CN111883085B - Device for improving stable work of liquid crystal equipment - Google Patents
Device for improving stable work of liquid crystal equipment Download PDFInfo
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- CN111883085B CN111883085B CN202011036458.4A CN202011036458A CN111883085B CN 111883085 B CN111883085 B CN 111883085B CN 202011036458 A CN202011036458 A CN 202011036458A CN 111883085 B CN111883085 B CN 111883085B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3696—Generation of voltages supplied to electrode drivers
Abstract
The invention provides a device for improving the stable work of liquid crystal equipment, which comprises a waveform generating unit, a comparing unit, a driving control unit, an overcurrent and undervoltage protection unit and a liquid crystal driving unit which are electrically connected in sequence, wherein the level signal output end of the liquid crystal driving unit is connected with a liquid crystal panel unit, the output end of the overcurrent and undervoltage protection unit is also connected with the input end of the driving control unit, and the overcurrent and undervoltage protection unit comprises a fifth resistor, an operational amplifier, a comparator, a sixth resistor, an NPN type field effect transistor, a first diode and a seventh resistor. In the power-on and power-off processes of the system, the stable and reliable operation of the system can be realized by making the voltage of the anode end of the comparator lower than that of the cathode end of the comparator, so that the working state of a subsequent unit is effectively ensured, and the damage of an abnormal state to the system is reduced; the working state of the over-current and under-voltage state system is safe and stable by adopting a self-adaptive adjusting and controlling mode, so that the stability of the liquid crystal display driving equipment is improved.
Description
Technical Field
The invention belongs to the technical field of liquid crystal display, and particularly relates to a device for improving stable work of liquid crystal equipment.
Background
In the conventional liquid crystal display device, the working stability of the liquid crystal driving device is not high, mainly because the power supply device has the problem of slow charging and discharging, the liquid crystal display device is easily damaged by uncertain factors in the charging and discharging processes and the working process, and the stability of the liquid crystal display device is further influenced. Therefore, the liquid crystal display device needs a stable power scheme to supply power, so that the normal operation of the display device can be ensured. Meanwhile, the core module of the liquid crystal driving device is an integrated circuit scheme, so that on the premise of ensuring the normal work of the liquid crystal driving device, a safe and controllable power supply scheme is required to be provided to realize the stable work of the liquid crystal driving device, and the damage of the integrated circuit is avoided to cause economic loss.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a device for improving the stable work of liquid crystal equipment, which adopts an overcurrent and undervoltage protection unit combined with a drive control unit to realize the fast charge and slow discharge of the liquid crystal equipment, can effectively protect the liquid crystal equipment under uncertain factors, ensure the stable work of the liquid crystal equipment, reduce the possibility of damage of the liquid crystal equipment in the power-on and power-off processes and improve the work stability of the liquid crystal equipment.
The technical solution for realizing the purpose of the invention is as follows:
the utility model provides an improve device of liquid crystal apparatus steady operation, includes the wave form generating element, the comparison unit, the drive control unit, overflows undervoltage protection unit and the liquid crystal drive unit that connect electrically in proper order, and wave form generating element, comparison unit, drive control unit have all connect the work level, and liquid crystal drive unit's level signal output part connects the liquid crystal display panel unit, and the output that overflows undervoltage protection unit still is connected with drive control unit's input, wherein: the waveform generating unit is used for receiving an externally input level signal, generating a waveform signal with a certain frequency according to the level signal and then sending the waveform signal to the comparing unit; the comparison unit is used for receiving the waveform signal, comparing the waveform signal with the direct current signal, generating a driving control signal and outputting the driving control signal to the driving control unit, wherein the frequency of the driving control signal is the same as that of the waveform signal; the driving control unit is used for receiving the driving control signal, generating a stable level signal and outputting the stable level signal to the liquid crystal driving unit through the overcurrent and undervoltage protection unit; the overcurrent and undervoltage protection unit is used for monitoring whether the level signal output by the drive control unit generates overcurrent, starting a circuit protection state and transmitting the circuit protection state to the drive control unit if the level signal output by the drive control unit generates overcurrent, and not processing the overcurrent and undervoltage protection state if the level signal output by the drive control unit does not generate overcurrent; the overcurrent and undervoltage protection unit comprises a fifth resistor, an operational amplifier, a comparator, a sixth resistor, an NPN type field effect transistor, a first diode and a seventh resistor, wherein one end of the fifth resistor is connected with the non-inverting input end of the operational amplifier and serves as the input end of the overcurrent and undervoltage protection unit to be connected with the output end of the drive control unit, and the other end of the fifth resistor is connected with the inverting input end of the operational amplifier and serves as the output end of the overcurrent and undervoltage protection unit to be connected with the voltage input end of the liquid crystal drive unit; the output end of the operational amplifier is connected with the non-inverting input end of the comparator, the inverting input end of the comparator inputs reference voltage, the output end of the comparator is connected with one end of a sixth resistor, and the other end of the sixth resistor is connected with the base electrode of the NPN type field effect transistor; an emitting electrode of the NPN type field effect transistor is grounded, a collector electrode of the NPN type field effect transistor is connected with a negative electrode of a first diode, an anode of the first diode is connected with one end of a seventh resistor, and the other end of the seventh resistor is connected with an input end of the driving control unit; and a liquid crystal driving unit for receiving the stable level signal of the driving control unit and outputting an operation level signal used as the liquid crystal panel unit.
