A non-isolated step-down LED constant current driving circuit

Abstract

The utility model provides a kind of non-isolated step-down type LED constant current drive circuit, it is characterized by, including rectifier module, input filter capacitor, output filter capacitor, power inductance, freewheeling diode and constant current drive chip;The positive pole of input filter capacitor is connected the positive pole output end of rectifier module, the power supply pin of constant current drive chip, the cathode of freewheeling diode and the positive pole of output filter capacitor respectively, its negative pole connects the negative pole output end of rectifier module;The anode of freewheeling diode is connected the one end of power inductance and the control pin of constant current drive chip, the other end of power inductance is connected the negative pole of output filter capacitor respectively;The constant current drive chip includes base island, pin, power tube and main control chip, the power tube is pasted on base island, the main control chip is stacked on power tube and is equipped with DAF film between the bottom surface of main control chip and power tube to realize bonding and insulation.

Description

Technical Field

[0001] This utility model relates to LED driving circuits, and more particularly to a non-isolated step-down LED constant current driving circuit. Background Technology

[0002] Advances in packaging technology have enabled fully functional integrated circuits to be fabricated into functional chips, which can then be used as the basis for other circuits, greatly improving the flexibility and efficiency of circuit design. For example, constant current driver chips are commonly used in LED driver circuits, requiring only a few external components, significantly reducing system cost and size. These constant current driver chips typically employ a single-island or dual-island structure, directly mounting the main control chip and power transistors on the islands, and then connecting the main control chip, power transistors, and pins via wires.

[0003] As LED driver circuits demand increasingly higher power density from constant current driver chips, larger power transistors are required. However, due to limitations in base island size and distance from the device to the base island edge, the available base island area for the main control chip and power transistors is limited, making it difficult to further increase the size of the power transistors, thus restricting the designable driving power of the constant current driver chip. Summary of the Invention

[0004] This utility model proposes a non-isolated step-down LED constant current drive circuit, which is specifically implemented through the following technical means: A non-isolated step-down LED constant current drive circuit, characterized in that it includes a rectifier module, an input filter capacitor, an output filter capacitor, a power inductor, a freewheeling diode, and a constant current drive chip; The positive terminal of the input filter capacitor is connected to the positive output terminal of the rectifier module, the power supply pin of the constant current drive chip, the cathode of the freewheeling diode, the positive terminal of the output filter capacitor, and the positive output terminal of the non-isolated step-down LED constant current drive circuit, and its negative terminal is connected to the negative output terminal of the rectifier module. The anode of the freewheeling diode is connected to one end of the power inductor, and the other end of the power inductor is connected to the negative terminal of the output filter capacitor and the negative output terminal of the non-isolated step-down LED constant current drive circuit, respectively. The control pin of the constant current drive chip is connected to the power inductor. The constant current drive chip includes a base island, pins, a power transistor, and a main control chip. The power transistor is mounted on the base island, and the main control chip is stacked on top of the power transistor. A DAF film is provided between the bottom surface of the main control chip and the power transistor to achieve bonding and insulation.

[0005] In one or more embodiments of this utility model, the constant current driving chip adopts an ESOP8 package structure, and the heat conductor located on the back of the base island is exposed on the bottom surface of the package.

[0006] In one or more embodiments of this utility model, the distance from the main control chip to each side of the power transistor is greater than or equal to the value L1, the distance from the power transistor to the short side of the base island is greater than or equal to the value L2, and the distance to the long side of the base island is greater than or equal to the value L3; the values ​​L1, L2 and L3 will affect the chip's fixation reliability, heat conduction, packaging stress and the overall packaging yield and performance.

[0007] In one or more embodiments of this utility model, the first pin of the constant current drive chip is the GND pin, the second, third and seventh pins are the NC pins, the fourth pin is the HV pin, the fifth and sixth pins are the Drain pins, and the eighth pin is the CS pin; the fourth pin and the eighth pin are arranged diagonally.

[0008] In one or more embodiments of this utility model, the heat conductor extends to the drain pin and the two are in surface contact, thereby improving the chip's heat dissipation performance.

