Ripple injection enhancement circuit and ripple injection enhanced COT mode DC-DC converter
By dynamically adjusting the ripple injection coefficient according to the duty cycle in the COT mode DC-DC converter, ripple injection under large duty cycle is enhanced, and the problem of insufficient ripple under large duty cycles is solved, and the stable application of the system is achieved under different duty cycles is achieved.
Patent Information
- Application Number
- CN202411960695.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-28
- Publication Date
- 2025-04-11
AI Technical Summary
In COT mode DC-DC converter, as the duty cycle increases, the amplitude of the ripple signal generated by the internal ripple injection network will decrease, resulting in insufficient ripple injection under large duty cycles, affecting system stability.
By quantifying the magnitude of the duty cycle, when the duty cycle increases, the coefficient of ripple injection is increased. The actual injection ripple is the ripple generated by the ripple injection network multiplied by the coefficient of ripple injection, thereby enhancing the injection ripple with a large duty cycle.
Without affecting normal duty cycle applications, injection ripple under large duty cycles are enhanced to ensure the stability and responsiveness of the system under different duty cycles.
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Figure CN119813735A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present disclosure relate to the field of voltage conversion, and in particular, to a ripple injection enhancement circuit, a ripple injection enhanced COT mode DC-DC converter, and an electronic device. Background Art
[0002] COT mode (Constant On-Time Mode) is a control mode of the switching regulator. Different from the traditional current mode control (Current Mode Control) or voltage mode control (Voltage Mode Control), the core idea of COT mode is to control the on-time of the switch to remain constant, rather than directly controlling the duty cycle or output current of the switch. Its advantage is that it can avoid high-frequency noise and provide higher conversion efficiency, which is suitable for systems with faster load changes. However, in the case of rapid load changes, COT mode may be affected by output voltage fluctuations or ripples. In order to keep the system stable, the output resistive ripple needs to be greater than the capacitive ripple.
[0003] In modern DC-DC converters, ceramic capacitors are usually used as output capacitors because they have a low equivalent series resistance (ESR). The role of ESR is to provide a certain resistive ripple component. If the ESR value is too low, the capacitive ripple of the output will dominate, making the resistive ripple relatively small, affecting the stability of the system. Usually, the resistive ripple is enhanced by injecting additional ripple through an internal ripple injection network (such as resistors, capacitors, op amps, etc.). Since the design of the internal ripple injection network is based on a certain switching frequency and ripple characteristics, as the duty cycle continues to increase, the amplitude of the ripple signal it generates will decrease with the increase of the duty cycle. When the ripple injection signal is insufficient, the system may experience subharmonic oscillations, resulting in unstable output or even collapse. Therefore, insufficient internal ripple injection limits the application of internal ripple injection COT mode DC-DC converters under large duty cycles. Therefore, the ripple injection network needs to be adjusted or enhanced to ensure the application under large duty cycles. Summary of the invention
[0004] In order to solve the problem, the embodiments described in this article provide a ripple injection enhancement circuit and a ripple injection enhanced COT mode DC-DC converter. By quantifying the size of the duty cycle, when the duty cycle increases, the ripple injection coefficient is increased. The actual injected ripple is the ripple generated by the ripple injection network multiplied by the ripple injection coefficient. The injected ripple with a large duty cycle can be enhanced without affecting the normal duty cycle application, thereby realizing the application of small duty cycle to large duty cycle.
[0005] According to a first aspect of the present disclosure, a ripple injection enhancement circuit is provided, which is used to provide a compensation injection current according to the duty cycle of a COT mode DC-DC converter, the compensation injection current is negatively correlated with the input voltage of the DC-DC converter, and positively correlated with the output voltage of the DC-DC converter, and the ripple injection enhancement circuit includes: a first voltage-controlled current source, a second voltage-controlled current source, a first current mirror, a second current mirror, a third current mirror, a fourth current mirror, a fifth current mirror and a current source, the first voltage-controlled current source is used to convert the output voltage of the DC-DC converter into an output current; the second voltage-controlled current source is used to convert the input voltage of the DC-DC converter into an input current; the first current mirror, the second current mirror, and the third current mirror constitute a first differential circuit, which is used to make a difference between the input current and the output current to obtain a first current difference, and the fourth current mirror and the fifth current mirror constitute a second differential circuit, which is used to make a difference between the current generated by the current source and the first current difference to obtain a second current difference, and the second current difference is used as the compensation injection current.
