GB2331377A - Circuit for regulating a flyback transformer - Google Patents
Circuit for regulating a flyback transformer Download PDFInfo
- Publication number
- GB2331377A GB2331377A GB9812340A GB9812340A GB2331377A GB 2331377 A GB2331377 A GB 2331377A GB 9812340 A GB9812340 A GB 9812340A GB 9812340 A GB9812340 A GB 9812340A GB 2331377 A GB2331377 A GB 2331377A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage
- signal
- auxiliary
- brightness
- resistor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
- H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
- H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
- H04N3/18—Generation of supply voltages, in combination with electron beam deflecting
- H04N3/185—Maintaining dc voltage constant
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Dc-Dc Converters (AREA)
- Television Receiver Circuits (AREA)
- Details Of Television Scanning (AREA)
Abstract
A circuit for regulating high voltage in a monitor comprises a power supply circuit (100) having a voltage converting unit (110) for converting externally supplied AC voltage to DC voltage. The power supply circuit (100) also has a PWM unit (120) for inputting the DC voltage and for outputting a pulse signal, and a horizontal deflection voltage generating unit (130) for switching in accordance with the pulse signal and for outputting externally supplied horizontal deflection voltage (B+). A flyback transformer (200) has a first winding (210) for supplying the horizontal deflection voltage in accordance with a horizontal driving signal (HD), and a second winding (220) for inducing high voltage and for generating a brightness signal when current flows in the first winding. The flyback transformer (200) also has an auxiliary winding (230) for inducing and outputting auxiliary voltage when the current flows in the first winding (210). A high voltage regulating means section (300) is arranged to control a switching cycle of the pulse signal in accordance with the amplitudes of the brightness signal and the auxiliary signal.
Description
1 2331377 CIRCUIT FOR REGULATING A FLYBACK TRANSFORMER
BACKGROUND OF THE INVENTION
The present invention relates to a circuit for regulating high voltage of a flyback transformer in a monitor.
In a conventional monitor, an electron emitted from a cathode of a Cathode Ray Tube (CRT) is accelerated in accordance with voltage applied to io a grid terminal and then is deflected by a magnetic field generated by a deflection coil. The deflected electron collides with a phosphor screen, so a picture is formed.
The CRT is supplied with heating voltage of about 6.3V, focusing grid voltage and screen grid voltage both of which are supplied to a grid terminal for focusing the emitted electron, and high voltage of about 25KV supplied to an anode terminal for accelerating the emitted electron.
Brightness of a picture varies in accordance with the quantity of current which flows to the anode terminal of the CRT and the magnitude of the high voltage. That is, if the picture is in brightness of a white pattern, the quantity of current which flows to the anode terminal of the CRT increases, the magnitude of the high voltage is decreased, and the size of a picture is decreased.
Figure 1 is a view for shovAng a construction of a circuit for regulating high voltage of a flyback transformer in a conventional monitor. Here, the high voltage generating circuit comprises a voltage converting unit 1 for converting an externally supplied alternative current (AC) voltage to direct current (DC) voltage; a pulse width modulating (PWM) unit 2 for inputting the DC voltage and for outputting a pulse signal; a horizontal deflection voltage generating unit 3 for switching on and off in accordance with the pulse signal and for outputting an externally supplied horizontal deflection voltage 13+; a flyback transformer (FBT) 4 for generating high voltage and an auxiliary voltage in accordance with the horizontal deflection voltage 13+; and a high voltage regulating unit 5 for controlling a switching cycle of the pulse signal in accordance with the auxiliary voltage to maintain constant the high voltage 2 varied in accordance with the brightness of the picture.
Here, the FBT 4 includes first winding 41 in which a current flows in accordance with the supply of a horizontal driving signal HD and the horizontal deflection voltage B+, a second winding 42 for inducing the high voltage in accordance with the quantity of current which flows in the first winding 41, and an auxiliary winding 43 for inducing auxiliary voltage to stabilize the magnitude of the high voltage in accordance with the current which flows in the first winding 41.
Further, the construction of the high voltage regulating unit 5 will be described in detail below. One end of resistor 51 which bypasses the auxiliary voltage is connected to the anode of diode 52 for rectifying the auxiliary voltage, and the cathode of diode 52 is connected to one end of capacitor 53 for rectifying the output voltage of diode 52. The other end of the capacitor 53 is grounded.
The cathode of the diode 52 is connected to one end of a resistor 54 for bypassing the rectifying voltage of the capacitor 43, and the other end of the resistor 54 is connected to one end of a resistor 55 for dividing the rectifying voltage of the capacitor 53. Further, the other end of the resistor 54 is connected to a variable resistor 56 to be controlled in accordance with the frequency of a horizontal synchronization signal. The other end of the variable resistor 56 is grounded.
