CN218183559U - LED constant current drive circuit, LED drive control chip and LED lighting equipment - Google Patents

Abstract

The utility model provides a LED constant current drive circuit, LED drive control chip and LED lighting apparatus, it is through establishing ties on the basis of original first LED constant current driver and has the second LED constant current driver of compensation function all the way, from this when the first power tube short circuit of original first LED constant current driver, compensate the electric current ILED of LED light source of flowing through the second LED constant current driver that increases newly, can be close or be less than the ILED virtual value of system normal work with electric current ILED's effective value control, make entire system still can normally work after the power tube short circuit takes place from this, avoid LED lighting apparatus because of the problem of sending the heat under the power tube short circuit abnormal conditions and too big and damage.

Description

LED constant current drive circuit, LED drive control chip and LED lighting equipment

Technical Field

The utility model relates to a LED lighting drive technical field, in particular to LED constant current drive circuit, LED drive control chip and LED lighting apparatus.

Background

In the current LED lighting driving technology, one widely used driving technology is linear constant current driving, which can omit a magnetic element, and is beneficial for an LED driver to realize small volume, long service life, and meet EMI standards.

However, the conventional linear constant current driving product basically has no protection measure against short circuit of a power tube (such as a MOS tube) thereof, and due to the characteristic of linear constant current driving, when the driven power tube is short-circuited, an LED lamp connected with the power tube can still work, so that many users can continue to use the LED lighting device to continuously illuminate under the condition that the power tube in the LED lighting device is not short-circuited. This causes a sudden increase in the amount of heat generated by the LED lighting device, and if not, the lighting device housing is melted, and if not, there is a risk of fire, and therefore, a method for dealing with this problem is required.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a LED constant current drive circuit, LED drive control chip and LED lighting apparatus can avoid the problem of LED lighting apparatus because of giving out heat too big and damage under the power tube short circuit abnormal conditions.

In order to achieve the above object, the utility model provides a LED constant current driving circuit, it includes:

the first LED constant current driver is used for adjusting current flowing through an LED light source and provided with a first power tube, and the drain electrode of the first power tube is coupled with the LED light source;

and the second LED constant current driver is used for limiting the current flowing through the LED light source when the first power tube is in short circuit, and is coupled with the source electrode of the first power tube.

Optionally, when the first power tube is short-circuited, a constant current value achieved by the second LED constant current driver driving the LED light source is equal to or less than a constant current value achieved by the first LED constant current driver driving the LED light source when the first LED constant current driver normally works.

Optionally, the LED constant current driving circuit further includes a first sampling module, the second LED constant current driver further includes a second control module and a second power tube, the second control module is coupled to a gate of the second power tube, a drain of the second power tube is coupled to the first power tube, a source of the second power tube is coupled to the first sampling module, the first sampling module is grounded, and the second control module controls a conduction state of the second power tube according to a second reference voltage and a sampling voltage of the first sampling module.

Optionally, the first LED constant current driver further includes a first control module, where the first control module is coupled to a gate of the first power transistor, and the first control module controls a conduction state of the first power transistor according to a first reference voltage.

Optionally, the LED constant current driving circuit further includes a second sampling module, one end of the second sampling module is coupled to the first power tube, the other end of the second sampling module is coupled to the second power tube, and the first control module controls a conduction state of the first power tube according to a first reference voltage and a sampling voltage of the second sampling module.

Optionally, a target constant current value achieved by the first LED constant current driver driving the LED light source is determined by the first reference voltage and the second sampling module, and a target constant current value achieved by the second LED constant current driver driving the LED light source is determined by the second reference voltage and the first sampling module.

Optionally, the second reference voltage is a variable voltage, when the first power tube normally works, the second reference voltage is an upper limit voltage value of the variable voltage, and a target constant current value achieved by the first LED constant current driver driving the LED light source is smaller than a target constant current value achieved by the second LED constant current driver driving the LED light source, and meanwhile, when the second reference voltage is the upper limit voltage value of the variable voltage, the on-resistance of the second power tube is lower than when the second reference voltage is another voltage value of the variable voltage.

Optionally, the second LED constant current driver further includes a second line compensation circuit, and the second line compensation circuit is configured to detect a voltage at a coupling of the first LED constant current driver and the second LED constant current driver, and adjust the second reference voltage downward when the detected voltage exceeds a preset voltage threshold.

Optionally, the second line compensation circuit includes a second voltage sampling processing circuit and a second compensation voltage threshold judgment circuit, an input end of the second voltage sampling processing circuit is coupled to a drain of a second power transistor in the second LED constant current driver, an output end of the second voltage sampling processing circuit is coupled to an input end of the second compensation voltage threshold judgment circuit, and an output end of the second compensation voltage threshold judgment circuit is an output end of the second line compensation circuit.

