CN110536518A

CN110536518A - Adjusting control circuit controls chip, power supply change-over device and removes stroboscopic method

Info

Publication number: CN110536518A
Application number: CN201910925081.9A
Authority: CN
Inventors: 闾建晶
Original assignee: Shanghai Semiconducto Ltd By Share Ltd
Current assignee: Shanghai Semiconducto Ltd By Share Ltd
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2019-12-03

Abstract

The present invention relates to adjusting control circuit, Switching Power Supply control chip, drive LED power supply change-over device and remove stroboscopic method.The adjusting control circuit is used to control the output of the Switching Power Supply of low PF, the Switching Power Supply includes power switch and received input voltage includes power frequency ingredient, the adjusting control circuit includes low-pass filtering module and output current-modulation module, wherein, low-pass filtering module access PWM dim signal and sampled signal simultaneously generate filtering modulation voltage and export, it exports current-modulation module and low-pass filtering module is electrically connected, it utilizes the filtering modulation voltage modulating switch power source of low-pass filtering module output at least in dcm mode, when input voltage changes because of the ripple of power frequency ingredient, in several switch periods under current PWM dim signal, the average current value of the corresponding Switching Power Supply output of each switch periods is constant.The ripple that power input voltage can be inhibited to introduce using the adjusting control circuit helps to eliminate stroboscopic.

Description

Adjusting control circuit controls chip, power supply change-over device and removes stroboscopic method

Technical field

The present invention relates to electronic circuit field more particularly to adjusting control circuit, control chip, power supply change-over device and Remove stroboscopic method.

Background technique

LED with small in size, brightness is high, power consumption is low, fever less, long service life and have colourful color kind The advantages that class, is widely applied in many fields such as illumination, displays.In LED driving at present, frequently with low power factor The Switching Power Supply of (being, for example, less than 0.7 power factor) drives LED operation, wherein is periodically carried out by power switch ON/OFF can obtain in load and stablize output.In order to adjust the brightness of load LED, come additionally by adjusting control circuit Control the ON/OFF of power switch.

In numerous LED light regulating technologies, PWM is dimmed to be obtained due to high efficiency, the remote transmission of support, compatibility by force Obtained extensive research and application.However, the prior art is when using PWM dim signal control power switch, however it remains with Lower two aspect more distinct issues:

One, dead-time problem is dimmed, this problem is especially apparent in copped wave output electric current direct using PWM dim signal, It has been observed that if the failing edge of PWM dim signal just within the turn-off time of power switch when, the variation pair of PWM duty cycle The switch of power switch is without influence, i.e., position PWM dim signal is caused in output electric current on output electric current without influence with light modulation There are step-like portion (referred to as light modulation dead zone) on the mechanical periodicity curve of signal, user experience is influenced；

Two, stroboscopic problem, the study found that when being dimmed using the direct copped wave output electric current of PWM dim signal, load There are the ripples that frequency is PWM dim signal frequency for electric current on LED, although also having by filtering PWM dim signal through RC Afterwards again input control chip come avoid light modulation dead zone scheme, but due to the voltage of input load usually by alternating voltage it is direct Rectifying and wave-filtering and obtain, output electric current is commonly present working frequency ripple wave, therefore there are still dodge frequency problem.

Therefore, there is still a need for being further improved the brightness adjustment control mode to LED, asked with solving light modulation dead-time problem and dodging frequency Topic.Although this sentence LED light modulation be example, described problem can also spread to it is other needs more delicately adjust load variation, It eliminates in the application for dodging frequency phenomenon.

Summary of the invention

In view of above-mentioned the problems of the prior art, the present invention provides adjusting control circuit, Switching Power Supply control chip, Drive the power supply change-over device of LED and remove stroboscopic method, help to eliminate the existing light modulation dead zone of existing LED dimming arrangement and Stroboscopic phenomenon.

On one side, the present invention provides a kind of adjusting control circuit, the output of the Switching Power Supply for controlling low PF, described Switching Power Supply includes power switch, and the Switching Power Supply receives the input voltage comprising power frequency ingredient, the adjusting control circuit Include:

Low-pass filtering module, input terminal are matched for accessing PWM dim signal and the sampled signal from the Switching Power Supply It is set to and filtering modulation voltage is generated based on the PWM dim signal and the sampled signal and is exported；

Current-modulation module is exported, is electrically connected with the low-pass filtering module, is configured to modulate electricity using the filtering Pressure modulates the Switching Power Supply at least in dcm mode, when the input voltage changes because of the ripple of power frequency ingredient, currently In several switch periods under PWM dim signal, the average current value of the corresponding Switching Power Supply output of each switch periods It is constant.

Optionally, the output current-modulation module is controlled described by the variation of the dead time of modulation DCM mode The effective duty cycle in each period in several switch periods is constant.

Optionally, the output current-modulation module includes effective duty ratio modulation unit, the effective duty cycle modulation Unit includes charging and discharging currents modulation subunit, charge and discharge electronic unit and charge and discharge logic control subelement；The charge and discharge electricity Stream modulation subunit and charge and discharge logic control subelement are configured to control the charge and discharge electronic unit.

Optionally, the charging and discharging currents modulation subunit is configured to adjust the charge and discharge using the filtering modulation voltage The charging and discharging currents value of electronic unit.

Optionally, the charge and discharge logic control subelement is configured to receive patrolling for the turn-on and turn-off of the power switch Control signal is collected, the charge and discharge moment of the charge and discharge electronic unit is controlled.

Optionally, the output current-modulation module includes inductance peak value modulation unit, the inductance peak value modulation unit It is configured to modulate inductance peak value corresponding from different PWM dim signals using the filtering modulation voltage.

Optionally, the filtering modulation voltage follows the variation of the PWM dim signal and changes.

Optionally, the inductance peak value modulation unit includes constant-current source circuit, bleeder circuit and clamp circuit；The perseverance The output size of current of current source circuit follows the filtering modulation voltage to change；The bleeder circuit and the constant-current source circuit Output coupling；The clamp circuit couples with the output of the bleeder circuit and exports the corresponding inductance peak value.

Optionally, the low-pass filtering module includes:

PWM dim signal pretreatment unit is configured to access the PWM dim signal, utilizes the PWM dim signal pair Reference voltage carries out copped wave, generates dimmer voltage signal；And

Low-pass filter is configured to access the dimmer voltage signal and the sampled signal, exports the filtering modulation Voltage.

Optionally, the low-pass filter is wave digital lowpass filter.

Optionally, the Switching Power Supply is using isolation reverse exciting topological, non-isolated buck topology, non-isolated buck topology And one of non-isolated Boost topology topological circuit structure.

On one side, the present invention provides a kind of control chip of Switching Power Supply, for control low PF Switching Power Supply it is defeated Out, the Switching Power Supply includes power switch, and above-mentioned adjusting control circuit is equipped in the control chip.

On one side, the present invention provides a kind of power supply change-over device for driving LED, and the power supply change-over device includes rectification Circuit, low PF switching power circuit, above-mentioned adjusting control circuit and LED light string, wherein the rectification circuit is configured to access It is executed after alternating current and rectifies and export；The output of the switching power circuit and the rectification circuit couples, and being configured to will be described Electric power needed for the output of rectification circuit is converted into LED light string；The adjusting control circuit be configured to receive PWM dim signal and The brightness for controlling the LED light string changes with the variation of the PWM dim signal.

