AN10961_15 Datasheet, PDF (12/57 Pages) NXP Semiconductors – Dimmable CFL using the UBA2027X family

NXP Semiconductors
AN10961
Dimmable CFL using the UBA2027X family
At nominal lamp power, the average input current the charge pump delivers, the input
current and the input power are calculated in Equation 1 and Equation 2:
Average input current:
I_i(av) = f_s(hb) ⋅ C_y2 ⋅ V_i + f_s(hb) ⋅ C_y2 ⋅
------------^I--^L---^r--^e--^s------------
C_y2 ⋅ f_s(hb) ⋅ π
–
V_bus
(1)
Input power:
P_i
=
1_--
2
⋅
f_s(hb)
⋅
C_y2
⋅
V_i(p
2
k)
+
-²-
π
⋅
f_s(hb)
⋅
C_y2
⋅
V_i(pk)
⋅
-------------^I--^r--^e---^s-------------
C_y2 ⋅ f_s(hb) ⋅ π
–
V_bus
(2)
Where:
• V_i(pk) = peak input voltage
• f_s(hb) = the half-bridge switching cycle
• V_bus = bus voltage (see Figure 5)
See Ref. 3 for more information.
There is no unity power factor condition for the VSCS charge pump with enlarged
conduction angle. The second term in Equation 1 is always > 0, because the current
source charge pump is dominant over the voltage source charge pump.
The power delivered to the lamp is:
P_lamp
=
--^V----^l--^a---^m---^p---²--
ω_s ⋅ L_res
⋅



-_π----²-_â‹---_V^â‹---^V-_l-_a--^b-_m--^u-_p-^s_{}
2
⋅
(1
–
ω_s2
⋅
L_res
⋅
2
C)
–
(1
–
ω
2
s
⋅
L_res
⋅
(C
+
2
C_res))
(3)
Where:
• ω_s = 2π ⋅ f_s
• V_lamp = lamp RMS voltage
• L_res = resonant indicator
• C_res = resonant capacitor plus the equivalent resonant capacitor (see Section 5)
• C = inductive mode heating circuit secondary capacitance which is transferred to the
primary side.
The expression for P_lamp in Equation 3 has been derived using the equivalent circuit
shown in Figure 8.
AN10961
Application note
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 8 June 2012
© NXP B.V. 2012. All rights reserved.
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