Constant-frequency switching power supply converter and control method

Abstract

The invention provides a constant-frequency switching power supply converter and a control method, and the converter comprises a comparator which is used for outputting a high-level signal V Ctrl when the negative input end voltage is smaller than the positive input end voltage; the control logic and drive circuit is used for starting a power tube MN when the signal V Ctrl is at a high level to enter a conduction stage; the self-adaptive conduction time generator is used for starting timing to generate conduction time after entering a conduction stage, and when the signal V TRIG is at a high level, the conduction stage is controlled to be ended, and the conduction time is self-adaptively changed along with the actual duty ratio of the constant-frequency switching power supply converter; the zero cross detection circuit is used for detecting the magnitude of the inductive current in real time and outputting a zero current detection signal when the inductive current returns to zero; and the control logic and driving circuit is used for responding to the zero-current detection signal and generating a driving signal to turn off the high-side power tube MP. And the switching frequency stability under wide working voltage and wide load current is relatively good.

Description

Technical Field

[0001] This invention relates to the field of switching power supply control technology, and in particular to a constant frequency switching power supply converter and control method. Background Technology

[0002] A switching power supply is a device that uses integrated circuits (ICs) to control the switching on and off of power transistors, thereby stabilizing the output voltage. The most common switching power supply is the DC-DC converter, which includes three basic architectures: buck, boost, and buck-boost. Its modulation methods include pulse width modulation (PWM), pulse frequency modulation (PFM), and pulse skipping modulation (PSM), and its control methods are mainly voltage mode and current mode. Currently, the transient response speed of DC-DC converters has become an increasingly important focus, and constant on-time (COT) control mode is widely used due to its fast response speed. However, traditional COT control mode lacks a clock signal, resulting in poor switching frequency stability and consequently, poor electromagnetic interference (EMI) characteristics, increasing the design difficulty of EMI handling. To solve this problem, it is necessary to obtain a duty cycle-related voltage signal to minimize EMI.

[0003] Currently, existing solutions mainly involve optimized on-time control technology, which uses a low-pass filter composed of resistor-capacitor (RC) components to obtain a duty cycle-related voltage signal, thereby controlling the on-time length. However, optimized on-time control technology requires a large RC value to achieve good switching frequency accuracy, which results in a large area and poor transient response performance. Furthermore, the switching frequency stability under different duty cycle conditions is not effectively improved, leading to poor switching frequency stability under a wide range of input and output voltages. Summary of the Invention

[0004] The purpose of this invention is to provide a constant frequency switching power supply converter and control method to solve the problem of poor switching frequency stability under wide input and output voltage in the prior art.

[0005] To address the aforementioned technical problems, the embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a constant frequency switching power supply converter, comprising: A comparator is used to output a high-level signal when the voltage at the negative input terminal is less than the voltage at the positive input terminal. V Ctrl ; The control logic and drive circuitry, connected to a comparator, are used to input signals... V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase; An adaptive conduction time generator, connected to the control logic and drive circuit, is used to initiate a timing operation to generate the conduction time after the power transistor MN enters the conduction phase, and outputs a trigger signal. V TRIG When the level is high, the control conduction phase ends, and the conduction time is the time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. The zero-crossing detection circuit is connected to the control logic and drive circuit to detect the magnitude of the inductor current in real time. When the inductor current returns to zero, it outputs a zero current detection signal. The control logic and drive circuitry are also used to generate a drive signal in response to a zero-current detection signal to turn off the high-side power transistor MP.

[0006] A second aspect of the present invention provides a control method for a constant frequency switching power supply converter, comprising: When the voltage at the negative input terminal is less than the voltage at the positive input terminal, a high-level signal is output. V Ctrl ; In signal V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase; After the power transistor MN enters the conduction phase, a timing operation is started to generate the conduction time, and a trigger signal is output. V TRIG When the level is high, the control conduction phase ends, and the conduction time is an adaptive time that varies with the actual duty cycle. The magnitude of the inductor current is detected in real time, and a zero current detection signal is output when the inductor current returns to zero. In response to the zero current detection signal, a drive signal is generated to turn off the high-side power transistor MP.

[0007] Compared to existing technologies, the constant frequency switching power supply converter and control method provided by this invention include a comparator for outputting a high-level signal when the voltage at the negative input terminal is less than the voltage at the positive input terminal. V Ctrl The control logic and drive circuitry, connected to a comparator, are used to input signals...V Ctrl When the signal is high, the power transistor MN is turned on, allowing it to enter the conduction phase. An adaptive conduction time generator, connected to the control logic and drive circuit, is used to initiate a timing operation to generate the conduction time after the power transistor MN enters the conduction phase. When the output trigger signal is high... V TRIG When the signal is high, the control conduction phase ends, and the conduction time adaptively varies with the actual duty cycle of the constant-frequency switching power supply converter. The zero-crossing detection circuit, connected to the control logic and drive circuit, is used to detect the inductor current in real time. When the inductor current returns to zero, it outputs a zero-current detection signal. The control logic and drive circuit also generate a drive signal to turn off the high-side power transistor MP in response to the zero-current detection signal. In this way, the control logic, drive circuit, and adaptive conduction time generator obtain a precise actual duty cycle. The conduction time adaptively varies with the actual duty cycle of the constant-frequency switching power supply converter, resulting in a precise conduction time length. Ultimately, this fixes the system's switching frequency, minimizing electromagnetic interference and ensuring good switching frequency stability under wide operating voltage and load current conditions. Attached Figure Description

