A method and circuit for mode switching of an ultra-low power DC-DC converter

Abstract

The application discloses a kind of ultra-low power consumption DC-DC converter mode switching method and circuit, the method includes: using inductance current sensing module detection obtains induction voltage;Using Type-II compensation module is amplified, obtains amplification error voltage;Based on comparator module respectively on induction voltage and amplification error voltage, preset threshold voltage and amplification error voltage are compared, and duty cycle control signal and low-power duty cycle control signal are obtained, then through drive circuit duty cycle control signal conversion, obtain two non-overlapping grid control signals.The circuit includes: including zero-crossing detection circuit, adaptive conduction time generation module, inductance current sensing module, drive circuit, Type-II compensation module and comparator module.By using the application, the error between the output voltages of multiple modes can be reduced, and adaptive mode switching based on load current can be realized with less static current.The application can be widely applied in the technical field of DC-DC converter.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converter technology, and in particular to an ultra-low power DC-DC converter mode switching method and circuit. Background Technology

[0002] As the core of the power management unit, the DC-DC converter needs to maintain high efficiency in various operating modes of IoT devices. In reality, many IoT systems remain in standby mode for extended periods, only activating at specific times. The static power consumption of the DC-DC converter in standby mode accounts for a significant portion of the system's power budget. Ultra-low-power DC-DC converters consuming only nanoamps of quiescent current are of great research value, playing a crucial role in reducing energy loss and extending battery life in IoT systems. Furthermore, as smart devices become increasingly powerful, their current consumption during operation also increases; for example, smartwatches can draw hundreds of milliamps. Therefore, DC-DC converters should have a wide load range to support the ever-increasing functionality of these devices. Thus, ultra-low-power buck converters with a wide load current range are of significant research value.

[0003] Existing control techniques, such as hysteresis control, can achieve low power consumption under ultra-light loads because the controller only requires a low-power comparator. However, due to the large delay of the comparator, the output ripple increases significantly under heavy loads, making it difficult to achieve a wide load current range under ultra-low power budgets using only one control method. Therefore, multi-mode control is considered. However, existing multi-mode control methods generally use different control circuits between modes. Different control circuits have different adjustment errors for the output voltage, resulting in significant differences in the output DC voltage across different modes. Summary of the Invention

[0004] To address the aforementioned technical problems, the objective of this invention is to provide an ultra-low power DC-DC converter mode switching method and circuit that can reduce the error between the output voltages of multiple modes, improve the output voltage regulation rate, and achieve adaptive mode switching based on load current with less quiescent current.

[0005] The first technical solution adopted in this invention is: an ultra-low power DC-DC converter mode switching circuit, including a zero-crossing detection circuit, an adaptive on-time generation module, an inductor current sensing module, a drive circuit, a Type-II compensation module, a comparator module, a first inductor, a first PMOS transistor, a first NMOS transistor, an input voltage, and an output voltage, wherein:

[0006] The first input terminal of the zero-crossing detection circuit is connected to the first terminal of the first inductor, the drain of the first PMOS transistor, and the drain of the first NMOS transistor. The second input terminal of the zero-crossing detection circuit is connected to the gate of the first NMOS transistor. The output terminal of the zero-crossing detection circuit is connected to the first input terminal of the driving circuit, and is used to monitor the inductor current.

[0007] The adaptive on-time generation module has its first input terminal connected to the input voltage, its second input terminal connected to the output voltage, and its output terminal connected to the second input terminal of the drive circuit; it is used to generate a signal to control the on-time of the power transistor and automatically adjust the on-time of the main power transistor.

[0008] The input terminal of the inductor current sensing module is connected to the first terminal of the first inductor, and the output terminal is connected to the inverting input terminal of the comparator module; it is used to detect the current of the inductor and convert it into a voltage signal proportional to the sampled current.