In the above described construction of the conventional high voltage generating circuit for a monitor, the externally supplied AC voltage is supplied to the voltage converting unit 1, so the voltage converting unit 1 converts the AC voltage to DC voltage.
The DC voltage is supplied to the PWM unit 2, so the PWM unit 2 inputs the DC voltage and outputs the pulse signal. The pulse signal is inputted to the horizontal deflection voltage generating unit 3. The horizontal deflection voltage generating unit 3 switches on and off in accordance with the pulse signal, to thereby output the externally supplied horizontal deflection voltage B+.
3 The horizontal deflection voltage B+ and the horizontal driving signal HD are supplied to the first winding 41 of the FBT unit 4, so a current flows in the first winding 41 according to the horizontal deflection voltage B+ and the horizontal driving signal HD (the horizontal driving signal HD is a pulse signal which has low and high voltage levels), therefore a voltage is induced in the second winding 42.
The induced voltage, which is high voltage, of the second winding 42 is supplied to the anode terminal of the CRT.
Additionally, the auxiliary voltage of the auxiliary winding 43 is supplied to the diode 52 through the resistor 51, so the diode 52 rectifies the output voltage of the resistor 51.
The output voltage of the diode 52 is supplied to the capacitor 53, so the capacitor 53 smoothes the output voltage of the diode 52. The smoothed voltage of the capacitor 53 is supplied to the resistors 54 and 55, and the variable resistor 56.
The resistors 54 and 55, and the variable resistor 56 divide the smoothed voltage of the capacitor 53, and the divided voltage is supplied to the PWM unit 2.
If the quantity of current which flows in the second winding increases when a picture is in brightness of a white pattern, the induced voltage and the auxiliary voltage are decreased. That is, if the magnitude of the auxiliary voltage which is supplied to the PWM unit 2 is decreased, the switching cycle of the pulse signal increases.
The pulse signal is supplied to the horizontal deflection voltage generating unit 3, so the horizontal deflection voltage B+ increases. Therefore, the magnitude of the high voltage increases.
When the frequency of the horizontal synchronization signal is about 31 KHz and a picture is in brightness of a white pattern, the magnitude of the high voltage supplied to the anode terminal of the CRT is about 25KY 4 Further, when the frequency of the horizontal synchronization signal is about 31 KHz and the picture is in brightness of a black pattern, the magnitude of the high voltage is about 26.02W Therefore, the difference of the magnitudes of the two different high voltages is about 100OV.
Further, when the frequency of the horizontal synchronization signal is about 68KHz and the picture is in brightness of a white pattern, the magnitude of the high voltage supplied to the anode terminal of the CRT is about 25.3W Further, when the frequency of the horizontal synchronization signal is about io 68KHz and the picture is in brightness of the black pattern, the magnitude of the high voltage is about 26W Therefore, the difference of the magnitudes of the two different high voltages is about 680V.
However, in a conventional high voltage regulating circuit for a monitor, when the magnitude of the high voltage is changed from 25KV to 26.02KV, since the number of turns of the second winding is more than that of the auxiliary winding, a response time for which the auxiliary voltage affects the high voltage becomes long, to thereby cause the size of the picture to be changed. Accordingly, the quality of the picture may deteriorate.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a circuit for regliLating high voltage of a flyback transformer in a monitor in which the identified problems are reduced.
According to a first aspect of the present invention there is provided a circuit for regulating high voltage in a monitor includes a power supply section having a voltage converting unit for converting externally supplied AC voltage to DC voltage, a PWM unit for inputting the DC voltage and for outputting a pulse signal, a horizontal deflection voltage generating unit for switching in accordance with the pulse signal and for outputting externally supplied horizontal deflection voltage; a FBT for generating high voltage, auxiliary voltage, and brightness signal in accordance with the horizontal deflection voltage and a horizontal driving signal; and high voltage regulating section for controlling a switching cycle of the pulse signal in accordance with a magnitude of the auxiliary voltage and amplitude of the brightness signal.
An embodiment of a circuit of the invention changes the switching cycle of a pulse signal in accordance with brightness voltage, and an auxiliary voltage is capable of stabilizing the magnitude of the high voltage.
According to an embodiment of the present invention, the externally supplied AC voltage is supplied to a voltage converting unit of the power supply section which converts the externally supplied AC voltage to DC io voltage. The DC voltage is supplied to the PWM unit which inputs the DC voltage and outputs a pulse signal. The pulse signal is supplied to a horizontal deflection voltage generating unit which switches in accordance with the pulse signal and outputs externally supplied horizontal deflection voltage. Further, the horizontal deflection voltage and a horizontal driving signal are supplied to a FBT which generates high voltage, auxiliary voltage, and brightness signal in accordance with the horizontal deflection voltage and a horizontal driving signal. Additionally, the brightness signal and the auxiliary voltage are inputted to high voltage regulating section which controls a switching cycle of the pulse signal in accordance with the auxiliary voltage and the brightness signal.
