A chopper power supply includes a transformer having first and second primary winding segments as well as first and second secondary winding segments respectively associated with the first and second primary winding segments. First and second switching transistors respond to a control source so that the first transistor connects the first primary winding segment to first and second opposite polarity terminals of a DC power supply at a time mutually exclusive from the time the second primary winding segment is connected to the DC terminals via the second transistor and vice versa. Each of the secondary winding segments includes first and second portions disposed on opposite sides of the primary winding segment associated with the secondary winding segment. The portions of the first secondary winding segment are connected in series with each other and coupled to the first primary winding segment so that voltages induced in the portions of the first secondary winding segment add together. The portions of the second secondary winding segment are connected in series with each other and coupled to the second primary winding segment so that the voltages induced in the portions of the secondary segment add together.

A digital picture display device in which, due to a location-dependent, determined brightness drive of pixels in a picture formed line and field-sequentially, it is possible to obtain an oscilloscopic image in the form of a waveform profile on a display screen (TV, OSC). A digital signal comparison circuit (COMP) having a first input (I1) for receiving location information in the form of an actual line number (L-act) and a second input (I2) for receiving from a line buffer circuit (W-buf) digital values of the waveform profile to be displayed. The signal comparison circuit produces a binary drive signal (BDS) at its output. The line buffer circuit (W-buf) is filled from a digital picture source (DPS) via a series arrangement of another line buffer circuit (L-buf) for storing the picture information associated with a selected line having a selectable first line number (L-sel), a multiplier or divider circuit (SCAL) for obtaining picture line strips made up of different numbers of picture lines via selectable factors (W-fac) for displaying the waveform profile on different scales, and a subtractor circuit (SUB) for moving the bottom line of the picture line display strips having the different heights by means of a selectable second line number (L-bot). The digital picture display device provides an accurate location of the movable waveform profile which can be observed on a desired scale.

A method and apparatus for suppressing capacitive current in transformers is described. The winding of a transformer is constructed or modified into two substantially identical winding halves wired in a series aiding configuration. Two leads emanate from the center point of the winding, where the two halves are connected in series. This center point is at a constant potential throughout the switching cycle of the transformer. Suppression of the capacitive current in the input/output leads of the transformer is achieved by introducing common mode impedance into each lead and a corresponding center tap lead. The common mode impedance can be introduced in a variety of ways such as: running the pair of leads through a toroid, bead or sleeve of magnetic material; winding the leads on a magnetic toroid or rod; or using the magnetic core structure to introduce the impedance. Placement of any of these magnetic materials in substantial proximity to the lead pairs as arranged will suppress the capacitive current due to the coupling of the leads and the magnetic material.

An output transformer for use with a push-pull vacuum tube amplifier using a multifilar ribbon in which primary windings and secondary windings co-exist. The multifilar ribbon is wound continuously around a common core side-by-side to form successive layers. The primary windings are connected in series by turning the multifilar ribbon after the layers of multifilar ribbon have been wound and connecting the turned end of the multifilar ribbon to the beginning end of the multifilar ribbon. The winding scheme increases the coupling between the first half primary, the second half primary and the secondary without reducing performance at high frequencies. The secondary windings are connected in series or in parallel to obtain the proper turns ratio for the transformer. A method of interconnecting the secondary windings for different turns ratios is also provided.

A wideband audio output transformer for use with a push-pull vacuum tube amplifier using a multifilar ribbon in which primary windings and secondary windings coexist. The multifilar ribbon is wound continuously around a common core side by side to form successive layers. The primary windings are connected in series by turning the multifilar ribbon after the layers of multifilar ribbon have been wound and connecting the trailing end of the multifilar ribbon to the beginning end of the multifilar ribbon. Two additional wires are added in parallel with wires of the primary windings in the multifilar ribbon to redistribute the effective capacitance throughout the windings. The winding scheme eliminates the signal imbalance of an output transformer with a balanced push-pull primary winding and an unbalanced secondary winding at high frequencies. The winding scheme also increases the coupling between the first half primary, the second half primary and the secondary windings without compromising transformer performance at high frequencies. The secondary windings are connected in parallel to obtain the proper turns ratio for the transformer. The center tap of the balanced push-pull primary winding and one side of the unbalanced secondary winding is connected to AC ground.