Uniphase Corporation

Apple Inc.

Boschert, Inc.

Boschert Associates

Charles O Forge

David S Schoenwald

Apparatus for operating electroluminescent panels. An electroluminescent panel is driven by a voltage source feeding a modified bridge driven by a pulse width modulated signal. By using a pulse frequency above the range of human hearing and a modulating signal that is a sine wave of the proper frequency for operating the panel, a sine wave is generated across the panel without requiring bulky low frequency magnetic components.

High efficiency supply for electroluminescent panels

Method and apparatus for producing an auxiliary voltage in a switching power supply. One or more auxiliary windings are coupled to the main inductor of the switching power supply. A synchronous switch is used in conjunction with the auxiliary winding to provide rectification and additionally provides waveform averaging which improves efficiency and voltage regulation over varying load conditions.

High efficiency auxiliary switching power supplies

An analog direct current to one MHz information channel is provided, with high acccuracy and 10K volt input-output isolation. The information channel has a voltage to current converter which receives the analog input signal, and whose output is modulated by a square wave generator and provided to a center tap of the primary winding of a transformer. On the output side, the secondary winding of the transformer provides the signal to a precision rectifier which recovers the analog input signal.

Modulator - demodulator transformer coupled D.C. to one Mhz information

A circuit for providing current to a laser tube permits high current, high output voltage, and high frequency modulation response (e.g., up to about 1 MHz, in one embodiment) with low power dissipation. This is accomplished by combining the output current from two current sources, one of which is a high amplitude low frequency current mode switched mode power supply, while the other current source is a low amplitude, high frequency current source.

Circuit for providing fast output current control in a current mode

A current mode switching regulator power supply with an improved regulator system achieves a constant operating period by predetermining the off time of the switching transistor. The off time is programmed by the input and output voltages acting on a resistor-capacitor timing circuit enabled by a current mode controller.

Current mode switching regulator with programmed offtime

A DC switch mode power supply operating from an AC input power source typically has an input stage which includes a rectifier for rectifying the AC input power waveform to provide a DC voltage to the switch mode power supply. This rectifier includes a capacitive storage circuit for storing the DC power to be supplied to the switch mode power supply. To protect the circuit against current surges during start-up, normally an open relay is provided in parallel with a current limiting resistor. This resistor can burn out under some circumstances. This invention replaces the resistor with a capacitor divider circuit containing at least one capacitor in series between the storage capacitor and one of the terminals from the input power supply. A second capacitor can also be provided in parallel with the storage capacitor and one of the diodes of the rectifier. Another diode of the rectifier is in series with the storage capacitor. The resulting circuit limits the initial current surge to the storage capacitor and also functions as a charge pump to make possible the storage of a charge on the storage capacitor greater than the peak input voltage.

Current limiting scheme for the AC input circuit to a switch mode power

A DC to square wave inverter (100) includes a saturable transformer (T102). The current through the saturable transformer (T102) is determined by the load current of the inverter (100). Current through the saturable transformer (T102) flows through two diodes (D100, D101) and through the base emitter junction of a power transistor (Q101). As the load current increases, the current through the diodes (D100, D101) and the power transistor (Q101) increases. This causes an increase in the voltage across the saturable transformer (T102), thus decreasing the amount of time it takes for the saturable transformer to go into saturation. A negative resistance element is coupled in series between the diodes (D100, D101) and the saturable transformer (T102). The voltage rise across the negative resistance element increases in response to increased current coming out of the saturable transformer (T102) and through the diodes (D100, D101). Similarly, the voltage rise across the negative resistance element decreases when the current out of the saturable transformer (T102 ) decreases. This is because the negative resistance element is actually a resistor (R100) coupled across a second transformer (T103). The current through the windings of the second transformer (T103) is fixed by the current through the saturable transformer (T102). However, the current through the second transformer (T103) flows in a direction opposite the current from the saturable transformer (T102). Accordingly, the negative resistance element cancels any increased voltage drop across the diodes and transistor caused by increased load current.

Apparatus for maintaining constant frequency in a DC to square wave

A power supply uses first and second saturable reactor means connected to receive complementary first and second input voltages. The first saturable reactor means is disconnected from the first input voltage when the second saturable reactor means is connected to the second input voltage and vice versa. The power supply includes structure for sensing a variation in the power supply output voltage from a desired value and for producing a control signal in response thereto. A signal representative of volt-seconds, generated in a feedback path, is passed through both first and second saturable reactor means to adjust the flux in the particular saturable reactor means not connected to its input signal. This sets the initial flux in that saturable reactor means the next time it is connected to its input voltage. A change in the power to be supplied by the power supply causes a change in the time necessary to saturate each of the two saturable reactors. The two saturable reactors are connected and disconnected to their corresponding input voltages on a periodic basis. The system is capable of responding to changes in demand for this power within one-half period of switching between said first and second saturable reactors.

Switching mode power supply using saturable reactors

An adjustable output transformer using a pair of adjacent facing pot cores, the first of which carries both primary and secondary windings, the second having only a shorted winding around one leg. The shorted winding inhibits flux through its leg and the corresponding portion of the adjacent leg on the first core so that the secondary voltage may be varied by adjusting the relative rotational positions of the two cores and hence the amount of flux linking the secondary winding.

Variable ratio transformer

Pulsewidth determining circuitry for switching regulator power supplies employs a saturable reactor current comparator that controls a circuit that switches off the primary current whenever it instantaneously exceeds a value dependent upon a control signal derived from the power supply D.C. output level.

Growing community of inventors

Los Altos, CA, United States of America

Charles O Forge