Optionally, the second control module includes a second operational amplifier and a second voltage source, an output terminal of the second operational amplifier is connected to a gate of the second power transistor, a first input terminal of the second operational amplifier is coupled to an output terminal of the second voltage source, and a second input terminal of the second operational amplifier is coupled to a connection point of the second power transistor and the first sampling module.

Optionally, the first LED constant current driver further includes a first line compensation circuit, where the first line compensation circuit is configured to detect a drain voltage of the first power tube, and compensate an output of the first LED constant current driver according to the detected drain voltage.

Optionally, under compensation of the first line compensation circuit and the second line compensation circuit, a peak value of a current realized by the first LED constant current driver driving the LED light source alone is smaller than a peak value of a current realized by the second LED constant current driver driving the LED light source alone, and a trough value of a current realized by the first LED constant current driver driving the LED light source alone is larger than a trough value of a current realized by the second LED constant current driver driving the LED light source alone.

Optionally, the first line compensation circuit includes a first voltage sampling processing circuit and a first compensation voltage threshold judgment circuit, an input end of the first voltage sampling processing circuit is coupled to the drain of the first power transistor, an output end of the first voltage sampling processing circuit is coupled to an input end of the first compensation voltage threshold judgment circuit, and an output end of the first compensation voltage threshold judgment circuit is an output end of the first line compensation circuit.

Optionally, the first control module includes a first operational amplifier and a first voltage source, an output terminal of the first operational amplifier is connected to a control electrode of the first power transistor, an output terminal of the first operational amplifier is connected to a gate of the first power transistor, a first input terminal of the first operational amplifier is coupled to an output terminal of the first voltage source, and a second input terminal of the first operational amplifier is coupled to a source of the first power transistor.

Optionally, the LED constant current driving circuit further includes an abnormality detection module for prompting that the first power tube is short-circuited, one end of the abnormality detection module is coupled to the source of the first power tube, and the abnormality detection module includes an audio alarm and/or an alarm indicator.

Based on same utility model conceive, the utility model discloses still provide a LED drive control chip, include if LED constant current drive circuit.

Based on same utility model the design, the utility model also provides a LED lighting device, it includes the LED light source and if it is coupled the utility model discloses a LED drive control chip.

Compared with the prior art, the technical scheme of the utility model, following beneficial effect has:

through establish ties the second LED constant current driver that has compensation function all the way on original first LED constant current driver's basis, from this when the first power tube short circuit of original first LED constant current driver, compensate the electric current ILED of LED light source of flowing through the second LED constant current driver that increases newly, can be close to or be less than the ILED effective value of system normal operating with electric current ILED's effective value control, make entire system still can normally work after taking place the MOS pipe short circuit from this, avoid LED lighting apparatus because of the problem that the heat is too big and damage under the MOS pipe short circuit abnormal conditions.

Drawings

Fig. 1 is a schematic diagram of a conventional typical LED constant current driving circuit system.

Fig. 2 is a schematic diagram of the LED constant current driving circuit system shown in fig. 1 when a MOS transistor short circuit occurs.

Fig. 3 is a schematic diagram of a system architecture of an LED constant current driving circuit according to a first embodiment of the present invention.

Fig. 4 is a schematic diagram of an example structure of a second line compensation circuit in the LED constant current driving circuit shown in fig. 3.

Fig. 5 is a schematic diagram of a relationship between a voltage at DRAIN2 of a second LED constant current driver and a second reference voltage Vref2 in the LED constant current driving circuit shown in fig. 4.

Fig. 6 is a schematic diagram of waveforms of signals before and after a MOS1 short circuit occurs in the LED constant current driving circuit shown in fig. 3.

Fig. 7 is a schematic diagram of a system architecture of an LED constant current driving circuit according to a second embodiment of the present invention.

Fig. 8 is a schematic diagram of an example structure of a first line compensation circuit in the LED constant current driving circuit shown in fig. 7.

Fig. 9 is a schematic diagram showing waveforms of signals before and after MOS1 short-circuit occurs in the LED constant current driving circuit shown in fig. 7.

Fig. 10 is a schematic diagram of a system architecture of an LED constant current driving circuit according to a third embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention. It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. It will be understood that when an element is referred to as being "connected to," "coupled to" other elements, it can be directly connected to the other elements or intervening elements may be present. In contrast, when an element is referred to as being "directly connected to" another element, there are no intervening elements present. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

Fig. 1 shows a typical LED constant current driving circuit, after being rectified by a rectifier bridge 11 and filtered by a filter circuit 12, an AC voltage of an AC source 10 passes through an LED light source 13 and enters an LED constant current driver 14, a sampling resistor R outside the LED constant current driver 14 samples a current ILED flowing through the LED light source 13 and feeds the current ILED back to the LED constant current driver 14, and an internal circuit of the LED constant current driver 14 controls the current ILED flowing through the LED light source 13 according to a sampling result of the sampling resistor R, thereby implementing constant current driving.

