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94 Threads found on Control Constant Current
Hi everyone, I would thoroughly appreciate if you guys could point me any kind of surveys on dc-dc control schemes/techniques or maybe papers that talk abou the different types of control techniques. Regards.
Anyone knows what suitable constant current LED driver to use to control LED CCT for tunable white light application?
Hello, The attached is the mains input voltage and current waveforms of a 67W, Offline Flyback converter that has no big smoothing capacitor after its mains rectifier. The flyback operates in constant off time mode. As you can see the power factor is overall better than an offline SMPS using a big smoothing capacitor after the mains rectifier. I
can any one help me out for Vf=7 volt I=10 to 20mA (variable) constant current control circuit for UV LED 134762
hi, I want implement a constant current source with PWM control. 10mA is required at a load 1Kohm. The PWM should turn ON and OFF the load . The PWM frequency is 100Hz to 1KHZ with duty cycle of 10% to 80%. Regards
Hi can anyone help me to make work the constant current circuit with TL494 Half bridge config , constant Voltage is working , in constant current mode even the the ic can control the current the wave form is oscillating in sawtooth shape at 50hz to 100hz in some range (...)
Hi, I am using dspic30f5011 controller and I can generate PWM wave by using output capture compare module.Now,I want to control the 4-wire bipolar stepper motor with PWM i.e, rotation speed.So,what driver I have to use? Thanks and Regards, M SAI KIRAN.
I have 6 LEDs in my board connected to the GPIO pins of the MCU. I want to design a circuit for constant current control with supply current in uA(when all LEDs are OFF) The question appears to be incorrect, or perhaps unclear. Are you meaning you want to control the driven current of 6 (...)
Hi. Recently I saw a control circuit of Automatic voltage stabiliser which uses Nuvoton W79E251 MCU. On scrutiny of datasheet, it is noticed that the said MCU has no ADC module. No external ADC chip has been used in the circuit. Yet the 7-segment display shows the voltage perfectly. Sample of output voltage is coupled only to analogue comparator mo
so i think i need keep on read current through shunt res ? and need to control through PWM right? That's the usual way to operate stepper motor with constant current. Unipolar motors like yours are more often operated with constant voltage, yours is obviously designed for a lower voltage than 12V. In (...)
Ok. But You see a problem in reference voltage peak-to-peak variation across temperature or only reference value across corners? If second case, I'm not sure if You are able to overcame it without trimming - opamp replicate one VGS to other with the same threshold variation (which from ff to ss could be quite high and independent to designer), so r
constant voltage = the PSU tries to maintain the voltage you set with the voltage knob constant current = the voltage is adjusted to try to maintain the current you set with the current knob. In constant voltage mode, the current knob normally works as a (...)
In order to get uniform brightness on the single color ones, is it sufficient to connect the same (value & tolerance) resistor to all the LEDs or should I develop a constant current source using transistors? Putting several LEDs in series, it turns the current control easiest, ensuring that flow the same cur
Rs has no meaning for L298 itself. It will be used in constant current control, e.g. in combination with L297. Read the datasheet. The Rs resistance values value has two implications: - power dissipation I?Rs - suitable input voltage range of the current comparator in L297 or similar circuit
Description Primary current voltage: ?40V~?50V/7A Secondary current voltage: ?20V/1.5A Output power: 660W Dimension(L*W*H): 210*110*65mm Application: amplifier, instrument, meter, communication, industry control, DC machine driver and other places with DC constant voltage. Input voltage range: AC160V-270V Vp-p: (...)
Your question isn't clear, please give more information. If you keep the terminal voltage constant, the power supplied is entirely decided by the load current (connected devices) and you cannot control that from the power source. I'm also not sure what you expect to do with PWM unless it is at significantly lower frequency than the single (...)
You will want to specify the Voltage and current of the LEDs and power source available to amplify the signal. and drive the LED current to control brightness. 12-24V is a wide range. Do you mean 12~14V? Do they have electronics included for fixed power?
A better Bang for the Buck (intended pun) is to design a low voltage drop linear regulator after the buck SMPS which maintains the constant low voltage drop, while the linear regulator minimizes the ripple and has the benefit of current limit control down zero with wide BW ripple rejection and low step-load regulation error. In the old days (...)
A straightforward control scheme for the switched mode pre-regulator maintains constant voltage difference across the linear regulator. The topology has the advantage that it works independent of a particular setpoint, also tracks transistions between constant voltage and constant current etc.
If you can give some ideas about how we can do this design, it will be great. Here's a relatively simple laser diode driver circuit with photo diode control:
In actual practice wouldn't you just set the maximum current and pwm the voltage to keep a constant current. A V/f operated inverter is voltage controlled, the current varies according to the load. current limiting may be implemented as an auxilary function. It should be mentioned (...)
I would have gone with something much simpler. A light sensor which directly controls the current or PWM to a bank of LED lights.
current mode control is probably best. constant off time control is also good sometimes. Sometimes Boundary conduction mode is done as in BCM PFC's. constant frequency current mode needs slope compensation if duty >50%. Voltage mode is possible and needs type 3.....but very few voltage (...)
The concept is to run the LED at full current but for limited time. Instead of controlling the brightness by changing the current, you keep the current constant but flash the LED so rapidly that your vision can't see it, typically 200 times per second or faster. I normally use around 1,000 flashes per (...)
