CN107750076B - LED driving circuit - Google Patents

LED driving circuit Download PDF

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Publication number
CN107750076B
CN107750076B CN201711171124.6A CN201711171124A CN107750076B CN 107750076 B CN107750076 B CN 107750076B CN 201711171124 A CN201711171124 A CN 201711171124A CN 107750076 B CN107750076 B CN 107750076B
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China
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circuit
resistor
electrically connected
voltage
led
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CN107750076A (en
Inventor
余贵川
汪小兵
郭腾跃
曾冉冉
曾凤频
何光洪
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Shenzhen Sct Optronics Co ltd
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Shenzhen Sct Optronics Co ltd
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • 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
    • G09G3/3406—Control of illumination source

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Led Devices (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

The invention discloses an LED driving circuit. The LED driving circuit comprises a plurality of LED branches, wherein at least one LED is connected in series on each LED branch, and the LEDs are used for emitting light according to the current on the LED branches; a driving circuit for outputting a constant current to the LED branch in a pulse width period of the received PWM signal; the current monitoring circuit is used for monitoring the current passing through the LED branch and converting the current of the LED branch into a monitoring voltage; the isolation feedback circuit is electrically connected with the current monitoring circuit and is used for outputting a dimming control signal according to the monitoring voltage and the PWM signal; and the control circuit is electrically connected with the driving circuit and the isolation feedback circuit and is used for adjusting the duty ratio of the PWM signal output to the driving circuit according to the dimming control signal. The LED driving circuit provided by the invention realizes constant-current driving LED dimming by using PWM.

Description

LED driving circuit
Technical Field
The embodiment of the invention relates to the technical field of liquid crystal display, in particular to an LED driving circuit.
Background
At present, most backlight LEDs in the liquid crystal display technology are driven by a power panel with a constant current function, so that the high integration of the power panel can be realized.
The power panel with the constant current function can replace the constant current panel on the original module liquid crystal glass, so that the television board card can be driven normally, and the original constant current panel can be replaced. Most of the power boards with constant current functions in the market simply drive backlight LEDs of liquid crystal display technology, and only carry out voltage dimming on the LEDs, so that the dimming effect is poor.
Disclosure of Invention
The invention provides an LED driving circuit for realizing LED dimming driven by constant current by PWM.
The embodiment of the invention provides an LED driving circuit, which comprises:
the LED light source comprises a plurality of LED branches, wherein at least one LED is connected in series on each LED branch, and the LEDs are used for emitting light according to the current on the LED branches;
A driving circuit for outputting a constant current to the LED branch in a pulse width period of the received PWM signal;
The current monitoring circuit is used for monitoring the current passing through the LED branch and converting the current of the LED branch into a monitoring voltage;
the isolation feedback circuit is electrically connected with the current monitoring circuit and is used for outputting a dimming control signal according to the monitoring voltage and the PWM signal;
And the control circuit is electrically connected with the driving circuit and the isolation feedback circuit and is used for adjusting the duty ratio of the PWM signal output to the driving circuit according to the dimming control signal.
Further, the isolation feedback circuit is used for converting the voltage of the pulse width time period of the PWM signal into a reference voltage, outputting a first dimming control signal when the monitoring voltage is larger than the reference voltage, and outputting a second dimming control signal when the monitoring voltage is smaller than the reference voltage; outputting a third dimming signal in a non-pulse width period of the PWM signal;
The control circuit is used for reducing the duty ratio of the PWM signal according to the first dimming signal, increasing the duty ratio of the PWM signal according to the second dimming signal and closing the driving circuit according to the third dimming signal.
The embodiment of the invention provides an LED driving circuit, which comprises a plurality of LED branches, a driving circuit, a current monitoring circuit, an isolation feedback circuit and a control circuit; the driving circuit outputs constant current to the LED branch circuit through the pulse width time period of the received PWM signal; the current monitoring circuit monitors the current passing through the LED branch circuit and converts the current of the LED branch circuit into a monitoring voltage; the isolation feedback circuit outputs a dimming control signal according to the monitoring voltage and the PWM signal; the control circuit adjusts the duty ratio of the PWM signal output to the driving circuit according to the dimming control signal, and then adjusts the constant current output by the driving circuit, so that the LED dimming driven by constant current is realized by PWM.
Drawings
Fig. 1 is a block diagram of an LED driving circuit according to an embodiment of the present invention;
FIG. 2A is a circuit block diagram of an isolated feedback circuit provided by an embodiment of the present invention;
Fig. 2B is a circuit diagram of a voltage conversion circuit according to an embodiment of the present invention;
FIG. 2C is a circuit diagram of a voltage conversion circuit and a comparison output circuit according to an embodiment of the present invention;
FIG. 2D is a circuit diagram of an isolated feedback circuit according to an embodiment of the present invention;
FIG. 2E is a circuit diagram of another isolated feedback circuit provided by an embodiment of the present invention;
FIG. 3 is a circuit diagram of a plurality of LED legs according to an embodiment of the present invention;
FIG. 4A is a circuit block diagram of a current monitoring circuit provided by an embodiment of the present invention;
Fig. 4B is a circuit diagram of an idle signal detection circuit according to an embodiment of the present invention;
FIG. 4C is a circuit diagram of a current monitoring circuit according to an embodiment of the present invention;
FIG. 4D is a circuit diagram of another current monitoring circuit according to an embodiment of the present invention;
Fig. 4E is a circuit diagram of another current monitoring circuit according to an embodiment of the invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Fig. 1 is a block diagram of an LED driving circuit according to an embodiment of the present invention, where the LED driving circuit includes:
A plurality of LED branches 10, each LED branch 10 being connected in series with at least one LED for emitting light according to the current on the LED branch 10;
A driving circuit 20 for outputting a constant current to the LED branch 10 during a pulse width period of the received PWM signal;
A current monitoring circuit 30 for monitoring the current through the LED branch 10 and converting the current of the LED branch 10 into a monitored voltage;
an isolation feedback circuit 40 electrically connected to the current monitoring circuit 30 for outputting a dimming control signal according to the monitored voltage and the PWM signal;
The control circuit 50 is electrically connected to the driving circuit 20 and the isolation feedback circuit 40, and is configured to adjust the duty ratio of the PWM signal output to the driving circuit 20 according to the dimming control signal.
