CN102231514B - Soft recovery control circuit of output short circuit - Google Patents

Abstract

The invention provides a soft recovery control circuit of an output short circuit. In the process of initial energization, before an output voltage at an FB port does not exceed the set reference voltage V9, a soft recovery control module of the soft recovery control circuit does not have an effect on a switching module; after the output voltage at the FB port is normal, if the output voltage at the FB port is less than the reference voltage V9, the soft recovery control module outputs turn-off signals to a switching control module of the soft recovery control circuit and the switching control module turns off the switching module; the soft recovery control module continues to detect the output voltage and load current at the FB port, and the load current is compared with a threshold current, when the load current is less than the threshold current of the soft recovery control module, the soft recovery control module opens the switching control module, and the output voltage at the FB port is recovered to normal. The soft recovery control circuit is used for solving the blocking problem at the time of remote control within a close range and improving the anti-interference capacity of an ASK/OOK RF (radio frequency) receiving circuit at the same time of not influencing the sensitivity.

Description

The soft-restoration control circuit of output short-circuit

The application is that the application number of applying on September 29th, 2009 is that 200910153619.5 invention and created names are dividing an application of the soft-restoration control circuit of < < output short-circuit and the application > > in DC-DC transducer thereof

Technical field

The present invention relates to power management techniques, relate in particular to power source short-circuit protection technology.

Background technology

At present; the application of electric power management circuit is very extensive; the circuit that the overwhelming majority is load supplying by switching tube; as Switching Power Supply, low-dropout regulator etc.; all need to possess output short circuit protection function; when output overloading or short circuit, open output short circuit protection function, avoid circuit itself and load to be damaged because of electric current greatly.The short circuit protection module of output short circuit protection circuit as shown in Figure 1 (13) judges whether short circuit according to the output voltage values of load end; and then output control signals to switch control module (12), complete or intermittent closing switch module (11).For Switching Power Supply; when output short-circuit is to when ground; can reduce the frequency of oscillator or the peak-peak cut-off current of inductor; the mode of turning back by frequency or peak value cut-off current guarantees that the electric current of inductor has the more time to decay, and has reduced power consumption and has made load and circuit itself is protected.

Output short circuit protection module shown in Fig. 1 is in the application of asynchronous buck DC-DC transducer, as shown in Figure 2, and wherein:

Described switch module (11) is PMOS switching tube M1, and the source electrode of M1 is as the VIN port of DC-DC transducer, and the drain electrode of M1 is as the SW port of DC-DC transducer, the grid connecting valve control module (12) of M1;

Described switch control module (12) comprises clapp oscillator A2, error amplifier A3, comparator A4, logical circuit A5 and drive circuit A6;

Described short block (13) comprises the frequency comparator A1 that turns back, and the output voltage that it detects FB port reduces the frequency of clapp oscillator in switch control module (12) when output short-circuit;

Described reference voltage V 1, V2 can produce for circuit is outside, can be also internal reference voltage source or its dividing potential drop;

Buck DC-DC transducer be connected to form DC-DC converting system with peripheral component, and as shown in Figure 2, peripheral component comprises divider resistance R1 and the R2 of LC filter network that inductance L 1 and capacitor C 1 form, Schottky diode D1, output voltage.At output short-circuit or load, course of work when excessive is this DC-DC converting system: output VOUT end is because load is excessive or be shorted to ground, and its magnitude of voltage reduces, to the output voltage V of its FB port _fBwhile being less than the reference voltage V 1 of setting, the frequency module of turning back is turned down switching frequency to the lower frequency f2 setting by f1; Under certain a certain amount of excessive load, its output voltage stabilization is at fixing low-voltage VO _l, duty ratio now

The inductive current waveform of the converting system of buck DC-DC shown in Fig. 2 as shown in Figure 3, peak value is the peak value current limliting Ipeak that DC-DC converter inside is set, valley is made as Ivale, if system works at continuous mode, ON time and the deadline of switching tube are respectively:

$T_{\mathrm{ON}}=\frac{D}{f2},T_{\mathrm{OFF}}=\frac{1-D}{f2}$ (wherein $D=\frac{{\mathrm{VO}}_L}{\mathrm{VIN}}$ )

Ripple current on inductance is:

$\mathrm{\&Delta;I}=\mathrm{Ipeak}-\mathrm{Ivale}=\frac{\mathrm{VIN}-{\mathrm{VO}}_L}{L}\&times;T_{\mathrm{ON}}=\frac{\mathrm{VIN}-{\mathrm{VO}}_L}{L}\&times;\frac{D}{f2}=\mathrm{VIN}\&times;\frac{1-D}{L}\&times;\frac{D}{f2}---\left(1\right)$

Average inductor current is:

$\mathrm{Iavg}=\frac{1}{2}(\mathrm{Ipeak}+\mathrm{Ivale})=\mathrm{Ipeak}-\frac{1}{2}\&times;\mathrm{VIN}\&times;\frac{1-D}{L}\&times;\frac{D}{f2}---\left(2\right)$

If the quiescent current of chip is I during work _q, by formula (2) can release input VIN provide to output VOUT average current Idis be:

$\mathrm{Idis}=D\&times;\mathrm{Iavg}=D\&times;(\mathrm{Ipeak}-\frac{1}{2}\&times;\mathrm{VIN}\&times;\frac{1-D}{L}\&times;\frac{D}{f2})---\left(3\right)$

Input the total current of VIN as shown in Figure 4:

$I_{\mathrm{total}}=I_Q+\mathrm{Idis}=I_Q+D\&times;(\mathrm{Ipeak}-\frac{1}{2}\&times;\mathrm{VIN}\&times;\frac{1-D}{L}\&times;\frac{D}{f2})$

During normal operation, the maximum carrying load ability of buck DC-DC transducer is:

${\mathrm{Iload}}_{\max }=\mathrm{\&eta;}\&times;(\mathrm{Ipeak}-\frac{1}{2}\&times;\mathrm{VIN}\&times;\frac{1-D}{L}\&times;\frac{D}{f1})\&times;D---\left(4\right)$

When output short-circuit or excessive load are removed, output voltage gos up, when output voltage is greater than

its dividing potential drop V _fBsurpass to the threshold point V1 setting, switching frequency is got back to normal value f1, at load current, is reduced to the Iload being less than in formula (4) _maxtime, output voltage can return to normally completely.