[0008] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 A schematic diagram of the circuit framework of a constant frequency switching power supply converter is shown. Figure 2 A schematic diagram of the circuit framework of an adaptive on-time generator is shown. Figure 3 A schematic diagram of the working logic framework of the adaptive on-time generator is shown. Figure 4 The waveform diagrams of the adaptive on-time generator under different operating modes are schematically shown. Figure 5 A schematic diagram of a ramp voltage generation circuit is shown. Figure 6 A schematic diagram illustrating the switching frequency as a function of load current and input voltage is shown. Figure 7 A flowchart illustrating the control method of a constant frequency switching power supply converter is shown schematically. Detailed Implementation

[0009] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0010] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0011] The methods described in the embodiments of the present invention will be explained in detail below.

[0012] Figure 1 A schematic diagram of the circuit framework of a constant frequency switching power supply converter according to an embodiment of the present invention is shown. See also: Figure 1 As shown, a constant frequency switching power supply converter may include: A comparator is used to output a high-level signal when the voltage at the negative input terminal is less than the voltage at the positive input terminal. V Ctrl ; The control logic and drive circuitry, connected to a comparator, are used to input signals... V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase; An adaptive conduction time generator, connected to the control logic and drive circuit, is used to initiate a timing operation to generate the conduction time after the power transistor MN enters the conduction phase, and outputs a trigger signal. V TRIG When the level is high, the control conduction phase ends, and the conduction time is the time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. The zero-crossing detection circuit is connected to the control logic and drive circuit to detect the magnitude of the inductor current in real time. When the inductor current returns to zero, it outputs a zero current detection signal. The control logic and drive circuitry are also used to generate a drive signal in response to a zero-current detection signal to turn off the high-side power transistor MP.

[0013] In this embodiment, the negative input terminal voltage includes voltage. V SEN and feedback voltage V FB The positive input voltage includes the valley voltage. V SEN_Valley ,Voltage V REF and voltage V OSThe constant frequency switching power converter also includes an inductor current sampling circuit, a valley sampling circuit, an output error correction circuit, and a feedback resistor network connected to the comparator. Inductor current sampling circuit, used to acquire inductor current in real time and generate voltage. V SEN ; Valley sampling circuit, used for voltage V SEN Perform valley sampling and output the corresponding valley voltage. V SEN_Valley ; Output error correction circuit, used to generate voltage V OS ; Feedback resistor network, used to obtain feedback voltage V FB .

[0014] In this embodiment, the constant frequency switching power supply converter further includes an inductor. L ,resistance DCR ,capacitance C L ,resistance R ESR and resistance R L ;inductance L The first terminal and voltage V IN Connection, Inductance L The second end and the resistor DCR The first end is connected to the resistor. DCR The second terminal, the drain of power transistor MN, and the drain of high-side power transistor MP are all connected. The source of power transistor MN is grounded. The gate of power transistor MN is connected to the control logic and the drive circuit. The gate of high-side power transistor MP is connected to the control logic and the drive circuit. The source of high-side power transistor MP, the inductor current sampling circuit, and the capacitor... C L First terminal, resistor R L The first end and the resistor R FB2 The first terminal is connected to the voltage. V OUT ,capacitance C L The second end and the resistor R ESR The first end is connected to the resistor. R ESR The second terminal is grounded, resistor R L The second terminal is grounded, resistor R FB2The second end, resistor R FB1 Both the first terminal and the negative input terminal of the comparator are connected, and the resistor is... R FB1 The second terminal is grounded.

[0015] Specifically, the output error correction circuit can also improve the system's load regulation, and the adaptive on-time generator controls the on-time T. ON It can adaptively change according to the actual duty cycle of the system, so that the switching frequency of the switching power supply converter remains constant relative to the load current, input voltage and output voltage in continuous conduction mode.

[0016] In this embodiment, Figure 2 A schematic diagram of the circuit framework of an adaptive on-time generator is shown below. Figure 2 As shown, the adaptive on-time generator includes: A ramp voltage generating circuit is used to generate a ramp voltage at the beginning of the conduction phase. V Fast and slope voltage V Slow ; Average value sampling circuit, used for voltage V LPF Sample output voltage V duty ; The target comparator, connected to both the ramp voltage generation circuit and the average value sampling circuit, is used to compare voltages via comparator CMP2. V duty and slope voltage V Fast In voltage V duty equal to ramp voltage V Fast At that time, comparator CMP2 outputs a control signal. V Avg,Ctrl and reset the ramp voltage V Fast The voltage is compared using comparator CMP1. V duty and slope voltage V Slow In voltage V duty and slope voltage V Slow When they are equal, comparator CMP1 outputs a turn-on control signal. V Trig The timing is adjusted to end the conduction period, thus ending the conduction phase and resetting the ramp voltage. V Slow Control signalsV Avg,Ctrl Used to indicate that the average value sampling circuit has entered the hold phase, and to activate the control signal. V Trig Used to indicate when the conduction time enters the end stage, the conduction time is the time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. The average value sampling circuit is also used to detect received control signals. V Avg,Ctrl Then, it enters the holding phase to maintain the voltage. V duty Unchanged; upon receiving the turn-on control signal V Trig After that, it enters the end phase of the conduction time, and the voltage... V duty It is the voltage that is proportional to the actual duty cycle.

