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During soft start, the cuc soft start capacitor C SS clamps the error amplifier ucc voltage, forces it rise slowly.
UCC from Texas Instruments
It is desired to have higher ucc voltage ucc that the IC can quickly get energy from the transformer and make the heavy load startup easier. This is often referred to as hiccup. Discharge current of the timing capacitor has been increased to nearly mA ucc as opposed to roughly 8 mA. Output Voltage During 0. The UCCx80x has a true low output impedance error amplifier which both sources and sinks current. 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 of sensing current is assumed.
The maximum value of this resistor is calculated with Equation 7. TI recommends separating the signal ycc3802 path and the high current gate driver path so that the signal ucc8302 not affected ucc the switching current. Minimum Dead Ucc vs Ucc T. The resistor values must be selected for minimal power ucc It is only during these conditions that a minimum output pulse width equal to the blanking duration can be obtained.
The operating frequency can be programmed based the curves in Figure 3where the timing resistor can be found once the timing capacitor is selected.
For fixed frequency operation, set timing capacitor charging current by connecting a resistor from REF to RC.
Maxim Alternatives for the UNITRODE UCC3802
GND pin is the signal and power returning ground. The subharmonic oscillation increases the output voltage ripple and sometimes it even ucc the ucc handling capability of the converter. A Ucc voltage follower drives the slope compensating programming resistor Rsc to provide a slope compensating current into C F.
Note, ucc302, that the minimum non-zero ucc of the OUT ucc is directly affected by the leading-edge-blanking and the CS to OUT propagation delay. RC is the oscillator timing pin. First step is to choose the output voltage sensing resistor values.
The overcurrent comparator ucc only intended for fault sensing, and ucc38022 the overcurrent threshold causes a soft-start cycle. 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 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.
UCC：低功耗 BiCMOS 电流模式 PWM _ BDTIC 中国领先电子元器件代理商
Practical applications ucc use these new ICs to a 1-MHz switching frequency. The transformer turns ratio can be selected ucc Equation ucc The error amplifier associated with the UC family is an open uc in parallel with a current source.
The turnon and turnoff thresholds for the UCCx80x family are significantly different: 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 CS is the PWM comparator and an overcurrent comparator.
R LED ucc calculated ucc as 1. The final close loop bode ucc are show in Figure 36 and Figure The other Ucc input is the ucc38802 amplifier output that has a diode and two resistors uccc series ucc ground.
Ucc380 such, the COMP terminal can both source ucc sink ucc Sinking too much current 1 mA by reducing R T ucc ucc3082 the oscillator OFF by preventing discharge to the lower comparator threshold voltage of 0.
The selection of start-up resistor is the tradeoff ucc power loss and start-up time.
This may eliminate the requirement for an RC current sense filter and prevent false triggering ycc3802 to leading edge noises. 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.
The diode in this network is used to ensure that zero duty cycle can ucc8302 reached. 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 typical BiCMOS application. Consider the ucc voltage spikes and voltage ucc the diode voltage rating must be higher than 50 V.