阅读说明：本技术 一种便于实现升压转换器超低静态电流的控制器 (Controller convenient to realize ultralow quiescent current of boost converter ) 是由 刘若华 其他发明人请求不公开姓名 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种便于实现升压转换器超低静态电流的控制器,其中,控制器包括：比较器、自适应定时器、直通控制驱动器、纹波注入模块、反馈网络和参考电压,所述比较器的正输入端耦接参考电压,该参考电压提供对温度、输入电压Vin、输出电压VOUT和负载电流不敏感的参考电压信号VREF,所述比较器的负输入端耦接纹波注入模块,且纹波注入模块包括纹波发生器和电感电流仿真器,所述比较器输出信号Vtrigger,且所述纹波注入模块输出信号Vcontrol,所述比较器的输出端耦接自适应定时器,本发明通过控制器采用恒定导通时间架构控制升压转换器重载时保持恒定的开关频率,轻载时有着超低的静态功耗。(The invention discloses a controller convenient for realizing ultralow quiescent current of a boost converter, wherein the controller comprises: the boost converter comprises a comparator, an adaptive timer, a direct-through control driver, a ripple injection module, a feedback network and a reference voltage, wherein the positive input end of the comparator is coupled with the reference voltage, the reference voltage provides a reference voltage signal VREF insensitive to temperature, input voltage Vin, output voltage VOUT and load current, the negative input end of the comparator is coupled with the ripple injection module, the ripple injection module comprises a ripple generator and an inductive current simulator, the comparator outputs a signal Vtrigger and a signal Vcontrol, and the output end of the comparator is coupled with the adaptive timer.)

1. A controller, comprising: the device comprises a comparator, a self-adaptive timer, a direct connection control driver, a ripple injection module, a feedback network and a reference voltage;

the positive input end of the comparator is coupled with a reference voltage, and the reference voltage provides a reference voltage signal VREF insensitive to temperature, an input voltage Vin, an output voltage VOUT and load current;

the negative input end of the comparator is coupled with the ripple injection module, and the ripple injection module comprises: a ripple generator and an inductive current simulator;

the comparator outputs a signal Vtrigger and the ripple injection module outputs a signal Vcontrol;

the output end of the comparator is coupled with the self-adaptive timer, and after the signal Vtrigger goes high, the timer generates a pulse OnTime based on the voltage of the input voltage Vin and the output voltage VOUT;

the output end of the adaptive timer is coupled with a through control driver, and the through control driver is provided with three output ends, wherein the first output end is used as one output end output signal HGATE of the controller and is coupled to the grid electrode of the MOS tube M2, the second output end is used as the other output end output signal LGATE of the controller and is coupled to the grid electrode of the MOS tube M1, the third output end output signal Rcontrol is coupled to the ripple injection module, and the output signal Rcontrol is used for generating ripple voltage;

the feedback network outputs a feedback voltage FB coupled to the ripple injection module, and the feedback network steps down the output voltage VOUT to the feedback voltage FB to feed back the feedback voltage FB to the ripple injection module.

2. A controller according to claim 1, wherein: in the process that the comparator judges the high and low of a signal Vcontrol and a reference voltage signal VREF, the controller always keeps running at an ultralow quiescent current; and the number of the first and second electrodes,

the comparator output signal Vtrigger will go high when signal Vcontrol is lower than the reference voltage signal VREF and go low when signal Vcontrol is higher than the reference voltage signal VREF.

3. A controller according to claim 1, wherein: the pulse OnTime of the adaptive timer can be adjusted based on different input voltage Vin and output voltage VOUT; and the number of the first and second electrodes,

the relationship between the pulse OnTime of the self-adaptive timer and the input voltage Vin and the output voltage VOUT is as follows:

the adaptive timer is turned on only when the comparator output signal Vtrigger goes high and the pulse OnTime goes low for maintaining ultra-low static power consumption.

4. A controller according to claim 1, wherein: the self-adaptive timer can control the direct-connection control driver to regulate the inductive current of the power device MOS tube M1 and the power device MOS tube M2 through the high level and the low level of the pulse OnTime; wherein the content of the first and second substances,

when OnTime is high, the through control driver controls a power device MOS tube M1 and a power device MOS tube M2 to increase the inductive current;

when OnTime is low, and the shoot-through control driver will control power devices MOS transistor M1 and MOS transistor M2 to discharge inductor current.