Consequently, the magnitude of high voltage is controlled to the amplitude of auxiliary voltage and the amplitude of brightness signal, so the quality of a picture can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows a construction of a conventional circuit for regulating high voltage of a flyback transformer in a monitor; Figure 2 shows a circuit for regulating high voltage of a flyback transformer in a monitor according to one embodiment of the present invention; and Figure 3 shows a circuit for regulating high voltage of a flyback transformer in a monitor according to another embodiment of the present invention.
6 DETAILED DESCRIPTION OF THE EMBODIMENTS
Figure 2 shows a circuit for regulating high voltage of a flyback transformer in a monitor according to one embodiment of the present invention. In Figure 2, reference numeral 100 denotes a power supply circuit having a voltage converting unit 110 for converting externally supplied AC voltage to DC voltage, a PWM unit 120 for inputting the DC voltage and for outputting a pulse signal, a horizontal deflection voltage generating unit 130 for switching on and off in accordance with the pulse signal and for outputting io externally supplied horizontal deflection voltage B+.
Reference numeral 200 denotes a flyback transformer (FBT) including a first winding 210 for supplying horizontal deflection voltage B+ in accordance with the horizontal driving signal HD in order for current to flow, a second is winding 220 for inducing high voltage and generating a brightness signal when the current flows in the first winding 210, and an auxiliary winding 230 for inducing auxiliary voltage when the current flows in the first winding 210.
Further, reference numeral 300 denotes a high voltage regulating section for controlling a switching cycle of the pulse signal in accordance with the amplitudes of the brightness signal and the auxiliary signal.
The high voltage regulating section 300 includes a brightness signal processor 310 for dividing an externally supplied voltage Wcl in accordance with the quantity of current which flows in the first winding 210 and for generating brightness voltage, auxiliary voltage processor 320 for rectifying and amplifying the auxiliary voltage supplied from the auxiliary winding 230, and feedback voltage outputting unit 330 for dividing the brightness voltage and auxiliary voltage and for outputting a feedback voltage to be supplied to the PWM unit 120.
The construction of the high voltage regulating section 300 will be described in detail. One end of the second winding 220 is connected to one end of a resistor 311 and one end of a capacitor 312 for rectifying the brightness signal, wherein the brightness signal is the quantity of current which flows in the second winding 220. The other end of both the resistor 311 7 and the capacitor 312 is grounded.
c is The extemally supplied voltage Vccl is supplied to one end of a resistor 313 for dividing the extennally supplied voltage Vccl and for outputting the brightness voltage. The brightness voltage is determined by the resistances of the resistors 311 and 313.
In the meantime, the output terminal of the auxiliary winding 230 is connected to one end of a resistor 321 for bypassing the auxiliary signal and io the other end of the resistor 321 is connected to the anode of the diode 322 for rectifying the auxiliary voltage, and the cathode of diode 322 is connected to one end of capacitor 324 for smoothing the output voltage of diode 322. The other end of the capacitor 324 is grounded.
The cathode of the diode 322 is connected to one end of a resistor 323 for bypassing the smoothed voltage of the capacitor 324 and the other end resistor 323 is connected to the base of a transistor 325 for inputting the output voltage of the resistor 323. The collector of the transistor 325 is connected to one end of externally supplied voltage Vcc2 and the emitter of the transistor 325 is connected to one end of a resistor 326 for determining the quantity of current which flows in the transistor 325 and for outputting the auxiliary voltage.
The other end of the resistor 313 is connected to the other end of the resistor 326 and one end of a resistor 331 of the feedback voltage outputting unit 330. Further, the other end of the resistor 331 is connected to a variable resistor 332 to be controlled in accordance with the frequency of a horizontal synchronization signal. The other end of the variable resistor 332 is grounded.
In connection with this embodiment of the present invention constructed as above, the operation and effect of the circuit for regulating high voltage in a monitor will be described with reference to the accompanying drawing.
The externally supplied AC voltage is supplied to the voltage converting unit 110, so the voltage converting unit 110 converts the AC voltage to DC 8 voltage.
The DC voltage is supplied to the PWM unit 120, so the PWM unit 120 inputs the DC voltage and outputs the pulse signal. The pulse signal is inputted to the horizontal deflection voltage generating unit 130. The horizontal deflection voltage generating unit 130 switches on and off in accordance with the pulse signal, and then outputs the externally supplied horizontal deflection voltage B+.