On one side, the present invention provides one kind and removes stroboscopic method, described applied to the brightness regulation of current mode light-emitting component Current mode light-emitting component is the load of a low PF Switching Power Supply for including power switch, described to go the stroboscopic method to include:

PWM dim signal and the sampled signal from the Switching Power Supply are accessed, based on the PWM dim signal and described Sampled signal generates filtering modulation voltage and exports；And the Switching Power Supply is modulated at least using the filtering modulation voltage In dcm mode, when the input voltage changes because of the ripple of power frequency ingredient, several under current PWM dim signal are opened It closes in the period, the average current value of the corresponding Switching Power Supply output of each switch periods is constant.

Adjusting control circuit provided by the invention includes low-pass filtering module and output current-modulation module, wherein low pass The input terminal of filter module is based on the PWM for accessing PWM dim signal and the sampled signal from the Switching Power Supply Dim signal and the sampled signal generate filtering modulation voltage and export, output current-modulation module and the low-pass filtering mould Block is electrically connected, and the output current-modulation module is configured to the filtering modulation voltage exported using low-pass filtering module modulation and opened Powered-down source, and make Switching Power Supply at least in dcm mode, when the input voltage changes because of the ripple of power frequency ingredient, In several switch periods under current PWM dim signal, the average electricity of the corresponding Switching Power Supply output of each switch periods Flow valuve is constant, so as to the ripple for inhibiting power input voltage to introduce, helps to eliminate stroboscopic.

The control chip of Switching Power Supply provided by the invention and the power supply change-over device of driving LED include above-mentioned light modulation control Circuit processed, thus have the advantages that with above-mentioned adjusting control circuit same or like.It is provided by the invention to remove stroboscopic method, and it is upper Stating adjusting control circuit has identical or corresponding feature, thus with above-mentioned adjusting control circuit with same or similar excellent Point.

Detailed description of the invention

Figure 1A to Fig. 1 D be respectively use non-isolated buck topology, non-isolated Boost topology, non-isolated buck it is topological, with And the circuit diagram of the Switching Power Supply of isolation reverse exciting topological.

Fig. 2A is a kind of circuit diagram of step-down constant current Switching Power Supply.

Fig. 2 B is inductive current in circuit shown in Fig. 2A with the waveform diagram of power switch state change.

Fig. 3 A is a kind of schematic diagram of adjusting control circuit.

Fig. 3 B is to utilize PWM dim signal, power switch and inductive current when adjusting control circuit as shown in Figure 3A Waveform diagram.

Fig. 4 A is the schematic diagram of another adjusting control circuit.

Fig. 4 B is to utilize PWM dim signal, supply voltage and inductive current when adjusting control circuit as shown in Figure 4 A Waveform diagram.

Fig. 5 is the schematic diagram of the adjusting control circuit of one embodiment of the invention.

Fig. 6 is the circuit diagram of the low-pass filter in one embodiment of the invention.

Fig. 7 A is the circuit diagram of effective duty cycle modulation unit in one embodiment of the invention.

The waveform of conductivity control signal is illustrated when Fig. 7 B is the effective duty cycle modulation unit using one embodiment of the invention Figure.

Fig. 8 A is the circuit diagram of inductance peak value modulation unit in one embodiment of the invention.

Fig. 8 B is the waveform diagram that inductance peak value changes with filtering modulation voltage in one embodiment of the invention.

Fig. 9 is the waveform diagram using input voltage when adjusting control circuit shown in fig. 5 and output electric current.

Description of symbols:

100- low-pass filtering module；110-PWM dim signal pretreatment unit；120- sample rate current processing unit；130- Low-pass filter；200- exports current-modulation module；210- effective duty cycle modulation unit；211- charging and discharging currents modulation is single Member；212- charge and discharge electronic unit；213- charge and discharge logic control subelement；220- inductance peak value modulation unit；221- constant-current source Circuit；222- bleeder circuit；223- clamp circuit；410- inductance peak comparator；420-RS trigger；430- drive module.

Specific embodiment

Below in conjunction with the drawings and specific embodiments to adjusting control circuit of the invention, control chip, power supply change-over device And stroboscopic method is gone to be described in further detail.According to following explanation, advantages and features of the invention will be become apparent from.It needs Bright, attached drawing is all made of very simplified form and using non-accurate ratio, only conveniently, lucidly to aid in illustrating The purpose of the embodiment of the present invention.

It should be noted that hereinafter terms " first " " second " etc. are used between similar element distinguish, and not It must be for describing certain order or time sequencing.It is appreciated that in the appropriate case, these terms so used are replaceable, Such as may make invention as described herein embodiment can be different from it is as described herein or shown in other sequentially operate.Class As, if method described herein includes series of steps, and the sequence of these steps presented herein is not necessarily The unique order of these steps can be performed, and some steps can be omitted and/or some other steps not described herein Suddenly this method can be added to.

It is right below first for loading as LED light string in order to understand design and technical effect of the invention more perfectly The Switching Power Supply of low power factor (i.e. low PF) including power switch and for control its output adjusting control circuit carry out It introduces.It is appreciated that Switching Power Supply described below and corresponding adjusting control circuit also can be applied to other types of bear It carries.

Figure 1A, Figure 1B, Fig. 1 C and Fig. 1 D are respectively using non-isolated decompression (Buck) topology, non-isolated boosting (Boost) The circuit of the Switching Power Supply of topological, non-isolated buck (Buck-boost) topology and isolation inverse-excitation type (Flyback) topology Schematic diagram.Referring to Figure 1A to Fig. 1 D, the Switching Power Supply of these four topological circuit structures includes power switch M1, and the power is opened M1 is closed to be configured to receive externally input turn-on and turn-off signal to generate periodic modulated signal in circuit.For controlling The turn-on and turn-off signal of power switch M1 processed and the external signal dimmed are usually PWM (pulse width modulation) light modulation letter Number.Switching Power Supply also comprises the inductance L1 (or such as transformer T1 in Fig. 1 D) being arranged with load in series, is opened using power The switch change of M1 and the auto-excitation type driving of inductance L1 (or transformer T1) are closed, relatively stable output electric current can be obtained.

Fig. 2A is a kind of circuit diagram of step-down constant current Switching Power Supply.Fig. 2 B is inductance electricity in circuit shown in Fig. 2A Flow the waveform diagram with power switch state change.A and Fig. 2 B referring to fig. 2, in the switching power circuit, electrifying startup Afterwards, when the grid G ATE of power switch M1 (for example, NMOS) is high level, power switch M1 conducting, forming direction is " electricity Source input (input voltage vin) -> LED load -> inductance L1- > power switch M1- > resistance R1- > " access, inductive current IL1 is begun to ramp up, and when inductive current IL1 rises to peak point current Ipk, the grid G ATE of power switch M1 is switched to low electricity Flat, then power switch M1 is turned off, and drain terminal voltage then rises until being slightly above power input voltage Vin, two pole of afterflow at this time Pipe D1 conducting, forming direction is " power input node -> LED load -> inductance L1- > sustained diode 1- > power input section The circuit of point ", then inductive current IL1 is begun to decline, and when being down to 0, control power switch M1 is connected again, then is carried out next The energy transmission of a switch periods.

