TL-494 IC Pulse Width Modulation Control Circuit Tutorial

The TL-494 IC is a versatile and widely used pulse width modulation (PWM) control circuit that can be applied to various PWM circuits due to its two error amplifiers and oscillator. This IC contains a control comparator, voltage reference, and two output transistors connected to VCC and ground.

To create a carrier frequency of around 10 kilohertz, we can connect a 10-kilo-ohm resistor and a 0.01 microfarad capacitor to the oscillator pins. Additionally, to turn on/off the ignition coil before MOSFETs, a crude control circuit was added to the TL-494 IC.

The control circuit created a PWM signal with a frequency of roughly 11 kilohertz and an inverted duty cycle of approximately 98%. This means that at 0% duty cycle, the MOSFETs are turned on, while at 2% duty cycle, they are turned off. By applying a voltage between zero volts and 3.3 volts to the time control pin, this duty cycle can be varied between 3% and 100%.

To test the PWM signal, a music signal was added to the dead time control pin using a function generator that created a 500-Hertz sine wave. The MOSFET gate voltage was checked again, and it successfully created an audio-modulated PWM signal.

However, when hooking up power to the MOSFETs, the plasma arc did not seem to be working correctly due to the high frequency used in the oscillator. To solve this issue, the carrier frequency was lowered to around 400 Hertz, which resulted in the establishment of a stable plasma arc and playback of frequencies created by the function generator.

The impedance of the transformer at low frequencies is only 7.3 ohms on the primary side, guaranteeing a high current flow. However, as the frequency increases up to 10 kilohertz, the impedance rises to 36.5 ohms, drastically reducing the energy transfer to the secondary coil and current flow.

A potential solution to this problem is using a high-frequency transformer with a diode on the secondary side to cancel out opposing secondary currents. Fortunately, an old CRT TV was found that contained such a flyback transformer, which was used in place of the ignition coil.

The flyback transformer had several pins to choose from, but pin 7 provided the anti-peak red high-voltage wire for the secondary side. After adding wires to the transformer and hooking it up to the MOSFETs as shown in the schematic, altering the oscillator capacitor and resistor values once again to higher frequencies, and applying the music signal to the dead time control pin, the real tests were conducted.

The utilization of the flyback transformer instead of the ignition coil proved to be a success. Although this project was more of a learning experience than something intended for daily use due to safety concerns with high voltage, I hope you enjoyed the video and will subscribe to my channel.