The weak point of above-mentioned DC-DC transducer output short circuit protection is: during due to output short-circuit, switch motion still, continuing, has been lost larger power consumption, as formula (3); And in output, while being recovered by short-circuit condition, there is no strictly to control the recovery threshold point of output current, need only load current be reduced to be less than the maximum of formula (4) can bringing onto load Iload _max, output voltage can return to normally completely.

In real work, when during short circuit, output voltage is undesired, to the requirement of chip power-consumption, be more low better; And when output is recovered by short circuit, may need to set different load current threshold points, I1, I2 ... In, and corresponding output voltage VO UT1, VOUT2......VOUTn;

Output short circuit protection circuit shown in Fig. 1 also has similar shortcoming: when output is owing to transshipping or being shorted to ground, if switch module is directly closed, short circuit must re-power while recovering; If intermittent closing switch module (so-called " having the hiccups " pattern, periodically detects output voltage state during short circuit), the increase of the loss of power in the time of certainly will causing short circuit.

Sum up two shortcomings of above-mentioned traditional output short circuit protection circuit: the one, unnecessary energy loss while having increased output short-circuit; The 2nd, there is no to set the output voltage threshold value that exits output short-circuit pattern, when output is recovered by short circuit, do not set the thresholding of load, the process control that does not yet have short circuit to recover.

Summary of the invention

The present invention will solve the deficiencies in the prior art, provides and can reduce energy loss, for the soft-restoration control circuit of power supply output short circuit protection.

Meanwhile, the present invention also provides the application circuit of the soft-restoration control circuit of short-circuit protection at DC-DC transducer.

A soft-restoration control circuit for output short-circuit, comprises switch module, switch control module and soft recovery control module, wherein:

The first input end of described switch control module connects the output of soft recovery control module, the output voltage of the second input input load end of switch control module, the input of the output connecting valve module of switch control module;

The output voltage of the input input load end of described soft recovery control module, this module compares the output voltage of load end and reference voltage V 9: in the initial power up of circuit, the output voltage of load end soft recovery control module before not surpassing the reference voltage V 9 of setting is inoperative to switch module, until the output voltage of load end reaches reference voltage V 9; If after this output voltage of load end is less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module; Soft recovery control module continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, the output voltage of load end recovers normal set point VOUT.

The soft-restoration control circuit of output short-circuit; can also comprise short circuit protection module; the output voltage of the input input load end of described short circuit protection module, the 3rd input of its output connecting valve control module, this module compares the output voltage of load end and reference voltage V 1:

When described reference voltage V 1> reference voltage V 9, if the output voltage of load end drops between reference voltage V 1 and V9, the soft-restoration control circuit of output short-circuit carries out work according to any one of following two kinds of working methods:

(A) short circuit protection module output control signal is by switch control module stopcock module, and soft recovery control module is inoperative to switch module;

(B) short circuit protection module output control signal reduces the frequency of switch module by switch control module, soft recovery control module is inoperative to switch module, if the output voltage of load end continues to be reduced to while being less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module, soft recovery control module continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, when the output voltage of load end is between reference voltage V 1 and V9, the control signal of short circuit protection module output reduces the frequency of switch module by switch control module, until the output voltage of load end surpasses reference voltage V 1, short circuit protection module is inoperative to the frequency of switch module, the soft-restoration control circuit of output short-circuit recovers normal operation.

When described reference voltage V 1≤reference voltage V 9, the mode of operation of the soft-restoration control circuit of output short-circuit is equal to the soft-restoration control circuit of the output short-circuit shown in Fig. 5 A.

DC-DC transducer comprises, the soft-restoration control circuit of output short-circuit, VIN port, SW port and FB port:

The soft-restoration control circuit of described output short-circuit, comprises switch module, switch control module and soft recovery control module, wherein:

The first input end of described switch control module connects the output of soft recovery control module, the output voltage of the second input input FB port of switch control module, the input of the output connecting valve module of switch control module;

The output voltage of the first input end input FB port of described soft recovery control module, this module compares the output voltage of FB port and reference voltage V 9: in the initial power up of circuit, the output voltage of FB port soft recovery control module before the reference voltage V 9 of surpass not setting is inoperative to switch module, until the output voltage of FB port is in normally; If after this output voltage of FB port is less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module; Soft recovery control module continues to detect output voltage and the load current of FB port, the load current of FB port and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, it is normal that the output voltage of FB port recovers;

Described VIN port connects the input of described switch module and the second input of soft recovery control module, described SW port connects the output of described switch module and the second output of soft recovery control module, described switch module is controlled VIN port to the electric current of SW port, when switch module conducting, electric current is from VIN port flow to SW port, otherwise there is no electric current from VIN port flow to SW port.

