CN103929860B - A kind of band soft start and the Dimmable LED driving chip of undervoltage lockout circuit - Google Patents

A kind of band soft start and the Dimmable LED driving chip of undervoltage lockout circuit Download PDF

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CN103929860B
CN103929860B CN201410176398.4A CN201410176398A CN103929860B CN 103929860 B CN103929860 B CN 103929860B CN 201410176398 A CN201410176398 A CN 201410176398A CN 103929860 B CN103929860 B CN 103929860B
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outfan
pin
drain electrode
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CN103929860A (en
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江金光
谭高建
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Wuhan University WHU
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Abstract

The invention belongs to LED driver field, relate to a kind of Dimmable LED driving chip, particularly to a kind of Dimmable LED driving chip with soft start and undervoltage lockout circuit.This chip is based on current PWM mode DC DC boost converter.Chip internal uses switching regulator PWM dimming strategies, the brightness of LED can carry out the wide dispersionless smooth adjustment of scope, and do not affect chip efficiency.Additionally, a kind of novel soft starting circuit of integrated chip, surge current when starting, overshoot voltage can be suppressed to be not damaged by with protection LED, driving chip.Finally, a kind of novel UVLO circuit of integrated chip, while saving chip area, it is ensured that stability that LED drive chip work when power supply source change in voltage, it is ensured that the reliability of LED luminescence.

Description

A kind of band soft start and the Dimmable LED driving chip of undervoltage lockout circuit
Technical field
The invention belongs to LED driver field, relate to a kind of Dimmable LED driving chip, particularly to a kind of Dimmable LED driving chip with soft start and undervoltage lockout circuit.
Background technology
Along with the energy-conservation concept of development of society is rooted in the hearts of the people, people the most actively find high efficiency light source, have reached energy-conservation purpose.White light LEDs, with advantages such as its higher luminous efficiency, longer service life, preferable environmental suitability, smooth dimming behaviors, has become a kind of excellent solid state light emitter.White light LEDs is widely used in off-line illumination, the such as backlight of indoor illumination light fitting, liquid crystal display.Generally multiple LED are connected, identical to ensure the brightness of each LED, promote overall brightness simultaneously.The electric current flow through to it due to the luminosity of LED is directly proportional, and unrelated with the voltage at its two ends, and therefore LED operationally needs a constant current source power supply.
Conventional LED driver is the dc-dc of a constant current output, and one fixed value during its output electric current, the LED luminosity driven necessarily cannot regulate, and limits the range of application of LED；Owing to DC-DC controls the inherent character of loop, driver on startup, controls loop and is in imbalance state, and such system can produce overshoot voltage and surge current, easily damages LED and LED drive chip；When normally working, owing to the voltage of LED driver input power can change simultaneously, the signal of LED driver meeting output error when input voltage is relatively low, LED is luminous unreliable and is likely to be broken.
Summary of the invention
The problems referred to above existed for tradition LED drive chip；Provide a kind of LED drive chip based on current PWM mode DC-DC boost converter.Driving chip is integrated with a kind of novel soft starting circuit, surge current when chip can be suppressed to start and overshoot voltage, and protection driving chip is not damaged by with LED；It is integrated with a novel undervoltage lockout circuit simultaneously, while saving chip area, it is ensured that when input supply voltage changes, the reliability of the work of driving chip and LED；Comprise a sleep block, park mode can be entered to save the energy with control chip.Chip uses switching regulator PWM count word dimming arrangement, in the case of the efficiency not affecting LED drive chip, it is achieved the wide scope non-dispersive smooth adjustment to LED luminosity.
The above-mentioned technical problem of the present invention is mainly addressed by following technical proposals:
A kind of band soft start and the Dimmable LED driving chip of undervoltage lockout circuit, it is characterised in that including: control loop, soft start loop, compensate loop and secondary control module；The input termination compensating loop controls loop output, controls loop output and connects the compensation input compensating loop；The voltage in soft start loop, current output terminal connect the control soft start voltage in loop, current input terminal, and soft start loop shares inductive current detection module with compensating loop；The output that enables of secondary control module terminates the Enable Pin of other modules, and each module Enable Pin uses classical switching regulator connected mode；The light modulation output termination of secondary control module controls the light modulation input in loop；
At above-mentioned a kind of band soft start and the Dimmable LED driving chip of undervoltage lockout circuit, LED drive chip comprises following six roots of sensation pin: power pins VIN, overvoltage protection input pin OVP, inductive current input pin LX, Voltage Feedback pin FB, dim signal input pin EN, pin GND；Wherein: VIN, GND are the common pin of all chip internal modules；LX pin is simultaneously as the input pin of inductive current detection module, and controls the output pin in loop；OVP pin is the voltage input pin in soft start loop, and EN pin is the control signal input of secondary control module；FB pin is the feedback signal input pin controlling loop.
