CN106558978A

CN106558978A - Switched power supply and its control circuit and control method

Info

Publication number: CN106558978A
Application number: CN201510639877.XA
Authority: CN
Inventors: 陈鸿钧; 张芳龙; 王德峻
Original assignee: Richtek Technology Corp
Current assignee: Richtek Technology Corp
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-05
Anticipated expiration: 2035-09-30
Also published as: CN106558978B

Abstract

The present invention proposes a kind of switched power supply and its control circuit and control method.Switched power supply, to convert input voltage into output voltage.Switched power supply includes power stage circuit and control circuit.Wherein power stage circuit switches wherein at least one power switch to convert input voltage into output voltage according to operation signal.Control circuit is coupled with power stage circuit, to produce operation signal.Control circuit includes marginal value adjustment circuit, according to input voltage or input current, to produce and accommodation overcurrent protection marginal value.Wherein, input current flows through power stage circuit.Wherein, overcurrent protection marginal value is to limit input current.Wherein, control circuit is not turned on power switch when input current exceedes overcurrent protection marginal value.

Description

Switched power supply and its control circuit and control method

Technical field

The present invention relates to a kind of switched power supply and its control circuit and control method, special A kind of switching power supply with accommodation overcurrent protection marginal value function is not referred to Device and its control circuit and control method.

Background technology

Figure 1A shows a kind of 100 schematic diagram of prior art switched power supply.Such as Figure 1A Shown, switched power supply 100 drives display pannel 10 to receive power supply.Cut Switching power supplier 100 is included：Power stage circuit 101, control circuit 102, and show drive Galvanic electricity road 103.As illustrated, 101 receives input voltage Vin of power stage circuit, and according to control The operation signal that circuit processed 102 is produced, operates power switch therein, and produces output voltage Vout.Display driving circuit 103 receives output voltage, to drive display pannel 10.

One of problem of above-mentioned prior art is that switched power supply 100 is electric from receiving Source is to display pannel 10 is driven, middle to pass through many circuits, also including wire etc., its The summation of resistance, can be considered line resistance as depicted, with impedance R.As line resistance is with impedance R, when input current Iin flows through power stage circuit 101, produces input current Iin and is multiplied by impedance R Pressure drop.When display pannel 10 refreshes (refresh) in picture switching, one section of liquid crystal is had anti- During turning, referred to as during blanking (blanking interval).During this blanking, control electricity Road 102 may require that raising input current Iin, and the work of operation signal is raised than (duty), because The of a relatively high pressure drop of this generation, causes input voltage vin to decline.Figure 1B shows input voltage The signal waveform schematic diagram of Vin, output voltage Vout and input current Iin when normal operating. As shown in Figure 1B, during blanking, input current Iin rises, and input voltage vin declines, output Voltage Vout rises.During this blanking, due to the decline of input voltage vin, may cause defeated Enter voltage Vin less than under-voltage locking (under voltage lock out, UVLO) level, and make whole System closedown.

Fig. 2 shows a kind of using under-voltage locking level is reduced, to avoid the schematic diagram of system closedown. As shown in Fig. 2 reducing under-voltage locking level, UVLO ' is downgraded from UVLO, can be kept away really Exempt from, during blanking, to cause system closedown because input voltage vin is too low.However, this measure is improved Switched power supply 100 operational risk, and under-voltage locking level is in many applications In, all need to be set in higher level, also make this measure infeasible.

6,445, No. 144 patent applications of United States Patent (USP) US, show a kind of side for solving the above problems Method.Which is using detecting input current, feedback control switching switch, to limit the upper of input current Lower limit.However, consequently, it is possible to need additional many power switch and circuit, increasing electric energy Consumption with manufacture cost.

In view of this, the present invention is directed to above-mentioned the deficiencies in the prior art, proposes a kind of suitching type Power supply unit and its control circuit and control method.The present invention is according to input voltage or input electricity Stream, accommodation overcurrent protection marginal value not only can reduce input current in if necessary, Input voltage is avoided less than under-voltage locking level, without downgrading under-voltage locking level；It is not required to again Other adding power circuit is wanted, with the electric energy for controlling manufacturing cost with consume.

The content of the invention

It is an object of the invention to overcome the deficiencies in the prior art and defect, a kind of suitching type is proposed Power supply unit and its control circuit and control method, according to input voltage or input current, fit Answering property adjusts overcurrent protection marginal value, and input current not only can be reduced in if necessary, it is to avoid Input voltage is less than under-voltage locking level, without downgrading under-voltage locking level；Again need not be another Outer adding power circuit, with the electric energy for controlling manufacturing cost with consume.

It is, up to above-mentioned purpose, one of viewpoint to be sayed, the invention provides a kind of suitching type is electric Source supply, an input voltage is converted to an output voltage, the switched-mode power supply is supplied Device is answered to include：One power stage circuit, according to an operation signal, switches wherein at least one power Switch for the input voltage to be converted to the output voltage；And a control circuit, with the power Level circuit coupling, to produce the operation signal, the control circuit includes marginal value adjustment electricity Road, according to the input voltage or an input current, to produce and one overcurrent of accommodation Protection marginal value；Wherein, the input current flows through the power stage circuit；Wherein, the overcurrent Protection marginal value, to limit the input current；Wherein, the control circuit is in the input current During more than the overcurrent protection marginal value, the power switch is not turned on.

Wherein in a kind of preferred embodiment, the marginal value adjustment circuit is under the input voltage During drop, adaptability downgrades the overcurrent protection marginal value, and drops to not in the input voltage During higher than first input voltage of acquiescence, the overcurrent protection marginal value is made to be maintained at an overcurrent Protect minimum marginal value；And when the input voltage rises, adaptability increases the overcurrent protection Marginal value, and when the input voltage rises to and is not less than second input voltage of acquiescence, make The overcurrent protection marginal value is maintained at an overcurrent protection maximum critical value；Wherein, the acquiescence First input voltage is less than second input voltage of acquiescence, and the minimum marginal value of the overcurrent protection Less than the overcurrent protection maximum critical value.

Wherein in a kind of preferred embodiment, the marginal value adjustment circuit is on the input current When rising, adaptability downgrades the overcurrent protection marginal value, and reaches in input current rising During one default first input current, the overcurrent protection marginal value is made to be maintained at an overcurrent protection Minimum marginal value, and the input current is maintained in default first input current；And in the input When electric current declines, adaptability increases the overcurrent protection marginal value, and under the input current When being down to not higher than one default second input current, the overcurrent protection marginal value is made to be maintained at one Overcurrent protection maximum critical value；Wherein, default first input current presets second higher than this Input current, and the minimum marginal value of the overcurrent protection is less than the overcurrent protection maximum critical value.

