TWM586027U - LED driving circuit and control chip - Google Patents

Abstract

This creative embodiment provides an LED (Light Emitting Diode) driving circuit and a control chip. The driving circuit includes a rectifier circuit and a constant current control circuit, wherein the rectifier circuit is used to output a direct current, and the constant current control circuit includes: A control chip, a voltage dividing circuit, a load module, an output capacitor, and a current setting circuit. The control chip includes an output current setting pin, a sink pin, and an input voltage sensing pin. The voltage dividing circuit is connected to the output of the rectifier circuit and a reference. Between ground, the output of the voltage divider circuit is connected to the input voltage sensing pin, the load module is connected between the output of the rectifier circuit and the drain pin, and the output capacitor is connected in parallel at both ends of the load module; the current setting circuit Connect between the output current setting pin and the reference ground. The input voltage sensing pin is used to determine whether to enter the leading edge dimming mode, the trailing edge dimming mode, or the non-dimming mode based on the output of the voltage dividing circuit. According to the above technical solution, an inductive magnetic core is not needed, and a small circuit size and fewer system components are realized.

Description

LED drive circuit and control chip

This creation relates to the technical field of LED (Light Emitting Diode, light emitting diode), and more specifically, to an LED driving circuit and a control chip.

Light Emitting Diode (LED) is a kind of semiconductor device that can emit light. Its core is the PN junction. It has the electrical characteristics of ordinary diodes. The luminous flux of an LED is proportional to the current flowing through the LED. With this feature, the dimming effect of LEDs is incomparable with other traditional lighting. Traditional lighting fixtures such as incandescent lamps will reduce their working efficiency when dimming, and when LEDs are dimming, due to the reduced current in the circuit, some The power consumption of the resistance component will be reduced, and the luminous efficiency will be improved.

However, the traditional LED TRIAC dimming scheme usually uses the switching scheme of electrolytic capacitors and inductive magnetic core devices, which will cause the driving circuit to be too large to adapt to small volume applications such as bulbs and filament lamps. As a result, the system cost is too high to meet user requirements for low cost.

In order to solve one or more of the aforementioned technical problems, this creative embodiment provides an LED driving circuit and a control chip, which can implement an LED driving circuit that does not require an inductive magnetic core device, and realizes a small driving circuit, few system components, and low cost. Meet the actual application needs of customers.

On the one hand, the embodiment of the present invention provides an LED driving circuit including a rectifier circuit and a constant current control circuit, wherein the rectifier circuit is used to output a direct current, and the constant current control circuit includes: a control chip, a voltage dividing circuit, a load module, and an output. Capacitor and current setting circuit, wherein the control chip includes an output current setting pin, a sink pin, an input voltage sensing pin, and a voltage dividing circuit connection Between the output of the rectifier circuit and the reference ground, the output of the voltage divider circuit is connected to the input voltage sensing pin; the load module is connected between the output of the rectifier circuit and the drain pin; the output capacitor is connected in parallel to the load module Both ends; the current setting circuit is connected between the output current setting pin and the reference ground. The input voltage sensing pin is used to determine whether to enter the leading edge dimming mode, the trailing edge dimming mode, or the non-dimming mode based on the output of the voltage dividing circuit.

According to the LED driving circuit provided in this creative embodiment, the current setting circuit includes one or more resistors connected in series.

According to the LED driving circuit provided in this creative embodiment, the voltage dividing circuit includes a first resistor and a second resistor connected in series, and an output terminal of the voltage dividing circuit is derived from a common terminal of the first resistor and the second resistor.

According to the LED driving circuit provided in this creative embodiment, the control chip may further include a high-voltage sustaining current input pin, and the constant current control circuit may further include a current-limiting circuit connected to the output of the rectifier circuit and the high-voltage sustaining current input. Between the feet.

According to the LED driving circuit provided in this creative embodiment, the constant current control circuit may further include an output capacitor discharge cut-off module, which is connected in series between the output of the rectifier circuit and the load module.

