Abstract:
A PWM controller according to the present invention provides a technique to control the output voltage and output current of the power supply without the feedback control circuit in the secondary side of the transformer. In order to achieve better regulation, an adaptive load and a feedback synthesizer are equipped into the PWM controller, which associated with the auxiliary winding of the transformer regulate the output voltage of the power supply as a constant. Furthermore, a programmable power limiter in the PWM controller controls the power that is delivered from the primary side to the output of the power supply. The threshold of the power limit is varied in accordance with the change of output voltage. Because the output power is the function of the output voltage of the power supply, a constant current output is realized when the output current of the power supply is greater than a maximum value.
Abstract:
A pulse width modulated soft-switching power converter has a transformer with a primary winding and a secondary winding, a secondary circuit coupled to the secondary winding, and a pair of main switches and a pair of auxiliary switches coupled to the primary winding. The main switches and auxiliary switches intermittently conduct an input voltage source to the primary winding of the transformer to operate the soft-switching power converter in four operation stages in each switching cycle. The main switches conduct the input voltage source to the transformer in a first operation stage. In a second operation stage, the conduction is cut off. The transformer operates as an inductor with the auxiliary switches switched on under zero-voltage or zero-current switching mode in a third operation stage. In the fourth operation stage, auxiliary switches are switched off to achieve zero-voltage transition.
Abstract:
A regulated power supply having power factor correction control includes a multi-vector error amplifier. The multi-vector error amplifier provides an error signal that is used to regulate a switching mechanism of the power supply. The multi-vector error amplifier acts to provide a low distortion error signal during steady-state operation, while responding rapidly and smoothly to sudden load changes.
Abstract:
A method and apparatus to dynamically modify the internal compensation of a low drop-out (LDO) voltage regulator is presented. The process involves creating an additional equivalent series resistance (ESR) from an internal circuit. The additional ESR of the internal circuit is sufficient to ensure the DC output stability. This allows the ESR of the output capacitance to be reduced to zero if desired, for improved transient response.
Abstract:
A PFC-PWM controller with a power saving means is disclosed. A built-in current synthesizer generates a bias current in response to feedback voltages sampled from the PWM circuit and the PFC circuit. The bias current modulates the oscillation frequency to further reduce the switching frequencies of the PWM signal and the PFC signal under light-load and zero-load conditions. Thus, power consumption is greatly reduced. The PFC and the PWM switching signals interleave each other, so that power can be transferred more smoothly from the PFC circuit to the PWM circuit. The saturation of the switching components can be avoided by limiting the maximum on-time of the PWM signal. Further, an external resistor is used to start up the PFC-PWM controller and to provide an AC template signal for PFC control.
Abstract:
Incorporating the PWM function with the power saving means develops the PWM controller in which the switching frequency is decreased in response to the decrease of the load. Further, the current-driven design minimizes the circuitry and reduces the cost of the PWM controller. Since most of the control signals are operated in current mode, the die size of integrated circuit of the PWM controller is greatly reduced. An off-time modulator is provided for power saving in which the discharge current of the oscillator is modulated. Keeping the maximum on-time of the PWM signal as a constant and increasing the off-time of the PWM signal extends the switching period in light load conditions. The off-time modulation is the function of a feedback current, which is derived from the feedback loop. An array of current operation is designed to generate the feedback voltage for the PWM control and meanwhile produces a modulated discharge current for power saving. A minimum discharge current is limited to prevent the switching frequency from flowing into the audio-band. Moreover, the minimum discharge current is switched on/off in response to the state of the supply voltage in which the minimum discharge current is disabled when the supply voltage is high, and enabled once the supply voltage is lower than a threshold voltage; thereby preventing insufficient power from being supplied from the auxiliary bias winding for the PWM controller.
Abstract:
A pulse width modulated soft-switching power converter, having a pair of main switches and a pair of auxiliary switches coupled to the primary winding of the transformer. The main switches and auxiliary switches intermittently conduct an input voltage source to the primary winding to operate the soft-switching power converter in four operation stages in each switching cycle. The main switches conduct the input voltage source to the transformer in a first operation stage. In a second operation stage, the conduction is cut off. The transformer operates as an inductor with the auxiliary switches switched on under zero-voltage or zero-current switching mode in a third operation stage. In the fourth operation stage, the auxiliary switches are switched off, whereby the flyback energy achieves the zero-voltage transition. A zero-voltage-detection is employed to optimize the zero-voltage switching. The switching frequency is decreased in response to the decrease of the load. Furthermore, the auxiliary switching is restricted in accordance with the decrease of the load. Therefore reducing the power consumption in the light load and no load conditions.
Abstract:
The present invention relates to a digitally controlled switched-mode power supply, which achieves the effectiveness to save on power and enable more accurate voltage through control of a digital circuit, The power supply is provided with a control circuit, and the control circuit primarily includes a digital unit and a switching controller, wherein functionality of the digital unit enables transmitting an input voltage signal to the switching controller, and when the switching controller transmits voltage to the digital unit, then the digital unit is able to feed a signal back to control the switching controller. Accordingly, the digital unit is able to accurately sense the input load voltage at all times, and thereby achieve advancement to enable saving on power and more accurate voltage.
Abstract:
The present invention provides a primary-side flyback power converter that supplies a constant voltage output and a constant current output. To generate a well-regulated output voltage under varying load conditions, a PWM controller is included in the power converter in order to generate a PWM signal controlling a switching transistor in response to a flyback voltage sampled from a first primary winding of the power supply transformer. Several improvements are included in this present invention to overcome the disadvantages of prior-art flyback power converters. Firstly, the flyback energy of the first primary winding is used as a DC power source for the PWM controller in order to reduce power consumption. A double sample amplifier samples the flyback voltage just before the transformer current drops to zero. Moreover, an offset current is pulled from a detection input of the double sample amplifier in order to generate a more accurate DC output voltage. The offset current is generated in response to the temperature in order to compensate for temperature-induced voltage fluctuations across the output rectifier. Ultimately, in order to maintain a constant output current, the PWM controller modulates the switching frequency in response to the output voltage.
Abstract:
A method and apparatus to dynamically modify the internal compensation of a low drop-out (LDO) voltage regulator is presented. The process involves creating an additional equivalent series resistance (ESR) from an internal circuit. The additional ESR of the internal circuit is sufficient to ensure the DC output stability. This allows the ESR of the output capacitance to be reduced to zero if desired, for improved transient response.