Ultra-low output voltage ripple control circuit and method and BUCK device

Abstract

The invention provides an ultra-low output voltage ripple control circuit and method and a BUCK device. The ultra-low output voltage ripple control circuit comprises a logic control and drive circuit and a two-stage feedback loop circuit. The logic control and drive circuit outputs a reduced voltage according to an input voltage and then inputs the reduced voltage into the two-stage feedback loop circuit; the two-stage feedback loop circuit obtains a first feedback voltage and a second feedback voltage according to the step-down voltage; and the logic control and drive circuit adjusts the on or off of the switching circuit according to the first feedback voltage and the second feedback voltage to realize the output voltage of the ultra-low output voltage ripple. The second-stage filter circuit is added to form a two-stage feedback loop circuit to achieve ultralow output voltage ripples, the output voltage can be accurately controlled by adding second-stage feedback loop control, and meanwhile, the whole loop is more stable by compensating a pole introduced by the feedback loop.

Description

Technical Field

[0001] The present application belongs to the field of power supply control technology, and in particular, relates to an ultra-low output voltage ripple control circuit, method and BUCK device. Background Art

[0002] In the field of power control technology, voltage converters are often deployed in various electronic devices to convert power supply voltage into the required working voltage. Buck control devices are a type of DC-DC converter, which are often used to convert higher DC voltages into lower DC voltages.

[0003] In actual applications, when the BUCK control device is connected or disconnected from the load, the load current will change instantaneously, which will lead to unstable output voltage of the BUCK control device. In addition, DC voltage is often obtained by rectifying and filtering AC voltage. Due to unclean filtering, there will be residual AC components, and even if it is powered by a battery, ripples will be generated due to load fluctuations.

[0004] When powering sensitive systems with precision loads, the buck power supply needs to meet the ultra-low ripple requirement, but the traditional BUCK circuit is difficult to achieve. Therefore, an ultra-low output voltage ripple control circuit is urgently needed to meet the ultra-low voltage ripple requirement of the buck power supply output.

[0005] The above statements are only used to provide background technical information related to the present application. Unless otherwise stated herein, the contents described in this section are not prior art for the contents of other parts of the present application. Summary of the invention

[0006] The ultra-low output voltage ripple control circuit proposed by the present invention enables the output voltage to be accurately controlled by adding feedback loop control, and at the same time makes the overall loop more stable by compensating for the pole introduced by the feedback loop.

[0007] According to a first aspect of an embodiment of the present application, an ultra-low output voltage ripple control circuit is provided, comprising a logic control and drive circuit and a two-stage feedback loop circuit; after the logic control and drive circuit outputs a step-down voltage according to an input voltage, the step-down voltage is input into the two-stage feedback loop circuit; The two-stage feedback loop circuit obtains a first feedback voltage and a second feedback voltage according to the step-down voltage; The logic control and driving circuit adjusts the on or off state of the switch circuit according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit to achieve an output voltage with ultra-low output voltage ripple.

[0008] In some embodiments of the present application, the two-stage feedback loop circuit includes a voltage fast loop feedback circuit and a voltage slow loop feedback circuit; The voltage fast loop feedback circuit is used to generate a first output voltage after the step-down voltage is subjected to a first filtering, and to generate a first feedback voltage after the first output voltage is subjected to a first voltage division; The voltage slow loop feedback circuit is used to generate a second output voltage after the first output voltage is subjected to a second filtering, and to generate a second feedback voltage after the second output voltage is subjected to a second voltage division.

[0009] In some embodiments of the present application, the two-stage feedback loop circuit further includes a feedback voltage processing circuit; The input end of the feedback voltage processing circuit is connected to the output end of the voltage fast loop feedback circuit and the output end of the voltage slow loop feedback circuit; The feedback voltage processing circuit is used to obtain a control voltage according to the first feedback voltage and the second feedback voltage; the control voltage is used to generate a modulation signal; The logic control and drive circuit adjusts the on or off of the switch circuit according to the modulation signal to achieve an output voltage with ultra-low output voltage ripple.

[0010] In some embodiments of the present application, the voltage fast loop feedback circuit includes a first filter circuit and a first voltage divider circuit; The input end of the first filter circuit is connected to the output end of the logic control and drive circuit; the output end of the first filter circuit is connected to the first voltage divider circuit; A first filtering circuit, used for filtering the stepped-down voltage after the logic control and driving circuit steps down the voltage to obtain a first output voltage; The first voltage divider circuit is used to obtain a first feedback voltage after performing a first voltage division according to the first output voltage.

[0011] In some embodiments of the present application, the voltage slow loop feedback circuit includes a second filter circuit and a second voltage divider circuit; The input end of the second filter circuit is connected to the output end of the first filter circuit; the output end of the second filter circuit is connected to the second voltage divider circuit; A second filtering circuit, used for performing a second filtering on the first output voltage to obtain a second output voltage; The second voltage divider circuit is used to obtain a second feedback voltage after performing a second voltage division according to the second output voltage.

[0012] In some embodiments of the present application, the feedback voltage processing circuit includes a high-pass circuit, a first error amplifier circuit, a second error amplifier circuit, a current summing circuit, and an integral compensation circuit; The first feedback voltage at the output end of the voltage fast loop feedback circuit is connected to the input end of the high-pass circuit; the output end of the high-pass circuit is connected to the negative input end of the first error amplifier circuit, and the positive input end of the first error amplifier circuit is connected to a constant voltage; The first error amplifier circuit obtains a first difference voltage according to the first feedback voltage and the constant voltage; The second feedback voltage at the output end of the voltage slow loop feedback circuit is connected to the negative input end of the second error amplifier circuit, and the positive input end of the second error amplifier circuit is connected to the reference voltage; The second error amplifier circuit obtains a second difference voltage according to the second feedback voltage and the reference voltage; The current summing circuit superimposes the first difference voltage and the second difference voltage and inputs the superimposed voltage into the integral compensation circuit for compensation to obtain a control voltage.