5. A controller according to claim 1, wherein: the through control driver generates a LowPower signal through an input signal ISEN; wherein the content of the first and second substances,

when the power devices M1 and M2 output low currents, ISEN indicates low level current and LowPower signal goes high.

6. A controller according to claim 1, wherein: the ripple injection module generates a ripple voltage near the feedback voltage FB, and the ripple voltage is added to a node voltage of the feedback voltage FB; and the number of the first and second electrodes,

when Rcontrol is high, the ripple voltage rises slowly, and when Rcontrol is low, the ripple voltage drops slowly.

7. A boost converter, comprising: MOS transistor M1, MOS transistor M2, inductor L1, input capacitor CIN, output capacitor COUT, upper tube current meter, lower tube current meter, chip bias circuit, fault detector and the controller of any one of claims 1-6;

the controller output signal LGate and signal HGate are coupled to a gate terminal of M1 and a gate terminal of M2, respectively;

one end of the inductor L1 is coupled to the input capacitor CIN and loaded with the input voltage VIN, and the other end is coupled to the drains of the MOS transistor M1 and the MOS transistor M2;

the source electrode of the MOS transistor M2 is coupled with an output capacitor COUT and is loaded with an output voltage VOUT;

the upper tube current meter is coupled with the drain electrode of the MOS tube M2 and detects the current amount flowing through the M2 by outputting high and low levels of an ISEN signal;

the lower tube current meter is coupled with the drain electrode of the MOS tube M1 and is used for detecting the amount of current flowing through the M1;

the chip biasing circuit is provided with an enable signal EN and used for generating reference current and reference voltage for the circuit;

the LowPower signal generated by the direct control driver is loaded on the upper tube ammeter, the lower tube ammeter, the chip biasing circuit and the fault detector respectively, and the LowPower signal is used for selectively setting the upper tube ammeter, the lower tube ammeter, the chip biasing circuit and the fault detector into an ultra-low power mode according to the power of the converter, so that the quiescent current of the circuit is reduced, and the ultra-low quiescent current is realized.

8. A boost converter according to claim 7, wherein: the inductor current will flow to the MOS transistor M1 or the MOS transistor M2; wherein the content of the first and second substances,

the current flowing through the MOS transistor M1 flows to the ground terminal of the input capacitor CIN, and returns the energy to the input voltage VIN again through the input capacitor CIN;

the current flowing through the MOS transistor M2 will flow to the output capacitor COUT and transfer the power energy to the output voltage VOUT.

9. A boost converter according to claim 7, wherein: a comparison point SW is arranged at the coupling point of the drain electrode of the MOS tube M2, the drain electrode of the MOS tube M2 and the inductor L1; wherein the content of the first and second substances,

when the current flows from the output voltage VOUT to SW, the upper tube ammeter outputs an ISEN signal as a high level;

when current flows from SW to the output voltage VOUT, the upper tube current meter outputs an ISEN signal at a low level.

10. A boost converter according to claim 9, wherein: the inductance current simulator collects the SW and Rcontrol signals and generates simulation ripple voltage; wherein the content of the first and second substances,

when SW is low, ripple voltage rises; when SW is high, ripple voltage drops; when SW is high impedance, there is no ripple voltage and the speed at which the ripple voltage rises and falls can be automatically adjusted according to VIN and VOUT.

Technical Field

The invention relates to the technical field of power supplies, in particular to a controller convenient for realizing ultralow quiescent current of a boost converter.

Background

In a converter, there are many different methods for controlling a boost converter in order to obtain a precise and stable output voltage. The boost converter control design scheme commonly used at present includes: a current mode or voltage mode control loop adopting fixed switching frequency (PWM), a voltage mode control loop adopting variable switching frequency (PFM) and a control loop adopting the mixed design of the fixed switching frequency and the variable switching frequency are adopted, the fixed switching frequency is used when the load current is large (heavy load), and the variable switching frequency is automatically switched when the load current is small (light load);

for schemes that employ fixed switching frequencies, the control circuitry within the boost converter cannot meet sufficient quiescent current to ensure speed and bandwidth; for the scheme adopting the variable switching frequency, the output voltage ripple can be increased, the efficiency is reduced, and the frequency domain noise is increased; for the scheme adopting the switching frequency mixed design, more circuit modules can be introduced, and because different circuit designs are used in different modes, the ultralow quiescent current is difficult to realize in the seamless transition from the PWM mode to the PFM mode;

for example, in the patent US10340796B2, additional circuit modules such as ADC and current estimator added in the boost converter require additional circuits consuming static current; for the buck design in patent CN201110076368.2 and similar buck designs: the design of a low quiescent current synchronous rectification buck DC-DC converter controls the buck converter with a Constant On Time (COT) architecture that can achieve the low quiescent current effect in the buck converter, but the architecture cannot be directly applied to a boost converter to achieve the low quiescent current effect.

