CN205566093U - Circuit, device and switching power supply system that line voltage compensation overcurrent protection is ordered - Google Patents

Abstract

The utility model provides a circuit, device and switching power supply system that line voltage compensation overcurrent protection is ordered, the circuit that line voltage compensation overcurrent protection is ordered includes: power MOS manages switch circuit, is used for control closed and the disconnection of power MOS pipe, offset current obtains the circuit, obtains a sample voltage and the 2nd sample voltage respectively including a sampling circuit and the 2nd sampling circuit, a sample voltage and the 2nd sample voltage change electric current unit, output offset current as difference signal input to voltage, overcurrent protection point regulator circuit for with the 3rd sample voltage and process the adjusted reference voltage of offset current inputs electric current limit comparator, perhaps with reference voltage and process three adjusted sample voltage of offset current imports electric current limit comparator output control signal with control closed and the disconnection of power MOS pipe. The utility model discloses can unify the flow point of crossing under the different line voltages.

Description

Circuit, device and the switch power supply system of a kind of line voltage compensation over-current protection point

Technical field

The utility model relates to a kind of power supply control field, particularly relates to the electricity of a kind of line voltage compensation over-current protection point Road, device and switch power supply system.

Background technology

AC-DC power supply is in addition to the requirement of performance powered products to be met, and the safeguard measure of himself is the most extremely important.Its In, overcurrent protection is a necessary defencive function.Overcurrent protection (Over Current Protection) is exactly to work as electric current When exceeding predetermined maximum, make a kind of protected mode of protection device action.Exceed pre-when flowing through the electric current by protection original paper During certain numerical value first adjusted, protection device starts, and with the selectivity of time limit safety action, makes circuit breaker trip or provide report Alert signal.But, when ac input voltage changes in the range of 85Vac～265Vac, over-current protection point (i.e. crossing flow point) is generally Change with input line voltage change, cause the over-current protection point of high and low line voltage seriously to drift about, i.e. crossing during line voltage height is flowed Over-current protection point when protection point is low with line voltage has a long way to go, and sometimes, the mistake flow point ratio under high line voltage is under low line voltage Even can exceed one times.This was unfavorable for the uniformity of flow point.

It is applicable to not line voltage descended flow point conforming overcurrent protection scheme just to become ability in consideration of it, how to find Field technique personnel's problem demanding prompt solution.

Utility model content

The shortcoming of prior art in view of the above, the purpose of this utility model is to provide a kind of line voltage compensation to cross stream Circuit, device and the switch power supply system of protection point, serious for solving the over-current protection point of high and low line voltage in prior art The problem that drift can not use consistent mistake flow point.

For achieving the above object and other relevant purposes, the utility model provides a kind of line voltage compensation over-current protection point Circuit, the circuit of described line voltage compensation over-current protection point includes: the circuit of described line voltage compensation over-current protection point includes: merit Rate metal-oxide-semiconductor on-off circuit, including a power MOS pipe and a rest-set flip-flop, for control the conducting of described power MOS pipe with Cut-off；Compensate current acquisition circuitry, be connected with described power MOS pipe on-off circuit, including the first sample circuit, the second sampling electricity Road and a voltage turn current unit, and the sampling time of the first sample circuit and the second sample circuit is different, at power MOS pipe Obtaining the first sampled voltage and the second sampled voltage during conducting respectively, described first sampled voltage and the second sampled voltage are as difference Sub-signal is input to described voltage and turns current unit, and output compensates electric current；Over-current protection point adjusts circuit, with described compensation circuit Acquisition circuit is connected, for the 3rd sampled voltage is separately input to electricity with the reference voltage after described compensation electric current adjusts The first input end of ductility limit comparator and the second input, or by the 3rd sampled voltage after described compensation electric current adjusts First input end and the second input with reference voltage is separately input to electric current limit comparator, then compares described electric current limit The output signal of device as control signal to control the conducting of described power MOS pipe and cut-off；When electric current limit comparator first When the voltage of input is more than the voltage of the second input, control the cut-off of described power MOS pipe.

Alternatively, current foldback circuit farther includes ON-OFF control circuit, the output signal of described electric current limit comparator The cut-off of described power MOS pipe is controlled by described ON-OFF control circuit.

Alternatively, described power MOS pipe on-off circuit also includes: one the feedback signal of output voltage is modulated into height/ Low level circuit unit, an output clock signal and the oscillator of maximum ON time signal, adjust through described circuit unit The level of system and clock signal together decide on the turn-on instant of described power MOS pipe；Described maximum ON time signal deciding is every The maximum ON time of described power MOS pipe in individual turn-on cycle；When described maximum ON time signal is low level, RS touches Send out device to be reset, output low level so that described power MOS pipe ends.

