop of the switching converter corresponding to the first resistor Rset3.

[0091] Figure 5C FIG. 1 is a waveform diagram of a second current reference signal and an inductor current sampling signal provided according to another embodiment of the present disclosure. In some embodiments, Figure 5A and 5C As shown, the first resistor Rset2 and the first resistor Rset4 are both greater than the preset resistance threshold Rvt, and the first resistor Rset2 is greater than the first resistor Rset4. The first current reference adjustment value -Vt02 corresponding to the first resistor Rset2 and the first current reference adjustment value -Vt04 corresponding to the first resistor Rset4 are both negative values, and the first current reference adjustment value -Vt02 is less than the first current reference adjustment value -Vt04. It is easy to understand that at the moment when the main switch tube Q1 ends the on-time Ton of the current switching cycle, the second current reference signal Vref corresponding to the first resistor Rset2 is less than the second current reference signal Vref corresponding to the first resistor Rset4, that is, at the moment when the main switch tube Q1 ends the on-time Ton of the current switching cycle, the inductance peak current Vcs_ipk4 of the primary loop of the switching converter corresponding to the first resistor Rset4 is greater than the inductance peak current Vcs_ipk2 of the primary loop of the switching converter corresponding to the first resistor Rset2.

[0092] It can be understood that when the output power is less than the expected output power, the first current source Iset1 and / or the first resistor Rset are adjusted to decrease, and the second current reference signal Vref can be increased to improve the output power of the switching converter. When the output power is greater than the expected output power, the first current source Iset1 and / or the first resistor Rset are adjusted to increase, and the second current reference signal Vref can be reduced to reduce the output power of the switching converter.

[0093] It can be understood that when the first current reference adjustment value Vt0 is a positive value, the longer the on-time of the main switch tube Q1 is, the smaller the second current reference signal Vref is. When the first current reference adjustment value Vt0 is a negative value, the longer the on-time of the main switch tube Q1 is, the larger the second current reference signal Vref is.

[0094] For different input voltages and different expected output powers, the present invention can bidirectionally adjust the inductor peak current, which can reduce the peak inductor current as well as increase the peak inductor current, thereby bidirectionally adjusting the output power. Compared with the prior art, which can only adjust the peak inductor current by adjusting the extended on-time, the adjustment range is wider and the adjustment method is more flexible.

[0095] Figure 7 The flowchart of the control method of the switching converter provided according to an embodiment of the present disclosure is shown. The switching converter includes a main switch tube and an inductor connected to each other and a control circuit. Figure 7 As shown, the control method of the switching converter includes:

[0096] In step S710 , a compensation signal is generated according to an output feedback signal of the switching converter.

[0097] In step S720, a first current reference signal is generated according to the compensation signal, a first current reference adjustment value is set according to the expected output power, the first current reference signal is adjusted according to the first current reference adjustment value to obtain a second current reference signal, and a control signal for controlling the on and off of the main switch tube is generated according to the second current reference signal and the inductor current sampling signal.

[0098] In step S730, a driving signal is output to the control end of the main switch tube according to the control signal.

[0099] Since the process of controlling the switching converter according to the embodiment of the present disclosure has been described in detail in the device embodiment above, it will not be repeated here.

[0100] In summary, in the control circuit of the switching converter provided by the present disclosure, the first current reference adjustment value can be flexibly set according to the expected output power, and then the first current reference signal can be adjusted according to the first current reference adjustment value to obtain the second current reference signal, and the on and off of the main switch tube can be controlled according to the second current reference signal and the inductor current sampling signal, thereby improving the flexibility of adjusting the output power of the switching converter for a wide range of input voltage occasions. There is no need to adjust the output power of the switching converter by correcting the value of the first current reference signal for different main power tubes and different shutdown delays, which improves the output power adjustment efficiency of the switching converter.

[0101] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly illustrating the present disclosure, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present disclosure.