[0006] Optionally, the first voltage-controlled current source includes a first operational amplifier, a first resistor, and a first switch tube, and the second voltage-controlled current source includes a second operational amplifier, a second resistor, and a second switch tube; the non-inverting input terminal of the first operational amplifier is connected to the output voltage sampling terminal of the DC-DC converter, the reverse input terminal is connected to the source of the first switch tube, the output terminal is connected to the gate of the first switch tube, the drain of the first switch tube is connected to the first current mirror, and the source is connected to the first resistor; the non-inverting input terminal of the second operational amplifier is connected to the input voltage sampling terminal of the DC-DC converter, the reverse input terminal is connected to the source of the second switch tube, the output terminal is connected to the gate of the second switch tube, the drain of the second switch tube is connected to the third current mirror, and the source is connected to the second resistor.
[0007] Optionally, the first current mirror is used to copy the output current to the second current mirror, the third current mirror is used to copy the input current to the second current mirror, the second current mirror is used to differentiate the input current and the output current to obtain a first current difference, and feed the first current difference back to a second differential circuit composed of a fourth current mirror and a fifth current mirror; the fourth current mirror is used to copy the current generated by the current source, and the fifth current mirror is used to differentiate the current generated by the current source from the first current difference to obtain a second current difference.
[0008] Optionally, the resistance values of the first resistor and the second resistor are equal, and the first current difference is: Ia=K0*(Vin-Vo) / R, wherein K0 is the proportional coefficient, Vin is the input voltage, Vo is the output voltage, and R is the resistance value of the first resistor and the second resistor; the second current difference is: Iinject=Ib-Ia=Ib-K0*(Vin-Vo) / R, wherein Ib is the current of the current source, Ia is the first current difference, and the second current difference is negatively correlated with the input voltage and positively correlated with the output voltage.
[0009] According to a second aspect of the present disclosure, a ripple injection enhanced COT mode DC-DC converter is provided, comprising: a ripple injection enhancement circuit, a ripple injection network, a ripple injection transconductance amplifier, a PWM transconductance amplifier and a COT mode DC-DC converter as described in the first aspect of the present disclosure;
[0010] The ripple injection network injects a ripple signal into the feedback loop of the COT mode DC-DC converter by connecting a ripple injection transconductance amplifier; the ripple injection enhancement circuit is used to inject a compensation injection current into the tail current of the ripple injection transconductance amplifier according to the duty cycle of the COT mode DC-DC converter; the ripple injection transconductance amplifier and the PWM transconductance amplifier are both connected to the feedback node of the COT mode DC-DC converter, the PWM transconductance amplifier is used to convert the feedback voltage into a current according to the transconductance of the PWM transconductance amplifier, and the ripple injection transconductance amplifier is used to convert the injected ripple signal into a current according to the transconductance of the ripple injection transconductance amplifier.
[0011] Optionally, in a ripple injection enhanced COT mode DC-DC converter, the COT mode DC-DC converter includes: a high-end tube, a low-end tube, a drive control logic, an output inductor, an output capacitor, an upper voltage divider resistor, a lower voltage divider resistor and a PWM comparator; the common end of the upper voltage divider resistor and the lower voltage divider resistor is connected to the input end of the PWM transconductance operational amplifier to form a feedback loop; the PWM comparator is used to output a PWM control signal according to the comparison result between the feedback voltage and the reference voltage, and the PWM control signal controls the switching state of the high-end tube and the low-end tube through the drive control logic, and when the conduction time of the high-end tube or the low-end tube reaches the set value, the high-end tube or the low-end tube is turned off.
[0012] Optionally, in a ripple injection enhanced COT mode DC-DC converter, the ripple injection network includes a voltage divider resistor, a filter resistor, a filter capacitor and an RC filter circuit, the switching signal of the DC-DC converter is divided by the voltage divider resistor and the filter resistor to obtain a first voltage signal, and the switching signal of the DC-DC converter is low-pass filtered by the filter resistor, the filter capacitor and the RC filter circuit to obtain a second voltage signal; the ripple injection transconductance amplifier is used to generate an injected ripple signal according to the difference between the first voltage signal and the second voltage signal.
[0013] Optionally, in the COT mode DC-DC converter with enhanced ripple injection, the gain of the ripple injection network to the feedback node is: K = K1K2, K1 = R1 / (R1+R LPF ), K2 = Gm_ripple / Gm_pwm, where R LPF is the resistance of the filter resistor, R1 is the resistance of the voltage divider resistor, Gm_ripple is the transconductance of the ripple injection transconductance amplifier, and Gm_pwm is the transconductance of the PWM transconductance amplifier.
