CN203840595U - High-linearity large-dynamic light modulating circuit used for LED backlight source - Google Patents
High-linearity large-dynamic light modulating circuit used for LED backlight source Download PDFInfo
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- CN203840595U CN203840595U CN201420138742.6U CN201420138742U CN203840595U CN 203840595 U CN203840595 U CN 203840595U CN 201420138742 U CN201420138742 U CN 201420138742U CN 203840595 U CN203840595 U CN 203840595U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
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Abstract
The utility model discloses a high-linearity large-dynamic light modulating circuit used for an LED backlight source and relates to the field of electric circuits. According to the utility model, one end of a sixth resistor is connected with a PWM pulse control signal source; the other end of the sixth resistor and one end of a tenth resistor are connected with a base electrode of a fourth NPN transistor; one end of a seventh resistor and a collective electrode of the fourth NPN transistor are connected with a collective electrode of a fifth NPN transistor; a transmitting electrode of the fourth NPN transistor is connected with a base electrode of the fifth NPN transistor; the other end of the tenth resistor, a transmitting electrode of the fifth NPN transistor and one end of a second capacitor are in ground connection; the other end of the seventh resistor is connected with the negative electrode of the LED backlight source; and the positive electrode of the LED backlight source and the other end of the second capacitor are connected with a DC stabilized power supply V+. The high-linearity large-dynamic light modulating circuit provided by the utility model has characteristics of being simple in circuit, low in cost, stable in working state, excellent in linearity and large in dynamic range.
Description
Technical field
The utility model relates to electronic circuit field, relates in particular to a kind of high linear, large dynamic LED-backlit source light adjusting circuit.
Background technology
Low and middle-end vehicle audio generally adopts LCD display, because LCD display is a kind of passive luminescent device, so need backlight (generally adopting at present LED) to throw light on.Daytime, ambient light was strong, and for ensureing definition, LCD display needs higher backlight illumination; And a little less than night ambient light, dazzling for preventing, LCD display needs lower and adjustable backlight illumination.User requires more and more higher to the brightness value of vehicle audio LCD display under daytime environment, more and more lower to the requirement of LCD display minimum brightness value under night environment, so just needs to adopt high linear, LED-backlit source light adjusting circuit greatly dynamically.
Common LED-backlit source light adjusting circuit is as Fig. 1 and Fig. 2.In Fig. 1 and Fig. 2, for the DC amplification factor hFE(that avoids master control tubulation Q1, Q3 exists certain discreteness) Q1, Q3 operating state are impacted, and then affect peak value operating voltage and the brightness thereof in LED-backlit source, Q1, Q3 are operated in degree of depth saturation condition (saturation is not less than 10, Vce ≈ 0V) conventionally.Because Q1, Q3 are bipolar transistors, work in degree of depth saturation condition and flow through larger electric current simultaneously, switching characteristic variation, be in particular in: Q1, Q3 because base stage stored and need to extend a period of time compared with the reason of multi-charge and could end, also within each pwm signal cycle, Q3 ON time will be obviously longer than the time of pwm signal in high level.If now LED-backlit source needs super large scope, large dynamic light adjustment, in the time that minimum brightness need to be transferred in LED-backlit source, the duty ratio of pwm signal just need to be transferred to very low (sometimes may be low to below 0.5%), correspondingly Q1, the ON time of Q3 just needs very short, work as Q1, Q3 switching characteristic is poor to be enough to when even longer compared with the aforementioned time to conducting time expand, Q1, Q3 has just lost on-off action, the linearity variation of light modulation when concrete manifestation is exactly low-light level (brightness in LED-backlit source and the duty ratio of pwm control signal relation no longer in direct ratio), backlight minimum brightness is higher and cannot turn down (because the duty ratio of pwm signal may be low to approaching 0 again worse, do not continue to the space of lowering).
