An349, And link (v, Is reached. - the exl core counts until t – Cirrus Logic AN349 User Manual
Page 5: Gnd ifb iac, Stby, Switching frequency of l6562 across line
AN349
AN349REV1
5
Figure 7. CS1601 Block Diagram
The basic principle of operation of the L6562 can be summarized as follows:
-
The L6562 is a CRM controller which sets a peak current reference which is a function of the line voltage multiplied with
the output of the error amplifier.
-
During the design phase, the maximum steady-state power is defined by the current-sense resistor setting the
overcurrent threshold. The selection of inductor shifts the frequency profile across load conditions and line voltages.
-
The zero-cross detect (ZCD) pin detects when the inductor current resets to zero.
The frequency of operation across the line voltage is shown in Figure 8.
Figure 8. L6562 Switching Frequency vs. Line Voltage at Low Line
The basic principle of operation of CS1601 can be summarized as follows:
-
The CS1601 is a mixed DCM/CRM controller and is a voltage-mode IC which measures the output voltage and computes
a given switching frequency scheme at every line voltage.
-
The maximum power is specified by the selection of the inductor. The frequency is computed based on the line voltage.
-
The CS1601 measures the line (V
rect
) and link (V
link
) voltages and compares them against a reference.
-
The EXL Core™ signal processing core computes the correct T
on
, T
off
, and switching frequency for the measured line
and link voltages and programmed PID coefficients.
-
The EXL Core turns off the gate once T
on
is reached.
-
The EXL Core counts until T
off
time is reached or until zero-cross detection (ZCD) — whichever is first.
-
Figure 9 and Figure 10 show the frequency profile across the operating range for a CS1601-based solution.
V
Z
POR
+
-
V
ST(th)
V
STP(th)
Voltage
Regulator
8
VDD
5
ZCD
+
-
V
ZCD (th)
7
GD
Zero Cross
Detect
6
GND
IFB
IAC
V
DD
t
LEB
V
DD
15k
24k
3
V
DD
15k
24k
1
ADC
ADC
t
ZCB
4
CS
600
+
-
CS
Threshold
+
-
CS Clamp
V
CS(clamp )
V
CS(th)
STBY
V
DD
600k
2
Switching Frequency of L6562 Across Line
0
10
20
30
40
50
60
70
80
0
45
90
135
180
225
270
315
360
Phase Angle (degrees)
S
w
it
ch
in
g
F
req
u
e
n
c
y (
K
H
z
)