[0014] Optionally, in a COT mode DC-DC converter with enhanced ripple injection, the resistive ripple of the feedback node is:
[0015]
[0016] The capacitive ripple of the feedback node is:
[0017]
[0018] Among them, R ESR is the output capacitor C o The equivalent resistance, R eff The equivalent resistance of the ripple injection network, R FT R is the upper voltage divider resistor of the output voltage. FB is the lower voltage divider resistor of the output voltage, V in is the input voltage, V o is the output voltage, T on is the on-time, L is the output inductance; the resistive ripple is greater than the capacitive ripple, so that (R eff +R esr )·C o >T on / 2, where R LPF The filter resistor of the ripple injection network, C LPF It is the filter capacitor of the ripple injection network; when the duty cycle increases, the compensation injection current increases, which increases the transconductance ratio of the ripple injection transconductance amplifier and the PWM transconductance amplifier, and the equivalent resistance of the ripple injection network increases, so that the resistive ripple is kept larger than the capacitive ripple when the duty cycle increases.
[0019] According to a third aspect of the present disclosure, an electronic device is provided, comprising the ripple injection enhanced COT mode DC-DC converter according to the second aspect of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. It should be noted that the drawings described below only relate to some embodiments of the present disclosure, but are not intended to limit the present disclosure, wherein:
[0021] Figure 1 is a circuit structure diagram of a COT mode BUCK type DC-DC circuit with ripple injection according to an embodiment of the present disclosure;
[0022] Figure 2 is a circuit structure diagram of a COT mode BUCK type DC-DC circuit with enhanced ripple injection according to an embodiment of the present disclosure;
[0023] Figure 3is a circuit structure diagram of a ripple injection enhancement circuit according to an embodiment of the present disclosure.
[0024] It should be noted that the elements in the drawings are schematic and not drawn to scale. DETAILED DESCRIPTION
[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present disclosure.
[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person skilled in the art to which the subject matter of the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together directly or through one or more intermediate components.
[0027] The COT mode DC-DC converter is a switching power supply that uses a continuous conduction mode. Its switching cycle is determined by the change of the inductor current waveform, rather than being controlled by a fixed PWM frequency. Specifically, the control signal in the COT mode is based on the inductor current or output voltage feedback, and the duration of each switching cycle is dynamic, depending on the load change and the inductor current feedback.
[0028] Since the output capacitors of DC-DC converters generally use ceramic capacitors, their ESR (equivalent series resistance) is relatively small, and additional internal ripple injection is required to improve the dynamic response and stability of the system. When the system is running, the ripple injection network generates a ripple signal of a certain amplitude and injects it into the feedback loop. However, as the duty cycle increases, the proportion of the on time in the switching cycle increases, which means that the output ripple frequency decreases accordingly, and the ripple signal amplitude generated by the internal ripple injection network will gradually decrease, which results in the injected ripple being insufficient to maintain the stability or responsiveness of the system under large duty cycles.
[0029] Figure 1 is a circuit structure diagram of a COT mode BUCK type DC-DC circuit with ripple injection according to an embodiment of the present disclosure. Figure 1As shown in FIG. 1 , the COT mode DC-DC converter includes a ripple injection network (RIN), a ripple injection transconductance amplifier G m_ripple 、PWM transconductance amplifier G m_pwm And COT mode DC-DC converter. Among them, the ripple injection network RIN is connected to the ripple injection transconductance amplifier G m_ripple Inject a ripple signal into the feedback loop of the COT mode DC-DC converter; the ripple is injected into the transconductance amplifier G m_ripple and PWM transconductance amplifier G m_pwm Both are connected to the feedback node FB of the COT mode DC-DC converter, the PWM transconductance amplifier G m_pwm It is used to convert the feedback voltage into current according to the transconductance of the PWM transconductance amplifier, and the ripple injection transconductance amplifier is used to convert the injected ripple signal into current according to the transconductance of the ripple injection transconductance amplifier.
