CN104466912A - Linear voltage regulator with short-circuit protection function - Google Patents
Linear voltage regulator with short-circuit protection function Download PDFInfo
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- CN104466912A CN104466912A CN201410706834.4A CN201410706834A CN104466912A CN 104466912 A CN104466912 A CN 104466912A CN 201410706834 A CN201410706834 A CN 201410706834A CN 104466912 A CN104466912 A CN 104466912A
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Abstract
The invention provides a linear voltage regulator with a short-circuit protection function. The linear voltage regulator with the short-circuit protection function comprises an adjustment transistor, an output voltage control circuit, a short-circuit judgment circuit, a short-circuit protection circuit and a current limiting circuit. During the normal working period of the linear voltage regulator, the output voltage control circuit controls the value of output voltages to be maintained to be the expected value of the output voltages. During the short-circuit period, the short-circuit protection circuit controls the adjustment transistor to be turned off intermittently, and currents flowing through the adjustment transistor in the short-circuit period are limited to be lower than the currents in the normal working period through the circuit limiting circuit. The power loss of the adjustment transistor in the short-circuit period is effectively reduced, and the phenomenon of overheating is avoided, so that a heat protection module in the system in which the linear voltage regulator is integrated cannot be triggered, and the normal work of the entire system can not be affected.
Description
Technical field
The present invention relates to field of power electronics, in particular, relate to a kind of linear voltage regulator with short-circuit protection.
Background technology
Linear voltage regulator (such as linear voltage regulator, low dropout regulator are called for short LDO) owing to having the advantages such as cost is low, noise is little, quiescent current is little, and is widely used in the application systems such as power management.In the power management chip being integrated with linear voltage regulator; because linear voltage regulator will provide larger electric current; when output short-circuit; the direct ground connection of output of linear voltage regulator; excessive electric current flows through the Correctional tube of linear voltage regulator; the damage of whole power management chip may be caused, therefore in linear voltage regulator, usually also need short-circuit protection circuit, to prevent the damage causing linear voltage regulator and power management chip during load short circuits.
In prior art; the short-circuit protection method of conventional linear voltage regulator is: when the output voltage of linear voltage regulator being detected lower than certain value; output current is restricted to and is less than or equal to the lower short circuit Limited Current of a value; thus the electric current avoiding flowing through Correctional tube is excessive and cause burning out of Correctional tube, achieve the short-circuit protection to linear voltage regulator.When adopting this short-circuit protection method of prior art to realize the short-circuit protection of linear voltage regulator; Correctional tube is in conducting state always, and power loss during short circuit on Correctional tube is the product of the input voltage of linear voltage regulator and the difference of output voltage and Limited Current.During due to short circuit, the output voltage of linear voltage regulator is usually lower, and short circuit Limited Current can not arrange as far as possible low (too low when satisfied startup, easily cause false triggering), therefore short-circuit dissipation during short circuit on Correctional tube is still larger, and especially when input voltage is larger, short-circuit dissipation can be larger.Excessive short-circuit dissipation easily causes the temperature in power management chip to raise, when temperature is raised to certain value, may the thermal protection module of triggering voltage managing chip inside, and each road circuit of whole power management chip is all turned off.
Visible, adopt prior art this short-circuit protection method to realize the short-circuit protection of linear voltage regulator, when can make short circuit, the loss of Correctional tube is comparatively large, and the thermal protection module of easy triggering system during long-time short circuit, and affect the normal operation of whole system.
Summary of the invention
In view of this, the invention provides a kind of linear voltage regulator with short-circuit protection, to solve in prior art when realizing the short-circuit protection of linear voltage regulator, the problem that easy influential system normally runs because short-circuit dissipation is comparatively large.
There is a linear voltage regulator for short-circuit protection, comprise Correctional tube, output voltage controlling circuit, short circuit decision circuitry and short-circuit protection circuit;
Between the direct-flow input end that described Correctional tube is connected to described linear voltage regulator and output end of pressure-stabilizing, described output voltage controlling circuit characterizes the error signal of the desired output voltage of described linear voltage regulator and the difference of output voltage for exporting, to control the pressure drop of described Correctional tube, the value of described current output voltage is made to be maintained the value of described desired output voltage;
Described short circuit decision circuitry is used for generating short circuit index signal according to the size of described current output voltage, and when described current output voltage is less than or equal to short-circuit threshold value voltage, described short circuit index signal is effective status;
Described short-circuit protection circuit is used for during described index signal is effective status, control the step shutoff of described Correctional tube.
