CN103561517B - Executive circuit, multi-way LED lamp cascade control circuit and control method - Google Patents
Executive circuit, multi-way LED lamp cascade control circuit and control method Download PDFInfo
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Abstract
The present invention discloses a kind of executive circuit, multi-way LED lamp cascade control circuit and control method, and described control method comprises: sample to the voltage of each LED string loop or electric current; Integration is carried out to each LED string loop sampled result; Within the periodicity control time of the operating time and low level Dead Time with high level, periodically to perform: within the operating time of each control cycle, lamp string integral result being reached to preset value turns off until this execution cycle terminates; In the Dead Time of each execution cycle, each LED string loop is turned off.This programme utilizes current integration circuit to carry out integration to the electric current of LED of often going here and there in one-period, and compares according to this integral result and the integrated value preset, thus makes the Different treatments of the switch controlling respective LED string.
Description
Technical Field
The invention relates to an execution circuit, a multi-path LED lamp string control circuit and a control method.
Background
The LED has been widely used in lcd tvs, and the driving of the LED has been rapidly developed. Due to the structural requirement and the requirement of 3D function of the large-size liquid crystal television, most of the LED lamp strings are multi-string, and some LED lamp strings even can reach dozens of ways. For the multi-path driving, a linear constant current mode is often adopted to reduce the cost of the system. However, due to the difference of the voltage drop of the LED lamps, the voltage difference between each path of LED lamp string is also greatly different, and if the brightness is balanced by adopting a linear constant current mode, the power loss of the switching tube is greatly increased, so that the efficiency is reduced, and the switching tube with high power consumption is higher in cost. With the increasing drive current of the LED lamp string, the linear constant current mode becomes more embarrassing.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an execution circuit, a multi-channel LED string control circuit and a control method, which implement on-off operation of a switch tube in an LED string by an integrated current control method under the condition of ensuring brightness balance between LED strings.
To achieve the above object, the present invention provides an execution circuit, which includes an integrator having a positive input terminal, a negative input terminal, and an output terminal, and further includes:
the sampling circuit is arranged in a tested loop and used for sampling the current or the voltage in the tested loop and outputting a sampling result to the negative input end of the integrator;
the first controlled unit is connected with the sampling circuit in the tested loop in series;
and the second controlled unit is connected between the positive input end of the integrator and the ground.
Wherein the first controlled unit and the second controlled unit receive a periodic control signal having a high level working time and a low level dead time to periodically perform:
in the working time, the positive input end of the controlled integrator of the second controlled unit is at a low level, the first controlled unit is controlled to conduct the tested loop, and the integrator integrates the sampling result output by the sampling circuit and then outputs the integrated result;
in the dead time, the positive input end of the controlled integrator of the second controlled unit is at a high level, the first controlled unit is controlled to disconnect the tested loop, and the integrator performs reverse integration on the sampling result output by the sampling circuit and outputs the result.
Preferably, the second controlled unit includes: a capacitor, an electronic switch composed of a controlled end and two input ends
The high-voltage power supply comprises a capacitor, an electronic switch, a resistor, an integrator and a voltage regulator, wherein the capacitor is connected with two input ends of the electronic switch in parallel, one end of the capacitor is connected with a low level, the other end of the capacitor is connected with a high level through the resistor, and the positive input end of the integrator is connected between the resistor and the capacitor;
during working time, the electronic switch is controlled to conduct two input ends of the electronic switch, so that the positive input end of the integrator is at a low level;
in the dead time, the electronic switch is controlled to turn off two input ends of the electronic switch, so that the positive input end of the integrator is at a high level.
Preferably, the execution circuit further comprises a comparator, wherein the comparator comprises a first input end, a second input end and an output end;
the first input end of the comparator receives an integration result output by the output end of the integrator;
a second input end of the comparator receives or sets a preset value;
and the comparator compares the integration result with a preset value, and if the integration result is smaller than the preset value in the working time, a low level is output to enable the first controlled unit to turn off the tested loop.
Preferably, the tested loop comprises a load, a first controlled unit and a sampling circuit which are sequentially connected in series, and the sampling circuit is arranged at the negative end of the tested loop;
the execution circuit also comprises a voltage detection circuit used for detecting the real-time voltage of the detected loop; the voltage detection circuit comprises an input end and an output end, the input end is connected between a load of the tested loop and the first controlled unit, and the output end outputs a detection voltage result.