[0030] Reference Figure 1 As shown in the figure, the COT mode DC-DC converter includes a high-end tube HSMOS, a low-end tube LSMOS, a drive control logic Logic, an output inductor L, and an output capacitor C O , upper voltage divider resistor R FT , the lower voltage divider resistor R FB and PWM comparator. The upper voltage divider resistor R FT And the lower voltage divider resistor R FB The common terminal is connected to the PWM transconductance amplifier G as the feedback node. m_pwm The input terminal forms a feedback loop. PWM transconductance amplifier G m_pwm For the feedback voltage V fb With reference voltage V ref The comparison result outputs a PWM control signal, and the PWM control signal controls the switching state of the high-end tube HSMOS and the low-end tube LSMOS through the driving control logic Logic. When the conduction time of the high-end tube HSMOS or the low-end tube LSMOS reaches the set value, the high-end tube or the low-end tube is turned off.
[0031] Specifically, when V fb Less than V ref When the switch control signal is output by the driving control logic Logic, the high-end tube is turned on and the low-end tube is turned off, entering the charging stage, causing the output voltage ripple to rise, and the feedback voltage to rise to a level greater than the reference voltage, so that the switch control signal is maintained at a high level. At the same time, the switch control signal controls the On-Timer fixed on-time generation module to start timing. After the fixed on-time, the fixed on-time generation module outputs a high-level narrow pulse, thereby turning off the high-end tube and turning on the low-end tube, entering the freewheeling stage, until the next feedback voltage V is detected. fb Less than the reference voltage V refThe above process is repeated so that the output voltage finally maintains a stable state.
[0032] The internal injection ripple is generated by a ripple injection network (RIN). According to one embodiment of the present disclosure, the ripple injection network includes a filter resistor, a filter capacitor, a voltage divider resistor and an RC filter circuit. The switching signal V SW The voltage is divided by the voltage divider resistor and the filter resistor, and the switch signal is low-pass filtered by the filter resistor, the filter capacitor, and the RC filter circuit. The number of stages of the RC filter circuit can be increased as needed, and this solution does not limit this.
[0033] Reference Figure 1 As shown, the ripple injection network RIN includes the voltage divider resistor R1, the filter resistor R LPF 、Filter capacitor C LPF and the fifth resistor R5, the sixth resistor R6, the first filter capacitor C LPF1 , the second filter capacitor C LPF2 The RC filter circuit composed of the DC-DC converter switching signal V SW Through the voltage divider resistor R1, filter resistor R LPF The voltage division ratio of the ripple injection network is K1 = R1 / (R1+R LPF ), switching signal V SW After the voltage divider resistor R1 and the filter resistor R LPF 、Filter capacitor C LPF The first voltage signal Vripple is converted into a sinusoidal form after voltage division and filtering, and is injected into the transconductance amplifier G as a ripple. m_ripple An input terminal.
[0034] Then through the fifth resistor R5, the sixth resistor R6, the first filter capacitor C LPF1 , the second filter capacitor C LPF2 The RC filter circuit composed of the two components performs low-pass filtering to obtain a second voltage signal, which is approximately equal to K1*V O The fixed value is used as ripple to inject into the transconductance amplifier G m_ripple The ripple is injected into the transconductance amplifier G m_ripple Used for sinusoidal signal Vripple and K1*V O The signals are compared and the output differential ripple signal is injected into the feedback loop of the DC-DC converter.
[0035] The gain of the ripple injection network to the feedback node is: K = K1K2, K1 = R1 / (R1+R LPF ), K2 = Gm_ripple / Gm_pwm, where R LPFis the resistance of the filter resistor, R1 is the resistance of the voltage divider resistor, Gm_ripple is the transconductance of the ripple injection transconductance amplifier, and Gm_pwm is the transconductance of the PWM transconductance amplifier.
[0036] According to one embodiment of the present disclosure, the calculation formulas of the resistive ripple Vripple_R and the capacitive ripple Vripple_C of the feedback node are as follows:
[0037]
[0038] Among them, R ESR is the equivalent resistance of the output capacitor Co, R eff The equivalent resistance of the ripple injection network RIN, R FT R is the upper voltage divider resistor of the output voltage. FB is the lower voltage divider resistor of the output voltage, Vin is the input voltage, Vo is the output voltage, Ton is the conduction time, and L is the output inductor.
[0039] In order to ensure loop stability, the output resistive ripple must be greater than the capacitive ripple, that is, the resistive ripple of the feedback node must be greater than the capacitive ripple, that is, V ripple_R >V ripple_C , according to V ripple_R The calculation formula and V ripple_C The calculation formula is:
[0040] (R eff +R esr )·C o >T on / 2.