[0017] In this embodiment, the average value sampling circuit includes a sample-and-hold circuit and a capacitor C. LPF Resistance R LPF Switch S1, transistor M P Transistor M N and inverter INV; Control voltage V GN Connect the input terminal of inverter INV to the inverter, and connect the output terminal of inverter INV to transistor M. P Gate and transistor M N The gate of the transistor M P The source and transistor M N The source terminals are connected, transistor M P Source and voltage V X Connected, transistor M N Source-side ground potential GND; transistor M P Transistor M N The common terminal is connected to the second terminal of switch S1, and the first terminal of switch S1 is connected to resistor R. LPF The second terminal is connected to the resistor R. LPF The first terminal, capacitor C LPF Both the first terminal and the second terminal of the sample-and-hold circuit are connected, and capacitor C LPF The second terminal is grounded at the potential GND, and the first terminal of the sample-and-hold circuit is connected to the target comparator.

[0018] In this embodiment, the positive input terminal of comparator CMP1, the first terminal of the sample-and-hold circuit, and the positive input terminal of comparator CMP2 are all connected, and the negative input terminal of comparator CMP1 is connected to the ramp voltage. V SlowThe output of comparator CMP1 is connected to the control logic and drive circuit, and the negative input of comparator CMP2 is connected to the ramp voltage. V Fast The output of comparator CMP2 is connected to the control terminal of the sample-and-hold circuit.

[0019] Specifically, the output voltage at the first terminal of the sample-and-hold circuit V duty The positive input of comparator CMP2 is a voltage. V duty The inverting input is a ramp voltage. V Fast Output voltage V Avg,Ctrl As a control signal for the sample-and-hold circuit, when V Fast = V duty At that time, the comparator CMP2 output voltage V Avg,Ctrl When the voltage is high, the sample-and-hold circuit S / H enters the hold phase. V duty The voltage remains unchanged; V duty Simultaneously, it serves as the positive input terminal of comparator CMP1, and is related to the voltage at the negative input terminal of CMP1. V Slow When comparing, V Slow = V duty At that time, comparator CMP1 outputs a control signal. V Trig End of conduction time T ON stage.

[0020] Specifically, Figure 3 The schematic diagram illustrates the working logic framework of the adaptive on-time generator. See [link / reference] Figure 3 As shown, when the conduction time phase begins, V Fast < V duty The sample-and-hold circuit operates during the sampling phase. V Fast Voltage continues to rise; compare ramp voltage V Fast and voltage V duty ,when V duty = V Fast When the time is reached, the sample-and-hold circuit enters the hold phase, which will hold the current value. Vduty Voltage, and reset voltage signal V Fast The comparator CMP2 outputs a control signal. V Avg,Ctrl Among them, control signals V Avg,Ctrl Used to control the precise acquisition voltage of the sample-and-hold circuit. V LPF The average value. The sample-and-hold circuit receives the control signal. V Avg,Ctrl Previously in the sampling phase, control signals were received. V Avg,Ctrl Then comes the retention phase, i.e., extraction. V Fast = V duty Voltage at time V duty The value of the voltage at this time. V duty The value is the voltage. V LPF The average value. Furthermore, the voltage at this time... V duty and slope voltage V Slow When comparing, V duty = V Slow At that time, the comparator CMP1 outputs a turn-on control signal. V Trig Turn off the power transistor, ending the conduction time T. ON and reset voltage signal V Slow This completes one conduction cycle of the low-side power transistor. The conduction time T is achieved. ON The converter adaptively follows the changes in the actual duty cycle D to ensure that the frequency f of the switching control signal remains constant, thereby enhancing the switching frequency stability of the converter.

[0021] The adaptive conduction time generator of the present invention can precisely control the conduction time length and ensure that the switching signal frequency f remains constant in continuous conduction mode under different load currents, different input voltages and output voltages.

