Description of the basic circuit
1. t1~t2:
A positive pulse is applied to base of the output transistor from the drive circuit, and a forward base current is flowing. The output transistor is turned on in sufficient saturation area. As a result, the collector voltage is almost equal to the ground voltage and the deflection current increases from zero to a value in proportionally. (The current reaches maximum at t2, and a right half of picture is scanned up to this period.)
2. t2:
The base drive voltage rapidly changes to negative at t2 and the base current becomes zero. The output transistor turns off, collector current reduces to zero, and the deflection cur- rent stops to increase.
3. t2~t3:
The drive voltage turns off at t2, but the deflection current can not reduce to zero immediately because of inherent na- ture of the coil and continues to flow, gradually decreasing by charging the resonant capacitor C0. At the same time, the capacitor voltage or the collector voltage is gradually in- creases, and reaches maximum voltage when the deflection current reaches zero at t3. Under this condition, all electro- magnetic energy in the deflection coil at t2 is transferred to the resonant capacitor in a form of electrostatic energy.
4. t3~t4:
Since the charged energy in the resonant capacitor discharges through the deflection coil, the deflection current increases in reverse direction, and voltage at the capacitor gradually reduces. That is, the electrostatic energy in the resonant ca- pacitor is converted into a electromagnetic energy in this process.
5. t4:
When the discharge is completed, the voltage reduces to zero, and the deflection current reaches maximum value in re- verse direction. The t2~t4 is the horizontal flyback period, and the electron beam is returned from right end to the left end on the screen by the deflection current stated above. The operation for this period is equivalent to a half cycle of the resonant phenomenon with L and C0, and the flyback period is determined by L and C0.
6. t4~t6:
For this period. C0 is charged with the deflection current having opposite polarity to that of the deflection current stated in "3.", and when the resonant capacitor voltage ex- ceeds VCC, the damper diode D conducts. The deflection current decreases along to an exponential function (approxi- mately linear) curve and reaches zero at t6. Here, operation returns to the state described under "1.", and the one period of the horizontal scanning completes. For this period a left half of the screen is scanned.
In this way, in the horizontal deflection scanning, a current flowing through the damper diode scans the left half of the screen; the current developed by the horizontal output tran- sistor scans the right half of the screen; and for the flyback period, both the damper diode and the output transistor are cut off and the oscillation current of the circuit is used. Us- ing the oscillation current improves efficiency of the circuit. That is, about a half of deflection current (one fourth in terms of power) is sufficient for the horizontal output transistor.
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| t1 | t2 | t3 t4 t5 | t6 |
A | TR | 0 |
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| base voltage |
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B | TR | 0 |
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| base current |
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C | TR |
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| collector | 0 |
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| current |
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D | D | 0 |
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| damper |
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| current (SW2) |
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E | Switch |
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| current | 0 |
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F | Resonant |
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| capacitor | 0 |
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| current (Co) |
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G | Deflection |
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| current (Lo) | 0 |
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HTR collector
voltage 0
Fig.
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