Linear regulator steady flow, power tube IRF3205

 

0-15V 0-5A, adjustable experimental maintenance power supply

 

With LM317 fan power supply circuit

 

You can not use fan control circuit, are generally to increase the cooling tube area. RF3205 can be used 75NF75, can also use other models of high-power NMOS field tube, select the conduction resistance as small as possible.

 

PCB size: 100 * 50MM 

 

Principle: TL431 as a 2.5V voltage reference comes with a reverse output op amp, and OC output mode, different from the ordinary op amp complementary output. U1 is connected to 5V voltage reference, U2 is equivalent to 2.5V precision regulator tube, because TL431 as a voltage comparator used, his threshold voltage is higher, between 2.45 ~ 2.55V, so use U2 lift current resistor Of the weak signal voltage.

 

U3 and Q3 and other components of the steady flow control circuit, the load current tends to increase, the sense resistor R0 on the pressure drop increases, U3 will tend to turn on, the Q3 reverse output high level, on the one hand through the LED2 as stable Flow indication, the other is added to the U4 adjustment side R, so U4 K-side output voltage decreases, adjust the IRF3205 output voltage also tends to reduce, to keep the load current stability. By controlling the U4 regulator terminal voltage, you can achieve the output voltage adjustment or output current setting.

 

If you use the digital meter, you also need to have a power supply to the meter head, if the transformer does not have the appropriate winding, you can add a small transformer to the meter power supply. Digital meter power consumption is small, the working current is relatively stable, you can also use the circuit 5V voltage to do the first power supply. At this time need to reduce R4, increase the output current Q2. Add a voltage, current indicator header, you can debug the power:

1. Adjust the output voltage to 5V, the current adjustment potentiometer to adjust the current minimum, short-circuit lead output

(Also available digital multimeter 200mA current connected to the output), adjust the VR3 to minimize the output current.

2. Remove the power supply output of the short wiring (or 200mA file multimeter pen line), and then carefully callback VR3, so that the output voltage back to short before the voltage, the minimum stable current is fine.