Known to the waveform of inductive current IL1 in each switch periods of Switching Power Supply, the output of above-mentioned Switching Power Supply Current average is Ipk/2, and the output electric current Iout due to flowing through LED load when stable state is equal to inductive current IL1, can It obtains formula (1),

Iout=Ipk/2 (1)

In order to can the output electric current to above-mentioned Switching Power Supply control, a kind of control mode is to utilize PWM light modulation letter Number directly output electric current of Chopper driving circuit.Fig. 3 A is a kind of schematic diagram of adjusting control circuit.Referring to Fig. 3 A, in the light modulation In control circuit, PWM dim signal is accessed from DIM pin, and the sampled signal of Switching Power Supply is accessed from CS pin, brightness adjustment control electricity The switch control signal that road generates is exported from GATE pin.The GATE pin is also used to carry out demagnetization detection.

Fig. 3 B is to utilize PWM dim signal, power switch and inductive current when adjusting control circuit as shown in Figure 3A Waveform diagram.Referring to Fig. 3 B, adjusting control circuit shown in Fig. 3 A, when PWM dim signal is high level, power switch are utilized M1 can keep normal switch to act, and when PWM dim signal is low level, the switch motion of power switch M1 stops.But when When the failing edge of PWM dim signal falls in the shutdown section of power switch M1 just, the variation nothing of the duty ratio of PWM dim signal Method directly affects the switch motion of power switch M1, i.e., PWM dim signal is on output electric current without influence, the time zone without influence Between for " light modulation dead zone ".The duty ratio for dimming dead zone can use turn-off time (Toff) and the PWM dim signal of power switch M1 Frequency (Fpwm) product representation.By taking the switching frequency of power switch M1 is 60kHz, duty ratio is 50% as an example, Toff is about It is generally 500Hz~2kHz for 8.3us, Fpwm, then the duty ratio for dimming dead zone is 0.4%~1.7%.Dim the presence in dead zone Current curve is exported when not only resulting in light modulation and step part occurs, and the Fpwm the high, it is wider to dim dead zone, and utilize PWM tune The dimming mode of the direct copped wave of optical signal will lead to inductive current IL1 and the output of Switching Power Supply exists and PWM dim signal frequency The consistent ripple of rate, causes noise and stroboscopic more serious, therefore user experience is very poor.

In order to eliminate light modulation dead zone, ripple caused by the direct copped wave output electric current of PWM dim signal, another kind light modulation are avoided Mode is to be input to adjusting control circuit again after first carrying out RC filtering processing to PWM dim signal.Fig. 4 A is another light modulation control The schematic diagram of circuit processed.A referring to fig. 4 draws by the filtered PWM dim signal of RC from DIM in this adjusting control circuit Foot access, when dimming controlling module is handled to obtain the most short shutdown of inductance peak value Vpk and power switch M1 to input signal Between MOT (Minimum OffTime).Inductance peak value Vpk is related to inductive current peak Ipk, and (Ipk=Vpk/Rcs, Rcs are to adopt Sample resistance, i.e. R1 in Fig. 2A), current period power can be obtained respectively and is opened with most short turn-off time MOT according to inductance peak value Vpk Close the turn-on time finish time and finish time turn-off time of M1.

Fig. 4 B is to utilize PWM dim signal, supply voltage and inductive current when adjusting control circuit as shown in Figure 4 A Waveform diagram.At this point, the different variations according to inductive current in each switch periods, the output of Switching Power Supply include three kinds Mode: continuous conduction mode (Continuous Conduction Mode, CCM), critical conduction mode (BCM, Boundary Conduction Mode) and discontinuous conduction mode (Discontinuous Conduction Mode, abbreviation DCM).Three kinds The foundation of the switching of mode is the turn-off time Toff and the relationship of inductance (or transformer) demagnetization time of power switch M1.Specifically , when most short turn-off time MOT of power switch M1 being less than or equal to the demagnetization time Tdis of inductance (or transformer), switch electricity The output in source is critical conduction mode (i.e. BCM mode), at this time Toff=Tdis；When the most short turn-off time of power switch M1 When MOT is greater than the demagnetization time Tdis of inductance (or transformer), the output of Switching Power Supply is discontinuous conduction mode (i.e. DCM mould Formula), Toff=MOT at this time.It include that inductive current is zero or approaches in each power switch period in dcm mode The period that the inductive current is zero or near zero is hereafter denoted as the dead time of DCM mode by zero period.

B referring to fig. 4, using adjusting control circuit shown in Fig. 4 A, PWM dim signal is filtered by RC, can be to avoid figure Light modulation dead zone in adjusting control circuit shown in 3A and caused by being superimposed with the frequency of PWM dim signal because of output electric current Stroboscopic problem, still, adjusting control circuit shown in Fig. 4 A, which needs that RC element is additionally arranged in control chip exterior, to be filtered, Circuit complexity is increased, and since low-frequency ripple rejection ability is poor, thus still has stroboscopic problem.It says in detail below It is bright.

As shown in Figure 4 A and 4 B shown in FIG., in dcm mode, the average output current Iout of Switching Power Supply meets formula (2):

Iout=Ipk/2*Deff (2)

Wherein, Deff is the effective duty cycle that Switching Power Supply exports in a switch periods of power switch.Still with Fig. 2 Shown in for voltage reducing type voltage stabilizing circuit, effective duty cycle Deff can be defined as the excitation time Ton of inductance L1, and (i.e. power is opened The turn-on time of pass) and demagnetization the sum of time Tdis account for the ratio of entire switch periods, that is, meet formula (3),

Deff=(Ton+Tdis)/(Ton+MOT)=1/ (1+ (MOT-Tdis)/(Ton+Tdis)) (3)

For the non-isolated Boost topology as shown in Figure 1B to Fig. 1 D, non-isolated buck topology and isolation inverse-excitation type Topology, according to similar reasoning process, available formula (4),

Deff=Tdis/ (Ton+Tdis+T3) (4)

In formula (4), Ton, Tdis and T3 are respectively corresponding Switching Power Supply in each switch periods of power switch M1 The excitation time of inductance (or transformer), demagnetization time and dead time, difference are that the corresponding Switching Power Supply of formula (3) exists There is output in the section Ton, and it is 0 that the corresponding Switching Power Supply of formula (4) exports in the section Ton and the section T3.Due in CCM mould Effective duty cycle Deff is 100% under formula and BCM mode, and the stroboscopic of adjusting control circuit as shown in Figure 4 in dcm mode Problem is more prominent, therefore the output of following main description DCM mode lower switch power supply.

Formula (4) can be obtained according to the characteristic of inductance,

Ton=Ipk*L/ (Vin-Vout) (5)

Wherein, Ipk is the peak value (i.e. peak point current) of the inductive current IL1 in a switch periods of power switch M1, L For the inductance of inductance L1, Vin is the input voltage of Switching Power Supply, and Vout is output voltage.According to formula (5) it is found that Vin is got over Greatly, Ton is then smaller, thus causes such as phenomenon following in Fig. 4 B: the excitation time of the corresponding inductance L1 of the input voltage vin of increase Ton2 is less than the corresponding excitation time Ton1 (i.e. Ton2 < Ton1) of lesser input voltage vin.

