LM6009 Adjustable Step-Up/Step-Down Exhaust Fan

The task requires
designing an adjustable step-up/step-down welding fume extraction fan system that can adjust fan speed and suction power according to the actual working environment and welding intensity. An LM6009 DC-DC converter circuit should be implemented.
Problem Analysis
: 1. Power Supply Design: Design a variable output voltage DC-DC converter using the LM6009 chip. The input voltage can be between 5V and 35V, and the output voltage should automatically adjust according to the fan's needs.
2. Fan Control: Utilize the adjustable step-up/step-down function of the LM6009 to control the fan voltage, thereby adjusting the fan speed and achieving dynamic fume extraction.
3. Mechanical Design: The design uses a JLCPCB box, making the entire system easy to move and position. The suction port is designed with a large opening to adapt to different welding operation scenarios.
4. Safety Protection Measures: The system includes temperature monitoring and overload protection to prevent equipment overheating and circuit damage.
5. Observable Voltage and Current: An observable voltage, current, and power meter is used. A potentiometer is used to adjust the voltage and current.
 
Overall Design Block Diagram
and Schematic Diagram:
USB1 uses TYPE-C pin 4 as the power input for the entire board. A 6V/2A fuse is used for circuit break protection. A switch is used to easily turn the fan on and off. H1 and H2 are the two test points at the input terminals.
The pre-amplifier uses a combination of one large and one small capacitor for filtering, and an M4 reverse protection diode. Connecting pin 2 to H5 controls the power-on; the default is a floating high-level input. Pin 5 uses an external resistor divider network; FB detects and adjusts the output voltage. The feedback threshold voltage is 1.25V. The output stage uses another combination of one small and one large capacitor for filtering. An inductor + capacitor combination is used to achieve low ripple output.
A 10k potentiometer is used to adjust the output; ADJ (1.25V) is adjustable. The output voltage is adjusted by changing the ratio of R2 and R1. For example: R2=10K R1=0.33K. VOUT=1.25*(1+R2/R1) yields a maximum output voltage of 40V.
 
PCB design description:
This circuit uses a type C input, and switches for control and short-circuit protection. This pistol-like design is convenient to combine with a JLCPCB box, a Delta fan, and an external voltage and current meter. This circuit uses a large area filling method to replace the wiring, especially the delta output of LM6009, which is filled with a large area and has vias for heat dissipation, so that it does not get hot while handling large current.
(1) The line for handling large current should be thick, short, and without bends.
(2) The line for pin 1 (GND) and pin 4 (VIN) should be thick, short, and without bends, and the input electrolytic capacitor CIN should be close to pin 4 (VIN) and pin 1 (GND). (This is mainly to reduce the parasitic inductance and high voltage switching interference caused by the resistance of the input power supply wiring).
(3) The output line of pin 3 (SW) should be thick, short, and without bends. The inductor and freewheeling diode should be close to the output terminal of pin 3 (SW).
(4) The trace of pin 5 (FB) should be connected to the output filter capacitors C1, C2, and D1. The PCB trace should be kept away from L1 and D1 to avoid noise interference.
(5) The back pad of the chip is SW, which is connected to pin 3. The chip efficiency is generally very high, around 90%. When the input power is large, at 55W, the entire system loss is around 5.5W and the system temperature is high. After improving the heat dissipation (adding heat sinks and heat dissipation through the back holes), the output current capability can be improved and the output power can be increased.


Physical demonstration and instructions: The soldering sequence should be
noted
.