A low-ripple and dynamic bandwidth control circuit and control method for a switching power supply

Abstract

This invention relates to a low-ripple and dynamic bandwidth control circuit and method for a switching power supply, comprising: a ripple detection module for acquiring the ripple component of the output voltage of the switching power supply; a dynamic bandwidth judgment module for determining the ripple offset based on the acquired ripple component of the output voltage and outputting a dynamic bandwidth control signal; and a dynamic loop compensator for dynamically adjusting the loop bandwidth based on the dynamic bandwidth output control signal, controlling the ripple component of the output voltage within a set threshold range. Compared with the prior art, this invention has fast output voltage control capability, high switching power supply output voltage control accuracy, and low ripple.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a low ripple and dynamic bandwidth control circuit and control method for switching power supplies. Background Technology

[0002] Switching power supplies are widely used in various electronic devices to provide high-quality, high-efficiency power. They come in many types depending on the control method. Currently, the most popular control modes include voltage-mode, current-mode, and constant on-time.

[0003] Voltage molds have the advantage of high output voltage accuracy, but the disadvantages are slow response speed and complex compensation network.

[0004] Current-mode circuits have the advantages of high output voltage accuracy, fast response speed, and simple compensation network, and have fewer disadvantages. However, compared with architectures specifically designed for fast response, the response speed is still relatively slow.

[0005] The constant conduction mode architecture has the fastest response speed, but it also has the disadvantages of low voltage accuracy and insufficient flexibility in implementing other functions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a low-ripple and dynamic bandwidth control circuit and method for switching power supplies.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A low-ripple and dynamic bandwidth control circuit for a switching power supply, comprising:

[0009] Ripple detection module: used to acquire the ripple component of the output voltage of the switching power supply;

[0010] Dynamic bandwidth determination module: Determines the ripple offset based on the ripple component of the acquired output voltage and outputs a dynamic bandwidth control signal;

[0011] Dynamic loop compensator: It dynamically adjusts the loop bandwidth according to the dynamic bandwidth output control signal to control the ripple component of the output voltage within the set threshold range.

[0012] Preferably, the ripple detection module includes an operational amplifier, which is used to amplify the ripple component of the output voltage of the switching power supply and input it to the dynamic bandwidth judgment module.

[0013] Preferably, the relationship between the dynamic bandwidth control signal output by the dynamic bandwidth determination module and the ripple component of the output voltage is expressed as follows:

[0014]

[0015] Where Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vref is the reference value of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1, and Vdd are constants, n is the slope of the curve, and n is a constant.

[0016] Preferably, the dynamic bandwidth determination module is implemented using the following circuit topology:

[0017] The system includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a first output diode, a second output diode, and an output resistor. The positive input of the first operational amplifier is connected to a first reference voltage, and the negative input of the first operational amplifier is grounded. The positive input of the second operational amplifier is connected to the output signal of a ripple detection module, and the negative input of the second operational amplifier is connected to a second reference voltage. The positive input of the third operational amplifier is connected to a third reference voltage, and the negative input of the third operational amplifier is connected to the output signal of the ripple detection module. The voltage magnitudes of the first, second, and third reference voltages are Vdd, Vmin, and Vmax, respectively. The output terminal of the second operational amplifier is connected to the cathode of the first output diode, and the output terminal of the third operational amplifier is connected to the cathode of the second output diode. The output terminal of the first operational amplifier is connected to the anodes of the first and second output diodes to form a connection point. The connection point is grounded through the output resistor, and the connection point outputs a dynamic bandwidth control signal.

[0018] Preferably, the dynamic loop compensator includes a resistor-capacitor network with dynamically adjustable resistance and capacitance values. The resistor-capacitor network dynamically adjusts the resistance value of the network to change the loop zero point according to the dynamic bandwidth output control signal, and the resistor-capacitor network dynamically adjusts the capacitance value of the network to change the loop pole point according to the dynamic bandwidth output control signal.