Described switch control module comprises clapp oscillator, error amplifier, comparator, logic and driver module:

The input of described clapp oscillator is as the input of switch control module, and output produces the ramp voltage signal of fixed frequency;

Described error amplifier compares the output voltage of FB port and reference voltage V 2, makes the output voltage stabilization of FB port in reference voltage V 2, described reference voltage V 9< reference voltage V 2;

Described comparator compares the ramp voltage of the output voltage of error amplifier and clapp oscillator output, when the output voltage of error amplifier is greater than the ramp voltage of clapp oscillator, the signal of comparator output opening switch module is to logic and driver module, otherwise the signal of comparator output stopcock module is to logic and driver module;

Unlatching or the conducting of described logic and driver module control switch module:

(A) if the signal of soft recovery control module output stopcock module, the direct closing switch module of logic and driver module;

(B) if the signal of soft recovery control module output opening switch module, whether the signal deciding that exports logic and driver module to according to comparator opening switch module: if comparator output is the signal of opening switch module, opening switch module, if comparator output is the signal of stopcock module, stopcock module.

Described switch module is a PMOS switching tube M1, and the source electrode of M1 is as the VIN port of DC-DC transducer, and the drain electrode of M1 is as the SW port of DC-DC transducer, and the grid of M1 connects the output of logic and driver module;

Described metal-oxide-semiconductor M1 can be P-channel enhancement type metal-oxide-semiconductor; Also described PMOS pipe M1 can be replaced with to positive-negative-positive triode.

The soft-restoration control circuit of output short-circuit, can also comprise short circuit protection module, wherein:

The output voltage of the input input FB port of described short circuit protection module, the 3rd input of its output connecting valve control module, short circuit protection module compares the output voltage of FB port and reference voltage V 1, described reference voltage V 1< reference voltage V 2;

When described reference voltage V 1> reference voltage V 9, if the output voltage of FB port drops between reference voltage V 1 and V9, the soft-restoration control circuit of output short-circuit carries out work according to any one of following two kinds of working methods:

(A) short circuit protection module output control signal is by switch control module stopcock module, and soft recovery control module is inoperative to switch module;

(B) short circuit protection module output control signal reduces the frequency of switch module by switch control module, soft recovery control module is inoperative to switch module, if the output voltage of FB port continues to be reduced to while being less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module, soft recovery control module continues to detect output voltage and the load current of FB port, the load current of FB port and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, at the output voltage of FB port between reference voltage V 1 and V9, the control signal of short circuit protection module output reduces the frequency of switch module by switch control module, until the output voltage of FB port surpasses reference voltage V 1, short circuit protection module is inoperative to the frequency of switch module, the soft-restoration control circuit of output short-circuit recovers normal operation.

When described reference voltage V 1≤reference voltage V 9, the mode of operation of the soft-restoration control circuit of output short-circuit is equivalent to short circuit protection module and does not exist.

Described short circuit protection module is the frequency comparator A1 that turns back, the turn back positive input terminal input reference voltage V1 of comparator Al of frequency, and the turn back negative input end of comparator A1 of frequency connects FB port, the turn back output termination clapp oscillator modules A 2 of comparator A1 of frequency; The mode of turning back by frequency guarantees that the electric current of inductor has the more time to decay, and has reduced power consumption and has made load and circuit itself is protected.

Soft recovery control module can adopt the soft recovery control module of resistance as mentioned above, and it comprises:

Photodetector on circuit, soft recovery resistance, second switch pipe and threshold value comparator, after soft recovery resistance and second switch pipe string connection, be connected across VIN port and the SW port of described DC-DC converter circuit, the output of the grid connect threshold comparator of second switch pipe, the input input reference voltage V9 of photodetector and the output voltage of FB port on circuit, the input of the output connect threshold comparator of photodetector on circuit, before the output voltage of FB port reaches reference voltage V 9 for the first time, on circuit, photodetector detects by edge or time-controlled mode does not enable threshold value comparator, the signal of soft recovery control module output opening switch module, after the output voltage of FB port reaches reference voltage V 9 for the first time, on circuit, photodetector thinks that circuit has powered on, output control signal enables threshold value comparator, compare the output voltage of FB port and the size of reference voltage V 9, if the output voltage of FB port is less than the signal of 9 output stopcock modules of reference voltage V to logic and driver module, otherwise the signal of output opening switch module is to logic and driver module,

Described second switch pipe M9, different according to the polarity of its control signal, can be N channel enhancement metal-oxide-semiconductor, can be also P-channel enhancement type metal-oxide-semiconductor, can also be the combination of NMOS pipe and PMOS pipe;

The mode of the soft recovery of described resistance, can also be in parallel a plurality of by the structure after soft recovery resistance and second switch pipe string company at VIN port and SW port, the structure after soft recovery resistance and switching tube series winding is controlled respectively in the output of each threshold value comparator, and each threshold value comparator is set respectively reference voltage V 9 separately ... Vn; The enabling of each threshold value comparator controlled by photodetector on circuit, at the output voltage of FB port, reach for the first time the reference voltage V 9 of each threshold value comparator ... before maximum in Vn, on circuit, photodetector does not enable each threshold value comparator, the signal of soft recovery control module output opening switch module, at the output voltage of FB port, reach for the first time the reference voltage V 9 of each threshold value comparator ... after maximum in Vn, on circuit, photodetector thinks that circuit has powered on, and output control signal enables corresponding threshold value comparator; Combinational logic module is carried out logical process by the output of each threshold value comparator, and output unlatching or cut-off signals are to logical circuit and driver module.