Preferably, described linear voltage regulator also comprises output voltage feedback circuit, for generating the feedback voltage of described current output voltage.
Preferably, described short circuit decision circuitry comprises the first comparator,
The first input end of described first comparator receives described feedback voltage, and the second input receives the second reference voltage signal characterizing described short-circuit threshold value voltage, and output exports described short circuit index signal.
Preferably, described linear voltage regulator also comprises buffering drive circuit, and described buffering drive circuit is connected between the output of described output voltage controlling circuit and the control end of described Correctional tube.
Preferably, described output voltage controlling circuit comprises the first error amplifier;
The first input end of described first error amplifier receives the first reference voltage that characterizes described desired output voltage, and the second input receives described feedback voltage, and output exports described error signal.
Preferably, between the output that described short-circuit protection circuit is connected to described short circuit decision circuitry and the output of described output voltage controlling circuit,
During described short circuit index signal is effective status, described short-circuit protection circuit is step is reduced to zero by described error signal, to make the step shutoff of described Correctional tube.
Preferably, described short-circuit protection circuit comprises first control circuit and the first switch;
Described first switch is connected between the output and ground of described output voltage controlling circuit;
Described first control circuit receives described short circuit index signal, during described short circuit index signal is disarmed state, control described first switch to turn off always, during described short circuit index signal is effective status, control described first switch to turn off in first time period, conducting in the second time period;
Described first time period and the second time period replace two time periods occurred during being the effective status of described short circuit index signal.
Preferably, described first control circuit comprises the first pulse-generating circuit, the second pulse-generating circuit, the 3rd pulse-generating circuit, the first timer, the second timer, first or door, first and door and rest-set flip-flop;
The input of described first pulse-generating circuit receives described short circuit index signal, output is connected to the first input end of described first or door, described first or the reset terminal of the second input of door, the reset terminal of described rest-set flip-flop and described second timer be all connected with the output of described 3rd pulse-generating circuit;
Described first receives described short circuit index signal and described first or the output signal of door respectively with two inputs of door, and output is connected to the input end of described first timer;
The output of described first timer is connected with the set end of described rest-set flip-flop, and the output of described rest-set flip-flop exports the control signal for controlling described first switch conduction and shutoff;
The input of described second pulse-generating circuit receives described control signal, output is connected with the reset terminal of described first timer, the input end of described second timer respectively, and the output of described second timer is connected with the input of described 3rd pulse-generating circuit.
Preferably, described linear voltage regulator also comprises current-limiting circuit,
When described short circuit index signal is disarmed state, the electric current that described current-limiting circuit controls to flow through described Correctional tube is less than or equal to the first Limited Current,
When described short circuit index signal is effective status, the electric current that described current-limiting circuit controls to flow through described Correctional tube is less than or equal to the second Limited Current,
Described second Limited Current is less than described first Limited Current.
Preferably, described current-limiting circuit comprises current sampling circuit, current limliting benchmark generative circuit, the second error amplifier and diode;
Described current detection circuit is for obtaining the sampled voltage characterizing and flow through described Correctional tube electric current;
Described current limliting benchmark generative circuit is when described short circuit index signal is disarmed state, export the 3rd reference voltage characterizing described first Limited Current, when described short circuit index signal is effective status, export the 4th reference voltage of table sign second Limited Current, described 4th reference voltage is less than described 3rd reference voltage;
The first input end of described second error amplifier is connected with the output of described current sampling circuit, and the second input is connected with described current limliting benchmark generative circuit, and output is connected with the negative electrode of described diode;
The anode of described diode is connected with the output of described output voltage controlling circuit.
Have upper visible; the linear voltage regulator with short-circuit protection disclosed in the embodiment of the present application; the value of desired output voltage is maintained by the value of output voltage controlling circuit control output voltage in normal work period; and during short circuit; controlled by short-circuit protection circuit that Correctional tube is step is turned off; the power loss of effective reduction Correctional tube during short circuit; there will not be overheated phenomenon; thus the thermal protection module that can not trigger in the system of this linear voltage regulator integrated, thus can not affect the normal work of whole system.And during short circuit; be a less electric current by the current limit flowing through Correctional tube by current-limiting circuit; further reduce the power loss of Correctional tube, make this linear voltage regulator can realize the protection of self during short circuit, again the not normal work of other circuit in its integrated system.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to the accompanying drawing provided.