Preferably, the integrator comprises:
the first operational amplifier is provided with a first input end, a second input end and an output end, and a first capacitor is connected between the first input end and the output end of the first operational amplifier;
one end of the first resistor is connected with the first input end of the first operational amplifier, and the other end of the first resistor is connected with the second input end of the first electronic switch;
one end of the second resistor is connected with the second input end of the first operational amplifier, and the other end of the second resistor is connected with the first input end of the second electronic switch;
and the anode and the cathode of the reset diode are respectively connected with the first input end of the first operational amplifier and the second input end of the first electronic switch.
Preferably, the output end of the integrator is connected to the second input end of the comparator, the output ends of the comparator are respectively connected to the controlled end of the first controlled unit and the controlled end of the second controlled unit, and the first input end of the comparator is connected to the signal input end of the preset value;
the comparator comprises a second operational amplifier, a first diode, a second diode, a third resistor, a fourth resistor and a fifth resistor;
wherein,
the output end of the second operational amplifier is connected with the negative end of a first diode, and the positive end of the first diode is connected with the controlled end of the first controlled unit;
the output end of the operational amplifier is connected with one end of a third resistor, and the other end of the third resistor is connected with the controlled end of the first controlled unit;
the controlled end of the first controlled unit is connected with a fourth resistor, and the other end of the fourth resistor is connected with the controlled end of the second controlled unit;
a second diode is connected in parallel with the fourth resistor;
and a fifth resistor is also arranged between the output end of the operational amplifier and the second controlled unit.
In order to achieve the above object, the present invention provides a multi-channel LED light string control circuit for controlling a plurality of LED light string circuits, wherein each LED light string circuit is correspondingly provided with an integration unit, and the multi-channel LED light string control circuit at least comprises:
the integration unit is the execution circuit, and the tested loop is the LED lamp string loop;
the control unit is provided with a detection end and a control signal output end, and the detection end is connected with the output end of the execution circuit;
the control signal output end is connected with the controlled ends of the first controlled unit and the second controlled unit, and sends periodic control signals with high-level working time and low-level dead time to the first controlled unit and the second controlled unit through the control signal output end so as to periodically execute:
in the control signal working time:
if the integral result received by the detection end reaches a preset value, the positive input end of the controlled execution circuit of the second controlled unit is at a low level, the first controlled unit is controlled to conduct the tested loop, and the execution circuit integrates the sampling result output by the sampling circuit and outputs the integrated result;
if the integral result received by the detection end is smaller than a preset value, the first controlled unit is controlled to turn off the detected loop until the current control period is finished;
in the dead time of the control signal, the positive input end of the controlled execution circuit of the second controlled unit is at high level, the first controlled unit is controlled to disconnect the tested loop, and the execution circuit carries out reverse integration on the sampling result output by the sampling circuit and then outputs the result.
Preferably, the LED lamp further comprises a voltage detection circuit for detecting the voltage in the LED lamp string loop and outputting the detection result to the control unit,
the control unit is used for controlling the working time of the signal: further performing:
if the voltage detection results of all the lamp strings reach a preset value, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the preset value, a control signal is output to improve the power supply voltage of all the lamp strings.
In order to achieve the above object, the present invention provides a multi-LED light string loop control method, which is implemented by using the above control circuit, and comprises the following steps:
sampling the voltage or current of each LED lamp string loop;
integrating the sampling result of each LED lamp string loop;
during a periodic control time having an on-time at a high level and a dead time at a low level, to periodically perform:
within the working time of each control period, the lamp string with the integration result reaching the preset value is turned off until the execution period is finished;
each LED string loop is turned off during the dead time of each execution cycle.
Preferably, during the working time of each control cycle, further performing:
if the integral results of all the lamp strings reach the voltage threshold, reducing the working voltage of all the lamp strings; comparing the integral result of each lamp string with a preset value; and if any integration result does not reach the voltage threshold value, the power supply voltage of all the lamp strings is increased.
Preferably, the method further comprises the following steps: detecting the voltage of the LED lamp strings in real time, and if the voltage detection results of all the lamp strings reach a voltage threshold value, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the voltage threshold value, a control signal is output to improve the power supply voltage of all the lamp strings.
Preferably, the control unit receives a PWM signal;
and the control unit adjusts the ratio of the working time to the dead time in the periodic control signal according to the duty ratio of the PWM signal.
The control unit adjusts the preset value according to the duty ratio of the PWM signal; wherein the preset value = an initial preset value x duty cycle value of the PWM signal.
The formula for changing the dead time according to the duty ratio value of the PWM signal is:
dead time = (1-duty value) × (T-initial dead time).
