GB2031679A - Switching regulator for a television apparatus - Google Patents

Abstract

A controllable switch 14 is coupled to a source 10 of unregulated direct voltage and in a closed loop with a filter inductor 16 and a storage capacitor 18 and has its on-off state controlled at the horizontal deflection rate, e.g. by deflection circuit 22, to control the voltage across the capacitor. A diode 24 is coupled with the filter inductor and storage capacitor to form a second series circuit through which current can continue to (ow in the inductor 16 when the controllable switch is opened. The controllable switch is used to regulate the voltage applied to the horizontal deflection circuit 22. A turn-off winding couples a retrace pulse to the switch 14 during each horizontal retrace interval in preparation for the following regulation interval. The current variations in the filter inductor cause the diode to become nonconductive at times, thereby changing the average time during which the filter inductor parallels the deflection winding and varying the retrace pulse duration in such a manner as to improve the regulation. <IMAGE>

Description

SPECIFICATION Switching regulator for a television apparatus This invention relates to a switching regulator having improved characteristics for a television display arrangement.

In order to avoid the weight and cost of a line isolation transformer, television receivers may be supplied with power directly from the ac power line through a rectifier and filter. The filtered direct voltage will vary in proportion to the variations in the ac power line voltage, which may be undesirable. Also, the value of the filtered direct voltage will be approx imatelythe peak value of the alternating-current input, and may be greater or less than the desired value.

It is possible to produce a regulated output voltage of lesser magnitude than the raw dc input by use of a series-pass regulator circuit, but this has the disadvantage of substantial power dissipation when the load current and/orthe difference between the raw voltage and the regulated voltage are large.

Recently, an emphasis on reduced power consumption has lead to the increased use of switching regulators for powering television receivers. In switching regulators, a switch coupled to the raw direct-voltage supply is periodically turned on and off with a duty cycle adapted for regulation of the controlled voltage. United States Patent 4,024,434 issued May 17, 1977 in the name of Joosten et al.

illustrates the use of a transistor operated as a switch for reduced dissipation. While the power dissipation is reduced by this form of operation, transistors often have low gain and require considerable base drive in order to operate in the low-power saturated mode. Further, the inductor often associated with the switching regulator requires a so-called freewheeling diode to prevent application of excessive voltages to the transistor at turn-off and to recover energy stored in the inductor.

By the use of controlled rectifiers such as SCR's the base drive problem associated with the use of transistor switches is obviated. The SCR is regenerative, and when gated into conduction remains conductive as long as forward bias is maintained across the main conduction path. Thus, a gate pulse may be momentarily applied to the SCR control electrode to initiate conduction and then need no longer be supplied to maintain conduction. The controlled-rectifier switch is turned off when forward current diminishes to zero and attempts to reverse, normally caused by application of a reverse voltage from an external source.The SCR is advantageous by comparison with the transistor, not only because of its gating characteristics, but also because application of reverse voltages exceeding the reverse voltage breakdown of the device do not result in its destruction but merely switch it into the conductive mode.

United States Patent 3,970,780 issued July20, 1976 in the name of Minoura, describes a switching regulator in which an SCR is used as the control element for controllably charging a capacitor from the unregulated supply through a series connection of an inductor and a winding coupled to the horizontal deflection circuit. In the Minoura arrangement, the inductor must be small enough so that the current in the inductor and SCR can be reduced to zero during the retrace interval by the difference between the unregulated direct voltage and the turn-off voltage pulse across the winding. As a result, relatively large peak currents flow in the inductor and in the storage capacitor during the capacitor charging interval. These relatively large currents undesirably result in relatively large 12R or heating losses.Also, the turn-off requirements and the relatively large changes in regulator current with changes in load current, such as those resulting from kinescope beam current changes, produce large changes in regulator peak currents. These changes in peak current passing through the regulator SCR and turn-off windings result in changes in the amount of energy coupled between the winding and the horizontal output transistor of the deflection circuit, and contri butt two retrace time modulation and storage time modulation in the base of the output transistor as a function of beam current. The storage time modulation causes bending of vertical lines displayed on the raster.It is desirable to reduce the retrace time modulation and bends resulting from beam current changes, to reduce peak currents and heating losses and to reduce the load-dependent variation in the voltage pulse available to the turn-off regulator SCR in order that a larger filter inductor may be used.

