CN102412793A - Protective circuit - Google Patents
Protective circuit Download PDFInfo
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- CN102412793A CN102412793A CN2010102958943A CN201010295894A CN102412793A CN 102412793 A CN102412793 A CN 102412793A CN 2010102958943 A CN2010102958943 A CN 2010102958943A CN 201010295894 A CN201010295894 A CN 201010295894A CN 102412793 A CN102412793 A CN 102412793A
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Abstract
The invention provides a protective circuit, which is used for preventing an operational amplifier from being damaged due to short circuit by mistake, and at least comprises a temperature detection circuit, a control circuit and a pair of second current limiting circuits, wherein the temperature detection circuit produces an over-temperature signal when the temperature is over a preset value, or produces a normal signal when the temperature is lower the critical value of the preset temperature; the control circuit sends a control signal according to the over-temperature signal, and cuts off the current output path of the operational amplifier according to the over-temperature signal or conducts the current output path of the operational amplifier according to the normal signal; the second current limiting circuits are conducted by the control signal, and are used for limiting the current of the operational amplifier to be output into second current. According to the invention, the current output of the operational amplifier can be dynamically adjusted, so that the potential risks resulting in damage, which is caused by the short circuit, can be avoided.
Description
Technical field
The present invention relates to a kind of protective circuit, particularly a kind of protective circuit that is applied to prevent that operational amplifier (Operational Amplifier) from damaging because of the mistake short circuit.
Background technology
In general; The buffer (Buffer) of operational amplifier (or being referred to as operational amplifier) Chang Zuowei one element output uses among a chip; When because carelessness and mistake during with the output short circuit (Short) of operational amplifier; Operational amplifier can be because of great electric current output of the effect output of short circuit, and this big electric current may let the bulk temperature of chip raise, and is serious even can make chip break down or burn.
The present one short-circuit protection means known, when temperature surpassed a predetermined temperature threshold value, the output current of restriction operation amplifier reduced the too high and probability that causes fault or burn of chip temperature.Though this practice can reduce operational amplifier because of big electric current that short circuit caused; But can't thoroughly avoid the possibility of damaging, main cause is if the operational amplifier problem of short-circuit continues for a long time and do not solve, even if electric current diminishes; Temperature still possibly continue to rise to the temperature that can bear above chip; In brief, the method only is to slow down the speed that temperature rises, and chip still is exposed among the risk that is burnt out.
Therefore, how can be the time when the short circuit of operational amplifier output mistake through a kind of method or means, avoid Yin Wendu too high and the probability of damaging takes place effectively and completely, this is the target that relevant research and development manufacturer makes great efforts.
Summary of the invention
The present invention provides a kind of and is applied to prevent that operational amplifier is because of missing the protective circuit that short circuit is damaged.
According to disclosed protective circuit, protective circuit comprises a temperature sensing circuit, a control circuit and a pair of second current-limiting circuit at least.Temperature sensing circuit in order to detected temperatures, and produces an excess temperature signal when temperature surpasses a predetermined value, when temperature is lower than predetermined value, produce a normal signal.Control circuit is coupled to this temperature sensing circuit, when receiving this excess temperature signal, sends a control signal, and according to this excess temperature signal by or according to the electric current outgoing route of this normal signal conducting operational amplifier.Second current-limiting circuit is opened by control signal institute conducting, is output as one second electric current in order to the electric current of restriction operation amplifier.
When operational amplifier surpasses a predetermined set value because of the mistake short circuit causes chip temperature to rise; The electric current outgoing route of the earlier direct shutoff operation amplifier of meeting; Let the electric current of operational amplifier be output as zero, after normal temperature falls back in the temperature that is detected, again operational amplifier conducting electric current is again exported; And second electric current that the size of current to that the restriction operation amplifier is exported is less; If this second less electric current still makes temperature continue to be increased to above predetermined value, then can carry out the adjusting of temperature once more by the electric current outgoing route of operational amplifier.
