Ripple signal generation circuit and switching converter

Abstract

The invention provides a ripple signal generation circuit and a switching converter, and the ripple signal generation circuit comprises a first signal unit which comprises a first adjustment module and a first output module; the second signal unit comprises a second adjusting module and a second output module, and an output node of the second output module is connected with a second node of the first output module; in the switching period, the first adjusting module and the second adjusting module work cooperatively to adjust the voltage of the first node and the output node of the first output module, and a ripple signal is obtained according to the voltage difference value of the first node and the output node. The ripple signal generation circuit provided by the invention mixes the triangular wave signal and the sawtooth wave signal to generate the ripple signal. Therefore, the ripple signal not only has the advantages of the triangular wave signal to ensure the stability of the system, but also has the advantages of the sawtooth wave signal to improve the dynamic response performance of the system.

Description

A ripple signal generation circuit and a switching converter Technical Field

[0001] This invention belongs to the field of switching power supplies, specifically relating to a ripple signal generation circuit and a switching converter. Background Technology

[0002] The output of the switching converter is connected to an output capacitor Co, which is used to filter the output voltage to obtain a smooth output waveform. Due to the capacitive characteristic of the output capacitor Co, the output voltage of the switching converter lags behind the inductor current signal. Therefore, a sufficient equivalent series resistance (ESR) needs to be connected in series with the output capacitor Co to ensure stable system operation. However, adding the ESR in series can lead to a large output ripple. Therefore, most existing technologies use ripple compensation to solve the above problem and meet the system stability requirements.

[0003] Taking constant on-time (COT) control as an example, the on-time of the main power transistor is constant during the control process. By comparing the compensation signal Vcomp and the ripple signal Vripple, the freewheeling transistor is turned off and the main power transistor is turned on when the ripple signal Vripple is equal to the compensation signal Vcomp. The compensation signal Vcomp is obtained from the error operational amplifier based on the output feedback signal Vfb and the reference signal Vref.

[0004] Currently, triangular wave signals are generally used as ripple signals during compensation to improve system stability. Additionally, sawtooth wave signals can be used as ripple signals to accelerate system response. However, for operating conditions that require both system stability and dynamic performance, the commonly used triangular wave and sawtooth wave signals are insufficient. Summary of the Invention

[0005] To address the technical problem that existing technologies cannot simultaneously satisfy stability and dynamic performance in ripple signals, this invention proposes a ripple signal generation circuit and a switching converter. The ripple signal generation circuit is used for output ripple compensation of the switching converter. The ripple signal generation circuit includes:

[0006] The first signal unit includes a first adjustment module and a first output module;

[0007] The second signal unit includes a second adjustment module and a second output module, wherein the output node of the second output module is connected to the second node of the first output module.

[0008] During the switching cycle, the first adjustment module and the second adjustment module work together to adjust the voltage of the first node and the output node of the first output module, and obtain the ripple signal based on the voltage difference between the first node and the output node.

[0009] Furthermore, during the switching cycle,

[0010] When the first adjustment module works alone, the first output module generates a triangular wave signal;

[0011] When the second adjustment module works alone, the second output module generates a sawtooth wave signal;

[0012] The ripple signal is generated by the first adjustment module and the second adjustment module working together, and the ripple signal is a mixture of the triangular wave signal and the sawtooth wave signal.

[0013] Furthermore, when the first adjustment module and the second adjustment module work individually and collaboratively, the voltage changes of the first node remain consistent, and the voltage changes of the output node remain consistent.

[0014] Specifically, the amplitude of the ripple signal gradually decreases during the main power transistor's conduction period and is reset to zero when the main power transistor is turned off, while the amplitude of the ripple signal gradually increases during the freewheeling transistor's conduction period.

[0015] Furthermore, during the discontinuity period, the amplitude of the ripple signal remains unchanged.

[0016] Specifically, during the switching cycle,

[0017] During the rising phase of the inductor current, the first adjustment module adjusts the voltage of the first node.

[0018] During the inductor current decrease phase, the second adjustment module adjusts the voltage of the output node, and the first adjustment module adjusts the voltage of the first node.

