ALL HI!
At present, lm5176 is used to design the circuit, with input of 8 ~ 36V and output of 12V / 12a. Two upper tubes and two lower tubes are used in parallel to form buck and boost circuits.How to calculate the power consumption of lm5176 itself at the maximum output power. thank you! The power consumption of lm5176 is the sum of the power consumption of VIN and VCC?
HI! Stefan!
Thank you for your reply！
My understanding is that the power consumption of lm5176 includes the sum of VIN and VCC power consumption. Vin can be replaced by Vbias power supply. Vin is used to drive the low-end field tube and the logic power supply inside the chip, while VCC is mainly used to drive the high-end field tube. According to which current is VIN calculated? Is it operating current according to VIN in IQ? Maximum 4mA? The current driving the field tube is ihdrv1,2 and ildrv1,2 current?Can you provide the calculation formula and parameters?Is it calculated according to the current parameters indicated by the arrow in the figure below?
HI Sheng,
Vcc is used to drive the low side driver as you can see from below figure from the datasheet:
The supply for the high side is generated by the small external charge pump (Diode / C ) on SWx and BOOTx
Best regards,
Stefan
What is the maximum current consumed by the internal linear regulator? How to determine this?As shown in the figure below, is it 4mA or 65mA? Or how much current?
The above logic working current is calculated according to 4mA?If Vbias is used instead of VIN, what is the current?
Hi Sheng,
the current is the same but the losses in the linear regulator will be different.
please not that Vcc will be regulated to
this means the the voltage on the linear regulator (Vin or Bias side) multiplied by the current will show up as losses in the device.
So it depends on which path is used and what is the voltage level there.
Best regards,
Stefan
HI! Stefan!！
As shown in the figure below, the power consumption of the driving part of lm5176 is calculated according to the current and resistance in the figure? P=I2R？How does the driving power consumption of lm5176 distinguish between full load and no-load output?
HI! Stefan!！
Is it how to calculate the power consumption of the upper and lower tube driving circuit in the figure below?
HI! Stefan!！
How is PD calculated in the figure below? I use the design function of TI official website to obtain power consumption.
Hi Sheng,
you can use following formulas:
Switching Current
=(Vin-Vdd)*Fsw*(Qg_Q1+Qg_Q2)+(RHDRV1,2pullup+RHDRV1,2pulldown)*Fsw*Qg_Q1*Vdd/(RHDRV1,2pullup+2*Rgate1+RHDRV1,2pulldown)+(RLDRV1,2pullup+RLDRV1,2pulldown)*Fsw*Qg_Q2*Vdd/(RLDRV1,2pullup+2*Rgate2+RLDRV1,2pulldown)
Switching Current Loss
Buck: (Qg_Q1+Qg_Q2)*Fsw*Vin;
Boost:(Qg_Q3+Qg_Q4)*Fsw*Vin;
BB: (Qg_Q1+Qg_Q2+Qg_Q3+Qg_Q4)*Fsw/2)*Vin
with this mapping
Best regards,
Stefan
HI! Stefan!！
VDD is the output voltage of the internal linear regulator?
Internal logic power consumption P = (vin-vcc) * IQ (4mA) calculation of lm5176? If I use Vbias as the input voltage, the internal logic power consumption P = (vbias-vcc) * IQ calculation? What is the IQ current value at this time? Note: VCC is the output voltage of the internal linear regulator.
The driving voltage of Q2 field tube is the output voltage of internal linear regulator (7.35v). What is the driving boost voltage of Q1 field tube?
Hi Sheng,
you are right Vdd and Vcc are identical in this conversation. (Just the source where i took this information used different names).
So Vdd is the output of the regulator.
Yes, if VBias is used then vin needs to be replaced by VBias in the above formula.
IQ is independent of VBias or Vin (as long as the voltage is above Vcc).
The supply for Q1 is generated by the small charge pump between BOOT1 and SW1
Best regards,
Stefan
HI! Stefan!！
I probably understand the calculation method of chip power consumption. Now let me calculate, please help confirm whether it is correct.
The design input voltage of the power supply is 8 ~ 36V, but it is usually 24V input, so the input voltage Vin = 24V and the output voltage is 12V / 12A.
Most of the time, the circuit works in the buck mode, so I first calculate the chip power consumption according to the buck circuit mode.The field tube used in the step-down circuit is csd18532q5b. His Qg= 44nc.
Calculated according to Buck: (qg_q1 + qg_q2) * FSW * VIN, PD = (4 * 44 * 10 ^ - 9) * 400 * (10 ^ 3) * 24 = 1.689w.（FSW=400K）
Total power consumption Pt = logic circuit power consumption + drive circuit power consumption. PT=((VBIAS-VCC)*Iq)+1.689=((12-7.35)*4*10^-3)+1.689=1.707W.According to the chip manual, IQ = 4mA
Then the power consumption of the chip in step-down mode is 1.707w. Is this right?
HI! Stefan!！
According to my circuit design above, the switch MOS tube and freewheeling MOS tube of buck circuit use two MOS tubes in parallel respectively. When calculating power consumption, do not consider four MOS tubes?
