Everything You Need To Know To Find The Best Does a bridge rectifier reduce voltage?

0 Members and 1 Guest are viewing this topic.

With competitive price and timely delivery, Hornby Electronic sincerely hope to be your supplier and partner.

baltazar99

• Newbie
• Posts: 8
• Country:

Reducing voltage on a full bridge rectifier

« on: July 15, , 10:25:00 pm » Hi,

please bear with me, i am still trying to learn the basics.
I have built a full bridge rectifier using 4 diodes and a couple of uF capacitors in parallel. the secondary AC voltage of the transformer I am using is 26v which gets converted to around 38v DC with the rectifier.

I am trying to power a soldering iron controller with requires 26v DC with an output current of 6amps. What are my options to reduce the voltage to 26v DC with 6 amps current?

NB: I have tried a voltage divider with 10 k resistors as R1 and 25k as R2 which gave me the correct voltage but as soon as I plugged in the load the output voltage dropped to 3v.

Thanks in advance for your help.

bob

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #1 on: July 15, , 10:36:10 pm » A dropping resistor is always a poor solution, as is a voltage divider.  A regulator is better.

If you analyze your circuit, you will find that the output voltage without a load is about the peak voltage of the winding, less the diode drops.  If you want to load this with a few Amperes, the output drops to a value that depends on the size of the transformer, diodes, and capacitors.  The analysis isn't simple but is covered in most basic electricity or electronics textbooks.

If you want to use a voltage divider, your choice of resistor value is very crucial.  In your case, you raised the source impedance to such an extent that you couldn't get useful output current.  Check out the Thevenin theorem.

There are many solutions to your problem but each has its own flaws.  I won't make a list here, but the very fact that you asked the question indicates that you need to learn some stuff.

xavier60

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #2 on: July 16, , 01:49:22 am »

Hi,

please bear with me, i am still trying to learn the basics.
I have built a full bridge rectifier using 4 diodes and a couple of uF capacitors in parallel. the secondary AC voltage of the transformer I am using is 26v which gets converted to around 38v DC with the rectifier.

I am trying to power a soldering iron controller with requires 26v DC with an output current of 6amps. What are my options to reduce the voltage to 26v DC with 6 amps current?

NB: I have tried a voltage divider with 10 k resistors as R1 and 25k as R2 which gave me the correct voltage but as soon as I plugged in the load the output voltage dropped to 3v.

Thanks in advance for your help.

The rectified voltage will still be 26V RMS with no capacitors. But it's likely that the controller needs filtered DC. Show us its schematic. « Last Edit: July 16, , 01:56:06 am by xavier60 » HP A dso, Fluke 87V dmm,  Agilent UA psu,  FY function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.

bobbydazzler

• Regular Contributor
• Posts: 137
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #3 on: July 16, , 02:05:51 am » 6amps you will probably need some kind of  switching power supply, also possible you need more capacitance on the output to the rectifier(to maintain the output voltage above 26v).  Resistive divider isn't going to work nor is some kind of linear psu because of the high current.

gbaddeley

• Regular Contributor
• Posts: 214
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #4 on: July 16, , 02:55:48 am »

6amps you will probably need some kind of  switching power supply, also possible you need more capacitance on the output to the rectifier(to maintain the output voltage above 26v).  Resistive divider isn't going to work nor is some kind of linear psu because of the high current.

A linear regulator will work, and is simpler than smps regulator, but is less efficient. If you can tolerate a few tens of watts of heat dissipation, use linear.

Alternatively, use a slightly lower voltage tranny, and bigger filter caps (10,000uF or more). Glenn

bobbydazzler

• Regular Contributor
• Posts: 137
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #5 on: July 16, , 03:27:20 am » Well it's for a soldering station, I'd assume the iron is the only thing that will actually run at 26v(the board most likely has a linear regulator onboard for the electronics).  In that case a linear supply with a giant heatsink/fan isn't practical I'd think, doubtful the soldering iron would care about a noisy 26v rail from a smps.

Anthocyanina

• Frequent Contributor
• Posts: 412
• Country:
• The Sara

Re: Reducing voltage on a full bridge rectifier

« Reply #6 on: July 16, , 03:31:31 am »

A linear regulator will work, and is simpler than smps regulator, but is less efficient. If you can tolerate a few tens of watts of heat dissipation, use linear.