In accordance with a preferred embodiment of the invention, a switching regulator for a television apparatus includes a controllable switch, an inductor and a horizontal deflection generator, forming a first series circuit coupled across a source of unregulated direct voltage for providing a path for an increasing current flow in the inductor during those intervals in which the switch is closed. The switch includes a gate and a main current conducting path which when forward biased remains open or nonconductive until a signal is applied to the gate and which thereafter remains closed or conductive so long as the forward bias is maintained. Coupling means couple horizontal rate signals from the deflection generator to the main current conducting path for controlling the opening of the switch.A diode is coupled to the inductor to form a path for a decreasing current flow in the inductor during at least a portion of the intervals in which the switch is open. A capacitor is coupled to the deflection generator for filtering the current flow in the inductor to form an operating voltage for the deflection generator. A control circuit is coupled to the deflection generator and to the gate for controlling the closing of the switch for controlling the average of the increasing and decreasing currents in the inductor to control the energizing voltage in a feedback manner.

In the drawing: FIGURES 1-4 are diagrams in block and schematic form of alternative switching portions of a television display apparatus embodying the invention; FIGURES 5 and 6 illustrate as amplitude-time waveforms certain periodic voltages and currents occurring in the apparatus of FIGURES 1-4 during operation; FIGURE 7 illustrates a further embodiment of an apparatus according to the invention, in block and schematic diagram form; FIGURE 8 illustrates an apparatus similar to that of FIGURE7; and FIGURE 9 illustrates a voltage time waveform of retrace pulses occurring in the apparatus of FIGURE 8 during operation.

In FIGURE 1, supply terminals 10 and 12 are adapted to be coupled to a source of unregulated direct voltage such as rectified and filtered powerline voltage. The anode-cathode path of an SCR 14, a filter inductor 16 and a horizontal deflection circuit 22 are coupled together at circuit points 26 and 30 in the order mentioned to form a first series circuit. The series circuit is coupled across supply terminals 10 and 12 by a secondary winding 20b of a transformer 20. A storage capacitor 18 is coupled between circuit point 30 and supply terminal 12. Deflection circuit 22 is energized by the voltage appearing across the capacitor.A diode 24 has its anode connected to supply terminal 12, hereinafter referred to as "ground", and its cathode connected at circuit point 26 to a terminal of inductor 16 to form a closed second series path or circuit for the flow of current through inductor 16, capacitor 18 and diode 24.

Avoltage control circuit illustrated as a block 36 is coupled to ground, and by a conductor 28 to circuit point 30. Voltage control circuit 36 may be of the type well-known in the art and exemplified in the aforementioned Minoura patent. Voltage control circuit 36 senses the voltage between point 30 and ground and produces periodic gating pulses which are coupled by means of a transformer 32 to the gate of SCR 14 to maintain the voltage at point 30 substantially constant relative to ground. A conductor 34 couples horizontal deflection circuit 22 with voltage control circuit 36 for synchronization of the periodic gating pulses with the horizontal deflection in known manner.The primary winding 20a of transformer 20 is coupled to horizontal deflection circuit 22 for coupling retrace voltage pulses from the horizontal deflection circuit to the main anode-cathode current conducting path of SCR 14 by way of a turn-off sec ondarywinding 20b for periodically opening or rendering SCR 14 nonconductive.

In operation, voltage control circuit 36 produces SCR gating pulses illustrated as V36 of FIGURE 5a, which are produced in timed relation with the retrace voltage pulses illustrated as V20a of FIGURE 5b produced across primary winding 20a by horizontal deflection circuit 22. Immediately before time TO as illustrated in FIGURE 5, the voltage produced by winding 20b is small and SCR 14 is conductive, thereby making the voltage between circuit point 26 and terminal 12 positive, as illustrated by V26 of FIGURE 5c, and reverse-biasing diode 24. With SCR 14 conductive, the unregulated voltage is applied across the series combination of winding 20b, inductor 16, and horizontal deflection circuit 22, producing an increasing current in inductor 16 and in winding 20b, as illustrated by 116 of FIGURE 5d and 120b of FIGURE 5e.The current charges capacitor 18 and also supplies the requirements of horizontal deflection circuit 22. The charging of capacitor 18 causes the voltage at point30 to increase slightly.