[0019] Preferably, the dynamic loop compensator includes several parallel RC branches and several parallel capacitor branches, wherein the RC branches and capacitor branches are connected in parallel with each other, the RC branch includes a capacitor in series and an adjustable resistor, the resistance value of the adjustable resistor is controlled by the dynamic bandwidth output control signal, and the capacitor branch includes a capacitor in series and a switch, the open and closed states of the switch are controlled by the dynamic bandwidth output control signal.

[0020] A method for controlling low ripple and dynamic bandwidth of a switching power supply, the method being based on the aforementioned control circuit, the method comprising:

[0021] Obtain the ripple component of the output voltage of the switching power supply;

[0022] Determine whether the ripple component of the output voltage of the switching power supply exceeds a set threshold. If so, generate a dynamic bandwidth control signal based on the ripple component of the output voltage.

[0023] The loop bandwidth is dynamically adjusted based on the dynamic bandwidth control signal to control the ripple component of the output voltage within a set threshold range.

[0024] Preferably, the dynamic bandwidth control signal is generated using the following formula:

[0025]

[0026] Where Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vref is the reference value of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1, and Vdd are constants, n is the slope of the curve, and n is a constant.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) Based on the output voltage of the switching power supply, the present invention dynamically adjusts the loop frequency response of the entire system. When the output voltage changes beyond the set value, the unity gain frequency of the loop is increased, which has a fast output voltage control capability. At the same time, the output voltage control accuracy of the switching power supply is high and the ripple is small.

[0029] (2) The present invention can dynamically change the RC network configuration of the dynamic loop compensator according to the output voltage ripple, and quickly adjust the loop bandwidth by adjusting the zero poles, thereby improving the circuit system’s ability to respond quickly to changes in output voltage. Attached Figure Description

[0030] Figure 1 This is a diagram of a common current-mode buck switching power supply.

[0031] Figure 2 for Figure 1 Bode plot of loop frequency in a switching power supply circuit;

[0032] Figure 3 This is a schematic block diagram of a switching power supply circuit controlled by the dynamic bandwidth control circuit of the present invention.

[0033] Figure 4 This is a topology diagram of a switching power supply circuit controlled by the dynamic bandwidth control circuit of the present invention.

[0034] Figure 5 This is a schematic diagram of a circuit example for a ripple detection module;

[0035] Figure 6 A comparison chart of the dynamic bandwidth control signal output by the dynamic bandwidth judgment module and the output voltage when the power is off;

[0036] Figure 7 This is a graph of the dynamic bandwidth control signal in this embodiment;

[0037] Figure 8 This is a schematic diagram of a circuit example of the dynamic bandwidth determination module in this embodiment;

[0038] Figure 9 The output-input characteristic diagram is shown for the operational amplifier.

[0039] Figure 10 A schematic diagram of an existing fixed compensation circuit example;

[0040] Figure 11 This is a schematic diagram of a circuit example of the dynamic loop compensator in this implementation;

[0041] Figure 12 This is a loop response diagram of a switching power supply controlled by the control circuit of the present invention. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Note that the following description of the embodiments is merely illustrative and is not intended to limit its applicability or use, nor is the present invention limited to the following embodiments.

[0043] Example

[0044] Figure 1 This diagram illustrates a common current-mode buck switching power supply. Figure 2 For the corresponding loop frequency Bode plot, by Figure 2 It is evident that as the output voltage ripple increases, its loop unity-gain bandwidth decreases, which is detrimental to the circuit system's rapid response to changes in output voltage.

[0045] Based on this, this embodiment provides a low-ripple and dynamic bandwidth control circuit for a switching power supply, such as... Figure 3 indivual Figure 4 As shown, a low ripple and dynamic bandwidth control circuit for a switching power supply in this embodiment includes:

[0046] Ripple detection module: used to acquire the ripple component of the output voltage of the switching power supply;

[0047] Dynamic bandwidth determination module: Determines the ripple offset based on the ripple component of the acquired output voltage and outputs a dynamic bandwidth control signal;

[0048] Dynamic loop compensator: It dynamically adjusts the loop bandwidth according to the dynamic bandwidth output control signal to control the ripple component of the output voltage within the set threshold range.