[0019] Specifically, when the first adjustment module operates independently, it obtains the triangular wave signal based on the voltage difference between the first node and the second node.

[0020] During the rising phase of the inductor current, the voltage at the first node gradually increases while the voltage at the second node remains constant; during the falling phase of the inductor current, the voltage at the first node gradually decreases while the voltage at the second node remains constant.

[0021] Specifically, when the second adjustment module operates independently, it obtains the sawtooth wave signal based on the voltage value of the output node.

[0022] During the rising phase of the inductor current, the voltage of the output node remains unchanged. During the falling phase of the inductor current, the voltage of the output node is first reset to zero and then gradually increases.

[0023] Specifically, during the rising phase of the inductor current, the voltage of the first node gradually increases, while the voltage of the output node remains unchanged.

[0024] During the inductor current decrease phase, the voltage of the first node gradually decreases, and the voltage of the output node is first reset to zero and then gradually increases.

[0025] Preferably, the first output module includes: a first capacitor with its positive terminal connected to the first node and its negative terminal grounded, a second capacitor with its positive terminal connected to the second node and its negative terminal grounded, and a first resistor connected between the first node and the second node;

[0026] The second output module includes an output capacitor. The output node and the second node are connected through the output capacitor. The positive terminal of the output capacitor is connected to the output node, and the negative terminal of the output capacitor is connected to the second node.

[0027] Preferably, the first adjustment module includes a first current source, a first switch, and a second resistor. The first switch is connected to the first current source and a first capacitor, and the second resistor is connected in parallel with the first capacitor. The first switch is closed during the rising phase of the inductor current and open during the falling phase of the inductor current.

[0028] Preferably, the second adjustment module includes a second current source, a second switch, and a third switch. The second current source is connected to the positive terminal of the output capacitor through the second switch, and the third switch is connected to the positive terminal of the output capacitor and the ground terminal. The third switch is closed when the main power transistor is turned off, and the third switch is opened and the second switch is closed during the inductor current decrease phase.

[0029] Furthermore, it also includes a fourth switch connected between the second resistor and the first node, and a fifth switch connected between the output node and the third switch. When both the main power transistor and the freewheeling transistor are turned off, the fourth and fifth switches are open, and during the conduction periods of the main power transistor and the freewheeling transistor, the fourth and fifth switches are on.

[0030] A switching converter includes the ripple signal generation circuit described above.

[0031] The ripple signal generation circuit proposed in this invention mixes triangular wave signals and sawtooth wave signals to generate a ripple signal. Therefore, the ripple signal possesses both the advantages of triangular wave signals—ensuring system stability—and the advantages of sawtooth wave signals—improving the system's dynamic response performance. Attached Figure Description

[0032] Figure 1 is a circuit diagram of the ripple signal generation circuit in CCM mode;

[0033] Figure 2 shows the waveforms of the triangular wave signal, sawtooth wave signal, and ripple signal in CCM mode;

[0034] Figure 3 is a circuit diagram of the ripple signal generation circuit in DCM mode;

[0035] Figure 4 shows the waveform of the ripple signal in DCM mode;

[0036] Figure 5 shows a simulation diagram of ripple compensation for the ripple signal;

[0037] Figure 6 shows a simulation diagram of ripple compensation for a triangular wave signal;

[0038] Figure 7 shows a simulation diagram of ripple compensation for sawtooth wave signals. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0040] As mentioned in the background section, using triangular wave signals or sawtooth wave signals as ripple signals for output ripple compensation cannot simultaneously meet the system's requirements for stability and dynamic response. Since triangular wave signals exhibit better stability in applications, and sawtooth wave signals exhibit better dynamic response capabilities, this invention proposes a hybrid processing method for triangular wave signals and sawtooth wave signals, resulting in a signal that possesses both stability and dynamic response capabilities.

[0041] Based on the above design concept, this invention proposes a ripple signal generation circuit, comprising:

[0042] The first signal unit includes a first adjustment module and a first output module;

[0043] The second signal unit includes a second adjustment module and a second output module, and the output node of the second output module is connected to the second node of the first output module.

