CN114157135A - PWM-PFM seamless switching controller with hysteresis function and control method thereof - Google Patents
PWM-PFM seamless switching controller with hysteresis function and control method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
Abstract
The invention provides a PWM-PFM seamless switching controller with a hysteresis function and a control method thereof, relating to the technical field of integrated circuits. The system comprises a switching controller, a current detection device and a control device, wherein the switching controller comprises a current detection device and is used for detecting load current and generating a starting request and a left-right switching request; the left threshold switching controller and the right threshold switching controller are used for detecting a switching request and a circuit starting response and generating an actual switching signal; the switching controller is used for realizing the switching of PWM/PFM, obtaining a control signal and generating a PWM and PFM closing request; and the PWM and PFM controller is used for generating PWM and PFM control signals and generating a start response signal in time. The invention provides a method for generating an actual switching signal by using three load characteristic values of a switching point, a left threshold and a right threshold, thereby realizing the delayed switching of PWM and PFM, avoiding the repeated switching of PWM and PFM, simultaneously, obtaining a starting target control mode before switching, avoiding the generation of larger voltage drop due to slow starting of a circuit, and realizing the seamless switching of PWM/PFM.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a PWM-PFM seamless switching controller with a hysteresis function and a control method thereof.
Background
In a DC-DC switching power supply, Pulse Width Modulation (PWM) and Pulse Frequency Modulation (PFM) are two common modulation modes, the PWM fixes the switching frequency, controls the on-time of a power tube in a DC-DC system by adjusting the duty cycle, and further adjusts the output voltage, the PFM fixes the switching time, and controls the switching frequency of the power tube by adjusting the off-time, thereby realizing the adjustment of the output voltage.
The PWM and PFM modulation modes have respective advantages and disadvantages, when the load is light, the PFM has higher conversion efficiency due to variable switching frequency, but other system performances such as output ripple and response speed are all weaker than those of the PWM in the full load range, the PWM has excellent performance when the load is heavy, but when the load is light, due to the higher switching frequency, the switching loss and the conduction loss occupy a larger proportion, the conversion efficiency is extremely low when the load is light, and the application of the PWM controlled DC-DC switching power supply in the light load range is limited.
In order to solve the problem that the conversion efficiency of a PWM control mode is extremely low under light load, a dual-mode control DC-DC system combining PWM and PFM is adopted to operate, under the mode, the system is controlled by PFM under light load, and the system is controlled by PWM under heavy load, so that the advantages of the two control modes are fully exerted, and the high conversion efficiency of the system in a full load range is realized. In order to realize the combination of PWM and PFM, a PWM/PFM switching controller is indispensable, but the existing PWM/PFM switching controller has a simple structure, and adopts a single switching point to realize the switching between PWM and PFM, the output voltage has large fluctuation during the switching, and when the system works near the switching point, the PWM and PFM have the possibility of repeated switching, which brings a great test to the stability of the system.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a PWM-PFM seamless switching controller with a hysteresis function and a control method thereof. The corresponding starting signal, the left switching signal and the right switching signal can be output according to the three load characteristic values of the left threshold, the switching median and the right threshold, the hysteresis switching of the PWM and the PFM is realized, and the output voltage can not generate large voltage fluctuation in the switching process.
In one aspect, a PWM-PFM seamless switching controller with hysteresis function includes: the device comprises a current detection device, a starting circuit, a left switching controller, a right switching controller, a PWM controller, a PFM controller and a switching controller.
