CN105655983B - The guard method of output short-circuit and protection circuit - Google Patents
The guard method of output short-circuit and protection circuit Download PDFInfo
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- CN105655983B CN105655983B CN201610168690.0A CN201610168690A CN105655983B CN 105655983 B CN105655983 B CN 105655983B CN 201610168690 A CN201610168690 A CN 201610168690A CN 105655983 B CN105655983 B CN 105655983B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
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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
- H02M1/36—Means for starting or stopping converters
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- Power Engineering (AREA)
- Protection Of Static Devices (AREA)
- Dc-Dc Converters (AREA)
Abstract
A kind of protection circuit of output short-circuit; for controlling start-up circuit to the charging of shunt capacitance C1; to carry out interval detection to the Switching Power Supply that output short-circuit occurs and restart control; the protection circuit; with input terminal and shutdown output end; input terminal, when output short-circuit occurs for Switching Power Supply, forms detection delay by the discharge process time of shunt capacitance via controller for connecting with the output end of start-up circuit, one end of shunt capacitance C1 and feeder ear VDD；Subsequent Switching Power Supply stops working, and into the time of having a rest, shunt capacitance successively carries out a charging process, secondary discharge process and recharging process, and before the recharging process of shunt capacitance is completed, Switching Power Supply does not work；Wherein, shunt capacitance is discharged through protection circuit during secondary discharge；When the recharging process of shunt capacitance is completed, the time of having a rest terminates, and protection circuit cancels cut-off signals, reset switch power supply.
Description
Technical field
The present invention relates to Switching Power Supplies, the in particular to guard method of the output short-circuit of Switching Power Supply and protection circuit.
Background technique
When Switching Power Supply band starts compared with large capacitive load, since capacitance voltage cannot be mutated, the foundation of output voltage
Time is long, and controller needs work long hours to be completed to start with control switch power supply.And theoretically, output short-circuit is with infinite
Big capacitor start, in order to distinguish capacitive load starting and output short-circuit, usual controller can directly or indirectly detect output electricity
Pressure, if being still below setting value in preset time (hereinafter referred to as detection delay) interior output voltage, is determined as output short-circuit.If nothing
Specified otherwise, " short circuit " being mentioned above also are the output short-circuit of Switching Power Supply, and " output voltage " is also the output of Switching Power Supply
Voltage, " power supply " are also Switching Power Supply.
In order to meet capacitive load requirement, this detection delay is about 80ms~160ms, is even needed in some applications
Up to 400ms, therefore even if short trouble has occurred and that, Switching Power Supply will also continue working in detection delay, this will be produced
Heat amount；And under most of applications, it is desirable that Switching Power Supply can be restored to work normally automatically after short trouble exclusion, i.e.,
The case where exporting it is required that Switching Power Supply intermittently detects, therefore working in detection delay can repeatedly occur until troubleshooting；If
The time (hereinafter referred to as time of having a rest) that Switching Power Supply stops working is insufficient, then the heat generated can be accumulated, and makes switch electricity
Cause thermal damage is crossed in source.
In order to avoid Switching Power Supply crosses cause thermal damage, achieve the purpose that short-circuit protection, forefathers are made that comparable more effort.Such as
Shown in Fig. 1, after power supply output short-circuit, auxiliary winding can not power to controller, and shunt capacitance C1 discharges to maintain controller work
Make, until controller is under-voltage, stopping output drive signal, Switching Power Supply stops working the decline of capacitor C1 voltage；Start-up circuit with
Lesser charging current gives shunt capacitance C1 charging, and controller is allowed to restart, output drive signal, Switching Power Supply work again
Make.The method exactly lengthens the time of having a rest using the principle of low current charge time length to radiate to Switching Power Supply, but simultaneously
Also the starting time of power supply is increased.
According to capacitor charge and discharge formulaAnd above-mentioned principle can obtain, the detection delay T of above-mentioned short-circuit protection methodD
With time of having a rest TR
Wherein, C1For the capacitance of shunt capacitance C1, Δ V be controller restart voltage threshold and brownout threshold it
Difference, IRunElectric current needed for being worked normally for controller, ICFor the charging current of start-up circuit.Comprehensive (1) and (2) Shi Ke get is short
Duty ratio (being hereinafter referred to as restarted automatically dynamic duty ratio) D of road protection lower switch power supply discontinuous operationRST
In charging current I it can be seen from (3) formulaCSmaller (such as IC=80uA) application, the above method can obtain
It is lesser to be restarted automatically dynamic duty ratio DRST, to realize that Switching Power Supply sufficiently radiates, but charging current is small and when can bring starting
Between long drawback.In the application harsh to starting time requirement, power supply manufacturer can use big charging current (such as IC≥IRun)
Start controller, if continuing to use above-mentioned short-circuit protection method, being restarted automatically dynamic duty ratio will be greater than 50%, may make to switch
Power supply is unable to fully radiate in short trouble, and then crosses cause thermal damage because of heat build-up.Which limits answering for this method
With.