[0009] The first input terminal of the driving circuit is connected to the output terminal of the zero-crossing detection circuit, the second input terminal is connected to the output terminal of the adaptive on-time generation module, the third input terminal is connected to the first output terminal of the comparator module, the fourth input terminal is connected to the second output terminal of the comparator module, the first output terminal is connected to the gate of the first PMOS transistor, and the second output terminal is connected to the gate of the first NMOS transistor; used to generate the gate control signal for driving the power transistor.

[0010] The Type-II compensation module has its first input terminal connected to the output voltage, its second input terminal connected to the reference voltage, and its output terminal connected to the comparator module; it is used to amplify the error between the reference voltage and the converter output feedback voltage.

[0011] The inverting input of the comparator module is connected to the output of the inductor current sensing module, the forward input is connected to the output of the Type-II compensation module, the first output of the comparator module is connected to the third input of the drive circuit, and the second output of the comparator module is connected to the fourth input of the drive circuit; these are used to generate the duty cycle control signal for the loop.

[0012] Furthermore, the comparator module includes a first comparator, a first bias current, a first switch, and a low-power comparator, wherein:

[0013] The positive input terminal of the first comparator is connected to the output terminal of the Type-II compensation module and the positive input terminal of the low-power comparator, the negative input terminal is connected to the output terminal of the inductor current sensing module, and the output terminal of the first comparator is connected to the third input terminal of the drive circuit.

[0014] One end of the first switch is connected to the negative terminal of the power supply of the first comparator, and the other end is connected to the first bias current.

[0015] The positive input terminal of the low-power comparator is connected to the threshold voltage, and the output terminal of the low-power comparator is connected to the fourth input terminal of the drive circuit.

[0016] Through this optimized comparator module, the signal potential change at the output terminal of the low-power comparator realizes the switching from light load to low-power mode, the signal potential change at the output terminal of the first comparator realizes the switching from heavy load to light load mode, and the first switch can be turned off in low-power mode due to the influence of the output of the low-power comparator, further reducing power consumption.

[0017] Furthermore, the Type-II compensation module includes an error amplifier, a second switch, a third switch, a fourth resistor, a second capacitor, a second bias current, and a third bias current, wherein:

[0018] The error amplifier's inverting input is connected to the output voltage, its non-inverting input is connected to the reference voltage, and its output is connected to one end of the second switch; the other end of the second switch is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to one end of the second capacitor; and the other end of the second capacitor is grounded.

[0019] One end of the third switch is connected to the first DC bias terminal of the error amplifier, and the other end is connected to the second bias current.

[0020] The third bias current is connected to the second DC bias of the error amplifier.

[0021] The preferred Type-II compensation module amplifies the error between the output voltage and the reference voltage. At the same time, the multiplexing of the Type-II compensation module in heavy load, light load and low power mode also reduces the error of the output voltage. The second and third switches of the Type-II compensation module are affected by the output of the low power comparator and can be turned off in low power mode, further reducing power consumption.

[0022] Furthermore, the inductor current sensing module includes a fifth resistor, an adder, and a first amplified voltage, wherein:

[0023] One end of the fifth resistor is connected to the first inductor, and the other end is grounded;

[0024] The input terminal of the adder is connected to the fifth resistor and the first amplified voltage, and the output terminal is connected to the inverting input terminal of the first comparator.

[0025] The first amplified voltage is selected based on the change in load current and is used to amplify the induced voltage.

[0026] This optimized inductor current sensing module enables the amplified induced voltage to reflect changes in the inductor current.

[0027] The second technical solution adopted in this invention is: a method for switching modes of an ultra-low power DC-DC converter, comprising the following steps:

[0028] The inductor current is detected and converted using an inductor current sensing module to obtain the induced voltage.

[0029] The error between the reference voltage and the converter output feedback voltage is amplified using the Type-II compensation module to obtain the amplified error voltage;

[0030] The duty cycle control signal is obtained by comparing the induced voltage and the amplified error voltage using the comparator module.

[0031] The comparator module compares the preset threshold voltage and the amplified error voltage to obtain a low-power duty cycle control signal.

[0032] The duty cycle control signal or the low-power duty cycle control signal is converted by the driving circuit to obtain two non-overlapping gate control signals.

