DC/DC converters – reliable voltage supply for on-board systems and vehicles
Many navigation devices, radios, GPS receivers, sensors and electronic loads are designed exclusively for 12 V. In vehicles and on-board systems with a 24 V battery bank, a DC/DC converter is the technically clean way to provide the required 12 V – without an extra 12 V battery, without a separate charger and without uneven battery load. philippi supplies the converter ranges from alfatronix for this purpose.
In brief: A DC/DC converter produces a stable, regulated 12 V supply from the 24 V battery voltage. This eliminates an additional 12 V battery with charger and the harmful practice of tapping a partial voltage from the 24 V battery bank.
Why a DC/DC converter instead of a centre tap on the battery bank?
Uneven loading of individual batteries through a direct partial-voltage tap considerably shortens the service life of the battery system and leads to unstable voltage. A DC/DC converter draws current evenly from the entire 24 V system – the batteries are loaded equally and the output voltage remains stable and regulated.
Typical applications
Navigation devices and chartplotters, radios and VHF marine radio, GPS systems and AIS receivers, radar and communication technology, sensors and controls, vehicle electronics in trucks and commercial vehicles, and measuring and monitoring systems.
Common technical features of the PV S and PV i series
Compact, robust aluminium housing with nylon end caps, switch-mode technology in SMD design, electronic protection against overheating and overvoltage, reverse polarity protection via internal fuse, 6.3 mm blade connections, supplied with mounting clip.
| Feature | Details |
|---|
| Input voltage range | 17–32 V |
| Output voltage | 13.6–13.9 V (regulated) |
| Efficiency | typ. 93 % |
| Protection class | IP 53 |
| Mounting | Mounting clip (supplied) |
| Warranty | Manufacturer's lifetime warranty |
All versions at a glance
PV S series – standard, without galvanic isolation
The compact standard solution for all common 24 V to 12 V applications.
| Model | Continuous output | Typical use |
|---|
| PV 3S | 3 A (36 W) | Single small loads, sensors |
| PV 6S | 6 A (72 W) | GPS, VHF radio, navigation |
| PV 12S | 12 A (144 W) | Several loads, instrumentation |
| PV 18S | 18 A (216 W) | Larger groups of loads |
| PV 24S | 24 A (288 W) | Extensive 12 V supply |
PV i series – with galvanically isolated output
For isolated power supplies on boats and in vehicles. Galvanic isolation prevents ground loops, protects sensitive electronics and is particularly recommended on aluminium and steel boats and in systems with several grounding points.
| Model | Continuous output | Typical use |
|---|
| PV 3i | 3 A (36 W) | Sensors, sensitive electronics |
| PV 6i | 6 A (72 W) | Navigation devices, radio |
| PV 12i | 12 A (144 W) | Several isolated loads |
| PV 24i | 24 A (288 W) | Extensive isolated supply |
DD 24-12 600 – high-power converter for large currents
For high 12 V current demand in a 24 V system: 50 A (600 W) continuous – the most powerful converter in the range, for example for motor yachts and commercial vehicles.
DD 12-24 – step-up converter from 12 V to 24 V
For the opposite case – 24 V loads in 12 V systems:
| Model | Input | Output | Power |
|---|
| DD 12-24 72 | 12 V | 24 V | approx. 3 A (72 W) |
| DD 12-24 240 | 12 V | 24 V | approx. 10 A (240 W) |
| DD 12-24 600 | 12 V | 26.5 V | 600 W |
DDi 12-12 / DDi 24-24 – same voltage, galvanically isolated
The DDi series does not convert the voltage but isolates input and output galvanically at the same voltage – for example to decouple navigation computers, communication systems and sensitive measuring equipment from the rest of the system.
| Model | Voltage | Continuous output |
|---|
| DDi 12-12 36 | 12 V / 12 V | 3 A |
| DDi 12-12 72 | 12 V / 12 V | 6 A |
| DDi 24-24 240 | 24 V / 24 V | 10 A |
Galvanic isolation – when necessary, when recommended?
Necessary for: aluminium and steel boats (avoiding ground loops), professional communication and navigation systems, systems with several independent grounding points.
Recommended for: sensitive measuring electronics, radios, computers and tablets on board – wherever interference and hum loops could impair function.
Not strictly required for: simple 12 V loads in well-structured systems with a clean grounding point.
Frequently asked questions about DC/DC converters
What is the difference between PV S and PV i?
Both series convert 24 V into regulated 12 V and are technically identical in design. The difference: the PV i series has a galvanically isolated output that completely separates input and output electrically. This is recommended wherever ground loops or interference are a problem, for example on aluminium and steel boats.
What output do I need?
The required continuous output is the sum of all connected 12 V loads, plus some reserve. For individual navigation devices and radios, 3 to 6 A is usually enough; for several loads, 12 to 24 A is recommended. For very high 12 V demand in a 24 V system there is the DD 24-12 600 with 50 A.
Why not use a centre tap on the 24 V battery bank?
A centre tap loads the two 12 V batteries of a 24 V bank unevenly. The more heavily loaded battery discharges faster, leading to capacity differences, premature wear and, in the worst case, failure of the entire battery bank. A DC/DC converter, by contrast, draws current evenly from the whole 24 V system.
How is the converter mounted?
The PV S and PV i converters are inserted into the supplied mounting clip and connected via 6.3 mm blade terminals. This is quick, saves space and simplifies servicing: they can be replaced without tools. As with any load, the supply cable is sized and fused according to the input current.
Are there converters for other voltage combinations?
Yes. In addition to the 24 V to 12 V converters, there are step-up converters from 12 V to 24 V (DD 12-24), converters from 48 V to 12 V (DD 48/12) and galvanically isolating converters with the same voltage for 12 V/12 V and 24 V/24 V (DDi). This allows mixed systems to be supplied cleanly too.