[0049] Ripple detection amplifies the ripple of the output voltage and provides it to the subsequent bandwidth determination circuit for further processing. The amplified signal has a higher signal-to-noise ratio. In this embodiment, the ripple detection module includes an operational amplifier, which amplifies the ripple component of the switching power supply output voltage and inputs it to the dynamic bandwidth determination module. The implementation method is as follows: Figure 5 As shown.

[0050] like Figure 6 As shown, in this embodiment, the loop bandwidth control function is not triggered when the ripple is within 1%. Once the output voltage Vout jumps beyond the low ripple threshold (e.g., -1%) due to some reason, such as a sudden change in load current Iload, the "Dynamic Bandwidth Judgment" output will generate a control voltage Vdy proportional to this jump. This control voltage will be output to the next stage, the "Dynamic Loop Compensator" (DTC). The DTC linearly adjusts the dynamic loop compensator based on the received control signal Vdy, thereby changing the zero and pole points of the loop compensation, improving the loop response speed, and achieving the goal of quickly restoring the output voltage.

[0051] like Figure 7 As shown, the relationship between the dynamic bandwidth control signal output by the dynamic bandwidth determination module and the ripple component of the output voltage is expressed as follows:

[0052]

[0053] Where Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vref is the reference value of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1, and Vdd are constants, n is the slope of the curve, and n is a constant.

[0054] Figure 7 In the diagram, Vc is an existing curve, and Vc is the output of the error amplifier, which, along with Vdy, is input to the dynamic loop compensator. Vc is expressed as:

[0055]

[0056] Where VDD is a constant, m is the slope of the curve, and m is a constant.

[0057] In this embodiment, Vdd = 2.5V, VDD = 5V, and Vmin = Vref * 0.99, Vmax = Vref * 1.01, where Vref is the reference value of the output voltage of the switching power supply.

[0058] like Figure 8 As shown, the dynamic bandwidth determination module is implemented through the following circuit topology:

[0059] The system includes a first operational amplifier K1, a second operational amplifier K2, a third operational amplifier K3, a first output diode D2, a second output diode D3, and an output resistor R1. The positive input of the first operational amplifier K1 is connected to a first reference voltage, and the negative input of the first operational amplifier K1 is grounded. The positive input of the second operational amplifier K2 is connected to the output signal of the ripple detection module, and the negative input of the second operational amplifier K2 is connected to a second reference voltage. The positive input of the third operational amplifier K3 is connected to a third reference voltage, and the negative input of the third operational amplifier K3 is connected to the output signal of the ripple detection module. The voltage magnitudes of the first, second, and third reference voltages are Vdd, Vmin, and Vmax, respectively. The output of the second operational amplifier K2 is connected to the cathode of the first output diode D2, and the output of the third operational amplifier K3 is connected to the cathode of the second output diode D3. The output of the first operational amplifier K1 is connected to the anodes of the first and second output diodes D2 and D3 to form a connection point. The connection point is grounded through the output resistor R1, and the connection point outputs a dynamic bandwidth control signal.

[0060] The operational amplifier described above has an output current value and an input voltage value. Its output-input characteristics can be expressed as follows: Figure 9 As shown, it is represented as: Iout = k * Vin.

[0061] Combination Figure 8 In this embodiment, when the output voltage Vfb of the ripple detection is ≤ Vref*0.99, the total output current Idy only includes the outputs generated by the two operational amplifiers K1 and K2. K3, due to the unidirectional conduction of the second output diode D3, cannot output current, thus achieving... Figure 7 The portion of the Vdy curve where Vfb is less than or equal to 0.99Vref;

[0062] When the output voltage of the ripple detection, Vref*0.99 < Vfb < Vref*1.01, is less than Vfb, the total output current Idy only includes the output generated by the single operational amplifier K1. K2 and K3, due to the unidirectional conduction of the first output diode D2 and the second output diode D3, cannot output current. This achieves... Figure 7 The middle part of the Vdy curve;

[0063] When the output voltage Vfb of the ripple detection is greater than or equal to Vref*1.01, the total output current Idy only includes the outputs generated by the two operational amplifiers K1 and K3. K2, due to the unidirectional conduction of the first output diode D2, cannot output current. This achieves... Figure 7 The portion of the Vdy curve where Vfb is greater than or equal to 1.01Vref;

[0064] The final current Idy is converted into the output voltage Vdy through the output resistor R1.