In addition to above-mentioned short-circuit protection method, also some controllers are to detect output electricity indirectly by output voltage feed circuit
Pressure, if detected value be lower than given threshold, by setting detection delay and time of having a rest when timer with complete with it is above-mentioned
Similar short-circuit protection process.In general, being more reliably restarted automatically dynamic duty ratio less than 20%, and it is based on capacitive load energy
The considerations of power, the design value of detection delay are about 80ms~160ms；Based on the considerations of heat dissipation, time of having a rest corresponding design value
About 1s~2s；And controller internal oscillator frequency is generally in the order of magnitude of kHz, such as in the application of AC input,
Controller oscilator frequency is 80kHz, i.e., the period is 12.5us, therefore to realize detection delay and time of having a rest, and timer needs
The timing that 80000 times are completed based on cycle oscillator needs 16~17 D touchings if timer is designed with d type flip flop
Send out device.
These d type flip flops and its required line area can greatly increase the area of controller, so increase controller at
This, especially in the technique that can integrate 700V start-up circuit, the characteristic size of these techniques is generally 0.8um~1um, increases
Area can be more.And this method defines detection delay, also just limits maximum capacitive load, and then limits control
The application range of device.
In conclusion in order to improve the reliability of short-circuit protection, the application range of extending controller, while also to minimize
Controller area, reduces cost, it is necessary to design a kind of novel short-circuit protection circuit.
Summary of the invention
(1) technical problems to be solved
1, a kind of short-circuit protection method is provided, when can obtain suitable detection delay and rest by simply designing
Between, while it is small to have both circuit area again, the advantages that having a wide range of application.
2, a kind of protection circuit using above-mentioned short-circuit protection method is provided.
(2) technical solution
The technical solution that the present invention solves above-mentioned first technical problem is:
A kind of output short-circuit protection method, includes the following steps:
When output short-circuit occurs for Switching Power Supply, the discharge process time for carrying out shunt capacitance via controller is as automatic
Restart the detection delay of duty ratio；It can be seen that the present invention can design detection delay by shunt capacitance, with extending controller
Application range；Before protection circuit revocation cut-off signals, charged by input voltage to shunt capacitance, then pass through protection electricity
Road is shunt capacitance electric discharge, so that shunt capacitance charges, generates the electricity of height alternating variation in feeder ear VDD to discharge cycle
Pressure, and then the charging process for making shunt capacitance alternate in the discharge process with detection delay is to the charging process time of phase every other week
As it is restarted automatically the time of having a rest of dynamic duty ratio.
As a further improvement of the present invention, the time of having a rest for being restarted automatically dynamic duty ratio, with detection delay
The charging process that discharge process alternates to the phase every other week charging process time overall length, be to start from shunt capacitance via controller
Discharge process complete when, charging process time and delay time, delay time including shunt capacitance pass through to side
The periodicity of the charge and discharge process of road capacitor is counted to set.
As a further improvement of the present invention, it is restarted automatically the time of having a rest of dynamic duty ratio, by filling to shunt capacitance
Electric process counted twice to set, that is, includes the charging process time and the charge and discharge of a shunt capacitance of a shunt capacitance
The electric overall process time.The time of having a rest is started with end time of detection delay, and by counting mode come when setting
Between length, that is, be restarted automatically dynamic duty ratio it is specific setting include the following steps,
As a further improvement of the present invention, when output short-circuit occurs for Switching Power Supply, by shunt capacitance via controller
Discharge process time forms detection delay；The time of having a rest is subsequently entered, the primary charging of shunt capacitance is started, in bypass electricity
Before the charging process held is completed, counter output is maintained high level；It is completed in a charging process of shunt capacitance
When, counter carry, counter output switching activity is low level；Shunt capacitance starts secondary discharge process and recharging therewith
Process, before the recharging process of shunt capacitance is completed, counter output is maintained low level；Wherein, secondary discharge mistake
Shunt capacitance is through protecting circuit to discharge in journey；When the recharging process of shunt capacitance is completed, counter is counted, meter
Number device output switching activity is high level, and the time of having a rest terminates, and protection circuit cancels cut-off signals, reset switch power supply.Switching Power Supply
It can use the time of having a rest sufficiently to radiate, avoided cause thermal damage, even if the charging current of start-up circuit is very big, Switching Power Supply
There is time enough to radiate.If Switching Power Supply output short-circuit failure does not exclude, shunt capacitance returns to primary electric discharge again
Process, protection circuit repeats the above process, in cycles until troubleshooting.Therefore Switching Power Supply can be certainly after troubleshooting
Restore normally to export dynamicly.
As a further improvement of the present invention, described to be restarted automatically duty ratio, it then follows proportionate relationship, by operating current
IRun, charging current ICAnd the operating current I of protection circuitSIt determines, specifically follows following relational expression:
Wherein, DRSTTo be restarted automatically dynamic duty ratio, TDFor detection delay, TRFor the time of having a rest.
