CN212435993U

CN212435993U - LED drive circuit

Info

Publication number: CN212435993U
Application number: CN202020911799.0U
Authority: CN
Inventors: 凌学友; 周俊
Original assignee: On Bright Electronics Shanghai Co Ltd
Current assignee: On Bright Electronics Shanghai Co Ltd
Priority date: 2020-05-26
Filing date: 2020-05-26
Publication date: 2021-01-29
Anticipated expiration: 2030-05-26
Also published as: TWM606353U

Abstract

The utility model provides a LED drive circuit, including AC input rectification filter circuit, detection control circuit, power conversion transmission transformer and output rectification filter circuit. The detection control circuit includes: a control chip; the first end and the second end of the dimming signal acquisition circuit are respectively connected to the second output end and the first output end of the alternating current input rectification filter circuit, and the third end of the dimming signal acquisition circuit is connected to the control chip; the first end of the starting circuit is connected to the third output end of the alternating current input rectifying and filtering circuit and the first end of the power conversion transmission transformer, the second end of the starting circuit is grounded, and the third end of the starting circuit is connected to the control chip; the drain electrode of the switching tube is connected to the second end of the power conversion transmission transformer, the gate electrode of the switching tube is connected to the control chip, and the source electrode of the switching tube is connected to the control chip; and the first end of the output information sampling circuit is connected to the second end of the power conversion transmission transformer, and the second end of the output information sampling circuit is connected to the control chip.

Description

LED drive circuit

Technical Field

The utility model relates to a circuit field, more specifically relates to a LED drive circuit.

Background

A Light Emitting Diode (LED) is a semiconductor device that converts electrical energy into Light energy. The core of the LED is a PN junction, and the luminous flux of the LED is proportional to the current flowing through the LED. Compared with conventional lighting fixtures such as incandescent lamps, LEDs have the advantages of high electro-optic conversion, low operating voltage, small size, long life, and the like.

However, the current thyristor dimming LED driving circuit has the following problems: the silicon controlled dimmer has poor compatibility, a transformer structure is complex, and isolation application and non-isolation application cannot be compatible. Therefore, a new type of thyristor dimming LED driving circuit is needed.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present invention provides a novel LED driving circuit.

According to the utility model discloses LED drive circuit, including alternating current input rectifier and filter circuit, detection control circuit, power conversion transmission transformer and output rectifier and filter circuit, wherein, it includes to detect control circuit: the control chip comprises a dimming information detection pin, an external switch tube gate electrode driving pin, an internal switch tube drain electrode pin and an output information sampling pin; the first end and the second end of the dimming signal acquisition circuit are respectively connected to the second output end and the first output end of the alternating current input rectifying and filtering circuit, the third end of the dimming signal acquisition circuit is connected to the dimming information detection pin, and the fourth end of the dimming signal acquisition circuit is grounded; the first end of the starting circuit is connected to the third output end of the alternating current input rectifying and filtering circuit and the first end of the power conversion transmission transformer, the second end of the starting circuit is grounded, and the third end of the starting circuit is connected to the gate pole driving pin of the external switching tube; the drain electrode of the switching tube is connected to the second end of the power conversion transmission transformer, the gate electrode of the switching tube is connected to the gate electrode driving pin of the external switching tube, and the source electrode of the switching tube is connected to the drain electrode pin of the internal switching tube; and the first end of the output information sampling circuit is connected to the second end of the power conversion transmission transformer, the second end of the output information sampling circuit is connected to the output information sampling pin, and the third end of the output information sampling circuit is grounded.

For traditional silicon controlled rectifier LED drive circuit of adjusting luminance, according to the utility model discloses LED drive circuit has following advantage: the method has the advantages of realizing high silicon controlled rectifier dimmer compatibility (being compatible with various silicon controlled rectifiers), realizing transformer structure refinement (transformer non-isolation single-winding or isolation double-winding application), being compatible with non-isolation application and isolation application, and being compatible with silicon controlled rectifier dimming (leading edge/trailing edge dimming mode) application and non-dimming application at the same time.

Drawings

The invention may be better understood from the following description of particular embodiments thereof taken in conjunction with the accompanying drawings, in which:

fig. 1 shows a schematic structural diagram of a non-isolated application of a LED driver circuit according to an embodiment of the present invention;

fig. 2 shows a schematic structural diagram of an isolated application of an LED driver circuit according to an embodiment of the present invention;

fig. 3 shows a schematic diagram of an operating state waveform of an LED driving circuit according to an embodiment of the present invention;

fig. 4 shows a waveform schematic diagram of a leading edge dimming mode of operation of an LED driving circuit according to an embodiment of the present invention; and

fig. 5 shows a waveform diagram of a trailing edge dimming operation mode of an LED driving circuit according to an embodiment of the present invention.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below with reference to the accompanying drawings. Example implementations can be embodied in many forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example implementations to those skilled in the art. In the drawings, the size of regions and components may be exaggerated for clarity. Further, in the drawings, the same reference numerals denote the same or similar structures, and thus detailed descriptions thereof will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the primary technical ideas of the invention.

Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Fig. 1 shows a schematic structural diagram of a non-isolated application of an LED driver circuit according to an embodiment of the present invention. As shown in fig. 1, the LED driving circuit 100 may include an Alternating Current (AC) input rectifying and filtering circuit 110, a detection control circuit 120, a power conversion transmission transformer 130, and an output rectifying and filtering circuit 140.

