Samsung Electronics Co., Ltd.

Fairfield Korea Semiconductor Ltd.

Fairchild Korea Semiconductor Ltd.

Maeng-Ho Seo

Nak-Choon Choi

Kyung-Hee Jang

Sang-Heum Yeon

An electronic ballast for use in illuminating a lamp includes a voltage reference generator that uses a plurality of current amplifiers and resistors having substantially identical resistance characteristics to remain stable in response to temperature variations and despite resistance process dispersion. The reference voltage generator further includes an ON/OFF controller and a dimming function that may be controlled via a single input terminal. Additionally, the dimming function uses a capacitor to prevent abrupt changes in an input signal from causing abrupt changes in a feedback signal that controls an output frequency of the ballast.

Electronic ballast having a stable reference voltage and a multifunction input for soft dimming and ON/OFF control

Disclosed is a Power Factor Correction (PFC) controller which comprises a boost converter, an error amplification unit, a calculator, and a switching driver. The error amplification unit reduces the error voltage of the output voltage of the boost converter to a specific reference voltage. The calculator receives first and second input voltages proportional to the input power of the converter and the output voltage of the error amplification unit, and outputs the voltage proportional to the first input voltage and the output voltage of the error amplification unit and inversely proportional to the second input voltage. The switching driver controls the switch to OFF when the voltage which detects the current flowing to switch of the boost converter becomes equal to the output voltage of the calculator, and controls the switch to ON when the zero current of the coil of the boost converter is detected.

Power factor correction (PFC) controller

Disclosed is an SMPS with a constant power control circuit. The constant power control circuit comprises a current detector located in a secondary coil of a transformer and which detects a current flowing to the secondary coil; a current controller including a first comparator that compares a voltage corresponding to the current detected by the current detector with a predetermined first reference voltage; a load, which is electrically coupled to the secondary coil of the transformer, for receiving the power flowing to the secondary coil; a voltage controller detecting a voltage at the load, comparing the detected voltage with a second reference voltage, and outputting a difference between the voltages; a constant power controller receiving the current detected by the current detector, detecting the voltage of the secondary coil, comparing the detected voltage with the first reference voltage, and outputting a difference between the voltages; an amplifier receiving outputs of the voltage detector, the current detector, and the constant power detector, and amplifying the outputs to a predetermined gain value and outputting the result; and a switching controller receiving an output of the amplifier and determining the power of the secondary coil, and controlling the switching duty of the switching element depending on whether the determined power of the secondary coil is above or below the first reference voltage.

SMPS with constant power control circuit

A sequential feedback control system for an electronic ballast provides feedback control during soft start and dimming operations. The system includes a feedback control portion that generates a feedback signal responsive to the power consumption of the ballast and receives a control signal for controlling the power consumption of the ballast. A dimming controller generates a dimming signal responsive to a time signal, and a soft start controller generates a soft start signal responsive to the time signal. An adder generates the control signal by adding the feedback signal and the dimming signal. The dimming controller includes a first resistor for setting the steady state power level during dimming operations and a second resistor for setting the rate of change of the power level.

Sequential feedback control system for an electronic ballast

A power factor correction circuit for a boost converter includes a current feedforward loop that senses the input voltage by detecting variations in the rate of change of current in an inductor, thereby eliminating the need for a voltage feedforward loop. A current sense circuit generates a current signal responsive to the input current flowing through the inductor when a switching transistor is turned on. A comparator compares the current signal to a sawtooth signal, thereby generating a control signal for turning the transistor off. The output of the converter is controlled by a voltage feedback loop which includes an error amplifier that generates an error signal responsive to the output voltage. The error signal is then multiplied by the current signal before the current signal is compared to the sawtooth signal.

Power factor correction circuit having an error signal multiplied by a

A power factor correction circuit for a boost-type voltage converter determines the input voltage by sensing the rate at which the current through an inductor changes when a switching transistor is turned on. The circuit includes a current sense circuit which generates a control signal in response to the current flowing in the inductor. The control signal is compared with a sawtooth signal to control the input current waveform. An output detecting circuit generates a comparison reference signal for regulating the output voltage of the converter. The comparison reference signal is summed with the control signal to provide a comparison signal. A comparison circuit compares the comparison signal with the sawtooth signal and generates a pulse width modulated signal for controlling the switch. A compensation signal generator generates a compensated comparison signal in response to a ripple component in the output signal of the converter. The compensated comparison signal is summed with the sawtooth signal to compensate for distortion in the input current, thereby increasing the power factor. An amplifier in the sense circuit allows a low value sense resistor to be used.

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Bucheon, South Korea

Maeng-Ho Seo