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Questions tagged [constant]

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Led driver compliance voltage

I want to design a led driver providing constant current to relative high power LEDS such as CREE XLamp series. These LEDs typically can be operated with 1A and upwards with a forward voltage of 12V ...
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1answer
47 views

Trouble getting AL8861 LED Driver to illuminate LEDs

I am trying to get a AL8861 LED driver hooked up. Right now I've connected it to a single LED (this one) to test (see circuit below). I eventually intend to connect it to a DAC5578 Digital to Analog ...
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1answer
72 views

MOSFET Constant current - Current mirror circuit

I have been reading this current mirror/constant current circuit using MOSFET. MOSFET Constant-Current Source How does the current not change through Q2 when the voltage at Q2 increases? Ref.Fig1 ...
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2answers
168 views

Capacitor charging efficiency with a constant power source

I have a question. It is easy to derive the efficiency for loading a capacitor from a constant voltage or a constant current source, basically because exponential functions and constants are very, ...
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2answers
71 views

Trying to split the current output of an LED driver

I am currently using an 8 channel LED driver wher I have set the outputs to produce 20mA of constant current. Problem is I have 11 LEDs to drive. So I have decided to connect two LEDs in paralled to ...
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3answers
519 views

Making an efficient constant current source

I need help making an efficient constant current driver. I want to power my home with LED light strips for lighting and decorative purposes. I need to be able to turn each strip on and off ...
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1answer
62 views

Internal constant current driver for LED short circuits and blows when connected to AC main (120v) without DC load

I have AC 85-265V to 0.3A 8-12W DC 22-40V Internal constant current power supply for LED spot lights. This is the exact model https://www.lightinthebox.com/en/p/0-3a-8-12w-dc-22-40v-to-ac-85-265v-...
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2answers
66 views

Connect VGA cooling fan (12vdc - 0.1A) to constant current driver (120Vac to 12- 22vdc @ 0.3A)

I have an AC driven COB LED which can be connected directly to the AC main in house (120v). I would like to attach a cooling fan to the COB which requires 12vdc @ 0.1A. I have a constant current ...
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2answers
580 views

how to pass parameter variable to module in verilog

I need some help changing dynamically parameters of one module I'm trying to extract part of network data that it comes from the top module and goes to the internal modules In specific I have one ...
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3answers
133 views

Implementing a constant current source circut that can be switched off by a voltage signal

Does anyone know how to implement a constant current source circuit that is able to output 10mA constantly, ideally the load of the circuit would be a 100uF capacitor in series with 100 Ohms. Is ...
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1answer
54 views

Wiring a voltage specific device onto a constant current circuit?

I've got a bunch of LEDs wired in series to a constant current driver. The driver runs the circuit at 500ma to 700mA (I can vary it up or down a little) and can supply 50 to 100 volts, maximum 60 ...
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1answer
66 views

RC time constant in circuit with two caps with different potential

I'm trying to develop a model for the switching speed of a MOSFET. In reducing the equivalent diagram I have come up with this circuit with a resistor and two capacitors in parallel. The catch is ...
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1answer
65 views

Analysis of Buck COnverter

In an analysis of buck converter, we make few assumptions. Those are: The circuit is operating in steady state. The inductor current is continuous. The capacitor is very large and the output voltage ...
4
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1answer
362 views

Associate std_logic_vector constant with input port VHDL-200X

I am trying to configure a chip over SPI interface using FPGA Spartan 6 Eval board. I just need to configure, I do not need to read the data from the chip, it will be done by another interface. ...
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3answers
137 views

Understanding constant current circuit

I've been learning about different constant current circuit designs and just recently stumbled upon this one. All I know is that the highlighted resistor is the load resistor and when varied, like a ...
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2answers
572 views

Calculating Slew Rate from a time-constant

I have to choose an OP-AMP mainly based on slew rate. I am using the op-amp as a differential comparator with dynamic (time) hysteresis with a time-constant 3*tau=500µs. My upper threshold of the ...
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2answers
93 views