The ac input rectifying-smoothing circuit 110 in the LED driving circuit 100 shown in fig. 1 is first described in detail below. Specifically, the ac input rectifying and filtering circuit 110 may include a fuse, a thyristor dimmer, a rectifying diode, and a filter capacitor for rectifying and filtering the input ac power. As an example, as shown in fig. 1, the ac input rectifying and smoothing circuit 110 may include a fuse F1, a thyristor dimmer DIM1, a first rectifying diode D1, a second rectifying diode D2, a third rectifying diode D3, a fourth rectifying diode D4, and a smoothing capacitor C1. The first and third rectifying diodes D1 and D3 may be connected in series to form a first series circuit, the second and fourth rectifying diodes D2 and D4 may be connected in series to form a second series circuit, and the first series circuit, the second series circuit, and the filter capacitor C1 may be connected in parallel to each other.

A first input terminal of the AC input rectifying-filtering circuit 110 may be connected to the positive pole of the AC power source AC and may be connected to a first terminal of the triac dimmer DIM1 via a fuse F1, a second terminal of the triac dimmer DIM1 may be connected to a first output terminal of the AC input rectifying and smoothing circuit 110 and a common terminal of the first rectifying diode D1 and the third rectifying diode D3, a second input terminal of the AC input rectifying and smoothing circuit 110 may be connected to a negative terminal of the AC power source AC, a second output terminal of the AC input rectifying and smoothing circuit 110, and a common terminal of the second rectifying diode D2 and the fourth rectifying diode D4, a third output terminal of the AC input rectifying and smoothing circuit 110 may be connected to negative terminals of the first rectifying diode D1 and the second rectifying diode D2 and a first terminal of the filter capacitor C1, and positive terminals of the third rectifying diode D3 and the fourth rectifying diode D4 and a second terminal of the filter capacitor C1 may be grounded.

It should be understood that although fig. 1 shows that the ac input rectifying and smoothing circuit 110 in the LED driving circuit 100 may include four rectifying diodes (D1, D2, D3, and D4), in other embodiments, the ac input rectifying and smoothing circuit 110 may include any suitable number of rectifying diodes (e.g., two rectifying diodes). In addition, the fuse F1 of the ac input rectifying and filtering circuit 110 in the LED driving circuit 100 may be replaced by a fuse resistor, a winding resistor, or an inductor.

The detection control circuit 120 in the LED driving circuit 100 shown in fig. 1 is described in detail below. Specifically, the detection control circuit 120 may include a control chip U1, a dimming signal collection circuit 1201, a start circuit 1202, a switching tube Q1, and an output information sampling circuit 1203.

The control chip U1 may include a DIM information detection pin DIM, an external switch GATE driver pin GATE, an internal switch drain pin SW, and an output information sampling pin FB.

Specifically, the dimming information detection pin DIM can be used to detect dimming information provided by the triac dimmer 1 in the ac input rectifier filter circuit 110 for dimming. For example, the dimming information detection pin DIM may be connected to the dimming signal collection circuit 1201 to detect the dimming information provided by the thyristor dimmer DIM1 in the ac input rectifying and filtering circuit 110 via the dimming signal collection circuit 1201. The external switch GATE driver GATE may be used to drive the GATE of the switch outside of the control chip U1. For example, the external switch tube GATE driving pin GATE may be connected to the start circuit 1202 and the GATE of the switch tube Q1 outside the control chip U1 to control the on and off of the switch tube Q1. The internal switch drain leg SW may be the drain of the switch inside the control chip U1. The output information sampling pin FB may be used to sample the output information. For example, the output information sampling pin FB may be connected to the output information sampling circuit 1203.

The first end and the second end of the dimming signal collection circuit 1201 may be respectively connected to the second output end and the first output end of the ac input rectification filter circuit 110, the third end of the dimming signal collection circuit 1201 may be connected to the dimming information detection pin DIM of the control chip U1, and the fourth end of the dimming signal collection circuit 1201 may be grounded.

In particular, the dimming signal acquisition circuit 1201 may include a resistor. As an example, the dimming signal collection circuit 1201 may include a resistor R1, a resistor R2, and a resistor R3, wherein a first end of the resistor R1 may be connected to the first end of the dimming signal collection circuit 1201, a first end of the resistor R2 may be connected to the second end of the dimming signal collection circuit 1201, a second end of the resistor R1 may be connected to the second end of the resistor R2, the first end of the resistor R3, and the third end of the dimming signal collection circuit 1201, and a second end of the resistor R3 may be connected to the fourth end of the dimming signal collection circuit 1201.

The first terminal of the start-up circuit 1202 may be connected to the third output terminal of the ac input rectifying-smoothing circuit 110 and the first terminal of the power conversion transmission transformer 130, the second terminal of the start-up circuit 1202 may be grounded, and the third terminal of the start-up circuit 1202 may be connected to the GATE driver pin GATE of the external switching tube of the control chip U1.

Specifically, the start-up circuit 1202 may include a resistor and a capacitor. As an example, the start-up circuit 1202 may include a resistor R4 and a capacitor C4, wherein a first terminal of the resistor R4 may be connected to the first terminal of the start-up circuit 1202, a second terminal of the resistor R4 may be connected to the first terminal of the capacitor C4 and the third terminal of the start-up circuit 1202, and a second terminal of the capacitor C4 may be connected to the second terminal of the start-up circuit 1202.