Exemplary operation circuit connects as follows, and power supply VDD is just terminating VIN pin, and the anode of VDD passes through input capacitance C simultaneouslyINGround connection；Inductance L is connected between VIN pin and LX pin, and LX pin connects commutation diode D positive pole, and diode D negative pole passes through output capacitance COGround connection, diode D cathode voltage i.e. output voltage VO；VOConnecing the positive pole of OVP pin and load LEDs, the negative pole of LEDs passes through feedback resistance R simultaneouslyFGround connection, the FB pin of driving chip connects the negative pole of LEDs；PWM dim signal passes through EN pin access chip.
In the Dimmable LED driving chip of above-mentioned a kind of band soft start and undervoltage lockout circuit, described control loop includes a reference source and biasing module, error amplifier, PWM comparator, three input AND, tunable optical latch module, N-type driver, power switch NM2；Topology connection is as follows: a reference source meets VIN pin, reference voltage output end V with the voltage input end of biasing moduleB0Connect the negative input end of error amplifier EA；Feedback pin FB connects the positive input terminal of error amplifier EA, the positive input terminal of EA is the feedback input end controlling loop, the negative input end of the output termination PWM comparator of error amplifier EA, the positive input terminal of PWM comparator is the compensation input controlling loop, output termination three input of PWM comparator and the input of door AND；Other two inputs of AND are respectively and control the soft start voltage in loop, current input terminal, the R input of the output termination light modulation latch module of AND, the outfan of the S input termination oscillator module of light modulation latch module, the ENB input of the Dim input termination sleep block of light modulation latch module, Dim end i.e. controls the light modulation input in loop；The outfan Q of light modulation latch module connects N-type and drives the input of module；N-type drives the grid of the output termination power switch NM2 of module, and the drain electrode of NM2 connects LX pin, the source ground of NM2, and the drain electrode of NM2 is the outfan controlling loop.
Described compensation loop includes ramp voltage module, slope compensation module, inductive current detection module；Topology connection is as follows: the outfan V of current detection moduleSENSEConnect the current input terminal of slope compensation module；The outfan of the input termination oscillator module of ramp voltage module, the voltage input end of the output termination slope compensation module of ramp voltage module；The positive input terminal of the output termination PWM comparator of slope compensation module, the outfan of slope compensation module i.e. compensates the outfan in loop, and the input of inductive current detection module i.e. compensates loop input；Described inductive current detection module includes metal-oxide-semiconductor NM1, resistance R1And R2, the grid of metal-oxide-semiconductor NM1 connects N-type and drives the outfan of module, and the drain electrode of NM1 connects LX pin, and the drain electrode of NM1 is the input of inductive current detection module, and the source electrode of NM1 meets R1One end；R1The other end pass through R2Ground connection, R1With R2Common port be the outfan V of inductive current detection moduleSENSE；
Described soft start loop includes overvoltage protection comparator, soft starting circuit, overcurrent protection comparator, inductive current detection module；Topology connection is as follows: the outfan V of inductive current detection moduleSENSEConnect the negative input end of overcurrent protection comparator, output termination three input of overcurrent protection comparator and the input of door AND；The input of inductive current detection module is respectively with the outfan of overcurrent protection comparator, the input in soft start loop and current output terminal；The input end of clock of soft starting circuit connects the outfan of oscillator module, and voltage input end meets VIN pin, voltage output end VSTConnect overcurrent protection and compare positive input terminal；A reference source and the reference voltage output end V of biasing moduleB1Connecing the positive input terminal of overvoltage protection comparator, OVP pin passes through resistance RP1With resistance RP2Ground connection after series connection, resistance RP1With resistance RP2Common port connect the negative input end of overvoltage protection comparator, the outfan of overvoltage protection comparator is that the voltage output end in soft start loop connects and the input of door AND；
Described secondary control module includes under-voltage locking module, dormancy control module；Topology connection is as follows: VIN connects the input of undervoltage lockout circuit, and output signal U V of undervoltage lockout circuit connects the control signal UV input of sleep block；Pin EN connects the input of Schmidt trigger Smit, the output of Smit terminates the input of reverse INV, the outfan of INV is the ENB input of the light modulation output termination sleep block of secondary control module, and the input end of clock of sleep block connects the outfan of oscillator module；Sleep block SDB output termination a reference source and the Enable Pin of biasing module, SD output terminate the Enable Pin of remaining module.