WEBVTTKind: captionsLanguage: enin order to playback your favorite music nowadays all you have to do is to connect the audio signal to an amplifier and then connect the amplified signal to a loudspeaker it will move its cone according to the audio signal and thus create a spreading sound wave through the area that we can hear pretty awesome concept when you think about it but of course not only loudspeakers can vibrate air molecules in a previous video for example I showed you how we can abuse a transformer in order to create audible music but in this video we will go one step further by creating a lethal plasma arc which as you can hear can also produce hiroba sounds the long the way here we will learn a bit about ignition coils flyback transformers and a very handy pwm ICEA which only requires a handful of complementary components to establish the singing plasma arc so let's not waste any more time and let's get started with the builds this video is sponsored by jlc PCB uploader Gerber files to get custom PCBs easily their professional PCB production has the most competitive price in the world so feel free to test out their fast delivery and high quality PCBs today first off how can we create this plasma arc well we need a high electric field strength between two conductors with an approximate voltage of around thirty thousand volts per centimeter of distance which brings me to the obvious warning for this kind of high voltage project if you have no idea about electronics then do not try to create such a high voltage since it can be lethal and note that we know that we need a high voltage how can we create it for that I got myself an ignition coil from items on mopeds it is normally used to create the spark for the ignition of the fuel which means we should be able to create a high voltage with its rights to examine that I added a wire to a third terminal and measured the existing resistance between all the three terminals what I measured was a low resistance of around 4 ohms between pin 1 and 15 and a high resistance of around eight point six five kilo ohms between the terminals 1 and 15 and the remaining terminal and since we depend on a transformer to create a high voltage I concluded that the ignition coil consists of a long enamel copper wire wrapped around a ferromagnetic material with three connection points the close points are the terminals 1 and 15 which build up the primary coil of the transformer and the far away connection point is the remaining terminal which in combination with the terminal 15 builds up the secondary coil according to the resistance measurements there should be a turns ratio of around 2164 meaning that if we apply 15 volts ac on the primer area we should get around 32,000 460 volts ac on the secondary but since applying such a high power AC signal to the primary year is not that easy to accomplish with a function generator I tried out a simpler methods to test the ignition coil transformer by letting three amps flow through the primary coil with my lab bench power supply and magnetic fields is pulled up which after disconnecting the power supply collapses this reduces the magnetic flux density and thus the magnetic flux and therefore induces a voltage into the secondary which due to the turns ratio should be pretty high but as you can see here apparently not powerful enough to create a spark to fix that I added a capacitor in parallel to the primary in order to create a tank circuits which lets energy oscillate a bit longer on the primary side and thus allows for enough energy transfer to the second area to finally create the spark in conclusion that means we now got our required high voltage transformer to create the plasma but how can we modulate a high voltage to play back music what we need is a PWM signal with a carrier frequency higher than the maximum frequency of the music for this example I went with 10 kilo Hertz next we need to increase / decrease the duty cycle of this PWM signal according to the frequency of the music which looks something like this on the oscilloscope now this can be hard to grasp but this modulated duty cycle contains the information for our music and thus lets the arc vibrate with its frequency which creates the sounds and to create the signal I utilized the TL for night for pulse width modulation control circuits IC which is very useful for all kinds of PWM circuits since it contains two error amplifiers and oscillator at that time control comparator f5 foods voltage reference and two output transistors by connecting its pins to VCC and ground like a shown here we can connect a 10 kilo ohm resistor and a 0.01 micro farad capacitor to the oscillator pins in order to create a carrier frequency of around 10 kilohertz additionally since I let I want to turn on / off the ignition coil before MOSFETs I added a rather crude control circuit for its to the TL 494 IC and by measuring the signal on its gates we can see our created pwm signal with a frequency of roughly 11 kilohertz and an inverted duty cycle of 98% that means we got at that time around 2% which is generated by the time control pin that is tied to ground but by applying a voltage between zero volts and 3.3 volts this that time can be varied between 3% and 100% which is basically the duty cycle of modulation I talked about earlier and if you want to learn more about the ICEA for which there's plenty of information then I would highly recommend you to check out its datasheet anyway here what we can do now is simply adding our music signal to the dead time control pin but for first test I rather utilized my function generator which created F 500 Hertz sine voltage and by checking the MOSFET gate voltage once again we can see that we successfully created our audio modulated PWM signal which means it was time to hook up power to the MOSFETs and have a look at the singing plasma arc which apparently still does not feel like working correctly the solution for this problem was lowering the carrier frequency of the system to around 400 Hertz and as you can see here by utilizing a lower frequency the plasma arc can be established and can also play back flow of frequencies created by my function generator but the question remains why this ignition coil transformer does not work at higher frequencies for which there are several answers the first one is that why the impedance at a low frequency is only 7.3 ohms on the primary which guarantees a big current flow this impedance increases up to 36 point 5 ohms at 10 kilohertz which decreases the current flow drastically and thus also the energy transfer to the secondary coil but not only that while the current builds up in the primary this secondary current is created which opposes the primary currents and especially at a high frequency reduces the energy transfer if only there would be a high frequency transformer with maybe a diode on the second area to cancel out the opposing secondary currents wait a transformer like this can be found in CRT TVs and is called a flyback transformer luckily a friend of mine got an old one laying around which after I opened up its enclosure offered me a usable flyback transformer so I cut off all of its wires removed the main circuit board it was sitting on and used some solder wick to get rid of it solder connections after then removing it from the PCB year I had a closer look at it and realized that it got quite a few pins to choose from thankfully though by googling it spot number I found a schematic of my transformer the pins are utilized for my plasma arc speaker weapon 3 and 9 for the primary sites and pin 7 anti peak red high voltage wire for the secondary sites and after adding wires to the transformer hooking it up to the MOSFETs like it shown in the schematic altering the oscillator capacitor and resistor once again to the high frequency values and adding the proper music signal to the dead time control pin it was finally time for the real tests and as you can hear the utilization of the flyback transformer instead of the ignition coil was a big success now I will not bother soldering all the components to purport since this was more like a learning experience project then something I want to use on a daily basis because let's face it high voltage is dangerous and does not offer that Goods open audio quality and with that being said I hope you enjoyed this video if so don't forget to Like share and subscribe stay creative and I will