CN112953180A - Switching power supply on-time control method and device and switching power supply - Google Patents

Switching power supply on-time control method and device and switching power supply Download PDF

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Publication number
CN112953180A
CN112953180A CN202110453024.2A CN202110453024A CN112953180A CN 112953180 A CN112953180 A CN 112953180A CN 202110453024 A CN202110453024 A CN 202110453024A CN 112953180 A CN112953180 A CN 112953180A
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switching
load
time
light
power supply
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CN112953180B (en
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李征
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Jiangsu Applied Power Microelectronics Co ltd
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Jiangsu Applied Power Microelectronics Co ltd
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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
    • 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
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a switching power supply on-time control method, a switching power supply on-time control device and a switching power supply, wherein the method comprises the following steps: acquiring operation parameters of the switching power supply, wherein the operation parameters comprise switching tubular state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions; determining light-load opening time and heavy-load opening time according to the voltage parameters, wherein the light-load opening time is less than the heavy-load opening time; determining whether a light-load switching-on condition is met or not according to the current parameter, the tubular state parameter of the switch and the waiting duration; and if the light-load switching-on condition is met, controlling a switch unit of the switching power supply to continuously switch on and off at least once in light-load switching-on time. According to the invention, the on-time of the switch unit is adjusted by monitoring the operating parameters under the light-load working condition and the heavy-load working condition, so that the switch unit is continuously switched on and off for multiple times under the light-load working condition, thereby being beneficial to reducing the output ripple under the light-load working condition and improving the output voltage quality.

Description

Switching power supply on-time control method and device and switching power supply
Technical Field
The invention relates to the technical field of power electronics, in particular to a switching power supply and a method and a device for controlling the on-time of the switching power supply.
Background
A switching power supply is a high-frequency electric energy conversion device, and typically includes a DC/DC converter, which may adopt the following circuit topologies: the buck converter circuit, the boost converter circuit and the flyback circuit can all work in an inductive current-cutoff or follow current mode.
At present, a DC/DC converter is widely powered by a battery, and in order to prolong the service life of the battery, the DC/DC converter needs to have higher conversion efficiency. In order to improve the conversion efficiency, the current DC/DC converter needs to avoid negative current no matter which control mode is adopted.
In a DC/DC converter with a conversion efficiency requirement, a Constant-On-Time (COT) mode is generally adopted.
Taking a step-down DC/DC converter as an example, fig. 1 is a schematic diagram of a waveform of an inductor current of a conventional step-down DC/DC converter. In COT mode, as shown in FIG. 1, each switching period TPThe main power tube is switched on for a constant time Ton, and the auxiliary power tube is switched on for the rest of the time in each switching period. The on-time Ton of the main power tube is constant under the condition that the input voltage Vi and the output voltage Vo are constant, and does not change with the load condition, that is, under the light load and heavy load working conditions, the on-time of the existing DC/DC converter (switching power supply) is not changed.
As shown in fig. 1, during each switching period TPInternal, inductive current ILHigher than the load current IldWill cause the output voltage Vo to generate a certain output ripple, which is generated by the inductor current ILAnd a load current IldThe difference value of (a) determines that under the heavy-load working condition, the DC/DC converter works in a freewheeling mode, and the inductive current I is within the time period of t1-t2LHigher than the load current IldGenerating positive ripples; in the time period of t2-t3, the inductive current ILBelow the load current IldGenerating negative ripples; under the working condition of light load, the DC/DC converter works in a cut-off mode, and the inductive current ILHigher than the load current I during the whole switching periodldAnd positive ripples are generated, and the output voltage ripples under the light-load working condition can reach 4 times under the heavy-load working condition within the same turn-on time, so that the following problems exist: the excessive ripple may affect the normal operation of the downstream circuit, for example, generate harmonic waves in the load circuit, interfere with the logic relationship of the digital circuit, bring noise interference, and affect the imageAudio quality, which affects the performance of the electronic system.
Disclosure of Invention
The invention provides a switching power supply on-time control method, which can effectively shorten the on-time under the light load working condition, solves the problem of overlarge output voltage ripple caused by unchanged on-time of the conventional switching power supply, and is beneficial to improving the power output quality.
