CN106549559B - The control circuit of switching power unit - Google Patents
The control circuit of switching power unit Download PDFInfo
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- CN106549559B CN106549559B CN201510603351.6A CN201510603351A CN106549559B CN 106549559 B CN106549559 B CN 106549559B CN 201510603351 A CN201510603351 A CN 201510603351A CN 106549559 B CN106549559 B CN 106549559B
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Abstract
The embodiment of the present invention provides a kind of control circuit of switching power unit; voltage sense signal is generated by the correction signal of main electrode voltage and input voltage; and overvoltage protection detection is carried out based on the voltage sense signal; it can not be influenced by input voltage; high-precision progress overvoltage protection detection; for example, can with there is no supply voltage VccThe unrelated carry out overvoltage protection detection of the specification of the insulation of winding or nonisulated power supply.
Description
Technical field
The present invention relates to switch power technology field more particularly to a kind of control circuits of switching power unit.
Background technique
Currently, Switching Power Supply is widely used, Switching Power Supply generates overvoltage and damages device in order to prevent, needs to detect and open
The overvoltage in powered-down source simultaneously carries out overvoltage protection.
Existing Zenith tracking generally by the way that detection circuit is arranged in the buffer circuit of the first winding side of transformer,
It is able to detect and the overvoltage generated is risen by input overvoltage and output voltage.Also can detecte be likely to occur it is excessively electric
Pressure, and the overvoltage of switch (such as MOSFET etc.) can be prevented.For example, Japanese Unexamined Patent Publication 2006-506035A disclose it is similar
The prior art.
It should be noted that the above description of the technical background be intended merely to it is convenient to technical solution of the present invention carry out it is clear,
Complete explanation, and facilitate the understanding of those skilled in the art and illustrate.Cannot merely because these schemes of the invention
Background technology part is expounded and thinks that above-mentioned technical proposal is known to those skilled in the art.
Summary of the invention
When stating prior art detection overvoltage in use, in the case where worldwide there are a variety of input specifications,
Output over-voltage protection (Over Voltage Protection, OVP) detection in, detection accuracy according to input voltage not
It is very different together.For example, reaching the electricity of the detection voltage of transformer first winding side in the case where input voltage is weaker
Pressure amplitude degree will increase.Therefore, when carrying out the detection of output over-voltage, after exporting substantial increase, vibration stops, therefore, meeting
Damage the component etc. of transformer secondary winding side.
The embodiment of the present invention provides a kind of control circuit of switching power unit, can not be influenced by input voltage, high
The carry out overvoltage protection (OVP) of precision detects.
According to a first aspect of the embodiments of the present invention, a kind of control circuit of switching power unit, the control electricity are provided
Road has the switch element for the first winding for being connected to transformer, when voltage is input into the primary side of the transformer, leads to
It crosses the control circuit and switch control is carried out to the switch element, so that voltage caused by the secondary winding of the transformer is whole
Levelling is sliding and is output to load, wherein the control circuit of the switching power unit has main electrode voltage detecting circuit, described
Main electrode voltage detecting circuit detects main electrode voltage during the disconnection of the switch element, the main electrode voltage
Detection circuit according to the main electrode voltage signal detected, and the primary side based on the input voltage correction signal,
Voltage sense signal, and the voltage sense signal and reference voltage are generated, to carry out overvoltage protection.
According to a second aspect of the embodiments of the present invention, wherein the correction signal is generated by voltage-current converter circuit, institute
It states voltage-current converter circuit and the voltage of the primary side of the input is converted into current signal.
According to a third aspect of the embodiments of the present invention, wherein the voltage-current converter circuit has preset inclined
Set current circuit.
According to a fourth aspect of the embodiments of the present invention, wherein the main electrode voltage detecting circuit is electric by the main electrode
The detection moment of pressure signal is set as being switched in the switch element and disconnects and carry out after defined delay time.
