Switching power supply control circuit

Abstract

The present invention provides a switching power supply control circuit, comprising: a switching power supply, a PWM control module, a switch conduction control module and a digital module; wherein: the switching power supply includes a first switch branch and a second switch branch; a first end of the first switch branch is connected to an input voltage terminal, a second end thereof is connected to a first reference node, and a control end thereof is connected to a first end of the PWM control module; a first end of the second switch branch is connected to the first reference node, a second end thereof is connected to a ground terminal, and a control end thereof is connected to a second end of the PWM control module; an input end of the PWM control module is used for receiving a PWM pulse signal, a first end thereof outputs a first driving signal, and a second end thereof outputs a second driving signal; a first end of the switch conduction control module is connected to the first reference node, and a second end thereof is connected to a third end of the PWM control module. The switching power supply control circuit provided by the present invention ensures the continuity of the loop operation and effectively gets rid of sub-harmonic oscillation.

Description

Technical Field

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

[0002] DC-DC switching power supplies have multiple control modes. According to the sampling signal, they can generally be divided into voltage mode and current mode. The voltage mode performs negative feedback by sampling the output voltage, and the current mode performs negative feedback by sampling the input current and the output voltage. Common current mode architectures include: Peak-Current Mode, Average-Current Mode, and Hysteretic-Current Mode; classified by the duty cycle modulation method, they include Pulse Width Modulation (PWM), Pulse Frequency Modulation (PFM), Constant On Time (COT), Fixed Off Time (FOT), Bang-Bang control, etc.

[0003] Among them, the COT mode has a very fast response speed, but due to the fixed conduction time, the maximum duty cycle is limited. If the main switch conduction time (TON) is set too large, it is easy to cause large ripples in the light load mode; the conduction time of the FOT mode will increase with the increase of the load to increase the duty cycle. The disadvantage is that the fixed off time cannot be set too low. If it is too low, when the load is relatively light or the input and output voltages are close, the frequency is relatively high and the efficiency is reduced.

[0004] In summary, the prior art has the following defects:

[0005] 1. The peak current control mode requires slope compensation, and the size of the compensation parameter has a great influence on the performance. Insufficient compensation is easy to cause oscillation, and excessive compensation is easy to reduce the system response;

[0006] 2. It is easy to generate subharmonic oscillation after being interfered by noise;

[0007] 3. The average current mode loop design is complex.

[0008] Generally speaking, although the traditional current mode structure has good performance and easy loop compensation, it needs to provide a slope compensation signal under specific circumstances to avoid subharmonic oscillation, so there are limitations in use. Summary of the Invention

[0009] The present invention provides a switching power circuit to solve the problem of subharmonic oscillation of the traditional current mode structure.

[0010] According to a first aspect of the present invention, there is provided a switching power supply control circuit, comprising:

[0011] a switching power supply, a PWM control module, and a switch conduction control module; wherein:

[0012] the switching power supply includes a first switch branch and a second switch branch; a first end of the first switch branch is connected to an input voltage terminal, a second end thereof is connected to a first reference node, and a control end of the first switch branch is connected to a first end of the PWM control module; a first end of the second switch branch is connected to the first reference node, a second end thereof is connected to a ground terminal, and a control end of the second switch branch is connected to a second end of the PWM control module;

[0013] the input terminal of the PWM control module is configured to receive a PWM pulse signal, output a first driving signal through the first end, and output a second driving signal through the second end, the first driving signal is input to the first switch branch to conduct the input voltage terminal and the first reference node, and the second driving signal is input to the second switch branch to conduct the first reference node and the ground terminal;

[0014] a first end of the switch conduction control module is connected to the first reference node, a second end thereof is connected to a third end of the PWM control module, the switch conduction control module is configured to collect a current at the first reference node, and when the current at the first reference node exceeds a preset threshold, turn off the first switch branch and turn on the second switch branch through the PWM control module; otherwise, adjust the PWM pulse signal by using the current at the first reference node.

[0015] Optionally, the switch conduction control module includes: a current acquisition circuit, connected to the switching power supply, configured to collect a current at the first reference node and process it into a sinking current for output.