In the Dimmable LED driving chip of above-mentioned a kind of band soft start and undervoltage lockout circuit, described control loop dims latch module and uses switching regulator PWM count tone of Chinese characters optical mode, light modulation latch R input connects the R input of d type flip flop 1 by phase inverter INV1, light modulation latch S input connects the S input of d type flip flop 1 simultaneously, input with phase inverter INV2, the input of output termination NAND gate NAND1 of INV2, the input of Dim input termination NAND gate NAND2 of light modulation latch；The Q output of d type flip flop 1 connects the input of NAND1, and the input of the output termination NAND2 of NAND1, the outfan of NAND2 is the outfan Q of light modulation latch.
In the Dimmable LED driving chip of above-mentioned a kind of band soft start and undervoltage lockout circuit, the inner topology of described soft starting circuit connects as follows: the drain electrode of N-type metal-oxide-semiconductor NMt connects VIN pin, the grid of NMt connects operational amplifier OPA outfan, and the source electrode of NMt connects the negative input end of OPA；The positive input termination a reference source of OPA and the V of biasing moduleB1Outfan, resistance Rd0, Rd1, Rd2, Rd3, Rd4 be sequentially connected in series, the end ground connection of Rd4, the negative input end of the upper termination OPA of Rd0；Rd0With Rd1Common port be the outfan V of soft starting circuitST；Switch metal-oxide-semiconductor NMd1Drain electrode connecting resistance Rd0With Rd1Common port, switch metal-oxide-semiconductor NMd2Drain electrode connecting resistance Rd1With Rd2Common port, switch metal-oxide-semiconductor NMd3Drain electrode connecting resistance Rd2With Rd3Common port, switch metal-oxide-semiconductor NMd4Drain electrode connecting resistance Rd3With Rd4Common port；NMd1Drain electrode meets the outfan Q of time delay module 11, NMd2Drain electrode meets the outfan Q of time delay module 22, NMd1Drain electrode meets the outfan Q of time delay module 33, NMd4Drain electrode meets the outfan Q of time delay module 44；NMd1、NMd2、NMd3、NMd4Source class unify ground connection.Enable Pin EN of time delay module 1 connects the SD outfan of sleep block, the outfan Q enabling termination time delay module 1 of time delay module 21, the outfan Q enabling termination time delay mould 2 of time delay module 32, the outfan Q enabling termination time delay module 3 of time delay module 43；The input end of clock Clk of time delay module 1,2,3,4 connects the outfan of oscillator module.
In the Dimmable LED driving chip of above-mentioned a kind of band soft start and undervoltage lockout circuit, the under-voltage locking inside modules Topology connection in described secondary control module is as follows: a reference source and the outfan V of biasing moduleBPConnect PMOS PMU1With PMU7Grid, PMU1Source electrode meet VIN pin, PMU1Drain electrode connect NMOS tube NMU1Drain electrode；NMU1Source ground, grid meets the outfan VB of a reference source and biasing moduleU2, NMU1Drain electrode connect PMOS PMU3Grid, PMU3Source electrode connect PMOS PMU2Drain electrode, PMU2Source electrode meet VIN pin, PMU2Grid meet the outfan VB of a reference source and biasing moduleU2；PMU3Drain electrode connect PMOS PMU4Source electrode, PMU4Grid connect the outfan of phase inverter INV4, the drain electrode of PMu4 connects NMOS tube NMU2Drain electrode；NMU2Source ground, grid meets the outfan V of a reference source and biasing moduleBN.PMOS PMU5Source electrode connect VIN pin, grid meets the outfan VB of a reference source and biasing moduleU1, drain electrode connects PMOS PMU6Source electrode；PMU6Grid meet NMU1Drain electrode, drain electrode meet NMU2Drain electrode.PMU7Source electrode connect VIN pin, drain electrode connects NMOS tube NMU3Drain electrode；NMU3Source ground, grid meets NMU2Drain electrode.PMOS PMU8Source electrode connect VIN pin, grid and NMOS tube NMU4Grid be connected be followed by NMU3Drain electrode, drain electrode and NMU4Drain electrode be connected, NMU4Source electrode connect NMOS tube NMU5Drain electrode；NMU5Source ground, grid meets NMU2Grid.The input termination NM of phase inverter INV4U4Drain electrode, output termination Schmidt trigger Smit2 input, Smit2 exports under-voltage locking signal UV.
In the Dimmable LED driving chip of above-mentioned a kind of band soft start and undervoltage lockout circuit, oscillator module uses constant-current source to build 5 grades of ring oscillators of capacitor charge and discharge structure；The band gap reference that a reference source and biasing module use classical audion to do temperature-compensating builds；Compensating the ramp voltage module in loop uses classical ramp voltage agitator based on comparator to build；Slope compensation module uses classical OTA amplifier built-up.
Therefore, the invention have the advantages that 1. application circuit simple in construction, it is only necessary to 5 peripheral components can do in work；2. advantageously reduce power consumption with sleep mode；3. while not affecting driving chip efficiency, LED luminance can carry out relative broad range non-dispersive smooth adjustment, when 4. starting, surge current and overshoot voltage are suppressed, and protection LED is not damaged by with driving chip effectively；5. changing at input supply voltage, the work of LED and driving core has higher reliability.