The drain of the switch Q1 may be connected to the second terminal of the power conversion transmission transformer 130, the GATE of the switch Q1 may be connected to the external switch GATE driver GATE of the control chip U1, and the source of the switch Q1 may be connected to the internal switch drain SW of the control chip U1. As an example, the switching tube Q1 may be a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET).

A first terminal of the output information sampling circuit 1203 may be connected to the second terminal of the power conversion transmission transformer 130, a second terminal of the output information sampling circuit 1203 may be connected to the output information sampling pin FB of the control chip U1, and a third terminal of the output information sampling circuit 1203 may be grounded.

Specifically, the output information sampling circuit 1203 may include a resistor. As an example, the output information sampling circuit 1203 may include a resistor R5 and a resistor R6, wherein a first terminal of the resistor R5 may be connected to a first terminal of the output information sampling circuit 1203, a second terminal of the resistor R5 may be connected to a second terminal of the output information sampling circuit 1203 and a first terminal of the resistor R6, and a second terminal of the resistor R6 may be connected to a third terminal of the output information sampling circuit 1203.

Further, as an example, the control chip U1 may further include an inner loop compensation pin COMP, a chip power supply pin VDD, a ground pin GND, and an output current detection pin CS. In particular, the inner loop compensation pin COMP may be used for loop compensation. For example, the inner loop compensation pin COMP may be grounded via the loop compensation capacitor C2. The chip power pin VDD may be used to power the control chip U1. For example, the chip power pin VDD may be grounded via a capacitor C3. The ground pin GND may be used as a reference ground of the control chip U1. The output current setting pin CS may be used to set the output current. For example, the output current setting pin CS may be via a resistor R_CSThe control chip U1 can adjust the resistance R through grounding_CSThe output current value is set according to the resistance value.

The power conversion transmission transformer 130 in the LED driving circuit 100 shown in fig. 1 is described in detail below. Specifically, the power conversion transmission transformer 130 may include an inductance. As an example, power conversion transmission transformer 130 may include an inductance L1. A first terminal of the inductor L1 may serve as a first terminal of the power conversion transmission transformer 130, and is connected to the third output terminal of the ac input rectifying and filtering circuit 110, the first terminal of the start-up circuit 1202 in the detection control circuit 120, and the first terminal of the output rectifying and filtering circuit 140. A second terminal of the inductor L1 may serve as a second terminal of the power conversion transmission transformer 130, and is connected to the drain of the switching tube Q1 in the detection control circuit 120, a first terminal of the output information sampling circuit 140 in the detection control circuit 120, and a second terminal of the output rectifying and filtering circuit 140.

The output rectifying and filtering circuit 140 in the LED driving circuit 100 shown in fig. 1 is described in detail below. Specifically, the output rectifying and filtering circuit 140 may include an output rectifying diode and a filter capacitor. As an example, the output rectifying and filtering circuit 140 may include an output rectifying diode D5 and a filter capacitor C5. The anode of the output rectifying diode D5 may serve as the second terminal of the output rectifying filter circuit 140, and is connected to the second terminal of the power conversion transmission transformer 130, i.e., the second terminal of the inductor L1. The cathode of the output rectifying diode D5 may be connected to the anode of the filter capacitor C5. The cathode of the filter capacitor C5 may be connected to the first terminal of the power conversion and transmission transformer 130, i.e., the first terminal of the inductor L1, as the first terminal of the output rectifying and filtering circuit 140.

Further, an LED load circuit may be connected across the filter capacitor C5. For example, a first terminal of the LED load circuit may be connected to the anode of the filter capacitor C5, and a second terminal of the LED load circuit may be connected to the cathode of the filter capacitor C5.

The LED load circuit may be a LED light string including one or more LEDs. The LED light string may include any suitable number of LED light beads. In the embodiment shown in FIG. 1, the LED lamp beads included in the LED lamp string are shown connected together in series, but in other embodiments, the LED lamp beads may be connected in parallel. In addition, LED lamp pearl can be straight following formula or side income formula LED lamp pearl, the utility model discloses do not restrict this. In the LED driving circuit shown in fig. 1, a first end of the LED load circuit may be connected to an anode of the LED string, and a second end of the LED load circuit may be connected to a cathode of the LED string.

Fig. 2 shows a schematic structural diagram of an isolated application of an LED driving circuit according to an embodiment of the present invention. As shown in fig. 2, the LED driving circuit 200 may include an Alternating Current (AC) input rectifying and filtering circuit 210, a detection control circuit 220, a power conversion transmission transformer 230, and an output rectifying and filtering circuit 240.

The ac input rectifying-smoothing circuit 210 in the LED driving circuit 200 shown in fig. 2 is first described in detail below. Specifically, the ac input rectifying and filtering circuit 210 may include a fuse, a thyristor dimmer, a rectifying diode, and a filter capacitor for rectifying and filtering the input ac power. As an example, as shown in fig. 2, the ac input rectifying and filtering circuit 210 may include a fuse F1, a thyristor dimmer DIM1, a first rectifying diode D1, a second rectifying diode D2, a third rectifying diode D3, a fourth rectifying diode D4, and a filter capacitor C1. The first and third rectifying diodes D1 and D3 may be connected in series to form a first series circuit, the second and fourth rectifying diodes D2 and D4 may be connected in series to form a second series circuit, and the first series circuit, the second series circuit, and the filter capacitor C1 may be connected in parallel to each other.