The invention has the beneficial effects that:
according to the scheme, the current integrating circuit is used for integrating the current of each string of LED lamps in an execution period, and the integration result is compared with the preset integration value, so that the on-off of each LED lamp string is controlled, the voltages at two ends of the lamp strings are adjusted, and the PWM dimming of each lamp string, the current integration balance among each path and the lamp string protection are realized. The method meets the requirement that the output brightness of each LED lamp string is approximately the same to a certain extent, reduces the loss, increases the efficiency, improves the reliability and reduces the cost of devices.
Drawings
Fig. 1 is a circuit diagram of an integrating circuit according to embodiment 1 of the present invention;
FIG. 2 is a circuit diagram of an integrating circuit according to embodiment 2 of the present invention;
FIG. 3 is a circuit diagram of an integrating circuit according to embodiment 3 of the present invention;
FIG. 4 is a circuit diagram of a control circuit according to embodiment 4 of the present invention;
FIG. 5 is a circuit diagram of a control circuit according to embodiment 5 of the present invention;
FIG. 6 is a circuit diagram of a control circuit according to embodiment 6 of the present invention;
FIG. 7 is a first execution equivalent diagram of embodiment 5;
FIG. 8 is a second execution equivalent diagram of embodiment 5;
fig. 9 is a voltage waveform chart in an execution cycle of embodiment 5.
Detailed Description
The invention is further described with reference to the accompanying drawings.
Example 1:
the invention relates to an execution circuit, which comprises an integrator with a positive input end, a negative input end and an output end, and also comprises:
the sampling circuit is arranged in a tested loop and used for sampling the current or the voltage in the tested loop and outputting a sampling result to the negative input end of the integrator;
the first controlled unit is connected with the sampling circuit in the tested loop in series;
and the second controlled unit is connected between the positive input end of the integrator and the ground.
In the execution process, the first controlled unit and the second controlled unit receive a periodic control signal with high-level working time and low-level dead time so as to periodically execute:
in the working time, the positive input end of the controlled integrator of the second controlled unit is at a low level, the first controlled unit is controlled to conduct the tested loop, and the integrator integrates the sampling result output by the sampling circuit and then outputs the integrated result;
in the dead time, the positive input end of the controlled integrator of the second controlled unit is at a high level, the first controlled unit is controlled to disconnect the tested loop, and the integrator performs reverse integration on the sampling result output by the sampling circuit and outputs the result.
The second controlled unit includes: the capacitor and the electronic switch are composed of a controlled end and two input ends;
the high-voltage power supply comprises a capacitor, an electronic switch, a resistor, an integrator and a voltage regulator, wherein the capacitor is connected with two input ends of the electronic switch in parallel, one end of the capacitor is connected with a low level, the other end of the capacitor is connected with a high level through the resistor, and the positive input end of the integrator is connected between the resistor and the capacitor;
during working time, the electronic switch is controlled to conduct two input ends of the electronic switch, so that the positive input end of the integrator is at a low level;
in the dead time, the electronic switch is controlled to turn off two input ends of the electronic switch, so that the positive input end of the integrator is at a high level.
The purpose of the scheme is to integrate the current of each string of LED lamps in an execution period by using a current integration circuit, and compare the integration result with a preset integration value, thereby controlling the on and off of each LED string. Therefore, the loss can be reduced, the efficiency is increased, the reliability is improved, and the cost of the device is reduced.
Fig. 1 shows a specific circuit diagram obtained by the scheme. In fig. 1, the sampling resistor is the sampling circuit. And the first controlled unit and the second controlled unit are used for controlling a first electronic switch and a second electronic switch in a circuit diagram. According to the scheme, control instructions made according to the integration result are sent to the first electronic switch and the second electronic switch to achieve different stages of turn-off, so that the control function of the electronic switch and other elements in the circuit are achieved together.
The circuit diagram described above is explained below:
the integrator comprises a first operational amplifier, a first resistor, a second resistor, a first capacitor and a reset diode; the first controlled unit comprises a first electronic switch; the second controlled unit comprises a second electronic switch and a second capacitor; the sampling circuit comprises a sampling resistor;
wherein,
the first operational amplifier is provided with a first input end, a second input end and an output end, and a first capacitor is connected between the first input end and the output end of the first operational amplifier;
one end of the first resistor is connected with the first input end of the first operational amplifier, and the other end of the first resistor is connected with the second input end of the first electronic switch;
the first input end of the first electronic switch is connected with the negative end of the light bar, the second input end of the first electronic switch is connected with one end of the sampling resistor, and the other end of the sampling resistor is grounded;
one end of the second resistor is connected with the second input end of the first operational amplifier, and the other end of the second resistor is connected with the first input end of the second electronic switch;
the first input end and the second input end of the second electronic switch are connected with the second capacitor, and the first input end of the second electronic switch is connected with the external voltage input end; the second input end of the first switch is grounded;
and the anode and the cathode of the reset diode are respectively connected with the first input end of the first operational amplifier and the second input end of the first electronic switch.
