Self-adaptive ripple injection circuit for COT controller and control method

Abstract

The invention discloses a self-adaptive ripple injection circuit for a COT controller and a control method, which can automatically adjust a compensation resistor according to an output load, can dynamically detect output current and mode changes, and can automatically correct the slope and amplitude of ripple injection according to operating conditions so as to keep a system stable. The circuit comprises a driving module, the driving module is in control connection with an upper switch tube Q1 and a lower switch tube Q2, the driving module is used for controlling alternate conduction of the upper switch tube Q1 and the lower switch tube Q2, the upper switch tube Q1 and the lower switch tube Q2 are connected with an inductor L, the inductor L is connected with a compensation resistor module, and the compensation resistor module is in control connection with a ripple injection control unit. The ripple injection control unit can judge a continuous conduction mode and an intermittent conduction mode, the ripple injection slope is improved according to a current zero-crossing mark signal in the continuous conduction mode, ripple injection is reduced or canceled in the intermittent conduction mode, and the resistance topological structure of the compensation resistance module is controlled and changed, so that the ripple injection size is adjusted.

Description

Technical Field

[0001] This invention relates to the field of switching power supply control technology, and specifically to an adaptive ripple injection circuit and control method for a COT controller. Background Technology

[0002] In COT controllers, to maintain system stability, a ripple signal is often injected into the error amplifier or comparator to ensure consistent switching cycles. However, the ripple injection slope in traditional circuits is usually a fixed value, leading to the following problems: the optimal injection amount varies under different input voltage / output current conditions; a fixed slope can easily cause insufficient phase margin under high loads and excessive jitter under low loads; and manual adjustment of external capacitor / resistor values ​​is required to maintain stability. Therefore, an architecture that can automatically adjust the ripple injection amount according to operating conditions is needed.

[0003] In COT controllers, to maintain system stability, methods such as... are often used. Figure 1 The RC network shown (R A And C A The ripple generated by the injected inductor current is fed into FB to stabilize the system. At a specific power level, to meet the requirements of system stability and output ripple being less than a certain order of magnitude, R... A and C A The settings are as follows:

[0004]

[0005] To maintain a certain system noise level, C A It is usually set to a fixed value, as shown below:

[0006]

[0007] Therefore, to meet the requirements under different operating conditions (such as duty cycle, output load, etc.), R can be adjusted. A To set different compensation parameters. In traditional design, R A The fixed value means the system can only operate stably under certain specific conditions; if a wider range of output voltage is required, the application engineer must manually adjust the external circuit structure (such as RFB1, RFB2, etc.) to maintain system stability, which causes inconvenience in use. Summary of the Invention

[0008] To address the problems in the prior art, this invention provides an adaptive ripple injection circuit and control method for a COT controller, which can automatically adjust the compensation resistor according to the output load, dynamically detect changes in output current and mode, and automatically correct the slope and amplitude of ripple injection according to operating conditions to maintain system stability.

[0009] To achieve the above objectives, the present invention provides an adaptive ripple injection circuit for a COT controller, comprising a driving module, which controls the upper switch Q1 and the lower switch Q2 to conduct alternately. The driving module controls the upper switch Q1 and the lower switch Q2 to conduct alternately. The upper switch Q1 and the lower switch Q2 are connected to an inductor L, which is connected to a compensation resistor module. The compensation resistor module is controlled to be connected to a ripple injection control unit. The ripple injection control unit can determine continuous conduction mode and intermittent conduction mode. In continuous conduction mode, it increases the ripple injection slope according to the current zero-crossing flag signal. In intermittent conduction mode, it decreases or cancels ripple injection and controls the change of the resistor topology of the compensation resistor module to adjust the ripple injection magnitude.

[0010] Furthermore, the ripple injection control unit is sequentially connected to an AND gate U1 and an NOT gate U2. The AND gate U1 and the NOT gate U2 control the connection of the compensation resistor module. The output signal of the ripple injection control unit is output as a control signal after passing through the AND gate U1 and the NOT gate U2. The control signal output controls the resistance value of the connection resistor of the compensation resistor module.