According to a fifth aspect of the embodiments of the present invention, wherein the main electrode voltage detecting circuit is electric by the main electrode
The detection moment of pressure signal is set as being switched to disconnections in the switch element, and by recently previous with the switch element
It is carried out after corresponding delay time during a connection.
According to a sixth aspect of the embodiments of the present invention, wherein the main electrode voltage is the shoulder voltage of drain electrode.
According to a seventh aspect of the embodiments of the present invention, wherein the main electrode voltage detecting circuit is electric by the main electrode
Pressure signal subtracts the correction signal of the voltage of the primary side of the input, obtains the voltage sense signal.
The beneficial effects of the present invention are: output voltage inspection is generated by the correction signal of main electrode voltage and input voltage
Signal is surveyed, and overvoltage protection (OVP) detection is carried out based on the voltage sense signal, it can not be by the shadow of input voltage
It rings, high-precision progress overvoltage protection detection, for example, can be with no supply voltage (Vcc) winding insulation or nonisulated electricity
The unrelated carry out overvoltage protection detection of the specification in source.
Referring to following description and accompanying drawings, only certain exemplary embodiments of this invention is disclosed in detail, specifies original of the invention
Reason can be in a manner of adopted.It should be understood that embodiments of the present invention are not so limited in range.In appended power
In the range of the spirit and terms that benefit requires, embodiments of the present invention include many changes, modifications and are equal.
The feature for describing and/or showing for a kind of embodiment can be in a manner of same or similar one or more
It uses in a other embodiment, is combined with the feature in other embodiment, or the feature in substitution other embodiment.
It should be emphasized that term "comprises/comprising" refers to the presence of feature, one integral piece, step or component when using herein, but simultaneously
It is not excluded for the presence or additional of one or more other features, one integral piece, step or component.
Detailed description of the invention
Included attached drawing is used to provide to be further understood from the embodiment of the present invention, and which constitute one of specification
Point, for illustrating embodiments of the present invention, and come together to illustrate the principle of the present invention with verbal description.Under it should be evident that
Attached drawing in the description of face is only some embodiments of the present invention, for those of ordinary skill in the art, is not paying wound
Under the premise of the property made is laborious, it can also be obtained according to these attached drawings other attached drawings.In the accompanying drawings:
Fig. 1 be include the embodiment of the present invention 1 control circuit switching power unit circuit structure diagram；
Fig. 2 be the delay time of the embodiment of the present invention 1 be it is certain in the case where drain voltage detection sequence figure；
Fig. 3 be the delay time of the embodiment of the present invention 1 be variation in the case where drain voltage detection sequence figure；
Fig. 4 is the structure chart of the delay circuit that can generate variable delay time of the embodiment of the present invention 1；
Fig. 5 be include the embodiment of the present invention 2 control circuit switching power unit circuit structure diagram.
Specific embodiment
Referring to attached drawing, by following specification, aforementioned and other feature of the invention be will be apparent.In specification
In attached drawing, only certain exemplary embodiments of this invention is specifically disclosed, which show the portions that can wherein use principle of the invention
Divide embodiment, it will thus be appreciated that the present invention is not limited to described embodiments, on the contrary, the present invention includes falling into appended power
Whole modifications, modification and equivalent in the range of benefit requirement.
Embodiment 1
The embodiment of the invention provides a kind of control circuits of switching power unit.Fig. 1 includes the embodiment of the present invention 1
The circuit structure diagram of the switching power unit of control circuit.As shown in Figure 1, input voltage detection circuit is by resistance R1, R2 and fortune
It calculates amplifier Voltage follower to constitute, is connected with comparator on operational amplifier Voltage follower output terminal
BR(IN/OUT).Comparator BR (IN/OUT) is controlled in the case where input voltage is less than specified value or overvoltage is inputted to PWM
The signal that circuit output processed stops switch motion.
