Common applications of low-end drivers in systems - MOS management

Common applications of low-end drivers in systems - MOS management

This article introduces some common applications that use low-end drivers in the system. The drivers of these power transformers involve isolated gate MOSFETs. It will include necessary calculations and graphical data to better demonstrate the evaluation made.

In many low to medium power applications, the low side (ground reference) MOSFET is driven by the output pin of the PWM control IC to switch inductive loads. If the PWM output circuit can drive MOSFETs with acceptable switching times without dissipating too much power, then this solution is acceptable.

As the power demand of the system increases, the number of switches and related driving circuits also increases. As the complexity of control circuits increases, it has become increasingly common for IC manufacturers to omit onboard drivers due to grounding and noise issues.

When it is important to improve efficiency and increase power VIN density, synchronous rectifiers (SR) are increasingly being used instead of standard rectifiers. Isolated power stages typically provide tens of amperes of current in each rectifier branch, in parallel with two or more low impedance MOSFETs, which require current pulses of several amperes to switch devices in the required time of less than 100ns.

External drivers can provide these high current pulses and offer a method to implement timing to eliminate through and optimize efficiency for controlling SR operations. In addition, the driver can convert the logic control voltage into the most efficient MOSFET driving level.

Low end drivers are also used to drive transformers, which provide isolated MOSFET gate drive circuits or communication across power isolation boundaries. In these applications, drivers are required to handle issues specific to transformer drivers.

Low end drivers, although typically represented as ideal voltage sources that can provide or absorb current determined by the series impedance of the circuit, in reality, the available current for the driver is limited by discrete or integrated circuit designs.