Further, the device for improving the stable operation of the liquid crystal device comprises a waveform generating unit, wherein the waveform generating unit comprises a hysteresis comparator and a resistance-capacitance network which are connected, the resistance-capacitance network comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a second capacitor, one end of the first resistor, the third resistor and the fourth resistor is connected with a power supply voltage, the other end of the fourth resistor is connected with the output end of the hysteresis comparator, the other end of the first resistor and one end of the second resistor are connected with the anode end of the hysteresis comparator, the other end of the second resistor and one end of the second capacitor are connected with a common reference point, the third resistor is connected with the fifth resistor in series, the other end of the second capacitor and the other end of the fifth resistor are connected with the cathode end of the hysteresis comparator, and the cathode end of the hysteresis comparator is used as the output end of the waveform generating.
Further, in the stable operating apparatus of the liquid crystal display device of the present invention, the waveform signal generated by the waveform generating unit is a triangular wave signal, and the two thresholds of the hysteresis comparator in the waveform generating unit are respectively a peak level and a trough level of the triangular wave signal.
Further, the device for improving the stable operation of the liquid crystal device of the present invention comprises a comparator, a transistor, a first resistor, a capacitor, a second resistor and a third resistor, wherein a cathode terminal of the comparator is connected to an output terminal of the waveform generating unit as an input terminal of the comparing unit, and an output terminal of the comparator is connected to an input terminal of the driving control unit as an output terminal of the comparing unit; the anode end of the comparator, one end of the first resistor, one end of the capacitor and the emitter of the transistor are connected to one point, one end of the second resistor and one end of the third resistor are connected to the base of the transistor, the other end of the first resistor and the other end of the second resistor are connected to a power supply voltage, the other end of the capacitor, the collector of the transistor and the other end of the third resistor are connected to a common reference point, and the second resistor is an adjustable resistor.
Further, in the apparatus for improving stable operation of a liquid crystal device according to the present invention, the driving control signal generated by the comparing unit is a pulse width modulation signal with an adjustable duty ratio.
Further, the device for improving the stable operation of the liquid crystal device of the present invention comprises a driving control unit including a field effect transistor, a transistor, an inductor, a capacitor, a diode and a fourth resistor, wherein one end of the fourth resistor is connected to the output end of the comparing unit as the input end of the driving control unit, and the other end of the fourth resistor is connected to the gate of the field effect transistor; the drain electrode of the field effect transistor is connected with a power supply voltage, the source electrode of the field effect transistor is connected with the cathode of the diode and the inductor, the other end of the inductor is connected with the capacitor and the collector of the transistor and serves as the output end of the drive control unit to be connected with the input end of the over-current and under-voltage protection unit, the anode of the diode, the other end of the capacitor and the emitter of the transistor are all connected with a common reference point, and the base electrode of the transistor is.
Furthermore, according to the device for improving the stable operation of the liquid crystal device, the resistance of the fifth resistor in the over-current and under-voltage protection unit is small, the fifth resistor plays a role in limiting current during normal operation, and plays a role in sampling and feedback when the current is too large.
Further, according to the device for improving the stable operation of the liquid crystal device, the NPN type field effect transistor in the over-current and under-voltage protection unit is turned off in an over-current state, so that an isolation effect is achieved.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. the device for improving the stable work of the liquid crystal display equipment realizes quick charge and slow discharge on the premise of not increasing a complex circuit, can effectively protect the liquid crystal display equipment and ensures the stable work of the liquid crystal display equipment;
2. the device for improving the stable work of the liquid crystal equipment protects the stable work and the reliability of the equipment by controlling the time sequence of the input signal of the input end of the comparison unit in the power-on and power-off processes, and reduces the possibility of damage of the equipment in the power-on and power-off processes;
3. the device for improving the stable work of the liquid crystal display equipment stops the work of the liquid crystal display equipment by quickly closing the control signal under the influence of external factors such as overlarge current and the like, protects the liquid crystal display equipment from being burnt, and ensures the safety of the work of a circuit.
Drawings
Fig. 1 is a block diagram of an apparatus for improving stable operation of a liquid crystal device according to the present invention.
Fig. 2 is a signal timing diagram during the operation of the apparatus for improving the stable operation of the liquid crystal device of the present invention.
Fig. 3 is a diagram showing a structure of a comparison unit of the apparatus for improving stable operation of a liquid crystal device of the present invention.
