On-time generating circuit capable of self-adapting to input and output voltage

Abstract

The invention discloses a self-adaptive input and output voltage conduction time generation circuit, which comprises an electric energy conversion module, a current mirror module and a conduction time generation module, and is characterized in that an electric energy conversion unit is used for accessing an input voltage signal of a BUCK converter and converting the input voltage signal into a first current signal; the current mirror module is used for generating a second current signal based on the first current signal and outputting a comparison voltage signal according to the second current signal; the conduction time generation module is used for obtaining a reference voltage signal according to an output voltage signal of the BUCK converter; obtaining a second trigger pulse according to the reference voltage signal and the comparison voltage signal; and according to the external trigger pulse and the second trigger pulse, generating a switch control pulse signal used for controlling the conduction time length, and a current mirror output control signal used for controlling the comparison voltage signal output value. According to the invention, the relation between the system conduction time and the switching frequency can be decoupled, the stability of the switching frequency when the BUCK system is in a steady state is improved, and the influence of EMI interference is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a conduction time generating circuit capable of adaptively adapting input and output voltages. Background Art

[0002] Synchronous buck converters offer a variety of feedback control modes. RB-COT control is a method based on output voltage ripple. The feedback loop primarily consists of a comparator (COMP), a constant on-time generator (ConstantOn-Timer), logic, and a driver circuit. This control loop is relatively simple, requiring no op amp clamps or compensators. Load changes are directly reflected in the comparator for further adjustment, resulting in faster load transient response. At light loads, the system switching frequency is reduced, minimizing power stage switching losses and improving system conversion efficiency. This makes it suitable for applications requiring large step-down ratios and fast load transient response.

[0003] However, RB-COT control depends on the ESR resistance of the output capacitor. Too small an ESR will cause system stability problems, while too large an ESR will cause large output voltage ripple, thereby affecting output accuracy. In addition, the system switching frequency is not fixed and the anti-EMI interference capability is poor. Summary of the Invention

[0004] The purpose of the present invention is to provide an on-time generating circuit with adaptive input and output voltages, which can decouple the relationship between the on-time of the system and the switching frequency, improve the stability of the switching frequency in the steady state of the buck system, and reduce the impact of EMI interference.

[0005] The technical solution adopted by the present invention is: a conduction time generating circuit with adaptive input and output voltages, comprising an electric energy conversion module, a current mirror module and a conduction time generating module, wherein:

[0006] The power conversion unit is used to receive the input voltage signal of the BUCK converter and convert the input voltage signal into a first current signal;

[0007] The current mirror module is used to proportionally copy the first current signal to obtain a second current signal, and output a comparison voltage signal to the on-time generation module according to the second current signal;

[0008] The on-time generation module is used to: receive an external trigger pulse and an output voltage signal of the buck converter; obtain a reference voltage signal based on the output voltage signal; obtain a second trigger pulse based on the reference voltage signal and the comparison voltage signal; and generate a switch control pulse signal for controlling the on-time length and a current mirror output control signal for controlling the output value of the comparison voltage signal based on the external trigger pulse and the second trigger pulse.

[0009] It should be noted that the aforementioned on-time refers to the on-time of the controllable switch in the buck circuit, which controls the connection between the power input and output terminals. The above technical solution of the present invention aims to adapt the on-time to the input and output voltages, so that the on-time is not affected by the switching frequency.

[0010] Optionally, the on-time generation circuit of the present invention further includes a reference start module, which is used to generate an initial reference voltage signal and transmit it to the on-time generation module;

[0011] In the initial stage of powering on the BUCK converter, the on-time generation module generates the second trigger pulse according to the initial reference voltage signal and the comparison voltage signal output by the current mirror module.

[0012] After the BUCK converter is powered on, the output voltage The initial state is zero and cannot be used as a reference voltage for the comparator. Therefore, in the present invention, a reference voltage is provided by a reference startup module at this stage to avoid false triggering output of the conduction time generation module.