Alternatively, described power MOS pipe on-off circuit farther includes: first and door, second and door, and nor gate is described After modulation, the feedback signal of output voltage and clock signal are separately input to two inputs of described first and door, first and door Output be connected with the S end of rest-set flip-flop；Output and the lead-edge-blanking circuit output end of described electric current limit comparator are electrically connected Being connected to the input of second and door, second to be electrically connected to two of nor gate defeated with the output of door and maximum ON time signal Entering end, the output of described nor gate is electrically connected to the R end of rest-set flip-flop.

Alternatively, the circuit of described line voltage compensation over-current protection point also includes a lead-edge-blanking circuit, passes through forward position Blanking circuit carries out obtaining sampled voltage after processing.

Alternatively, described compensation current acquisition circuitry also includes a timer, and described timer turns at power MOS pipe Time trigger, export the first sampling control signal and the second sampling control signal with control respectively the first sample circuit and second sampling The sampling time of circuit.

Alternatively, described compensation current acquisition circuitry also includes a proportional amplifier, and described proportional amplifier is with described First sample circuit and the second sample circuit connect, after being amplified by the 3rd sampled voltage, then by described first sampling control The 3rd sampled voltage after amplifying is sampled by signal processed and the second sampling control signal.

Alternatively, described first sample circuit includes the first switch, and the first electric capacity, when described first sampling control signal is During high level, the first switch Guan Bi, otherwise first switch off, thus obtain the first sampled voltage；Described second sample circuit Including second switch, the second electric capacity, when described second sampling control signal is high level, described second switch is closed, otherwise Second switch disconnects, thus obtains the second sampled voltage.

Alternatively, over-current protection point adjusts circuit and includes: a reference current source, and the reference current of reference current source flows through the One resistance is to produce reference voltage, and the peak point current flowing through power MOS pipe is directly proportional to reference voltage.

Alternatively, the drain voltage of described power MOS pipe connects the first divider resistance, the 7th switch, the second divider resistance Rear ground connection；Described 3rd sampled voltage is the voltage between the first divider resistance and the second divider resistance；Described 7th switch exists Closing during the conducting of described power MOS pipe, other times disconnect；The output of described compensation current acquisition circuitry is connected to described Between reference current source and the first resistance, for adjusting the reference voltage inputting described electric current limit comparator.

Alternatively, described 3rd sampled voltage is the source voltage of described power MOS pipe；The source electrode of described power MOS pipe Connecting the first sampling resistor, the other end ground connection of described first sampling resistor, the source electrode of described power MOS pipe limits with described electric current Connecting the second resistance and the 3rd switch between comparator, described compensation electric current is adjusted by described second resistance and inputs described electric current 3rd sampled voltage of limit comparator；Described 3rd switch closes during described power MOS pipe turns on, and other times disconnect； The first input end of described electric current limit comparator connects the 4th switch to ground；Described 4th switch turns at described power MOS pipe Period disconnects, and other times close；It is connected between the source electrode of described power MOS pipe and the first input end of described proportional amplifier 5th switch, described 5th switch closes during described power MOS pipe turns on, and other times disconnect；Described proportional amplifier First input end connect the 6th switch to ground, described 6th switch described power MOS pipe turn on during disconnect, other times Guan Bi.

The utility model also provides for the device of a kind of line voltage compensation over-current protection point, described line voltage compensation overcurrent protection The device of point includes the circuit of line voltage compensation over-current protection point as above.

The utility model also includes a kind of switch power supply system, and described switch power supply system includes line voltage as above Compensate the circuit of over-current protection point.

As it has been described above, circuit, device and the Switching Power Supply system of a kind of line voltage compensation over-current protection point of the present utility model System, has the advantages that two fixed time points of sampling flow through the electricity of power MOS pipe by when power MOS pipe turns on Stream, generates the compensation electric current proportional with line voltage, and regulates the peak point current flowing through power MOS with this compensation electric current. Line voltage is the highest, and the current differential that two fixed time points flow through power MOS pipe is the biggest, and the compensation rate of peak point current is the biggest, Thus obtain the mistake flow point little with line voltage change.The utility model is applicable to discontinuous conduction mode (DCM) and leads continuously The various topology AC-DC Switching Power Supplies of logical pattern (CCM), are particularly suited for the Switching Power Supply of continuous conduction mode (CCM).

Accompanying drawing explanation

Fig. 1 is shown as the module signal of an embodiment of the circuit of line voltage compensation over-current protection point of the present utility model Figure.

The circuit theory of the embodiment that Fig. 2 is shown as the circuit of line voltage compensation over-current protection point of the present utility model is shown It is intended to.

The signal waveform of the embodiment that Fig. 3 is shown as the circuit of line voltage compensation over-current protection point of the present utility model is shown It is intended to.