Fig. 4 is a structural view of a waveform generating unit of the apparatus for improving stable operation of a liquid crystal device of the present invention.
Fig. 5 is a structural view of a driving control unit of the apparatus for improving stable operation of a liquid crystal device of the present invention.
Fig. 6 is an overall block diagram of an apparatus for improving stable operation of a liquid crystal device of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The device comprises a waveform generating unit, a comparison unit, a drive control unit, an overcurrent and undervoltage protection unit and a liquid crystal drive unit which are electrically connected in sequence, wherein the waveform generating unit, the comparison unit and the drive control unit are all connected with a working level, the level signal output end of the liquid crystal drive unit is connected with a liquid crystal panel unit, and the output end of the overcurrent and undervoltage protection unit is also connected with the input end of the drive control unit. Wherein:
and the waveform generating unit is used for receiving an externally input level signal, generating a waveform signal with a certain frequency according to the level signal and sending the waveform signal to the comparing unit. The waveform generating unit comprises a hysteresis comparator and a resistance-capacitance network which are connected, wherein the resistance-capacitance network comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a second capacitor, one end of the first resistor, the third resistor and the fourth resistor is connected with a power supply voltage, the other end of the fourth resistor is connected with the output end of the hysteresis comparator, the other end of the first resistor and one end of the second resistor are connected with the anode end of the hysteresis comparator, the other end of the second resistor and one end of the second capacitor are connected with a common reference point, the third resistor is connected with the fifth resistor in series, the other end of the second capacitor and the other end of the fifth resistor are connected with the cathode end of the hysteresis comparator, and the cathode end of the hysteresis comparator, which serves as the output end of the waveform generating unit, is connected. The waveform signal generated by the waveform generating unit is a triangular wave signal, and two threshold values of a hysteresis comparator in the waveform generating unit are respectively the peak level and the trough level of the triangular wave signal.
And the comparison unit is used for receiving the waveform signal, comparing the waveform signal with the direct current signal, generating a driving control signal and outputting the driving control signal to the driving control unit, wherein the frequency of the driving control signal is the same as that of the waveform signal. The comparison unit comprises a comparator, a first transistor, a first resistor, a capacitor, a second resistor and a third resistor, wherein the cathode end of the comparator is used as the input end of the comparison unit and connected with the output end of the waveform generation unit, and the output end of the comparator is used as the output end of the comparison unit and connected with the input end of the drive control unit; an anode end of the comparator, one end of the first resistor, one end of the capacitor and an emitting electrode of the first transistor are connected to a point in a shared mode, one end of the second resistor and one end of the third resistor are connected with a base electrode of the first transistor, the other end of the first resistor and the other end of the second resistor are connected with a power supply voltage, and the other end of the capacitor, a collecting electrode of the first transistor and the other end of the third resistor are connected with a common reference point. The driving control signal generated by the comparison unit is a pulse width modulation signal with adjustable duty ratio. The second resistor is an adjustable resistor. The first transistor is a P-type triode, and the voltage of the emitter of the transistor is 0.7V greater than the voltage of the base of the transistor. The first resistor has a resistance of the order of hundreds of kilohms and the second and third resistors have a resistance of the order of tens of kilohms.
And the drive control unit is used for receiving the drive control signal, generating a stable level signal and outputting the stable level signal to the liquid crystal drive unit through the overcurrent and undervoltage protection unit. The driving control unit comprises a field effect transistor, a second transistor, an inductor, a capacitor, a diode and a fourth resistor, wherein one end of the fourth resistor is used as the input end of the driving control unit and is connected with the output end of the comparison unit, and the other end of the fourth resistor is connected with the grid electrode of the field effect transistor; the drain electrode of the field effect transistor is connected with a power supply voltage, the source electrode of the field effect transistor is connected with the cathode of the diode and the inductor, the other end of the inductor is connected with the capacitor and the collector of the second transistor and serves as the output end of the driving control unit to be connected with the fifth resistor of the over-current and under-voltage protection unit, the anode of the diode, the other end of the capacitor and the emitter of the second transistor are all connected with the common reference point, and the base of the second transistor is connected with the sixth resistor of the over-current. Under the normal working condition or the overcurrent condition, the normal work and the turn-off of the circuit can be maintained more quickly and stably through the exchange of the transistor and the signal of the overcurrent protection unit.
And the overcurrent and undervoltage protection unit is used for monitoring whether the level signal output by the drive control unit generates overcurrent, starting a circuit protection state and transmitting the circuit protection state to the drive control unit if the level signal output by the drive control unit generates overcurrent, and not processing the overcurrent and undervoltage protection state if the level signal output by the drive control unit does not generate overcurrent. The overcurrent and undervoltage protection unit converts a load working current signal of the liquid crystal driving unit into a voltage signal by using the sampling resistor and the operational amplifier, compares the voltage signal with a reference voltage by using the comparator, rapidly reduces a control signal output by the comparison unit to a low level when the current is too large, and simultaneously enables energy on the inductor to be rapidly released, so that a working device is closed, the liquid crystal load is protected from being burnt, and the liquid crystal display device is stable.
