New answers tagged

2

Using PWM without smoothing causes increased I2R losses in the Peltier element that reduces the available cooling and efficiency. Ideally you need to run the Peltier element with DC that is proportionally controlled to the level needed to maintain the cooling. The controller can use high-speed PWM with inductive filtering to increase overall electrical ...


3

It's an AP3125AKTR-G1 Green mode PWM controller from BCD/Diodes Incorporated.


0

simulate this circuit – Schematic created using CircuitLab This won't reverse it. Will continue to look at it tommorrow. I'm not sure I can do it without a negative supply. https://www.falstad.com/circuit/circuitjs.html?ctz=...


1

Does 'neutral position' imply a 50% duty cycle? No. The RC servo standard is not duty cycle despite being called PWM. It is the pulse length (actual time) not width (duty cycle) that they care about, not duty cycle.. 1.5ms is center. 1 and 2ms are the extremes. That's what this says: Most servos expect a pulse at least every 20ms (50Hz). For analog servos, ...


0

@ Andy aka Thank you very much for the information. I have tried the circuit and your assumption was correct regarding the Rt. I have wired values as per the original formula and the frequency was close to intended value. I need 25Khz PWM so need 50Khz oscillator. In this circuit which I tried, RV1 gives control over PWM close to 50% which is maximum in ...


4

In this specific case, the power dissipated by the resistor would double. The more general principal, which is always applicable in all cases is that the average power dissipated by a resistor is the mean value of the instantaneous power calculated over one period. So even if you have an irregular or arbitrary repeating voltage or current waveform, you can ...


1

If you double V and halve D, does the average power dissipation double? Yes it does and it's easily proven by inspection and simple numbers. If R = 1, D = 0.5 and V = 1 volt, the power is 50% of 1²/1 = 0.5 watts. If V doubles to 2 and D halves to 0.25 then the power is 25% of 2²/1 = 1 watt. It applies to any resistor and has nothing to do with thermal time ...


2

I need a open loop system where I can Vary the PWM duty cycle within the range using a potentiometer without taking a sample from output. Is it possible with this chip? Clues are in the data sheet such as this lab test fixture: - Look bottom left and you'll see a switch that can be set to position 1 - this applies a 10 kohm feedback resistor to the error ...


1

If the core saturates, the CS pin will exceed 1V and cause the controller to latch off after 15ms or something like that, until the power is cycled. You can monitor the voltage on that pin and see if that is occurring. Also, measure the primary inductance and see if it is as designed (and double-check your design), preferably under bias if your LCR bridge ...


1

Q1/Q2 is the primary oscillator, PC1 is the photocoupler to feedback Q3 Zener current and thus overvoltage, Q3 is an adjustable Zener. How the Q1/Q2 functions with PWM are unclear, with primary ripple voltage and dynamic load current.


0

This design is likely proprietary so normally not available to the public, however reverse engineering is easy as there are few parts. Q1 combined with a feedback winding from T1 forms a resonate oscillator. PC1 is an opto-coupler used to provide feedback so output is locked to a specific DC voltage. That is why T1 has 4 primary pins, 2 to drive the ...


0

Please show the schematic. From the PCB I can see that one terminal of the motor is connected to the +VE power input (not ground). The transistor Q1 then connects the other terminal to ground with the PWM signal. It basically looks ok.


2

The MOSFET is acting as a source follower and therefore, the voltage it develops at the source is somewhat less than the voltage applied at the gate. So, if T2 collector can produce (say) 12 volts then T3's gate receives 12 volts and T3's source will be a volt or so lower at 10 or 11 volts (maybe even lower with some FETs). This means that the power ...


3

Question The OP wishes to control the speed of a DC motor using PWM or regulator. He also wishes to change the direction of the motor. Answer This answer is in two parts: Short and Long. The short answer is kind of an introduction to the long answer. Short Answer Part A - Clarifications A.1 - AC to DC Switching Power Supply and DC-DC Step down voltage ...


4

You can use PWM control under the following two conditions: The average voltage applied does not exceed the rated voltage of the motor. This ensures that the average power rating of the motor is not exceeded. The duration of the PWM pulse does not cause the winding current to saturate. The rotor windings act like an inductor, which smooths the current, but ...


1

I put a resistor between GPIO and gate, then the resistor is going to create a damping effect. Right? Yes. Series resistance is good. Without damping the Gate capacitance and wiring inductance form a high Q tuned circuit that 'rings', causing possibly unacceptable EMI or even circuit misoperation. The higher frequency I have, the less voltage is going to ...


0

The reason to choose an asynchronous PWM could be variable frequency output where one can still use a fixed frequency carrier. Variable frequency carrier is hard to implement.


Top 50 recent answers are included