Fig. 1 is a kind of structure chart with the linear voltage regulator of short-circuit protection disclosed in the embodiment of the present application;
Fig. 2 is the circuit diagram with a kind of optional manner of the linear voltage regulator of short-circuit protection shown in Fig. 1;
Fig. 3 is the working waveform figure with the linear voltage regulator of short-circuit protection shown in Fig. 2;
The optional implementation circuit diagram of the another kind that Fig. 4 is the first control circuit in the linear voltage regulator shown in Fig. 2;
Fig. 5 is the working waveform figure of the first control circuit shown in Fig. 4.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearly
Fig. 1 is a kind of structure chart with the linear voltage regulator of short-circuit protection disclosed in the embodiment of the present application.
With reference to figure 1, the linear voltage regulator 100 disclosed in the embodiment of the present application with short-circuit protection comprises a Correctional tube 01, output voltage controlling circuit 02, short circuit decision circuitry 03 and short-circuit protection circuit 04, and this linear voltage regulator is generally low pressure difference linear voltage regulator.Wherein, Correctional tube is connected to direct-flow input end (the reception input voltage V of linear voltage regulator 100
iNone end) and output end of pressure-stabilizing (export current output voltage V
oUTone end) between.Correctional tube 01 can but P-type mos field-effect transistor (MOSFET) M be not limited to as shown in Figure 1
1, can also be the transistor of N-type MOSFET or other type, by using the MOSFET of P type as Correctional tube 01 in various embodiments of the present invention.Output voltage controlling circuit 02 is for exporting the desired output voltage (this voltage swing is generally determined according to load) and current output voltage V that characterize linear voltage regulator 100
oUTthe error signal of the difference of (i.e. the voltage of linear voltage regulator 100 reality output), to control (i.e. between short circuit index signal SHORT dynamic stage that short circuit decision circuitry exports) pressure drop of Correctional tube 01 in described linear voltage regulator 100 normal work period, thus finally make current output voltage V
oUTvalue be maintained the value of described desired output voltage.That is, linear voltage regulator 100 is in non-shorting period, as expectation output voltage and current output voltage V
oUTwhen difference increases, the increase of described error signal, makes the pressure drop of Correctional tube 01 reduce, thus makes current output voltage V
oUTraise, to reduce desired output voltage and current output voltage V
oUTdifference, on the contrary, if current output voltage V
oUTvalue exceed the output voltage of expectation, then the pressure drop controlling Correctional tube 01 increases, thus makes current output voltage V
oUTreduce, to make current output voltage V
oUTreduce with the difference of desired output voltage, final realization controls current output voltage V
oUTvalue be maintained the value of described desired output voltage.
Short circuit decision circuitry 03 is for according to current output voltage V
oUTsize generate short circuit index signal SHORT, when there is short circuit in linear voltage regulator 100, current output voltage V
oUTbe reduced to and be less than or equal to short-circuit threshold value voltage, short circuit index signal SHORT is effective status.In the present embodiment and subsequent embodiment signal effective status can but be not limited to high level, in other embodiment, effective status also can refer to low level state.
Short-circuit protection circuit 04 controls the step shutoff of Correctional tube 01 during being effective status at described short circuit index signal SHORT.Short-circuit protection circuit 04 can be connected between decision circuitry 03 and the output of output voltage controlling circuit.During short circuit index signal SHORT is effective status; the step error signal by the output of output voltage controlling circuit 02 of short-circuit protection circuit 04 was reduced to for zero a period of time; thus Correctional tube 01 can be turned off within this time period, the control of Correctional tube 01 not by output voltage controlling circuit 02 within this time period.During the short circuiting work pattern of pressurizer 100; short-circuit protection circuit 04 controls Correctional tube 01 every a period of time and turns off; Correctional tube 01 during this period turn-on and turn-off alternately successively occurs; instead of be in conducting state always; power loss during effectively reducing short circuit on Correctional tube 01; make Correctional tube 01 not easily damaged, and avoid the problem that Correctional tube 01 triggers the system of this pressurizer integrated thermal protection module because of overheated causes whole system normally to run.
