CN106527563A - Overcurrent protection circuit for negative output LDO stabilizer - Google Patents
Overcurrent protection circuit for negative output LDO stabilizer Download PDFInfo
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- CN106527563A CN106527563A CN201611165361.7A CN201611165361A CN106527563A CN 106527563 A CN106527563 A CN 106527563A CN 201611165361 A CN201611165361 A CN 201611165361A CN 106527563 A CN106527563 A CN 106527563A
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- circuit
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- npn pipe
- termination
- colelctor electrode
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/569—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Emergency Protection Circuit Devices (AREA)
- Continuous-Control Power Sources That Use Transistors (AREA)
- Amplifiers (AREA)
Abstract
The invention belongs to the field of electronic technology, and particularly relates to an overcurrent protection circuit for a negative output LDO stabilizer. The circuit includes an overcurrent signal VS generating circuit, an overcurrent signal reference voltage VT generating circuit and a comparison output circuit. The output end of the VS generating circuit is connected with the negative input end of the comparator. The input end of the VS generating circuit is connected with the base of the adjusting tube. The VT generating circuit is connected with a temperature independent current source. The output end of the VT generating circuit is connected with the positive input end of the comparison output circuit. The negative input end of the comparison output circuit is connected with the output end of the VS generating circuit. The positive input end of the comparison output circuit is connected with the output of the VT generating circuit. The output end of the comparison output circuit is connected with the output point of the error amplifier (EA) which is also called the base point of the adjusting tube.
Description
Technical field
The invention belongs to integrated circuit fields, and in particular to (LOW DROP-OUT are linearly steady for a kind of LDO of negative voltage output
Depressor) circuit current foldback circuit.
Background technology
Traditional LDO circuit is by the part such as bandgap reference circuit, error amplifier, power tube and resistance-feedback network group
Into bandgap reference circuit produces a reference voltage V unrelated with temperature and power supplyREF, operational amplifier and power tube MPComposition
Feedback circuit be used for keep stablizing for output voltage.
In actual application, overheat protector, overcurrent protection and reverse output protection etc. can be also added in circuit.Protect
The effectively start of protection circuit can make chip secure work, it is to avoid the factor such as excessively stream causes wafer damage.
In conventional overcurrent protection circuit, typically a small resistor can be connect in power tube emitter stage, output current flows through little electricity
Resistance RS, produce a pressure drop VS, then VSIt is compared with a threshold voltage, and then limits output current.But, due to
The resistance general precision of little resistance is not high, and in order to improve the precision of current limit threshold, can add unavoidably to trim etc. improves to precision
Link, wastes chip area.Small resistor added by emitter stage can increase input and output pressure reduction in the case of big output current, also,
Reduce the efficiency of chip.
The content of the invention
It is an object of the invention to provide a kind of current foldback circuit of negative output LDO circuit, can reduce the big output of circuit
The precision of the threshold point of pressure reduction and raising overcurrent protection during electric current, and design simple.
The technical scheme is that：A kind of current foldback circuit of negative output LDO voltage stabilizer, it is characterised in that include
Over-current signal VSProduce circuit, over-current signal reference voltage VTProduce circuit and compare output circuit；The VSProduce the defeated of circuit
Go out to terminate the negative input end of comparator, VSProduce the ground level of the input termination adjustment pipe of circuit；The VTProduce the input of circuit
Meet a temperature independent current source, the VTThe output termination for producing circuit compares the positive input terminal of output circuit；It is described
The relatively negative input termination V of output circuitSThe outfan of circuit, compares the positive input termination V of output circuitTProduce the defeated of circuit
Go out end, compare output termination error amplifier (EA) output point of output circuit, that is, adjust pipe ground level point.