[0044] During the switching cycle, the first adjustment module and the second adjustment module work together to adjust the voltage magnitude of the first node and the voltage magnitude of the output node of the first output module, thereby obtaining the ripple signal based on the voltage difference between the first node and the output node.

[0045] Specifically, during the switching cycle, when the first regulating module operates alone, the first output module generates a triangular wave signal, specifically obtained based on the voltage difference between the first node and the second node of the first output module. When the second regulating module operates alone, the second output module generates a sawtooth wave signal, specifically obtained based on the voltage value of the output node (equivalent to obtaining a sawtooth wave signal based on the voltage difference between the output node and the ground terminal). However, in this invention, the first and second regulating modules operate collaboratively during the switching cycle, so the corresponding ripple signal is a mixture of triangular and sawtooth wave signals.

[0046] In summary, the ripple signal generation circuit proposed in this invention couples a first signal unit capable of outputting a triangular wave signal and a second signal unit capable of outputting a sawtooth wave signal, thereby generating a mixed signal of triangular and sawtooth wave signals, which is the ripple signal. Therefore, the ripple signal possesses both the advantages of the triangular wave signal—ensuring system stability—and the advantages of the sawtooth wave signal—improving the system's dynamic response performance.

[0047] Furthermore, it is particularly important to emphasize that not every coupling design of two circuits that can separately output triangular wave and sawtooth wave signals can achieve the mixing of these two signals. Generally, when two circuits are coupled together, they influence each other, potentially altering key parameters such as the operating process, current loop, and node voltage of each circuit. It is precisely this mutual influence caused by coupling that prevents the mixing of triangular and sawtooth wave signals. However, in this invention, the voltage changes at the first node and the output node remain consistent whether the first and second adjustment modules operate independently or collaboratively. That is, compared to the independent operation of the first and second signal units, coupling the first and second signal units does not affect the changes at the first and output nodes. Therefore, the ripple signal generation circuit proposed in this invention can be formed by coupling two signal units and achieve the mixing of triangular and sawtooth wave signals based on the voltage difference between the first and output nodes.

[0048] Specifically, in CCM mode, when the first and second regulation modules work together, during the rising inductor current phase, the first regulation module adjusts the voltage of the first node of the first output module, causing the voltage of the first node to gradually increase. At this time, the voltage of the output node remains unchanged. During the falling inductor current phase, the second regulation module adjusts the voltage of the output node, and the first regulation module adjusts the voltage of the first node. When the main power transistor is turned off, the potential of the output node is reset to zero. Then, when the freewheeling diode is turned on, the voltage of the output node gradually increases, and the voltage of the first node gradually decreases. Therefore, during the switching cycle, the ripple signal is obtained based on the voltage difference between the first node and the output node. During the main power transistor's conduction period, the amplitude of the ripple signal gradually decreases and is reset to zero when the main power transistor is turned off. During the freewheeling diode's conduction period, the amplitude of the ripple signal gradually increases.

[0049] Similarly, in DCM mode, when the first and second regulation modules work together, during the rising inductor current phase, the first regulation module adjusts the voltage of the first node of the first output module, causing the voltage of the first node to gradually increase. At this time, the voltage of the output node remains unchanged. During the falling inductor current phase, the second regulation module adjusts the voltage of the output node, and the first regulation module adjusts the voltage of the first node. When the main power transistor is turned off, the potential of the output node is cleared to zero and then gradually increases, while the voltage of the first node gradually decreases. When the inductor current crosses zero, the first regulation module disconnects from the first node, and the second regulation module disconnects from the output node, keeping the voltages of the first and output nodes constant. Therefore, during the switching cycle, the ripple signal is obtained based on the voltage difference between the first and output nodes. During the main power transistor's conduction period, the amplitude of the ripple signal gradually decreases and is reset to zero when the main power transistor is turned off. During the freewheeling transistor's conduction period, the amplitude of the ripple signal gradually increases. During the discontinuous phase (when both the main power transistor and the freewheeling transistor are turned off), the amplitude of the ripple signal remains constant.