[0022] Figure 4 The waveform diagrams of the adaptive on-time generator in different operating modes are schematically shown. (See attached image) Figure 4 As shown, when the constant frequency switching power supply converter operates in Continuous Conduction Mode (CCM), the control signal... V DCMAvgCtrlMaintain a high level, and switch S1 is closed. When the control signal... V GN When the level is high, the system enters T. ON Stage, voltage V X The voltage obtained after RC filtering V LPF The voltage begins to rise. V duty equal to voltage V LPF Simultaneously, ramp voltage V Fast and V Slow It also begins to rise. Furthermore, when the ramp voltage... V Fast equal to voltage V duty At that time, comparator CMP2 outputs a control signal. V Avg,Ctrl and reset voltage V Fast Sample and hold circuit control voltage V duty It remains unchanged. Furthermore, when the ramp voltage... V Slow equal to voltage V LPF At that time, comparator CMP1 outputs a control signal. V Trig and reset voltage V Slow Furthermore, control signals V Trig When it is high, it will control the voltage signal. V GN When the signal goes low, the low-side power transistor is turned off, and the high-side power transistor is turned on. This indicates the system's on-time T. ON At the end of the phase, the system enters the turn-off (Toff) phase. If the system is operating in Discontinuous Conduction Mode (DCM), when both high-side and low-side transistors are off, the zero-crossing detection (ZCD) of the control signal is triggered, outputting a high level, and further control signals... V DCMAvgCtrl When the output is low, switch S1 is open, indicating that the system has entered timed sleep mode. T SLEEP Stage, voltage V LPF It will remain unchanged, ensuring the voltage. V LPF existT SLEEP The phase will not continue to discharge to ground; in the next T... ON It will continue to function normally when the phase arrives.

[0023] In this embodiment, Figure 5 A schematic diagram of a ramp voltage generation circuit is shown below. Figure 5 As shown, the ramp voltage generating circuit includes resistors R1, R2, and R... C1 Resistance R C2 Capacitor C slow Capacitor C fast Transistor M1, Transistor M2, Transistor M3, Transistor M4, Transistor M5, Transistor M6, Transistor M7, Transistor M8, Transistor M9, Transistor M 10 Transistor M 11 Transistor M 12 Transistor M 13 Transistor M 14 and transistor M 15 ; The first terminal of resistor R1 is connected to the voltage V X The transistors are connected in series. The second terminal of resistor R1 is connected to the drain of transistor M1. The source, drain, and gate of transistor M2 are all connected. The source of transistor M2 is grounded. The gate of transistor M3 is connected to the gate of transistor M2. The source of transistor M3 is grounded. The drain of transistor M3 is connected to the drain, gate, and gate of transistor M4 and transistor M5. The source of transistor M4 is connected to the power supply. V DD Connection: The source of transistor M5 is connected to the power supply V. DD The connections are as follows: the drain of transistor M5 is connected to the drain of transistor M6, and the gate of transistor M7 is connected to the ground; the gate of transistor M6 is connected to the source of transistor M7, and the drain of transistor M8 is connected to the drain of transistor M7. The drain of transistor M7 is connected to the drain of transistor M9; the source of transistor M8 is connected to the first terminal of resistor R2; and the gate of transistor M8 is connected to the power supply. V DD With the connection made, the second terminal of resistor R2 is grounded, and the source of transistor M9 is connected to the power supply. V DD Connection, the gate of transistor M9 is connected to transistor M 10 Gate connection, transistor M 10 Drain, resistor R C1 The first terminal and transistor M 12 The drains of transistor M are all connected. 10 Source and power supply V DDConnection, resistor R C1 The second terminal is connected to capacitor C Slow The first terminal is connected to capacitor C. Slow The second terminal is grounded, transistor M 12 Source and power supply V DD Connection, transistor M 12 The gate of transistor M1 is connected to the gate of transistor M4. 14 Drain and resistor R C1 First terminal and ramp voltage V Slow Connection, transistor M 14 The source is grounded, transistor M 11 The gate of transistor M1 is connected to the gate of transistor M9. 11 Source and power supply V DD Connection, transistor M 11 The drain of the transistor M 13 Drain and resistor R C2 The first terminal is connected to resistor R. C2 The second terminal is connected to capacitor C Fast The first terminal is connected to capacitor C. Fast The second terminal is grounded, transistor M 13 The gate of transistor M1 is connected to the gate of transistor M4. 13 Source and power supply V DD Connection, transistor M 15 Drain and resistor R C2 First terminal, ramp voltage V Fast All connected, transistor M 15 The source electrode is grounded.

[0024] Specifically, the ramp voltage generation circuit can generate voltage at T ON Stage-based generation of ramp voltage V Slow and slope voltage V Fast The slope of its ramp voltage is determined by resistor R1, resistor R2, and capacitor C. slow Capacitor C fast Transistor M1 and transistor M8 control the circuit. Additionally, resistor R is also included. C1 Resistance R C2 Used to compensate for comparator delay in an adaptive on-time generator.

[0025] Considering the on-resistance Rds1 of transistor M1, the current... for: (1); in, This is the gate-source voltage of transistor M2. is the on-resistance of transistor M1.

[0026] Considering the on-resistance Rds8 of transistor M8, the current... for: (2); in, This is the gate-source voltage of transistor M6. is the on-resistance of transistor M8.

[0027] Transistors M2 and M6 have the same dimensions, transistors M1 and M8 have the same dimensions, and resistors R1 and R2 have the same values. Therefore: (3); in, This is the nominal resistance value. This is the nominal value of the on-resistance.