Therefore, through above-mentioned circuit framework, the present invention is to export according to the electric current that comes dynamically to adjust operational amplifier through two stage current switching with the temperature, comes thoroughly to solve the risk that chip or the hiding quilt of circuit is burnt out because of short circuit.
About characteristic of the present invention, the real work and effect, conjunction with figs. is made most preferred embodiment and is specified as follows.
Description of drawings
Fig. 1 is applied to the embodiment of the protective circuit of an operational amplifier for the present invention.
Fig. 2 is an operational amplifier application drawing 1 in the sketch map of operational amplifier output current during in short circuit.
Description of reference numerals in the above-mentioned accompanying drawing is following:
10 temperature sensing circuits
11 control circuits
111 latchs
112 first reversers
113 second reversers
12 initial circuits
13A, 13B first current-limiting circuit
14A, 14B second current-limiting circuit
The Vo output
+ VDD positive voltage source
-VDD negative voltage source
Q conducting output
R the RESET input
The S set input
Q1 first output transistor
Q2 second output transistor
The Q3 first positive switch
The Q4 first negative switch
The Q5 second positive switch
The Q6 second negative switch
The Imax maximum current
Ilow second electric current
Embodiment
Please refer to shown in Figure 1ly, Fig. 1 is applied to the embodiment of the protective circuit of an operational amplifier for the present invention.Generally speaking; The internal circuit design of operational amplifier can be divided three big blocks as input stage circuit, gain stage circuit and output-stage circuit haply, and the outside of operational amplifier comprises an output end vo, a positive input terminal, a negative input end, one positive voltage source+VDD and one negative voltage source-VDD, and circuit at different levels are then coupled by a plurality of transistors and form; Have different frameworks according to dissimilar operational amplifiers; Because this part is known by one skilled in the art of the present invention, therefore, is the simplification length; This specification only describes to the applied scope of protective circuit when writing, and other circuit partial structurtes at different levels are not then tired out and stated.
Protective circuit of the present invention mainly is arranged in the operational amplifier in the output-stage circuit; Output-stage circuit is made up of one first output transistor Q1 and one second output transistor Q2; The first output transistor Q1 is coupled between positive voltage source+VDD and the output end vo; The second output transistor Q2 is coupled between negative voltage source-VDD and the output end vo, and the output-stage circuit of operational amplifier has a pair of first current- limiting circuit 13A, 13B in addition, is respectively coupled to the first output transistor Q1 and the second output transistor Q2; With the output current of restriction operation amplifier, this general normal maximum output current (Io maximum) that is referred to as operational amplifier.
Protective circuit of the present invention comprises a temperature sensing circuit 10, a control circuit 11 and a pair of second current-limiting circuit 14A, 14B; Temperature sensing circuit 10 is in order to detected temperatures; And when temperature surpasses a predetermined value, produce an excess temperature signal,, temperature produces a normal signal when being lower than predetermined value.Control circuit 11 is coupled to this temperature sensing circuit 10, when receiving this excess temperature signal, sends a control signal, and according to this excess temperature signal by or according to the electric current outgoing route of this this output end vo of normal signal conducting.The second current-limiting circuit 14A, 14B are output as one second electric current by the conducting of control signal institute in order to the electric current that limits output end vo.
Each second current-limiting circuit 14A, 14B comprise an input, a control end and an output; Input is coupled to second corresponding positive switch Q5 or the output of the second negative switch Q6; The second current-limiting circuit 14A, the control end of 14B are connected in the output of the second current- limiting circuit 14A, 14B and are coupled to the corresponding first output transistor Q1 or the second output transistor Q2.
In present embodiment, latch 111 is a setting-reset latch (S-R Latch).The first positive switch Q3 and the second positive switch Q5 are that (the first negative switch Q4 and the second negative switch Q6 are the metal oxide semiconductor transistor of a N type for Metal Oxide Semiconductor, MOS) transistor for the metal-oxide semiconductor (MOS) of a P type.