Described soft recovery control module can also adopt the mode of the soft recovery of current source, comprise: photodetector on circuit, internal current source I, soft restoring current source and mirror image pipe thereof, the 3rd switching tube and threshold value comparator, described soft restoring current source is that the arbitrary current source I of DC-DC converter inside exports by the mirror image of mirror image pipe, it can be P-channel enhancement type metal-oxide-semiconductor, also can replace with positive-negative-positive triode, it can also be the cascade structure of a plurality of P-channel enhancement type metal-oxide-semiconductors or a plurality of positive-negative-positive triodes, mirror current source and the series connection of the 3rd switching tube, VIN port and SW port described in cross-over connection again, the input input reference voltage V9 of photodetector and the output voltage of FB port on circuit, the input of the output connect threshold comparator of photodetector on circuit, before the output voltage of FB port reaches V9 for the first time, on circuit, photodetector detects by edge or time-controlled mode does not enable threshold value comparator, the signal of soft recovery control module output opening switch module, after the output voltage of FB port reaches V9 for the first time, on circuit, photodetector thinks that circuit has powered on, and output control signal enables threshold value comparator, if threshold value comparator enables, judge the output voltage of FB port and the size of reference voltage V 9, if V _fBbe less than the signal of 9 output stopcock modules of reference voltage V to logic and driver module, otherwise the signal of output opening switch module is to logic and driver module,

Described the 3rd switching tube, different according to the polarity of its control signal, can be N channel enhancement metal-oxide-semiconductor, can be also P-channel enhancement type metal-oxide-semiconductor, can also be the combination of NMOS pipe and PMOS pipe;

The mode of the soft recovery of described current source, can also be in parallel a plurality of by the structure after mirror current source and the 3rd switching tube series winding at VIN port and SW, and the structure of controlling respectively by after mirror current source and the 3rd switching tube series winding is controlled in the output of each threshold value comparator, each threshold value comparator is set reference voltage V 9 separately ... Vn, the enabling of each threshold value comparator controlled by photodetector on circuit, output voltage at FB port reaches reference voltage V 9 for the first time ... before maximum in Vn, on circuit, photodetector does not enable each threshold value comparator, the signal of soft recovery control module output opening switch module, output voltage at FB port reaches reference voltage V 9 for the first time ... after maximum in Vn, upper photodetector thinks that circuit has powered on, output control signal enables corresponding threshold value comparator, combinational logic module is carried out logical process by the output of each threshold value comparator, determine that output unlatching or cut-off signals are to logic and driver module.

Beneficial effect of the present invention is: the soft-restoration control circuit of the output short-circuit that employing the present invention proposes is passable, by setting the reference voltage of the output voltage of short-circuit condition, whether soft recovery control module decision circuitry enters short-circuit condition, enter after short-circuit condition the switching tube of closing switch module completely, chip power-consumption while having reduced output short-circuit, and when output is recovered by short circuit, by the reference voltage of the soft recovery control module of correct setting, the size in soft recovery resistance or soft restoring current source, only load lower than the output current value of setting in time, it is normal that output voltage just recovers, avoid repeatedly entering the situation of output short-circuit pattern, and controlled the time that output is recovered by short circuit.

Accompanying drawing explanation

Fig. 1 is traditional output short circuit protection circuit part-structure figure.

Fig. 2 is the part-structure of traditional asynchronous buck DC-DC transducer and the DC-DC converting system figure that is connected and forms with peripheral component.

Fig. 3 is that conventional buck DC-DC converter circuit flows through the current waveform figure of external inductance in output short-circuit situation.

Fig. 4 is conventional buck DC-DC converter circuit arrival current curve figure in output short-circuit situation.

Fig. 5 is the structure chart of soft-restoration control circuit of the present invention.

Fig. 6 is the buck DC-DC converter structure figure that the present invention comprises soft-restoration control circuit.

Fig. 7 is the buck DC-DC converter structure figure of the present invention's output short circuit protection mode of adopting soft recovery resistance.

Fig. 8 is the buck DC-DC converter structure figure of the present invention's output short circuit protection mode of adopting soft restoring current source.

Fig. 9 is the buck DC-DC converter structure figure of the present invention's output short circuit protection mode of adopting a plurality of soft recovery resistance.

Figure 10 is the buck DC-DC converter structure figure that the present invention adopts the output short circuit protection mode in a plurality of soft restoring currents source.

Figure 11 is the output voltage curve chart that the present invention adopts single soft recovery resistance or front and back, soft restoring current source buck DC-DC converter circuit to be recovered by output short-circuit.

Figure 12 is the output voltage curve chart that the present invention adopts a plurality of soft recovery resistance or soft restoring current source parallel connection front and back buck DC-DC converter circuit to be recovered by output short-circuit.

Embodiment

Below in conjunction with accompanying drawing, content of the present invention is further illustrated.

A soft-restoration control circuit for output short-circuit, comprises switch module (21), switch control module (22) and soft recovery control module (27), as shown in Figure 5A, and wherein:

The input of described switch control module (22) connects the output of soft recovery control module (27), and the output voltage of input load end, the input of the output connecting valve module (21) of switch control module (22);

The output voltage of described soft recovery control module (27) input load end, this module (27) compares the output voltage of load end and reference voltage V 9: in the initial power up of circuit, by edge, detect or time-controlled mode, the output voltage that makes load end soft recovery control module (27) before not surpassing the reference voltage V 9 of setting is inoperative to switch module (22), until the output voltage of load end is in normally; If after this output voltage of load end is less than reference voltage V 9, soft recovery control module (27) is exported cut-off signals to switch control module (22), switch control module (22) stopcock module (21); Soft recovery control module (27) continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module (27), soft recovery control module (27) opening switch control module (22), it is normal that the output voltage of load end recovers.