Since Ipk, Tdis, MOT are theoretically also steady state value in the case where the duty ratio of PWM dim signal is fixed, because And if Vin increase, according to formula (2) and formula (3), effective duty cycle Deff and average output current Iout reduce.This explanation, benefit When being dimmed with adjusting control circuit as shown in Figure 4 A, the average output current Iout of Switching Power Supply can be by input voltage Vin influences.In practical applications, the input voltage vin of Switching Power Supply is usually obtained by the direct rectifying and wave-filtering of alternating voltage, thus It include necessarily twice of power frequency ingredient (100Hz or 120Hz), according to above-mentioned analysis, the average output current of Switching Power Supply at this time There is also working frequency ripple waves by Iout.When the load LED lighted is taken pictures or imaged, apparent water wave wave can be showed, i.e., " power frequency flashing " phenomenon.

As the above analysis, it not can solve stroboscopic using two kinds of adjusting control circuits as shown in Figure 3A and 4A Problem.In addition, both adjusting control circuits belong to opened loop control, wherein inductance peak comparator be used to believe sampling Number and inductance peak value Vpk be compared to obtain current period power switch M1 turn-on time finish time, however, passing through When integrated circuit fabrication process manufactures above-mentioned adjusting control circuit (or control chip), comparator can have certain imbalance electricity Pressure, and inductance peak value Vpk is smaller, and the influence of the offset voltage is more obvious, this will affect the output of Switching Power Supply, and there are larger Deviation.By taking inductance peak value Vpk is up to 400mV and offset voltage is 10mV as an example, when dimming depth is 10%, Vpk= 40mV, since the output electric current of Switching Power Supply is directly proportional to inductance peak value Vpk, thus dim depth be 10% when, offset voltage The deviation that will lead to output electric current reaches 25%, and the deviation for exporting electric current has an impact to the luminous flux and colour temperature of LED, 25% In Visually already belong to more apparent deviation, it is therefore necessary to limit light modulation depth and be higher than 10%.In order to reduce the shadow of offset voltage It rings, needing to control light modulation depth cannot be too low, so that light modulation depth is limited, which also limits the raisings of LED matrix performance.

In order to be improved and be solved the problems such as being limited above-mentioned light modulation dead zone, stroboscopic and light modulation depth, below A kind of adjusting control circuit is introduced by embodiment, which is used to control the defeated of the Switching Power Supply of low PF Out, the Switching Power Supply includes power switch, and the Switching Power Supply receives the input voltage comprising power frequency ingredient, the switch electricity Source may include topological circuit structure shown in any of Figure 1A to Fig. 1 D or Fig. 2.

Fig. 5 is the schematic diagram of the adjusting control circuit of one embodiment of the invention.Referring to Fig. 5, in the embodiment of the present invention, first It is related to a kind of adjusting control circuit.The adjusting control circuit includes low-pass filtering module 100.The low-pass filtering module 100 Input terminal for accessing PWM dim signal and the sampled signal from the Switching Power Supply, be configured to the PWM light modulation Signal and the sampled signal generate filtering modulation voltage and export.Since low-pass filtering module 100 has low-pass filtering effect, The frequency of the ripple frequency and PWM dim signal in sampled signal can be substantially eliminated, filtering modulation voltage generated is approximate DC voltage.

As shown in figure 5, the low-pass filtering module 100 of the present embodiment specifically may include PWM dim signal pretreatment unit 110, sample rate current processing unit 120 and low-pass filter 130.Specifically, the PWM dim signal pretreatment unit 110 It can be configured to access PWM dim signal, copped wave carried out to reference voltage Vref using current PWM dim signal, generates light modulation Voltage signal VP.The duty ratio Dpwm and reference voltage Vref of current PWM dim signal can be used in the size of dimmer voltage signal VP Between product calculate.Sample rate current processing unit 120 can be configured to according to the output current sample of Switching Power Supply and zero electricity Stream detection signal, generates sampled signal VN.As an example, the adjusting control circuit of the present embodiment is as shown in Figure 2 for driving Step-down constant current Switching Power Supply, specifically for the switch control signal of output driving power switch M1.Sample rate current processing unit 120 input terminal can be connect with the node between power switch M1 and resistance R1, what in addition sample rate current processing unit 120 accessed At the time of output electric current is zero in the current switch period of zero current detection signal ZCD offer Switching Power Supply.The sample rate current Processing unit 120 handles the sample rate current of switching circuit, and embodiment is calculated in conjunction with zero current detection signal ZCD and corresponds to The sampled signal VN of the average output current of switch periods, sampled signal VN cover the systematical difference of Switching Power Supply, sampling letter Number meet relationship between VN and the average output current of Switching Power Supply: VN=k*Iout, k are the system constants of Switching Power Supply.Institute Stating sample rate current processing unit 120 can be using circuit structure disclosed in this field.In order to carry out zero electricity to each switch periods Stream detection, adjusting control circuit shown in fig. 5 further include demagnetization detection module 300, and the demagnetization detection module 300 is configured to connect Enter the demagnetization signal from Switching Power Supply, generate zero current detection signal ZCD and exports to low-pass filtering module 100 and output electricity Flow modulation module 200.In order to realize the function of demagnetization detection, demagnetization detection module 300 can be using the disclosed demagnetization in this field Detection circuit.

The low-pass filter 130 is configured to access the dimmer voltage signal and the sampled signal, and exports a filter Wave modulation voltage VCOMP.Low-pass filter may include low-pass filter circuit disclosed in this field, wherein low-pass filtering function by In using lower cutoff frequency, the high-frequency signal in circuit, the filtering that low-pass filter 130 exports can be obstructed or weakened Modulation voltage VCOMP is approximately direct current.

In order to improve filter capacity, the usually used analogue low pass filtering in the products such as driving circuit, power supply adaptor The bandwidth of device is lower, and the capacitance of used filter capacitor is larger, and can not be together with integrated circuit or integrated chip, outside The filter capacitor set will increase the complexity of adjusting control circuit, and low-pass filtering, Ke Yiti are realized using digital filtering technique The integrated level of high circuit simplifies the complexity of circuit and improves circuit stability, and in the present embodiment, low-pass filter 130 is preferred Using wave digital lowpass filter.

Fig. 6 is the schematic diagram of the low-pass filter in one embodiment of the invention.Referring to Fig. 6, in an embodiment, above-mentioned light modulation Control circuit use wave digital lowpass filter, the wave digital lowpass filter be configured to the dimmer voltage signal VP that will access with Sampled signal VN carries out digitized difference Integral Processing and generates difference integrated signal, and the difference integrated signal is carried out Stored counts is then converted into the filtering signal output of simulation.The filtering principle of the wave digital lowpass filter is as follows: oscillator It generates clock signal clk and is input to sigma Delta modulator and forward-backward counter, while sampled signal VN and dimmer voltage signal VP It is input to sigma Delta modulator as differential signal, after sigma Delta modulator is handled, exports serial data stream SEL.If sampling letter Number VN is lower than dimmer voltage signal VP, then " 1 " quantity is more in SEL, and " 0 " quantity is few, similarly, if sampled signal VN ratio is adjusted Photoelectric signal VP high, then " 1 " quantity is few in SEL, and " 0 " quantity is more；Then, SEL signal is input into forward-backward counter, Determine forward-backward counter output binary code be plus " 1 " still subtract " 1 ", SEL be high level when, forward-backward counter it is defeated Digital signal adds " 1 " out, and when SEL is low level, the output digit signals of forward-backward counter subtract " 1 ", and forward-backward counter is defeated N-bit binary code Q<N-1:0>out, these binary codes are input to N-bit DAC, handle by DAC, i.e. output simulation letter Number filtering modulation voltage VCOMP.Above-mentioned wave digital lowpass filter includes sigma Delta modulator, forward-backward counter and DAC, can be with By the working frequency ripple wave on sampled signal VN to filtering out, the filtering modulation voltage VCOMP close to direct current is obtained.It is low using this number Bandpass filter is as the low-pass filter in adjusting control circuit shown in fig. 5, after closed loop reaches stable state, dimmer voltage letter Number VP and sampled signal VN is equal.Using wave digital lowpass filter, the integrated level of control circuit on the one hand can be improved, in addition shape At feedback control loop be conducive to the influence of offset voltage in comparator caused by reducing because of integrated circuit fabrication process, help to subtract The output error of small Switching Power Supply helps to deepen light modulation depth.

