摘要:
Disclosed is an active power factor correction integrated circuit for a boost converter, comprising a bias voltage generator coupled to an external power source through a first pin, for generating internal bias voltages used for the integrated circuit; a zero crossing detector coupled magnetically to the inductor through a second pin, for detecting a time at which a voltage across the inductor is zero to provide a zero crossing detection signal; an oscillator reset by the zero crossing detection signal for generating a pulse signal; a flip-flop for generating a first control signal in response to the zero crossing detection signal or the pulse signal; a switching element responsive to the first control signal for enabling a boosted voltage to be provided to the load; an over-current detector for generating an over-current signal when a current flowing through the switching element is over a predetermined value; and a voltage variation detector for detecting variation of a load voltage to generate a variation detection signal and generating a second control signal enabling the boosted voltage to flow through the switching element to a ground in response to both the variation detection signal and the over-current signal. With the integrated circuit, the number of the IC pin and the number of the peripheral components thereof may be considerably reduced.
摘要:
A controller for a switching mode power supply has connections for receiving direct operating potential, a voltage comparator for comparing a fraction of the direct operating potential to a first direct reference potential for developing a voltage comparator output signal, an oscillator for generating oscillations of a prescribed frequency, a pulse width modulator for supplying pulses at a rate determined by those oscillations and with a width controlled by the comparator output signal, and an under-voltage lock-out circuit producing a controlling signal to selectively disable the output pulse signal. The controller is included in a switching mode power supply receiving input power having a direct input potential. The switching mode power supply has a transformer for transforming an alternating voltage generated from the direct input potential; a rectifier for rectifying transformed alternating voltage to produce a direct output potential; a regulator sinking current responsive to the direct output potential from said rectifier being larger or smaller larger than a second direct reference potential; a photo-coupler conducting as input current the current sunk by the regulator, converting the current into an optical signal, and then converting said optical signal into an electric signal; and a switching controlling unit producing a controlling signal to control selective application of the direct input potential to the transformer in response to output current demanded by the photo-coupler. The switching controlling unit comprises a switching-mode-power-supply controller for performing the function of power supply, feedback and soft-start, in response to an operating voltage signal supplied thereto through external pins thereof; a resistor and capacitor converting the magnitude of the current supplied from the photo-coupler into the operating voltage signal; and a switching transistor cyclically tuned on and off in response to a pulse signal produced from the switching-mode-power-supply controller. The switching transistor selectively applies the direct input potential to the transformer for generating the alternating voltage that is transformed.
摘要:
A resonant convertor control system regulates a resonant AC current based on the amount of input power consumed by the system. The switching frequency and resonant AC current are limited by a phase difference assurance circuit that compares the phase of a drive signal with the phase of the resonant AC current. By detecting the phase of the resonant current instead of the resonant voltage, it eliminates the need for the costly components required to detect the resonant voltage. The system includes a main power supply for supplying a DC power signal and an inverter that converts the DC power signal to a resonating AC current signal responsive to a drive signal from a drive stage. An input current controller receives a first sense signal that indicates the power consumed by the main power supply and generates a first control signal that regulates the power consumed by the load. A phase difference assurance circuit generates a second control signal responsive to phase difference between the resonant AC current signal and the drive signal. The second control signal adjusts the frequency signal responsive to the second control signal, thereby assuring a phase difference between the second sense signal and the drive signal and eliminating excessive current flow in the inverter.
摘要:
A battery charging circuit controls between rapid charging and trickle charging used to charge a NiCd/NiMH battery. The circuit perceives when the rapid charging operation has completely charged the battery and thereafter converts the charging operation to a trickle charging in order to compensate for the charging loss of a battery due to the leakage discharge. The form of charging is controlled by restricting the maximum amount of current provided to the battery using current-mode pulse width modulation.
摘要:
A pulse width modulation control circuit of the present invention causes variation amplitudes of a sawtooth voltage in a sawtooth oscillator being synchronized by an external signal to be lowered thereby improving characteristics with respect to both a noise and a system control. The pulse width modulation control circuit includes a sawtooth oscillating means for generating a sawtooth voltage after receiving the synchronizing signal, that is, a synchronizing frequency; a sawtooth controller for receiving the sawtooth voltage generated from the sawtooth oscillating means, also receiving a reference voltage with respect to the sawtooth voltage, and outputting a current controlling constantly an amplitude of the sawtooth voltage to the sawtooth oscillating means; and a pulse width modulating means for receiving an output voltage, also receiving a reference voltage with respect to the output voltage, then receiving the sawtooth voltage generated from the sawtooth oscillating means 100, modulating a pulse width.
摘要:
A soft start pulse width modulation integrated circuit having a reduced number of external connection terminals, a single one of which transmits the soft start signal superimposed upon an external sync signal. The soft start pulse width modulation integrated circuit includes a comparison voltage signal generating circuit, a soft start and external sync generation circuit, a comparator, a triangle signal generator and a pulse width modulator. The voltage level of a comparison voltage signal is increased over time in response to a feedback signal. A DC voltage signal is generated having a voltage level which increases over time but at a lesser rate than the comparison voltage signal and is superimposed with an external sync signal. The superimposed signal is compared with a reference signal and the resulting compared signal determines a triangular signal generated therefrom which has one of two different oscillation modes: a variable natural mode, and a regulated synchronized mode. The pulse width modulator receives the triangular signals and outputs a pulse-width modulated signal from a single external connection which is dependent upon the oscillation output received from the triangular signal generator.
摘要:
A multi-output switching regulator includes a rectifier circuit portion for converting an alternating current into a direct current, a boost converter portion for boost-converting the direct current, an inverter portion for storing the output from the boost converter portion in a primary winding of a transformer and transferring the stored energy to a secondary winding, a fly-back type first constant voltage output portion for outputting energy transferred to a first secondary winding of the transformer as a first constant voltage and for storing the first constant voltage in an equivalent flux inductance of the transformer and transferring the stored energy to a second secondary winding, and a second constant voltage output portion for outputting energy transferred to the second secondary winding of the transformer as a second constant voltage. Input power factor correction is achieved as well as the outputting of two constant voltages.
摘要:
A power factor correction circuit includes a boost converter, a zero-current detector for detecting a period in which an inductor current is zero, a half-wave rectifier for supplying a power voltage proportional to an output voltage of the boost converter, a control voltage generator for generating a control voltage to control the turn-on time timing of a sense-FET, a turn-on controller for making constant a turn-on duration of the sense-FET, an over current detector for generating a signal when a mirror terminal current of the sense-FET is greater than a predetermined current, an OR gate for performing a logic OR operation of the output signals of the turn-on controller and the over current detector, an output current controller for generating a gate drive signal of the sense-FET, and an under voltage lock out for turning off the power voltage when the power voltage is less than a predetermined voltage. This circuit enables an external pin count to be reduced by having a built-in boost converter controller and a built-in sense-FET in a single package.