The horizontal deflection voltage B+ and the horizontal driving signal HD are supplied to the first winding 210 of the FBT 200, so a current flows in the first winding 210 according to the horizontal deflection voltage B+ and the horizontal driving signal HD, therefore the second winding 220 is induced.
is The induced voltage of the second winding 220 is supplied to the anode terminal of the CRT as the high voltage.
Further, the current which flows in the second winding 220 is supplied to the brightness signal processor 310. That is, the brightness signal is supplied to the resistor 311 and the capacitor 312, so the resistor 311 and the capacitor 312 rectify the brightness signal. The externally supplied voltage Vccl supplied through the resistor 313 is superimposed to the rectifying voltage, so the brightness voltage is outputted.
Also, the auxiliary voltage of the auxiliary winding 230 is supplied to the diode 322 through the resistor 321, so the diode 322 rectifies the output voltage of the resistor 321.
The output voltage of the diode 322 is supplied to the capacitor 324, so the capacitor 324 smooths the output voltage of the diode 322. Further the smoothed voltage of the capacitor 324 is supplied to the transistor 325 through the resistor 323, so a current flows from the collector of transistor 325 to the emitter thereof. The quantity of current is determined by the resistance of the resistor 326, so the auxiliary voltage is outputted.
The brightness voltage and the auxiliary voltage are supplied to the 9 resistor 331 and the variable resistor 332, so the resistor 331 and the variable resistor 332 divide the brightness voltage and the auxiliary voltage and generate the feedback voltage. Further the feedback voltage is supplied to the PWM unit 120. That is, the magnitude of feedback voltage is determined by the magnitudes of the auxiliary voltage and the brightness voltage.
In other words, if the quantity of current which flows to the second winding increases when the picture is in brightness of a white pattern, the brightness voltage and the auxiliary voltage are decreased. That is, if the io magnitude of the auxiliary voltage which is supplied to the PWM unit 2 decreases, the switching cycle of the pulse signal is enlarged.
The pulse signal is supplied to the horizontal deflection voltage generating unit 130, so the horizontal deflection voltage B+ increases.
Therefore, the magnitude of high voltage increases.
When the frequency of the horizontal synchronization signal is about 31 KHz and the picture is in brightness of the white pattern, the magnitude of high voltage supplied to the anode terminal of the CRT is about 25. 38KV.
Further when the frequency of the horizontal synchronization signal is about 31 KHz and the the picture is in brightness of the black pattern, the magnitude of high voltage is about 26.01 KV. Therefore, the difference of the magnitudes of the two different high voltages is about 630V.
Further, when the frequency of the horizontal synchronization signal is about 68KHz and the picture is in brightness of the white pattern, the magnitude of high voltage supplied to the anode terminal of the CRT is about 25.58KV. Further when the frequency of the horizontal synchronization signal is about 31 KHz and the picture is in brightness of the black pattern, the amplitude of high voltage is about 26.01 KV. Therefore, the difference of magnitudes of the two different high voitages is about 420V.
Figure 3 shows a circuit for regulating high voltage of a flyback transformer in a monitor according to another embodiment of the present invention. In Figure 3, reference numeral 100 denotes a power supply section having a voltage converting unit 110 for converting an externally supplied AC voltage to a DC voltage, a PWM unit 120 for inputting the DC voltage and for outputting a pulse signal, a horizontal deflection voltage generating unit 130 for switching on and off in accordance with the pulse signal and for outputting externally supplied horizontal deflection voltage B+.
Reference numeral 200 denotes an FBT including first winding 210 in which a current flows in accordance with the supply of a horizontal driving signal HD and the horizontal deflection voltage B+, a second winding 220 for inducing the high voltage in accordance with the quantity of current which io flows in the first winding 210, and an auxiliary winding 230 for inducing auxiliary voltage to stabilize the magnitude of the high voltage in accordance with the current which flows in the first winding 210.
Further, the reference numeral 400 denotes a high voltage regulating section for controlling a switching cycle of the pulse signal in accordance with the amplitudes of the brightness signal and the auxiliary signal.
The high voltage regulating section 400 includes a brightness signal processor 410 for dividing externally supplied voltage Vccl in accordance with the quantity of current which flows in the first winding 210 and for outputting brightness voltage, brightness voltage controlling unit 420 for controlling the brightness voltage in accordance with an externally supplied mode signal CS, auxiliary voltage processor 430 for rectifying and amplifying the auxiliary voltage supplied from the auxiliary winding 230, and feedback voltage outputting unit 440 for dividing the brightness voltage and auxiliary voltage and for outputting feedback voltage to be suppled to the PWM unit 120. Here the mode signal such as a high level (about 5V) and a low level (about OV) is determined by the frequency of a horizontal synchronization signal.
