DIY Voltage Doubler & Multiplier – Easy Circuits for High Voltage

Voltage doublers and voltage multiplier circuits are used to increase the voltage. They are a better alternative compared to step-up transformers. We often use them to convert AC voltage to a higher DC voltage.

Voltage multiplier circuits are useful in applications that need a very high voltage, such as industrial lasers and air ionizers. With that said, we also use it in a lower-voltage application, like a simple 9VAC to 25VDC converter circuit.

Today, we (I, my son and you) will learn how voltage doublers and multipliers work, explore their circuit configurations, and build a basic low-voltage tripler circuit. There will also be several example circuits, including doubler, tripler, and quadrupler circuits, as well as full- and half-wave variants.

Half-Wave Cascade 9VAC to 25VDC Voltage Doubler Circuit

This circuit is also known as the half-wave voltage doubler or Grainasher circuit. The circuit itself is quite simple; it consists of an AC source connected to two capacitors and two diodes. Apart from doubling the voltage, this circuit also acts as an AC-to-DC converter.

You may wonder why the output is 25V instead of 18V when the input is 9V (9 × 2 = 18). The answer is because DC voltage is 40% (×1.4) higher than AC voltage. And the voltage from the transformer is alternating current (AC), whereas the voltage across the capacitor is direct current (DC). […]

Real-World Circuit Behavior

Furthermore, we have already tested this circuit to see its real-world electrical characteristics. In short, we measure the DC voltage of both capacitors. Here are the results we found.

Unsurprisingly, the circuit works. The voltage across C1 is about 12.4V, while the voltage across C2 (the output) is twice that, at 25V. If you would like to try this circuit for yourself, here are the parts that we used.

We use this principle in the LED VU Meter circuit using transistors or ICs. And Crystal Tester Circuit.
The audio signal (AC) is boosted to a higher DC voltage for the next transistor stage.
This is a good idea because it’s simple and inexpensive.

Full-Wave 9VAC to 25VDC Voltage Doubler Circuit

This is another form of a voltage doubler circuit, which we may refer to as a full-wave voltage doubler. It uses the same components as the previous circuit. It still converts AC to DC and doubles the voltage, but it does it in a different way.

This circuit charges two capacitors with an opposite polarity voltage. The positive capacitor acts as the positive supply, whereas the negative one acts as the GND. The output voltage is the potential difference between the two capacitors’ voltages.

If that sounds a little confusing, the circuit schematics will help clear things out.

We can divide the full-wave doubler into two rectifier circuits. These two circuits, which are half-wave rectifiers (A.K.A. the Villard circuit), convert AC to DC. The first circuit produces a positive voltage while the other a negative voltage.

• The circuit on the upper left receives 9VAC and outputs +12.4VDC, a negative voltage rectifier. 
• The circuit on the lower left receives the same 9VAC but outputs -12.4VDC, a positive voltage rectifier. 

So, if we combine these two circuits into one, we will get a circuit that can supply DC voltage at +12.4V and -12.4V while using the same GND. But also, the potential difference between +12.4V and -12.4V is about 25V (doubles the voltage). 

Thus, if we use that to our advantage and connect a load to both the positive and negative outputs, we will have a 25V power supply. Still, we have also tested this circuit on a breadboard and measured the output voltage to be at 25V, as seen below.

Note: In this experiment, my son used non-polarized capacitors (10µF  50V) to avoid any mistakes with polarity.

Read more: All Power Supply Circuits on our sites.

Full-Wave Voltage Quadrupler Version

You may notice that the full-wave voltage doubler above uses the same half-wave rectifier as the first doubler circuit. So, what will happen if we do a full-wave version of the first doubler circuit? 

The answer is this full-wave voltage quadrupler circuit. It converts 9AC to 50VDC, and it is basically two Grainacher circuits with opposite polarities.

This circuit combines the idea behind the previous full- and half-wave voltage doubler circuits to get a voltage quadrupler. Much like the previous circuit, we can separate the circuit into two:

• The upper half, which is a positive doubler, produces a positive voltage (+25V). 
• The lower half of the circuit, a negative doubler, outputs a negative voltage (-25V).

The potential difference between +25V and -25V is approximately 50V. So, if we connect a load to this, it will receive 50V in total. And because this is a full-wave quadrupler, it is superior to the half-wave one created by cascading two half-wave voltage doublers.

Read also: Ultimate Guide to Dual Power Supply Circuits (Beginner-Friendly)

Bridge Voltage Doubler Circuit

This circuit uses a diode bridge rectifier to convert AC into positive and negative DCs. It then uses the potential difference between the outputs to double the output voltage. Because of the diode bridge, it requires more components compared to the full-wave doubler form earlier.

Half-Wave Cascade 9VAC to 38VDC Voltage Tripler Circuit

Now, we already mentioned both the voltage doubler and quadrupler; how about the one in between, the voltage tripler? That would be this 9VAC to 38VDC half-wave voltage tripler circuit. It may look different, but it actually is the first circuit with one extra diode-capacitor cell.

Real-World Circuit Behavior

The next thing is to see the circuit characteristic. So, in the same breadboard shown above, measure the DC voltage across each capacitor. The results we end up with are the following.

The voltage across C2 (the first capacitor) is about 12.4V. For C1, it is at 25V. Lastly, C3 has a voltage roughly triple that of C2 at 38V.

Common Problems and Tips With Voltage Multiplier

There are a couple of tricky things about designing a voltage multiplier. So, we list some of the problems we ran into in the past below as useful tips. Taking the following into consideration, it will make working with a dangerous high-voltage circuit a little bit safer.

Components Voltage Rating

One of the most crucial factors when designing a voltage multiplier is the maximum voltage rating of the components. If we choose components with a lower voltage rating than the actual voltage, they may become damaged or broken. […]

Designs And Components

In all the example circuits above, we have used the polarized Electrolytic capacitors. However, non-polarized capacitors, such as those made from Mylar or Ceramic, also work. The reason we use the Electrolytic capacitors is that they have a higher capacitance.

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