Please cooperate with reference to figure 1 and shown in Figure 2, Fig. 2 is an operational amplifier application drawing 1 in the sketch map of operational amplifier output current during in short circuit.Through assisting of current diagram; When this begins to explain protective circuit of the present invention how in the operational amplifier short circuit; Come the output current of dynamic adjustment operational amplifier through above-mentioned circuit framework; In addition, like the characteristic of the known operational amplifier of those of ordinary skill of the present invention, the first positive switch Q3 that the first output transistor Q1 is coupled, the second positive switch Q5, the first current-limiting circuit 13A and the second current-limiting circuit 14A are all corresponding relevant with the first negative switch Q4, the second negative switch Q6, the first current-limiting circuit 13B and the second current-limiting circuit 14B that the second output transistor Q2 is coupled; Both operation principles are identical; So describe when operating in positive bias to operational amplifier in this, also promptly the part of the first output transistor Q1 is described, remaining part is not then tired out and is stated.
Moreover, the convenience of understanding for helping and describing, below for the explanation of signal voltage level; To represent high potential with logical one, represent electronegative potential, it should be noted that with logical zero; This is merely the usefulness in order to the illustration of narration relativeness, is not in order to limit technical characterictic of the present invention.
Please refer again to Fig. 1 and Fig. 2, at first, when operational amplifier when switching on first; Initial circuit 12 can be seen the RESET input R of 1 signal to latch 111 off, comes reset latch 111, to remove any state that possibly be stored on the latch 111; Initial circuit 12 can be kept this signal a period of time of 1, and after the bias voltage of wait operational amplifier circuit at different levels was set and accomplished, the signal with 1 switched to 0; In this, the signal of above-mentioned reset signal definition described for this reason 1.
When the output end vo of this operational amplifier is a short-circuit condition, the output end vo of operational amplifier is exported a maximum current ImaX under the restriction of first current-limiting circuit, and makes that because of the relation of short circuit temperature begins to rise.
When temperature surpasses this predetermined value that temperature sensing circuit 10 sets; Temperature sensing circuit 10 can send one 1 signal; What this signal of 1 can be sent to first reverser 112 and latch 111 respectively is provided with input S; First reverser 112 can these signals of 1 of transposition be opened the first positive switch Q3 in 0, and then closes the first output transistor Q1.The conducting output Q of latch 111 is then according to the signal that input S received 1 is set; Send one 1 signal to the second reverser 113; Second reverser 113 is 0 with received 1 signal transposition; And the second positive switch Q5 opened, be an excess temperature signal in this with 1 the signal definition that temperature sensing circuit 10 is sent, will be the signal definition that the second positive switch Q5 opens one control signal.
This moment is because being closed by the first positive switch Q3 of the first output transistor Q1, and the output current of operational amplifier is vanishing, and lets temperature descend.
When temperature is lower than the predetermined value that temperature sensing circuit 10 sets; Temperature sensing circuit 10 can send one 0 signal; What this signal of 0 can be sent to first reverser 112 and latch 111 respectively is provided with input S; First reverser 112 is 1 cutting out the first positive switch Q3 with 0 signal transposition, because the first positive switch Q3 is closed, and the output transistor Q1 that wins can be unlocked again; This moment, operational amplifier can be exported electric current again, and 0 the signal definition of being sent in this temperature sensing circuit 10 is a normal signal.
Please note; Though the signal that temperature sensing circuit 10 is sent has been a normal signal from the excess temperature conversion of signals, the RESET input R of latch 111 is 0, so the output signal of the conducting output Q of latch 111 still remains 1; It also is the state that the second positive switch Q5 still keeps unlatching; In this definition latch 111 is a lock-out state, and when latch 111 is lock-out state, the signal of conducting output Q output will keep 1 forever; The signal that is received of this set input S after ignoring is with the output of constant conducting output Q.