[0013] In some embodiments of the present application, a voltage comparison circuit is also included; The control voltage is input into the negative input terminal of the voltage comparison circuit; the positive input terminal of the voltage comparison circuit is connected to the compensation voltage; The voltage comparison circuit generates a modulation signal after comparing the control voltage and the compensation voltage.

[0014] According to a third aspect of an embodiment of the present application, there is provided an ultra-low output voltage ripple control method, comprising: Output a step-down voltage according to the input voltage; Obtaining a first feedback voltage and a second feedback voltage according to the step-down voltage; The on / off state of the switch circuit is regulated according to the first feedback voltage and the second feedback voltage to achieve an output voltage with ultra-low output voltage ripple.

[0015] In some implementations of the present application, obtaining a first feedback voltage and a second feedback voltage according to the step-down voltage includes: The step-down voltage is filtered by a first method to generate a first output voltage, and the first output voltage is divided by a first method to generate a first feedback voltage; The first output voltage is subjected to a second filtering process to generate a second output voltage, and the second output voltage is subjected to a second voltage division process to generate a second feedback voltage.

[0016] In some implementations of the present application, regulating the on or off of the switch circuit according to the first feedback voltage and the second feedback voltage includes: Obtaining a control voltage according to the first feedback voltage and the second feedback voltage; generating a modulation signal according to the control voltage; The on or off state of the switch circuit is adjusted according to the modulation signal.

[0017] In some implementations of the present application, obtaining a control voltage according to the first feedback voltage and the second feedback voltage includes: Obtaining a first difference voltage according to the first feedback voltage and the constant voltage; Obtaining a second difference voltage according to the second feedback voltage and the reference voltage; The first difference voltage and the second difference voltage are superimposed and then input into an integral compensation circuit for compensation to obtain a control voltage.

[0018] According to a third aspect of the embodiments of the present application, a BUCK control device is provided, comprising any of the above ultra-low output voltage ripple control circuits; the ultra-low output voltage ripple control circuit comprises a logic control and drive circuit and a two-stage feedback loop circuit; The logic control and driving circuit adjusts the on or off state of the switch circuit according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit to achieve an output voltage with ultra-low output voltage ripple.

[0019] An ultra-low output voltage ripple control circuit, method and BUCK device of the present application are adopted, and the ultra-low output voltage ripple control circuit includes a logic control and drive circuit and a two-stage feedback loop circuit; after the logic control and drive circuit outputs a buck voltage according to the input voltage, it inputs the two-stage feedback loop circuit; the two-stage feedback loop circuit obtains a first feedback voltage and a second feedback voltage according to the buck voltage; the logic control and drive circuit adjusts the conduction or shutdown of the switch circuit according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit, so as to achieve an output voltage with ultra-low output voltage ripple.

[0020] This application increases the feedback loop control so that the output voltage can be precisely controlled, and at the same time, the pole introduced by the compensation feedback loop is made more stable. While achieving the output ultra-low voltage ripple requirement, the system efficiency and output voltage load regulation rate are improved compared to the existing solutions.

[0021] Overall, the following are achieved: 1. Add two-stage LC filtering to achieve ultra-low output ripple. 2. Feedback the output voltage of the two-stage LC, and achieve precise control of the output voltage of the two-stage LC through loop regulation. 3. Feedback the output voltage of the first and second stages of LC, generate a zero point through the addition of fast and slow loops, compensate the two-stage LC, and achieve loop stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 A schematic diagram of a BUCK circuit provided in an embodiment of the present application; Figure 2 Another BUCK circuit schematic diagram provided in an embodiment of the present application; Figure 3 Another BUCK circuit schematic diagram provided in an embodiment of the present application; Figure 4: shows a structural schematic diagram of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application; Figure 5 : shows a structural schematic diagram of another ultra-low output voltage ripple control circuit provided according to an embodiment of the present application; Figure 6 : shows a structural schematic diagram of another ultra-low output voltage ripple control circuit provided according to an embodiment of the present application; Figure 7 : shows a structural schematic diagram of another ultra-low output voltage ripple control circuit provided according to an embodiment of the present application; Figure 8 : shows a circuit schematic diagram of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application; Fig. 9 A loop compensation Bode diagram provided according to an embodiment of the present application is shown in FIG. Fig.10 , a voltage waveform diagram of an output ripple of a two-stage LC dual voltage loop BUCK provided according to an embodiment of the present application is shown; Fig.11 A schematic diagram of the steps of an ultra-low output voltage ripple control method provided according to an embodiment of the present application is shown in FIG. Fig.12 A schematic diagram of the steps of another ultra-low output voltage ripple control method provided according to an embodiment of the present application is shown in FIG. Fig.13 : shows a schematic structural diagram of a BUCK control device according to an embodiment of the present application; Fig.14 Graph 1 shows a schematic diagram of the structure of an ultra-low output voltage ripple control system according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] Regarding this application, considering that when powering sensitive systems with precision loads, the buck power supply needs to meet the ultra-low ripple requirement, but the traditional BUCK circuit is difficult to achieve.

[0024] The buck control device can realize the voltage reduction process of DC to DC by providing a buck circuit.