[0033] Furthermore, the preset threshold voltage, and its acquisition confirmation specifically include:

[0034] Obtain the transfer function between the output voltage and the compensator output in the circuit;

[0035] Obtain the relationship between the load current and the switching frequency in the circuit;

[0036] Based on the switching frequency, the relationship between the load current and the output ripple amplitude of the compensator is obtained through parameter conversion.

[0037] The threshold voltage is set based on the relationship between the load current and the output ripple amplitude of the compensator.

[0038] Furthermore, the mathematical expression relating the load current to the compensator output ripple amplitude is as follows:

[0039]

[0040]

[0041]

[0042] Where ΔV E I represents the output ripple amplitude of the compensator. LOAD Represents the load current, ΔV OUT f represents the output voltage ripple amplitude. SW K represents the switching frequency. Z f represents a constant value. SW,CCM I represents the switching frequency of the DC-DC inductor when it is continuously conducting. L,PEAKR4 represents the peak-to-peak value of the inductor current, C2 represents the compensation resistor, and C3 represents the compensation capacitor.

[0043] The beneficial effects of the method and circuit of this invention are as follows: By reusing the Type-II compensation module, this invention still uses the error amplifier as the first-stage amplifier to detect the output voltage in different operating modes, and changes the compensation capacitor after the error amplifier to reduce the output voltage error between different modes, improve the conversion rate, and the ripple in different modes remains basically unchanged and is not disturbed; a comparator module is constructed based on the transfer function of the Type-II compensation module, and the switching to the low-power mode is realized by comparing the output waveform of the Type-II compensation module, thereby realizing mode switching without the need for an average load current detection circuit, and realizing adaptive mode switching based on load current with less static current. Attached Figure Description

[0044] Figure 1 This is a circuit structure framework diagram of an ultra-low power DC-DC converter mode switching method and circuit of the present invention;

[0045] Figure 2 This is a flowchart of the method steps of a mode switching method and circuit for an ultra-low power DC-DC converter according to the present invention.

[0046] Figure 3 This is a circuit structure framework diagram of a specific embodiment of the ultra-low power DC-DC converter mode switching method and circuit of the present invention.

[0047] Figure 4 This is a waveform diagram of the working operation of a mode switching method and circuit for an ultra-low power DC-DC converter according to the present invention.

[0048] Figure 5 This is a circuit diagram of the Type-II compensation module of an ultra-low power DC-DC converter mode switching method and circuit of the present invention.

[0049] Figure 6 This invention discloses a method and circuit for switching mode of an ultra-low power DC-DC converter. The relationship between the load circuit, switching frequency and Type-II compensation module gain under light load is shown in the figure.

[0050] Figure 7 This is a graph showing the test results of the efficiency of the ultra-low power DC-DC converter mode switching method and circuit of the present invention. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0052] Traditional current-mode PFM DC-DC converters operate in two modes: continuous conduction mode (CCM) and discontinuous conduction mode (DCM). In CCM, the inductor current never reaches zero during a switching cycle; in DCM, the inductor current always returns to zero during a switching cycle. In addition to current mode, this invention proposes a hiccup mode (HM) for the DC-DC converter control method. In this mode, the current mode and a low-power mode switch smoothly.

[0053] Reference Figure 1 This invention provides an ultra-low power DC-DC converter mode switching circuit, including a zero-crossing detection circuit, an adaptive on-time generation module, an inductor current sensing module, a drive circuit, a Type-II compensation module, a comparator module, a first inductor L, a first PMOS transistor MP, a first NMOS transistor MN, and an input voltage V. IN and output voltage V OUT ,in:

[0054] The first input terminal of the zero-crossing detection circuit is connected to port V. SW The first terminal of the first inductor L, the drain of the first PMOS transistor MP, and the drain of the first NMOS transistor MN are connected. The second input terminal of the zero-crossing detection circuit is connected to the port V. GN The gate of the first NMOS transistor MN is connected, and the output of the zero-crossing detection circuit is connected to the first input of the drive circuit for monitoring the inductor current.