Wherein in a kind of preferred embodiment, the marginal value adjustment circuit accommodation mistake Current protection marginal value so that the reason input current is too high and to be less than one pre- for the input voltage If under-voltage locking (under voltage lockout, UVLO) level.

Wherein in a kind of preferred embodiment, the output voltage to supply a display pannel, And during a blanking (blanking interval), the marginal value adjustment circuit is according to the input voltage Or the input current, the accommodation overcurrent protection marginal value；And during the blanking it Outward, the marginal value adjustment circuit maintain the overcurrent protection marginal value in one fix preset electricity Stream protection marginal value.

Wherein in a kind of preferred embodiment, the marginal value adjustment circuit includes：One voltage electricity Stream change-over circuit, by the input voltage or its related signal, to be converted to one first electric current； One first current modulating circuit, is coupled with the voltage-current converter circuit, to this is first electric Circulation is changed to the one first amplification electric current with its direct ratio, and according to an overcurrent protection upper limit current With the difference of the first amplification electric current, one second electric current is produced；One second current modulating circuit, Couple with the first current modulating circuit, second electric current to be converted to its direct ratio Second amplifies electric current, and according to an overcurrent protection lower current and the difference of the second amplification electric current Value, produces one the 3rd electric current；One the 3rd current modulating circuit, with the second current modulating circuit Coupling, the 3rd electric current to be converted to and the one the 3rd of its direct ratio amplification electric current, and according to The minimum marginal value electric current of one overcurrent protection and the 3rd electric current, produce a modulation electric current；And One current-to-voltage converting circuit, is coupled with the 3rd current modulating circuit, to the modulation is electric Circulation is changed to the overcurrent protection marginal value.

In the foregoing embodiments, the second current modulating circuit is preferably also enabled including one and is opened Powered-down road, to enable signal according to one, decides whether to produce the second amplification electric current.

In the foregoing embodiments, during preferable one blanking of DIYU of the enable signal, determine to produce The second amplification electric current；And during the blanking outside, decision do not produce this second amplify electric current； Wherein, the output voltage shows this is relevant to during supplying a display pannel, and the blanking During before showing the one of device panel, the picture end of scan to picture after starts scanning.

Wherein in a kind of preferred embodiment, the marginal value adjustment circuit includes：One input electricity Influenza slowdown monitoring circuit, to sense the input current, and produces a current sense signal；One voltage Current converter circuit, by the current sense signal, to be converted to one first electric current；One first Current modulating circuit, is coupled with the voltage-current converter circuit, first electric current to be changed It is the one first amplification electric current with its direct ratio, and according to the first amplification electric current and an over current protection The difference of shield lower current, produces one second electric current；One second current modulating circuit, with this One current modulating circuit is coupled, and is put with the one second of its direct ratio second electric current to be converted to High current, and according to an overcurrent protection upper limit current and the difference of the second amplification electric current, produce Raw one the 3rd electric current；One the 3rd current amplification circuit, is coupled with the second current modulating circuit, The 3rd electric current to be converted to one the 3rd amplification electric current with its direct ratio；One the 3rd electric current is adjusted Become circuit, couple with the second current modulating circuit, the 3rd electric current to be converted to and which One the 3rd amplification electric current of direct ratio, and according to the minimum marginal value electric current of an overcurrent protection with this Three electric currents, produce a modulation electric current；And a current-to-voltage converting circuit, with the 3rd electric current Modulation circuit is coupled, the modulation electric current is converted to the overcurrent protection marginal value.

In the foregoing embodiments, during preferable one blanking of DIYU of the enable signal, determine to produce 3rd electric current；And during the blanking outside, decision do not produce the 3rd electric current；Wherein, The output voltage is to be relevant to the display face during supplying a display pannel, and the blanking During before the one of plate, the picture end of scan to picture after starts scanning.

It is, up to above-mentioned purpose, another viewpoint to be sayed, the invention provides a kind of switched-mode power supply The control method of supply, the wherein switched power supply, an input voltage to be turned An output voltage is changed to, the control method of the switched power supply is included：According to an operation Signal and operate an at least power switch in a power stage circuit, the input voltage is converted to The output voltage；And according to the input voltage or an input current, produce and accommodation One overcurrent protection marginal value；With the overcurrent protection marginal value, the input current is limited；With And when the input current exceedes the overcurrent protection marginal value, it is not turned on the power switch；Its In, the input current flows through the power stage circuit.

Wherein in a kind of preferred embodiment, this according to the input voltage or the input current, The step of producing simultaneously accommodation overcurrent protection marginal value includes：Under the input voltage During drop, adaptability downgrades the overcurrent protection marginal value, and drops to not in the input voltage During higher than first input voltage of acquiescence, the overcurrent protection marginal value is made to be maintained at an overcurrent Protect minimum marginal value；And when the input voltage rises, adaptability increases the over current protection Shield marginal value, and when the input voltage rises to and is not less than second input voltage of acquiescence, The overcurrent protection marginal value is made to be maintained at an overcurrent protection maximum critical value；Wherein, this is write from memory The first input voltage is recognized less than second input voltage of acquiescence, and the overcurrent protection is minimum critical Value is less than the overcurrent protection maximum critical value.

Wherein in a kind of preferred embodiment, this according to the input voltage or the input current, The step of producing simultaneously accommodation overcurrent protection marginal value includes：On the input current When rising, adaptability downgrades the overcurrent protection marginal value, and reaches in input current rising During one default first input current, the overcurrent protection marginal value is made to be maintained at an overcurrent protection Minimum marginal value, and the input current is maintained in default first input current；And it is defeated in this When entering electric current decline, adaptability increases the overcurrent protection marginal value, and in the input current When dropping to not higher than one default second input current, it is maintained at the overcurrent protection marginal value One overcurrent protection maximum critical value；Wherein, default first input current higher than this default the Two input currents, and the minimum marginal value of the overcurrent protection is greatly critical less than the overcurrent protection Value.

Wherein in a kind of preferred embodiment, this according to the input voltage or the input current, The step of producing simultaneously accommodation overcurrent protection marginal value also includes：Make the input voltage Not the reason input current it is too high and be less than a default under-voltage locking (under voltage lockout, UVLO) level.

Wherein in a kind of preferred embodiment, the output voltage to supply a display pannel, And this is according to the input voltage or the input current, simultaneously accommodation overcurrent protection is produced The step of marginal value, includes：During a blanking, according to the input voltage or the input current, The accommodation overcurrent protection marginal value；And during the blanking outside, maintain the mistake Current protection marginal value is in a default overcurrent protection marginal value fixed.

