Abstract: The present invention discloses a ZCS discontinuous mode PFC controller having a power saving modulator. The controller turns on through the feedback resistor and the parasitic diode of the controller, thus eliminating the need for a startup resistor. To achieve ZCS, the inductor current is released to zero, while the switching signal is off, before the next switching cycle starts. In order to decrease the switching frequency for light load conditions, an off-time delay is inserted right before the start of every switching cycle. The off-time delay is modulated to be the function of the feedback voltage and supply voltage. When the supply voltage is lower than the limit voltage, the off-time delay will decrease to inhibit the decrease of a switching frequency therefore prevents a low supply voltage. The switching frequency is decreased in accordance with the decrease of the load. Consequently, the switching losses and power consumption for light load and no load conditions are reduced.

Abstract: A system and method for DC/DC conversion are provided in which a high accuracy digital pulse width modulator controller circuit controls a power switch to obtain a desired DC output. The control circuit amplifies the difference of a DC output sample in relation to voltage reference. The amplified difference is then compared with a portion of the DC output. The compared result is used for controlling the power switch. A ripple coming from the DC output side is overlaid upon either one of the inputs to the comparator depending upon the polarity of the ripple signal.

Abstract: To start a switching power supply in an energy saving manner, the method and device according to the invention transmits the energy that is collected by the Y-capacitors through a diode to a capacitor that is located on the secondary side. Once the voltage in the capacitor reaches a first predefinable minimum value, the voltage is applied to an impulse generator as an input voltage and the generator starts the switching power supply. Once the voltage in an additional capacitor on the secondary side reaches a second predefinable minimum value, the voltage in the capacitor is also applied as an input voltage to a control unit, preferably, a microprocessor, that controls the impulse generator.

Abstract: A switching power supply that can operate in critical conduction mode as self-oscillating power supply (SOP) during moderate load, and in discontinuous conduction mode (DCM) under the control of a pulse-width modulated signal under small load, whereby the power consumption of the supply is decreases continuously as the load is decreased. A frequency modulated self-oscillating switching power supply (FMSOP) having a power switch, the switch being held OFF, after a zero-current detector detects that an output current falls to zero, until allowed to turn ON after a pulse having a load-modulated width that corresponds to the load. The FMSOP operates with a switch controller that may include a flip-flop to latch the detector's signal, a load-modulated pulse generator, and a combinatorial logic gate to combine the pulse and the latched signal.

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: The present invention provides an integrated controller for use with a power supply employing a pulse width modulator and a method of operation thereof. In one embodiment, the integrated controller includes a primary control circuit configured to provide a control signal to the pulse width modulator. Additionally, the integrated controller includes a feedback circuit configured to monitor an output signal of the pulse width modulator and to modify the control signal thereby enabling a substantially monotonic increase in an output voltage of the power supply output voltage during a non-steady state period of operation thereof.

Abstract: Several synchronization circuits, a computer, a method of adjusting the operation of an oscillator, and method of operating a power converter are disclosed. The circuits and computer include a switch coupled to a current path. The switch receives a synchronizing signal, and is turned on by an active state of the synchronizing signal, and turned off by an inactive state of the synchronizing signal. The current path is configured to pass a current when the switch is off, and the switch is configured to pass the current when turned on. This abstract is provided to comply with the rules requiring an abstract that allow any reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A PWM controller having a saw-limiter for power limit without input voltage sensing. The saw-limiter has an adder, a reference voltage, a scaler and a saw-tooth signal that is generated by the PWM oscillator. The saw-limiter produces a saw-limited voltage. The PWM controller will turn off its output when the current-sense input signal of the PWM controller is higher than the saw-limited voltage. The saw-limited voltage is equal to the reference voltage while a PWM switching period starts. After that, the amplitude of the saw-limited voltage will gradually increase until it reaches its maximum voltage. Subsequently, a saw-tooth like waveform is generated for the saw-limited voltage. The slope of the current-sense input signal is proportional to the line voltage. Therefore, a higher line voltage creates a sharp slope for the current-sense input signal, which will be restricted by a lower saw-limited voltage and produces a shorter PWM signal.

Abstract: A series circuit of a primary winding 1 A of a transformer 1 and a switching element 2 is coupled to a DC source 3 and a voltage induced in a secondary winding 1B of the transformer 1 according to switching operation of the switching element 2 is rectified and smoothed by a rectifier smoothing circuit 9. Further, a Zener diode 21 is coupled across the switching element 2 with reverse polarity to the switching element 2. The Zener diode 21 may be coupled across a rectifier diode 5 which conducts during the ON period of the switching element 2.