[0041] Since the output capacitors are currently all ceramic capacitors with very small ESR resistance, the stability of the internal ripple injection COT mode Buck basically depends on the equivalent resistance R generated by the ripple injection. eff . R eff The expression can be calculated according to the following equation:
[0042]
[0043] The left side of the above equation is the resistive ripple required by the DC-DC converter, and the right side of the equation is the injected ripple signal of the ripple injection network, which is obtained
[0044] Among them, R LPF The filter resistor of the ripple injection network RIN, C LPF is the filter capacitor of the ripple injection network RIN, L is the output inductor, R FT R is the upper voltage divider resistor of the output voltage. FBis the lower voltage divider resistor of the output voltage, K is the gain of the ripple injection network to the feedback node, which describes how the ripple signal affects the feedback loop and thus affects the dynamic response of the system.
[0045] Specifically, the actual injected ripple signal is obtained by multiplying the original ripple generated by the ripple injection network by the dynamically adjusted ripple injection coefficient K. The gain K is affected by two parameters, namely, the voltage division ratio K1 = R1 / (R1+R LPF ) and ripple injection into the transconductance amplifier's transconductance G m_ripple The transconductance G of the PWM transconductance amplifier m_pwm The ratio K2=G m_ripple / G m_pwm .
[0046] K1 determines the ripple amplitude transmitted to the feedback node after passing through the ripple injection network. Transconductance defines the effect of input voltage changes on output current. The greater the gain of the transconductance op amp, the more significant the effect on signal transmission. m_ripple is the transconductance of the ripple injection op amp, controlling the ripple amplitude injected into the feedback loop. m_pwm It is the transconductance of the PWM control transconductance amplifier, which controls the gain of the PWM signal. By adjusting K1 and K2, the ripple injection effect under different working conditions can be effectively controlled. For small duty cycles, the amplitude of the original ripple signal is strong, so it is sufficient to keep a small injection coefficient. For large duty cycles, by increasing the injection coefficient, the ripple injection is enhanced, thereby ensuring that the appropriate ripple signal strength can be maintained under different duty cycles to avoid instability.
[0047] Limited by the output voltage and the withstand voltage of the internal devices, the ripple injection network voltage divider ratio K1 is basically fixed. Therefore, the injected ripple under large duty cycle can be enhanced by adjusting K2. When the device size of the transconductance amplifier is fixed, its transconductance is proportional to the square root of the tail current, that is, Therefore, in order to ensure the stability of the feedback loop, the ripple injection amount can be dynamically adjusted by introducing a ripple injection enhancement circuit to achieve applications from small duty cycle to large duty cycle.
[0048] Figure 2 is a circuit structure diagram of a COT mode BUCK type DC-DC circuit with enhanced ripple injection according to an embodiment of the present disclosure; Figure 2 As shown in FIG. 1 , a compensation injection current I can be injected into the tail current of the ripple injection transconductance amplifier through a ripple enhancement circuit (RIE) at a large duty cycle. inject , I inject With input voltage V in Negatively correlated with the output voltage Vo, positively correlated with the output voltage Vo. When the duty cycle gradually increases from small to large, the compensation injection current increases, and the ripple is injected into the transconductance G of the op amp.m_ripple The transconductance G of the PWM transconductance amplifier m_pwm The ratio K2 will also gradually increase from small to large, and the equivalent resistance R of the ripple injection network eff Increases so that the resistive ripple remains larger than the capacitive ripple when the duty cycle increases.
[0049] Figure 3 is a circuit structure diagram of a ripple injection enhancement circuit according to an embodiment of the present disclosure. Figure 3 As shown, the ripple injection enhancement circuit includes: a first voltage-controlled current source S1, a second voltage-controlled current source S2, a first current mirror M1, a second current mirror M2, a third current mirror M3, a fourth current mirror M4, a fifth current mirror M5 and a current source, wherein the first voltage-controlled current source S1 is used to convert the output voltage of the DC-DC converter into an output current; the second voltage-controlled current source is used to convert the input voltage of the DC-DC converter into an input current; the first current mirror M1, the second current mirror M2, and the third current mirror M3 form a first differential circuit, which is used to make a difference between the input current Iin and the output current Io to obtain a first current difference Ia, and the fourth current mirror M4 and the fifth current mirror M5 form a second differential circuit, which is used to make a difference between the current Ib generated by the current source and the first current difference Ia to obtain a second current difference, and the second current difference is used as the compensation injection current Iinject.