Wherein in a kind of preferred embodiment, this is produced and adaptability according to the input voltage The step of adjusting the overcurrent protection marginal value includes：By the input voltage or its related signal, Be converted to one first electric current；First electric current is converted to into the one first amplification electric current with its direct ratio, And according to an overcurrent protection upper limit current and the difference of the first amplification electric current, produce one second Electric current；Second electric current is converted to into the one second amplification electric current with its direct ratio, and according to a mistake Current protection lower current and the difference of the second amplification electric current, produce one the 3rd electric current；Should 3rd electric current is converted to one the 3rd amplification electric current with its direct ratio, and according to an overcurrent protection pole Little marginal value electric current and the 3rd electric current, produce a modulation electric current；And the modulation electric current is turned It is changed to the overcurrent protection marginal value.

In the foregoing embodiments, second electric current is converted to and is put with the one second of its direct ratio by this High current, and according to an overcurrent protection lower current and the difference of the second amplification electric current, produce The step of raw three electric current, preferably also includes：Signal is enabled according to one, decides whether to produce The second amplification electric current.

Wherein in a kind of preferred embodiment, this is produced and adaptability according to the input current The step of adjusting the overcurrent protection marginal value includes：The input current is sensed, and it is electric to produce one Influenza surveys signal；By the current sense signal, one first electric current is converted to；By first electric current The one first amplification electric current with its direct ratio is converted to, and it is excessively electric with one according to the first amplification electric current The difference of stream protection lower current, produces one second electric current；Second electric current is converted to and which One second amplification electric current of direct ratio, and according to an overcurrent protection upper limit current and second amplification The difference of electric current, produces one the 3rd electric current；3rd electric current is converted to one with its direct ratio Three amplify electric current；3rd amplification electric current is converted to into one the 4th amplification electric current with its direct ratio, And electric current is amplified with the 4th according to the minimum marginal value electric current of an overcurrent protection, produce a modulation Electric current；And the modulation electric current is converted to into the overcurrent protection marginal value.

In the foregoing embodiments, second electric current is converted to and is put with the one second of its direct ratio by this The step of high current, preferably also includes：According to one enable signal, decide whether produce this second Amplify electric current.

It is, up to above-mentioned purpose, another viewpoint to be sayed, the invention provides a kind of switched-mode power supply Control circuit in supply, to produce an operation signal, switches the switching power supply At least one power switch in device, and an input voltage is converted to into an output voltage, wherein, The control circuit includes a marginal value adjustment circuit, according to the input voltage, to produce and fit Answering property adjusts an overcurrent protection marginal value, and to limit the input current, wherein the marginal value is adjusted Whole circuit is included：One voltage-current converter circuit, to by the input voltage or its related signal, Be converted to one first electric current；One first current modulating circuit, with the voltage-current converter circuit coupling Connect, first electric current to be converted to and the one first of its direct ratio amplification electric current, and according to one Overcurrent protection upper limit current and the difference of the first amplification electric current, produce one second electric current；One Second current modulating circuit, is coupled with the first current modulating circuit, to by second electric current Be converted to and the one second of its direct ratio amplification electric current, and according to an overcurrent protection lower current with The difference of the second amplification electric current, produces one the 3rd electric current；One the 3rd current modulating circuit, with The second current modulating circuit is coupled, the 3rd electric current to be converted to and the 1 of its direct ratio the Three amplify electric current, and according to the minimum marginal value electric current of an overcurrent protection and the 3rd electric current, produce A raw modulation electric current；And a current-to-voltage converting circuit, with the 3rd current modulating circuit coupling Connect, the modulation electric current is converted to the overcurrent protection marginal value；The wherein over current protection Shield marginal value, to limit the input current；Wherein the control circuit exceedes in the input current During the overcurrent protection marginal value, the power switch is not turned on.

Wherein in a kind of preferred embodiment, when the input voltage declines, adaptability downgrades this Overcurrent protection marginal value, and not higher than one the first input of acquiescence is dropped in the input voltage During voltage, the overcurrent protection marginal value is made to be maintained at the minimum marginal value of an overcurrent protection；And When the input voltage rises, adaptability increases the overcurrent protection marginal value, and defeated in this Enter voltage to rise to when being not less than second input voltage of acquiescence, make the overcurrent protection marginal value It is maintained at an overcurrent protection maximum critical value.

It is, up to above-mentioned purpose, another viewpoint to be sayed, the invention provides a kind of switched-mode power supply Control circuit in supply, to produce an operation signal, switches the switching power supply At least one power switch in device, and an input voltage is converted to into an output voltage, wherein, The control circuit includes a marginal value adjustment circuit, according to the input current, to produce and fit Answering property adjusts an overcurrent protection marginal value, and to limit the input current, wherein the marginal value is adjusted Whole circuit is included：One input current sensing circuit, to sense the input current, and produces one Current sense signal；One voltage-current converter circuit, by the current sense signal, to change For one first electric current；One first current modulating circuit, is coupled with the voltage-current converter circuit, First electric current to be converted to and the one first of its direct ratio amplification electric current, and according to this first Amplify the difference of electric current and an overcurrent protection lower current, produce one second electric current；One second Current modulating circuit, is coupled with the first current modulating circuit, second electric current to be changed Be and the one second of its direct ratio amplification electric current, and according to an overcurrent protection upper limit current with this Two differences for amplifying electric current, produce one the 3rd electric current；One the 3rd current amplification circuit, with this Two current modulating circuits are coupled, and are put with the one the 3rd of its direct ratio the 3rd electric current to be converted to High current；One the 4th current modulating circuit, is coupled with the 3rd current amplification circuit, to incite somebody to action 3rd amplification electric current is converted to one the 4th amplification electric current with its direct ratio, and according to an overcurrent Protect minimum marginal value electric current to amplify electric current with the 4th, produce a modulation electric current；And one is electric Stream voltage conversion circuit, is coupled with the 3rd current modulating circuit, the modulation electric current to be turned It is changed to the overcurrent protection marginal value.

Wherein in a kind of preferred embodiment, the control circuit accommodation over current protection Shield marginal value so that the input voltage is not less than an acquiescence under-voltage locking (under voltage Lockout, UVLO) level.

Wherein in a kind of preferred embodiment, the output voltage to supply a display pannel, And during a blanking, the control circuit is according to the input voltage or the input current, adaptability Adjust the overcurrent protection marginal value；And during the blanking outside, the control circuit is maintained should Overcurrent protection marginal value is in a default overcurrent protection marginal value fixed.

Below by way of specific embodiment elaborate, when being easier to understand the purpose of the present invention, skill Art content, feature and its effect reached.