Abstract: An adaptive off-time modulator of a PWM controller is provided for power saving in the light-load and no-load conditions. The maximum on-time is kept as a constant and a bias current of the oscillator in the PWM controller is moderated to achieve the off-time modulation. Reduction of the bias current increases the off-time of the switching period. The bias current is a function of the supply voltage and the feedback voltage, which is derived from a voltage feedback loop. A threshold voltage defines the level of the light load. A limit voltage defines the low level of the supply voltage. A bias current synthesizer generates the bias current. Once the feedback voltage is decreased lower than the threshold voltage, the bias current is reduced linearly and the off-time of the switching period is increased gradually. When the supply voltage is lower than the limit voltage, the bias current increases and determines a maximum off-time of the switching period.

Abstract: Disclosed is a switching mode power supply that includes: a power supply section including a main switch coupled to the primary winding of a transformer, wherein the main switch in normal operation mode performs a switching operation at a predetermined duty, wherein the main switch in standby mode does not perform a switching operation during a first interval and performs a switching operation during a second interval at a first duty, thereby supplying power to the secondary winding of the transformer; a mode discriminator for sensing the reception of an external sync signal at the primary winding of the transformer and generating a signal for operating the main switch in normal operation mode or in standby mode according to whether or not the external sync signal is received; a control voltage generator having a first transistor to which a current corresponding to a signal output from the mode discriminator flows, and a first capacitor connected in parallel to the first transistor; and a switching controller

Abstract: A pulse width modulation controller is coupled to a feedback voltage that is proportional to the power supply output voltage. The controller adjusts a current sense threshold in the controller in response to the feedback voltage. An offset voltage is generated for a predetermined time after the power-up of the power supply. A sum of the offset voltage and a primary current sense node voltage is applied to a current sense input of the controller. The controller generates a switch control signal in response to the sum voltage being less than the current sense threshold. The duty cycle of an output control switch is changed by the switch control signal thus adjusting the output voltage ramp.

Abstract: A power converter, and more particularly a switched AC/DC converter, is provided with an input current shaping (ICS) function. The ICS function is carried out by adjusting the conducting angle of the input current for a rectifier coupled to a central tap of a main transformer, thereby obtaining a higher power factor. Owing to the action of the ICS, the ripples in the feedback signal are usually larger. The ripples are used to modulate the switching frequency to effectively disperse and planarize the electromagnetic energy distribution of the power supply, and to suppress the electromagnetic interference problems of the power supply.

Abstract: An improved soft switched AC power distribution system for minimizing electromagnetic interference and AC losses in an AC power distribution system. The improved AC power distribution system comprises a flyback transformer comprising a primary winding and at least one intermediate secondary winding. A synchronization control circuit is connectable to the primary winding while at least one load transformer is connectable to the at least one intermediate secondary winding. The at least one load transformer connectable to the at least one intermediate secondary winding is connectable via an EMI shielded connection with controllable voltage and current rise times.

Abstract: A flyback power converter includes a transformer for transferring an input voltage from a primary side to a secondary side. The secondary side includes a main output voltage loop and at least one auxiliary output loop connected with a magnetic amplifier. A pulse width modulation (PWM) controller controls a switch on the primary side of the transformer for turning on the switch and turning off the main output voltage loop and the auxiliary output voltage loop for storing a magnetizing energy on windings of the secondary side. The PWM controller further turns off the switch and turning on the main output voltage loop for providing a main voltage output and for magnetizing the magnetic amplifier connected to the auxiliary output voltage loop. The magnetic amplifier functioning as an auxiliary-loop switch for turning on the auxiliary output voltage loop when the magnetic amplifier is saturated with magnetization and turning off the main voltage output voltage loop for providing an auxiliary output voltage.

Abstract: A multiple output power supply circuit is disclosed. The power supply circuit comprises an input voltage wherein the input voltage is coupled to a driver and a transformer coupled to the input voltage wherein the transformer is coupled to at least one switch. The power supply circuit further comprises at least two rectifiers, each of the at least two rectifiers coupled to the transformer via a winding, each of the at least two rectifiers comprising at least one diode and a controlled switching device coupled in parallel. According to the present invention, the circuit in accordance with the present invention provides multiple power outputs in a substantially more efficient manner.

Abstract: A generic voltage converter outputs at least two voltages: a Vo potential that is regulated using output-to-input feedback to a PWM that controls duty cycle of the converter switch, and a VoAUX potential available from a post-linear regulator. Output-to-input feedback is provided from the post-linear regulator to a node in the PWM, e.g., COMP, SoftStart, VFB. Whenever the post-linear regulator senses excessive VoAUX current, feedback from the regulator commands the PWM to reduce converter duty cycle, which reduces VinAUX, as well as VoAUX and Vo, without cross-regulation. The topology minimizes thermal dissipation within the regulator pass element by saturating the pass element at maximum VoAUX current flow such that at maximum current flow there is minimal voltage drop across the pass element.

Abstract: A switch mode power supply (200, FIG. 2; 600, FIG. 6) includes a transformer (208), a transistor (212) that drives the primary winding of the transformer, and a controller (210, 610). The controller senses whether or not the transformer is reset and applies a switching control signal to a control terminal (220) of the transistor, accordingly. The signal is produced at a switching frequency, and the signal has a duty cycle that is limited based on whether or not the transformer is reset.