Three kinds of conventional ways that solve above-mentioned technical barrier are as follows:
One. increase R2, R4, make Q1, Q3 be operated in critical saturation condition, thereby improve its switching characteristic, the time that chopped pulse extends greatly.But because transistor DC amplification coefficient hFE exists larger discreteness, be difficult to guarantee Q1, Q3 conducting during so actual, be just operated in critical saturation condition (being likely operated in the even magnifying state of shallow saturation condition of different saturation depths), so just may additionally increase the difference of brightness between the individuality of LED-backlit source, or reduce the linearity and the dynamic range of the light modulation of LED-backlit source;
Two. make respectively Q1, Q3 into PMOS, nmos pass transistor; Do like this and may increase cost.If pwm signal amplitude is lower in addition, when the peak operation current in LED-backlit source is larger simultaneously, the nmos pass transistor of Fig. 2 circuit may enter saturation region (magnifying state), causes output impedance to become large, thereby additionally increases the difference of brightness between the individuality of LED-backlit source;
Three. respectively in the speed-up capacitor of R1, R4 two ends suitable capacity in parallel; Experiment finds that Fig. 1 does not have positive effect, and Fig. 2 has certain effect, but can cause the pwm pulse signal that outputs to LED-backlit source to occur overshoot and vibration, so likely can cause product electromagnetic radiation to exceed standard or disturb the normal work of other circuit;
Utility model content
The utility model is intended at least solve the technical problem existing in prior art, has proposed to special innovation a kind of high linearity, large dynamic LED-backlit source light adjusting circuit.To achieve these goals, the utility model changes Q3 into two discrete NPN transistor that connect by Darlington connection (being Q4 and the Q5 of Fig. 3 the inside) or a NPN Darlington transistor on Fig. 2 circuit base.Master control tubulation Q5 will work in critical saturation condition all the time like this, and irrelevant with its hFE, interlock circuit is shown in Fig. 3.
The utility model discloses a kind of high linear, large dynamic LED-backlit source light adjusting circuit, it is characterized in that, comprise the 6th resistance, the 7th resistance, the tenth resistance, the 4th NPN transistor, the 5th NPN transistor, the second electric capacity and LED-backlit source.Described the 6th resistance one end connects pwm pulse signal source, and described the 6th resistance other end and described the tenth resistance one end are connected respectively the base stage of described the 4th NPN transistor; Described the 7th resistance one end and the collector electrode of described the 4th NPN transistor are connected respectively the collector electrode of described the 5th NPN transistor; The emitter of described the 4th NPN transistor connects the base stage of described the 5th NPN transistor; The emitter of described the tenth resistance other end and described the 5th NPN transistor and described second electric capacity one end ground connection; Described the 7th resistance other end connects described LED-backlit source negative pole; Described LED-backlit source is anodal is connected D.C. regulated power supply V+ with the described second electric capacity other end.
Its beneficial effect is: low cost, stable, high linear, dynamic greatly.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the 4th NPN transistor, the 5th NPN transistor replace to a NPN Darlington transistor.
Its beneficial effect is: further simplify circuit, reduce costs simultaneously.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the 6th resistance is got 2.2K Ω～47K Ω, described the tenth resistance is got 3～5 times of described the 6th resistance.
Its beneficial effect is: prevent that the load of pwm control signal source is overweight, can be stably while ensureing the 5th master control transistor turns simultaneously in the time that critical saturation condition and pwm control signal are low level the 4th and the 5th NPN transistor can end completely, thereby avoid additionally increasing luminance difference between the individuality of LED-backlit source and further improve the linearity and the dynamic range thereof of this LED-backlit source light adjusting circuit.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the second electric capacity is got 1uF-100uF.
Its beneficial effect is: the electromagnetic radiation of the voltage of filtering circuit power supply clutter, stabilized power supply and reduction light adjusting circuit.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the second electric capacity is arranged on anodal port, described LED-backlit source.
Its beneficial effect is: dwindle the loop area in high-frequency pulse current loop, LED-backlit source, better the electromagnetic radiation of the voltage of filter out power clutter, stabilized power supply and reduction light adjusting circuit.
In sum, owing to having adopted technique scheme, the beneficial effects of the utility model are: circuit is simple, cost is low, stable working state, and simultaneously linearity excellence, dynamic range are large.
Brief description of the drawings
Above-mentioned and/or additional aspect of the present utility model and advantage accompanying drawing below combination is understood becoming the description of embodiment obviously and easily, wherein:
Fig. 1 is the schematic diagram of LED-backlit source light adjusting circuit in prior art;
Fig. 2 is the schematic diagram of LED-backlit source light adjusting circuit in prior art;
Fig. 3 is the schematic diagram of high linear, the large dynamic LED-backlit of the utility model source light adjusting circuit.
Embodiment
Describe embodiment of the present utility model below in detail, the example of described embodiment is shown in the drawings, and wherein same or similar label represents same or similar element or has the element of identical or similar functions from start to finish.Be exemplary below by the embodiment being described with reference to the drawings, only for explaining the utility model, and can not be interpreted as restriction of the present utility model.
