Samsung Electronics Co., Ltd.

Fairfield Korea Semiconductor Ltd.

Dong-Myeong Shin

Chang-Ho Kim

Kyung-Oun Jang

Nak-choon Choi

Kyung-ha Jee

Dae-Bong Kim

Dal-Young Jeon

Bok-Ki Song

The present invention relates to a ring oscillator having a variable frequency allowing its use in a variety of application circuits. The ring oscillator produces an oscillating pulse signal having a frequency adjustable by an external input voltage. The ring oscillator includes an oscillating signal for generating an oscillating pulse signal, a frequency adjusting circuit, and an inverting circuit. The frequency adjusting circuit adjusts the frequency of the oscillating pulse signal responsive to the external input voltage, the external input voltage being different than a source voltage. The inverting circuit inverts the oscillating pulse signal.

Ring oscillator having an externally adjustable variable frequency

A switching power supply having a high efficiency starting circuit uses a field effect transistor to provide initial starting current to a pulse width modulated signal generator within a switching control circuit. The field effect transistor (FET) has a drain connected to a source of supply voltage, a source connected to the PWM signal generator, and a gate connected to a feedback voltage that is derived from an output voltage of the switching power supply. During start up of the switching power supply, the FET provides current to the PWM signal generator. When the feedback voltage reaches a predetermined level, the FET supplies substantially near zero current to the PWM signal generator, thereby eliminating the electrical inefficiencies typically associated with a conventional switching power supply starting circuit.

Switching power supply having a high efficiency starting circuit

A zero-voltage switching type electronic ballast for a fluorescent lamp includes a pair of capacitors connected in series between first and second nodes of a DC power source; a pair of switching devices whose current passages are connected in series between the first and second nodes of the DC power source; a load resonant circuit portion having a serial resonant circuit between the connection node of the pair of capacitors and the connection node of the pair of switching devices, and a discharge lamp; capacitors each connected in parallel to the current passage of the switching devices; a driving transformer having a secondary side which includes first and second windings each connected to the respective switching devices and having opposite polarities, and a third winding having the same polarity as the first winding and connected between the connection node of the pair of switching devices and the load resonant circuit, and a primary side having a fourth winding to which a switching control signal of a predetermined high frequency is applied. A switching control signal generating circuit compares a comparison signal of a predetermined high frequency with first and second reference.

Zero-voltage switching type electronic ballast for fluorescent lamp

Growing community of inventors

Bucheon, South Korea

Dong-Myeong Shin