According to the LED driving circuit provided in this creative embodiment, the control chip may further include a high-voltage power input pin, which is connected to a common terminal of the output capacitor discharge cut-off module and the load module.

According to the LED driving circuit provided in this creative embodiment, the constant current control circuit may further include: a dummy load module, which is connected in parallel at both ends of the load module.

According to the LED driving circuit provided in this creative embodiment, the control chip may further include a closed-loop loop compensation pin, and the constant current control circuit may further include a loop compensation circuit. The loop compensation circuit is connected to the closed-loop compensation pin and the reference. Between the ground.

According to the LED driving circuit provided in this creative embodiment, the control chip may further include a temperature return point setting pin, and the temperature return point setting pin is connected to the reference ground through one or more resistors connected in series, or the temperature return point setting pin is left unconnected, or Temperature turning point setting foot Connect to reference ground.

On the other hand, the embodiment of the present invention provides a control chip for use in the LED driving circuit according to the first aspect, the control chip includes: an output current sampling sub-module, a constant current regulating sub-module, and a control circuit. Crystal, input voltage sensing sub-module and logic sub-module, wherein the input terminal of the output current sampling sub-module is connected to the output current setting pin, and the first input terminal of the constant current regulation sub-module is connected to the output current The first output terminal of the sampling sub-module, the gate of the control transistor is connected to the output of the constant current regulation sub-module, the drain of the control transistor is connected to the drain pin, and the source of the control transistor is connected to the output Current setting pin, the input terminal of the input voltage sensing submodule is connected to the input voltage sensing pin, the first input terminal of the logic submodule is connected to the output terminal of the input voltage sensing submodule, and the logic submodule The first output terminal is connected to the second input terminal of the constant current regulating sub-module.

The control chip provided by this creative embodiment further includes a high-voltage power supply input pin and a low-dropout linear voltage regulator sub-module, wherein the input end of the low-voltage-drop linear voltage regulator sub-module is connected to the high-voltage power supply input pin, and the low-dropout linear The voltage regulator sub-module is used to power the control chip.

The control chip provided by this creative embodiment further includes a temperature return point setting pin and a temperature selection sub-module, wherein an input end of the temperature selection sub-module is connected to a temperature return point setting pin and an output end of the temperature selection sub-module Connected to the second input of the logic submodule.

The control chip provided by this creative embodiment further includes a high-voltage sustaining current input pin and a sustaining current control sub-module, wherein the output terminal of the sustaining current control sub-module is connected to the high-voltage sustaining current input pin and the sustaining current control sub-module The first input terminal is connected to the second output terminal of the output current sampling sub-module, and the second input terminal of the sustain current control sub-module is connected to the second output terminal of the logic sub-module.

The control chip according to this creative embodiment further includes a closed-loop loop compensation pin, which is connected to the third input terminal of the constant current regulation sub-module.

The LED driving circuit and the control chip provided in this creative embodiment can realize an LED driving circuit without an inductive magnetic core, realize a small driving circuit, few system components, low cost, and meet the customer's actual application requirements.

C1‧‧‧ output capacitor

C2‧‧‧capacitor

CS‧‧‧Output current setting pin

COMP‧‧‧ closed-loop loop compensation pin

Drain‧‧‧Drain

D1, D2, D3, D4‧‧‧ rectified diodes

D5‧‧‧diode

F1‧‧‧Fuse resistance

GND‧‧‧ Chip reference ground

HV‧‧‧High-voltage power input pin

HVB‧‧‧ high voltage sustain current input pin

R1, R2, R3, R4, R5‧‧‧ resistance

TH‧‧‧Three gear temperature return point setting feet

U1‧‧‧control chip

VS‧‧‧Input voltage sensing pin

110‧‧‧Rectifier circuit

120‧‧‧Constant current control circuit

1201‧‧‧control chip

1202‧‧‧Voltage Dividing Circuit

1203‧‧‧Load Module

1204‧‧‧Current Setting Circuit

In order to explain the technical solution of this creative embodiment more clearly, the drawings used in this creative embodiment will be briefly introduced below. Obviously, the drawings described below are just some of the embodiments of this creative. Those of ordinary skill in the art can obtain other drawings according to these drawings without paying creative labor.