In a first aspect, an embodiment of the present invention provides a method for controlling an on-time of a switching power supply, including the following steps: acquiring operation parameters of the switching power supply, wherein the operation parameters comprise switching tubular state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions; determining light-load opening time and heavy-load opening time according to the voltage parameters, wherein the light-load opening time is less than the heavy-load opening time; determining whether a light-load opening condition is met or not according to the current parameter, the switching tube state parameter and the waiting duration; and if the light-load switching-on condition is met, controlling a switch unit of the switching power supply to be continuously switched on and off at least once within the light-load switching-on time.
Optionally, the method for controlling the on-time of the switching power supply further includes: determining whether a heavy-load opening condition is met or not according to the voltage parameter, the current parameter and the switching times; and if the heavy-load switching-on condition is met, controlling a switch unit of the switching power supply to be switched on for the heavy-load switching-on time.
Optionally, determining whether a heavy-duty turn-on condition is met according to the voltage parameter, the current parameter and the switching times includes the following steps: acquiring a first output voltage, an inductive current and the switching times of a main switching tube under a light-load working condition; and if the first output voltage is lower than a preset undervoltage threshold value and the inductive current is continuously larger than zero during the switching period of the main switching tube, judging that the heavy-load switching-on condition is met.
Optionally, determining the light-load turn-on time according to the voltage parameter includes: acquiring the minimum value of the output voltage under the light load working condition; and determining the light-load turn-on time according to the minimum turn-on time of the main switching tube corresponding to the minimum value of the output voltage.
Optionally, determining the heavy load on-time according to the voltage parameter includes: acquiring a second output voltage under a heavy-load working condition; and determining the heavy-load opening time according to the main switching tube opening time corresponding to the second output voltage.
Optionally, determining whether a light-load turn-on condition is met according to the current parameter, the switching tube state parameter, and the waiting duration, including the following steps: judging whether the current parameter reaches a preset turn-off condition or not; if the current parameter reaches a preset turn-off condition, controlling an auxiliary switching tube to be turned off; acquiring the waiting duration of the main switching tube and the auxiliary switching tube in the off state; and if the waiting duration reaches a preset waiting time threshold, judging that the light-load opening condition is met.
Optionally, the controlling the switching unit of the switching power supply to switch continuously for the light-load on time at least once includes the following steps: acquiring an output ripple of the switching power supply; determining the continuous switching times according to the output ripple waves; and outputting at least one conduction control signal to the switch unit according to the continuous switching times, wherein the duration of the conduction control signal is equal to the light-load switching-on time.
Optionally, the method for controlling the on-time of the switching power supply further includes: acquiring a preset switching-on control current, a preset switching-on cut-off voltage, a preset current change threshold value and a preset voltage change threshold value; adjusting the preset switching control current at least once according to the preset current change threshold value so as to enable the switching-on time to reach the light-load switching-on time gradually; or adjusting the preset switching-on cut-off voltage at least once according to the preset voltage change threshold value so as to enable the switching-on time to gradually reach the light-load switching-on time.
In a second aspect, an embodiment of the present invention further provides a device for controlling an on-time of a switching power supply, including: the switching unit is used for controlling the switching power supply to be switched on or switched off so that the switching power supply converts an input voltage into an output voltage; the detection unit is used for acquiring the operation parameters of the switching power supply, wherein the operation parameters comprise switching tubular state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions; the turn-on time generating unit is used for determining light-load turn-on time and heavy-load turn-on time according to the voltage parameter, wherein the light-load turn-on time is less than the heavy-load turn-on time; the load state judging unit is used for determining whether a light-load opening condition is met or not according to the current parameter, the switching tube state parameter and the waiting duration; and the switching-on control unit is used for controlling the switching unit of the switching power supply to be continuously switched on and off for at least one time in the light-load switching-on time when the light-load switching-on condition is met.
In a third aspect, an embodiment of the present invention further provides a switching power supply, including the above switching power supply on-time control device.