The construction of the high voltage regulating section 400 will now be described. One end of the second winding 220 is connected to one end of a resistor 411 and one end of a capacitor 412 for rectifying the brightness signal, wherein the brightness signal is the quantity of current which flows in the second winding 220. The other end of both the resistor 411 and the capacitor 412 is grounded.
11 The input terminal of the externally supplied voltage Vccl is connected to one end of a resistor 413 for receiving the externally supplied voltage Vccl and for outputting the brightness voltage. The brightness voltage is determined by the resistances of the resistors 411 and 413.
The other end of the resistor 411 is connected to the base of transistor 414 for inputting the brightness voltage.
Further, the collector of transistor 414 is connected to the input terminal io of an externally supplied voltage Wc2 and the emitter of transistor 414 is connected to one end of a resistor 415 for determining the quantity of current which flows from the collector of the transistor 414 to the emitter thereof.
Furthermore, the input terminal of mode signal CS is connected to one end of a resistor 421 of brightness voltage controlling unit 420 for dividing the mode signal CS and the other end of the resistor 421 is connected to one end of a resistor 422. Further the other end of the resistor 422 is grounded.
The other end of the resistor 421 is connected to the base of a transistor 423 for switching on and off in accordance with the dividing voltage of the resistors 421 and 422. The emitter of transistor 423 is grounded.
The input terminal of an externally supplied voltage Vec2 is connected to one end of a capacitor 424 for charging the externally supplied voltage Vec2, further the other end of the capacitor 424 is connected to the base of a transistor 425 for switching on and off in accordance with the switching state of the transistor 423.
The collector of the transistor 425 is connected to one end of the resistor 415, and the emitter of the transistor 425 is connected to one end of a resistor 416 for determining the quantity of current which flows from the collector of the transistor 415 to the emitter thereof. Further the other end of the resistor 416 is connected to the other end of the resistor 415.
On the other hand, the output terminal of the auxiliary winding 230 is connected to one end of a resistor 431 for bypassing the auxiliary signal and 12 the other end of the resistor 431 is connected to the anode of the diode 432 for rectifying the auxiliary voltage, and the cathode of diode 432 is connected to one end of capacitor 434 for smoothing the output voltage of diode 432. The other end of the capacitor 434 is grounded.
The cathode of the diode 432 is connected to one end of a resistor 433 for bypassing the smoothed voltage of the capacitor 434.
The other end of the resistor 415 is connected to the other end to the io resistor 433 and one end of a resistor 441 of the feedback voltage outputting unit 440. Further, the other end of the resistor 441 is connected to a variable resistor 442 to be controlled in accordance with the frequency of horizontal synchronization signal. The other end of the variable resistor 442 is grounded.
The operation and effect of another embodiment of the present invention as constructed above will be described with reference to the attached drawing.
To begin with, the externally supplied AC voltage is supplied to the voltage converting unit 110, so voltage converting unit 1 converts the AC voltage to DC voltage.
The DC voltage is supplied to the PWM unit 120, so the PWNA unit 120 inputs the DC voltage and outputs the pulse signal. The pulse signal is inputted to the horizontal deflection voltage generating unit 130. The horizontal deflection voltage generating unit 130 switches on and off in accordance with the pulse signal, and then outputs the externally supplied horizontal deflection voltage B+.
The horizontal deflection voltage B+ and the horizontal driving signal HD are supplied to the first winding 210 of the FBT 200, so a current flows in the first winding 210 according to the horizontal deflection voltage B+ and the horizontal driving signal HD, therefore the second winding 220 is induced.
The induced voltage of the second winding 220 is supplied to the anode terminal of the CRT as the high voltage.
Further, the current which flows in the second winding 220 is supplied to the brightness signal processor 410. That is, the brightness signal is supplied to the resistor 411 and the capacitor 412, so the resistor 411 and the capacitor 412 rectify the brightness signal. The externally supplied voltage Wcl supplied from the resistor 413 is superimposed to the rectifying voltage, so the brightness voltage is outputted.
The brightness signal is supplied to the transistor 414, so a current flows from the collector of the transistor 414 to the emitter thereof. At that io time, the quantity of current is determined by a resistance of the resistor 415.
Also, when the frequency of the horizontal synchronization signal is about 31 KHz, the mode signal CS inputted to the low level is supplied to the resistors 421 and 422, so the resistors 421 and 422 divide the mode signal CS.
The output signal of resistors 421 and 422 is supplied to the transistor 423, so the transistor 423 switches off. Further, the externally supplied voltage Wc2 is supplied to the capacitor 424, so the capacitor 424 charges the externally supplied voltage Wc2.
The charged voltage of the capacitor 424 is supplied to the transistor 425, so the transistor 425 switches on and a current flows from the collector of the transistor 425 to the emitter thereof. At that time, the quantity of current is determined by the resistance of the resistor 426.