Fig. 4 is shown as the circuit theory of another embodiment of the circuit of line voltage compensation over-current protection point of the present utility model Schematic diagram.

Fig. 5 illustratively comprises the one of the switch power supply system of the circuit of line voltage compensation over-current protection point of the present utility model The circuit theory schematic diagram of embodiment.

Element numbers explanation

The circuit of 1 line voltage compensation over-current protection point

11 power MOS pipe on-off circuits

12 compensate current acquisition circuitry

13 over-current protection points adjust circuit

Detailed description of the invention

By particular specific embodiment, embodiment of the present utility model being described below, those skilled in the art can be by this Content disclosed by specification understands other advantages of the present utility model and effect easily.

It should be clear that structure depicted in this specification institute accompanying drawings, ratio, size etc., the most only in order to coordinate specification to be taken off The content shown, understands for those skilled in the art and reads, being not limited to the utility model enforceable restriction bar Part, therefore do not have technical essential meaning, the modification of any structure, the change of proportionate relationship or the adjustment of size, do not affecting Under effect that the utility model can be generated by and the purpose that can reach, all should still fall in the technology disclosed in the utility model In the range of Rong Suoneng is contained.Meanwhile, in this specification cited as " on ", D score, "left", "right", " middle " and " one " Deng term, be merely convenient to narration understand, and be not used to limit the enforceable scope of the utility model, its relativeness It is altered or modified, is changing under technology contents without essence, when being also considered as the enforceable category of the utility model.

Overcurrent protection (Over Current Protection) is exactly when electric current exceedes predetermined maximum, makes protection A kind of protected mode of device action.When flow through by protection original paper in electric current exceed certain numerical value adjusted in advance time, protection Device starts, and with the selectivity of time limit safety action, makes circuit breaker trip or provide alarm signal.The utility model center line electricity The principle analysis that pressure compensates over-current protection point is as follows, as a example by the AC-DC power supply of a flyback topology, flyback topology Power output P of AC-DC power supply_OCan represent by equation below:

$P_O=\frac{L_P}{2}\·(I_2^2-I_1^2)\·f_{sw}\·\mathrm{\η}---\left(1\right)$

Wherein, L_PFor former limit inductance, I₁The initial current of former limit inductance, I when starting for each cycle₂For former limit inductance Peak point current, f_swFor switching frequency, η is efficiency.

For constant voltage source system, cross flow point I_OCPEquation below is then can use to represent:

$I_{OCP}=\frac{\frac{LP}{2}\·(I_2^2-I_1^2)\·f_{sw}\·\mathrm{\η}}{V_O}---\left(2\right)$

When line voltage changes in the range of 85Vac～265Vac, cross flow point I_OCP(when exporting electric current and exceeding flow point, will Starting protection device) also can and then change, reason has two: the turn-off delay (t of (1) power switch_d) cause not line voltage Under, the peak point current (I of inductance₂) different.A time delay (t has really been turned off to power MOS from sending cut-off signals_d), at this In time, inductive current continues to rise.Not under line voltage, the slope that inductive current rises is different, causes real peak value Electric current is the most different.(2) for the system of continuous conduction mode (CCM), cross flow point and additionally depend on each cycle when starting Inductance initial current (I₁), under high line voltage, power MOS pipe ON time is short, and under fixed frequency fsw, the turn-off time is just Long so that initial current (I₁) low；Under low line voltage the most contrary.Knowable to the two above analysis of causes, I under high line voltage₂Big and I₁Little, cause high line voltage to descend flow point higher than the mistake flow point under low line voltage.The mistake flow point of not compensated is under high line voltage One times even can be exceeded than under low line voltage.

The utility model discloses a kind of line voltage compensation and crosses the technology of flow point, it is adaptable to discontinuous conduction mode (DCM) and The switch power supply system of continuous conduction mode (CCM), is particularly suited for continuous conduction mode (CCM) switch power supply system.This reality With novel by when power MOS turns on, two fixed time points of sampling flow through the electric current of power MOS pipe, generation and line voltage Proportional compensation electric current, and the peak point current flowing through power MOS pipe is regulated with this compensation electric current.Line voltage is the highest, and two The current differential that individual fixed time point flows through MOS is the biggest, and the compensation rate of peak point current is the biggest, thus obtains little with line The mistake flow point of voltage change.The utility model is applicable to the switch power supply system of various topological structure, including flyback topology AC-DC power-supply system.

The utility model provides the circuit of a kind of line voltage compensation over-current protection point.As it is shown in figure 1, described line voltage compensation The circuit 1 of over-current protection point includes power MOS pipe on-off circuit 11, compensates current acquisition circuitry 12 and over-current protection point adjustment Circuit 13.Wherein:

Power MOS pipe on-off circuit 11 includes a power MOS pipe and a rest-set flip-flop, is used for controlling described power The conducting of metal-oxide-semiconductor and cut-off.