Description of the drawings

Figure 1A shows a kind of 100 schematic diagram of prior art switched power supply；

Figure 1B shows input voltage vin, output voltage Vout and input current Iin in normal Signal waveform schematic diagram during operation；

Fig. 2 shows a kind of using under-voltage locking level is reduced, to avoid the schematic diagram of system closedown；

Fig. 3 shows one embodiment of the present invention；

Fig. 4 A-4K show voltage-dropping type either synchronously or asynchronously, booster type, back-pressure type, buck-boost type, Rise back-pressure type or flyback type power stage circuit；

Fig. 5 show overcurrent protection marginal value OCP according to an embodiment of the invention with it is defeated Enter the relation schematic diagram of voltage Vin；

Fig. 6 shows second embodiment of the present invention；

Fig. 7 shows the 3rd embodiment of the present invention；

Fig. 8 shows input voltage of the invention and input current signal waveform schematic diagram；

Fig. 9 show overcurrent protection marginal value OCP according to an embodiment of the invention with it is defeated Enter the relation schematic diagram of electric current Iin；

Figure 10 shows the 4th embodiment of the present invention；

Figure 11 shows the 5th embodiment of the present invention.

Symbol description in figure

10 display pannels

100,200 switched power supplies

101,201 power stage circuits

102,202 control circuits

103,203 display driving circuits

2021 marginal value adjustment circuits

2022,3022 voltage-current converter circuits

2023,3023 first current modulating circuits

2024,3024 second current modulating circuits

2025 the 3rd current modulating circuits

2026,3026 current-to-voltage converting circuits

3021 input current sensing circuits

3025 the 3rd current amplification circuits

3027 the 4th current modulating circuits

EN enables signal

The first electric current of I1, Ic1

I1 ', Ic1 ' first amplifies electric current

The second electric current of I2, Ic2

I2 ', Ic2 ' second amplifies electric current

The 3rd electric current of I3, Ic3

I3 ', Ic3 ' the 3rd amplifies electric current

Ic4 the 4th amplifies electric current

Iin input currents

Iin1 presets the first input current

The default second input electricity of Iin2

Ilol, Ilo overcurrent protection lower current

The minimum marginal value electric current of Imin overcurrent protections

Imod modulation electric currents

Iupl, Iup overcurrent protection upper limit current

OCP overcurrent protection marginal values

OCPmax overcurrent protection maximum critical values

The minimum marginal value of OCPmin overcurrent protections

R impedances

R1, R2, Rsen resistance

SW enables on-off circuit

UVLO, UVLO ' under-voltage locking level

Vin input voltages

Vin1 gives tacit consent to the first input voltage

Vin2 gives tacit consent to the second input voltage

Vout output voltages

Specific embodiment

Schema in the present invention belongs to signal, is mostly intended to represent the coupling relation between each circuit, And the relation between each signal waveform, as circuit, signal waveform and frequency then and not according to Ratio is drawn.

Fig. 3 shows one embodiment of the present invention.As shown in figure 3, switched power supply 200 to be converted to output voltage Vout by input voltage vin, and by circuit of display driving 203, drive display pannel 10.Switched power supply 200 comprising power stage circuit 201, Control circuit 202, and circuit of display driving 203.Power stage circuit 201 according to operation signal, Switch wherein at least one power switch input voltage vin is converted to output voltage Vout.Work( Rate level circuit 201 includes at least one power switch, and which can be voltage-dropping type either synchronously or asynchronously, liter Die mould, back-pressure type, buck-boost type, liter back-pressure type or flyback type power stage circuit, such as Fig. 4 A-4K It is shown.Display driving circuit 203 drives display pannel 10 to receive output voltage Vout, Non-invention application emphasis, will not be described here.

Control circuit 202 is coupled with power stage circuit 201, to produce operation signal, control electricity Road 202 includes marginal value adjustment circuit 2021, to according to input voltage vin or input current Iin, Produce and accommodation overcurrent protection marginal value OCP.Wherein, input current Iin flows through work( Rate level circuit 201.Wherein, overcurrent protection marginal value OCP, to limit input current Iin. Control circuit 202 is not turned on power when input current Iin exceedes overcurrent protection marginal value OCP Switch.Control circuit 202 thus mechanism, feedback control input electric current Iin, make input current Iin Will not be too high, and cause input voltage vin be less than default under-voltage locking (under voltage Lockout, UVLO) level.So-called input current Iin it is too high or will not be too high standard, mainly Be the pressure drop caused by the impedance R of line group to be multiplied by as input current Iin, cause input voltage vin Decline, and make input voltage vin less than acquiescence under-voltage locking (under voltage lockout, UVLO) during level, then this input current Iin is exactly to be too high；If holding input voltage vin is higher than During the under-voltage locking level of acquiescence, then this input current Iin be exactly will not be too high.

In the present embodiment, marginal value adjustment circuit 2021 for example includes voltage-current converter circuit 2022nd, the first current modulating circuit 2023, the second current modulating circuit 2024, the 3rd electric current are adjusted Become circuit 2025, and current-to-voltage converting circuit 2026.For example, as shown in figure 5, critical For example when input voltage vin declines, adaptability downgrades overcurrent protection and faces value adjustment circuit 2021 Dividing value OCP, and when input voltage vin not higher than gives tacit consent to the first input voltage vin 1, made Current protection marginal value OCP is maintained at minimum marginal value OCPmin of overcurrent protection；And in input When voltage rises, adaptability increases overcurrent protection marginal value OCP, and in input voltage vin When being not less than the second input voltage vin 2 of acquiescence, overcurrent protection marginal value OCP is made to be maintained at electricity Stream protection maximum critical value OCPmax；Wherein, the first input voltage vin 1 of acquiescence is less than acquiescence the Two input voltage vins 2, and minimum marginal value OCPmin of overcurrent protection is less than overcurrent protection pole Big marginal value OCPmax.

Fig. 6 shows second embodiment of the present invention.The present embodiment shows marginal value adjustment circuit A kind of 2021 more specific embodiments.As shown in fig. 6, marginal value adjustment circuit 2021 for example includes Voltage-current converter circuit 2022, the first current modulating circuit 2023, the second current modulating circuit 2024th, the 3rd current modulating circuit 2025, and current-to-voltage converting circuit 2026.Wherein, electricity Current voltage change-over circuit 2022, by input voltage vin or its related signal, to be converted to first Electric current I1.It should be noted that, the related signal of so-called input voltage vin refers to and is relevant to input electricity The signal of pressure Vin, due to being limited to a variety of factors, voltage-current converter circuit 2022 is necessarily straight Meet receives input voltage Vin, and can receive and there is direct ratio with input voltage vin, or linearly Other signals of functional relationship, this is directly proportional to input voltage vin or has linear functional relation Other signals, the as related signal of input voltage vin.As illustrated, Voltage to current transducer Such as receives input voltage Vin of circuit 2022, and via low dropout voltage regulator as depicted (Low-dropout regulator, LDO), which includes resistance R1, and input voltage vin is changed For the first electric current I1.

