Showing papers on "Forward converter published in 1987"

Integrated uninterruptible power supply for personal computers

Abstract: A method and apparatus for providing uninterrupted DC and AC power for a desktop personal computer is described. The source of the uninterrrupted DC and AC power is derived from an integrated power supply that is sized to fit within the existing housings of most desktop personal computers as a plug-in replacement for existing power supplies. A high degree of efficiency is obtained using an integrated design with the main power conversion derived from a DC/DC dual primary resonant converter. The main primary of the resonant converter is driven from a high voltage DC bus which is supplied from AC mains when available. When the AC mains is unavailable, the second primary of the DC/DC dual primary resonant converter receives power from a low voltage battery source. Secondaries of the converter produce low voltage DC for driving the personal computer, high voltage DC for augmenting the high voltage DC bus, which in turn is used to drive a DC/AC inverter for supplying uninterrupted AC voltage for powering peripherals such as a monitor, printer, etc. A medium-voltage secondary is also sourced from the converter which drives a battery charger to recharge an internal battery pafck upon restoration of the AC mains.

Apparatus for controlling electric motor

Abstract: A control apparatus for controlling the main circuit for driving an AC electric motor consisting of a diode converter and a pulse width modulation (PWM) power converting device, in which it is arranged that the DC current as the output of the diode converter is detected by a current detector, the AC component of this DC current is filtered through a high-pass filter, and a pulse-width-modulation control is exercised by a control circuit in response to the output of the high-pass filter so that the DC current as the output of the diode converter may be smoothed out in the main circuit by the PWM power converting device. By such arrangement, this control apparatus of an electric motor is made smaller in size and simplified in structure and enabled to control the power factor of the power source of the diode converter to close to 1.0.

Pseudo-resonant full bridge DC/DC converter

Abstract: This paper proposes a new dc/dc converter topology which combines the ease of control and wide range of conventional dc/dc converters, with low switching losses, low dv/dt and low EMI that is typical of zero voltage switched resonant converters. Consequently, the ratings of these components are substantially lower than for similarly rated resonant topologies. Operation at very high frequencies is possible and is shown with the fabrication of a 200 watt, 1 MHz dc/dc converter.

Three-Phase AC/DC PWM Converter with Sinusoidal AC Currents and Minimum Filter Requirements

Abstract: A pulsewidth modulation (PWM) control technique suitable for fully controlled three-phase ac/dc converters is analyzed, which gives sinusoidal input currents and ideally smoothed dc voltage. The technique allows four-quadrant operation and full-range control of the input power factor. An extension to a simplified converter scheme, capable of one-quadrant operation, is also considered. Operation of the converter is analyzed under both ideal and actual conditions. Control implementation and design criteria are discussed and experimental results are reported.

Development of a Unipolar Converter for Variable Reluctance Motor Drives

Abstract: A new converter concept for driving the switched reluctance motor has been developed. This converter has only one switching device per phase, uses a unipolar dc supply, returns all the trapped energy to the source, and does not require bifilar windings; it is called a C-dump converter because the trapped energy is dumped in a capacitor and then returned to the dc source. The topology for several different C-dump converters is presented. In addition, the design and experimental results for a C-dump converter using a chopper to recover the energy dumped on the capacitor are presented.

Resonant forward converter

Abstract: A resonant forward converter at a switching frequency of 10 MHz provides a small volume point-of-load converter for distributed power systems. The leakage inductance of a transformer is made negligibly small relative to the magnetizing inductance of the transformer. This enables a resonant controllable switch on the primary side of a transformer and a secondary side rectified diode to be switched either on or off at the same time. The capacitance across the primary side switch and the secondary side diode rings with a resonant inductor connected in parallel with the transformer. Both the switch and diode, therefore, have zero voltage switching transitions. Further, the resonant inductor being connected in parallel with the transformer provides a resonant ring that is independent of load.

A new on-chip converter for submicrometer high-density DRAMs

Abstract: The converter described is a feedback-type voltage regulator which supplies a reduced voltage to an entire RAM circuit. A novel timing activation method was introduced to save power. The converter has been implemented on an experimental 4-Mb dynamic RAM. It was found that an even faster access time and higher reliability compared to a conventional design could be achieved by using an on-chip voltage converter and shorter channel transistors. This voltage converter is suitable for high-density, high-speed, and high-reliability DRAMs with submicrometer transistors.