In one embodiment, described power MOS pipe on-off circuit 11 also includes: described power MOS pipe on-off circuit is also Including: a circuit unit that the feedback signal of output voltage is modulated into high/low level, an output clock signal (Clock Signal) with the oscillator of maximum ON time signal (DCmax signal), the level modulated through described circuit unit and clock signal (Clock signal) together decides on the turn-on instant of described power MOS pipe；Described maximum ON time signal (DCmax signal) is certainly The maximum ON time of described power MOS pipe in fixed each turn-on cycle；When described maximum ON time signal is low level, Rest-set flip-flop is reset, output low level so that described power MOS pipe ends.Described output voltage is switch power supply system Output voltage, described switch power supply system includes the current foldback circuit in the utility model.In one embodiment, described merit Rate metal-oxide-semiconductor on-off circuit 11 farther includes: first and door, second and door, nor gate, the feedback of output voltage after described modulation Signal and clock signal are separately input to two inputs of described first and door, first and the output of door and rest-set flip-flop S end connects；The output of described electric current limit comparator and lead-edge-blanking circuit output end are electrically connected to the input of second and door, Second is electrically connected to two inputs of nor gate, the output of described nor gate with the output of door and maximum ON time signal End is electrically connected to the R end of rest-set flip-flop.

Compensate current acquisition circuitry 12 be connected with described power MOS pipe on-off circuit 11, including the first sample circuit, second Sample circuit and a voltage turn current unit, and the sampling time of the first sample circuit and the second sample circuit is different, in merit The first sampled voltage and the second sampled voltage, described first sampled voltage and the second sampling electricity is obtained respectively during the conducting of rate metal-oxide-semiconductor Pressure is input to described voltage as differential signal and turns current unit, and output compensates electric current.Described sample circuit includes switch and adopts Sample electric capacity.In one embodiment, described compensation current acquisition circuitry 12 can also include a proportional amplifier, described ratio Amplifier is connected with described first sample circuit and the second sample circuit, after being amplified by the 3rd sampled voltage, then by institute State the first sampling control signal and the second sampling control signal the 3rd sampled voltage after amplifying is sampled.An enforcement In example, described first sample circuit includes the first switch, the first electric capacity, when described first sampling control signal is high level, First switch Guan Bi, otherwise first switches off, thus obtains the first sampled voltage；Described second sample circuit includes that second opens Closing, the second electric capacity, when described second sampling control signal is high level, described second switch is closed, and otherwise second switch breaks Open, thus obtain the second sampled voltage.Described compensation current acquisition circuitry 12 can also include a timer, described timer Trigger when power MOS pipe turns on, export the first sampling control signal and the second sampling control signal and adopt to control first respectively Sample circuit and the sampling time of the second sample circuit.

Overcurrent protection adjusts circuit 13 and is connected with described compensation current acquisition circuitry 12, for by the 3rd sampled voltage and warp Cross the reference voltage after described compensation electric current adjusts and be separately input to first input end and second input of electric current limit comparator, Or the 3rd sampled voltage after described compensation electric current adjusts and reference voltage are separately input to electric current limit comparator First input end and the second input, then that the output signal of described electric current limit comparator is described to control as control signal The conducting of power MOS pipe and cut-off；When the voltage of the first input end of electric current limit comparator is more than the voltage of the second input, Control the cut-off of described power MOS pipe.Over-current protection point adjusts circuit 13 and includes: a reference current source, the benchmark of reference current source Electric current flows through the first resistance to produce reference voltage, and the peak point current flowing through power MOS pipe is directly proportional to reference voltage.At one In embodiment, the output signal of described electric current limit comparator controls described power MOS by described power MOS pipe on-off circuit 11 The cut-off of pipe.

In one embodiment, the circuit 1 of described line voltage compensation over-current protection point also includes a LEB (Leading Edge Blanking, lead-edge-blanking) circuit, sampled voltage could be obtained by carrying out after LEB processing of circuit.At primary current Control in loop, owing to switch conduction moment has pulse peak current, if sampling current value now being controlled, meeting Because the spike of pulse front edge produces false triggering action, lead-edge-blanking may be used for eliminating this false triggering hidden danger.An enforcement In example, the drain voltage of described power MOS pipe is ground connection, described sampled voltage after the first divider resistance and the second divider resistance Being the voltage between the first divider resistance and the second divider resistance, described compensation electric current is used for adjusting input described electric current limit comparator Reference voltage.In another embodiment, the source electrode of described power MOS pipe connects the first resistance, another of described first resistance End ground connection, described sampled voltage is the source voltage of described power MOS pipe；The source electrode of described power MOS pipe limits with described electric current Connecting the second resistance between comparator, described compensation electric current is adjusted by described second resistance and inputs described electric current limit comparator Sampled voltage.