[0025] Figure 1 A schematic diagram of a BUCK circuit provided in an embodiment of the present application. As an example, Figure 1 The BUCK circuit in the circuit adopts the peak current control mode, by sampling V OUT voltage, V OUT Voltage Divider V FB Feedback to the negative input of the error amplifier circuit gm, and the reference voltage V REFThe difference is magnified to V COMP The voltage can control the peak value of the inductor current. Through the voltage loop, the output voltage V can be accurately adjusted. OUT to the preset value.

[0026] See also Figure 1 , when the circuit operates in continuous conduction mode, V OUT Voltage ripple The expression is: ; Among them, Vo is the output voltage, Vi is the input voltage, f is the switching frequency, L is the inductance, and ESR is the equivalent resistance of the output capacitor. In common applications, f is from hundreds of kHz to several MHz, L is from hundreds of nH to tens of μH, and the capacitance Co is from tens to hundreds of μF. The ripple can be from tens of mV to several mV.

[0027] From the formula, we can see that increasing the switching frequency f can reduce the output ripple . In some applications, the frequency is increased to 10MHz to achieve a ripple of several hundred μV, but the increase in switching frequency will increase switching losses and reduce system efficiency. On the other hand, the switching frequency is limited by the minimum on-time and is not suitable for small duty cycle applications. If the output ripple is to be further reduced, it is difficult to further increase the switching frequency with existing technology. It can also be seen from the formula that increasing the inductance L can reduce the output ripple. However, increasing the inductance will increase or decrease the system loop bandwidth, making the transient response worse. At the same time, a large inductor will increase the size and cost of the solution, and the benefits of reducing ripple are limited.

[0028] Figure 2 Another BUCK circuit schematic diagram provided in the embodiment of the present application. Figure 1 The output ripple is reduced on the basis of Vdropout, and a linear regulator is connected in series after the circuit. The linear regulator has the characteristics of high power supply rejection ratio, which can convert the output voltage of the BUCK circuit into an ultra-low ripple output voltage. However, this solution has several disadvantages. First, the output current capacity of general linear regulators is small. For larger output current requirements, the cost of linear regulators will increase significantly. Secondly, the working conditions of the linear regulator need to meet the input and output voltages greater than the Vdropout voltage. When the load current is large, this will bring greater losses and significantly reduce the system efficiency.

[0029] Figure 3 Another BUCK circuit diagram provided in the embodiment of the present application. In order to reduce system cost and improve system efficiency, as Figure 3 As shown in FIG. 1 , two LC circuits are connected in series after the BUCK circuit. The two LC circuits can attenuate the BUCK output voltage ripple by a second-order coefficient, which can significantly reduce the output voltage ripple.

[0030] By setting a suitable LC, the output voltage ripple can be attenuated to the μV level. Figure 3 In this solution, the output voltage is not fed back to the BUCK system loop, that is, open-loop control, and the output voltage cannot be accurately controlled. When there is a certain equivalent series resistance DCR on the two-stage inductor, the larger output current will form a voltage drop on the resistance DCR, and the output voltage is no longer the expected value.

[0031] In summary, the present invention provides a preferred implementation of an ultra-low output voltage ripple control circuit, which enables the output voltage to be precisely controlled by adding feedback loop control, and at the same time makes the overall loop more stable by compensating for the pole introduced by the feedback loop.

[0032] The present invention provides an ultra-low output voltage ripple control circuit, method and BUCK device, which solves the problem that the output voltage cannot be accurately controlled. The output voltage is fed back to the system loop, and the loop is automatically adjusted, so that the voltage is accurately controlled.

[0033] The present invention also considers that adding two stages of LC will introduce additional lower conjugate poles. If the output voltage is directly fed back to the error amplifier circuit of the traditional BUCK circuit, the system will not be stable. Therefore, the present invention not only feeds back the output voltage of the two stages of LC, but also compensates for the poles introduced by the two stages of LC, making the overall loop more stable.

[0034] In order to make the technical solutions and advantages in the embodiments of the present application more clearly understood, the exemplary embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0035] Example 1 Figure 4 Detailed description is given in the figure which illustrates a schematic diagram of the structure of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application.

[0036] like Figure 4 As shown, an ultra-low output voltage ripple control circuit of an embodiment of the present application includes a logic control and drive circuit 10 and a two-stage feedback loop circuit 20; after the logic control and drive circuit outputs a step-down voltage according to the input voltage, the voltage is input into the two-stage feedback loop circuit 20; The two-stage feedback loop circuit 20 obtains a first feedback voltage V according to the step-down voltage FB1 And the second feedback voltage V FB2 ; The logic control and driving circuit is based on the first feedback voltage V of the two-stage feedback loop circuit 20. FB1And the second feedback voltage V FB2 , adjust the on or off of the switching circuit to achieve an output voltage with ultra-low output voltage ripple.

[0037] Figure 5 Detailed description is given in the figure which shows a schematic diagram of the structure of another ultra-low output voltage ripple control circuit provided according to an embodiment of the present application.

[0038] like Figure 5 As shown, the two-stage feedback loop circuit 20 includes a voltage fast loop feedback circuit 21 and a voltage slow loop feedback circuit 22; The voltage fast loop feedback circuit 21 is used to generate a first output voltage V after the step-down voltage is filtered first. OUT-LC1 , the first output voltage V OUT-LC1 After the first voltage division, the first feedback voltage V is generated FB1 ; The voltage slow loop feedback circuit 22 is used to convert the first output voltage V OUT-LC1 After the second filtering, the second output voltage V OUT-LC2 , the second output voltage V OUT-LC2 After the second voltage division, the second feedback voltage V is generated FB2 .