It, can sampled signal and PWM to switching circuit according to foregoing description it is found that the adjusting control circuit of the present embodiment Dim signal obtains the filtering modulation voltage VCOMP for being similar to direct current after carrying out low-pass filtering treatment.It is above-mentioned with continued reference to Fig. 5 Adjusting control circuit further includes the output current-modulation module 200 being electrically connected with the low-pass filtering module 100.The output Current-modulation module 200 is configured to using the filtering modulation voltage modulating switch power source, so that the Switching Power Supply at least exists Several switches week under DCM mode, when input voltage vin changes because of the ripple of power frequency ingredient, under current PWM dim signal In phase, the average current value of the corresponding Switching Power Supply output of each switch periods is constant.

According to formula (2) it is found that the average current value of Switching Power Supply output has with peak point current Ipk and effective duty cycle Deff It closes, wherein for constant PWM dim signal, duty ratio is fixed, and peak point current Ipk is close to steady state value, DCM mould at this time Effective duty cycle Deff under formula mainly with the excitation time of inductance in each period and the dead time T3 except the demagnetization time (i.e. inductive current be 0 time) it is related, it is preferred, therefore, that above-mentioned output current-modulation module 200 can by modulation dead zone when Between T3 variation and the effective duty cycle Deff that controls each switch periods under current PWM dim signal is constant, and then make every The average current value of the corresponding Switching Power Supply output of a switch periods is constant.It should be noted that according to Switching Power Supply Specific to design, at least partly switch periods under the above-mentioned adjustable current PWM dim signal of output current-modulation module 200 make The average current value for obtaining the corresponding Switching Power Supply output of wherein each switch periods is constant, that is, above-mentioned output current-modulation mould A part or nearly all switch periods under the adjustable current PWM dim signal of block 200 make each switch periods pair The average current value for the Switching Power Supply output answered is constant.Below it is preferred that, to adjust all of current PWM dim signal Output current-modulation module 200 is retouched for the average current value of the corresponding Switching Power Supply output of switch periods is all the same It states, it is to be understood that, " all switch periods " also include the situation close to all switch periods herein.

Specifically, output current-modulation module 200 may include effective duty cycle modulation unit 210, described to have referring to Fig. 5 Effect duty ratio modulation unit 210 is configured to modulate using above-mentioned filtering modulation voltage VCOMP several under current PWM dim signal The effective duty cycle in each period in switch periods is constant.Effective duty cycle modulation unit 210 can be according to modulated effective The logic control signal of conducting (GATE_ON) and the shutdown of duty ratio Deff, zero current detection signal ZCD and power switch, To detect finish time turn-off time of power switch M1, generation conductivity control signal ON.

Fig. 7 A is the circuit diagram of effective duty cycle modulation unit in one embodiment of the invention.Fig. 7 B is to utilize the present invention The waveform diagram of conductivity control signal when the effective duty cycle modulation unit of one embodiment.Implement referring to Fig. 7 A and Fig. 7 B, one In example, the effective duty cycle modulation unit 210 includes charging and discharging currents modulation subunit 211, charge and discharge electronic unit 212 and fills Discharge logic control subelement 213, and the charging and discharging currents modulation subunit 211 and charge and discharge logic control subelement 213 are used To control charge and discharge electronic unit 212.Specifically, the charging and discharging currents modulation subunit 211 can be configured to utilize above-mentioned low pass The filtering modulation voltage VCOMP that filter module 100 exports adjusts the charging and discharging currents value of charge and discharge electronic unit 212, the charge and discharge Electric logic control subelement 213 can be configured to receive the logic control signal of the turn-on and turn-off of power switch M1, to control The charge and discharge moment of charge and discharge electronic unit 212.Charging and discharging currents modulation subunit 211 and charge and discharge logic control subelement 213 It can be using the disclosed circuit structure that respective function can be achieved.As an example, as shown in Figure 7 A, charge and discharge electronic unit 212 can Including charging current source (corresponding charging current Icha), discharge current source (corresponding discharge current Idcha), first switch S1, the Active switch can be selected in two switch S2 and capacitor C1, first switch S1 and second switch S2, as metal-oxide-semiconductor, triode, JFET, The elements such as IGBT.Specifically, as shown in Figure 7 A, the charging current source, first switch S1, second switch S2, discharge current source It can be sequentially connected in series between the output end and ground of charging and discharging currents modulation sub-circuit 211；Charging and discharging currents modulation The input terminal of unit 211 is for accessing above-mentioned filtering modulation voltage VCOMP, the output end of charging and discharging currents modulation subunit 211 It is coupled with the charging current source and the input terminal in the discharge current source；The charge and discharge logic control subelement 213 it is defeated Enter to hold logic control signal and feedback letter for accessing the turn-on and turn-off of zero current detection signal ZCD, power switch M1 Number ONb, the output end of charge and discharge logic control subelement 213 are electrically connected with first switch S1 and second switch S2 respectively, such as Shown in Fig. 7 A, inputting between first switch S1 and the Continuity signal of second switch S2 is logic NOT, alternately to charge and put Electricity；RAMP node between one end connection first switch S1 and second switch S2 of capacitor C1, other end ground connection.Comparator is just RAMP node is connected to input terminal, negative input connects a reference voltage (this is sentenced for 5V), and the output end of comparator is used In output conductivity control signal ON.As shown in Figure 7 A, in order to obtain feedback signal ONb, the output end of comparator is provided with continuous Two NOT gates, node between two NOT gates acquires feedback signal ONb.

Referring to Fig. 7 A and Fig. 7 B and Fig. 2, as an example, being utilized in the power switch M1 switch periods of Switching Power Supply It may include following process that above-mentioned effective duty cycle modulation unit 210, which carries out charge and discharge: utilize filtering modulation voltage VCOMP, charge and discharge Electric 211 modulated charge current source of current-modulation subelement and discharge current source, wherein charging current source charges for capacitor C1, puts Electric current source discharges for capacitor C1.Charge and discharge logic control element 212 controls first switch S1 and second switch S2, wherein the One switch S1 can control the on-off of charging current Icha, and second switch S2 can control the on-off of discharge current Idcha.Work as function When the Continuity signal GATE_ON of rate switch M1 is rising edge, power switch M1 is begun to turn on, and first switch S1 shutdown, second opens S2 conducting is closed, capacitor C1 is discharged by discharge current Idcha, and the voltage of RAMP node is begun to decline from 5V, as power switch M1 When shutdown, capacitor C1 maintains electric discharge；When inductive current IL1 drops to zero, detect that demagnetization terminates, zero current detection signal ZCD gets higher level, and second switch S2 shutdown is connected in first switch S1, and capacitor C1 stops electric discharge and switchs to fill by charging current Icha The voltage of electricity, RAMP node is begun to ramp up from transform voltages Vx, when the voltage of RAMP node is higher than 5V, comparator overturning, Opening time signal ON gets higher level by low level, and power switch M1 enters turn on process next time.It can be obtained by above procedure Formula (5) out,

