An intelligent LED driving circuit and control method

Abstract

The present invention discloses an intelligent LED driving circuit and a control method, which are applied to the technical field of LED driving, and include: a current detection module, a signal modulation module, an error amplifier module, an oscillator module, a threshold comparator, a driving circuit, a switching tube, an LED load, and a detection resistor. The present invention can simultaneously achieve extremely deep dimming and avoid the phenomenon of raster jitter.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving, and particularly to an intelligent LED driving circuit and a control method. Background Art

[0002] In the prior art of intelligent pulse width modulation dimming systems, a constant current driving circuit with a full-on full-off output mode is usually used to drive LED lights. The advantage of this technology is that it can achieve extremely deep dimming, but the disadvantage is also obvious, that is, when dimming extremely deeply, the LED lights cannot avoid the phenomenon of raster jitter, which greatly affects the lighting experience.

[0003] Therefore, providing an LED driving circuit and a control method that can simultaneously achieve extremely deep dimming and avoid the phenomenon of raster jitter is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides an LED driving circuit and a control method that can simultaneously achieve extremely deep dimming and avoid the phenomenon of raster jitter.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An intelligent LED driving circuit includes:

[0007] A current detection module, a signal modulation module, an error amplifier module, an oscillator module, a threshold comparator, a driving circuit, a switching transistor, an LED load, and a detection resistor;

[0008] One end of the detection resistor is connected to the negative electrode of the LED load and the first input end of the current detection module;

[0009] The other end of the detection resistor is connected to the drain of the switching transistor and the second input end of the current detection module;

[0010] The output end of the current detection module is connected to the first input end of the error amplifier module;

[0011] The output end of the signal modulation module is connected to the second input end of the error amplifier module;

[0012] The output end of the error amplifier module is connected to the first input end of the threshold comparator;

[0013] The output end of the threshold comparator is connected to the input end of the driving circuit;

[0014] The output end of the driving circuit is connected to the gate of the switching transistor;

[0015] The source of the switching transistor is grounded;

[0016] The drain of the switching transistor is also connected to the cathode of the LED load;

[0017] The first output terminal of the oscillator module is connected to the third input terminal (enable input terminal) of the error amplifier module;

[0018] The second output terminal of the oscillator module is connected to the second input terminal of the threshold comparator;

[0019] The third output terminal of the oscillator module is connected to the third input terminal of the current detection module;

[0020] The anode of the LED load is connected to the input power supply.

[0021] For the above circuit, optionally, the first input terminal of the current detection module is the positive-phase input terminal of the current detection module; the second input terminal of the current detection module is the negative-phase input terminal of the current detection module.

[0022] For the above circuit, optionally, the first input terminal of the error amplifier module is the negative-phase input terminal of the error amplifier module; the second input terminal of the error amplifier module is the positive-phase input terminal of the error amplifier module; the third input terminal of the error amplifier module is the enable input terminal of the error amplifier module.

[0023] For the above circuit, optionally, it further includes a capacitor, and the series branch formed by the LED load and the detection resistor is connected in parallel with the capacitor.

[0024] An intelligent LED driving circuit control method is applied to an intelligent LED driving circuit as described in any one of the above, and the specific method is as follows:

[0025] The current detection module receives the second pulse signal generated by the oscillator module, detects the voltage across the detection resistor, obtains a detection voltage and converts the detection voltage into a feedback signal, and inputs the feedback signal into the first input terminal of the error amplifier module;

[0026] The signal modulation module converts the PWM signal into an analog modulation signal and inputs the analog modulation signal into the second input terminal of the error amplifier module;

[0027] The error amplifier module receives the first pulse signal generated by the oscillator module, amplifies the difference between the input feedback signal and the analog modulation signal, obtains an error output signal and inputs the error output signal into the first input terminal of the threshold comparator;

[0028] The threshold comparator compares the error output signal at the first input terminal of the threshold comparator with the sawtooth wave signal output by the oscillator module at the second input terminal of the threshold comparator, and outputs a comparison result signal to the drive circuit;

[0029] The drive circuit outputs a drive signal to the switching transistor to drive the switching transistor to operate, thereby controlling the output current of the LED load.

[0030] In the above method, optionally, when the output comparison result signal is 1, the drive signal is at a high level, causing the switching transistor to conduct;

[0031] When the output comparison result signal is 0, the drive signal is at a low level, causing the switching transistor to turn off.