In one embodiment, the circuit of line voltage compensation over-current protection point as in figure 2 it is shown, wherein, modulator (Modulator) element circuit (feedback signal of output voltage is modulated into the circuit unit of high/low level) is by output voltage Feedback signal (feedback) be modulated into high/low level, this level and Clock signal together decide on the open-minded of power MOS pipe Moment.Described output voltage is the output voltage of switch power supply system, and described switch power supply system includes in the utility model Current foldback circuit.Oscillator (Oscillator) produces two signal: Clock and DCmax.Clock signal and modulator (Modulator) output signal, through one and door, is connected to set (S) end of rest-set flip-flop, thus determines power MOS's Open the moment.DCmax determines the maximum ON time in each cycle, and when DCmax is low level, rest-set flip-flop is reset (Reset), Gate being dragged down, power MOS pipe turns off.Drain is the drain electrode of power MOS pipe, and Source is the source of power MOS pipe Pole.After the drain voltage (Drain voltage) of described power MOS pipe connects the first divider resistance, the 7th switch, the second divider resistance Ground connection；Described 3rd sampled voltage (Vsense) is the voltage between the first divider resistance and the second divider resistance；Described 7th Switching and close during described power MOS pipe turns on, other times disconnect；The output of described compensation current acquisition circuitry connects To between described reference current source and the first resistance, for adjusting the reference voltage inputting described electric current limit comparator.Drain electricity Pressure output voltage Vsense, Vsense after divider resistance are proportional to flow through the electric current of power MOS pipe during MOS turns on Idrain.The reference current (Iref) of reference current source flows through the first resistance (R1) to produce reference voltage (Vref), flows through merit The peak point current of rate metal-oxide-semiconductor is directly proportional to reference voltage.The peak value of Idrain is proportional to reference voltage Vref.

The waveform of each key point of the circuit of the line voltage compensation over-current protection point in Fig. 2 is as shown in Figure 3.Wherein, Vline represents the waveform of line voltage, and Gate represents the waveform that rest-set flip-flop exports, and pulse1 represents the first sampling control signal Waveform, pulse2 represents the waveform of the second sampling control signal, and Vref represents the waveform that reference current exports, and Vref1 represents not Through the waveform of the reference current output of overcompensation circuit regulation, Vref2 represents that the reference current when overcompensation circuit regulates is defeated The waveform shape gone out, Vsense represents the waveform of the 3rd sampled voltage, and Vsense1 represents the waveform of the first sampled voltage, Vsense2 Representing the waveform of the second sampled voltage, Icomp represents that voltage turns the waveform compensating electric current of current unit output.

The circuit of the line voltage compensation over-current protection point in Fig. 2 produces the compensation electric current Icomp's of reflection line voltage levels Detailed process is as follows: Vsense receives the input of proportional amplifier, and the output signal after scaling receives switch SW1 With the common port of SW2, the positive plate of another termination sampling/holding capacitor C1 of SW1, and it is input to subsequent voltage and turns electric current list The negative terminal of unit, the positive plate of another termination sampling/holding capacitor C2 of SW2, and be input to subsequent voltage and turn current unit Anode.The control signal of SW1 be the control signal of pulse1, SW2 be pulse2, pulse1 and pulse2 by Timer (regularly Device) produce, the input of Timer timer is Gate signal, at Gate rising edge time delay set time T1 and T2, respectively obtains Pulse1 and pulse2, as shown in Figure 3.When pulse is high, its switch conduction controlled, the output voltage of proportional amplifier passes It is delivered on the electric capacity of correspondence, namely sample phase；When burst pulse is low, its switch controlled cuts out, and this stage is for keeping Stage.Owing to the moment of sampling is different, therefore keeping the stage, the voltage on two electric capacity is the most different.Due to Pulse2 occurs a little later than pulse1, and Vsense is the voltage ramped up, therefore Vsense2 would generally compare Vsense1 is high.Voltage on the two electric capacity is input to follow-up voltage as differential signal and turns current unit, and voltage turns electric current The difference of the two voltage is converted into current signal Icomp by unit.Voltage turns current unit and meets following relation:

I_comp=k₁·(V_sense2-V_sense1) (3)

Wherein, k1 is the conversion coefficient that voltage turns electric current.

Owing to having following equation during turning at power MOS,

V_sense=k₂·R_dson·I_drain (4)

Wherein, k2 is electric resistance partial pressure coefficient, and Rdson is the conduction impedance of power MOS.