Two transistor flyback switching converter with current sensing for discontinuous operation

Abstract: Disclosed is a dual transistor flyback converter having a pair of synchronously driven switching transistors (20, 36) for switching voltage to a primary (12) of a flyback transformer (10). When driven into a cutoff state, transistor (36) isolates switching transistor (20) from the supply voltage (V1), thereby preventing a transformer reflected voltage from being superimposed on the supply voltage and imposing such voltage across the transistor (20). Clamp diodes (40, 42) maintain the switching transient voltage across the flyback transformer primary (12) between prescribed limits. Capacitor (48) allows the switching transient to pass and be clamped by the diodes (40, 42), but prevents the reflected secondary voltage from being clamped when the input voltage is low. A current sensing circuit (50) in series with the flyback transformer secondary (14) senses current flow during the power conversion cycle, and provides a digital indication to a PWM control circuit (66) to facilitate reliable discontinuous operation of the flyback converter.

Source volt-ampere/load volt-ampere differential converter

Abstract: A source V-A/load V-A differential converter (single quaddrant DC-DC topology) combines the canonical functions of both the boost and buck converter topologies. Basic advantages of the boost and buck topologies are retained, disadvantages of these and prior art compound topologies are eliminated, and several entirely new and useful functions are realized. These new functions include sub-microsecond source voltage/load step response (independent of feedback loop parameters), extremely wide source voltage range, very high conversion efficiency/power density, multiple auxiliary outputs with closely held voltage range parameters (without resort to minimum load, pre-load, or sub-regulation), galvanic input/output isolation, enhanced capacitance safety/energy storage, reduced gain bandwidth requirements, and intrinsic stability. The differential term derives from the transfer function for this new compound topology, i.e., x=δ(a+x).

Design Considerations for Very High Frequency Resonant Mode DC/DC Converters

Abstract: The demand for higher switching frequencies in power converters has rekindled interest in resonant mode topologies. Conventional resonant converter circuits, however, are not optimized for high-frequency operation. A new resonant mode dc/dc converter topology exhibits desirable characteristics including zero switching losses, elimination of snubbers, simple control strategy, and circuit operation that is insensitive to parasitics such as diode reverse recovery. Analysis and design techniques are discussed in detail and are experimentally verified with a 150-W prototype converter operating in the frequency range 500 kHz-1 MHz.

Switching converter with enhanced voltage clamping and energy recovery

Abstract: A power converter is provided with a pair of auxiliary windings coupled to the primary windings of the output transformer which serve as energy choke windings. An additional pair of choke windings are coupled between the input of the converter to a common terminal of the primary winding. These choke windings prevent excess voltage from appearing across the switching devices of the converter during the turn-off portions of the cycle.

The Double Converter: A Fully Regulated Two-Output DC-DC Converter

Abstract: A new type of two-output dc-dc converter is proposed With this ``double converter'' two completely regulated outputs can be obtained using only one switching element and very often without an extra transformer The operating principle is based on the discontinuous-conduction-mode operation of one output and the continuous-conduction-mode operation of the other output Both outputs are sensed, and the duty cycle of the switching element and the switching frequency are controlled at the same time A prototype has been built, and the results obtained are discussed

Frequency feedback on a current loop of a current-to-pressure converter

Abstract: A current-to-pressure (I/P) converter (20) provides an output pressure as a function of the magnitude of a variable input DC current. The I/P converter (20) includes a pressure sensor (64) which produces a feedback signal representative of the output pressure. Based upon the feedback signal and the magnitude of the input DC current, an electrical control signal is produced which controls a device (40) for varying the output pressure. The I/P converter (20) also includes a circuit (86) for generating a time-varying signal which is sent back over the current loop wires (28) through which the input DC current flows. The time-varying signal provides an indication of whether the I/P converter (20) is functioning properly. This permits diagnosis of possible causes of control system malfunctions without having to inspect the I/P converter (20) itself.

Integrated-magnetics power converter

Abstract: Novel switched mode boost-buck integrated magnetic power converters are disclosed featuring two winding bobbins, a new boost section with enhanced gain, means for operating the converter in a continuous mode of energy storage under minimum output loading conditions while providing adequate time for removing the magnetization energy of the transformer part of the integrated magnetics, and other new and different converter topologies.

