Televisions and Monitors
Power Semiconductor Applications
Philips Semiconductors
CHAPTER 4
Televisions and Monitors
4.1 Power Devices in TV Applications
(including selection guides)
4.2 Deflection Circuit Examples
4.3 SMPS Circuit Examples
4.4 Monitor Deflection and SMPS Example
317
Televisions and Monitors
Power Semiconductor Applications
Philips Semiconductors
Power Devices in TV & Monitor Applications
(including selection guides)
319
Televisions and Monitors
Power Semiconductor Applications
Philips Semiconductors
4.1.1 An Introduction to Horizontal Deflection
Introduction
This section starts with the operation of the power
semiconductors in a simple deflection test circuit leading to
a functional explanation of a typical TV horizontal deflection
circuit. The operation of the common correction circuits are
discussed and the secondary function of the horizontal
deflection circuit described.
Deflection Test Circuit
The horizontal deflection test circuit used to assess Philips
deflection transistors is shown in Fig. 1 below.
Lc
represents the horizontal deflection coils.
Fig. 1. Test Circuit for Deflection Transistors
This circuit is a simplification of a practical horizontal
deflection circuit. It can be used to produce the voltage and
currentwaveforms seen by both the transistor and the diode
in a real horizontal deflection circuit. It is, therefore, very
useful as a test circuit for switching times and power
dissipation. The waveforms produced by the test circuit are
shown in Fig. 2.
Fig. 2. Test Circuit Waveforms
Cycle of Operation
Briefly going through one cycle of operation, the sequence
of events is as follows. (This can be followed through on
the waveforms shown in detail in Fig. 3, by starting on the
left and following the stages numbered 1 to 8).
1. Turn on the deflection transistor by applying a positive
current drive to the base. The voltage on the collector is
now approximately0.5V because the device is fully on. This
means that the voltage across the coil, Lc, is the full line
voltage; in this