[0039] Figure 6 Detailed description is given in the figure which illustrates a schematic diagram of the structure of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application.

[0040] like Figure 6 As shown, in a specific implementation, the two-stage feedback loop circuit 20 further includes a feedback voltage processing circuit 30 .

[0041] An input end of the feedback voltage processing circuit 30 is connected to an output end of the voltage fast loop feedback circuit 21 and an output end of the voltage slow loop feedback circuit 22 .

[0042] The feedback voltage processing circuit 30 is used to process the first feedback voltage V FB1 And the second feedback voltage V FB2 , and obtain a control voltage; the control voltage is used to generate a modulation signal; the logic control and drive circuit adjusts the on or off of the switch circuit according to the modulation signal to achieve an output voltage with ultra-low output voltage ripple.

[0043] Figure 7 Detailed description is given in the figure which illustrates a schematic diagram of the structure of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application.

[0044] like Figure 7 As shown, the voltage fast loop feedback circuit 21 includes a first filter circuit 211 and a first voltage divider circuit 212 .

[0045] The input end of the first filter circuit 211 is connected to the output end of the logic control and driving circuit; the output end of the first filter circuit 211 is connected to the first voltage divider circuit 212 .

[0046] The first filter circuit 211 is used to filter the voltage dropped by the logic control and driving circuit to obtain a first output voltage V OUT-LC1 ; The first voltage divider circuit 212 is used to divide the first output voltage V OUT-LC1 After the first voltage division, the first feedback voltage V is obtained. FB1 .

[0047] like Figure 7 As shown, the voltage slow loop feedback circuit 22 includes a second filter circuit 221 and a second voltage divider circuit 222 .

[0048] An input end of the second filter circuit 221 is connected to an output end of the first filter circuit 211 ; an output end of the second filter circuit 221 is connected to a second voltage divider circuit 222 .

[0049] The second filter circuit 221 is used to filter the first output voltage V OUT-LC1 After the second filtering, the second output voltage V OUT-LC2 ; The second voltage divider circuit 222 is used to divide the second output voltage V OUT-LC2 After the second voltage division, the second feedback voltage V is obtained. FB2 .

[0050] Figure 8 Graph 1 shows a circuit diagram of an ultra-low output voltage ripple control circuit provided according to an embodiment of the present application.

[0051] like Figure 8 As shown, in the feedback voltage processing circuit 30, the first error amplifier circuit converts V FB2 and V REF The difference is amplified and converted into a first error current signal IOS1.

[0052] The second error amplifier circuit converts V FB1 V obtained through the high-pass circuit FB1_HF and A GND The difference is amplified and converted into a second error current signal IOS2.

[0053] The first error current signal IOS1 and the second error current signal IOS2 are summed by the current summing circuit and then integrated by the integral compensation circuit to obtain the total control voltage V COMP .

[0054] In the voltage comparison circuit 40, the control voltage V COMP and the peak current reference voltage VIPK By comparison, a PWM modulation signal is obtained.

[0055] In a further specific implementation, the feedback voltage processing circuit 30 includes a high-pass circuit 31 , a first error amplifier circuit gm1 , a second error amplifier circuit gm2 , a current summing circuit 32 , and an integral compensation circuit 33 .

[0056] like Figure 8 As shown, the high-pass circuit includes a unity gain buffer, a high-pass filter capacitor C HF , high pass filter resistor R HF The integral compensation circuit includes an integral compensation circuit composed of a resistor Rcomp and a capacitor Ccomp.

[0057] The first feedback voltage V at the output end of the voltage fast loop feedback circuit 21 FB1 The output end of the high-pass circuit is connected to the negative input end of the first error amplifier circuit gm1, and the positive input end of the first error amplifier circuit gm1 is connected to a constant voltage; the first error amplifier circuit gm1 is connected to the first feedback voltage V FB1 and a constant voltage to perform a difference operation to obtain a first difference voltage.

[0058] The second feedback voltage V at the output end of the voltage slow loop feedback circuit 22 FB2 The negative input terminal of the second error amplifier circuit gm2 is connected, and the positive input terminal of the second error amplifier circuit gm2 is connected to the reference voltage; the second error amplifier circuit gm2 is connected according to the second feedback voltage V FB2 A difference operation is performed on the reference voltage to obtain a second difference voltage.

[0059] Finally, the current summing circuit superimposes the first difference voltage and the second difference voltage and inputs the superimposed voltage into the integral compensation circuit for compensation to obtain the control voltage Vcomp.

[0060] like Figure 8 As shown, when the specific circuit is connected, the first filter circuit 211 includes a first inductor L1 and a first capacitor C1.

[0061] The logic control and drive circuit 10 includes a logic control and drive chip and a switch circuit. The switch circuit includes a first MOS switch tube S1 and a second MOS switch tube S2. The intermediate node between the first MOS switch tube S1 and the second MOS switch tube S2 serves as the output end of the logic control and drive circuit 10 to output a step-down voltage.

[0062] The output end of the logic control and driving circuit 10 is connected to the input end of the first inductor L1, and the output end of the first inductor L1 is connected to the first capacitor C1 and then grounded; the output end of the first inductor L1 outputs a first output voltage V OUT-LC1 .