The prior art can not meet the requirements of people at the present stage, and the technology for realizing the ultra-low static current effect of the existing boost converter is urgently needed to be reformed based on the present situation.

Disclosure of Invention

The present invention is directed to a controller for facilitating the realization of ultra-low quiescent current of a boost converter, so as to solve the above-mentioned problems in the prior art.

In one aspect the present invention provides a controller comprising: the device comprises a comparator, a self-adaptive timer, a direct connection control driver, a ripple injection module, a feedback network and a reference voltage;

the positive input end of the comparator is coupled with a reference voltage, the reference voltage provides a reference voltage signal VREF insensitive to temperature, input voltage Vin, output voltage VOUT and load current, the reference voltage signal VREF is loaded on the positive input end of the comparator, and the comparator outputs a signal Vthreshold;

preferably, the negative input end of the comparator is coupled to the ripple injection module, and the ripple injection module includes a ripple generator and an inductive current simulator, and the ripple injection module outputs a signal Vcontrol.

Preferably, the output terminal of the comparator is coupled to an adaptive timer, which responds to the rising edge of Vtrigger, and after Vtrigger goes high, the timer will generate a pulse OnTime based on the voltages of the input voltage Vin and the output voltage VOUT.

The output end of the self-adaptive timer is coupled with the direct connection control driver, and the self-adaptive timer controls the direct connection control driver to regulate the inductive currents on the power device MOS tube M1 and the power device MOS tube M2 through the high and low levels of the pulse OnTime;

the through control driver generates a LowPower signal through an input signal ISEN and has three paths of output ends;

preferably, the output signal HGATE of the first output terminal of the dc-link control driver and serving as one output terminal of the controller is coupled to the gate of the MOS transistor M2, the output signal LGATE of the second output terminal of the dc-link control driver and serving as the other output terminal of the controller is coupled to the gate of the MOS transistor M1, the output signal Rcontrol of the third output terminal of the dc-link control driver is coupled to the ripple injection module, and the output signal Rcontrol is used for generating a ripple voltage;

the feedback network outputs feedback voltage FB which is coupled with the ripple injection module;

preferably, the feedback network steps down the output voltage VOUT to a feedback voltage FB according to a required ratio and feeds back the feedback voltage FB to the ripple injection module, and the feedback loop makes the feedback voltage FB very close to the reference voltage signal VREF;

in another aspect, the present invention provides another technical solution, a boost converter, including: the circuit comprises a controller, a MOS tube M1, a MOS tube M2, an inductor L1, an input capacitor CIN and an output capacitor COUT;

the controller output signal LGate and the signal HGate are respectively coupled to the gate terminal of M1 and the gate terminal of M2, one end of the inductor L1 is coupled to the input capacitor CIN and loaded with the input voltage VIN, the other end is coupled to the drains of the MOS transistor M1 and the MOS transistor M2, the source of the MOS transistor M2 is coupled to the output capacitor COUT and loaded with the output voltage VOUT, and the inductor current flows through the converter in the following process: since the inductor current is continuous, its current will flow to the MOS transistor M1 or the MOS transistor M2, the current flowing through the MOS transistor M1 will flow to the ground terminal of the input capacitor CIN, and the energy will return to the input voltage VIN again through the input capacitor CIN, and the current flowing through the MOS transistor M2 will flow to the output capacitor COUT and transfer the power energy to the output voltage VOUT.