[0050] Specifically, in CCM mode, when the first regulating module operates alone, during the switching cycle, the voltage at the first node gradually increases while the voltage at the second node remains constant during the rising phase of the inductor current, and gradually decreases while the voltage at the second node remains constant during the falling phase of the inductor current. In DCM mode, when the first regulating module operates alone, during the switching cycle, the voltage at the first node gradually increases while the voltage at the second node remains constant during the rising phase of the inductor current, and gradually decreases while the voltage at the second node remains constant during the zero-crossing phase of the inductor current. Therefore, a triangular wave signal can be obtained based on the voltage difference between the first and second nodes.

[0051] Specifically, in CCM mode, when the second regulation module operates alone, during the switching cycle, the voltage at the output node remains constant during the rising phase of the inductor current, and during the falling phase of the inductor current, the voltage at the output node first resets to zero and then gradually increases. In DCM mode, when the second regulation module operates alone, during the switching cycle, the voltage at the output node remains constant during the rising phase of the inductor current, and during the falling phase of the inductor current, the voltage at the output node first resets to zero and then gradually increases. The voltage at the output node remains constant during the zero-crossing point of the inductor current.

[0052] The ripple signal generation circuit will be further explained below with reference to a specific circuit.

[0053] Preferably, as shown in Figure 1, in CCM mode, the first adjustment module includes a first current source I1, a first switch S1, and a second resistor R2. The first output module includes a first capacitor C1, a second capacitor C2, and a first resistor R1. The first current source I1 is connected to the positive terminal of the first capacitor C1 through the first switch S1. The negative terminal of the first capacitor C1 is grounded, and the positive terminal of the first capacitor C1 is the first node SW1. The positive terminal of the first capacitor C1 is connected to the positive terminal of the second capacitor C2 through the first resistor R1. The negative terminal of the second capacitor C2 is grounded, and the positive terminal of the second capacitor C2 is the second node SW2. The second resistor R2 is connected in parallel with the first capacitor C1. The second adjustment module includes a second current source I2, a second switch S2, and a third switch S3. The second output module includes an output capacitor CO. The second current source I2 is connected to the positive terminal of the output capacitor CO through the second switch S2. The negative terminal of the output capacitor CO is connected to the second node SW2, and the positive terminal of the output capacitor CO is the output node SW0. The third switch S3 is connected between the positive terminal of the output capacitor CO and the ground terminal. Taking pulse width modulation (PWM) as an example, when the PWM signal is high, it controls the first switch S1 to close, the second switch S2 to open, and the third switch S3 to open. At this time, the voltage of the first node SW1 gradually increases, the voltage of the second node SW2 remains unchanged (due to the large impedance of R1 and C1 for filtering), and the voltage of the output node SWO remains unchanged. When the PWM signal transitions to a low level, a control pulse is generated at the transition edge to briefly turn on the third switch S3, causing the output capacitor CO to be reset to zero. During the low-level period of the PWM signal, the first switch S1 is open, the second switch S2 is closed, the voltages of the output nodes SWO and SW2 gradually increase, and the voltage of the first node SW1 gradually decreases.

[0054] As shown in Figure 2, during the switching cycle, the ripple signal is obtained based on the voltage difference between the first node SW1 and the output node SW0, Vswo-Vsw1=(Vswo-Vsw2)+(Vsw2-Vsw1). Wherein, Vsw2-Vsw1 represents the triangular wave signal, Vswo-Vsw2 represents the sawtooth wave signal, and the ripple signal is the superposition of the triangular wave signal and the sawtooth wave signal.

[0055] The above analysis is based on the fact that the first signal unit and the second signal unit are coupled into a ripple signal generation circuit. Since the coupling does not affect the voltage change of the first node SW1 and the output node SWO, a triangular wave signal can still be obtained in the ripple signal generation circuit based on the voltage difference between the first node SW1 and the second node SW2, and a sawtooth wave signal can still be obtained based on the voltage difference between the output node SWO and the second node SW2 (the voltage of the output capacitor CO).

