CN104852563A - Switching power supply external soft start circuit - Google Patents
Switching power supply external soft start circuit Download PDFInfo
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- CN104852563A CN104852563A CN201510258209.2A CN201510258209A CN104852563A CN 104852563 A CN104852563 A CN 104852563A CN 201510258209 A CN201510258209 A CN 201510258209A CN 104852563 A CN104852563 A CN 104852563A
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- triode
- pwm controller
- electric capacity
- resistance
- power supply
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Abstract
The invention discloses a switching power supply external soft start circuit which is characterized by comprising a base electrode driving circuit, a triode and a PWM controller. The input end of the base electrode driving circuit is connected with the eighth pin of the reference voltage output end of the PWM controller U1. The output end of the base electrode driving circuit is connected with the base electrode of the triode Q1. The collection electrode of the triode is connected with the first pin of the output compensation end of the PWM controller U1 via a biasing resistor R3. The emission electrode of the triode is grounded. The fourth pin of the PWM controller U1 is connected with one end of a resistor R5 and one end of a capacitor C4. Input starting current and output overshoot voltage of a switching power supply are reduced via the external soft start circuit so that EMI performance of the power supply is improved and filter design cost is reduced without deterioration of stability of a voltage compensation loop.
Description
Technical field
The present invention relates to field of switch power, particularly the outside soft starting circuit of a kind of Switching Power Supply.
Background technology
Along with the development of power electronic technology, Switching Power Supply is widely used in the fields such as computer, communication, electronic equipment.Switching Power Supply, compared with linear power supply, has the advantages such as power conversion efficiency is high, voltage stabilized range is wide, volume is little.Meanwhile, Switching Power Supply also also exists some problems in the design, as power supply can produce a larger surge current at powered on moment.This is because converter output terminal is connected to jumbo filter capacitor usually, and capacitance voltage is zero in startup instantaneously, and voltage feedback loop makes power management chip export maximum duty cycle, and produces large surge current.Surge current can burn the power device in circuit, reduces functional reliability during power initiation.Therefore usually in the design of Switching Power Supply, increase soft starting circuit, the duty ratio of PWM driving pulse is slowly increased with limiting starting current from minimum value, thus the power device of available protecting converter.Soft starting circuit not only needs when circuit start, and also needs when phenomena of the failure such as circuit generation overcurrent, overvoltages to adopt.As circuit over current fault recover time, soft starting circuit work, makes duty ratio slowly increase, if continue to monitor over-current phenomenon avoidance, then starts current foldback circuit.
Visible, the design of soft starting circuit is extremely important for the reliably working of Switching Power Supply.Conventional soft starting circuit design as shown in Figure 1.Output voltage enters three-terminal voltage-stabilizing chip U1 after resistance R3 and R4 dividing potential drop, and usual U1 adopts the adjustable voltage stabilizing chip of TL431.After optocoupler D1 conducting, output voltage sampled signal is passed to elementary PWM power management chip.Soft starting circuit is made up of resistance R1, diode D2 and electric capacity C3.During circuit start, output voltage is charged to electric capacity C3 by D2, causes the cathode voltage of voltage stabilizing chip U1 slowly to rise, and avoids Docket No to export the PWM drive singal of maximum duty cycle.Although this soft starting circuit simplicity of design, resistance R1 and electric capacity C3 take part in the compensation circuit of TL431, may cause the reduction of loop stability.Adopt outside soft starting circuit just can avoid this problem, the art of this patent launches research based on such background.
Summary of the invention
The object of the invention is to design the outside soft starting circuit of a kind of Switching Power Supply.
To achieve these goals, embodiments provide the outside soft starting circuit of a kind of Switching Power Supply, comprise a base drive circuit, a triode and a PWM controller, wherein:
Reference voltage output end 8 pin of the input termination PWM controller U1 of described base drive circuit, the base stage of the output termination triode Q1 of described base drive circuit.
The output that the collector electrode of described triode meets PWM controller U1 by biasing resistor R3 compensates end 1 pin; The grounded emitter of described triode.
The 4 pin connecting resistance R5 of described PWM controller U1 and one end of electric capacity C4.
Further, described base drive circuit comprises resistance R1, electric capacity C1, resistance R2 and electric capacity C2.
Further, 8 pin of a termination PWM controller U1 of described electric capacity C1; The other end connecting resistance R1 of described electric capacity C1; The base stage of the one termination triode Q1 of described resistance R1.
Further, the base stage of a termination triode Q1 of described resistance R2 and electric capacity C2; The other end ground connection of described resistance R2 and electric capacity C2.