[0032] As can be seen from the above technical solutions, compared with the prior art, the present invention provides an LED drive circuit and a control method: when the present invention performs detection resistor detection, the operational amplifier used adopts a chopper regulation method to improve the detection accuracy, converts the detection signal into a loop feedback voltage SENSE, and at the same time, when performing error amplification, the error amplifier used also adopts a chopper regulation method to improve the LED dimming accuracy and achieve extremely deep dimming as a whole; it does not directly drive the LED lamp in a full-on and full-off output mode, and the LED lamp current is a ripple-free current, so the phenomenon of raster jitter is avoided, and the performance is advanced. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0034] Figure 1 It is a schematic structural diagram of an intelligent LED drive circuit provided by the present invention;

[0035] Figure 2 It is a schematic structural diagram of a current detection module provided by the present invention;

[0036] Figure 3 It is a schematic circuit diagram of a low-offset error amplifier module provided by the present invention;

[0037] Figure 4 It is a display of the dimming depth performance of the present invention. Detailed Embodiments

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Referring to Figure 1 as shown, the present invention discloses an intelligent LED driving circuit, including:

[0040] a current detection module, a signal modulation module, an error amplifier module, an oscillator module, a threshold comparator, a driving circuit, a switching transistor ( Figure 1 M1 in), an LED load, and a detection resistor ( Figure 1 RCS in);

[0041] One end of the detection resistor is connected to the negative electrode of the LED load and the first input end of the current detection module;

[0042] The other end of the detection resistor is connected to the drain of the switching transistor and the second input end of the current detection module;

[0043] The output end of the current detection module is connected to the first input end of the error amplifier module;

[0044] The output end of the signal modulation module is connected to the second input end of the error amplifier module;

[0045] The output end of the error amplifier module is connected to the first input end of the threshold comparator;

[0046] The output end of the threshold comparator is connected to the input end of the driving circuit;

[0047] The output end of the driving circuit is connected to the gate of the switching transistor;

[0048] The source of the switching transistor is grounded;

[0049] The drain of the switching transistor is also connected to the cathode of the LED load;

[0050] The first output end of the oscillator module is connected to the enable input end of the third input end of the error amplifier module;

[0051] The second output end of the oscillator module is connected to the second input end of the threshold comparator;

[0052] The third output end of the oscillator module is connected to the third input end of the current detection module;

[0053] The anode of the LED load is connected to the input power supply.

[0054] Further, the first input terminal of the current detection module is the positive-phase input terminal of the current detection module; the second input terminal of the current detection module is the negative-phase input terminal of the current detection module.

[0055] Further, the first input terminal of the error amplifier module is the negative-phase input terminal of the error amplifier module; the second input terminal of the error amplifier module is the positive-phase input terminal of the error amplifier module; the third input terminal of the error amplifier module is the enable input terminal of the error amplifier module.

[0056] Specifically, the error amplifier module is a low-offset error amplifier module.

[0057] Further, a capacitor is further included, and the series branch formed by the LED load and the detection resistor is connected in parallel with the capacitor.

[0058] And Figure 1 Corresponding to the intelligent LED driving circuit shown, the present invention also discloses a control method for an intelligent LED driving circuit, and the specific content is as follows:

[0059] The current detection module receives the second pulse signal VP2 generated by the oscillator module, detects the voltage across the detection resistor RCS, obtains the detection voltages (SEN+ and SEN-), converts the detection voltages (SEN+ and SEN-) into a feedback signal SENSE, and inputs the feedback signal SENSE to the first input terminal of the error amplifier module;

[0060] The signal modulation module converts the PWM signal into an analog modulation signal VA, and inputs the analog modulation signal VA to the second input terminal of the error amplifier module;

[0061] The error amplifier module receives the first pulse signal VP1 generated by the oscillator module, amplifies the difference between the input feedback signal SENSE and the analog modulation signal VA, obtains an error output signal EAOUT, and inputs the error output signal EAOUT to the first input terminal of the threshold comparator;

[0062] The threshold comparator compares the error output signal EAOUT at the first input terminal of the threshold comparator with the sawtooth wave signal OSCOUT output by the oscillator module at the second input terminal of the threshold comparator, and outputs a comparison result signal to the driving circuit;

[0063] The driving circuit outputs a driving signal to the switching transistor ( Figure 1 M1 in Figure 1 ), drives the switching transistor (

[0064] M1 in Figure 1M1) in it is turned on;

[0065] When the output comparison result signal CTRL is 0, the drive signal is at a low level, causing the switching transistor ( Figure 1 M1) in it to turn off.

[0066] Furthermore, when the PWM signal has a dimming depth lower than 0.5%, the level of the generated analog modulation signal is very small. To accurately compare the feedback signal SENSE and the analog modulation signal VA, the precision of the low-offset error amplifier needs to be improved, that is, the offset voltage should be small enough.