Relation between current and used energy

Thinking about a dc motor and a constant voltage battery, if you slow down the motor by resisting it physically without stopping it, its resistance increases, right? Therefore reducing the current in ...
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1answer
157 views

My RC Time Const. Calculations are wrong. Circuit changes my input signal

I have a simple RC circuit of 22 ohms and 3.3uF My measured values put the resistor at 22.10 ohms and the cap at 3.15 which gives me a time constant of 68.5 uS The signal applied is a 100Hz Square ...
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2answers
100 views

Parallel Regulator

Can anyone tell me how it works? In my opinion when U+ = U- the voltage Uo is constant no matter of the load resistor(R5). But this is only if U+=U-.
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1answer
45 views

Technology “dielectric constant” information

OK, so when working in a technology, say Bipolar, to build a high frequency amplifier, can I trust that the dielectric constant info for the various films contained in the electrical design rules, are ...
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2answers
617 views

Why does large inductance have a constant current through it?

I wanted to know, if an inductor is large, why would the current through it be constant? If an inductor is large, it means that it would be an open at moderate frequencies, and at DC the inductor is a ...
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1answer
328 views

Constant Voltage Load

Can someone tell me am i right? In constant voltage mode op amp compare voltage on noninverting input with voltage on inverting input and when U+ is larger than U- the load MOSFET turns on? If someone ...
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2answers
609 views

unstable pwm constant current

I am building a four channel constant current LED driver with PWM control. I have used the following circuit (replicated four times off a quad op amp). The circuit functions OK but as I wind the set ...
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1answer
743 views

Question about constant current region and voltage adjustment

first wanna thank anyone who can provide some thoughts on this. My doubt now is this. I'm using some meanwell power supplies and I'm a bit confused about max output they can handle. For an ...
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1answer
399 views

Low voltage, high current LED driver IC— does it exist? [closed]

I need an LED driver that can operate from a supply voltage as low as 3.3 volts and can put out a current of 350 mA or higher. The LEDs I'm using have a forward voltage of 2.7 volts at 350 mA. I only ...
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1answer
313 views

What is the formula for the dependence between modulating input voltage - output current for two transistor constant current sink

In a constant current sink from the two npn transistors, load and sensing resistor, application of increasing voltage on the base of the transistor produces practically linear increase in output ...
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1answer
90 views

Why do I get constant voltage across load of single phase inverter even with increasing input voltage

I built a single phase inverter, as shown below. However, for PWM gate control signal of maximum 9V peak, i noticed that the output PWM voltage across the a 10k resistive load does not increase above ...
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1answer
92 views

MOSFET has constant current

I have the following simple circuit. However, when I put the multimeter on the receiving end I'm always getting a current and I can't shut the gate, can anyone help please? I'm using the following ...
2
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1answer
2k views

DAC controlled constant current source

Was given the task of creating the simplest constant current source that can supply up to 50 mA with an ~700 ohm load. I can use any IC's out there. I stumbled across the chip here from linear tech: ...
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3answers
985 views

Precision voltage reference divider vs. constant current source to drive an RTD sensor

I need to measure temperature with an RTD between 0-300 C. I believe I have two options to make this work: A constant current source feeding the RTD A precision voltage reference and a resistor ...
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1answer
229 views

What are the constraints when choosing R value for a RC time constant?

I am planning to use a RC circuit to satisfy power up ramp rate requirements. Does the R value depends on system current?
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1answer
195 views

PWMing the output of a constant current driver

I have a set of led panels that come with AC-DC constant current drivers. Is it acceptable to use a MOSFET to pwm the LED (MOSFET goes between the driver and the LED)? Also the microcontroller that ...
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1answer
4k views

Difference between controlled current and constant voltage charging

Modern charging of lithium and nickel based batteries starts with a constant current, until a certain voltage and then a constant voltage until the current falls to some level that indicates end of ...
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1answer
796 views

Low Overhead Constant Current LED Driver

I have a 3V3 rail and want to run an LED with a Vf=3.1V at 10mA with a constant current source. I'm used to circuits like the one below but the problem is that I only have 200mV of overhead and ...