[0063] The output end of the first filter circuit 211, i.e., the output end of the first inductor L1, is connected to the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 in sequence and then grounded. The common node of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 outputs the first feedback voltage V FB1 ; The first feedback voltage V FB1 Input unity gain buffer, the output of unity gain buffer X1 is connected to high pass filter capacitor C HF And the high-pass filter resistor R HF Grounded at the back; high-pass filter capacitor C HF And the high-pass filter resistor R HF The common end of the first error amplifier circuit gm1 is connected to the negative input end, and the constant power supply is connected to the positive input end of the first error amplifier circuit gm1; The first error amplifier circuit gm1 is based on the first feedback voltage V FB1 and a constant voltage to obtain a first difference voltage.

[0064] like Figure 8 As shown, the second filtering circuit 221 includes a second inductor L2 and a second capacitor C2.

[0065] The output end of the first filter circuit 211, i.e., the output end of the first inductor L1, is connected to the input end of the second inductor L2. The output end of the second inductor L2 is connected to the second capacitor C2 and then grounded. The output end of the second inductor L2 outputs a second output voltage V OUT-LC2 .

[0066] like Figure 8 As shown, the second voltage-dividing circuit 222 includes a third voltage-dividing resistor R3 and a fourth voltage-dividing resistor R4.

[0067] The output end of the second filter circuit 221, i.e., the output end of the second inductor L2, is connected to the third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4 in sequence and then grounded. The common node of the third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4 outputs the second feedback voltage V FB2 .

[0068] The second feedback voltage V FB2 Input the negative input terminal of the second error amplifier circuit gm2, the reference voltage V REF The circuit is connected to the positive input terminal of the second error amplifier circuit gm2; the second error amplifier circuit gm2 is connected to the positive input terminal of the second error amplifier circuit gm2 according to the second feedback voltage V FB2 And the reference voltage V REF , and obtain a second difference voltage.

[0069] like Figure 7 and 8As shown, the control circuit of the present application also includes a voltage comparison circuit 40, and the control voltage Vcomp of the feedback voltage processing circuit 30 is input into the negative input terminal of the voltage comparison circuit 40; the positive input terminal of the voltage comparison circuit 40 is connected to the compensation voltage; finally, the voltage comparison circuit 40 generates a modulation signal after comparing the control voltage and the compensation voltage.

[0070] Specifically, the total difference voltage Vcomp obtained by superimposing the first difference voltage at the output end of the first voltage divider circuit 212 and the second difference voltage at the output end of the second voltage divider circuit 222 is input to the negative input end of the voltage comparison circuit comp; the compensation voltage Vipk of the compensation voltage Vipk circuit is input to the positive input end of the voltage comparison circuit comp.

[0071] Finally, the voltage comparison circuit comp generates a modulation signal after comparing the total voltage difference with the compensation voltage Vipk.

[0072] In principle, as further explained, Figure 8 As shown, the control circuit of the embodiment of the present application simultaneously feeds back the output voltage V of the first LC OUT-LC1 And the output voltage V of the two-stage LC OUT-LC2 .

[0073] The output voltage of the two-stage LC is V OUT-LC2 After the voltage is divided by the voltage divider resistors R3 and R4, V FB2 Feedback to the negative input terminal of the main error amplifier circuit gm1 and the reference voltage V REF The difference is magnified to V COMP voltage, controlling the peak value of the inductor current.

[0074] Through the voltage outer loop, the output voltage V can be accurately adjusted OUT- LC2 to the preset value.

[0075] The output voltage of the first LC is V OUT-LC1 After the voltage is divided by the voltage divider resistors R1 and R2, V FB1 First through a unity gain buffer X1, and C HP and R HP The high-pass network is sent to the negative input terminal of the auxiliary error amplifier circuit gm2, and the difference between it and the zero potential reference voltage input at the positive terminal is amplified and superimposed on V COMP Voltage, that is, voltage fast loop feedback V OUT-LC1 The AC signal is added to the main loop to produce a zero point to compensate for the pole introduced by the two-stage LC.

[0076] Fig. 9 A loop compensation Bode diagram provided according to an embodiment of the present application is shown in FIG.

[0077] like Fig. 9 The Bode diagram of loop compensation is shown in Figure 1.

[0078] The green line F represents the phase-frequency curve of the voltage slow loop. The green line F is the phase margin of the slow loop only. From point F1, it can be seen that it drops sharply near the bandwidth, and the system is unstable due to insufficient phase margin. If there is no compensation, a pair of conjugate poles brought by the two-stage LC will cause the phase-frequency curve to drop rapidly, resulting in loop instability.

[0079] The blue line D represents the phase-frequency curve of the voltage fast loop. It can be seen from point D1 in the figure that the zero pair introduced by the fast loop has a steep increase in phase margin and can compensate for the pole pair of the slow loop.

[0080] Therefore, after the fast loop is introduced, the phase-frequency curve of the fast and slow loops is shown as the red line E, which is the phase margin after the fast and slow loops are added and summed. It can be seen from point E1 that the change is gentle near the bandwidth and the phase margin is sufficient. Therefore, the zero point generated by the addition of the fast and slow loops can compensate for the poles brought by the two-stage LC, making the overall phase-frequency curve of the total loop smooth, and the phase margin is sufficient, ensuring the stability of the system.

[0081] Others, such as the cyan A line in the figure is the gain curve of the slow loop, the purple B line is the gain curve of the fast loop, and the yellow C line is the gain curve of the fast and slow loops added together. It can be seen that the yellow line is the gain curve after the fast and slow loops are added together, and it changes smoothly near the bandwidth.

[0082] Fig.10 Graph 2 shows a voltage waveform diagram of an output ripple of a two-stage LC dual voltage loop BUCK according to an embodiment of the present application.