Further, described triode Q1 adopts NPN type triode.
Further, described PWM controller adopts power of fixed frequency managing chip.
Further, described PWM controller adopts UC3843 to realize.
Embodiments providing the outside soft starting circuit of a kind of Switching Power Supply, in order to ensure the stability of Switching Power Supply, adopting outside soft starting circuit, to reduce overshoot current when Switching Power Supply starts and voltage.Compared to the prior art, the present invention reduces input starting current by outside soft starting circuit and exports overshoot voltage, improves the EMI performance of Switching Power Supply, reduces the cost of design of filter, can not cause the deterioration of power supply loop stability simultaneously.
Accompanying drawing explanation
In order to make the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail, wherein:
Fig. 1 is the schematic diagram of conventional soft starting circuit.
Fig. 2 is the schematic diagram of the outside soft starting circuit of Switching Power Supply of the present invention.
Embodiment
Below in conjunction with accompanying drawing, method of the present invention is described in further detail.
The schematic diagram of the outside soft starting circuit of Switching Power Supply that Fig. 2 provides for the embodiment of the present invention, as shown in the figure, comprises a base drive circuit, a triode and a PWM controller, wherein:
Reference voltage output end 8 pin of the input termination PWM controller U1 of described base drive circuit, the base stage of the output termination triode Q1 of described base drive circuit.
The output that the collector electrode of described triode meets PWM controller U1 by biasing resistor R3 compensates end 1 pin; The grounded emitter of described triode.
The 4 pin connecting resistance R5 of described PWM controller U1 and one end of electric capacity C4.
Further, described base drive circuit comprises resistance R1, electric capacity C1, resistance R2 and electric capacity C2.
Further, 8 pin of a termination PWM controller U1 of described electric capacity C1; The other end connecting resistance R1 of described electric capacity C1; The base stage of the one termination triode Q1 of described resistance R1.
Further, the base stage of a termination triode Q1 of described resistance R2 and electric capacity C2; The other end ground connection of described resistance R2 and electric capacity C2.
Further, described triode Q1 adopts NPN type triode.
Further, described PWM controller adopts power of fixed frequency managing chip.
Further, described PWM controller adopts UC3843 to realize.
Triode Q1 in the embodiment of the present invention is driven by the reference voltage output end mouth of PWM controller U1.Electric current is charged to capacitor C1 by R1, R2 and C2, and the voltage at C1 two ends will be increased to reference voltage V from zero
r, and the voltage at R2 two ends will drop to zero from a branch pressure voltage.When base stage threshold voltage higher than triode Q1 of the branch pressure voltage at resistance R2 two ends, Q1 opens normal work.Q1 conduction period, resistance R3 is by the source electric current of shunting PWM controller 1 pin, and the voltage compensating output 1 pin will slowly increase.When compensating the increase of output pin voltage, the ON time of PWM drive singal also increases gradually, and therefore power output will slowly increase, thus reduces starting current and export overshoot voltage.Lower starting current allows the filter that use cost is lower, improves the performance of power supply EMI simultaneously.
The ON time T of PWM drive singal
onby the compensation output pin voltage V of controller U1
1determine:
T
on＝K·(V
1-V
0)
Wherein K is proportionality coefficient; V
0for offset voltage.
The Time Calculation of outside soft start is as follows:
Wherein V
bfor the threshold voltage of triode Q1 conducting.
When the voltage rise at electric capacity C1 two ends is to reference voltage V
rtime, the voltage at resistance R2 two ends will be zero, triode Q1 to turn off, and soft start-up process terminates.Now, in resistance R3, no current passes through, and only has resistance R4 and electric capacity C3 to participate in voltage loop compensation circuit.Therefore, outside soft starting circuit can not affect the stability of voltage compensation loop after start-up course terminates.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.
Claims (7)
1. the outside soft starting circuit of Switching Power Supply, is characterized in that: comprise a base drive circuit, a triode and a PWM controller; Reference voltage output end 8 pin of the input termination PWM controller U1 of described base drive circuit, the base stage of the output termination triode Q1 of described base drive circuit; The output that the collector electrode of described triode meets PWM controller U1 by biasing resistor R3 compensates end 1 pin; The grounded emitter of described triode; The 4 pin connecting resistance R5 of described PWM controller U1 and one end of electric capacity C4.
2. converter according to claim 1, is characterized in that: described base drive circuit comprises resistance R1, electric capacity C1, resistance R2 and electric capacity C2.