The soft-restoration control circuit of output short-circuit; can also comprise short circuit protection module (23); as shown in Figure 5 B; the output voltage of described short circuit protection module (23) input load end; the input of its output connecting valve control module (22), this module (23) compares the output voltage of load end and reference voltage V 1:

When described reference voltage V 1> reference voltage V 9, if the output voltage of load end drops between reference voltage V 1 and V9, the soft-restoration control circuit of output short-circuit carries out work according to any one of following two kinds of working methods:

(A) short circuit protection module (23) output control signal is by switch control module (22) stopcock module (21), and soft recovery control module (27) is inoperative to switch module (21);

(B) short circuit protection module (23) output control signal reduces the frequency of switch module (21) by switch control module (22), soft recovery control module (27) is inoperative to switch module (21), if the output voltage of load end continues to be reduced to while being less than reference voltage V 9, soft recovery control module (27) is exported cut-off signals to switch control module (22), switch control module (22) stopcock module (21), soft recovery control module (27) continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module (27) opening switch control module (22), at the output voltage of load end between reference voltage V 1 and V9, the control signal of short circuit protection module (23) output reduces the frequency of switch module (21) by switch control module (22), until the output voltage of load end surpasses reference voltage V 1, short circuit protection module (23) is inoperative to the frequency of switch module (21), the soft-restoration control circuit of output short-circuit recovers normal operation.

When described reference voltage V 1≤reference voltage V 9, the mode of operation of the soft-restoration control circuit of output short-circuit is equal to the soft-restoration control circuit of the output short-circuit shown in Fig. 5 A.

DC-DC transducer comprises, the soft-restoration control circuit of output short-circuit, VIN port, SW port and FB port, as shown in Figure 6A:

The soft-restoration control circuit of described output short-circuit, comprises switch module (21), switch control module (22) and soft recovery control module (27), wherein:

The input of described switch control module (22) connects the output of soft recovery control module (27), and inputs the output voltage of FB port, the input of the output connecting valve module (21) of switch control module (22);

The output voltage of described soft recovery control module (27) input FB port, this module (27) compares the output voltage of FB port and reference voltage V 9: in the initial power up of circuit, by edge, detect or time-controlled mode, the output voltage that makes FB port soft recovery control module (27) before not surpassing the reference voltage V 9 of setting is inoperative to switch module (21), until the output voltage of FB port is in normally; If after this output voltage of FB port is less than reference voltage V 9, soft recovery control module (27) is exported cut-off signals to switch control module (22), switch control module (22) stopcock module (21); Soft recovery control module (27) continues to detect output voltage and the load current of FB port, the load current of FB port and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module (27) opening switch control module (22), it is normal that the output voltage of FB port recovers.

Described VIN port connects the input of described switch module (21) and the input of soft recovery control module (27), described SW port connects the output of described switch module (21) and the output of soft recovery control module (27), described switch module (21) is controlled VIN port to the electric current of SW port, when switch module (21) conducting, electric current is from VIN port flow to SW port, otherwise there is no electric current from VIN port flow to SW port.

Described switch control module (22) comprises clapp oscillator (223), error amplifier (224), comparator (222), logic and driver module (221):

The input of described clapp oscillator (223) connects described FB port, and output produces the ramp voltage signal of fixed frequency;

Described error amplifier (224) is by the output voltage V of DC-DC transducer FB port _fBcompare with reference voltage V 2, make V _fBvoltage stabilization is in reference voltage V 2, described reference voltage V 9< reference voltage V 2;

Described comparator (222) compares the ramp voltage of the output voltage of error amplifier (224) and clapp oscillator (223) output, when the output voltage of error amplifier (224) is greater than the ramp voltage of clapp oscillator (223), the signal of comparator (222) output opening switch module (21) is to logic and driver module (221), otherwise the signal of comparator (222) output stopcock module (21) is to logic and driver module (221), as shown in figure 13;

Unlatching or the conducting of described logic and driver module (221) control switch module (21):

(A) if the signal of soft recovery control module (227) output stopcock module (21), the direct closing switch module (21) of logic and driver module (221);

(B) if the signal of soft recovery control module (227) output opening switch module (21), whether the signal deciding that exports logic and driver module (221) to according to comparator (222) opening switch module (21): if comparator (222) output is the signal of opening switch module (21), opening switch module (21), if comparator (222) output is the signal of stopcock module (21), stopcock module (21);

Described switch module (21) is PMOS switching tube M1, and the source electrode of M1 is as the VIN port of DC-DC transducer, and the drain electrode of M1 is as the SW port of DC-DC transducer, and the grid of M1 connects the output of logic and driver module;

Described metal-oxide-semiconductor M1 can be P-channel enhancement type metal-oxide-semiconductor; Also described PMOS pipe M1 can be replaced with to positive-negative-positive triode.

The soft-restoration control circuit of output short-circuit, can also comprise short circuit protection module (23), as shown in Figure 6B, and wherein:

The output voltage of described short circuit protection module (23) input FB port, the input of its output connecting valve control module (22), this module (23) compares the output voltage of FB port and reference voltage V 1, described reference voltage V 1< reference voltage V 2;

When described reference voltage V 1> reference voltage V 9, if the output voltage of FB port drops between reference voltage V 1 and V9, the soft-restoration control circuit of output short-circuit carries out work according to any one of following two kinds of working methods:

(A) short circuit protection module (23) output control signal is by switch control module (22) stopcock module (21), and soft recovery control module (27) is inoperative to switch module (22);

(B) short circuit protection module (23) output control signal reduces the frequency of switch module (21) by switch control module (22), soft recovery control module (27) is inoperative to switch module (21), if the output voltage of FB port continues to be reduced to while being less than reference voltage V 9, soft recovery control module (27) is exported cut-off signals to switch control module (22), switch control module (22) stopcock module (21), soft recovery control module (27) continues to detect output voltage and the load current of FB port, the load current of FB port and threshold current are compared, when load current is less than the threshold current of soft recovery control module (27), soft recovery control module (27) opening switch control module (22), at the output voltage of FB port between reference voltage V 1 and V9, the control signal of short circuit protection module (23) output reduces the frequency of switch module (21) by switch control module (22), until the output voltage of FB port surpasses reference voltage V 1, short circuit protection module (23) is inoperative to the frequency of switch module (21), the soft-restoration control circuit of output short-circuit recovers normal operation.

