4.1 Outline of unstable operation at low temperature and countermeasures
■
At low temperatures, ESR of Cbc and power thermistor become high.
At this condition, the output voltage may become unstable due to the voltage drop on the inrush
current limiting components and Cbc. Please select the appropriate Cbc and R1.
■
The output voltage becomes unstable easily when the components temperature is low and startup
or dynamic load change.
Fig. 4.1 shows stable operation at 25ºC and unstable operation at -40ºC after startup and at dynamic
load changes. The power supply is repeatedly starting and stopping if unstable operation is happened.
Fig.4.1
Difference of
operation with
temperature
■
The operation is improved by increasing the temperature of the component.
<Notes for operation at ambient temperatures between -20ºC and -40ºC>
* Output voltage may be unstable continuously at low load current. In this case, minimum
load current is necessary.
* The output becomes stable after a few minutes operation because the characteristics of
thermistor and Cbc become stable.
A-10
Vac
Vin
Vo
Io
TUHS
2.1 Pin configuration
4. Operation Under Low Temperature Conditions
Start-up (TUHS25F12)
Load 0%
⇒
100% (TUHS25F12)
Vac
(100V/div)
Vin
(100V/div)
Vo
(5V/div)
(200ms/div)
Vac
(100V/div)
Vin
(100V/div)
Vo
(5V/div)
unstable
(200ms/div)
Io
(1A/div)
Vo
(5V/div)
(100ms/div)
Io
(1A/div)
Vo
(5V/div)
unstable
(100ms/div)
Vac
Vo
Io
TUHS
Ta=25
℃
Ta=-40
℃
Load
Applications Manual
TUHS series
Vin