[0083] like Fig.10 As shown, the output voltage V OUT-LC1 The ripple is 1.5mV, which is the value that can be achieved by traditional bucks. The output voltage V OUT-LC2 The ripple is 12uV, and the coefficient of two-stage LC attenuation is about 1 / 120, which is difficult to achieve by increasing the switching frequency and inductance size. On the other hand, the system output voltage is preset to 1.5V, which can also be accurately controlled through the feedback loop.

[0084] In summary, the embodiment of the present application achieves the final output voltage V OUT- LC2 Precise control Process: (Precise control refers to the DC characteristics in steady state) First, V OUT-LC2 The second feedback voltage V is obtained by dividing the voltage through the voltage dividing resistors R3 and R4 FB2 After that, it is fed back to the negative input terminal of gm1. gm1 is an error operational amplifier that amplifies the V FB2and the reference voltage V at the non-inverting input REF The difference between COMP The voltage goes to V IPK To compare and control the peak value of the inductor current.

[0085] When V FB2 Less than V REF , that is, V OUT-LC2 is lower than the preset voltage, then V COMP Increase, control the inductor current peak to increase, add more current to increase V OUT-LC2 When V FB2 Greater than V REF , that is, V OUT-LC2 higher than the preset voltage, then V COMP decreases, controlling the inductor current peak value to decrease, making V OUT-LC2 Reduce. V FB2 The negative input terminal of gm1 is fed back into the loop to form negative feedback, thereby accurately adjusting V FB2 , so that V OUT-LC2 is precisely controlled.

[0086] Although the sum of gm1 and gm2 gives V COMP , that is, there is V in the loop FB1 and V FB2 Two voltages are negatively fed back, but in steady state, V FB1 The change is very small, so the small AC signal error at the input end of gm2 is very small, while on the other hand, the DC signal cannot pass through C HF and R HF The high-pass network is composed of FB2 The accuracy will not be affected by V FB1 The impact of feedback.

[0087] Regarding the process of achieving loop stability in the embodiment of the present application: (stability refers to the AC characteristics under transient conditions) During transient changes, V OUT- LC1 Through R FB1 and R FB2 The first feedback voltage V is obtained by voltage division FB1 , through a unity gain buffer, C HF and R HF After the high-pass network, the feedback is fed back to the negative input terminal of gm2, which can adjust V faster. COMP , to control the peak value of the inductor current. The sum of the output currents of gm1 and gm2 can generate a zero point to compensate for the conjugate poles of the two-stage LC, making the overall loop more stable.

[0088] Compared with the prior art, the embodiments of the present application achieve ultra-low output ripple while ensuring the accuracy of the output voltage and improving system efficiency.

[0089] Overall, the following are achieved: 1. Add two-stage LC filtering to achieve ultra-low output ripple. 2. Feedback the output voltage of the two-stage LC, and achieve precise control of the output voltage of the two-stage LC through loop regulation. 3. Feedback the output voltage of the first and second stages of LC, generate a zero point through the addition of fast and slow loops, compensate the two-stage LC, and achieve loop stability.

[0090] The ultra-low output voltage ripple control circuit of the present application includes a logic control and drive circuit and a two-stage feedback loop circuit; after the logic control and drive circuit outputs a step-down voltage according to the input voltage, the step-down voltage is input into the two-stage feedback loop circuit; the two-stage feedback loop circuit obtains a first feedback voltage and a second feedback voltage according to the step-down voltage; the logic control and drive circuit adjusts the on or off state of the switch circuit according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit, thereby realizing an output voltage with an ultra-low output voltage ripple.

[0091] This application increases the feedback loop control so that the output voltage can be precisely controlled, and at the same time, the pole introduced by the compensation feedback loop is made more stable. While achieving the output ultra-low voltage ripple requirement, the system efficiency and output voltage load regulation rate are improved compared to the existing solutions.

[0092] Example 2 The present application also provides an ultra-low output voltage ripple control method. For details not disclosed in the ultra-low output voltage ripple control method of this embodiment, please refer to the specific implementation content of the ultra-low output voltage ripple control circuit in other embodiments.

[0093] Fig.11 Detailed description is given in the figure which illustrates a step diagram of an ultra-low output voltage ripple control method provided according to an embodiment of the present application.

[0094] like Fig.11 As shown, an ultra-low output voltage ripple control method includes: S1: Outputs step-down voltage according to input voltage; S2: Get the first feedback voltage V according to the step-down voltage FB1 And the second feedback voltage V FB2 ; S3: According to the first feedback voltage V FB1 And the second feedback voltage V FB2 Adjust the on or off state of the switch circuit to achieve an output voltage with ultra-low output voltage ripple.

[0095] Fig.12 Detailed description is given in the figure which illustrates a step diagram of an ultra-low output voltage ripple control method provided according to an embodiment of the present application.

[0096] like Fig.12 As shown, in S2, the first feedback voltage V is obtained according to the step-down voltage FB1 And the second feedback voltage V FB2 ,include: S21: Generate a first output voltage V after filtering the stepped-down voltage OUT-LC1 , the first output voltage V OUT-LC1 After the first voltage division, the first feedback voltage V is generated FB1 ; S22: The first output voltage V OUT-LC1 After the second filtering, the second output voltage V OUT-LC2 , the second output voltage V OUT-LC2 After the second voltage division, the second feedback voltage V is generated FB2 .

[0097] In specific implementation, in S3, according to the first feedback voltage V FB1 And the second feedback voltage V FB2 Adjust the on or off of the switch circuit, including: 1) According to the first feedback voltage V FB1 And the second feedback voltage V FB2 , and obtain the control voltage.