A high frequency, low volume, point-of-load power supply for distributed power systems

Abstract: A resonant version of the dc-dc forward converter is presented in this paper. It is a topology capable of operation in the 10 MHz range, and it can be used for very low volume, point-of-load conversion in distributed power systems. In comparison to other resonant topologies, this converter takes advantage of a very low transformer leakage inductance to achieve zero-voltage switching of all its power semiconductor devices. Its resonant ring is also independent of load current. A 50 watt prototype operating at 3.6 MHz and a discussion of the component work necessary to reach 10 MHz are presented.

Phase controlled DC-AC converter with high frequency switching

Abstract: A novel type of the sinusoidal DC-AC converter is presented, where a pair of switches is placed in each side of the primary and the secondary of the isolation transformer. This converter is controlled by the phase difference between the two pairs of switches. As a result, the transformer is miniaturized by making the switching frequency high. This converter is especially suitable for small UPS systems.

Active snubber forward converter

Abstract: In a forward converter power supply comprising a transformer having a primary winding connected to a primary circuit and a secondary winding connected to a secondary circuit, and a switching transistor in the primary circuit, an active network snubber in the primary circuit for receiving and storing continuing current from the transformer primary winding upon switching of the transistor and for returning current through the transformer primary winding so as to resent the transformer and thereby returning parasitic energy in the transformer caused by leakage inductance and magnetizing current to the energy source. The snubber comprises a capacitor for receiving and storing continuing current from said primary winding upon switching of the transistor, a diode for providing a path for flow of the continuing current from the primary winding to the capacitor and an electronic switch operatively connected to the capacitor to the primary winding and to the switching transistor for returning current from the capacitor to the primary winding upon further switching of the transistor. The capacitor is connected so that the voltage thereon automatically adjusts to reset the transformer upon the further switching of the transistor. The electronic switch and the switching transistor are operatively connected in a manner so as to be always in opposite conducting states.

Overload-protection methods for switching-mode DC/DC converters: Classification/ analysis/ and improvements

Abstract: Switching-mode DC/DC converters must be protected against overload, to prevent failure of the converter or the external current-carrying hardware. This paper collects, classifies, analyzes, and evaluates the known protection methods, and describes a new negative-feedback frequency modulator which prevents short-circuit-current runaway. Test data prove the effectiveness of the new scheme.

Pulse width modulator used for a power converter with a transformer

Abstract: This apparatus is a power converter which delivers a pulse produced based on a dc voltage to the primary side of a transformer with its polarity being changed per half cycle to take out an ac power from the secondary side thereof. By modulating the pulse width of a pulse delivered, the output power becomes adjustable. By detecting a current on the primary side of the transformer, current change rates at positive and negative half cycles are calculated. By comparing these change rates at the both cycles, magnetic deviation of the transformer can be detected. With the pulse width correcting means, pulse widths of pulse delivered at positive and negative cycles are adjusting so as to cancel such a magnetic deviation. The control for preventing magnetic deviation described above is realized as a control having a very fast response. In addition, such a control enables the transformer to be operative in a range extremely close to the range where the transformer is saturated.

D.C. voltage converter with overload protection

Abstract: In a d.c. voltage converter 1 including a series arrangement of a transformer 3 and a pulse-switched current source 7 the power converted by means of the transformer 3 is kept constant with the aid of a control circuit 13. In the event of a short-circuit in one of the secondary windings 5-1, 5-2 a voltage drop across an auxiliary winding 6 of the transformer 3 is used to limit the converted power during the short-circuit.

DC to DC converter

Abstract: A DC to DC converter of the switched capacitor kind is described in which controlled solid state switches are used to effect the switching and to limit the current passed to the capacitors in dependence upon that required to match a load.

High efficiency battery adapter

Abstract: Extremely high efficiency is achieved in a DC to DC converter by using a relaxation oscillator in which two transistors alternately conduct current to the primary winding of a step-up transformer. The transistors are interconnected by a resistor and capacitor in series so that when the converter is lightly loaded, the saturable reactor in the circuit will be self-resonant, so as to draw only minimal power from the battery source. The converter also includes a battery charge level monitor circuit that prevents the DC to DC converter from oscillating and thus providing power unless the battery is above a minimum charge level when its voltage is applied to the converter. In a preferred embodiment, the converter provides an output of up to 100 watts.