The switching power supply and the switching-on time control device provided by the embodiment of the invention are used for realizing the switching-on time control method, the method determines the light-load switching-on time and the heavy-load switching-on time according to the operating parameters of the switching power supply under the light-load working condition and the heavy-load working condition, judges whether the switching power supply meets the light-load switching-on condition or not according to the operating parameters, controls the switching unit of the switching power supply to be continuously switched on and off at least once according to the light-load switching-on time when the light-load switching-on condition is met, and solves the problem of overlarge output voltage ripple caused by unchanged switching time of the conventional switching power supply, thereby being beneficial to shortening the switching-on time under the light-load working condition, reducing the variation amplitude of inductive current, reducing the output ripple under.
Drawings
FIG. 1 is a schematic diagram of a current waveform of an inductor of a conventional buck DC/DC converter;
FIG. 2 is a circuit schematic of a buck DC/DC converter of the related art;
fig. 3 is a flowchart of a method for controlling the on-time of a switching power supply according to an embodiment of the present invention;
fig. 4 is a flowchart of another method for controlling the on-time of a switching power supply according to an embodiment of the present invention;
FIG. 5 is a waveform diagram of an output ripple in the prior art;
fig. 6 is a schematic waveform diagram of an output ripple according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a switching power supply on-time control device according to a second embodiment of the present invention;
fig. 8 is a schematic structural diagram of a switching power supply according to a third embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
In the related art, a switching power supply (e.g., a DC/DC converter) generally includes a main switching tube and an auxiliary switching tube, and the main switching tube and the auxiliary switching tube complete a switching operation under control of a conduction control signal to convert an input voltage into an output voltage. In different types of switching power supplies, the connection modes of the main switching tube and the auxiliary switching tube are different. Typically, in a step-down DC/DC converter, a power tube connected to an input power supply (Vi) is a main power tube, and a ground connected thereto is an auxiliary power tube. In the step-up DC/DC converter, the main power transistor is connected to ground, and the auxiliary power transistor is connected to output voltage. In the step-up/down DC/DC converter, the input power source is connected to the main power transistor, and the output power source is connected to the auxiliary power transistor, which is not limited to this.
Fig. 2 is a circuit schematic diagram of a step-down DC/DC converter in the related art.
As shown in fig. 2, the buck DC/DC converter includes a main switch Q1, an auxiliary switch Q2, an output inductor L, an output capacitor C, a load Rld, and a transconductance amplifier gm, wherein the main switch Q1 is connected to an input power Vi, and the auxiliary switch Q2 is grounded.
As shown in fig. 2, when the current decreases to around 0A, the auxiliary power Q2 is turned off, so that the inductor current stops at 0A, and the DC/DC converter enters a cut-off Mode. In the current-cutoff mode, each time the switching action is started, the load ld is usually required to slowly reduce the output voltage (Vo) until the feedback voltage Vs is lower than the reference voltage Vref, so that the output slope of the transconductance amplifier gm is a small ramp wave, and the output slope is intersected with the current sampling voltage which is kept unchanged. The time interval of each switch activation is longer and longer as the load Rld is reduced, i.e. the frequency of the switch action is lower and lower.
Example one
Fig. 3 is a flowchart of a method for controlling the on-time of a switching power supply according to an embodiment of the present invention, where the embodiment is applicable to an application scenario where the on-time of the switching power supply is shortened under a light load condition, the switching power supply may be a DC/DC converter, and the method may be executed by a controller configured with a switching power supply on driver and a hardware structure.
As shown in fig. 3, the method for controlling the on-time specifically includes the following steps:
step S1: and acquiring operation parameters of the switching power supply, wherein the operation parameters comprise switching tube state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions.
In this embodiment, a preset load threshold may be set according to historical data of a load of the switching power supply, a specific numerical value of the preset load threshold is not limited, and if a load value of an output end of the switching power supply is lower than the preset load threshold, the current switching power supply is in a light-load working condition; and if the load value of the output end of the switching power supply is greater than or equal to the preset load threshold value, the current switching power supply is in a heavy load working condition.
Optionally, the voltage parameter comprises an input voltage and an output voltage of the switching power supply; the current parameters comprise an inductive current and a load current; the switch tube state parameters comprise a main switch tube on state, a main switch tube off state, an auxiliary switch tube on state and an auxiliary switch tube off state; the switching times comprise the switching times of a main switching tube, wherein the switching-on and the switching-off of the main switching tube are recorded as one time.
