# Is transformerless power supply safe?

## Is transformerless power supply safe?

Here’s the punchline: transformerless power supplies are safely useable only in situations where the entire device can be enclosed and nobody can accidentally come in contact with any part of it. That means no physical electrical connections in or out — RF and IR are fair game.

### What is transformerless power supply?

Definition: A transformerless power supply converts high AC input voltage ( 120V or 230V) to the desired output DC low voltage ( 3V or 5V or 12V) with low current output in milliamps. It is used in low power electronic applications like LED bulbs, toys, and household appliances.

#### How are transformerless power supplies calculated?

Maximum Current

1. XC1 = 1/(2 x 3.14 x 50 x 680 x 10-9) = 4683Ω
2. X1 = XC1 // R1 = (XC1 x R1)/ (XC1 + R1) = (4683 x 470 x 103)/ (4683 + 470 x 103) = 4637Ω (Parallel Resistances)
3. Zener Voltage, Vz = 12V.
4. Vin = 230V.
5. Diode Drop, Vd = 0.7V.
6. I = (Vin – Vd – Vz)/(X1 + R1) = (230 – 0.7 – 12)/(4637 + 100) = 0.046A = 46mA.

What do you need to know about Transformerless power supply?

In this project, we will design Transformerless Power Supply for low current applications. Basically a transformerless power supply is just a voltage divider network that takes the 220V AC as input and divides it down to Lower DC voltage that we want. The AC voltage need is rectified through a few diodes and regulated to a maximum voltage.

How to calculate capacitor current in Transformerless power supply?

Before we understand the formula for determining and optimizing the mains capacitor in a transformerless power supply, it might be vital that you first summarize a regular transformerless power supply design. The following diagram demonstrates a classic transformerless power supply design:

## How many volts does a 400 V transformer supply produce?

For example, a 1 µF, 400 V (breakdown voltage) when connected to a 220 V x 1.4 = 308V (after bridge) mains supply will produce a maximum of 70 mA of current and an initial voltage reading of 308 Volts. However this voltage will show a very linear drop as the output gets loaded and current is drawn from the “70 mA” reservoir.

### Why are SMPS power supplies used instead of Transformers?

However, since the size of transformers cannot be compromised, circuits employing these kinds of power supplies tend to become quite heavy and bulky. SMPS power supplies are becoming pretty popular as they avoid the use of transformers and thus are able to maintain their compactness and weight to the lowest levels.