First current modulating circuit 2023 is coupled with voltage-current converter circuit 2022, to by One electric current I1 is for example with 1:The ratio of M1 is converted to the first amplification electric current I1 ' with its direct ratio, and root Amplify the difference of electric current I1 ' according to overcurrent protection upper limit current Iupl and first, produce the second electric current I2.In the present embodiment, the first current modulating circuit 2023 such as but not limited to includes current mirror electricity Road and fixed current source, and the first electric current I1 is converted to and put with the first of its direct ratio by current mirroring circuit High current I1 ', and overcurrent protection upper limit current Iupl is for example provided by fixed current source；Wherein, Second electric current I2, first amplify electric current I1 ', and the relational expression between overcurrent protection upper limit current Iupl For：I2=Iupl-I1 '.

Second current modulating circuit 2024 is coupled with the first current modulating circuit 2023, to by Two electric current I2 are for example with 1:The ratio of M2 is converted to the second amplification electric current I2 ' with its direct ratio, and root Amplify the difference of electric current I2 ' according to overcurrent protection lower current Ilol and second, produce the 3rd electric current I3.In the present embodiment, the second current modulating circuit 2024 such as but not limited to includes current mirror electricity Road and fixed current source, and the second electric current I2 is converted to and put with the second of its direct ratio by current mirroring circuit High current I2 ', and overcurrent protection lower current Ilol is for example provided by fixed current source；Wherein, 3rd electric current I3, second amplify electric current I2 ', and the relational expression between overcurrent protection lower current Ilol For：I3=Ilol-I2 '.

3rd current modulating circuit 2025 is coupled with the second current modulating circuit 2024, to by Three electric current I3 are for example with 1:The ratio of M3 is converted to the 3rd amplification electric current I3 ' with its direct ratio, and root Amplify electric current I3 ' according to the minimum marginal value electric current Imin of overcurrent protection and the 3rd, produce modulation electric current Imod.In the present embodiment, the 3rd current modulating circuit 2025 such as but not limited to includes electric current Mirror circuit and fixed current source, and the 3rd electric current I3 is converted to current mirroring circuit with its direct ratio the Three amplify electric current I3 ', and the minimum marginal value electric current Imin of overcurrent protection is for example by fixed current source There is provided；Wherein, modulation electric current Imod, the 3rd amplification electric current I3 ', and overcurrent protection is minimum faces Relational expression between dividing value electric current Imin is：Imod=I3 '+Imin.

Current-to-voltage converting circuit 2026 is coupled with the 3rd current modulating circuit 2025, adjusting Time-dependent current Imod is converted to overcurrent protection marginal value OCP.Wherein, current-to-voltage converting circuit 2026 for example include resistance R2, flow through the pressure reduction produced by resistance R2 with modulation electric current Imod, make For overcurrent protection marginal value OCP.

In the present embodiment, the value of minimum marginal value OCPmin of overcurrent protection is：

OCPmin=Imin × R2

And the value of overcurrent protection maximum critical value OCPmax is：

OCPmax=(Imin+Iupl × M3) × R2

According to the present embodiment, the first input voltage vin 1 of acquiescence is：

Giving tacit consent to the second input voltage vin 2 is：

And in Fig. 5, giving tacit consent between the second input voltage vin 2 of the first input voltage vin 1 and acquiescence, mistake Current protection marginal value OCP rise slope slop be：

That is, user can as needed, the appropriate resistance R1, resistance R2, excessively electric of selecting Stream protection upper limit current Iupl, overcurrent protection lower current Ilol, overcurrent protection are minimum critical Value electric current Imin and current mirror magnification ratio M1, M2, M3, to obtain overcurrent protection Minimum marginal value OCPmin, overcurrent protection maximum critical value OCPmax, the first input voltage Vin1, acquiescence the second input voltage vin 2, and overcurrent protection marginal value OCP rise slope slop。

Fig. 7 shows the 3rd embodiment of the present invention.This enforcement it is different from second embodiment it Place, in being the present embodiment, the second current modulating circuit 2024 also includes enabling on-off circuit SW, According to signal EN is enabled, to decide whether that producing second amplifies electric current I2 '.In the present embodiment, Enable signal EN and can determine that producing second amplifies electric current I2 ' during blanking；And during blanking Outside, decision does not produce the second amplification electric current I2 ', and during blanking outside, marginal value adjustment Circuit 2021 maintains overcurrent protection marginal value OCP in fixed default overcurrent protection marginal value, Be relevant to the minimum marginal value electric current Imin of overcurrent protection lower current Ilol, overcurrent protection with One fixed value of resistance R2.Wherein, output voltage Vout is to supply display pannel 10, And be relevant to during blanking the front picture end of scan to the rear picture of display pannel 10 start scanning During.

Fig. 8 shows that input voltage vin of the invention is illustrated with input current Iin signal waveforms Figure.Compared to prior art, change of the present invention according to input voltage vin or input current Iin, Particularly during aforementioned blanking, the decline of input voltage vin and the rising of input current are adapted to Property adjustment overcurrent protection marginal value OCP, using the mechanism of overcurrent protection, limit input current Iin, with avoid input voltage vin less than acquiescence under-voltage locking (under voltage lockout, UVLO) level (particularly during blanking).In figure, heavy line part represents of the invention defeated Enter the signal waveform schematic diagram of voltage Vin and input current Iin, and thick dashed line part represents existing skill The input voltage vin of art and the signal waveform schematic diagram of input current Iin.

Fig. 9 show overcurrent protection marginal value OCP according to an embodiment of the invention with it is defeated Enter the relation schematic diagram of electric current Iin.Show that the present invention can be using marginal value adjustment circuit 2021 in defeated When entering electric current Iin risings, adaptability downgrades overcurrent protection marginal value OCP, and in input electricity When stream Iin risings reach default first input current Iin1, maintain overcurrent protection marginal value OCP In minimum marginal value OCPmin of overcurrent protection, and input current Iin is maintained in default first input Electric current Iin1；And when input current Iin declines, adaptability increases overcurrent protection marginal value OCP, And when input current Iin not higher than default second input current Iin2, make overcurrent protection critical Value OCP is maintained at overcurrent protection maximum critical value OCPmax；Wherein, preset the first input electricity Stream Iin1 is higher than to preset the second input current Iin2, and minimum marginal value OCPmin of overcurrent protection Less than overcurrent protection maximum critical value OCPmax.