In description of the present utility model, it will be appreciated that, term " longitudinally ", " laterally ", " on ", D score, " front ", " afterwards ", " left side ", " right side ", " vertically ", " level ", " top ", " end " " interior ", orientation or the position relationship of instructions such as " outward " are based on orientation shown in the drawings or position relationship, only the utility model and simplified characterization for convenience of description, instead of device or the element of instruction or hint indication must have specific orientation, with specific orientation structure and operation, therefore can not be interpreted as restriction of the present utility model.
In description of the present utility model, unless otherwise prescribed and limit, it should be noted that, term " installation ", " being connected ", " connection ", " connection " should be interpreted broadly, for example, can be mechanical connection or electrical connection, also can be the connection of two element internals, can be to be directly connected, and also can indirectly be connected by intermediary, for the ordinary skill in the art, can understand as the case may be the concrete meaning of above-mentioned term.
This LED-backlit source light adjusting circuit only needs to use two discrete NPN transistor that connect by Darlington connection or a NPN Darlington transistor, three conventional, electric-resistance and a common little electric capacity just can realize high linear, large dynamic LED-backlit source dimming function, have that circuit is simple, cost is low, stable working state, while linearity excellence, the feature that dynamic range is large.
See accompanying drawing 3: the utility model discloses a kind of high linear, large dynamic LED-backlit source light adjusting circuit, it is characterized in that, comprise the 6th resistance, the 7th resistance, the tenth resistance, the 4th NPN transistor, the 5th NPN transistor, the second electric capacity and LED-backlit source.Described the 6th resistance one end connects pwm pulse signal source, and described the 6th resistance other end and described the tenth resistance one end are connected respectively the base stage of described the 4th NPN transistor; Described the 7th resistance one end and the collector electrode of described the 4th NPN transistor are connected respectively the collector electrode of described the 5th NPN transistor; The emitter of described the 4th NPN transistor connects the base stage of described the 5th NPN transistor; The emitter of described the tenth resistance other end and described the 5th NPN transistor and described second electric capacity one end ground connection; Described the 7th resistance other end connects described LED-backlit source negative pole; Described LED-backlit source is anodal is connected D.C. regulated power supply V+ with the described second electric capacity other end.
Its beneficial effect is: low cost, stable, high linear, dynamic greatly.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the 4th NPN transistor, the 5th NPN transistor replace to a NPN Darlington transistor.
Its beneficial effect is: further simplify circuit, reduce costs simultaneously.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the 6th resistance is got 2.2K Ω～47K Ω, described the tenth resistance is got 3～5 times of described the 6th resistance.
Its beneficial effect is: prevent that the load of pwm control signal source is overweight, can be stably while ensureing the 5th master control transistor turns simultaneously in the time that critical saturation condition and pwm control signal are low level the 4th and the 5th NPN transistor can end completely, thereby avoid additionally increasing luminance difference between the individuality of LED-backlit source and further improve the linearity and the dynamic range thereof of this LED-backlit source light adjusting circuit.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the second electric capacity is got 1uF-100uF.
Its beneficial effect is: the electromagnetic radiation of the voltage of filtering circuit power supply clutter, stabilized power supply and reduction light adjusting circuit.
Described high linearity, large dynamic LED-backlit source light adjusting circuit, preferred, comprising: described the second electric capacity is arranged on anodal port, described LED-backlit source.
Its beneficial effect is: dwindle the loop area in high-frequency pulse current loop, LED-backlit source, better the electromagnetic radiation of the voltage of filter out power clutter, stabilized power supply and reduction light adjusting circuit.
The operation principle of this LED-backlit source light adjusting circuit is described as follows:
See Fig. 3, by choosing resistance R 6 and the R7 of suitable resistance, the saturation during by Q4 transistor turns is controlled between 5～100; Pwm signal Q4 base stage voltage to earth when the low level is controlled at below 1V simultaneously.Because when Q4 conducting in degree of depth saturation condition, so now Vce4 ≈ 0V, due to Vcb5=Vce4, so Vcb5 ≈ 0V, so no matter the DC amplification factor hFE5 of Q5 is how many, when Q5 conducting all by steady operation in critical saturation condition (unsaturation type switch), therefore export the time that pwm pulse signal is extended very short; In the time that pwm control signal is low level, Q4 and Q5 transistor also can end completely.Even if input so the very pwm signal of low duty ratio, this LED-backlit source light adjusting circuit also can be in close proximity to desirable linear response.Stable working state during again due to Q5 conducting, Vce5=Vcb5+Vbe5 ≈ Vbe5, and emitter junction pressure drop Vbe difference very little (silicone tube is about 0.6～0.7V) between same model transistor individuality, so the transistorized individual difference of Q4, Q5 can cause additional effect to the low brightness values in LED-backlit source hardly.Because Fig. 3 circuit has increased buffer transistor Q4, the load current in pwm control signal source is compared former Fig. 2 and is greatly reduced in addition.