Step S2: and determining light-load opening time and heavy-load opening time according to the voltage parameters, wherein the light-load opening time is less than the heavy-load opening time.
The light-load on-time can be the minimum time for maintaining the conduction of the main switching tube when the switching power supply is in a light-load working condition, and the heavy-load on-time can be the maximum time for maintaining the conduction of the main switching tube when the switching power supply is in a light-load working condition.
Step S3: and determining whether the light-load switching-on condition is met or not according to the current parameter, the tubular state parameter of the switch and the waiting duration.
The waiting duration refers to the duration of the main switching tube and the auxiliary switching tube in the off state during the on-load working period of the switching power supply; the current parameter may comprise an inductor current value IL。
Optionally, step S3 of the method includes the steps of:
judging whether the current parameter reaches a preset turn-off condition;
and if the current parameter reaches a preset turn-off condition, controlling the auxiliary switching tube to be turned off.
Acquiring the waiting duration of the main switching tube and the auxiliary switching tube in the off state;
and if the waiting duration reaches a preset waiting time threshold, judging that the light-load opening condition is met.
The preset waiting time threshold may be the longest standby time for maintaining the output voltage of the switching power supply to meet the load requirement, and the specific value of the preset waiting time threshold may be set according to the historical operating parameters of the switching power supply, which is not limited thereto.
It should be noted that, under the light load condition, the smaller the value of the load, the longer the waiting duration.
Step S4: and if the light-load switching-on condition is met, controlling a switch unit of the switching power supply to continuously switch on and off at least once in light-load switching-on time.
Specifically, under the light load working condition, the switching power supply works in a cutoff mode, after the main switching tube is closed, the auxiliary switching tube is controlled to be switched on, and the inductance current value I is continuously monitoredLAt the value of the inductance current ILBefore the voltage is reduced to 0A, the auxiliary switching tube is controlled to be turned offSo as to make the inductance current value ILThe switching power supply comprises a main switching tube, an auxiliary switching tube, a circuit, a switching unit and a switching unit, wherein the main switching tube and the auxiliary switching tube are both in a turn-off state, the circuit enters a waiting stage, the duration time of the waiting stage is timed, if the waiting duration time reaches a preset waiting time threshold, a light-load turn-on condition is judged to be met, the light-load turn-on time is set according to the current input voltage value and the current output voltage value, the auxiliary switching tube is controlled to be turned off after the switching unit receives a turn-on control signal, the main switching tube is controlled to be continuously switched for multiple times, the turn-on time of each switch of the main switching tube is equal to the light-load turn-on time, the problem that the output voltage ripple is overlarge due to the fact that the turn-on time of the existing switching power supply is unchanged is solved, the turn-on time.
Fig. 4 is a flowchart of another method for controlling the on-time of the switching power supply according to the first embodiment of the present invention.
Optionally, as shown in fig. 4, the method for controlling the on-time of the switching power supply further includes the following steps:
step S5: and determining whether the heavy-load opening condition is met or not according to the voltage parameter, the current parameter and the switching times.
Optionally, determining whether the heavy load turn-on condition is met according to the voltage parameter, the current parameter and the switching frequency includes the following steps:
acquiring a first output voltage Vo1, an inductive current and the switching times of a main switching tube under a light-load working condition;
if the first output voltage Vo1 is lower than the predetermined undervoltage threshold and the inductor current I is generated during the switching period of the main switch tubeLAnd if the current value is continuously larger than zero, judging that the heavy load opening condition is met.
In this embodiment, the preset value of the under-voltage threshold is slightly lower than the required value of the load output voltage, and if the preset value of the under-voltage threshold is too large, the output voltage drop value is large, and the under-voltage protection of the downstream circuit is triggered; if the preset undervoltage threshold is set too small, when the value of the load is higher than the preset load threshold, the problem that the output voltage cannot be recovered within the switching-on time of the main switching tube for switching on and light load is easily caused, and a person skilled in the art can set the preset undervoltage threshold according to the real-time load output voltage requirement value without limitation.
Step S6: and if the overload switching-on condition is met, controlling a switching unit of the switching power supply to be switched on for the overload switching-on time.