A first input terminal of the AC input rectifying-filtering circuit 210 may be connected to the positive pole of the AC power source AC and may be connected to a first terminal of the triac dimmer DIM1 via a fuse F1, a second terminal of the triac dimmer DIM1 may be connected to a first output terminal of the AC input rectifying and smoothing circuit 210 and a common terminal of the first rectifying diode D1 and the third rectifying diode D3, a second input terminal of the AC input rectifying and smoothing circuit 210 may be connected to a negative terminal of the AC power source AC, a second output terminal of the AC input rectifying and smoothing circuit 210, and a common terminal of the second rectifying diode D2 and the fourth rectifying diode D4, a third output terminal of the AC input rectifying and smoothing circuit 210 may be connected to negative terminals of the first rectifying diode D1 and the second rectifying diode D2 and a first terminal of the filter capacitor C1, and positive terminals of the third rectifying diode D3 and the fourth rectifying diode D4 and a second terminal of the filter capacitor C1 may be grounded.

It should be appreciated that although fig. 2 illustrates that the ac input rectifying and smoothing circuit 210 in the LED driving circuit 200 may include four rectifying diodes (D1, D2, D3, and D4), in other embodiments, the ac input rectifying and smoothing circuit 210 may include any suitable number of rectifying diodes (e.g., two rectifying diodes). In addition, the fuse F1 of the ac input rectifying and filtering circuit 210 in the LED driving circuit 200 may be replaced by a fuse resistor, a winding resistor, or an inductor.

The detection control circuit 220 in the LED driving circuit 200 shown in fig. 2 will be described in detail. Specifically, the detection control circuit 220 may include a control chip U1, a dimming signal acquisition circuit 2201, a starting circuit 2202, a switching tube Q1, and an output information sampling circuit 2203.

In particular, the dimming information detection pin DIM can be used to detect dimming information provided by the triac dimmer 1 in the ac input rectifier filter circuit 210 for dimming. For example, the dimming information detection pin DIM may be connected to the dimming signal acquisition circuit 2201 to detect the dimming information provided by the thyristor dimmer DIM1 in the ac input rectifying and filtering circuit 210 via the dimming signal acquisition circuit 2201. The external switch GATE driver GATE may be used to drive the GATE of the switch outside of the control chip U1. For example, the external switch tube GATE driving pin GATE may be connected to the start circuit 2202 and the GATE of the switch tube Q1 outside the control chip U1 to control the on and off of the switch tube Q1. The internal switch drain leg SW may be the drain of the switch inside the control chip U1. The output information sampling pin FB may be used to sample the output information. For example, the output information sampling pin FB may be connected to the output information sampling circuit 2203.

The first end and the second end of the dimming signal collection circuit 2201 may be respectively connected to the second output end and the first output end of the ac input rectification filter circuit 210, the third end of the dimming signal collection circuit 2201 may be connected to the dimming information detection pin DIM of the control chip U1, and the fourth end of the dimming signal collection circuit 2201 may be grounded.

Specifically, the dimming signal acquisition circuit 2201 may include a resistor. As an example, the dimming signal acquisition circuit 2201 may include a resistor R1, a resistor R2, and a resistor R3, wherein a first end of the resistor R1 may be connected to the first end of the dimming signal acquisition circuit 2201, a first end of the resistor R2 may be connected to the second end of the dimming signal acquisition circuit 2201, a second end of the resistor R1 may be connected to the second end of the resistor R2, the first end of the resistor R3, and the third end of the dimming signal acquisition circuit 2201, and a second end of the resistor R3 may be connected to the fourth end of the dimming signal acquisition circuit 2201.

A first terminal of the start-up circuit 2202 may be connected to the third output terminal of the ac input rectifying and filtering circuit 210 and the first terminal of the power conversion transmission transformer 230, a second terminal of the start-up circuit 2202 may be grounded, and a third terminal of the start-up circuit 2202 may be connected to the GATE driver pin GATE of the external switching tube of the control chip U1.

Specifically, the startup circuit 2202 may include a resistor and a capacitor. As an example, the start-up circuit 2202 may include a resistor R4 and a capacitor C4, wherein a first terminal of the resistor R4 may be connected to a first terminal of the start-up circuit 2202, a second terminal of the resistor R4 may be connected to a first terminal of the capacitor C4 and a third terminal of the start-up circuit 2202, and a second terminal of the capacitor C4 may be connected to the second terminal of the start-up circuit 2202.

The drain of the switch Q1 may be connected to the second terminal of the power conversion transmission transformer 230, the GATE of the switch Q1 may be connected to the external switch GATE driver GATE of the control chip U1, and the source of the switch Q1 may be connected to the internal switch drain SW of the control chip U1. As an example, the switching tube Q1 may be a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET).

A first terminal of the output information sampling circuit 2203 may be connected to the second terminal of the power conversion transmission transformer 230 and the drain of the switching tube Q1, a second terminal of the output information sampling circuit 2203 may be connected to the output information sampling pin FB of the control chip U1, and a third terminal of the output information sampling circuit 2203 may be grounded.