Accompanying drawing explanation
Accompanying drawing 1 show the exemplary operation circuit diagram of designed LED drive chip.
Accompanying drawing 2 show designed LED drive chip inner function module connection figure.
Accompanying drawing 3 show designed LED drive chip internal dimming circuit and sleep block schematic diagram.
Accompanying drawing 4 show the internal soft starting circuit schematic diagram of designed LED drive chip.
Accompanying drawing 5 show designed LED drive chip internal under-pressure lock circuit schematic diagram.
Specific embodiments
Below by embodiment, and combine accompanying drawing, technical scheme is described in further detail.
Embodiment:
Explain the object, technical solutions and advantages of the present invention in order to clearer, with example, the present invention is further detailed below in conjunction with the accompanying drawings.
Accompanying drawing 1 show the exemplary operation circuit of the designed Dimmable LED driver with soft start and undervoltage lockout circuit.It is characterized in that LED drive chip comprises following six roots of sensation pin: power pins VIN, overvoltage protection input pin OVP, inductive current input pin LX, Voltage Feedback pin FB, dim signal input pin EN, pin GND.It is chip power supply that power supply VDD is just terminating VIN pin, and the anode of VDD passes through input capacitance CINGround connection, CINThe high-frequency noise in VDD can be filtered；Inductance L is connected between VIN pin and LX pin, and LX pin connects the positive pole of commutation diode D, and the negative pole of diode D passes through output capacitance COGround connection, diode D cathode voltage is output voltage VO；VOConnect OVP pin, provide the foundation of overvoltage protection for chip, to limit the upper limit of output voltage；Vo connect load LEDs(series connection LED multi-path) positive pole, the negative pole of LEDs pass through feedback resistance RFGround connection, the negative pole of LEDs connects driving chip FB pin, and the voltage of resistance RF is as feedback, it is ensured that driving chip outputting current steadily is in designed value；PWM dim signal passes through EN pin access chip, also serves as dormant control signal simultaneously.The value of the constant current of chip output is determined by the reference voltage of RF and chip internal, changes the amplitude of output electric current by changing RF, to drive multi-way LED lamp.From LED drive chip designed seen from accompanying drawing 1, it is only necessary to 5 peripheral components can be achieved with the driving to LED, reduce use difficulty and cost.After tested: the output driving force of designed driving chip reaches 1 ~ 1000mA, keeps higher conversion efficiency simultaneously, and in a wider scope, it is achieved the non-dispersive smooth adjustment to LED luminance.
Accompanying drawing 2 show the inner function module connection figure of designed LED drive chip, it is characterised in that the basic framework of driving chip is current PWM mode DC-DC boost converter.Its main topology is by controlling loop, soft start loop, compensating loop, four parts of secondary control module and form.The input termination compensating loop controls loop output, controls loop output and connects the compensation input compensating loop；The voltage in soft start loop, current output terminal connect the control soft start voltage in loop, current input terminal, and soft start loop shares inductive current detection module with compensating loop；The output that enables of secondary control module terminates the Enable Pin of other modules, and each module Enable Pin uses classical switching regulator connected mode；The light modulation output termination of secondary control module controls the light modulation input in loop；VIN, GND are the common pin of all chip internal modules；LX pin is simultaneously as the input pin of inductive current detection module, and controls the output pin in loop；OVP pin is the voltage input pin in soft start loop, and EN pin is the control signal input of secondary control module；FB pin is the feedback signal input pin controlling loop.Error amplifier compares RFVoltage and reference voltage V B0Obtain error signal, control loop and error signal is converted to, the driving signal of a variable duty ratio, the DC current of output is needed to drive power switch pipe NM2 to obtain；Control loop works is under current PWM mode, when duty can produce subharmonic oscillation more than 50% system, compensates loop and inhibits subharmonic oscillation, it is ensured that control the stability in loop；It is in imbalance state when system has just started time error amplifier, system is operated in maximum duty cycle state, can produce surge current and overshoot voltage, may damage LED and driving chip, soft start loop can eliminate surge current and overshoot voltage, it is ensured that LED and the safety of driving chip；During normal work, input voltage VDD can change, and when VDD is less than certain value, the signal of chip output error, LED work is unreliable, and under-voltage locking module can close driving chip when VDD is too low, it is ensured that LED and the reliability of driving chip work.