Claims

1. A control circuit of a switching converter, the switching converter comprising a main switch tube and an inductor connected to each other and a control circuit, the control circuit comprising: A feedback compensation unit, configured to generate a compensation signal according to an output feedback signal of the switching converter; a control unit, configured to generate a first current reference signal according to the compensation signal, set a first current reference adjustment value according to the expected output power, adjust the first current reference signal according to the first current reference adjustment value to obtain a second current reference signal, and generate a control signal for controlling the on / off of the main switch tube according to the second current reference signal and the inductor current sampling signal; A driver is used to output a driving signal to the control end of the main switch tube according to the control signal.

2. The control circuit according to claim 1, wherein: The control unit comprises: A first current reference signal generating module, configured to generate the first current reference signal according to the compensation signal; The current reference adjustment module sets the first current reference adjustment value according to the expected output power, and the first current reference adjustment value is a positive value or a negative value according to the relationship between the expected output power and the set power.

3. The control circuit according to claim 2, wherein: When the expected output power is less than the set power, the first current reference adjustment value is a positive value, and when the expected output power is greater than the set power, the first current reference adjustment value is a negative value.

4. The control circuit according to claim 2 or 3, wherein: The current reference adjustment module comprises: A regulating circuit, which obtains an adjustment voltage according to the expected output power; The first operator calculates a preset voltage representing the set power and the adjustment voltage to obtain the first current reference adjustment value.

5. The control circuit according to claim 4, wherein: The current reference adjustment module further includes a second operator, configured to perform an operation on the first current reference signal and the first current reference adjustment value to obtain the second current reference signal.

6. The control circuit according to claim 4, wherein: The current reference adjustment module also includes: A first adjustment module, when the first current reference adjustment value is a positive value, is used to obtain the second current reference signal according to the on-time of the main switch tube and the first current reference adjustment value; The second adjustment module is configured to obtain the second current reference signal according to the on-time of the main switch tube and the first current reference adjustment value when the first current reference adjustment value is a negative value.

7. The control circuit according to claim 6, wherein: The first adjustment module includes a first capacitor and a first computing device, wherein when the first current reference adjustment value is a positive value, a first current is given during the on-time of the main switch tube to charge the first capacitor to obtain a first voltage; the first computing device obtains the second current reference signal according to the first voltage, the first current reference adjustment value and the first current reference signal; The second adjustment module includes a second capacitor and a second computing device, wherein when the first current reference adjustment value is a negative value, a second current is given during the conduction time of the main switch tube to charge the second capacitor to obtain a second voltage; and the second computing device obtains the second current reference signal according to the second voltage, the first current reference adjustment value and the first current reference signal.

8. The control circuit according to claim 7, wherein: When the first current reference adjustment value is a positive value, the longer the on-time of the main switch tube is, the smaller the second current reference signal is; When the first current reference adjustment value is a negative value, the longer the on-time of the main switch tube is, the larger the second current reference signal is.

9. The control circuit according to claim 4, wherein: The regulating circuit includes a first electronic device, and the adjustment voltage is obtained by regulating the magnitude of the power signal on the first electronic device according to the expected output power.

10. The control circuit according to claim 9, wherein: The first electronic device is a first resistor. A first current is given to flow through the first resistor, and the adjustment voltage is obtained by adjusting the size of the first resistor according to the expected output power.

11. The control circuit according to claim 9 or 10, wherein: The control circuit is integrated in the chip, and the first electronic device is arranged outside the chip.

12. A switching converter, comprising: A control circuit as claimed in any one of claims 1 to 11.

13. A control method for a switching converter, the switching converter comprising a main switch tube and an inductor connected to each other and a control circuit, the control method comprising: generating a compensation signal according to an output feedback signal of the switching converter; generating a first current reference signal according to the compensation signal, setting a first current reference adjustment value according to the expected output power, adjusting the first current reference signal according to the first current reference adjustment value to obtain a second current reference signal, and generating a control signal for controlling the on and off of the main switch tube according to the second current reference signal and the inductor current sampling signal; A driving signal is output to the control end of the main switch tube according to the control signal.

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