[0011] Furthermore, the compensation resistor module includes resistors R1, R2, R3, R4, and R5 connected in sequence, as well as NOT gates U3 and U4 connected in sequence. The input of NOT gate U3 is connected to the output of NOT gate U2, the output of NOT gate U3 is connected to the control terminal of switch M1, the output of NOT gate U4 is connected to the control terminal of switch M2, the source of switch M1 and the drain of switch M2 are connected between resistors R2 and R3, and the drain of switch M1 and the source of switch M2 are connected between resistors R4 and R5.

[0012] Furthermore, the ripple injection control unit includes:

[0013] The output current detection module is used to detect the direction and magnitude of the output current and generate a zero-crossing flag signal;

[0014] The current control module is used to control the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope.

[0015] The voltage / current switching module is used to detect the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and select the corresponding ripple injection parameters to generate a ripple signal.

[0016] The comparison and pulse generation module is used to control the switch conduction time based on the ripple signal to maintain stable output voltage;

[0017] It also includes an injection control module, which controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

[0018] Furthermore, the output current detection module and the voltage / current switching module adopt ZCD modules.

[0019] Furthermore, the current control module employs an RC circuit.

[0020] Furthermore, the comparison and pulse generation module includes a comparator and a pulse generator connected together. The output of the comparator is connected to the Ton module. The comparator outputs a CLKoff signal, which is input to the Ton module to adjust the duty cycle and period of the Ton signal.

[0021] In another aspect, the present invention provides an adaptive ripple injection control method for a COT controller, employing the aforementioned adaptive ripple injection circuit for a COT controller, comprising: a ripple injection control unit that detects the output current and the zero-crossing point of the output current in real time; determines a continuous conduction mode or an intermittent conduction mode based on the output current and voltage; increases the ripple injection slope based on the current zero-crossing flag signal in the continuous conduction mode; and decreases or cancels ripple injection in the intermittent conduction mode by controlling and changing the resistor topology of the compensation resistor module, thereby adjusting the ripple injection magnitude.

[0022] Furthermore, the ripple injection control unit uses an output current detection module to detect the direction and magnitude of the output current and generate a zero-crossing flag signal; the current control module controls the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope; the voltage / current switching module detects the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and selects the corresponding ripple injection parameters to generate a ripple signal; the comparison and pulse generation module controls the switch conduction time according to the ripple signal to maintain output voltage stability; the injection control module controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

[0023] Furthermore, the comparison and pulse generation module includes a comparator and a pulse generator connected together. The output of the comparator is connected to the Ton module. The comparator outputs a CLKoff signal, which is input to the Ton module to adjust the duty cycle and period of the Ton signal.

[0024] Compared with existing technologies, this invention can determine continuous conduction mode and intermittent conduction mode. In continuous conduction mode, it increases the ripple injection slope based on the current zero-crossing flag signal, and decreases or cancels ripple injection in intermittent conduction mode. It controls and changes the resistor topology of the compensation resistor module to adjust the ripple injection magnitude. It can automatically adjust the compensation resistor according to the output load, dynamically detect the output current and mode changes, and automatically correct the ripple injection slope and amplitude according to the operating conditions to maintain system stability. Compared with the fixed compensation resistor method of existing technologies, the system has stronger stability and achieves a wider range of output voltage. It does not require adjustment of the external circuit structure, operates efficiently, adapts to different loads and operating modes, and has strong adaptability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the circuit principle of a COT controller in the prior art;

[0026] Figure 2 This is a schematic diagram of the Buck system and ripple injection compensation circuit of the present invention;

[0027] Figure 3 This is a schematic diagram of the adaptive ripple injection circuit of the present invention;

[0028] Figure 4 This is a schematic diagram of the ripple injection control circuit of the present invention;

[0029] Figure 5a This is a normal waveform diagram for COT control in a scenario between DCM and CCM; Figure 5b This is a waveform diagram of subharmonic oscillations occurring in COT control;

[0030] Figure 6a This is a simulation waveform diagram of fixed-slope ripple injection using existing technology; Figure 6b This is a simulation waveform diagram of the adaptive ripple injection of the present invention. Detailed Implementation

[0031] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] This invention provides an adaptive ripple injection circuit for a COT controller, see [link to relevant documentation]. Figure 2The system includes a drive module, which controls the upper switch Q1 and the lower switch Q2 to conduct alternately. The upper switch Q1 and the lower switch Q2 are connected to an inductor L, which is connected to the output load. The inductor L is also connected to a compensation resistor module, which controls the ripple injection control unit. The ripple injection control unit can determine the continuous conduction mode (CCM) and discontinuous conduction mode (DCM). In the continuous conduction mode, the ripple injection slope is increased according to the current zero-crossing flag signal. In the discontinuous conduction mode, the ripple injection is reduced or canceled. The control unit changes the resistor topology of the compensation resistor module to adjust the ripple injection magnitude.