[0056] Further analysis is conducted on the case where the first and second signal units are not coupled. Specifically, when the first signal unit operates independently, switch S1 is turned on when the PWM signal is high, causing the voltage of the first node SW1 to gradually increase while the voltage of the second node SW2 remains unchanged. When the PWM signal is low, switch S1 is turned off, causing the voltage of the first node SW1 to gradually decrease while the voltage of the second node SW2 remains unchanged. Therefore, during the switching cycle, a triangular wave signal is obtained based on the voltage difference between the first node SW1 and the second node SW2. When the second signal unit operates independently, the negative terminal of the output capacitor CO is grounded. When the PWM signal is high, switches S2 and S3 are turned off, and the voltage of the output node SWO remains unchanged. When the PWM signal transitions to a low level, switch S3 is turned on at the transition edge, clearing the voltage of the output node SWO to zero. During the low-level period of the PWM signal, switch S2 is turned on and switch S3 is turned off, causing the voltage of the output node SWO to gradually increase. Therefore, during the switching cycle, a sawtooth wave signal is obtained based on the voltage of the output node SWO.

[0057] As can be seen from the above specific circuit analysis, when the first signal unit and the second signal unit work independently and in concert, the voltage change of the first node remains consistent, and the voltage of the output node also remains consistent.

[0058] Furthermore, considering that the switching converter can operate in DCM mode, as shown in Figure 3, the ripple signal generation circuit also includes a fourth switch S4 and a fifth switch S5. The fourth switch S4 is connected between the second resistor R2 and the first capacitor C1, and the fifth switch S5 is connected between the output capacitor CO and the second switch S2. The fourth and fifth switches S4 and S5 are controlled by a zero-crossing detection signal. When the zero-crossing detection signal is invalid, the fourth and fifth switches S4 and S5 are closed; when the zero-crossing detection signal is valid, the fourth and fifth switches S5 are open. A valid zero-crossing detection signal indicates that the inductor current is zero, and an invalid zero-crossing detection signal indicates that the inductor current is not zero. Therefore, as shown in Figure 4, during the discontinuous period, the first capacitor C1 and the output capacitor CO are suspended, and the amplitude of the ripple signal remains unchanged.

[0059] The ripple signal generated by the ripple signal generation circuit is a superposition of a triangular wave signal and a sawtooth wave signal, possessing both the stability of the triangular wave signal and the dynamic response performance of the sawtooth wave signal. This can be verified through simulation data, as shown in Figures 5 and 6. Ripple compensation was performed using both the triangular wave signal and the aforementioned ripple signal, with other conditions remaining the same, assuming the switching converter switches from heavy load to light load. The output voltage drop was 22mV when ripple compensation was performed using the triangular wave signal, and 16mV when ripple compensation was performed using the aforementioned ripple signal. Clearly, the ripple signal exhibits better dynamic performance than the triangular wave signal.

[0060] Furthermore, as shown in Figures 5 and 7, ripple compensation was performed using both a sawtooth wave signal and the aforementioned ripple signal, with other conditions remaining the same, assuming the switching converter switched from heavy load to light load. When using the sawtooth wave signal for ripple compensation, the output voltage overshoot was 11mV. When using the aforementioned ripple signal for ripple compensation, the output voltage overshoot was 2mV. Clearly, the ripple signal is more stable than the sawtooth wave signal.

[0061] Furthermore, the present invention also proposes a switching converter that includes the ripple signal generation circuit described above, so as to ensure both stability and dynamic performance when performing output ripple compensation.

[0062] It should be noted that the specific implementations and corresponding illustrations provided are merely one way of describing the implementation method of the present invention, and are not intended to limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principles and essence of the present invention, but all such changes and modifications fall within the protection scope of the present invention.

[0063] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0064] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A ripple signal generation circuit, used for output ripple compensation of a switching converter, characterized in that, include: The first signal unit includes a first adjustment module and a first output module; The second signal unit includes a second adjustment module and a second output module, wherein the output node of the second output module is connected to the second node of the first output module. During the switching cycle, the first adjustment module and the second adjustment module work together to adjust the voltage of the first node and the output node of the first output module, and obtain the ripple signal based on the voltage difference between the first node and the output node.