The disclosed linear voltage regulator 100 with short-circuit protection of the present embodiment also comprises output voltage feedback circuit 05, and it is for generating current output voltage V
oUTfeedback voltage.Output voltage controlling circuit 02 and short circuit decision circuitry 03 can receive this feedback voltage respectively, to generate described error signal and short circuit index signal SHORT, so only need the proportionate relationship controlling feedback voltage and output voltage, just can realize the adjustment to different output voltage.
The disclosed linear voltage regulator 100 with short-circuit protection of the present embodiment also comprises buffering drive circuit 06; it is connected between the output 02 of output voltage controlling circuit and the control end of Correctional tube 01; for receiving the error signal that output voltage controlling circuit 02 generates; and export the control signal of Correctional tube 01, to control the pressure drop of Correctional tube 01.Buffering drive circuit 06 can increase or reduce the drive current of Correctional tube fast, effectively can improve the response speed of linear voltage regulator to load variations.
The disclosed linear voltage regulator 100 with short-circuit protection of the present embodiment also comprises current-limiting circuit 07, and it is for the output current according to short circuit index signal Restricted Linear pressurizer 100.During short circuit index signal SHORT is disarmed state, linear voltage regulator 100 is in normal operating conditions, if output current is less than or equal to the first Limited Current, cut-off current 07 does not control the size of output current, namely inoperative to the control of Correctional tube 01 during this period.At output current once be greater than the first Limited Current, current-limiting circuit 07 starts to limit output current, it can drag down the value of the error signal that output voltage controlling circuit 02 exports, reduce to control Correctional tube 01 pressure drop, and then output current is reduced within the first Limited Current or the first Limited Current, avoid linear voltage regulator 100 operationally, Correctional tube 01 is because of the excessive and phenomenon damaged of the electric current that bears.Between the value that the value of the first Limited Current is generally arranged on Correctional tube 01 trouble free service electric current and the output current of linear voltage regulator 100 full load.During short circuit index signal SHORT is effective status, the electric current that current-limiting circuit 07 control flow check crosses Correctional tube is less than or equal to the second Limited Current, and what the second Limited Current was arranged is less than the first Limited Current.Therefore during linear voltage regulator 100 short circuit; the electric current flowing through Correctional tube 01 be one lower than electric current during normal work; thus during can reducing short circuit further, the power loss on Correctional tube 01, avoids the thermal protection module of its triggering system and affects the normal work of whole system.
Therefore; the linear voltage regulator with short-circuit protection disclosed in the embodiment of the present application; the value of desired output voltage is maintained by the value of output voltage controlling circuit control current output voltage in normal work period; and during short circuit; controlled by short-circuit protection circuit that Correctional tube is step is turned off; the power loss of effective reduction Correctional tube during short circuit; there will not be overheated phenomenon; thus the thermal protection module that can not trigger in the system of this linear voltage regulator integrated, thus can not affect the normal work of whole system.And during short circuit; be lower than electric current during normal work by the current limit flowing through Correctional tube by current-limiting circuit; further reduce the power loss of Correctional tube; make this linear voltage regulator can realize the protection of self during short circuit, do not affect again the normal work of other circuit in integrated system.
Fig. 2 is the circuit diagram with a kind of optional manner of the linear voltage regulator of short-circuit protection shown in Fig. 1.
With reference to figure 2; sets forth the specific implementation circuit of output voltage controlling circuit 02 in Fig. 1, short circuit decision circuitry 03, short-circuit protection circuit 04, output voltage feedback circuit 05, drive circuit 06 and current-limiting circuit 07 in the present embodiment, but the specific implementation of each circuit is not limited to mode as shown in Figure 2.