Alternatively, use a slightly lower voltage tranny, and bigger filter caps (10,000uF or more).

wouldn't a linear regulator dissipate about 50-60W from dropping the voltage and feeding 6 amps to the load? this sounds like the job for a switched dc to dc converter

baltazar99

• Newbie
• Posts: 8
• Country:

xavier60

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #8 on: July 16, , 09:24:51 am »

the controller is a Hakko T12 clone from AliExpress.

https://www.aliexpress.com/item/.html?spm=a2g0o.detail..27.24fN2DqGs&gps-id=pcDetailBottomMoreOtherSeller&scm=...0&scm_id=...0&scm-url=...0&pvid=a55b4fd8-b22e--831a-bf22aa&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:...0,pvid:a55b4fd8-b22e--831a-bf22aa,tpp_buckets:668%230%%_668%%%234_%230%%230_%%%_668%%%_668%%%_668%%%_668%%%_668%%%230_668%%%&&pdp_ext_f=%257B%scene%%253A%%%257D

Only a single 26v voltage source is needed to power both controller and iron. the problem is that the maximum voltage it can handle is 30v which is less than the output from the bridge rectifier. I tried a LM regulator with input from the positive diodes and the voltage did not drop enough.

It actually states that it has a 30V 60A MOSFET, so that rules out supplying it directly with unfiltered 26V RMS pulsed DC which it could have so easily been designed to accept. I would rather power it from a conventional transformer instead of SMPS.
A linear regulator might be practical. The filtered DC will drop somewhat when loaded and what exactly is the current draw of a T12 cartridge?
HP A dso, Fluke 87V dmm,  Agilent UA psu,  FY function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.

Zero999

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #9 on: July 16, , 09:48:35 am » What's wrong with using an SMPS? Mains frequency transformers are big and bulky and linear regulators horribly inefficient.

Use a switched mode power supply.  Something like this.
https://www.meanwell-web.com/en-gb/ac-dc-single-output-power-supply-with-pfc-3-stage-enp--180--24

baltazar99

• Newbie
• Posts: 8
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #10 on: July 16, , 09:49:16 am » i am trying to use the controller with a C245 cartridge which draws 6 amps on 26volts. The controller can support many types of soldering tips. The power supply itself used to be for an old soldering station.

xavier60

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #11 on: July 16, , 09:52:46 am »

What's wrong with using an SMPS? Mains frequency transformers are big and bulky and linear regulators horribly inefficient.

Use a switched mode power supply.  Something like this.
https://www.meanwell-web.com/en-gb/ac-dc-single-output-power-supply-with-pfc-3-stage-enp--180--24

For me it's the possible EMI which would be a real problem for me. For most users it wouldn't matter.
I will try something like this some day. https://www.rchelicopterfun.com/t12-soldering-station.html
HP A dso, Fluke 87V dmm,  Agilent UA psu,  FY function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.

Zero999

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #12 on: July 16, , 10:02:16 am »

What's wrong with using an SMPS? Mains frequency transformers are big and bulky and linear regulators horribly inefficient.

Use a switched mode power supply.  Something like this.
https://www.meanwell-web.com/en-gb/ac-dc-single-output-power-supply-with-pfc-3-stage-enp--180--24

For me it's the possible EMI which would be a real problem for me. For most users it wouldn't matter.
I will try something like this some day. https://www.rchelicopterfun.com/t12-soldering-station.html

It's only a soldering iron, so I don't see how EMI is an issue. There are quite likely other things in your lab which emit more EMI such as LED lighting, mobile phones, Wi-Fi etc. A decent, SMP with good fitering, isn't very noisy.

xavier60

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #13 on: July 16, , 10:02:44 am »

i am trying to use the controller with a C245 cartridge which draws 6 amps on 26volts. The controller can support many types of soldering tips. The power supply itself used to be for an old soldering station.

It still can be done. Problem is, get it wrong, series pass transistors break down, controller's MOSFET then breaks down causing the iron to turn red hot before burning out. « Last Edit: July 16, , 10:08:44 am by xavier60 » HP A dso, Fluke 87V dmm,  Agilent UA psu,  FY function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.

PKTKS

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #14 on: July 16, , 10:03:11 am »

Hi,

please bear with me, i am still trying to learn the basics.
I have built a full bridge rectifier using 4 diodes and a couple of uF capacitors in parallel. the secondary AC voltage of the transformer I am using is 26v which gets converted to around 38v DC with the rectifier.

I am trying to power a soldering iron controller with requires 26v DC with an output current of 6amps. What are my options to reduce the voltage to 26v DC with 6 amps current?

NB: I have tried a voltage divider with 10 k resistors as R1 and 25k as R2 which gave me the correct voltage but as soon as I plugged in the load the output voltage dropped to 3v.

Thanks in advance for your help.