[0050] According to an embodiment of the present disclosure, the first voltage-controlled current source S1 includes a first operational amplifier A1, a first resistor R0, and a first switch tube Q1, and the second voltage-controlled current source S2 includes a second operational amplifier A2, a second resistor R2, and a second switch tube Q2; the positive input terminal of the first operational amplifier A1 is connected to the output voltage sampling terminal K0V of the DC-DC converter. O The reverse input end is connected to the source of the first switch tube Q1, the output end is connected to the gate of the first switch tube Q1, the drain of the first switch tube Q1 is connected to the first current mirror M1, and the source is connected to the first resistor R0; the positive input end of the second operational amplifier A2 is connected to the input voltage sampling end K0V of the DC-DC converter in The reverse input terminal is connected to the source of the second switch tube Q2, the output terminal is connected to the gate of the second switch tube Q2, the drain of the second switch tube Q2 is connected to the third current mirror M3, and the source is connected to the second resistor R2. The first resistor R0 and the second resistor R2 have the same resistance value.
[0051] The first current mirror M1 is used to copy the output current Io to the second current mirror M2, the third current mirror M3 is used to copy the input current Iin to the second current mirror M2, the second current mirror M2 is used to make a difference between the input current Iin and the output current Io to obtain a first current difference Ia, and feed the first current difference Ia back to the second differential circuit composed of the fourth current mirror M4 and the fifth current mirror M5; the fourth current mirror M4 is used to copy the current Ib generated by the current source, the fifth current mirror M5 is used to make a difference between the current Ib generated by the current source and the first current difference Ia to obtain a second current difference, and mirror it to the output end as a compensation injection current Iinject output.
[0052] Therefore, the ripple enhancement circuit provided by the present disclosure converts the sampled input voltage K0*V in And output voltage K0*V o Converted into current, I in =K0*Vin / R,I O =K0*V O / R, where K0 is the proportionality coefficient, Vin is the input voltage, Vo is the output voltage, and R is the resistance of the first resistor R0 and the second resistor R2; then the first current difference is obtained by subtracting: Ia=K0*(Vin-Vo) / R, and then the difference is obtained by the fixed current Ib, and finally the required injection current I is obtained by the current mirror. inject =Ib-K0*(Vin-Vo) / R, which is negatively correlated with the input voltage Vin and positively correlated with the output voltage Vo.
[0053] The duty cycle of the COT mode DC-DC converter is determined by the dynamic changes of the switch on-time and the switching period, that is, the on-time of the switch tube in each switching period is a constant value, and the off-time is automatically adjusted according to the changes in the load and input voltage. Therefore, the duty cycle in the COT mode is a function of the system's operating conditions (such as input voltage, output voltage, load current, etc.). In the COT mode, the on-time t on The off time t is proportional to the ratio of the input voltage Vin to the output voltage Vo. off Depends on the load current and the difference between input and output voltage. D=t on / T sw =t on / (t on +t off ), when the load current changes, the off time will be adjusted accordingly, so that the duty cycle changes. Therefore, when the load changes from a small duty cycle (lower current) to a large duty cycle (higher current), the ripple injection enhancement circuit can provide a compensating injection current according to the duty cycle of the COT mode DC-DC converter.
[0054] That is, when the duty cycle increases from small to large, the compensation injection current I inject =Ib-K0*(Vin-Vo) / R increases, the ratio K2 of the transconductance Gm_ripple of the ripple injection amplifier and the transconductance Gm_pwm of the PWM transconductance amplifier will gradually increase, and the equivalent resistance R of the ripple injection network will increase. eff Increase, so that the resistive ripple can be kept larger than the capacitive ripple when the duty cycle increases, (R eff +R esr )·C o >T on / 2.
[0055] When the load current increases and the duty cycle becomes larger, the ripple injection current will also increase accordingly. By injecting a high-frequency ripple signal into the feedback loop of the COT mode DC-DC converter to simulate the change of the external load, the ripple amplitude is artificially increased during the switching cycle, which helps to improve the stability of the system under high load and avoid excessive load changes causing output voltage fluctuations. This enhancement method should not destroy the normal operation of the DC-DC converter, maintain the stability of the output voltage, and adapt to changes in a larger load range by adjusting the ripple characteristics.
[0056] The embodiment of the present disclosure also provides an electronic device. The electronic device includes a COT mode DC-DC converter with ripple injection enhancement according to the embodiment of the present disclosure, and the DC-DC converter includes a ripple injection enhancement circuit provided by the embodiment of the present disclosure, which can enhance the injection ripple of a large duty cycle without affecting the normal duty cycle application, and realize the application of small duty cycle to large duty cycle. The electronic device is, for example, a mobile device, a computer and network device, an industrial control device, a high-frequency device, etc.
