CN201984786U - LED (light-emitting diode) backlight current-sharing circuit adopting capacitors for balancing - Google Patents
LED (light-emitting diode) backlight current-sharing circuit adopting capacitors for balancing Download PDFInfo
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- CN201984786U CN201984786U CN2011200300440U CN201120030044U CN201984786U CN 201984786 U CN201984786 U CN 201984786U CN 2011200300440 U CN2011200300440 U CN 2011200300440U CN 201120030044 U CN201120030044 U CN 201120030044U CN 201984786 U CN201984786 U CN 201984786U
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Abstract
The utility model relates to an LED backlight current-sharing circuit adopting capacitors for balancing. The LED backlight current-sharing circuit comprises a half-bridge drive circuit, a transformer resonance circuit, a first balance rectifier circuit, two LED light bars and a detection feedback circuit which are sequentially connected, and the detection feedback circuit is connected with the half-bridge drive circuit and the two LED light bars. The LED backlight current-sharing circuit is used for driving an LED backlight of an LCD (liquid crystal display) panel, and has the characteristics of simple circuit, high efficiency, energy saving, low cost and the like.
Description
Technical field
The utility model relates to a kind of LED-backlit an ancient unit of weight current circuit that adopts capacitance balancing.
Background technology
It is more and more that LCD display and LCD TV adopt the ratio of LED-backlit at present, and each panel adopts a few string LED Light Bar, and every string LED Light Bar adopts a few LEDs diodes to be together in series.Because the I-E characteristic of LED diode presents indicial response, and there is bigger otherness between each monomer, so, if directly each LED Light Bar is together in parallel, the current imbalance that can cause each LED string can influence the brightness uniformity and the colour temperature of panel like this.
In order to address the above problem, the method that generally adopts is at present: with a DC-DC voltage boosting circuit boost in voltage is arrived certain value, give each LED Light Bar power supply, do an ancient unit of weight stream for every string LED Light Bar with current mirror again.The current mirror of forming by triode or MOSFET of promptly between the negative terminal of each LED Light Bar and ground, respectively connecting.Utilize an ancient unit of weight properties of flow of current mirror to guarantee the electric current unanimity of every string LED Light Bar.Adopt this scheme to exist following shortcoming, at first current mirror an ancient unit of weight current circuit can produce extra power consumption, lowers efficiency, and next increases current mirroring circuit, has increased cost.
Summary of the invention
In view of this, the purpose of this utility model provides a kind of LED-backlit an ancient unit of weight current circuit that adopts capacitance balancing.
LED-backlit an ancient unit of weight current circuit of employing capacitance balancing of the present utility model, comprise half-bridge drive circuit, transformer resonance circuit, the first balance rectification circuit, the two LED lamp strings that connect successively and be connected in described half-bridge drive circuit and the detection feedback circuit of LED lamp string, it is characterized in that, the described first balance rectification circuit comprises: one first balancing capacitance, its first end are exported first end with the transformer secondary output of described transformer resonance circuit and are connected; One second balancing capacitance, its first end are exported second end with the transformer secondary output of described transformer resonance circuit and are connected; One first diode, its negative pole is connected plus earth with second end of described first balancing capacitance, the positive pole of one the 3rd diode; One second diode, its negative pole is connected minus earth with second end of described second balancing capacitance, the positive pole of one the 4th diode; One first filter capacitor, its positive pole is connected minus earth with the negative pole of described the 3rd diode and the input end of one the one LED lamp string; And one second filter capacitor, it is anodal to be connected minus earth with the negative pole of described the 4th diode and the input end of one the 2nd LED lamp string.
In the utility model one embodiment, described half-bridge drive circuit comprises: first switching tube and second switch pipe; Described transformer resonance circuit comprises a resonant inductance, a transformer and an isolated DC electric capacity; First end of described resonant inductance is connected with the drain electrode of the source electrode of first switching tube and second switch pipe, and second end of described resonant inductance is connected elementary second end of described transformer through this isolated DC capacity earth with elementary first end of described transformer.
In the utility model one embodiment, further comprise second balance rectification circuit that is connected to the transformer resonance circuit and the 3rd, the 4th LED lamp string that is connected with this second balance rectification circuit output end.