Figure 10 shows the 4th embodiment of the present invention.The present embodiment shows marginal value adjustment circuit 2021 another kind of more specific embodiments.As shown in Figure 10, marginal value adjustment circuit 2021 is for example Including input current sensing circuit 3021, voltage-current converter circuit 3022, the first current modulating Circuit 3023, the second current modulating circuit 3024, the 3rd current amplification circuit the 3025, the 4th are electric Stream modulation circuit 3027, and current-to-voltage converting circuit 3026.Wherein, input current sensing electricity Road 3021 is to sense input current Iin, and produces current sense signal, and which for example utilizes resistance Rsen is concatenated with power stage circuit 101, is interrogated using obtaining the cross-pressure on resistance Rsen as current sense Number.Voltage-current converter circuit 3022 is by current sense signal, to be converted to the first electric current Ic1. As illustrated, voltage-current converter circuit 3022 for example includes error amplifier circuit and low pressure drop Current sense signal is converted to first electric by manostat (Low-dropout regulator, LDO) Stream Ic1.

First current modulating circuit 3023 is coupled with voltage-current converter circuit 2022, to by One electric current Ic1 is for example with 1:The ratio of M1 is converted to the first amplification electric current Ic1 ' with its direct ratio, and According to the first difference for amplifying electric current Ic1 ' and overcurrent protection lower current Ilo, the second electric current is produced Ic2.In the present embodiment, the first current modulating circuit 3023 such as but not limited to includes current mirror Circuit and fixed current source, and the first electric current Ic1 is converted to current mirroring circuit with its direct ratio the One amplifies electric current Ic1 ', and overcurrent protection lower current Ilo is for example provided by fixed current source；Its In, the second electric current Ic2, first amplify electric current Ic1 ', and between overcurrent protection lower current Ilo Relational expression is：Ic2=Ic1 '-Ilo.

Second current modulating circuit 3024 is coupled with the first current modulating circuit 3023, to by Two electric current Ic2 are for example with 1:The ratio of M2 is converted to the second amplification electric current Ic2 ' with its direct ratio, and The difference of electric current Ic2 ' is amplified according to overcurrent protection upper limit current Iup and second, the 3rd is produced electric Stream Ic3.In the present embodiment, the second current modulating circuit 3024 such as but not limited to includes electric current Mirror circuit and fixed current source, and the second electric current Ic2 is converted to and its direct ratio by current mirroring circuit Second amplifies electric current Ic2 ', and overcurrent protection upper limit current Iup is for example provided by fixed current source； Wherein, the 3rd electric current Ic3, second amplify electric current Ic2 ', and between overcurrent protection upper limit current Iup Relational expression be：Ic3=Iup-Ic2 '.

3rd current amplification circuit 3025 is coupled with the second current modulating circuit 3024, to by Three electric current Ic3 are for example with 1:The ratio of M3 is converted to the 3rd amplification electric current Ic3 ' with its direct ratio. In the present embodiment, the 3rd current amplification circuit 3025 such as but not limited to includes current mirroring circuit.

4th current modulating circuit 3027 is coupled with the 3rd current amplification circuit 3025, to by Three amplification electric current Ic3 ' are converted to the 4th amplification electric current Ic4 with its direct ratio, and according to overcurrent protection Minimum marginal value electric current Imin and the 4th amplifies electric current Ic4, produces modulation electric current Imod.In this reality Apply in example, the 4th current modulating circuit 3027 such as but not limited to includes current mirroring circuit and fixation Current source, and the 3rd amplification electric current Ic3 ' is converted to the 4th amplification with its direct ratio by current mirroring circuit Electric current Ic4, and the minimum marginal value electric current Imin of overcurrent protection is for example provided by fixed current source； Wherein, modulation electric current Imod, the 4th amplify electric current Ic4 and the minimum marginal value electricity of overcurrent protection Stream Imin between relational expression be：Imod=Ic4+Imin.

Current-to-voltage converting circuit 3026 is coupled with the 4th current modulating circuit 3027, adjusting Time-dependent current Imod is converted to overcurrent protection marginal value OCP.Wherein, current-to-voltage converting circuit 3026 for example include resistance R2, flow through the pressure reduction produced by resistance R2 with modulation electric current Imod, make For overcurrent protection marginal value OCP.

Figure 11 shows the 5th embodiment of the present invention.The present embodiment is different from the 4th embodiment Part, in being the present embodiment, the second current modulating circuit 3024 also includes enabling on-off circuit SW, according to signal EN is enabled, to decide whether that producing second amplifies electric current Ic2 '.In this reality Apply in example, enable signal EN and can determine that producing second amplifies electric current Ic2 ' during blanking；And Outside during blanking, decision does not produce the second amplification electric current Ic2 ', and during blanking outside, Marginal value adjustment circuit 2021 maintains overcurrent protection marginal value OCP in fixed default overcurrent Protection marginal value, that is, be relevant to overcurrent protection upper limit current Iup, overcurrent protection minimum critical One fixed value of value electric current Imin and resistance R2.Wherein, output voltage Vout is aobvious to supply Show device panel 10, and the front picture end of scan of display pannel 10 is relevant to during blanking to rear During picture starts scanning.

More than have been for preferred embodiment to illustrate the present invention, the above, only make this area Technical staff is apparent to present disclosure, not for limit the present invention right model Enclose.Under the same spirit of the present invention, those skilled in the art can think and various equivalence changes. For example, in each embodiment, icon is directly connected to two circuits or inter-module, can plant does not affect master Other circuits or component of function, therefore " coupling " are wanted to should be regarded as including directly or indirectly connecting. And for example, electric current is amplified with direct proportion, is not limited to current mirroring circuit, can also extend to other and have The circuit of identical amplification effect；For another example, the positive and negative terminal of amplifier circuit and comparator circuit can be with Exchange, it is only necessary to correspondence modification interlock circuit or the meaning of signal height level.It is all this kind of Kind, all of the invention can teach and analogize and obtain, therefore, the scope of the present invention should cover Address other all equivalence changes.

Claims

1. a kind of switched power supply, electric an input voltage is converted to an output Pressure, it is characterised in that the switched power supply is included：

One power stage circuit, according to an operation signal, switching wherein at least one power switch with The input voltage is converted to into the output voltage；And

One control circuit, is coupled with the power stage circuit, to produce the operation signal, the control Circuit processed includes a marginal value adjustment circuit, to according to the input voltage or an input current, Produce and one overcurrent protection marginal value of accommodation；

Wherein, the input current flows through the power stage circuit；

Wherein, overcurrent protection marginal value, to limit the input current；

Wherein, the control circuit in the input current exceed the overcurrent protection marginal value when, no Turn on the power switch.

2. switched power supply as claimed in claim 1, wherein, the marginal value is adjusted When the input voltage declines, adaptability downgrades the overcurrent protection marginal value to circuit, and in When the input voltage drops to not higher than one the first input voltage of acquiescence, face the overcurrent protection Dividing value is maintained at the minimum marginal value of an overcurrent protection；And when the input voltage rises, adapt to Property increases the overcurrent protection marginal value, and rises in the input voltage and be not less than an acquiescence During the second input voltage, make the overcurrent protection marginal value be maintained at an overcurrent protection and greatly face Dividing value；

Wherein, first input voltage of acquiescence is less than second input voltage of acquiescence, and this is excessively electric The minimum marginal value of stream protection is less than the overcurrent protection maximum critical value.