At time TO, deflection circuit 22 initiates a retrace pulse. As the retrace voltage rises, the voltage at the anode of SCR 14 becomes progressively more negative. The energy associated with the magnetic field of inductor 16 causes current to continue to flow through SCR 14 until a time T1 at which the anode of SCR 14 is at substantially ground potential and circuit point 26 is negative with respect to ground by the forward conduction drop of the SCR. At this time; diode 24 takes over conduction from SCR 14. Further increase in the retrace voltage pulse magnitude reverse-biases SCR 14 and renders it nonconductive.

In the interval after time T1, SCR 14 is nonconductive and a portion of the energy associated with the magnetic field of inductor 16 is transferred to capacitor 18 by a decreasing circulating current through the second series path including inductor 16, capacitor 18 and diode 24 as illustrated by 124 of FIGURE 5f. At a later time T2 the retrace interval ends, and SCR 14 once again becomes forward biased. However, SCR 14 does not conduct until a later time T3 at which a gating pulse is applied to the gate of the SCR to render it conductive. At time T3, the voltage at point 26 increases to substantially equal the sum of the unregulated direct voltage and the voltage across winding 20b.Diode 24 becomes back biased and therefore nonconductive, and inductor current 116 once again begins to increase, continuing transfer of charge to capacitor 18 and deflection circuit 22 as energy is once again stored in inductor 16.

As described, the current in inductor 16 decreases from a time near the beginning of the retrace interval until time T3 at which SCR 14 is gated into conduction. At time T3, the current in inductor 16 stops decreasing and begins to increase. The current is filtered by capacitor 18 to form an energizing voltage for deflection circuit 22. The energizing voltage is regulated by control of time T3. Thus, if the regulated voltage at terminal 30 relative to ground tends to decrease below the desired value, control circuit 36 produces a gating pulse V36 earlier during the deflection cycle, as illustrated by time T3' in FIGURE 5. As shown by the dashed lines in FIGURES 5c-5d, earlier gating results in a net increase in the average of current 116 through winding 16.Such a net increase can maintain the regulated voltage at point 30 in the presence of an increased current drain by deflection circuit 22, or can compensate a tendency to a low regulated voltage produced by a low value of unregulated voltage, or by other causes.

As described, the operation of the arrangement of FIGURE 1 applies when inductor 16 is relatively large. For smaller values of inductance of inductor 16, the current in the winding may be reduced to zero before time T3 at which the SCR is gated ON, in which case voltage V26 at circuit point 26 will rise to equal the regulated voltage when current flow ceases in inductor 16 and diode 24.

While the foregoing explanation describes capacitor 18 as being coupled between the regulated voltage terminal 30 and ground, capacitor 18 may be connected between circuit point 30 and other reference voltage points. FIGURE 2 illustrates an arrangement similar to that of FIGURE 1 in which a different reference point for storage capacitor 18 is used, and also illustrates the interchange of the series connection of winding 20b and SCR 14. In FIGURE 2, elements corresponding to those of FIG URE 1 are given the same reference numerals, in the 200 series. In FIGURE 2, terminals 210 and 212 are adapted to be coupled to a source of unregulated direct voltage.A controllable switch in the form of an SCR 214 has its main current conducting path serially coupled at circuit points 226 and 230 with a filter inductor 216 and a horizontal deflection circuit 222, and the series combination is coupled across the terminals of the unregulated source. A storage capacitor 218 is coupled between circuit point 230 and terminal 210. A diode 224 has its anode coupled to terminal 212 of the source and its cathode connected to inductor 216 at circuit point 226 to form a series circuit with inductor 216 and capacitor 218 in which current can flow in a closed path including terminals 210,212 and the unregulated voltage source.A voltage control circuit 236 is coupled to terminal 212 and to circuit point 230 for sensing the voltage across horizontal deflection circuit 222 and is also coupled by means of a transformer 232 to the gate of SCR 214 for controlling the switching of the SCR to maintain the voltage across the deflection circuit substantially constant. Voltage control circuit 236 is also coupled to deflection circuit 222 by a conductor 234 for synchronizing the switching of SCR 214 with the deflection cycle. Aturn-offwinding 220b of a transformer 220 is coupled between circuit point 226 and the cathode of SCR 214. Winding 220a of transformer 220 is coupled to horizontal deflection circuit 222. Transformer 220 couples retrace pulses produced by horizontal deflection circuit 222 to SCR 214 for periodically rendering the SCR nonconductive.For purposes of explanation, terminal 212 is hereinafter referred to as "ground".