[0055] The first input terminal of the adaptive conduction time generation module is connected to the input voltage V. IN Connect the second input terminal to the output voltage V. OUT The output terminal is connected to the second input terminal of the drive circuit; it is used to generate a signal to control the on-time of the power transistor and automatically adjust the on-time of the main power transistor.

[0056] The input terminal of the inductor current sensing module is connected to the first terminal of the first inductor L, and the output terminal is connected to the inverting input terminal of the comparator module; it is used to detect the current of the inductor and convert it into a voltage signal proportional to the sampled current.

[0057] The first input terminal of the driving circuit is connected to the output terminal of the zero-crossing detection circuit, the second input terminal is connected to the output terminal of the adaptive on-time generation module, the third input terminal is connected to the first output terminal of the comparator module, the third input terminal is connected to the second output terminal of the comparator module, the first output terminal is connected to the gate of the first PMOS transistor MP, and the second output terminal is connected to the gate of the first NMOS transistor MN; used to generate the gate control signal for driving the power transistor.

[0058] The first input terminal of the Type-II compensation module is connected to the output voltage V. IN Connect the second input terminal to the reference voltage V. REF The output terminal is connected to the comparator module; it is used to amplify the error between the reference voltage and the converter output feedback voltage.

[0059] The inverting input of the comparator module is connected to the output of the inductor current sensing module, the forward input is connected to the output of the Type-II compensation module, the first output of the comparator module is connected to the third input of the drive circuit, and the second output of the comparator module is connected to the fourth input of the drive circuit; these are used to generate the duty cycle control signal for the loop.

[0060] Specifically, refer to Figure 3 This invention provides a specific embodiment of a DC-DC converter, which includes a first inductor L, a first PMOS transistor MP, a first NMOS transistor MN, a first capacitor C1, a first resistor R1, a second resistor R2, a third resistor R3, and an input voltage V. IN and output voltage V OUT ,in:

[0061] The source of the first PMOS transistor MP and the input voltage V IN The drain of the first NMOS transistor MN is connected to the drain of the first NMOS transistor MN, and the gate is connected to the driving circuit. The drain of the first NMOS transistor MN is connected to the first inductor L, and the gate is connected to the driving circuit. The first inductor L is connected to the first capacitor C1. One end of the first capacitor C1 is connected to the first resistor R1, and the other end is grounded. One end of the first resistor R1 is connected to the second resistor R2, and the other end is grounded. One end of the second resistor R2 is connected to the output voltage V. OUT One end is connected to the first resistor, and the other end is connected to the third resistor R3. One end of the third resistor R3 is grounded, and the other end is connected to the Type-II compensation module. The first PMOS transistor MP and the first NMOS transistor MN receive the gate control signal generated by the driving circuit, thereby turning off or turning on the power transistors MP and MN to adjust the output voltage error. The first capacitor C1 and the first resistor R1 serve as the load capacitor and load resistor, respectively. The second resistor R2 and the third resistor R3 constitute the output voltage feedback, feeding the output voltage back to the Type-II compensation module.

[0062] Specifically, refer to Figure 3 This invention provides a specific embodiment of a Type-II compensation module, which includes an error amplifier, a second switch K2, a third switch K3, and a reference voltage V. REF The components are: fourth resistor R4, second capacitor C2, second bias current I2, and third bias current I3, where:

[0063] The inverting input terminal of the error amplifier is connected to port V. FB The second resistor R2 and the third resistor R3 are connected at one end, and the positive input terminal is connected to the reference voltage V. REF The output terminal is connected to one end of the second switch K2; the other end of the second switch K2 is connected to one end of the fourth resistor R4; the other end of the fourth resistor R4 is connected to one end of the second capacitor C2; the other end of the second capacitor C2 is grounded; one end of the third switch K3 is connected to the first DC bias terminal of the error amplifier, and the other end is connected to the second bias current I2; the third bias current I3 is connected to the second DC bias terminal of the error amplifier.

