Find out the latest advancements in the gate driver ICs and how these technologies help develop more reliable power converters.
Gate drivers are an integral part of switching power converters as they provide an interface between microcontroller and power switches like MOSFETs and IGBTs. The gate driver cores usually include all commonly required driver functions for easy integration. And the gate drivers must perform reliably as the output of a switching DC-DC converter mainly depends on the behavior of gate driver circuits. Following are all new advancements in gate drivers within the last year.
Low Propagation Delay
Propagation delay is an important aspect of gate drivers to be taken into consideration, especially for high switching frequency applications. Propagation delay refers to the delay between input value change and output value change. For faster response time, minimum propagation delay is desirable. Moreover, unmatched delay within multiple channel gate drivers degrades performance. Therefore, delay matching is required for robustness and high reliability when using channels parallelly. The latest gate drivers feature very low propagation delays.
Latest Microchip technology gate drivers feature 27ns typical delay times. Some of the Infineon technologies EiceDRIVER gate driver ICs present propagation delay of only 30ns and also combine delay matching features. Texas Instruments DRV8300 features typical 4nS propagation delay matching. Texas Instruments UCC27289 features propagation delay as low as 16ns. On Semiconductors NCP51810 indicates a maximum propagation delay of less than 50ns.
Improved Common-Mode Transient Immunity
Isolated gate drivers are very widely used in solar inverters, electric vehicles (EVs), network power, etc. The isolated gate drivers, in addition to driving MOSFETs or IGBTs, provide galvanic isolation. Common-mode transient immunity (CMTI) is an important parameter for high-frequency isolated gate drivers as they deal with a differential voltage between two separate ground references. CMTI is defined as the maximum tolerable rate of rising or fall of the common-mode voltage applied. In other words, CMTI dictates how fast common-mode transients can be subjected. It is measured in kV/us or V/ns, and high CMTI means that the two isolated circuits function correctly as per the specifications.
Infineon Technologies EiceDRIVER isolated gate drivers feature the highest CMTI of greater than 200kV/μs. TI’s isolated gate drivers UCC21710 and UCC21759-Q1 provide >150V/ns CMTI. Another isolated gate driver by TI, UCC23514, features a minimum 150kV/µs CMTI.
Soft Turn-Off and Miller Clamp
The desaturation (DESAT) fault detection feature in gate drivers protects power switches against short-circuit events. During such fault events, turning the power switch off too quickly can generate a high voltage spike at the power switch collector. Therefore, most latest gate drivers employ a soft turn-off sequence. The soft turn-off is done by increasing the gate voltage discharge time during the turn-off to reduce the rapid current changes after DESAT faults.
Miller clamp is not a new technique in gate drivers, but it is commonly used in the latest SiC gate drivers. One of the common problems faced when driving power switches like IGBTs is parasitic turn-on due to the miller capacitor. Therefore, a miller clamp is used that supplies the gate with a lower impedance path to reduce the chance of Miller capacitance induced turn-on.
Smart Gate Drive Architecture
Smart Gate Drive is an exclusive feature by Texas Instruments for enhancing gate drive operation to drive an electric motor. The Smart Gate Drive technology allows more control over external MOSFETs providing design engineers flexibility. This new architecture manages dead time to prevent shoot-through, controls slew rate to decrease electromagnetic interference (EMI), and optimizes propagation delay for optimal performance.
Gate drivers play an important role in rapid electrification of automobiles and development of renewable energy systems. As the demand for high efficiency power converters is increasing, there arises the need for high-performance gate driver ICs for various power electronics applications.
By: Darshil Patel
Technology Journalist, Electronics For You Enterprise.