Control loop to be made up of with door AND, light modulation latch module, N-type driver, power switch NM2 totally seven parts with biasing module, error amplifier, PWM comparator, three inputs a reference source.The Topology connection controlling loop is as follows: a reference source meets VIN pin, reference voltage output end VB with the voltage input end of biasing module0Connect the negative input end of error amplifier；Feedback pin FB connects the positive input terminal of error amplifier EA, the positive input terminal of EA is the feedback input end controlling loop, the negative input end of the output termination PWM comparator of error amplifier, the positive input terminal of PWM comparator is the compensation input controlling loop, output termination three input of PWM comparator and the input of door AND；Other two inputs of AND are respectively and control the soft start voltage in loop, current input terminal, the R input of the output termination light modulation latch module of AND, the outfan of the S input termination oscillator module of light modulation latch module, the ENB input of the Dim input termination sleep block of light modulation latch module, Dim end i.e. controls the light modulation input in loop；The outfan Q of light modulation latch module connects N-type and drives the input of module；N-type drives module output drive signal, and exports the grid arriving power switch NM2, and the drain electrode of NM2 connects LX pin, the source ground of NM2, and the drain electrode of NM2 is the outfan controlling loop.Control loop achieves and input voltage VDD is converted to constant current IOOutput.
Compensate loop composition to be made up of ramp voltage module, slope compensation module, inductive current detection module totally three parts.Inductive current detection module is by NMOS tube NM1, resistance R1And R2Composition, the grid of metal-oxide-semiconductor NM1 connects N-type and drives the outfan of module, and the drain electrode of NM1 connects LX pin, and the drain electrode of NM1 is the input of inductive current detection module, and the source electrode of NM1 meets R1One end；R1The other end pass through R2Ground connection, R1With R2Common port be inductive current detection mould outfan VSENSE。VSENSEConnect the current input terminal of slope compensation module；The outfan of the input termination oscillator module of ramp voltage module, the voltage input end of the output termination slope compensation module of ramp voltage module；The positive input terminal of the output termination PWM comparator of slope compensation module, the outfan of slope compensation module i.e. compensates the outfan in loop, and the input of inductive current detection module i.e. compensates loop input.
Soft start loop is made up of totally overvoltage comparator, soft starting circuit, overcurrent protection comparator, inductive current detection module four parts.Its Topology connection is as follows: the outfan V of inductive current detection moduleSENSEConnect the negative input end of overcurrent protection comparator, output termination three input of overcurrent protection comparator and the input of door AND；The input of inductive current detection module is respectively with the outfan of overcurrent protection comparator, the input in soft start loop and current output terminal；Soft starting circuit input end of clock connects the outfan of oscillator module, and the voltage input end of soft starting circuit meets VIN pin, voltage output end VSTConnect overcurrent protection comparator positive input terminal；A reference source and the reference voltage output end V of biasing moduleB1Connecing the positive input terminal of overvoltage protection comparator, OVP pin passes through resistance RP1With RP2Ground connection after series connection, resistance RP1With RP2Common port connect the negative input end of overvoltage protection comparator, the outfan of overvoltage protection comparator is that the voltage output end in soft start loop connects and the input of door AND.Overvoltage protection comparator limits the amplitude of output voltage, and overcurrent protection comparator limits the peak value of inductive current.
The Topology connection of secondary control module is as follows: VIN connects the input of undervoltage lockout circuit, and output signal U V of undervoltage lockout circuit connects the control signal UV input of sleep block；Pin EN connects the input of Schmidt trigger Smit, and the output of Smit terminates the input of reverse INV, and the ENB input of the output termination sleep block of INV, the input end of clock of sleep block connects the outfan of oscillator module；Sleep block SDB output signal turns off other modules (for drawing the connection of SD, SDB and other modules in accompanying drawing) for a reference source and the shutoff of biasing module, SD output signal.
Accompanying drawing 3 show designed LED drive chip internal dimming circuit and sleep block schematic diagram.Light modulation latch uses switching regulator PWM count word dimming arrangement, and its internal connection is as follows.Light modulation latch R input connects the R input of d type flip flop 1 by phase inverter INV1, light modulation latch S input connects the S input of d type flip flop 1 and the input of phase inverter INV2 simultaneously, the input of output termination NAND gate NAND1 of INV2, the input of light modulation latch Dim input termination NAND gate NAND2；The Q output of d type flip flop 1 connects the input of NAND1, and the input of the output termination NAND2 of NAND1, the outfan of NAND2 is the outfan Q of light modulation latch.This dimming mode, change be the output meansigma methods (dutycycle) of electric current rather than amplitude will not cause LED luminescence dispersion, nor affect on the efficiency of LED simultaneously.The inside of sleep block connects as follows: ENB input connects the S input of d type flip flop 2 and Enable Pin EN of enumerator simultaneously, and the input end of clock of enumerator connects the outfan of oscillator module, the R input of the output termination d type flip flop 2 of enumerator；The outfan of d type flip flop 2 connects the input of reverser INV3 and NAND gate NAND3 simultaneously, and the UV input of another input termination sleep block of NAND3, INV3 exports SDB signal, and NAND3 exports SD signal.LED drive chip is fully closed when EN ground connection and when being continued above 4ms.When under-voltage locking signal is effective, and SD signal turns off all modules in addition to a reference source with biasing module, chip locked output electric current is 0.