The output ports of the current detection device comprise a first output port to a third output port, the input ports of the switching controller comprise a first input port to a fourth input port, and the input ports of the left switching controller and the right switching controller comprise a first input port and a second input port; the first output port of the current detection device is connected with the first input port of the left switching controller, the second output port of the current detection device is connected with the input port of the starting circuit, and the third output port of the current detection device is connected with the first input port of the right switching controller;
the output ports of the starting circuit comprise a first output port and a second output port; the first output port of the starting circuit is connected with the first input port of the PWM controller, and the second output port of the starting circuit is connected with the first input port of the PFM controller;
the input ports of the PWM controller and the PFM controller comprise a first input port and a second input port, and the output ports thereof comprise a first output port and a second output port; the first output port of the PWM controller is connected with the second input port of the right switching controller, the second output port of the PWM controller is connected with the first input port of the switching controller, the first output port of the PFM controller is connected with the second input port of the left switching controller, and the second output port of the PFM controller is connected with the second input port of the switching controller;
the output port of the right switching controller is connected with the third input port of the switching controller, the output port of the right switching controller is connected with the second input port of the PFM controller, the output port of the left switching controller is connected with the fourth input port of the switching controller, the output port of the left switching controller is connected with the second input port of the PWM controller, and the output port of the switching controller is a control signal;
the current detection device is composed of a first comparator, a second comparator and a third comparator, wherein the in-phase end of the first comparator is connected with a left threshold voltage VREFL, the inverting end of the first comparator is connected with a voltage signal VH representing the magnitude of current, and the output end of the first comparator is a first output port of the current detection device. The in-phase end of the second comparator is connected with VH, the inverting end of the second comparator is connected with the switching threshold voltage VREFM, the output end of the second comparator is a second output port of the current detection device, the in-phase end of the third comparator is connected with VH, the inverting end of the third comparator is connected with the right threshold voltage VREFR, and the output port of the third comparator is a third output port of the current detection device.
The starting circuit comprises a first inverter, a first D flip-flop and a second D flip-flop, wherein an input port of the first inverter is a first input of the starting circuit, an output port of the first inverter is connected with a clock port Clk end of the second D flip-flop, a reset port R of the second D flip-flop is connected with a PFM turn-off signal of an output port of the left switching controller, a data end D of the second D flip-flop is connected with a power supply VDD, an output end Q of the second D flip-flop is a second output port of the starting circuit, the clock port Clk of the first D flip-flop is connected with an input port of the first inverter, namely, the first input of the start-up circuit, the data D end of the first D flip-flop is connected with the power supply VDD, the reset port R of the first D flip-flop is connected with the PWM off signal of the output port of the right switching controller, and the output end Q of the first D flip-flop is the first output port of the start-up circuit.
The left switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the left switching controller, a second input of the AND gate is a second input of the left switching controller, and an output of the AND gate is an output port of the left switching controller to generate a PFM (pulse frequency modulation) turn-off signal;
the right switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the right switching controller, a second input of the AND gate is a second input of the right switching controller, and an output of the AND gate is an output port of the right switching controller to generate a PWM turn-off signal.
The switching controller comprises an alternative data selector and an RS trigger, wherein the R end of the RS trigger is a third input port of the switching controller, the S end of the RS trigger is a fourth input port of the switching controller, the Q end of the RS trigger is connected with a control port of the alternative data selector, the 0 end of the alternative data selector is a first input port of the switching controller, the 1 end of the alternative data selector is a second input port of the switching controller, and the output of the alternative data selector is the output of the switching controller.
On the other hand, the PWM-PFM seamless switching control method with the hysteresis function is realized based on the PWM-PFM seamless switching controller with the hysteresis function, and comprises the following steps:
when VREFR > VH > VREFM, the second output of the current detection device is high, at which time the PWM controller is started;
when VH is greater than VREFR, the third output of the current detection device is high, at the moment, the PFM mode is switched to the PWM mode, namely the Q end of the output of an RS trigger in the switching controller jumps from 1 to 0, and the alternative data selector selects the 0 end, namely the signal of the first input port of the switching controller, namely the PWM control signal is output;
when VREFL < VH < VREFM, the second output of the current detection means is low, at which time the PFM controller is started;
when VH < VREFL, the first output of the current detection device is high, and then the PWM mode is switched to the PFM mode, namely the output Q end of an RS trigger in the switching controller jumps from 0 to 1, and the alternative data selector selects the output 1 end, namely the signal of the second input port of the switching controller, namely the PFM control signal is output;
step 2, adjusting the working state of the system according to the change of the load current to realize a PWM-PFM seamless switching control method;
the adjustment is specifically as follows:
when the load is light load, namely VH < VREFL, the PFM controller works, the PWM controller is closed, and the alternative data selector selects the 1 input channel;
when the load is heavy load, namely VH is greater than VREFR, the PFM controller is closed, the PWM controller works, and the data selector selects a 0 input channel;
when the load is between a left switching threshold value VREFL and a right switching threshold value VREFR, the system keeps an initial working state;