[0013] Optionally, the reference startup module includes a self-biased common-source common-gate current mirror unit powered by a power supply VDD and with controllable conduction, a charging capacitor C2 is connected in series to the output side current loop, one end of the charging capacitor C2 is grounded, and the other end serves as the output end of the initial reference voltage signal, and is connected to the reference voltage signal acquisition end of the conduction time generation module. After stabilization, the voltage of the output-side switch tube in the self-biased cascode current mirror unit connected to C2 rises, causing the gate-source voltage of the switch tube to be lower than the turn-on threshold and then turn off. That is, the reference startup module fails. Thereafter, the reference voltage of the on-time generation module will be generated by the output voltage of the BUCK circuit.

[0014] Optionally, the on-time generation module includes a reference voltage acquisition unit, a comparator and an SR latch;

[0015] The reference voltage acquisition unit includes a voltage divider resistor connected in series between the output voltage input terminal of the BUCK converter and the ground terminal. The voltage dividing point of the voltage divider circuit leads to the reference voltage signal acquisition terminal through the resistor R4 and is connected to the inverting input terminal of the comparator;

[0016] The non-inverting input terminal of the comparator is connected to the comparison voltage signal output by the current mirror module, the output terminal of the comparator is connected to the R trigger terminal of the SR latch, the S trigger terminal of the SR latch is connected to the external trigger pulse, and the Q output terminal outputs the switch control pulse signal. The output terminal outputs the current mirror output control signal;

[0017] The external trigger pulse is used to trigger the switch control pulse signal to jump to the rising edge at its rising edge, so that the buck converter is turned on; the second trigger pulse output by the comparator is used to trigger the switch control pulse signal to jump to the falling edge at its rising edge, so that the buck converter is turned off, that is, the length of the conduction time is determined.

[0018] Optionally, the voltage divider circuit includes a resistor R5 and a resistor R6 connected in series between the output voltage input terminal of the BUCK converter and the ground terminal, and the voltage divider point is the connection point between the resistor R5 and the resistor R6;

[0019] The resistor R4 is selected to have a large resistance value so that the voltage drop across it approaches 0. The function of the resistor R4 is to superimpose the voltage and reduce the output voltage when the reference voltage is collected. The output voltage of the BUCK converter and the resistance values ​​of resistors R4, R5, and R6 are all parameters related to the conduction time.

[0020] Optionally, a charging capacitor C1 is connected to the output side circuit of the current mirror circuit, and the second current signal can charge the charging capacitor C1; one end of the charging capacitor C1 is grounded, and the other end is used to output the comparison voltage signal, that is, connected to the non-inverting input end of the comparator in the conduction time generation module;

[0021] The two ends of the charging capacitor C1 are connected in parallel with the switch tube M 21 , switch tube M 21 The control terminal of the current mirror is connected to the output control signal of the current mirror. When the conduction time ends, M 21 After the high-level signal is connected, the charging capacitor C1 begins to discharge, and the output comparison voltage signal begins to decrease until the next switching cycle begins. The rising edge of the Q end of the SR register is triggered by the external trigger pulse to determine the rising edge of the conduction time. 21 Connect a low-level signal to shut down and C1 starts charging again.

[0022] Optionally, the power conversion module includes an operational amplifier and a current output circuit connected between a power supply VDD and a ground terminal;

[0023] The current output circuit is connected to a PMOS transistor M1 and a resistor R3, the source of the PMOS transistor M1 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded;

[0024] Resistors R1 and R2 are connected in series between the input voltage VCC access terminal and the ground terminal of the BUCK converter. The non-inverting input terminal of the operational amplifier is connected to the connection point of the resistors R1 and R2, the inverting input terminal is connected to the source of the PMOS transistor M1, and the output terminal is connected to the gate of the PMOS transistor M1.

[0025] In the above embodiment, the input voltage VCC of the buck converter is transmitted to the operational amplifier via the resistor divider circuit, thereby generating the first current signal on the current output line as the input of the current mirror circuit, thereby realizing the electrical energy conversion of the input voltage of the buck converter.