The present invention also provides a kind of protection circuits of output short-circuit, for controlling start-up circuit filling to shunt capacitance C1
Electricity protects circuit, has input terminal and shutdown to carry out interval detection to the Switching Power Supply that output short-circuit occurs and restart control
Output end, input terminal with the output end of start-up circuit, one end of shunt capacitance C1 and feeder ear VDD for connecting, in switch electricity
When output short-circuit occurs for source, the discharge process time for carrying out shunt capacitance via controller is the inspection for being restarted automatically dynamic duty ratio
Survey delay；Then protection circuit revocation cut-off signals before, input voltage give shunt capacitance charging, then by protection circuit be side
The electric discharge of road capacitor, so that the charging of shunt capacitance, the voltage alternately changed in feeder ear VDD generation height to discharge cycle,
And then the charging process for making shunt capacitance alternate in the discharge process with detection delay to the phase every other week charging process time i.e.
For the time of having a rest for being restarted automatically dynamic duty ratio；At the end of between during the break, protection circuit cancels cut-off signals, to restart out
Powered-down source.
As the further improvement of protection circuit of the invention, the protection circuit further includes counter, for bypass
The charging-discharging cycle number of capacitor is counted；The time of having a rest for being restarted automatically dynamic duty ratio, in the electric discharge with detection delay
The charging process that process alternates to the phase every other week charging process time overall length, be to start from putting for shunt capacitance via controller
When electric process is completed, charging process time and delay time, counter including shunt capacitance pass through to shunt capacitance
The periodicity of charge and discharge process counted to set delay time.
As the further improvement of protection circuit of the invention, the protection circuit further includes counter, the protection electricity
Road is restarted automatically dynamic duty ratio, sets the time of having a rest by counter, when output short-circuit occurs for Switching Power Supply, by bypassing
The discharge process time of capacitor via controller forms detection delay；The primary charging for then beginning to shunt capacitance, is bypassing
Before charging process of capacitor is completed, counter output is maintained high level；It is complete in a charging process of shunt capacitance
When, counter carry, counter output switching activity is low level；Shunt capacitance starts secondary discharge process and secondary fills therewith
Electric process, before the recharging process of shunt capacitance is completed, counter output is maintained low level；Wherein, secondary discharge
Shunt capacitance is through protecting circuit to discharge in the process；When the recharging process of shunt capacitance is completed, counter is counted,
Counter output switching activity is high level, and the time of having a rest terminates, and protection circuit cancels cut-off signals, reset switch power supply.
As the further improvement of protection circuit of the invention, the protection circuit, including comparator 111, NOT gate 112,
Counter 113 and NAND gate 114, the positive input energy of comparator 111 select to be the high voltage limit of access according to its output level,
Or access lower bound voltage, anti-phase input are connect with feeder ear VDD, export the input with NOT gate 112 and counter 113 respectively
Connection；The enabled output end as protection circuit is also drawn in the output of comparator 111, gives starting electricity to export enable signal
Road；First input of the output of NOT gate 112 as NAND gate 114, exporting for counter 113 are defeated as the second of NAND gate 114
Enter, shutdown end of the output of NAND gate 114 as protection circuit.The counter 113 can be used 1 d type flip flop and realize,
The present invention is not needed to increase additional trigger to design and be stopped with what detection delay matched by cleverly logical process
The time is ceased, can farthest reduce area, save the cost, while switch power supply system design difficulty can also be simplified.
The present invention provides a kind of controller of Switching Power Supply again, including above-mentioned protection circuit and start-up circuit, the control
The pin (D) that there is device processed the input terminal of self-start circuit to draw, for the of the same name of the transformer primary winding with Switching Power Supply
End connection；The input terminal of the protection circuit and the output end of start-up circuit connect, and are incorporated as feeder ear (VDD).
The above are the primitive technology schemes of protection circuit, and specific working principle and correlation analysis will be embodied below
Mode part detailed description.The circuit solutions are corresponding with method scheme, and the principle of each scheme or technical characteristic is made
With and bring beneficial effect it is identical, details are not described herein.
" output " of the present invention refers to the working condition that signal activation is controlled to late-class circuit at effective status,
Such as " output cut-off signals, shutdown driver etc. functional circuits " what is referred to is exactly to activate cut-off signals, control the function such as driver
Energy circuit, makes its work in off state.Conversely, " revocation " refers to becoming signal into invalid state again, such as " revocation shutdown letter
Number, reset switch power supply " what is referred to is exactly to become cut-off signals again invalid state, so that the functional circuits such as driver restore to open
State, reset switch power supply." effective status " refers to " high level ", " low level ", " rising edge " and " failing edge "
Etc. any one state in known signals feature, and " invalid state " refer to it is logically opposite with " effective status "
Vertical state.