when the load is changed from light load to heavy load, the method comprises the following steps:
step S1, when the load is gradually increased to make VH larger than VREFM, the second output of the current detection device is logic 1, then the load current is already larger than the switching median value, and the PWM controller is started;
step S2, starting the PWM controller, generating a start response signal after the start is finished, transmitting the start response signal to the right switching controller, and outputting a PWM control signal to a 0 input channel of the switching controller;
step S3, when the load gradually increases and VH is greater than VREFR, the output of the right switching controller is logic 1, and the signal is simultaneously a PFM shutdown signal and transmitted to the PFM controller to turn off the PFM controller;
step S4, the RS flip-flop of the switching controller receives the reset signal, and the generated output signal is logic 0, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 0, and selects the 0 input channel, and outputs the PWM control signal, thereby completing the conversion from the PFM mode to the PWM mode;
when the load is changed from heavy load to light load, the method comprises the following steps:
step D1, when the load is gradually decreased to make VH smaller than VREFM, the second output of the current detection device is logic 0, then the load current is already smaller than the switching median value, and the PFM controller is started;
step D2, the PFM controller starts to start, generates a start response signal after the start is finished and transmits the start response signal to the left switching controller, and outputs a PFM control signal to the 1 input channel of the switching controller;
step D3, when the load is gradually decreased to make VH smaller than VREFL, the output of the left switching controller is logic 1, the signal is PWM turn-off signal at the same time, and the signal is transmitted to the PWM controller to turn off the PWM controller;
step D4, the RS flip-flop of the switching controller receives the set signal, and the generated output signal is logic 1, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 1, and selects the 1 input channel, and outputs the PFM control signal, thereby completing the conversion from the PWM mode to the PFM mode.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:
the invention provides a PWM-PFM seamless switching controller with a hysteresis function and a control method thereof.A left threshold, a switching median, a right threshold, a left switching controller and a right switching controller are additionally arranged in the existing PWM/PFM switching controller. In the prior art, switching is completed immediately after receiving a switching signal, at this time, the start of the PWM/PFM controller is not completed, and a control signal output by the PWM/PFM controller is not an expected control signal, which results in large fluctuation of the output voltage of the system. According to the invention, the switching of the modes is delayed by setting the left and right switching thresholds and the PWM/PFM starting response signal, and enough time is reserved for the starting of the PWM/PFM controller, so that the accuracy of a system control signal is ensured, and the seamless and delayed switching of the two modes of PWM and PFM is realized.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a switching controller according to the present invention;
FIG. 2 is an overall circuit diagram of the switching controller according to the present invention;
FIG. 3 is a flow chart of the operation of the switching controller of the present invention;
fig. 4 is a specific circuit diagram of a switching controller according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In one aspect, a PWM-PFM seamless switching controller with hysteresis function, as shown in fig. 1 and 2, includes: the device comprises a current detection device, a starting circuit, a left switching controller, a right switching controller, a PWM controller, a PFM controller and a switching controller.
The output ports of the current detection device comprise a first output port to a third output port, the input ports of the switching controller comprise a first input port to a fourth input port, and the input ports of the left switching controller and the right switching controller comprise a first input port and a second input port; the first output port of the current detection device is connected with the first input port of the left switching controller, the second output port of the current detection device is connected with the input port of the starting circuit, and the third output port of the current detection device is connected with the first input port of the right switching controller;
the output ports of the starting circuit comprise a first output port and a second output port; the first output port of the starting circuit is connected with the first input port of the PWM controller, and the second output port of the starting circuit is connected with the first input port of the PFM controller;
the input ports of the PWM controller and the PFM controller comprise a first input port and a second input port, and the output ports thereof comprise a first output port and a second output port; the first output port of the PWM controller is connected with the second input port of the right switching controller, the second output port of the PWM controller is connected with the first input port of the switching controller, the first output port of the PFM controller is connected with the second input port of the left switching controller, and the second output port of the PFM controller is connected with the second input port of the switching controller;
the output port of the right switching controller is connected with the third input port of the switching controller, the output port of the right switching controller is connected with the second input port of the PFM controller, the output port of the left switching controller is connected with the fourth input port of the switching controller, the output port of the left switching controller is connected with the second input port of the PWM controller, and the output port of the switching controller is a control signal;
the current detection device is composed of a first comparator, a second comparator and a third comparator, wherein the in-phase end of the first comparator is connected with a left threshold voltage VREFL, the inverting end of the first comparator is connected with a voltage signal VH representing the magnitude of current, and the output end of the first comparator is a first output port of the current detection device. The in-phase end of the second comparator is connected with VH, the inverting end of the second comparator is connected with the switching threshold voltage VREFM, the output end of the second comparator is a second output port of the current detection device, the in-phase end of the third comparator is connected with VH, the inverting end of the third comparator is connected with the right threshold voltage VREFR, and the output port of the third comparator is a third output port of the current detection device.
