# Questions tagged [duty-cycle]

Duty Cycle is the ratio between duration of a pulse and the entire period of a (repeating) square wave, expressed in %.

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### Can I use a brushed DC motor at higher-than-rated duty cycle at reduced load?

I have a linear actuator powered by a brushed DC motor which I got from an adjustable bed. The actuator label has the following information: Input Voltage: 24V DC Max Load: 6000N (Push) Speed: 4.2mm/...
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### Two formulas for defining RMS and average of a waveform through a diode [duplicate]

A textbook problem where we have this given current waveform through a diode. We are required to determine the maximum and RMS values of it [ Irms and Ip ] giving the average current= something ...
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### RMS of sine wave curve defined between two points

Could someone explain for the following attachment (waveform image) how were exactly the values of "RMS" and "average" determined this way (for that curve of sine)? Given the duty ...
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### How to choose Duty Cycle value for a Full-Bridge DC/DC Converter

I've noticed that while designing DC/DC converters, some sources (at the bottom of the website, comment of Benjamin Lough) suggest a "rule of thumb" duty cycle of 70%, while others (This is ...
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### Why is Duty cycle for CC LED driver voltage specific, when Output voltage has a compliant range?

Commercial CC drivers usually mention "x-yV output" range which means that the output voltage has a compliance range where CC operation will be maintained in constant current mode. But then ...
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### Can one CC boost LED driver be used for 2 different loads separately?

I have a constant current boost LED controller (TPS92691) which I am designing to output 4A switching between two LED strings. This is with a 2S lipo battery. One string has a stack forward voltage of ...
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### SG3525 feedback identification

This is from a UPS which creates 350VDC from 12VDC, How does this arrangement work to control presumably the duty cycle of SG3525? Compensation (pin 9) and inverting input (pin 1) are connected ...
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### STM32 24VDC PWM fan speed control with optocoupler

I am using this circuit to control a 24V fan at a frequency of 31kHz (MCU - 72 MHz, Prescaler - 9, Counter period - 255): The scheme works. But I want to add an optocoupler to the circuit, I did it ...
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### Why is it difficult to write the close loop transfer function of a frequency modulated DC-DC converter (for eg - LLC converter)?

I know how to derive and write the transfer function of duty cycle/pulse width modulated DC-DC converter. We need to linearize the switches and then write KVL/KCL equations and then derive the output ...
356 views

### How to create a PWM source with fixed frequency and decreasing duty cycle (at some interval) in LTspice?

I'm trying to simulate a PWM signal whose duty cycle decreases by a fixed amount over a given interval from 100% to 0. For example, if the PWM frequency is 2 MHz, I want to ramp down the on-time from ...
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### Boost converter duty cycle

In my circuit, I’m trying to solve the duty cycle to obtain an average dissipation of 5 W in the diode. Input voltage: 100 V Inductor: 10 mH RL: 100 Ω C: 10 uF Freq: 10 kHz Diode on voltage: 0.7 V ...
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### PWM switching, Regarding the control voltage

If V desired and V actual is subtracted, in this diagram, how does the V control which should be very same used as reference? My question is that, the V control can be very small, how can it be able ...
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### Voltage not varying with duty cycle

I want to make a circuit that changes voltages with the duty cycle as well as doubles that for me. I therefore made a voltage doubler circuit along with alternating PWM wave. But as I changed the duty ...
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### Understanding violation of the common mode voltage range of the input in ZCD [closed]

Trying to reproduce an analog circuit using LM324 to have at output 100Hz squarewave 5% duty cycle from 230Vac mains frequency. The circuit has to be in sync with it. Picture and LTSpice simulation ...
508 views

### Schmitt trigger transistor duty cycle

I built this Schmitt trigger using transistors (2N3704). Input is a square wave coming from an OCXO, 1 MHz, 50% duty cycle. I obtain a square wave with 70% duty cycle. What can possibly be the cause?
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### PWM IC duty cycle not increasing