[0026] Optionally, the formula for the on-time is:

[0027]

[0028] Where, Indicates the on-time, ~ are the resistance values ​​of resistors R1~R6 respectively, is the current replication ratio of the current mirror circuit, 、 are the input voltage and output voltage of the BUCK converter respectively.

[0029] In a second aspect, the present invention provides a method for controlling the on-time generating circuit for adaptive input and output voltages according to the first aspect, comprising:

[0030] Before or when the BUCK converter is powered on, the power supply VDD is powered on, and the self-biased cascode current mirror unit in the reference startup module is controlled to operate by an external drive signal so that the self-biased cascode current mirror unit can output the initial reference voltage signal to the conduction time generation module;

[0031] Determine the external trigger pulse according to the required switching frequency, and input the external trigger pulse to the S terminal of the SR latch after the BUCK converter is powered on to periodically trigger the rising edge of the on-time according to the switching frequency;

[0032] The switch control pulse signal output from the Q terminal of the SR latch is obtained to control the on or off of the BUCK converter.

[0033] In the above control method, the on-time is adaptively adjusted by the input voltage, output voltage and circuit parameters of the on-time generating circuit. The external trigger pulse can be set to a pulse with a small duty cycle to ensure that the S and R terminals of the SR latch do not input high-level signals at the same time.

[0034] Beneficial effects

[0035] The present invention realizes an on-time generating circuit that can adjust the on-time length according to the adaptive input voltage and output voltage. The on-time is independent of the switching frequency, which can improve the stability of the switching frequency in the steady state of the buck system and reduce the impact of EMI interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 FIG2 is a schematic diagram of a principle circuit of a buck converter in a constant on-time control mode in the prior art;

[0037] Figure 2 Shown is a schematic diagram of the principle of the on-time control circuit of the present invention;

[0038] Figure 3 The figure shows a screenshot of the transient waveform of the AOT circuit when the buck converter chip is operating in steady state at a switching frequency of 2MHz.

[0039] Figure 4 The following screenshots show the transient waveforms of the AOT circuit output signal when the buck converter is at different switching frequencies.

[0040] Figure 5 The following table shows the buck input voltage V IN A screenshot of the transient waveform of the AOT circuit output signal when φ changes. DETAILED DESCRIPTION

[0041] The following is a further description with reference to the accompanying drawings and specific embodiments.

[0042] Figure 1 The schematic circuit diagram of a conventional constant on-time (RB-COT) buck converter is shown. Its operating principle is as follows: When the system output feedback voltage is less than the reference voltage, the PWM comparator output flips to set the RS trigger. Through drive and control logic adjustments, the high-side transistor M0 is turned on and the low-side transistor M1 is turned off, entering the charging phase and causing the system output voltage to rise. When the feedback voltage rises to a value greater than the reference voltage, the switch control signal is maintained at a high level through the RS trigger, and the switch control signal output by the RS trigger is also turned off. The fixed on-time generation module On-Timer is controlled to start timing. After the fixed on-time, the fixed on-time generation module outputs a high-level narrow pulse to reset the trigger, thereby turning off the high-end tube M0 and turning on the low-end tube M1, entering the freewheeling stage. The above process is repeated until the next time the feedback voltage is detected to be less than the reference voltage, so that the output voltage finally maintains a stable state.

[0043] In traditional fixed on-time control, taking the buck converter in continuous conduction CCM mode as an example, we have:

[0044]

[0045] in, is the on-time, is the switching period, is the switching frequency, is the system output voltage, is the input voltage.

[0046] From the above formula, we can see that the on-time It is not only related to the system input and output conditions, but also to the switching frequency Therefore, the system is susceptible to EMI electromagnetic interference.

[0047] In view of the above situation, the present invention proposes an adaptive on-time (AOT) control technology for input and output voltage, so that the system on-time and switching frequency are It is irrelevant, thereby improving the stability of the system switching frequency and improving the electromagnetic compatibility (EMC) of the BUCK circuit.