[0064] The Type-II compensation module operates in Continuous Conductive Mode (CCM), Discontinuous Conductive Mode (DCM), and Low Power Mode (LP). The fourth resistor R4 and the second capacitor C2 constitute RC error compensation. By adjusting the compensation capacitor in different modes, the output voltage error between modes can be reduced, and the conversion rate can be improved. The reference voltage V is then converted by an error amplifier. REF Error V with converter output feedback voltage FB Amplification can improve the accuracy of the output voltage. In low-power mode, the third switch K3 and the second switch K2 of the error amplifier will be closed. At this time, the second bias current I2 is blocked, and only the third bias current I3 is biased to save power. In addition, the output of the error amplifier is disconnected from the RC error compensation, increasing the voltage slew rate in low-power mode.

[0065] Specifically, refer to Figure 3 The present invention provides a specific embodiment of an inductor current sensing module, which includes a fifth resistor R5, an adder, and a first amplification voltage V. S1 ,in:

[0066] One end of the fifth resistor R5 is connected to the first inductor L, and the other end is grounded;

[0067] The input terminal of the adder is connected to the fifth resistor R5 and the first amplified voltage V. S1 The output terminal is connected to the inverting input terminal of the first comparator U1.

[0068] The first amplified voltage is selected based on the change in load current and is used to amplify the induced voltage.

[0069] V is obtained by converting the induced current through the fifth resistor R5. SEN1 It can reflect changes in inductor current, but V SEN1 The voltage difference between the Type-II compensation module and the output voltage is too large to be directly compared. Therefore, an adder is used to input the first amplified voltage V, which is selected based on the change in load current. S1 , for V SEN1 Amplification is performed to obtain the amplified induced voltage V. SEN .

[0070] Specifically, refer to Figure 3 The present invention provides a specific embodiment of a comparator module, which includes a first comparator U1, a first bias current I1, a first switch K1, and a low-power comparator LP, wherein:

[0071] The positive input of the first comparator U1 is connected to the Type-II compensation module, the negative input is connected to the inductor current sensing module, and the output is connected to the drive circuit; one end of the first switch K1 is connected to the negative terminal of the power supply of the first comparator, and the other end is connected to the first bias current I1; the positive input of the low-power comparator LP is connected to the threshold voltage V. CREF The inverting input is connected to the Type-II compensation module, and the output is connected to the driver circuit. Both the first comparator U1 and the low-power comparator LP have an input connected to the output of the Type-II compensation module. When the DC-DC converter's operating mode is switched, the Type-II compensation module is still used as the first-stage amplifier to detect the output voltage. The compensation capacitor following the Type-II compensation module is changed to reduce the output voltage error between different modes, improve the conversion rate, and ensure that the ripple remains essentially unchanged and unaffected by interference across different modes.

[0072] Reference Figure 4 When the DC-DC converter is under heavy load, the inductor current is in continuous conduction mode. The zero-crossing detection circuit, adaptive conduction time generation module, inductor current sensing module, drive circuit, Type-II compensation module, and comparator module are all operational. At this time, the inductor current changes continuously, and the output V of the low-power comparator... LP =0, the first comparator U1 is in working state, and the first comparator U1 will convert the output V of the Type-II compensation module. E With inductor current sampling signal V SEN Comparison, when V SEN Decrease to equal V E At that time, the first comparator U1 outputs a high (V) value. C=1); When the DC-DC converter is under light load, i.e., the load current I LOAD When the inductor current I decreases, the converter automatically enters pulse frequency modulation (PFM) control to reduce the switching frequency. L When the zero-crossing time becomes zero, all high-power modules, including the zero-crossing detection circuit, the adaptive on-time generation module, and the inductor current sensing module, are turned off, and the output V of the low-power comparator is reduced. LP =0, the first comparator U1 is in working state, and the first comparator U1 will convert the output V of the Type-II compensation module. E With inductor current sampling signal V SEN When comparing, when V E Rise to equal V SEN When the comparator output is high (V), the comparator output is high. C =1), the inductor current of the DC-DC converter is in discontinuous conduction mode; when the DC-DC converter is under ultra-light load conditions, V E Decrease to equal to or less than V CREF Low-power comparator output V LP =1, at this time the converter switches to low-power control. (V) LP With the control switch K1 open, the comparator is in a non-operating state, and the low-power comparator outputs V from the error amplifier. E A voltage V related to the load voltage CREF In comparison, the bias current of the error amplifier changes from high to low to save power; the second switch K2 of the Type-II compensation module is opened to accelerate V... E The slew rate. The Type-II compensation module, along with a low-power comparator, acts as a comparator to monitor V. OUT Whenever the low-power comparator outputs V... LP When the signal goes low, the first comparator U1, the error amplifier, and the Type-II compensation module all return to the current mode (CM-AOT) state to determine whether to enable the charging pulse and whether to re-enter the low-power state.