3. switched power supply as claimed in claim 1, wherein, the marginal value is adjusted When the input current rises, adaptability downgrades the overcurrent protection marginal value to circuit, and in When input current rising reaches default first input current, the overcurrent protection marginal value is made It is maintained at the minimum marginal value of an overcurrent protection, and maintains the input current default first defeated in this Enter electric current；And when the input current declines, adaptability increases the overcurrent protection marginal value, And when the input current drops to not higher than one default second input current, make the overcurrent Protection marginal value is maintained at an overcurrent protection maximum critical value；

Wherein, default first input current presets the second input current higher than this, and this is excessively electric The minimum marginal value of stream protection is less than the overcurrent protection maximum critical value.

4. switched power supply as claimed in claim 1, wherein, the marginal value is adjusted The circuit accommodation overcurrent protection marginal value so that the input voltage not reason input Electric current is too high and be less than a default under-voltage locking level.

5. switched power supply as claimed in claim 1, wherein, the output voltage is used To supply a display pannel, and during a blanking, the marginal value adjustment circuit is defeated according to this Enter voltage or the input current, the accommodation overcurrent protection marginal value；And in the blanking Outside period, the marginal value adjustment circuit maintains the overcurrent protection marginal value in the pre- of a fixation If overcurrent protection marginal value.

6. switched power supply as claimed in claim 1, wherein, the marginal value is adjusted Circuit includes：

One voltage-current converter circuit, by the input voltage or its related signal, to be converted to One first electric current；

One first current modulating circuit, is coupled with the voltage-current converter circuit, to by this One electric current is converted to the one first amplification electric current with its direct ratio, and according to an overcurrent protection upper limit Electric current and the difference of the first amplification electric current, produce one second electric current；

One second current modulating circuit, is coupled with the first current modulating circuit, to by this Two electric currents are converted to the one second amplification electric current with its direct ratio, and according to an overcurrent protection lower limit Electric current and the difference of the second amplification electric current, produce one the 3rd electric current；

One the 3rd current modulating circuit, is coupled with the second current modulating circuit, to by this Three electric currents are converted to one the 3rd amplification electric current with its direct ratio, and minimum according to an overcurrent protection Marginal value electric current amplifies electric current with the 3rd, produces a modulation electric current；And

One current-to-voltage converting circuit, is coupled with the 3rd current modulating circuit, this to be adjusted Time-dependent current is converted to the overcurrent protection marginal value.

7. switched power supply as claimed in claim 6, wherein, second electric current is adjusted Become circuit and also on-off circuit is enabled including one, to enable signal according to one, decide whether to produce The second amplification electric current.

8. switched power supply as claimed in claim 7, wherein, the enable signal, During a blanking, determine to produce the second amplification electric current；And during the blanking outside, certainly It is fixed not produce the second amplification electric current；Wherein, the output voltage is to supply a display pannel, And the picture end of scan is opened to picture after before the one of the display pannel is relevant to during the blanking During beginning to scan.

9. switched power supply as claimed in claim 1, wherein, the marginal value is adjusted Circuit includes：

One input current sensing circuit, to sense the input current, and produces a current sense Signal；

One voltage-current converter circuit, by the current sense signal, to be converted to one first electric Stream；

One first current modulating circuit, is coupled with the voltage-current converter circuit, to by this One electric current is converted to and the one first of its direct ratio amplification electric current, and according to this first amplify electric current with The difference of one overcurrent protection lower current, produces one second electric current；

One second current modulating circuit, is coupled with the first current modulating circuit, to by this Two electric currents are converted to the one second amplification electric current with its direct ratio, and according to an overcurrent protection upper limit Electric current and the difference of the second amplification electric current, produce one the 3rd electric current；

One the 3rd current amplification circuit, is coupled with the second current modulating circuit, to by this Three electric currents are converted to one the 3rd amplification electric current with its direct ratio；

One the 4th current modulating circuit, is coupled with the 3rd current amplification circuit, to by this Three amplification electric currents are converted to one the 4th amplification electric current with its direct ratio, and according to an overcurrent protection Minimum marginal value electric current amplifies electric current with the 4th, produces a modulation electric current；And

One current-to-voltage converting circuit, is coupled with the 4th current modulating circuit, this to be adjusted Time-dependent current is converted to the overcurrent protection marginal value.

10. switched power supply as claimed in claim 9, wherein, second electric current is adjusted Become circuit and also on-off circuit is enabled including one, to enable signal according to one, decide whether to produce The second amplification electric current.

11. switched power supplies as claimed in claim 10, wherein, the enable signal, During a blanking, determine to produce the second amplification electric current；And during the blanking outside, certainly It is fixed not produce the second amplification electric current；Wherein, the output voltage is to supply a display pannel, And the picture end of scan is opened to picture after before the one of the display pannel is relevant to during the blanking During beginning to scan.

A kind of 12. control methods of switched power supply, the wherein switching power supply Device, an input voltage is converted to an output voltage, it is characterised in that the suitching type electricity The control method of source supply is included：

An at least power switch in one power stage circuit is operated according to an operation signal, should Input voltage is converted to the output voltage；And

According to the input voltage or an input current, produce and one overcurrent protection of accommodation Marginal value；

With the overcurrent protection marginal value, the input current is limited；And

When the input current exceedes the overcurrent protection marginal value, the power switch is not turned on；

Wherein, the input current flows through the power stage circuit.

The control method of 13. switched power supplies as claimed in claim 12, wherein, This produces simultaneously accommodation overcurrent protection and faces according to the input voltage or the input current The step of dividing value, includes：

When the input voltage declines, adaptability downgrades the overcurrent protection marginal value, and in When the input voltage drops to not higher than one the first input voltage of acquiescence, face the overcurrent protection Dividing value is maintained at the minimum marginal value of an overcurrent protection；And

When the input voltage rises, adaptability increases the overcurrent protection marginal value, and in The input voltage is risen to when being not less than second input voltage of acquiescence, faces the overcurrent protection Dividing value is maintained at an overcurrent protection maximum critical value；

The control method of 14. switched power supplies as claimed in claim 12, wherein, This produces simultaneously accommodation overcurrent protection and faces according to the input voltage or the input current The step of dividing value, includes：

When the input current rises, adaptability downgrades the overcurrent protection marginal value, and in When input current rising reaches default first input current, the overcurrent protection marginal value is made It is maintained at the minimum marginal value of an overcurrent protection, and maintains the input current default first defeated in this Enter electric current；And

When the input current declines, adaptability increases the overcurrent protection marginal value, and in When the input current drops to not higher than one default second input current, face the overcurrent protection Dividing value is maintained at an overcurrent protection maximum critical value；

The control method of 15. switched power supplies as claimed in claim 12, wherein, This produces simultaneously accommodation overcurrent protection and faces according to the input voltage or the input current The step of dividing value, also includes：The reason input current is too high and to be less than one pre- to make the input voltage If under-voltage locking level.