[0048] Example 1

[0049] refer to Figure 1 This embodiment introduces a conduction time generation circuit with adaptive input and output voltages, including a power conversion module, a current mirror module, and a conduction time generation module, wherein:

[0050] The power conversion unit is used to receive the input voltage signal of the BUCK converter and convert the input voltage signal into a first current signal;

[0051] The current mirror module is used to proportionally copy the first current signal to obtain a second current signal, and output a comparison voltage signal to the on-time generation module according to the second current signal;

[0052] The on-time generation module is used to: receive an external trigger pulse and an output voltage signal of the buck converter; obtain a reference voltage signal based on the output voltage signal; obtain a second trigger pulse based on the reference voltage signal and the comparison voltage signal; and generate a switch control pulse signal for controlling the on-time length and a current mirror output control signal for controlling the output value of the comparison voltage signal based on the external trigger pulse and the second trigger pulse.

[0053] The switch control pulse signal is used to drive the on and off of a controllable switch in the BUCK circuit for controlling the connection state between the power input terminal and the output terminal.

[0054] The on-time duty cycle of the switch control pulse signal generated in this embodiment can be adjusted to suit the input voltage and the output voltage, so that the on-time is not affected by the switching frequency.

[0055] Considering that in the initial stage of power-on of the BUCK converter, there is no voltage output at its output terminal because the reference voltage signal cannot be collected. Therefore, the initial reference voltage signal can be provided externally or through other circuits to achieve the provision of the initial period.

[0056] Example 2

[0057] Based on Example 1, this example also has the following design.

[0058] like Figure 1 The on-time generation circuit of this embodiment further includes a reference startup module for generating an initial reference voltage signal and transmitting the signal to the on-time generation module. In the initial stage of powering on the BUCK converter, the on-time generation module generates the second trigger pulse based on the initial reference voltage signal and the comparison voltage signal output by the current mirror module.

[0059] That is, the on-time generation circuit of this embodiment includes a power conversion module, a current mirror module, a reference startup module and an on-time generation module, and its specific implementation is described as follows.

[0060] 1. Power conversion module

[0061] Resistors R1~R3, operational amplifier OPA, NMOS tube M2 and PMOS tube M1 constitute the power conversion module, which is used to collect input voltage and convert the voltage signal into a current signal. Specifically:

[0062] Buck converter input voltage V IN After voltage division by resistors R1 and R2, the current is transmitted to the non-inverting input of the operational amplifier OPA. In the current output circuit, the source of M2 is connected to the power supply VDD, the drain is connected to the drain of M1, the source of M1 is connected to one end of resistor R3, and the other end of resistor R3 is grounded.

[0063] Using the virtual short characteristic of the op amp, we have V P =V N , voltage V N The current I1 is formed through the resistor R3 and flows through the NMOS tube M1.

[0064] (1)

[0065] The current I1 can be expressed as:

[0066] (2)

[0067] 2. Current Mirror Module

[0068] MOS tubes M3~M14 form a high-precision current mirror circuit, where and Gate interconnect, used to carry current .M9~M 12 The circuit is used to make M9 and M 13 The port voltages are equal, thus suppressing the copy error caused by channel length modulation, M 12 、M 13 、M 14 A negative feedback loop is formed to increase the output impedance of the MOS tube M 13 It can accurately copy the current of MOS tube M8 and obtain the second current signal .

[0069] The output side of the current mirror circuit is connected to a charging capacitor C1, and the current flowing through M 14 The current is expressed as I C1 , i.e. the second current signal, and , m represents the replication ratio of the current mirror circuit, It can charge the charging capacitor C1. One end of the charging capacitor C1 is grounded, and the other end is used to output the comparison voltage signal to the non-inverting input end of the comparator in the conduction time generation module; the two ends of the charging capacitor C1 are connected to the switch tube M 21 , switch tube M 21 The control terminal of the M is connected to the current mirror output control signal output by the conduction time generation module. 21 After the high-level signal is connected, the charging capacitor C1 begins to discharge, and the output comparison voltage signal begins to decrease until the next switching cycle begins. The rising edge of the Q end of the SR register is triggered by the external trigger pulse to determine the rising edge of the conduction time. 21 Connect a low-level signal to shut down and C1 starts charging again.