5-Vx=Idcha* (Ton+Tdis)=Icha*T3 (5)

For convolution (4) it is found that for non-isolated decompression (Buck) topology, effective duty cycle Deff meets formula (6),

Deff=(Ton+Tdis)/(Ton+Tdis+T3)=Icha/ (Icha+Idcha) (6)

It can corresponding to non-isolated Boost topology, non-isolated buck topology and isolation this topological diagram of reverse exciting topological To obtain following formula, such as formula (7) by changing the charge and discharge logic control in Fig. 7 A,

5-Vx=Idcha*Tdis=Icha* (T3+Ton) (7)

Effective duty cycle Deff corresponding with formula (7) meets formula (8),

Deff=Tdis/ (Ton+Tdis+T3)=Icha/ (Icha+Idcha) (8)

By formula (6) and formula (8) it is found that effective duty cycle modulation unit 210 each switch periods charging current Icha With discharge current Idcha by filtering modulation voltage VCOMP modulation, and effective duty cycle Deff is by filtering modulation voltage VCOMP modulation, thus, by filtering modulation voltage VCOMP modulation, obtained effective duty cycle Deff is no longer by power input The influence of the power frequency ingredient of voltage Vin, according to formula above-mentioned (2), the power frequency ingredient of Switching Power Supply exported on electric current Iout It can be eliminated.

Using the adjusting control circuit of above-described embodiment (as shown in Figure 5), when being dimmed, PWM dim signal can be sent out Changing.For the output of the modulating switch power source when PWM dim signal changes, referring to Fig. 5, in an embodiment, output Current-modulation module 200 may also include inductance peak value modulation unit 220, and the inductance peak value modulation unit 220 is configured to utilize The filtering modulation voltage VCOMP that low-pass filtering module 100 exports modulates inductance peak value corresponding from different PWM dim signals.

Specifically, the filtering modulation voltage can be made to follow the variation of the PWM dim signal and change.Inductance peak value Modulation unit 220 can be configured to modulate corresponding inductance peak value Vpk in the inductance peak maximum and inductance peak value minimum of setting With filtering modulation voltage VCOMP linear change in the same direction between value.Fig. 8 A is inductance peak value modulation unit in one embodiment of the invention Circuit diagram.Referring to Fig. 8 A, as an example, the inductance peak value modulation unit 220 may include constant-current source circuit 221, divide Volt circuit 222 and clamp circuit 223, the output size of current of the constant-current source circuit 221 follow above-mentioned filtering modulation voltage The output of VCOMP variation, the bleeder circuit 222 and the constant-current source circuit couples, the clamp circuit 223 and the partial pressure The output of circuit 222 couples and exports inductance peak value Vpk corresponding with current PWM dim signal.

Fig. 8 B is the waveform diagram that inductance peak value changes with filtering modulation voltage in one embodiment of the invention.Specifically, The constant-current source circuit 221 may include operational amplifier and metal-oxide-semiconductor M1, and bleeder circuit 222 includes the voltage of resistance R1, R2 composition Buffer, to realize the partial pressure to filtering modulation voltage VCOMP, the output voltage V1 of bleeder circuit is equal to VCOMP*R2/ (R1+ R2).Clamp circuit 223 can carry out following clamper function: when output voltage V1 > Vpk_High (inductance peak maximum), Vpk =Vpk_High；As output voltage V1 < Vpk_Low, Vpk=Vpk_Low (inductance peak value minimum value)；When V1 is between Vpk_ When between Low and Vpk_High, Vpk=V1.Mode shown in Fig. 8 A and Fig. 8 B is not limited to for the modulation of inductance peak value Vpk, As long as making inductance peak value Vpk in a certain range with filtering modulation voltage VCOMP by the modulation of filtering modulation voltage VCOMP Monotone increasing, to realize the effect for modulating inductance peak value corresponding from different PWM dim signals.

By above-mentioned output current-modulation module 200 modulation after, in the embodiment, Switching Power Supply in dcm mode, In When input voltage changes because of the ripple of power frequency ingredient, in all switch periods under current PWM dim signal, each switch week The phase average current value of corresponding Switching Power Supply output is constant.Specifically, output current-modulation module 200 can pass through effective duty Than the effective duty cycle that the variation that modulation unit 210 modulates dead time T3 makes each period under current PWM dim signal Deff is constant, to export constant.In addition, output current-modulation module 200 can also be modulated by inductance peak value modulation unit 220 Inductance peak value Vpk corresponding to different PWM dim signals.Referring to Fig. 5, the adjusting control circuit of the present embodiment may also include inductance Peak comparator 410, the inductance peak comparator 310 is configured to inductance peak value Vpk and the letter of the sampling from Switching Power Supply It number is compared, generates shutdown control signal to obtain the turn-on time finish time of each switch periods.

The adjusting control circuit of the present embodiment may also include rest-set flip-flop 420, and the rest-set flip-flop 320 is configured to receive electricity Feel the shutdown control signal that peak comparator 310 exports and the conductivity control signal ON that effective duty cycle modulation unit 210 exports, According to the level of shutdown the control signal and conductivity control signal, the switch control for power switch M1 in Switching Power Supply is generated Signal processed.

As an example, the reset terminal of the rest-set flip-flop, which receives the shutdown, controls signal, when the sampled signal reaches When inductance peak value Vpk, shutdown control signal is high level, i.e., the reset terminal of the described rest-set flip-flop becomes high level, then exports Switch control signal is cut-off signals；The set end of the rest-set flip-flop receives conductivity control signal ON, when dead time T3 is tied Shu Shi, conductivity control signal become high level, and the set end of rest-set flip-flop becomes high level, then the switch control signal exported is Continuity signal.

As shown in figure 5, control circuit may also include drive module 430 in the present embodiment.The drive module 430 configures For receive rest-set flip-flop 420 export Continuity signal or cut-off signals (being digital signal), handled (such as carry out signal Amplification, DAC conversion etc.) to obtain the driving signal that can directly control power switch M1.

Fig. 9 is the waveform diagram using input voltage when adjusting control circuit shown in fig. 5 and output electric current.Referring to figure 5 and Fig. 9, wherein input voltage vin includes power frequency ingredient, according to the analysis of formula (5) it is found that the excitation time Ton of inductance L1 exists Vin can shorten when increasing, i.e. Ton2 < Ton1, and when using adjusting control circuit (such as Fig. 5) of above-described embodiment, low pass filtered The filtering modulation voltage VCOMP that wave module 100 exports is modulated the Switching Power Supply, may make any current PWM light modulation letter In all switch periods under number, the average current value of the corresponding Switching Power Supply output of each switch periods is constant.Specifically It is constant the effective duty cycle in each period can be controlled by the variation of modulation dead time T3, for example, can modulate makes The dead time T32 of switch periods where obtaining Ton2 shortens relative to the dead time T31 of switch periods where Ton1, that is, passes through Period, which shortens, has ensured that effective duty cycle Deff is constant, since the average output current of Switching Power Supply is mainly by effective duty cycle Deff is determined, therefore the average output current in two neighboring period can be made to be held essentially constant, and helps to solve stroboscopic problem.