[0033] Specifically, the ripple injection control unit is sequentially connected to a logic AND gate U1 and a logic NOT gate U2. The logic AND gate U1 and the logic NOT gate U2 control the connection of the compensation resistor module. The output signal of the ripple injection control unit is output as a control signal after passing through the logic AND gate U1 and the logic NOT gate U2. The control signal output controls the resistance value of the connection resistor of the compensation resistor module.

[0034] See Figure 3 The compensation resistor module includes resistors R1, R2, R3, R4, and R5 connected in sequence, as well as logic gates U3 and U4. The input of logic gate U3 is connected to the output of logic gate U2. Resistors R1 to R5 are connected to the SW points across the inductor L. The output of logic gate U3 is connected to the control terminal of switch M1, and the output of logic gate U4 is connected to the control terminal of switch M2. The source of switch M1 and the drain of switch M2 are connected between resistors R2 and R3, and the drain of switch M1 and the source of switch M2 are connected between resistors R4 and R5.

[0035] When the system enters CCM or switches between CCM / DCM modes, the ripple injection control unit outputs TBT_HFSW, which is a high-level (ON) signal, through the AND gate U1 and the NOT gate U2. Then, through the NOT gate U3 and the NOT gate U4, it drives the switching transistors M1 and M2 to turn on or off, thereby automatically changing the resistor topology of resistors R1 to R5 and adjusting the magnitude of the injected ripple to maintain the stability of the system under different load conditions.

[0036] TBT_HFSW can be started by the system to determine whether to enter DCM or CCM mode. That is, the system working mode can be determined by the ZCD signal. If the ZCD signal can be reliably detected in each cycle, it means that the system is working in DCM mode. If the ZCD signal is not detected for a long time or the ZCD signal is continuously invalid, it means that the system is working in CCM mode.

[0037] The ripple injection control unit includes:

[0038] The output current detection module is used to detect the direction and magnitude of the output current and generate a zero-crossing flag signal.

[0039] The current control module is used to control the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope.

[0040] The voltage / current switching module is used to detect the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and select the corresponding ripple injection parameters to generate a ripple signal.

[0041] The comparison and pulse generation module is used to control the switch conduction time based on the ripple signal to maintain stable output voltage;

[0042] It also includes an injection control module, which controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

[0043] The output current detection module and voltage / current switching module of this invention employ a ZCD module. The ZCD module can detect the direction and magnitude of the output current, generate a zero-crossing flag signal, and generate a signal to activate switching transistors M1 and M2, thereby adjusting the resistance value of the compensation resistor and changing the ripple injection slope. The current control module uses an RC circuit.

[0044] See Figure 4 The comparison and pulse generation module includes a comparator and a pulse generator connected together. The comparator's output is connected to the Ton module, and the comparator outputs a CLKoff signal. The CLKoff signal is input to the Ton module to adjust the duty cycle and period of the Ton signal. Ripple injection control is Ri. After injection, it is compared with the compensation signal Vc output from the feedback loop to drive the COT module, i.e. Figure 4 The Ton module generates power switch control signals to stabilize the system.

[0045] The present invention also provides an adaptive ripple injection control method for a COT controller, which can dynamically detect changes in output current and mode, and automatically correct the slope and amplitude of ripple injection according to operating conditions to maintain system stability.

[0046] Principle of ripple injection control method:

[0047] In typical COT control scenarios that fall between DCM and CCM, see the normal waveform diagram. Figure 5a During the T3 period, V vicThe waveforms of the (compensation-generated ramp) and Vo (output ramp) signals are straight lines with different slopes, while the feedback signal V fb It's Vo and V vic The weighted sum. Represented as follows:

[0048] S fb =k1S vo +k2S vic

[0049] The dashed waveform represents steady-state V. fb The signal, the solid line waveform, is a perturbation V. fb The signal has three distinct periods in its waveform. V fb The slope of the signal during the "off" period, S fb A negative value indicates a negative slope. (In a steady state, the slope is negative). Waveform V fb and V ref When the waveform intersects in the "DCM modulation region" with a constant on-time, it will quickly return to a steady state. This mechanism is self-correcting, and the system itself is stable.