The overcurrent and undervoltage protection unit comprises a fifth resistor, an operational amplifier, a comparator, a sixth resistor, an NPN type field effect transistor, a first diode and a seventh resistor, wherein one end of the fifth resistor is connected with the non-inverting input end of the operational amplifier and serves as the input end of the overcurrent and undervoltage protection unit to be connected with the output end of the drive control unit, and the other end of the fifth resistor is connected with the inverting input end of the operational amplifier and serves as the output end of the overcurrent and undervoltage protection unit to be connected with the voltage input end of the liquid crystal drive unit; the output end of the operational amplifier is connected with the non-inverting input end of the comparator, the inverting input end of the comparator inputs reference voltage, the output end of the comparator is connected with one end of a sixth resistor, and the other end of the sixth resistor is connected with the base electrode of the NPN type field effect transistor; an emitting electrode of the NPN type field effect transistor is grounded, a collector electrode of the NPN type field effect transistor is connected with a negative electrode of the first diode, an anode of the first diode is connected with one end of the seventh resistor, and the other end of the seventh resistor is connected with an input end of the driving control unit.
The reference voltage of the over-current protection unit is a fixed value calculated from more than 40% of the normal operating current. And an NPN type field effect tube in the overcurrent and undervoltage protection unit is turned off in an overcurrent state to play an isolation role. The fifth resistor in the overcurrent and undervoltage protection unit has small resistance value, plays a role in current limiting during normal work and plays a role in sampling feedback when the current is overlarge. Under an overcurrent state, the resistance value of the fifth resistor is small, and the voltage drop between the two ends of the fifth resistor is small, so that the fifth resistor needs to be amplified by the operational amplifier and then compared with a reference voltage. When the circuit normally works, the sampling voltage at the two ends of the fifth resistor passes through the amplifier and then outputs a voltage smaller than or equal to the reference voltage, the comparator outputs a low level signal according to a comparison result, the third triode is turned off at a low level, the first diode is cut off, at the moment, the fourth transistor of the control module unit is in a cut-off state, the control unit has no influence, and all modules of the circuit normally work; when the current of the liquid crystal display device is too large, the sampling voltage at the two ends of the fifth resistor is greater than the reference voltage after passing through the amplifier, the comparator outputs a high level signal according to the comparison result, the high level of the third triode is conducted, the negative electrode of the first diode is low level, the positive electrode of the first diode is high level, the first diode is in a conducting state, the control signal level of the comparison unit is lowered to low level, the field effect transistor of the control unit is turned off and turned off at low level, meanwhile, the fourth transistor of the control module unit is conducted, the energy on the inductor is rapidly released, therefore, the liquid crystal load is prevented from being burnt due to sudden increase of the current, the safety of the driving device is effectively protected, and meanwhile, the stability and the safety of an effective.
And a liquid crystal driving unit for receiving the stable level signal of the driving control unit and outputting an operation level signal used as the liquid crystal panel unit.
Example 1
As shown in fig. 1, the apparatus for improving stable operation of a liquid crystal device provided by the present invention includes a waveform generating unit, a comparing unit, a driving control unit, an over-current and under-voltage protection unit and a liquid crystal driving unit, which are electrically connected in sequence, wherein the waveform generating unit, the comparing unit and the driving control unit are respectively connected with a working level VIN, and an output terminal of the liquid crystal driving unit is connected with a liquid crystal panel unit.
The waveform generating unit receives an externally input level signal VIN and generates a waveform signal with a certain frequency required by the comparing unit according to the input signal. As shown in fig. 4, the waveform generating unit includes a hysteretic comparator and a resistance-capacitance network connected to each other, the resistance-capacitance network includes a resistor RK1, a resistor RK2, a resistor RK3, a resistor RK4, a resistor RK5, and a capacitor CK, one end of the resistor RK1, one end of the resistor RK3, and one end of the resistor RK4 are all connected to the supply voltage VIN, the other end of the resistor RK4 is connected to an output end of the hysteretic comparator, the other end of the resistor RK1 is connected to an anode end of the hysteretic comparator and one end of the resistor RK2, the other end of the resistor RK2 and one end of the capacitor CK are all connected to a common reference point, the other end of the resistor RK3 is connected to one end of the resistor RK5, the other end of the capacitor CK and the other end of the resistor RK5 are both connected to a cathode end of the hysteretic comparator, and. In this embodiment, the signal generated by the waveform generating unit is a triangular wave signal, two threshold values, i.e., levels of a peak and a trough of the triangular wave signal, are set for the input level signal VIN through the hysteresis comparator, and then a triangular wave signal with a fixed frequency is generated according to an internal resistance-capacitance network. The frequency of the generated triangular wave signal can be adjusted by modifying the parameters of the resistance-capacitance network, the triangular wave signal is output to the comparison unit, and the frequency of the triangular wave determines the frequency of the driving control signal output by the comparison unit.