I was working on the UCC3895 PWM generator but am having a problem getting a complete duty cycle up to 100. I have used the following diagram for my circuit: I wanted to use the UCC3895 to get a PWM ...
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### PWM phase shift controller IC confusion

I was reading one of the datasheets regarding the control of an H-bridge i.e. UCC3895. As far as I understand, this is a PWM controller to drive a full bridge inverter. I have a few confusions ...
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### NE555, 50% duty cycle at 110kHz

I want to get an NE555 chip with a 50% duty cycle to 108-110kHz in output. I have already experimented with various online calculators and values. However, I never get the values that allow me to do ...
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### Output time period of each pulse signals to determine the duty cycle

Dear all, I build on an oscillator and want to detect its duty cycle in order to compenstate the oscillator which is used to sensing the environment change. After I get the V(vtime_all) which shows ...
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### What is the formula for measuring squarewave duty cycle from a spectrum?

Several engineers have told me that digital signal (squarewave) duty cycle can be measured accurately by comparing the amplitude of the 2nd (or 3rd - says another guy) relative to the fundamental. ...
1 vote
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### Duty Cycle and Filtering in Switching Power Supplies

I have a few confusions to clear up. The first one is about the switching power supply. Does the power supply simply work on the bases of the duty cycle? Like If I have a pulsating signal of 50% duty ...
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### STM32 PWM output duty cycle is not accurate

I am using an STM32f051C8T6 and I am trying to control the PWM duty cycle, however, the duty cycle is inaccurate. I set it to be 50%, but the output is less than 40%. Also, the frequency is wrong; I ...
144 views

### Duty cycle that varies with time

Controlling the intensity of an LED with a 555 and a potentiometer is fairly straightforward. Like this circuit (feel free to criticize). I would like to go one step further and have the duty cycle ...
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### Maximum voltage of a PWM

It seems that some buck converter designs use PWM to change the average voltage sent to the load : which means that for it's (ON) duty cycle, the load will see a higher voltage than required/specified ...
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### Flyback transformer design process review

I was hoping I could get some verification on my flyback design process, and some questions answered. The document I was following is from Fairchild, AN4137, and the steps below essentially outline ...
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### Square wave (+-15V) to positive DC

How can I convert a square wave signal from -15V to 15V to a positive DC signal? Here are the details of my problem: I'm trying to build a duty cycle for a buck converter in the following way: I want ...
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### Relationship between pulse forward current vs pulse duration

I'm having trouble understanding why this application note for this proximity sensor suggests reducing the current for the IRED depending on the on time pulse duration. What is the relationship ...
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### Servo motor duty cycle to angle

I am trying to control a servo motor using a square signal with a varying duty cycle. The data sheet of the motor says that the frequency of the signal should be 20 ms. In addition, if I need to ...
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### PWM converters: operation over and under 50% duty cycle

I have a DC/DC Flyback converter based on the UC2844 regulator and I would like to use other regulators of the same UCx84x family. Reading the datasheet, I found that there are regulators that can ...
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### In LTspice, why does sine wave PWM simulation fail for small and large duty cycles?

I had been trying to find a way to simulate a PWM signal for a sine wave, other than using a large and cumbersome PWL file, or using a comparator between a sine signal and a sawtooth for the carrier. ...
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### Formula for current vs duty cycle in step-up pwm circuit?

