RD7 Просмотр технического описания (PDF) - Power Integrations, Inc
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производитель
RD7
Power Integrations, Inc
RD7 Datasheet PDF : 12 Pages
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RD7
Component Listing
Reference
Value
Part Number
Manufacturer
C1
C2
C3
C4
C5
C6
Cc*
Css*
D1
D2
D3
L1
RF1
R1
R2
R3
T1**
U1
U2
VR1
10 nF, 1 KV, Disc
2.2 nF 1 KV, Disc
270 µF 25 V
100 µF 25 V
47 µF, 10 V
0.1 µF, 50 V
0.1 µF, 50 V
5GAS10
DD222
ECA-1EFQ271
ECE-A1EGE101
ECE-A1AGE470
ECU-S1H104MEA
ECU-S1H104MEA
Cera-Mite
Philips
Panasonic
Panasonic
Panasonic
Panasonic
Panasonic
600 V, 1A, UFR
40 V, 3 A, Schottky
75 V, Switching
3.3 µH, 5 A
1 Ω Fuse Resistor 1/2 W
47 K, 1/2 W
10 Ω, 1/4 W
100 Ω, 1/4 W
Optocoupler, Controlled CTR
3.9 V, Zener, 2%
UF4005
1N5822
1N4148
622LY-3R3M
BW1/2F 1 Ω 5%
5053CX47K00J
5043CX10R00J
5043CX100R0J
TRD7
TOP221P or TOP221G***
LTV817A
1N5228C
General Instrument
General Instrument
Liteon
Toko
RCD
Philips
Philips
Philips
Custom
Power Integrations
Liteon
APD
Table 2. Parts List For the RD7. (* Optional, for Css values see Figure 9. **T1 is available from Premier Magnetics (714) 362-4211 as P/N
TDS-1185-9818, and from Coiltronics (561) 241-7876 as P/N CTX14-14193-X1. *** TOP221G can be used with layout modifications.)
General Circuit Description
The RD7 is a low-cost, flyback switching power supply using
the TOP221P. The circuit shown in Figure 2 provides a nominal
output power of 3.5 W at 5 VDC output. The power supply
operates from a DC voltage of 90 to 375 VDC. In a typical
application this DC voltage is derived from a rectified and
filtered AC main voltage of 85 to 265 VAC. The 5 V output is
directly sensed by optocoupler U2 and Zener diode VR1. The
output voltage is determined by the Zener diode (VR1) voltage
and the voltage drop across the optocoupler (U2) LED and
resistor R2. Other output voltages are possible by adjusting the
transformer turns ratios and the value of the Zener diode VR1.
The positive rail of the high voltage DC input is connected to
one side of the primary winding of T1. Capacitor C1 filters the
high voltage supply, and is necessary only if the connections
between the high voltage DC supply and the RD7 are long. The
other side of the transformer primary is driven by the integrated,
high-voltage MOSFET inside the TOP221. D1, R1, and C2
clamp voltage spikes caused by transformer leakage inductance
to a safe value and reduce ringing at the DRAIN of U1.
The secondary winding is rectified and filtered by D2 and C3
to generate a 5 V output. L1 and C4 provide additional filtering
to reduce high frequency ripple voltage. R3 and VR1 provide
a slight pre-load on the 5 V output to improve load regulation
at light loads. R3 also provides bias current for Zener VR1 to
improve regulation.
Soft start can be added to eliminate turn-on overshoot. With C
ss
placed across VR1, the optocoupler current is increased during
turn-on time. This increased current limits the duty cycle and
slows down the rising output voltage (See Figure 9). The bias
winding output is rectified and filtered by D3 and C6 to provide
a bias voltage for U2. C5 filters internal MOSFET gate drive
charge current spikes on the CONTROL pin, determines the
auto-restart frequency, and compensates the control loop. Cc is
needed when the supply is operating in a noisy environment
(e. g. when the power supply is sharing the same input rectifier
and filter capacitor with another power supply). C filters high
c
frequency noise.
The schematic of Figure 4 shows an enhanced version of the
RD7. The circuit comprising R2, R3, R4, R5 and U3 improves
overall output regulation to ±2%. Optional soft start capacitor
Css is used to eliminate turn-on overshoot. The bias supply
output can be used to provide a +12 V, non-isolated output by
changing C6 to 100 µF as shown in Figure 4. C6 is added to
reduce output ripple to a primary load.
The circuit performance data shown in Figures 5 to 12 was
3 B
4/99
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