[0073] The adaptive on-time generation module generates a signal to control the on-time of the power transistor based on the values ​​of the input and output voltages, and automatically adjusts the on-time of the main power transistor to achieve a constant switching frequency in continuous conduction mode.

[0074] The zero-crossing detection circuit monitors the inductor current. When the inductor current drops to zero, it outputs a control signal to turn off the power transistor, preventing the inductor current from reversing. This allows the converter to enter discontinuous conduction mode (DCM) under light load, reducing a significant amount of energy loss and improving the power supply's conversion efficiency. The zero-crossing current detection circuit is mainly composed of circuits such as a high-speed comparator.

[0075] The driver circuit converts the output V of the low-power comparator. LP The first comparator U1 outputs V C It is converted into two non-overlapping gate control signals for turning on and off the power transistors. The circuit is mainly composed of digital logic gate circuits.

[0076] like Figure 2 As shown, a method for switching the mode of an ultra-low power DC-DC converter includes the following steps:

[0077] The inductor current is detected and converted using an inductor current sensing module to obtain the induced voltage.

[0078] The error between the reference voltage and the converter output feedback voltage is amplified using the Type-II compensation module to obtain the amplified error voltage;

[0079] The duty cycle control signal is obtained by comparing the induced voltage and the amplified error voltage using the comparator module.

[0080] The comparator module compares the preset threshold voltage and the amplified error voltage to obtain a low-power duty cycle control signal.

[0081] The driving circuit converts the duty cycle control signal and the low-power duty cycle control signal to obtain two non-overlapping gate control signals.

[0082] Specifically, the inductor current sensing module detects the inductor current, and the induced current is converted into a first induced voltage through a sensing resistor. However, if the first induced voltage is too small, the output voltage V of the error amplifier will be limited by the common-mode output voltage swing of the error amplifier. E The voltage cannot be too small to be directly compared with the first induced voltage value. Therefore, an amplification voltage is selected and set based on the change in load current. The first induced voltage value is amplified by an adder to a level that is easy to compare with the output of the Type-II compensation module. Then, the Type-II compensation module is used to amplify the error between the reference voltage and the converter output feedback voltage to obtain the amplified error voltage.

[0083] Obtain the transfer function between the output voltage and the compensator output in the circuit;

[0084] Specifically, the Type-II compensation module used in the embodiments of the present invention is as follows: Figure 5 As shown in the diagram, based on the Type-II compensation module circuit diagram, the expression for the transfer function of its output voltage and the compensator output is as follows:

[0085]

[0086] Wherein, ΔV E ΔV represents the output ripple amplitude of the compensator.OUT f represents the output voltage ripple amplitude. SW K represents the switching frequency. Z R4 represents a constant value, C2 represents a compensation resistor, and C2 represents a compensation capacitor.