According to the technical scheme provided by the embodiment of the invention, the driving circuit outputs constant current to the LED branch circuit through the pulse width time period of the received PWM signal; the current monitoring circuit monitors the current passing through the LED branch circuit and converts the current of the LED branch circuit into a monitoring voltage; the isolation feedback circuit outputs a dimming control signal according to the monitoring voltage and the PWM signal; the control circuit adjusts the duty ratio of the PWM signal output to the driving circuit according to the dimming control signal, and then adjusts the constant current output by the driving circuit, so that the LED dimming driven by constant current is realized by PWM.
Specifically, the isolation feedback circuit 40 is configured to convert the voltage of the PWM signal in the pulse width period into the reference voltage, output the first dimming control signal when the monitored voltage is greater than the reference voltage, and output the second dimming control signal when the monitored voltage is less than the reference voltage; outputting a third dimming signal in a non-pulse width period of the PWM signal; the control circuit 50 is configured to decrease the duty ratio of the PWM signal according to the first dimming signal, increase the duty ratio of the PWM signal according to the second dimming signal, and turn off the driving circuit 20 according to the third dimming signal.
It can be understood that the magnitude of the monitored voltage reflects the magnitude of the current flowing through the LED, and when the monitored voltage is greater than the reference voltage, the monitored voltage indicates that the total current of the LED increases, the isolated feedback circuit 40 outputs a first dimming control signal, and feeds back the first dimming control signal to the control circuit 50, and the control circuit 50 reduces the voltage across the LED and the current flowing through the LED by reducing the duty ratio of the PWM signal; when the monitored voltage is less than the reference voltage, the isolation feedback circuit 40 outputs a second dimming control signal, which is fed back to the control circuit 50, and the control circuit 50 increases the voltage across the LED by increasing the duty cycle of the PWM signal, thereby increasing the current flowing through the LED. In the non-pulse width time period of the PWM signal, the dimming is not performed, and the third dimming signal is generated by the isolated feedback circuit 40 and fed back to the control circuit 50 to turn off the driving circuit 20.
Fig. 2A is a circuit block diagram of an isolated feedback circuit provided in an embodiment of the present invention, referring to fig. 2A, the isolated feedback circuit may include a voltage conversion circuit 41, a comparison output circuit 42, and an isolated output circuit 43.
The input terminal of the voltage conversion circuit 41 is used for inputting a PWM signal, outputting a first reference voltage during a pulse width period of the PWM signal, and outputting a second reference voltage during a non-pulse width period of the PWM signal.
Fig. 2B is a circuit diagram of a voltage conversion circuit according to an embodiment of the present invention, referring to fig. 2B, on the basis of the above embodiment, the voltage conversion circuit includes: a first operational amplifier, a first voltage dividing circuit 411, a first resistor R1, a voltage regulator U1, and a second voltage dividing circuit 412; the first voltage dividing circuit 411 has a first end for inputting PWM signals, a second end grounded, and a third end electrically connected to the positive input terminal 2in+ of the first operational amplifier; the first end of the first resistor R1 is electrically connected with the negative input end 2 IN-and the output end 2OUT of the first operational amplifier, the second end of the first resistor R1 is electrically connected with the first end of the voltage stabilizer U1, and the second end of the voltage stabilizer U1 is grounded; the second voltage divider circuit 412 has a first terminal electrically connected to the first terminal of the voltage regulator U1, a second terminal electrically connected to ground, and a third terminal electrically connected to the second input terminal of the comparison output circuit 42.
The first voltage dividing circuit 411 includes a second resistor R2 and a third resistor R3; the first end of the second resistor R2 is used for inputting a PWM signal, and the second end is electrically connected with the first end of the third resistor R3 and the positive input end 2IN+ of the first operational amplifier; the second end of the third resistor R3 is grounded; the second voltage dividing circuit 412 includes a fourth resistor R3, a fifth resistor R5, and a sixth resistor R6; the first end of the fourth resistor R4 is electrically connected with the second end of the first resistor R1, the first end of the fifth resistor R5 is electrically connected with the second end of the fourth resistor R4, the first end of the sixth resistor R6 is electrically connected with the second end of the fifth resistor R5 and the second input end of the comparison output circuit 42, and the second end of the sixth resistor R6 is grounded; the voltage conversion circuit 411 further includes a first capacitor C1, where the first capacitor C1 is connected in parallel with the third resistor R3.
Referring to fig. 2B, it can be understood that, IN the pulse width period of the PWM signal, the PWM signal is at a high level, and the high level is divided by the first voltage dividing circuit 411 and then is input to the positive input terminal 2in+ of the first operational amplifier, and is output after passing through the first operational amplifier, and is limited by the first resistor R1 and then is supplied to the voltage stabilizer U1 to form a first reference voltage, for example, a reference voltage of 2.5V; in the non-pulse width time period of the PWM signal, the PWM signal is 0, and the output of the PWM signal is 0 through the first operational amplifier, namely the second reference voltage.