In the present embodiment, Correctional tube 01 is P type MOS (metal-oxide-semiconductor) memory M
1, M
1source electrode receive input voltage V
iN, drain electrode exports current output voltage V
oUT.Output voltage feedback circuit 05 be one by resistance R
1with resistance R
2the resitstance voltage divider formed, resistance R
1one end and M
1drain electrode be connected, to receive current output voltage V
oUT, the other end is by resistance R
2ground connection, resistance R
1, R
2the Nodes be connected exports and characterizes current output voltage V
oUTfeedback voltage V
fB.Output voltage controlling circuit 02 comprises the first error amplifier EA
1, buffering drive circuit is the first inverter N
1.The EA of the first error amplifier
1in-phase input end receive the first reference voltage V of desired output voltage characterizing linear voltage regulator 100
rEF1, inverting input receives feedback voltage V
fB, output terminals A place output error signal V
a, and by the first reverser N
1be connected to Correctional tube M
1grid (control end), the first comparator CP
1in-phase input end receive the second reference voltage V for characterizing short-circuit threshold value voltage described in a upper embodiment
rEF2, end of oppisite phase receives feedback voltage V
fB, output output short-circuit index signal SHORT.Current-limiting circuit 07 comprises current sampling circuit, the second error amplifier EA
2, diode D
1and by K switch
1, resistance R
3, R
4the current limliting benchmark generative circuit formed.Wherein, resistance R
3, R
4be connected in series in the 3rd reference voltage V
rEF3and between earth terminal, K switch
1with resistance R
3be connected in parallel, and its on off state is controlled by the non-signal of short circuit index signal, when short circuit index signal is low level (disarmed state), K switch
1conducting always, resistance R
3with R
4junction export the 3rd reference voltage V
rEF3, when short circuit index signal is high level (effective status), K switch
1turn off, resistance R always
3with R
4junction export the 4th reference voltage V
rEF4, wherein, V
rEF4=R
rEF3× R
3/ (R
3+ R
4).Current sampling circuit can with Correctional tube M
1one end be connected, flow through Correctional tube M for obtaining sign
1the sampled voltage V of electric current
c, i.e. V
cwith flow through M
1current in proportion.The in-phase input end of the second error amplifier is connected to resistance R
3with R
4connecting place, to receive the current-limiting points voltage V at this place
b(namely during short circuit index signal disarmed state, receive the 3rd reference voltage V
rEF3, during short circuit index signal effective status, receive the 4th reference voltage V
rEF4), output and diode D
1negative electrode be connected, the anode of diode is connected to the output of output voltage controlling circuit 02, i.e. the first error amplifier EA
1output.
Short-circuit protection circuit 04 comprises first control circuit 04-1 and the first switch S
1, wherein the first switch S
1be connected to the first error amplifier EA
1output (output of output voltage controlling circuit 02) and earth terminal between, first control circuit for receiving short circuit index signal SHORT, to control the first switch S
1switch motion, during short circuit index signal SHORT is disarmed state, first control circuit controls the first switch S
1turn off, during short circuit index signal SHORT is effective status, first control circuit 04-1 controls the first switch S always
1turn off in first time period, conducting in the second time period, with step by error signal V
abe reduced to zero.First time period and the second time period are two time periods alternately occurred during short circuit index signal SHORT is effective status.Namely first control circuit controls the first switch S
1the sampling action that first conducting a period of time turns off a period of time is again carried out during linear voltage regulator 100 short circuit.
First control circuit 04-1 comprises the first pulse-generating circuit OS in the present embodiment
1, the second pulse-generating circuit OS
2, the 3rd pulse-generating circuit OS
3, the first timer Tm
1, the second timer Tm
2, first or door OR
1, first and door AND
1and rest-set flip-flop.First pulse-generating circuit OS
1input receive described short circuit index signal SHORT, output is connected to first or door OR
1first input end, first or door OR
1the second input, the reset terminal " S " of rest-set flip-flop and the second timer Tm
1reset terminal all with the 3rd pulse-generating circuit OS
3output be connected.First with door AND
1two inputs receive short circuit index signal SHORT and first or door OR respectively
1output signal, output is connected to the first timer Tm
1input end.First timer Tm
1output be connected with the set end " R " of rest-set flip-flop, the output of rest-set flip-flop exports the control signal Q for controlling described first switch conduction and shutoff
2.Second pulse-generating circuit OS
2input reception control signal Q
2, output respectively with reset terminal, the second timer Tm of the first timer Tm1
2input end be connected, the second timer Tm
2output and the 3rd pulse-generating circuit OS
3input be connected.
Fig. 3 is the working waveform figure of the linear voltage regulator shown in Fig. 2.