Fig. 1 shows a schematic structural diagram of an LED driving circuit provided by an embodiment of the present invention; Fig. 2 shows a schematic structural diagram of an LED driving circuit provided by another embodiment of the present invention; A schematic structural diagram of a control wafer provided in the embodiment; FIG. 4 shows a schematic structural diagram of a control wafer provided in another embodiment of the present invention.

The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed in order to provide a comprehensive understanding of this creation. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present creation by showing an example of the present creation.

It should be noted that, in the case of no conflict, the embodiments in this creation and the features in the embodiments can be combined with each other. The embodiments will be described in detail below with reference to the drawings.

As an example, reference is made to FIG. 1, which shows a schematic structural diagram of an LED driving circuit provided by an embodiment of the present invention.

As shown in FIG. 1, the LED driving circuit may include a rectifier circuit 110 and a constant current control circuit 120.

In some embodiments, the rectifier circuit 110 may be used to convert AC power to output DC power, and the rectifier circuit 110 may be a bridge rectifier circuit. It should be noted that, in other embodiments, the rectifier circuit may also be a full-wave rectifier circuit, a half-wave rectifier circuit, and the like, and there is no limitation on this creation.

In some embodiments, the constant current control circuit 120 may include a control chip 1201, a voltage dividing circuit 1202, a load module 1203, an output capacitor C1, and a current setting circuit 1204.

The control chip 1201 includes an output current setting pin CS, a drain pin Drain, and an input voltage sensing pin VS.

In the embodiment shown in FIG. 1, the voltage dividing circuit 1202 may be connected between the output of the rectifier circuit and the reference ground, and the output terminal of the voltage dividing circuit 1202 may be connected to the input voltage sensing pin of the control chip 1201. VS, the load module 1203 can be connected between the output of the rectifier circuit and the drain pin Drain of the control chip 1201. The output capacitor C1 can be connected in parallel to both ends of the load module 1203, and the current setting circuit 1204 can be connected to the control chip 1201. The output current is set between CS and the reference ground.

The rectifier circuit 110 can rectify the AC power input to obtain a DC voltage. The DC voltage can be divided by the voltage dividing circuit 1202 to obtain a divided voltage signal value. The divided voltage signal value can be input to the input voltage sense. The measuring pin VS, so that the input voltage sensing pin VS can be used to determine whether to enter a leading edge dimming mode, a trailing edge dimming mode or a non-dimming mode based on the output of the voltage dividing circuit.

It should be noted that the thyristor dimming can be used to adjust the current or voltage of the power supply so that the LED light string as a load can produce different intensity light output.

For example, there are many types of LED dimming: linear dimming, thyristor dimming, pulse width modulation dimming, and so on.

Specifically, for TRIAC dimming, the TRIAC dimming mode can be divided into a leading edge dimming mode and a trailing edge dimming mode. Among them, the thyristor leading-edge phase-cut dimming mode, when performing phase cutting, starts at AC phase 0 and the input voltage is chopped. There is no voltage input until the thyristor is turned on. After the current edge dimming is triggered, It still needs to load the current for a period of time to maintain it in the on state. When this current is turned off or weakened, the leading edge dimming mode is turned off. And the thyristor trailing-edge phase-cut dimming mode turns on when the phase is cut, starting from AC phase 0, disconnecting after a period of time, and maintaining the disconnected state to the end of the half cycle. After zero, repeat the same operation , Thereby changing the effective value of the AC current.

It should be understood that, since LEDs are characteristic semiconductor devices, It has a negative temperature characteristic, so it needs to be stable and protected in the application process. LEDs, unlike ordinary incandescent light bulbs, can be directly connected to 220V AC mains. LED is a low voltage driver with a safe voltage. It is necessary to design a circuit that meets the requirements to drive its normal work.

