CN1877944A - Reverse current protection circuit for switching power supply - Google Patents
Reverse current protection circuit for switching power supply Download PDFInfo
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- CN1877944A CN1877944A CN 200510075984 CN200510075984A CN1877944A CN 1877944 A CN1877944 A CN 1877944A CN 200510075984 CN200510075984 CN 200510075984 CN 200510075984 A CN200510075984 A CN 200510075984A CN 1877944 A CN1877944 A CN 1877944A
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- reverse current
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- 239000003990 capacitor Substances 0.000 claims abstract description 26
- 238000012544 monitoring process Methods 0.000 claims abstract description 6
- 238000012806 monitoring device Methods 0.000 claims abstract 8
- 230000008878 coupling Effects 0.000 claims abstract 3
- 238000010168 coupling process Methods 0.000 claims abstract 3
- 238000005859 coupling reaction Methods 0.000 claims abstract 3
- 230000006378 damage Effects 0.000 claims description 10
- 230000001681 protective effect Effects 0.000 description 20
- 208000027418 Wounds and injury Diseases 0.000 description 9
- 208000014674 injury Diseases 0.000 description 9
- 230000008676 import Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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Abstract
A reverse current protection circuit for a switching power supply includes an input power source, an electromagnetic interference filter, an input filter capacitor, a DC-DC converter, a switching device and a reverse current protection circuit, the reverse current protection circuit includes a transistor switch coupled to the input power source and having a control terminal and at least two current conduction terminals, a monitoring device coupled to the transistor switch for monitoring a change in a polarity of a voltage across the current conduction terminals and generating a driving signal in response to the change in the polarity of the voltage across the current conduction terminals, and a signal coupler coupled between the transistor switch and the monitoring device for coupling the driving signal to the control terminal to turn off the transistor switch and block a discharge loop of the reverse current; the invention can use the reverse current protection circuit to protect the internal circuit components from being damaged by the short circuit of the input end when the input end of the switching power supply is short-circuited.
Description
Technical field
The present invention relates to a kind of reverse current protective circuit; and relate in particular to a kind of reverse current protective circuit; it can be when the input short circuit of switched power supplier the time; protection switched power supplier internal circuit unit avoids suffering the injury that backward current caused of sending from input filter capacitor.
Background technology
Fig. 1 shows the typical representative graph according to the switched power supplier of prior art.Switched power supplier 100 shown in Figure 1 is made up of an input power supply 101 (being generally a direct current voltage), an Electromagnetic interference filter (EMI filter) 102, one input filter capacitor 103, a polarity detector (polarity detector) 104, one burst current limiter (inrush current limiter) 105, one switching device 106 and 107 of DC-DC converters (DC-DC converter).Electromagnetic interference filter 102 is coupled to input power supply 101 and it is used for eliminating formed differential mode noise of circuit (differential mode noise) or common mode noise (common mode noise).Input filter capacitor 103 is coupled to Electromagnetic interference filter 102 and it is used for the input direct voltage that smooth-going (smooth) provided by input power supply 10.Switching device 106 is coupled to input filter capacitor 103 and is finished by a tandem switching transistor circuit (cascaded switching transistor circuit) usually, and it is used in the mode that replaces input direct voltage being coupled to DC-DC converter 107.DC-DC converter 107 is coupled to switching device 106 and is used for converting input direct voltage to one or more predetermined direct voltages to meet a series of specification requirement.The polarity that polarity detector 104 is used for detecting the reversing of input direct voltage and prevents input direct voltage is by reversal connection.Burst current limiter 105 is used for avoiding the surge of burst current (inrush current).
When operate as normal, input filter capacitor 103 can be charged fully so that remove high-frequency harmonic (high-frequency harmonics) in the input direct voltage.Yet, if the input short circuit of switched power supplier, input filter capacitor 103 just can discharge stored energy, and at the huge backward current of input filter capacitor 103 to the input direction of switched power supplier, just can flow and come via being positioned near the input internal circuit unit, for example Electromagnetic interference filter 102, polarity detector 104, burst current limiter 105 and switching device 106.These internal circuit units quite are difficult to resist for the impact surge of backward current, and if the discharge loop of backward current can't cut off at once, these internal circuit units will burn.
Therefore, under the situation that input is short-circuited, be stored in the input side that energy in the input filter capacitor just can be released into switched power supplier, and internal circuit unit will fault under the protection that does not have safety device.
In view of this, along its trend development a kind of reverse current protective circuit, it can protect the internal circuit unit of switched power supplier when the input short circuit, avoid being originated from the caused injury of backward current of input filter capacitor.
Summary of the invention
A purpose of the present invention is to provide a reverse current protective circuit, when the input short circuit time, avoids suffering the caused injury of backward current that is discharged by input filter capacitor in order to the internal circuit unit of protection switched power supplier.
Another object of the present invention is to provide a switched power supplier, it uses a reverse current protective circuit to protect internal circuit unit to avoid suffering because the caused injury of input of short circuit.