The starting circuit comprises a first inverter, a first D flip-flop and a second D flip-flop, wherein an input port of the first inverter is a first input of the starting circuit, an output port of the first inverter is connected with a clock port Clk end of the second D flip-flop, a reset port R of the second D flip-flop is connected with a PFM turn-off signal of an output port of the left switching controller, a data end D of the second D flip-flop is connected with a power supply VDD, an output end Q of the second D flip-flop is a second output port of the starting circuit, the clock port Clk of the first D flip-flop is connected with an input port of the first inverter, namely, the first input of the start-up circuit, the data D end of the first D flip-flop is connected with the power supply VDD, the reset port R of the first D flip-flop is connected with the PWM off signal of the output port of the right switching controller, and the output end Q of the first D flip-flop is the first output port of the start-up circuit.
The left switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the left switching controller, a second input of the AND gate is a second input of the left switching controller, and an output of the AND gate is an output port of the left switching controller to generate a PFM (pulse frequency modulation) turn-off signal;
the right switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the right switching controller, a second input of the AND gate is a second input of the right switching controller, and an output of the AND gate is an output port of the right switching controller to generate a PWM turn-off signal.
The switching controller comprises an alternative data selector and an RS trigger, wherein the R end of the RS trigger is a third input port of the switching controller, the S end of the RS trigger is a fourth input port of the switching controller, the Q end of the RS trigger is connected with a control port of the alternative data selector, the 0 end of the alternative data selector is a first input port of the switching controller, the 1 end of the alternative data selector is a second input port of the switching controller, and the output of the alternative data selector is the output of the switching controller.
On the other hand, a PWM-PFM seamless switching control method with hysteresis function is implemented based on the PWM-PFM seamless switching controller with hysteresis function, as shown in fig. 3, and includes the following steps:
when VREFR > VH > VREFM, the second output of the current detection device is high, at which time the PWM controller is started;
when VH is greater than VREFR, the third output of the current detection device is high, at the moment, the PFM mode is switched to the PWM mode, namely the Q end of the output of an RS trigger in the switching controller jumps from 1 to 0, and the alternative data selector selects the 0 end, namely the signal of the first input port of the switching controller, namely the PWM control signal is output;
when VREFL < VH < VREFM, the second output of the current detection means is low, at which time the PFM controller is started;
when VH < VREFL, the first output of the current detection device is high, and then the PWM mode is switched to the PFM mode, namely the output Q end of an RS trigger in the switching controller jumps from 0 to 1, and the alternative data selector selects the output 1 end, namely the signal of the second input port of the switching controller, namely the PFM control signal is output;
step 2, adjusting the working state of the system according to the change of the load current to realize a PWM-PFM seamless switching control method;
the adjustment is specifically as follows:
when the load is light load, namely VH < VREFL, the PFM controller works, the PWM controller is closed, and the alternative data selector selects the 1 input channel;
when the load is heavy load, namely VH is greater than VREFR, the PFM controller is closed, the PWM controller works, and the data selector selects a 0 input channel;
when the load is between a left switching threshold value VREFL and a right switching threshold value VREFR, the system keeps an initial working state;
when the load is changed from light load to heavy load, the method comprises the following steps:
step S1, when the load is gradually increased to make VH larger than VREFM, the second output of the current detection device is logic 1, then the load current is already larger than the switching median value, and the PWM controller is started;
step S2, starting the PWM controller, generating a start response signal after the start is finished, transmitting the start response signal to the right switching controller, and outputting a PWM control signal to a 0 input channel of the switching controller;
step S3, when the load gradually increases and VH is greater than VREFR, the output of the right switching controller is logic 1, and the signal is simultaneously a PFM shutdown signal and transmitted to the PFM controller to turn off the PFM controller;
step S4, the RS flip-flop of the switching controller receives the reset signal, and the generated output signal is logic 0, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 0, and selects the 0 input channel, and outputs the PWM control signal, thereby completing the conversion from the PFM mode to the PWM mode;
when the load is changed from heavy load to light load, the method comprises the following steps:
step D1, when the load is gradually decreased to make VH smaller than VREFM, the second output of the current detection device is logic 0, then the load current is already smaller than the switching median value, and the PFM controller is started;
step D2, the PFM controller starts to start, generates a start response signal after the start is finished and transmits the start response signal to the left switching controller, and outputs a PFM control signal to the 1 input channel of the switching controller;
step D3, when the load is gradually decreased to make VH smaller than VREFL, the output of the left switching controller is logic 1, the signal is PWM turn-off signal at the same time, and the signal is transmitted to the PWM controller to turn off the PWM controller;
step D4, the RS flip-flop of the switching controller receives the set signal, and the generated output signal is logic 1, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 1, and selects the 1 input channel, and outputs the PFM control signal, thereby completing the conversion from the PWM mode to the PFM mode.
