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| | #1 |
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hi i wonder if anyone can give me some help on my problem. im trying to generate a 100 - 150 kh square wave using a 555 timer. although i am able to generate perfect square waves at 50 - 70 Khz, i cant seem to be able to get a perfect square wavon the output a higher frequencies. can anyone help me figure this out. im not very experienced in using electronic components. maybe my supply voltages have something to do with this as i am using the correct resistora and caps according to the furmulas. also can someone help me with a circuit using a tl5100cp as its supposed to be able to create output frequencies of between 20kHz and 500 kHz | |
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| | #2 |
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If you're highly concerned about getting a perfect 50% duty square wave, then perhaps you should instead generate a signal twice the desired frequency and pass it through a divide-by-2 (such as a D flip flop with an inverter between Q and D).
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| | #3 |
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For a start, what are you trying to do?.
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| | #4 |
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describe what it looks like.
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| | #5 |
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You cannot quite get a 50% duty cycle with a 555, but almost, provided the discharge resistor (between pins 6 and 7) is much larger than the charge resistor (between pin 7 and Vcc). eg 1M and 1K. Trouble is for the high frequency tou are looking for you would then need a mighty small cap. Haven't done the sums. | |
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| | #6 | |
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| | #7 |
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Thank you guys it a part of a driver circuit for an induction heater. The rest of the circuit works fine at lower frequencies. i use a 2nF cap. | |
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| | #8 | |
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| | #9 | |
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| | #10 |
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For induction heating, you want an AC signal. A single transistor driver will be very inefficient; use a push pull circuit. A D type flip flop and AND gate can make the push pull drive which does not have to be (does not want to be) 50% duty cycle because you need some dead time while the transistors are switching.
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| | #11 |
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Where was the duty cycle mentioned? Use a TS555 because they're more stable at higher frequencies. The circuit for 50% duty cycle is on the datasheet. What sort of driver are you using? I recommend adding a capacitor in parallel with the coil to provide a resonant circuit which will boost the efficiency
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| Tags |
| frequency, grr, high, square, wave |
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