In the utility model one embodiment, further comprise the 3rd balance rectification circuit that is connected to the transformer resonance circuit and the 5th, the 6th LED lamp string that is connected with the 3rd balance rectification circuit output end.
The utlity model has following advantage:
When (1) constant current is worked, having the LED Light Bar of voltage differences, can be the resistance that resistance does not wait with each LED Light Bar equivalence.
(2) each and capacitances in series that waits capacity of every string LED Light Bar driven by a unified alternate current-changing source then.Because the voltage delay electric current 90 of electric capacity degree, so that the voltage on voltage on each LED Light Bar and the electric capacity that is in series with it carries out is vector superposed, the voltage after this stack is that the voltage of drive source all equates.Like this, as long as the appearance value of control capacittance and the frequency of drive current just can limit the current imbalance that is caused by each LED Light Bar equivalent resistance difference within the acceptable range.
(3) will be multiplexed with the resonant capacitance of series resonance power supply with the current balance type electric capacity that LED Light Bar is in series.
(4) can utilize the leakage inductance of transformer to be used as the resonant inductance of series resonance power supply, also can add an inductance and be used as resonant inductance.
(5) because and the electric capacity that is in series of each LED Light Bar itself have the characteristic of an ancient unit of weight stream, so, just can reach needed electric current as long as get a string arbitrarily electric current as feedback.
Description of drawings
Fig. 1 is a schematic block circuit diagram of the present utility model.
Fig. 2 is the utility model embodiment 6 string LED-backlit driving circuit synoptic diagram.
Fig. 3 is the circuit diagram that the utility model balance rectification circuit drives two string LED lamps.
Fig. 4 is the circuit connection diagram that Fig. 3 two string LED lamp equivalences become two resistance.
Fig. 5 is the circuit equivalent figure under the positive and negative semiperiod state of Fig. 3 transformer output current.
Fig. 6 is the schematic equivalent circuit that Fig. 5 simplifies.
Fig. 7 is the equivalent schematic of 6 string LED-backlit driving circuits.
Fig. 8 is the half bridge series resonance schematic equivalent circuit.
That Fig. 9 is that LED Light Bar equivalent resistance is respectively is minimum, maximum, during the normality value LED Light Bar working current to the gain trace figure of input voltage.
Embodiment
Below in conjunction with drawings and Examples the utility model is described further.
As shown in Figure 1, the utility model provides a kind of LED-backlit an ancient unit of weight current circuit that adopts capacitance balancing, comprise half-bridge drive circuit, transformer resonance circuit, the first balance rectification circuit, the two LED lamp strings that connect successively and be connected in described half-bridge drive circuit and the detection feedback circuit of LED lamp string, it is characterized in that, the described first balance rectification circuit comprises: one first balancing capacitance C1, and its first end is connected with T901 level output of transformer first end of described transformer resonance circuit; One second balancing capacitance C2, its first end is connected with T901 level output of transformer second end of described transformer resonance circuit; One first diode D1, its negative pole is connected plus earth with second end of the described first balancing capacitance C1, the positive pole of one the 3rd diode D3; One second diode D2, its negative pole is connected plus earth with second end of the described second balancing capacitance C2, the positive pole of one the 4th diode D4; One first filter capacitor C3, its positive pole is connected minus earth with the negative pole of described the 3rd diode D3 and the input end of one the one LED lamp string; And one second filter capacitor C4, it is anodal to be connected minus earth with the negative pole of described the 4th diode D4 and the input end of one the 2nd LED lamp string.
See also Fig. 2, Fig. 2 is the utility model embodiment 6 string LED-backlit driving circuit synoptic diagram, is a unit with two string LED Light Bar, and 6 LED lamp strings can be divided into three unit in the diagram, and their circuit theory diagrams are the same.So LED string number can be expanded or reduce in couples, only needs and connect corresponding balance rectification circuit.The elementary employing half-bridge resonance driving circuit of the utility model transformer T901, switching tube Q919, Q920 are the half-bridge resonance switching tubes; L911 is a resonant inductance, also can be made up of the leakage inductance of transformer T901; Transformer T901 can regard an impedance transformer as, transforms to secondary load equivalent elementary; C928 plays the effect of isolated DC, and and the load equivalent capacitances in series after as the resonant capacitance of transducer.