The operation of the arrangement of FIGURE 2 differs from that of FIGURE 1 in that the flow of current in the load represented by horizontal deflection circuit 222 causes a current flow in capacitor 218 which tends to cause the capacitor to charge, i.e., tends to cause the voltage across the plates of the capacitor to increase. Since the unregulated direct voltage changes relatively slowly compared with the deflection frequency, from line to line the voltage between terminals 210 and ground may be taken as being constant. As capacitor 218 charges, therefore, the voltage at circuit point 230 decreases relative to ground. Thus, just as in FIGURE 1, the flow of load current tends to cause a decrease in the load voltage.

In order to raise the voltage across the horizontal deflection circuit in the arrangement of FIGURE 2, capacitor 218 must be discharged. This is accomplished when SCR 214 is conductive through the first series circuit path extending from capacitor 218 to SCR 214, winding 220b and inductor 216 back to the capacitor. During the interval in which SCR 214 is conductive, current is also supplied through SCR 214 and inductor 216 to deflection circuit 222.When SCR 214 is rendered nonconductive by the retrace pulse applied by winding 220b, the energy stored in the magnetic field associated with inductor 216 is used to continue the supply of current to deflection circlit 222 and the discharge of capacitor 218 through the second series circuit path extending from inductor 216 to circuit point 230, capacitor 218, the unregulated voltage source and through diode 224 back to inductor 216. In so doing, a portion of the stored energy is returned to the unregulated voltage source.

The detailed operation of the arrangement of FIG URE 2 can be explained with the aid of FIGURES.

Immediately prior to time TO at which retrace voltage pulses are produced by deflection circuit 222, SCR 214 is conductive and the voltage at circuit point 226 substantially equals the sum of the unregulated voltage and the voltage across winding 220b, as illustrated by V226 of FIGURE 5c. The current in inductor 216 is increasing as illustrated by 1216 of FIGURE 5d under the impetus of the voltage across capacitor 218. The current in inductor 216 also flows through winding 220b at this time, as illustrated in FIGURE 5e. At a time TO, a retrace pulse V220a is applied to the primary of transformer 220, and a pulse voltage is applied between circuit point 226 and the cathode of SCR 214 poled to make circuit point 226 negative and the cathode of SCR 214 positive.So long as SCR 214 is conductive, its cathode is at substantially the unregulated direct voltage, and therefore circuit point 226 is driven progressively more negative as the retrace voltage increases. At a time T1 at which the voltage pulse appearing across winding 220b substantially equals the unregulated direct voltage, circuit point 226 becomes 1 Vbe negative with respect to ground, and diode 224 becomes conductive. Further increases in the pulse voltage across winding 220b cannot make circuit point 226 more negative, and therefore the cathode of SCR 214 becomes more positive than terminal 210 and the SCR becomes nonconductive.

When SCR 214 becomes nonconductive at time T1, current continues to flow through inductor 216 to circuit point 230 and through capacitor 218, but instead of returning through SCR 214, passes as described from terminal 210 to 212 of the unregulated source and returns to inductor 216 by way of diode 224. A portion of the current flow of inductor 216 also flows by way of circuit point 230 to deflection circuit 222 and returns by way of diode 224. A portion of the energy stored in the magnetic field associated with inductor 216 is thus returned to the unregulated source and a portion is supplied to deflection circuit 222. At time T2, the retrace interval ends and SCR 214 is again forward-biased but remains nonconductive until a latertimeT3 at which a gating pulse V236 is generated by voltage control circuit236, as illustrated in FIGURES. AttimeT3, SCR 214 becomes conductive and the voltage at circuit point 226 rises, again rendering diode 224 nonconductive. Inductor 216 is coupled by SCR 214 across capacitor 218 and capacitor 218 begins to discharge, transferring the energy stored as voltage across its plates to inductor 216 by the series path including SCR 214, as described.

This results in a progressive increase in the current of SCR 216 as illustrated in FIGURE 5d.