Each technical solution of method and circuit of the invention and principle, effect of technical characteristic etc. are analyzed above,
Now beneficial effects of the present invention are summarized as follows:
1, protection can be effectively performed when short trouble occurs in Switching Power Supply, be restarted automatically dynamic duty ratio and do not started
The limitation of circuit charging current can fully ensure that Switching Power Supply only cause thermal damage, can automatically restore just again after troubleshooting
Often output.
2, have a wide range of application, be particularly suitable for applications in the big occasion of start-up circuit charging current.
3, circuit structure is simple, and area is small, can further save the cost of controller, improves integrated level.
4, the difficulty that can simplify system design and debugging, in design, Power Engineer is only needed according to capacitive load
It is required that determining shunt capacitance C1, the time of having a rest to match with detection delay can be obtained, high reliablity can be simply obtained
Be restarted automatically dynamic duty ratio, it is ensured that Switching Power Supply will not cross cause thermal damage when short-circuit.
Detailed description of the invention
Fig. 1 is the circuit diagram for realizing short-circuit protection using controller in the prior art；
Fig. 2 is the application circuit schematic diagram for applying the controller of short-circuit protection method of the invention；
Fig. 3 is the schematic block circuit diagram of the controller of the embodiment of the present invention one, wherein protection circuit and start-up circuit are integrated
In control
In device processed；
Fig. 4 is the circuit diagram of the protection circuit of the controller of the embodiment of the present invention one；
Fig. 5 is the signal timing diagram of the controller of the embodiment of the present invention one；
Fig. 6 is the schematic block circuit diagram of the controller of the embodiment of the present invention two, wherein protect circuit integration in controller,
Starting
Circuit is external circuits.
Fig. 7 is the signal timing diagram of the controller of the embodiment of the present invention two.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further described.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and do not have to
It is of the invention in limiting.
Embodiment 1
Fig. 2 show the application circuit schematic diagram for applying the controller 100 of short-circuit protection method of the present invention.Such as Fig. 2 institute
Show, the pin VDD of controller 100 (being hereafter also known as feeder ear VDD) is connect with diode D1 cathode, and furthermore feeder ear VDD is also
It is connect through shunt capacitance C1 with reference；Primary side winding NP of the pin D of controller 100 through transformer T and Switching Power Supply input
Voltage VINIt connects, herein Switching Power Supply input voltage VINIt can be DC voltage, the input voltage after being also possible to rectification；Draw
Foot CS is through resistance RCSIt connects with reference to ground, pin GND directly with reference is connect；Pin FB is connect with output voltage feed circuit 10,
For detecting output voltage and then controller 100 being allowed to realize loop control, in the present invention, output voltage feed circuit 10 is not joined
With output short circuit protection process, the circuit is hereafter no longer referred to.The power switch tube of application circuit shown in Fig. 2 has been integrated with
In controller 100, the connection relationship of other elements in the power switch tube and Fig. 2 is identical as common circuit of reversed excitation, and with this
It invents unrelated, hereafter repeats no more.
Fig. 3 show in the controller 100 of the embodiment of the present invention one functional block diagram relevant to protection circuit 110.Such as Fig. 3
Shown, the circuit integrated in controller 100 includes protection circuit 110 and start-up circuit 120, other circuits of controller 100 are not
The principle of the present invention explanation is influenced, Fig. 3 is not showed that.Such as controller 100 further includes the functions such as reference circuit and driver electricity
Road, wherein reference circuit is to generate high voltage limit V mentioned belowHWith lower bound voltage VL, reference circuit structure and its voltage
Production method is unrelated with technical problem solved by the invention；Driver, to control the switch state of power switch tube, in turn
Control switch power supply carries out energy conversion.Switching Power Supply input voltage VINStart-up circuit is input to through primary side winding NP, pin D
120, start-up circuit 120 is by Switching Power Supply input voltage VINIt is converted into charging current ICIt is filled to the shunt capacitance C1 of feeder ear VDD
Electricity, furthermore the control terminal of start-up circuit 120 is connect with protection circuit 110, to the enable signal exported according to protection circuit 110
The state of EN controls charging current ICOn-off；The input of protection circuit 110 is connect with feeder ear VDD, to detect VDD's
Voltage, and then adjust the state of cut-off signals SD (Shut Down)；Cut-off signals SD can turn off the functional circuits such as driver,
That is, being off when cut-off signals SD is in effective status by functional circuits such as cut-off signals SD control drivers
State, only reference circuit and protection circuit 110 in consumption energy, start-up circuit 120 converts V in controller 100INEnergy simultaneously
It is stored in shunt capacitance C1, does not consume energy, therefore the power consumption of controller 100 is greatly decreased, energy decrease speed is also substantially put
It is slow.To simplify the explanation, hereafter the energy that reference circuit consumes is included in protection circuit, i.e., protection electricity mentioned below
Road operating current ISOperating current comprising reference circuit；Likewise, controller 100 works normally required electric current IRunAlso
Included IS, hereafter repeat no more.