[0098] In specific implementation, first, according to the first feedback voltage V FB1 and a constant voltage to obtain a first difference voltage; secondly, according to the second feedback voltage V FB2 and a reference voltage to obtain a second difference voltage; finally, the first difference voltage and the second difference voltage are superimposed and input into an integral compensation circuit for compensation to obtain a control voltage.

[0099] According to the first feedback voltage V FB1 Performing a first difference operation to generate a first difference voltage includes: according to the first feedback voltage V FB1 Compare with the constant voltage to determine the first feedback voltage V FB1 Whether it exceeds the constant voltage; if so, generating a first difference voltage.

[0100] According to the second feedback voltage V FB2 Performing a second difference operation to generate a second difference voltage includes: according to the second feedback voltage V FB2 and reference voltage V REF Compare and determine the first feedback voltage V FB1 Whether it exceeds the reference voltage V REF range; if exceeded, a second difference voltage is generated.

[0101] 2) Generate a modulation signal according to the control voltage.

[0102] The specific implementation includes: obtaining a total difference voltage according to the first feedback voltage and the second feedback voltage; determining whether the total difference voltage exceeds the compensation voltage Vipk range; and generating a modulation signal if the total difference voltage exceeds the compensation voltage Vipk range.

[0103] 3) Adjust the on or off of the switching circuit according to the modulation signal.

[0104] In some embodiments of the present application, according to the first feedback voltage V FB1 And the second feedback voltage V FB2 , get the control voltage, including: By adopting the ultra-low output voltage ripple control method of the present application, the on or off state of the switch circuit is adjusted according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit to achieve an output voltage with ultra-low output voltage ripple.

[0105] The output voltage can be precisely controlled by adding feedback loop control, and the pole introduced by the compensation feedback loop makes the overall loop more stable. While achieving the output ultra-low voltage ripple requirement, the system efficiency and output voltage load regulation rate are improved compared to existing solutions.

[0106] Example 3 This embodiment provides a BUCK control device. For details not disclosed in the BUCK control device of this embodiment, please refer to the specific implementation content of the ultra-low output voltage ripple control circuit in other embodiments.

[0107] Fig.13 A structural schematic diagram of a BUCK control device according to an embodiment of the present application is shown in FIG.

[0108] like Fig.13 As shown, the BUCK control device includes: an ultra-low output voltage ripple control circuit; the ultra-low output voltage ripple control circuit includes a logic control and drive circuit 10 and a two-stage feedback loop circuit 20.

[0109] The logic control and driving circuit 10 generates a first feedback voltage V according to the two-stage feedback loop circuit 20. FB1 And the second feedback voltage V FB2 , adjust the on or off of the switching circuit to achieve an output voltage with ultra-low output voltage ripple.

[0110] The BUCK control device of the present application can accurately control the output voltage by adding feedback loop control, and at the same time, the pole introduced by the compensation feedback loop is made more stable. While achieving the output ultra-low voltage ripple requirement, the system efficiency and output voltage load regulation rate are improved compared with the existing solutions.

[0111] Example 4 This embodiment provides an ultra-low output voltage ripple control system. For details not disclosed in the ultra-low output voltage ripple control system of this embodiment, please refer to the specific implementation content of the ultra-low output voltage ripple control circuit or method in other embodiments.

[0112] Fig.14 Graph 1 shows a schematic diagram of the structure of an ultra-low output voltage ripple control system according to an embodiment of the present application.

[0113] like Fig.14 As shown, the ultra-low output voltage ripple control system 400 includes: a storage unit 402: used to store executable instructions; and a processing unit 401: used to connect to the storage unit 402 to execute the executable instructions to complete the ultra-low output voltage ripple control method.

[0114] Those skilled in the art will understand that Fig.14 It is only an example of the ultra-low output voltage ripple control system 400 and does not constitute a limitation of the ultra-low output voltage ripple control system 400. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the ultra-low output voltage ripple control system 400 may also include input and output devices, network access devices, buses, etc.

[0115] The so-called processing unit 401 (Central Processing Unit, CPU) can also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application-specific integrated circuits (Application Specific Integrated Circuit, ASIC), field-programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processing unit 401 can also be any conventional processor, etc. The processing unit 401 is the control center of the ultra-low output voltage ripple control system 400, and uses various interfaces and lines to connect various parts of the entire ultra-low output voltage ripple control system 400.

[0116] The storage unit 402 can be used to store computer-readable instructions. The processing unit 401 implements various functions of the ultra-low output voltage ripple control system 400 by running or executing the computer-readable instructions or modules stored in the storage unit 402 and calling the data stored in the storage unit 402. The storage unit 402 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the ultra-low output voltage ripple control system 400, etc. In addition, the storage unit 402 can include a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM) or other non-volatile / volatile storage devices.

[0117] If the module integrated in the ultra-low output voltage ripple control system 400 is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also instruct the relevant hardware to complete it through computer-readable instructions. The computer-readable instructions can be stored in a computer-readable storage medium, and when the computer-readable instructions are executed by the processor, the steps of each of the above-mentioned method embodiments can be implemented.

[0118] Example 5 This embodiment provides a computer-readable storage medium on which a computer program is stored; the computer program is executed by a processor to implement the ultra-low output voltage ripple control circuit in other embodiments.

[0119] In summary, by using the ultra-low output voltage ripple control system and storage medium of the present application, the output voltage can be precisely controlled by adding feedback loop control, and the pole introduced by the compensation feedback loop is made more stable. While achieving the output ultra-low voltage ripple requirement, the system efficiency and output voltage load regulation rate are improved compared to the existing solutions.