FIG. 4 shows an embodiment of the present invention, which includes a current detection device, a start circuit, a left switch controller, a right switch controller, a PWM controller, a PFM controller, and a switch controller.
The current detection device is used for judging the left switching threshold value VREFL and the right switching threshold value VREFR of the reference voltage, switching the relation between the median value VREFM and the voltage value VH representing the magnitude of the load current, and changing the state of the output voltage according to the magnitude relation of the voltage, thereby determining the subsequent working state of the system. If VH is greater than VREFM, the second output of the current detection device is high, and the PWM controller is started; if VH > VREFR, the third output of the current detection device is high, and the modulation mode is switched from the PFM mode to the PWM mode; if VH < VREFM, the second output of the current detection device is low, and the PFM controller is started; if VH < VREFL, the first output of the current detection device is in high modulation mode and is switched from PWM mode to PFM mode.
The starting circuit is used for receiving the second output of the current detection and generating corresponding starting signals of the PWM controller and the PFM controller according to the state of the second output. And if the second output state of the current detection device is low, generating a PWM controller starting signal. Meanwhile, the starting circuit receives the PFM turn-off signal and the PWM turn-off signal and generates the turn-off signals of the PWM and PFM controllers in time.
The left switching controller and the right switching controller respectively receive the first output and the second output of the current detection device and generate actual switching signals of PWM and PFM according to the states of the first output and the second output. And timely generating a PWM turn-off signal and a PFM turn-off signal after the switching is finished.
The switching controller is used for receiving switching signals of PWM and PFM, and selecting a PWM control signal and a PFM signal according to the switching signals to complete the actual switching of two modulation modes.
The PWM controller is used for generating PWM control signals and comprises an error amplifier, a voltage comparator, a first phase inverter and a second phase inverter, wherein the in-phase end of the error amplifier is connected with a reference voltage VREF, the inverting end of the error amplifier is connected with a feedback signal, the output of the error amplifier is connected with the in-phase end of the voltage comparator, the output of the error amplifier is connected with the input end of the first phase inverter, the output of the first inverter is connected with the input end of the second inverter, and the output of the second phase inverter is the first output of the PWM controller, namely a PWM starting completion signal. The inverting terminal of the voltage comparator is connected with the triangular wave modulation signal VM, and the output of the voltage comparator is the second output of the PWM controller, namely the PWM signal.
The PFM controller is used for generating PFM signals and comprises a voltage comparator, a D trigger and an AND gate. The output end of the voltage comparator is the first output of the PFM controller, namely a PFM starting completion signal, the clock end of the D trigger is connected with a clock signal, the output Q end of the D trigger is connected with the first input of an AND gate, the second input of the AND gate is connected with the clock signal, and the output of the AND gate is the second output of the PFM controller, namely a PFM signal.
The working flow after the circuit is powered on is as follows:
after the circuit is powered on, the circuit firstly obtains a voltage signal VH representing the magnitude of current, the relation between VH and VREFM is judged, if VH is larger than VREFM, the second output of the current detection device is high, the starting circuit generates a PWM starting signal, the PWM controller starts to start, but at the moment, the system does not complete the switching between PWM and PFM. And after the PWM controller is started, outputting a PWM starting completion signal, if VH is greater than VREFR and the PWM starting completion signal is high, generating a PWM switching signal by the right switching controller, and after receiving the signal, selecting to output the PWM signal by the switching controller to complete the switching of PFM and PWM.
If VH < VREFM, the second output of the current detection device is low, the start circuit generates PFM start signal, PFM controller starts, but the system does not complete the switch between PWM and PFM. The PFM controller outputs a PFM start completion signal after starting, if VH < VREFL and the PFM start completion signal is high, the left switching controller generates a PFM switching signal, and the switching controller selectively outputs the PFM signal after receiving the signal to complete the switching of the two modes.