The first input end of the comparison output circuit 42 is used for inputting the monitoring voltage, and the second input end is electrically connected with the 41 output end of the voltage conversion circuit and is used for adjusting the voltage output by the output end according to the monitoring voltage, the first reference voltage and the second reference voltage.
Fig. 2C is a circuit diagram of a voltage conversion circuit and a comparison output circuit according to an embodiment of the present invention, referring to fig. 2C, the comparison output circuit includes a second operational amplifier, a seventh resistor R7, a second capacitor C2 and a third capacitor C3; the positive input terminal 1in+ of the second operational amplifier is electrically connected with the output terminal of the voltage conversion circuit 41, the negative input terminal 1 IN-is electrically connected with the first pole of the second capacitor C2 and the first pole of the third capacitor C3, the output terminal 1OUT is electrically connected with the second pole of the third capacitor C3 and the first terminal of the seventh resistor R7, the positive input terminal 1in+ of the second operational amplifier is used as the second input terminal of the comparison output circuit 42, and the negative input terminal 1 IN-of the second operational amplifier is used for inputting the monitoring voltage signal FB; the second end of the seventh resistor R7 is electrically connected to the second pole of the second capacitor C2.
An input terminal of the isolation output circuit 43 is electrically connected to an output terminal of the comparison output circuit 42, and is configured to feed back a voltage output from the output terminal of the comparison output circuit 42 to the control circuit.
Referring to fig. 2C, IN the pulse width period of the PWM signal, the first reference voltage generated by the voltage regulator U1 IN the voltage conversion circuit is divided by the second voltage division circuit 412 and then input to the positive input terminal 1in+ of the second operational amplifier, the negative input terminal 1 IN-of the second operational amplifier is used for inputting the monitoring voltage signal FB, the monitoring voltage signal FB is from the current monitoring circuit, and the voltage output by the output terminal 1OUT of the second operational amplifier is fed back to the control circuit.
Fig. 2D is a circuit diagram of an isolated feedback circuit according to an embodiment of the present invention, referring to fig. 2D, the isolated output circuit 43 includes an optocoupler OC, an eighth resistor R8 and a ninth resistor R9; the first end 1 of the optical coupler OC is electrically connected with the first end of the eighth resistor R8 and the first end of the ninth resistor R9, and the second end 2 of the optical coupler OC is electrically connected with the second end of the ninth resistor R9 and the output end of the comparison output circuit 42; the third terminal 3 and the fourth terminal 4 of the optocoupler OC are used for outputting an electrical signal to a control circuit; the second terminal of the eighth resistor R8 inputs the power supply voltage VSS.
The comparison output circuit 42 and the isolation output circuit 43 further include a first diode D1 and a tenth resistor R10 therebetween; the second end 2 of the optocoupler OC is electrically connected to the output of the comparison output circuit 42 via a first diode D1 and a tenth resistor R10 connected in series; the first end of the tenth resistor R10 is electrically connected to the output end of the comparison output circuit 42, the second end of the tenth resistor R10 is electrically connected to the cathode of the first diode D1, and the anode of the first diode D1 is electrically connected to the second end of the optocoupler OC.
The first diode D1 is used for isolating the output signal of the comparison output circuit, and the tenth resistor R10 is used for limiting current, so as to prevent the first diode D1 from being burnt out due to excessive current.
When the total current of the LED rises, the monitoring voltage signal FB rises and exceeds the voltage reference of the forward input end 1IN+ of the second operational amplifier, the output voltage of the output end 1OUT of the second operational amplifier is reduced, the current flowing through the optocoupler OC is increased, and the control circuit reduces the voltage of the LED, so that the current flowing through the LED is reduced; when the total current of the LED decreases, the monitor voltage signal FB decreases, and when the monitor voltage signal FB is lower than the voltage reference of the forward input terminal 1in+ of the second operational amplifier, the output voltage of the output terminal 1OUT of the second operational amplifier increases, so that the current flowing through the optocoupler OC decreases, and the control circuit increases the voltage across the LED, thereby increasing the current flowing through the LED. This is repeated to maintain the current of the LED within a constant range.
IN the non-pulse width time period of the PWM signal, when the output voltage of the signal passing through the output end 2OUT of the first operational amplifier is 0, the input voltage of the forward input end 1in+ of the second operational amplifier is 0, the output voltage of the output end 1OUT of the second operational amplifier is 0, the current flowing through the optocoupler OC is the largest, the control circuit turns off the driving circuit, the voltage at the two ends of the LED is 0, and no current flows through the LED. Increasing the positive duty ratio in the PWM signal with the same frequency, and increasing the power of the LED; the positive duty cycle is reduced and the LED power is reduced.
Fig. 2E is a circuit diagram of another isolated feedback circuit according to an embodiment of the present invention, in another implementation manner of the embodiment of the present invention, referring to fig. 2E, the isolated feedback circuit further includes a fault feedback circuit 44, where the fault feedback circuit 44 includes a first triode Q1, an eleventh resistor R11, a twelfth resistor R12, and a thirteenth resistor R13; an eleventh resistor R11 is connected in series between the first pole (collector) of the first transistor 11 and the second terminal 2 of the optocoupler OC; the second electrode (emitter) of the first triode Q1 is grounded, the base electrode of the first triode Q1 is electrically connected with the first end of the twelfth resistor R12, the second end of the twelfth resistor R12 is used for inputting a fault detection signal PP, and the fault detection signal PP reflects whether the LED branch is short-circuited or open-circuited; the thirteenth resistor R23 is connected in parallel to the base and the second pole (emitter) of the first transistor Q1.
