| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 94 === The UC384X series is a high performance fixed frequency current mode controllers especially design for off-line and DC−to−DC converter applications. It was used about two decades. Its integrated circuits feature a trimmed oscillator for precise duty cycle control, gain error amplifier, current sensing comparator, and a high current totem pole output for driving a power MOSFET. And it included a protective feature consisting of input and reference under-voltage lockouts each with hysteresis, cycle−by−cycle current limiting for output over current protection. Unfortunately, it needs to use lots of external circuits to achieve.
In this thesis, a PWM controller has a saw-tooth limit for output power protection of DC-DC converter without input voltage compensation circuits is presented. This PWM controller will turn off its output when the current-sense signal of the PWM controller is higher than the reference saw-tooth limited voltage. At the mean while, this PWM controller has an excellent output power protection of DC-DC converter by a short delay time of current-sensing signal to its output. This feature makes external circuits of PWM controller simple and improves the mean time between failures (MTBF) of converter by decreasing part counts simultaneously.
The experimental waveform and test result on a 5V/2A power board are shown to verify the feasibility of the proposal. The results are satisfactory.
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