Further, the VSProducing circuit includes NPN pipe QS, first resistor R0；The VTProducing circuit includes the
Two NPN pipe Q0, the 3rd NPN pipe Q1, second resistance R1, 3rd resistor R2, the first ideal current source I0；It is described to compare output circuit bag
Include first comparator CP, the 4th NPN pipe Q2, the first electric capacity C1；
The first NPN pipe QSGround level connect adjustment pipe QPGround level, its colelctor electrode connecting resistance R0, emitter stage connects negative input
Power supply；
First resistor R0The other end ground connection；
The 2nd NPN pipe Q0Ground level connect 3rd resistor R2One end, its colelctor electrode connects 3rd resistor R2The other end,
Emitter stage connects negative input power supply；
The first current source I0One termination the 2nd NPN pipe Q0Colelctor electrode, the other end ground connection；
The 3rd NPN pipe Q1Ground level meets the 2nd NPN pipe Q0Colelctor electrode, its colelctor electrode connects second resistance R1One end, send out
Emitter-base bandgap grading connects negative output power supply；
Second resistance R1The other end ground connection；
The negative input of first comparator CP terminates NPN pipe QSColelctor electrode, its positive input terminates the 3rd NPN pipes
Q1Colelctor electrode, output termination the 4th NPN pipe Q2Ground level；
The 4th NPN pipe Q2Colelctor electrode connect error amplifier and adjustment pipe QPJunction point, emitter stage level connects negative input
Power supply；
The electric electric capacity C1One termination the 4th NPN pipe Q2Ground level, the 4th NPN pipe Q of another termination2Colelctor electrode.
Description of the drawings
Fig. 1 conventional overcurrent protection circuit structural representations；
The current foldback circuit schematic diagram of negative output LDO of Fig. 2 the design.
Specific embodiment
Below in conjunction with the accompanying drawings, describe technical scheme in detail.
As shown in Fig. 2 the current foldback circuit of negative output LDO described herein includes in the following embodiments：One
The individual feedback circuit comprising error amplifier, an over-current signal VSProduce circuit, an excessively stream threshold voltage VTProduce circuit,
One is compared output circuit.
The negative input of error amplifier terminates one and produces bandgap voltage reference V by internalref, error amplifier is just
The outfan V of input termination LDOout, form unity negative feedback.The output of error amplifier and power tube QPBase stage and compare
The outlet tube Q of circuit2Colelctor electrode be connected.Described over-current signal voltage VSProduce circuit, by with power tube emitter area into
1：The sampling tube and current-to-voltage convertor R of K0Composition.The base stage of sampling tube and emitter stage respectively with the base stage of power tube and send out
Emitter-base bandgap grading is connected, colelctor electrode connecting resistance R0One end, resistance is another to terminate to ground.In order to reduce the power consumption of current foldback circuit, can be with
Select K=1/1000 to achieve the goal.When the impact of Early voltage is not considered, the relation of sample rate current and output current can be by
(1) know.ISFor LDO output currents IoutSample rate current, K is the emitter area ratio of sampling tube and power tube.Then by (2)
Formula obtains the occurrence of VS voltages.
VS=IS*R1 (2)
The excessively stream threshold voltage VTCircuit is produced by a current source I0, high-precision current mirror amplifier and resistance R1Group
Into.QOAnd Q1Composition current mirror, emitter area ratio are 1：n.Q0And Q1Emitter stage meet Vin, Q0With Q1One is inserted in the middle of base stage
The individual resistance R for improving mirror image precision2, then Q1Base stage meets Q again0Colelctor electrode.While Q0Colelctor electrode connect one end of current source.
The other end earthing potential of current source.Resistance R1It is connected on ground potential and Q1Between colelctor electrode.Do not considering R2In the case of, QOIt is
Diode connected mode, forms the input pipe of current mirror amplifier.I0Stream enters Q0Afterwards, through Q1V is obtained after scalingTCircuit
Output current.This electric current is by resistance R1Change into voltage VT.Shadow of the scaling precision of current mirror by transistor base current
Ring, so the accuracy in order to improve amplification coefficient, can be in Q0The resistance R of appropriate resistance that base stage adds2, with relative to Q0For
Improve Q1Base potential, offsets QOAnd Q1The error that base current brings.Therefore, VTVoltage can be obtained by (3), and wherein, n is electricity
The rate mu-factor of stream mirror, I0For current source benchmark.
VT=n*I0 (3)
The comparison circuit is made up of a comparator and outlet tube.VSVoltage produces the negative input end of termination comparator
Son, VTVoltage produces the positive input terminal of termination comparator.The output of comparator connects the base stage of comparison circuit outlet tube.Outlet tube
Emitter stage meet Vin, colelctor electrode connects the outfan of error amplifier, namely is exactly the base stage of power tube.In normal output current model
In enclosing, voltage VSMore than VT, comparator is output as low level, less than comparison circuit outlet tube Q2Cut-in voltage VBE2, therefore ratio
Do not work compared with circuit.When output current reaches threshold point, i.e. voltage VSEqual to VTWhen, the output of comparator by low transition into
High level, the outlet tube Q of comparison circuit2Start working.Now, a part of driving current of power tube transfers Jing Q2Flow Vin。
As the driving current of power tube reduces, the output current of LDO no longer increases, and reaches current limliting purpose.During excessively stream, constant output
Electric current is tried to achieve by (4).