As shown in figure 5, the adjusting control circuit of the embodiment of the present invention samples Switching Power Supply, and will be adjusted using filtering Voltage modulated Switching Power Supply processed, realizes closed-loop control.For example, low-pass filter 130 receives when changing PWM dim signal To dimmer voltage signal VP and sampled signal VN, if VP > VN, the filtering modulation voltage VCOMP that low-pass filter 130 exports is modulated Inductance peak value Vpk increase so that Switching Power Supply output peak point current increase, and then feed back sampled signal VN increase, VP and VN reaches unanimity；As VP < VN, the filtering modulation voltage VCOMP modulation inductance peak value Vpk that low-pass filter 130 exports reduces, So that the sampled signal VN that the peak point current of Switching Power Supply output reduces, and then feeds back reduces, VP and VN is also made to reach unanimity. After the loop of above-mentioned adjusting control circuit reaches stable state, the dimming control voltage VP that is obtained according to PWM dim signal and according to defeated The sampled signal VN obtained out is equal, i.e. VP=VN, due to sampled signal VN=k*Iout, dimmer voltage signal VP=Dpwm* Vref, Dpwm are the duty ratio of PWM dim signal, and Vref is the reference voltage in low-pass filtering module 100.Convolution (2) can Know, at this time the average output current Iout=Dpwm*Vref/k of Switching Power Supply, it is seen that average output current Iout and PWM at this time The duty ratio Dpwm of dim signal is directly proportional, consequently facilitating realizing the light modulation of high linearity.

In embodiment presented above, input is eliminated by fixing effective duty cycle under current PWM dim signal Ripple is influenced to output bring on voltage.However embodiment of the present invention is not limited to dim here, corresponding to a PWM Under signal, as long as each period average current value is not influenced by the variation of input voltage, the line eliminated of the invention can be also played The technical effect of wave.Therefore, those skilled in the art create through the invention in disclosed technical solution and specification Specific embodiment description, obtained technical inspiration should be readily available following technical scheme.For example, passing through specific implementation The enlightenment of formula (2) in mode, under corresponding PWM dim signal, which can multiplying by control Ipk and Deff Product is constant, and to realize, each period output electric current Iout will not change with output voltage Vin in several periods, also can achieve this The effect of each embodiment being previously mentioned in specific embodiment elimination stroboscopic achieved.

Further, the low-pass filtering module of the adjusting control circuit preferably uses wave digital lowpass filter.Number is low Bandpass filter does not need external bulky capacitor, helps to improve circuit level and stability, subtract relative to simulation low-pass filter The influence of few offset voltage is conducive to increase light modulation depth.Experiment display, controlling load using above-mentioned adjusting control circuit is The output of the Switching Power Supply of LED, wherein wave digital lowpass filter is used, relative to light adjusting circuit as shown in Figure 4 A, imbalance electricity Pressure drop is down to 1/10 hereinafter, light modulation depth is reduced to 1%.After filtering the modulation of modulation voltage VCOMP, Switching Power Supply is true Under fixed PWM dim signal, average output current value Iout of the power switch M1 in its all switch periods be it is equal, i.e., Embodying has extremely strong rejection ability to the ripple of power input voltage Vin.Above-mentioned adjusting control circuit avoids light modulation dead zone, Light modulation whole process improves light modulation consistency without step sense, helps to eliminate stroboscopic and noise.It is average after loop reaches stable state It is directly related with PWM dim signal frequency to export electric current, the dimming curve of high linearity may be implemented.

The embodiment of the present invention is additionally related to a kind of control chip of Switching Power Supply, and the control chip is for controlling low PF The output of the Switching Power Supply of (such as PF is less than or equal to 0.7), the Switching Power Supply includes power switch, is set in the control chip There is the above-mentioned adjusting control circuit including low-pass filtering module 100 and output current-modulation module 200.It is described in the present embodiment Control chip is, for example, LED control chip, and the load of the Switching Power Supply controlled can be LED light string, but not limited to this, it is described Control chip also can have other control purposes, and the load of the Switching Power Supply of the control chip controls is also possible to other need The element of load variation is more delicately adjusted, in one embodiment, the control chip is also possible to OLED control chip.

The Switching Power Supply can have the topological circuit structure such as any of Figure 1A to Fig. 1 D.That is, the switch electricity The electricity such as isolation reverse exciting topological, non-isolated buck topology, non-isolated buck topology and non-isolated Boost topology can be used in source One of line structure.Power switch in the Switching Power Supply can be the switch member such as metal-oxide-semiconductor, triode, JFET, IGBT Part.

Referring to Fig. 5, as an example, the control chip of Switching Power Supply may include packaging body, the packaging body in an embodiment It is equipped with DIM pin, CS pin and GATE pin, is equipped in the packaging body above-mentioned including low-pass filtering module 100 and defeated The adjusting control circuit of current-modulation module 200 out, wherein the DIM pin is for accessing PWM dim signal and being supplied to this Adjusting control circuit, the CS pin are used to access the sampled signal from Switching Power Supply and are supplied to the adjusting control circuit, The power switch M2 that the GATE pin is used to obtain the driving signal of adjusting control circuit output and is input in Switching Power Supply (as shown in Figure 2 A).In alternative embodiment, the GATE pin is also used to receive the demagnetization signal of Switching Power Supply and is supplied to this The demagnetization detection module 300 of adjusting control circuit.In a further embodiment, the demagnetization signal of Switching Power Supply can also be by another Outer pin such as FB pin obtains, the FB pin can be concatenated by divider resistance into Switching Power Supply inductance or transformer come Obtain demagnetization signal.The invention is not limited thereto, and in a further embodiment, the power switch of Switching Power Supply can also be with control core Piece is integrated to form, thus control chip can also be not provided with certain pins described herein.

The embodiment of the present invention further relates to a kind of power supply change-over device for driving LED, and the power supply change-over device includes rectification Circuit, the switching power circuit of low PF, the above-mentioned adjusting control circuit including low-pass filtering module and output current-modulation module And LED light string.Wherein, the rectification circuit executes rectification after being configured to access alternating current and exports；The switch power supply The output of road and the rectification circuit couples, and is configured to electric power needed for the output of the rectification circuit is converted into LED light string； The adjusting control circuit is configured to receive PWM dim signal to control the brightness of LED light string with the PWM dim signal Change and changes.

The rectification unit can be to use four diodes to form full-bridge rectifiers with by the rectifier bridge of AC rectification Circuit.In the switching power circuit, excitation and demagnetization of the power switch for regulating and controlling inductance (or transformer) are operated, for LED light string adjusts corresponding bright under the excitation and demagnetization operation.Such as Figure 1A to Fig. 1 D can be used in the switching power circuit Any of shown in topological circuit structure.For control power switch turn-on and turn-off adjusting control circuit such as Fig. 5 institute Show, structure and work can refer to the present embodiment description as described in adjusting control circuit.Adjusting control circuit can be with chip Form is arranged in the power supply change-over device of driving LED.