When described reference voltage V 1≤reference voltage V 9, the mode of operation of the soft-restoration control circuit of output short-circuit is equal to the soft-restoration control circuit of the output short-circuit shown in Fig. 6 A.

Described short circuit protection module (23) is the frequency comparator A1 that turns back, the turn back positive input terminal input reference voltage V1 of comparator A1 of frequency, the turn back negative input end of comparator Al of frequency connects the FB port of DC-DC transducer, the turn back output termination clapp oscillator (223) of comparator A1 of frequency; The mode of turning back by frequency guarantees that the electric current of inductor has the more time to decay, and has reduced power consumption and has made load and circuit itself is protected.

Described reference voltage V 1, V2, V9 can produce by circuit is outside, can be also internal reference voltage source or its dividing potential drop.

Described soft recovery control module can adopt the soft recovery control module of resistance, and as shown in Figure 7, it comprises:

Photodetector A7, soft recovery resistance R 9, second switch pipe M9 and threshold value comparator A9 on circuit, after soft recovery resistance R 9 and switching tube M9 series connection, be connected across VIN port and the SW port of described DC-DC converter circuit, the output of the grid connect threshold comparator A9 of second switch pipe M9, the input input reference voltage V9 of photodetector A7 and the output voltage V of FB port on circuit _fB, the input of the output connect threshold comparator A9 of photodetector A7 on circuit, in the output voltage V of FB port _fBbefore reaching for the first time reference voltage V 9, on circuit, photodetector A7 detects by edge or time-controlled mode does not enable threshold value comparator A9, and the signal of soft recovery control module output opening switch module, in the output voltage V of FB port _fBafter reaching for the first time reference voltage V 9, on circuit, photodetector A7 thinks that circuit has powered on, and output control signal enables threshold value comparator A9; The output voltage V that compares FB port _fBwith the size of reference voltage V 9, if the output voltage V of FB port _fBbe less than the signal of 9 output stopcock modules of reference voltage V (21) to logic and driver module (221), otherwise the signal of output opening switch module (21) is to logic and driver module (221);

Described second switch pipe M9, different according to the polarity of its control signal, can be N channel enhancement metal-oxide-semiconductor, can be also P-channel enhancement type metal-oxide-semiconductor, can also be the combination of NMOS pipe and PMOS pipe;

Circuit theory shown in Fig. 7 is as follows:

After in soft recovery control module (27-1), threshold value comparator A9 enables, if output feedback voltage V _fBbe less than the reference voltage V 9 of setting, think and enter short-circuit mode, now threshold value comparator A9 is output as low level, second switch pipe M9 conducting, pass through the effect to logic module A5 simultaneously, and strengthened by driver module A6 signal, close the first switching tube M1, now input VIN and no longer by the first switch M1, to SW port, provide electric current, and only by soft recovery resistance R 9, provide weak current to SW port; If the load current I of output _lOADbe greater than

(ignoring the impact of switching tube M9 conducting resistance), output will maintain a certain low-voltage state V always _o, V _osatisfied condition is to be for load provides size

electric current; If output load current value is reduced to

with interior (wherein

), when resistance R 9 provides electric current for load, to output capacitance C1 charging, output voltage slowly rises, extremely

time, the output switching activity of threshold value comparator A9, transfers high level to by low level, closing switch pipe M9 no longer by A5, switching tube M1 being controlled, DC-DC transducer recovers normal mode of operation, and by output voltage stabilization at normal set point VOUT.

So, by the magnitude of voltage of reasonable setting V9, correctly choose the resistance of R9, can obtain the voltage and current threshold point of two output short circuit protections, and export the soft recovery time of being recovered by short circuit:

$V_{\mathrm{TH}}=\frac{\mathrm{VOUT}\&times;V9}{V_{\mathrm{FB}}}---\left(5\right)$

$I_{\mathrm{TH}}=\frac{\mathrm{VIN}-V_{\mathrm{TH}}}{R9}=\frac{\mathrm{VIN}-\frac{\mathrm{VOUT}\&times;V9}{V_{\mathrm{FB}}}}{R9}---\left(6\right)$

Suppose that load when output short-circuit recovers is I _lOAD(I wherein _lOADbe less than the I in formula (6) _tH), the weak current source that R9 provides, to capacitor C 1 charging, is ignored the electric current on output divider resistance R1, R2, meets following formula:

(wherein v is the output voltage of a certain moment t) (7)

Voltage when output is started to recover by short circuit is V0, and formula (7) integration is obtained:

t=R9×C1×[In(VIN-V0-R9×I _LOAD)-In(VIN-v-R9×I _LOAD)]

Can release so export by short circuit and return to reference voltage V _tHsoft recovery time of T _sSfor:

T _SS=R9×C1×[In(VIN-V0-R9×I _LOAD)-In(VIN-V _TH-R9×I _LOAD)] (8)

As shown in Figure 8, the mode of the soft recovery of described resistance, can also be in parallel a plurality of by the structure after soft recovery resistance R 9 and switching tube M9 series winding at VIN port and SW port, each threshold value comparator A9 ... the structure after soft recovery resistance R 9 is contacted with switching tube M9, each threshold value comparator A9 are controlled respectively in the output of An ... An sets respectively reference voltage V 9 separately ... Vn; Each threshold value comparator A9 ... the enabling of An controlled by electro-detection A7 on circuit, in the output voltage V of FB port _fBreach for the first time V9 ... maximum max (V9 in Vn ... Vn) before, on circuit, photodetector A7 makes A9 ... An does not enable, and the signal of soft recovery control module output opening switch module, in the output voltage V of FB port _fBreach for the first time max (V9 ... Vn) afterwards, on circuit, photodetector A7 thinks that circuit has powered on, and output control signal makes corresponding threshold value comparator A9 ... An enables; Combinational logic modules A 8, by each threshold value comparator A9 ... logical process is carried out in the output of An, and output unlatching or cut-off signals are to logical circuit and driver module (221).

