A control circuit controlling output current at the primary side of a power converter is provided. A waveform detector generates a current-waveform signal. A discharge-time detector detects a discharge-time of a secondary side switching current. An oscillator generates an oscillation signal for determining the switching frequency of the switching signal. An integrator generates an integrated signal by integrating an average current signal with the discharge-time. The average current signal is generated in response to the current-waveform signal. The time constant of the integrator is correlated with the switching period of the switching signal, therefore the integrated signal is proportional to the output current. An error amplifier amplifies the integrated signal and provides a loop gain for output current control. A comparator controls the pulse width of the switching signal in reference to the output of the error amplifier. Therefore, the output current of the power converter can be regulated.

Control circuit for controlling output current at the primary side of a power converter

A switching power supply capable of correcting a power factor without using a shunt resistor is provided. The switching power supply includes a rectifier for rectifying an AC power supply, boosting means including a power MOSFET for boosting an output of the rectifier, a smoothing capacitor for smoothing an output of the boosting means, voltage-dividing resistors for detecting a voltage between main terminals of the power MOSFET, a switch for selecting only the voltage by which the power MOSFET is in on-state from voltages detected by the voltage-dividing resistors, an amplifier for amplifying the voltage selected by the switch and outputting the same as a current corresponding value of a current flowing in the power MOSFET, voltage-dividing resistors for detecting the output voltage, and driving means which form a pulse signal based on the current corresponding value and the output voltage for driving the power MOSFET by the pulse signal.

Switching power supply

A power converter comprises a direct current (DC)-DC converter configured to receive an input voltage in a primary domain, a transformer coupled to and driven by the DC-DC converter and supplying an output voltage in a secondary domain, and a transmission path configured to pass a digital feedback signal through an isolation barrier from the secondary domain to the primary domain.

Dc-dc converter with isolation

A power supply protecting the electric device circuit when over-voltage is applied, is provided. The power supply has a rectifying unit rectifying AC power externally supplied, into first and second DC power and outputting the first and the second DC power; a main power supply transformer boosting the first DC power and supplying the boosted first DC power to the electric device circuit; a switching controlling unit driven by the second DC power, performing the operation on the main power supply transformer that causes the first DC power to be boosted when the second DC power is received; and a controlling unit determining whether the second DC power is to be supplied to the switching controlling unit, wherein the controlling unit senses the voltage supplied to the electric device circuit and interrupts supplying the second DC power to the switching controlling unit if the sensed voltage exceeds a given value.

Power supply capable of protecting electric device circuit

The present invention comprises methods and circuits for spread spectrum frequency modulation that reduce peak spectral noise at the outputs or inputs of switching regulators. More specifically, the present invention modulates the operating frequency of the switching regulator in accordance with a frequency modulation waveform having a shape coordinated to a peak noise amplitude waveform that describes the correlation between the operating frequency of a switching regulator and the peak noise amplitude at the regulator's input or output absent spread spectrum frequency modulation.

Methods and circuits for frequency modulation that reduce the spectral noise of switching regulators

An output isolated, switching power supply (100) has a transformer (73) with a primary (91) and two secondaries (92, 93), and electronic switch (75) in series with the primary, a first rectifier (87) and filter (88) on the first secondary (93) to provide bias power during both startup and operating modes, and a second rectifier (80) and filter (82) on the second secondary (92) to provide regulated output power. A resistor-capacitor network (78, 74) on the primary side provides an initial operating condition, such as a single control pulse, to the electronic switch which causes sufficient energy to be transferred through the first secondary to supply sufficient startup energy to operate a current control integrated circuit (89) on the secondary side in a staged fashion. After the initial operating condition, the current control integrated circuit generates and applies a control signal to the electronic switch through an isolation circuit (77) to cause the electronic switch to turn on and off in controlled fashion in order to deliver regulated power to the output of the supply. The low voltage, secondary side, current control integrated circuit provides a further aspect of the present invention.

Start-up circuit for flyback converter having secondary pulse width modulation control

A three-terminal low-voltage PWM controller chip includes a first terminal for receiving operating bias current supply and a feedback control signal related to an output parameter of an electrical circuit to be controlled; a second terminal connected to an output switch providing digital width-modulated control pulses to control duty cycle of the electrical circuit; a third terminal ground connection; a clocked pulse width modulation circuit responsive to current flow between the second terminal and the third terminal and the feedback control value for controlling the digital output switch; and, feedback signal separation circuitry for separating the feedback control signal from the operating bias current supply. A start-up circuit is also provided.

Three-terminal, low voltage pulse width modulation controller ic

A CMOS digital PWM controller chip (10) includes a clock generator (14) for directly generating a sampling clock at a frequency higher than a control pulse rate without requiring a phase locked loop, an oversampling analog-to-digital converter (24) clocked by the sampling clock for converting error signals into filtered digital values, an output for controlling duty cycle of an electrical device in accordance with width-modulated digital control pulses supplied at the control pulse rate, and, digital control logic for generating the width-modulated digital control pulses in relation to the digital values. The digital control logic may include a linear feedback shift register to pseudo-randomize the digital control pulses to reduce electromagnetic interference.

Chuck Wong

Papers

Start-up circuit for flyback converter having secondary pulse width modulation control

Three-terminal, low voltage pulse width modulation controller ic

Cmos digital pulse width modulation controller