Example 2:
the present embodiment is different from embodiment 1 in that: on the basis of the execution circuit described in embodiment 1, a comparator is added, and the comparator is used to compare the integration result with a preset value, and to turn on and off the first electronic switch and the second electronic switch in the above figure according to the comparison result. The comparator comprises a first input end, a second input end and an output end. The first input end of the comparator receives an integration result output by the output end of the integrator; the second input terminal of the comparator receives a preset value.
And the comparator compares the integration result with a preset value, and if the integration result is smaller than the preset value in the working time, a low level is output to enable the first controlled unit to turn off the tested loop.
Fig. 2 shows a circuit diagram of the scheme of example 2. In the circuit diagram of fig. 2, the circuit of fig. 1 needs to be connected to illustrate that: the output end of the integrator is connected with the second input end of the comparator, the output end of the comparator is respectively connected with the controlled end of the first electronic switch and the controlled end of the second electronic switch, and the first input end of the comparator is connected with the signal input end of the preset value;
the comparator comprises a second operational amplifier, a first diode, a second diode, a third resistor, a fourth resistor and a fifth resistor;
wherein,
the output end of the second operational amplifier is connected with the negative end of a first diode, and the positive end of the first diode is connected with the controlled end of the first electronic switch;
the output end of the operational amplifier is connected with one end of a third resistor, and the other end of the third resistor is connected with the controlled end of the first electronic switch;
the controlled end of the first electronic switch is connected with a fourth resistor, and the other end of the fourth resistor is connected with the controlled end of the second electronic switch;
a second diode is connected in parallel with the fourth resistor;
and a fifth resistor is also arranged between the output end of the operational amplifier and the second electronic switch.
Example 3:
in this embodiment, a voltage detection circuit is added on the basis of embodiment 2. The voltage of the negative end of the load in the circuit is detected by the voltage detection circuit, so that the voltage at two ends of the load is controlled to be increased or decreased.
The method specifically comprises the following steps:
the tested loop comprises a load, a first controlled unit and a sampling circuit which are sequentially connected in series, and the sampling circuit is arranged at the negative end of the tested loop;
the execution circuit also comprises a voltage detection circuit used for detecting the real-time voltage of the detected loop; the voltage detection circuit comprises an input end and an output end, the input end is connected between a load of the tested loop and the first controlled unit, and the output end outputs a detection voltage result.
Fig. 3 shows a circuit diagram of the scheme of embodiment 3. In the circuit diagram of fig. 3, the circuit of fig. 2 needs to be connected to illustrate that: the voltage detection circuit is a diode, the cathode of the diode is connected with the negative end of the corresponding lamp string, and the anodes of all the diodes are connected together to form the output end of the voltage detection circuit.
The voltage detection circuit added in this embodiment is to detect the voltage in the detected loop in real time, so as to send out a PWM control signal by the controller according to the detection result, and increase or decrease the working voltage of all the light strings, thereby implementing PWM dimming of each light string, current balancing among the light strings, and light string protection.
Example 4:
the embodiment of the invention provides a multi-path LED lamp string control circuit, which is used for controlling a plurality of LED lamp string loops, wherein each LED lamp string loop is correspondingly provided with an integration unit, and the control circuit at least comprises:
the integration unit is the execution circuit in embodiment 1, and the detected loop is the LED lamp string loop;
the control unit is provided with a detection end and a control signal output end, and the detection end is connected with the output end of the integrating circuit;
the control signal output end is connected with the controlled ends of the first controlled unit and the second controlled unit, and sends periodic control signals with high-level working time and low-level dead time to the first controlled unit and the second controlled unit through the control signal output end so as to periodically execute:
in the control signal working time:
if the integration result received by the detection end reaches a preset value, the positive input end of the integration circuit controlled by the second controlled unit is at a low level, the first controlled unit is controlled to conduct the detected loop, and the integration circuit integrates the sampling result output by the sampling circuit and outputs the integrated result;
if the integral result received by the detection end does not reach a preset value, the first controlled unit is controlled to turn off the detected loop until the current control period is finished.