For achieving the above object,, propose a kind of switched power supplier, comprise an input power supply, in order to an input electric power to be provided according to main aspect of the present invention; One Electromagnetic interference filter retains in differential mode noise or common mode noise in the circuit in order to elimination; One input filter capacitor should be imported electric power in order to smooth-going; One DC-to-DC converter becomes one or more predetermined voltage levels in order to will import power conversions; One switching device is used for will importing electric power in the mode that replaces and is coupled to DC-DC converter; And a reverse current protective circuit, avoid suffering the caused injury of backward current that discharges by this input filter capacitor in order to the protection internal circuit unit.This reverse current protective circuit comprises a transistor switch, is coupled to this input power supply and has a control end (control terminal) and at least two conduction of current ends (current-conducting terminals); One supervising device is coupled to this transistor switch, in order to the change of the polarity of voltage that monitors this conduction of current end of cross-over connection, and answers the polarity of voltage of this conduction of current end of cross-over connection to change to produce a drive signal; And a signal coupler, be coupled between this transistor switch and this supervising device, in order to this drive signal is coupled to this control end so that this transistor switch is ended, and block the discharge loop of this backward current by this.
Specifically, a kind of reverse current protective circuit, in order to protect the internal circuit unit of a power supply unit, when an input short circuit of this power supply unit, make it avoid suffering the injury of a backward current, it comprises: a transistor switch is coupled to this input and has a control end and at least two conduction of current ends; One supervising device, be coupled to this transistor switch, in order to monitoring the change of the polarity of voltage of cross-over connection on these two conduction of current ends, and, produce a drive signal and come by this transistor switch in response to the change of the polarity of voltage of cross-over connection on these two conduction of current ends; And a signal coupler, be coupled between this transistor switch and this supervising device, in order to this drive signal is coupled to this control end.
This power supply unit is a switched power supplier.This transistor switch is formed by a single N type MOSFET or a tandem N type MOSFET circuit.This supervising device is made up of a voltage comparator, and this signal coupler is made up of a positive-negative-positive bipolar junction transistor.
A kind of switched power supplier comprises: an input power supply, in order to an input electric power to be provided; One input filter capacitor is coupled to this input power supply, should import electric power in order to smooth-going; An and reverse current protective circuit; be coupled between this input power supply and this input filter capacitor; when the input short circuit of this power supply unit, avoid suffering the injury of the backward current that discharges by this input filter capacitor in order to the internal circuit unit of protecting this switched power supplier.
This input power supply is a direct current voltage.Described switched power supplier also comprises: an Electromagnetic interference filter, be coupled to this input power supply, and retain in differential mode noise or common mode noise in this switched power supplier in order to elimination; One power supply changeover device becomes at least one predetermined voltage level in order to will import power conversions; And a switching device, be coupled to this power supply changeover device, be used for should importing electric power and be coupled to this power supply changeover device in the mode that replaces.This power supply changeover device is a DC-to-DC converter.
This reverse current protective circuit also comprises: a transistor switch is coupled to this input power supply and has a control end and at least two conduction of current ends; One supervising device, be coupled to this transistor switch, in order to monitoring the change of the polarity of voltage of cross-over connection on these two conduction of current ends, and, produce a drive signal and come by this transistor switch in response to the change of the polarity of voltage of cross-over connection on these two conduction of current ends; And a signal coupler, be coupled between this transistor switch and this supervising device, in order to this drive signal is coupled to this control end.
This transistor switch is formed by a single N type MOSFET or a tandem N type MOSFET circuit.This supervising device is made up of a voltage comparator, and this signal coupler system is made up of a positive-negative-positive bipolar junction transistor.
From above we as can be seen; reverse current protective circuit; can in order to the protection switched power supplier internal circuit unit when the input short circuit time; when a switched power supplier includes reverse current protective circuit; use the reverse current protective circuit can be the time when the input short circuit of switched power supplier; protection switched power supplier internal circuit unit avoids suffering the injury that backward current caused of sending from input filter capacitor.
Above-mentioned and further feature of the present invention and advantage can obtain best understanding by following description and with reference to accompanying drawing.
Description of drawings
Fig. 1 is the circuit diagram of the typical exchange formula power supply unit of prior art;
Fig. 2 has a preferred embodiment of the switched power supplier of reverse-current protection circuit for the present invention.
Wherein, description of reference numerals is as follows:
100,200 switched power suppliers
101,201 input power supplys
102,202 Electromagnetic interference filter (electromagnetic interface filter)
103,203 input filter capacitors
104 polarity detectors
105,204 burst current limiters
106,205 switching devices
107,206 DC-to-DC converter
207 reverse current protective circuits
31 transistor switches
32 supervising devices
33 signal couplers
Embodiment
See also Fig. 2, Fig. 2 has the circuit diagram of one of preferred embodiment of the switched power supplier of reverse current protective circuit for the present invention.
As shown in Figure 2, switched power supplier 200 comprises input power supply (being generally a direct current voltage) 201, one Electromagnetic interference filter (EMI filter) 202, one input filter capacitor 203, a burst current limiter 204, a switching device 205, a DC-to-DC converter 206 and a reverse current protective circuit 207.The function of input power supply 201, Electromagnetic interference filter 202, input filter capacitor 203, burst current limiter 204, switching device 205 and DC-to-DC converter 206 and operating principle are all similar with the function and the operating principle of the corresponding thing of Fig. 1, and are omitted in this explanation with them.