The voltage at circuit point 230 of FIGURE 2 is regulated by controlling the average current through inductor 216, which is established by the time T3 during the deflection cycle at which SCR 214 is gated into conduction. Thus, if the regulated voltage at terminal 230 relative to ground tends to decrease below the desired value, control circuit 236 produces a gating pulse V236 earlier during the deflection cycle, as illustrated by time T3' of FIGURE 5. As shown by the dashed lines in FIGURES 2c-2e, earlier gating results in a net increase in the average of current 1216 through inductor 216 which can discharge capacitor 218 to a greater extent to maintain the regulated voltage in the presence of an increased current drain by deflection circuit 222 or compensate for a low regulated voltage.As in the case of FIGURE 1, the description of the operation is for the case in which inductor 216 has a relatively large inductance; with a smaller inductance the current in inductor 216 may decrease to zero before time T3, whereupon diode 224 will become nonconductive and circuit point 226 will assume the regulated voltage.

In the embodiments of FIGURES 1 and 2, the turn-of or secondary winding is coupled in series with the SCR. It is possible to arrange the turn-off or secondary winding in series with the diode, as illustrated in FIGURE 3. In FIGURE 3, elements corresponding to those of FIGURE 1 have the same reference numeral in the 300 series. In FIGURE 3, termi nals310 and 312 are adapted to be connected to a source of unregulated direct voltage. An SCR 314 acting as a controllable switch is coupled at a circuit point 326 with a filter inductor316, which in turn is coupled at a circuit point 330 with a deflection circuit 322, and the series combination is coupled across terminals 310 and 312 to form a first series path for the flow of current in inductor 316.Capacitor 318 is coupled between circuit point 330 and terminal 312 for filtering the current flowing in inductor 316 to form an energizing voltage for deflection circuit 332.

A diode 324 has its cathode connected to circuit point 326 and its anode coupled to terminal 312 (ground) by way of a turn-off secondary winding 320b of a transformer 320 to form a closed path for the flow of current through inductor 316, capacitor 318, winding 320b and diode 324 back to inductor 316. The primary winding 320a of transformer 320 is coupled to horizontal deflection circuit 322. A voltage control circuit 336 is coupled by a conductor 328 across capacitor 318 for sensing the voltage to be regulated and is also coupled by a conductor 334 to the horizontal deflection circuit for receiving synchronizing pulses therefrom. Voltage control circuit 336 produces time-modulated SCR gating pulses which are coupled to the gate of SCR 314 by a transformer 332.

Referring to the waveforms of FIGURES, immediately prior to the time TO at which the retrace interval beings, SCR 314 is conductive and circuit point 326 is at essentially the voltage of the unregulated source, as illustrated by FIGURE 6c. Diode 324 is nonconductive, and its anode is at a voltage negative with respect to ground by the voltage across winding 320b, as illustrated by V301 of FIGURE 6b. The current through inductor 316 is increasing in the path extending from terminal 310 of the unregulated source, through SCR 314 and inductor 316, as illustrated by 1316 of FIGURE 6d, under the impetus of the difference between the voltages at circuit points 326 and 330. A portion of this current is supplied to horizontal deflection circuit 322 and the remainder charges capacitor 318.

At time TO. deflection circuit 322 produces a retrace voltage pulse which is coupled to secondary winding 320b of transformer 320. This voltage is poled to make circuit point 301 positive with respect to ground. Diode 324 remains nonconductive until the voltage at point 301 rises at a time T1 to 1 Vbe above the voltage of circuit point 326.

At time T1, diode 324 and winding 320b provide an alternate path for the flow of current through inductor 316. After time T1,the retrace voltage pulse causes a further increase in the voltage at both circuit points 301 and 326, and SCR 314 then becomes nonconductive. At a later time, the retrace pulse voltage at circuit point 301 reaches a peak and begins to decrease. After pulse 301 decreases below the regulated B+. decreasing current continues to flow through inductor 316 in a circular path including capacitor 318, winding 320b and diode 324 as energy associated with the magnetic field of inductor 316 continues to be transferred to capacitor 318. At a time T2, the decreasing voltage at circuit points 301 and 326 causes SCR 314 to again become forward biased. However, SCR 314 does not become conductive until a gating pulse is applied.

The retrace pulse ends at a time T3, and current continues to circulate through inductor 316, capacitor 318 and diode 324, as illustrated by 1316 of FIGURE 6d. At a time T4, voltage control circuit gates SCR 314 into conduction, raising the voltage at circuit point326 and rendering diode 324 nonconductive, thereby initiating an interval of increase in the current of inductor 316. As in the case of FIGURES 1 and 2, the regulated voltage between circuit point 330 and ground is maintained by control of the average value of current 1316, which in turn is established by relative gating time T4 at which SCR 314 is rendered conductive.