Just get one of these ...

** IT WILL SOLVE YOUR PROBLEM VERY NICELY **

You will have your bridge working at 36 with proper regulation
up to 24V at 5A should be more than enough

https://www.aliexpress.com/item/.html

Done a couple of these to myself
Affordable and reliable.

Paul

mikerj

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #15 on: July 16, , 10:16:28 am »

I have built a full bridge rectifier using 4 diodes and a couple of uF capacitors in parallel.

...
I am trying to power a soldering iron controller with requires 26v DC with an output current of 6amps.

Which diodes have you used in your bridge rectifier?  They'd better be big high current ones.

baltazar99

• Newbie
• Posts: 8
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #16 on: July 16, , 10:17:11 am »

i am trying to use the controller with a C245 cartridge which draws 6 amps on 26volts. The controller can support many types of soldering tips. The power supply itself used to be for an old soldering station.

It still can be done. Problem is, get it wrong, series pass transistors break down, controller's MOSFET then breaks down causing the iron to turn red hot before burning out.

Yes you are right, i have already fried a couple of cartridges getting red hot.

baltazar99

• Newbie
• Posts: 8
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #17 on: July 16, , 10:20:42 am » i have used IN
https://components101.com/diodes/1n-power-diode-pinout-equivalents-datasheet

PKTKS

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #18 on: July 16, , 10:23:22 am » get yourself a proper 5A bridge

https://www.aliexpress.com/item/.html

Mount on  a  good heatsink..

And hopefully your TRAFO can bear that..
Solder Irons pull huge spikes..

Paul

baltazar99

• Newbie
• Posts: 8
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #19 on: July 16, , 11:51:44 am » i managed to get the voltage down to 26v using 2 zener diodes in series but they got way too hot.
i will see what options people have been suggesting to be tried. It looks like an IC Regulator with variable output might be the best option. thanks to all for helping out

xavier60

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #20 on: July 16, , 12:04:37 pm »

i managed to get the voltage down to 26v using 2 zener diodes in series but they got way too hot.
i will see what options people have been suggesting to be tried. It looks like an IC Regulator with variable output might be the best option. thanks to all for helping out

You need to understand the relationship of voltage current and wattage.
To safely dissipate the approximately 72 watts of heat produced by the difference between 38 and 26 volts at 6 amps, you will need 4 large TO-247 power transistors on  a large heatsink. Something like large audio amplifier output transistor on a heatsink from a large audio amplifier.
The fact that the iron will be powered at some low duty cycle most of the time, makes things a bit easier.` HP A dso, Fluke 87V dmm,  Agilent UA psu,  FY function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.

Zero999

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #21 on: July 16, , 12:37:45 pm »

the controller is a Hakko T12 clone from AliExpress.

https://www.aliexpress.com/item/.html?spm=a2g0o.detail..27.24fN2DqGs&gps-id=pcDetailBottomMoreOtherSeller&scm=...0&scm_id=...0&scm-url=...0&pvid=a55b4fd8-b22e--831a-bf22aa&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:...0,pvid:a55b4fd8-b22e--831a-bf22aa,tpp_buckets:668%230%%_668%%%234_%230%%230_%%%_668%%%_668%%%_668%%%_668%%%_668%%%230_668%%%&&pdp_ext_f=%257B%scene%%253A%%%257D

Only a single 26v voltage source is needed to power both controller and iron. the problem is that the maximum voltage it can handle is 30v which is less than the output from the bridge rectifier. I tried a LM regulator with input from the positive diodes and the voltage did not drop enough.

A transformer and rectifier is a bad idea. The output voltage is unregulated and it's big and bulky. You'll be fine with any power supply between 24V and 28V, rated to at least 6A.

Here's another suggestion.
https://www.amazon.co.uk/Meanwell-Medical-Adapter-GSM160B24-R7B-Switching/dp/B07G59T56W

tunk

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #22 on: July 16, , 12:52:06 pm » An old laptop PSU/charger would probably work fine.
It is ~19-20V, but will work unless you need a very high power solder station.

tszaboo

• Super Contributor
• Posts:
• Country:
• Current job: ATEX product design

Re: Reducing voltage on a full bridge rectifier

« Reply #23 on: July 16, , 01:06:35 pm » The proper way of writing it is either:
FULL BRIDGE (shaky camera) rectifier
or
bridge rectifier

There is no in-between.

Zero999

• Super Contributor
• Posts:
• Country:

Re: Reducing voltage on a full bridge rectifier

« Reply #24 on: July 16, , 01:27:42 pm »

An old laptop PSU/charger would probably work fine.
It is ~19-20V, but will work unless you need a very high power solder station.

