DC-to-DC converter
[1][2] Where higher power was needed, a motor–generator unit was often used, in which an electric motor drove a generator that produced the desired voltage.
(The motor and generator could be separate devices, or they could be combined into a single "dynamotor" unit with no external power shaft.)
[3] Although by 1976 transistor car radio receivers did not require high voltages, some amateur radio operators continued to use vibrator supplies and dynamotors for mobile transceivers requiring high voltages although transistorized power supplies were available.
[4] While it was possible to derive a lower voltage from a higher with a linear regulator or even a resistor, these methods dissipated the excess as heat; energy-efficient conversion became possible only with solid-state switch-mode circuits.
DC-to-DC converters are used in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries primarily.
DC-to-DC converters which are designed to maximize the energy harvest for photovoltaic systems and for wind turbines are called power optimizers.
Transformers used for voltage conversion at mains frequencies of 50–60 Hz must be large and heavy for powers exceeding a few watts.
DC-to-DC techniques that use transformers or inductors work at much higher frequencies, requiring only much smaller, lighter, and cheaper wound components.
Switching conversion is often more power-efficient (typical efficiency is 75% to 98%) than linear voltage regulation, which dissipates unwanted power as heat.
[5] The higher efficiency of a switched-mode converter reduces the heatsinking needed, and increases battery endurance of portable equipment.
Another important improvement in DC-DC converters is replacing the flyback diode with synchronous rectification[6] using a power FET, whose "on resistance" is much lower, reducing conduction losses.
However, all switching regulator topologies can be made bidirectional and able to move power in either direction by replacing all diodes with independently controlled active rectification.
Like all high-frequency circuits, their components must be carefully specified and physically arranged to achieve stable operation and to keep switching noise (EMI / RFI) at acceptable levels.
In these DC-to-DC converters, energy is periodically stored within and released from a magnetic field in an inductor or a transformer, typically within a frequency range of 300 kHz to 10 MHz.
The vibrator oscillated mechanically, with contacts that switched the polarity of the battery many times per second, effectively converting DC to square wave AC, which could then be fed to a transformer of the required output voltage(s).