In the dead time of the control signal, the positive input end of the controlled integrating circuit of the second controlled unit is at high level, the first controlled unit is controlled to disconnect the tested loop, and the integrating circuit carries out reverse integration on the sampling result output by the sampling circuit and then outputs the result.
In the implementation of the present embodiment, the above-mentioned integration unit is the execution circuit described in embodiment 1. Referring to fig. 4, it can be seen that: and the output end of the execution circuit is connected with the detection end of the control unit. And the controlled ends of the first controlled unit and the second controlled unit are connected with the control signal output end of the control unit. One input end of the first electronic switch in each execution circuit is connected with the negative end of the light string, the control unit (the controller in the figure) is connected with a control power supply, and the power supply supplies power to the light string.
The control circuit in the scheme is realized in a control mode by the following steps:
first, how the voltage value after the integration processing is obtained will be explained with reference to the structure in fig. 1: when the loop to be tested is electrified, the first electronic switch and the second electronic switch are all switched on under a control signal sent by a control signal output end (GATE) of the controller. The power supply provides an initial voltage for the LED lamp string to emit light, the stored current flows through the LED lamp string and simultaneously flows through the sampling resistor, and a sampling voltage is formed at two ends of the sampling resistor. The integration unit performs integration processing on the sampling voltage.
The integration process described above is such that: due to the fact that the first electronic switch is turned on, current starts to charge on the first capacitor through the first resistor, voltage exists at the output end of the first operational amplifier, the voltage is obtained after integration processing of the integration unit, and the voltage at the output end of the first operational amplifier is continuously increased within the working time of the preset period.
The voltage value of the output end of the first operational amplifier is compared with a preset voltage value in the controller, and the comparison processing comprises the following steps:
in the first case:
in the working time of the execution cycle, the specific treatment of the LED lamp string according to the comparison result is as follows:
and when the voltage value obtained by the integration processing does not reach the preset voltage value, closing the corresponding LED lamp string. The concrete embodiment is as follows: the first electronic switch is turned off, the first capacitor starts to discharge, the reset diode starts to be conducted, and finally the first capacitor is discharged to the ground to complete the reset of the integral unit. The reset means that the first capacitor discharges to zero. Because the first capacitance is also in a no-charge state at the beginning of the integration state. In the next cycle, the LED string is turned off again.
Because the dead time is arranged in the preset period, after the dead time is entered under the normal condition, all the lamp strings are turned off, and the specific embodiment is as follows: the first electronic switch is turned off, the first capacitor starts to discharge, and the reset diode starts to conduct. The second electronic switch is turned off and the second capacitor is charged, so that the positive terminal voltage of the operational amplifier is the external output voltage VCC. At this time, the voltage at the output terminal of the operational amplifier is VCC.
In the second case:
in the dead time in the execution cycle, a case different from the above occurs, and the case is specifically treated as follows:
(1) and when one string of the LED strings enters the dead time, the voltage value obtained by integration is not equal to or less than the preset voltage value, and the working voltage of all the strings is increased.
(2) And when all the LED lamp strings enter the dead time, the voltage value obtained by integration is equal to or less than the preset voltage value, and the working voltage of all the lamp strings is reduced.
By processing the integration result, PWM dimming of each path and current integration balance among paths and string protection are realized.
Example 5:
as shown in fig. 5, the present embodiment is different from embodiment 4 in that: on the basis of embodiment 4, a comparator is added.
The comparator comprises a first input end, a second input end and an output end;
the first input end of the comparator receives an integration result output by the output end of the integration circuit;
a second input end of the comparator receives or sets a preset value;
and the comparator compares the integration result with a preset value, and if the integration result is smaller than the preset value in the working time, a low level is output to enable the first controlled unit to turn off the tested loop.
The voltage detection circuit is used for detecting the real-time current or voltage of the tested loop in the control stage of the periodic control signal.
The circuit connection of example 4 was changed after the addition:
the output end of the integrator is connected with the second input end of the comparator, the output end of the comparator is respectively connected with the controlled end of the first electronic switching tube and the controlled end of the second electronic switching tube, and the first input end of the comparator is connected with the signal input end of the preset value;
the comparator comprises a second operational amplifier, a first diode, a second diode, a third resistor, a fourth resistor and a fifth resistor;
wherein,
the output end of the second operational amplifier is connected with the negative end of a first diode, and the positive end of the first diode is connected with the controlled end of the first electronic switch;
the output end of the operational amplifier is connected with one end of a third resistor, and the other end of the third resistor is connected with the controlled end of the first electronic switch;
the controlled end of the first electronic switch is connected with a fourth resistor, and the other end of the fourth resistor is connected with the controlled end of the second electronic switch;
a second diode is connected in parallel with the fourth resistor;
and a fifth resistor is also arranged between the output end of the operational amplifier and the second electronic switch.