[0028] Therefore, current The expression is: (4); (5); in, This is the equivalent total resistance.

[0029] The current acts on capacitor C, and the ramp voltage can be obtained. V Slow and V Fast The slope expression: (6); (7); in, For ramp voltage V Slow The slope, This is the integrating capacitor for the slow channel. For ramp voltage V Fast The slope, This is the integrating capacitor for the fast channel.

[0030] resistor R C1 and resistance R C2 The presence of this voltage will generate a fixed voltage drop across the resistor to compensate for the comparator's delay. Combining this with the slope expression for the ramp voltage, the ramp voltage value can be expressed as: (8); (9); in, This refers to the conduction time.

[0031] Figure 2 The input terminals of the comparator CMP1 are voltages. V duty and voltage V Slow voltage V duty The expression is: (10); in, This represents the actual duty cycle that the system needs to achieve.

[0032] Combine equations (8) and (9), and consider the delay of the target comparator. When the voltage V duty equal to voltage V Slow The conduction time T can be derived from this. ON The relationship between the actual duty cycle D and the actual duty cycle D is as follows: (11); (12); in, The system delay time of the target comparator.

[0033] will have Items and with The terms cancel each other out, thus eliminating comparator delay. Impact: (13); (14); When the designed resistor R C1 When the value satisfies formula (14), formula (12) can be simplified to: (15); (16); in, The switching cycle of the system is only related to the resistance. and capacitor C slow related.

[0034] This invention provides a constant frequency switching power supply converter, which generates a precise on-time T by accurately acquiring the actual duty cycle information of the constant frequency switching power supply converter.ON When the constant-frequency switching power supply converter operates in CCM mode, it achieves a constant switching frequency without clock clamping, efficiently and stably stabilizing the system switching frequency over a wide input voltage, wide output voltage, and wide load current range. Furthermore, the switching frequency can quickly recover to the target value when the load current experiences a step change. When the constant-frequency switching power supply converter switches from DCM mode to CCM mode, the switching frequency can also quickly recover to the target value, minimizing electromagnetic interference. It overcomes the switching frequency stability problem of traditional RC filter schemes under wide input and output voltages, as well as the contradiction between switching frequency accuracy and response speed. This allows the COT architecture switching power supply to simultaneously possess the advantages of fast transient response speed and high switching frequency stability. The design scheme of this invention is applicable to the design of any COT architecture switching power supply.

[0035] Figure 6 A schematic diagram illustrating the switching frequency as a function of load current and input voltage is shown below. Figure 6 As shown, when the load current I LOAD When the load current is relatively low, the constant frequency switching power supply converter operates in DCM mode, where the switching frequency increases with increasing load current. LOAD When the voltage is sufficiently high, the constant frequency switching power supply converter automatically enters CCM mode. In this mode, the switching frequency of the constant frequency switching power supply converter no longer changes with the load current, but instead changes with the input voltage. V IN and load current I LOAD The change value is only 18kHz, i.e., Δ f SW =18kHz, Δ is calculated f SW / f SW =1.67%, the switching frequency stability of the constant frequency switching power supply converter is significantly improved.

[0036] Based on the above Figure 1 As can be seen from the implementation method, the constant frequency switching power supply converter in this embodiment of the invention includes a comparator, which is used to output a high-level signal when the voltage at the negative input terminal is less than the voltage at the positive input terminal. V Ctrl The control logic and drive circuitry, connected to a comparator, are used to input signals... V Ctrl When the signal is high, the power transistor MN is turned on, allowing it to enter the conduction phase. An adaptive conduction time generator, connected to the control logic and drive circuit, is used to initiate a timing operation to generate the conduction time after the power transistor MN enters the conduction phase. When the output trigger signal is high...V TRIG When the signal is high, the control conduction phase ends, and the conduction time adaptively varies with the actual duty cycle of the constant-frequency switching power supply converter. The zero-crossing detection circuit, connected to the control logic and drive circuit, is used to detect the inductor current in real time. When the inductor current returns to zero, it outputs a zero-current detection signal. The control logic and drive circuit also generate a drive signal to turn off the high-side power transistor MP in response to the zero-current detection signal. In this way, the control logic, drive circuit, and adaptive conduction time generator obtain a precise actual duty cycle. The conduction time adaptively varies with the actual duty cycle of the constant-frequency switching power supply converter, resulting in a precise conduction time length. Ultimately, this fixes the system's switching frequency, minimizing electromagnetic interference and enabling good switching frequency stability under wide operating voltage and wide load current conditions.

[0037] Based on the same inventive concept, as an implementation of the above-mentioned constant frequency switching power supply converter, this embodiment of the invention also provides a control method for the constant frequency switching power supply converter.

[0038] Figure 7 This is a flowchart of the control method for a constant frequency switching power supply converter in an embodiment of the present invention. See [link / reference]. Figure 7 As shown, the control method for this constant frequency switching power supply converter may include: S701: When the voltage at the negative input terminal is less than the voltage at the positive input terminal, a high-level signal is output. V Ctrl .