After hysteresis switching is generated by means of the three comparison thresholds, the modulation mode of the system in the switching interval (between VREFL and VREFR) is determined by the modulation mode of the system before entering the switching interval, if the load is changed from light load to heavy load, the modulation mode of the system in the switching interval is a PFM modulation mode, and if the load is changed from heavy load to light load, the modulation mode of the system in the switching interval is a PWM modulation mode. The introduction of the hysteresis interval solves the problem that two modes are frequently switched near a single switching point, so that a dual-mode control system is more stable.
The foregoing description is only exemplary of the preferred embodiments of the disclosure and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention in the embodiments of the present disclosure is not limited to the specific combination of the above-mentioned features, but also encompasses other embodiments in which any combination of the above-mentioned features or their equivalents is made without departing from the inventive concept as defined above. For example, the above features and (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure are mutually replaced to form the technical solution.
Claims (8)
1. A PWM-PFM seamless switching controller with hysteresis function, comprising: the device comprises a current detection device, a starting circuit, a left switching controller, a right switching controller, a PWM controller, a PFM controller and a switching controller;
the output ports of the current detection device comprise a first output port to a third output port, the input ports of the switching controller comprise a first input port to a fourth input port, and the input ports of the left switching controller and the right switching controller comprise a first input port and a second input port; the first output port of the current detection device is connected with the first input port of the left switching controller, the second output port of the current detection device is connected with the input port of the starting circuit, and the third output port of the current detection device is connected with the first input port of the right switching controller;
the output ports of the starting circuit comprise a first output port and a second output port; the first output port of the starting circuit is connected with the first input port of the PWM controller, and the second output port of the starting circuit is connected with the first input port of the PFM controller;
the input ports of the PWM controller and the PFM controller comprise a first input port and a second input port, and the output ports thereof comprise a first output port and a second output port; the first output port of the PWM controller is connected with the second input port of the right switching controller, the second output port of the PWM controller is connected with the first input port of the switching controller, the first output port of the PFM controller is connected with the second input port of the left switching controller, and the second output port of the PFM controller is connected with the second input port of the switching controller;
the output port of the right switching controller is connected with the third input port of the switching controller, the output port of the right switching controller is connected with the second input port of the PFM controller, the output port of the left switching controller is connected with the fourth input port of the switching controller, the output port of the left switching controller is connected with the second input port of the PWM controller, and the output port of the switching controller is the control signal.
2. The PWM-PFM seamless switching controller with hysteresis function of claim 1, wherein the current detection device comprises a first comparator, a second comparator, and a third comparator, wherein the non-inverting terminal of the first comparator is connected to the left threshold voltage VREFL, the inverting terminal of the first comparator is connected to the voltage signal VH representing the magnitude of the current, and the output terminal of the first comparator is the first output port of the current detection device; the in-phase end of the second comparator is connected with VH, the inverting end of the second comparator is connected with the switching threshold voltage VREFM, the output end of the second comparator is a second output port of the current detection device, the in-phase end of the third comparator is connected with VH, the inverting end of the third comparator is connected with the right threshold voltage VREFR, and the output port of the third comparator is a third output port of the current detection device.
3. The PWM-PFM seamless switching controller with hysteresis function as claimed in claim 1, wherein said start-up circuit comprises a first inverter, a first D flip-flop, and a second D flip-flop, wherein the input port of said first inverter is the first input of the start-up circuit, the output port of the first inverter is connected to the clock port Clk of the second D flip-flop, the reset port R of the second D flip-flop is connected to the PFM off signal of the output port of the left switching controller, the data port D of the second D flip-flop is connected to the power VDD, the output port Q of the second D flip-flop is the second output port of the start-up circuit, the clock port Clk of the first D flip-flop is connected to the input port of the first inverter, which is the first input of the start-up circuit, the data D of the first D flip-flop is connected to the power VDD, the reset port R of the first D flip-flop is connected to the PWM off signal of the output port of the right switching controller, the output end Q of the first D flip-flop is a first output port of the starting circuit.
4. The PWM-PFM seamless switching controller with hysteresis function as claimed in claim 1, wherein said left switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the left switching controller, a second input of the AND gate is a second input of the left switching controller, an output of the AND gate is an output port of the left switching controller, generating a PFM off signal;
the right switching controller is composed of an AND gate, a first input port of the AND gate is a first input of the right switching controller, a second input of the AND gate is a second input of the right switching controller, and an output of the AND gate is an output port of the right switching controller to generate a PWM turn-off signal.