Specifically, since the inductor current cannot abruptly change, it takes a certain time for the inductor current to increase to a level required by the load when the load increases, during which the increased load current is supplied by the output capacitor, resulting in the output voltage being pulled low. When the light load runs, the on time of the main switching tube in each switching period is equal to the light load on time, the first output voltage Vo1 of the switching power supply is continuously detected, and if the first output voltage Vo1 is lower than a preset undervoltage threshold value, it is determined that the current light load on time cannot meet the load requirement.
When the output voltage is under-voltage, the switch tube continuously acts, the auxiliary switch tube is only opened for the allowed shortest time, so that the output voltage is recovered to the load output voltage requirement value as soon as possible, the inductive current is usually not reduced to 0A in the period, therefore, when the first output voltage is lower than the preset under-voltage threshold value and the inductive current is continuously greater than zero in the switching period of the main switch tube, the condition that the heavy load opening condition is met can be judged, and the conduction control signal is output to control the opening time of the switch unit to be continuously the heavy load opening time.
Optionally, when judging whether the load becomes a heavy load, it can also be judged whether the switching frequency of the main switching tube is greater than that of the main switching tube under all light load conditions.
Optionally, determining the light-load turn-on time according to the voltage parameter includes: acquiring the minimum value of the output voltage under the light load working condition; and determining the light-load turn-on time according to the minimum turn-on time of the main switching tube corresponding to the minimum value of the output voltage.
The minimum value of the output voltage may be an ideal output voltage of the switching power supply when the load Rld is minimum, for example, the minimum value of the load Rld may be equal to a sampling resistance value of the output voltage.
In this embodiment, the light-load on-time may be set to be greater than or equal to the minimum on-time of the main switching tube.
Specifically, there is a certain delay in the transmission of the on-state control signal, and the minimum on-time of the main switching tube satisfies the following conditions: when the load Rld is approximately zero, the conduction control signal output to the main switching tube continues the minimum on-time of the main switching tube, the main switching tube can be driven to be on, and the output voltage of the switching power supply reaches the minimum output voltage value after multiple times of switching.
It should be noted that, if the light-load on-time is less than the minimum on-time of the main switching tube, the switching tube may not perform the switching operation and the on-control signal is already finished, so that the switching tube cannot be turned on.
Optionally, the light-load on-time satisfies the following condition: the switch unit is continuously switched on for a plurality of times for light load switching-on time, and the output ripple of the switch power supply just enables the output ramp wave of the transconductance amplifier gm to be slightly lower than the current sampling voltage.
Specifically, in the current interruption mode, the switching power supply can be ensured to operate continuously only when a certain ripple exists in the output voltage. Each switching action can cause certain ripples to be superposed on the previous output voltage, so that the current output voltage is higher than the output voltage actually required by the load. The transconductance amplifier then reacts by pulling the output low according to the high voltage difference. The larger the voltage difference between the current output voltage and the output voltage actually required by the load, the lower the transconductance amplifier output ramp. When the ramp wave output by the transconductance amplifier is too low to be intersected with the current sampling voltage, the switching action of the switching tube is suspended. The optimum output ripple is thus just such that the output ramp of the transconductance amplifier gm is slightly lower than the current sample voltage.
Optionally, determining the heavy load on-time according to the voltage parameter includes the following steps: acquiring a second output voltage under a heavy-load working condition; and determining the heavy-load opening time according to the main switching tube opening time corresponding to the second output voltage.
The second output voltage is determined according to the specific value of the load when the value of the load is higher than the preset load threshold, and the larger the value of the load is, the higher the second output voltage is, the smaller the value of the load is, and the smaller the second output voltage is.
Specifically, before the controller of the switching power supply outputs the conduction control signal, the load on the output side of the switching power supply is detected, the second output voltage is determined according to the value of the load, the minimum duty ratio of the conduction control signal is calculated according to the second output voltage, and the main switching tube on time corresponding to the minimum duty ratio is determined as the heavy load on time.
Optionally, the controlling the switching unit of the switching power supply to switch continuously at least once with a light-load on-time includes the following steps: acquiring an output ripple of the switching power supply; determining the continuous switching times according to the output ripple waves; and outputting at least one conduction control signal to the switch unit according to the continuous switching times, wherein the duration of the conduction control signal is equal to the light-load switching-on time.