[0016] Optionally, the switching power supply includes an output voltage terminal, and the switching frequency control circuit further includes a first inductor and a first resistor connected in series between the first reference node and the output voltage terminal, a first end of the current acquisition circuit is connected to a node between the first inductor and the first resistor, and a second end of the current acquisition circuit is connected to a node between the first resistor and the output voltage terminal; the first end and the second end of the current acquisition circuit are respectively configured to collect currents at corresponding nodes and output corresponding sinking currents through a third end and a fourth end of the current acquisition circuit.

[0017] Optionally, the switch conduction control module further includes: an overcurrent comparator, a positive-phase input terminal of the overcurrent comparator is connected to a third terminal of the current acquisition circuit, and a negative-phase input terminal of the overcurrent comparator is used to input a reference voltage corresponding to the preset threshold; an output terminal of the overcurrent comparator is connected to a third terminal of the PWM control module, and the overcurrent comparator is configured to compare the pull current output from the third terminal of the current acquisition circuit with the reference voltage corresponding to the preset threshold. When the pull current output from the third terminal of the current acquisition circuit is greater than the reference voltage, an off signal is output to control the PWM control module to turn off the first switch branch and turn on the second switch branch.

[0018] Optionally, it further includes: a PWM comparator, a positive-phase input terminal of the PWM comparator is used to input a PWM compensation signal, and a negative-phase input terminal of the PWM comparator is connected to a fourth terminal of the current acquisition circuit; an output terminal of the PWM comparator is connected to an input terminal of the PWM control module; the PWM comparator is configured to compare the pull current output from the fourth terminal of the current acquisition circuit with the PWM compensation signal to generate the PWM pulse signal and send it to the PWM control module.

[0019] Optionally, it further includes: a compensation network, connected to the positive-phase input terminal of the PWM comparator to generate the PWM compensation signal to the PWM comparator to generate the PWM pulse signal.

[0020] Optionally, it further includes: a voltage-dividing lower resistor, a voltage-dividing upper resistor, and an operational amplifier. The voltage-dividing upper resistor and the voltage-dividing lower resistor are connected in series between the output voltage terminal and the ground; a positive-phase input terminal of the operational amplifier is connected to a node between the voltage-dividing upper resistor and the voltage-dividing lower resistor, a negative-phase input terminal of the operational amplifier is connected to an output terminal of the operational amplifier, and an output terminal of the operational amplifier is connected to a fourth terminal of the current acquisition circuit. The operational amplifier is configured to receive the divided output voltage of the switching power supply to generate a following voltage and act on the pull current output from the fourth terminal of the current acquisition circuit.

[0021] Optionally, it further includes: an error amplifier, a positive-phase input terminal of the error amplifier is connected to a node between the voltage-dividing upper resistor and the voltage-dividing lower resistor, a negative-phase input terminal of the error amplifier is used to access a reference target voltage, and an output terminal of the error amplifier is connected to an output terminal of the compensation network. The error amplifier is configured to compare the error between the divided output voltage of the switching power supply and the reference target voltage, and adjust the PWM compensation signal to precisely control the output voltage of the switching power supply.

[0022] Optionally, the PWM control module further includes a PWM time control module, which includes a first signal generation unit, a second signal generation unit, and a third signal generation unit for adjusting the conduction time of the PWM pulse signal; wherein, the first signal generation unit is configured to receive a PWM signal and a PWM pulse signal to generate a minimum off-time control signal; the second signal generation unit is configured to receive the minimum off-time control signal and generate a maximum on-time control signal; the third signal generation unit is configured to receive the maximum on-time control signal and generate a minimum on-time control signal.

[0023] Optionally, the PWM control module further includes a switch tube driving unit, connected to the PWM time control module, for receiving the PWM pulse signal adjusted by the PWM time control module to generate the first driving signal and the second driving signal.

[0024] The switching power supply control circuit provided by the present invention collects the current of the switching power supply and adopts a hybrid current mode and time control structure, which ensures the continuity of the loop operation and can achieve the advantages comparable to those of the traditional current mode architecture. By setting the PWM time control module and combining peak current control, the deficiency of sub-harmonic oscillation is effectively eliminated. Among them, the current of the first switch branch is used as the on-time control, making it easy to implement the loop compensation method.

[0025] At the same time, the present invention isolates the influence of the inductor current of the switching power supply on the output voltage through an operational amplifier, and at the same time improves the applicable range of the circuit structure to realize that the output voltage directly superimposes the inductor current component after resistor voltage division; this way of superimposing current feedback effectively improves the continuity of the switching power supply operation, especially the continuity of the switching from light load to heavy load.