What is the formula for average current with step-up PWM circuit (and about 30 kHz frequency and 300 uH inductor) that charges battery at 72 volts, and source is 24 volts, relative to duty cycle? I ...
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### Stretch duty cycle of square wave where amplitude changes

I have a signal coming from a photodiode detector, the pulse is really short, so the integration time is very small, and the total power measured is very small (very close to the noise of the detector)...
116 views

### Circuit for producing logic high when input is oscillating

I want to make a circuit which produces a logic high signal upon receiving an oscillating input voltage. In the past I have gotten away using an RC delay signal. When my input signal wasn't ...
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### Calculate duty cycle of device's on and sleep state to drain coin cell in given amount of time

I am trying to drain a 25 mAh ECR1216 coin cell in 2 days. My device draws 6 mA when on, and about 15 μA when on standby. I am having a hard time determining a duty cycle for on/standby time to drain ...
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### Impedance, square waves, and duty cycle

Will a coil present a different impedance to a 10 kHz sine wave as opposed to a 10 kHz square wave with a 10% duty cycle? I could not find a way to calculate it, are there any formulas available?
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### Question - LC Tank - Resonance , Duty Cycle , Back EMF

I was wondering about that for some time now but didn't have the time to try it myself , maybe some of you guys will help me out with this question : What happens when LC Tank is operated in its ...
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### TLC555 Constant Frequency, Adjustable Duty Cycle [closed]

For my Senior Design Project, I am designing a battery charger based on a synchronous buck converter topology. The MCU (Teensy LC) I'm using cannot produce PWM with a high enough frequency (488.28Hz), ...
1 vote
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### Change the duty cycle of pulses

I'm trying to raise the duty cycle of short pulses (about 10%) through the range up to ideally 80% using a potentiometer. I've seen variable pulse generator designs using 555s, but my trigger is ...
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### How to optimally decide modified square wave duty cycle for an inverter?

Some high-end inverters synthesize a sine wave with high speed pulse width modulation and low-pass filtering, but most cheaper inverters use a square wave or a modified square wave. Modified square ...
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### Could a CPU execute the fetch-execute cycle without a microsequencer/microcode?

VERY SPECIFIC QUESTION, PLEASE READ THROUGH ALL OF IT From wikipedia: "The sequence of operations that the control unit goes through to process an instruction is in itself like a short computer ...
1 vote
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### PWM signal generator circuit does not work in real life

I designed the motor soft start circuit in the figure below. I ran the circuit in simulation programs, but when I tried it on a breadboard in real life, I could not get a PWM signal. When I examined ...
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### While using this library (FastPwmPin.h) output frequency is coming exactly but not duty ratio?

I am doing a simple power supply for that I need PWM signal to turn ON and OFF the MOSFET. For this I am using arduino UNO for PWM signal generation. So I used a library called FastPwmPin.h to ...
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### Adressing timing issues on a pipelined logic circuit

Original title: How to modify the duty cycle of crystal oscillator? I have a 25.175 MHz crystal oscillator with a duty cycle of 50%. How can I reduce the waveform to a 25% duty cycle? It doesn't have ...
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### Making duty cycle with CTC mode in AVR without using interrupt

I am writing a program to make an output with a 30% duty cycle and a frequency of 3 kHz using an ATmega32 microcontroller. My controller's frequency is 8 MHz and I am going to decrease it to 1 MHz by ...
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### Increase minimum PWM duty cycle for high resolution PWM

I'm working on a project involving driving LEDs at a 20kHz PWM frequency with 1024 bit resolution. I've calculated that the minimum pulse time, (1/frequency)/resolution, would result in a minimum ...
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### I have modified a simple blocking oscillator. How can the frequency, duty cycle or efficiency be otherwise increased?

In this schematic is a simple blocking oscillator. Note that this won't simulate, as Circuit Lab does not have the type of toroid needed, but if you breadboard or prototype this circuit it will work ...
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### precise 50 Hz oscillator [closed]

I need an astable multi-vibrator at exactly 50 or 100 Hz with exactly 50% duty cycle. using circuits like 555 can't give me that with the common well-known values of components R and C , let alone the ...
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### Precise square wave generator 32768 Hz

I need to create a circuit to generate a square wave with 50% duty at 32768 Hz +/- 5 Hz. The output of the circuit will drive an NPN transistor ( 0.2 A , 24VDC ). The cost of the component is not a ...