Fig. 4 show the circuit diagram of the protection circuit 110 of the embodiment of the present invention 1.As shown in figure 4, protection circuit 110
Including comparator 111, NOT gate 112, counter 113 and NAND gate 114.111 positive of comparator is inputted according to the defeated of comparator 111
Level is the high voltage limit V of access to select outH, or access lower bound voltage VL, in embodiment 1, when comparator 111 exports height
When level, the first normal phase input end VP1 is selected, i.e. selection access height is rationed the power supply flat VH, when exporting low level, select the second positive
Input terminal VP2, i.e. selection access lower bound voltage VL；Its anti-phase input is connect with feeder ear VDD, to detect vdd voltage, is exported
It is connected respectively with the input of NOT gate 112 and counter 113；First input of the output of NOT gate 112 as NAND gate 114, counts
Second input of the output of device 113 as NAND gate 114, the output of NAND gate 114 is the cut-off signals SD.Implementing
In example 1, under original state, the input of 111 positive of comparator and high voltage limit VHConnection, later when comparator 111 exports high level
When, positive inputs and high voltage limit VHConnection；When exporting low level, with lower bound voltage VLConnection.The output of comparator 111 is drawn again
Out as enabled output end, for exporting enable signal EN, to control start-up circuit 120, to pass through control start-up circuit 120
To control the on-off of charging current Ic, and then the charging rhythm of control shunt capacitance C1.
Fig. 5 show the signal schematic representation of the embodiment of the present invention 1.Fig. 5 does not draw signal schematic representation in strict accordance with ratio,
And most of details is had ignored, such as ignore factors influence caused by signal such as dead resistance of the ring of leakage inductance, winding,
It is further assumed that primary side inductance always works at continuous conduction mode to omit LC resonance waveform.Cut-off signals SD's of the invention
Effective status is high level, its opposite invalid state is low level, i.e., in the voltage V of cut-off signals SDSDWhen for high level, close
Functional circuits, the Switching Power Supplies such as disconnected driver do not work, and in the voltage V of cut-off signals SDSDWhen for low level, opening driver
Equal functional circuits, Switching Power Supply work.The working principle of circuit 110 is protected below with reference to the present invention will be described in detail shown in Fig. 5.
As shown in figure 5, being supplied by auxiliary winding NA to controller 100 after controller 100 is completed to start and work normally
Electricity, the voltage V of feeder ear VDDDDMaintain high voltage limit VHWith lower bound voltage VLBetween, the voltage V of enable signal ENENFor low electricity
It is flat, first input of the high level as NAND gate 114, the output voltage V of counter are converted into through NOT gate 112QFor high level, i.e.,
NAND gate 114 second input also be high level, therefore as shown in figure 5, at this time NAND gate 114 export cut-off signals SD electricity
Press VSDFor low level, the functional circuits such as driver are worked normally, the voltage V of pin DDImpulse waveform is presented；
When Switching Power Supply breaks down, for this sentences Switching Power Supply output short-circuit failure, the output voltage of Switching Power Supply
It is zeroed because of short circuit, so that auxiliary winding can not power to controller 100 again, shunt capacitance C1 releases energy to maintain to control
The work of device 100 processed, voltage VDDIt begins to decline；
Work as VDD≤VLWhen, enable signal EN overturning, VENBecome high level, VQIt is still high level, therefore VSDIt is turned into high electricity
It is flat, to turn off the functional circuits such as driver, VDPresented no longer in the form of impulse waveform, Switching Power Supply stops working, no longer into
The conversion of row energy；And simultaneously because VENBecome high level, start-up circuit 120 is enabled, by input voltage VINIt is converted into charging current
ICIt charges to shunt capacitance C1, VDDIt begins to ramp up；
Work as VDD≥VHWhen, VENBecome low level, that is, produces failing edge, counter realizes " carry " operation, so that VQBecome
For low level, therefore VSDIt is still maintained at high level, Switching Power Supply does not work still, and auxiliary winding does not provide energy；And due to VENBecome
At low level, start-up circuit 120 is not enabled, and charging terminates, and shunt capacitance C1 is by protecting circuit slowly to discharge until VDD≤VL,
VENBecome high level, start-up circuit is enabled, again to shunt capacitance C1 charging until VDD≥VH, at this moment VENDecline is generated again
Edge, counter " carry ", so that VQBecome high level, and then makes VSDBecoming low level again, the functional circuits such as driver reopen,
Switching Power Supply work, carries out energy conversion；
If short trouble does not exclude, shunt capacitance C1 can still release energy to maintain the work of controller 100, voltage VDDUnder
Drop is until VDD≤VL, then protect circuit 110 that can repeat the above process, in cycles until troubleshooting.