With reference to figure 3, the work sheet according to Fig. 3 carrys out the course of work of the linear voltage regulator shown in analysis chart 2.At t
0to t
1moment, the feedback voltage V of linear voltage regulator
fBbe maintained the first reference voltage V
rEF1near, the electric current flowing through Correctional tube (is equaled output current I by current-limiting circuit
oUT) be restricted to the first Limited Current I
lIMIT1or within it, the linear voltage regulator in this stage is in normal operating conditions.At t
1in the moment, the output of linear voltage regulator is short-circuited, feedback voltage V
fBsuddenly the second reference voltage V is reduced to
rEF2or below, now short circuit index signal SHORT becomes useful signal, current-limiting points voltage V
bit is now the 4th reference voltage V
rEF4, current-limiting circuit will flow through Correctional tube M
1current limit be the second Limited Current first Limited Current I
lIMIT2or within it.First pulse-generating circuit OS
1produce a pulse signal clk
1, this signal is through first or door OR
1rear output is still a pulse signal, because now short circuit index signal SHORT is 1 (1 represents high level, and 0 represents low level), then first with door AND
1output be also a pulse signal, the first timer Tm
1start, and timing is to t
2moment, at t
2before moment, the first timer Tm
1output is 0, and rest-set flip-flop exports Q
1, the first switch S
1keep turning off.Until t
2moment arrives, the first timer Tm
1timing completes, and its signal T1 exported becomes 1, and rest-set flip-flop exports Q
1become 1, the first switch S
1conducting, the first error amplifier EA
1the current potential of output terminals A point be pulled to 0, i.e. error signal V
avalue reduce to zero, the first inverter N
1output become the highest, make Correctional tube M
1be turned off.At M
1output voltage and the output current of blocking interval linear voltage regulator are 0, now Correctional tube M
1no power waste.While Correctional tube is turned off, rest-set flip-flop exports Q
1be the 1, second pulse-generating circuit OS
2produce a pulse signal clk
2, this signal triggers the second timer Tm
2start working, simultaneously also by the first timer Tm
1reset (clearing) so that next reclocking.As the second timer Tm
2timer is to t
3time, timing completes, its signal T exported
2become the 1, three pulse-generating circuit OS
3export a pulse signal clk
3rest-set flip-flop is resetted, the output signal Q of rest-set flip-flop
1become 0, the first switch S
1again be turned off, the current potential of A point is no longer pulled low to 0, simultaneously the 3rd pulse-generating circuit OS
3output by the second timer Tm
2reset.If short circuit index signal SHORT is still effective status, i.e. short circuit index signal SHORT is 1, then the first timer Tm
1be restarted and reclocking a period of time time, the first K switch
1conducting again, Correctional tube M
1again turn off a period of time, repeat this process (the step shutoff of Correctional tube) until short circuit index signal SHORT becomes 0, the first timer Tm always
1be prohibited, the first switch S
1be turned off, A point voltage recovers normal operating conditions always, and circuit recovers normal.
The optional implementation circuit diagram of the another kind that Fig. 4 is the first control circuit in the linear voltage regulator shown in Fig. 2.
With reference to figure 4, first control circuit 04-1 comprises the second inverter N
2(not gate), second or door OR
2, second switch S
2, the 3rd switch S
3, the first electric capacity C
1, the second electric capacity C
2, the first current source I
1, the second current source I
2, the second comparator CP
2, the 3rd comparator CP
3, second and door AND
2, the 3rd inverter N
3, the 4th inverter N
4and the 4th pulse-generating circuit OS
4.
Wherein, N
2receive short circuit index signal SHORT, output and second or door OR
2an input be connected, second or door OR
2another input receive the 4th pulse-generating circuit OS
4output pulse signal, output respectively with second switch S
2, the 3rd switch S
3control end be connected.Second switch S
2with the first electric capacity C
1be connected in parallel, the first current source I
1also with the first electric capacity C
1be connected in parallel, and the first electric capacity C
1one end ground connection, the other end is connected to the second comparator CP
2inverting input, to export the first electric capacity C to this end
1on voltage V
d.Second comparator CP
2in-phase end receive one the 5th reference voltage V
rEF5, the signal T that output exports
3be passed to second and door AND
2an input, second with door AND
2another two inputs receive short circuit index signal SHORT and the 3rd comparator CP respectively
3output signal T
4, output is by the 4th inverter N
4export the first switch S
1switch controlling signal Q
1.3rd switch S
3with the second electric capacity C
2be connected in parallel, the second current source I
2also with the second electric capacity C
2be connected in parallel, and the second electric capacity C
2one end ground connection, the other end is connected to the 3rd comparator CP
3inverting input, to export the second electric capacity C to this end
2on voltage V
e, the 3rd comparator CP
3in-phase end receive the 6th reference voltage V
rEF6, output is connected to the 3rd inverter N simultaneously
3input, the 3rd inverter N
3output and the 4th pulse-generating circuit OS
4input be connected.