Specifically, the output information sampling circuit 2203 may include a resistor. As an example, the output information sampling circuit 2203 may include a resistor R5 and a resistor R6, wherein a first terminal of the resistor R5 may be connected to a first terminal of the output information sampling circuit 2203, a second terminal of the resistor R5 may be connected to a second terminal of the output information sampling circuit 2203 and a first terminal of the resistor R6, and a second terminal of the resistor R6 may be connected to a third terminal of the output information sampling circuit 2203.

The power conversion transmission transformer 230 in the LED driving circuit 200 shown in fig. 2 is described in detail below. Specifically, the power conversion transmission transformer 230 may include an absorption circuit 2301 and a transformer T1, wherein the transformer T1 may achieve input-output isolation. For example, the absorption circuit 2301 may include a resistor, a capacitor, and a diode, and the transformer T1 may include a primary winding and a secondary winding. As an example, as shown in fig. 2, the absorption circuit 2301 may include a resistor R7, a capacitor C6, and a diode D6, and the transformer T1 may include a primary winding N_PAnd secondary winding N_S。

The first terminal of the resistor R7 and the first terminal of the capacitor C6 may be used as the first terminal of the power conversion transmission transformer 230, and are connected to the third output terminal of the ac input rectifying-smoothing circuit 210, the first terminal of the starting circuit 2202, and the primary winding N of the transformer T1_PA second terminal of the resistor R7 may be connected to a second terminal of the capacitor C6 and a diodeThe cathode of the transistor D6 and the anode of the diode D6 may be used as the second terminal of the power conversion transmission transformer 230, and are connected to the drain of the switching transistor Q1, the first terminal of the output information sampling circuit 2203, and the primary winding N of the transformer T1_PSecond terminal of transformer T1, secondary winding N_SMay be connected to the output rectifying and filtering circuit 240.

The output rectifying and filtering circuit 240 in the LED driving circuit 200 shown in fig. 2 is described in detail below. Specifically, the output rectifying and filtering circuit 240 may include an output rectifying diode and a filter capacitor. As an example, the output rectifying and filtering circuit 240 may include an output rectifying diode D5 and a filter capacitor C5. The anode of the output rectifying diode D5 may be used as the first terminal of the output rectifying filter circuit 240 and connected to the secondary winding N of the transformer T1_SA cathode of the output rectifying diode D5 may be connected to an anode of the filter capacitor C5, and a cathode of the filter capacitor C5 may be connected to the secondary winding N as a second terminal of the output rectifying and filtering circuit 240_SThe second end of (a).

The LED load circuit may be a LED light string including one or more LEDs. The LED light string may include any suitable number of LED light beads. In the embodiment shown in FIG. 2, the LED lamp beads included in the LED lamp string are shown connected together in series, but in other embodiments, the LED lamp beads may be connected in parallel. In addition, LED lamp pearl can be straight following formula or side income formula LED lamp pearl, the utility model discloses do not restrict this. In the LED driving circuit shown in fig. 2, a first end of the LED load circuit may be connected to an anode of the LED string, and a second end of the LED load circuit may be connected to a cathode of the LED string.

The operating states of the LED driving circuit (isolated application or non-isolated application) according to the embodiment of the present invention as described above with reference to fig. 1 and 2 are divided into a non-dimming operating mode and a dimming operating mode.

Fig. 3 shows a waveform schematic diagram of a non-dimming operation mode of an LED driving circuit according to an embodiment of the present invention. The following first describes the operation of the non-dimming operation mode of the LED driving circuit according to an embodiment of the present invention, which can be divided into four stages, and the four stages are respectively described in detail below.

The first stage is as follows: an AC input voltage of the AC power source AC is rectified and filtered by the AC input rectifying and filtering circuit to become a dc voltage (e.g., a sine wave) VIN. As the dc voltage VIN gradually increases, the capacitor C4 can be charged via the following loop: the filter capacitor C1 → the resistor R4 → the capacitor C4 → the grounding pin GND of the control chip U1 → the filter capacitor C1. As the capacitor C4 is gradually charged, the switch Q1 may gradually conduct. With the switching tube Q1 turned on gradually, the dc voltage VIN can charge the external capacitor C3 of the chip power pin VDD of the control chip U1 through the following loops: filter capacitor C1 → inductor L1/primary winding N of transformer T1_P→ the drain of the switching tube Q1 → the source of the switching tube Q1 → the internal switching tube drain pin SW of the control chip U1 → the chip supply pin VDD of the control chip U1 → the capacitor C3 → the ground pin GND of the control chip U1 → the capacitor C1. For example, when the voltage of the external capacitor C3 of the chip power pin VDD of the control chip U1 is higher than the turn-on voltage of the control chip U1, the control chip U1 may start to operate. Then, the control chip U1 may detect the dimming information (e.g., including a voltage value and a time value) through the dimming signal collection circuit connected to the dimming information detection pin DIM, and then determine whether the LED driving circuit turns on the triac dimmer DIM1 based on the detected dimming information, and accordingly enter the dimming operation mode or the non-dimming operation mode (in this example, enter the non-dimming operation mode) according to the determination result. For example, the dimming signal acquisition circuit may be a sampling resistor voltage division circuit, and the voltage value in the dimming information may be calculated based on the following formula: (R3 × VAC1)/(R3+ R2) and (R3 × VAC2)/(R3+ R1), where VAC1 is the voltage at the second terminal of the thyristor dimmer DIM1 and VAC2 is the voltage at the second input terminal of the ac input rectifying and smoothing circuit, as shown in fig. 1 and 2.