[0026] Since the frequency is not limited, stable operation (without sub-harmonic oscillation) can be achieved without slope compensation, and the anti-noise performance is excellent.

[0027] In addition, since the AC feedback amount of the present invention includes the inductor current, the dependence on the parasitic equivalent resistance of the output voltage terminal capacitor can be reduced, thereby reducing the voltage ripple of the output voltage, and having the fast response characteristics of the COT architecture. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the composition of the switching power supply control circuit provided by the present invention;

[0030] Figure 2 It is a circuit diagram of the switching power supply control circuit provided by an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the composition of the PWM time control module in an embodiment of the present invention;

[0032] Figure 4 It is a waveform diagram of the output voltage, reference voltage, and follower voltage in an embodiment of the present invention;

[0033] Figure 5 It is a waveform diagram of the inductor current and related PWM signals in an embodiment of the present invention. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0036] Next, the technical solutions of the present invention will be described in detail with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0037] Refer to Figure 1 As shown, this embodiment provides a switching power supply control circuit, including: a switching power supply 10, a PWM control module 20, and a switch conduction control module 30; wherein:

[0038] The switching power supply 10 includes a first switching branch 11 and a second switching branch 12. The first end of the first switching branch 11 is connected to the input voltage terminal (VIN), its second end is connected to the first reference node X1, and the control end of the first switching branch 11 is connected to the first end of the PWM control module 20; the first end of the second switching branch 12 is connected to the first reference node X1, its second end is connected to the ground terminal (GND), and the control end of the second switching branch 12 is connected to the second end of the PWM control module 20; the first switching branch 11 is configured to conduct the input voltage (VIN) and the first reference node X1 under the action of the first driving signal (HS), and the second switching branch 12 is configured to conduct the first reference node X1 and the ground terminal (GND) under the action of the second driving signal (LS);

[0039] The input end of the PWM control module 20 is used to receive the PWM pulse signal, and under the action of the PWM pulse signal, output the first driving signal (HS) through its first end and output the second driving signal (LS) through its second end; and

[0040] The first end of the switch conduction control module 30 is connected to the first reference node X1, and the second end of the switch conduction control module 30 is connected to the third end of the PWM control module 20; the switch conduction control module 30 is used to collect the current at the first reference node X1, and when the current at the first reference node X1 exceeds the preset threshold, turn off the first switching branch 11 and turn on the second switching branch 12 through the PWM control module 20; otherwise, adjust the PWM pulse signal using the current at the first reference node X1.

[0041] This switching power supply control circuit simultaneously collects the current between the first switching branch 11 and the second switching branch 12 through the switch conduction control module 30. The switch conduction control module 30 combines the peak current control technology and adjusts the output of the PWM control module 20 according to the magnitude of the collected current. Specifically, when the current exceeds the preset threshold, turn off the first switching branch and turn on the second switching branch. Otherwise, adjust the PWM pulse signal through the PWM control module to further adjust the first driving signal (HS) and the second driving signal (LS) to ensure the normal operation of the switching power supply. This method ensures the continuity of the loop operation and also overcomes the deficiency of sub-harmonic oscillation through peak current control.

[0042] Reference Figure 2As shown, the switching power supply in this embodiment is specifically configured to include a first switching branch 11 formed by a first-phase power transistor M1 and a second switching branch 12 formed by a second-phase power transistor M2. Among them, the input voltage terminal VIN is set at the input end of the first-phase power transistor M1. A storage inductor L0 and a sampling resistor RS are connected in series between the first reference node X1 between the first-phase power transistor M1 and the second-phase power transistor M2 and the output voltage terminal Vout in sequence. Among them, RLOAD is the output load of the switching power supply, which is used here to simulate the actual usage situation of the user side. Of course, in other preferred embodiments, the switching power supply can be changed into other power supplies with two switching branches as needed, and only a storage inductor or other types and quantities of energy storage elements can be set between its first reference node X1 and the output voltage terminal Vout as needed.

[0043] In a further preferred embodiment, referring to Figure 2 As shown, the switch conduction control module 30 includes: a current acquisition circuit U6, which is connected to the switching power supply 10 and is used to acquire the current of the first reference node X1 and process it into a pull current (source current) convenient for subsequent comparison processing and then output.