The embodiment of the present invention further relates to one kind and removes stroboscopic method, described applied to the brightness regulation of current mode light-emitting component Current mode light-emitting component is the load of a low PF Switching Power Supply for including power switch.It is described that go stroboscopic method that can use above-mentioned Adjusting control circuit including low-pass filtering module 100 and output current-modulation module 200.The light-dimming method includes following step It is rapid:

First step: access PWM dim signal and the sampled signal from the Switching Power Supply are dimmed based on the PWM Signal and the sampled signal generate filtering modulation voltage and export；

Second step: the Switching Power Supply is modulated at least in dcm mode using the filtering modulation voltage, described defeated When entering voltage and changing because of the ripple of power frequency ingredient, in several switch periods under current corresponding PWM dim signal, Mei Gekai The average current value for closing the period corresponding Switching Power Supply output is constant.

Above-mentioned current mode light-emitting component is, for example, LED or OLED device etc., light emission luminance with flow through the electric current of element at Direct ratio, thus it is constant by the average current value that control switch power supply exports, it can be achieved that light modulation to LED or OLED device.

It is above-mentioned to go stroboscopic method specifically be using the Switching Power Supply and adjusting control circuit (such as Fig. 5 to Fig. 8 of the present embodiment It is shown) it executes.Specifically, in first step PWM dim signal can be accessed using low-pass filtering module 100 and from institute The sampled signal for stating Switching Power Supply generates filtering modulation voltage based on the PWM dim signal and the sampled signal and exports. In second step, specifically can may be used using the output current-modulation module 200 being electrically connected with the low-pass filtering module 100 The several of current PWM dim signal are controlled to modulate the variation of dead time T3 by effective duty cycle modulation unit 210 The effective duty cycle in each period in switch periods is constant.And the filter can be utilized by inductance peak value modulation unit 220 Wave modulation voltage modulates inductance peak value Vpk corresponding to different PWM dim signals.

Stroboscopic method is removed using above-mentioned, Switching Power Supply is in several switch periods under current PWM dim signal, switch electricity Average output current value of the source in each switch periods tends to be equal, to show as having the ripple of input voltage vin Extremely strong rejection ability.Above-mentioned adjusting control circuit avoids light modulation dead zone, and light modulation is whole without step sense, and it is consistent to improve light modulation Property, help to eliminate stroboscopic and noise.

In different circuits is realized, may there is the structure of modules (or unit) in adjusting control circuit of the invention Institute is different, it is to be understood that, without departing from the technical principles of the invention, change their implementation and the electricity that is formed Road also should belong to protection scope of the present invention.

Foregoing description is only the description to present pre-ferred embodiments, not to any restriction of interest field of the present invention, Anyone skilled in the art without departing from the spirit and scope of the present invention, may be by the methods and techniques of the disclosure above Content makes possible variation and modification to technical solution of the present invention, therefore, anything that does not depart from the technical scheme of the invention, Any simple modifications, equivalents, and modifications to the above embodiments according to the technical essence of the invention, belong to this hair The protection scope of bright technical solution.

Claims

1. a kind of adjusting control circuit, the output of the Switching Power Supply for controlling low PF, the Switching Power Supply includes power switch, The Switching Power Supply receive include power frequency ingredient input voltage, which is characterized in that the adjusting control circuit includes:

Low-pass filtering module, input terminal are configured to for accessing PWM dim signal and the sampled signal from the Switching Power Supply Filtering modulation voltage is generated based on the PWM dim signal and the sampled signal and is exported；And

Current-modulation module is exported, is electrically connected with the low-pass filtering module, is configured to utilize the filtering modulation voltage tune Make the Switching Power Supply at least in dcm mode, when the input voltage changes because of the ripple of power frequency ingredient, current PWM In several switch periods under dim signal, the average current value of the corresponding Switching Power Supply output of each switch periods is not Become.

2. adjusting control circuit as described in claim 1, which is characterized in that the output current-modulation module passes through modulation The variation of the dead time of DCM mode and the effective duty cycle for controlling each period in several switch periods is constant.

3. adjusting control circuit as claimed in claim 2, which is characterized in that the output current-modulation module includes effectively accounting for Than modulation unit, the effective duty cycle modulation unit includes charging and discharging currents modulation subunit, charge and discharge electronic unit and fills sky Discharge logic control subelement；The charging and discharging currents modulation subunit and charge and discharge logic control subelement are configured to control institute State charge and discharge electronic unit.

4. adjusting control circuit as claimed in claim 3, which is characterized in that the charging and discharging currents modulation subunit is configured to The charging and discharging currents value of the charge and discharge electronic unit is adjusted using the filtering modulation voltage.

5. adjusting control circuit as claimed in claim 3, which is characterized in that the charge and discharge logic control subelement is configured to The logic control signal for receiving the turn-on and turn-off of the power switch, when controlling the charge and discharge of the charge and discharge electronic unit It carves.

6. adjusting control circuit as claimed in claim 1 to 5, which is characterized in that the output current-modulation module packet Include inductance peak value modulation unit, the inductance peak value modulation unit be configured to modulate using the filtering modulation voltage from it is different The corresponding inductance peak value of PWM dim signal.

7. adjusting control circuit as claimed in claim 6, which is characterized in that the filtering modulation voltage follows the PWM tune The variation of optical signal and change.

8. adjusting control circuit as claimed in claim 7, which is characterized in that the inductance peak value modulation unit includes constant-current source Circuit, bleeder circuit and clamp circuit；The output size of current of the constant-current source circuit follows the filtering modulation voltage to become Change；The output of the bleeder circuit and the constant-current source circuit couples；The output coupling of the clamp circuit and the bleeder circuit It connects and exports the corresponding inductance peak value.

9. adjusting control circuit as described in claim 1, and be characterized in that, the low-pass filtering module includes:

PWM dim signal pretreatment unit is configured to access the PWM dim signal, using the PWM dim signal to reference Voltage carries out copped wave, generates dimmer voltage signal；And

10. adjusting control circuit as claimed in claim 9, and be characterized in that, the low-pass filter is digital low-pass filtering Device.

11. such as adjusting control circuit described in any one of claim 1 to 5, which is characterized in that the Switching Power Supply is using isolation One of reverse exciting topological, non-isolated buck topology, non-isolated buck topology and non-isolated Boost topology topological circuit Structure.

12. a kind of control chip of Switching Power Supply, the output of the Switching Power Supply for controlling low PF, the Switching Power Supply includes function Rate switch, which is characterized in that adjusting control circuit as described in any one of claim 1 to 11 is equipped in the control chip.

13. a kind of power supply change-over device for driving LED, which is characterized in that the power supply change-over device includes rectification circuit, low PF Switching power circuit, adjusting control circuit as described in any one of claim 1 to 11 and LED light string, wherein

The rectification circuit executes rectification after being configured to access alternating current and exports；

The output of the switching power circuit and the rectification circuit couples, and is configured to for the output of the rectification circuit being converted into Electric power needed for LED light string；

The brightness that the adjusting control circuit is configured to receive PWM dim signal and control the LED light string is dimmed with the PWM The variation of signal and change.

14. one kind removes stroboscopic method, applied to the brightness regulation of current mode light-emitting component, the current mode light-emitting component is a packet Include the load of the low PF Switching Power Supply of power switch, which is characterized in that described to go the stroboscopic method to include:

PWM dim signal and the sampled signal from the Switching Power Supply are accessed, the PWM dim signal and the sampling are based on Signal generates filtering modulation voltage and exports；And

The Switching Power Supply is modulated at least in dcm mode using the filtering modulation voltage, in the input voltage because of power frequency The ripple of ingredient and when changing, in several switch periods under current PWM dim signal, each switch periods are corresponding described to be opened The average current value of powered-down source output is constant.