3. the converter according to the arbitrary claim of claim 1 to 2, is characterized in that: 8 pin of a termination PWM controller U1 of described electric capacity C1; The other end connecting resistance R1 of described electric capacity C1; The base stage of the one termination triode Q1 of described resistance R1.
4. the converter according to the arbitrary claim of claim 1 to 2, is characterized in that: the base stage of a termination triode Q1 of described resistance R2 and electric capacity C2; The other end ground connection of described resistance R2 and electric capacity C2.
5. converter according to claim 1, is characterized in that: described triode Q1 adopts NPN type triode.
6. converter according to claim 1, is characterized in that: described PWM controller adopts power of fixed frequency managing chip.
7. converter according to claim 1, is characterized in that: described PWM controller adopts UC3843 to realize.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510258209.2A CN104852563A (en) | 2015-05-20 | 2015-05-20 | Switching power supply external soft start circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510258209.2A CN104852563A (en) | 2015-05-20 | 2015-05-20 | Switching power supply external soft start circuit |
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| Publication Number | Publication Date |
|---|---|
| CN104852563A true CN104852563A (en) | 2015-08-19 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510258209.2A Pending CN104852563A (en) | 2015-05-20 | 2015-05-20 | Switching power supply external soft start circuit |
Country Status (1)
| Country | Link |
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| CN (1) | CN104852563A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106851883A (en) * | 2016-12-28 | 2017-06-13 | 广东格兰仕集团有限公司 | A kind of soft starting circuit and its method for becoming micro-wave oven |
| CN107733219A (en) * | 2017-11-01 | 2018-02-23 | 广州金升阳科技有限公司 | A kind of Switching Power Supply output soft start circuit |
| CN109067166A (en) * | 2018-09-19 | 2018-12-21 | 西安微电子技术研究所 | A kind of Discrete control soft starting circuit of DC/DC converter |
| CN112886807A (en) * | 2021-02-07 | 2021-06-01 | 上海空间电源研究所 | Soft start realizing device and method |
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| CN2577362Y (en) * | 2002-09-28 | 2003-10-01 | 深圳市赛格导航科技股份有限公司 | Vehicle operation state monitoring instrument |
| CN101414748A (en) * | 2007-10-19 | 2009-04-22 | 深圳迈瑞生物医疗电子股份有限公司 | Method for starting control circuit and protecting power supply control chip |
| CN201623627U (en) * | 2010-01-04 | 2010-11-03 | 青岛海信电器股份有限公司 | Power PFC circuit and television set having the same |
| CN103117583A (en) * | 2013-02-28 | 2013-05-22 | 山东润峰电子科技有限公司 | Full-automatic low static power consumption charger |
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2015
- 2015-05-20 CN CN201510258209.2A patent/CN104852563A/en active Pending
Patent Citations (4)
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| CN2577362Y (en) * | 2002-09-28 | 2003-10-01 | 深圳市赛格导航科技股份有限公司 | Vehicle operation state monitoring instrument |
| CN101414748A (en) * | 2007-10-19 | 2009-04-22 | 深圳迈瑞生物医疗电子股份有限公司 | Method for starting control circuit and protecting power supply control chip |
| CN201623627U (en) * | 2010-01-04 | 2010-11-03 | 青岛海信电器股份有限公司 | Power PFC circuit and television set having the same |
| CN103117583A (en) * | 2013-02-28 | 2013-05-22 | 山东润峰电子科技有限公司 | Full-automatic low static power consumption charger |
Non-Patent Citations (1)
| Title |
|---|
| ROBERT N BUONO等: "实现长时间PWM软启动的简单电路", 《电子设计技术》 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106851883A (en) * | 2016-12-28 | 2017-06-13 | 广东格兰仕集团有限公司 | A kind of soft starting circuit and its method for becoming micro-wave oven |
| CN106851883B (en) * | 2016-12-28 | 2020-04-03 | 广东格兰仕集团有限公司 | Soft start circuit and method for variable frequency microwave oven |
| CN107733219A (en) * | 2017-11-01 | 2018-02-23 | 广州金升阳科技有限公司 | A kind of Switching Power Supply output soft start circuit |
| CN109067166A (en) * | 2018-09-19 | 2018-12-21 | 西安微电子技术研究所 | A kind of Discrete control soft starting circuit of DC/DC converter |
| CN112886807A (en) * | 2021-02-07 | 2021-06-01 | 上海空间电源研究所 | Soft start realizing device and method |
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Application publication date: 20150819 |