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MOTIX™ 6EDL7141 PWM truncation – KBA237306

MOTIX™ 6EDL7141 PWM truncation – KBA237306

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Community Translation(JP): MOTIX™ 6EDL7141 PWMトランケーション – KBA237306

Infineon’s MOTIX™ 6EDL7141 gate driver IC has an inherent hardware-based PWM truncation protection that limits the current flowing into the motor by switching off the PWM signal immediately after overcurrent protection (OCP) detection.

For OCP detection, two overcurrent comparators are implemented to monitor the current in both positive and negative directions. Both comparators monitor the current flowing through the shunts. If PWM truncation is activated, the PWM module immediately interrupts the PWM signal without having to wait for the microcontroller to decide when the OCP level is reached. This ensures the fastest possible reaction time to the OCP event.

All the three GHx signals are pulled down automatically when the configured peak current level is reached. The low side remains unaffected until the PWM resets, increasing the current in the motor again. This happens on a PWM, cycle-by-cycle basis.

Figure 1 shows an example of how PWM truncation works.

Infineon_Team_0-1682926189412.pngFigure 1 Positive OCP PWM truncation work

Note: Truncation always occurs on the high side, except for the 1PWM mode with alternate recirculation, where the truncation occurs on the low side during high-side recirculation periods and on the high side during low-side recirculation periods.

If PWM truncation is active, PWM truncation takes place upon an OCP event in all phases. For example, if the protection is triggered in the current sense amplifier A, then PWM signals in phases A, B, and C will be truncated. This enables a single-shunt system to utilize any of the current sense amplifiers.

Blanking is applied to the truncation logic on both the rising and falling edges of the high side, as described in Figure 2; see register CS_BLANK for blanking times. Blanking from all phases is OR’ed, which prevents any mistriggering of the PWM truncation during the blanking time selected by the user.

If truncation is enabled, the deglitching filter is automatically disabled. This means that if truncation is enabled, the nFAULT pin signals that a PWM truncation has occurred. For this, the OCP fault trigger configuration bit (CS_OCPFLT _CFG) of the Current Sense Amplifier Configuration Register (CSAMP_CFG) has to be set to values other than b11 (see Table 1).

Table 1 CSA_OCP fault trigger configuration bit

Configuration bit

Bits

Type

Values

CS_OCPFLT _CFG

15:14

rw

Current sense amplifier OCP fault trigger configuration

OCP fault trigger configuration

b00: Count 8 OCP events

b01: Count 16 OCP events

b10: Trigger on all OCP events

b11: No fault trigger (PWM Truncation continues as defined in bitfield CS_TRUNC_DIS in register CSAMP_CFG2)

 


Infineon_Team_1-1682926328269.png

Figure 2 Current sense amplifier protections schematic block diagram

By default, the PWM truncation function is disabled in the BPA Motor Control GUI. Click "Enable" from the drop-down menu to enable this function, as shown in Figure 3.

Infineon_Team_2-1682926369679.png

Figure 3 Sceenshot BPA Motor Control GUI

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