In the present embodiment, main electrode voltage detecting circuit is protected for example including resistance R5, delay circuit Delay and sampling
Hold circuit S/H.Wherein, main electrode voltage detecting circuit detects main electrode voltage during the disconnection of switch element Q1,
And according to the main electrode voltage signal detected, and the primary side based on input voltage correction signal, generate output electricity
Pressure detection signal, and compare the voltage sense signal and reference voltage, to carry out overvoltage protection.
In the present embodiment, main electrode voltage is, for example, the shoulder voltage of the drain electrode of switch element Q1, main electrode voltage detecting
The shoulder voltage of drain electrode is subtracted the correction signal of the voltage of the primary side of input by circuit, obtains voltage sense signal.
In the present embodiment, switch element Q1 can be various existing switch elements, for example, switch element Q1 is gold
Category-oxide semiconductor field effect transistor (Metal-Oxide-Semiconductor Field-Effect
Transistor, MOSFET).
In the present embodiment, which can be generated by voltage-current converter circuit, the voltage-current converter circuit
The voltage of the primary side of the input is converted into current signal.For example, the voltage-current converter circuit includes operational amplifier
Voltage follower, resistance R3 and the mirror circuit being made of transistor Q2, Q3.
In the present embodiment, which has preset bias current circuit, for example, the biasing
Current circuit includes comparator BR (IN/OUT, brown-in-out), resistance R4 and the mirror being made of transistor Q4, Q5 electricity
Road.
In the present embodiment, which can set according to actual needs, for example, according to the parameter of Switching Power Supply
And overvoltage protection needs and set.
The course of work of the control circuit of the present embodiment is specifically described below.
In the present embodiment, in the output of operational amplifier Voltage follower, by resistance R3, be connected to by
The collector of transistor Q5 in the mirror circuit that transistor Q2, Q3 are constituted, and the mirror circuit that is made of transistor Q4, Q5.Here,
In the mirror circuit that transistor Q2, Q3 are constituted, input electricity is exported from operational amplifier Voltage follower by resistance R3
Press signal code.That is, the collector current I of transistor Q3q3Introduce the drain voltage for detection switch element Q1
, flow through resistance R5, the electric current of R6.As a result, for the drain voltage of detection switch element Q1, the voltage of resistance R6 become with
The voltage that input voltage signal distinguishes, and produce the voltage proportional to the first winding voltage of transformer T1.
In the present embodiment, in the mirror circuit being made of transistor Q4, Q5, from comparator BR (IN/OUT, brown-
In-out reference voltage V)r1, connected by resistance R4.Here, equal by setting the resistance value of resistance R3 and resistance R4, with
Input voltage is starting point at the time of reaching brown-in voltage, and go into circulation input voltage signal electric current Iq3.Accordingly it is also possible to
It says, transistor Q4, the mirror circuit that Q5 is constituted is bias current circuit.
In the present embodiment, by arbitrarily setting the electricity of resistance R5, R6 of the drain voltage for detection switch element Q1
Resistance value, adjustable OV terminal correction voltage is relative to input voltage VinValue inclination.For example, if by resistance R5, R6
Resistance value is set as low resistance, the compensating value of input voltage is increased, if being set to high resistance, for input voltage
Compensating value becomes smaller.
In the present embodiment, in sampling and holding circuit S/H, since the falling of the ON signal of control circuit PWM, one
The voltage of resistance R6 is sampled and is kept after fixed delay time.In addition, delay circuit Delay generates delay time.
In the present embodiment, the voltage of the resistance R6 after sampling and holding, by comparator OVP, with reference voltage Vr2
It is compared, if it is decided that the voltage of the resistance R6 for sampling and after keeping is greater than reference voltage Vr2, signal is output to latch
(Latch) circuit, and the movement of stopping control circuit PWM.Start to carry out overvoltage protection movement as a result,.
In the present embodiment, in latch (Latch) circuit by more input overvoltage signals of comparator OVP,
Carry out overvoltage protection movement, it is possible to have prevent the function of malfunction.
