High-side and low-side gate driver is widely used in half-bridge, full-bridge, push-pull, synchronous buck, two-switch forward, active clamp forward converters. Infineon has a wide portfolio of high-side and low-side gate driver, and always promotes the product to the newest technology and best performance generation. In this article, the new generation 120V boot high-side and low-side driver 2EDL803X is introduced.
This article introduces 6 improvements that the new generation compared to the previous generation 2EDL8x2x.
Improvement 1: Increased HB breakdown voltage
Below shows the HB I-V curve comparison of 2EDL8x2x and 2EDL803x as well as the competitor device UCC27201A at VDD=12V and room temperature. The 2EDL8x2x shows a lower HB level (~112V) where the current starts to increase whereas the 2EDL803x shows a higher level (~129V). Also, the current leaking in 2EDL803x is significantly lower compared with the 2EDL8x2x.
Improvement 2: Lower HB quiescent current
HB quiescent current is the current consumed in the high-side section of the driver when there is no PWM switching. The HB quiescent current of 2EDL803x has been reduced significantly as can be seen in the graph below:
2EDL8x2x HB QUIESCENT CURRENT 2EDL803x HB QUIESCENT CURREN
Improvement 3: Lower boot diode voltage drop
2EDL8x2x
Due to technology limitation, the internal boot diode is implemented using 2 diodes in series to achieve the 120V HB requirement. This resulted in a higher diode voltage drop of ~2.1V @IF = 100mA.
2EDL803x
The technology used allows the implementation of the internal boot diode using a single device that can support the 120V HB requirement. The result is a lower diode voltage drop (~1.4V) compared with 2EDL8x2x.
Improvement 4: Lower propagation delay
The two generations driver propagation delay time is as below:
2EDL8x2x
2EDL803x
Lower propagation delay means faster response time. It is desirable especially for high switching frequency application
Improvement 5: Improved HB-HS UVLO Release Time
2EDL8x2x HB-HS UVLO Implementation
When the boot voltage is too low, the propagation delays of level shifter and pre-driver are prolonged. This creates a pulse prolongation which, especially at turn-off, can induce cross-conduction.
A 5us UVLO delay time and a PWM synchronization scheme in the level-shifter are implemented as a safety logic to guarantee operation with suitable supply voltage and, thereby, preventing shoot-through. The UVLO synchronization is done in such a way that the HO output is blocked when UVLO is released while the HI is high. HO is only propagated when the UVLO is released while the PWM is low.
2EDL803x HB-HS UVLO Implementation
The UVLO has much shorter delay time. No PWM synchronization is used. The faster level-shifter allows for fast turn-off of HO without pulse prolongation.
Improvement 6: Removed transient detector
2EDL8x2x Level Shifter with Transient Detector
The transient detector is designed to prevent re-toggling of the HO output caused by the phase node movement. The re-toggling is a known weakness in the level shifter brought by the special design needed to overcome technology limitations, in particular very high parasitic capacitances to ground. The transient detector monitors the phase node movement and blocks the HO output from changing state whenever the rate of change is larger than the dV/dt activation threshold (~0.2V/ns). The decision to change state will only propagate through if the transient detector active state is removed, meaning when the phase node dV/dt is below the activation threshold.
Customer’s measurement on a brick board: turn-off time of the secondary side MOSFET varies due to the transient detector activation as the input voltage is swept from 48V to 54V
2EDL8x2x secondary side waveform sweeps from 48V to 54V input
2EDL803x More Robust Level Shifter
For the 2EDL803x, this transient detector block is already removed because the technology used in this driver already allows for HV devices that can meet the 120V HB requirement.
Customer’s measurement on a brick board: turn-off and dead-time of the secondary side MOSFET is almost constant thanks to the more robust level shifter and missing transient detector
2EDL803x secondary side waveform sweeps from 48V to 54V input
Summary
Thanks to the 6 improvements, the new generation 2EDL803x gate driver can have better performance in half-bridge, full-bridge, push-pull, synchronous buck, two-switch forward, active clamp forward converters applications.