Automatic phase margin compensation circuit

Abstract

The utility model discloses an automatic phase margin compensation circuit. The system comprises a loop phase automatic compensation module arranged in a closed-loop system and a loop stability detection module connected between the output end of the closed-loop system and the loop phase automatic compensation module. The loop stability detection module can detect the frequency of the output signal of the loop and can start to automatically search a compensation position and compensate the phase margin of the loop when the frequency of the output signal is far higher than a set frequency threshold value. The system has the advantages that when the loop stability detection module judges that the loop is unstable, the loop phase automatic compensation module can provide phase compensation for the loop, so that the phase margin of the loop is enough, the loop is stable, and the stability of the loop is effectively improved through the addition of the loop stability detection module and the phase automatic compensation module.

Description

Technical Field

[0001] The utility model relates to a circuit structure which is mainly used for stability adjustment and phase margin compensation of a multi-pole closed-loop system, in particular to an automatic phase margin compensation circuit. Background Art

[0002] In the readout system of inertial sensors, closed-loop systems are widely used due to their excellent performance such as low noise and high linearity; however, with the complexity of modern application requirements, the complexity of inertial sensor closed-loop readout systems is also increasing. Therefore, more poles are introduced into the closed-loop readout system. Since a pole will bring a 90-degree phase shift to the system; therefore, when there are two or more poles in a system, insufficient phase margin will cause system oscillation.

[0003] In summary, when multiple poles appear in a closed-loop system, it is very necessary to use phase margin compensation technology in the closed loop to improve the system phase margin to ensure the stability and robustness of the system. The implementation of phase margin compensation technology usually involves the use of compensators or filters to change the frequency response of the system. Common phase margin compensation techniques include gain margin compensation, phase shift compensation, and filter compensation. These techniques can change the frequency response of the system by adjusting the gain and phase of the system, thereby increasing the phase margin of the system. Although phase margin compensation technology can improve the stability and performance of the system, its design and implementation are not easy. It requires a deep understanding of the characteristics and requirements of the system, and precise analysis and design. In addition, phase margin compensation technology also needs to take into account the actual application environment and constraints of the system. Therefore, the design of phase margin compensation for different systems has certain difficulties and differences. Summary of the invention

[0004] The technical problem to be solved by the utility model is to provide an automatic phase margin compensation circuit which can effectively improve loop stability.

[0005] In order to solve the above technical problems, the automatic phase margin compensation circuit of the utility model includes a loop phase automatic compensation module arranged in a closed-loop system and a loop stability detection module connected between the output end of the closed-loop system and the loop phase automatic compensation module. The loop stability detection module can detect the frequency of the loop output signal and can automatically search for the compensation position and compensate the loop phase margin when the output signal frequency is much higher than the set frequency threshold.

[0006] The main body of the loop stability detection module is a frequency detector and phase detector.

[0007] The frequency detector includes a reference frequency f REF Input and feedback frequency f DIVAt the input end, the phase frequency detector can transmit the phase difference between the two signals to the CP in the form of voltage on and off.

[0008] The frequency and phase detector also includes two rising edge triggered D flip-flops with reset terminals and a logic AND gate.

[0009] The loop phase automatic compensation module is composed of an RC phase shift network and an automatic search unit.

[0010] The RC phase shift network is provided with a capacitor array for adjusting the frequency position compensated by the RC phase shift network.

[0011] The RC phase shift network is connected in series in the signal loop.

[0012] The capacitor array within the RC phase shift network has a switch array.

[0013] The advantages of the utility model are:

[0014] Compared with traditional loop phase compensation, it includes a loop stability detection module and a loop phase automatic compensation module, and the loop stability detection module is connected between the output end of the closed-loop system and the loop phase automatic compensation module. It can automatically and quickly perform phase compensation on the loop without significantly increasing the power consumption of the circuit. Therefore, when the loop stability detection module determines that the loop is unstable, the loop phase automatic compensation module can provide a phase compensation for the loop so that the loop phase margin is sufficient to make the loop stable. By adding the loop stability detection module and the phase automatic compensation module, the stability of the loop is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system block diagram of the automatic phase margin compensation circuit of the utility model;

[0016] Figure 2 It is a schematic diagram of the structure of the frequency and phase detector in the utility model;

[0017] Figure 3 It is a conversion diagram of the working state of the frequency and phase detector in the utility model;

[0018] Figure 4 This is a structural diagram of a capacitor array in an RC phase shift network in the present utility model. DETAILED DESCRIPTION

[0019] The automatic phase margin compensation circuit of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementations.

[0020] As shown in the figure, the automatic phase margin compensation circuit of the utility model includes a loop phase automatic compensation module 102 set in a closed-loop system 100 and a loop stability detection module 101 connected between the output end of the closed-loop system and the loop phase automatic compensation module, wherein the loop stability detection module is mainly composed of a phase frequency detector (PFD) to determine whether the loop has oscillated; the loop phase automatic compensation module 102 is mainly composed of an RC phase shift network and an automatic search unit, wherein the RC phase shift network is composed of a capacitor array and a resistor, so that phase compensation for different frequency points can be achieved, the automatic search unit can quickly search for the frequency point that needs phase compensation and adjust the size of the capacitor array in the RC phase shift network for phase compensation, and finally make the loop reach a stable state, the loop stability detection module 101 can detect the frequency of the loop output signal and can start to automatically search for the compensation position and compensate the loop phase margin when the output signal frequency is much higher than the set frequency threshold, so that the loop phase margin is sufficient and the loop stops oscillating.