[0009] In one or more embodiments of this utility model, the constant current drive chip has an HV pin, a GND pin, a CS pin, and a Drain pin. The HV pin is connected to the positive output terminal of the rectifier module, the GND pin is connected to the negative terminal of the input filter capacitor, the CS pin is connected to the negative terminal of the input filter capacitor via a sampling resistor Rs, and the Drain pin is connected to a power inductor. Connecting the GND pin and the CS pin to the negative terminal of the input filter capacitor can avoid the surge risk caused by directly connecting to the negative output terminal of the rectifier module and protect the internal circuit of the chip.

[0010] Compared with existing technologies, the advantages of this invention are: simple and reliable circuit structure, fewer peripheral components, saving circuit costs and reducing circuit size. Meanwhile, to meet output power requirements, a stacked packaging structure is adopted on chips of the same ESOP8 package specification, stacking the main control chip on the power transistor, maximizing the removal of size limitations on the power transistor. The main control chip achieves bonding and insulation with the power transistor through a DAF film, resulting in better insulation consistency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the LED constant current drive circuit of this utility model.

[0012] Figure 2 This is a schematic diagram of the wafer wiring structure of the LED constant current driver chip of this utility model.

[0013] Figure 3 This is a schematic diagram of the cross-sectional structure of the LED constant current driver chip of this utility model.

[0014] Figure 4This is an internal equivalent module diagram of the LED constant current drive chip of this utility model. Detailed Implementation

[0015] The following is a further description of the scheme of this application with reference to the accompanying drawings: See appendix Figures 1 to 3 The non-isolated step-down LED constant current driver circuit includes a rectifier module, an input filter capacitor C1, an output filter capacitor C2, a power inductor LM, a freewheeling diode D1, and a constant current driver chip U1. The constant current driver chip U1 has an HV pin (power supply pin), a GND pin, a CS pin, and a Drain pin (control pin). The positive terminal of the input filter capacitor C1 is connected to the positive output terminal of the rectifier module, the HV pin of the constant current driver chip U1, the cathode of the freewheeling diode D1, the positive terminal of the output filter capacitor C2, and the positive output terminal of the non-isolated step-down LED constant current driver circuit. Its negative terminal is connected to the negative output terminal of the rectifier module. The freewheeling diode D1 has its anode connected to one end of the power inductor LM and the drain pin of the constant current drive chip U1. The other end of the power inductor LM is connected to the negative terminal of the output filter capacitor C2 and the negative output terminal of the non-isolated step-down LED constant current drive circuit. The GND pin is connected to the negative terminal of the input filter capacitor C1, and the CS pin is connected to the negative terminal of the input filter capacitor C1 via the sampling resistor Rs. The cathode of the freewheeling diode D1 is connected to the positive terminal of the output filter capacitor C2, and its anode is connected to the power inductor LM. In this circuit structure, the constant current drive chip U1 has fewer external components, saving circuit cost and reducing circuit size.

[0016] The constant current drive chip U1 adopts an ESOP8 package structure, which includes a base island 1, pins 2, a power transistor 3, and a main control chip 4. The power transistor 3 is mounted on the base island 1, and the main control chip 4 is stacked on top of the power transistor 3. A DAF film 5 is provided between the bottom surface of the main control chip and the power transistor 3 to achieve adhesion and insulation. The constant current drive chip U1 adopts a stacked package structure, which maximizes the removal of the size limitation on the power transistor 3, thereby meeting the requirements of higher drive output power. A heat conductor is provided on the back of the base island 1, and the lower end surface of the heat conductor is exposed on the bottom surface of the package to achieve better heat dissipation performance.

[0017] Furthermore, the distance from the main control chip 4 to each side of the power transistor 3 is greater than or equal to the value L1, the distance from the power transistor 3 to the short side (non-pin side) of the base island 1 is greater than or equal to the value L2, and the distance to the long side (pin side) of the base island 1 is greater than or equal to the value L3. The values ​​of L1, L2, and L3 affect the chip's fixation reliability, heat conduction, packaging stress, and the overall package yield and performance. In this embodiment, the value L1 is 250 micrometers, the value L2 is 300 micrometers, and the value L3 is 500 micrometers.