As shown in figure 5, VSDHigh level lasting time TRAs time of having a rest, Switching Power Supply can use time of having a rest TR
Sufficiently radiated, and VDDBy high voltage limit VHDrop to lower bound voltage VLAnd VSDFor low level time TDAs detection is prolonged
When, the two times are alternately present during protection, so that energy wink quick-recovery is normally defeated after troubleshooting for Switching Power Supply
Out.
In conclusion the present invention detects the output state of power supply by auxiliary winding indirectly, if output short-circuit auxiliary around
Group can not energize, then shunt capacitance is discharged to VDD≤VL, with " informing " controller 100, " generation of output short-circuit failure ".
Detection delay T of the inventionDWith time of having a rest TRIt can be debugged by shunt capacitance C1.In embodiment 1, it controls
Device 100 works normally required electric current IRun=800uA, high voltage limit VH=18V, lower bound voltage VL=8V, start-up circuit 120
Charging current IC=2mA protects the operating current I of circuit 110S=80uA.It can according to capacitor charge and discharge formula and above-mentioned principle
, detection delay TDMeet following expression formula
Time of having a rest TRMeet following expression formula
Composite type (4) and formula (5) can obtain, and be restarted automatically dynamic duty ratio DRST-Meet following expression formula
Compared with the formula (3) of the prior art, the molecule of 1 formula of embodiment (6) is no longer by charging current ICIt determines, but depends on
In the operating current I of protection circuit 110S；Simultaneously it can be seen that I from the expression formula of formula (6) denominatorCAnd ISDifference it is bigger, point
Female closer IS+IRun；Such as in ICMuch larger than ISApplication under, after engineering approximation, be restarted automatically dynamic duty ratio DRSTOnly depend on
In IRunAnd IS, so reduce DRSTOriginal intention not contradiction with power on time is reduced, has been solved perfectly the technology of the prior art
Limitation.The beneficial effect of formula (6) essentially by counter to shunt capacitance charging-discharging cycle count so that the time change again and
It introduces.
In order to meet the needs of capacitive load, embodiment 1 will test delay TDIt is designed as 100ms, then according to formula (4) and upper
State data, it can be deduced that C1=8uF, time of having a rest T can be obtained by then bringing formula (5) intoR=1.08s is restarted automatically dynamic duty ratio
DRST=8.5%, it is sufficient to meet the cooling requirements of the Switching Power Supply short-circuit protection of most of power grade.
By formula (6) it is found that those skilled in the art can rationally design control according to practical situations
Device works normally required electric current IRun, charging current ICAnd the operating current I of protection circuitS, obtain and be suitably restarted automatically
Dynamic duty ratio DRSTMeet relevant design requirement under other application field, these all should belong to thought of the invention, all fall within
Within rights protection scope of the present invention.
In conclusion the counter of the embodiment of the present invention 1 is substantially a binary counter, it can on circuit structure
To use 1 d type flip flop to realize, compared with the prior art uses " 16~17 d type flip flops ", circuit area is substantially reduced,
The cost of controller can be further saved, integrated level is improved.And on the basis of excessively not increasing circuit area, this technology neck
The those of ordinary skill in domain can increase the digit of counter according to practical situations, come obtain it is smaller be restarted automatically it is dynamic
Duty ratio DRST, these all should belong to thought of the invention, all fall within rights protection scope of the present invention.
Embodiment 2
Fig. 6 show in the controller 200 of the embodiment of the present invention 2 functional block diagram relevant to protection circuit 210, such as Fig. 6
Shown, unlike the first embodiment, controller 200 is opened without built-in start-up circuit, the pin VDD of controller 200 through plug-in
Dynamic circuit 20 and Switching Power Supply input voltage VINConnection, the connection relationship of auxiliary winding NA, diode D1 and shunt capacitance C1 with
Embodiment 1 is identical, repeats no more.The application circuit and pin connection relationship of controller 200 are similar to Example 1, and do not influence
Principle illustrates below, hereafter repeats no more, Fig. 6 is not showed that yet.
The start-up circuit 20 of embodiment 2 can be according to the voltage V of controller 200DDTo control the charging electricity of shunt capacitance C1
The on-off of stream:
Work as VDD≤ 5V, start-up circuit 20 charge to shunt capacitance C1；Work as VDD>=20V, start-up circuit 20 stop giving bypass electricity
Hold C1 charging, the charging current I of start-up circuit 20C=6mA.
Same as Example 1, controller 200 works normally required electric current IRun=800uA < IC, high voltage limit VH=
18V, lower bound voltage VL=8V protects the operating current I of circuit 210S=80uA protects the circuit structure of circuit 210, work former
It manages same as Example 1, but circuit 210 is protected not export enable signal EN.