Illustratively, the fault detection signal PP is in a high-resistance state in a normal state of the LED, and becomes a high-level signal when the LED fails (opens, shorts, etc.). When the fault detection signal PP is a high level signal, the first triode Q1 is turned on, the second end 2 of the optocoupler OC is turned on with the ground, the optocoupler OC is saturated by the power supply voltage VSS, and the signal input control circuits at the third end 3 and the fourth end 4 of the optocoupler OC enter protection locking.
Fig. 3 is a circuit diagram of a plurality of LED branches provided by the embodiment of the present invention, at least one LED is connected in series between the ports 1 and 2 of each branch, and a fourteenth resistor R14 is connected in series to each LED branch; the first end (LED+) of the LED branch is electrically connected with a first power supply of the driving circuit, and the first end of the fourteenth resistor R14 is electrically connected with the second end 2 of the LED branch; the current monitoring circuit comprises a plurality of fifteenth resistors R15 which are connected in parallel, wherein a first end of the fifteenth resistor R15 is electrically connected with a second end of the fourteenth resistor R14, and a second end of the fifteenth resistor R15 is grounded; the first terminal of the fifteenth resistor R15 outputs the monitor voltage signal FB to the output terminal of the current detection circuit.
Referring to fig. 3, fig. 3 also shows a circuit diagram of a circuit part of the current monitoring circuit in the embodiment of the present invention, where the current monitoring circuit further includes a sixteenth resistor R16 and a second diode D2; a first end of the sixteenth resistor R16 is electrically connected with a first end of the fifteenth resistor R15, and a second end of the sixteenth resistor R16 is electrically connected with a first input end of the comparison output circuit; the second diode D2 is connected in parallel with the fifteenth resistor R15.
The fifteenth resistor R15 is used for detecting the current flowing through the LED and converting the current into the monitoring voltage signal FB, the second diode D2 is used for preventing the circuit damage caused by the current flowing through the fifteenth resistor R15, and the sixteenth resistor R16 is used for improving the input impedance and reducing the interference for the monitoring voltage signal FB.
Fig. 4A is a circuit block diagram of a current monitoring circuit according to an embodiment of the present invention, referring to fig. 4A, the current monitoring circuit includes a state monitoring circuit 31, an idle signal detecting circuit 32, and a short circuit signal detecting circuit 33.
The state monitoring circuit 31 is configured to monitor the open state and the short state of the LED branch, and output a first monitoring signal corresponding to the open state of the LED branch at a first output terminal thereof, and output a second monitoring signal corresponding to the short state of the LED branch at a second output terminal thereof.
The first monitoring signal is an idle state monitoring signal, and the second monitoring signal is a short circuit state monitoring signal.
Fig. 3 also shows a circuit diagram of a status monitoring circuit according to an embodiment of the present invention, referring to fig. 3, the status monitoring circuit includes a plurality of monitoring sub-circuits 311, each monitoring sub-circuit 311 corresponds to an LED branch; the monitoring sub-circuit 311 includes a third diode D3 and a fourth diode D4, where an anode of the third diode D3 is electrically connected to the first output terminal OLP of the state monitoring circuit, a cathode of the third diode D3 is electrically connected to the corresponding LED branch, an anode of the fourth diode D4 is electrically connected to a cathode of the third diode D3, and a cathode of the fourth diode D4 is electrically connected to the second output terminal OCP of the state monitoring circuit.
The first output end OLP of the state monitoring circuit monitors the open-circuit state of the LED branch and outputs an idle state monitoring signal, and the second output end OCP monitors the short-circuit state of the LED branch and outputs a short-circuit state monitoring signal.
The input end of the no-load signal detection circuit is electrically connected with the first output end OLP of the state monitoring circuit, and is used for determining whether the LED branch circuit is broken or not according to the first monitoring signal and outputting a first state signal corresponding to the broken circuit.
When a certain LED branch circuit is broken, no current passes through the broken LED branch circuit, so that a loop is formed by a third diode D3, a fourteenth resistor R14 and a fifteenth resistor R15 connected with the LED branch circuit, and a low level signal is output by a first output end OLP of the state monitoring circuit, and is an idle state monitoring signal.
Fig. 4B is a circuit diagram of an idle signal detection circuit according to an embodiment of the present invention, referring to fig. 4B, the idle signal detection circuit includes a third operational amplifier, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, and a fifth diode D5; the positive input end 1IN+ of the third operational amplifier is electrically connected with the first end of the twenty-first resistor R21, and the negative input end 1 IN-of the third operational amplifier is electrically connected with the first end of the twenty-second resistor R22 and the first end of the twenty-third resistor R23; a second terminal of the twenty-first resistor R21 and a second terminal of the twenty-second resistor R22 are used for inputting the reference voltage REF; the second end of the twenty-third resistor R23 is electrically connected with the first output end OLP of the state monitoring circuit; the output end 1OUT of the third operational amplifier is electrically connected with the anode of the fifth diode D5; the cathode of the fifth diode D5 is electrically connected to the control circuit.