For example, the detection moment of main electrode voltage signal can be set as in switch element Q1 by main electrode voltage detecting circuit
It is switched to disconnection (OFF) and is carried out after defined delay time.It is certain that Fig. 2, which is the delay time of the embodiment of the present invention 1,
In the case where drain voltage detection sequence figure.As shown in Fig. 2, when delay time is certain delay time T1, to switch member
The V of part Q1dsVoltage is sampled and is kept.The V of the switch element Q1 at the T1 moment after switch disconnects (OFF)dsVoltage phase
There is a little variation than the amplitude when nearest previous connection (ON).
In another example the detection moment of main electrode voltage signal can also be set as in switch member by main electrode voltage detecting circuit
Part Q1 is switched to disconnection (OFF), and by during the nearest previous connection (ON) with switch element Q1 when corresponding delay
Between after carry out.Fig. 3 be the delay time of the embodiment of the present invention 1 be variation in the case where drain voltage detection sequence figure.Such as Fig. 3
Shown, according to nearest previous connection (ON) amplitude of switch element Q1, delay time changes between T2~T6, therefore root
According to the V of switch element Q1dsThe sampling of voltage and holding voltage can measure the voltage before the decline of shoulder voltage starts, so as to
To read in more correct numerical value.
Fig. 4 is the structure chart of the delay circuit that can generate variable delay time of the embodiment of the present invention 1.As shown in figure 4,
Delay circuit is by single-shot trigger circuit, comparator DL, constant current source CC1, CC2, switching switch SW1, capacitor C6 and benchmark electricity
Press Vr4It constitutes.By current source CC1, CC2 and switching switch SW1 control, switching switch SW1's is cut for the charging and discharging of capacitor C6
Change the output signal progress using control circuit PWM.Capacitor C6 is charged using the ON signal of control circuit PWM, is utilized
OFF signal discharges, and in electric discharge, is being less than reference voltage Vr4At the time of, by exporting high level letter to single-shot trigger circuit
Number, to sampling and holding circuit S/H output sampling and keep signal.
As can be seen from the above embodiments, output voltage detection letter is generated by the correction signal of main electrode voltage and input voltage
Number, and overvoltage protection (OVP) detection is carried out based on the voltage sense signal, and it can not be influenced by input voltage, it is high
The carry out overvoltage protection detection of precision, for example, can be with no supply voltage (Vcc) winding insulation or nonisulated power supply
The unrelated carry out overvoltage protection detection of specification.
Embodiment 2
The embodiment of the invention provides a kind of control circuits of switching power unit.Fig. 5 includes the embodiment of the present invention 2
The circuit structure diagram of the switching power unit of control circuit.
As shown in figure 5, compared with the switching power unit of embodiment 1, eliminate delay circuit, sampling and holding circuit,
The bias current circuit of the resistance R7 of buffer circuit and a part as input voltage correction signal circuit.In addition, drain electrode
The link position of the shoulder voltage detection resistances R5 of voltage is changed to the capacitor C1's of buffer circuit from the drain electrode of switch element Q1
Hot side.In addition, joined R4 near diode D1 in buffer circuit, voltage detecting movement is not influenced.
In the present embodiment, the record in the working principle of the control circuit of switching power unit and process and embodiment 1
Similar, details are not described herein again.
As can be seen from the above embodiments, output voltage detection letter is generated by the correction signal of main electrode voltage and input voltage
Number, and overvoltage protection (OVP) detection is carried out based on the voltage sense signal, and it can not be influenced by input voltage, it is high
The carry out overvoltage protection detection of precision, for example, can be with no supply voltage (Vcc) winding insulation or nonisulated power supply
The unrelated carry out overvoltage protection detection of specification.
Combining specific embodiment above, invention has been described, it will be appreciated by those skilled in the art that this
A little descriptions are all exemplary, and are not limiting the scope of the invention.Those skilled in the art can be according to the present invention
Spirit and principle various variants and modifications are made to the present invention, these variants and modifications are also within the scope of the invention.