[0087] Reference Figure 6 When the switching frequency is less than the zero-point frequency, A VE The absolute value of (f) decreases as the switching frequency decreases. When the switching frequency is greater than the zero-point frequency, A VE The absolute value of (f) becomes K z This constant value is called K. Z This is for platform gain. Figure 6 As can be seen in the lower part, there is a close relationship between the switching frequency and the load current of the circuit. Under light load, the switching frequency of the converter decreases as the load current decreases. The relationship between the load current and the switching frequency in the circuit is expressed as follows:

[0088]

[0089] Among them I LOAD f represents the load current. SW,CCM I represents the switching frequency of the DC-DC inductor when it is continuously conducting. L,PEAK f represents the peak-to-peak value of the inductor current. SW Indicates the switching frequency.

[0090] Since the output voltage ripple is mainly dominated by the inductor charge and is almost independent of the load current, the mathematical expression for the relationship between the load current and the output ripple amplitude of the compensator is as follows:

[0091]

[0092]

[0093]

[0094] Where ΔV E I represents the output ripple amplitude of the compensator. LOAD Represents the load current, ΔV OUT f represents the output voltage ripple amplitude. SW K represents the switching frequency. Z f represents a constant value. SW,CCM I represents the switching frequency of the DC-DC inductor when it is continuously conducting. L,PEAK R4 represents the peak-to-peak value of the inductor current, C2 represents the compensation resistor, and C3 represents the compensation capacitor.

[0095] According to the formula, V can be approximated. EThe ripple amplitude is ΔV OUT K Z The finding that the load current is doubled can be used for switching from discontinuous conduction mode to low-power mode. ΔV needs to be calculated in advance. OUT K Z times, and set V. CREF When V E Below V CREF When this happens, the mode transition event will be triggered.

[0096] One comparator is constructed based on the threshold voltage and the output of the Type-II compensation module; another comparator is constructed based on the induced voltage and the multiplexed output of the Type-II compensation module. These two comparators form a comparator module, with the amplified error voltage of the Type-II compensation module serving as the common input to both comparators. The comparator module compares the induced voltage and the amplified error voltage to obtain the duty cycle control signal; it also compares the preset threshold voltage and the amplified error voltage to obtain the low-power duty cycle control signal. The driving circuit then converts the duty cycle control signal and the low-power duty cycle control signal to obtain two non-overlapping gate control signals.

[0097] Reference Figure 7 In a specific embodiment of the present invention, the efficiency over a wide load range under three different input voltages was tested. Specifically, the inverted triangle curve represents an input voltage of 2.9V, the right triangle curve represents an input voltage of 4.2V, and the left triangle curve represents an input voltage of 5.5V. As can be seen from the changes in load current, using the present invention, the efficiency curve can remain stable under different operating modes, and a high efficiency is achieved under low load conditions. Only under extremely low load current conditions does the efficiency curve show a further slight decline.

[0098] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0099] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A mode switching circuit for an ultra-low power DC-DC converter, characterized in that, It includes a zero-crossing detection circuit, an adaptive on-time generation module, an inductor current sensing module, a drive circuit, a Type-II compensation module, a comparator module, a first inductor, a first PMOS transistor, a first NMOS transistor, input voltage, and output voltage, wherein: The first input terminal of the zero-crossing detection circuit is connected to the first terminal of the first inductor, the drain of the first PMOS transistor, and the drain of the first NMOS transistor; the second input terminal of the zero-crossing detection circuit is connected to the gate of the first NMOS transistor; and the output terminal of the zero-crossing detection circuit is connected to the first input terminal of the driving circuit. The adaptive on-time generation module has its first input terminal connected to the input voltage, its second input terminal connected to the output voltage, and its output terminal connected to the second input terminal of the drive circuit. The input terminal of the inductor current sensing module is connected to the first terminal of the first inductor, and the output terminal is connected to the inverting input terminal of the comparator module. The first input terminal of the driving circuit is connected to the output terminal of the zero-crossing detection circuit, the second input terminal is connected to the output terminal of the adaptive on-time generation module, the third input terminal is connected to the first output terminal of the comparator module, the fourth input terminal is connected to the second output terminal of the comparator module, the first output terminal is connected to the gate of the first PMOS transistor, and the second output terminal is connected to the gate of the first NMOS transistor. The Type-II compensation module has its first input terminal connected to the output voltage, its second input terminal connected to the reference voltage, and its output terminal connected to the comparator module. The inverting input of the comparator module is connected to the output of the inductor current sensing module, the forward input is connected to the output of the Type-II compensation module, the first output of the comparator module is connected to the third input of the drive circuit, and the second output of the comparator module is connected to the fourth input of the drive circuit.