When the LED is disconnected, the voltage of the OLP terminal is enabled to be lower than the reference voltage REF, and the third operational amplifier outputs a high level in a forward saturated mode. The fault detection signal PP is in a high-resistance state in a normal working state, and is influenced by the high level output by the forward saturation of the third operational amplifier, the output high level signal is transmitted to the fault detection signal PP through the fifth diode D5, the fault detection signal PP is changed from the high-resistance state to the high level state, and the transmission to the control circuit can turn off the whole LED drive. After the open circuit fault is removed, the voltage at the OLP end is recovered to a high level, the voltage which is input into the third operational amplifier after being divided by the twenty-third resistor R23 and the twenty-second resistor R22 is larger than the reference voltage REF, so that the third operational amplifier outputs a low level, the fault detection signal PP can recover to a high-resistance state, and a self-recovery mechanism for protecting multiple paths of LED branches under the open circuit condition is ensured. When no fault exists in the fault detection signal PP, no electric signal is output, the output end 1OUT of the third operational amplifier is isolated by the fifth diode D5, and the impedance to the ground is extremely high.
The input end of the short-circuit signal detection circuit 33 is electrically connected with the second output end OCP of the state monitoring circuit, and is used for determining whether the LED branch is short-circuited according to the second monitoring signal and outputting a second state signal corresponding to the short-circuit; the control circuit is used for turning off the driving circuit according to the first state signal and the second state signal.
Fig. 4C is a circuit diagram of a current monitoring circuit according to an embodiment of the present invention, referring to fig. 4C, where the short-circuit signal detection circuit includes a third voltage division branch 331, a sixth diode D6, a seventh diode D7, and a fourth operational amplifier based on the above embodiment; the first end of the 331 of the third voltage dividing branch is electrically connected with a first power supply LED+ of the driving circuit, the second end of the 331 of the third voltage dividing branch is grounded, the third end of the 331 of the third voltage dividing branch is electrically connected with a second output end OCP of the state monitoring circuit, and the fourth end of the 331 of the third voltage dividing branch is electrically connected with a positive input end 2IN+ of the fourth operational amplifier; the fourth operational amplifier has a positive input terminal 2in+ electrically connected to the negative electrode of the sixth diode D6, a negative input terminal 2 IN-electrically connected to the positive electrode of the sixth diode D6 and the positive electrode of the seventh diode D7 for inputting the reference voltage REF, and an output terminal 2 OUT; the negative electrode of the seventh diode D7 is electrically connected to the control circuit.
The sixth diode D6 is used to cause a self-locking mechanism, when the LED is shorted, the voltage at the OCP terminal becomes larger, the voltage at the forward input terminal 2in+ of the fourth operational amplifier after voltage division is greater than the reference voltage REF, the fourth operational amplifier outputs a high level IN forward saturation, and the sixth diode D6 causes the self-locking mechanism, the fourth operational amplifier outputs the high level to change the fault detection signal PP from the high-resistance state to the high-level state, and the fault detection signal PP is transmitted to the control circuit to lock the whole LED driving circuit. After the short circuit fault is removed, the voltage at the OCP end is recovered to a normal state, the voltage at the forward input end 2in+ of the fourth operational amplifier is smaller than the reference voltage REF after passing through the first voltage dividing branch 331, so that the fourth operational amplifier outputs a low level, the locking mechanism is automatically released, the fault detection signal PP is recovered to a high-resistance state, and the LED driving circuit operates normally.
Fig. 4D is a circuit diagram of another current monitoring circuit according to an embodiment of the present invention, in another implementation manner of the embodiment of the present invention, referring to fig. 4D, a first erroneous determination limiting circuit 34 may be further included at an output end of the no-load detection circuit, where the first erroneous determination limiting circuit 34 includes a second triode Q2, a third triode Q3, a twenty-fourth resistor R24, a twenty-fifth resistor R25, a twenty-sixth resistor R26, a twenty-seventh resistor R27, and a seventh capacitor C7; the output end 1OUT of the third operational amplifier is electrically connected with the cathode of the fifth diode D5 through the second triode Q2; the first pole (collector) of the second triode Q2 is electrically connected with the cathode of the fifth diode D5, the second pole (emitter) is electrically connected with the output end 1OUT of the third operational amplifier, and the base is electrically connected with the first end of the twenty-fourth resistor R24; the second end of the twenty-fourth resistor R24 is used for inputting a power supply voltage VSS; a twenty-fifth resistor R25 is connected in series between the base of the second transistor Q2 and the first pole (collector) of the third transistor Q3; the second electrode (emitter) of the third triode Q3 is grounded, the base electrode is electrically connected with the first end of a twenty-sixth resistor R26, and the second end of the twenty-sixth resistor R26 is used for inputting PWM signals; the twenty-seventh resistor R27 and the seventh capacitor C7 are all connected in parallel to the base and the second pole (emitter) of the third transistor Q3.
The first misjudgment limiting circuit 34 is used for preventing the idle signal detection circuit from outputting a high-level signal to the fault detection signal PP to cause misjudgment that the current state is in the open-circuit protection state, when the PWM signal is at the high level (0), the third triode Q3 is in the off state, the power supply voltage VSS is loaded to the second triode Q2, and the second triode Q2 is off, so that the third triode Q3 and the second triode Q2 are only turned on when the PWM signal is at the low level, and the open-circuit protection signal is only effective.