And a second stage: controlThe chip U1 can control the conduction of the switch (e.g., MOSFET) therein, so that the dc voltage VIN can store energy for the inductor L1/transformer T1 via the following loop: filter capacitor C1 → inductor L1/primary winding N of transformer T1_P→ the drain of the transistor Q1 → the source of the transistor Q1 → the drain SW of the internal transistor of the control chip U1 → the output current setting CS of the control chip U1 → the resistor R_CS→ the ground pin GND of the control chip U1 → the filter capacitor C1. The control chip U1 can set the external resistor R of the pin CS by setting the output current_CSTo control the energy stored in inductor L1/transformer T1. For example, when the control chip U1 detects the resistor R_CSWhen the voltage at the two ends reaches the voltage threshold set by the control chip U1, the control chip U1 may control the switching tube (e.g., MOSFET) therein to turn off, so as to open the loop, and stop storing energy for the inductor L1/transformer T1. Furthermore, by varying the resistance R_CSThe magnitude of the output current can be adjusted.

And a third stage: the control chip U1 can control the switch tube (e.g. MOSFET) therein to open, so that the energy stored in the inductor L1/transformer T1 can be discharged to the output terminal through the following loop: inductor L1/secondary winding N of transformer T1_S→ output rectifier diode D5 → filter capacitor C5 → inductor L1/secondary winding N of transformer T1_S. The control chip U1 can detect the output information (e.g., energy transmission time (demagnetization time), and output voltage) via the output information sampling circuit connected to the output information sampling pin FB, in combination with the output voltage based on the resistance R_CSThe information such as the loop compensation that output current, loop compensation electric capacity C2 provided of setting, through the inside control circuit of control chip U1 (its usable any suitable algorithm, the utility model discloses do not restrict this) realize output constant current and output overvoltage protection etc..

A fourth stage: when the AC power supply AC is turned off and the voltage of the dc voltage VIN decreases, or when the control chip U1 triggers protection to forcibly turn off the power supply loop of the chip power pin VDD, the voltage of the capacitor C3 externally connected to the chip power pin VDD of the control chip U1 decreases accordingly. When the voltage of the capacitor C3 is lower than the lowest working voltage threshold set by the control chip U1, the control chip U1 may stop working until the AC power supply AC is turned on again or the protection reset is released, and the control chip U1 may return to the first stage working again.

The control chip U1 may cycle through the first through fourth phases described above. The waveforms of the two operating states from top to bottom in FIG. 3 show the resistance R in sequence_CSVoltage V across_CSAnd the voltage V of the output information sampling pin FB of the control chip U1_FBThe waveform of (2).

Fig. 4 shows a waveform diagram of a leading edge dimming operation mode of the LED driving circuit according to an embodiment of the present invention, and fig. 5 shows a waveform diagram of a trailing edge dimming operation mode of the LED driving circuit according to an embodiment of the present invention. The following first describes the operation of the leading edge or trailing edge dimming operation mode of the LED driving circuit according to an embodiment of the present invention, which can be divided into seven stages, and the seven stages are described in detail below.

The first stage is as follows: an AC input voltage of the AC power source AC is rectified and filtered by the AC input rectifying and filtering circuit to become a dc voltage (e.g., a sine wave) VIN. As the dc voltage VIN gradually increases, the capacitor C4 can be charged via the following loop: the filter capacitor C1 → the resistor R4 → the capacitor C4 → the grounding pin GND of the control chip U1 → the filter capacitor C1. As the capacitor C4 is gradually charged, the switch Q1 may gradually conduct. With the switching tube Q1 turned on gradually, the dc voltage VIN can charge the external capacitor C3 of the chip power pin VDD of the control chip U1 through the following loops: filter capacitor C1 → inductor L1/primary winding N of transformer T1_P→ the drain of the switching tube Q1 → the source of the switching tube Q1 → the internal switching tube drain pin SW of the control chip U1 → the chip supply pin VDD of the control chip U1 → the capacitor C3 → the ground pin GND of the control chip U1 → the capacitor C1. For example, when the voltage of the external capacitor C3 of the chip power pin VDD of the control chip U1 is higher than the turn-on voltage of the control chip U1, the control chip U1 may start to operate. Then, the control chip U1 may detect the dimming information through the dimming signal acquisition circuit connected to the dimming information detection pin DIM(e.g., including a voltage value and a time value), and then determines whether the LED driving circuit turns on the triac dimmer DIM1 based on the detected dimming information, and accordingly enters a dimming operation mode or a non-dimming operation mode (in this example, enters the dimming operation mode) according to the determination result. For example, the dimming signal acquisition circuit may be a sampling resistor voltage division circuit, and the voltage value in the dimming information may be calculated based on the following formula: (R3 × VAC1)/(R3+ R2) and (R3 × VAC2)/(R3+ R1), where VAC1 is the voltage at the second terminal of the thyristor dimmer DIM1 and VAC2 is the voltage at the second input terminal of the ac input rectifying and smoothing circuit, as shown in fig. 1 and 2.