It should be noted that switched power supplier 200 comprises the reverse current protective circuit 207 between input power supply 201 and input filter capacitor 203.This reverse current protective circuit 207 mainly is made up of a transistor switch 31, a supervising device 32 and a signal coupler 33.Transistor switch 31 generally is made up of a single N type MOSFET or a tandem N type MOSFET circuit (cascaded N-channel MOSFET circuit), and it is coupled to input power supply 201.Supervising device 32 is coupled to transistor switch 31 and the preferably is finished by a voltage comparator, and wherein a reverse input end of the voltage comparator non-inverting input that is coupled to a conduction of current end (the current-conducting terminal) 311 of transistor switch 31 and voltage comparator is coupled to another conduction of current end 312 of transistor switch 31.Supervising device 32 is used for monitoring the change of the polarity of voltage of cross-over connection on conduction of current end 311 and 312, and answers the change of the polarity of voltage of cross-over connection on conduction of current end 311 and 312 to produce a drive signal.Signal coupler 33 is coupled between transistor switch 31 and the supervising device 32, and the preferably is finished by the bipolar junction transistor of a positive-negative-positive (PNP-type BJT).The drive signal that signal coupler 33 is used for being exported by supervising device 32 is coupled to the control end of transistor switch 31 so that the ON/OFF of oxide-semiconductor control transistors switch 31.Function and operating principle about according to a preferred embodiment of the present invention reverse current protective circuit 207 will be described in detail as follows.
When normal running, input current flows to negative input end 212 by the positive input terminal 211 of input power supply 201, and transistor switch 31 is understood conductings (turn on) and gone up conduction current in forward direction (forward direction).That is to say that electric current is flowed to the source terminal 311 of transistor switch 31 by the drain electrode end 312 of transistor switch 31.At this moment, the drain voltage of transistor switch 31 is greater than the source voltage of transistor switch 31, and therefore HIGH signal of voltage comparator 32 outputs is to positive-negative-positive bipolar junction transistor 33, and this positive-negative-positive bipolar junction transistor 33 then can end (turn off).Yet, if during the input short circuit of switched power supplier 200, just input filter capacitor 203 discharges its energy stored by inducing a backward current opposite with the input current flow direction.Therefore, transistor switch 31 is understood conductings (turn on) and is gone up conduction current in reverse direction (reverse direction), and the source voltage of transistor switch 31 is greater than the drain voltage of transistor switch 31.Therefore, the polarity of voltage of cross-over connection on the conduction of current end of transistor switch 31 just can change, and LOW signal of voltage comparator 32 output as a drive signal to positive-negative-positive bipolar junction transistor 33.So bipolar junction transistor 33 just can conducting, and by this drive signal (LOW signal) is coupled to the gate terminal of transistor switch 31.Therefore, transistor switch 31 can be driven signal and drives and end at once.Therefore, originate from the discharge loop of the backward current of input filter capacitor 203 and just can be blocked, and the internal circuit unit of switched power supplier just can avoid because the caused injury of surge of backward current by the transistor switch 31 that ends.
Even if the present invention has been described in detail by the above embodiments can by those skilled in the art appoint execute that the craftsman thinks and all as modify, yet the scope of neither disengaging institute of the present invention desire protection.
Claims (11)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510075984 CN1877944A (en) | 2005-06-07 | 2005-06-07 | Reverse current protection circuit for switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510075984 CN1877944A (en) | 2005-06-07 | 2005-06-07 | Reverse current protection circuit for switching power supply |
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| Publication Number | Publication Date |
|---|---|
| CN1877944A true CN1877944A (en) | 2006-12-13 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200510075984 Pending CN1877944A (en) | 2005-06-07 | 2005-06-07 | Reverse current protection circuit for switching power supply |
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| CN (1) | CN1877944A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101656418B (en) * | 2008-08-20 | 2012-12-12 | 台达电子工业股份有限公司 | Fan system and power reverse protection device thereof |
| CN111865058A (en) * | 2020-07-09 | 2020-10-30 | 苏州明纬科技有限公司 | An input end protection circuit and a power conversion device |
| CN113644624A (en) * | 2020-05-11 | 2021-11-12 | 台达电子工业股份有限公司 | Transmission and distribution system with electric shock protection function and operation method thereof |
-
2005
- 2005-06-07 CN CN 200510075984 patent/CN1877944A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101656418B (en) * | 2008-08-20 | 2012-12-12 | 台达电子工业股份有限公司 | Fan system and power reverse protection device thereof |
| CN113644624A (en) * | 2020-05-11 | 2021-11-12 | 台达电子工业股份有限公司 | Transmission and distribution system with electric shock protection function and operation method thereof |
| CN113644624B (en) * | 2020-05-11 | 2024-03-01 | 台达电子工业股份有限公司 | Transmission and distribution system with electric shock protection function and operation method thereof |
| CN111865058A (en) * | 2020-07-09 | 2020-10-30 | 苏州明纬科技有限公司 | An input end protection circuit and a power conversion device |
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