CN207083251U - PWM light adjusting circuits and LED drive circuit - Google Patents
PWM light adjusting circuits and LED drive circuit Download PDFInfo
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- CN207083251U CN207083251U CN201720533896.9U CN201720533896U CN207083251U CN 207083251 U CN207083251 U CN 207083251U CN 201720533896 U CN201720533896 U CN 201720533896U CN 207083251 U CN207083251 U CN 207083251U
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- thermal compensation
- compensation signal
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Abstract
The utility model discloses a kind of PWM light adjusting circuits and LED drive circuit.The reference signal for characterizing PWM dim signals and the current sampling signal for characterizing average inductor current are subjected to Error processing, obtain characterizing the thermal compensation signal of master power switch pipe ON time；Described thermal compensation signal is compared with ramp signal, for controlling master power switch pipe to turn off；The maximum switching frequency of master power switch pipe is adjusted according to the thermal compensation signal；Wherein, when actual switch frequency is higher than maximum switching frequency, master power switch pipe is not turned on.Due to the limitation of minimum ON time and maximum switching frequency, it have impact on LED light modulation depth, the utility model make use of PWM dim signals to continue to lower the relation between thermal compensation signal, so as to according to thermal compensation signal come adjusting switch frequency, so as to reduce the average output current of load.The utility model improves the light modulation depth of PWM light modulations.
Description
Technical field
A kind of electric and electronic technical field is the utility model is related to, more particularly to a kind of PWM light adjusting circuits and LED driving electricity
Road.
Background technology
In LED applications, some occasions need the brightness to LED to be adjusted and control, i.e., by adjusting LED load
Output average current come realize light modulation.PWM light modulations are one kind of light-dimming method, and the PWM light modulations of prior art typically pass through tune
The dutycycle for saving pwm signal changes the brightness of LED, so as to realize light modulation.A kind of LED driving electricity of band PWM light adjusting circuits
As shown in figure 1, by taking reverse exciting topological as an example, FB is voltage feedback loop pin on road, the signal for characterizing output voltage is received, when defeated
When going out secondary inductor current afterflow to zero, FB signals meeting output control signal allows primary side switch pipe M to turn on again, and entrance is next
Individual switch periods.GATE pins open shut-off for driving switch pipe；SNP pins are big for sampling primary side inductive current
It is small；DPWM pins connect the PWM dim signals of outside input；COMP pins are as system balance controlling switch.
Specific PWM light adjusting circuits principle in Fig. 1 is as shown in Fig. 2 by controlling PWM duty cycle to change reference signal VREF
Size, sample obtained voltage VSNPAfter average treatment, with the reference signal VREFBy error amplifier
OTA, output thermal compensation signal VCOMP。VCOMPCompared with ramp signal caused by the harmonic oscillator of slope, when ramp signal is more than
VCOMPDuring signal, comparator exports a high level, on-off switching tube M.Therefore in the case where the slope of ramp signal is constant,
VCOMPSize determine switching tube service time Ton length, VCOMPSmaller, Ton is shorter, as shown in Figure 3.Controlled by system
Limitation, Ton have a minimum value Ton (min).Work as VCOMPThe Ton values of decision also want small than minimum ON time Ton (min)
When, service time keeps Ton (min) constant, and the minimum output current of LED load is also limited by Ton (min), no longer with
The dutycycle of PWM dim signals reduces and reduced, therefore limits LED light modulation depth.
Utility model content
The purpose of this utility model is to provide a kind of PWM light adjusting circuits and LED drive circuit, is deposited for solving prior art
The limited technical problem of light modulation depth, realize that further depth dims by adjusting maximum switching frequency.