Referring to fig. 2, when the power transistor MOS in the LED constant current driver 14 is short-circuited (as shown by a dashed short in fig. 2), even if the operational amplifier U2' inside the LED constant current driver 14 detects that the voltage across the sampling resistor R becomes high, the operational amplifier U2' inside the LED constant current driver 14 can adjust the gate voltage of the power transistor MOS in time based on the reference voltage Vref of the reference voltage source U1' and the voltage across the sampling resistor R, and the current ILED flowing through the LED light source cannot be controlled to be constant, because the voltage rectified by the rectifier bridge 11 is directly applied to the two ends of the LED light source 13 and the sampling resistor R, and the sampling resistor R generally has a small value, so the current limiting effect is poor, and after the power transistor MOS is short-circuited, the current ILED is still violent, and the heat productivity of the LED light source 13 is greatly increased due to the increase of the current ILED. For a user of the LED lighting device, even if the light emitting intensity of the LED light source 13 after the power transistor MOS is short-circuited becomes high, the user can continue to use the LED lighting device, and at this time, the user can have a great safety risk while the user can easily melt the housing of the LED lighting device, and even then the user can have a risk of causing a fire.

Based on this, the utility model provides a LED constant current drive circuit, LED drive control chip and LED lighting apparatus, it has the LED constant current driver of two way series connection, when the power tube MOS short circuit that is used for driving the luminous LED constant current driver of LED light source, another way LED constant current driver compensates the current ILED of the LED light source of flowing through, can be close or be less than the ILED virtual value (being the target constant current value) of system normal work time with current ILED's effective value control, make entire system still can normally work after taking place power tube MOS short circuit from this, avoid LED lighting apparatus because of the problem of the too big damage of the heat generation under power tube MOS short circuit abnormal conditions.

The technical solution provided by the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in simplified form and are not to precise scale, and are provided for convenience and clarity in order to facilitate the description of the embodiments of the present invention.

First embodiment

Referring to fig. 3, the present embodiment provides an LED constant current driving circuit, which includes a first LED constant current driver 14 and a second LED constant current driver 15. The first LED constant current driver 14 has a first power transistor MOS1, a drain of the first power transistor MOS1 is coupled to the LED light source 13, and the first LED constant current driver 14 is configured to adjust a current flowing through the LED light source 13. The second LED constant current driver 15 is coupled to the source of the first power transistor MOS1, and is configured to limit a current flowing through the LED light source 13 when the first power transistor MOS1 is short-circuited. Further, when the first power transistor MOS1 is short-circuited, the constant current value achieved by the second LED constant current driver 15 driving the LED light source 13 alone is equal to or less than the constant current value achieved by the first LED constant current driver 14 driving the LED light source 13 alone during normal operation. Therefore, when the first power tube MOS1 is short-circuited, the second LED constant current driver 15 can protect the entire system including the LED constant current driving circuit and the LED light source 13 driven by the LED constant current driving circuit.

In this embodiment, the second LED constant current driver 15 has a second power transistor MOS2, where the second power transistor MOS2 and the first power transistor MOS1 may be MOS transistors, and may also be triodes or other types of power transistors.

The second power transistor MOS2 and the first power transistor MOS1 are both MOS transistors as an example.

The LED constant current driving circuit of this embodiment further includes a first sampling module 16 and a second sampling module 17.

One end of the second sampling module 17 is coupled to the source of the first power transistor MOS1 of the first LED constant current driver 14, and the other end is coupled to the drain of the second power transistor MOS2 of the second LED constant current driver 15. One end of the first sampling module 16 is coupled to the source of the second power transistor MOS2, and the other end is grounded. The second sampling module 17 can avoid voltage disturbance on the second power transistor MOS2, and improve the high voltage resistance of the whole system.

As an example, the first sampling module 16 is a sampling resistor Rcs2, and the second sampling module 17 is a sampling resistor Rcs1. The DRAIN1 of the first power transistor MOS1 is coupled to the LED light source 13, and the source of the first power transistor MOS1 is coupled to one end of the sampling resistor Rcs1. The DRAIN of the second power transistor MOS2 is coupled to the other end (i.e., DRAIN2 node) of the sampling resistor Rcs1.