[0044] Furthermore, the switching power supply control circuit is further configured to include a first inductor (i.e., the above-mentioned storage inductor L0) and a first resistor (i.e., the above-mentioned sampling resistor RS) connected in series between the first reference node X1 and the output voltage terminal Vout. The first end of the current acquisition circuit U6 is connected to the node between the first inductor L0 and the first resistor RS, and the second end of the current acquisition circuit U6 is connected to the node between the first resistor RS and the output voltage terminal Vout. The current acquisition circuit U6 here is configured to simultaneously acquire the current at the node between the first inductor L0 and the first resistor RS and the current at the node between the first resistor RS and the output voltage, and process the acquired currents into pull currents respectively. Specifically, after acquiring the current, it is processed into a pull current through a preset ratio, and then output through the OUT1 and OUT2 ports of U6 respectively. Among them, I(out1) = I(inductor) / n (where n is the first preset ratio coefficient); I(out2) = I(inductor) / m (where m is the second preset ratio coefficient).

[0045] Preferably, the switch conduction control module further includes: an overcurrent comparator U4, the positive input terminal of the overcurrent comparator U4 is connected to the third terminal of the current acquisition circuit U6, and the negative input terminal of the overcurrent comparator U4 is used to input a reference voltage corresponding to the above preset threshold; the output terminal of the overcurrent comparator U4 is connected to the third terminal of the PWM control module. The overcurrent comparator U4 is used to compare the pull current output from the third terminal of the current acquisition circuit U6 (i.e., I(out2) output from the OUT2 port) with the reference voltage corresponding to the preset threshold. When the pull current I(out2) output from the third terminal of the current acquisition circuit U6 is greater than the reference voltage corresponding to the preset threshold, an off signal is output to control the PWM control module to turn off the first switch branch and turn on the second switch branch. Among them, reference Figure 2 As shown, the preset threshold of the current here is jointly determined by the reference voltage (CL2_REF), the second preset proportional coefficient m, and the resistance value of the pull-up resistor RLIM of the overcurrent comparator. After an overcurrent occurs, the off signal is immediately output to turn off the PWM (pwm = 0), the upper transistor (the first-phase power transistor M1) is turned off, and the lower transistor (the second-phase power transistor M2) is turned on. Before the overcurrent is released, the upper transistor (the first-phase power transistor M1) is not allowed to be turned on. After the overcurrent release is completed, the ILIM signal output by the overcurrent comparator U4 can control the PWM control module to be reset so that the first switch branch of the circuit continues to work.

[0046] Preferably, the switching power supply control circuit further includes: a PWM comparator U1, the positive input terminal of the PWM comparator U1 is used to input a PWM compensation signal, and the negative input terminal of the PWM comparator U1 is connected to the fourth terminal of the current acquisition circuit U6; the output terminal of the PWM comparator U1 is connected to the input terminal of the PWM control module 20. The PWM comparator U1 is used to compare the signal (CS1) corresponding to the pull current output from the fourth terminal of the current acquisition circuit U6 with the PWM compensation signal (compf) to generate a PWM pulse signal (pulse) and send it to the above-mentioned PWM control module. In this embodiment, the rising edge of the PWM pulse signal is used to generate an off signal (the end signal of the first phase).

[0047] Further, the switching power supply control circuit further includes: a compensation network U3, connected to the positive input terminal of the PWM comparator U1 to generate a PWM compensation signal to the PWM comparator U1 to generate a PWM pulse signal.

[0048] Further, the switching power supply control circuit further includes: a voltage-dividing lower resistor R4, a voltage-dividing upper resistor R5, and an operational amplifier U5. The voltage-dividing upper resistor R5 and the voltage-dividing lower resistor R4 are connected in series between the output voltage terminal Vout and the ground; the positive input terminal of the operational amplifier U5 is connected to the node between the voltage-dividing upper resistor R5 and the voltage-dividing lower resistor R4, the negative input terminal of the operational amplifier U5 is connected to the output terminal of the operational amplifier U5, and the output terminal of the operational amplifier U5 is connected to the fourth terminal of the current acquisition circuit. The operational amplifier U5 is configured to receive the divided output voltage Vfb of the switching power supply to generate a following voltage Vfb_bf, and superpose and act on the pull current (I(out1) output from the OUT2 port) output from the fourth terminal of the current acquisition circuit U6 to obtain the above signal CS1, and further adjust the generated PWM pulse signal.