To achieve the above object, the utility model provides a kind of PWM light adjusting circuits, including：
Thermal compensation signal generation circuit, its first input end receive PWM dim signals, and its second input, which receives, to be characterized averagely
The current sampling signal of inductive current, when the output end output of the thermal compensation signal generation circuit characterizes the conducting of master power switch pipe
Between thermal compensation signal；According to the size of the thermal compensation signal, the ON time length of controlling switch pipe；
Switching frequency adjusts circuit, receives the thermal compensation signal, and master power switch pipe is adjusted according to the thermal compensation signal
Switching frequency.
Optionally, described thermal compensation signal generation circuit includes error amplifier, the first input of the error amplifier
End receives the reference signal for characterizing the PWM dim signals, and its second input receives the current sample letter for characterizing inductive current
Number average value, the output end connection compensating electric capacity of the error amplifier, the voltage in the compensating electric capacity is as the compensation
Signal.
Optionally, described thermal compensation signal generation circuit includes the first current source and the second current source；Adjusted by the PWM
Optical signal controls first current source to charge compensating electric capacity, and second current source is produced according to the current sampling signal
The compensating electric capacity is discharged；Or control first current source to discharge compensating electric capacity by the PWM dim signals,
Second current source is produced according to the current sampling signal to charge to the compensating electric capacity；Voltage in the compensating electric capacity
As the thermal compensation signal.
Optionally, in dimming process, the dutycycle of the PWM dim signals persistently reduces so that master power switch pipe
ON time be decreased to minimum ON time, the thermal compensation signal further reduces and subtracted with the dutycycle of PWM dim signals
It is small, switching frequency is now reduced according to the reduction of the thermal compensation signal, so as to further reduce the average output for flowing through load
Electric current.
Optionally, when the switching frequency of master power switch pipe reaches maximum switching frequency, the thermal compensation signal is reduced to
First threshold, when the thermal compensation signal is less than the first threshold, the maximum switching frequency with the reduction of thermal compensation signal and
Reduce.
Optionally, when the thermal compensation signal is decrease continuously to Second Threshold, the maximum switching frequency reaches minimum value,
Now the thermal compensation signal continues to reduce then maximum switching frequency and no longer reduced, and the Second Threshold is less than the first threshold.
Optionally, whether the ON time that described PWM light adjusting circuits also include being used to judge master power switch pipe reduces
To the enabled module of minimum ON time, whether the ON time for judging master power switch pipe in the enabled module is decreased to most
During small ON time, then send and characterize enabled signal to switching frequency regulation circuit, and cause switching frequency regulation electricity
Road enables.
Optionally, it is to pass through judgement that whether the ON time for judging master power switch pipe, which is decreased to minimum ON time,
Whether the thermal compensation signal reaches the first threshold to realize.
Optionally, described thermal compensation signal is compared with ramp signal, for controlling master power switch pipe to turn off the moment.
The utility model also provides a kind of LED drive circuit, including：A kind of PWM light adjusting circuits of any of the above.
Optionally, described LED drive circuit also includes being used for the zero passage detection module for detecting the current over-zero moment, described
Switching frequency regulation circuit and the output end of the zero passage detection module connect two inputs with door respectively, it is described with
Gate output terminal output characterizes the signal that master power switch pipe is opened.
Compared with prior art, the technical scheme of the utility model has advantages below：Due to minimum ON time and most
The limitation of big switching frequency, have impact on depth light modulation, and the utility model make use of the pass between PWM dim signals and thermal compensation signal
System, so as to according to thermal compensation signal come adjusting switch frequency, so as to reduce the average output current of load.The utility model is lifted
The light modulation depth of PWM light modulations.
Brief description of the drawings
Fig. 1 is the structural representation of the LED drive circuit of prior art application PWM light adjusting circuits；
Fig. 2 is the structural representation of prior art PWM light adjusting circuits；
Fig. 3 is the working waveform figure of prior art PWM light adjusting circuits；
Fig. 4 is the structural representation of the utility model PWM light adjusting circuits；
Fig. 5 is the waveform diagram of thermal compensation signal and maximum switching frequency；
Fig. 6 is the waveform diagram of inductive current and ON time；
Fig. 7 is a kind of electrical block diagram of thermal compensation signal generation circuit.