As an example, referring to fig. 3, in this embodiment, the first LED constant current driver 14 includes a first control module 14a, a first power transistor MOS1, and a first power supply circuit U3, and the first control module 14a includes a first voltage source U1 and a first operational amplifier U2.

The first power supply circuit U3 is coupled to a connection node of the filter circuit (i.e., the filter capacitor Cin in fig. 3) 12 and the LED light source 13, and is used for supplying power to an internal circuit of the first LED constant current driver 14.

The input end of the first voltage source U1 is coupled to a connection node (not labeled) between the sampling resistor Rcs1 and the second power transistor MOS 2. The first input terminal "+" of the first operational amplifier U2 is coupled to the output terminal of the first voltage source U1 to receive the first reference voltage Vref1 provided by the first voltage source U1, the second input terminal "-" of the first operational amplifier U2 is coupled to a connection node (i.e., DRAIN 1) between the sampling resistor Rcs1 and the source of the first power transistor MOS1 to receive the sampling voltage obtained by sampling the current ILED by the sampling resistor Rcs1, and the output terminal of the first operational amplifier U2 is coupled to the gate of the first power transistor MOS1 to provide the signal G1 to the gate of the first power transistor MOS1 to control the on and off of the first power transistor MOS 1. Namely, the first control module 14a controls the conduction state of the first power transistor MOS1 according to the first reference voltage Vref1 and the sampling voltage of the second sampling module 17. The target constant current value (i.e., ILED1 in fig. 6) achieved by the first LED constant current driver 14 driving the LED light source 13 alone is determined by the first reference voltage Vref1 and the second sampling module 17 (i.e., the sampling resistor Rcs 1), and specifically, the target constant current value that can be achieved by the first LED constant current driver 14 driving the LED light source 13 alone in normal operation is Vref1/Rcs1.

As an example, referring to fig. 3, the second LED constant current driver 15 includes a second control module 15a, a second power supply circuit U6, and a second power transistor MOS2, and the second control module 15a includes a second voltage source U4, a second operational amplifier U5, and a second line compensation circuit U7.

The second power supply circuit U6 is coupled to a connection node of the filter circuit 12 (i.e., the filter capacitor Cin in fig. 3) and the LED light source 13, and is used for supplying power to an internal circuit of the second LED constant current driver 15.

The drain of the second power transistor MOS2 is coupled to the input terminal of the second line compensation circuit U7 and the other end of the sampling resistor Rcs1, the source of the second power transistor MOS2 is coupled to one end of the sampling resistor Rcs2, and the other end of the sampling resistor Rcs2 is grounded. The gate of the second power transistor MOS2 is coupled to the output terminal of the second operational amplifier U5, the first input terminal "+" of the second operational amplifier U5 is coupled to the output terminal of the second voltage source U4, and the second input terminal "-" of the second operational amplifier U5 is coupled to a connection node (not labeled) between the sampling resistor Rcs2 and the source of the second power transistor MOS 2; the control terminal of the second voltage source U4 is coupled to the output terminal of the second line compensation circuit U7, and the second voltage source U4 adjusts the second reference voltage Vref2 provided to the second operational amplifier U5 under the control of the second line compensation circuit U7. Namely, the second control module 15a controls the conduction state of the second power transistor MOS2 according to the second reference voltage Vref2 and the sampling voltage of the first sampling module 16. Specifically, after the first power tube MOS1 is short-circuited, the second LED constant current driver 15 drives the LED light source 13 separately, and the achievable target constant current value is Vref2/Rcs2.

It should be understood that the first LED constant current driver 14 and the second LED constant current driver 15 in the present embodiment may be implemented by any suitable driver circuit design, and the second line compensation circuit U7 in the second LED constant current driver 15 may also be implemented by any suitable circuit design.

As an example, referring to fig. 4, the second line compensation circuit U7 of the present embodiment includes a second voltage sampling processing circuit U71 and a second compensation voltage threshold judgment circuit U72. An input end of the second voltage sampling processing circuit U71 is coupled to a DRAIN (i.e., DRAIN2 node) of the second power transistor MOS2, an output end of the second voltage sampling processing circuit U71 is coupled to an input end of the second compensation voltage threshold judging circuit U72, and an output end of the second compensation voltage threshold judging circuit U72 is coupled to a control end of the second voltage source U4.

The second voltage sampling processing circuit U71 samples the voltage of the DRAIN2 node and divides the voltage, and after the second compensation voltage threshold judgment circuit U72 performs threshold judgment on the divided voltage output by the second voltage sampling processing circuit U71, if the divided voltage output by the second voltage sampling processing circuit U71 reaches a preset compensation voltage threshold, the second compensation voltage threshold judgment circuit U72 outputs a corresponding voltage signal to control the second voltage source U4 to adjust the value of the second reference voltage Vref2. That is, the second reference voltage Vref2 received by the second operational amplifier U5 in the second control module 15a is a variable voltage.