FIGURE 4 illustrates an embodiment of the invention similar to FIGURE 3 in that the turn-off winding and diode are connected in series. The arrangement of FIGURE 4 differs in that the storage capacitor has a different reference point and the SCR is coupled to the negative terminal of the source of unregulated voltage.

In FIGURE 4, terminals 410 and 412 are adapted to be coupled to the source of unregulated direct voltage. An SCR 414 has its cathode connected to tor minal 412 and its anode coupled by way of circuit point 426, filter inductor 416, ground and horizontal deflection circuit 422 to terminal 410. The ground point corresponds to circuit point 30 of FIGURE 1. A storage capacitor 418 is coupled between input tor minal 412 and ground for filtering the voltage across deflection circuit 422. A diode 424 has its anode connected to circuit point 426 and its cathode coupled by way of a turn-off secondary winding 420b of a transformer 420 to the positive terminal 410 of the source of unregulated voltage. Horizontal deflection circuit 422 produces retrace pulses which are coupled to winding 420b. A voltage control circuit 436 is coupled by a conductor 429 across the horizontal deflection circuit for sensing the horizontal deflection circuit energizing voltage appearing between terminal 410 and ground and for producing control pulses which are coupled to the gate of SCR 414 by a transformer 432.

The voltage across horizontal deflection circuit 422 equals the difference between the unregulated supply voltage and the voltage across capacitor 418.

Current flow in deflection circuit 422 resulting from its operation causes charge to accumulate on capacitor418 during those intervals in which SCR 414 is nonconductive, thereby increasing the voltage across the capacitor and tending to decrease the voltage available to deflection circuit 422. The regulated voltage is controlled by controllably discharging capacitor 418 through a series path extending from the capacitor through inductor 416 to circuit point 426, to SCR 414 and back to the capacitor, and when the SCR is nonconductive through an alternate path extending from capacitor 418 through inductor 416 to a circuit point 426, through diode 424, winding 420b and through terminal 410 to the source and back to the capacitor by terminal 412.

The waveforms of FIGURE 6 are similar in appearance to the waveforms occurring in the arrangement of FIGURE 4 during operation, but may differ in polarity and by a fixed offset voltage as a result of the different voltage reference point. Immediately before the time TO of the beginning of the retrace interval, SCR 414 is conducting and diode 424 is nonconducting. The current through inductor 416 is increasing under the impetus of the voltage across capacitor 418 as energy is transferred from capacitor 418 to inductor 416. During the retrace interval, winding 420b produces a pulse voltage at the cathode of diode 424 which is increasingly negative with respect to terminal 410.When the pulse voltage makes the cathode of diode 424 approximately 1 Vbe negative with respect to circuit point 426, SCR 414 becomes nonconductive and diode 424 becomes conductive to provide decreasing current flow through the alternate series path including diode 424, winding 420b, the unregulated source, capacitor 418 and inductor416. At the end of the retrace interval, the voltage across winding 420b is small, and current continues to flow through diode 424 and the alternate series path. As a result, circuit point 426 is at a voltage near that of terminal 410, and SCR 414 is forward biased.During the interval extending from the end of the retrace interval to the time when SCR 414 is rendered conductive, inductor 416 is essentially coupled across the unregulated source, and the current in inductor 416 decreases as it gives up energy to the source. The decrease in current in inductor 416 ends at a time corresponding to T4 of FIGURES, at which time SCR 414 is gated into conduction, the voltage at circuit point 426 becomes negative and renders diode 424 nonconductive. The voltage of capacitor418 is once again impressed across inductor 416 to begin to increase the current and energy stored in inductor 416.

Regulation of the voltage across horizontal deflection ci rcuit 422 in the arrangement of FIGURE 4, is, as in the other illustrated embodiments, by control of the average of the periodically increasing and decreasing current through inductor 416, which in turn is controlled by variable gating time T4.

FIGURE 7 illustrates the regulating, deflection and ultor generating portions of a television receiver which embodies the instant invention.

In FIGURE 7, an unregulated B+ supplyterminal 10 is connected to a source of pulsating direct current such asa rectifier coupled to the AC power line.