Embodiment
Preferred embodiment of the present utility model is described in detail below in conjunction with accompanying drawing, but the utility model is not merely
It is limited to these embodiments.The utility model covers any replacement made in spirit and scope of the present utility model, modification, equivalent
Method and scheme.
Thoroughly understand in order that the public has to the utility model, in following the utility model preferred embodiment specifically
Understand concrete details, and description without these details can also understand that this practicality is new completely for a person skilled in the art
Type.
The utility model is more specifically described by way of example referring to the drawings in the following passage.It should be noted that accompanying drawing
Non- accurately ratio is used using more simplified form and, only to convenience, lucidly aid in illustrating the utility model
The purpose of embodiment.
As shown in figure 4, a kind of particular circuit configurations of the utility model PWM light adjusting circuits are illustrated, because PWM dims electricity
Road can be integrated in piece, therefore illustrates the situation of its each pin, and DPWM pins are the input of PWM dim signals, are used
In receiving the PWM dim signals, SNP pins are sampling pin, and the sampled signal of inductive current is characterized for receiving, and GATE draws
Pin is connected with the control terminal of master power switch pipe.
Described PWM light adjusting circuits include error amplifier OTA and switching frequency regulation circuit, the input of PWM dim signals
To DPWM pins, the adjusted corresponding reference signal V of control module is passed through according to its dutycycleREF, described reference signal
VREFInput to error amplifier OTA first input end；Inductive current sampled signal is inputted to SNP pins, and at averaged value
After reason, for characterizing inductive current average value, input to error amplifier OTA the second input, the error amplifier OTA
Output end output characterize master power switch pipe ON time thermal compensation signal VCOMP；Described thermal compensation signal VCOMPBelieve with slope
Number VSAMCompare in comparator U40, the set end R of comparator U40 output result to rest-set flip-flop, for controlling main power
Switching tube turns off.
Switching frequency regulation circuit receives the thermal compensation signal VCOMP, especially after maximum switching frequency is reached, according to
The thermal compensation signal VCOMPAdjust the maximum switching frequency of master power switch pipe；Wherein, actual switch frequency switchs higher than maximum
During frequency, master power switch pipe is not turned on.
In dimming process, as what is dimmed downwards gos deep into, the dutycycle of the PWM dim signals persistently reduces so that
The ON time of master power switch pipe is decreased to minimum ON time, and the switching frequency of master power switch pipe reaches maximum switch frequency
Rate, the thermal compensation signal reduce and reduced with the dutycycle of PWM dim signals, and now the switching frequency adjusts circuit according to institute
State thermal compensation signal VCOMPReduction reduce maximum switching frequency, so as to further reduce the average output current for flowing through load.
Using the LED drive circuit of the utility model PWM light adjusting circuits, including above-mentioned PWM light adjusting circuits, for main power
Opening for switching tube can use various ways, and being illustrated in Fig. 5 has used zero passage detection module, for detecting secondary current zero passage
At the moment, now control master power switch pipe open-minded, but it is not open-minded in the case where switching frequency is more than maximum switching frequency.It is described
Switching frequency regulation circuit and the output end of the zero cross detection circuit connect two inputs with door respectively, it is described with
Gate output terminal output characterizes the signal that master power switch pipe is opened.
