VIPER37HE STMicroelectronics, VIPER37HE Datasheet - Page 28

• Manufacturer Part Number: VIPER37HE
• Description: AC/DC Switching Converters ViperPlus Fixed Freq 800V 30mQ 265 Vac
• Manufacturer: STMicroelectronics
• Type: Off Line Switcherr

Specifications of VIPER37HE

• Product Category: AC/DC Switching Converters
• Rohs: yes
• Input / Supply Voltage (max): 23.5 V
• Input / Supply Voltage (min): 8.5 V
• Switching Frequency: 115 kHz
• Supply Current: 3.5 mA
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: Through Hole
• Package / Case: SDIP-10
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 25 C
• Number Of Outputs: 1
• Output Power: 25 W

Operation description
8.11
28/35
Figure 30. FB pin configuration 1
Figure 31. FB pin configuration 2
Burst mode operation at no load or very light load
When the load decreases, the feedback loop reacts by lowering the feedback pin voltage. If
it falls below the burst mode threshold, V
be switched on. After the MOSFET stops, as a result of the feedback reaction to the energy
delivery stop, the feedback pin voltage increases and when it exceeds the level, V
V
reported in
power alternates between periods of time in which the Power MOSFET is switching and is
enabled, with periods of time when the Power MOSFET is not switching; this working mode
is called burst mode. The power delivered to the output during switching periods exceeds
the load power demands; the excess of power is balanced from the non-switching period
where no power is processed. The advantage of burst mode operation is an average
switching frequency much lower then the normal operation working frequency, up to a few
hundred hertz, minimizing all frequency related losses. During burst mode the drain current
peak is clamped to the level, I
FBbmhys
, the power MOSFET starts switching again. The burst mode thresholds are
Table 8
and
Rfb1
Cfb1
Figure 32
Cfb
D_BM
Doc ID 022218 Rev 1
Cfb
shows this behavior. Depending on the output load, the
, reported in
CONTROL
FBbm
PWM
CONTROL
REFERENCES
BURST-MODE
PWM
, the Power MOSFET is no longer allowed to
REFERENCES
BURST-MODE
Table 8
4.8V
4.8V
.
OLP comparator
BURST-MODE
PWM
From sense FET
+
+
OLP comparator
-
-
LOGIC
BURST-MODE
PWM
From sense FET
+
+
-
-
LOGIC
To disable logic
To PWM Logic
To disable logic
BURST
To PWM Logic
BURST
FBbm
VIPER37
+