[0021] Furthermore, the phase frequency detector (PFD) includes a reference frequency f REF Input and feedback frequency f DIV At the input end, the phase frequency detector (PFD) can transmit the phase difference between the two signals to the CP in the form of voltage on and off. The structure of the PFD is as follows: Figure 2 As shown, it also includes two D flip-flops with rising edge triggers of reset terminals and a logic AND gate. The data terminal D of the D flip-flop is always connected to a high level. The PFD is controlled by a reference frequency f REF and feedback frequency f DIV The rising edge of the clock triggers the UP and DN rectangular pulse signals of high level to generate. UP and DN are provided to the reset signal Reset of the D flip-flop through the AND gate. When UP and DN are both high level, the reset signal restores them to the level.

[0022] The transition diagram of the PFD working state can be used Figure 3 It means that for an ideal three-state PFD, the output UP and DN signals will not be high at the same time.

[0023] Its three working states are as follows:

[0024] State 1: When the input reference frequency f REF The phase of (threshold frequency) leads the feedback frequency f DIV (output signal frequency), the output UP of PDF is a high-level rectangular pulse, and the pulse width corresponds to the phase difference between the two input signals. REF (Threshold frequency) The rectangular pulse starts when the rising edge of the signal arrives, and at the feedback frequency f DIV(Output signal frequency) The rectangular pulse ends when the rising edge of the signal arrives, and DN is always at a low level at this time;

[0025] State 2: When the feedback frequency f REF The phase of (output signal frequency) leads the input reference frequency f DIV (threshold frequency), the output DN of the PFD is a high-level rectangular pulse, and the pulse width corresponds to the phase difference between the two input signals. The feedback frequency f DIV (Output signal frequency) The rectangular pulse starts when the rising edge of the signal arrives, and the input reference frequency f REF (Threshold frequency) When the rising edge of the signal arrives, the rectangular pulse ends, and the output UP remains at a low level;

[0026] State 3: When the input reference frequency f REF (threshold frequency) and feedback frequency f DIV When the (output signal frequencies) are completely in phase, the UP and DN signals are always low level.

[0027] The RC phase shift network is used to increase the phase margin of the loop, where C is composed of a capacitor array. This is because the frequency position that requires phase compensation is different for different loops, and the position of the phase compensation of the RC phase shift network can be changed by adjusting the capacitance of the capacitor array.

[0028] The structure of the RC phase shift network and the capacitor array is as follows: Figure 4 As shown. The automatic search unit, after receiving the signal from the frequency detector, starts to adjust the size of the capacitor in the capacitor array, using an adjustment method from small to large. Each time the automatic search unit adjusts the size of the capacitor array, the frequency detector will be reset. The reset frequency detector will compare the reference frequency f again. REF and feedback frequency f DIV If the reference frequency f REF Greater than the feedback frequency f DIV This indicates that the phase compensation loop after the RC phase shift network has reached a stable state and there is no oscillation. If the reference frequency f REF Still less than or equal to the feedback frequency f DIV , it indicates that the phase compensation of the RC phase shift network has not made the loop reach a stable state. At this time, the automatic search network will further increase the capacitance of the capacitor array, thereby moving the compensation frequency point. After the automatic search module adjusts the RC phase shift network, the loop phase margin is sufficient to make the loop stable.

[0029] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. An automatic phase margin compensation circuit, characterized in that: The invention comprises a loop phase automatic compensation module (102) arranged in a closed-loop system (100) and a loop stability detection module (101) connected between the output end of the closed-loop system and the loop phase automatic compensation module. The loop stability detection module (101) can detect the frequency of the loop output signal and can automatically search for the compensation position and compensate the loop phase margin when the output signal frequency is much higher than a set frequency threshold.

2. The automatic phase margin compensation circuit according to claim 1, characterized in that: The main body of the loop stability detection module (101) is a frequency and phase detector.

3. The automatic phase margin compensation circuit according to claim 2, characterized in that: The frequency detector includes a reference frequency f REF Input and feedback frequency f DIV At the input end, the phase frequency detector can transmit the phase difference between the two signals to the CP in the form of voltage on and off.

4. The automatic phase margin compensation circuit according to claim 2, characterized in that: The frequency and phase detector also includes two rising edge triggered D flip-flops with reset terminals and a logic AND gate.

5. The automatic phase margin compensation circuit according to claim 1, 2, 3 or 4, characterized in that: The loop phase automatic compensation module (102) is composed of an RC phase shift network and an automatic search unit.

6. The automatic phase margin compensation circuit according to claim 5, characterized in that: The RC phase shift network is provided with a capacitor array for adjusting the frequency position compensated by the RC phase shift network.

7. The automatic phase margin compensation circuit according to claim 6, characterized in that: The RC phase shift network is connected in series in the signal loop.

8. The automatic phase margin compensation circuit according to claim 7, characterized in that: The capacitor array within the RC phase shift network has a switch array.

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