The beneficial effects of the utility model are: circuit is simple, cost is low, stable working state, and simultaneously linearity excellence, dynamic range are large.
In the description of this specification, the description of reference term " a kind of preferred implementation ", " embodiment ", " some embodiment ", " example ", " concrete example " or " some examples " etc. means to be contained at least one embodiment of the present utility model or example in conjunction with specific features, structure, material or the feature of this embodiment or example description.In this manual, the schematic statement of above-mentioned term is not necessarily referred to identical embodiment or example.And specific features, structure, material or the feature of description can be with suitable mode combination in any one or more embodiment or example.
Although illustrated and described embodiment of the present utility model, those having ordinary skill in the art will appreciate that: in the situation that not departing from principle of the present utility model and aim, can carry out multiple variation, amendment, replacement and modification to these embodiment, scope of the present utility model is limited by claim and equivalent thereof.
Claims (5)
1. high linearity, a large dynamic LED backlight light-adjusting circuit, is characterized in that, comprises the 6th resistance, the 7th resistance, the tenth resistance, the 4th NPN transistor, the 5th NPN transistor, the second electric capacity and LED-backlit source; Described the 6th resistance one end connects pwm pulse signal source, and described the 6th resistance other end and described the tenth resistance one end are connected respectively the base stage of described the 4th NPN transistor; Described the 7th resistance one end and the collector electrode of described the 4th NPN transistor are connected respectively the collector electrode of described the 5th NPN transistor; The emitter of described the 4th NPN transistor connects the base stage of described the 5th NPN transistor; The emitter of described the tenth resistance other end and described the 5th NPN transistor and described second electric capacity one end ground connection; Described the 7th resistance other end connects described LED-backlit source negative pole; Described LED-backlit source is anodal is connected D.C. regulated power supply V+ with the described second electric capacity other end.
2. high linear, large dynamic LED backlight light-adjusting circuit according to claim 1, is characterized in that, comprising: described the 4th NPN transistor, the 5th NPN transistor replace to a NPN Darlington transistor.
3. high linear, large dynamic LED backlight light-adjusting circuit according to claim 1, is characterized in that, comprising: described the 6th resistance is got 2.2K Ω～47K Ω, described the tenth resistance is got 3～5 times of described the 6th resistance.
4. high linear, large dynamic LED backlight light-adjusting circuit according to claim 1, is characterized in that, comprising: described the second electric capacity is got 1uF-100uF.
5. high linear, large dynamic LED backlight light-adjusting circuit according to claim 1, is characterized in that, comprising: described the second electric capacity is arranged on anodal port, described LED-backlit source.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420138742.6U CN203840595U (en) | 2014-03-26 | 2014-03-26 | High-linearity large-dynamic light modulating circuit used for LED backlight source |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420138742.6U CN203840595U (en) | 2014-03-26 | 2014-03-26 | High-linearity large-dynamic light modulating circuit used for LED backlight source |
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| CN203840595U true CN203840595U (en) | 2014-09-17 |
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| CN201420138742.6U Expired - Lifetime CN203840595U (en) | 2014-03-26 | 2014-03-26 | High-linearity large-dynamic light modulating circuit used for LED backlight source |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111081192A (en) * | 2019-12-05 | 2020-04-28 | 芜湖宏景电子股份有限公司 | Two-stage brightness control circuit for backlight lamp of vehicle-mounted multimedia display screen |
| CN111237228A (en) * | 2018-11-28 | 2020-06-05 | 明纬(广州)电子有限公司 | Control circuit with speed regulation function |
-
2014
- 2014-03-26 CN CN201420138742.6U patent/CN203840595U/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111237228A (en) * | 2018-11-28 | 2020-06-05 | 明纬(广州)电子有限公司 | Control circuit with speed regulation function |
| CN111237228B (en) * | 2018-11-28 | 2022-06-07 | 明纬(广州)电子有限公司 | Control circuit with speed regulation function |
| CN111081192A (en) * | 2019-12-05 | 2020-04-28 | 芜湖宏景电子股份有限公司 | Two-stage brightness control circuit for backlight lamp of vehicle-mounted multimedia display screen |
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Granted publication date: 20140917 |