JPH03237878A - High voltage generating circuit - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution by providing a high voltage generating circuit separately from and independently of a horizontal output circuit, using an output transistor(TR) of the high voltage generating circuit in common for a switching element of a switching power supply and applying an output voltage of the switching power supply directly to the high voltage generating circuit. CONSTITUTION:Configuration of integration of a power supply circuit and a high voltage generating circuit is adopted, and the power supply circuit is configurated to be a switching power supply. The high voltage generating circuit consists of a TR Q1, a series circuit comprising diodes D2, D3, a capacitor C4 connecting in parallel with the diode D5, a series circuit comprising a flyback transformer FBT connected across the capacitor C4 and a capacitor C3 and a phase control circuit 10 controlling the TR Q1. The secondary coil of the flyback transformer FBT connects to an anode electrode via a diode D2 and to a control terminal of the phase control circuit 10 via a voltage detector VR. Thus, the circuit constitution is simplified.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high voltage generation circuit of a separate horizontal output circuit in which a horizontal output circuit and a high voltage generation circuit of a television receiver are configured separately and independently. .

[Conventional technology]

Conventionally, the high voltage applied to the anode electrode of a cathode ray tube is obtained by boosting the retrace pulse of a horizontal deflection circuit using a flyback transformer. However, when the beam current increases or decreases due to changes in screen brightness, the anode voltage also fluctuates, which leads to changes in screen size and focus performance.

Therefore, a circuit system has been proposed in which the horizontal output circuit and the high voltage generation circuit are completely separated and made independent to prevent mutual influence. FIG. 7 is a block diagram showing such a conventional separated high voltage generating circuit.

In FIG. 7, the output of the horizontal drive circuit 1 is connected to the base terminal of the output transistor Q1, and the output of the horizontal drive circuit 1 is connected to the base terminal of the output transistor Q1.
A damper diode D1 and a resonant capacitor C1 are connected in parallel between the collector and emitter terminals of the transistor 1. Further, the power supply voltage from the rectifier circuit 2 and the stabilized power supply circuit 3 is supplied to the collector connection line of the transistor Q1 via the high voltage regulator 4 and the primary coil of the flyback transformer FBT. The secondary coil of the flyback transformer FBT is connected to the anode electrode of the picture tube via the diode D2, and further connected to the voltage detector V.
It is input to the control terminal of the high voltage regulator 4 via R.

In this configuration, when a drive pulse is output from the horizontal drive circuit 1, the current flowing through the ONL of the transistor Q1 and the flyback transformer FBT increases linearly. When the transistor Q1 is turned off, the magnetic energy stored in the fly hack transformer FBT flows in a direction to charge the capacitor C1. When charging of the capacitor C1 is completed, the capacitance stored in the capacitor C1 now flows toward the flyback transformer FBT, producing a current in the opposite direction. When the capacitor C1 finishes discharging, the magnetic energy stored in the flyback transformer FBT flows through the diode D1, and the current flowing in the transformer FBT gradually decreases.

In this case, the flyback pulse generated when the capacitor C1 is charged by the magnetic energy stored in the flyback transformer FBT is
The voltage is supplied to the primary coil of T, and a higher voltage is generated in the secondary coil. This high voltage is supplied to the anode electrode via the diode D2, and simultaneously detected by the voltage detector VR and supplied to the control terminal of the high voltage regulator 4.

The high voltage regulator 4 receives this detected voltage, adjusts the value of the output voltage, and acts to keep the anode voltage constant.

[Problem to be solved by the invention]

However, the above-mentioned conventional example requires a stabilizing power supply circuit 3 to absorb fluctuations in the human-powered AC voltage and a high-voltage regulator 4 to control the value of the high voltage generated in the secondary coil of the flyback transformer FBT. This has the disadvantage that the overall circuit configuration becomes complicated.

An object of the present invention is to provide a novel high voltage generation circuit with a simplified circuit configuration.

[Means to solve the problem]

This invention includes a high voltage generation circuit that supplies a flyback pulse to the primary coil of a flyback transformer and a high voltage output obtained from the secondary coil to the anode electrode of a picture tube, and a DC voltage that is supplied to this high voltage generation circuit. A common transistor is used as the output transistor that constitutes the high-voltage generation circuit and the switching transistor that constitutes the switching power supply, and the on-time of the transistor is controlled according to the high-voltage output obtained from the secondary coil. The output of the switching power supply is adjusted to stabilize the high voltage output.

[For production]

In this configuration, the output transistor provided in common to the high voltage generation circuit and the switching power supply is controlled on/off by a drive pulse, and for the high voltage generation circuit, the output transistor is connected to the primary coil of the flyback transformer. A pulse is applied to generate a higher voltage in the secondary coil, which is then applied to the anode electrode of the picture tube.