Fig. 7 show the signal schematic representation of the embodiment of the present invention 2.As shown in fig. 7,2 difference from Example 1 of embodiment
It also resides in, works as VDDSlightly smaller than lower bound voltage VLOr VDDSlightly larger than high voltage limit VHWhen, start-up circuit 20 will not all act immediately, and
It is that must wait until voltage VDDWhen reaching given threshold (5V or the 20V) of start-up circuit 20, the state (on-off) of charging current is
It can change, i.e., as shown in fig. 7, when cut-off signals SD becomes low level, VDDSlightly larger than high voltage limit VH, after Switching Power Supply is restarted,
Even if output short-circuit failure does not exclude yet, start-up circuit also can be with electric current IC- IRunContinue to be charged to shunt capacitance C1 until VDD
=20V.Therefore the detection delay T of embodiment 2DMeet following expression formula
Time of having a rest TRMeet following expression formula
If will detection delay TDIt is designed as 100ms, then can calculate C1=6.5uF, time of having a rest TR=1.49s, automatic weight
Start duty ratio DRST=6.3%, it can satisfy the Switching Power Supply cooling requirements of more high-power grade.
The above is only the preferred embodiment of the present invention, it is noted that above preferred embodiment is not construed as to this hair
Bright limitation.Above content according to the invention is not departing from this hair using the ordinary technical knowledge and customary means of this field
Under the premise of bright above-mentioned basic fundamental thought, the present invention can also make the modification, replacement or change of other diversified forms, these
It all falls within rights protection scope of the present invention.
Claims (10)
1. a kind of guard method of output short-circuit, the setting for being restarted automatically dynamic duty ratio include the following steps,
When output short-circuit occurs for Switching Power Supply, the discharge process time for carrying out shunt capacitance via controller is to be restarted automatically
The detection delay of dynamic duty ratio；
It before protection circuit revocation cut-off signals, is charged by input voltage to shunt capacitance, then passing through protection circuit is side
The electric discharge of road capacitor, so that the charging of shunt capacitance, the voltage alternately changed in feeder ear VDD generation height to discharge cycle,
And then the charging process time of the charging process to be alternated with shunt capacitance in the discharge process with detection delay to phase every other week are made
For the time of having a rest for being restarted automatically dynamic duty ratio.
2. the guard method of output short-circuit according to claim 1, it is characterised in that: described to be restarted automatically dynamic duty ratio
Time of having a rest, in the time overall length of the charging process of the charging process that the discharge process with detection delay alternates to phase every other week,
Be start from shunt capacitance via controller discharge process complete when, charging process time including a shunt capacitance and prolong
Slow time, delay time are counted to set by the periodicity of the charge and discharge process to shunt capacitance.
3. the guard method of output short-circuit according to claim 1, it is characterised in that: described to be restarted automatically dynamic duty ratio
Time of having a rest count twice by the charging process to shunt capacitance to set, that is, includes the charging of a shunt capacitance
The charge and discharge overall process time of process time and a shunt capacitance.
4. the guard method of output short-circuit according to any one of claim 1 to 3, it is characterised in that: the automatic weight
Start the time of having a rest of duty ratio, started with the end time of detection delay, and by counting mode come setting time length,
Be restarted automatically dynamic duty ratio it is specific setting include the following steps,
When output short-circuit occurs for Switching Power Supply, detection is formed by the discharge process time of shunt capacitance via controller and is prolonged
When；
The time of having a rest is subsequently entered, the primary charging of shunt capacitance is started, before a charging process of shunt capacitance is completed,
Counter output is maintained high level；
When a charging process of shunt capacitance is completed, counter carry, counter output switching activity is low level；It is other therewith
Road capacitor starts secondary discharge process and recharging process, before the recharging process of shunt capacitance is completed, counter
Output is maintained low level；Wherein, shunt capacitance is discharged through protection circuit during secondary discharge；
When the recharging process of shunt capacitance is completed, counter is counted, and counter output switching activity is high level, when rest
Between terminate, protection circuit cancel cut-off signals, reset switch power supply.
5. the guard method of output short-circuit according to claim 4, it is characterised in that: it is described to be restarted automatically duty ratio, it abides by
The proportionate relationship followed, by operating current IRun, charging current ICAnd the operating current I of protection circuitSIt determines, specifically follows as follows
Relational expression:
Wherein, DRSTTo be restarted automatically dynamic duty ratio, TDFor detection delay, TRFor the time of having a rest.
6. a kind of protection circuit of output short-circuit, for controlling start-up circuit to the charging of shunt capacitance C1, come to exporting
The Switching Power Supply of short circuit carries out interval detection and restarts control, it is characterised in that: the protection circuit has input terminal and shutdown
Output end, input terminal are used to connect with the output end of start-up circuit, one end of shunt capacitance C1 and feeder ear VDD,
When output short-circuit occurs for Switching Power Supply, the discharge process time for carrying out shunt capacitance via controller is to be restarted automatically
The detection delay of dynamic duty ratio；
Then before protection circuit revocation cut-off signals, input voltage charges to shunt capacitance, then is by the protection circuit
Shunt capacitance electric discharge, so that the charging of shunt capacitance, the electricity alternately changed in feeder ear VDD generation height to discharge cycle
Pressure, and then the charging process to be alternated with shunt capacitance in the discharge process with detection delay is to the charging process time of phase every other week
As the time of having a rest for being restarted automatically dynamic duty ratio；
At the end of between during the break, the protection circuit cancels cut-off signals, to reset switch power supply.