Wherein the number of the at least one turn-on control signal is equal to the number of consecutive switching times.
Specifically, under a light-load working condition, the circuit operates in a cutoff mode, the duration time of a conducting control signal of a main switching tube of a switching unit is kept to be the shortest each time, namely the duration time is kept to be the light-load switching-on time, so that the output ripple is the smallest, the output ripple cannot be guaranteed to be low enough to output the output ramp wave of the transconductance amplifier gm once after being reduced, the output ripple is gradually increased to the amplitude required by the output voltage through continuous switching for multiple times, the output ripple is prevented from being overlarge, and the quality of the output voltage is favorably improved.
FIG. 5 is a waveform diagram of an output ripple in the prior art; fig. 6 is a waveform diagram of an output ripple according to an embodiment of the present invention.
Referring to fig. 5 and fig. 6 in combination, the switching power supply in the prior art is the same as the circuit in the embodiment of the present invention, where Vi is 5.5V, Vo is 1V, L is 1uH, C is 22uF, and Ild is 1mA, and if the on-time is kept constant in the cut-off and freewheeling modes, the on-time of the main switching tube is 497nS and the inductor current I is equal to 497nS in the freewheeling mode at each switching time, and the on-time of the main switching tube is equal to 497nS in the freewheeling modeLThe amplitude of the variation is 2.1A, and the generated output ripple is equal to 87 mV. In the current-breaking mode, the conduction time of the switch tube is equal to 62nS in each switching process, and continuous switching is requiredThe circuit can be turned off for 3 times to enter a waiting state, i.e. the inductive currentLThe variation amplitude of the output ripple is reduced to about 600mA, and the output ripple is reduced to 16 mV.
In this embodiment, the light-load on time is less than the heavy-load on time, and the specific method for shortening the on time may be determined according to the method for generating the on time.
For example, when the main switch tube is turned on, the capacitor may be charged by a constant current (e.g., the constant current may be IREF), and the timing is started, and when the capacitor voltage reaches a preset voltage Value (VREF), the timing is ended, and the main switch tube is turned off. The on-time generated in this way can be reduced if necessary, VREF can be reduced or IREF can be increased. No matter what way to adjust the on-time, the application of the present invention will not be affected, and the present invention is not limited thereto.
Optionally, the determining the on-time by the switching power supply on-time control method includes: acquiring a preset switching-on control current, a preset switching-on cut-off voltage, a preset current change threshold value and a preset voltage change threshold value; adjusting the preset switching control current at least once according to the preset current change threshold value so as to enable the switching-on time to gradually reach the light-load switching-on time; or adjusting the preset turn-on cut-off voltage at least once according to the preset voltage change threshold value so as to enable the turn-on time to gradually reach the light-load turn-on time.
Specifically, the on-time of the switching unit may be gradually decreased according to the condition of the load, for example: VREF is slowly decreased or IREF is increased, the longer the wait time, the shorter the on-time at the next switch. Because the conduction time is shortened along with the lightening of the load, the output ripple is reduced, the size of the output ripple is prevented from changing suddenly, and the quality of the output electric energy is improved.
Optionally, after the waiting duration reaches the preset waiting time threshold, the on-time is further shortened to the light-load on-time in one step, and the output ripple is reduced by controlling the switching unit to switch for multiple times.
Example two
The second embodiment of the invention provides a switching power supply on-time control device, which can execute the switching power supply on-time control method provided by any embodiment of the invention and has corresponding functional modules and beneficial effects of the execution method.
Fig. 7 is a schematic structural diagram of a switching power supply on-time control device according to a second embodiment of the present invention.
As shown in fig. 7, the switching power supply on-time control apparatus 100 includes: the power supply device includes a switching unit 10, a detection unit 20, an on time generation unit 30, a load state determination unit 40, and an on control unit 50. The switching unit 10 is configured to control the switching power supply to be turned on or off, so that the switching power supply converts an input voltage into an output voltage; the detection unit 20 is configured to obtain operation parameters of the switching power supply, where the operation parameters include a switching tubular state parameter, a voltage parameter, a current parameter, a waiting duration, and switching times under a light load condition and a heavy load condition; the turn-on time generating unit 30 is used for determining light-load turn-on time and heavy-load turn-on time according to the voltage parameter, wherein the light-load turn-on time is less than the heavy-load turn-on time; the load state judging unit 40 is used for determining whether the light-load switching-on condition is met according to the current parameter, the tubular state parameter of the switch and the waiting duration; and the switching-on control unit 50 is used for controlling the switching unit 10 of the switching power supply to be continuously switched on and off at least once in light-load switching-on time when the light-load switching-on condition is met.