Here we are with the string of two LED in the circuit theory diagrams, i.e. LED_string_3, and the principle explanation is done in the driving of LED_string_4, specifically as shown in Figure 3.Because secondary two winding (winding 10-11/12 of transformer T901; Winding 9-7/8), its 7/8 end and 10 ends are ends of the same name, so be anti-phase characteristic at 11/12 end of T901 level and the voltage on 7/8 end; 9,10 ends link to each other, and are the virtual ground state, and promptly current potential equals zero near the mid point of two windings of contacting mutually of T901 level of transformer, is equivalent to ground connection.
Please refer to Fig. 4, Fig. 4 is the circuit connection diagram that Fig. 3 two string LED lamp equivalences become two resistance, LED Light Bar can equivalence be an ohmic load when operate as normal, and resistance is that LED Light Bar both end voltage is divided by the working current that flows through LED Light Bar.Below in order to explain orally conveniently, suppose that the equiva lent impedance of each LED Light Bar equates, be expressed as R_DC_string.
The utility model circuit is owing to adopt the half bridge series resonance circuit structure, so T901 level output current is sinusoidal wave, the electric current of establishing the terminal 11/12 of the transformer T901 that flows through is
, then meanwhile, the electric current of the terminal 7/8 of the T901 that flows through is
During positive half period, D933 ends, the D943 conducting, and 921 chargings reach and power to load LED Light Bar3 to capacitor C; The D936 conducting, D925 ends, and capacitor C 945 is given load LED Light Bar4 power supply.
During negative half-cycle, the D933 conducting, D943 ends, and capacitor C 921 is given load LED Light Bar3 power supply; D936 ends, and the D925 conducting is to capacitor C 945 chargings and to load LED Light Bar4 power supply.
Because
The time,
The working current of LED Light Bar3 so flow through:
The current effective value of D943 of flowing through is:
If the equivalent resistance that eyes right into from D933 is R_AC_3, then:
So:
Semiperiod in addition, the electric current D925 that flows through uses with quadrat method and can obtain identical equivalent resistance.So its equivalent electrical circuit as shown in Figure 5.The circuit of positive and negative semiperiod in Fig. 5 circuit is further just simplified as shown in Figure 6.
If flowing through the effective value of the electric current of R_AC_string_3_4 is I1_rms; The equiva lent impedance of LED Light Bar equates to be R_DC_string that its working current is Iop.Then:
Equally according to said method, can abbreviation go out the equivalent electrical circuit of other 4 string LED Light Bar.As shown in Figure 7.Fig. 7 is the equivalent schematic of 6 string LED-backlit driving circuits among Fig. 2.If the number of secondary turns of transformer T901 is N divided by the ratio of primary turns, C952=C953=C935=C941=C955=C958=Cb; The equiva lent impedance of 6 string LED Light Bar equates to be R_AC_string.Then:
L911 is the resonant inductance of half bridge series resonance circuit in the diagram; C_balance_eff and C928 series connection are as the resonant capacitance of half-bridge resonance circuit; R_string_eff is load.
Shown in Figure 8 is in the half bridge series resonance equivalent electrical circuit, and the electric current of supposing to flow through equivalent load R_string_eff is I_eff, supposes that the half-bridge supply voltage is V_B.Then:
The first harmonic of the square wave of the D utmost point of Q920 is:
；
The electric current that flows through equivalent load R_string_eff is:
；
Resonance frequency is:
Quality factor is:
The total impedance of resonant tank is Z:
So the working current of LED Light Bar to the transport function of input voltage is:
LED Light Bar working current is to the gain trace figure of input voltage when please refer to Fig. 9 and be LED Light Bar equivalent resistance and being respectively minimum, maximum, normality value.
Wherein: R_string_eff_min: be meant that LED Light Bar equivalent resistance hour is transformed into the equivalent resistance of primary;
R_string_eff_max: be meant that LED Light Bar equivalent resistance is transformed into the equivalent resistance of primary when maximum;
R_string_eff_normal: be meant that LED Light Bar equivalent resistance is transformed into the equivalent resistance of primary when being the normality value; So the frequency of operation of control half bridge series resonance just can change gain, regulates the working current of LED Light Bar.As long as the electric current of getting a string or a few arbitrarily string LED Light Bar just can reach the working current of stablizing each LED Light Bar as feedback, reach the purpose of an ancient unit of weight stream constant current.