5. The PWM-PFM seamless switching controller with hysteresis function as claimed in claim 1, wherein said switching controller comprises an alternative data selector and an RS flip-flop, wherein the R terminal of the RS flip-flop is the third input port of the switching controller, the S terminal of the RS flip-flop is the fourth input port of the switching controller, the Q terminal of the RS flip-flop is connected to the control port of the alternative data selector, the 0 terminal of the alternative data selector is the first input port of the switching controller, the 1 terminal of the alternative data selector is the second input port of the switching controller, and the output of the alternative data selector is the output of the switching controller.
6. A PWM-PFM seamless switching control method with hysteresis function based on the PWM-PFM seamless switching controller with hysteresis function of claim 1, comprising the steps of:
step 1, the current detection device starts working, a left switching threshold value VREFL is detected, a middle value VREFM is switched, and the relation between a right switching threshold value VREFR and a voltage signal VH representing the magnitude of load current is detected;
and 2, adjusting the working state of the system according to the change of the load current to realize the PWM-PFM seamless switching control method.
7. The PWM-PFM seamless switching control method with hysteresis function as claimed in claim 6, wherein said relation in step 1 specifically comprises:
when VREFR > VH > VREFM, the second output of the current detection device is high, at which time the PWM controller is started;
when VH is greater than VREFR, the third output of the current detection device is high, at the moment, the PFM mode is switched to the PWM mode, namely the Q end of the output of an RS trigger in the switching controller jumps from 1 to 0, and the alternative data selector selects the 0 end, namely the signal of the first input port of the switching controller, namely the PWM control signal is output;
when VREFL < VH < VREFM, the second output of the current detection means is low, at which time the PFM controller is started;
when VH < VREFL, the first output of the current detection device is high, and at this time, the PWM mode is switched to the PFM mode, i.e., the output Q of the RS flip-flop in the switching controller jumps from 0 to 1, and the alternative data selector selects the output 1, i.e., the signal at the second input port of the switching controller, i.e., outputs the PFM control signal.
8. The PWM-PFM seamless switching control method with hysteresis function as claimed in claim 6, wherein said adjusting in step 2 is specifically:
when the load is light load, namely VH < VREFL, the PFM controller works, the PWM controller is closed, and the alternative data selector selects the 1 input channel;
when the load is heavy load, namely VH is greater than VREFR, the PFM controller is closed, the PWM controller works, and the data selector selects a 0 input channel;
when the load is between a left switching threshold value VREFL and a right switching threshold value VREFR, the system keeps an initial working state;
when the load is changed from light load to heavy load, the method comprises the following steps:
step S1, when the load is gradually increased to make VH larger than VREFM, the second output of the current detection device is logic 1, then the load current is already larger than the switching median value, and the PWM controller is started;
step S2, starting the PWM controller, generating a start response signal after the start is finished, transmitting the start response signal to the right switching controller, and outputting a PWM control signal to a 0 input channel of the switching controller;
step S3, when the load gradually increases and VH is greater than VREFR, the output of the right switching controller is logic 1, and the signal is simultaneously a PFM shutdown signal and transmitted to the PFM controller to turn off the PFM controller;
step S4, the RS flip-flop of the switching controller receives the reset signal, and the generated output signal is logic 0, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 0, and selects the 0 input channel, and outputs the PWM control signal, thereby completing the conversion from the PFM mode to the PWM mode;
when the load is changed from heavy load to light load, the method comprises the following steps:
step D1, when the load is gradually decreased to make VH smaller than VREFM, the second output of the current detection device is logic 0, then the load current is already smaller than the switching median value, and the PFM controller is started;
step D2, the PFM controller starts to start, generates a start response signal after the start is finished and transmits the start response signal to the left switching controller, and outputs a PFM control signal to the 1 input channel of the switching controller;
step D3, when the load is gradually decreased to make VH smaller than VREFL, the output of the left switching controller is logic 1, the signal is PWM turn-off signal at the same time, and the signal is transmitted to the PWM controller to turn off the PWM controller;
step D4, the RS flip-flop of the switching controller receives the set signal, and the generated output signal is logic 1, that is, the mode selection signal received by the alternative data selector in the switching controller is logic 1, and selects the 1 input channel, and outputs the PFM control signal, thereby completing the conversion from the PWM mode to the PFM mode.
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