Optionally, the load state judgment unit 40 is further configured to determine whether a heavy load turn-on condition is met according to the voltage parameter, the current parameter, and the switching frequency; the turn-on control unit 50 is further configured to control the switching unit 10 of the switching power supply to continuously turn on the heavy-load turn-on time when the operation parameter satisfies the heavy-load turn-on condition.
Optionally, the load state determining unit 40 is further configured to obtain a first output voltage, an inductive current, and a switching frequency of the main switching tube under a light load condition, and determine that a heavy load turn-on condition is met when the first output voltage is lower than a preset undervoltage threshold, the switching frequency of the main switching tube reaches a preset frequency threshold, and the inductive current of the main switching tube switching device is continuously greater than zero.
Optionally, the turn-on time generating unit 30 is configured to obtain a minimum output voltage value under a light-load condition, and determine a minimum turn-on time of the main switching tube corresponding to the minimum output voltage value as the light-load turn-on time.
Optionally, the on-time generating unit 30 is further configured to obtain a second output voltage under the heavy load condition, and determine the on-time of the main switching tube corresponding to the second output voltage as the heavy load on-time.
Optionally, the turn-on control unit 50 is further configured to determine whether the current parameter reaches a preset turn-off condition, and drive the auxiliary switching tube to turn off when the current parameter reaches the preset turn-off condition; the load state determination unit 40 is further configured to obtain a waiting duration that the main switching tube and the auxiliary switching tube are both in an off state, and determine that the current operating parameter meets a light-load switching-on condition when the waiting duration reaches a preset waiting time threshold.
Optionally, the turn-on control unit 50 is further configured to obtain an output ripple of the switching power supply, determine a continuous switching time according to the output ripple, and output at least one turn-on control signal to the switching unit according to the continuous switching time, where a duration of the turn-on control signal is equal to the light-load turn-on time.
Optionally, the turn-on time generating unit 30 is configured to obtain a preset turn-on control current, a preset turn-on cut-off voltage, a preset current change threshold and a preset voltage change threshold, and adjust the preset turn-on control current at least once according to the preset current change threshold, so that the turn-on time gradually reaches the light-load turn-on time; or adjusting the preset turn-on cut-off voltage at least once according to the preset voltage change threshold value so as to enable the turn-on time to gradually reach the light-load turn-on time.
The switching power supply on-time control device provided by the embodiment of the invention is used for realizing an on-time control method, the method determines the light-load on-time and the heavy-load on-time through the operating parameters of the switching power supply under the light-load and heavy-load working conditions, judges whether the switching power supply meets the light-load on-condition or not according to the operating parameters, and controls the switching unit of the switching power supply to continuously switch for at least one time at the light-load on-time when the light-load on-condition is met until the switching tube jumps out of the light-load working condition.
EXAMPLE III
Based on the above embodiments, the third embodiment of the present invention provides a switching power supply.
Fig. 8 is a schematic structural diagram of a switching power supply according to a third embodiment of the present invention.
As shown in fig. 8, the switching power supply 200 includes the switching power supply on-time control device 100.
The switching power supply provided by the embodiment of the invention is provided with the switching-on time control device which is used for realizing the switching-on time control method, the method determines the light-load switching-on time and the heavy-load switching-on time according to the operation parameters of the switching power supply under the light-load working condition and the heavy-load working condition, judges whether the switching power supply meets the light-load switching-on condition or not according to the operation parameters, and controls the switching unit of the switching power supply to be continuously switched on and off at least once according to the light-load switching-on time until the switching tube jumps out of the light-load working condition when meeting the light-load switching-on condition.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (10)

1. A switching power supply on-time control method is characterized by comprising the following steps:
acquiring operation parameters of the switching power supply, wherein the operation parameters comprise switching tubular state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions;
determining light-load opening time and heavy-load opening time according to the voltage parameters, wherein the light-load opening time is less than the heavy-load opening time;
determining whether a light-load opening condition is met or not according to the current parameter, the switching tube state parameter and the waiting duration;
and if the light-load switching-on condition is met, controlling a switch unit of the switching power supply to be continuously switched on and off at least once within the light-load switching-on time.