It is known that the slope of inductive current Idrain and line voltage are proportional, such as, a flyback system is come Say there is a following equation:

$\frac{{\mathrm{\ΔI}}_{drain}}{\mathrm{\Δ}t}=k_3\·V_{line}---\left(5\right)$

Wherein, k3 is constant.(4) formula is substituted into (5) formula, can obtain:

$\frac{V_{sense2}-V_{sense1}}{T_2-T_1}=k_2\·k_3\·R_{dson}\·V_{line}---\left(6\right)$

(6) formula is substituted into (3) formula, can obtain:

I_comp=k₁·k₂·k₃·R_dson·(T₂-T₁)·V_line (7)

As known from the above, owing to k1, k2, k3, Rdson, T1 and T2 are fixed value, therefore electric current Icomp and line electricity are compensated Pressure Vline is directly proportional, and during line voltage height, Icomp is big, and when line voltage is low, Icomp is little.

Producing after compensating electric current Icomp, the concrete grammar of this compensation electric current regulation power MOS pipe peak point current is as follows:

Compensation electric current Icomp is connected to Vref, Icomp and Iref and jointly acts on, and flows through resistance R1, produces reference voltage Vref:

V_ref=(I_ref-I_comp)·R₁ (8)

Iref is fixed reference electric current, and when line voltage height, Icomp is big, causes Vref low；Line voltage is the most contrary time low.

Vref connects the negative input end of electric current limit comparator, and Vsense connects the positive input terminal of electric current limit comparator.Power During MOS conducting, Vsense and Vref compares, when Vsense is higher than Vref, and electric current limit comparator output high level, will Gate drags down, and closes power MOS pipe.

Understanding, peak point current Idrain_pk is determined by Vref, and the relation of Idrain_pk and compensation electric current Icomp is such as Under:

$I_{drain\_pk}=\frac{V_{ref}}{k_2\·R_{dson}}+k_3\·V_{line}\·T_{delay}=\frac{(I_{ref}-I_{comp})\·R_1}{k_2\·R_{dson}}+k_3\·V_{line}\·T_{delay}---\left(9\right)$

Wherein Tdelay is the shutoff time delay of internal circuit.

From the equation it can be seen that compensate electric current Icomp to have adjusted peak point current Idrain_pk: line voltage is the highest, Icomp is the biggest, so that the peak point current Idrain_pk under high line voltage and the Idrain_pk under low line voltage is equal (right In DCM system), or the peak point current Idrain_pk under high voltage less than the Idrain_pk under low line voltage (for CCM system System).

In another embodiment, as shown in Figure 4, it is with the line shown in Fig. 2 for the circuit of line voltage compensation over-current protection point The circuit of voltage compensation over-current protection point differ primarily in that sampled voltage Vsense is that the source end from power MOS pipe is adopted Sample, the compensation electric current of generation is for compensating Vsense, rather than Vref.Wherein, described 3rd sampled voltage (Vsense) is described The source voltage of power MOS pipe；The source electrode of described power MOS pipe connects the first sampling resistor (Rcs), described first sampling resistor (Rcs) other end ground connection, be connected between the source electrode of described power MOS pipe and described electric current limit comparator the second resistance (R2) and 3rd switch, described compensation electric current adjusts the 3rd sampling electricity inputting described electric current limit comparator by described second resistance (R2) Pressure (Vsense)；Described 3rd switch closes during described power MOS pipe turns on, and other times disconnect；Described electric current limit ratio The first input end of relatively device connects the 4th switch to ground；Described 4th switch disconnects during described power MOS pipe turns on, other Time closes；The 5th switch, institute it is connected between the source electrode of described power MOS pipe and the first input end of described proportional amplifier A Stating the 5th switch to close during described power MOS pipe turns on, other times disconnect；The first input end of described proportional amplifier Connecting the 6th switch and arrive ground, described 6th switch disconnects during described power MOS pipe turns on, other times Guan Bi.Concrete real Applying method is described below:

After the compensation electric current Icomp proportional with line voltage produces, it is noted that inside Icomp here and front embodiment Icomp in opposite direction, in other words, front embodiment voltage turn current unit output sink electric current (drawing electric current), in this embodiment Voltage turns current unit output source electric current (filling electric current).Voltage turns the output of current unit and is connected on one end of resistance R2, R2 The source electrode of another termination power MOS, the source electrode of power MOS receives ground through a resistance Rcs.Icomp produces on R2 Pressure drop and line voltage are directly proportional, and Vsense voltage can be expressed as:

V_sense=V_source+I_comp·R₂ (10)

The expression formula of peak point current Idrain_pk can be obtained by above formula:

$I_{drain\_pk}=\frac{I_{ref}\·R_1-I_{comp}\·R_2}{R_{cs}}+K_3\·V_{line}\·T_{delay}---\left(11\right)$

Compensation electric current Icomp, by compensating Vsense, have adjusted peak point current Idrain_pk: line voltage is the highest, Icomp It is the biggest, so that the peak point current Idrain_pk under high line voltage and the Idrain_pk under low line voltage is equal (for DCM System), or the peak point current Idrain_pk under high voltage is less than the Idrain_pk (for CCM system) under low line voltage.

