@Dzoro @bertus One of the frequent threads we moderators frequently have to shut down is transformerless power supplies to create high DC voltages. I have decided to show one way to do this that meets AAC TOS and COD ( Terms of Service and Code of Conduct .
Parts List
Qty 1 U1 7555 CMOS Timer IC
Qty 1 U2 LM317 3Terminal variable voltage Regulator IC
Qty 1 T1 Transformer 120VAC to 12VAC center tap optional
Qty 4 D1-D4 1N4006 Diodes A Diode Bridge with suitable specs can be substituted
Qty 1 Q1 TIP 102 NPN Power Darlington Transistor
Qty 1 Q2 TIP 107 PNP Power Darlington Transistor
Qty 1 C1 .01µF 16VDC (or higher) Capacitor
Qty 2 C2,C9 0.1µF 16VDC Capacitor
Qty 2 C3,C4 10µF 16VDC Electrolytic Capacitor
Qty 1 C6 1000µf 16VDC Electrolytic Capacitor
Qty 1 C7 100µf 300VDC (or higher) Electrolytic Capacitor
Qty 1 C8 100µF 16VDC Electrolytic Capacitor
Qty 1 R1 1KΩ ¼W 5% Resistor
Qty 1 R2 1.2MΩ ¼W 5% Resistor
Qty 4 R3,R4,R5,R6 100KΩ ¼W 5% Resistor
Qty 1 R7 120Ω ¼W 5% Resistor
Qty 1 R8 1KΩ trimmer variable Resistor
Qty 1 R9 36Ω ¼W 5% Resistor
Warning This supply creates Dangerous voltages and lethal currents. If you do not treat it with caution it can kill you, and it will hurt the entire time you are dying. Neither All about Circuits or the author assumes liability for this circuit, Build at your own risk!
Now that the warning is out of the way, I would rate this circuit suitable for intermediate to advanced users. CMOS chips (the 7555) can be easily zapped with static electricity, so ESD precautions are advised. This circuit is as of yet untested. but I have high confidence it will work as is.
The voltage generated is not regulated, When loaded it may drop substantially, I will draw a regulated version in the near future. Since the transistors will be operating in their linear region heat sinking will be required.
The voltage can be increased even more by grounding the center tap of the transformer It is up to the user to adjust the diodes and capacitor C7 specs to compensate the added strain on these components.
Theory of Operation
I have always felt the conventional 555 was a remarkable IC. The CMOS version (such as the 7555 addresses the 555 weaknesses and adds a few more. Among the things it improves on is a much wider range of power supply voltages (typically 2VDC to 18 VDC)and a true rail to rail output. The AC level is a function of the power supply voltage fed to the 7555.This comes at a price as it can only drive microamps at the lower supply voltages. For this reason I made the transistor drivers as high impedance as I could. The back to back capacitors allow polarized electrolytics to be used, as they are much easier to acquire than large unpolarized electrolytic capacitors. The transistor circuit drive circuits will only handle the AC signal, Both the 555 and755 are fairly stable in frequency over their power supply ranges. I chose 60 Hz because that is what most USA transformers are designed for if there is a request for it I will calculate the values for 50Hz and our EU friends.
I spent quite a while coming up withe the resistor values for U2, it will adjust1.625VDC to 10.8V. This will cover the voltages a user might need.
Parts List
Qty 1 U1 7555 CMOS Timer IC
Qty 1 U2 LM317 3Terminal variable voltage Regulator IC
Qty 1 T1 Transformer 120VAC to 12VAC center tap optional
Qty 4 D1-D4 1N4006 Diodes A Diode Bridge with suitable specs can be substituted
Qty 1 Q1 TIP 102 NPN Power Darlington Transistor
Qty 1 Q2 TIP 107 PNP Power Darlington Transistor
Qty 1 C1 .01µF 16VDC (or higher) Capacitor
Qty 2 C2,C9 0.1µF 16VDC Capacitor
Qty 2 C3,C4 10µF 16VDC Electrolytic Capacitor
Qty 1 C6 1000µf 16VDC Electrolytic Capacitor
Qty 1 C7 100µf 300VDC (or higher) Electrolytic Capacitor
Qty 1 C8 100µF 16VDC Electrolytic Capacitor
Qty 1 R1 1KΩ ¼W 5% Resistor
Qty 1 R2 1.2MΩ ¼W 5% Resistor
Qty 4 R3,R4,R5,R6 100KΩ ¼W 5% Resistor
Qty 1 R7 120Ω ¼W 5% Resistor
Qty 1 R8 1KΩ trimmer variable Resistor
Qty 1 R9 36Ω ¼W 5% Resistor
Warning This supply creates Dangerous voltages and lethal currents. If you do not treat it with caution it can kill you, and it will hurt the entire time you are dying. Neither All about Circuits or the author assumes liability for this circuit, Build at your own risk!
Now that the warning is out of the way, I would rate this circuit suitable for intermediate to advanced users. CMOS chips (the 7555) can be easily zapped with static electricity, so ESD precautions are advised. This circuit is as of yet untested. but I have high confidence it will work as is.
The voltage generated is not regulated, When loaded it may drop substantially, I will draw a regulated version in the near future. Since the transistors will be operating in their linear region heat sinking will be required.
The voltage can be increased even more by grounding the center tap of the transformer It is up to the user to adjust the diodes and capacitor C7 specs to compensate the added strain on these components.
Theory of Operation
I have always felt the conventional 555 was a remarkable IC. The CMOS version (such as the 7555 addresses the 555 weaknesses and adds a few more. Among the things it improves on is a much wider range of power supply voltages (typically 2VDC to 18 VDC)and a true rail to rail output. The AC level is a function of the power supply voltage fed to the 7555.This comes at a price as it can only drive microamps at the lower supply voltages. For this reason I made the transistor drivers as high impedance as I could. The back to back capacitors allow polarized electrolytics to be used, as they are much easier to acquire than large unpolarized electrolytic capacitors. The transistor circuit drive circuits will only handle the AC signal, Both the 555 and755 are fairly stable in frequency over their power supply ranges. I chose 60 Hz because that is what most USA transformers are designed for if there is a request for it I will calculate the values for 50Hz and our EU friends.
I spent quite a while coming up withe the resistor values for U2, it will adjust1.625VDC to 10.8V. This will cover the voltages a user might need.
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