The current which flows in the transistor 414 and the current which flows in the transistor 425 are supplied to the resistor 441 and variable resistor 442 of the feedback voltage outputting unit 440.
Furthermore, the auxiliary voltage of the auxiliary winding 230 is supplied to the diode 432 through the resistor 431, so the diode 432 rectifies the output voltage of the resistor 431.
The output voltage of the diode 432 is supplied to the capacitor 434, so the capacitor 434 smooths the output voltage of the diode 432 and the 14 auxiliary voltage is outputted through resistor 433.
The brightness voltage and the auxiliary voltage are supplied to the resistor 441 and the variable resistor 442, so the resistor 441 and the variable resistor 442 divide the brightness voltage and the auxiliary voltage and output the feedback voltage to the PWM unit 120.
Accordingly, the amplitude of feedback voltage is determined by the auxiliary voltage and the brightness voltage, wherein the brightness voltage io which is determined by the resistance of resistors 415 and 426 and the auxiliary voltage is outputted from the resistor 433.
When the frequency of the horizontal synchronization signal is about 31 KHz and the picture is in brightness of the white pattern, the magnitude of high voltage supplied to the anode terminal of CRT is about 25.56KV. Further, when the frequency of the horizontal synchronization signal is about 31 KHz and the picture is in brightness of the black pattern, the magnitude of high voltage is about 26.01 KV. Therefore, the difference of magnitudes of the two different high voltages is about 450V. In the meantime, when the frequency of the horizontal synchronization
signal is about 68KHz, the mode signal CS inputted to the high level is supplied to the resistors 421 and 422, so the resistors 421 and 422 divide the mode signal CS.
The output signal of resistors 421 and 422 is supplied to the transistor 423, so the transistor 423 switches on. Therefore, the charged voltage of the capacitor 424 is supplied to the emitter of the transistor 423, so the transistor 425 switches off.
The current which flows in the transistor 414 through the resistor 415 is supplied to the resistor 441 and variable resistor 442 of the feedback voltage outputting unit 440.
Also, the auxiliary voltage of the auxiliary winding 230 is supplied to the diode 432 through the resistor 431, so the diode 432 rectifies the output is voltage of the resistor 431.
The output voltage of the diode 432 is supplied to the capacitor 434, so the capacitor 434 smooths the output voltage of the diode 432 and the auxiliary voltage is outputted through the resistor 433.
The brightness voltage and the auxiliary voltage are supplied to the resistor 441 and the variable resistor 442, so the resistor 441 and the variable resistor 442 divide the brightness voltage and the auxiliary voltage and output io the feedback voltage to the PWM unit 120.
Accordingly, the amplitude of feedback voltage is determined by the auxiliary voltage and the brightness voltage, wherein the brightness voltage which is determined by the resistance of resistor 415 and the auxiliary voltage is outputted from the resistor 433.
When the frequency of the horizontal synchronization signal is about 68KHz and the picture is in brightness of the white pattern, the magnitude of high voltage supplied to the anode terminal of CRT is about 25.58KV. Further, when the frequency of the horizontal synchronization signal is about 68KHz and the picture is in brightness of the black pattern, the magnitude of high voltage is about 26.01 KV. Therefore, the subtraction of magnitude of high voltage is about 430V.
By employing the circuit for regulating a high voltage of a flyback transformer in a monitor according to the embodiments of the present invention, the high voltage is changed by the brightness voltage and the auxiliary voltage and the response time for which high voltage is increased is quick when the brightness of the white pattern is changed to that of the black pattern. Therefore, the high voltage which is varied in accordance with the brightness of the picture becomes constant, so the quality of picture can be enhanced.
Whilst embodiments of the present invention have been illustrated and described, it will be appreciated that changes in form and details may be made without departing from the scope of the invention as defined by the 16 appended claims. For instance, while the preferred embodiments of the present invention herein are described for a monitor, the present invention may be applied to every video signal processing system such as general VCRs.
17
Claims (10)
1. A circuit for regulating high voltage of a flyback transformer in a monitor, comprising: 5 a power supply means having a voltage converting unit for converting an externally supplied alternative current (AC) voltage to direct current (DC) voltage, a pulse width modulating (PWM)unit for inputting said DC voltage and for outputting a pulse signal, a horizontal deflection voltage generating unit for switching on and off in accordance with said pulse signal and for outputting io externally supplied horizontal deflection voltage; a flyback transformer including first winding for receiving said horizontal deflection voltage in accordance with a horizontal driving signal in order for current to flow, second winding for inducing high voltage and for generating a brightness signal when said current flows in said first winding, and an auxiliary is winding for inducing auxiliary voltage when said current flows in said first winding; and a high voltage regulating means for controlling a switching cycle of said pulse signal in accordance with the amplitudes of said brightness signal and said auxiliary signal.
