CN208739452U - A kind of backlight circuit and combination instrument - Google Patents
A kind of backlight circuit and combination instrument Download PDFInfo
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- CN208739452U CN208739452U CN201820864585.5U CN201820864585U CN208739452U CN 208739452 U CN208739452 U CN 208739452U CN 201820864585 U CN201820864585 U CN 201820864585U CN 208739452 U CN208739452 U CN 208739452U
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- circuit
- backlight
- current
- bipolar junction
- junction transistor
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Abstract
The utility model provides a kind of backlight circuit, including booster circuit and one or more backlight branches, and each backlight branch includes that one or more back lights and back light are concatenated with lamp resistance, and backlight branch further includes constant-current drive circuit.Backlight circuit and combination instrument provided by the utility model can adapt to the Width funtion input of combination instrument, keep the brightness stability of display screen, improve the experience of driver and passenger；By setting the output mode of booster circuit, reduces with lamp resistance R1 power consumption, and the device to generate heat on distributed circuit plate, improve the reliability of backlight circuit.
Description
Technical field
The utility model relates to automotive fields, and in particular to a kind of backlight circuit and combination instrument.
Background technique
Combination instrument all includes usually display screen in vehicle, and Fig. 1 shows the backlight circuit of display screen, including backlight
Light source led 1, LED2, with lamp resistance R1 and for the diode D of protection.
Backlight circuit is generally directly powered using on-vehicle battery, and the voltage V of on-vehicle battery changes at any time, combination instrument
Input requirements for on-vehicle battery are: the pressure drop of 5V-19V, LED1+LED2 are 6.5V, then combination instrument can only operate in electricity
Cell voltage is greater than 6.5V, is unable to satisfy the input voltage requirement of combination instrument.
If increasing diode D, pressure drop 1V, then combination instrument can only operate in cell voltage greater than 7.5V.
In addition, will cause the brightness change of display screen when on-vehicle battery voltage Vbat variation, thus it will affect and drive people
The riding experience of member.
Solving the problems, such as a kind of mode for the input voltage requirement for being unable to satisfy combination instrument is: in diode D and with lamp electricity
It hinders and increases booster circuit B between R1, as shown in Fig. 2, by boosting, so that combination instrument can satisfy the input electricity of combination instrument
Pressure request.
Booster circuit output voltage may be only configured to the ceiling voltage more than or equal to on-vehicle battery, such as 19V, match lamp resistance
R1 power consumption is larger, for example, rated current be 80mA when, power be (19-6.5) * 80=1000mW, as long as and backlight circuit work,
Always it is such power consumption, thus will cause that backlight circuit plate local pyrexia is more serious, to influences the reliable of backlight circuit
Property.
Summary of the invention
Aiming at the problems existing in the prior art, problem to be solved in the utility model is to provide a kind of backlight circuit, energy
Enough under combination instrument Width funtion input condition (5V-19V), the brightness constancy of display screen is kept, the experience of driver and passenger is improved.
The utility model provides a kind of backlight circuit, including booster circuit and one or more backlight branches, each back
Light branch includes that one or more back lights and back light are concatenated with lamp resistance, and backlight branch further includes constant current driving
Circuit.
Further, the driving current of constant-current drive circuit is the rated current of backlight branch.
Further, constant-current drive circuit is bipolar transistor driving circuit.
Further, bipolar transistor driving circuit include the first bipolar junction transistor, the second bipolar junction transistor with
The collector of current-limiting resistance, the first bipolar junction transistor is connect with the first end of backlight branch, the hair of the first bipolar junction transistor
Emitter-base bandgap grading is grounded by current-limiting resistance.
Further, the resistance value of current-limiting resistance is by the voltage and back between the base stage and emitter of the second bipolar junction transistor
The rated current of light branch determines.
Further, the base stage of the first bipolar junction transistor is connect with the collector of the second bipolar junction transistor, and first pair
The emitter of bipolar transistor is connect with the base stage of the second bipolar junction transistor, the emitter ground connection of the second bipolar junction transistor.
Further, the supply voltage of backlight circuit is less than or equal to the first setting voltage, the output voltage of booster circuit
For the first setting voltage.
Further, the supply voltage of backlight circuit is greater than the first setting voltage, and the output voltage of booster circuit follows back
The supply voltage of optical circuit.
Further, the return difference of the output voltage of booster circuit is less than or equal to 0.6V.
Further, backlight circuit further includes diode.
The utility model also provides a kind of combination instrument, including display screen, and the backlight circuit of display screen is above-mentioned backlight
Circuit.
Compared with prior art, backlight circuit and combination instrument provided by the utility model, have the advantages that liter
Volt circuit adapts to the Width funtion input of combination instrument, keeps the brightness stability of display screen, improves the experience of driver and passenger；By setting
The output mode for determining booster circuit is reduced with lamp resistance R1 power consumption, and the device to generate heat on distributed circuit plate, improves backlight electricity
The reliability on road.
Detailed description of the invention
Fig. 1 is the schematic diagram of display backlight circuit in the prior art；
Fig. 2 is the schematic diagram of the display backlight circuit with booster circuit in the prior art；
Fig. 3 is the schematic diagram of the backlight circuit (including a backlight branch) of one embodiment of the utility model；
Fig. 4 is the schematic diagram for controlling the output voltage of booster circuit；
Fig. 5 is the schematic diagram of the backlight circuit (including multiple backlight branches) of another embodiment of the utility model.
Specific embodiment
As shown in figure 3, the backlight circuit of one embodiment of the utility model, the display for combination instrument in vehicle
Shield, in the present embodiment, display screen is 3.5 cun of TFT display screens, rated current 80mA.
Backlight circuit includes booster circuit B and a backlight branch, and backlight branch includes one or more back lights
LED1, LED2 and back light are concatenated with lamp resistance R, and backlight branch further includes constant-current drive circuit.
The driving current of constant-current drive circuit is the rated current of backlight branch.
Constant-current drive circuit is used, back light LED1, LED2 are worked under constant electric current, to guarantee
Back light LED1, LED2 brightness stability, improves the experience of driver and passenger.
In the present embodiment, constant-current drive circuit is bipolar transistor driving circuit, including the first bipolar junction transistor T1,
The collector of second bipolar junction transistor T2 and current-limiting resistance R2, the first bipolar junction transistor T1 and the first end of backlight branch connect
It connects, the emitter of the first bipolar junction transistor T1 is grounded by current-limiting resistance R2.
The base stage of first bipolar junction transistor T1 is connect with the collector of the second bipolar junction transistor T2, the first ambipolar crystalline substance
The emitter of body pipe T1 is connect with the base stage of the second bipolar junction transistor T2, the emitter ground connection of the second bipolar junction transistor T2.
The resistance value of current-limiting resistance R2 is by the voltage and backlight circuit between the base stage and emitter of the second bipolar junction transistor
Rated current determine:
Wherein, VBE_T2 is pressure drop between the base stage of the second bipolar junction transistor T2 and emitter (BE), usually takes 0.65V；I
For the rated current of backlight branch.
Constant-current drive circuit can also be using special driving chip or current mirror circuit etc..
At this point, matching the power consumption P of lamp resistance R1R1Are as follows:
PR1=(19V-6.5V-VCE_T1)*I。
In order to improve the reliability of backlight circuit, heating device on distributed circuit plate is needed.
In the present embodiment, the supply voltage Vbat of backlight circuit is less than or equal to the first setting voltage, booster circuit it is defeated
Voltage Vout is the first setting voltage out, such as first sets voltage as 10V, and the supply voltage Vbat of backlight circuit is less than or waits
In 10V, the output voltage Vout of booster circuit is 10V, to meet the input voltage requirement of combination instrument.
Voltage with lamp resistance R1 are as follows:
VR1=10V-6.5V=3.5V；
PR1=3.5*I=3.5*80=280mW
During backlight circuit work, due to using constant-current drive circuit, current Iconst, therefore match lamp resistance R1 power consumption
It is constant.
The supply voltage Vbat of backlight circuit is greater than the first setting voltage, and the output voltage of booster circuit follows backlight circuit
Supply voltage Vbat, i.e. the supply voltage Vbat of backlight circuit is greater than 10V, and the output voltage Vout of booster circuit follows backlight
The supply voltage Vbat of circuit.
Specifically, the voltage V of back light LED1, LED2LEDAre as follows:
VLED=VLED1+VLED2=6.5V；
Under rated current, the voltage V of back light LED1, LED2LEDWith the voltage V for matching lamp resistanceR1The sum of set for first
Constant voltage (10V), the part that supply voltage Vbat is higher than the first setting voltage can be fallen on the first bipolar junction transistor T1, work as electricity
When source voltage reaches maximum value 19V:
VCE_T1=19-10=9V；
PT1=9*I=9*80=720mW；
Wherein, VCE_T1The part for being above the first setting voltage can fall in the collector and hair of the first bipolar junction transistor T1
Voltage between emitter-base bandgap grading, PT1For the power consumption of the first bipolar junction transistor T1, it is up to 720mW.