The target constant current values realized when the first LED constant current driver 14 and the second LED constant current driver 15 separately drive the LED light source 13 respectively depend on the resistance values of the sampling resistor Rcs1 and the sampling resistor Rcs2, the target constant current value realized when the first LED constant current driver 14 separately drives the LED light source 13 is set to Vref1/Rcs1, the target constant current value realized when the second LED constant current driver 15 separately drives the LED light source 13 is set to Vref2/Rcs2, and in the system, vref1/Rcs1 is less than Vref2/Rcs2, that is, the target constant current value realized when the first LED constant current driver 14 separately drives the LED light source 13 is smaller than the target constant current value realized when the second LED constant current driver 15 separately drives the LED light source 13. When the first power tube MOS1 works normally, the second reference voltage Vref2 may be an upper limit voltage value Vref2max of the variable voltage, so that the conduction degree of the second power tube MOS2 is high, and at this time, the second power tube MOS2 is in a state of low on-resistance, that is, the on-resistance of the second power tube MOS2 when the second reference voltage Vref2 is the upper limit voltage value Vref2max of the variable voltage is low when the second reference voltage Vref2 is another voltage value of the variable voltage, so that the second LED constant current driver 15 does not affect the normal constant current work of the whole system when the first LED constant current driver 14 works normally.

Referring to fig. 6, the compensation voltage threshold of the second compensation voltage threshold determination circuit U72 is positively correlated with the node DRAIN2 voltage during normal operation of the circuit, for example, the compensation voltage threshold of the second compensation voltage threshold determination circuit U72 may be K times of the node DRAIN2 voltage during normal operation, where K represents a ratio of the divided voltage output by the second voltage sampling processing circuit U71 to the node DRAIN2 voltage, as shown by an inflection point at a dashed line in fig. 5. When the voltage of the node DRAIN2 becomes high and the divided voltage output by the second voltage sampling processing circuit U71 reaches the compensation voltage threshold, the second reference voltage Vref2 is reduced by the line compensation modulation of the second line compensation circuit U7, so as to reduce the constant current value driven by the second constant current driver 15.

With reference to fig. 1 to fig. 6, the LED constant current driving circuit of the present embodiment has the following working principle:

when the system normally works, after the AC voltage of the AC source 10 is rectified by the rectifier bridge 11 and filtered by the filter circuit 12, the AC voltage passes through the LED light source 13 and enters the first LED constant current driver 14, the sampling resistor Rcs1 outside the first LED constant current driver 14 samples the current ILED flowing through the LED light source 13 and feeds the current ILED back to the first LED constant current driver 14, and the internal circuit of the first LED constant current driver 14 controls the current ILED flowing through the LED light source 13 according to the sampling result of the sampling resistor Rcs1, so that constant current driving is realized. A short shown in fig. 6 is a short-circuit signal schematic waveform of the first power tube MOS1, the short is 0 before time t1, the first power tube MOS1 is not short-circuited, the entire system normally operates, the target constant current value ILED1= Vref1/Rcs1 that is realized by the first LED constant current driver 14 driving the LED light source 13, because ILED1 is less than Vref2/Rcs2, the output node G2 of the second operational amplifier U5 in the second LED constant current driver 15 after Rcs2 sampling is modulated to a higher voltage before time t1, the conduction degree of the second power tube MOS2 is higher, and therefore the voltage of the DRAIN2 node of the second LED constant current driver 15 portion (i.e., close to the MOS2 voltage drop, as shown by the DRAIN2 curve in fig. 6) maintains a lower voltage before time t1, at this time, the second LED driver 15 does not substantially affect the normal operation of the entire system.

When the first power transistor MOS1 is short-circuited, that is, short is 1 at t1 in fig. 6, the first LED constant current driver 14 loses control of the current ILED flowing through the LED light source 13. Due to the short circuit of the first power transistor MOS1, when the voltage of the AC source 10 rises, the voltage of the DRAIN2 node rises, and the second line compensation circuit U7 in the second LED constant current driver 15 performs current compensation according to the voltage of the DRAIN2 node to control the current ILED flowing through the LED light source 13 to fall. As shown in fig. 6, the ILED waveform is the current compensated by the second line compensation circuit U7, and as can be seen from fig. 6, after t1, the voltage of the DRAIN2 node is increased and then adjusted to a relatively stable value, and the DRAIN2 voltage becomes high, vref2 will be decreased by line compensation modulation, and when DRAIN2 is high, ILED will also decrease accordingly (when the DRAIN2 voltage is highest, ILED will decrease to the valley value ILED2 min), so that ILED is reduced by this method, and thus after MOS1 short circuit, the whole system can still work normally, and the risk of excessive heating of the LED light source 13 due to MOS1 short circuit will not occur.