2. A circuit for regulating high voltage of a flyback in a monitor as claimed in Claim 1, wherein said high voltage regulating means includes: a brightness signal processor for dividing externally supplied first voltage in accordance with the quantity of current which flows in said first 25 winding and for outputting brightness voltage; an auxiliary voltage processor for rectifying and amplifying said auxiliary voltage supplied from said auxiliary winding; and a feedback voltage outputting unit for dividing said brightness voltage and said auxiliary voltage and for outputting feedba6k voltage to be supplied 30 to said PWM unit.
3. A circuit for regulating high voltage of a flyback transformer in a monitor as claimed in Claim 1, wherein said high voltage regulating means includes: a brightness signal processor for dividing externally supplied first 35 voltage in accordance with the quantity of current which flows in said first winding and for outputting brightness voltage; 18 a brightness voltage controlling unit for controlling said brightness voltage in accordance with a mode signal of a low level and a high level determined by the frequency of a horizontal synchronization signal, an auxiliary voltage processor for rectifying and amplifying said auxiliary voltage supplied from said auxiliary winding; and a feedback voltage outputting unit for dividing said brightness voltage and said auxiliary voltage and for outputting a feedback voltage to be supplied to said PWM unit.
io
4. A circuit for regulating high voltage of a flyback transformer in a monitor as claimed in Claim 2, wherein said brightness signal processor comprises: a first resistor and a first capacitor connected in parallel with respect to one end of the second winding for rectifying the brightness signal, wherein the brightness signal is the quantity of current which flows in the second winding; and a second resistor for receiving said externally supplied first voltage, for dividing said externally supplied first voltage, and for outputting said brightness voltage.
5. A circuit for regulating high voltage of a flyback transformer in a monitor as claimed in Claim 2, said auxiliary voltage processor includes: a third resistor connected to the output terminal of the auxiliary winding for bypassing the auxiliary signal; a first diode connected to the other end of said third resistor for halfwaveform rectifying the auxiliary signal; a second capacitor connected to the cathode of said first diode for smoothing the output voltage of said first diode; a fourth resistor connected to the cathode of said first diode for bypassing the smoothed voltage of said second capacitor; a first transistor connected to the other end of fourth resistor for inputting the output voltage of the fourth resistor; and a fifth resistor connected to the emitter of said first transistor for determining the quantity of current which flows in said first transistor and for outputting the auxiliary voltage in accordance the input of the first transistor.
6. A circuit for regulating high voltage of a flyback transformer in a monitor 19 is as claimed in Claim 3, said brightness signal processor comprises: a sixth resistor and a third capacitor connected in parallel with respect to one end of the second winding for rectifying the brightness signal; a seventh resistor connected to a connecting point of said sixth resistor and third capacitor for supplying said rectifying voltage, for dividing the externally supplied first voltage and said rectfying voltage, and for outputting said brightness voltage; an NPN type second transistor for inputting the output voltage of said seventh resistor; and an eighth resistor for determining the quantity of a current which flows in said second transistor and for outputting the brightness voltage in accordance the input of said second transistor.
7. A circuit for regulating a high voltage of a flyback transformer in a monitor as claimed in Claim 3, wherein said brightness voltage controlling unit includes: a ninth resistor and tenth resistor connected in series with respect to the input terminal of said mode signal which is changed in accordance with a horizontal synchronization signal, for inputting said mode signal, and for dividing the mode signal; a third transistor for receiving said output voltage of said ninth resistor and for switching on and off in accordance with said dividing signal; a fourth capacitor for charging an externally supplied second voltage in accordance with said switching state of said third transistor; a fourth transistor for inputting said charged voltage of said fourth capacitor and for switching on and off; and an eleventh resistor for receiving said output voltage of said fourth transistor, for determining the quantity of a current which flows in said fourth transistor, and for controlling said magnitude of said brightness voltage.
8. A circuit for regulating high voltage of a flyback transformer in a monitor as claimed in Claim 3, said auxiliary voltage processor comprises: a twelfth resistor for inputting said auxiliary signal of said auxiliary winding and for bypassing said auxiliary signal of said auxiliary winding; a second diode for receiving said output signal of said twelfth resistor and for rectifying the auxiliary voltage; a fifth capacitor for inputting said output signal of second diode and for smoothing the output voltage of second diode; and a thirteenth resistor for receiving said rectifying voltage of said fifth capacitor, for bypassing said smoothed voltage, and for supplying said bypassed voltage to said feedback voltage outputting unit.