With reference to shown in figure 5, when the switching frequency of master power switch pipe reaches maximum switching frequency, the thermal compensation signal
VCOMPIt is reduced to first threshold VCOMP1, in the thermal compensation signal VCOMPLess than the first threshold VCOMP1When, the maximum switch
Frequency is with thermal compensation signal VCOMPReduction and reduce.Although the two linear change, linear change are illustrated in Figure 5
It is used only for illustrating, actual conditions and non-critical linear change.In the thermal compensation signal VCOMPIt is decrease continuously to Second Threshold
VCOMP2When, the maximum switching frequency reaches minimum value, now the thermal compensation signal VCOMPContinue to reduce then maximum switching frequency
No longer reduce, the Second Threshold VCOMP2Less than the first threshold VCOMP1, the minimum value of described maximum switching frequency can be with
It is default, then, in the situation of the preset value, Second Threshold V is also just correspondingly determinedCOMP2。
In order to which in the case of normal light modulation, maximum switching frequency does not follow thermal compensation signal to change, so there is provided enabled mould
Block, the enabled module are used to judge whether the ON time of master power switch pipe is decreased to minimum ON time.It is i.e. described
PWM light adjusting circuits also include being used to judge thermal compensation signal VCOMPWhether first threshold V is reachedCOMP1(it is used for characterizing master power switch
Whether the ON time of pipe is decreased to minimum ON time) enabled module, judge thermal compensation signal V in the enabled moduleCOMP
Reach first threshold VCOMP1When, then send and characterize enabled signal to switching frequency regulation circuit, and cause switching frequency
Regulation circuit enables.
When the dutycycle of PWM dim signals reduces, the current sampling signal for characterizing average inductor current keeps basic
It is constant, detect that the state is continued above certain time or dutycycle decrease beyond certain amplitude by the enabled module, then by institute
State enabled module output enable signal.Certainly, except both the above judgment mode, also in the presence of other possible judgment modes.
With reference to shown in figure 6, the oscillogram of inductive current and ON time is illustrated, this accompanying drawing is intended to illustrate the utility model
Light modulation principle.In the case of not considering loss, the energy stored in inductance can be discharged into load LED lamp, a switch week
The energy that inductance stores in phase is more, exports that the electric current of LED is bigger, and lamp is brighter.Then have：
Ipk is peak point current, and P1 is the energy that ON time is Ton memory storages, and P2 is the unit in a switch periods
Time energy.From formula (3), the unit interval energy stored in a switch periods is except relevant with Ton, also with switch frequently
Rate fsw is relevant.Dutycycle D with input PWM dim signals reduces, and internal thermal compensation signal reduces therewith, during switch conduction
Between Ton it is constant in the case of, the average value of sampled feedback signal is constant, the output V of error amplifierCOMPIt can reduce accordingly, from
And the actual Ton of switch conduction also reduces, the average value of sampled feedback signal also reduces, the output V of error amplifierCOMPReach flat
Weighing apparatus.As the dutycycle of dim signal continues to reduce, Ton can further reduce, until when Ton is reduced to Ton (min), switch
The switching frequency of pipe reaches maximum switching frequency fsw (max) limitation, and the average value of sampled feedback signal keeps constant, and interior
Portion's reference voltage reduces as dutycycle reduces, so the output signal V of error amplifierCOMPIt may proceed to reduce, now use
VCOMP de-regulation fsw, maximum switching frequency fsw (max) are with VCOMPReduce and reduce, understood according to formula (3), the unit interval
Interior power output just reduces as maximum switching frequency fsw (max) reduces accordingly, it is achieved thereby that LED output current
Further modulated by PWM dim signals dutycycle.