[0065] Existing conventional circuits do not generate Vdy; only the Vc circuit generates Vc.

[0066] Figure 10 This is a circuit diagram of an existing simple fixed compensation circuit, which cannot dynamically adjust the zeros and poles of the network.

[0067] like Figure 11 As shown, the dynamic loop compensator of this invention employs a resistor-capacitor (RC) network with dynamically adjustable resistance and capacitance values. The RC network dynamically adjusts its resistance value to change the loop zero point based on the dynamic bandwidth output control signal, and dynamically adjusts its capacitance value to change the loop poles. The dynamic loop compensator includes several parallel RC branches and several parallel capacitor branches. The RC and capacitor branches are connected in parallel. Each RC branch includes a capacitor connected in series and an adjustable resistor. The resistance value of the adjustable resistor is controlled by the dynamic bandwidth output control signal. Each capacitor branch includes a capacitor connected in series and a switch. The open and closed states of the switch are controlled by the dynamic bandwidth output control signal.

[0068] Combination Figure 11 In this embodiment, R1, R2, R3, ..., Rn are all variable resistors controlled by Vdy and are functions of Vdy. Vdy comes from the dynamic bandwidth determination circuit in the preceding stage. After the output voltage ripple value exceeds ±1%, the dynamic bandwidth determination circuit generates a Vdy control signal, which dynamically modifies the values ​​of R1, R2, R3, ..., Rn to adjust the zero point position of the transfer function of the system loop.

[0069] Among them, SW1, ..., SWn are all controlled by the switching of Vdy, and the switching is a function of Vdy. After the output voltage ripple value exceeds ±1%, Vdy dynamically controls SW1, ..., SWn to adjust the position of the transfer function poles of the system loop.

[0070] By dynamically changing the poles and zeros of the system's compensation loop, the goal of dynamically adjusting the crossover frequency point Fcross is achieved. For example... Figure 12As shown, as the output voltage ripple increases, its loop unity-gain bandwidth dynamically changes proportionally to the ripple intensity. This improves the circuit system's ability to respond quickly to changes in output voltage.

[0071] In addition to the common Vc input, the control circuit input of this invention adds a dynamic control input Vdy. Different values ​​of the Vdy voltage can change the configuration of the resistor and capacitor network of the compensation circuit, thereby changing the compensation characteristic curve of the circuit. By reasonably configuring multiple sets of R and C values, the desired compensation characteristic curve can be obtained.

[0072] Furthermore, based on the aforementioned low-ripple and dynamic bandwidth control circuit for switching power supplies, this embodiment provides a method for controlling low-ripple and dynamic bandwidth of switching power supplies. This method is based on, and includes:

[0073] Obtain the ripple component of the output voltage of the switching power supply;

[0074] Determine whether the ripple component of the output voltage of the switching power supply exceeds a set threshold. If so, generate a dynamic bandwidth control signal based on the ripple component of the output voltage.

[0075] The loop bandwidth is dynamically adjusted based on the dynamic bandwidth control signal to control the ripple component of the output voltage within a set threshold range.

[0076] The dynamic bandwidth control signal is generated using the following formula:

[0077]

[0078] Where Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vref is the reference value of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1, and Vdd are constants, n is the slope of the curve, and n is a constant.

[0079] The dynamic bandwidth control technology of this invention is mainly applied in switching power supply applications, including typical PWM switching power supply applications such as Buck and Boost converters. The aim is to improve the rapid response of the switching power supply to changes in output voltage.

[0080] The above embodiments are merely illustrative and do not constitute a limitation on the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the technical spirit of the present invention.