In addition, a peak value ILED2max of the ILED after the MOS1 short circuit is greater than a target constant current value ILED1 when the first LED constant current driver 14 normally operates, and a valley value ILED2min is less than the target constant current value ILED1 when the first LED constant current driver 14 normally operates. As an example, although the target constant current value achieved when the second LED constant current driver 15 drives the LED light source alone is Vref2/Rcs2, which is greater than the target constant current value ILED1= Vref1/Rcs1 achieved by the first LED constant current driver 14, since the second LED constant current driver 15 is provided with the second line compensation circuit U7, it may control the effective value of the current ILED (i.e., the corresponding target constant current value after MOS1 short circuit) to be close to the target effective value ILED1 of the current when the first LED constant current driver 14 operates normally, so that the illumination intensity of the LED light source 13 is stable before and after MOS1 short circuit.

As another example, the current compensation degree implemented by the second LED constant current driver 15 is higher, so that the effective value of the current ILED after the MOS1 short circuit is greatly reduced, and is lower than the effective value of the current ILED1 when the first LED constant current driver 14 normally operates, so that the illumination intensity of the LED light source after the MOS1 short circuit is relatively reduced before the MOS1 short circuit, and the reduction degree enables a user to visually and obviously perceive. Therefore, after the first power tube MOS1 is short-circuited, the whole system can still work, but the illumination intensity of the LED light source 13 is obviously reduced, so that the abnormality of the lighting equipment is reminded to a user, and the lighting equipment is stopped to be used in time.

It should be understood that the second LED constant current driver 15 and the first LED constant current driver 14 may be implemented by two chips, or may be integrated in the same chip.

Based on this, please refer to fig. 3 to fig. 6, the present embodiment further provides an LED driving control chip, which includes the LED constant current driving circuit according to the present embodiment, that is, the second LED constant current driver 15 and the first LED constant current driver 14 are integrated in the same chip.

Referring to fig. 3 to fig. 6, the present embodiment further provides an LED lighting device, which includes an LED light source 13 and an LED driving control chip coupled thereto according to the present embodiment.

Optionally, referring to fig. 3, the LED lighting device of this embodiment further includes a rectifier bridge 11 and a filter circuit 12, an input end of the rectifier bridge 11 is connected to the ac power supply 10, and the filter circuit 12 is coupled to an output end of the rectifier bridge 11 to filter an output of the rectifier bridge 11.

As an example, referring to fig. 3, the filter circuit 12 includes a filter capacitor Cin.

It should be understood that, in this embodiment, the specific circuit structure of the first sampling module 16, the second sampling module 17 and the filter circuit 12 is only an example, and the technical solution of the present invention is not limited thereto, and in other embodiments of the present invention, the first sampling module 16, the second sampling module 17 and the filter circuit 12 may also be implemented by using any other suitable electronic components or electronic circuits, for example, the first sampling module 16 and the second sampling module 17 may be replaced by a thyristor, a MOS transistor working in a variable resistance region, or a circuit formed by combining a resistor and these electronic components.

It should be noted that, in each example of this embodiment, the first sampling module 16 is a circuit independent of the second LED constant current driver 15, and the second sampling module 17 is a circuit independent of the first LED constant current driver 14, but the technical solution of the present invention is not limited thereto, and in other embodiments of the present invention, the first sampling module 16 may also be internally disposed in the second LED constant current driver 15, and the second sampling module 17 may also be internally disposed in the first LED constant current driver 14.

Furthermore, in the utility model discloses in other embodiments, also can omit the setting of second sampling module 17 for first voltage source U1's one end ground connection, the second input of first operational amplifier U2 is directly coupled with the DRAIN electrode of second power tube MOS2, in order to simplify the circuit and save circuit area, but such setting, on the one hand can introduce the pressure drop on the second power tube MOS2 as the partly of the feedback voltage that first operational amplifier U2 received, because the pressure drop of second power tube MOS2 is unstable, consequently, the feedback voltage fluctuation that first operational amplifier U2 received is great, on the other hand, when first power tube MOS1 short circuit, the voltage of node DRAIN2 can be than higher. Therefore, the scheme is suitable for application scenarios that the voltage resistance of the second LED constant current driver 15 is high and the circuit stability requirement is low.