Described soft recovery control module also can adopt the soft recovery control module of current source, and as shown in Figure 9, it comprises:

Photodetector A7, internal current source I, soft restoring current source M9 and mirror image pipe M2 thereof, the 3rd switching tube M91 and threshold value comparator A9 on circuit, described soft restoring current source M9 is that the arbitrary current source I of DC-DC converter inside exports by the mirror image of mirror image pipe M2, it can be P-channel enhancement type metal-oxide-semiconductor, also can replace with positive-negative-positive triode, it can also be the cascade structure of a plurality of P-channel enhancement type metal-oxide-semiconductors or a plurality of positive-negative-positive triodes, mirror current source M9 and the 3rd switching tube M91 series connection, then VIN port and SW port described in cross-over connection; The input input reference voltage V9 of photodetector A7 and the output voltage V of FB port on circuit _fB, the input of the output connect threshold comparator A9 of photodetector on circuit; Output voltage V at FB port _fBbefore reaching V9 for the first time, on circuit, photodetector A7 detects by edge or time-controlled mode does not enable threshold value comparator A9, and the signal of soft recovery control module output opening switch module, in the output voltage V of FB port _fBafter reaching V9 for the first time, on circuit, photodetector A7 thinks that circuit has powered on, and output control signal makes threshold value relatively play A9 to enable; If threshold value comparator A9 enables, judge the output voltage V of FB port _fBwith the size of reference voltage V 9, if V _fBbe less than the signal of 9 output stopcock modules of reference voltage V (21) to logic and driver module (221), otherwise the signal of output opening switch module (21) is to logic and driver module (221);

Described switching tube M9, different according to the polarity of its control signal, can be N channel enhancement metal-oxide-semiconductor, can be also P-channel enhancement type metal-oxide-semiconductor, can also be the combination of NMOS pipe and PMOS pipe;

Circuit theory is as shown in Figure 9 as follows:

After in soft recovery control module (27-3), threshold value comparator A9 enables, if output feedback voltage V _fBbe less than the reference voltage V 9 of setting, think that output enters short-circuit mode, now threshold value comparator A9 is output as low level, switching tube M9 conducting, pass through the effect to logic module A5 simultaneously, and by driver module A6 signal, strengthened closing switch pipe M1, now input VIN and no longer by the first switch M1, to SW port, provide electric current, and only by weak current source I9, provide current to SW port; If the load current I of output _lOADbe greater than I9, output will maintain a certain low-voltage state V always _o, V _osatisfied condition is to be the electric current of I9, for example load for load provides size

For resistor-type load R _lOAD, V _o=R _lOAD* I9;

If output load current value is reduced in I9, when current source I9 provides current to load, to output capacitance C1 charging, output voltage slowly rises, extremely

time, the output switching activity of threshold value comparator A9, transfers high level to by low level, closing switch pipe M9 no longer by A5, switching tube M1 being controlled, DC-DC transducer recovers normal mode of operation, and by output voltage stabilization at normal set point VOUT.

So, by the magnitude of voltage of reasonable setting V9, correctly choose the resistance of I9, can obtain the voltage and current threshold point of two output short circuit protections, and export the soft recovery time of being recovered by short circuit:

$V_{\mathrm{TH}}=\frac{\mathrm{VOUT}\&times;V9}{V_{\mathrm{FB}}}---\left(9\right)$

I _TH=I9 (10)

Suppose that load when output short-circuit recovers is I _lOAD(I wherein _lOADbe less than the I in formula (10) _tH), the weak current source that current source I9 provides, to capacitor C 1 charging, meets following formula:

(wherein V is the output voltage of a certain moment t) (11)

Suppose that magnitude of voltage when output is started to recover by short circuit is that (for example load is resistor-type load R to V0 _lOAD, V0=R _lOAD* I _lOAD), formula (11) integration can be released so be exported by short circuit return to reference voltage V _tHsoft recovery time of T _sSfor:

$T_{\mathrm{SS}}=\frac{C1\&times;(V_{\mathrm{TH}}-V0)}{I9-I_{\mathrm{LOAD}}}---\left(12\right)$

As shown in figure 10, the mode of the soft recovery of described current source, can also be in parallel a plurality of by the structure after mirror current source M9 and the 3rd switching tube M91 series winding, each threshold value comparator A9 at VIN port and SW ... the structure of controlling respectively by after mirror current source M9 and the 3rd switching tube M91 series winding is controlled in the output of An; Each threshold value comparator is set reference voltage V 9 separately ... Vn, threshold value comparator A9 ... the enabling of An controlled by photodetector A7 on circuit, in the output voltage V of FB port _fBreach for the first time reference voltage V 9 ... maximum max (V9 in Vn ... Vn) before, on circuit, photodetector A7 makes each threshold value comparator A9 ... An does not enable, and the signal of soft recovery control module output opening switch module, in the output voltage V of FB port _fBreach for the first time max (V9 ... Vn) afterwards, upper photodetector A7 thinks that circuit has powered on, output control signal makes corresponding threshold value comparator A9 ... An enables, combinational logic modules A 8 is by each threshold value comparator A9 ... logical process is carried out in the output of An, determines that output unlatching or cut-off signals are to logic and driver module (221).