Abstract: A pwm controller 10 which includes a Vcc node (pin 6); a start-up current source 180 connected to the Vcc node; and a driver circuit 150, 190 also connected to the Vcc node, wherein the pwm controller 10 is arranged to operate in a first phase in which the start-up current source supplies 180 current to the Vcc node but the driver circuit is turned off; a second phase in which the driver circuit 150, 190 is enabled and draws current from the Vcc node; and a third phase in which both the start-up current source 180 and the driver circuit 150, 190 are turned off whereby very little current may be drawn from the Vcc node (pin 6) during the third phase.

Abstract: A switching regulator (18) for use in a switching power supply (10) detects a fault condition by looking for presence of feedback signals during a timer period. If feedback is present but less than a threshold value during the timer period, then the switching power supply (10) is operating normally. If feedback is not present during the timer period, then the switching power supply is in a fault condition. One way of implementing the timer is to charge and discharge by-pass capacitor (23). The timer period is the time for the VCC voltage to drop from a maximum value to a predetermined threshold. When a fault is detected, the gate drive signal from the switching regulator is disabled for a period of time before attempting auto-restart.

Abstract: Control circuitry for controlling the delivery of power from a source voltage to a load in a transformer coupled power converter. The control circuitry includes a power switch having an input coupled to the source, an output, and an activation gate, the power switch, when cycled ON and OFF, defining a pulses of power at the load. A pulse generator is coupled to the power switch, the pulse generator producing a train of constant frequency, constant ON time switching pulses for driving the power switch activation gate. A pulse rate controller responsive to an error signal is coupled between the pulse generator and the power switch, the pulse rate controller regulating an output voltage at the load by controlling the rate of switching pulses delivered to the power switch activation gate over time. The error signal is derived by estimating the output voltage at each switching cycle from the primary side current, while compensating for the expected loss between the source and the load for each power switch cycle.

Abstract: An output voltage regulation system allows independent output regulation of multi-output dc-dc switched-mode power converters. The channel resistance of MOSFET synchronous output rectifiers are controlled to obtain the voltage drop required to keep the respective output between predetermined limits concurrent with wide excursions in output load. A typical circuit has a transformer with an input winding coupled to a dc source. A transformer has at least a first and second output winding. A switched-mode regulator means samples a portion of the first output voltage and provides at least a first pulse-width modulated drive voltage having a first state and a second state to a first input semiconductor switch control terminal. The drive voltage first state turns the input semiconductor switch on and the drive voltage second state turns the input semiconductor switch off.

Abstract: A power supply circuit includes an input stage having a primary winding of a transformer, a drive pulse circuit producing clock and drive pulses, and an input control circuit for driving the primary winding with the drive pulse; and an output stage including a secondary winding, a first transistor having an input, and an output path connected with one end of the secondary winding; a second transistor having an input, and an output path connected with another end of the secondary winding; the first and second transistors being connected with the drive pulse circuit and the second transistor controlled to turn off by the clock pulse immediately before the first transistor turns on; an inductor connected to the output paths of one of the first and second transistors; and a capacitive circuit connected to the inductor.

Abstract: A high voltage flyback power supply provides slope-based primary feedback to control the off-time of the power supply. When a negative slope is detected at a low side of a primary winding of the power supply, an off-time cycle is terminated and a next on-time cycle is initiated. The slope-based off-time primary feedback helps to keep the off-time of the power supply in sync with ringing of the primary leakage inductance and the primary-side capacitance of the power supply. Such a power supply is particularly useful for battery-powered systems with low voltage rails. The power supply can also include on-time feedback to shorten the on-time of the power supply after the secondary-side voltage rises beyond a certain relatively high voltage level. In this way, the transformer of the power supply is charged less when the power supply is driving relatively light loads.

Abstract: An output voltage regulation system allows independent output regulation of multi-output dc-dc switched-mode power converters. The channel resistance of MOSFET synchronous output rectifiers are controlled to obtain the voltage drop required to keep the respective output between predetermined limits concurrent with wide excursions in output load. A typical circuit has a transformer with an input winding coupled to a dc source. A transformer has at least a first and second output winding. A switched-mode regulator means samples a portion of the first output voltage and provides at least a first pulse-width modulated drive voltage having a first state and a second state to a first input semiconductor switch control terminal. The drive voltage first state turns the input semiconductor switch on and the drive voltage second state turns the input semiconductor switch off.

Abstract: A device for generating an electrical signal of a required form, preferably a sine wave suitable for a ringer, comprising an amplifier for producing an output signal of a required form, a power supply generator for supplying a power supply voltage to the amplifier, and a circuit for producing a first feedback signal to control the power supply voltage based on the output signal. Additionally, the amplifier provides comparison of a reference input signal with a second feedback signal formed from the output signal.