A filter capacitor 13 is connected between terminal 10 and ground for filtering the pulsating direct current and generating the raw energizing voltage for the remainder of the apparatus. A controllable switch in the form of an SCR 14 has its anode connected to terminal 10 and its cathode connected to one end of a winding 16b of a transformer 16'. The other end of winding 1 sub is connected to one end of a filter inductor 17. The other end of filter inductor 17 is coupled to ground by a filter capacitor 18. The junction Br of inductor 17 and capacitor 18 is connected to one end of a winding 1 spa of transformer 16'. Winding 1 6a acts as the input inductor for a horizontal deflection circuit designated generally as 22.

Deflection circuit 22 includes an NPN transistor 23 having its emitter coupled to ground and its collector connected to the end of winding 16a remote from junction Br. A damper diode 25 is coupled across the collector-emitter conducting path of transistor 23. A deflection winding 29 associated with a kinescope 31 is coupled in series with an S-shaping capacitor33, and the series combination is coupled in parallel with diode 25. A retrace capacitor 35 is connected in parallel with diode 25 to supplement the capacitance of winding 29 to aid in establishing the proper duration of the retrace interval.A winding 1 sic of transformer 16' has one end connected to ground and the other end coupled by way of a rectifier illustrated as a diode 37 to the ultor of kinescope 31 for peakrectifying the retrace pulses to generate the direct ultor voltage for the kinescope. A horizontal oscillator illustrated as a block 38 produces drive signals at the horizontal deflection frequency which are applied to the base of transistor 23. Horizontal oscillator 38 also produces synchronizing pulses at the horizontal rate which are coupled to a voltage control circuit illustrated as a block 40. Control circuit 40 is coupled to junction Br and is also coupled to the gate of SCR 14 for controlling the SCR in known manner to maintain the voltage at junction Br at a constant value. Diode 342 is connected between ground and the junction of winding 16b and inductor 17.

In normal operation, voltage control circuit 40 triggers SCR 14 into conduction at a time during the horizontal trace interval. During the interval in which SCR 14 is conductive, current in inductor 17 increases at a rate determined by the voltage across winding 1 6b plus the difference between the regulated voltage VBr at junction Br and the raw B+ across capacitor 13. At the end of the horizontal trace interval, a retrace voltage pulse is generated across capacitor 35. The voltage pulse is coupled from winding 16a to winding 16b. The voltage pulse across winding 16b is poled in such a manner as to tend to reverse-bias SCR 14 and to reduce the current flowing in inductor 17. Inductor 17 may be of any value which is needed, since during retrace the current in the inductor is carried by diode 342 and capacitor 18.When the current in winding 16b reaches zero, SCR 14 becomes nonconductive in preparation for the next cycle of regulating action.

Regulation of voltage VBr is accomplished, in the arrangement of FIGURE 7, by duty cycle modulation of the conduction of SCR 14, which is accomplished by changing the time during the horizontal deflection interval at which SCR 14 is gated into conduction.

If compensation of retrace pulse amplitude as a function of kinescope beam current is desired, the embodiment shown in FIGURE 8 may be used.

In FIGURE 8, elements corresponding to those of FIGURE 7 are designated by the same reference numbers. FIGURE 8 includes a tapped winding 416 of transformer 16'. The tap divides winding 416 into two portions 416a and 416b. A diode 442 is connected between ground and the tap on winding 416.

In operation of the arrangement of FIGURE 8, voltage control circuit 40 gates SCR 14 into conduction at a time during the horizontal trace interval which is controlled to maintain the regulated voltage VBr across capacitor 18 and deflection circuit 22 at a substantially constantvalue. Gating-time control of SCR 14 causes the voltage across inductor 17 to be applied for varying intervals and results in differing currents at the beginning of the retrace interval, as described above. Changes in kinescope beam current cause corresponding increases in the loading on capacitor 18 and in the current flowing through inductor 17 at the beginning of the retrace interval.

During the retrace interval, the retrace pulse appearing across capacitor 35 is coupled by winding 1 6a to winding 416. That portion of the pulse appearing across winding 416a will render SCR 14 nonconductive when the pulse magnitude equals the unregulated direct voltage. Thus, the arrangement of FIG URE 8 provides reliable turn-off of the SCR regardless of the magnitude of inductor 17, as in FIGURE 7.