In Figure 10, set the threshold point of a plurality of soft restore circuits, corresponding corresponding output voltage V _tH1... V _tHn, load current I _tH1i _tHnwith soft recovery time of T _sS1t _sSn, for the mode of the soft recovery of current source:

vm is the reference voltage that threshold value comparator Am sets, 1≤m≤n;

I _tHm=(n-m+1) * I, I is soft restoring current source current value, 1≤m≤n;

Establishing respectively load current and the output voltage values exported while being started to recover by short circuit is I _lOAD(I _lOAD<I _tHm), V0:

If V _tHp-1≤ V0≤V _tHp(1≤p≤m, 1≤m≤n),

$T_{\mathrm{SSm}}=\frac{C1\&times;(V_{\mathrm{THp}}-V0)}{I_{\mathrm{THp}}-I_{\mathrm{LOAD}}}+\underset{q=p+1}{\overset{m}{\mathrm{\&Sigma;}}}\frac{C1\&times;(V_{\mathrm{THq}}-V_{\mathrm{THq}-1})}{I_{\mathrm{THq}}-I_{\mathrm{LOAD}}},p\&le;q\&le;m,1\&le;p\&le;m,1\&le;m\&le;n;$

Judgement enters condition that output enters short-circuit mode and can be defined as VOUT and be less than V _tH1v _tHnin any one V _tHm, but once output enters short-circuit mode, only has load current to be less than corresponding current threshold I _tHm, output voltage just can return to V _tHm, the output switching activity of threshold value comparator Am, transfers high level to by low level, closing switch pipe Mn no longer by A5, switching tube M1 being controlled, DC-DC transducer recovers normal mode of operation, and by output voltage stabilization at normal set point VOUT.

The soft-restoration control circuit of the output short circuit protection of the DC-DC transducer as shown in Fig. 7-10, by setting the output voltage threshold value of short circuit, judges whether to enter short-circuit mode; By choosing the current value of resistance or current source, set output load current threshold, and then judge whether to return to normal mode of operation by short circuit, the size of resistance or current source current value, determined the soft recovery time that short circuit recovers, if peripheral electric capacity or feedback resistive network change, can adjust the size of voltage threshold V9 and resistance R 9 or current value I 9, the soft recovery time that obtains holding water.

Figure 11 is for adopting single soft recovery resistance or the output voltage curve chart of front and back, soft restoring current source buck DC-DC converter circuit when output short-circuit recovers; The output voltage curve chart of Figure 12 for adopting a plurality of soft recovery resistance or soft restoring current source parallel connection front and back buck DC-DC converter circuit to recover at output short-circuit.

The invention discloses the soft-restoration control circuit of output short circuit protection, and by its concrete application at DC-DC converter circuit, describe the specific embodiment of the present invention and effect with reference to the accompanying drawings.Should be understood that: above-described embodiment is just to explanation of the present invention, rather than limitation of the present invention, any innovation and creation that do not exceed within the scope of connotation of the present invention, include but not limited to the soft recovery control principle of output short-circuit of the present invention to be applied to the fields such as other Switching Power Supply or low-dropout regulator, output is entered to the modification of the judgment mode of short-circuit mode, modification to the implementation in soft recovery resistance in soft recovery control module and soft restoring current source, to the change of the local structure of circuit (as utilize those skilled in the art thinkable technical method replace the threshold value comparator module A9 in the present invention, replace the connected mode of switching tube M9 and R9 or I9, by R9 ... Rn changes series system into by parallel way, by R9 ... Rn, I9 ... In changes a certain ratio value or random different value etc. into by identical value), replacement to the type of components and parts or model, and the replacement of other unsubstantialities or modification, within all falling into protection range of the present invention.

Claims (1)

1. the soft-restoration control circuit of output short-circuit, is characterized in that comprising switch module, switch control module and soft recovery control module, wherein:

The first input end of described switch control module connects the output of soft recovery control module, the output voltage of the second input input load end of switch control module, the input of the output connecting valve module of switch control module;

The output voltage of the input input load end of described soft recovery control module, soft recovery control module compares the output voltage of load end and reference voltage V 9: in the initial power up of circuit, the output voltage of load end soft recovery control module before not surpassing the reference voltage V 9 of setting is inoperative to switch module, until the output voltage of load end reaches reference voltage V 9; If after this output voltage of load end is less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module; Soft recovery control module continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, the output voltage of load end recovers normal set point VOUT;

Characterized by further comprising short circuit protection module; the output voltage of the input input load end of described short circuit protection module; the 3rd input of its output connecting valve control module; short circuit protection module compares the output voltage of load end and reference voltage V 1; during described reference voltage V 1> reference voltage V 9; if the output voltage of load end drops between reference voltage V 1 and reference voltage V 9, the soft-restoration control circuit of output short-circuit carries out work according to any one of following two kinds of working methods:

(A) short circuit protection module output control signal is by switch control module stopcock module, and soft recovery control module is inoperative to switch module;

(B) short circuit protection module output control signal reduces the frequency of switch module by switch control module, soft recovery control module is inoperative to switch module, if the output voltage of load end continues to be reduced to while being less than reference voltage V 9, soft recovery control module is exported cut-off signals to switch control module, switch control module stopcock module, soft recovery control module continues to detect output voltage and the load current of load end, the load current of load end and threshold current are compared, when load current is less than the threshold current of soft recovery control module, soft recovery control module opening switch control module, when the output voltage of load end is between reference voltage V 1 and reference voltage V 9, the control signal of short circuit protection module output reduces the frequency of switch module by switch control module, until the output voltage of load end surpasses reference voltage V 1, short circuit protection module is inoperative to the frequency of switch module, the soft-restoration control circuit of output short-circuit recovers normal operation.

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