[0067] Refer to Figure 2 As shown, the present invention discloses a schematic structural diagram of a current detection module, specifically as follows:

[0068] The positive input terminal VSEN+ of the current detection module is connected to one end of the resistor R302, and the other end of the resistor R302 is connected to one end of the switches S303 and S304, and is also connected to the source electrode of the switching transistor MP303.

[0069] The negative input terminal VSEN- of the current detection module is connected to one end of the resistor R301, and the other end of the resistor R301 is connected to one end of the switches S301 and S302. The other end of the switch S301 is connected to the other end of the switch S303, and is also connected to the source electrode of the switching transistor MP301. The gate electrode of the switching transistor MP301 is connected to the gate electrode of the switching transistor MP302. The two ends of the switch S305 are respectively connected to the drain electrode and the gate electrode of the switching transistor MP301, the two ends of the switch S306 are respectively connected to the drain electrode and the gate electrode of the switching transistor MP302, the two ends of the switch S307 are respectively connected to the drain electrode of the switching transistor MP302 and the gate electrode of the switching transistor MP303, and the two ends of the switch S308 are respectively connected to the drain electrode of the switching transistor MP301 and the gate electrode of the switching transistor MP303. The current source I1 is connected to the drain electrode of the switching transistor MP301, and the other end is connected to GND. The current source I2 is connected to the drain electrode of the switching transistor MP302, and the other end is connected to GND. The resistor R303 is connected to the drain electrode of the switching transistor MP303, and the other end is connected to GND.

[0070] Its working principle is as follows:

[0071] When the pulse signal VP2+ is at a low level and the pulse signal VP2- is at a high level, switches S302 / S303 are turned off, switches S301 / S304 are turned on, resistor R302 is connected to switch transistor MP303, resistor R301 is connected to switch transistor MP21, switches S306 / S308 are turned on, switches S305 / S307 are turned off, R301 = R302, current ISEN = (VSEN+ - VSEN-) / R302, that is, the voltage of SEN+ is higher than the voltage of VSEN-, this voltage difference is ΔV = VSEN+ - VSEN-, the current generated by dividing ΔV by resistor R302 will flow into resistor R303, voltage VOUT = ISEN*R303 = (VSEN+ - VSEN-)*R303 / R302, by adjusting the ratio of resistor R303 and resistor R302, the amplification factor of the detected voltage can be detected.

[0072] When the pulse signal VP2+ is at a high level and the pulse signal VP2- is at a low level, switches S302 / S303 are turned on, switches S301 / S304 are turned off, switches S305 / S307 are turned on, switches S306 / S308 are turned off, the detection function is the same as before and is all realized, but at this time resistor R301 is connected to switch transistor MP302, resistor R302 is connected to switch transistor MP301, through this chopper regulation method, the matching of switch transistor MP301 and switch transistor MP302 can be improved, and the detection accuracy can be improved.

[0073] Refer to Figure 3 As shown, the present invention discloses a circuit structure of a low offset error amplifier module, specifically as follows:

[0074] The gate of input switch transistor MP402 of the low offset error amplifier is common with switches S41 and S44; the gate of switch transistor MP401 is common with switches S42 and S44; input signal Vio+ is common with switches S41 and S43; input signal Vio- is common with switches S42 and S43.

[0075] The sources of switch transistors MP401 and MP402 are connected and then connected to one end of current source Ib1; the drain of switch transistor MP401, the drain of switch transistor MN403 and the source of switch transistor MN405 are connected; the drain of switch transistor MP402 is connected to the drain of switch transistor MN404 and the source of switch transistor MN406.

[0076] The gates of switch transistors MN403 and MN404 are connected to node Vb2; the gate and drain of switch transistor MN11 are connected; the gates of switch transistors MN405 and MN406 are connected to node Vb1.

[0077] The drain of switching transistor MN405 is connected to the drain of switching transistor MP406; the gate and drain of switching transistor MP406 are connected and also connected to the gate of switching transistor MP407; the drain of switching transistor MN406 is connected to the drain of switching transistor MP408; the gate and drain of switching transistor MP408 are connected and also connected to the gate of switching transistor MP409.

[0078] The drain of switching transistor MP407 is connected to the drain of switching transistor MN409 and also connected to switches S45 and S48; the drain of switching transistor MP409 is connected to the drain of switching transistor MN10 and also connected to switches S46 and S47; the gate of switching transistor MN409 is connected to the gate of MN410 at node Vb1; the source of switching transistor MN409 is connected to the drain of switching transistor MN407; the source of switching transistor MN410 is connected to the drain of switching transistor MN8; the gate of switching transistor MN407 is connected to the gate of MN408 and also connected to switches S45 and S46 at node Vb4.

[0079] Vb1 and Vb2 are connected to an external bias voltage.

[0080] Switches S47 and S48 are connected and output EAOUT.