Fig. 5 is the working waveform figure of the first control circuit shown in Fig. 4.
With reference to figure 5, the job control process of the first control circuit 04-1 shown in analysis chart 4.At t
0in the moment, short circuit index signal SHORT becomes 1, second with door AND
2output signal nd
2be 1, then switch controlling signal Q
1it is the 0, first switch S
1turn off, Correctional tube M
1conducting, second or door OR
2output is 0, second switch S
2with the 3rd switch S
3all turn off, the first current source I
1with the second current source I
2respectively to the first electric capacity C
1with the second electric capacity C
2charging, voltage V
dwith voltage V
estart to rise, until t
1moment, voltage V
drise to V
rEF5, signal T
3saltus step is 0, due to voltage V
ealso do not rise to V
rEF6, then now signal T
4be still 1, signal nd
2saltus step is 0, Q
1saltus step is the 1, first switch S
1start conducting, Correctional tube M
1start to be turned off, until t
2moment, voltage V
erise to V
rEF6, signal T
4saltus step is 0 once, i.e. third party's phase device N
3output saltus step be the 1, four pulse-generating circuit OS
4be triggered and export a pulse signal clk
4, this signal makes second or door OR
2become 1, then second switch S
2with Three S's
3equal conducting, voltage V
dand V
eall be pulled low to zero rapidly, signal T
3saltus step is 1, signal T
4also become 1, then signal nd at once
2become 1, switch controlling signal Q
1become 0, the first switch S
1be turned off, Correctional tube is by M
1conducting, if next short circuit index signal SHORT is still effectively, then repeats this process, makes the first switch S
1the shutoff replaced in the short circuit index signal SHORT valid period and conducting, thus make Correctional tube M
1during this period by the turn-on and turn-off replaced, i.e. step shutoff.Until short circuit index signal SHORT becomes during 0, second switch S
1with the 3rd switch S
3switched on, switch controlling signal Q
1be in disarmed state, the first switch S
1turn off during this period always, make A point voltage recover normal operating conditions, circuit recovers normal.
Have upper visible; the linear voltage regulator with short-circuit protection disclosed in the embodiment of the present application; the value of desired output voltage is maintained by the value of output voltage controlling circuit control output voltage in normal work period; and during short circuit; controlled by short-circuit protection circuit that Correctional tube is step is turned off; the power loss of effective reduction Correctional tube during short circuit; there will not be overheated phenomenon; thus the thermal protection module that can not trigger in the system of this linear voltage regulator integrated, thus can not affect the normal work of whole system.And during short circuit; be a less electric current by the current limit flowing through Correctional tube by current-limiting circuit; further reduce the power loss of Correctional tube, make this linear voltage regulator can realize the protection of self during short circuit, again the not normal work of other circuit in its integrated system.
In this specification, each embodiment adopts the mode of going forward one by one to describe, and what each embodiment stressed is the difference with other embodiments, between each embodiment same or similar part mutually see.
To the above-mentioned explanation of the disclosed embodiments, professional and technical personnel in the field are realized or uses the present invention.To be apparent for those skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein can without departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.
Claims (10)
1. there is a linear voltage regulator for short-circuit protection, comprise Correctional tube, output voltage controlling circuit, short circuit decision circuitry and short-circuit protection circuit;
Between the direct-flow input end that described Correctional tube is connected to described linear voltage regulator and output end of pressure-stabilizing, described output voltage controlling circuit characterizes the error signal of the desired output voltage of described linear voltage regulator and the difference of current output voltage for exporting, to control the pressure drop of described Correctional tube during short circuit index signal is for disarmed state, the value of described current output voltage is made to be maintained the value of described desired output voltage;
Described short circuit decision circuitry is used for generating described short circuit index signal according to the size of described current output voltage, and when described current output voltage is less than or equal to short-circuit threshold value voltage, described short circuit index signal is effective status;
Described short-circuit protection circuit is used for controlling the step shutoff of described Correctional tube during described short circuit index signal is effective status.