Fig. 4E is a circuit diagram of another current monitoring circuit provided by the embodiment of the present invention, in another implementation manner of the embodiment of the present invention, referring to fig. 4E, the current monitoring circuit provided by the embodiment of the present invention may further include a second erroneous judgment limiting circuit 35, where the second erroneous judgment circuit 35 includes a first MOS transistor T1, a second MOS transistor T2, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a thirty-eighth resistor R30, an eighth diode D8, and an eighth capacitor C8; the first electrode (drain electrode) of the first MOS tube T1 is electrically connected with the positive input end of the third operational amplifier, the second electrode (source electrode) is grounded, the grid electrode is electrically connected with the first end of the twenty-eighth resistor R28, and the second end of the twenty-eighth resistor R28 is input with a power supply voltage; the first electrode (drain electrode) of the second MOS tube T2 is electrically connected with the grid electrode of the first MOS tube, the second electrode (source electrode) is grounded, the grid electrode is electrically connected with the first end of the twenty-ninth resistor R29, and the second end of the twenty-ninth resistor R29 is used for inputting a starting signal; the anode and the cathode of the eighth diode D8 are respectively and electrically connected with the first end and the second end of the twenty-ninth resistor R29; the thirty-first resistor R30 and the eighth capacitor C8 are connected in parallel to the gate and the second pole (source) of the second MOS transistor.
The second misjudgment limiting circuit 35 is used for shielding the reference voltage REF input by the forward input end 1in+ of the third operational amplifier of the no-load signal detection circuit when the first MOS transistor T1 and the second MOS transistor T1 are conducted within a very short time during starting, and preventing the detection circuit from misjudging the LED driving circuit to be IN open-circuit protection during starting. After the LED is started stably, the first MOS tube T1 and the second MOS tube T1 are cut off, the idle signal detection circuit enters a normal detection state, and the open-circuit fault protection function of the driving circuit is recovered.
According to the technical scheme, the working state of the LED is detected through the current monitoring circuit, the LED is broken and broken fault detection is carried out, and the PWM is utilized to realize constant current drive LED dimming and LED fault detection and protection.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims (15)

1. An LED driving circuit, comprising:
the LED light source comprises a plurality of LED branches, wherein at least one LED is connected in series on each LED branch, and the LEDs are used for emitting light according to the current on the LED branches;
A driving circuit for outputting a constant current to the LED branch in a pulse width period of the received PWM signal;
The current monitoring circuit is used for monitoring the current passing through the LED branch and converting the current of the LED branch into a monitoring voltage;
the isolation feedback circuit is electrically connected with the current monitoring circuit and is used for outputting a dimming control signal according to the monitoring voltage and the PWM signal;
The control circuit is electrically connected with the driving circuit and the isolation feedback circuit and is used for adjusting the duty ratio of the PWM signal output to the driving circuit according to the dimming control signal;
The isolation feedback circuit further comprises a voltage conversion circuit;
The input end of the voltage conversion circuit is used for inputting the PWM signal, outputting a first reference voltage in a pulse width time period of the PWM signal and outputting a second reference voltage in a non-pulse width time period of the PWM signal;
The isolation feedback circuit comprises a comparison output circuit;
The first input end of the comparison output circuit is used for inputting the monitoring voltage, the second input end of the comparison output circuit is electrically connected with the output end of the voltage conversion circuit and used for adjusting the voltage output by the output end according to the monitoring voltage, the first reference voltage and the second reference voltage;
the comparison output circuit comprises a second operational amplifier, a seventh resistor, a second capacitor and a third capacitor;
The positive input end of the second operational amplifier is electrically connected with the output end of the voltage conversion circuit, the negative input end of the second operational amplifier is electrically connected with the first pole of the second capacitor and the first pole of the third capacitor, the output end of the second operational amplifier is electrically connected with the second pole of the third capacitor and the first end of the seventh resistor, and the negative input end of the second operational amplifier is used for inputting the monitoring voltage;
the second end of the seventh resistor is electrically connected with the second pole of the second capacitor;
the magnitude of the monitor voltage reflects the magnitude of the current flowing through the LED;
The isolation feedback circuit is used for converting the voltage of the pulse width time period of the PWM signal into a reference voltage, outputting a first dimming control signal when the monitoring voltage is larger than the reference voltage, and outputting a second dimming control signal when the monitoring voltage is smaller than the reference voltage; outputting a third dimming control signal in a non-pulse width period of the PWM signal;
The control circuit is used for reducing the duty ratio of the PWM signal according to the first dimming control signal, increasing the duty ratio of the PWM signal according to the second dimming control signal and closing the driving circuit according to the third dimming control signal.
2. The LED driver circuit of claim 1, wherein the isolated feedback circuit further comprises an isolated output circuit;
The input end of the isolation output circuit is electrically connected with the output end of the comparison output circuit, and is used for feeding back the voltage output by the output end of the comparison output circuit to the control circuit.
3. The LED driving circuit according to claim 1, wherein the voltage conversion circuit includes: the circuit comprises a first operational amplifier, a first voltage dividing circuit, a first resistor, a voltage stabilizer and a second voltage dividing circuit;
The first end of the first voltage dividing circuit is used for inputting the PWM signal, the second end of the first voltage dividing circuit is grounded, and the third end of the first voltage dividing circuit is electrically connected with the positive input end of the first operational amplifier;
the first end of the first resistor is electrically connected with the negative input end and the output end of the first operational amplifier, the second end of the first resistor is electrically connected with the first end of the voltage stabilizer, and the second end of the voltage stabilizer is grounded;
The first end of the second voltage dividing circuit is electrically connected with the first end of the voltage stabilizer, the second end of the second voltage dividing circuit is grounded, and the third end of the second voltage dividing circuit is electrically connected with the second input end of the comparison output circuit.