[0081] The sources of switching transistors MP406, MP407, MP408, and MP409 are all connected to power supply VDD. The sources of switching transistors MN403, MN407, MN408, and MN404 are all connected to GND.

[0082] The working principle is as follows:

[0083] When the pulse signal VP1- is at a low level and the pulse signal VP1+ is at a high level, switches S43 and S44 are turned off, switches S41 and S42 are turned on, Vio+ is connected to the gate of switching transistor MP402, Vio- is connected to the gate of switching transistor MP401, switches S45 and S47 are turned on, and switches S46 and S48 are turned off. The output signal EAOUT is connected to the drain of switching transistor MP409 and the drain of switching transistor MN410.

[0084] When the pulse signal VP1+ is at a low level and the pulse signal VP1- is at a high level, switches S41 and S42 are turned off, switches S43 and S44 are turned on, Vio+ is connected to the gate of switching transistor MP401, Vio- is connected to the gate of switching transistor MP402, switches S46 and S48 are turned on, and switches S45 and S47 are turned off. The output signal EAOUT is connected to the drain of switching transistor MP407 and the drain of switching transistor MN409.

[0085] See Figure 4 shown is the dimming depth performance display of an intelligent LED driving circuit according to the present invention. From Figure 4It can be seen that, compared with the prior art, under the condition of avoiding the raster jitter phenomenon, the dimming performance can still reach an extremely deep dimming depth.

[0086] The above description of the disclosed embodiments is presented in a progressive manner to enable those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

[0087] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for a system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0088] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. An intelligent LED driving circuit, characterized in that, Comprising: a current detection module, a signal modulation module, an error amplifier module, an oscillator module, a threshold comparator, a drive circuit, a switching transistor, an LED load, and a detection resistor; One end of the detection resistor is connected to the cathode of the LED load and the first input terminal of the current detection module; The other end of the detection resistor is connected to the drain of the switching transistor and the second input terminal of the current detection module; The output terminal of the current detection module is connected to the first input terminal of the error amplifier module; The output terminal of the signal modulation module is connected to the second input terminal of the error amplifier module; The output terminal of the error amplifier module is connected to the first input terminal of the threshold comparator; The output terminal of the threshold comparator is connected to the input terminal of the drive circuit; The output terminal of the drive circuit is connected to the gate of the switching transistor; The source of the switching transistor is grounded; The drain of the switching transistor is also connected to the cathode of the LED load; The first output terminal of the oscillator module is connected to the enable input terminal of the third input terminal of the error amplifier module; The second output terminal of the oscillator module is connected to the second input terminal of the threshold comparator; The third output terminal of the oscillator module is connected to the third input terminal of the current detection module; The anode of the LED load is connected to the input power supply.

2. An intelligent LED drive circuit according to claim 1, wherein The first input terminal of the current detection module is the positive-phase input terminal of the current detection module; the second input terminal of the current detection module is the negative-phase input terminal of the current detection module.

3. An intelligent LED drive circuit according to claim 1, wherein The first input terminal of the error amplifier module is the negative-phase input terminal of the error amplifier module; the second input terminal of the error amplifier module is the positive-phase input terminal of the error amplifier module; the third input terminal of the error amplifier module is the enable input terminal of the error amplifier module.

4. An intelligent LED drive circuit according to claim 1, wherein It further includes a capacitor, and the series branch formed by the LED load and the detection resistor is connected in parallel with the capacitor.

5. An intelligent LED driving circuit control method, characterized in that, When applied to an intelligent LED drive circuit according to any one of claims 1-4, the specific method is as follows: The current detection module receives the second pulse signal generated by the oscillator module, detects the voltage across the detection resistor, obtains a detection voltage and converts the detection voltage into a feedback signal, and inputs the feedback signal into the first input terminal of the error amplifier module; The signal modulation module converts the PWM signal into an analog modulation signal and inputs the analog modulation signal into the second input terminal of the error amplifier module; The error amplifier module receives the first pulse signal generated by the oscillator module, amplifies the difference between the input feedback signal and the analog modulation signal, obtains an error output signal and inputs the error output signal into the first input terminal of the threshold comparator; The threshold comparator compares the error output signal at the first input terminal of the threshold comparator with the sawtooth wave signal output by the oscillator module at the second input terminal of the threshold comparator, and outputs a comparison result signal to the drive circuit; The drive circuit outputs a drive signal to the switching transistor to drive the switching transistor to operate, thereby controlling the output current of the LED load.

6. The intelligent LED drive circuit control method according to claim 5, wherein when the output comparison result signal is 1, the drive signal is at a high level, causing the switching transistor to conduct; when the output comparison result signal is 0, the drive signal is at a low level, causing the switching transistor to turn off.

Images