Synchronous or asynchronous? Select the right DC-DC converter to ensure boost system performance

    Did you know that for every 10°C increase in the environment, component life is reduced by 50%? [1] Will a steep drop or change in power supply cause premature failure or even complete burnout of system components? In fact, most people believe that power sensitive products require a durable and efficient power supply, which is essential. But what structure? Synchronous or asynchronous? Let‘s discuss the pros and cons of each of these two structures.

    Every hardware system requires a power supply, and the power supply voltage is mostly higher than the circuit requirements. For example, the power input is 9V, and it needs to be reduced to 5V to ensure the normal operation of the system. You have the following options:

    1. Parallel regulators with basic voltage regulation functions, such as Zener diodes. The Zener diode and its current limiting resistance reduce the voltage from 9V to 5V, and the Zener diode current limiting resistance has a voltage drop of 4V. This method generates heat and wastes energy.

    2.   5V linear Regulator (LDO). Similarly, if the input is 9V, the output is 5V; The pressure drop on the LDO is 4V. If the circuit consumes 1A current, the LDO dissipates 4W power. It can also be said that the wasted 4W of power is released as heat.

    DC-DC converter. In this way, the switch performs pulse width modulation (i.e. PWM) on the output inductance and capacitance. When the output voltage reaches 5V and the PWM duty cycle drops to near zero, the current consumed by the switch is very small, and the power loss of the response is also very low. This is undoubtedly the most efficient design choice.

    3. The input voltage of DC-DC converter can be any value, the standard value is 6V, 9V, 12V, 24V, 48V. Transformers reduce 120VAC to a standard voltage, then rectifier, filter, and adjust to a DC voltage for commercial or industrial equipment. For example, the phone system uses 48V, which is determined by the battery backup voltage. If the AC grid goes down, the battery backup system will be seamless. Portable devices are a different matter. These devices generally use DC power from the battery output, but require further voltage regulation. Because the battery voltage drops after a certain period of time, the output voltage needs to be boosted to maintain stability. If the system is operating at 3.3V, it needs to be maintained at 3.3V even if the battery voltage drops.

    In the design of the power supply, you can choose a "seemingly" low cost solution, such as the simple parallel regulator or Zener diode described above. Note that the reason we say "seemingly" low cost is only because it looks that way on the bill of materials. These methods have hidden and additional power consumption costs, which cause the system to heat up and shorten the life of the electronic components. In addition, the LDO output noise is very low, but the disadvantage is high power consumption, large differential pressure, and short battery life.

    Designers are now turning to DC-DC converters to achieve an optimal balance of output in terms of efficiency, heat dissipation, accuracy, transient response, and cost. Simple and direct is a good choice... But the process of achieving an optimal DC-DC power supply design is like navigating a minefield without a map. The operating temperature of the converter limits the maximum output power, and the operating temperature increases with the reduction of the size of the industrial equipment. In addition, most units generally do not have forced cooling/ventilation or have very limited cooling conditions. So, what‘s the best option for DC-DC?