[0049] Further, the switching power supply control circuit further includes: an error amplifier U7. The positive input terminal of the error amplifier U7 is connected to the node between the voltage-dividing upper resistor R5 and the voltage-dividing lower resistor R4. The negative input terminal of the error amplifier U7 is used to access a reference target voltage. The output terminal of the error amplifier U7 is connected to the output terminal of the compensation network U3. The error amplifier U7 is configured to compare the error between the divided output voltage Vfb of the switching power supply and the reference target voltage VREF, and adjust the PWM compensation signal to precisely control the output voltage of the switching power supply.

[0050] Reference Figure 2 As shown, the PWM control module in this embodiment further includes a PWM time control module U2. Further reference Figure 3 As shown, the PWM time control module U2 includes a first signal generation unit I01, a second signal generation unit I02, and a third signal generation unit I03 for adjusting the conduction time of the PWM pulse signal; wherein, the first signal generation unit I01 is configured to receive the PWM signal and the PWM pulse signal to generate a minimum turn-off time control signal; the second signal generation unit I02 is configured to receive the minimum turn-off time control signal and generate a maximum conduction time control signal; the third signal generation unit I03 is configured to receive the maximum conduction time control signal and generate a minimum conduction time control signal. The PWM time control module U2 controls and adjusts the minimum turn-off time, the maximum conduction time, and the minimum conduction time of the PWM pulse signal through the above first signal generation unit I01, second signal generation unit I02, and third signal generation unit I03. For a specific embodiment of the internal circuit of U2 to implement the above functions of controlling and adjusting the PWM pulse signal, reference can be made to Patent CN201711138251.6, or those skilled in the art can set it to other specific circuit structures that can implement the above functions according to needs.

[0051] After the overcurrent comparator U4 controls the first comparison branch to turn off and the overcurrent release is completed, the overcurrent comparator U4 outputs an ILIM signal to control the PWM time control module U2 to reset, so that its output is reset to 0, and the first switch branch of the circuit continues to work. Furthermore, U2 realizes generating a first phase turn-on signal in the continuous mode.

[0052] Further preferably, referring to Figure 2 As shown, the PWM control module further includes a switch tube driving unit U8, which is connected to the PWM time control module U2 and is used to receive the PWM pulse signal adjusted by the PWM time control module U2 to generate a first driving signal (HS) and a second driving signal (LS).

[0053] Further referring to Figure 2 , the working process of this switching power supply control circuit is as follows:

[0054] At startup, the initial voltage of the output voltage terminal Vout is 0V, while the VREF voltage is the reference target voltage. Usually, there is a soft start, and the VREF voltage ramps up slowly to the target voltage. Vfb follows VREF until it reaches the target voltage; Vout = Vfb * (1 + R5 / R4), where R4 is the lower voltage-dividing resistor and R5 is the upper voltage-dividing resistor.

[0055] At this time, the error amplifier U7 compares the input error, thereby raising or lowering the compf voltage. Here, the compensation network U3 is set as a loop filter, and U7 and U3 jointly determine the speed (bandwidth) of the loop. In this embodiment, if Vfb < VREF, the output current of U7 raises compf; if Vfb > VREF, the opposite is true.

[0056] And the operational amplifier U5 performs the following functions: 1. Copy (buffer) the Vfb voltage to improve the driving ability; 2. Isolate Vfb and Vfb_bf. Due to the high-impedance input characteristic of the operational amplifier, the change of Vfb_bf will not affect Vfb; here, since the speed of U5 is much higher than the loop bandwidth, the AC quantity of Vfb_bf is approximately equal to Vfb; Vfb_bf follows the change of the Vfb signal, that is, a follower. In a specific application example, the waveform relationship of the output voltage Vout, the divided Vfb, and the reference target voltage VREF is referred to Figure 4 as shown.

[0057] During this process, the current acquisition circuit U6 acquires the inductor current, processes it into sink current, and then outputs I(out1) and I(out2) respectively. In this embodiment, for the upper transistor, a sampling transistor with a device size of 1 / n of M1 is used as the mirror transistor, and the mirrored current is 1 / n of M1. The same applies to the lower transistor sampling. Additionally, by connecting a sampling resistor RS in series at the inductor end, the voltage drop across it is RS*IL (IL is the inductor current, i.e., I(inductor)). By making this voltage drop fall on different reference resistors, it can be converted into corresponding sink current. By setting the ratio of the reference resistor to RS, I(out1) and I(out2) can be obtained.