[0070] The output impedance of the current mirror circuit can be expressed as:

[0071] (3)

[0072] 3. Benchmark Startup Module

[0073] MOS tube M 15 ~M 20 , charging capacitor C2 and resistor R7, MOS tube M 15 ~M 18 and resistor R7 form a self-biased cascode current mirror, which is powered by power supply VDD and M 15 and M 16 The conduction is controllable, and a charging capacitor C2 is connected in series to the output side current loop, one end of C2 is grounded, and the other end serves as the output end of the initial reference voltage signal, and is connected to the reference voltage signal acquisition end of the conduction time generation module.

[0074] During the power-on process of the BUCK converter, the output voltage The initial state is zero and cannot be used as the reference voltage of the on-time generation module. Therefore, at this stage, the voltage on capacitor C2 is used as the initial reference voltage signal to be transmitted to the on-time generation module. After stabilization, M 20 The gate-source voltage of the tube is less than the threshold voltage, so M 20 The tube is turned off, that is, the reference startup module fails, and the reference voltage V REF By the steady-state output voltage Partial pressure is generated.

[0075] 4. On-time generation module

[0076] The on-time generation module includes a reference voltage acquisition unit, a comparator and an SR latch; the reference voltage acquisition unit includes a voltage dividing resistor connected in series between the output voltage access terminal of the BUCK converter and the ground terminal, namely resistors R5 and R6. Their connection point is the voltage dividing point, which is led out through resistor R4 as the reference voltage signal acquisition terminal and connected to the inverting input terminal of the comparator COMP; the non-inverting input terminal of the comparator is connected to the comparison voltage signal output by the current mirror module, the output terminal of the comparator is connected to the R trigger terminal of the SR latch, the S trigger terminal of the SR latch is connected to the external trigger pulse, and the Q output terminal outputs the switch control pulse signal. The output terminal outputs the current mirror output control signal;

[0077] The external trigger pulse is used to trigger the switch control pulse signal to jump to the rising edge at its rising edge, so that the buck converter is turned on; the second trigger pulse output by the comparator is used to trigger the switch control pulse signal to jump to the falling edge at its rising edge, so that the buck converter is turned off. The rising edge and falling edge of the on-time are determined by the external trigger pulse and the output of the comparator COMP, respectively, that is, the length of the on-time is determined.

[0078] The following table shows the circuit of the present invention. and SR latch port state and capacitance under different size relationships Charge and discharge state. It is an external control signal, which is used to trigger the SR latch Q output terminal to jump to the rising edge at its rising edge. It can be a pulse with the same frequency as the switching frequency and a smaller duty cycle, as long as it does not cause the S and R terminals of the SR latch to input high levels at the same time. It can be used as the input signal of the R terminal of the SR latch, or it can be modulated with an external signal and input to the R terminal of the SR latch to better match the requirements of the SR latch for the input trigger signal and ensure the trigger sensitivity, so that the conduction time of the present invention can effectively adapt to the changes in the input and output voltages.

[0079]

[0080] When the circuit reaches steady state, the conduction time T on It can be expressed as:

[0081] (4)

[0082] Since the negative terminal voltage of the comparator V REF By output voltage The partial pressure is obtained, so we have:

[0083] (5)

[0084] The function of the resistor R4 is to superimpose the voltage. The value of the resistor R4 is large, and the voltage drop across it can be ignored.

[0085] Combining Equations 1 to 5, we can get the on-time T on for:

[0086] (6)

[0087] It can be seen from the above formula that the on-time is no longer related to the switching frequency f SW It is only related to the input and output voltages and internal circuit parameters of the BUCK converter.

