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Dimmable Light Ballast with Power Factor Correction, Rev. 1
Freescale Semiconductor 33
4.2.4 Power Supply
The function of the switch mode power supply (SMPS) is to feed the inverter and output buffer circuit with
15
V and to supply the microcontroller stage by 5 V (see Table 4-3). The SMPS is supplied from the
DC-bus voltage. It uses the monolithic high-voltage regulator NCP1010 from ON Semiconductor
connected as recommended by the manufacturer. It can provide 15
VDC @ 100 mA. To achieve a 5 V
power supply from a 15
V source, a step-down resistor R32, 5V1 Zener diode D13, and filtering capacitor
C25 are used.
VCC
1
FB
2
DRAIN
3
GND
4
IC3
NCP1010-SOT223
12
+
C23
1uF
450V
1 2
+
C20
22uF
35V
1 2
C24
1nF 25V
L8
4.7mH
12
+
C21
100uF
35V
1 2
C22
1uF
25V
GND
1 2
C25
220nF
GND
1
23
4
U3
SFH6106
GND GND
D14
BZV55C13
D12
MURA160
15V/1
GND
R32
390R
D13
BZV55C5V1
GND GND
15V 5V
DCB
TL-RAD EZK
Figure 4-6. Dimmable Light Ballast — Power Supply
Table 4-3. Supplied Voltages
Voltage Supply
+15V Driving stage, Output buffer circuit
+5V Microcontroller stage