DC/DC converter with high efficiency and small load

Abstract: DC/DC chopping converter comprising a hysteresis comparator 42 contained within a regulating circuit 4 for controlling operation matched to the load CH of the converter. The hysteresis comparator modifies the width and the frequency of chopping control pulses (CD) as a function of the load. The control pulses have a substantially constant frequency F and a width substantially proportional to the load when the latter is greater than a predetermined value, and have a substantially constant width and a variable frequency F/N substantially inversely proportional to the load when the latter is less than the predetermined value. The variable-frequency operation reduces the losses due to transfers of energy to a filtering capacitor 13 of a chopping and filtering circuit 1 and thus contributes to improving the small-load efficiency of the converter.

DC/DC voltage converter having a transformer

Abstract: The described DC/DC voltage converter contains a transformer (UT) whose primary current is controlled by a switching transistor (T) and on whose secondary side one or more switches are arranged in the longitudinal paths and/or transverse paths. In order to keep the power loss on the switches as low as possible, it is provided for power MOS field-effect transistors (FT1, FT2) in the inverse mode to be used as switches. In order to open and close the power MOS field-effect transistors (FT1, FT2), the transformer (UT) contains separate secondary coils (L4, L6) which are connected in the gate-source circuit of the power MOS field-effect transistors (FT1, FT2). Pulse-forming circuits (Zl1, Zl2) ensure that the power MOS field-effect transistors (FT1, FT2) are changed from the off-state into the on-state and from the on-state into the off-state at the desired point in time.

An implementation of current-mode control for a series-resonant DC-DC converter

Abstract: A new implementation of the (average) current mode control for a series resonant converter operated in the frequency range higher than the circuit resonant frequency will be introduced. The controller design is based on the ASDTIC (Analog-Signal-to-Discrete-Time- Interval Converter) concept but has some improvements over the original design which often suffered from static and dynamic instabilities. Some experimental results of a breadboarded converter with this new controller will be presented and the near-optimum fast response characteristics of the combination of this controller and the load current feedforward will be included to show the similarity between the current-mode controller for switching-mode converters and series-resonant converters.

Speed-limited electrically compensated constant speed drive

Abstract: An electrically compensated constant speed drive (10) which is speed limited so that power flow through the speed compensation link is unidirectional includes a permanent magnet generator (pmG) which is interconnected with a permanent magnet motor (pmm) by a power converter (30). The permanent magnet generator (pmG) and the permanent magnet motor (pmm) are controlled by first and second independent control loops. The power converter (30) includes an AC/DC converter (54) coupled to electrical power windings of the permanent magnet generator (pmG), a filter (58) coupled to the output of the AC/DC converter (54) and an inverter (56) coupled between the filter (58) and electrical power windings of the permanent magnet motor (pmm). The permanent magnet generator (pmG), AC/DC converter (54), filter (58) and the first control loop together develop a voltage on a DC bus. The voltage on the DC bus, which is coupled to the inverter (56) is sufficient to operate the permanent motor (pmm) with the required speed and torque, and thus the second control loop need not implement a voltage control scheme, such as a PWM control.

Start-up circuit for an integrated-magnetic power converter

Abstract: An innovative start-up circuit is disclosed which uses ordinary solid-state components and which may be used with a wide variety of switched mode boost-buck integrated magnetic power converters, including those having only two winding bobbins, a boost section with enhanced gain, and several new and different core arrangements. The start-up circuit comprises a winding which is transformer coupled to the drive transformer, a capacitor which is charged by the application of power to the input of the converter, switching means for switching current from the input of the converter to the drive transformer in response to the charging of the capacitor, and means for preventing the capacitor from operating the switching means after the converter is placed into operation.

Variable input voltage DC to DC converter with switching transistor drive current regulator

Abstract: The DC to DC converter includes a coupled inductor having a primary winding and a feedback winding. A drive current regulator circuit receives a variable input voltage from the feedback winding but transmits a constant base drive current to the base terminal of the converter switching transistor. The base drive regulator circuit thereby enables the DC to DC converter to operate at high levels of efficiency over wide ranges of DC input voltages such as twelve to forty-eight volts DC.

Switched capacitor filter for use with a digital-to-analog (D/A) converter

Abstract: The output of a digital-to-analog (D/A) converter is coupled to the input of a filter. The D/A converter is initialized each time a new digital word is applied to the D/A converter for conversion, whereby each data conversion cycle (T D ) includes an initialization interval (T I ) followed by a conversion interval (T C ). During T I the output of the D/A converter is driven to a reference level and during T C to the output of the D/A converter corresponds to the value of the input signal. The input section of the filter stores the D/A output just prior to initialization and, for during T I , coupling the stored value within the filter for processing while inhibiting the coupling to the filter of the reference level present at the D/A output.