In addition, when the LED driving circuit drives the LED, its ultimate purpose is to control the current flowing through the LED to reach or approximate the value of the original design requirements, and to make it stable without being affected by or reducing the power supply voltage, temperature, and forward direction. Factors such as bias differences affect the required brightness and prevent LED life from being shortened or damaged. For example, light emitting diode driving can be divided into constant voltage driving and constant current driving according to types.

The output current setting pin CS can be used to adjust the output current value, so that the average value of the output current satisfies the design value, or is within a preset threshold range of the design value.

Among them, the drain pin is also called an internal metal-oxide semiconductor field effect transistor (MOSFET) drain, which is connected to the cathode of the LED lamp to a linear thyristor dimming constant current circuit.

In some embodiments, the voltage dividing circuit 1202 may include a plurality of resistors connected in series. In a series circuit, the circuits on each resistor are equal, and the sum of the voltages across the resistors is equal to the total voltage of the circuit. Less than the total circuit voltage. In other embodiments, the voltage dividing circuit may include a sliding varistor and the like. There is no limitation on this creation, the voltage dividing circuit 1202 can be any circuit that can implement the voltage dividing function.

In some embodiments, the load module 1203 may include an LED light string. As one example, the bulbs on the LED string can be connected in parallel, and as another example, the bulbs on the LED string can be connected in series. In addition, the bulb can be a direct-injection type or a patch-type LED light.

In some embodiments, the current setting circuit 1204 may include one or more resistors connected in series, and the current setting circuit may be used to set a current flowing through the load module.

Through the above technical solution provided by this creative embodiment, an inductive magnetic core device is unnecessary, the driving circuit is small in size, and it conforms to electromagnetic interference (Electromagnetic Interference (EMI) standard, and to a certain extent, achieves technical effects such as fewer system components, reduced costs, and meeting user actual application requirements.

The following describes the LED driving circuit provided by another embodiment of the present invention in detail through a specific example. This example is merely exemplary, and is not intended to limit the present invention. The details are as follows: As an example, refer to FIG. 2 and FIG. 2. A schematic structural diagram of an LED driving circuit according to another embodiment of the present invention is shown.

Specifically, as shown in FIG. 2, the LED driving circuit includes a rectifier circuit 110 and a constant current control circuit 120 that are electrically connected.

In this embodiment, the rectifier circuit 110 may be a bridge rectifier circuit. The rectifier circuit is configured to convert AC power to DC power. For example, the rectifier circuit 110 may include a fuse resistor F1 and a plurality of rectifier diodes, such as a rectifier diode. Volumes D1, D2, D3, D4.

As an example, the input terminal of the rectifier circuit 110 is connected to AC power. The first input terminal of the rectifier circuit 110 can be connected to one end of the fuse resistor F1, and the other end of the fuse resistor F1 can be connected to the anode of the rectifier diode D1 and the rectifier diode D1. The anode of the rectifier diode D2 can be connected to the anode of the rectifier diode D2, the anode of the rectifier diode D2 can be connected to the anode of the rectifier diode D4 and the second input terminal of the rectifier circuit 110, and the anode of the rectifier diode D4 can be connected to The anode of the rectifying diode D3, and the anode of the rectifying diode D3 may be connected to the anode of the rectifying diode D1.

In addition, the first output terminal of the rectifier circuit 110 may be connected to the negative electrode of the rectifier diode D1 and the negative electrode of the rectifier diode D2, and the second output terminal of the rectifier circuit 110 may be connected to the positive electrode and the rectifier diode D3 of the rectifier diode D3. The anode and reference ground of the polar body D4.

It should be noted that, in other embodiments, the rectifier circuit may also be a full-wave rectifier circuit, a half-wave rectifier circuit, and the like, and there is no limitation on this creation.

In this embodiment, the constant current control circuit 120 includes a control chip U1, a voltage dividing circuit, a load module, an output capacitor C1, a current limiting module, an output capacitor discharge cutoff module, a dummy load module, a current setting circuit, Loop compensation module.