Accompanying drawing 4 show the schematic diagram of the internal soft starting circuit of designed LED drive chip.The drain electrode of N-type metal-oxide-semiconductor NMt connects VIN pin, and the source electrode of NMt connects the negative input end of OPA；The positive input termination a reference source of OPA and the V of biasing moduleB1Outfan, resistance Rd0, Rd1, Rd2, Rd3, Rd4 connect with this, the end ground connection of Rd4, the end of Rd0 connects the negative input end of OPA；Rd0With Rd1Common port be the outfan V of soft starting circuitST；Switch metal-oxide-semiconductor NMd1Drain electrode connecting resistance Rd0With Rd1Common port, switch metal-oxide-semiconductor NMd2Drain electrode connecting resistance Rd1With Rd2Common port, switch metal-oxide-semiconductor NMd3Drain electrode connecting resistance Rd2With Rd3Common port, switch metal-oxide-semiconductor NMd4Drain electrode connecting resistance Rd3With Rd4Common port；NMd1Drain electrode meets the outfan Q of time delay module 11, NMd2Drain electrode meets the outfan Q of time delay module 22, NMd1Drain electrode meets the outfan Q of time delay module 33, NMd4Drain electrode meets the outfan Q of time delay module 44；NMd1、NMd2、NMd3、NMd4Source class unify ground connection.Enable Pin EN of time delay module 1 connects the SD outfan of sleep block, the outfan Q enabling termination time delay module 1 of time delay module 21, the outfan Q enabling termination time delay mould 2 of time delay module 32, the outfan Q enabling termination time delay module 3 of time delay module 43；The input end of clock Clk of time delay module 1,2,3,4 connects the outfan of oscillator module.When circuit start, Qm0 can be changed to successively, switching tube NM by 1dmCan be successively by being conducting to disconnection, VSTProduce an ascending manner stepped-up voltage having 5 steps.Owing to the peak value of inductive current is by overcurrent protection comparator and VSTLimiting, the electric current on such inductance is also stepped, will not produce surge current, simultaneously output capacitance COThe speed of charging is limited, and the most also will not produce overshoot voltage in output.
Accompanying drawing 5 show shown LED drive chip undervoltage lockout circuit schematic diagram: the outfan V of a reference source and biasing moduleBPConnect PMOS PMU1With PMU7Grid, PMU1Source electrode connect VIN pin, the drain electrode of PMU1 connects NMOS tube NMU1Drain electrode；NMU1Source ground, grid meets the outfan VB of a reference source and biasing moduleU2, NMU1Drain electrode connect PMOS PMU3Grid, PMU3Source electrode connect PMOS PMU2Drain electrode, PMU2Source electrode meet VIN pin, PMU2Grid meet the outfan VB of a reference source and biasing moduleU2；PMU3Drain electrode connect PMOS PMU4Source electrode, PMU4Grid connect the outfan of phase inverter INV4, the drain electrode of PMu4 connects NMOS tube NMU2Drain electrode；NMU2Source ground, grid meets the outfan V of a reference source and biasing moduleBN.PMOS PMU5Source electrode connect VIN pin, grid meets the outfan VB of a reference source and biasing moduleU1, drain electrode connects PMOS PMU6Source electrode；PMU6Grid meet NMU1Drain electrode, drain electrode meet NMU2Drain electrode.PMU7Source electrode connect VIN pin, drain electrode connects NMOS tube NMU3Drain electrode；NMU3Source ground, grid meets NMU2Drain electrode.PMOS PMU8Source electrode connect VIN pin, grid and NMOS tube NMU4Grid be connected be followed by NMU3Drain electrode, drain electrode and NMU4Drain electrode be connected, NMU4Source electrode connect NMOS tube NMU5Drain electrode；NMU5Source ground, grid meets NMU2Grid.The input termination NM of phase inverter INV4U4Drain electrode, output termination Schmidt trigger Smit2 input, Smit2 exports under-voltage locking signal UV.When input voltage VDD is less than VBU1+VTH5Time, chip locked output electric current is 0, when input voltage goes back up to VBU2+VTH2Time, under-voltage locking state is released from driving chip and normally works, LED normal luminous.VTH2With VTH5It is PM respectivelyU2With PMU5Threshold voltage.
Specific embodiment described herein is only to present invention spirit explanation for example.Described specific embodiment can be made various amendment or supplements or use similar mode to substitute by those skilled in the art, but without departing from the spirit of the present invention or surmount scope defined in appended claims.