[0088] Combined with the above theoretical analysis, the present invention uses simulation software to perform functional simulation verification on the proposed AOT circuit with adaptive input and output voltage. Figure 3 The figure shows the transient waveform of the AOT circuit when the BUCK converter chip is operating in a steady state at a switching frequency of 2MHz. VO_AOT is the switching control pulse signal, which is the output of the AOT circuit. The green waveform represents the voltage V C1 The pink waveform represents the reference voltage V of the comparator module. REF When capacitor C1 starts to charge, the rising edge of the pulse signal at the S end of the SR latch triggers the rising edge of the VO_AOT signal. C1 rises to greater than V REF When the comparator flips, triggering the falling edge of the VO_AOT signal, thus determining the on-time of the BUCK circuit.

[0089] like Figure 4The transient waveforms of the AOT circuit output signal when the buck converter is at different switching frequencies are shown to verify that the on-time of the AOT circuit proposed in this invention, which is adaptive to input and output voltage adjustment, is independent of the switching frequency. Therefore, when both the input and output voltages remain unchanged, the VO_AOT on-time remains unchanged at system switching frequencies of 10 MHz and 2 MHz, and is independent of the switching frequency. Figure 5 It shows that when the BUCK input voltage V IN When the AOT circuit outputs the transient waveform of the signal, when V IN When jumping from 24V to 48V, it can be seen that as V IN As the on-time increases, the AOT circuit adaptively adjusts the on-time, and the on-time becomes shorter, while the switching period of the system does not change significantly, which verifies the correctness of formula (6).

[0090] Example 3

[0091] This embodiment introduces a control method for the on-time generating circuit for adaptive input and output voltages described in Embodiment 2, including:

[0092] Before or when the BUCK converter is powered on, the power supply VDD is powered on, and the self-biased cascode current mirror unit in the reference startup module is controlled to operate by an external drive signal so that the self-biased cascode current mirror unit can output the initial reference voltage signal to the conduction time generation module;

[0093] Determine the external trigger pulse according to the required switching frequency, and input the external trigger pulse to the S terminal of the SR latch after the BUCK converter is powered on to periodically trigger the rising edge of the on-time according to the switching frequency;

[0094] The switch control pulse signal output from the Q terminal of the SR latch is obtained to control the on or off of the BUCK converter.

[0095] In summary, the present invention implements an on-time generator circuit that can adaptively adjust the on-time length based on the input voltage and output voltage. The on-time is no longer affected by the switching frequency, thereby improving the switching frequency stability of the buck system in steady state and reducing the impact of EMI interference.

[0096] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0097] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0098] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0099] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0100] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. A conduction time generating circuit with adaptive input and output voltage, characterized in that: It includes an energy conversion module, a current mirror module and a conduction time generation module, wherein: The power conversion unit is used to receive the input voltage signal of the BUCK converter and convert the input voltage signal into a first current signal; The current mirror module is used to proportionally copy the first current signal to obtain a second current signal, and output a comparison voltage signal to the on-time generation module according to the second current signal; The on-time generation module is used to: receive an external trigger pulse and an output voltage signal of the buck converter; obtain a reference voltage signal based on the output voltage signal; obtain a second trigger pulse based on the reference voltage signal and the comparison voltage signal; and generate a switch control pulse signal for controlling the on-time length and a current mirror output control signal for controlling the output value of the comparison voltage signal based on the external trigger pulse and the second trigger pulse.

2. The on-time generating circuit for adaptive input and output voltage according to claim 1, wherein: It also includes a reference startup module for generating an initial reference voltage signal and transmitting it to the on-time generation module; In the initial stage of powering on the BUCK converter, the on-time generation module generates the second trigger pulse according to the initial reference voltage signal and the comparison voltage signal output by the current mirror module.

