Why does this rectifier have a large AC output voltage?

In summary, the conversation discusses the creation of a bridge rectifier for a circuit to light up several LEDs. After completing the rectifier, the person measures the voltages between various points and notices an AC voltage between two points that were supposed to be DC-only. The AC voltage is almost twice the original transformer voltage. The image of the resistor code is blurry, but the person mentions it is 2.2k. They also mention using a multi-meter for AC voltage measurements and suggest using half a bridge rectifier and multiplying the peak voltage by 2. It is also suggested to use a capacitor to clean up the power supply and reduce noise. The person also shares a resource for understanding where the AC voltage is coming from.
  • #1
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I made a (bridge) rectifier for a simple circuit that would make several LEDs light up. When it was finished, I used a multimeter to measure the voltages between several points and got the readings you can see in http://users.pandora.be/k-a-d/rectifier.jpg". Why is there still an AC voltage between the two points that were supposed to be DC-only? And why is it almost twice the original transformer voltage? The resistor code is pretty blurry in the image; it's 2.2k if it helps.
 

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  • #2
How are you getting that 20V AC number? I'm guessing it's with a multi-meter of some sort. A cheap way to make AC voltage measurements is to use half a bridge rectifier, measure peak voltage, and multiply by 2.

You could test this by measuring the AC voltage of a battery using the same tool.

P.S. You might want to stick a capacitor in there to clean up the power supply. Otherwise it will be noisy.
 
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  • #3
Indeed, the reading comes from a multimeter. I simply switched between "V DC" and "V AC".
 
  • #4
Take a look at http://www.allaboutcircuits.com/vol_3/chpt_3/4.html" to see where you're getting the AC.

Regards
 
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1. Why is the AC output voltage of this rectifier so high?

The AC output voltage of a rectifier depends on the properties of the rectifying element used, such as diodes or transistors. It also depends on the input voltage and the type of rectifier circuit. If the rectifier is designed to have a high AC output voltage, it is likely due to the intended purpose and application of the rectifier.

2. What factors affect the AC output voltage of a rectifier?

The main factors that affect the AC output voltage of a rectifier are the input voltage, the type of rectifying element used, and the design of the rectifier circuit. Other factors such as temperature, load resistance, and component quality can also have an impact.

3. Can the AC output voltage of a rectifier be adjusted?

In most cases, the AC output voltage of a rectifier cannot be adjusted. However, there are some types of rectifiers, such as variable voltage rectifiers, that allow for some level of voltage adjustment. This is achieved through the use of additional circuitry or components.

4. Why is a high AC output voltage desirable in some rectifiers?

A high AC output voltage is desirable in some rectifiers because it allows for the efficient conversion of AC power to DC power. This is especially important in applications where a stable and reliable DC voltage is needed, such as in electronic devices. A high AC output voltage also reduces the need for additional voltage regulation circuits.

5. Can a rectifier with a high AC output voltage be dangerous?

Yes, a rectifier with a high AC output voltage can be dangerous if proper precautions are not taken. It is important to handle and use high voltage rectifiers with caution and to follow safety guidelines. Additionally, the high voltage can damage electronic components if not properly regulated and controlled.

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