UC1861-1868
UC2861-2868
UC3861-3868
Resonant-Mode Power Supply Controllers
FEATURES
DESCRIPTION
• Controls Zero Current Switched (ZCS) The UC1861-1868 family of ICs is optimized for the control of Zero Curor Zero Voltage Switched (ZVS)
rent Switched and Zero Voltage Switched quasi-resonant converters. DifQuasi-Resonant Converters
ferences between members of this device family result from the various
combinations of UVLO thresholds and output options. Additionally, the
• Zero-Crossing Terminated One-Shot
one-shot pulse steering logic is configured to program either on-time for
Timer
ZCS systems (UC1865-1868), or off-time for ZVS applications (UC1861• Precision 1%, Soft-Started 5V
1864).
Reference
The primary control blocks implemented include an error amplifier to com• Programmable Restart Delay
pensate the overall system loop and to drive a voltage controlled oscillator
Following Fault
(VCO), featuring programmable minimum and maximum frequencies. Triggered by the VCO, the one-shot generates pulses of a programmed maxi• Voltage-Controlled Oscillator (VCO)
mum width, which can be modulated by the Zero Detection comparator.
with Programmable Minimum and
Maximum Frequencies from 10kHz to This circuit facilitates “true” zero current or voltage switching over various
line, load, and temperature changes, and is also able to accommodate the
1MHz
resonant components' initial tolerances.
• Low Start-Up Current (150µA typical)
Under-Voltage Lockout is incorporated to facilitate safe starts upon
• Dual 1 Amp Peak FET Drivers
power-up. The supply current during the under-voltage lockout period is
typically less than 150µA, and the outputs are actively forced to the low
• UVLO Option for Off-Line or DC/DC
state.
(continued)
Applications
Device
UVLO
Outputs
“Fixed”
1861
16.5/10.5
Alternating
Off Time
1862
16.5/10.5
Parallel
Off Time
1863
36014
Alternating
Off Time
1864
36014
Parallel
Off Time
1865
16.5/10.5
Alternating
On Time
1866
16.5/10.5
Parallel
On Time
1867
36014
Alternating
On Time
1868
36014
Parallel
On Time
BLOCK DIAGRAM
Pin numbers refer to the J and N packages.
10/98
UDG-92018