The above only is preferred embodiment of the present utility model, and all equalizations of being done according to the utility model claim change and modify, and all should belong to covering scope of the present utility model.
Claims (4)
1. LED-backlit an ancient unit of weight current circuit that adopts capacitance balancing, comprise half-bridge drive circuit, transformer resonance circuit, the first balance rectification circuit, the two LED lamp strings that connect successively and be connected in described half-bridge drive circuit and the detection feedback circuit of LED lamp string, it is characterized in that the described first balance rectification circuit comprises:
One first balancing capacitance, its first end are exported first end with the transformer secondary output of described transformer resonance circuit and are connected;
One second balancing capacitance, its first end are exported second end with the transformer secondary output of described transformer resonance circuit and are connected;
One first diode, its negative pole is connected plus earth with second end of described first balancing capacitance, the positive pole of one the 3rd diode;
One second diode, its negative pole is connected plus earth with second end of described second balancing capacitance, the positive pole of one the 4th diode;
One first filter capacitor, its positive pole is connected minus earth with the negative pole of described the 3rd diode and the input end of one the one LED lamp string; And
One second filter capacitor, its positive pole is connected minus earth with the negative pole of described the 4th diode and the input end of one the 2nd LED lamp string.
2. LED-backlit an ancient unit of weight current circuit of employing capacitance balancing according to claim 1, it is characterized in that: described half-bridge drive circuit comprises: first switching tube and second switch pipe; Described transformer resonance circuit comprises a resonant inductance, a transformer and an isolated DC electric capacity; First end of described resonant inductance is connected with the drain electrode of the source electrode of first switching tube and second switch pipe, and second end of described resonant inductance is connected elementary second end of described transformer through this isolated DC capacity earth with elementary first end of described transformer.
3. LED-backlit an ancient unit of weight current circuit of employing capacitance balancing according to claim 1 and 2 is characterized in that: further comprise second balance rectification circuit that is connected to the transformer resonance circuit and the 3rd, the 4th LED lamp string that is connected with this second balance rectification circuit output end.
4. LED-backlit an ancient unit of weight current circuit of employing capacitance balancing according to claim 3 is characterized in that: further comprise the 3rd balance rectification circuit that is connected to the transformer resonance circuit and the 5th, the 6th LED lamp string that is connected with the 3rd balance rectification circuit output end.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011200300440U CN201984786U (en) | 2011-01-28 | 2011-01-28 | LED (light-emitting diode) backlight current-sharing circuit adopting capacitors for balancing |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2011200300440U CN201984786U (en) | 2011-01-28 | 2011-01-28 | LED (light-emitting diode) backlight current-sharing circuit adopting capacitors for balancing |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102097060A (en) * | 2011-01-28 | 2011-06-15 | 福建捷联电子有限公司 | LED backlight current equalizing circuit using capacitance balance |
| CN106205505A (en) * | 2016-08-23 | 2016-12-07 | 深圳市华星光电技术有限公司 | Backlight drive circuit |
| CN113179568A (en) * | 2021-04-09 | 2021-07-27 | 深圳市立创普电源技术有限公司 | Multi-output constant-current control circuit and driving power supply |
-
2011
- 2011-01-28 CN CN2011200300440U patent/CN201984786U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102097060A (en) * | 2011-01-28 | 2011-06-15 | 福建捷联电子有限公司 | LED backlight current equalizing circuit using capacitance balance |
| CN106205505A (en) * | 2016-08-23 | 2016-12-07 | 深圳市华星光电技术有限公司 | Backlight drive circuit |
| CN106205505B (en) * | 2016-08-23 | 2018-09-04 | 深圳市华星光电技术有限公司 | Backlight drive circuit |
| CN113179568A (en) * | 2021-04-09 | 2021-07-27 | 深圳市立创普电源技术有限公司 | Multi-output constant-current control circuit and driving power supply |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20110921 Termination date: 20150128 |
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| EXPY | Termination of patent right or utility model |