At this moment, second positive switch Q5 meeting conducting, the second current-limiting circuit 14A make the output current that flows through the first output transistor Q1 to be restricted to one second electric current I low by the second current-limiting circuit 14A, and the second electric current I low can be much smaller than maximum current Imax.
But; Because the short-circuit state of operational amplifier is not got rid of yet; With output current be restricted to that the second electric current I low gets rid of not exclusively still that temperature rises maybe, therefore, in case when temperature surpasses this predetermined value that temperature sensing circuit 10 sets; Temperature sensing circuit 10 can send out the excess temperature signal once more, repeats above-mentioned start relation then and is excluded up to problem of short-circuit.
In sum; The present invention is through the means of temperature detection, and when temperature surpassed a predetermined set value, directly the electric current of shutoff operation amplifier was exported earlier; Let the electric current of operational amplifier be output as zero; After normal temperature falls back in waiting temperature, let operational amplifier output current again again, and the size of restriction output current is by maximum current to the second electric current; With the temperature is according to the electric current output that comes dynamically to adjust operational amplifier, makes chip or the hiding risk that is burnt out of circuit with thorough solution because of short circuit.
Claims (10)
1. a protective circuit is applied to an operational amplifier, and this protective circuit comprises:
One temperature sensing circuit in order to detecting a temperature, and produces an excess temperature signal when this temperature surpasses a predetermined value, when this temperature is lower than this predetermined value, produce a normal signal;
One control circuit is coupled to this temperature sensing circuit, and sends a control signal according to this excess temperature signal, in addition according to this excess temperature signal or the corresponding conducting of this normal signal or by the electric current output of this operational amplifier; And
A pair of second current-limiting circuit couples this control circuit, and by this control signal institute conducting, is output as one second electric current in order to the electric current that limits this operational amplifier.
2. protective circuit as claimed in claim 1, wherein, this operational amplifier comprises an output, a positive voltage source, a negative voltage source, one first output transistor and one second output transistor, this control circuit comprises:
One latch, in order to receiving this excess temperature signal or this normal signal of this temperature sensing circuit, and according to this this control signal of excess temperature signal output;
One first positive switch; Have an input, a control end and an output; This input of this first positive switch couples this positive voltage source; This control end of this first positive switch is coupled to this temperature sensing circuit, and this output of this first positive switch is coupled to this first output transistor; And
One second positive switch; Have an input, a control end and an output; This input of this second positive switch is coupled to this positive voltage source; This control end of this second positive switch is coupled to this latch, and this output of this second positive switch is coupled to this to one of second current-limiting circuit.
3. protective circuit as claimed in claim 2, wherein, this control circuit also comprises:
One first negative switch; Have an input, a control end and an output; This input of this first negative switch couples this negative voltage source, and this control end of this first negative switch couples this temperature sensing circuit, and this output of this first negative switch is coupled to this second output transistor; And
One second negative switch; Have an input, a control end and an output; This control end that this input of this second negative switch couples this negative voltage source, this second negative switch couples this latch, and this output of this second negative switch couples this to another of second current-limiting circuit.
4. protective circuit as claimed in claim 2, wherein, when this temperature sensing circuit sent this excess temperature signal, this first positive switch cut out this first output transistor.
5. protective circuit as claimed in claim 2, wherein, when this temperature sensing circuit sends this normal signal, this this first output transistor of first positive switch open.
6. protective circuit as claimed in claim 2, wherein, this control signal is opened this second positive switch, and this second current-limiting circuit of coupling of this second positive switch conduction institute correspondence is output as this second electric current with the electric current that limits this operational amplifier simultaneously.
7. protective circuit as claimed in claim 2, wherein, this latch comprises:
One set input couples this temperature sensing circuit, and in order to receive this excess temperature signal or this normal signal of this temperature sensing circuit, wherein, when this latch received this excess temperature signal first, this latch can get into a lock-out state;
One conducting output is exported this control signal; And
One the RESET input is coupled to an initial circuit, in order to receive a reset signal.