With reference to shown in figure 7, a kind of particular circuit configurations of thermal compensation signal generation circuit, the circuit structure and Fig. 4 are illustrated
In difference, pass through two kinds of implementations, it is intended that illustrate that thermal compensation signal generation circuit can be achieved by various ways, while
It is not limited to both modes.Described thermal compensation signal generation circuit includes the first current source i1 and the second current source i2；Pass through institute
Stating PWM dim signals controls the first current source i1 to charge compensating electric capacity C, according to the current sampling signal VSNPProduce
Second current source discharges the compensating electric capacity C；Or first current source is controlled by the PWM dim signals
I1 discharges compensating electric capacity C, according to the current sampling signal VSNPThe second current source i2 is produced to the compensating electric capacity C
Charging；Voltage on the compensating electric capacity C is as the thermal compensation signal.In this accompanying drawing, PWM dim signals control described first
Current source i1, it is to control the first current source i1 to be averaged compensating electric capacity discharge and recharge by PWM dim signal controlling switch K1
Electric current, the current sampling signal VSNPBy current generating circuit, the second electricity of the direct ratio that is inversely proportional with resistance R resistance is produced
Stream source i2, described current generating circuit are realized by amplifier and resistance R.The first current source i1 and the second current source i2 directions
On the contrary, the reference signal VREF and current sample of PWM dim signals control are judged by the two discharge and recharge to compensating electric capacity
Signal VSNPAverage value difference, can obtain current sampling signal V by switching K2SNPAverage value, utilize compensating electric capacity
On voltage adjust the ON time of main switch to control output current, the discharge and recharge in compensating electric capacity is reached balance.
Although embodiment is separately illustrated and illustrated above, it is related to the common technology in part, in ordinary skill
Personnel apparently, can be replaced and integrate between the embodiments, be related to one of embodiment and the content recorded is not known, then
Refer to another embodiment on the books.
Embodiments described above, the restriction to the technical scheme protection domain is not formed.It is any in above-mentioned implementation
Modifications, equivalent substitutions and improvements made within the spirit and principle of mode etc., should be included in the protection model of the technical scheme
Within enclosing.
Claims (10)
1. a kind of PWM light adjusting circuits, including：
Thermal compensation signal generation circuit, its first input end receive PWM dim signals, and its second input, which receives, characterizes average inductance
The current sampling signal of electric current, the output end output of the thermal compensation signal generation circuit characterize master power switch pipe ON time
Thermal compensation signal；According to the size of the thermal compensation signal, the ON time length of controlling switch pipe；
Switching frequency adjusts circuit, receives the thermal compensation signal, and the switch of master power switch pipe is adjusted according to the thermal compensation signal
Frequency.
2. PWM light adjusting circuits according to claim 1, it is characterised in that：Described thermal compensation signal generation circuit includes missing
Poor amplifier, the first input end of the error amplifier receive the reference signal for characterizing the PWM dim signals, and it is second defeated
Entering end and receive the current sampling signal average value for characterizing inductive current, the output end of the error amplifier connects compensating electric capacity,
Voltage in the compensating electric capacity is as the thermal compensation signal.
3. PWM light adjusting circuits according to claim 1, it is characterised in that：Described thermal compensation signal generation circuit includes the
One current source and the second current source；First current source is controlled to charge compensating electric capacity by the PWM dim signals, according to
The current sampling signal produces second current source and the compensating electric capacity is discharged；Or pass through the PWM dim signals
Control first current source to discharge compensating electric capacity, second current source is produced to described according to the current sampling signal
Compensating electric capacity charges；Voltage in the compensating electric capacity is as the thermal compensation signal.
4. according to the PWM light adjusting circuits described in claim 1 or 2 or 3, it is characterised in that：In dimming process, the PWM light modulations
The dutycycle of signal persistently reduces so that the ON time of master power switch pipe is decreased to minimum ON time, the compensation letter
Number with PWM dim signals dutycycle further reduce and reduce, now according to the reduction of the thermal compensation signal come reduce switch
Frequency, so as to further reduce the average output current for flowing through load.
5. according to the PWM light adjusting circuits described in claim 1 or 2 or 3, it is characterised in that：In the switch frequency of master power switch pipe
When rate reaches maximum switching frequency, the thermal compensation signal is reduced to first threshold, is less than first threshold in the thermal compensation signal
During value, the maximum switching frequency reduces with the reduction of thermal compensation signal.
6. PWM light adjusting circuits according to claim 5, it is characterised in that：Second is decrease continuously in the thermal compensation signal
During threshold value, the maximum switching frequency reaches minimum value, and now the thermal compensation signal continues to reduce then that maximum switching frequency is no longer
Reduce, the Second Threshold is less than the first threshold.