Second embodiment

Referring to fig. 7, the present embodiment provides an LED constant current driving circuit, which is different from the first embodiment in that in the LED constant current driving circuit of the present embodiment, the first LED constant current driver 14 further includes a first line compensation circuit U8. The input end of the first line compensation circuit U8 is coupled to the drain of the first power transistor MOS1, and the output end of the first line compensation circuit U8 is coupled to the control end of the first voltage source U1.

Referring to fig. 8, as an example, the first line compensation circuit U8 includes a first voltage sampling processing circuit U81 and a first compensation voltage threshold judgment circuit U82, an input terminal of the first voltage sampling processing circuit U81 is an input terminal of the first line compensation circuit U8 and is coupled to a drain of the first power transistor MOS1, an output terminal of the first voltage sampling processing circuit U81 is coupled to an input terminal of the first compensation voltage threshold judgment circuit U82, and an output terminal of the first compensation voltage threshold judgment circuit U82 is an output terminal of the first line compensation circuit U8 and is coupled to a control terminal of the first voltage source U1.

The first line compensation circuit U8 is configured to detect a DRAIN voltage of the first power transistor MOS1 (i.e., a voltage of the node DRAIN 1), and control the first voltage source U1 to adjust the first reference voltage Vref1 provided to the first operational amplifier U2 according to the detected DRAIN voltage (i.e., the voltage of the node DRAIN 1), so as to compensate the current ILED of the LED light source driven by the first LED constant current driver 14.

Referring to fig. 9, on the basis that the first LED constant current driver 14 has a first line compensation circuit U8 and the second LED constant current driver 15 has a second line compensation circuit U7, a peak value ILED1max of the current ILED that is realized by the first LED constant current driver 14 alone driving the LED light source 13 when the first LED constant current driver 14 normally operates is smaller than a peak value ILED2max of the current ILED that is realized by the second LED constant current driver 15 alone driving the LED light source 13 after the first power transistor MOS1 is short-circuited, and is larger than a valley value ILED2min of the current ILED that is realized by the second LED constant current driver 15 alone driving the LED light source 13 after the first power transistor MOS1 is short-circuited; when the first LED constant current driver 14 works normally, the valley value ILED1min of the current ILED realized by independently driving the LED light source 13 is greater than the valley value ILED2min of the current ILED realized by independently driving the LED light source 13 by the second LED constant current driver 15 after the first power tube MOS1 is short-circuited.

From this, this embodiment, an application is, can be through the compensation of first line compensating circuit U8 and second line compensating circuit U7, make the effective value of the electric current before and after the short circuit of first power tube MOS1 be close, and then guarantee before and after the short circuit of first power tube MOS1, LED light source 13's illumination is stable, avoids influencing user and uses experience. Another application case is that, through the compensation effect of the first line compensation circuit U8 and the second line compensation circuit U7, the current compensation value of the second power tube MOS2 can be larger, and then the effective value of the current after the short circuit of the first power tube MOS1 is greatly reduced relatively before the short circuit, so that the brightness of the LED light source 13 obviously becomes dark relatively before the short circuit of the first power tube MOS1 after the short circuit of the first power tube MOS1, thereby reminding a user that the lighting device is abnormal, and stopping using the lighting device in time, thereby avoiding the potential safety hazard caused by the user continuing to use the lighting device under the condition of the short circuit of the MOS tubes.

The embodiment also provides an LED driving control chip, which includes the LED constant current driving circuit according to the embodiment.

The present embodiment further provides an LED lighting device, which includes an LED light source 13 and an LED driving control chip coupled thereto as described in the present embodiment.

Third embodiment

Referring to fig. 10, the present embodiment provides an LED constant current driving circuit, which is different from the first and second embodiments in that the LED constant current driving circuit of the present embodiment further includes an abnormality detection module 18 for prompting that the first power transistor MOS1 is short-circuited, and one end of the abnormality detection module 18 is coupled to a DRAIN2 node (i.e., the other end of the sampling resistor Rcs 1).

The anomaly detection module 18 may include an audible alarm and/or an alarm indicator light. Therefore, when the first power tube MOS1 is short-circuited, the abnormality detection module 18 can detect that the voltage of the DRAIN2 node is abnormal, and then remind the user equipment of abnormality through abnormal flashing lights with sound or other colors, so that the user can replace the lighting equipment in time.

The embodiment also provides an LED driving control chip, which includes the LED constant current driving circuit according to the embodiment.

The present embodiment further provides an LED lighting device, which includes an LED light source 13 and an LED driving control chip coupled thereto as described in the present embodiment.

The above description is only for the description of the preferred embodiments of the present invention, and not for any limitation of the scope of the present invention, and any modification and modification made by those skilled in the art according to the above disclosure all belong to the scope of the technical solution of the present invention.