[0058] During this process, the overcurrent comparator U4 performs cycle-by-cycle overcurrent protection. When overcurrent occurs, the upper transistor turns off and the lower transistor turns on. Before the overcurrent is released, the upper transistor is not allowed to turn on and conduct; the currents collected by the upper and lower transistors are represented as Is = IL / m. When Is*RLIM > CL2_REF, it indicates that the current exceeds the preset value, ILIM becomes high, the upper transistor immediately turns off, and the lower transistor turns on; conversely, when ILIM is low, the loop operates normally.

[0059] During this process, the PWM time control module U2 controls and adjusts the minimum off-time, maximum on-time, and minimum on-time of the PWM pulse signal, and is mainly used to generate the first-phase turn-on signal in continuous mode:

[0060] In continuous mode, since the inductor current IL is continuous, when reaching the peak current to turn off, the pulse ( Figure 3 PU input to U2) only maintains a low level for a very short time (the CS1 level, due to the superposition of the inductor current signal, is always greater than the compf voltage input to U1. In one embodiment here, the waveform relationships of the inductor current I(L1-P), PWM pulse signal, compf / CS1 signal, and pulse signal are referred to Figure 5 as shown), which is used to turn off the first phase and turn on the second phase. Since the turn-off of the second phase has a minimum off-time control, it is equivalent to a constant off-time in continuous mode (the off-time is the minimum off-time of the U2-I02 module);

[0061] In discontinuous mode, it is in the working and on-time control mode. The on-time is controlled by the I02 / I03 control of the U2 module, superimposed with the inductor current and mainly controlled by the voltage across RLIM superimposed with the inductor current. Since the inductor superimposed amount is mainly controlled by the inductor current in both discontinuous mode and continuous mode, the stability model is approximately the same as the peak current structure, so the loop compensation is relatively simple.

[0062] Since the PWM time control module U2 is provided in this switching power supply control circuit, there is no need to switch in the burst mode (light load), and the operating frequency and duty cycle will be automatically adjusted. In addition, since there is no fixed switching period, the jitter of the inductor current will not be amplified, resulting in sub-harmonic oscillation. Therefore, even without slope compensation, the loop is very stable, which can effectively improve the anti-noise ability.

[0063] In summary, the switching power supply control circuit provided by the present invention controls the PWM time control module U2 through the switch-on (TON) control module and combines peak current control, thus overcoming the deficiency of sub-harmonic oscillation. Among them, the current of the first switch branch is used as the on-time control, which is similar to the traditional peak current control, and the loop compensation method is easy to implement.

[0064] In addition, this switching power supply control circuit realizes Vfb buffering through the operational amplifier U5, isolates the influence of the inductor current IL on Vfb, and at the same time improves the applicable range of the circuit structure (since Vfb is voltage-divided by a resistor and has no driving ability). Without the existence of U5, this architecture can only directly feedback through VOUT (Vout has a large capacitor and driving ability), and cannot directly superimpose the inductor current component after voltage division by a resistor.

[0065] Since the AC feedback amount includes the inductor current, it can reduce the dependence on the capacitor parasitic equivalent resistance ESR of the capacitor COUT at the Vout end, thereby reducing the voltage ripple of Vout.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A switching power supply control circuit, characterized in that, Comprising: A switching power supply, a PWM control module, and a switch conduction control module; wherein: The switching power supply includes a first switch branch and a second switch branch; the first end of the first switch branch is connected to the input voltage terminal, its second end is connected to the first reference node, and the control end of the first switch branch is connected to the first end of the PWM control module; the first end of the second switch branch is connected to the first reference node, its second end is connected to the ground terminal, and the control end of the second switch branch is connected to the second end of the PWM control module; Wherein, the switching power supply is specifically configured to include a first switch branch composed of first-phase power tubes and a second switch branch composed of second-phase power tubes; The input end of the PWM control module is used to receive a PWM pulse signal, output a first driving signal through the first end, and output a second driving signal through the second end. The first driving signal is input into the first switch branch to conduct the input voltage terminal and the first reference node, and the second driving signal is input into the second switch branch to conduct the first reference node and the ground terminal; and The first end of the switch conduction control module is connected to the first reference node, the second end of the switch conduction control module is connected to the third end of the PWM control module. The switch conduction control module is used to collect the current at the first reference node, and when the current at the first reference node exceeds a preset threshold, turn off the first switch branch and turn on the second switch branch through the PWM control module; otherwise, adjust the PWM pulse signal using the current at the first reference node; The switch conduction control module includes: a current acquisition circuit, connected to the switching power supply, for collecting the current at the first reference node and processing it into a sink current for output; The switching power supply includes an output voltage terminal. The switch-mode power control circuit further includes: a lower voltage-dividing resistor, an upper voltage-dividing resistor, and an operational amplifier. The upper voltage-dividing resistor and the lower voltage-dividing resistor are connected in series between the output voltage terminal and the ground; the non-inverting input terminal of the operational amplifier is connected to the node between the upper voltage-dividing resistor and the lower voltage-dividing resistor, the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the fourth end of the current acquisition circuit. The operational amplifier is used to receive the divided output voltage of the switching power supply to generate a follower voltage and act on the sink current output from the fourth end of the current acquisition circuit.