Claims (6)
1. a kind of control circuit of switching power unit, the control circuit has one of the first winding for being connected to transformer
The drain electrode of switch element, the switch element is connect with the first winding of the transformer, when voltage is input into the transformation
When the primary side of device, switch control is carried out to the switch element by the control circuit, so that the transformer is secondary
Voltage commutation caused by winding is smooth and is output to load,
The control circuit of the switching power unit is characterized in that,
The control circuit of the switching power unit has main electrode voltage detecting circuit, and the main electrode voltage detecting circuit exists
Main electrode voltage is detected during the disconnection of the switch element, the main electrode voltage is the drain electrode of the switch element
Shoulder voltage,
The main electrode voltage detecting circuit is according to the main electrode voltage signal detected, and the primary side based on the input
Voltage correction signal, generate voltage sense signal, and the voltage sense signal and reference voltage, from
And carry out overvoltage protection.
2. the control circuit of switching power unit according to claim 1, which is characterized in that
The correction signal is generated by voltage-current converter circuit, and the voltage-current converter circuit is by the primary side of the input
Voltage be converted to current signal.
3. the control circuit of switching power unit according to claim 2, which is characterized in that
The voltage-current converter circuit has preset bias current circuit.
4. the control circuit of switching power unit according to claim 1, which is characterized in that
The detection moment of the main electrode voltage signal is set as cutting in the switch element by the main electrode voltage detecting circuit
It is changed to and disconnects and carried out after defined delay time.
5. the control circuit of switching power unit according to claim 1, which is characterized in that
The detection moment of the main electrode voltage signal is set as cutting in the switch element by the main electrode voltage detecting circuit
It is changed to disconnection, and is carried out after corresponding delay time during the nearest previous connection with the switch element.
6. the control circuit of switching power unit according to claim 1, which is characterized in that
The main electrode voltage signal is subtracted the benefit of the voltage of the primary side of the input by the main electrode voltage detecting circuit
Positive signal obtains the voltage sense signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201510603351.6A CN106549559B (en) | 2015-09-21 | 2015-09-21 | The control circuit of switching power unit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510603351.6A CN106549559B (en) | 2015-09-21 | 2015-09-21 | The control circuit of switching power unit |
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| CN106549559A CN106549559A (en) | 2017-03-29 |
| CN106549559B true CN106549559B (en) | 2019-04-12 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112531646B (en) * | 2020-12-03 | 2023-07-28 | 上海晶丰明源半导体股份有限公司 | Overvoltage protection circuit and method and switching power supply |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6385059B1 (en) * | 2000-11-14 | 2002-05-07 | Iwatt, Inc. | Transformer-coupled switching power converter having primary feedback control |
| US6611439B1 (en) * | 2002-10-28 | 2003-08-26 | System General Corporation | PWM controller for controlling output power limit of a power supply |
| CN1996732A (en) * | 2005-11-28 | 2007-07-11 | 松下电器产业株式会社 | Switch power device and semiconductor device using same |
| CN102780397A (en) * | 2011-05-10 | 2012-11-14 | 鸿富锦精密工业（深圳）有限公司 | Buck converter circuit |
| CN103501114A (en) * | 2013-09-17 | 2014-01-08 | 电子科技大学 | Flyback converter with critical connection mode |
-
2015
- 2015-09-21 CN CN201510603351.6A patent/CN106549559B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6385059B1 (en) * | 2000-11-14 | 2002-05-07 | Iwatt, Inc. | Transformer-coupled switching power converter having primary feedback control |
| US6611439B1 (en) * | 2002-10-28 | 2003-08-26 | System General Corporation | PWM controller for controlling output power limit of a power supply |
| CN1996732A (en) * | 2005-11-28 | 2007-07-11 | 松下电器产业株式会社 | Switch power device and semiconductor device using same |
| CN102780397A (en) * | 2011-05-10 | 2012-11-14 | 鸿富锦精密工业（深圳）有限公司 | Buck converter circuit |
| CN103501114A (en) * | 2013-09-17 | 2014-01-08 | 电子科技大学 | Flyback converter with critical connection mode |
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