Claims (15)

1. An LED constant current driving circuit, comprising:

the first LED constant current driver is used for adjusting current flowing through an LED light source and is provided with a first power tube, and the drain electrode of the first power tube is coupled with the LED light source;

and the second LED constant current driver is used for limiting the current flowing through the LED light source when the first power tube is in short circuit, and is coupled with the source electrode of the first power tube.

2. The LED constant current driving circuit according to claim 1, wherein when the first power transistor is short-circuited, a constant current value achieved by the second LED constant current driver driving the LED light source is equal to or less than a constant current value achieved by the first LED constant current driver driving the LED light source during normal operation.

3. The LED constant current driving circuit according to claim 1, further comprising a first sampling module, wherein the second LED constant current driver further comprises a second control module and a second power tube, the second control module is coupled to a gate of the second power tube, a drain of the second power tube is coupled to the first power tube, a source of the second power tube is coupled to the first sampling module, the first sampling module is grounded, and the second control module controls a conduction state of the second power tube according to a second reference voltage and a sampling voltage of the first sampling module.

4. The LED constant current drive circuit according to claim 3, wherein the first LED constant current driver further comprises a first control module, the first control module is coupled to a gate of the first power tube, and the first control module controls a conduction state of the first power tube according to a first reference voltage.

5. The LED constant current driving circuit according to claim 4, further comprising a second sampling module, wherein one end of the second sampling module is coupled to the first power tube, the other end of the second sampling module is coupled to the second power tube, and the first control module controls a conduction state of the first power tube according to a first reference voltage and a sampling voltage of the second sampling module.

6. The LED constant current driving circuit according to claim 5, wherein a target constant current value achieved by the first LED constant current driver driving the LED light source is determined by the first reference voltage and the second sampling module, and a target constant current value achieved by the second LED constant current driver driving the LED light source is determined by the second reference voltage and the first sampling module.

7. The LED constant current driving circuit according to claim 6, wherein the second reference voltage is a variable voltage, and when the first power transistor operates normally, the second reference voltage is an upper limit voltage value of the variable voltage, and a target constant current value achieved by the first LED constant current driver driving the LED light source is smaller than a target constant current value achieved by a second LED constant current driver driving the LED light source, and an on-resistance of the second power transistor when the second reference voltage is the upper limit voltage value of the variable voltage is made lower than when the second reference voltage is another voltage value of the variable voltage.

8. The LED constant current drive circuit according to any one of claims 3-7, wherein the second LED constant current driver further comprises a second line compensation circuit for detecting a voltage at a coupling of the first LED constant current driver and the second LED constant current driver and adjusting the second reference voltage down when the detected voltage exceeds a preset voltage threshold.

9. The LED constant current driving circuit according to claim 8, wherein the second line compensation circuit includes a second voltage sampling processing circuit and a second compensation voltage threshold determination circuit, an input terminal of the second voltage sampling processing circuit is coupled to a drain of a second power transistor in the second LED constant current driver, an output terminal of the second voltage sampling processing circuit is coupled to an input terminal of the second compensation voltage threshold determination circuit, and an output terminal of the second compensation voltage threshold determination circuit is an output terminal of the second line compensation circuit.

10. The LED constant current drive circuit according to any one of claims 1-7 or 9, wherein the first LED constant current driver further comprises a first line compensation circuit, and the first line compensation circuit is used for detecting a drain voltage of the first power tube and compensating the output of the first LED constant current driver according to the detected drain voltage.

11. The LED constant current drive circuit according to claim 3, wherein the second control module comprises a second operational amplifier and a second voltage source; the output end of the second operational amplifier is connected with the grid electrode of the second power tube, the first input end of the second operational amplifier is coupled with the output end of the second voltage source, and the second input end of the second operational amplifier is coupled with the connection position of the second power tube and the first sampling module.

12. The LED constant current drive circuit according to claim 4, wherein the first control module comprises a first operational amplifier and a first voltage source; the output end of the first operational amplifier is connected with the grid electrode of the first power tube, the first input end of the first operational amplifier is coupled with the output end of the first voltage source, and the second input end of the first operational amplifier is coupled with the source electrode of the first power tube.

13. The LED constant current driving circuit according to claim 1, further comprising an abnormality detection module for prompting the first power tube to generate a short circuit, wherein one end of the abnormality detection module is coupled to the source electrode of the first power tube, and the abnormality detection module comprises an audible alarm and/or an alarm indicator light.

14. An LED drive control chip, characterized by comprising the LED constant current drive circuit as claimed in any one of claims 1 to 13.

15. An LED lighting device comprising an LED light source and the LED driving control chip of claim 14 coupled thereto.

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