see you next timein order to playback your favorite music nowadays all you have to do is to connect the audio signal to an amplifier and then connect the amplified signal to a loudspeaker it will move its cone according to the audio signal and thus create a spreading sound wave through the area that we can hear pretty awesome concept when you think about it but of course not only loudspeakers can vibrate air molecules in a previous video for example I showed you how we can abuse a transformer in order to create audible music but in this video we will go one step further by creating a lethal plasma arc which as you can hear can also produce hiroba sounds the long the way here we will learn a bit about ignition coils flyback transformers and a very handy pwm ICEA which only requires a handful of complementary components to establish the singing plasma arc so let's not waste any more time and let's get started with the builds this video is sponsored by jlc PCB uploader Gerber files to get custom PCBs easily their professional PCB production has the most competitive price in the world so feel free to test out their fast delivery and high quality PCBs today first off how can we create this plasma arc well we need a high electric field strength between two conductors with an approximate voltage of around thirty thousand volts per centimeter of distance which brings me to the obvious warning for this kind of high voltage project if you have no idea about electronics then do not try to create such a high voltage since it can be lethal and note that we know that we need a high voltage how can we create it for that I got myself an ignition coil from items on mopeds it is normally used to create the spark for the ignition of the fuel which means we should be able to create a high voltage with its rights to examine that I added a wire to a third terminal and measured the existing resistance between all the three terminals what I measured was a low resistance of around 4 ohms between pin 1 and 15 and a high resistance of around eight point six five kilo ohms between the terminals 1 and 15 and the remaining terminal and since we depend on a transformer to create a high voltage I concluded that the ignition coil consists of a long enamel copper wire wrapped around a ferromagnetic material with three connection points the close points are the terminals 1 and 15 which build up the primary coil of the transformer and the far away connection point is the remaining terminal which in combination with the terminal 15 builds up the secondary coil according to the resistance measurements there should be a turns ratio of around 2164 meaning that if we apply 15 volts ac on the primer area we should get around 32,000 460 volts ac on the secondary but since applying such a high power AC signal to the primary year is not that easy to accomplish with a function generator I tried out a simpler methods to test the ignition coil transformer by letting three amps flow through the primary coil with my lab bench power supply and magnetic fields is pulled up which after disconnecting the power supply collapses this reduces the magnetic flux density and thus the magnetic flux and therefore induces a voltage into the secondary which due to the turns ratio should be pretty high but as you can see here apparently not powerful enough to create a spark to fix that I added a capacitor in parallel to the primary in order to create a tank circuits which lets energy oscillate a bit longer on the primary side and thus allows for enough energy transfer to the second area to finally create the spark in conclusion that means we now got our required high voltage transformer to create the plasma but how can we modulate a high voltage to play back music what we need is a PWM signal with a carrier frequency higher than the maximum frequency of the music for this example I went with 10 kilo Hertz next we need to increase / decrease the duty cycle of this PWM signal according to the frequency of the music which looks something like this on the oscilloscope now this can be hard to grasp but this modulated duty cycle contains the information for our music and thus lets the arc vibrate with its frequency which creates the sounds and to create the signal I utilized the TL for night for pulse width modulation control circuits IC which is very useful for all kinds of PWM circuits since it contains two error amplifiers and oscillator at that time control comparator f5 foods voltage reference and two output transistors by connecting its pins to VCC and ground like a shown here we can connect a 10 kilo ohm resistor and a 0.01 micro farad capacitor to the oscillator pins in order to create a carrier frequency of around 10 kilohertz additionally since I let I want to turn on / off the ignition coil before MOSFETs I added a rather crude control circuit for its to the TL 494 IC and by measuring the signal on its gates we can see our created pwm signal with a frequency of roughly 11 kilohertz and an inverted duty cycle of 98% that means we got at that time around 2% which is generated by the time control pin that is tied to ground but by applying a voltage between zero volts and 3.3 volts this that time can be varied between 3% and 100% which is basically the duty cycle of modulation I talked about earlier and if you want to learn more about the ICEA for which there's plenty of information then I would highly recommend you to check out its datasheet anyway here what we can do now is simply adding our music signal to the dead time control pin but for first test I rather utilized my function generator which created F 500 Hertz sine voltage and by checking the MOSFET gate voltage once again we can see that we successfully created our audio modulated PWM signal which means it was time to hook up power to the MOSFETs and have a look at the singing plasma arc which apparently still does not feel like working correctly the solution for this problem was lowering the carrier frequency of the system to around 400 Hertz and as you can see here by utilizing a lower frequency the plasma arc can be established and can also play back flow of frequencies created by my function generator but the question remains why this ignition coil transformer does not work at higher frequencies for which there are several answers the first one is that why the impedance at a low frequency is only 7.3 ohms on the primary which guarantees a big current flow this impedance increases up to 36 point 5 ohms at 10 kilohertz which decreases the current flow drastically and thus also the energy transfer to the secondary coil but not only that while the current builds up in the primary this secondary current is created which opposes the primary currents and especially at a high frequency reduces the energy transfer if only there would be a high frequency transformer with maybe a diode on the second area to cancel out the opposing secondary currents wait a transformer like this can be found in CRT TVs and is called a flyback transformer luckily a friend of mine got an old one laying around which after I opened up its enclosure offered me a usable flyback transformer so I cut off all of its wires removed the main circuit board it was sitting on and used some solder wick to get rid of it solder connections after then removing it from the PCB year I had a closer look at it and realized that it got quite a few pins to choose from thankfully though by googling it spot number I found a schematic of my transformer the pins are utilized for my plasma arc speaker weapon 3 and 9 for the primary sites and pin 7 anti peak red high voltage wire for the secondary sites and after adding wires to the transformer hooking it up to the MOSFETs like it shown in the schematic altering the oscillator capacitor and resistor once again to the high frequency values and adding the proper music signal to the dead time control pin it was finally time for the real tests and as you can hear the utilization of the flyback transformer instead of the ignition coil was a big success now I will not bother soldering all the components to purport since this was more like a learning experience project then something I want to use on a daily basis because let's face it high voltage is dangerous and does not offer that Goods open audio quality and with that being said I hope you enjoyed this video if so don't forget to Like share and subscribe stay creative and I will see you next time