The voltage detection circuit is a diode, the cathode of the diode is connected with the negative end of the corresponding lamp string, and the anodes of all the diodes are connected together to form the output end of the voltage detection circuit.
The effect of adding the comparator is: the comparison unit of the controller in embodiment 1 is externally arranged, and the comparison work of the controller is carried out by hardware, so that the calculation of the whole system becomes relatively simple. The processing result of the control is as follows: within the working time of each execution period, the lamp string with the integration result reaching the preset value is turned off until the execution period is finished; each LED string is turned off during the dead time of each execution cycle. In terms of control, generally, if the voltage value in the control unit generally needs to be converted by an AD converter and then compared with a preset value, which is costly, the present embodiment uses an analog comparator to implement the comparison, which greatly simplifies the computational complexity of the control unit. And the first electronic switch and the second electronic switch are controlled by the output end of the comparator, so that the control is simpler.
The voltage detection circuit is added to have the following functions: the voltage of the lamp strings is detected in real time, so that the controller sends out PWM control signals according to the detection result, the working voltage of all the lamp strings is increased or decreased, and the effects of light string brightness balance and lamp string protection are achieved.
When the comparator is controlled, two situations are divided:
1. in the working time of a period, when the current of the LED lamp string is (over) high, the integral value output from the output end of the first operational amplifier is earlier than a preset value, and at the moment, the output end of the second operational amplifier outputs a low level, so that the first electronic switch can be turned off. An equivalent is made on the basis of fig. 5 for the second electronic switch, which results in fig. 7, in which the second electronic switch is still in a conducting state because a third resistor and a second diode are present between the signal GATE1 at the control signal output terminal of the second electronic switch receiving controller and the output terminal of the second operational amplifier.
2. During the dead time, GATE1 at the control signal output of the controller is low, and the second electronic switch is off because the output of the second operational amplifier is still low. For the second electronic switch, fig. 8 is obtained by performing an equivalent operation on the basis of fig. 5, in the diagram, because the second electronic switch receives the signal GATE1 at the control signal output end of the controller and the first diode and the fourth resistor exist at the output end of the second operational amplifier, because the fourth resistor is a load resistor, the GATE1 makes the GATE of the first electronic switch low under the action of the first diode, and the first electronic switch continues to keep the off state. The first electronic switch is turned off, and the first capacitor on the integrator discharges through the reset diode and the sampling resistor to the ground, so that the integrator is reset.
From the above explanation, waveform diagrams of the respective voltage signals as shown in fig. 9 can be obtained.
When the voltage detection circuit is used for controlling, in a very short time before the dead time of each execution cycle, if the voltage detection circuit detects that at least one lamp strip has voltage, the voltage of all the lamp strips is reduced; if the voltage detection circuit detects that at least one lamp strip does not have voltage, the voltage of all the lamp strips is increased.
Example 6:
as shown in fig. 6, the present embodiment is different from embodiment 5 in that: under the embodiment 5, a voltage detection circuit is added for detecting the voltage in the LED lamp string loop and outputting the detection result to the control unit,
the control unit is used for controlling the working time of the signal: further performing:
if the voltage detection results of all the lamp strings reach the voltage threshold, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the voltage threshold value, a control signal is output to improve the power supply voltage of all the lamp strings.
The concrete structure is as follows: and the voltage detection end of the control end is respectively connected with the first input end of the first electronic switch in each voltage integrating circuit through a diode.
The voltage detection circuit is added to have the following functions: the voltage of the lamp strings is detected in real time, so that the controller sends out PWM control signals according to the detection result, the working voltage of all the lamp strings is increased or decreased, and the effects of light string brightness balance and lamp string protection are achieved.
The invention discloses a multi-LED lamp string loop control method, which comprises the following concrete implementation steps:
sampling the voltage or current of each LED lamp string loop;
integrating the sampling result of each LED lamp string loop;
during a periodic control time having an on-time at a high level and a dead time at a low level, to periodically perform:
within the working time of each control period, the lamp string with the integration result reaching the preset value is turned off until the execution period is finished;
each LED string loop is turned off during the dead time of each execution cycle.