And a second stage: at the moment when the AC power source AC is turned on and the triac dimmer DIM1 is turned on, the control chip U1 may control the switching tube (e.g., MOSFET) therein to output a constant current during the period T1 through the following loops: filter capacitor C1 → inductor L1/primary winding N of transformer T1_P→ the drain of the switching tube Q1 → the source of the switching tube Q1 → the drain SW of the internal switching tube of the control chip U1 → the ground GND of the control chip U1 → the filter capacitor C1, so as to speed up the stable and fast turn-on of the triac dimmer DIM 1.

And a third stage: the control chip U1 may operate during the period T2 according to the second and third phases of the non-dimming mode of operation of the LED driver circuit described above with reference to fig. 4 to deliver energy to the output terminal. As shown in fig. 4 and 5, the period T2 exists only in the leading edge dimming operation mode, and there is no period T2 in the trailing edge dimming operation mode.

A fourth stage: the control chip U1 suspends its operation during the period T3.

The fifth stage: the control chip U1 operates according to the third phase (i.e., according to the second and third phases of the non-dimming operation mode of the LED driving circuit described above with reference to fig. 4) during the period T4. Throughout the period T, the control chip U1 may detect dimming information (e.g., including a voltage value and a time value) through a dimming signal acquisition circuit to which the dimming information detection pin DIM is connected, and then determine a current phase-cut angle of the triac dimmer DIM1 based on the detected dimming information. Further, the periods T2 and T4 may be sized based on the magnitude of the phase-cut angle, thereby implementing a dimming function. For example, the dimming signal acquisition circuit may be a sampling resistor voltage division circuit, and the voltage value in the dimming information may be calculated based on the following formula: (R3 × VAC1)/(R3+ R2) and (R3 × VAC2)/(R3+ R1), where VAC1 is the voltage at the second terminal of the thyristor dimmer DIM1 and VAC2 is the voltage at the second input terminal of the ac input rectifying and smoothing circuit, as shown in fig. 1 and 2.

The sixth stage: the controller chip U1 operates during the second phase during the period T5 to ensure that the minimum current to maintain the triac dimmer DIM1 on is supplied until it returns to the second phase to operate during the period T1. The high compatibility of the triac dimmer DIM1 is mainly realized in that, during the whole phase-cut sine wave period T (the leading edge dimming operation mode T is T1+ T2+ T3+ T4+ T5, and the trailing edge dimming operation mode T is T1+ T3+ T4+ T5), the control chip U1 may correspond the output current to the average current in the input period T, and concentrate the output current to the periods T2 and T4 (the leading edge dimming operation mode) or the period T4 (the trailing edge dimming operation mode) for output. This not only ensures that the average output current during the period T is constant, but also increases the average value of the input current during the periods T2 and T4 (leading edge dimming mode) or the period T4 (trailing edge dimming mode). Ensuring that the input average current is not less than the minimum current required to maintain the thyristor dimmer DIM1 on during periods T2 and T4 (leading edge dimming mode) or period T4 (trailing edge dimming mode) avoids LED flicker caused by the thyristor dimmer DIM1 turning off. Control during period T3 may prevent triac dimmer DIM1 from turning off. The LED drive circuit circularly works at each stage in the period T, and high compatibility of the silicon controlled rectifier dimmer is realized.

A seventh stage: when the AC power supply AC is turned off and the voltage of the dc voltage VIN decreases, or when the control chip U1 triggers protection to forcibly turn off the power supply loop of the chip power pin VDD, the voltage of the capacitor C3 externally connected to the chip power pin VDD of the control chip U1 decreases accordingly. When the voltage of the capacitor C3 is lower than the lowest working voltage threshold set by the control chip U1, the control chip U1 may stop working until the AC power supply AC is turned on again or the protection reset is released, and the control chip U1 may return to the first stage working again.

The waveforms of the three working states from top to bottom in fig. 4 and 5 show the dc voltage VIN and the ac voltage V sequentially_ACWith a resistor R_CSVoltage V across_CSThe waveform of (2).

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An LED drive circuit, includes AC input rectification filter circuit, detection control circuit, power conversion transmission transformer, and output rectification filter circuit, wherein:

the detection control circuit includes:

the control chip comprises a dimming information detection pin, an external switch tube gate electrode driving pin, an internal switch tube drain electrode pin and an output information sampling pin;

a first end and a second end of the dimming signal acquisition circuit are respectively connected to a second output end and a first output end of the alternating current input rectifying and filtering circuit, a third end of the dimming signal acquisition circuit is connected to the dimming information detection pin, and a fourth end of the dimming signal acquisition circuit is grounded;

a first end of the starting circuit is connected to the third output end of the alternating current input rectifying and filtering circuit and the first end of the power conversion transmission transformer, a second end of the starting circuit is grounded, and a third end of the starting circuit is connected to the gate electrode driving pin of the external switching tube;

the drain electrode of the switching tube is connected to the second end of the power conversion transmission transformer, the gate electrode of the switching tube is connected to the gate electrode driving pin of the external switching tube, and the source electrode of the switching tube is connected to the drain electrode pin of the internal switching tube; and

and a first end of the output information sampling circuit is connected to a second end of the power conversion transmission transformer, a second end of the output information sampling circuit is connected to the output information sampling pin, and a third end of the output information sampling circuit is grounded.