[0057] In summary, according to the ripple injection enhancement circuit and the ripple injection enhanced COT mode DC-DC converter of the embodiment of the present disclosure, the relationship between the duty cycle and the input-output voltage is used to generate the compensation injection current, and the compensation injection current is dynamically adjusted according to the duty cycle, so as to compensate the ripple signal, which can ensure the application of the DC-DC converter from a small duty cycle to a large duty cycle; the combination of the current mirror and the voltage-controlled current source is used to accurately control the current to achieve compensation, which simplifies the traditional feedback control circuit and reduces the complexity of the circuit structure. Through accurate current differential and compensation injection current, the system can be kept stable when the load or input voltage changes rapidly, and the COT mode DC-DC converter with internal ripple injection can enhance the injection ripple of the large duty cycle without affecting the normal duty cycle application, thereby ensuring the stability of the feedback loop.
[0058] Unless the context clearly indicates otherwise, the singular form of the words used herein and in the appended claims includes the plural and vice versa. Thus, when referring to the singular, the plural form of the corresponding term is generally included. Similarly, the words "comprise" and "include" are to be interpreted as inclusive rather than exclusive. Likewise, the terms "include" and "or" should be interpreted as inclusive unless such interpretation is expressly prohibited herein. Where the term "example" is used herein, particularly when it is located after a group of terms, the "example" is merely exemplary and illustrative and should not be considered exclusive or comprehensive.
[0059] Further aspects and scopes of adaptability become apparent from the description provided herein. It should be understood that various aspects of the present application can be implemented individually or in combination with one or more other aspects. It should also be understood that the description and specific embodiments herein are intended for purposes of illustration only and are not intended to limit the scope of the present application.
[0060] Several embodiments of the present disclosure are described in detail above, but it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure is defined by the attached claims.
Claims
1. A ripple injection enhancement circuit, characterized in that: The ripple injection enhancement circuit is used to provide a compensation injection current according to the duty cycle of the COT mode DC-DC converter, wherein the compensation injection current is negatively correlated with the input voltage of the DC-DC converter and positively correlated with the output voltage of the DC-DC converter. The ripple injection enhancement circuit comprises: a first voltage-controlled current source, a second voltage-controlled current source, a first current mirror, a second current mirror, a third current mirror, a fourth current mirror, a fifth current mirror and a current source; the first voltage-controlled current source is used to convert the output voltage of the DC-DC converter into an output current; the second voltage-controlled current source is used to convert the input voltage of the DC-DC converter into an input current; the first current mirror, the second current mirror and the third current mirror constitute a first differential circuit, which is used to obtain a first current difference by subtracting the input current from the output current; the fourth current mirror and the fifth current mirror constitute a second differential circuit, which is used to obtain a second current difference by subtracting the current generated by the current source from the first current difference, and use the second current difference as the compensation injection current.
2. The ripple injection enhancement circuit according to claim 1, characterized in that: The first voltage-controlled current source includes: a first operational amplifier, a first resistor, and a first switch tube, and the second voltage-controlled current source includes a second operational amplifier, a second resistor, and a second switch tube; the non-inverting input terminal of the first operational amplifier is connected to the output voltage sampling terminal of the DC-DC converter, the reverse input terminal is connected to the source of the first switch tube, the output terminal is connected to the gate of the first switch tube, the drain of the first switch tube is connected to the first current mirror, and the source is connected to the first resistor; The non-inverting input terminal of the second operational amplifier is connected to the input voltage sampling terminal of the DC-DC converter, the inverting input terminal is connected to the source of the second switch tube, the output terminal is connected to the gate of the second switch tube, the drain of the second switch tube is connected to the third current mirror, and the source is connected to the second resistor.
3. The ripple injection enhancement circuit according to claim 1, characterized in that: The first current mirror is used to copy the output current to the second current mirror, the third current mirror is used to copy the input current to the second current mirror, the second current mirror is used to obtain a first current difference by subtracting the input current from the output current, and feed the first current difference back to a second differential circuit composed of the fourth current mirror and the fifth current mirror; The fourth current mirror is used to replicate the current generated by the current source, and the fifth current mirror is used to subtract the current generated by the current source from the first current difference to obtain the second current difference.