4. The LED driving circuit according to claim 3, wherein the first voltage dividing circuit includes a second resistor and a third resistor;
The first end of the second resistor is used for inputting the PWM signal, and the second end of the second resistor is electrically connected with the first end of the third resistor and the positive input end of the first operational amplifier; the second end of the third resistor is grounded;
The second voltage dividing circuit comprises a fourth resistor, a fifth resistor and a sixth resistor;
The first end of the fourth resistor is electrically connected with the second end of the first resistor, the first end of the fifth resistor is electrically connected with the second end of the fourth resistor, the first end of the sixth resistor is electrically connected with the second end of the fifth resistor and the second input end of the comparison output circuit, and the second end of the sixth resistor is grounded;
the voltage conversion circuit further comprises a first capacitor connected in parallel with the third resistor.
5. The LED driving circuit of claim 2, wherein the isolated output circuit comprises an optocoupler, an eighth resistor, and a ninth resistor;
the first end of the optical coupler is electrically connected with the first end of the eighth resistor and the first end of the ninth resistor, and the second end of the optical coupler is electrically connected with the second end of the ninth resistor and the output end of the comparison output circuit;
The third end and the fourth end of the optocoupler are used for outputting electric signals to the control circuit;
The second end of the eighth resistor inputs a power supply voltage.
6. The LED driving circuit of claim 5, further comprising a first diode and a tenth resistor; the second end of the optical coupler is electrically connected with the output end of the comparison output circuit through a first diode and the tenth resistor which are connected in series;
the first end of the tenth resistor is electrically connected with the output end of the comparison output circuit, the second end of the tenth resistor is electrically connected with the negative electrode of the first diode, and the positive electrode of the first diode is electrically connected with the second end of the optical coupler.
7. The LED driver circuit of claim 5, further comprising a fault feedback circuit comprising a first transistor, an eleventh resistor, a twelfth resistor, and a thirteenth resistor;
the eleventh resistor is connected in series between the first pole of the first triode and the second end of the optical coupler;
the second electrode of the first triode is grounded, the base electrode of the first triode is electrically connected with the first end of the twelfth resistor, the second end of the twelfth resistor is used for inputting a fault detection signal, and the fault detection signal reflects whether the LED branch is short-circuited or broken;
The thirteenth resistor is connected in parallel with the base electrode and the second electrode of the first triode.
8. The LED driver circuit of claim 2, wherein a fourteenth resistor is further connected in series with the LED branch; the first end of the LED branch is electrically connected with a first power supply of the driving circuit, and the first end of the fourteenth resistor is electrically connected with the second end of the LED branch;
The current monitoring circuit comprises a plurality of fifteenth resistors connected in parallel, a first end of each fifteenth resistor is electrically connected with a second end of each fourteenth resistor, and the second end of each fifteenth resistor is grounded;
The first end of the fifteenth resistor outputs a monitoring voltage to the output end of the current monitoring circuit.
9. The LED driving circuit of claim 8, further comprising a sixteenth resistor and a second diode;
a first end of the sixteenth resistor is electrically connected with a first end of the fifteenth resistor, and a second end of the sixteenth resistor is electrically connected with a first input end of the comparison output circuit; the second diode is connected in parallel with the fifteenth resistor.
10. The LED driving circuit according to claim 1, further comprising a state monitoring circuit, an idle signal detection circuit, and a short circuit signal detection circuit;
The state monitoring circuit is used for monitoring the open-circuit state and the short-circuit state of the LED branch, outputting a first monitoring signal corresponding to the open-circuit state at a first output end of the state monitoring circuit, and outputting a second monitoring signal corresponding to the short-circuit state at a second output end of the state monitoring circuit;
The input end of the no-load signal detection circuit is electrically connected with the first output end of the state monitoring circuit, and is used for determining whether the LED branch circuit is broken or not according to the first monitoring signal and outputting a first state signal corresponding to the broken circuit;
The input end of the short-circuit signal detection circuit is electrically connected with the second output end of the state monitoring circuit, and is used for determining whether the LED branch is short-circuited or not according to the second monitoring signal and outputting a second state signal corresponding to the short circuit;
The control circuit is used for closing the driving circuit according to the first state signal and the second state signal.
11. The LED driving circuit of claim 10, wherein the status monitoring circuit comprises a plurality of monitoring sub-circuits, each of the monitoring sub-circuits corresponding to a LED leg;
The monitoring sub-circuit comprises a third diode and a fourth diode, wherein the positive electrode of the third diode is electrically connected with the first output end of the state monitoring circuit, the negative electrode of the third diode is electrically connected with the corresponding LED branch, the positive electrode of the fourth diode is electrically connected with the negative electrode of the third diode, and the negative electrode of the fourth diode is electrically connected with the second output end of the state monitoring circuit.
12. The LED driving circuit of claim 10, wherein the no-load signal detection circuit comprises a third operational amplifier, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, and a fifth diode;
The positive input end of the third operational amplifier is electrically connected with the first end of the twenty-first resistor, and the negative input end of the third operational amplifier is electrically connected with the first end of the twenty-second resistor and the first end of the twenty-third resistor; a second end of the twenty-first resistor and a second end of the twenty-second resistor are used for inputting a reference voltage; the second end of the twenty-third resistor is electrically connected with the first output end of the state monitoring circuit;
The output end of the third operational amplifier is electrically connected with the positive electrode of the fifth diode; and the cathode of the fifth diode is electrically connected with the control circuit.
13. The LED driving circuit according to claim 10, wherein the short-circuit signal detection circuit includes a third voltage dividing branch, a sixth diode, a seventh diode, and a fourth operational amplifier;
The first end of the third voltage dividing branch is electrically connected with a first power supply of the driving circuit, the second end of the third voltage dividing branch is grounded, the third end of the third voltage dividing branch is electrically connected with a second output end of the state monitoring circuit, and the fourth end of the third voltage dividing branch is electrically connected with a positive input end of the fourth operational amplifier;
The positive input end of the fourth operational amplifier is electrically connected with the negative electrode of the sixth diode, the negative input end of the fourth operational amplifier is electrically connected with the positive electrode of the sixth diode and the positive electrode of the seventh diode, and the output end of the fourth operational amplifier is electrically connected with the input reference voltage;
And the negative electrode of the seventh diode is electrically connected with the control circuit.
