L6726A_07 STMICROELECTRONICS [STMicroelectronics], L6726A_07 Datasheet - Page 11

• Manufacturer Part Number: L6726A_07
• Description: Single phase PWM controller
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

L6726A
5.1
Power dissipation
L6726A embeds high current MOSFET drivers for both high side and low side MOSFETs: it
is then important to consider the power that the device is going to dissipate in driving them
in order to avoid overcoming the maximum junction operative temperature.
Two main terms contribute in the device power dissipation: bias power and drivers power.
●
●
External gate resistors helps the device to dissipate the switching power since the same
power P
resulting in a general cooling of the device.
Figure 4.
Device Bias Power (P
supply pins and it is simply quantifiable as follow (assuming to supply HS and LS
drivers with the same VCC of the device):
Drivers power is the power needed by the driver to continuously switch on and off the
external MOSFETs; it is a function of the switching frequency, the voltage supply of the
driver and total gate charge of the selected MOSFETs. It can be quantified considering
that the total power P
dissipated by three main factors: external gate resistance (when present), intrinsic
MOSFET resistance and intrinsic driver resistance. This last term is the important one
to be determined to calculate the device power dissipation. The total power dissipated
to switch the MOSFETs results:
where V
SW
will be shared between the internal driver impedance and the external resistor
Soft start (left) and disable (right)
BOOT
P
SW
- V
=
PHASE
F
SW
SW
DC
is the voltage across the bootstrap capacitor.
⋅
) depends on the static consumption of the device through the
P
dissipated to switch the MOSFETs (easy calculable) is
[
DC
Q
gHS
=
⋅
V
(
CC
V
BOOT
⋅
(
I
CC
–
+
V
I
PHASE
BOOT
)
)
+
Q
gLS
⋅
V
CC
Driver section
]
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