As an example, the control chip U1 includes, in addition to the pins described above, a high-voltage power input pin HV, a high-voltage sustain current input pin HVB, a third-stage temperature return point setting pin TH, and a closed-loop loop compensation. Pin COMP, chip reference ground pin GND, etc.

The high-voltage power supply input pin can be used to supply power to the control chip U1, for example, to supply power to one or more sub-modules in the control chip, such as an output current sampling sub-module, a sustain current control sub-module, and a constant current regulator. Modules, input voltage sensing submodules, logic submodules, and temperature selection submodules.

In addition, the chip reference ground pin GND is usually connected to the thermal pad of the chip.

In addition, the high-voltage sustaining current input pin can be used to provide a sustaining current required when the dimmer performs dimming. Among them, a dimmer is an electrical device that changes the luminous flux of a light source in a lighting device and adjusts the level of illuminance, and its purpose is to adjust different brightness of the light.

In addition, the three-speed temperature return point setting foot can be left floating, can be connected to the reference ground, and can be connected to the reference ground through one or more resistors connected in series. And, the first-stage temperature return point is grounded, the second-stage temperature return point is suspended, and the third-stage temperature return point is connected to a certain resistance value.

As an example, the voltage dividing circuit may include resistors R1 and R2. However, it should be noted that in other embodiments, the voltage dividing circuit may include N voltage dividing resistors connected in series, and N is an integer greater than 2. In yet another embodiment, a sliding varistor may be used instead of the resistors R1 and R2. There are no restrictions on this creation.

As an example, the load module may include LED light strings, such as a plurality of LEDs connected in series.

As an example, the constant current control circuit 120 further includes a current limiting module, which may include one or more resistors connected in series. For example, in the embodiment shown in FIG. 2, only one resistor R3 is shown, which is not intended to limit the present invention.

As an example, the constant current control circuit 120 further includes an output capacitor discharge cutoff module, which may include one or more diodes connected in series. For example, in Figure 2 In the illustrated embodiment, only one diode D5 is shown. In other embodiments, diode D5 may not be present.

As an example, the constant current control circuit 120 further includes a dummy load module, which may include one or more resistors connected in series. For example, in the embodiment shown in FIG. 2, only one resistor R5 is shown. There are no restrictions on this creation.

As an example, the constant current control circuit 120 further includes a current setting circuit, which may include one or more resistors connected in series. For example, in the embodiment shown in FIG. 2, only one resistor R4 is shown.

As an example, the constant current control circuit 120 further includes a loop compensation module, which may include one or more capacitors connected in series. For example, in the embodiment shown in FIG. 2, only one capacitor C2 is shown.

In the embodiment shown in FIG. 2, the first terminal of the resistor R1 (that is, the first input terminal of the voltage dividing circuit) is connected to the first output terminal of the rectifier circuit, and the second terminal of the resistor R1 (that is, the branch terminal) The output terminal of the voltage circuit is connected to the input voltage sensing pin VS. The first terminal of the resistor R2 (that is, the second input terminal of the voltage dividing circuit) is connected to the second output terminal of the rectifier circuit and the second terminal of the resistor R2. The terminal (ie, the output terminal of the voltage dividing circuit) is connected to the second terminal of the resistor R1 and the input voltage sensing pin VS.

As an example, the first terminal of the current limiting resistor R3 may be connected to the first terminal of the resistor R1, and the second terminal of the current limiting resistor R3 may be connected to the high-voltage sustaining current input pin HVB.

As an example, the anode of the diode D5 may be connected to the first end of the current limiting resistor R3, and the anode of the diode D5 is connected to the high-voltage power supply input pin HV.

As an example, the anode of the LED string can be connected to the anode of the diode D5 and the high-voltage power supply input pin HV, and the anode of the LED string can be connected to the drain pin Drain. Among them, the diode D5 can be used to prevent the output capacitor C1 from being discharged through the HVB.