7. the protection circuit of output short-circuit according to claim 6, it is characterised in that: the protection circuit further includes counting
Device is counted for the charging-discharging cycle number to shunt capacitance；The time of having a rest for being restarted automatically dynamic duty ratio, with inspection
Survey the charging process that alternates of discharge process of delay to the phase every other week charging process time overall length, be to start from shunt capacitance
When the discharge process of via controller is completed, charging process time and delay time, counter including shunt capacitance are logical
It crosses and the periodicity of the charge and discharge process of shunt capacitance is counted to set delay time.
8. the protection circuit of output short-circuit according to claim 6, it is characterised in that: the protection circuit further includes counting
Device, the protection circuit are restarted automatically dynamic duty ratio, set the time of having a rest by counter,
When output short-circuit occurs for Switching Power Supply, detection is formed by the discharge process time of shunt capacitance via controller and is prolonged
When；
The primary charging for then beginning to shunt capacitance, before a charging process of shunt capacitance is completed, counter output dimension
It holds as high level；
When a charging process of shunt capacitance is completed, counter carry, counter output switching activity is low level；It is other therewith
Road capacitor starts secondary discharge process and recharging process, before the recharging process of shunt capacitance is completed, counter
Output is maintained low level；Wherein, shunt capacitance is discharged through protection circuit during secondary discharge；
When the recharging process of shunt capacitance is completed, counter is counted, and counter output switching activity is high level, when rest
Between terminate, protection circuit cancel cut-off signals, reset switch power supply.
9. the protection circuit of the output short-circuit according to any one of claim 6 to 8, it is characterised in that: the protection electricity
Road, including comparator (111), NOT gate (112), counter (113) and NAND gate (114), the positive input energy of comparator (111)
It is selected to be the high voltage limit of access according to its output level, or access lower bound voltage, anti-phase input and feeder ear (VDD) are even
It connects, output is connected with the input of NOT gate (112) and counter (113) respectively；The output of comparator (111) is also drawn as protection
The enabled output end of circuit, for exporting enable signal to start-up circuit；The output of NOT gate (112) is as NAND gate (114)
First input, second input of the output of counter (113) as NAND gate (114), the output of NAND gate (114) is as protection
The shutdown end of circuit.
10. a kind of controller of Switching Power Supply, including protection circuit as claimed in claim 9 and start-up circuit, it is characterised in that:
The pin (D) that there is the controller input terminal of self-start circuit to draw, for the transformer primary winding with Switching Power Supply
Same Name of Ends connection；The input terminal of the protection circuit and the output end of start-up circuit connect, and are incorporated as feeder ear
(VDD)。
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| CN201610168690.0A CN105655983B (en) | 2016-03-23 | 2016-03-23 | The guard method of output short-circuit and protection circuit |
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| CN105655983B true CN105655983B (en) | 2019-01-15 |
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| CN107846141B (en) * | 2016-10-12 | 2020-04-14 | 昆山启达微电子有限公司 | Power supply starting circuit |
| CN107947123B (en) * | 2017-10-24 | 2024-08-06 | 杭州必易微电子有限公司 | ACDC switching power supply protection circuit and ACDC switching power supply device |
| CN110011279B (en) * | 2019-03-18 | 2021-05-28 | 苏州伟创电气科技股份有限公司 | Switching power supply protection circuit and switching power supply protection method |
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| US20050185353A1 (en) * | 2003-06-06 | 2005-08-25 | Electronic Theatre Controls, Inc. | Overcurrent protection for solid state switching system |
| CN201408985Y (en) * | 2009-04-17 | 2010-02-17 | 中兴通讯股份有限公司 | Short-circuit protection circuit for switching power supply |
| CN202309527U (en) * | 2011-11-09 | 2012-07-04 | 深圳市同洲电子股份有限公司 | Flyback switching power supply output short-circuit protection circuit |
| CN104201652A (en) * | 2014-09-10 | 2014-12-10 | 广州金升阳科技有限公司 | Power protection control method |
| CN105186459A (en) * | 2015-09-30 | 2015-12-23 | 广州金升阳科技有限公司 | Method and circuit for output short circuit protection of switching power supply |
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| US20050185353A1 (en) * | 2003-06-06 | 2005-08-25 | Electronic Theatre Controls, Inc. | Overcurrent protection for solid state switching system |
| CN201408985Y (en) * | 2009-04-17 | 2010-02-17 | 中兴通讯股份有限公司 | Short-circuit protection circuit for switching power supply |
| CN202309527U (en) * | 2011-11-09 | 2012-07-04 | 深圳市同洲电子股份有限公司 | Flyback switching power supply output short-circuit protection circuit |
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