**
Transformer** is used to convert

**high volt AC**to

**low volt AC**(

**Step down**) or low volt AC to high volt AC (

**Step up**). So step-down transformer is generally used to convert

**230 Volt AC**to low volt AC which can be used to make a

**DC power supply**after

**rectification**and

**smoothing**. But a

**Non polarized capacitor**can act like a transformer to step down the high volt AC to low volt AC. Say, 230 V AC to 40 VAC. Let us see how the capacitor is doing this.

See the above image. When a **capacitor** (**C**) and a **resistor** (**R**) are connected to AC lines, a **constant current** can be maintained through the** resistor** (R) so long as the **“Reactance”** of the Capacitor is greater than the **“ resistance”** of the Resistor. The current flow depends on the value of the capacitor assuming that **V1** (input voltage) is greater than **V2** (Output voltage). Thus the current through the resistor is

So theoretically, a **105 K 400 V** capacitor (**1 uF**) gives **70 mA** current through it when it gets **230 Volt AC**. This value changes when the value of the capacitor changes. That is , **high capacitance** gives **more current** and lower value less current. Anyway, the maximum current available will be between 70 mA and 150 mA in the capacitors now available. So these capacitors can only be used to make power supply for less current applications.

**Reactance** of the capacitor and its ability to deliver current are directly proportional. Reactance of the capacitor is expressed as

The **image** below shows a simple **Capacitor power supply** using 105 K 400 V capacitor. It gives 30-40 volts DC with a current of **60-70 mA.**

So after calculating the Reactance of the capacitor, it is easy to find the current delivering capacity. It is **important to note** that, the **current** from the capacitor depends on the **input voltage**. As you know, the AC voltage will not be steady normally. So if it drops to **200 V or less**, a corresponding **reduction** in the **voltage and current** will reflect in the output of the capacitor.

The **table** below shows the tested Voltage and current from different types of **X rated capacitors** now commonly used.

The **table** below shows the Tolerance codes of the **X rated capacitor**. Commonly, the capacitors are available as **K, J** etc after its **EIA code**. For example **105 K** means **1 uF** capacitor with **+ or – 10 % Tolerance**. So in actual use, its value may show a 10 increases or decrease.

**Caution:** The power supply based on the Capacitor is **dangerous** since it is directly connected to **high volt AC** without any galvanic isolation. So **do not** **construct** this kind of circuit unless you are competent and experienced to do that. A simple carelessness can give a **fatal shock** or **burst a fire**. **Do not test** or **trouble shoot** the circuit **when connected to mains**. Take all precautions while testing such circuits like wearing gloves and foot wear.