The boost converter further includes: the device comprises an upper tube ammeter, a lower tube ammeter, a chip biasing circuit and a fault detector;

the upper tube current meter is coupled with the drain electrode of the MOS tube M2 and outputs the high-low level of the ISEN signal to detect the current amount flowing through the M2, a comparison point SW is arranged at the coupling point of the drain electrode of the MOS tube M2, the drain electrode of the MOS tube M2 and the inductor L1, and when the current flows to the SW from the output voltage VOUT, the upper tube current meter outputs the ISEN signal as the high level; when the current flows from the SW to the output voltage VOUT, the upper tube current meter outputs an ISEN signal as a low level;

the lower tube current meter is coupled with the drain electrode of the MOS tube M1 and is used for detecting the amount of current flowing through the M1;

the chip biasing circuit is provided with an enable signal EN, enables a circuit in the converter, generates a reference current and a reference voltage for the circuit, and regulates the output voltage VOUT to be the required voltage when the input voltage VIN and the enable signal EN are both effective.

The fault detector is used to detect any abnormalities and fault conditions occurring in the circuitry of the converter, including under-voltage detection, over-temperature detection, over-current protection, and the like.

Has the advantages that:

the invention is convenient to realize the ultra-low static current of the boost converter, has good efficiency under the conditions of heavy load and light load, and has good output ripple, good transient response and ultra-low static current;

when the power device MOS tube M1 and the MOS tube M2 output heavy loads, the LowPower signal is at low level, the controller is in a PWM mode, the Rcontrol signal is continuously switched, the ripple injection module continuously generates slow ripple voltage near the feedback voltage FB, and after the ripple injection module is started, the comparator, the adaptive timer, the power device MOS tube M1 and the MOS tube M2 are continuously switched;

when the power device MOS tube M1 and the MOS tube M2 output light loads, and LowPower signals are high level continuously for several times, the controller enters a PFM mode, a Rcontrol signal is not switched, the output of the comparator is only changed to be high when a feedback voltage FB is lower than a reference voltage signal VREF, and an OnTime pulse is generated after a signal Vtrigger is changed to be high, and then the power device MOS tube M1 and the MOS tube M2 are triggered to be switched; when the ISEN signal indicates that a small current is output and the feedback voltage FB is higher than the reference voltage signal VREF, the pass-through control driver will put the power devices MOS transistor M1 and MOS transistor M2 in a high-impedance state, and the boost controller will be in an idle state, consuming a very low quiescent current.

Drawings

FIG. 1 is a schematic circuit diagram of a controller according to the present invention;

FIG. 2 is a schematic diagram of a boost converter according to the present invention;

FIG. 3 is a diagram of the boost converter of the present invention entering PFM mode;

FIG. 4 is a diagram illustrating the boost converter exiting PFM mode according to the present invention;

fig. 5 is a circuit diagram of a buck converter in the current market.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the invention without making any creative effort, shall fall within the protection scope of the invention.

Referring to fig. 1, in one aspect, the present invention provides a controller in an alternative embodiment, applied in a boost converter, for achieving the effect of low quiescent current of the boost converter, the controller including: the device comprises a comparator, a self-adaptive timer, a direct connection control driver, a ripple injection module, a feedback network and a reference voltage;

the positive input end of the comparator is coupled with a reference voltage, the reference voltage provides a reference voltage signal VREF insensitive to temperature, input voltage Vin, output voltage VOUT and load current, the reference voltage signal VREF is loaded at the positive input end of the comparator, the comparator outputs a signal Vtrigger, the negative input end of the comparator is coupled with a ripple injection module, the ripple injection module comprises a ripple generator and an inductive current simulator, the ripple injection module outputs a signal Vcontrol, when the signal Vcontrol is lower than the reference voltage signal VREF, the comparator output signal Vtrigger goes high, when the signal Vcontrol is higher than the reference voltage signal VREF, the comparator output signal Vtrigger goes low, and in the process that the comparator judges the level of the signal Vcontrol and the reference voltage signal VREF, the controller always keeps ultra-low static current operation.

The output end of the comparator is coupled with the self-adaptive timer, the self-adaptive timer reacts to the rising edge of the Vtrigger, after the Vtrigger goes high, the timer generates a pulse OnTime based on the voltage of the input voltage Vin and the output voltage VOUT, in order to realize fixed frequency, the pulse OnTime of the self-adaptive timer needs to be adjusted based on different input voltages Vin and output voltages VOUT, and the relationship between the pulse OnTime of the self-adaptive timer and the input voltage Vin and the output voltage VOUT is as follows:the adaptive timer is turned on only when the comparator output signal Vtrigger goes high and the pulse OnTime goes low.

