DGD2136

Document Number DS38611 Rev. 7 - 4

11 of 14

www.diodes.com

November 2021

© Diodes Incorporated

DGD2136

Design Notes

Over the past decade, in white goods, there has been a transition from AC motors to brushless DC motors; correspondingly power switching is

required to drive the BLDC motors. For even greater efficiency and cost reduction, 3-phase gate driver ICs are used to optimimally drive

MOSFETs and IGBTs. The DGD2136, 3-Phase Half-Bridge Gate Driver IC, is a good choice for 3-phase motor applications because of ease of

design, reliability, and less space used than 3 x single channel gate driver ICs.

In the inductive 3-phase motor circuit environment, MOSFET/IGBT turn-on produces significant current spikes; and the currents are the highest

and the system is the noisiest during startup. In certain applications, with significant noise on the ground lines of VSS-COM (for example during

startup), the DGD2136 is susceptible to the noise and can enter fault condition. And if the fault is long enough, the MCU will detect the fault

situation, disable inputs and turn off the system. In effect there is a stall at startup. Figure 27 and Figure 28 show startup in a 240V refrigerator

compressor application (FO*-MCU (blue) - fault signal at MCU, COM-VSS (yellow) and VS (green) - motor voltage).

This Design Tip will provide two solutions, depending on the current sense circuit, to decrease the IC ground noise and ensure the DGD2136 does

not enter fault condition and there is no stall at startup.

Solution 1

If the 3 phase current sensing configuration is similar to Figure 29 or Figure 30, then the best solution is to short the line between VSS and COM

directly at the IC. This provides a more stable ground at the IC, and the current sense circuit operates normally (see Figures 31 and 32).

Figure 27. During startup when the current is high,

COM-VSS noise is high (yellow), fault conditions

occur (blue), compressor will eventually stall, 2ms/div

Figure 28. During startup, current is high, COM-VSS

noise is high, fault conditions occur, compressor will

eventually stall, 100us/div

Figure 29. Shorting VSS-COM at IC for current sense

configuration A

Figure 30. Shorting VSS-COM at IC for current

sense configuration B