8. protective circuit as claimed in claim 7 wherein, in the initial time of this initial circuit after this operational amplifier energising, is sent this reset signal to this latch, in order to remove this lock-out state of this latch.
9. protective circuit as claimed in claim 3; Wherein, Should respectively comprise an input, a control end and an output to second current-limiting circuit; Respectively this input of this second current-limiting circuit is coupled to this output of this second positive switch or this second negative switch, and respectively the control end of this second current-limiting circuit is connected in the output of this second current-limiting circuit respectively and is coupled to corresponding this first output transistor or this second output transistor.
10. protective circuit as claimed in claim 3; Wherein, This latch is a setting-reset latch; This first positive switch and this second positive switch are the metal oxide semiconductor transistor of a P type, and this first negative switch and this second negative switch are the metal oxide semiconductor transistor of a N type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010295894.3A CN102412793B (en) | 2010-09-21 | 2010-09-21 | Protective circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010295894.3A CN102412793B (en) | 2010-09-21 | 2010-09-21 | Protective circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102412793A true CN102412793A (en) | 2012-04-11 |
| CN102412793B CN102412793B (en) | 2014-04-02 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201010295894.3A Expired - Fee Related CN102412793B (en) | 2010-09-21 | 2010-09-21 | Protective circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN102412793B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105320015A (en) * | 2014-06-03 | 2016-02-10 | 中国科学院微电子研究所 | Over-temperature warning and over-temperature protection method and device based on microcontroller |
| CN108768314A (en) * | 2018-07-18 | 2018-11-06 | 天津大学 | A kind of circuit that amplifier negative port is protected with discrete component |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63229757A (en) * | 1987-03-19 | 1988-09-26 | Nippon Denso Co Ltd | Semiconductor device |
| US5600575A (en) * | 1994-10-05 | 1997-02-04 | Anticole; Robert B. | Drive protection monitor for motor and amplifier |
| US6448857B1 (en) * | 2000-04-13 | 2002-09-10 | Niles Audio Corporation | Audio amplifier controller having soft start circuit protection and associated methods |
| US20020125945A1 (en) * | 2001-03-08 | 2002-09-12 | Taylor Stewart Sidney | Method and apparatus for protecting radio frequency power amplifiers |
| CN1960170A (en) * | 2005-10-31 | 2007-05-09 | 松下电器产业株式会社 | Output offset protection for power amplifier |
-
2010
- 2010-09-21 CN CN201010295894.3A patent/CN102412793B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63229757A (en) * | 1987-03-19 | 1988-09-26 | Nippon Denso Co Ltd | Semiconductor device |
| US5600575A (en) * | 1994-10-05 | 1997-02-04 | Anticole; Robert B. | Drive protection monitor for motor and amplifier |
| US6448857B1 (en) * | 2000-04-13 | 2002-09-10 | Niles Audio Corporation | Audio amplifier controller having soft start circuit protection and associated methods |
| US20020125945A1 (en) * | 2001-03-08 | 2002-09-12 | Taylor Stewart Sidney | Method and apparatus for protecting radio frequency power amplifiers |
| CN1960170A (en) * | 2005-10-31 | 2007-05-09 | 松下电器产业株式会社 | Output offset protection for power amplifier |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105320015A (en) * | 2014-06-03 | 2016-02-10 | 中国科学院微电子研究所 | Over-temperature warning and over-temperature protection method and device based on microcontroller |
| CN108768314A (en) * | 2018-07-18 | 2018-11-06 | 天津大学 | A kind of circuit that amplifier negative port is protected with discrete component |
Also Published As
| Publication number | Publication date |
|---|---|
| CN102412793B (en) | 2014-04-02 |
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Granted publication date: 20140402 Termination date: 20140921 |
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