[0018] Furthermore, the first pin of the constant current drive chip is the GND pin, the second, third and seventh pins are the NC pins, the fourth pin is the HV pin, the fifth and sixth pins are the Drain pins, and the eighth pin is the CS pin; the fourth and eighth pins are arranged diagonally, that is, the HV pin is kept as far away as possible from the CS pin and other low-voltage pins.

[0019] Furthermore, the heat conductor 6 extends and connects to the drain pin with a surface contact between them. This contact between the heat conductor 5 and the drain pin enhances the heat dissipation performance of the power transistor 3. Additionally, appropriately increasing the copper area of ​​the drain pin also helps improve the chip's heat dissipation performance.

[0020] See appendix Figure 4 The constant current driver chip U1 detects the peak current of the power inductor LM cycle by cycle. The CS pin is connected to the input of the internal peak current comparator and compared with the internal 384mV threshold voltage.

[0021] When power transistor 3 is turned on, the current flowing through power inductor LM rises from zero. When the voltage at pin CS reaches the internal detection threshold, power transistor 3 is turned off. When power transistor 3 is turned off, the current flowing through power inductor LM decreases from its peak value. When the inductor current drops to zero, the internal logic of main control chip 4 turns power transistor 3 back on.

[0022] The above preferred embodiments should be regarded as illustrative examples of the embodiments of the present application. Any technical deductions, substitutions, improvements, etc. that are similar to or based on the present application should be considered within the scope of protection of this patent.

Claims

1. A non-isolated step-down LED constant current drive circuit, characterized in that, It includes a rectifier module, input filter capacitor, output filter capacitor, power inductor, freewheeling diode, and constant current driver chip; The positive terminal of the input filter capacitor is connected to the positive output terminal of the rectifier module, the power supply pin of the constant current drive chip, the cathode of the freewheeling diode, the positive terminal of the output filter capacitor, and the positive output terminal of the non-isolated step-down LED constant current drive circuit, and its negative terminal is connected to the negative output terminal of the rectifier module. The anode of the freewheeling diode is connected to one end of the power inductor, and the other end of the power inductor is connected to the negative terminal of the output filter capacitor and the negative output terminal of the non-isolated step-down LED constant current drive circuit, respectively. The control pin of the constant current drive chip is connected to the power inductor. The constant current drive chip includes a base island, pins, a power transistor, and a main control chip. The power transistor is mounted on the base island, and the main control chip is stacked on top of the power transistor. A DAF film is provided between the bottom surface of the main control chip and the power transistor to achieve bonding and insulation.

2. The non-isolated step-down LED constant current drive circuit according to claim 1, characterized in that, The constant current drive chip adopts an ESOP8 package structure, with the heat conductor on the back of the base island exposed on the bottom surface of the package.

3. The non-isolated step-down LED constant current drive circuit according to claim 2, characterized in that, The distance from the main control chip to each side of the power transistor is greater than or equal to the value L1, the distance from the power transistor to the short side of the base island is greater than or equal to the value L2, and the distance to the long side of the base island is greater than or equal to the value L3.

4. The non-isolated step-down LED constant current drive circuit according to claim 3, characterized in that, The value L1 is 250 micrometers, the value L2 is 300 micrometers, and the value L3 is 500 micrometers.

5. The non-isolated step-down LED constant current drive circuit according to claim 2, characterized in that, The constant current driver chip has the following pins: pin 1 is GND, pins 2, 3 and 7 are NC, pin 4 is HV, pins 5 and 6 are Drain, and pin 8 is CS; pins 4 and 8 are arranged diagonally.

6. The non-isolated buck LED constant current drive circuit according to claim 5, characterized in that, The heat conductor extends to the drain foot and the two are in surface contact.

7. The non-isolated step-down LED constant current drive circuit according to claim 1, characterized in that, The constant current drive chip has an HV pin, a GND pin, a CS pin, and a Drain pin. The HV pin is connected to the positive output terminal of the rectifier module, the GND pin is connected to the negative terminal of the input filter capacitor, the CS pin is connected to the negative terminal of the input filter capacitor via a sampling resistor Rs, and the Drain pin is connected to the power inductor.

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