As an improvement of the method, the method is characterized in that the voltage of each LED lamp string loop is integrated in each execution period, and the integrated result is compared with a preset value, so that a corresponding processing result is made. The LED light string is cut off, PWM dimming of each light string, current integral balance among all the light strings and light string protection can be effectively realized.
During the working time of each control cycle, further executing:
if the integral results of all the lamp strings reach a preset value, reducing the working voltage of all the lamp strings; comparing the integral result of each lamp string with a preset value; and if any integration result does not reach the preset value, the power supply voltage of all the lamp strings is increased.
The scheme integrates the current of each string of LED lamps in an execution period by using a current integration method, compares the integration result with a preset integration value, and adjusts the voltages at two ends of the string of lamps according to the comparison result, thereby realizing the PWM dimming of each string of lamps, the current balance among each path of lamps and the protection of the strings of lamps.
In addition, another method for changing the operating voltage of the light string comprises the following steps: detecting the voltage of the LED lamp strings in real time, and if the voltage detection results of all the lamp strings reach a voltage threshold value, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the voltage threshold value, a control signal is output to improve the power supply voltage of all the lamp strings.
The scheme detects the voltage in the detected loop in real time, thereby changing the voltages at two ends of the lamp string, and realizing PWM dimming of each lamp string, current balance among each circuit and lamp string protection.
As a further improvement of the invention, the invention also provides a solution for changing the preset value. The method specifically comprises the following steps: the controller receives a PWM signal from an external device and changes the preset value using a duty value of the PWM signal.
Preset = initial preset value PWM signal duty cycle value;
the initial preset value is a voltage value preset in the production process of the mainboard/host computer so as to meet normal work.
Similarly, the invention also provides a scheme for changing the periodic control signal. The method specifically comprises the following steps: the duty cycle value of the PWM signal is used by the controller to vary the ratio of the on-time to the dead-time in the periodic control signal. The concrete formula is as follows:
dead time = (1-PWM signal duty ratio) (T-initial dead time)
The initial dead time is a ratio preset in the production process of the mainboard/host to meet normal work.
By using the change of the preset value and the dead time, the dimming setting of the display screen can be realized. According to the formula, when the duty ratio of the PWM signal received by the controller is higher, the preset value is also higher, the dead time is shorter, the voltage on the LED lamp strip is higher, the time for which the voltage continuously acts on the LED lamp strip is longer, and therefore the display screen is brighter; on the contrary, when the duty ratio of the PWM signal received by the controller is low, the preset value is also low, the dead time is long, the voltage on the LED light bar is low, the time for which the voltage continuously acts on the LED light string is short, and thus the display screen is dark.
The above description is only for the 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 are also included in 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 (12)
1. An LED light string execution circuit, said execution circuit comprising an integrator having a positive input terminal, a negative input terminal, and an output terminal, further comprising:
the sampling circuit is arranged in a tested loop and used for sampling the current or the voltage in the tested loop and outputting a sampling result to the negative input end of the integrator;
the first controlled unit is connected with the sampling circuit in the tested loop in series;
the second controlled unit is connected between the positive input end of the integrator and the ground;
wherein the first controlled unit and the second controlled unit receive a periodic control signal having a high level working time and a low level dead time to periodically perform:
in the working time, the positive input end of the controlled integrator of the second controlled unit is at a low level, the first controlled unit is controlled to conduct the tested loop, and the integrator integrates the sampling result output by the sampling circuit and then outputs the integrated result;
in the dead time, the positive input end of the controlled integrator of the second controlled unit is at a high level, the first controlled unit is controlled to disconnect the tested loop, and the integrator performs reverse integration on the sampling result output by the sampling circuit and outputs the result.
2. The LED light string actuating circuit of claim 1, wherein the second controlled unit comprises: the capacitor and the electronic switch are composed of a controlled end and two input ends;
the high-voltage power supply comprises a capacitor, an electronic switch, a resistor, an integrator and a voltage regulator, wherein the capacitor is connected with two input ends of the electronic switch in parallel, one end of the capacitor is connected with a low level, the other end of the capacitor is connected with a high level through the resistor, and the positive input end of the integrator is connected between the resistor and the capacitor;
during working time, the electronic switch is controlled to conduct two input ends of the electronic switch, so that the positive input end of the integrator is at a low level;
in the dead time, the electronic switch is controlled to turn off two input ends of the electronic switch, so that the positive input end of the integrator is at a high level.