9. A circuit for regulating a flyback transformer for a video signal processing system, the flyback transformer being arranged in response to a horizontal deflection voltage to generate a brightness signal and an auxiliary io voltage, the circuit comprising regulating means for controlling the switching cycle of a pulse signal in accordance with the amplitudes of the brightness signal and the auxiliary signal, wherein said pulse signal is applied to a horizontal deflection voltage generator to control the switching thereof.
is
10. A circuit for regulating a flyback transformer for a video signal processing system substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019970060398A KR19990040085A (en) | 1997-11-17 | 1997-11-17 | Monitor's High Voltage Regulation Circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9812340D0 GB9812340D0 (en) | 1998-08-05 |
| GB2331377A true GB2331377A (en) | 1999-05-19 |
Family
ID=19524855
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9812340A Withdrawn GB2331377A (en) | 1997-11-17 | 1998-06-08 | Circuit for regulating a flyback transformer |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH11187281A (en) |
| KR (1) | KR19990040085A (en) |
| GB (1) | GB2331377A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1401194A1 (en) * | 2002-09-19 | 2004-03-24 | Lg Electronics Inc. | Voltage stabilizing circuit for video display appliance |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100588142B1 (en) | 2000-01-13 | 2006-06-09 | 삼성전자주식회사 | A circuit for autometically controlling a high-voltage in a video display system |
| JP5255902B2 (en) * | 2008-05-16 | 2013-08-07 | パナソニック株式会社 | Switching power supply |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2141883A (en) * | 1983-04-22 | 1985-01-03 | Pioneer Electronic Corp | A high voltage generating circuit |
| GB2273427A (en) * | 1990-04-30 | 1994-06-15 | Thomson Consumer Electronics | Power supply |
| US5463290A (en) * | 1994-05-02 | 1995-10-31 | Thomson Consumer Electronics, Inc. | Power supply stabilization circuit with separate AC/DC negative feedback paths |
-
1997
- 1997-11-17 KR KR1019970060398A patent/KR19990040085A/en not_active Application Discontinuation
-
1998
- 1998-06-02 JP JP10152717A patent/JPH11187281A/en not_active Withdrawn
- 1998-06-08 GB GB9812340A patent/GB2331377A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2141883A (en) * | 1983-04-22 | 1985-01-03 | Pioneer Electronic Corp | A high voltage generating circuit |
| GB2273427A (en) * | 1990-04-30 | 1994-06-15 | Thomson Consumer Electronics | Power supply |
| US5463290A (en) * | 1994-05-02 | 1995-10-31 | Thomson Consumer Electronics, Inc. | Power supply stabilization circuit with separate AC/DC negative feedback paths |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1401194A1 (en) * | 2002-09-19 | 2004-03-24 | Lg Electronics Inc. | Voltage stabilizing circuit for video display appliance |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9812340D0 (en) | 1998-08-05 |
| JPH11187281A (en) | 1999-07-09 |
| KR19990040085A (en) | 1999-06-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5357175A (en) | Deflection and high voltage circuit | |
| KR100202313B1 (en) | High voltage control circuit | |
| US4801852A (en) | CRT horizontal deflection circuit enabling horizontal sweep width adjustment with stabilized EHT output | |
| KR19980064826A (en) | High voltage generator | |
| GB2331377A (en) | Circuit for regulating a flyback transformer | |
| US4728868A (en) | High voltage generating circuit | |
| KR100669952B1 (en) | High-voltage power supply for video display apparatus | |
| US6690126B2 (en) | Power supplying apparatus for electron gun in CDT | |
| US6456020B1 (en) | Circuit for stabilizing a screen voltage of a video display apparatus | |
| JP3265390B2 (en) | High voltage generation circuit for CRT | |
| GB2141883A (en) | A high voltage generating circuit | |
| KR100286803B1 (en) | Focus unit having high voltage feedback of fly back transformer | |
| JPS62145971A (en) | Vertical deflection width controlling circuit | |
| JP2990747B2 (en) | Horizontal deflection centering circuit | |
| KR19990052750A (en) | Screen voltage automatic adjustment circuit of monitor | |
| JP2692445B2 (en) | Horizontal deflection high voltage generation circuit | |
| JPH10285500A (en) | Crt display device | |
| KR970067524A (en) | Horizontal deflection output circuit | |
| JPS61134181A (en) | Horizontal deflecting circuit | |
| KR200156528Y1 (en) | Circuit for automatically limiting brightness in a monitor | |
| KR0116714Y1 (en) | Flyback transformer | |
| KR19990003853A (en) | Horizontal Deflection Circuit in Multi-Mode Monitors | |
| KR19990052749A (en) | Circuit for supplying screen voltage of parabolic waveform in monitor | |
| JP3360454B2 (en) | High voltage generation circuit | |
| JPH0265566A (en) | Television deflecting system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |