CN203313488U - Backlight driving circuit and lamp bar light-adjusting unit - Google Patents
Backlight driving circuit and lamp bar light-adjusting unit Download PDFInfo
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- CN203313488U CN203313488U CN2013203147672U CN201320314767U CN203313488U CN 203313488 U CN203313488 U CN 203313488U CN 2013203147672 U CN2013203147672 U CN 2013203147672U CN 201320314767 U CN201320314767 U CN 201320314767U CN 203313488 U CN203313488 U CN 203313488U
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Abstract
The utility model discloses a backlight driving circuit and a lamp bar light-adjusting unit. The backlight driving circuit comprises at least a BOOST unit, an MCU signal processing unit and the lamp bar light-adjusting unit. The lamp bar light-adjusting unit is used for changing a work current of a lamp bar which is connected between a voltage output terminal of the BOOST unit and a current adjusting terminal of the lamp bar light-adjusting unit according to control signals, wherein the control signals are sent by the MCU signal processing unit, and are received by a control signal input terminal. The backlight driving circuit also comprises a first feedback circuit detecting an output voltage of the BOOST unit, and the first feedback circuit feeds the output voltage back to a control terminal of the BOOST unit, so that the output voltage of the voltage output terminal is controlled. By employing the backlight driving circuit and the lamp bar light-adjusting unit, switching work between 2D and 3D of a television set is well completed, and a stable current is provided for each lamp bar. Compared with the prior art that a BOOST topology circuit is constructed by special chips, circuits are simplified, universality is improved, and preparing cost is reduced.
Description
Technical Field
The utility model relates to a drive technical field in a poor light especially relates to a drive circuit and lamp strip unit of adjusting luminance in a poor light.
Background
The LED is used as a backlight source of a liquid crystal television, and is increasingly widely applied to the television. Since the synchronization of the backlight and the liquid crystal image in the 3D display will show a better display effect, it is a trend that the chapters are smoothly formed when the multiple LED lamps are lit up according to a certain timing.
At present, a special adjusting chip is needed for adjusting and controlling the current required by an LED lamp in multiple paths of lamp bars of a liquid crystal display television so as to ensure that the current of each path of lamp bar is equal, thereby meeting the requirement of television picture display.
Fig. 1 is a circuit diagram of a Boost topology mode in which a dedicated adjustment chip is used in a conventional six-way street lamp. The backlight driving circuit shown in fig. 1 has a BOOST unit, a dimming unit, an MCU signal processing unit, and a 2D/3D switching unit, which use a chip dedicated to the middle as a core to meet the requirement of adjusting the backlight current in the 2D/3D state. Such a dedicated chip is expensive, which greatly increases the production cost of the product.
SUMMERY OF THE UTILITY MODEL
To the above problem, an object of the present invention is to provide a backlight driving circuit and light bar dimming unit with strong versatility, simple structure and low cost.
In order to achieve the above object, the backlight driving circuit of the present invention at least comprises a boost unit, a mcu signal processing unit, and a light bar dimming unit; wherein,
the boost unit is provided with a control end and a voltage output end and is used for boosting the input voltage according to the feedback signal received by the control end and then outputting the working voltage of the lamp strip through the voltage output end;
the mcu signal processing unit is provided with a control signal output end, a feedback signal output end and a feedback signal input end and is used for sending a control signal to the light bar dimming unit through the control signal output end, processing a received signal of the feedback signal input end and then outputting a first feedback signal to the control end of the boost unit through the feedback signal output end;
the lamp strip dimming unit is provided with a control signal input end, a lamp strip current adjusting end and a feedback signal output end and is used for changing the working current of the lamp strip connected between the voltage output end of the BOOST unit and the current adjusting end of the lamp strip dimming unit according to a control signal received by the control signal input end and sent by the MCU signal processing unit, and detecting that the working voltage of the lamp strip is output to the feedback signal input end of the MCU through the feedback signal output end;
the BOOST converter further comprises a first feedback circuit connected to the voltage output end and the control end of the BOOST unit and used for detecting the output voltage of the BOOST unit and forming a second feedback signal to be fed back to the control end of the BOOST unit so as to control the output voltage of the voltage output end.
Preferably, the light bar dimming unit is a constant current control unit having a control signal input end and a light bar current adjusting end, wherein the constant current control unit controls the working current of the light bar connected to the light bar current adjusting end according to the control signal received by the control signal input end; the detection circuit is connected between the lamp strip access end and the ground and used for detecting the working voltage in the lamp strip working loop and outputting a feedback voltage signal through the feedback signal output end.
Preferably, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode, a second resistor and an operational amplifier; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the control signal input end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
Preferably, the current stabilizing circuit is at least composed of a first resistor, one end of the first resistor is connected with the emitter of the triode, and the other end of the first resistor is grounded.
Preferably, the light bar dimming unit further comprises an anti-misoperation circuit, the circuit comprises a third resistor, one end of the third resistor is connected with a voltage VREF, and the other end of the third resistor is connected with a connection point of the current stabilizing circuit and the positive phase input end of the operational amplifier and is used for providing a bias voltage for the operational amplifier.
Preferably, the control signal input end is composed of a fourth resistor, a fifth resistor and a sixth resistor which are connected in series, wherein a signal connection end of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded.
Preferably, the light bar voltage detection circuit is formed by connecting a diode, a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor, wherein the cathode of the diode is connected with the negative end of the light bar, the anode of the diode is connected with one end of the first voltage-dividing resistor, and the other end of the first voltage-dividing resistor is connected with a voltage VCC; one end of the second voltage-dividing resistor is connected with the anode of the diode, and the other end of the second voltage-dividing resistor is connected with the feedback signal output end; one end of the third voltage dividing resistor is connected with the feedback signal output end, and the other end of the third voltage dividing resistor is grounded.
Preferably, the control signal input end further comprises a ninth resistor connected in parallel with the sixth resistor; the current stabilizing circuit further comprises an eighth resistor connected with the first resistor in parallel.
In order to achieve the above object, the utility model discloses a lamp strip dimming circuit, including the constant current control unit who has a control signal input end and a lamp strip current adjustment end, wherein, constant current control unit according to the control signal control connection received of control signal input end at the operating current of the lamp strip of lamp strip current adjustment end.
Preferably, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode, a second resistor and an operational amplifier; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the control signal input end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
The utility model has the advantages that:
the utility model discloses completion TV set 2D 3D's that can be fine switching work to can provide a stable electric current of each street lamp strip, compare in prior art use the BOOST topological circuit that steps up that special chip found, the utility model discloses the commonality is stronger, only utilizes general BOOST BOOST unit, MCU chip commonly used to and lamp strip dimmer circuit can satisfy the needs of different electric currents under the 2D 3D signal, and thereby increase lamp strip voltage detection circuit can feed back electric current to the electric current in MCU adjustment lamp strip return circuit, the circuit has been simplified to this structure, has improved the commonality, has reduced the cost of manufacture.
Drawings
FIG. 1 is a prior art circuit diagram;
fig. 2 is a circuit diagram of a backlight driving circuit according to an embodiment of the present invention;
fig. 3 is a schematic view of a light bar dimming unit according to embodiment 1 of the present invention;
fig. 4 is a schematic view of the light bar dimming unit according to embodiment 4 of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings.
The backlight driving circuit of the embodiment of the utility model at least comprises a BOOST boosting unit, a mcu signal processing unit and a light bar dimming unit, wherein,
the BOOST unit is provided with a control end and a voltage output end and is used for outputting the working voltage of the lamp strip through the voltage output end after boosting the input voltage;
the mcu signal processing unit is provided with a control signal output end, a feedback signal output end and a feedback signal input end and is used for sending a control signal to the light bar dimming unit through the control signal output end, processing a signal received from the feedback signal input end and then outputting a feedback signal to the control end of the BOOST unit through the feedback signal output end;
the lamp strip dimming unit is provided with a control signal input end, a lamp strip current adjusting end and a feedback signal output end and is used for changing the working current of the lamp strip connected between the voltage output end of the BOOST unit and the current adjusting end of the lamp strip dimming unit according to a control signal sent by the MCU signal processing unit and received by the control signal input end, and detecting that the working voltage of the lamp strip is output to the feedback signal input end of the MCU through the feedback signal output end;
the BOOST control circuit comprises a BOOST unit, a first feedback circuit and a second feedback circuit, wherein the first feedback circuit is connected to the voltage output end and the control end of the BOOST unit and used for detecting the output voltage of the BOOST unit and feeding the output voltage back to the control end of the BOOST unit to control the output voltage of the voltage output end.
The utility model discloses a theory of operation does:
as shown in fig. 2, in the figure, the components of the BOOST unit serving as the BOOST part are a MOS transistor V31 and an inductor L1, and the inductor L1 is connected to the input voltage (24V). When the lamp strip starts to be started, the MOS tube is opened or closed, so that the input voltage finally generates voltage superposition through the inductor, and finally the working voltage for lighting the lamp strip is output by the voltage output end. After the lamp strip is started for the first time, the BOOST boosting unit carries out voltage feedback on the voltage output end, the feedback voltage generates a voltage at the FB point under the action of the divider resistor, the voltage is compared with the reference voltage of the BOOST boosting unit, a PWM duty ratio control signal is sent to the MOS tube according to the comparison result, the switching frequency of the MOS tube is adjusted, and then the voltage of the voltage output end is adjusted to be stably supplied to the lamp strip.
In the lighting process of the light bar, the mcu signal processing unit detects the voltage difference between the resistor R14 and the resistor R15, acquires voltage difference signals, sends feedback voltage signals to the BOOST voltage boosting unit after the voltage difference signals are processed, generates a voltage at the FB point, compares the voltage with the reference voltage of the BOOST voltage boosting unit, sends a PWM duty ratio control signal to the MOS tube according to the comparison result, adjusts the switching frequency of the MOS tube, and further adjusts the voltage of the voltage output end to enable the voltage to be stably supplied to the light bar.
The mcu signal processing unit sends a 2D/3D control signal to the light bar dimming unit so that the light bar dimming unit adjusts the working current of the light bar.
When the PWM control signal from the mcu signal processing unit is at a high level in the 2D state, the PWM3D pin of the mcu signal processing unit is at a high impedance state, and the control signal input terminal only receives a constant input voltage (e.g. 3.3V in the figure), which is divided to ground by the voltage dividing resistor to provide a voltage to the non-inverting input terminal of the operational amplifier N904B. Since the transistor V2, the second resistor R9, and the operational amplifier N904B are connected to form a deep negative feedback circuit, in this state, the inverting input terminal and the non-inverting input terminal of the operational amplifier are 'virtual short', that is, the voltage at the inverting input terminal of the operational amplifier is close to the voltage at the non-inverting input terminal. The circuit utilizes the characteristic that the voltage of a non-inverting input end in the circuit is reflected at an inverting input end, and the working current of the light bar connected with the first resistor in series is changed by changing the working current of the first resistor R8 according to the change of the voltage.
When the PWM control signal is at a low level, the voltage at the positive input terminal of the operational amplifier is zero, so that the working current flowing through the light bar is zero, and the light bar is turned off.
When the signal is at a high level, the signal and a voltage generated by a constant input voltage at a potential point of the resistor R3 and the resistor R4 are applied to a non-inverting input end of the operational amplifier, so as to obtain a 3D current for operating the light bar. When the signal is at a low level, the voltage is zero, the working current flowing through the lamp strip is zero, and the lamp strip is closed.
As a further explanation of the present invention:
the lamp strip dimming unit comprises a constant current control unit with a control signal input end and a lamp strip current adjusting end, wherein the constant current control unit controls the working current of a lamp strip connected to the lamp strip current adjusting end according to a control signal received by the control signal input end.
The utility model discloses can real-time detection and receive 2D 3D control signal, then to the real-time effective control of lamp strip operating current. Compared with a circuit which uses a professional chip and is provided with a special 2D/3D conversion chip, the structure is simpler, and the implementation is more convenient.
As the utility model discloses improve still further the circuit in still include a lamp strip voltage detection circuit, the voltage signal feedback of this unit detection lamp strip negative terminal feeds back to the mcu signal processing unit, this circuit makes according to feedback signal and handles regulation lamp strip voltage. The lamp strip voltage detection circuit obtains the voltage condition of the negative end of the lamp strip, reduces the voltage to the acceptable range of the mcu, reduces the output voltage through feedback when the detected voltage exceeds a preset value, and improves the output voltage when the detected voltage is lower than the preset value. The unit can detect the lamp strip in real time, and the normal working state of the lamp strip is guaranteed.
Example 1
Fig. 3 shows an embodiment of the present invention, and the above solution is further explained with reference to the embodiment:
in this embodiment, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode V2, a second resistor R9 and an operational amplifier N904B; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the 2D/3D control signal access end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
The working principle of the circuit is as follows: the triode, the second resistor and the operational amplifier are connected to form a deep negative feedback circuit, and in the state, the inverting input end and the positive input end of the operational amplifier are 'virtual short', namely the voltage of the inverting input end of the operational amplifier is close to the voltage of the positive input end. The circuit utilizes the characteristic to enable the voltage of the positive phase input end in the circuit to be reflected at the negative phase input end, and the working current of the first resistor is changed by utilizing the change of the voltage, so that the working current of the lamp strip connected with the first resistor in series is changed. The method comprises the following specific steps:
when a 2D/3D signal is input into the positive phase input end, the triode is conducted, so that the operational amplifier works in the deep negative feedback, the voltage on the negative phase input end is equal to the voltage on the positive phase input end, and a virtual short is formed; at the moment, the negative end of the lamp strip is connected to the collector of the triode, after the triode is conducted, the negative end of the lamp strip passes through the triode, the first resistor R8 and finally is grounded, a lamp strip working circuit is formed, when a 2D/3D signal is input, the voltage change occurs at the input end controlled by the 2D/3D control signal, and due to the 'virtual short' characteristic, the voltage on the reverse phase input end is made to follow the voltage change of the positive phase input end, so that the voltages at the two ends of the first resistor are made to change, because the resistance value of the first resistor is constant, according to the formula U-I-R, the current of the first resistor is made to change along with the difference of the voltages, so that the current of the lamp strip circuit is made to change, the purpose of controlling the working current of the lamp strip circuit is achieved, and the purpose of controlling the. The light bar dimming unit of the embodiment may further include a fourth resistor R921 connected in parallel with the first resistor in the current stabilizing circuit, so that the current in the light bar loop can be adjusted during debugging by changing the resistance of the fourth resistor.
In fig. 3, the control signal input terminal is composed of a fourth resistor R3, a fifth resistor R4 and a sixth resistor R5 which are connected in series, wherein the signal connection terminal of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded. In the circuit, the 2D PWM dimming signal and/or the 3D PWM control dimming signal and the constant input voltage are respectively connected to the non-inverting input terminal (e.g., + terminal in the figure) of the operational amplifier N904B through the resistors R3, R4 and R5, and the two signals are connected to different positions of the circuit, so that the voltages output to the operational amplifier are different, the current flowing through the first resistor is changed, and the working current of the light bar is further adjusted.
Example 2
This embodiment is now further described with reference to fig. 4:
the light bar dimming unit in this embodiment further includes an anti-misoperation circuit.
In this embodiment, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode V2, a second resistor R9 and an operational amplifier N904B; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the 2D/3D control signal access end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
The working principle of the circuit is as follows: the triode, the second resistor and the operational amplifier are connected to form a deep negative feedback circuit, and in the state, the inverting input end and the positive input end of the operational amplifier are 'virtual short', namely the voltage of the inverting input end of the operational amplifier is close to the voltage of the positive input end. The circuit utilizes the characteristic to enable the voltage of the positive phase input end in the circuit to be reflected at the negative phase input end, and the working current of the first resistor is changed by utilizing the change of the voltage, so that the working current of the lamp strip connected with the first resistor in series is changed. The method comprises the following specific steps:
when a 2D/3D signal is input into the positive phase input end, the triode is conducted, so that the operational amplifier works in the deep negative feedback, the voltage on the negative phase input end is equal to the voltage on the positive phase input end, and a virtual short is formed; at the moment, the negative end of the lamp strip is connected to the collector of the triode, after the triode is conducted, the negative end of the lamp strip passes through the triode, the first resistor R8 and finally is grounded, a lamp strip working circuit is formed, when a 2D/3D signal is input, the voltage change occurs at the input end controlled by the 2D/3D control signal, and due to the 'virtual short' characteristic, the voltage on the reverse phase input end is made to follow the voltage change of the positive phase input end, so that the voltages at the two ends of the first resistor are made to change, because the resistance value of the first resistor is constant, according to the formula U-I-R, the current of the first resistor is made to change along with the difference of the voltages, so that the current of the lamp strip circuit is made to change, the purpose of controlling the working current of the lamp strip circuit is achieved, and the purpose of controlling the. The light bar dimming unit of the embodiment may further include a fourth resistor R921 connected in parallel with the first resistor in the current stabilizing circuit, so that the current in the light bar loop can be adjusted during debugging by changing the resistance of the fourth resistor.
In fig. 3, the control signal input terminal is composed of a fourth resistor R3, a fifth resistor R4 and a sixth resistor R5 which are connected in series, wherein the signal connection terminal of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded. In the circuit, the 2D PWM dimming signal and/or the 3D PWM control dimming signal and the constant input voltage are respectively connected to the non-inverting input terminal (e.g., + terminal in the figure) of the operational amplifier N904B through the resistors R3, R4 and R5, and the two signals are connected to different positions of the circuit, so that the voltages output to the operational amplifier are different, the current flowing through the first resistor is changed, and the working current of the light bar is further adjusted. In addition, an eighth seventh resistor R910 can be arranged in parallel with the seventh sixth resistor, and participate in the whole work together.
The anti-misoperation circuit comprises a third resistor, one end of the third resistor is connected with a voltage VREF, and the other end of the third resistor is connected with a connection point of the current stabilizing circuit and the positive phase input end of the operational amplifier and is used for providing a bias voltage for the operational amplifier. This can effectively prevent the operational amplifier from malfunctioning when the input is zero.
Example 3
The light bar dimming unit in this embodiment further includes a light bar voltage detection unit, which is further described with reference to fig. 4.
In this embodiment, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode V2, a second resistor R9 and an operational amplifier N904B; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the 2D/3D control signal access end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
The working principle of the circuit is as follows: the triode, the second resistor and the operational amplifier are connected to form a deep negative feedback circuit, and in the state, the inverting input end and the positive input end of the operational amplifier are 'virtual short', namely the voltage of the inverting input end of the operational amplifier is close to the voltage of the positive input end. The circuit utilizes the characteristic to enable the voltage of the positive phase input end in the circuit to be reflected at the negative phase input end, and the working current of the first resistor is changed by utilizing the change of the voltage, so that the working current of the lamp strip connected with the first resistor in series is changed. The method comprises the following specific steps:
when a 2D/3D signal is input into the positive phase input end, the triode is conducted, so that the operational amplifier works in the deep negative feedback, the voltage on the negative phase input end is equal to the voltage on the positive phase input end, and a virtual short is formed; at the moment, the negative end of the lamp strip is connected to the collector of the triode, after the triode is conducted, the negative end of the lamp strip passes through the triode, the first resistor R8 and finally is grounded, a lamp strip working circuit is formed, when a 2D/3D signal is input, the voltage change occurs at the input end controlled by the 2D/3D control signal, and due to the 'virtual short' characteristic, the voltage on the reverse phase input end is made to follow the voltage change of the positive phase input end, so that the voltages at the two ends of the first resistor are made to change, because the resistance value of the first resistor is constant, according to the formula U-I-R, the current of the first resistor is made to change along with the difference of the voltages, so that the current of the lamp strip circuit is made to change, the purpose of controlling the working current of the lamp strip circuit is achieved, and the purpose of controlling the. The light bar dimming unit of the embodiment may further include an eighth resistor R921 connected in parallel with the first resistor in the current stabilizing circuit, so that the current in the light bar loop can be adjusted during debugging by changing the resistance of the fourth resistor.
In fig. 3, the control signal input terminal is composed of a fourth resistor R3, a fifth resistor R4 and a sixth resistor R5 which are connected in series, wherein the signal connection terminal of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded. In the circuit, the 2D PWM dimming signal and/or the 3D PWM control dimming signal and the constant input voltage are respectively connected to the non-inverting input terminal (e.g., + terminal in the figure) of the operational amplifier N904B through the resistors R3, R4 and R5, and the two signals are connected to different positions of the circuit, so that the voltages output to the operational amplifier are different, the current flowing through the first resistor is changed, and the working current of the light bar is further adjusted. In the circuit, the 2D PWM dimming signal and the 3D PWM dimming signal are respectively connected to the non-inverting input terminal (for example, the + terminal in the figure) of the operational amplifier N904B through the resistors R909, R709 and R911, and the two signals are connected to different positions of the circuit, so that the voltages output to the operational amplifier are different, and are used as different reference potentials to be compared with the potentials of the inverting input terminals; thereby achieving the purpose of marking 2D/3D input signals. In addition, an eighth resistor R910 can be arranged in parallel with the seventh resistor, and the eighth resistor R910 and the seventh resistor participate in the whole work together.
The lamp strip voltage detection circuit is formed by connecting a diode VD3, a first voltage-dividing resistor R13, a second voltage-dividing resistor R14 and a third voltage-dividing resistor R15, wherein the cathode of the diode is connected with the negative end of the lamp strip, the anode of the diode is connected with one end of the first voltage-dividing resistor, and the other end of the first voltage-dividing resistor is connected with a voltage VCC; one end of the second voltage-dividing resistor is connected with the anode of the diode, and the other end of the second voltage-dividing resistor is connected with the feedback signal output end; one end of the third voltage dividing resistor is connected with the feedback signal output end, and the other end of the third voltage dividing resistor is grounded. The unit takes the voltage at the negative terminal of the lamp strip, reduces the voltage to the acceptable range of the mcu through resistance voltage division (R14 and R15), reduces the output voltage through feedback when the detected voltage exceeds a preset value, and improves the output voltage when the detected voltage is lower than the preset value.
Example 4
The light bar dimming unit in this embodiment further includes an anti-misoperation circuit and a light bar voltage detection unit, which will be further described with reference to fig. 4.
In this embodiment, the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode V2, a second resistor R9 and an operational amplifier N904B; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the 2D/3D control signal access end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
The working principle of the circuit is as follows: the triode, the second resistor and the operational amplifier are connected to form a deep negative feedback circuit, and in the state, the inverting input end and the positive input end of the operational amplifier are 'virtual short', namely the voltage of the inverting input end of the operational amplifier is close to the voltage of the positive input end. The circuit utilizes the characteristic to enable the voltage of the positive phase input end in the circuit to be reflected at the negative phase input end, and the working current of the first resistor is changed by utilizing the change of the voltage, so that the working current of the lamp strip connected with the first resistor in series is changed. The method comprises the following specific steps:
when a 2D/3D signal is input into the positive phase input end, the triode is conducted, so that the operational amplifier works in the deep negative feedback, the voltage on the negative phase input end is equal to the voltage on the positive phase input end, and a virtual short is formed; at the moment, the negative end of the lamp strip is connected to the collector of the triode, after the triode is conducted, the negative end of the lamp strip passes through the triode, the first resistor R8 and finally is grounded, a lamp strip working circuit is formed, when a 2D/3D signal is input, the voltage change occurs at the input end controlled by the 2D/3D control signal, and due to the 'virtual short' characteristic, the voltage on the reverse phase input end is made to follow the voltage change of the positive phase input end, so that the voltages at the two ends of the first resistor are made to change, because the resistance value of the first resistor is constant, according to the formula U-I-R, the current of the first resistor is made to change along with the difference of the voltages, so that the current of the lamp strip circuit is made to change, the purpose of controlling the working current of the lamp strip circuit is achieved, and the purpose of controlling the. The light bar dimming unit of the embodiment may further include a fourth resistor R921 connected in parallel with the first resistor in the current stabilizing circuit, so that the current in the light bar loop can be adjusted during debugging by changing the resistance of the fourth resistor.
In fig. 3, the control signal input terminal is composed of a fourth resistor R3, a fifth resistor R4 and a sixth resistor R5 which are connected in series, wherein the signal connection terminal of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded. In the circuit, the 2D PWM dimming signal and/or the 3D PWM control dimming signal and the constant input voltage are respectively connected to the non-inverting input terminal (e.g., + terminal in the figure) of the operational amplifier N904B through the resistors R3, R4 and R5, and the two signals are connected to different positions of the circuit, so that the voltages output to the operational amplifier are different, the current flowing through the first resistor is changed, and the working current of the light bar is further adjusted. In addition, a seventh resistor R910 can be arranged in parallel with the sixth resistor, and the seventh resistor R and the sixth resistor are jointly involved in the whole work.
The anti-misoperation circuit comprises a third resistor R6, wherein one end of the third resistor is connected with a voltage VREF, and the other end of the third resistor is connected with a connection point of the current stabilizing circuit and the positive phase input end of the operational amplifier and is used for providing a bias voltage for the operational amplifier. This can effectively prevent the operational amplifier from malfunctioning when the input is zero.
The lamp strip voltage detection circuit is formed by connecting a diode VD3, a first voltage-dividing resistor R13, a second voltage-dividing resistor R14 and a third voltage-dividing resistor R15, wherein the cathode of the diode is connected with the negative end of the lamp strip, the anode of the diode is connected with one end of the first voltage-dividing resistor, and the other end of the first voltage-dividing resistor is connected with a voltage VCC; one end of the second voltage-dividing resistor is connected with the anode of the diode, and the other end of the second voltage-dividing resistor is connected with the feedback signal output end; one end of the third voltage dividing resistor is connected with the feedback signal output end, and the other end of the third voltage dividing resistor is grounded. The unit takes the voltage at the negative terminal of the lamp strip, reduces the voltage to the acceptable range of the mcu through resistance voltage division (R14 and R15), reduces the output voltage through feedback when the detected voltage exceeds a preset value, and improves the output voltage when the detected voltage is lower than the preset value.
The above is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.
Claims (10)
1. A backlight driving circuit is characterized by at least comprising a boost unit, a mcu signal processing unit and a light bar dimming unit; wherein,
the boost unit is provided with a control end and a voltage output end and is used for boosting the input voltage according to the feedback signal received by the control end and then outputting the working voltage of the lamp strip through the voltage output end;
the mcu signal processing unit is provided with a control signal output end, a feedback signal output end and a feedback signal input end and is used for sending a control signal to the light bar dimming unit through the control signal output end, processing a received signal of the feedback signal input end and then outputting a first feedback signal to the control end of the boost unit through the feedback signal output end;
the lamp strip dimming unit is provided with a control signal input end, a lamp strip current adjusting end and a feedback signal output end and is used for changing the working current of the lamp strip connected between the voltage output end of the BOOST unit and the current adjusting end of the lamp strip dimming unit according to a control signal received by the control signal input end and sent by the MCU signal processing unit, and detecting that the working voltage of the lamp strip is output to the feedback signal input end of the MCU through the feedback signal output end;
the BOOST converter further comprises a first feedback circuit connected to the voltage output end and the control end of the BOOST unit and used for detecting the output voltage of the BOOST unit and forming a second feedback signal to be fed back to the control end of the BOOST unit so as to control the output voltage of the voltage output end.
2. The backlight driving circuit of claim 1, wherein the light bar dimming unit comprises a constant current control unit having a control signal input terminal and a light bar current adjustment terminal, wherein the constant current control unit controls the operating current of the light bar connected to the light bar current adjustment terminal according to the control signal received by the control signal input terminal; the detection circuit is connected between the lamp strip access end and the ground and used for detecting the working voltage in the lamp strip working loop and outputting a feedback voltage signal through the feedback signal output end.
3. The backlight driving circuit according to claim 2, wherein the constant current control unit is composed of a current stabilizing circuit and a deep negative feedback circuit composed of a triode, a second resistor and an operational amplifier; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the control signal input end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
4. The backlight driving circuit according to claim 3, wherein the current stabilizer circuit is at least a first resistor, one end of the first resistor is connected to the emitter of the transistor, and the other end of the first resistor is grounded.
5. The backlight driving circuit of claim 2, wherein the light bar dimming unit further comprises an anti-misoperation circuit comprising a third resistor, one end of the third resistor is connected to a voltage VREF, and the other end of the third resistor is connected to a connection point between the current stabilizing circuit and the positive input terminal of the operational amplifier for providing a bias voltage to the operational amplifier.
6. The backlight driving circuit according to claim 2, wherein the control signal input terminal is composed of a fourth resistor, a fifth resistor and a sixth resistor connected in series, wherein a signal connection terminal of the fourth resistor is used for connecting a constant input voltage; the connection point of the fifth resistor and the fourth resistor is used for connecting a 2D/3D control signal, the connection point of the sixth resistor and the fifth resistor is connected with the positive phase input end of the operational amplifier, and the other end of the sixth resistor is grounded.
7. The backlight driving circuit according to claim 2, wherein the lamp strip voltage detecting circuit comprises a diode, a first voltage dividing resistor, a second voltage dividing resistor and a third voltage dividing resistor, wherein the diode has a negative terminal connected to the negative terminal of the lamp strip, a positive terminal connected to one end of the first voltage dividing resistor, and the other end of the first voltage dividing resistor is connected to a voltage VCC; one end of the second voltage-dividing resistor is connected with the anode of the diode, and the other end of the second voltage-dividing resistor is connected with the feedback signal output end; one end of the third voltage dividing resistor is connected with the feedback signal output end, and the other end of the third voltage dividing resistor is grounded.
8. The backlight driving circuit according to claim 3, wherein the control signal input terminal further comprises a ninth resistor connected in parallel with the sixth resistor; the current stabilizing circuit further comprises an eighth resistor connected with the first resistor in parallel.
9. The light bar dimming unit is characterized by comprising a constant current control unit with a control signal input end and a light bar current adjusting end, wherein the constant current control unit controls the working current of a light bar connected to the light bar current adjusting end according to a control signal received by the control signal input end.
10. The light bar dimming unit of claim 9, wherein the constant current control unit comprises a current stabilizing circuit and a deep negative feedback circuit comprising a triode, a second resistor and an operational amplifier; wherein,
the second resistor is connected between the base of the triode and the output end of the operational amplifier; the emitter of the triode is connected with the inverting input end of the operational amplifier, and the collector of the triode is used for being connected with the negative end of the light bar; the positive phase input end of the operational amplifier is connected with the control signal input end to serve as a control loop; one end of the current stabilizing circuit is connected with the emitting electrode of the triode, and the other end of the current stabilizing circuit is grounded.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2013203147672U CN203313488U (en) | 2013-06-03 | 2013-06-03 | Backlight driving circuit and lamp bar light-adjusting unit |
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| CN2013203147672U CN203313488U (en) | 2013-06-03 | 2013-06-03 | Backlight driving circuit and lamp bar light-adjusting unit |
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| CN203313488U true CN203313488U (en) | 2013-11-27 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103957644A (en) * | 2014-05-14 | 2014-07-30 | 深圳市华星光电技术有限公司 | LED backlight source for liquid crystal display device |
| CN104253957A (en) * | 2014-09-17 | 2014-12-31 | 广州视源电子科技股份有限公司 | Low-power-consumption constant-current and backlight control circuit and television |
| CN105487588A (en) * | 2016-01-12 | 2016-04-13 | 四川长虹电器股份有限公司 | Constant current source circuit capable of being regulated and controlled in real time and constant current control method thereof |
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| CN105957475A (en) * | 2015-12-27 | 2016-09-21 | 天津市品通电力科技有限公司 | Display screen control circuit of electric power instrument |
| CN107635312A (en) * | 2015-06-19 | 2018-01-26 | 青岛海信电器股份有限公司 | A kind of LED drive circuit and liquid crystal display device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103957644A (en) * | 2014-05-14 | 2014-07-30 | 深圳市华星光电技术有限公司 | LED backlight source for liquid crystal display device |
| WO2015172402A1 (en) * | 2014-05-14 | 2015-11-19 | 深圳市华星光电技术有限公司 | Led backlight source for liquid crystal display device |
| CN103957644B (en) * | 2014-05-14 | 2017-04-26 | 深圳市华星光电技术有限公司 | LED backlight source for liquid crystal display device |
| CN104253957A (en) * | 2014-09-17 | 2014-12-31 | 广州视源电子科技股份有限公司 | Low-power-consumption constant-current and backlight control circuit and television |
| CN104253957B (en) * | 2014-09-17 | 2017-09-29 | 广州视源电子科技股份有限公司 | Low-power-consumption constant-current and backlight control circuit and television |
| CN107635312A (en) * | 2015-06-19 | 2018-01-26 | 青岛海信电器股份有限公司 | A kind of LED drive circuit and liquid crystal display device |
| CN105889859A (en) * | 2015-10-02 | 2016-08-24 | 蒋超 | LED rod type lighting device capable of being charged by solar energy and wind energy day and night |
| CN105957475A (en) * | 2015-12-27 | 2016-09-21 | 天津市品通电力科技有限公司 | Display screen control circuit of electric power instrument |
| CN105487588A (en) * | 2016-01-12 | 2016-04-13 | 四川长虹电器股份有限公司 | Constant current source circuit capable of being regulated and controlled in real time and constant current control method thereof |
| CN105487588B (en) * | 2016-01-12 | 2017-03-29 | 四川长虹电器股份有限公司 | A kind of constant-current source circuit and its constant current control method of real-time monitoring |
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