Toshiba TW40F80 manual High Voltage Circuit, Cr-Block, Anode

6. HIGH VOLTAGE CIRCUIT

C2

VCP1 =		VCP	1
	C1 + C2

6-1. High Voltage Regulator			C2
	VCP2 =			VCP	2
6-1-1. Outline		C1	+ C2
Generally, four kinds of methods exist to stabilize a high	VCP =		C2	VCP2	3
voltage in high voltage output circuits using the FBT:		C1	+ C2

(1)Stabilization by varying the power supply voltage.

(2) Stabilization by varying L value with a saturable reac-			The VCP2 developed across C2 is DC-clamped with a diode
			D1 and the resultant voltage is smoothed with a diode D2
tance connected in series with the primary winding of
			and a capacitor C3. Thus processed voltage is obtained at
the FBT.
			the point B . This voltage is used to provide a base current
(3) Stabilization by varying equivalent capacitance of the			for the transistor Q1 or to flow the collector current. The
resonant capacitor C0.			voltage at the point B decreases with the circuit impedance
(4) Stabilization by superimposing a DC or pulse (this			and finally lowers up to a VCE saturation voltage of Q1.
varies the high voltage) on a lower voltage side of the			Then, VCP2 is not clamped by D2 with the voltage at the
high voltage winding of the FBT.
			point B . Since the VCP is expressed as a sum of VCP1 and
In this unit, pulse transformer is eliminated and the regula-			VCP2 as shown by equation	3 , VCP decreases by amount
tor circuit using the method (3) is employed. The block dia-			the VCP2 is decreased. This varies the high voltage.
gram is shown in Fig. 9-19.			Q1 collector current is controlled by Q1 base current which
		Z450
			is an output of the comparison inverted amplifier. That is,
		CR-BLOCK
			the Q1 base current is controlled by a voltage obtained by
		T461	comparing a detection voltage of the top breeder of the FBT
		FBT
			(9.1V) and a DC voltage of 9V.
Hotizonal		ANODE
output	DY
	125V		Horizontal	C1 LH	FBT
			output		LP
	PW output

		CS	+B
-27V	D1	B
	C2	D2

High voltage Reg.		C3
		Q1
			High voltage
	V.		Reg.
			output amp
	Ref.

Fig. 9-19 Basic circuit for high voltage regulator

emplyed in the unit

6-1-2. Theory of Operation

Fig. 9-20 shows a basic circuit of the high voltage regulator used in the unit.

The high voltage regulator circuit splits a resonant capacitor C0 to C1 and C2. thereby dividing the collector voltage (VCP) of the H output transistor with C1 and C2.

Here, assume each voltage developed across C1 and C2 as VCP1 and VCP1, respectively,

each relation can be expressed by the above equations 1 ~ 3 .

Fig. 9-20

VCP = VCP1 + VCP2

VCP 1

VCP 2

Fig. 9-21

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