2. The switching power supply on-time control method according to claim 1, further comprising the steps of:
determining whether a heavy-load opening condition is met or not according to the voltage parameter, the current parameter and the switching times;
and if the heavy-load switching-on condition is met, controlling a switch unit of the switching power supply to be switched on for the heavy-load switching-on time.
3. The switching power supply on-time control method according to claim 2, wherein determining whether a heavy-duty on condition is satisfied according to the voltage parameter, the current parameter and the switching times comprises the steps of:
acquiring a first output voltage, an inductive current and the switching times of a main switching tube under a light-load working condition;
and if the first output voltage is lower than a preset undervoltage threshold value and the inductive current is continuously larger than zero during the switching period of the main switching tube, judging that the heavy-load switching-on condition is met.
4. The switching power supply on-time control method according to claim 1, wherein determining the light-load on-time according to the voltage parameter comprises the steps of:
acquiring the minimum value of the output voltage under the light load working condition;
and determining the light-load turn-on time according to the minimum turn-on time of the main switching tube corresponding to the minimum value of the output voltage.
5. The switching power supply on-time control method according to claim 1, wherein determining the heavy-load on-time according to the voltage parameter comprises the steps of:
acquiring a second output voltage under a heavy-load working condition;
and determining the heavy-load opening time according to the main switching tube opening time corresponding to the second output voltage.
6. The switching power supply on-time control method according to claim 1, wherein determining whether a light-load on condition is satisfied according to the current parameter, the switching tube state parameter and the waiting duration comprises the following steps:
judging whether the current parameter reaches a preset turn-off condition or not;
if the current parameter reaches a preset turn-off condition, controlling an auxiliary switching tube to be turned off;
acquiring the waiting duration of the main switching tube and the auxiliary switching tube in the off state;
and if the waiting duration reaches a preset waiting time threshold, judging that the light-load opening condition is met.
7. The method for controlling the on-time of the switching power supply according to claim 1, wherein the step of controlling the switching unit of the switching power supply to be continuously switched on and off at least once in the light-load on-time comprises the following steps:
acquiring an output ripple of the switching power supply;
determining the continuous switching times according to the output ripple waves;
and outputting at least one conduction control signal to the switch unit according to the continuous switching times, wherein the duration of the conduction control signal is equal to the light-load switching-on time.
8. The switching power supply on-time control method according to claim 1, further comprising the steps of:
acquiring a preset switching-on control current, a preset switching-on cut-off voltage, a preset current change threshold value and a preset voltage change threshold value;
adjusting the preset switching control current at least once according to the preset current change threshold value so as to enable the switching-on time to reach the light-load switching-on time gradually;
or adjusting the preset switching-on cut-off voltage at least once according to the preset voltage change threshold value so as to enable the switching-on time to gradually reach the light-load switching-on time.
9. An on-time control device for a switching power supply, comprising:
the switching unit is used for controlling the switching power supply to be switched on or switched off so that the switching power supply converts an input voltage into an output voltage;
the detection unit is used for acquiring the operation parameters of the switching power supply, wherein the operation parameters comprise switching tubular state parameters, voltage parameters, current parameters, waiting duration and switching times under light load working conditions and heavy load working conditions;
the turn-on time generating unit is used for determining light-load turn-on time and heavy-load turn-on time according to the voltage parameter, wherein the light-load turn-on time is less than the heavy-load turn-on time;
the load state judging unit is used for determining whether a light-load opening condition is met or not according to the current parameter, the switching tube state parameter and the waiting duration;
and the switching-on control unit is used for controlling the switching unit of the switching power supply to be continuously switched on and off for at least one time in the light-load switching-on time when the light-load switching-on condition is met.
10. A switching power supply, comprising: the switching power supply on-time control apparatus of claim 9.
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