The control method of 16. switched power supplies as claimed in claim 12, wherein, The output voltage is to supply a display pannel, and this is according to the input voltage or the input electricity The step of stream, generation the accommodation overcurrent protection marginal value, includes：

During a blanking, according to the input voltage or the input current, the accommodation mistake Current protection marginal value；And

Outside during the blanking, the overcurrent protection marginal value presetting in a fixation is maintained Current protection marginal value.

The control method of 17. switched power supplies as claimed in claim 12, wherein, This is wrapped according to the step of the input voltage, generation the accommodation overcurrent protection marginal value Include：

By the input voltage or its related signal, one first electric current is converted to；

First electric current is converted to into the one first amplification electric current with its direct ratio, and it is excessively electric according to one Stream protection upper limit current and the difference of the first amplification electric current, produce one second electric current；

Second electric current is converted to into the one second amplification electric current with its direct ratio, and it is excessively electric according to one Stream protection lower current and the difference of the second amplification electric current, produce one the 3rd electric current；

3rd electric current is converted to into one the 3rd amplification electric current with its direct ratio, and it is excessively electric according to one The minimum marginal value electric current of stream protection and the 3rd electric current, produce a modulation electric current；And

The modulation electric current is converted to into the overcurrent protection marginal value.

The control method of 18. switched power supplies as claimed in claim 17, wherein, Second electric current is converted to the one second amplification electric current with its direct ratio for this, and according to an overcurrent The step of difference of protection lower current and the second amplification electric current, one three electric current of generation, also Including：Signal is enabled according to one, decides whether to produce the second amplification electric current.

The control method of 19. switched power supplies as claimed in claim 18, wherein, The enable signal, during a blanking, determines to produce the second amplification electric current；And in the blanking Outside period, decision does not produce the second amplification electric current；Wherein, the output voltage is to supply Picture scanning knot before the one of the display pannel is relevant to during one display pannel, and the blanking During after Shu Zhiyi, picture starts scanning.

The control method of 20. switched power supplies as claimed in claim 12, wherein, This is wrapped according to the step of the input current, generation the accommodation overcurrent protection marginal value Include：

The input current is sensed, and produces a current sense signal；

By the current sense signal, one first electric current is converted to；

First electric current is converted to and the one first of its direct ratio amplification electric current, and according to this first Amplify the difference of electric current and an overcurrent protection lower current, produce one second electric current；

Second electric current is converted to into the one second amplification electric current with its direct ratio, and it is excessively electric according to one Stream protection upper limit current and the difference of the second amplification electric current, produce one the 3rd electric current；

3rd electric current is converted to into one the 3rd amplification electric current with its direct ratio；

3rd amplification electric current is converted to and the one the 4th of its direct ratio amplification electric current, and according to one The minimum marginal value electric current of overcurrent protection amplifies electric current with the 4th, produces a modulation electric current；With And

The control method of 21. switched power supplies as claimed in claim 20, wherein, The step of second electric current is converted to the one second amplification electric current with its direct ratio for this also includes：Root Signal is enabled according to one, decides whether to produce the second amplification electric current.

The control method of 22. switched power supplies as claimed in claim 21, wherein, The enable signal, during a blanking, determines to produce the second amplification electric current；And in the blanking Outside period, decision does not produce the second amplification electric current；Wherein, the output voltage is to supply Picture scanning knot before the one of the display pannel is relevant to during one display pannel, and the blanking During after Shu Zhiyi, picture starts scanning.

Control circuit in a kind of 23. switched power supplies, to produce an operation signal, Switch at least one power switch in the switched power supply, and an input voltage is changed For an output voltage, it is characterised in that the control circuit includes a marginal value adjustment circuit, use According to the input voltage, to produce and one overcurrent protection marginal value of accommodation, to limit The input current, wherein, the marginal value adjustment circuit is included：

One the 3rd current modulating circuit, is coupled with the second current modulating circuit, to by this Three electric currents are converted to one the 3rd amplification electric current with its direct ratio, and minimum according to an overcurrent protection Marginal value electric current and the 3rd electric current, produce a modulation electric current；And

One current-to-voltage converting circuit, is coupled with the 3rd current modulating circuit, this to be adjusted Time-dependent current is converted to the overcurrent protection marginal value；

The wherein overcurrent protection marginal value, to limit the input current；

Wherein the control circuit is not led when the input current exceedes the overcurrent protection marginal value Lead to the power switch.

Control circuit in 24. switched power supplies as claimed in claim 23, wherein, When the input voltage declines, adaptability downgrades the overcurrent protection marginal value, and defeated in this Enter voltage drop to not higher than one acquiescence the first input voltage when, make the overcurrent protection marginal value It is maintained at the minimum marginal value of an overcurrent protection；And when the input voltage rises, adaptability is adjusted The overcurrent protection marginal value is risen, and is risen in the input voltage and is not less than an acquiescence second During input voltage, the overcurrent protection marginal value is made to be maintained at an overcurrent protection maximum critical value.

Control circuit in a kind of 25. switched power supplies, to produce an operation signal, Switch at least one power switch in the switched power supply, and an input voltage is changed For an output voltage, it is characterised in that the control circuit includes a marginal value adjustment circuit, use According to the input current, to produce and one overcurrent protection marginal value of accommodation, to limit The input current, wherein, the marginal value adjustment circuit is included：

Control circuit in 26. switched power supplies as claimed in claim 25, wherein, When the input current rises, adaptability downgrades the overcurrent protection and faces the marginal value adjustment circuit Dividing value, and when the input current rises and reaches default first input current, make this excessively electric Stream protection marginal value is maintained at the minimum marginal value of an overcurrent protection, and maintain the input current in Default first input current；And when the input current declines, adaptability increases the overcurrent Protection marginal value, and when the input current drops to not higher than one default second input current, The overcurrent protection marginal value is made to be maintained at an overcurrent protection maximum critical value；

Control circuit in 27. switched power supplies as described in claim 23 or 25, Wherein, control circuit accommodation overcurrent protection marginal value so that the input voltage It is not less than an acquiescence under-voltage locking level.

Control circuit in 28. switched power supplies as described in claim 23 or 25, Wherein, the output voltage is to supply a display pannel, and during a blanking, the control Circuit according to the input voltage or the input current, the accommodation overcurrent protection marginal value； And during the blanking outside, the control circuit maintains the overcurrent protection marginal value in a fixation Default overcurrent protection marginal value.