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PDF RT7300 Data sheet ( Hoja de datos )
| Número de pieza | RT7300 | |
| Descripción | Active PFC Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT7300
Active PFC Controller with Critical Conduction Mode
General Description
The RT7300 is an active Power Factor Correction (PFC)
controller with critical conduction mode (CRM) operation
that is designed to meet line current harmonic regulations
for the applications of AC/DC adapters, electronic ballasts
and medium off-line power converters (<300W). The CRM
and Feed-Forward schemes provide near unity power factor
across a wide range of input voltages and output powers.
The totem-pole gate driver with 600mA sourcing current
and 800mA sinking current provides powerful driving
capability for P-MOSFET to improve conversion efficiency.
The RT7300 features an extra low start-up current (≤20μA)
and supports a disable function to reduce power
consumption in standby mode, which makes it easy to
comply with energy saving regulations such as Blue Angel,
Energy Star and Energy 2000.
This controller integrates comprehensive safety protection
functions for robust designs including input under voltage
lockout, output over voltage protection, under voltage
protection and cycle-by-cycle current limit.
The RT7300 is a cost-effective solution for PFC power
converter with minimum external components. It is
available in the SOP-8 package.
Features
Critical Conduction Mode (CRM) Operation
Constant On-Time Control (Voltage Mode)
Near Unity Power Factor
Ultra Low Start-up Current (<20μA)
Input Voltage Feed-Forward Compensation
Wide Supply Voltage Range from 12V to 25V
Totem Pole Gate Driver with 600mA/−800mA
Maximum Frequency Clamping (120kHz)
DCM THD Optimization
Fast Dynamic Response
Light Load Burst Mode Operation
Brown-in/Brown-out Detection
Disable Function
Maximum/Minimum On-Time Limit
Cycle-by-Cycle Current Limit
Output Over Voltage Protection (OVP)
Output Under Voltage Protection (UVP)
Under Voltage Lockout (UVLO)
RoHS Compliant and Halogen Free
Simplified Application Circuit
BD
Line
LPFC
Neutral
CSIN
RZCD
RAUX
DVDD
CVDD
RFF1
RSTART
RFF2
CFF
RG
GD
ZCD
CS
RT7300
VDD
INV
DOUT
Q1
RCS
COUT
VOUT+
VOUT-
ROUT1
CINV
ROUT2
COMP
FF
GND
RCOMP
CCOMP1
CCOMP2
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS7300-01 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT7300
Bias &
Band Gap
UVLO
+ Hys. = 7V
-
+
16V
10µs
De-Bounce
OVP
+
-
+
27V
VDD
29V
Figure 4. VDD and UVLO
Feedback Voltage Detection
Figure 5 shows the feedback voltage detection circuit.
The INV pin is the inverting input of the Error Amplifier
with 2.5V reference voltage. Over voltage and under voltage
protections are provided with threshold voltage 2.75V and
0.4V respectively. If the INV voltage is over 2.75V or under
0.4V, the gate driver will be disabled to prevent output
over voltage condition or feedback open condition. Although
the INV is an input pin with high impedance, it is suggested
that the bias current of the potential divider should be over
30μA for noise immunity.
COMP
VOUT+
ROUT1
ROUT2
INV
CINV
2.5V
2.75V
0.4V
+GM
-
- OVP
+
- UVP
+
Figure 5. Feedback Voltage Detection
Transconductance Error Amplifier
The RT7300 implements transconductance error amplifier
with non-linear GM design to regulate the Boost output
voltage and provide fast dynamic response. The
transconductance value is 100μA/V in normal operation.
When the INV voltage increases over 2.75V or decreases
under 2.25V, the output of error amplifier will source or
sink 1mA maximum current at COMP pin respectively
shown as Figure 6. Thus, the non-linear GM design can
provide fast response for the dynamic load of PFC
converters even though the bandwidth of control loop is
lower than line frequency.
ICOMP_Sourcing Current
Max. Sourcing Current >1mA
UV
0.4V
2.25V
OV
2.5V 2.75V
GM = 100µA/V
INV
Figure 6. Non-linear GM
Feed-Forward Compensation
The FF pin is an input pin with high impedance to detect
the line input voltage shown as Figure 7. A proper voltage
divider should be applied to sense the line voltage after
bridge diode rectifier. Since the FF voltage is proportional
to the line input voltage, it provides a feed-forward signal
to compensate the loop bandwidth for high line and low
line input conditions. The FF pin is also used for the
detection of Brown-in and Brown-out functions to protect
converter from over stress at low input voltage situation.
VCSIN
RFF1
FF
RFF2 CFF
1.1V -
+
-
0.6V +
80µs
De-bounce
Brown-In
80µs
De-bounce
Brown-Out
Feed- Forward & THD
Optimize Ramp Generator
2.5V
G+ M
-
+ PWM OFF
-
INV COMP
Figure 7. FF Detection Circuit
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS7300-01 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT7300
Typical Application Circuit
Typical Application Circuit for Boost PFC Pre-Regulator
F1
Line
BD
Neutral
RNTC
LPFC
DS
CSIN
RZCD
RAUX
CAUX
DZ DVDD
CVDD
RFF1
RSTART
RFF2
CFF
DOUT
RG
Q1
VOUT+
COUT
RCS
VOUT-
7
GD
5 ZCD
CS 4
RT7300
RS
CCS
ROUT1
8 VDD
INV 1
CINV
ROUT2
3 FF
COMP 2
RCOMP
CCOMP1
GND 6
CCOMP2
Typical Application Circuit for Single Stage PFC Converter
F1
Line
BD
Neutral
RNTC
CSIN
RFF1
RFF2
RSTART
RG
RZCD
RAUX
DVDD
CVDD
CFF
7
GD RS
5 ZCD
CS 4
RT7300
CCS
8 VDD
RINV 1 INV
DINV
3 FF
COMP 2
CCOMP
GND 6
T1
Q1
RCS
U2B
DOUT
COUT1
RS
DZ
RSN
Q2
COUT2
U2A
RCN
RFB1 CFB1
U3
CN VDD
OUT
CP
RT8456
FB
GND
RFB2 CFB2
VOUT+
VOUT-
ROUT1
ROUT2
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS7300-01 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet RT7300.PDF ] | |
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