The comparison unit receives the triangular wave type output by the waveform generation unit, inputs the triangular wave type to the cathode end of a comparator in the comparison unit, and compares the triangular wave type with an input signal of the anode end to realize the output of a driving control signal. The driving control signal is a Pulse Width Modulation (PWM) signal with adjustable duty ratio, and the frequency of the PWM signal is the same as that of the triangular wave signal. The input of the anode end of the comparator is a direct current level signal which controls the duty ratio of the output PWM signal, and the duty ratio of the output PWM signal can be controlled by adjusting the level of the level signal. As shown in fig. 3, the comparison unit includes a comparator B, a transistor Q, a resistor R1, a capacitor C, an adjustable resistor R2, and a resistor R3. An anode terminal of the comparator B is connected to one end of the resistor R1, and a cathode terminal of the comparator B is connected to an output terminal of the waveform generating unit. The other end of the resistor R1 is connected to the supply voltage VIN. Capacitor C has one end connected to one end of resistor R1 and the other end connected to a common reference point. The e pole of the transistor Q is connected with the end point connected with the capacitor C and the resistor R1, the C pole of the transistor Q is connected with the common reference point, the b pole of the transistor Q is connected with one end of the resistor R3, and the other end of the resistor R3 is connected with the common reference point. The adjustable resistor R2 has one end connected to the supply voltage and the other end connected to the b-pole of the transistor Q. The control signal output by the comparison unit is a Pulse Width Modulation (PWM) signal, the duty ratio of the control signal is adjustable, and when the frequency of the waveform generation unit is fixed, the control signal is a signal with a constant period and a variable duty ratio.
The driving control unit receives the driving control signal output by the comparison unit, and realizes the stable output of the level signal required by the liquid crystal driving unit by controlling the work of the internal switching element and the energy storage element of the driving unit. In this embodiment, as shown in fig. 5, the switching element is a power MOS transistor Q2, and the energy storage element is an inductance element L and a capacitance element Cd. The gate of the MOS transistor Q2 is connected in series with the resistor R4 and then serves as the input end of the drive control unit and is connected with the output end of the comparison unit, the drain of the MOS transistor Q2 is connected with the supply voltage VIN, the diode D, the inductive element L and the capacitive element Cd are sequentially connected end to end, and the cathode of the diode D and the connection end of the inductive element L are connected with the source of the MOS transistor Q2. The connection end of the anode of the diode D and the capacitance element Cd is connected with a common reference point, and the connection end of the inductance element L and the capacitance element Cd is used as the output end of the drive control unit. The transistor Q4 is an accelerated current release element in an overcurrent state, the collector of the transistor Q4 is connected with the connection end of the inductive element L and the capacitive element Cd, the emitter of the transistor Q4 is connected with the common reference point, and the base of the transistor Q4 is connected with the overcurrent undervoltage protection unit. The driving control unit receives the PWM control signal, realizes the switching of the MOS transistor Q2 and realizes the generation of stable level through two states of normal operation and follow current operation of the inductance element L.
As shown in fig. 6, the over-current and under-voltage protection unit includes a resistor R5, an operational amplifier a1, a comparator a2, a resistor R6, a transistor Q3, a diode D1, and a resistor R7. The resistor R5 is a resistor with a small resistance value, and plays a role of current limiting during normal operation, and is used as a sampling feedback resistor when the current is too large. One end of the resistor R5 is electrically connected to the output terminal of the driving control unit and the non-inverting input terminal of the operational amplifier a1 through a node D0, and the other end is electrically connected to the inverting input terminal of the operational amplifier a1 and the input terminal of the liquid crystal driving unit through a node E0. The operational amplifier a1 receives and amplifies the voltage across the resistor R5 as a sampling resistor, and the output terminal is electrically connected to the input terminal of the comparator a2 via the node F0. The comparator A2 converts the output voltage U of the node F0F0And a reference voltage VrefAnd comparing, and outputting a comparison result by the output end. Because the resistance of the resistor R5 is small, in this embodiment, the value of the resistor R5 is about 0.1-0.5 ohm, which plays a role of current limiting during normal operation, and if it is too large, the current output to the liquid crystal driving unit is too small, which affects the operation of the liquid crystal panel unit; in an overcurrent state, the resistor R5 is used as a sampling feedback resistor, and because the voltage drop between the two ends is very small, the resistor R5 needs to be amplified by a certain multiple through the operational amplifier A1 and then connected with a fixed reference voltagePressure VrefA comparison is made. The operational amplifier A1 has a magnification of 20 times, a normal operating current of 500mA, and an overcurrent state when the load current