From data above as can be seen that only when supply voltage reaches maximum value 19V, the power consumption P with lamp resistance R1R1
With the power consumption P of the first bipolar junction transistor T1T1The sum of be equal to 1000mW, and when supply voltage be less than 19V when, due to PT1It is less than
720mW, total power consumption are less than 1000mW.Therefore the power of backlight circuit had not only been reduced in this manner, but also dispersed electricity
Heating device on the plate of road improves the reliability of backlight circuit.
In addition, backlight flicker is caused in order to avoid booster circuit output Vout sets frequent switching near voltage first,
Such as setting return difference is less than or equal to 0.6V, when output voltage Vout is higher than 10.6V, the output voltage Vout of booster circuit is followed
The supply voltage Vbat of backlight circuit；When output voltage Vout is lower than 10V, output voltage Vout is 10V.
Specifically, it is realized using circuit as shown in Figure 4, is the booster circuit of standard, including control chip in dotted line frame
BC, energy storage inductor L, diode D2 and divider resistance R11, R12 etc..
Booster circuit sets 10V for the output voltage Vout of booster circuit by the resistance value of setting resistance R11, R12；
Controller acquires the output voltage Vout of booster circuit by the tie point of divider resistance R21 and R22, if be higher than 10.6V,
The control terminal EN of the control chip BC of booster circuit is closed, i.e., booster circuit does not work, and output voltage Vout follows backlight circuit
Supply voltage Vbat；And if the control terminal EN of the control chip BC of booster circuit is opened when being lower than 10V, i.e. booster circuit
Work, output voltage Vout are 10V.
As shown in figure 5, backlight circuit includes booster circuit B and multiple backlight branches, backlight branch includes one or more
A back light LED1, LED2 and back light are concatenated with lamp resistance R, and backlight branch further includes constant-current drive circuit.
The control terminal P1 of each constant-current drive circuit ..., PN, can come from the port of different controllers, can also come
From the port of the same controller, determine as the case may be.
Although the utility model has been disclosed in the preferred embodiments as above, the utility model is not limited to this.Any
Field technical staff, made various changes and modification, should all be included in this without departing from the spirit and scope of the utility model
In the protection scope of utility model, therefore the protection scope of the utility model should be defined by the scope defined by the claims..
Claims (10)
1. a kind of backlight circuit, including booster circuit and one or more backlight branches, backlight branch include one or more
Back light and back light are concatenated with lamp resistance, which is characterized in that backlight branch further includes constant-current drive circuit.
2. backlight circuit as described in claim 1, which is characterized in that the driving current of constant-current drive circuit is backlight branch
Rated current.
3. backlight circuit as claimed in claim 2, which is characterized in that constant-current circuit is bipolar transistor driving circuit.
4. backlight circuit as claimed in claim 3, which is characterized in that bipolar transistor driving circuit includes first ambipolar
Transistor, the second bipolar junction transistor and current-limiting resistance, the collector of the first bipolar junction transistor and the first end of backlight branch
Connection, the emitter of the first bipolar junction transistor are grounded by current-limiting resistance, the base stage of the first bipolar junction transistor and second pair
The collector of bipolar transistor connects, and the emitter of the first bipolar junction transistor is connect with the base stage of the second bipolar junction transistor,
The emitter of second bipolar junction transistor is grounded.
5. backlight circuit as claimed in claim 4, which is characterized in that the resistance value of current-limiting resistance is by the second bipolar junction transistor
The rated current of voltage and backlight branch between base stage and emitter determines.
6. backlight circuit as claimed in claim 2, which is characterized in that the supply voltage of backlight circuit is less than or equal to first and sets
Constant voltage, the output voltage of booster circuit are the first setting voltage.
7. backlight circuit as claimed in claim 2, which is characterized in that the supply voltage of backlight circuit is greater than the first setting electricity
Pressure, the output voltage of booster circuit follow the supply voltage of backlight circuit.
8. backlight circuit as claimed in claim 4, which is characterized in that the return difference of the output voltage of booster circuit is less than or equal to
0.6V。
9. backlight circuit as described in claim 1, which is characterized in that backlight circuit further includes diode.
10. a kind of combination instrument, which is characterized in that including display screen, the backlight circuit of the display screen is appointed for claim 1-9
Backlight circuit described in one.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820864585.5U CN208739452U (en) | 2018-06-05 | 2018-06-05 | A kind of backlight circuit and combination instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820864585.5U CN208739452U (en) | 2018-06-05 | 2018-06-05 | A kind of backlight circuit and combination instrument |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN208739452U true CN208739452U (en) | 2019-04-12 |
Family
ID=66023448
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201820864585.5U Active CN208739452U (en) | 2018-06-05 | 2018-06-05 | A kind of backlight circuit and combination instrument |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN208739452U (en) |
-
2018
- 2018-06-05 CN CN201820864585.5U patent/CN208739452U/en active Active
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