As an example, the dummy load resistor R5 may be connected in parallel at both ends of the LED string. Specifically, the first end of the dummy load resistor R5 may be connected to the positive pole of the LED light string, and the second end of the dummy load resistor R5 may be connected to the negative pole of the LED light string.

As an example, the output capacitor C1 may be connected in parallel across the dummy load resistor R5. That is, specifically, the first terminal of the output capacitor C1 may be connected to the positive pole of the LED light string, and the second terminal of the output capacitor C1 may be connected to the negative pole of the LED light string.

In addition, when in the charging mode, the LED string can be connected in parallel with the output capacitor C1. When in the discharge mode, the output capacitor C1 can discharge the LED.

As an example, the first terminal of the resistor R4 may be connected to the output current setting pin CS, and the second terminal of the resistor R4 may be connected to the first terminal of the resistor R2 and the second output terminal of the rectifier circuit. Among them, R4 can be used to set the current of the LED string.

As an example, the first terminal of the capacitor C2 can be connected to the closed-loop loop compensation pin COMP, and the second terminal of the capacitor C2 can be connected to the first terminal of the resistor R2, the second output terminal of the rectifier circuit, and the second terminal of the resistor R4. . Among them, the capacitor C2 can be used for internal loop compensation.

As an example, one or more resistors (not shown in the second figure) may be connected in series between the third-stage temperature return point setting pin TH and the second end of the resistor R4. In other embodiments, the resistor R4 may not be provided.

Referring to FIG. 3, FIG. 3 is a schematic structural diagram of a control chip U1 according to an embodiment of the present invention.

As an example, the control chip U1 may include an output current sampling sub-module CS Sense, a constant current regulation sub-module CC Regulator, a control transistor, an input voltage sensing sub-module VS Sense, and a logic sub-module Logic.

The input terminal of the output current sampling sub-module can be connected to the output current setting pin CS, and the first input terminal of the constant current regulation sub-module can be connected to the first output terminal of the output current sampling sub-module to control the transistor. The gate can be connected to the output of the constant current regulation sub-module, the drain of the control transistor can be connected to the drain pin Drain, the source of the control transistor can be connected to the output current setting pin CS, and the input voltage sensing sub-module The input of the group can be connected to the input voltage sensing pin VS, the first input of the logic sub-module can be connected to the output of the input voltage-sensing sub-module, and the first output of the logic sub-module can be connected to the constant The second input terminal of the current regulation sub-module.

Among them, the output current sampling sub-module can sample the average voltage on the CS pin, and the sampled signal can be transmitted to the constant current regulation sub-module after a series of processing, so that the constant current regulation sub-module generates a control signal. By using the control signal to control the gate voltage value of the power transistor, the output current value can be adjusted so that the average value of the output current meets the design value.

In addition, the rectified DC voltage can be input to a voltage-dividing circuit (for example, resistors R1 and R2) to divide the voltage to obtain a voltage-divided signal value, and the voltage-divided signal value can be transmitted to the input voltage sensor through the VS pin. The module, after processing by the input voltage sensing sub-module, generates a digital signal carrying VS information, and transmits the digital signal to the logic sub-module, which is used to judge entering the leading-edge dimming mode, the delayed dimming mode, or Non-dimming mode.

As an example, the average voltage on the CS pin is sampled by the output current sampling sub-module to obtain a sampling signal, and the sampling signal is subjected to a series of processing and then passed to the constant-current adjustment sub-module to generate a control signal. The signal controls the gate voltage value of the power transistor to adjust the output current value so that the average value of the output current meets the design value.

As an example, the rectifier circuit receives the AC voltage, converts it to a DC voltage, and inputs the DC voltage into the voltage dividing circuit. For example, the DC voltage is divided by the resistors R1 and R2 to obtain a divided signal value, which is transmitted to the input through the VS pin The voltage sensing sub-module, after processing by the input voltage sensing sub-module, generates a digital signal carrying VS information, and passes the digital signal to the logic sub-module, which is used to judge entering the leading edge dimming mode and the trailing edge dimming mode. Light mode or non-dimming mode.