During the retrace interval, diode 442 is conductive and the current in inductor 17 is reduced toward zero by the sum of the retrace-interval pulse appearing across winding 416b and regulated voltage VBr. At the same time, inductor 17 is coupled across winding 416b by diode 442 and capacitor 18, and the inductance of inductor 17 is effectively in parallel with flybackwinding 16a and deflection winding 29, as in the case of FIGURE 1. The length of time that current flows in inductor 17, and that diode 442 remains conductive during the retrace interval, depends upon the magnitude of the current flowing through inductor 17 at the beginning of the retrace interval. Consequently, increased kinescope beam current which causes an increased current in inductor 17 at the end of the retrace interval causes diode 442 to remain conductive during a greater portion of the retrace interval.This maintains inductor 17 effectively in parallel with windings 16a and 29 for a greater portion of the retrace interval, reducing the average inductance in parallel with capacitor 35 and thereby reduces the retrace interval. As shown in FIGURE 9, when the retrace interval is reduced so that retrace waveform 200 changes to waveform 210, the peak retrace voltage increases. Thus, the arrangement of FIGURE 8 provides an increased peak retrace voltage in response to increased beam current and thus provides regulation compensation together with reliable SCR turn-off of the arra ngement of FIGURE 7.

Other embodiments of the invention will be apparent to those skilled in the art. In particular, capacitor 18 may be connected to terminal 10 rather than to ground, in order to filter the regulating voltage. Windings 416a and 416b may be independent windings rather than a single tapped winding of transformer 16'. The capacitance of windings 16a and 29 may be controlled to eliminate the requirement for retrace capacitor 35. Also, the timing signal for the voltage control circuit may be derived from other points, such as transformer 16', rather than from the horizontal oscillator.

Claims (11)

1. A switching regulator for a television apparatus, comprising: a controllable switch, an inductor and a horizontal deflection generator forming a first series circuit coupled across a source of unregulated direct voltage for providing a path for an increasing current flow in said inductor during those intervals in which said switch is closed, said switch including a gate and a main current conduction path which when forward biased remains open until a signal is applied to said gate and which thereafter remains closed so long as said forward bias is maintained; coupling means coupling horizontal rate signals from said deflection generator to said main conduction path of said switch for controlling the opening thereof;; a diode coupled with said inductor to form a path for a decreasing current flow in said inductor during at least a portion of those intervals in which said switch is opened; a capacitor coupled to said deflection generator for filtering said current flow in said inductor to form an operating voltage for said deflection generator; and control means coupled to said deflection generator and to said gate for controlling the closing of said switch for co trolling the average of said increasing and decreasing currents in said inductor and thereby controlling said operating voltage in a feedback manner.

2. A regulator according to Claim 1 wherein said coupling means comprises a winding serially coupled with said main current conduction path.

3. A regulator according to Claim 1 wherein said coupling means comprises a winding serially coupled with said diode.

4. A regulator according to Claim 2 or 3 wherein said winding is magnetically coupled with said deflection generator.

5. A regulator according to Claim 1 wherein said capacitor is coupled to a terminal of said source.

6. A regulator according to Claim 1, in which said deflection generator includes a deflection switch, and a first winding, a deflection winding and retrace capacitance means coupled across said deflection switch for providing a path for the flow of defler'; current during recurrent trace and retrace intervals, said retrace intervals being dependent upon the inductance in parallel with said capacitance means; an ultor generator coupled to said first winding for generating an ultor voltage, variations in said ultor voltage resulting from variations in the ultor current and from variations in the duration of said retrace interval; and a second winding serially coupled with said inductor for providing a path for the flow of said increasing and decreasing currents, said second winding being coupled with said first winding for coupling said inductor in parallel with said deflection winding for altering the inductance in parallel with said capacitance and for altering said duration of said retrace interval in a manner tending to compensate for said variation in said ultorvoltage resulting from variations in the ultor current.

7. A regulator according to Claim 6 wherein said retrace capacitance means comprises interwinding capacitance of said deflection winding.

8. A regulator according to Claim 7 wherein said retrace capacitance means further comprises a retrace capacitor.

9. A regulator according to Claim 6 wherein said ultor generator is magnetically coupled to said first winding.

10. A regulator according to Claim 6 wherein said second winding is magnetically coupled with said first winding.

11. A switching regulator substantially as hereinbefore described with reference to any of Figures 14 or7 or8.