2. The ultra-low power DC-DC converter mode switching circuit according to claim 1, characterized in that, The comparator module includes a first comparator, a first bias current, a first switch, and a low-power comparator, wherein: The positive input terminal of the first comparator is connected to the output terminal of the Type-II compensation module and the positive input terminal of the low-power comparator, the negative input terminal is connected to the output terminal of the inductor current sensing module, and the output terminal of the first comparator is connected to the third input terminal of the drive circuit. One end of the first switch is connected to the negative terminal of the power supply of the first comparator, and the other end is connected to the first bias current. The positive input terminal of the low-power comparator is connected to the threshold voltage, and the output terminal of the low-power comparator is connected to the fourth input terminal of the drive circuit.

3. The ultra-low power DC-DC converter mode switching circuit according to claim 1, characterized in that, The Type-II compensation module includes an error amplifier, a second switch, a third switch, a fourth resistor, a second capacitor, a second bias current, and a third bias current, wherein: The error amplifier's inverting input is connected to the output voltage, its non-inverting input is connected to the reference voltage, and its output is connected to one end of the second switch; the other end of the second switch is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to one end of the second capacitor; and the other end of the second capacitor is grounded. One end of the third switch is connected to the first DC bias terminal of the error amplifier, and the other end is connected to the second bias current. The third bias current is connected to the second DC bias of the error amplifier.

4. The ultra-low power DC-DC converter mode switching circuit according to claim 1, characterized in that, The inductor current sensing module includes a fifth resistor, an adder, and a first amplifying voltage, wherein: One end of the fifth resistor is connected to the first inductor, and the other end is grounded; The input terminal of the adder is connected to the fifth resistor and the first amplified voltage, and the output terminal is connected to the inverting input terminal of the first comparator. The first amplified voltage is selected based on the change in load current and is used to amplify the induced voltage.

5. A switching method for an ultra-low power DC-DC converter mode switching circuit as described in any one of claims 1-4, characterized in that, Includes the following steps: The inductor current is detected and converted using an inductor current sensing module to obtain the induced voltage. The error between the reference voltage and the converter output feedback voltage is amplified using the Type-II compensation module to obtain the amplified error voltage; The duty cycle control signal is obtained by comparing the induced voltage and the amplified error voltage using the comparator module. The comparator module compares the preset threshold voltage and the amplified error voltage to obtain a low-power duty cycle control signal. The duty cycle control signal or the low-power duty cycle control signal is converted by the driving circuit to obtain two non-overlapping gate control signals.

6. The ultra-low power DC-DC converter mode switching method according to claim 5, characterized in that, The specific steps for obtaining and confirming the preset threshold voltage include: Obtain the transfer function between the output voltage and the compensator output in the circuit; Obtain the relationship between the load current and the switching frequency in the circuit; Based on the switching frequency, the relationship between the load current and the output ripple amplitude of the compensator is obtained through parameter conversion. The threshold voltage is set based on the relationship between the load current and the output ripple amplitude of the compensator.

7. The ultra-low power DC-DC converter mode switching method according to claim 6, characterized in that, The mathematical expression for the relationship between the load current and the output ripple amplitude of the compensator is as follows: in This indicates the output ripple amplitude of the compensator. Indicates the load current. Indicates the output voltage ripple amplitude. Indicates the switching frequency. Represents a constant value. This indicates the switching frequency of the inductor in a DC-DC converter when it is continuously conducting. This represents the peak-to-peak value of the inductor current. Indicates the compensation resistor. This indicates a compensation capacitor.

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