Claims (4)

1. a Dimmable LED driving chip for band soft start and undervoltage lockout circuit, it is special Levy and be, including: control loop, soft start loop, compensate loop and secondary control module； The input termination compensating loop controls loop output, controls loop output and connects compensation loop Compensate input；The voltage in soft start loop, current output terminal connect the soft start electricity controlling loop Pressure, current input terminal, soft start loop shares inductive current detection module with compensating loop；Auxiliary The output that enables helping control module terminates the Enable Pin of other modules, and each module Enable Pin is adopted By classical switching regulator connected mode；The light modulation output termination of secondary control module controls the tune in loop Light input end；
This Dimmable LED driving chip comprises following six roots of sensation pin: power pins VIN, mistake Pressure protection input pin OVP, inductive current input pin LX, Voltage Feedback pin FB, Dim signal input pin EN, pin GND；Wherein: VIN, GND are all cores The common pin of sheet internal module；LX pin is simultaneously as the input of inductive current detection module Pin, and control the output pin in loop；OVP pin is the voltage input in soft start loop Pin, EN pin is the control signal input of secondary control module；FB pin is for control back The feedback signal input pin on road；
Described control loop includes that a reference source compares with biasing module, error amplifier, PWM Device, three input AND, tunable optical latch module, N-type driver, power switch NM2； Topology connection is as follows: a reference source connects VIN pin, benchmark with the voltage input end of biasing module Voltage output end VB0Connect the negative input end of error amplifier EA；Feedback pin FB connects error The positive input terminal of amplifier EA, the positive input terminal of EA is the feedback input end controlling loop, The negative input end of the output termination PWM comparator of error amplifier EA, PWM comparator Positive input terminal be control loop compensation input, PWM comparator output termination three Input and the input of door AND；Other two inputs of AND are respectively and control the soft of loop Start voltage, current input terminal, the R input of the output termination light modulation latch module of AND, The outfan of the S input termination oscillator module of light modulation latch module, light modulation latch module The ENB input of Dim input termination sleep block, the light modulation that Dim end i.e. controls loop is defeated Enter end；The outfan Q of light modulation latch module connects N-type and drives the input of module；N-type is driven The grid of the output termination power switch NM2 of dynamic model block, the drain electrode of NM2 connects LX pin, The source ground of NM2, the drain electrode of NM2 is the outfan controlling loop；
Described compensation loop includes that ramp voltage module, slope compensation module, inductive current detect Module；Topology connection is as follows: the outfan V of current detection moduleSENSEConnect slope compensation module Current input terminal；The outfan of the input termination oscillator module of ramp voltage module, slope The voltage input end of the output termination slope compensation module of voltage module；Slope compensation module defeated Going out to terminate the positive input terminal of PWM comparator, the outfan of slope compensation module i.e. compensates loop Outfan, the input of inductive current detection module i.e. compensates loop input；Described inductance Current detection module includes metal-oxide-semiconductor NM1, resistance R1And R2, the grid of metal-oxide-semiconductor NM1 Pole connects N-type and drives the outfan of module, and the drain electrode of NM1 connects LX pin, the drain electrode of NM1 Being the input of inductive current detection module, the source electrode of NM1 meets R1One end；R1Another R is passed through in one end2Ground connection, R1With R2Common port be the outfan of inductive current detection module VSENSE；
Described soft start loop includes overvoltage protection comparator, soft starting circuit, overcurrent protection ratio Relatively device, inductive current detection module；Topology connection is as follows: the output of inductive current detection module End VSENSEConnect the negative input end of overcurrent protection comparator, the output termination of overcurrent protection comparator Three inputs and the input of door AND；The input of inductive current detection module and overcurrent protection The outfan of comparator is respectively, the input in soft start loop and current output terminal；Soft start The input end of clock of circuit connects the outfan of oscillator module, and voltage input end connects VIN pin, Voltage output end VSTConnect overcurrent protection and compare positive input terminal；A reference source and the benchmark of biasing module Voltage output end VB1Connecing the positive input terminal of overvoltage protection comparator, OVP pin passes through resistance RP1With resistance RP2Ground connection after series connection, resistance RP1With resistance RP2Common port connect overvoltage protection The negative input end of comparator, the outfan of overvoltage protection comparator is that the voltage in soft start loop is defeated Go out the input of termination and door AND；
Described secondary control module includes under-voltage locking module, dormancy control module；Topology connection As follows: VIN connects the input of undervoltage lockout circuit, output signal U V of undervoltage lockout circuit Connect the control signal UV input of sleep block；Pin EN meets Schmidt trigger Smit Input, Smit output terminate reverse INV input, the outfan of INV is The ENB input of the light modulation output termination sleep block of secondary control module, sleep block Input end of clock connects the outfan of oscillator module；Sleep block SDB output termination a reference source Enable Pin, the Enable Pin of SD output remaining module of termination with biasing module.