Claims

1. A switched mode power supply low ripple and dynamic bandwidth control circuit, characterized by, The method comprises the following steps: a ripple detection module for obtaining a ripple component of an output voltage of a switching power supply; a dynamic bandwidth judgment module for judging a ripple offset of the output voltage according to the obtained ripple component and outputting a dynamic bandwidth control signal; a dynamic loop compensator for dynamically adjusting a loop bandwidth according to the dynamic bandwidth control signal and controlling the ripple component of the output voltage to be within a set threshold range; the ripple detection module comprises an operational amplifier, and the operational amplifier is configured to amplify the ripple component of the output voltage of the switching power supply and input the ripple component into the dynamic bandwidth judgment module; the dynamic bandwidth judgment module is implemented through the following circuit topology: the dynamic bandwidth judgment module comprises a first conductive operational amplifier, a second conductive operational amplifier, a third conductive operational amplifier, a first output diode, a second output diode and an output resistor, the input positive pole of the first conductive operational amplifier is connected to a first reference voltage, the input negative pole of the first conductive operational amplifier is grounded, the input positive pole of the second conductive operational amplifier is connected to an output signal of the ripple detection module, the input negative pole of the second conductive operational amplifier is connected to a second reference voltage, the input positive pole of the third conductive operational amplifier is connected to a third reference voltage, the input negative pole of the third conductive operational amplifier is connected to the output signal of the ripple detection module, the voltages of the first reference voltage, the second reference voltage and the third reference voltage correspond to Vdd, Vmin and Vmax in sequence, the output end of the second conductive operational amplifier is connected to the cathode of the first output diode, the output end of the third conductive operational amplifier is connected to the cathode of the second output diode, the output end of the first conductive operational amplifier is connected to the anodes of the first output diode and the second output diode to form a connection point, the connection point is grounded through the output resistor, and the connection point outputs the dynamic bandwidth control signal; the dynamic loop compensator comprises a resistance-capacitance network with dynamically adjustable resistance value and capacitance value, the resistance-capacitance network dynamically adjusts the resistance value of the network to change a loop zero point according to the dynamic bandwidth output control signal, and the resistance-capacitance network dynamically adjusts the capacitance value of the network to change a loop pole according to the dynamic bandwidth output control signal.

2. The low-ripple and dynamic bandwidth control circuit for a switching power supply of claim 1, wherein, The relationship between the dynamic bandwidth control signal output by the dynamic bandwidth judgment module and the ripple component of the output voltage is represented as follows: wherein Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1 and Vdd are constants, n is a curve slope, and n is a constant.

3. The low-ripple and dynamic bandwidth control circuit for a switching power supply of claim 1, wherein, The dynamic loop compensator comprises a plurality of parallel resistance-capacitance branches and a plurality of parallel capacitance branches, the resistance-capacitance branches and the capacitance branches are connected in parallel with each other, each resistance-capacitance branch comprises a capacitor and an adjustable resistor connected in series, the resistance value of the adjustable resistor is controlled by the dynamic bandwidth output control signal, and each capacitance branch comprises a capacitor and a switch connected in series, and the opening and closing states of the switch are controlled by the dynamic bandwidth output control signal.

4. A method for low ripple and dynamic bandwidth control of a switching power supply, characterized by, The method is based on the control circuit according to any one of claims 1 to 3, and the method comprises the following steps: Obtaining a ripple component of an output voltage of a switching power supply; Determining whether the ripple component of the output voltage of the switching power supply exceeds a set threshold value, and if so, generating a dynamic bandwidth control signal based on the ripple component of the output voltage; Dynamically adjusting a loop bandwidth based on the dynamic bandwidth control signal to control the ripple component of the output voltage to be within the set threshold value.

5. The method of claim 4, wherein the low ripple and dynamic bandwidth control of a switching power supply is characterized by, The dynamic bandwidth control signal is generated by the following relationship: Wherein, Vdy is the dynamic bandwidth control signal, Vfb is the ripple component of the output voltage, Vmin is the minimum value of the output voltage, Vmax is the maximum value of the output voltage, Vfb0, Vfb1, Vdd are constants, n is the slope of the curve, and n is a constant.

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