[0039] The negative input voltage includes voltage. V SEN and feedback voltage V FB The positive input voltage includes the valley voltage. V SEN_Valley ,Voltage V REF and voltage V OS .

[0040] Specifically, when the voltage at the negative input terminal is less than the voltage at the positive input terminal, a high-level signal is output. V Ctrl Previously, the methods also included: Step A1: Real-time acquisition of inductor current and generation of voltage V SEN .

[0041] Step A2: Voltage V SEN Valley sampling is performed to generate the corresponding valley voltage. VSEN_Valley .

[0042] Step A3: Obtain the generated voltage V OS .

[0043] Step A4: Obtain the feedback voltage V FB .

[0044] S702, in signal V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase.

[0045] S703: After the power transistor MN enters the conduction phase, a timing operation is started to generate the conduction time. When the trigger signal is output... V TRIG When the level is high, the control conduction phase ends.

[0046] The conduction time is the time that adapts to the actual duty cycle.

[0047] Specifically, step S703 includes: Step B1: At the start of the conduction phase, a ramp voltage is generated. V Fast and slope voltage V Slow .

[0048] Step B2: Voltage V LPF Sampling is performed to obtain the voltage. V duty .

[0049] Step B3: Compare voltages V duty and slope voltage V Fast In voltage V duty equal to ramp voltage V Fast At that time, a control signal is generated. V Avg,Ctrl and reset the ramp voltage V Fast .

[0050] Step B4: Compare voltages V duty and slope voltage V Slow In voltage V duty and slope voltage V Slow When they are equal, a conduction control signal is generated.V Trig The timing is adjusted to end the conduction period, thus ending the conduction phase and resetting the ramp voltage. V Slow .

[0051] Among them, control signals V Avg,Ctrl Used to indicate that the average value sampling circuit has entered the hold phase. Turn-on control signal. V Trig Used to indicate when the conduction time enters the end phase. The conduction time is the time that adaptively varies with the actual duty cycle of the constant frequency switching power supply converter.

[0052] Step B5: Upon receiving the control signal V Avg,Ctrl Then, it enters the holding phase to maintain the voltage. V duty Unchanged; upon receiving the turn-on control signal V Trig Then, the conduction time ends.

[0053] Among them, voltage V duty It is the voltage that is proportional to the actual duty cycle.

[0054] S704: Real-time detection of inductor current magnitude; outputs a zero-current detection signal when the inductor current returns to zero.

[0055] S705, in response to a zero current detection signal, generates a drive signal to turn off the high-side power transistor MP.

[0056] The constant frequency switching power supply converter and control method of the present invention aim to overcome the shortcomings of existing technologies where the switching frequency fluctuates with changes in input voltage, output voltage, and load conditions. Specifically, the present invention achieves this by having the control logic, drive circuit, and average value sampling circuit in the adaptive on-time generator work together to accurately sample the actual duty cycle signal of the system in real time and compare it with a reference ramp voltage signal to directly generate a precise on-time control signal for the power switch. Furthermore, the present invention innovatively introduces a compensation mechanism to effectively eliminate the error caused by the inherent propagation delay of the comparator. Therefore, the present invention achieves high stability of the switching frequency over a wide operating voltage range and across the entire load range.

[0057] It should be noted that the above description of the control method embodiment for a constant frequency switching power supply converter is similar to the description of the constant frequency switching power supply converter embodiment described above, and has similar beneficial effects to the constant frequency switching power supply converter embodiment. For technical details not disclosed in the embodiments of the control method for the constant frequency switching power supply converter of the present invention, please refer to the description of the constant frequency switching power supply converter embodiment of the present invention for understanding.

[0058] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A constant frequency switching power supply converter, characterized in that, include: A comparator is used to output a high-level signal when the voltage at the negative input terminal is less than the voltage at the positive input terminal. V Ctrl ; Control logic and drive circuitry, connected to the comparator, are used to control the signal. V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase; An adaptive turn-on time generator, connected to the control logic and drive circuit, is used to initiate a timing operation to generate the turn-on time after the power transistor MN enters the turn-on phase, and outputs a trigger signal. V TRIG When the level is high, the control conduction phase ends, and the conduction time is a time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. The zero-crossing detection circuit is connected to the control logic and drive circuit to detect the magnitude of the inductor current in real time, and outputs a zero current detection signal when the inductor current returns to zero. The control logic and drive circuit are also used to generate a drive signal in response to the zero current detection signal to turn off the high-side power transistor MP.

2. The constant frequency switching power supply converter according to claim 1, characterized in that, The negative input terminal voltage includes voltage. V SEN and feedback voltage V FB The positive input voltage includes the valley voltage. V SEN_Valley ,Voltage V REF and voltage V OS The constant frequency switching power converter also includes an inductor current sampling circuit, a valley sampling circuit, an output error correction circuit, and a feedback resistor network connected to the comparator. The inductor current sampling circuit is used to acquire the inductor current in real time and generate the voltage. V SEN ; The valley sampling circuit is used to sample the voltage. V SEN Perform valley sampling and output the corresponding valley voltage. V SEN_Valley ; The output error correction circuit is used to generate the voltage. V OS ; The feedback resistor network is used to obtain the feedback voltage. V FB .