2. The ripple signal generation circuit as described in claim 1, characterized in that, During the switching cycle, when the first adjustment module works alone, the first output module generates a triangular wave signal; when the second adjustment module works alone, the second output module generates a sawtooth wave signal; wherein, the ripple signal is generated by the first adjustment module and the second adjustment module working together, and the ripple signal is a mixed signal of the triangular wave signal and the sawtooth wave signal.

3. The ripple signal generation circuit as described in claim 2, characterized in that, When the first adjustment module and the second adjustment module work individually and in concert, the voltage change of the first node remains consistent, and the voltage change of the output node remains consistent.

4. The ripple signal generation circuit as described in claim 1, characterized in that, The amplitude of the ripple signal gradually decreases during the main power transistor's conduction period and is reset to zero when the main power transistor is turned off; the amplitude of the ripple signal gradually increases during the freewheeling transistor's conduction period.

5. The ripple signal generation circuit as described in claim 4, characterized in that, During the discontinuous period, the amplitude of the ripple signal remains constant.

6. The ripple signal generation circuit as described in claim 1, characterized in that, During the switching cycle, during the rising phase of the inductor current, the first adjustment module adjusts the voltage of the first node; during the falling phase of the inductor current, the second adjustment module adjusts the voltage of the output node, and the first adjustment module adjusts the voltage of the first node.

7. The ripple signal generation circuit as described in claim 2, characterized in that, When the first adjustment module works independently, it obtains the triangular wave signal based on the voltage difference between the first node and the second node. During the rising phase of the inductor current, the voltage of the first node gradually increases while the voltage of the second node remains unchanged. During the inductor current decrease phase, the voltage at the first node gradually decreases while the voltage at the second node remains constant.

8. The ripple signal generation circuit as described in claim 2, characterized in that, When the second adjustment module works independently, it obtains the sawtooth wave signal based on the voltage value of the output node. During the rising phase of the inductor current, the voltage of the output node remains unchanged. During the falling phase of the inductor current, the voltage of the output node is first reset to zero and then gradually increased.

9. The ripple signal generating circuit as described in claim 6, characterized in that, During the inductor current rising phase, the voltage of the first node gradually increases, while the voltage of the output node remains unchanged; during the inductor current falling phase, the voltage of the first node gradually decreases, while the voltage of the output node is first reset to zero and then gradually increases.

10. The ripple signal generation circuit as described in claim 1, characterized in that, The first output module includes: a first capacitor with its positive terminal connected to the first node and its negative terminal grounded; a second capacitor with its positive terminal connected to the second node and its negative terminal grounded; and a first resistor connected between the first node and the second node. The second output module includes an output capacitor; the output node and the second node are connected through the output capacitor; the positive terminal of the output capacitor is connected to the output node; and the negative terminal of the output capacitor is connected to the second node.

11. The ripple signal generation circuit as described in claim 10, characterized in that, The first adjustment module includes a first current source, a first switch, and a second resistor. The first switch is connected to the first current source and a first capacitor. The second resistor is connected in parallel with the first capacitor. The first switch is closed during the rising phase of the inductor current and open during the falling phase of the inductor current.

12. The ripple signal generation circuit as described in claim 10, characterized in that, The second adjustment module includes a second current source, a second switch, and a third switch. The second current source is connected to the positive terminal of the output capacitor through the second switch, and the third switch is connected to the positive terminal of the output capacitor and the ground terminal. The third switch is closed when the main power transistor is turned off, and the third switch is opened and the second switch is closed during the inductor current decrease phase.

13. The ripple signal generating circuit as described in claim 11 or 12, characterized in that, It also includes a fourth switch connected between the second resistor and the first node, and a fifth switch connected between the output node and the third switch. When both the main power transistor and the freewheeling transistor are turned off, the fourth and fifth switches are open, and during the conduction periods of the main power transistor and the freewheeling transistor, the fourth and fifth switches are on.

14. A switching converter, characterized in that, Includes the ripple signal generation circuit according to any one of claims 1-13.

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