CN205693558U - A kind of output overvoltage protection circuit and Switching Power Supply - Google Patents
A kind of output overvoltage protection circuit and Switching Power Supply Download PDFInfo
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- CN205693558U CN205693558U CN201620479477.7U CN201620479477U CN205693558U CN 205693558 U CN205693558 U CN 205693558U CN 201620479477 U CN201620479477 U CN 201620479477U CN 205693558 U CN205693558 U CN 205693558U
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Abstract
The utility model discloses a kind of output overvoltage protection circuit and Switching Power Supply; output overvoltage protection circuit includes chip to be protected; connect between second pin and the 8th pin of described chip to be protected and have resistance; described second pin is also by capacity earth; described electric capacity and paralleled power switches; switching tube is connected with the secondary of optocoupler, and the first pin of the secondary and chip to be protected of optocoupler is connected.This utility model, without Replacing Scheme, can be modified on the basis of primary circuit, shortens the construction cycle.
Description
Technical field
This utility model relates to field of switch power, is specifically related to a kind of output overvoltage protection circuit and Switching Power Supply.
Background technology
In small-sized accessory power supply field, occur in that a variety of chip carrying output over-voltage protection.But due to
The advantages such as UC3842 serial application is extensive, low price, technology maturation, buying convenience will still have the biggest market part in future
Volume.Having higher requirement power supply now with increasing occasion, foreign market requires the electricity being likely to be exposed people
Road under any circumstance voltage must not exceed 42.4V, feedback control loop can be cut away test when test, in this case cannot
Realize overvoltage protection by negative feedback, and depend merely on the pin function that 3842 chips carry and be difficulty with.The most close existing side
Case is directly to change the expense of chip circuit with over-voltage protecting function.
If for the purpose reaching output over-voltage protection, it may be necessary to use new chip and new scheme, so make
Obtain the construction cycle and cost all can rise, thus existing growth requirement can not be met.
Utility model content
For solving the deficiency that prior art exists, the utility model discloses a kind of output overvoltage protection circuit and switch electricity
Source, this programme purpose is for being similar to the 3842 this chips circuit realiration overvoltage protection without overvoltage protection own, method letter
Single reliable, it is not necessary to test for a long time.
For achieving the above object, concrete scheme of the present utility model is as follows:
A kind of output overvoltage protection circuit, including chip to be protected, second pin and the 8th of described chip to be protected draws
Between foot connect have resistance, described second pin also by capacity earth, described electric capacity and paralleled power switches, switching tube and optocoupler
Secondary be connected, the first pin of the secondary and chip to be protected of optocoupler is connected；
When normally working, this chip first pin to be protected can persistently open switching tube, the second pin voltage is dragged down,
Normal circuit operation；
Once overvoltage or cut away feedback control loop, optocoupler ends, and switching tube ends, and the 8th pin of chip to be protected passes through institute
State resistance to charge to described electric capacity, drag down the first pin voltage of chip to be protected when being charged to setting voltage, make the dutycycle be
0。
Further, described chip to be protected is UC3842.
Further, the 8th pin of described chip to be protected passes through capacity earth, described electric capacity and the electric capacity being in series
And resistance is in parallel.
Further, the first pin and the 3rd pin of described chip to be protected is connect by respective electric capacity respectively
Ground.
Further, Switching Power Supply, including output overvoltage protection circuit, the 7th pin and prime of described chip to be protected
Current rectifying and wave filtering circuit is connected, and described prime current rectifying and wave filtering circuit is connected with starting charging circuit, the 6th of described chip to be protected
Pin and the second pin are all connected with Switching Power Supply major loop, and Switching Power Supply major loop is connected with secondary output circuit, described time
Level output circuit is connected with the primary of optocoupler by resistance.
Further, described prime current rectifying and wave filtering circuit include the protection circuit that is made up of critesistor and varistor and
The poor common mode absorbing circuit being connected with this protection circuit be connected, described poor common mode absorbing circuit successively with rectification circuit and filtered electrical
Road is connected, and is also associated with starting charging circuit between rectification circuit and filter circuit.
Further, described poor common mode absorbing circuit includes the first electric capacity, inductance and the second electric capacity being in parallel, described whole
Current circuit is the bridge circuit of four diode compositions, and described filter circuit is in parallel by multiple electric capacity and forms.
Further, described startup charging circuit includes two electric capacity being in parallel, and the common port of two electric capacity is with multiple
The resistance circuit being in series is connected, and the common port of said two electric capacity is the 7th pin that VCC end receives chip to be protected, is used for
Startup for chip to be protected provides electric current.