3. The constant frequency switching power supply converter according to claim 1, characterized in that, The adaptive on-time generator includes: A ramp voltage generating circuit is used to generate a ramp voltage at the beginning of the conduction phase. V Fast and slope voltage V Slow ; Average value sampling circuit, used for voltage V LPF Sample output voltage V duty ; The target comparator, connected to both the ramp voltage generation circuit and the average value sampling circuit, is used to compare the voltage via comparator CMP2. V duty and the slope voltage V Fast At the voltage V duty Equal to the ramp voltage V Fast At that time, the comparator CMP2 outputs a control signal. V Avg,Ctrl and reset the ramp voltage V Fast The voltage is compared using comparator CMP1. V duty and the slope voltage V Slow At the voltage V duty and the slope voltage V Slow When they are equal, the comparator CMP1 outputs a turn-on control signal. V Trig The timing is stopped to end the conduction period, thus ending the conduction phase and resetting the ramp voltage. V Slow The control signal V Avg,Ctrl The on-control signal is used to indicate that the average value sampling circuit enters the hold phase. V Trig This is used to indicate that the conduction time has entered the end stage, and the conduction time is a time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. The average value sampling circuit is also used to receive the control signal. V Avg,Ctrl Then, it enters the holding phase to maintain the voltage. V duty Unchanged; upon receiving the conduction control signal V Trig Then, it enters the conduction time end phase, and the voltage... V duty It is the voltage that is proportional to the actual duty cycle.

4. The constant frequency switching power supply converter according to claim 3, characterized in that, The ramp voltage generating circuit includes resistors R1, R2, and R... C1 Resistance R C2 Capacitor C slow Capacitor C fast Transistor M1, Transistor M2, Transistor M3, Transistor M4, Transistor M5, Transistor M6, Transistor M7, Transistor M8, Transistor M9, Transistor M 10 Transistor M 11 Transistor M 12 Transistor M 13 Transistor M 14 and transistor M 15 ; The first terminal of the resistor R1 is connected to the voltage. V X The resistor R1 is connected to the drain of transistor M1. The source of transistor M1, the drain of transistor M2, and the gate of transistor M2 are all connected. The source of transistor M2 is grounded. The gate of transistor M3 is connected to the gate of transistor M2. The source of transistor M3 is grounded. The drain of transistor M3 is connected to the drain of transistor M4, the gate of transistor M4, and the gate of transistor M5. The source of transistor M4 is connected to the power supply. V DD The source of transistor M5 is connected to the power supply V. DD The connections are as follows: the drain of transistor M5 is connected to the drain of transistor M6 and the gate of transistor M7; the source of transistor M6 is grounded; the gate of transistor M6 is connected to the source of transistor M7 and the drain of transistor M8; the drain of transistor M7 is connected to the drain of transistor M9; the source of transistor M8 is connected to the first terminal of resistor R2; and the gate of transistor M8 is connected to the power supply. V DD The resistor R2 is connected to ground, and the source of transistor M9 is connected to the power supply. V DD The gate of transistor M9 is connected to the gate of transistor M. 10 The gate connection of the transistor M 10 The drain, the resistor R C1 The first terminal and the transistor M 12 The drains of the transistors are all connected, and the transistor M 10 The source and the power supply V DD Connection, the resistor R C1 The second terminal is connected to the capacitor C Slow The first end is connected to the capacitor C. Slow The second terminal of the transistor is grounded, and the transistor M 12 The source and the power supply V DD Connection, the transistor M 12 The gate of is connected to the gate of the transistor M4, and the transistor M 14 The drain and the resistor R C1 The first terminal and the slope voltage V Slow Connection, the transistor M 14 The source of the transistor is grounded, and the transistor M 11 The gate of is connected to the gate of transistor M9, and transistor M... 11 The source and the power supply V DD Connection, the transistor M 11 The drain of the transistor M 13 The drain and the resistor R C2 The first end of each resistor is connected to the resistor R. C2 The second terminal is connected to the capacitor C Fast The first end is connected to the capacitor C. Fast The second terminal of the transistor is grounded, and the transistor M 13 The gate of is connected to the gate of the transistor M4, and the transistor M 13 The source and the power supply V DD Connection, the transistor M 15 The drain and the resistor R C2 The first terminal, the ramp voltage V Fast All are connected, the transistor M 15 The source electrode is grounded.

5. The constant frequency switching power supply converter according to claim 3, characterized in that, The average value sampling circuit includes a sample-and-hold circuit and a capacitor C. LPF Resistance R LPF Switch S1, transistor M P Transistor M N and inverter INV; Control voltage V GN The input terminal of the inverter INV is connected, and the output terminal of the inverter INV is connected to the transistor M. P The gate and the transistor M N The gate of the transistor M P The source of the transistor M N The source of the transistor M is connected to the source. P Source and voltage V X Connected, the transistor M N The source terminal ground potential GND; the transistor M P The transistor M N The common terminal is connected to the second terminal of the switch S1, and the first terminal of the switch S1 is connected to the resistor R. LPF The second end is connected to the resistor R. LPF The first terminal, the capacitor C LPF The first terminal and the second terminal of the sample-and-hold circuit are both connected, and the capacitor C LPF The second terminal of the sample-and-hold circuit is grounded at the potential GND, and the first terminal of the sample-and-hold circuit is connected to the target comparator.