2. The switching power supply control circuit according to claim 1, wherein The switch-mode power control circuit further includes a first inductor and a first resistor connected in series between the first reference node and the output voltage terminal. The first end of the current acquisition circuit is connected to the node between the first inductor and the first resistor, and the second end of the current acquisition circuit is connected to the node between the first resistor and the output voltage terminal; The first end and the second end of the current acquisition circuit are respectively used to collect the current at the corresponding node and output the corresponding sink currents through the third end and the fourth end of the current acquisition circuit.

3. The switching power supply control circuit according to claim 2, wherein The switch conduction control module further includes: an overcurrent comparator, the positive input terminal of the overcurrent comparator is connected to the third terminal of the current acquisition circuit, and the negative input terminal of the overcurrent comparator is used to input a reference voltage corresponding to the preset threshold; the output terminal of the overcurrent comparator is connected to the third terminal of the PWM control module, and the overcurrent comparator is used to compare the pull current output from the third terminal of the current acquisition circuit with the reference voltage corresponding to the preset threshold. When the pull current output from the third terminal of the current acquisition circuit is greater than the reference voltage, an off signal is output to control the PWM control module to turn off the first switch branch and turn on the second switch branch.

4. The switching power supply control circuit according to claim 2, wherein It further includes: a PWM comparator, the positive input terminal of the PWM comparator is used to input a PWM compensation signal, and the negative input terminal of the PWM comparator is connected to the fourth terminal of the current acquisition circuit; the output terminal of the PWM comparator is connected to the input terminal of the PWM control module; the PWM comparator is used to compare the pull current output from the fourth terminal of the current acquisition circuit with the PWM compensation signal to generate the PWM pulse signal and send it to the PWM control module.

5. The switching power supply control circuit according to claim 4, characterized in that It further includes: a compensation network, connected to the positive input terminal of the PWM comparator to generate the PWM compensation signal to the PWM comparator to generate the PWM pulse signal.

6. The switching power supply control circuit according to claim 5, wherein, It further includes: an error amplifier, the positive input terminal of the error amplifier is connected to the node between the upper voltage-dividing resistor and the lower voltage-dividing resistor, the negative input terminal of the error amplifier is used to access a reference target voltage, and the output terminal of the error amplifier is connected to the output terminal of the compensation network. The error amplifier is used to compare the error between the output voltage after voltage division of the switching power supply and the reference target voltage, and adjust the PWM compensation signal to accurately control the output voltage of the switching power supply.

7. The switching power supply control circuit according to claim 1 or 4, characterized in that, The PWM control module further includes a PWM time control module, and the PWM time control module includes a first signal generation unit, a second signal generation unit, and a third signal generation unit for adjusting the conduction time of the PWM pulse signal; wherein, the first signal generation unit is configured to receive the PWM signal and the PWM pulse signal to generate a minimum off-time control signal; the second signal generation unit is configured to receive the minimum off-time control signal and generate a maximum on-time control signal; the third signal generation unit is configured to receive the maximum on-time control signal and generate a minimum on-time control signal.

8. The switching power supply control circuit according to claim 7, characterized in that, The PWM control module further includes a switch tube driving unit, connected to the PWM time control module, for receiving the PWM pulse signal adjusted by the PWM time control module to generate the first driving signal and the second driving signal.

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