The utility model also provides for the device of a kind of line voltage compensation over-current protection point, described line voltage compensation overcurrent protection The device of point includes the circuit of line voltage compensation over-current protection point as above.The dress of described line voltage compensation over-current protection point Put and can be packaged into a chip.The device of line voltage compensation over-current protection point can produce the compensation electricity of reflection line voltage levels Stream, regulates peak point current by this compensation electric current, so that cross flow point not with line voltage change.

The utility model also includes a kind of switch power supply system, and described switch power supply system includes line voltage as above Compensate the circuit of over-current protection point.The circuit of the line voltage compensation over-current protection point that the utility model describes can be widely used At switch power supply system.In one embodiment, described switch power supply system is inverse-excitation type switch power-supply system as shown in Figure 5 System.Inverse-excitation type switch power-supply system uses the circuit of above-mentioned line voltage compensation over-current protection point.Described inverse-excitation type switch power-supply system System includes: a rectifier bridge, a filtration module (C1), a former limit absorption module, a switch power controller, a voltage changing module T1, Secondary output module, a load, and a feedback module.Wherein, the input of described rectifier bridge is connected with civil power (AC IN), For being direct current (Vbus) by AC rectification, and it is sent to described filtration module (C1)；Described filtration module (C1) is used for Direct current is filtered；Described former limit absorption module, for reducing the due to voltage spikes that leakage inductance is formed on power MOS pipe, reduces EMI disturbs；Described voltage changing module T1 is connected with described former limit absorption module, the voltage x current between former limit, vice-side winding Mutual phase transformation；Described secondary output module is for the voltage and current extremely described load of output one vice-side winding；Described feedback Circuit is coupled in output quantity Vout, is used for producing one and is input to switch power controller (this switch power controller includes The circuit of described line voltage compensation over-current protection point) feedback signal FB (Feedback), this feedback signal FB is (as output The feedback signal of voltage) it is input to the circuit of described line voltage compensation over-current protection point, and clock signal co-controlling power MOS Pipe open the moment；Described switch power controller includes the circuit of line voltage compensation over-current protection point described in the utility model And power MOS pipe, the circuit of described line voltage compensation over-current protection point is used for controlling the on or off of power MOS pipe, from And control to be transferred to the voltage and current of load.The implementing of described line voltage compensation over-current protection point sees above Embodiment.Described line voltage compensation over-current protection point can be packaged into a chip or device.

In sum, circuit, device and the Switching Power Supply system of a kind of line voltage compensation over-current protection point of the present utility model System is capable of: flows through power MOS electric current by two set time point samplings during turning at power MOS pipe, carrys out perception The height of line voltage, generates the compensation electric current proportional with line voltage；Reference voltage Vref is regulated with the compensation electric current generated Or regulation current sample voltage Vsense, thus regulate peak point current.Realized not with line voltage by regulation peak point current The mistake flow point of change.The utility model is applicable to discontinuous conduction mode (DCM) and the various topologys of continuous conduction mode (CCM) AC-DC Switching Power Supply.So, the utility model effectively overcomes various shortcoming of the prior art and has high industrial exploitation value Value.

Above-described embodiment only illustrative principle of the present utility model and effect thereof are new not for limiting this practicality Type.Above-described embodiment all can be carried out by any person skilled in the art under spirit and the scope of the present utility model Modify or change.Therefore, art has usually intellectual such as without departing from the essence disclosed in the utility model All equivalences completed under god and technological thought are modified or change, and must be contained by claim of the present utility model.

Claims (12)

1. the circuit of a line voltage compensation over-current protection point, it is characterised in that the electricity of described line voltage compensation over-current protection point Road includes:

Power MOS pipe on-off circuit, including a power MOS pipe and a rest-set flip-flop, for controlling described power MOS pipe Conducting and cut-off；

Compensate current acquisition circuitry, be connected with described power MOS pipe on-off circuit, including the first sample circuit, the second sampling electricity Road and a voltage turn current unit, and the sampling time of the first sample circuit and the second sample circuit is different, at power MOS pipe Obtaining the first sampled voltage and the second sampled voltage during conducting respectively, described first sampled voltage and the second sampled voltage are as difference Sub-signal is input to described voltage and turns current unit, and output compensates electric current；