2. linear voltage regulator according to claim 1, is characterized in that, also comprises output voltage feedback circuit, for generating the feedback voltage of described current output voltage.
3. linear voltage regulator according to claim 2, is characterized in that, described short circuit decision circuitry comprises the first comparator,
The first input end of described first comparator receives described feedback voltage, and the second input receives the second reference voltage signal characterizing described short-circuit threshold value voltage, and output exports described short circuit index signal.
4. linear voltage regulator according to claim 2, is characterized in that, also comprises buffering drive circuit, and described buffering drive circuit is connected between the output of described output voltage controlling circuit and the control end of described Correctional tube.
5. linear voltage regulator according to claim 2, is characterized in that, described output voltage controlling circuit comprises the first error amplifier;
The first input end of described first error amplifier receives the first reference voltage that characterizes described desired output voltage, and the second input receives described feedback voltage, and output exports described error signal.
6. linear voltage regulator according to claim 1, is characterized in that, between the output that described short-circuit protection circuit is connected to described short circuit decision circuitry and the output of described output voltage controlling circuit,
During described short circuit index signal is effective status, described short-circuit protection circuit is step is reduced to zero by described error signal, to make the step shutoff of described Correctional tube.
7. linear voltage regulator according to claim 6, is characterized in that, described short-circuit protection circuit comprises first control circuit and the first switch;
Described first switch is connected between the output and ground of described output voltage controlling circuit;
Described first control circuit receives described short circuit index signal, during described short circuit index signal is disarmed state, control described first switch to turn off always, during described short circuit index signal is effective status, control described first switch to turn off in first time period, conducting in the second time period;
Described first time period and the second time period replace two time periods occurred during being the effective status of described short circuit index signal.
8. linear voltage regulator according to claim 7, it is characterized in that, described first control circuit comprises the first pulse-generating circuit, the second pulse-generating circuit, the 3rd pulse-generating circuit, the first timer, the second timer, first or door, first and door and rest-set flip-flop;
The input of described first pulse-generating circuit receives described short circuit index signal, output is connected to the first input end of described first or door, described first or the reset terminal of the second input of door, the reset terminal of described rest-set flip-flop and described second timer be all connected with the output of described 3rd pulse-generating circuit;
Described first receives described short circuit index signal and described first or the output signal of door respectively with two inputs of door, and output is connected to the input end of described first timer;
The output of described first timer is connected with the set end of described rest-set flip-flop, and the output of described rest-set flip-flop exports the control signal for controlling described first switch conduction and shutoff;
The input of described second pulse-generating circuit receives described control signal, output is connected with the reset terminal of described first timer, the input end of described second timer respectively, and the output of described second timer is connected with the input of described 3rd pulse-generating circuit.
9. according to the linear voltage regulator in claim 1-8 described in any, it is characterized in that, also comprise current-limiting circuit,
When described short circuit index signal is disarmed state, the electric current that described current-limiting circuit controls to flow through described Correctional tube is less than or equal to the first Limited Current,
When described short circuit index signal is effective status, the electric current that described current-limiting circuit controls to flow through described Correctional tube is less than or equal to the second Limited Current,
Described second Limited Current is less than described first Limited Current.
10. linear voltage regulator according to claim 9, is characterized in that, described current-limiting circuit comprises current sampling circuit, current limliting benchmark generative circuit, the second error amplifier and diode;
Described current detection circuit is for obtaining the sampled voltage characterizing and flow through described Correctional tube electric current;
Described current limliting benchmark generative circuit is when described short circuit index signal is disarmed state, export the 3rd reference voltage characterizing described first Limited Current, when described short circuit index signal is effective status, export the 4th reference voltage of table sign second Limited Current, described 4th reference voltage is less than described 3rd reference voltage;
The first input end of described second error amplifier is connected with the output of described current sampling circuit, and the second input is connected with described current limliting benchmark generative circuit, and output is connected with the negative electrode of described diode;
The anode of described diode is connected with the output of described output voltage controlling circuit.
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| CN104466912B (en) | 2017-08-25 |
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