exceeds 700mA, so that the reference voltage VrefThe maximum working current is 700mA, the voltage across the sampling resistor R5 is about 0.35V, the voltage input to the positive terminal of the comparator through the operational amplifier A1 is about 7V, and the voltage is taken as the voltage V of the negative input terminal of the comparatorref. One end of the resistor R6 is electrically connected with the output end of the comparator A2, the other end of the resistor R6 is electrically connected with the base electrode of the NPN type triode Q3, the voltage of the resistor R6 connected with the base electrode side of the transistor is Vctr, the voltage is the voltage output by the comparator A2, the voltage is connected with the base electrode of the transistor Q4 of the driving control unit, and the voltage at the point is monitored so as to control the rapid release of the inductance energy in the overcurrent state. The emitter of the NPN type triode Q3 is grounded, the collector is electrically connected to the cathode of the diode D1, the anode of the diode D1 is electrically connected to one end of the resistor R7, and the other end of the resistor R7 is electrically connected to the output end of the comparison unit. When the liquid crystal device normally works, the sampling voltage U at the two ends of the resistor R5D0E0The output voltage is less than or equal to the reference voltage V after passing through the operational amplifier A1refThe comparator A2 outputs a low level signal according to the comparison result, the triode Q3 is turned off at a low level, the diode D1 is cut off, and Vctr is at a low level, namely the base electrode of the transistor Q4 is at a low level, the transistor is cut off, the drive control unit is not influenced, and all modules of the circuit work normally; when the current of the liquid crystal device is overlarge, the sampling voltage at the two ends of the resistor R5 passes through the operational amplifier A1, and then the output voltage is larger than the threshold voltage VrefThe comparator A2 outputs a high level signal according to the comparison result, the triode Q3 is turned on at a high level, the cathode of the diode D1 is grounded, the anode is at a high level and is in a conducting state, the control signal output by the comparison unit is rapidly pulled down to a low level, the triode Q3 is turned off at a low level, the grid of the N-channel depletion type MOS tube Q2 is turned off at a high level, and meanwhile, Vctr is at a high level, namely, the base of the transistor Q4 is at a high level, the transistor is turned on, so that the current of the follow current loop is rapidly released through the transistor Q3, the release of energy on the inductor L is accelerated, the system is rapidly stopped, and the liquid crystal load is prevented from being burnt due to sudden. N ditchThe depletion MOS tube Q2 is turned off in an overcurrent state, so that an isolation effect is achieved, an excessive current is prevented from backflushing to the drive control unit and the comparison unit from the source electrode, adverse effects are prevented, and the stability of the circuit is effectively guaranteed.
The liquid crystal driving unit drives the liquid crystal panel unit to normally display and work by receiving the stable level signal output by the driving control unit.
The voltage output by the driving control unit changes according to the duty ratio change output by the comparison unit, and when the adjustable resistor R2 of the comparison unit is adjusted to a certain determined resistance value, the voltage output by the driving control unit is a certain value. The frequency of the driving control signal output by the comparison unit is the same as the frequency of the waveform generated by the waveform generation unit, and the driving control signal is adjusted and controlled by the interior of the waveform generation unit. The anode end of a comparator B in the comparison unit is connected with one end of a capacitor C, the voltage level of the anode end is slowly increased mainly through an RC network, the duty ratio of a control signal output by the comparison unit is gradually increased to a certain fixed value from 0, the slow starting process of a subsequent drive control unit can be realized, and therefore the stable and reliable working states of the subsequent drive control unit and a liquid crystal drive unit are protected. In this embodiment, the transistor Q is a P-type triode, the e-pole of the P-type triode is connected with one end of the capacitor C, the voltage at the two ends of the capacitor C is determined by the divided voltage of the resistor R2 and the resistor R3, and the b-pole voltage of the transistor Q can be determined by the divided voltage of the two resistors, so that the voltage following change can be realized according to the fixed level difference of the characteristic be of the transistor Q, and the control and the limitation of the anode terminal voltage of the comparison unit are realized. In this embodiment, the adjustable resistor R2 and the resistor R3 are both tens of k ohms, and the resistor R1 is hundreds of k ohms. When the voltage Vb of the b pole of the transistor is determined by the adjustable resistor R2 and the resistor R3, the e voltage Ve is equal to Vb + 0.7V.
Example 2
Fig. 2 shows the operation timing requirements of the present device during the whole system startup and shutdown process. In the process of power-on and power-off of a system, the voltage of the anode end of the comparator is required to be lower than the voltage of the cathode end of the comparator so as to realize stable and reliable operation of the system, otherwise, the phenomenon that the liquid crystal driving unit cannot work stably due to damage caused by overlarge current in the driving control unit is caused.
