ld7578h Leadtrend Technology, ld7578h Datasheet - Page 12

• Manufacturer Part Number: ld7578h
• Description: High Voltage Green-mode Pwm Controller With Over Temperature Protection
• Manufacturer: Leadtrend Technology

Oscillator and Switching Frequency
The switching frequency of LD7578H is fixed at 65KHz
internally to provide the optimized operations by
Leadtrend Technology Corporation
LD7578H-DS-00 February 2010
LD7578H
VCC
GND
OUT
CS
Fig. 15
Fig. 16
Can be removed if the negative
spike is not over spec. (-0.3V).
www.leadtrend.com.tw
250ns
blanking
time
12
considering the EMI performance, thermal treatment,
component sizes and transformer design.
Frequency Trembling
The LD7578H is implemented with adjustable frequency
trembling function, providing the power supply designers
with optimized EMI performance and lowest cost system
solution.
between ±4KHz to incorporate with the 65KHz switching
frequency.
Internal Slope Compensation
Stability is crucial for current mode control when it
operates at more than 50% of duty-cycle. To stabilize the
control loop, the slope compensation is required in the
traditional UC384X design by injecting the ramp signal
from the RT/CT pin through a coupling capacitor. In
LD7578H, the internal slope compensation circuit has
been implemented to simplify the external circuit design.
On/Off Control
The LD7578H can be controlled to turn off by pulling
COMP pin to lower than 1.2V. The gate output pin of
LD7578H will be disabled immediately under such
condition. The off mode can be released when the
pull-low signal is removed.
Dual-Oscillator Green-Mode Operation
There
implemented in different chips for the green-mode or
power saving requirements such as “burst-mode control”,
“skipping-cycle mode”, “variable off-time control “…etc.
The basic operation theory of all these approaches
intended to reduce the switching cycles under light-load or
no-load condition either by skipping some switching
pulses or reduce the switching frequency.
What LD7578H use to implement the power-saving
operation is Leadtrend Technology’s own IP.
are
The Trembling frequency is fixed internally
many
different
LD7578H
topologies
has
been