3. The LED light string actuator circuit of claim 1, further comprising a comparator, said comparator comprising first and second input terminals and an output terminal;
the first input end of the comparator receives an integration result output by the output end of the integrator;
a second input end of the comparator receives or sets a preset value;
and the comparator compares the integration result with a preset value, and if the integration result is smaller than the preset value in the working time, a low level is output to enable the first controlled unit to turn off the tested loop.
4. The LED light string execution circuit of claim 3, wherein the tested loop comprises a load, a first controlled unit and a sampling circuit connected in series in sequence, and the sampling circuit is arranged at the negative end of the tested loop;
the execution circuit also comprises a voltage detection circuit used for detecting the real-time voltage of the detected loop; the voltage detection circuit comprises an input end and an output end, the input end is connected between a load of the tested loop and the first controlled unit, and the output end outputs a detection voltage result.
5. A multi-path LED lamp string control circuit is used for controlling a plurality of LED lamp string loops and is characterized in that an integral unit is correspondingly arranged in each LED lamp string loop; the control circuit includes at least:
the integration unit is the execution circuit of any one of the claims 1 to 4, and the tested loop is the LED lamp string loop;
the control unit is provided with a detection end and a control signal output end, and the detection end is connected with the output end of the execution circuit;
the control signal output end is connected with the controlled ends of the first controlled unit and the second controlled unit, and sends periodic control signals with high-level working time and low-level dead time to the first controlled unit and the second controlled unit through the control signal output end so as to periodically execute:
in the control signal working time:
if the integral result received by the detection end reaches a preset value, the positive input end of the controlled execution circuit of the second controlled unit is at a low level, the first controlled unit is controlled to conduct the tested loop, and the execution circuit integrates the sampling result output by the sampling circuit and outputs the integrated result;
if the integral result received by the detection end is smaller than a preset value, the first controlled unit is controlled to turn off the detected loop until the current control period is finished;
in the dead time of the control signal, the positive input end of the controlled execution circuit of the second controlled unit is at high level, the first controlled unit is controlled to disconnect the tested loop, and the execution circuit carries out reverse integration on the sampling result output by the sampling circuit and then outputs the result.
6. The multi-channel LED light string control circuit of claim 5, further comprising a voltage detection circuit for detecting the voltage in the LED light string loop and outputting the detection result to the control unit,
the control unit is used for controlling the working time of the signal: further performing:
if the voltage detection results of all the lamp strings reach the voltage threshold, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the voltage threshold value, a control signal is output to improve the power supply voltage of all the lamp strings.
7. A multi-channel LED light string loop control method, which is implemented by using the control circuit of any one of the claims 5 to 6, and comprises the following steps:
sampling the voltage or current of each LED lamp string loop;
integrating the sampling result of each LED lamp string loop;
in a periodic control signal having an on-time at a high level and a dead time at a low level, to periodically perform:
within the working time of each control period, the lamp string with the integration result reaching the preset value is turned off until the execution period is finished;
each LED string loop is turned off during the dead time of each execution cycle.
8. The multi-channel LED light string loop control method according to claim 7, further comprising, during the on-time of each control cycle:
if the integral results of all the lamp strings reach a preset value, reducing the working voltage of all the lamp strings; comparing the integral result of each lamp string with a preset value; and if any integration result does not reach the preset value, the power supply voltage of all the lamp strings is increased.
9. The method of claim 8 further comprising the step of:
detecting the voltage of the LED lamp strings in real time, and if the voltage detection results of all the lamp strings reach a voltage threshold value, outputting a control signal to reduce the working voltage of all the lamp strings; if any voltage detection result does not reach the voltage threshold value, a control signal is output to improve the power supply voltage of all the lamp strings.
10. The multi-channel LED light string loop control method of claim 7, wherein the control unit receives a PWM signal;
and the control unit adjusts the ratio of the working time to the dead time in the periodic control signal according to the duty ratio of the PWM signal.
11. The multi-channel LED light string loop control method of claim 7, wherein the control unit receives a PWM signal; the control unit adjusts the preset value according to the duty ratio of the PWM signal; and the preset value is the initial preset value, namely the duty ratio value of the PWM signal.
12. The method of claim 10 wherein the dead time is varied according to the duty cycle value of the PWM signal by the formula:
the dead time is (1-PWM signal duty value) × (T-initial dead time), where T is the period time of the periodic control signal.
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Address after: 266100 Zhuzhou Road, Laoshan District, Shandong, No. 151, No. Patentee after: Hisense Visual Technology Co., Ltd. Address before: 266100 Zhuzhou Road, Laoshan District, Shandong, No. 151, No. Patentee before: QINGDAO HISENSE ELECTRONICS Co.,Ltd. |