Specifically, during the system power-on process, the rate of voltage rise on the capacitor C is controlled by controlling the resistance value of the resistor R2 and the capacitance value of the capacitor C to ensure that the voltage at the anode terminal of the transistor Q (i.e. the voltage on the capacitor C) is lower than the rate of voltage change at the cathode terminal of the transistor Q (i.e. the triangular wave voltage). In this embodiment, when Vb =7.3V is set, the triangular wave is established for T1=20ms when the system is powered on, and it is necessary to ensure the time when the voltage of Ve rises to 8V, that is, the time T2 when the slope of the voltage rise on the capacitor C intersects with the triangular wave is necessarily greater than 20 ms. By the method, the subsequent units can be effectively protected to work safely and reliably in the power-on process. Meanwhile, in the process of the voltage rise on the capacitor C, when the voltage on the capacitor C gradually rises from 0 to 8V, and the voltage on the capacitor C gradually approaches 8V, the transistor is in a conducting state, and the power supply voltage is discharged through the transistor Q via the resistor R1. When the capacitor voltage C is lower than 8V, the transistor Q is in a cut-off state at this time, so that the voltage of the capacitor C is continuously charged to 8V through the resistor R1, and the voltage of the capacitor C is in a stable state of 8V and is supplied to the anode terminal of the comparator B, thereby realizing the stable system operation in the power-on process. When the system is powered down at the time of T3, the power down rate of the voltage on the capacitor C is lower than the voltage drop rate output by the cathode end waveform generating unit through the transistor Q, so that the abnormal condition is reduced in the dynamic process of power up and power down of the system. When the system is in a power failure process, the voltage Vb is 0V, the voltage on the capacitor C is still 8V at the moment because the voltage on the capacitor cannot be suddenly changed, the transistor Q is conducted at the moment, the voltage on the capacitor C is rapidly discharged through the transistor, so that the slope of the voltage drop on the capacitor C is larger than that of the triangle wave drop, and the safety and the reliability of the system in the power failure process are ensured. In the process of stable work of the system, the comparison unit can output a stable control signal to ensure the normal work of the display equipment unit.
The foregoing is directed to embodiments of the present invention and, more particularly, to a method and apparatus for controlling a power converter in a power converter, including a power converter, a power.
Claims (8)
1. The utility model provides an improve device of liquid crystal apparatus steady operation which characterized in that, includes the wave form generating unit, the comparative unit, the drive control unit that electricity is connected in proper order, overflows undervoltage protection unit and liquid crystal drive unit, wave form generating unit, comparative unit, drive control unit have all connect the working level, and liquid crystal drive unit's level signal output part connects the liquid crystal display panel unit, and the output that overflows undervoltage protection unit still is connected with drive control unit's input, wherein:
the waveform generating unit is used for receiving an externally input level signal, generating a waveform signal with a certain frequency according to the level signal and then sending the waveform signal to the comparing unit;
the comparison unit is used for receiving the waveform signal, comparing the waveform signal with the direct current signal, generating a driving control signal and outputting the driving control signal to the driving control unit, wherein the frequency of the driving control signal is the same as that of the waveform signal;
the driving control unit is used for receiving the driving control signal, generating a stable level signal and outputting the stable level signal to the liquid crystal driving unit through the overcurrent and undervoltage protection unit; the driving control unit comprises a field effect transistor, a second transistor, an inductor, a capacitor, a diode and a fourth resistor, wherein one end of the fourth resistor is used as the input end of the driving control unit and is connected with the output end of the comparison unit, and the other end of the fourth resistor is connected with the grid electrode of the field effect transistor; the drain electrode of the field effect transistor is connected with a power supply voltage, the source electrode of the field effect transistor is connected with the cathode of the diode and the inductor, the other end of the inductor is connected with the capacitor and the collector of the second transistor and serves as the output end of the driving control unit to be connected with the fifth resistor of the over-current and under-voltage protection unit, the anode of the diode, the other end of the capacitor and the emitter of the second transistor are all connected with a common reference point, and the base electrode of the second transistor is connected with the sixth resistor of the over-;
the overcurrent and undervoltage protection unit is used for monitoring whether the level signal output by the drive control unit generates overcurrent, starting a circuit protection state and transmitting the circuit protection state to the drive control unit if the level signal output by the drive control unit generates overcurrent, and not processing the overcurrent and undervoltage protection state if the level signal output by the drive control unit does not generate overcurrent; the overcurrent and undervoltage protection unit comprises a fifth resistor, an operational amplifier, a comparator, a sixth resistor, an NPN type field effect transistor, a first diode and a seventh resistor, wherein one end of the fifth resistor is connected with the non-inverting input end of the operational amplifier and serves as the input end of the overcurrent and undervoltage protection unit to be connected with the output end of the drive control unit, and the other end of the fifth resistor is connected with the inverting input end of the operational amplifier and serves as the output end of the overcurrent and undervoltage protection unit to be connected with the voltage input end of the liquid crystal drive unit; the output end of the operational amplifier is connected with the non-inverting input end of the comparator, the inverting input end of the comparator inputs reference voltage, the output end of the comparator is connected with one end of a sixth resistor, and the other end of the sixth resistor is connected with the base electrode of the NPN type field effect transistor; an emitting electrode of the NPN type field effect transistor is grounded, a collector electrode of the NPN type field effect transistor is connected with a negative electrode of a first diode, an anode of the first diode is connected with one end of a seventh resistor, and the other end of the seventh resistor is connected with an input end of the driving control unit;
and a liquid crystal driving unit for receiving the stable level signal of the driving control unit and outputting an operation level signal used as the liquid crystal panel unit.
