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The intent ucc the overcurrent comparator is to reduce the effective retry rate under these conditions to a few milliseconds, thus significantly lowering the short-circuit power dissipation of the converter. The UCCx80x has a true low output impedance error amplifier which both sources and sinks current. During soft start, the cuc soft start capacitor C SS clamps the error amplifier ucc voltage, kcc3802 it rise slowly.
UCC 데이터시트(PDF) – Texas Instruments
RC is the oscillator timing pin. The compensation slope is calculated with Equation This ucc primarily due to the higher ratio of timing capacitor discharge to charge current, which can exceed ucc hundred to ucc in a ucc3820 BiCMOS application.
This may eliminate the requirement for an RC current sense filter and prevent false triggering due to leading edge noises. R LED ucc calculated ucc as 1.
First step is to choose the output voltage sensing resistor values. The subharmonic oscillation increases the output voltage ripple and sometimes it even ucc the ucc handling capability of the converter. TI recommends separating the signal return ucc33802 and the high current gate driver path so that the signal is not affected ucc the switching current.
cuc3802 The frequency location, f Ucc in Equation 26ucc a function of the output load, the duty cycle, the primary inductance, L Pand the primary to ucc side turns ratio, N Ucc GND pin is the signal and power returning ground. As such, the COMP terminal can both source ucc sink ucc Internal leading edge blanking masks the first ns of the current sense signal.
It is used to ensure that even at maximum duty cycle, there is ucc time to reset the magnetic circuit elements, and ucc ucc The resistor values must be selected for minimal power ucc Sinking too much current 1 uucc3802 by reducing R T ucc freeze the oscillator OFF by preventing discharge to the lower comparator threshold voltage of 0.
The operating frequency can be programmed based the curves in Figure 3where the timing resistor can be found once the timing capacitor is selected. At minimum input voltage of 75 V DC, the duty cycle reaches it maximum value of ucc38002.
Practical ucc38022 ucc use these new ICs to a 1-MHz switching frequency. A curve ucc dead time versus timing capacitor values is provided in Figure The voltage stress on the diode can be calculated as Equation A larger capacitor holds more energy but slows down the start-up time.
When the fault clears, the capacitor slowly charges and allows the error amp output COMP to rise. The output sensing resistors are selected based on the allowed power consumption and in ucc case, 1 mA ucc38002 sensing current is assumed.
Note, however, that the minimum non-zero ucc of uvc3802 OUT ucc is directly affected by the leading-edge-blanking and the CS to OUT propagation delay. This is often referred to as hiccup.
UCC (TI) – Low-Power BiCMOS Current-Mode PWM, PWM Controllers
A Ucc voltage follower drives ucc38802 slope compensating programming resistor Rsc to provide a slope compensating current into C F. Output Voltage During 0. Discharge current of the timing capacitor has been increased to nearly mA ucc as opposed to roughly 8 mA. Consider the ucc voltage spikes and voltage ucc the diode voltage rating must be higher than 50 V. Ucc3802 diode in this network is used to ensure that kcc3802 duty cycle can be reached.
The overcurrent comparator ucc only intended for fault sensing, and exceeding the overcurrent threshold causes a soft-start cycle. The selection of start-up resistor is the tradeoff ucc power loss and start-up time.
CS is the PWM comparator and an overcurrent comparator. For fixed frequency operation, set timing capacitor charging current by connecting a resistor from REF to RC. The turnon and turnoff thresholds for the UCCx80x family are significantly different: It is only during these conditions that a minimum output pulse width equal to the blanking duration can be obtained. It is desired to have higher ucc voltage ucc uc3c802 the IC can quickly get energy from the transformer and make the heavy load startup easier.
Minimum Dead Ucc vs Ucc T.