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BD9134MUV_14 Datasheet, PDF (11/25 Pages) Rohm – Synchronous Buck Converter with Integrated FET | |||
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BD9134MUV
4. Switching Regulator Efficiency
Efficiency η may be expressed by the equation shown below:
ï ï ï¨ ï½ VOUT ï´ IOUT ï´100 ï½ POUT ï´100 ï½ POUT ï´100 %
VIN ï´ LIN
PIN
POUT ï« Pdï¡
Efficiency may be improved by reducing the switching regulator power dissipation factors Pda as follows:
Dissipation factors:
(1) ON-Resistance Dissipation of Inductor and FETï¼Pd(I2R)
ï¨ ï© Pd I 2R ï¨ ï½ IOUT 2 ï´ RCOIL ï« RON ï©
Where:
RCOIL is the DC resistance of inductor.
RON is the ON-Resistance of FET.
IOUT is the Output current.
(2) Gate Charge/Discharge Dissipationï¼Pd(Gate)
Pdï¨Gateï© ï½ Cgs ï´ f ï´V 2
Where:
Cgs is the gate capacitance of FET.
F is the switching frequency.
V is the gate driving voltage of FET.
(3) Switching Dissipationï¼Pd(SW)
Pdï¨SW ï© ï½ VIN 2 ï´ CRSS ï´ IOUT ï´ f
I DRIVE
Where:
F is the reverse transfer capacitance of FET.
V is the peak current of gate.
(4) ESR Dissipation of Capacitorï¼Pd(ESR)
Pdï¨ESRï© ï½ I RMS 2 ï´ ESR
Where:
IRMS is the ripple current of capacitor.
ESR is the equivalent series resistance.
(5) Operating Current Dissipation of ICï¼Pd(IC)
Pdï¨ICï© ï½ VIN ï´ ICC
Where:
ICC is the circuit current.
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TSZ22111ã»15ã»001
11/21
TSZ02201-0J3J0AJ00150-1-2
03.Oct.2014 Rev.002
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