That will work, but bear in mind that, if it's designed for 26V, running at 19V, will only give you just over half of the maximum rated power. P = V2R, so 192/262 = 53%.

A bridge rectifier is a relatively simple but important electronic component, consisting of an arrangement of at least four diodes in a bridge circuit configuration. The main defining feature of a bridge rectifier diode is that its output polarity will always be the same, regardless of the polarity at its input terminals.

A key property of the diodes in a bridge rectifier is that they only allow current to flow through them in one direction. By arranging a series of diodes in a certain way, we can therefore ensure that the current output across the bridge rectifier is unidirectional, even if it is bidirectional at the input. As such, these diode devices are known as rectifiers, because they perform a process of current rectification (converting alternating current to direct current).

They play an important role in many types of device or circuit power supplies because raw AC power flowing from a mains source periodically changes its flow direction. As such, AC power effectively results in a back and forth motion of electrons coming from the mains source into the device circuitry.

For powering almost all device types based on a standard PCB electronic circuit, this bidirectional input current needs to be converted - or rectified - into a stream of electrons all flowing in the same direction. This results in a DC power (direct current) output signal, and thus a usable output Voltage from which the device or product in question can draw stable and consistent power.

The individual component that performs this key task in a discrete circuit is typically a diode known as a rectifier; specifically, a bridge rectifier, or diode bridge. Acting as a bridge rectifier is one of the most important roles for diodes in any type of electrical circuitry. Today, semiconductor diode bridges will be found in almost any electrically powered device.

A bridge rectifier arrangement is a particularly common feature of device power supplies. They effectively act as a transformer positioned between the AC socket input and the DC output that ultimately powers the circuitry and components in the device. Bridge rectifiers are typically attached to a circuit via a two-wire AC input connection.

This is also what would also happen in a simple electrical circuit if the flow direction of the input current was reversed. A rapid version of this effect is what an unmodified, or unrectified, AC power signal delivers - the flow of the alternating current continuously switches direction at very high speed.

The company is the world’s best Does a bridge rectifier reduce voltage? supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Without a component acting as a transformer to provide a DC input, something like an LED (the water wheel, in this comparison) attached to this AC circuit would flicker on and off repeatedly with the continual shifts in the current direction. This should illustrate why many electronic devices need a direct current (DC) power source to function properly.

In practice, the easiest way to answer the question ‘how do bridge rectifiers work?’ is to refer to a simple bridge rectifier circuit diagram. A basic bridge rectifier circuit clearly shows current always flowing in the same direction after passing through an arrangement of four diodes set in a bridge circuit, regardless of the polarity at the input.

With a suitable arrangement of four or more such diodes in a bridge circuit, you end up with a unidirectional or direct current output (DC power), regardless of the input current flow direction. In addition to performing this vital current conversion role, the same principle means that bridge rectifiers are also able to provide a degree of reverse-polarity protection.

Reverse polarity occurs when leads for a DC-powered device are connected back to front, or when batteries are inserted the wrong way up. Without a circuit component such as a diode bridge configuration in place, this reversed polarity can prevent the normal functioning of the product or device and may quickly damage the rest of a circuit under load.

Full-wave bridge rectifiers and half-wave bridge rectifiers ultimately perform the same role, but they each do so using slightly different methods. These components are sometimes referred to as full-bridge and half-bridge rectifiers. Due to differences in the way they handle incoming AC signals, there is an observable difference in overall operating efficiency (output voltage) between these two types of diode bridges.

• Full-wave rectification happens when the diode bridge actively converts the negative component of an AC input to a positive voltage and then rectifies the entire resulting signal into DC power (pulse current). This job is handled by two power diodes in the full-wave rectifier, one for each half of the waveform
• Half-wave rectification instead takes a different approach to the first step. Rather than converting the negative Voltage component, the half-wave rectifier uses a single diode to simply remove it altogether, before the rest of the bridge arrangement transforms the remaining half of the signal to a usable DC input

This means that full-wave rectifiers are more efficient than half-wave rectifiers because the full input waveform ends up being converted and used to power the rest of the circuit. This normally also results in a smaller ripple Voltage than can be observed using a half-wave bridge rectifier arrangement.

Ripple Voltages are an unwanted effect of signal smoothing processes and will vary depending on capacitance and load on a capacitor. Lower ripple Voltage means a more stable power signature, and thus a better overall flow of steady and smooth DC power to components and devices.

If you want to learn more, please visit our website China Fast Recovery Diode Manufacturer.