2. The apparatus according to claim 1, wherein the waveform generating unit comprises a hysteretic comparator and a resistor-capacitor network connected to each other, wherein the resistor-capacitor network comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a second capacitor, one end of the first resistor, the third resistor and the fourth resistor is connected to a power supply voltage, the other end of the fourth resistor is connected to an output end of the hysteretic comparator, the other end of the first resistor and one end of the second resistor are connected to an anode end of the hysteretic comparator, the other end of the second resistor and one end of the second capacitor are connected to a common reference point, the third resistor is connected in series with the fifth resistor, the other end of the second capacitor and the other end of the fifth resistor are connected to a cathode end of the hysteretic comparator, and the cathode end of the hysteretic comparator is connected to an input end of the comparing unit as an output end of the waveform generating.
3. The apparatus of claim 1 or 2, wherein the waveform signal generated by the waveform generating unit is a triangular wave signal, and the two thresholds of the hysteresis comparator in the waveform generating unit are respectively a peak level and a trough level of the triangular wave signal.
4. The apparatus of claim 1, wherein the comparing unit comprises a comparator, a first transistor, a first resistor, a capacitor, a second resistor, and a third resistor, wherein a cathode terminal of the comparator is connected to the output terminal of the waveform generating unit as an input terminal of the comparing unit, and an output terminal of the comparator is connected to the input terminal of the driving control unit as an output terminal of the comparing unit; the anode end of the comparator, one end of the first resistor, one end of the capacitor and the emitting electrode of the first transistor are connected to a point in common, one end of the second resistor and one end of the third resistor are both connected with the base electrode of the first transistor, the other end of the first resistor and the other end of the second resistor are both connected with a power supply voltage, the other end of the capacitor, the collector electrode of the first transistor and the other end of the third resistor are all connected with a common reference point, and the second resistor is an adjustable resistor.
5. The apparatus of claim 1 or 4, wherein the driving control signal generated by the comparing unit is a pulse width modulation signal with adjustable duty ratio.
6. The apparatus of claim 1, wherein the fifth resistor of the over-current and under-voltage protection unit is a small-resistance resistor for limiting current during normal operation and for sampling feedback when the current is too large.
7. The apparatus of claim 1, wherein the N-channel depletion type MOS transistor in the driving control unit is turned off for isolation in an overcurrent state.
8. The apparatus of claim 1, wherein the emitter voltage of the first transistor is 0.7V greater than the base voltage.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US7394209B2 (en) * | 2004-02-11 | 2008-07-01 | 02 Micro International Limited | Liquid crystal display system with lamp feedback |
| JP4646187B2 (en) * | 2004-02-12 | 2011-03-09 | 東北パイオニア株式会社 | Light emitting display device and drive control method thereof |
| JP2009058857A (en) * | 2007-09-03 | 2009-03-19 | Toshiba Matsushita Display Technology Co Ltd | Backlight device |
| CN103021365B (en) * | 2012-12-14 | 2015-01-21 | 京东方科技集团股份有限公司 | Device and method for adjusting gamma curve and liquid crystal display device |
| CN103050094B (en) * | 2012-12-27 | 2015-02-04 | 深圳市华星光电技术有限公司 | Overvoltage protection method for backlight driving circuit in 2D/3D (two-dimensional/three-dimensional) mode and backlight driving circuit applying overvoltage protection method |
| CN105405410A (en) * | 2015-11-20 | 2016-03-16 | 青岛海信电器股份有限公司 | Backlight driving circuit and driving method and display device thereof |
| CN107393491B (en) * | 2017-07-18 | 2018-08-14 | 深圳市华星光电半导体显示技术有限公司 | Clock signal output circuit and liquid crystal display device |
| CN108962165B (en) * | 2018-07-18 | 2021-08-31 | 南京熊猫电子制造有限公司 | Circuit and method for eliminating power-down residual image of IGZO display panel |
| CN109727585B (en) * | 2018-12-24 | 2021-07-06 | 惠科股份有限公司 | Display driving assembly and display device |
| CN109949775A (en) * | 2019-05-22 | 2019-06-28 | 南京熊猫电子制造有限公司 | A kind of power supply unit of liquid crystal display |
| CN211087888U (en) * | 2019-11-27 | 2020-07-24 | 广州视源电子科技股份有限公司 | Backlight driving circuit and electronic equipment |
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