14. The LED driving circuit of claim 12, further comprising a first misjudgment limiting circuit comprising a second transistor, a third transistor, a twenty-fourth resistor, a twenty-fifth resistor, a twenty-sixth resistor, a twenty-seventh resistor, and a seventh capacitor;
the output end of the third operational amplifier is electrically connected with the cathode of the fifth diode through the second triode;
The first pole of the second triode is electrically connected with the negative pole of the fifth diode, the second pole is electrically connected with the output end of the third operational amplifier, and the base electrode is electrically connected with the first end of the twenty-fourth resistor; the second end of the twenty-fourth resistor is used for inputting a power supply voltage;
the twenty-fifth resistor is connected in series between the base electrode of the second triode and the first electrode of the third triode;
The second electrode of the third triode is grounded, the base electrode of the third triode is electrically connected with the first end of the twenty-sixth resistor, and the second end of the twenty-sixth resistor is used for inputting the PWM signal;
and the twenty-seventh resistor and the seventh capacitor are connected in parallel with the base electrode and the second electrode of the third triode.
15. The LED driving circuit of claim 12, further comprising a second false positive limiting circuit; the second misjudgment limiting circuit comprises a first MOS tube, a second MOS tube, a twenty-eighth resistor, a twenty-ninth resistor, a thirty-eighth resistor, an eighth diode and an eighth capacitor;
the first electrode of the first MOS tube is electrically connected with the positive input end of the third operational amplifier, the second electrode is grounded, the grid electrode is electrically connected with the first end of the twenty-eighth resistor, and the second end of the twenty-eighth resistor inputs power supply voltage;
The first electrode of the second MOS tube is electrically connected with the grid electrode of the first MOS tube, the second electrode of the second MOS tube is grounded, the grid electrode of the second MOS tube is electrically connected with the first end of the twenty-ninth resistor, and the second end of the twenty-ninth resistor is used for inputting a starting signal;
the anode and the cathode of the eighth diode are respectively and electrically connected with the first end and the second end of the twenty-ninth resistor;
The thirty-first resistor and the eighth capacitor are both connected in parallel with the gate electrode of the second MOS transistor and the second electrode.
CN201711171124.6A 2017-11-22 2017-11-22 LED driving circuit Active CN107750076B (en)

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CN111818701A (en) * 2020-07-30 2020-10-23 浙江欧易新能源有限公司 Dimmable high-power LED driving power supply
CN112542141A (en) * 2020-12-01 2021-03-23 Tcl华星光电技术有限公司 Display device and driving method thereof
CN117479383B (en) * 2023-11-17 2024-06-18 上海衡亮电子科技股份有限公司 Circuit for automatically eliminating leakage of failed LED lamp beads

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102647826A (en) * 2011-02-18 2012-08-22 美格纳半导体有限公司 Pwm controlling circuit and led driver circuit having the same
CN103179717A (en) * 2011-12-20 2013-06-26 海洋王照明科技股份有限公司 LED (light emitting diode) dimming control circuit and LED lighting
CN103440848A (en) * 2013-09-02 2013-12-11 深圳市华星光电技术有限公司 Backlight driving circuit
CN105163431A (en) * 2015-08-21 2015-12-16 上海艾为电子技术股份有限公司 Drive circuit, light-emitting diode and mobile terminal
CN105554956A (en) * 2016-01-26 2016-05-04 安徽工程大学 Light emitting diode (LED) lamp lighting system based on pulse width modulation (PWM) dimming
CN105764185A (en) * 2016-03-18 2016-07-13 深圳Tcl数字技术有限公司 AC driving mixed dimming circuit and television
CN106535390A (en) * 2016-10-09 2017-03-22 深圳创维－Rgb电子有限公司 Constant current driving power supply and display equipment
CN207897177U (en) * 2017-11-22 2018-09-21 深圳中电数码显示有限公司 A kind of LED drive circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI511610B (en) * 2013-07-22 2015-12-01 Beyond Innovation Tech Co Ltd Light emitting diode driving apparatus and light emitting diode driving method

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102647826A (en) * 2011-02-18 2012-08-22 美格纳半导体有限公司 Pwm controlling circuit and led driver circuit having the same
CN103179717A (en) * 2011-12-20 2013-06-26 海洋王照明科技股份有限公司 LED (light emitting diode) dimming control circuit and LED lighting
CN103440848A (en) * 2013-09-02 2013-12-11 深圳市华星光电技术有限公司 Backlight driving circuit
CN105163431A (en) * 2015-08-21 2015-12-16 上海艾为电子技术股份有限公司 Drive circuit, light-emitting diode and mobile terminal
CN105554956A (en) * 2016-01-26 2016-05-04 安徽工程大学 Light emitting diode (LED) lamp lighting system based on pulse width modulation (PWM) dimming
CN105764185A (en) * 2016-03-18 2016-07-13 深圳Tcl数字技术有限公司 AC driving mixed dimming circuit and television
CN106535390A (en) * 2016-10-09 2017-03-22 深圳创维－Rgb电子有限公司 Constant current driving power supply and display equipment
CN207897177U (en) * 2017-11-22 2018-09-21 深圳中电数码显示有限公司 A kind of LED drive circuit

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