A kind of band soft start the most according to claim 1 and undervoltage lockout circuit adjustable Light LED drive chip, it is characterised in that dim latch module in described control loop and use Switching regulator PWM count tone of Chinese characters optical mode, light modulation latch R input is by phase inverter INV1 Connecing the R input of d type flip flop 1, light modulation latch S input connects d type flip flop 1 simultaneously S input, and the input of phase inverter INV2, the output termination NAND gate of INV2 The input of NAND1, the Dim input of light modulation latch terminates the defeated of NAND gate NAND2 Enter end；The Q output of d type flip flop 1 connects the input of NAND1, the output of NAND1 The input of termination NAND2, the outfan of NAND2 is the outfan of light modulation latch Q。
A kind of band soft start the most according to claim 1 and undervoltage lockout circuit adjustable Light LED drive chip, it is characterised in that the inner topology of described soft starting circuit connects such as Under: the drain electrode of N-type metal-oxide-semiconductor NMt connects VIN pin, and the grid of NMt connects operation amplifier Device OPA outfan, the source electrode of NMt connects the negative input end of OPA；The positive input termination of OPA A reference source and the V of biasing moduleB1Outfan, resistance Rd0, Rd1, Rd2, Rd3, Rd4 It is sequentially connected in series, the end ground connection of Rd4, the negative input end of the upper termination OPA of Rd0；Rd0With Rd1Common port be the outfan V of soft starting circuitST；Switch metal-oxide-semiconductor NMd1Leakage Pole connecting resistance Rd0With Rd1Common port, switch metal-oxide-semiconductor NMd2Drain electrode connecting resistance Rd1 With Rd2Common port, switch metal-oxide-semiconductor NMd3Drain electrode connecting resistance Rd2With Rd3Public End, switchs metal-oxide-semiconductor NMd4Drain electrode connecting resistance Rd3With Rd4Common port；NMd1Leakage Pole meets the outfan Q of time delay module 11, NMd2Drain electrode meets the outfan Q of time delay module 22, NMd1Drain electrode meets the outfan Q of time delay module 33, NMd4Drain electrode connects the output of time delay module 4 End Q4；NMd1、NMd2、NMd3、NMd4Source class unify ground connection；Time delay module 1 Enable Pin EN connects the SD outfan of sleep block, the enable termination time delay mould of time delay module 2 The outfan Q of block 11, the outfan Q enabling termination time delay mould 2 of time delay module 32, prolong Time module 4 enable termination time delay module 3 outfan Q3；Time delay module 1,2,3,4 Input end of clock Clk connect the outfan of oscillator module.
A kind of band soft start the most according to claim 2 and undervoltage lockout circuit adjustable Light LED drive chip, it is characterised in that the under-voltage locking mould in described secondary control module Block inner topology connects as follows: a reference source and the outfan V of biasing moduleBPConnect PMOS PMU1With PMU7Grid, PMU1Source electrode meet VIN pin, PMU1Drain electrode meet NMOS Pipe NMU1Drain electrode；NMU1Source ground, grid connects the defeated of a reference source and biasing module Go out to hold VBU2, NMU1Drain electrode connect PMOS PMU3Grid, PMU3Source electrode connect PMOS PMU2Drain electrode, PMU2Source electrode meet VIN pin, PMU2Grid connect benchmark Source and the outfan VB of biasing moduleU2；PMU3Drain electrode connect PMOS PMU4Source electrode, PMU4Grid connect the outfan of phase inverter INV4, the drain electrode of PMu4 connects NMOS tube NMU2 Drain electrode；NMU2Source ground, grid meets the outfan V of a reference source and biasing moduleBN； PMOS PMU5Source electrode connect VIN pin, grid connects the output of a reference source and biasing module End VBU1, drain electrode connects PMOS PMU6Source electrode；PMU6Grid meet NMU1Leakage Pole, drain electrode meets NMU2Drain electrode；PMU7Source electrode connect VIN pin, drain electrode meets NMOS Pipe NMU3Drain electrode；NMU3Source ground, grid meets NMU2Drain electrode；PMOS Pipe PMU8Source electrode connect VIN pin, grid and NMOS tube NMU4Grid be connected be followed by NMU3Drain electrode, drain electrode and NMU4Drain electrode be connected, NMU4Source electrode connect NMOS tube NMU5Drain electrode；NMU5Source ground, grid meets NMU2Grid；Phase inverter INV4 Input termination NMU4Drain electrode, output termination Schmidt trigger Smit2 input, Smit2 exports under-voltage locking signal UV.
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