2. The LED driving circuit according to claim 1, wherein the control chip further comprises:

an inner loop compensation pin, which is used for inner loop compensation and is grounded through a first capacitor;

the chip power supply pin is used for supplying power to the control chip and is grounded through a second capacitor;

the grounding pin is used as a reference ground of the control chip; and

the output current setting pin is used for setting the output current and is grounded through the first resistor.

3. The LED drive circuit of claim 1 wherein the dimming signal acquisition circuit comprises a resistor.

4. The LED driving circuit according to claim 3, wherein the resistor comprises a first resistor, a second resistor and a third resistor, wherein a first terminal of the first resistor is connected to a first terminal of the dimming signal acquisition circuit, a first terminal of the second resistor is connected to a second terminal of the dimming signal acquisition circuit, a second terminal of the first resistor is connected to a second terminal of the second resistor, a first terminal of the third resistor and a third terminal of the dimming signal acquisition circuit, and a second terminal of the third resistor is connected to a fourth terminal of the dimming signal acquisition circuit.

5. The LED driver circuit of claim 1, wherein the startup circuit comprises a resistor and a capacitor.

6. The LED driver circuit of claim 5, wherein a first terminal of the resistor is connected to a first terminal of the start-up circuit, a second terminal of the resistor is connected to a first terminal of the capacitor and a third terminal of the start-up circuit, and a second terminal of the capacitor is connected to a second terminal of the start-up circuit.

7. The LED drive circuit of claim 1, wherein the output information sampling circuit comprises a resistor.

8. The LED driver circuit of claim 7, wherein the resistor comprises a first resistor and a second resistor, wherein a first terminal of the first resistor is connected to a first terminal of the output information sampling circuit, a second terminal of the first resistor is connected to a second terminal of the output information sampling circuit and a first terminal of the second resistor, and a second terminal of the second resistor is connected to a third terminal of the output information sampling circuit.

9. The LED drive circuit of claim 1 wherein the ac input rectifying filter circuit comprises a fuse, a thyristor dimmer, a rectifying diode, and a filter capacitor.

10. The LED driver circuit of claim 9,

the rectifier diodes comprise a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode, wherein the first rectifier diode and the third rectifier diode are connected in series to form a first series circuit, the second rectifier diode and the fourth rectifier diode are connected in series to form a second series circuit, and the first series circuit, the second series circuit and the filter capacitor are connected in parallel; and is

The first input end of the alternating current input rectifying and filtering circuit is connected to the anode of an alternating current power supply and is connected to the first end of the silicon controlled rectifier dimmer through the fuse, the second end of the silicon controlled rectifier dimmer is connected to the first output end of the alternating current input rectifying and filtering circuit and the common end of the first rectifying diode and the third rectifying diode, the second input end of the alternating current input rectifying and filtering circuit is connected to the cathode of the alternating current power supply, the second output end of the alternating current input rectifying and filtering circuit and the common end of the second rectifying diode and the fourth rectifying diode, the third output end of the alternating current input rectifying and filtering circuit is connected to the cathode of the first rectifying diode and the cathode of the second rectifying diode and the first end of the filter capacitor, and the anode of the third rectifying diode and the second end of the filter capacitor are grounded.

11. The LED driving circuit according to claim 1, wherein the power conversion transmission transformer comprises an inductance.

12. The LED driving circuit according to claim 11, wherein a first terminal of the inductor is connected to the third output terminal of the ac input rectifying and filtering circuit, the first terminal of the start-up circuit, and the first terminal of the output rectifying and filtering circuit, and a second terminal of the inductor is connected to the drain of the switching tube, the first terminal of the output information sampling circuit, and the second terminal of the output rectifying and filtering circuit.

13. The LED drive circuit of claim 12 wherein the output rectifying filter circuit comprises an output rectifying diode and a filter capacitor.

14. The LED driving circuit according to claim 13, wherein an anode of the output rectifying diode is connected to the second terminal of the inductor, a cathode of the output rectifying diode is connected to an anode of the filter capacitor, and a cathode of the filter capacitor is connected to the first terminal of the inductor.

15. The LED drive circuit of claim 1, wherein the power conversion transmission transformer comprises:

the absorption circuit comprises a resistor, a capacitor and a diode; and

the transformer comprises a primary winding and a secondary winding.

16. The LED driving circuit according to claim 15, wherein the first terminal of the resistor and the first terminal of the capacitor are connected to the third output terminal of the ac input rectifying and filtering circuit, the first terminal of the start circuit, and the first terminal of the primary winding, the second terminal of the resistor is connected to the second terminal of the capacitor and the cathode of the diode, the anode of the diode is connected to the drain of the switching tube, the first terminal of the output information sampling circuit, and the second terminal of the primary winding, and the secondary winding is connected to the output rectifying and filtering circuit.

17. The LED drive circuit of claim 16 wherein the output rectifying filter circuit comprises an output rectifying diode and a filter capacitor.

18. The LED drive circuit of claim 17 wherein an anode of the output rectifier diode is connected to a first end of the secondary winding of the transformer, a cathode of the output rectifier diode is connected to an anode of the filter capacitor, and a cathode of the filter capacitor is connected to a second end of the secondary winding of the transformer.