Further, described Switching Power Supply major loop includes metal-oxide-semiconductor, one end of described metal-oxide-semiconductor by RCD absorbing circuit with
First primary coil of transformator is connected, and the described metal-oxide-semiconductor other end passes through resistance eutral grounding, and described metal-oxide-semiconductor the 3rd end divides two-way, and one
Resistance eutral grounding is passed through on road, and resistance of separately leading up to is connected with the outfan of chip to be protected, and the second primary coil of transformator is also
It is associated with polar capacitor, electric capacity and the first diode, between the second primary coil and the polar capacitor of transformator, is also associated with second
Diode.
Further, described secondary output circuit includes assisting winding, auxiliary winding to be in parallel with three electric capacity successively, the
Being connected between one electric capacity and auxiliary winding and have diode, connecting between second electric capacity and the 3rd electric capacity has inductance, and first
Individual electric capacity for polar capacitor, the positive terminal of this polar capacitor is connected with the primary of optocoupler by resistance, is used for powering for optocoupler.
The guard method of Switching Power Supply, including:
After the secondary short circuit of optocoupler, optocoupler cannot turn on therefore switching tube and be also switched off, and the 8th of chip the most to be protected draws
Foot can by resistance lasting to electric capacity charge thus raise the voltage of the second pin；
Due to the amplifier reverse input end that the second pin is chip internal to be protected, compare with internal setting voltage
Relatively, rapidly the first pin level can be dragged down when the second pin level reaches setting voltage, make dutycycle be 0 thus stop electricity
Pressure continues to raise；
First pin level drags down the level of rear second pin and can keep the setting time, in the meantime secondary output circuit
Secondary output voltage and auxiliary winding voltage also can persistently reduce；
After the voltage of auxiliary winding is less than the maintenance voltage of chip to be protected, chip turns off, and the 8th pin level is 0, the
Two pin level are discharged by electric capacity, and power supply restarts, and circuit now constantly can circulate in this state, enter mould of having the hiccups
Formula.
The beneficial effects of the utility model:
This utility model, without Replacing Scheme, can be modified on the basis of primary circuit, shortens the construction cycle.3842 make
Still having huge market for a kind of general chip, therefore buying conveniently and also has the biggest advantage in price.
Accompanying drawing explanation
Fig. 1 is this utility model prime rectification and starts charging circuit figure；
Fig. 2 is this utility model Switching Power Supply major loop and secondary output circuit figure；
Fig. 3 is that this utility model PWM controls and the schematic diagram of sample circuit.
Detailed description of the invention:
Below in conjunction with the accompanying drawings this utility model is described in detail:
This circuit is low power flyback sourse, and Fig. 1 is input rectifying filter circuit and the start-up circuit of circuit, wherein R1
Critesistor, R2 varistor, each serve as and prevent power-on impact current and the effect of anti-input lightning surge.C1, C2, L1 rise
Effect to absorption difference common mode disturbances.VCC receives 7 feet of UC3842, and the startup for 3842 provides electric current.
Fig. 2 is the major loop part of circuit and secondary output part, and wherein C20, R7, D2 constitute RCD absorbing circuit, mainly
Absorb the spike of metal-oxide-semiconductor shutdown moment.Driving of MOS is provided by 6 feet of 3842, secondary output 15V, auxiliary winding output 15V
To 3842 power supplies.
Fig. 3 is peripheral circuit and the feedback-system section of circuit chip.Compared with general circuit, this circuit adds
These devices of C13, Q2, R12 realize the function of output over-voltage protection.When normal circuit operation, TL431 (U32 of Fig. 3)
1 foot is about 2.5V, TL431 2 feet conductings, optocoupler primary turns on.The 1 foot electric current of 3842 arrives through secondary and the Q2 of optocoupler
Ground, the amplification through Q2 can move the 2 foot level of 3842 to 0V.The level of 2 feet does not interferes with 1 foot level, now electricity
Road is properly functioning.
If being not added with these devices, once being cut away by feedback control loop, as by the 1 of optocoupler, 2 foot short circuits, optocoupler cannot be led
Logical, the 1 foot level of 3842 can rise constantly, and dutycycle is relevant to the level of 1 foot, along with the continuous rising of 1 foot level
Dutycycle also can be increasing, output voltage as well as more and more higher until break through 42.4V.