4. The ripple injection enhancement circuit according to claim 2, characterized in that: The resistance values of the first resistor and the second resistor are equal, and the first current difference is: Ia=K0*(Vin-Vo) / R, wherein K0 is a proportionality coefficient, Vin is an input voltage, Vo is an output voltage, and R is a resistance value of the first resistor and the second resistor; The second current difference is: Iinject=Ib-Ia=Ib-K0*(Vin-Vo) / R, wherein Ib is the current of the current source, Ia is the first current difference, and the second current difference is negatively correlated with the input voltage and positively correlated with the output voltage.
5. A ripple injection enhanced COT mode DC-DC converter, characterized in that: include: A ripple injection enhancement circuit, a ripple injection network, a ripple injection transconductance amplifier, a PWM transconductance amplifier and a COT mode DC-DC converter as described in any one of claims 1 to 4; the ripple injection network injects a ripple signal into the feedback loop of the COT mode DC-DC converter by connecting to the ripple injection transconductance amplifier; the ripple injection enhancement circuit is used to inject the compensation injection current into the tail current of the ripple injection transconductance amplifier according to the duty cycle of the COT mode DC-DC converter; the ripple injection transconductance amplifier and the PWM transconductance amplifier are both connected to the feedback node of the COT mode DC-DC converter, the PWM transconductance amplifier is used to convert the feedback voltage into a current according to the transconductance of the PWM transconductance amplifier, and the ripple injection transconductance amplifier is used to convert the injected ripple signal into a current according to the transconductance of the ripple injection transconductance amplifier.
6. The ripple injection enhanced COT mode DC-DC converter according to claim 5, characterized in that: The COT mode DC-DC converter includes: a high-end tube, a low-end tube, a drive control logic, an output inductor, an output capacitor, an upper voltage-dividing resistor, a lower voltage-dividing resistor and a PWM comparator; the common end of the upper voltage-dividing resistor and the lower voltage-dividing resistor is connected to the input end of the PWM transconductance amplifier to form a feedback loop; the PWM comparator is used to output a PWM control signal according to the comparison result between the feedback voltage and the reference voltage, and the PWM control signal controls the switching state of the high-end tube and the low-end tube through the drive control logic, and when the conduction time of the high-end tube or the low-end tube reaches a set value, the high-end tube or the low-end tube is turned off.
7. The ripple injection enhanced COT mode DC-DC converter according to claim 6, characterized in that: The ripple injection network includes a voltage-dividing resistor, a filtering resistor, a filtering capacitor and an RC filtering circuit. The switching signal of the DC-DC converter is divided by the voltage-dividing resistor and the filtering resistor to obtain a first voltage signal. The switching signal of the DC-DC converter is low-pass filtered by the filtering resistor, the filtering capacitor and the RC filtering circuit to obtain a second voltage signal. The ripple injection transconductance amplifier is used to generate an injected ripple signal according to the difference between the first voltage signal and the second voltage signal.
8. The ripple injection enhanced COT mode DC-DC converter according to claim 7, characterized in that: The gain of the ripple injection network to the feedback node is: K = K1K2, K1 = R1 / (R1+R LPF ), K2 = Gm_ripple / Gm_pwm, where R LPF is the resistance of the filter resistor, R1 is the resistance of the voltage divider resistor, Gm_ripple is the transconductance of the ripple injection transconductance amplifier, and Gm_pwm is the transconductance of the PWM transconductance amplifier.
9. The ripple injection enhanced COT mode DC-DC converter according to claim 7, characterized in that: The resistive ripple of the feedback node is: The capacitive ripple of the feedback node is: Among them, R ESR is the equivalent resistance of the output capacitor, R eff The equivalent resistance of the ripple injection network, R FT R is the upper voltage divider resistor of the output voltage. FB is the lower voltage divider resistor of the output voltage, Vin is the input voltage, Vo is the output voltage, Ton is the conduction time, and L is the output inductance; The resistive ripple is larger than the capacitive ripple, so that (R eff +R esr )·C o >T on / 2, among which, R LPF The filter resistor of the ripple injection network, C LPF filter capacitors for the ripple injection network; When the duty cycle increases, the compensation injection current increases, so that the transconductance ratio of the ripple injection transconductance amplifier and the PWM transconductance amplifier increases, and the equivalent resistance of the ripple injection network increases, so that the resistive ripple is kept greater than the capacitive ripple when the duty cycle increases.
10. An electronic device, characterized in that: A COT mode DC-DC converter with ripple injection enhancement according to any one of claims 5 to 9.