[0050] When S fb For cases where >0, see [reference] Figure 5b In this case, V fb and V ref The intersection occurs at the end of cycle T2, therefore, there is no T3 period where both the transistor switch and diode are off and the output capacitor discharges to the load. In this case, it is no longer DCM mode. Therefore, the average output voltage Vo increases with time, and as Vo increases, S... vo Negative increase, S fb The value of decreases according to the formula. This process continues three times in the diagram until S... fb The value becomes negative. The number of times this process repeats depends on the circuit conditions; this phenomenon is called subharmonic oscillation. Therefore, the condition to ensure no oscillation occurs is as follows:

[0051] S fb =k1S vo +k2S vic S fb <0

[0052] Criterion obtained:

[0053]

[0054] Therefore, by monitoring the current and adjusting k2 in the circuit as needed, the system can be kept stable under different operating conditions.

[0055] The method of the present invention includes: a ripple injection control unit detects the output current and the zero-crossing point of the output current in real time; determines the continuous conduction mode or the intermittent conduction mode based on the output current and voltage; increases the ripple injection slope based on the current zero-crossing flag signal in the continuous conduction mode; and reduces or cancels the ripple injection in the intermittent conduction mode by controlling and changing the resistor topology of the compensation resistor module, thereby adjusting the ripple injection magnitude.

[0056] The ripple injection control unit uses an output current detection module to detect the direction and magnitude of the output current and generate a zero-crossing flag signal. The current control module controls the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope. The voltage / current switching module detects the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and selects the corresponding ripple injection parameters to generate a ripple signal. The comparison and pulse generation module controls the switch conduction time according to the ripple signal to maintain output voltage stability. The injection control module controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

[0057] Specifically, the following steps are included:

[0058] 1) Output current monitoring: Real-time monitoring of output current and its zero-crossing point;

[0059] 2) Mode determination: Determine whether the system is in CCM or DCM mode based on the output current and voltage;

[0060] 3) Parameter switching: In CCM mode, the ripple injection slope is different from that in DCM mode. By means of the method proposed in this invention, ripples with different slopes can be injected for different operating modes to stabilize control. The slope and amplitude of the ripple injection signal are generated by a variable current source or a PWM digital modulator. With this invention, false triggering can be reduced under high load (CCM) and loop stability can be improved under low load (DCM).

[0061] 4) Adaptive correction: Based on the current zero-crossing indicator signal, the slope of the injected current is gradually adjusted to keep the error voltage within a stable range;

[0062] 5) Controller execution: Inject the adjusted ripple signal into the comparator or error amplifier to complete dynamic compensation.

[0063] The control method of this invention can be used in COT control architectures of Buck, Boost, Buck-Boost, and multiphase converters. The adaptive ripple injection circuit detects near-zero and zero-crossing output currents and generates a flag signal as the basis for determining the system ripple injection amplitude. It can switch and adaptively adjust the ripple injection value required for stable CCM / DCM based on the operating environment of the system input and output voltages to maintain system stability. It is suitable for high-frequency COT controllers or power IC systems such as Buck / Boost. The adaptive ripple injection control method can dynamically detect changes in output current and mode, and automatically correct the slope and amplitude of ripple injection according to operating conditions to maintain system stability and adapt to different loads and operating modes.

[0064] Simulation experiments were conducted using existing fixed compensation resistor schemes and the present invention, respectively. See details below. Figure 6a and Figure 6b , Figure 6a and Figure 6b The curves from top to bottom represent the output voltage waveforms Vout and Vsw, respectively. It can be seen that the existing technology will have subharmonic oscillations under DCM. The present invention can maintain a stable switching waveform of the system under DCM, and therefore can be used to adapt to different loads and operating modes.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive ripple injection circuit for a COT controller, characterized in that, The system includes a drive module that controls the upper switch Q1 and the lower switch Q2 to conduct alternately. The upper switch Q1 and the lower switch Q2 are connected to an inductor L, which is connected to a compensation resistor module. The compensation resistor module is connected to a ripple injection control unit. The ripple injection control unit can determine continuous conduction mode and intermittent conduction mode. In continuous conduction mode, it increases the ripple injection slope based on the current zero-crossing flag signal. In intermittent conduction mode, it decreases or cancels ripple injection and controls the change of the resistor topology of the compensation resistor module to adjust the ripple injection magnitude.