The threshold point of output current is depended on：Resistance R0And R1Ratio, the ratio of n and K and current source I0Precision.
Electric capacity C1It is to ensure that in the case where excessively stream occurs, the stability of overcurrent protection loop..High-precision current source is in integrated circuit
In easily reach, so final under overcurrent condition, obtain high-precision output current value.
Claims (2)
1. a kind of current foldback circuit of negative output LDO voltage stabilizer, it is characterised in that including over-current signal VSProduce circuit, excessively stream
Electrical reference signal presses VTProduce circuit and compare output circuit；The VSThe negative input end of the output termination comparator of circuit is produced,
VSProduce the ground level of the input termination adjustment pipe of circuit；The VTProduce input one temperature independent electric current of termination of circuit
Source, the VTThe output termination for producing circuit compares the positive input terminal of output circuit；The negative input end for comparing output circuit
Meet VSThe outfan of circuit, compares the positive input termination V of output circuitTThe outfan of circuit is produced, compares the output of output circuit
Termination error amplifier (EA) output point, that is, adjust pipe ground level point.
2. according to claim 1, VSProducing circuit includes NPN pipe QS, first resistor R0；The VTProducing circuit includes
2nd NPN pipe Q0, the 3rd NPN pipe Q1, second resistance R1, 3rd resistor R2, the first ideal current source I0；It is described to compare output circuit
Including first comparator CP, the 4th NPN pipe Q2, the first electric capacity C1；
The first NPN pipe QSGround level connect adjustment pipe QPGround level, its colelctor electrode connecting resistance R0, emitter stage connects negative input power supply；
First resistor R0The other end ground connection；
The 2nd NPN pipe Q0Ground level connect 3rd resistor R2One end, its colelctor electrode connects 3rd resistor R2The other end, transmitting
Pole connects negative input power supply；
The first current source I0One termination the 2nd NPN pipe Q0Colelctor electrode, the other end ground connection；
The 3rd NPN pipe Q1Ground level meets the 2nd NPN pipe Q0Colelctor electrode, its colelctor electrode connects second resistance R1One end, emitter stage
Connect negative output power supply；
Second resistance R1The other end ground connection；
The negative input of first comparator CP terminates NPN pipe QSColelctor electrode, its positive input terminates the 3rd NPN pipe Q1's
Colelctor electrode, output the 4th NPN pipe Q of termination2Ground level；
The 4th NPN pipe Q2Colelctor electrode connect error amplifier and adjustment pipe QPJunction point, emitter stage level connect negative input electricity
Source；
The electric electric capacity C1One termination the 4th NPN pipe Q2Ground level, the 4th NPN pipe Q of another termination2Colelctor electrode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201611165361.7A CN106527563A (en) | 2016-12-16 | 2016-12-16 | Overcurrent protection circuit for negative output LDO stabilizer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201611165361.7A CN106527563A (en) | 2016-12-16 | 2016-12-16 | Overcurrent protection circuit for negative output LDO stabilizer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN106527563A true CN106527563A (en) | 2017-03-22 |
Family
ID=58340075
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201611165361.7A Pending CN106527563A (en) | 2016-12-16 | 2016-12-16 | Overcurrent protection circuit for negative output LDO stabilizer |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106527563A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110069092A (en) * | 2019-04-18 | 2019-07-30 | 上海华力微电子有限公司 | The current foldback circuit of LDO circuit device and LDO circuit |
-
2016
- 2016-12-16 CN CN201611165361.7A patent/CN106527563A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110069092A (en) * | 2019-04-18 | 2019-07-30 | 上海华力微电子有限公司 | The current foldback circuit of LDO circuit device and LDO circuit |
| US11204613B2 (en) | 2019-04-18 | 2021-12-21 | Shanghai Huali Microelectronics Corporation | LDO circuit device and overcurrent protection circuit thereof |
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| C06 | Publication | ||
| PB01 | Publication | ||
| WD01 | Invention patent application deemed withdrawn after publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20170322 |