Lower surface analysis once increases the effect of this circuit, (is now equivalent to Voltage Feedback ring after the 1 of optocoupler, 2 foot short circuits
Lost efficacy in road)；Or (output is more than 2.5V then TL431 more than reference voltage 1 foot of TL431 after the 15V set in output voltage overvoltage
2 feet can end, now do not have electric current to flow through the 1 of optocoupler, 2 feet, relatively similar with the 1 of optocoupler, 2 foot short circuit situation ratios) circuit opens
Beginning to enter protection act: optocoupler cannot turn on therefore Q2 and be also switched off, at this moment 8 feet of 3842 can be by lasting the charging to C13 of R12
Thus raise the voltage of 2 feet.Owing to 2 feet are the amplifier reverse input end within 3842, compare, when 2 with internal 2.5V
When foot level reaches 2.5V can rapidly by 1 foot level down for 0, make dutycycle be 0 (3,6 foot level perseverances are 0V) thus stop electricity
Pressure continues to raise.After 1 foot level drags down, the level of 2 feet can keep a period of time, in the meantime secondary output voltage and auxiliary around
Group voltage also can persistently reduce.After the voltage of auxiliary winding is less than the maintenance voltage of 3842, chip turns off (7 foot voltages reduce),
Chip closes 8 foot level of having no progeny and drops to 0V, therefore 2 foot level can by R105 from 3842 8 feet be put into 0V, when the level of 2
After dropping to 0V, protection act terminates, and now the voltage of each pin of 3842 chips is 0, is equivalent to chip and has carried out once resetting
Action, 7 feet of 3842 start again through starting resistance R4, R5 subsequently.If failture evacuation, then whole system can start normal work
Making, if feedback control loop still lost efficacy, circuit the most now can reenter above-mentioned protection act, goes round and begins again until fault is arranged
Remove.
When power supply normally works, 1 foot of 3842 can persistently open Q2, by 2 foot voltage pull-down, normal circuit operation.Once
Output overvoltage or cut away feedback control loop, TL431 ends, and optocoupler ends, therefore Q2 cut-off, and 8 feet of 3842 give electricity by resistance R12
Holding C13 charging, drag down the 1 foot voltage of 3842 when being charged to 2.5V, making dutycycle is 0, thus prevents output voltage to continue to rise
High.Wherein, cut away feedback control loop and be optocoupler 1,2 foot short circuit.
The RC time constant wherein selecting C13 with R12 needs to determine according to concrete circuit, and its principle selected is defeated
When going out zero load, the 2 foot voltages of 3842 rise to the time used by 2.5V and are less than output capacitor and rise to the time of 42.4V.
Below as a example by the power supply of an output 30W, wherein operating frequency is 100kHz, and the primary sensibility reciprocal of transformator is
1mH, current sampling resistor is 1 ohm, and output capacitance C17 is 1000uF, and circuit design is discontinuous operating mode.Due to 3842
3 foot voltages not can exceed that 1V, turns off mos pipe after arriving 1V, and therefore primary maximum current is 1A, it is assumed that eliminate feedback
Loop turns off after then switch periods 3 foot voltage all reaches 1V every time, and peak power the most now isWherein
L be 1mH, I be 1A, f be 100kHz.Voltage on electric capacity rises to the energy required for 42.4V from 15VWherein C be 1000uF, U1 be 15V, U2 be 42.4V.Then the charging interval is 0.8 ÷ 50=
160ms.Select RC in 160ms, 2.5V need to be charged to by the 5V of 8 feet, therefore according to simulation calculation can with value 47k with
4.7uF can be charged to 2.5V at 150ms, thus ensures overvoltage protection.
Although detailed description of the invention of the present utility model is described by the above-mentioned accompanying drawing that combines, but not new to this practicality
The restriction of type protection domain, one of ordinary skill in the art should be understood that on the basis of the technical solution of the utility model, ability
Field technique personnel need not to pay various amendments or deformation that creative work can make still at protection model of the present utility model
Within enclosing.
Claims (9)
1. an output overvoltage protection circuit, is characterized in that, including chip to be protected, the second pin of described chip to be protected and
Between 8th pin connect have resistance, described second pin also by capacity earth, described electric capacity and paralleled power switches, switching tube
Being connected with the secondary of optocoupler, the first pin of the secondary and chip to be protected of optocoupler is connected.
2. a kind of output overvoltage protection circuit as claimed in claim 1, is characterized in that, the 8th pin of described chip to be protected
By capacity earth, described electric capacity is in parallel with the electric capacity being in series and resistance.
3. a kind of output overvoltage protection circuit as claimed in claim 1, is characterized in that, the first pin of described chip to be protected
And the 3rd pin respectively by respective capacity earth.
4. a Switching Power Supply, including the arbitrary described output overvoltage protection circuit of the claims 1-3, is characterized in that, institute
The 7th pin stating chip to be protected is connected with prime current rectifying and wave filtering circuit, described prime current rectifying and wave filtering circuit and startup charged electrical
Road is connected, and the 6th pin and second pin of described chip to be protected are all connected with Switching Power Supply major loop, and Switching Power Supply master return
Road is connected with secondary output circuit, and described secondary output circuit is connected with the primary of optocoupler by resistance.
5. a kind of Switching Power Supply as claimed in claim 4, is characterized in that, described prime current rectifying and wave filtering circuit includes by temperature-sensitive electricity
Resistance and the protection circuit of varistor composition and the poor common mode absorbing circuit that is connected with this protection circuit are connected, the suction of described poor common mode
Receive circuit to be connected with rectification circuit and filter circuit successively, be also associated with between rectification circuit and filter circuit starting charged electrical
Road.