[0120] Those skilled in the art will appreciate that the terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms of "a", "said" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0121] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0122] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0123] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. An ultra-low output voltage ripple control circuit, characterized in that: It includes a logic control and drive circuit and a two-stage feedback loop circuit; the logic control and drive circuit outputs a step-down voltage according to the input voltage and then inputs the step-down voltage into the two-stage feedback loop circuit; The two-stage feedback loop circuit obtains a first feedback voltage and a second feedback voltage according to the step-down voltage; The logic control and drive circuit adjusts the on or off state of the switch circuit according to the first feedback voltage and the second feedback voltage to achieve an output voltage with ultra-low output voltage ripple.

2. The ultra-low output voltage ripple control circuit according to claim 1, characterized in that: The two-stage feedback loop circuit includes a voltage fast loop feedback circuit and a voltage slow loop feedback circuit; The voltage fast loop feedback circuit is used to generate a first output voltage after the step-down voltage is subjected to a first filtering, and to generate a first feedback voltage after the first output voltage is subjected to a first voltage division; The voltage slow loop feedback circuit is used to generate a second output voltage after performing a second filtering on the first output voltage, and to generate a second feedback voltage after performing a second voltage division on the second output voltage.

3. The ultra-low output voltage ripple control circuit according to claim 2, characterized in that: The voltage fast loop feedback circuit includes a first filter circuit and a first voltage divider circuit; The input end of the first filter circuit is connected to the output end of the logic control and drive circuit; the output end of the first filter circuit is connected to the first voltage divider circuit; The first filtering circuit is used to filter the stepped-down voltage of the logic control and driving circuit to obtain a first output voltage; The first voltage divider circuit is used to obtain a first feedback voltage after performing a first voltage division according to the first output voltage.

4. The ultra-low output voltage ripple control circuit according to claim 3, characterized in that: The voltage slow loop feedback circuit includes a second filter circuit and a second voltage divider circuit; The input end of the second filter circuit is connected to the output end of the first filter circuit; the output end of the second filter circuit is connected to the second voltage divider circuit; The second filtering circuit is used to obtain a second output voltage after performing a second filtering on the first output voltage; The second voltage divider circuit is used to obtain a second feedback voltage after performing a second voltage division according to the second output voltage.

5. The ultra-low output voltage ripple control circuit according to claim 2, characterized in that: The two-stage feedback loop circuit also includes a feedback voltage processing circuit; The input end of the feedback voltage processing circuit is connected to the output end of the voltage fast loop feedback circuit and the output end of the voltage slow loop feedback circuit; The feedback voltage processing circuit is used to obtain a control voltage according to the first feedback voltage and the second feedback voltage; the control voltage is used to generate a modulation signal; The logic control and drive circuit adjusts the on or off of the switch circuit according to the modulation signal to achieve an output voltage with ultra-low output voltage ripple.

6. The ultra-low output voltage ripple control circuit according to claim 5, characterized in that: The feedback voltage processing circuit includes a high-pass circuit, a first error amplification circuit, a second error amplification circuit, a current summing circuit and an integral compensation circuit; The first feedback voltage at the output end of the voltage fast loop feedback circuit is connected to the input end of the high-pass circuit; the output end of the high-pass circuit is connected to the negative input end of the first error amplifier circuit, and the positive input end of the first error amplifier circuit is connected to a constant voltage; The first error amplifier circuit obtains a first difference voltage according to the first feedback voltage and a constant voltage; The second feedback voltage at the output end of the voltage slow loop feedback circuit is connected to the negative input end of the second error amplifier circuit, and the positive input end of the second error amplifier circuit is connected to the reference voltage; The second error amplifier circuit obtains a second difference voltage according to the second feedback voltage and a reference voltage; The current summing circuit superimposes the first difference voltage and the second difference voltage and inputs the superimposed voltages into the integral compensation circuit for compensation to obtain a control voltage.

7. A method for controlling ultra-low output voltage ripple, characterized in that: include: Output a step-down voltage according to the input voltage; Obtaining a first feedback voltage and a second feedback voltage according to the step-down voltage; The on or off state of the switch circuit is regulated according to the first feedback voltage and the second feedback voltage to achieve an output voltage with ultra-low output voltage ripple.

8. The ultra-low output voltage ripple control method according to claim 7, characterized in that: The obtaining the first feedback voltage and the second feedback voltage according to the step-down voltage includes: Generate a first output voltage according to the step-down voltage after a first filtering, and generate a first feedback voltage after a first voltage division of the first output voltage; The first output voltage is subjected to a second filtering process to generate a second output voltage, and the second output voltage is subjected to a second voltage division process to generate a second feedback voltage.

9. The ultra-low output voltage ripple control method according to claim 7, characterized in that: The obtaining a control voltage according to the first feedback voltage and the second feedback voltage includes: Obtaining a first difference voltage according to the first feedback voltage and the constant voltage; Obtaining a second difference voltage according to the second feedback voltage and a reference voltage; The first difference voltage and the second difference voltage are superimposed and then input into an integral compensation circuit for compensation to obtain a control voltage.

10. A BUCK control device, characterized in that: The ultra-low output voltage ripple control circuit comprises the ultra-low output voltage ripple control circuit as claimed in any one of claims 1 to 7; the ultra-low output voltage ripple control circuit comprises a logic control and drive circuit and a two-stage feedback loop circuit; The logic control and driving circuit adjusts the on or off state of the switch circuit according to the first feedback voltage and the second feedback voltage of the two-stage feedback loop circuit to achieve an output voltage with ultra-low output voltage ripple.

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