The following specifically introduces the specific structure of the control chip U1 provided by another embodiment of the present invention through a specific example. For example, referring to FIG. 4, FIG. 4 shows a schematic structural diagram of the control chip U1 provided by another embodiment of the present invention.

In some embodiments, in addition to the various parts included in the control chip U1 as described in the foregoing embodiments, the control chip U1 may further include a high-voltage power input pin HV and a low-dropout linear voltage regulator sub-module (Low Dropout Regulator). , LDO), where the input terminal of the low-dropout linear regulator sub-module is connected to the high-voltage power supply input pin HV, and the low-dropout linear regulator The sub-module is used to supply power to the control chip U1.

Among them, referring to FIG. 2 and FIG. 4, AC power is converted into DC power through a rectifier circuit, and the high voltage obtained after rectification is input to the high-voltage power input pin HV, and then the voltage is regulated by the LDO sub-module to provide the internal voltage of the control chip U1. One or more sub-modules provide power.

In some embodiments, in addition to the various parts included in the control chip U1 as described in the previous embodiment, the control chip U1 may further include a temperature return point setting pin TH and a temperature selection sub-module, and a temperature selection sub-module. The input terminal of is connected to the temperature return point setting pin TH, and the output terminal of the temperature selection sub-module is connected to the second input terminal of the logic sub-module.

Among them, a current flows from the TH pin, and this current generates a different voltage value on the resistor (not shown in the second figure) connected to the TH pin. This voltage value is input to the temperature selection sub-module and passes through the temperature selection sub-module. The judgment of the third gear temperature return point signal is generated to the logic sub-module to realize the control of the third gear temperature return point temperature set by the chip U1.

In some embodiments, in addition to the various parts included in the control chip U1 as described in the previous embodiment, the control chip U1 may further include a high-voltage sustaining current input pin HVB and a sustaining current control sub-module, and the sustaining current control sub-module The output of the module can be connected to the high-voltage sustaining current input pin HVB. The first input of the sustaining current control sub-module can be connected to the second output of the output current sampling sub-module and the second of the sustaining current control sub-module. The input terminal can be connected to the second output terminal of the logic sub-module.

Among them, referring to FIG. 2 and FIG. 4, the high voltage obtained after rectification passes through one or more resistors connected in series (for example, resistor R3) and enters the sustain current control sub-module through the high-voltage sustain current input pin HVB, thereby generating a leading edge. Different sustain current control needed for dimmer and trailing edge dimmer.

In some embodiments, in addition to the various parts included in the control chip U1 as described in the previous embodiment, the control chip U1 may further include a closed loop compensation pin COMP, and the closed loop compensation pin may be connected to a constant current regulator. The third input terminal of the sub-module.

Among them, referring to Figure 2 and Figure 4, the closed-loop loop compensation pin can be used to compensate the loop of the constant current regulation sub-module to ensure linear constant current (Line CC) and load constant current. (Load CC) is in closed loop control.

Each part of this specification is described in a progressive manner, and the same or similar parts between the various embodiments may be referred to each other. Each embodiment focuses on the differences from other embodiments.

The above is only a specific implementation of this creation, but the scope of protection of this creation is not limited to this. Any person skilled in the technical field can easily think of various equivalent modifications within the technical scope disclosed by this creation. Or replacement, these modifications or replacements should be covered by the protection of this creation. Therefore, the protection scope of this creation shall be subject to the protection scope of the patent application scope.

Claims (14)