2. The adaptive ripple injection circuit for a COT controller according to claim 1, characterized in that, The ripple injection control unit is sequentially connected to a logic AND gate U1 and a logic NOT gate U2. The logic AND gate U1 and the logic NOT gate U2 control the connection of the compensation resistor module. The output signal of the ripple injection control unit passes through the logic AND gate U1 and the logic NOT gate U2 to output a control signal. The control signal output controls the resistance value of the connection resistor of the compensation resistor module.

3. The adaptive ripple injection circuit for a COT controller according to claim 2, characterized in that, The compensation resistor module includes resistors R1, R2, R3, R4, and R5 connected in sequence, as well as NOT gates U3 and U4. The input of NOT gate U3 is connected to the output of NOT gate U2, the output of NOT gate U3 is connected to the control terminal of switch M1, the output of NOT gate U4 is connected to the control terminal of switch M2, the source of switch M1 and the drain of switch M2 are connected between resistors R2 and R3, and the drain of switch M1 and the source of switch M2 are connected between resistors R4 and R5.

4. The adaptive ripple injection circuit for a COT controller according to claim 1, characterized in that, The ripple injection control unit includes: The output current detection module is used to detect the direction and magnitude of the output current and generate a zero-crossing flag signal; The current control module is used to control the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope. The voltage / current switching module is used to detect the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and select the corresponding ripple injection parameters to generate a ripple signal. The comparison and pulse generation module is used to control the switch conduction time based on the ripple signal to maintain stable output voltage; It also includes an injection control module, which controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

5. The adaptive ripple injection circuit for a COT controller according to claim 4, characterized in that, The output current detection module and voltage / current switching module adopt ZCD modules.

6. The adaptive ripple injection circuit for a COT controller according to claim 4, characterized in that, The current control module uses an RC circuit.

7. The adaptive ripple injection circuit for a COT controller according to claim 4, characterized in that, The comparison and pulse generation module includes a comparator and a pulse generator connected together. The output of the comparator is connected to the Ton module. The comparator outputs a CLKoff signal, which is input to the Ton module to adjust the duty cycle and period of the Ton signal.

8. An adaptive ripple injection control method for a COT controller, characterized in that, An adaptive ripple injection circuit for a COT controller, as described in any one of claims 1 to 7, includes: a ripple injection control unit that detects the output current and the zero-crossing point of the output current in real time; determines a continuous conduction mode or an intermittent conduction mode based on the output current and voltage; increases the ripple injection slope based on the current zero-crossing flag signal in the continuous conduction mode; reduces or cancels ripple injection in the intermittent conduction mode; and controls the change of the resistor topology of the compensation resistor module to adjust the ripple injection magnitude.

9. The adaptive ripple injection control method for a COT controller according to claim 8, characterized in that, The ripple injection control unit uses an output current detection module to detect the direction and magnitude of the output current and generate a zero-crossing flag signal; The current control module controls the current source or capacitor network according to the zero-crossing flag signal to change the ripple injection slope; the voltage / current switching module detects the input voltage and output voltage to determine whether the converter is operating in continuous conduction mode or intermittent conduction mode, and selects the corresponding ripple injection parameters to generate a ripple signal; the comparison and pulse generation module controls the switch conduction time according to the ripple signal to maintain the output voltage stability. The injection control module controls the compensation resistor module to change the resistor topology to generate an adaptive compensation resistor signal, and compares it with the compensation signal output by the feedback loop to drive the Ton module to generate a switching power supply control signal.

10. The adaptive ripple injection control method for a COT controller according to claim 9, characterized in that, The comparison and pulse generation module includes a comparator and a pulse generator connected together. The output of the comparator is connected to the Ton module. The comparator outputs a CLKoff signal, which is input to the Ton module to adjust the duty cycle and period of the Ton signal.

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