Over-current protection point adjusts circuit, obtains circuit with described compensation circuit and is connected, for by the 3rd sampled voltage and through institute State the reference voltage after compensating electric current adjustment and be separately input to first input end and second input of electric current limit comparator, or The 3rd sampled voltage after described compensation electric current adjusts and reference voltage are separately input to the first of electric current limit comparator Input and the second input, then limit the output signal of comparator as control signal to control described power using described electric current The conducting of metal-oxide-semiconductor and cut-off；When the voltage of the first input end of electric current limit comparator is more than the voltage of the second input, control Described power MOS pipe ends.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: described power MOS pipe On-off circuit also includes: a circuit unit that the feedback signal of output voltage is modulated into high/low level, an output clock Signal and the oscillator of maximum ON time signal, the level modulated through described circuit unit together decides on described with clock signal The turn-on instant of power MOS pipe；The maximum of described power MOS pipe in the described maximum each turn-on cycle of ON time signal deciding ON time；When described maximum ON time signal is low level, rest-set flip-flop is reset, output low level so that described Power MOS pipe ends.

The circuit of line voltage compensation over-current protection point the most according to claim 2, it is characterised in that: described power MOS pipe On-off circuit farther includes: first and door, second and door, nor gate, after described modulation output voltage feedback signal and time Clock signal is separately input to two inputs of described first and door, and first is connected with the S end of rest-set flip-flop with the output of door； The output of described electric current limit comparator and lead-edge-blanking circuit output end are electrically connected to the input of second and door, second and door Output and maximum ON time signal be electrically connected to two inputs of nor gate, the output electrical connection of described nor gate R end to rest-set flip-flop.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: described line voltage compensation The circuit of over-current protection point also includes a lead-edge-blanking circuit, could obtain sampling by carrying out after lead-edge-blanking processing of circuit Voltage.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: described compensation electric current obtains Sense circuit also includes a timer, and described timer triggers when power MOS pipe turns on, export the first sampling control signal and Second sampling control signal is to control the first sample circuit and the sampling time of the second sample circuit respectively.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: described compensation electric current obtains Sense circuit also includes that a proportional amplifier, described proportional amplifier connect with described first sample circuit and the second sample circuit Connect, after the 3rd sampled voltage is amplified, then by described first sampling control signal and the second sampling control signal to amplification After the 3rd sampled voltage sample.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: described first sampling electricity Road includes the first switch, the first electric capacity, when described first sampling control signal is high level, and the first switch Guan Bi, otherwise the One switches off, thus obtains the first sampled voltage；Described second sample circuit includes second switch, the second electric capacity, when described When second sampling control signal is high level, described second switch is closed, and otherwise second switch disconnects, thus obtains the second sampling Voltage.

The circuit of line voltage compensation over-current protection point the most according to claim 1, it is characterised in that: over-current protection point adjusts Circuit includes: a reference current source, and the reference current of reference current source flows through the first resistance to produce reference voltage, flows through power The peak point current of metal-oxide-semiconductor is directly proportional to reference voltage.

The circuit of line voltage compensation over-current protection point the most according to claim 8, it is characterised in that: described power MOS pipe Drain voltage connect the first divider resistance, the 7th switch, ground connection after the second divider resistance；Described 3rd sampled voltage is first Voltage between divider resistance and the second divider resistance；Described 7th switch closes during described power MOS pipe turns on, other Time separated；The output of described compensation current acquisition circuitry is connected between described reference current source and the first resistance, is used for Adjust the reference voltage inputting described electric current limit comparator.

The circuit of line voltage compensation over-current protection point the most according to claim 6, it is characterised in that: described 3rd sampling Voltage is the source voltage of described power MOS pipe；The source electrode of described power MOS pipe connects the first sampling resistor, and described first adopts The other end ground connection of sample resistance, is connected the second resistance and the between the source electrode of described power MOS pipe and described electric current limit comparator Three switches, described compensation electric current adjusts the 3rd sampled voltage inputting described electric current limit comparator by described second resistance；Institute Stating the 3rd switch to close during described power MOS pipe turns on, other times disconnect；First input of described electric current limit comparator End connects the 4th switch to ground；Described 4th switch disconnects during described power MOS pipe turns on, and other times close；Described Being connected the 5th switch between the source electrode of power MOS pipe and the first input end of described proportional amplifier, described 5th switch is in institute Closing during stating power MOS pipe conducting, other times disconnect；The first input end of described proportional amplifier connects the 6th switch and arrives Ground, described 6th switch disconnects during described power MOS pipe turns on, and other times close.

The device of 11. 1 kinds of line voltage compensation over-current protection points, it is characterised in that: the dress of described line voltage compensation over-current protection point Put the circuit including the line voltage compensation over-current protection point as described in any claim in claim 1 to 10.

12. 1 kinds of switch power supply systems, it is characterised in that: described switch power supply system includes as arbitrary in claim 1 to 10 The circuit of the line voltage compensation over-current protection point described in claim.