6. The constant frequency switching power supply converter according to claim 5, characterized in that, The positive input terminal of comparator CMP1, the first terminal of the sample-and-hold circuit, and the positive input terminal of comparator CMP2 are all connected. The negative input terminal of comparator CMP1 is connected to the ramp voltage. V Slow The output of comparator CMP1 is connected to the control logic and drive circuit, and the negative input of comparator CMP2 is connected to the ramp voltage. V Fast The output of the comparator CMP2 is connected to the control terminal of the sample-and-hold circuit.

7. The constant frequency switching power supply converter according to claim 2, characterized in that, The feedback resistor network includes resistors. R FB1 and resistance R FB2 The constant frequency switching power supply converter also includes an inductor. L ,resistance DCR ,capacitance C L ,resistance R ESR and resistance R L The inductor L The first terminal and voltage V IN Connection, the inductor L The second end is connected to the resistor DCR The first end is connected, the resistor DCR The second terminal, the drain of the power transistor MN, and the drain of the high-side power transistor MP are all connected. The source of the power transistor MN is grounded. The gate of the power transistor MN is connected to the control logic and drive circuit. The gate of the high-side power transistor MP is connected to the control logic and drive circuit. The source of the high-side power transistor MP, the inductor current sampling circuit, and the capacitor... C L The first end, the resistor R L The first end and the resistor R FB2 The first terminal is connected to the voltage. V OUT The capacitor C L The second end is connected to the resistor R ESR The first end is connected, the resistor R ESR The second terminal of the resistor is grounded. R L The second terminal of the resistor is grounded. R FB2 The second end, the resistor R FB1 The first terminal and the negative input terminal of the comparator are both connected, and the resistor R FB1 The second terminal is grounded.

8. A control method for a constant frequency switching power supply converter, characterized in that, The control method is implemented using the constant frequency switching power supply converter according to any one of claims 1 to 7, the control method comprising: When the voltage at the negative input terminal is less than the voltage at the positive input terminal, a high-level signal is output. V Ctrl ; In the signal V Ctrl When the voltage level is high, the power transistor MN is turned on, so that the power transistor MN enters the conduction phase; After the power transistor MN enters the conduction phase, a timing operation is started to generate the conduction time, and a trigger signal is output. V TRIG When the level is high, the control conduction phase ends, and the conduction time is a time that adaptively changes with the actual duty cycle. The magnitude of the inductor current is detected in real time, and a zero current detection signal is output when the inductor current returns to zero. In response to the zero current detection signal, a drive signal is generated to turn off the high-side power transistor MP.

9. The control method for a constant frequency switching power supply converter according to claim 8, characterized in that, After the power transistor MN enters the conduction phase, a timing operation is initiated to generate the conduction time, and a trigger signal is output. V TRIG When the level is high, the control conduction phase ends, including: A ramp voltage is generated at the start of the conduction phase. V Fast and slope voltage V Slow ; For voltage V LPF Sampling is performed to obtain the voltage. V duty ; Compare the voltages V duty and the slope voltage V Fast At the voltage V duty Equal to the ramp voltage V Fast At that time, a control signal is generated. V Avg,Ctrl and reset the ramp voltage V Fast ; Compare the voltages V duty and the slope voltage V Slow At the voltage V duty and the slope voltage V Slow When they are equal, a conduction control signal is generated. V Trig The timing is stopped to end the conduction period, thus ending the conduction phase and resetting the ramp voltage. V Slow The control signal V Avg,Ctrl The turn-on control signal is used to indicate that the average value sampling circuit has entered the hold phase. V Trig This is used to indicate that the conduction time has entered the end stage, and the conduction time is a time that adaptively changes with the actual duty cycle of the constant frequency switching power supply converter. Upon receiving the control signal V Avg,Ctrl Then, it enters the holding phase to maintain the voltage. V duty Unchanged; upon receiving the conduction control signal V Trig Then, it enters the conduction time end phase, and the voltage... V duty It is the voltage that is proportional to the actual duty cycle.

10. The control method for a constant frequency switching power supply converter according to claim 8, characterized in that, The negative input terminal voltage includes voltage. V SEN and feedback voltage V FB The positive input voltage includes the valley voltage. V SEN_Valley ,Voltage V REF and voltage V OS When the voltage at the negative input terminal is less than the voltage at the positive input terminal, a high-level signal is output. V Ctrl Previously, the method also included: Real-time acquisition of inductor current and generation of the voltage V SEN ; For the voltage V SEN Valley sampling is performed to generate the corresponding valley voltage. V SEN_Valley ; Obtain the generated voltage V OS ; Obtain the feedback voltage V FB .

Images