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MOTIX™ 6EDL7141 PWM modes – KBA237228

MOTIX™ 6EDL7141 PWM modes – KBA237228

Vinay
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The MOTIX™ 6EDL7141 gate driver can be used for generating six gate driver signals for different PWM modes from an MCU as follows:

Table 1   PWM modes

S. No.

PWM modes

Number of independent PWM inputs

1

6-PWM mode

PWM with 6 independent inputs

2

3-PWM mode

PWM with 3 independent inputs

3

1-PWM mode

PWM with 1 input and commutation pattern

PWM with 1 input and commutation with Hall sensor inputs

PWM with 1 input and commutation with Hall sensor inputs and alternating recirculation

1  6-PWM mode


In 6-PWM mode, the MCU sends six PWM signals to the 6EDL7141 gate driver. The gate driver inserts a configurable dead time to the PWM signals and avoids a dead short circuit of the leg. When PWM signals from the MCU to the gate driver are sent as HIGH for both higher and lower switches of the same leg, (see the second case (highlighted in red), PWM inputs to the gate driver: INHx and INLx both are High(1) in
Table 2), the gate driver switches off both high and low switches, i.e., GHx and GLx are LOW. See the second case where GHx and GLx both are LOW in the truth table (Table 2), and note the duration of 0.02 ms to 0.04 ms in PWM signals.

Table 2  Truth table for 6-PWM mode

IFX_Publisher2_0-1681890178651.png

 From these PWM signals, at the instant 0.02 ms to 0.04 ms, a dead short circuit happens from the controller side, the PWM High-side and Low-side switches are both switched ON, which must be avoided from the gate driver; during dead short circuit, the gate driver will not drive the switches.

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Figure 1   6-PWM mode: MCU pulses to the gate driver signal

6-PWM mode is used in applications such as light EVs, power tools, and gardening tools that require control of torqueand speed for BLDC motors.

2  3-PWM mode

In 3-PWM mode, the MCU sends three PWM signals to the 6EDL7141 gate driver. The gate driver inserts the dead time to the PWM signals and generates six gate driving signals from these three PWM signals sent from the MCU.

IFX_Publisher2_1-1681890382572.png

Figure 2  3-PWM Mode: MCU pulses to the gate driver signal

Three PWM signals are sent from the MCU to 6EDL7141 as shown in Figure 2. The remaining three PWM signals can be given with different frequencies (ULo, VLo, and WLo) as shown in Table 3.

IFX_Publisher2_0-1682586005979.png

From these PWM signals, note that the gate driver signals depend on the Low-side PWM signals (INLx).

  • If Low-side PWM signals (INLx) are LOW, and High-side PWM signals are HIGH, GHx are HIGH and GLx are LOW; if High-side PWM signals are LOW, GHx is LOW and GLx is HIGH.

INLx --> LOW

INHx --> HIGH

GHx --> HIGH

GLx --> LOW

INHX --> LOW

GHx --> LOW

GLx --> HIGH


  • If Low-side PWM signals (INLx) are HIGH, the output of the gate driver signals are LOW, i.e., GHx and GLx are LOW.

3-PWM mode is used in applications such as light EVs, power tools, and gardening tools which require contol of torque and speed for BLDC motors.

3 1-PWM mode

3.1  PWM with 1 input and commutation pattern

When the PWM_MODE register is set to b'010, 6EDL7141 is configured to 1-PWM mode. In this case, the duty cycle and frequency of the INHA signal is used to determine the duty cycle (or amplitude) and the frequency of the PWM outputs generated by 6EDL7141. The rest of inputs are captured to decide the commutation pattern or state of the outputs.

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Figure  3    1-PWM mode: PWM with 1 input and remaining commutation pattern

Table 4  

Signal

Description

INHA

PWM input. Defines the PWM output duty cycle and frequency

INLA, INHB, INLB

Provides timing for modulation pattern changes

INHC

Signalizes 12 step states. Must toggle every electrical 30 degrees.

INLC

This input is ignored in this mode. Recommended pull-down.

VSENSE/ nBRAKE signal

When active, 6EDL7141 will force the motor to brake

GHA, GLB, GHB, GLB, GHC, GLC

Complementary PWM output signal

3.2    PWM with 1 input and commutation with Hall sensor inputs (1-PWM mode with diode freewheeling)


To enable this, configure the PWM_MODE bitfield to value b'011. The truth table presented in
Table 5 dictates the commutation pattern. In this mode, 6EDL7141 together with the Hall sensor inputs determines the switching pattern of the PWM output signals. The duty cycle and frequency of the output signals is determined by the INHA duty cycle and frequency.

In 1-PWM mode, the MCU sends a PWM signal to the 6EDL7141 gate driver. The gate driver inserts the dead time to the PWM signals and generates six gate driving signals from the one PWM signal sent from the MCU. Of these six signals, one PWM signal is sent from the MCU to 6EDL7141, while the remaining five PWM signals can be open (all LOW) or can be given from the Hall sensor signals as shown in Figure 3.

Infineon_Team_2-1680516172245.png


Figure 4   1-PWM mode: PWM with 1 input and commutation with Hall sensor inputs

Infineon_Team_1-1680516087838.png

Figure  5 Phases energizing with respect to rotor position (CCW rotation)

Table  5 Truth table for PWM with 1 input and commutation with Hall sensor inputs

IFX_Publisher2_1-1682586127042.png

From Table 5, for Hall signals 101 in the CCW direction and for Hall signals 010 in CW direction, the same gate driver signals are given to switches. This means that the upper switch of A phase and lower switch of C phase are switched ON. The color coding refers to the same PWM switching for different rotor positions in CCW and CW directions respectively.

Note that when rotor is in (–30°, 30°] CCW rotation, AC phases are switched ON, and when rotor is in (150°, 210°] CW rotation, AC phases are switched ON i.e., 180° phase difference between CCW rotation and CW rotation.

Table 6  Truth table for PWM with 1 input and commutation with Hall sensor inputs

IFX_Publisher2_1-1681890081895.png1-PWM mode is used in open loop control applications.
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