The output end of the self-adaptive timer is coupled with a direct connection control driver, the self-adaptive timer controls the direct connection control driver to adjust the inductive current of a power device MOS tube M1 and a MOS tube M2 through the high and low levels of pulse OnTime, when OnTime is high level, the direct connection control driver controls the power device MOS tube M1 and the MOS tube M2 to increase the inductive current, and when OnTime is low level, the direct connection control driver controls the power device MOS tube M1 and the MOS tube M2 to release the inductive current;

the low power signal is generated by the through control driver through an input signal ISEN, the through control driver has three paths of output ends, wherein the first path of output end is coupled with the grid of the MOS tube M2 as an output end output signal HGATE of the controller, the second path of output end is coupled with the grid of the MOS tube M1 as another output end output signal LGATE of the controller, the third path of output end output signal Rcontrol is coupled with the ripple injection module, the output signal Rcontrol is used for generating ripple voltage, because the LowPower signal is generated by the ISEN signal, when the power device MOS tube M1 and the MOS tube M2 output low current, the ISEN represents low level current, the LowPower signal goes high, the boost converter will operate in a PFM mode, and the through control driver consumes 5nA or even less ultra-low static current.

The feedback network outputs a feedback voltage FB which is coupled with the ripple injection module, the feedback network reduces the voltage of the output voltage VOUT to be the feedback voltage FB according to a required proportion and feeds the feedback voltage FB back to the ripple injection module, a feedback loop enables the feedback voltage signal FB to be very close to a reference voltage signal VREF, the ripple injection module generates ripple voltage near the feedback voltage FB, when Rcontrol is at a high level, the ripple voltage rises slowly, when Rcontrol is at a low level, the ripple voltage drops slowly, the ripple voltage is added to a node voltage of the feedback voltage FB, and the ripple injection module consumes 5nA or even less of ultralow quiescent current.

Further, the controller controls the boost converter to seamlessly switch between the heavy load condition and the light load condition in the adaptive constant on-time as follows:

when the power device MOS transistor M1 and the MOS transistor M2 output heavy loads, the LowPower signal is at low level, the controller is in a PWM mode, the Rcontrol signal is continuously switched, the ripple injection module continuously generates slow ripple voltage near the feedback voltage FB, and after the ripple injection module is started, the comparator, the adaptive timer, the power device MOS transistor M1 and the MOS transistor M2 are continuously switched.

When the power device MOS tube M1 and the MOS tube M2 output light loads, and the LowPower signal is high level for several times continuously, the controller enters a PFM mode, the Rcontrol signal is not switched, the ripple injection module stops generating ripples, at this time, the voltage at Vcontrol is the same as the voltage of the feedback voltage FB, the output of the comparator only becomes high when the feedback voltage FB is lower than the reference voltage signal VREF, and after the signal Vtrigger becomes high, OnTime pulses are generated, and then the power device MOS tube M1 and the MOS tube M2 are triggered to switch; when the ISEN signal indicates that a small current is output and the feedback voltage FB is higher than the reference voltage signal VREF, the pass-through control driver will put the power devices MOS transistor M1 and MOS transistor M2 in a high-impedance state, and the boost controller will be in an idle state, consuming a very low quiescent current.

Referring to fig. 2, in another aspect, the present invention provides another alternative embodiment, a boost converter, which uses an adaptive constant on-time architecture to realize the switching between the PWM mode and the PFM mode, so as to realize the effect of ultra-low quiescent current;

the boost converter comprises a controller, a MOS tube M1, a MOS tube M2, an inductor L1, an input capacitor CIN and an output capacitor COUT;

the controller output signal LGate and the signal HGate are respectively coupled to the gate terminal of M1 and the gate terminal of M2, one end of the inductor L1 is coupled to the input capacitor CIN and loaded with the input voltage VIN, the other end is coupled to the drains of the MOS transistor M1 and the MOS transistor M2, the source of the MOS transistor M2 is coupled to the output capacitor COUT and loaded with the output voltage VOUT, and the inductor current flows through the converter in the following process: since the inductor current is continuous, its current will flow to the MOS transistor M1 or the MOS transistor M2, the current flowing through the MOS transistor M1 will flow to the ground terminal of the input capacitor CIN, and the energy will return to the input voltage VIN again through the input capacitor CIN, and the current flowing through the MOS transistor M2 will flow to the output capacitor COUT and transfer the power energy to the output voltage VOUT.