An LED driving circuit includes: a rectifier circuit for outputting direct current; a constant current control circuit including: a control chip including an output current setting pin, a drain pin, and an input voltage sensing pin; a voltage dividing circuit, the voltage dividing The circuit is connected between the output of the rectifier circuit and the reference ground, the output end of the voltage dividing circuit is connected to the input voltage sensing pin, and a load module is connected to the rectifier circuit. Between the output and the drain pin; an output capacitor, the output capacitor is connected in parallel at both ends of the load module; a current setting circuit, the current setting circuit is connected between the output current setting pin and the reference ground Between; it is characterized in that the input voltage sensing pin is used for judging to enter a leading edge dimming mode, a trailing edge dimming mode or a non-dimming mode based on the output of the voltage dividing circuit. The LED driving circuit according to item 1 of the scope of patent application, wherein the current setting circuit includes one or more resistors connected in series. The LED driving circuit according to item 1 of the patent application scope, wherein the voltage dividing circuit includes a first resistor and a second resistor connected in series, and an output terminal of the voltage dividing circuit is from the first The common terminal of the resistor and the second resistor is derived. The LED driving circuit according to item 1 of the scope of patent application, wherein the control chip further includes a high-voltage sustaining current input pin, and the constant current control circuit further includes: a current limiting circuit, the current limiting circuit is connected Between the output of the rectifier circuit and the high-voltage sustaining current input pin. The LED driving circuit according to item 1 of the scope of the patent application, wherein the constant current control circuit further comprises: an output capacitor discharge cut-off module, and the output capacitor discharge cut-off module is connected in series to the rectifier circuit. Between the output and the load module. The LED driving circuit according to item 1 of the patent application scope, wherein the control chip further includes a high-voltage power input pin, and the high-voltage power input pin is connected to the output capacitor discharge cut-off module and the load module. The public side of the group. The LED driving circuit according to item 1 of the scope of the patent application, wherein the constant current control circuit further comprises: a dummy load module, and the dummy load module is connected in parallel at both ends of the load module. The LED driving circuit according to item 1 of the patent application scope, wherein the control chip further includes a closed-loop loop compensation pin, and the constant current control circuit further includes: a loop compensation circuit, the loop compensation A circuit is connected between the closed-loop loop compensation pin and a reference ground. The LED driving circuit according to item 1 of the scope of patent application, wherein the control chip further includes a temperature return point setting pin, and the temperature return point setting pin is connected to the resistor through one or more resistors connected in series. The reference ground, or the temperature return point setting foot is suspended, or the temperature return point setting foot is connected to the reference ground. A control chip used in the LED driving circuit according to any one of items 1 to 9 of the patent application scope, wherein the control chip includes: an output current sampling sub-module, and the output current sampling sub-module The input end of the module is connected to the output current setting pin; the constant current adjustment sub-module, the first input end of the constant current adjustment sub-module is connected to the first output end of the output current sampling sub-module; A control transistor, a gate of the control transistor is connected to an output terminal of the constant current regulating sub-module, a drain of the control transistor is connected to the drain pin, and a source of the control transistor Connected to the output current setting pin; an input voltage sensing sub-module, and an input terminal of the input voltage sensing sub-module is connected to the input voltage sensing pin; a logic sub-module, the logic sub-module The first input terminal of the is connected to the output terminal of the input voltage sensing sub-module, and the first output terminal of the logic sub-module is connected to the second input terminal of the constant current regulation sub-module. The control chip according to item 10 of the scope of patent application, further comprising: a high-voltage power supply input pin; a low-dropout linear voltage regulator sub-module, the input end of the low-dropout linear voltage regulator sub-module is connected to the high-voltage power supply input Pin, the low-dropout linear voltage regulator sub-module is used to power the control chip. The control chip according to item 10 of the scope of patent application, further comprising: a temperature return point setting pin; a temperature selection sub-module, the input end of the temperature selection sub-module is connected to the temperature return point setting leg, the An output terminal of the temperature selection sub-module is connected to a second input terminal of the logic sub-module. The control chip according to item 10 of the scope of patent application, further comprising: a high-voltage sustaining current input pin; a sustaining current control sub-module whose output end is connected to the high-voltage sustaining current input pin, A first input terminal of the sustain current control sub-module is connected to a second output terminal of the output current sampling sub-module, and a second input terminal of the sustain current control sub-module is connected to the logic sub-module. The second output. The control chip according to item 10 of the scope of patent application, further comprising: a closed-loop loop compensation pin, the closed-loop loop compensation pin being connected to the third input terminal of the constant current regulating sub-module.