It's not yet obvious that your machine needs an electronic control at all. The majority of hydraulic drives is still controlled by pure mechanical valves, e.g. with construction machinery. Before you design an electronic controller you should be clear about it's specific purpose.
I guess what's confusing me is your statement c). You're not really trying to control V2 are you? You are trying to limit the current, right? There's a difference. You can't have a constant voltage AND a constant current unless you've got a fixed load. The way you've described it, you want to (...)
Here is a website (one of 100's) which has several constant current source circuits. Note that simultaneous control of output current AND voltage basically implies a very specific load. However, I assume the voltage range is the input voltage range, so no problem there.
Hi all, I'm building a circuit, wich I can't quite figure out, so any suggestions will be appreciated:) The circuit shall act as a constant current source for 3pcs Luxeon rebel leds (driven at 500mA as total for the 3, 166mA each) I need to be able to control the current downwards, by a analog voltage. Other (...)
hello everyone, The idea is to drive power LED's with an LM350 used as a constant current source as shown in the following scheme Now, the LED's can be dimmed by varying the resistor (R) between OUT and ADJ pin of the regulator. But the requirement is to control the birghtness of th
control signal can be easily isolated by optocouplers, for the isolated power supply, you'll need some kind of transformer based DC/DC converter.
As chuckey said, stepper motors are best used with current source drivers. It doesn't need to be complex, you just need a peak current mode control loop on each half bridge.
I am currently going over the concept of doing a valve tester as a final year project (EE), it would be microprocessor controlled and I would hope that it would give a reliable indication of the life left in a tube. Do you guys/gals have any feedback on this? Thank you Mick Carey
It's not clear why you would use a hall effect sensor in your design. Output voltage will be primarly kept constant by a voltage control loop. In case you want to use some kind of current feedforward, it could use a current transformer as the output is AC. But if you want a hall effect sensor for some reason, it's output (...)
Hello guys, I have a project in electronic which is to measure the current passing through the winding of a bipolar stepper motor, design an analog circuit and then convert the output value to this circuit with the help of a microcontroller which will have theses input configured in ADC Conversion, I just want to know if you have an idea og
I am have a differential vco using ring osc ckt when the control voltage at the tail current source is changed the amplitude changes, is there any logic which can tweak it the normal amplitude , any reference shall be very helpful Like in any other oscillator, a variable load is best used with a buffer ampli
Your constant current power supply doesn't have a fixed voltage output? Why does this surprise you, IT'S constant current!! Why are you using a constant current power supply to begin with, shouldn't you use a constant voltage supply? What does "pwm output is 255" mean? (...)
Some original joysticks used the Pot to control a VCO and thus frequency was the output, however DMM use constant current ( 0.0001mA to 1mA) to drive the probes and thus Resistance is the voltage on the probes.
Any Ideas? I have a small device that puts out AC 100volts and up to 125ma. It is a constant voltage device with a control to turn up the current. This is already a small amount of current but I need to limit the current to 2ma but keeping the voltage the same. The load varies from a minimum of 500 ohms to (...)
Perhaps the switching pulses are affecting the LM2575 control circuit. Try adding a small output capacitor to ground (say 0.1?F) and see if that makes any difference.
A current mode controller for the converter solves the problem.
Hi, I need to control the output current of a flyback converter to be constant using the dsPIC33FJ64MC802. the converter is to drive a 20W high power LED. I am using a hall effect sensor (LEM, LTSR 6NP)for output current sensing. i want to maintain my output current to a constant value of (...)
In Lahore this type of charger are sold with the name trickle charger kit. The kit control the phase angle of the transformer input by sensing the charging current and voltage of the battery. As a result the battery current remain constant and controllable.
Hi, I am making a meter that can measure low resistance (0.01 Ohm ~ 1 Ohm). For that, I want to make a dc dc converter that can control constant current 10A. Anyone has sample circuit? Also please tell me which chip should I use? Any analog IC or MCU will do. I have attached my initial thought. Is it correct? Thank you so much. (...)
Voltage and current control is present, but you cant expect constant high current if wind varies.
In this case it is the better to use a constant current, or driving it like a laser diode with monitor diode(would mean you need a photo transtistor for the feedback). This provides optical power control. Here are the LD principles: . Enjoy your design work!
The type of current limiting you're using is a basically a pretty crude control loop. You could get fancy and put an amplifier and compensation network, etc., and get sharper control, but to what end? What are you REALLY trying to accomplish? Do you want to maintain a constant current? A (...)
1st schematic should be emitter follower out, non inverting with negative feedback, and pull down resistor. but Q1 may overheat if Vin = 80V @ 100mA 2nd schematic may be overkill and also has positive feedback (NG) I suggest you use LM317 with transistor to use ADJ-OUT 1.250V internal reg drop for constant current control. See chip App (...)
In a real design, you'll use a voltage control loop rather than precalculated duty cycle. This is necessary to keep the voltage constant when changing to DCM operation at low load currents and also to compensate for various effects like inductor series resistance or switch saturation voltage.
I need to develop a program to control the pwm of the switch.. that is if we give command to the controller to operate in the constant VOLTAGE mode ,it should obey that... And if we give command to operate in constant current mode,it should be obey that... So how to control the (...)
Here's a description of how current-mode control works. Basically, the current through the load is being controlled in order to regulate the output voltage to a constant setpoint. Both the Linear Technology LTC3703 or LT3724 can output 10A at 3