3. The on-time generating circuit for adaptive input and output voltage according to claim 2, wherein: The reference startup module includes a self-biased common-source common-gate current mirror unit powered by a power supply VDD and with controllable conduction. A charging capacitor C2 is connected in series to its output-side current loop. One end of the charging capacitor C2 is grounded, and the other end serves as the output end of the initial reference voltage signal, and is connected to the reference voltage signal acquisition end of the conduction time generation module.

4. The on-time generating circuit for adaptive input and output voltage according to claim 3, wherein: The on-time generation module includes a reference voltage acquisition unit, a comparator and an SR latch; The reference voltage acquisition unit includes a voltage divider resistor connected in series between the output voltage input terminal of the BUCK converter and the ground terminal. The voltage dividing point of the voltage divider circuit leads to the reference voltage signal acquisition terminal through the resistor R4 and is connected to the inverting input terminal of the comparator; The non-inverting input terminal of the comparator is connected to the comparison voltage signal output by the current mirror module, the output terminal of the comparator is connected to the R trigger terminal of the SR latch, the S trigger terminal of the SR latch is connected to the external trigger pulse, and the Q output terminal outputs the switch control pulse signal. The output terminal outputs the current mirror output control signal; The external trigger pulse is used to trigger the switch control pulse signal to jump to the rising edge at its rising edge, so that the buck converter is turned on; the second trigger pulse output by the comparator is used to trigger the switch control pulse signal to jump to the falling edge at its rising edge, so that the buck converter is turned off, that is, the length of the conduction time is determined.

5. The on-time generating circuit for adaptive input and output voltage according to claim 4, wherein: The voltage divider circuit includes a resistor R5 and a resistor R6 connected in series between the output voltage input terminal of the BUCK converter and the ground terminal, and the voltage divider point is the connection point of the resistor R5 and the resistor R6; The resistor R4 is a resistor with a large resistance value so that the voltage drop across it approaches zero.

6. The on-time generating circuit for adaptive input and output voltage according to claim 5, wherein: The output side circuit of the current mirror circuit is connected to a charging capacitor C1, and the second current signal can charge the charging capacitor C1; one end of the charging capacitor C1 is grounded, and the other end is used to output the comparison voltage signal; The two ends of the charging capacitor C1 are connected in parallel with the switch tube M 21 , switch tube M 21 The control end is connected to the current mirror output control signal.

7. The on-time generating circuit for adaptive input and output voltage according to claim 6, wherein: The power conversion module includes an operational amplifier and a current output circuit connected between a power supply VDD and a ground terminal; The current output circuit is connected to a PMOS transistor M1 and a resistor R3, the source of the PMOS transistor M1 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; Resistors R1 and R2 are connected in series between the input voltage VCC access terminal and the ground terminal of the BUCK converter. The non-inverting input terminal of the operational amplifier is connected to the connection point of the resistors R1 and R2, the inverting input terminal is connected to the source of the PMOS transistor M1, and the output terminal is connected to the gate of the PMOS transistor M1.

8. The on-time generating circuit for adaptive input and output voltage according to claim 7, characterized in that: The formula for the on-time is: ； Where, represents the on-time, ~ are the resistance values ​​of resistors R1~R6 respectively, is the current replication ratio of the current mirror circuit, 、 are the input voltage and output voltage of the BUCK converter respectively.

9. A method for controlling the on-time generating circuit for adaptive input and output voltage according to any one of claims 3 to 8, characterized in that: include: Before or when the BUCK converter is powered on, the power supply VDD is powered on, and the self-biased cascode current mirror unit in the reference startup module is controlled to operate by an external drive signal so that the self-biased cascode current mirror unit can output the initial reference voltage signal to the conduction time generation module; Determine the external trigger pulse according to the required switching frequency, and input the external trigger pulse to the S terminal of the SR latch after the BUCK converter is powered on to periodically trigger the rising edge of the on-time according to the switching frequency; The switch control pulse signal output from the Q terminal of the SR latch is obtained to control the on or off of the BUCK converter.

Images