The boost converter further includes: the device comprises an upper tube ammeter, a lower tube ammeter, a chip biasing circuit and a fault detector;

the upper tube current meter is coupled with the drain electrode of the MOS tube M2 and outputs the high-low level of the ISEN signal to detect the current amount flowing through the M2, a comparison point SW is arranged at the coupling point of the drain electrode of the MOS tube M2, the drain electrode of the MOS tube M2 and the inductor L1, and when the current flows to the SW from the output voltage VOUT, the upper tube current meter outputs the ISEN signal as the high level; when the current flows from the SW to the output voltage VOUT, the upper tube current meter outputs an ISEN signal as a low level;

the lower tube current meter is coupled with the drain electrode of the MOS tube M1 and is used for detecting the amount of current flowing through the M1;

the chip biasing circuit is provided with an enable signal EN, enables a circuit in the converter, generates a reference current and a reference voltage for the circuit, and regulates the output voltage VOUT to be the required voltage when the input voltage VIN and the enable signal EN are both effective. For example: VIN is 3.3V, VREF is 1V, and the feedback network ratio of FB to VOUT is 1:5, then VOUT is 5V and FB will be adjusted to 1V.

The fault detector is used to detect any abnormalities and fault conditions occurring in the circuitry of the converter, including under-voltage detection, over-temperature detection, over-current protection, and the like.

Referring to fig. 5, fig. 5 is a schematic diagram of switching between PWM mode and PFM mode in a Buck converter using an adaptive constant on-time architecture, but this solution can only be used for Buck converters (Buck), but not for Boost converters (Boost), because when SW is high in a Buck converter (Buck), the inductor current rises; when SW is low, the inductive current is reduced; since SW is synchronized with the inductor current, SW can directly generate ripple voltage and can be directly injected to FB.

In a Boost converter (Boost), when SW is high, the inductor current drops; when SW is low, the inductive current rises; because SW and inductive current are asynchronous, SW can not produce ripple voltage directly, therefore ripple injection module of the invention not only include ripple generator but also have current simulator of inductance to design ripple to inject, the current simulator of inductance gathers SW and Rcontrol signal and produces the artificial ripple voltage, when SW is low, ripple voltage rises; when SW is high, ripple voltage drops; when SW is high impedance, ripple voltage is not generated, and the rising speed and the falling speed of the ripple voltage can be automatically adjusted according to VIN and VOUT;

further, the specific operating principle of the boost converter is as follows: when the boost converter is in stable operation, the output voltage VOUT supplies power to the converter load, current (ILOAD) continuously flows through the load, the charge stored in the output capacitor COUT continuously decreases, the VOUT voltage also decreases, the feedback signals FB and VOUT are proportional, and it decreases as VOUT and Vcontrol decrease, when FB is lower than VREF voltage, the output signal Vtrigger of the comparator becomes high, and after Vtrigger becomes high, the adaptive timer generates a turn-on pulse OnTime, the MOS transistor M1 is turned on, the inductor L1 starts to store energy, and after the turn-on pulse OnTime ends, the MOS transistor M2 is turned on, the energy of the inductor L1 is transferred to the output capacitor COUT, and at the same time, the VOUT voltage also starts to rise.

In order to realize the effect of ultra-low quiescent current, LowPower signals generated by the through control driver are loaded on an upper tube ammeter, a lower tube ammeter, a chip biasing circuit and a fault detector respectively, the LowPower signals are used for selectively setting the upper tube ammeter, the lower tube ammeter, the chip biasing circuit and the fault detector into an ultra-low power mode according to the power requirement of the converter, and the quiescent current of the circuit is reduced so as to realize the effect of ultra-low quiescent current.

Referring to FIG. 3, under heavy load conditions, i.e., MOS transistor M2 current flows from SW to VOUT, and the output of the top tube current meter ISEN will always be low; under light load conditions, when ILOAD current is low, i.e., MOS transistor M2 current flows from VOUT to SW, when this negative current is present, the ISEN signal makes the controller aware that it is in light load; after a few ISEN signal pulses, the controller knows that the converter is in a low power state and begins operating in PFM mode;

referring to fig. 4, when the current of the MOS transistor M2 does not flow from VOUT to SW, if the signal ISEN does not go high, the controller will exit the PFM mode and enter the PWM mode, so that the switching between the PFM mode and the PWM mode is realized while the effect of ultra-low quiescent current is realized.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.