![]() The reference voltage is generated by an ordinary diode. (This frequency changes depending on the supply voltage and LEDs forward drop voltage and current. This whole cycle above happens very quickly - as fast as 500,000 times a second. Shorting the output doesn't harm the circuit.) This method of controlling current is often called "cycle by cycle" current limiting. (This "true" current limiting also works as a buit-in short circuit protection. Eventually the comparator flips back again, and the cycle starts over. This current gradually decays, and as the current decays so does the voltage across the current sense resistors. Current then flows through the Schottky diode D3 to power the LEDs. Now because inductor is "charged", current doesn't stop flowing immediately. When it gets higher than the reference voltage, the comparator trips, which turns off Q3, which turns off current flowing into the inductor. As the current gets higher, the voltage at the comparator's negative input pin increases as well. Inductor does not allow current to shoot up immediately, so the current increases gradually. As the Q3 turns on, current flows through L1, LEDs, and the current sensing resistors. This voltage is compared to the reference voltage by a comparator. The resulting voltage is proportional to the current according to the Ohms Law. The output LED current flows through R10 and R11 (current sensing resistors). The circuit is built around a very common dual comparator IC: LM393 using buck converter topology. With Arduino you can simply use "AnalogWrite()" to control the brightness of high-power LEDs. This makes the "Poorman's Buck" perfect building block for Arduino or other microcontroller based LED projects - you can control many high-power LEDs from a microcontroller simply by sending PWM signal. All of the parts are easy to obtain, "off-the-shelf", though-hole parts.Įven though this driver is minimalistic, I added a current adjust function that doubles as a dimmer, and an input to control the output with PWM. So I created the "Poorman's Buck" - simple switch-mode (buck) constant current LED driver that's built without a microcontroller or a specialized IC. Poorman's Buck - Simple, Constant Current LED Driver Even my own Universal LED Driver can be overkill at times. Some projects call for a bear minimum, simple driver. However I realize that the finding and configuring the power supply is still not as simple as it can be commercially available LED drivers are convenient, but often overkill or not flexible. I'm sure many of you are incorporating LEDs as light sources in your projects. MyPID1.High-power LEDs over 1W are now quite inexpensive. Please help have a project submission.ĭouble aggKp1 = 2, aggKi1 = 1, aggKd1 = 2 // settiing aggressive values of Kp Ki Kd for PID1ĭouble consKp1 = 0.1, consKi1 = 0.05, consKd1 = 0.25 // settiing conservative values of Kp Ki Kd for PID1 ![]() Ive attached the power circuit diagram for your reference. else statement used for selecting boost and buck function correct? for buck and boost converter.is that fine.and ive multipled it with output1 & output 2 of PID? I based the duty ration of buck & boost fn on the basic voltage eqn. Ive used 2 seperate PID fns.can someone please check wether ive applied correctly? especially the output statement? The buck mode does not seem to generate a PWM? Input1 = analogRead(analogPin1) //read A2īoostDuty = 1 - (Input1 / 778) //calculate boost duty ratioĪnalogWrite(pwPin2, (boostDuty * 255 * Output1)) //write to D6Īs per value of v1 the buck mode or boost mode gets selected.Im facing the following problems: of PWM to 62.5kHzĭouble gap1 = abs(Setpoint1 - Input1) //distance away from setpointĭouble gap2 = abs(Setpoint2 - Input2) //distance away from setpoint MyPID1.SetMode(AUTOMATIC) // turn ON PID1 Input2 = analogRead(analogPin2) //take feedback of output in boost mode to PID2 Input1 = analogRead(analogPin1) //take feedback of output in boost mode to PID1 PinMode(pwPin2, OUTPUT) //set PWM 6 to output ![]() PinMode(pwPin1, OUTPUT) //set PWM 5 to output PID myPID2(&Input2, &Output2, &Setpoint2, consKp2, consKi2, consKd2, DIRECT) //PID2 PID myPID1(&Input1, &Output1, &Setpoint1, consKp1, consKi1, consKd1, DIRECT) //PID1 Im working on a dc-dc buck boost converter, with 2 different switching elements for bidirectional operation: #include ĭouble aggKp1 = 1, aggKi1 = 0.5, aggKd1 = 1 // settiing aggressive values of Kp Ki Kd for PID1ĭouble consKp1 = 0.1, consKi1 = 0.05, consKd1 = 0.25 // settiing aggressive values of Kp Ki Kd for PID1ĭouble aggKp2 = 1, aggKi2 = 0.5, aggKd2 = 1 // settiing aggressive values of Kp Ki Kd for PID2ĭouble consKp2 = 0.1, consKi2 = 0.05, consKd2 = 0.25 // settiing aggressive values of Kp Ki Kd for PID2 ![]()
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