7. PWM light adjusting circuits according to claim 5, it is characterised in that：Described PWM light adjusting circuits also include being used to sentence
Whether the ON time of disconnected master power switch pipe is decreased to the enabled module of minimum ON time, judges master in the enabled module
When the ON time of power switch pipe is decreased to minimum ON time, then sends enabled signal to the switching frequency of sign and adjust
Economize on electricity road, and switching frequency regulation circuit is enabled.
8. PWM light adjusting circuits according to claim 7, it is characterised in that：During the conducting of the judgement master power switch pipe
Between whether be decreased to minimum ON time by judging whether the thermal compensation signal reaches the first threshold to realize.
9. according to the PWM light adjusting circuits described in claim 1 or 2 or 3, it is characterised in that：Described thermal compensation signal is believed with slope
Number it is compared, for controlling master power switch pipe to turn off the moment.
10. a kind of LED drive circuit, including：Any one PWM light adjusting circuit of above claim 1-9.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201720533896.9U CN207083251U (en) | 2017-05-15 | 2017-05-15 | PWM light adjusting circuits and LED drive circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201720533896.9U CN207083251U (en) | 2017-05-15 | 2017-05-15 | PWM light adjusting circuits and LED drive circuit |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107172739A (en) * | 2017-05-15 | 2017-09-15 | 杰华特微电子（张家港）有限公司 | PWM light adjusting circuits and light-dimming method and LED drive circuit |
| CN110139425A (en) * | 2019-04-19 | 2019-08-16 | 云南省交通科学研究院有限公司 | Vcehicular tunnel wisdom illumination control apparatus and system |
| CN110582143A (en) * | 2019-10-09 | 2019-12-17 | 杰华特微电子（杭州）有限公司 | LED dimming circuit, dimming method and LED control circuit |
| CN111107691A (en) * | 2018-10-25 | 2020-05-05 | 深圳市必易微电子有限公司 | Solid-state lighting device driving module, switching power supply circuit and dimming method |
| CN112235905A (en) * | 2020-10-23 | 2021-01-15 | 青岛易来智能科技股份有限公司 | Brightness adjusting circuit, lamp and LED brightness control method |
| CN112804786A (en) * | 2019-11-13 | 2021-05-14 | 圣邦微电子（北京）股份有限公司 | LED drive circuit and control circuit thereof |
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- 2017-05-15 CN CN201720533896.9U patent/CN207083251U/en active Active
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107172739A (en) * | 2017-05-15 | 2017-09-15 | 杰华特微电子（张家港）有限公司 | PWM light adjusting circuits and light-dimming method and LED drive circuit |
| CN111107691A (en) * | 2018-10-25 | 2020-05-05 | 深圳市必易微电子有限公司 | Solid-state lighting device driving module, switching power supply circuit and dimming method |
| CN111107691B (en) * | 2018-10-25 | 2022-04-12 | 深圳市必易微电子股份有限公司 | Solid-state lighting device driving module, switching power supply circuit and dimming method |
| CN110139425A (en) * | 2019-04-19 | 2019-08-16 | 云南省交通科学研究院有限公司 | Vcehicular tunnel wisdom illumination control apparatus and system |
| CN110582143A (en) * | 2019-10-09 | 2019-12-17 | 杰华特微电子（杭州）有限公司 | LED dimming circuit, dimming method and LED control circuit |
| CN112804786A (en) * | 2019-11-13 | 2021-05-14 | 圣邦微电子（北京）股份有限公司 | LED drive circuit and control circuit thereof |
| CN112804786B (en) * | 2019-11-13 | 2022-10-14 | 圣邦微电子（北京）股份有限公司 | LED drive circuit and control circuit thereof |
| CN112235905A (en) * | 2020-10-23 | 2021-01-15 | 青岛易来智能科技股份有限公司 | Brightness adjusting circuit, lamp and LED brightness control method |
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