6. Switching Power Supply as claimed in claim 5 a kind of, is characterized in that, described poor common mode absorbing circuit include being in parallel the
One electric capacity, inductance and the second electric capacity, described rectification circuit is the bridge circuit of four diode compositions, and described filter circuit is by many
Individual electric capacity is in parallel composition.
7. a kind of Switching Power Supply as claimed in claim 5, is characterized in that, described startup charging circuit includes two be in parallel
Electric capacity, the common port of two electric capacity is connected with multiple resistance circuits being in series, and the common port of said two electric capacity is VCC termination
To the 7th pin of chip to be protected, provide electric current for the startup for chip to be protected.
8. a kind of Switching Power Supply as claimed in claim 4, is characterized in that, described Switching Power Supply major loop includes metal-oxide-semiconductor, described
One end of metal-oxide-semiconductor is connected with the first primary coil of transformator by RCD absorbing circuit, and the described metal-oxide-semiconductor other end passes through resistance
Ground connection, described metal-oxide-semiconductor the 3rd end divides two-way, leads up to resistance eutral grounding, separately leads up to the resistance output with chip to be protected
End is connected, and the second primary coil of transformator is parallel with polar capacitor, electric capacity and the first diode, the second former sideline of transformator
It is also associated with the second diode between circle and polar capacitor.
9. a kind of Switching Power Supply as claimed in claim 4, is characterized in that, described secondary output circuit includes assisting winding, auxiliary
Helping winding to be in parallel with three electric capacity successively, being connected between first electric capacity and auxiliary winding has diode, second electric capacity and
Connecting between 3rd electric capacity and have inductance, first electric capacity is polar capacitor, and the positive terminal of this polar capacitor passes through resistance and light
The primary of coupling is connected, for powering for optocoupler.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620479477.7U CN205693558U (en) | 2016-05-24 | 2016-05-24 | A kind of output overvoltage protection circuit and Switching Power Supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620479477.7U CN205693558U (en) | 2016-05-24 | 2016-05-24 | A kind of output overvoltage protection circuit and Switching Power Supply |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN205693558U true CN205693558U (en) | 2016-11-16 |
Family
ID=57261942
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201620479477.7U Active CN205693558U (en) | 2016-05-24 | 2016-05-24 | A kind of output overvoltage protection circuit and Switching Power Supply |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN205693558U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107359793A (en) * | 2017-08-22 | 2017-11-17 | 姚静洁 | A kind of direct-current switch power supply circuit |
| CN115664183A (en) * | 2022-11-21 | 2023-01-31 | 广东东菱电源科技有限公司 | Continuous startup and shutdown non-overshoot circuit |
-
2016
- 2016-05-24 CN CN201620479477.7U patent/CN205693558U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107359793A (en) * | 2017-08-22 | 2017-11-17 | 姚静洁 | A kind of direct-current switch power supply circuit |
| CN115664183A (en) * | 2022-11-21 | 2023-01-31 | 广东东菱电源科技有限公司 | Continuous startup and shutdown non-overshoot circuit |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CP03 | Change of name, title or address | ||
| CP03 | Change of name, title or address |
Address after: 250101 Electric Power Intelligent Robot Production Project 101 in Jinan City, Shandong Province, South of Feiyue Avenue and East of No. 26 Road (ICT Industrial Park) Patentee after: National Network Intelligent Technology Co., Ltd. Address before: 250101 Shandong city of Ji'nan province high tech Zone (Lixia District) Xinluo Avenue No. 2008 silver bearing building B block 626 Patentee before: Shandong Luneng Intelligent Technology Co., Ltd. |
|
| TR01 | Transfer of patent right | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20201210 Address after: Room 902, 9 / F, block B, Yinhe building, 2008 Xinluo street, hi tech Zone, Jinan City, Shandong Province Patentee after: Shandong Luneng Software Technology Co.,Ltd. intelligent electrical branch Address before: 250101 power intelligent robot production project 101 south of Feiyue Avenue and east of No.26 Road (in ICT Industrial Park) in Suncun District of Gaoxin, Jinan City, Shandong Province Patentee before: National Network Intelligent Technology Co.,Ltd. |
|
| CP01 | Change in the name or title of a patent holder | ||
| CP01 | Change in the name or title of a patent holder |
Address after: Room 902, 9 / F, block B, Yinhe building, 2008 Xinluo street, hi tech Zone, Jinan City, Shandong Province Patentee after: Shandong luruan Digital Technology Co.,Ltd. smart energy branch Address before: Room 902, 9 / F, block B, Yinhe building, 2008 Xinluo street, hi tech Zone, Jinan City, Shandong Province Patentee before: Shandong Luneng Software Technology Co.,Ltd. intelligent electrical branch |