In addition, for switching power supplies, the input terminal is divided into pulses and supplied to a smoothing circuit, the output voltage level is controlled by the ratio of on time and off time, and this output voltage is sent to a high voltage generation circuit as a direct current. Supplied directly as power source.

Fluctuations in the high voltage generated in the secondary coil of the flyback transformer are transmitted to a control section that controls the on/off time of the output transistor. The control section changes the pulse width of the drive pulse to change the on time of the transistor, thereby adjusting the output voltage level of the switching power supply. That is, when the high voltage increases, the output voltage level is lowered, and when the high voltage decreases, the output voltage level is increased to stabilize the high voltage output.

Therefore, according to the present invention, the conventional stabilizing power supply circuit, high voltage regulator, etc. are not required, and the circuit configuration can be simplified while maintaining the characteristics of the separate high voltage generating circuit.

〔Example〕

FIG. 1 shows the configuration of an embodiment of a high voltage generating circuit according to the present invention, and the same parts as those in FIG. 7 are given the same reference numerals and will be explained.

This embodiment has a configuration in which a power supply circuit and a high voltage generation circuit are integrally formed, and the power supply circuit includes a rectifier circuit 2 that rectifies an AC signal, a smoothing capacitor C2, and a diode connected to both ends of this capacitor C2. Da,) A series circuit of a transistor Q1 and a choke coil L, a diode D4 and a capacitor C connected in parallel to this choke coil L.
As shown in FIG. 2, it constitutes a switching power supply in which the capacitor C2 is the power supply and the transistor Q1 is the switching element.

The high voltage generation circuit is a transistor Ql, this transistor Q
a series circuit of diodes D5 and D6 as damper diodes connected between the collector and emitter terminals of 1;
A capacitor C4 connected in parallel to the diode D5, a series circuit of a flyback transformer FBT and a capacitor C3 connected to both ends of the capacitor C4, a phase control circuit 10 controlling the transistor Q1, and a secondary circuit of the flyback transformer FBT. The coil is connected to the anode electrode via the diode D2, and the voltage detector VR
The signal is input to the control terminal of the phase control circuit 10 through the .

FIG. 3 shows the configuration of an example of a phase system open circuit 10, including a sawtooth wave generation circuit 11 that outputs a sawtooth wave signal synchronized with a horizontal synchronization signal, a comparison voltage generation circuit 12, and these regeneration circuits 11 and 10. The output voltage value of the comparison voltage generation circuit 12 is controlled by the detected voltage from the voltage detector VR.

Next, the operation of the embodiment having this configuration will be explained with reference to the waveform diagram shown in FIG. In addition, in Figure 4, figure (
a) is the 0N10FF state of transistor Q1, figure (bl
is the current flowing through the flyback transformer FBT, Figure (C)
shows the voltage (flyback pulse) generated in the flyback transformer FBT, and Figure (d) shows the current flowing through the choke coil L, respectively.

First, time t when the transistor Q1 is turned on.

When the voltage accumulated in the capacitor C3 is applied as a DC voltage to the flyback transformer FBT, a loop of capacitor C3→transformer FBT→diode D6→transistor Q1→capacitor C8 is formed. In this state, the current flowing from the capacitor C3 to the transformer FBT increases slowly and linearly.

When transistor Q1 is turned off at time t1, a loop of capacitor C3→transformer FBT→capacitor C4-capacitor C3 is formed, and a resonant current flows through transformer FBT. This resonant current becomes zero at time t2, and at this time the voltage of capacitor C4 becomes maximum.

After time t2, the electrostatic energy stored in the capacitor C4 is discharged toward the transformer FBT, and a current flows in the opposite direction.

That is, a loop of capacitor Ca=) lance FBT-capacitor C8→capacitor C4 is formed. The magnitude of the current increases as the voltage of capacitor C4 decreases, and reaches its maximum at time t3 when the voltage of capacitor C4 becomes zero. A flyback pulse is generated between times t1 and t3.

After time t3, diode D5 becomes conductive,
A loop of capacitor C3-diode Ds-) lance FBT→capacitor C3 is formed, and it decreases linearly, contrary to the time to""tl, and becomes zero again at time ts (=to).

In the power supply circuit, when the transistor Q1 is turned on, an input voltage is applied to the choke coil L, a current proportional to time flows through the coil L, and energy is stored in the coil L. When the transistor Q1 is turned off, the energy stored in the coil L is supplied to the output side via the diode D4, and a current that decreases over time flows. Therefore, as shown in FIG. 4(d), a current flows through the choke coil L, increasing while the transistor Q1 is ON and decreasing while the transistor Q1 is OFF. The repetition frequency is f, the input voltage is VI, and the output current is I. , the ON time of the transistor Ql is T. When N, the output voltage v0 is Vo = (VI”
Tosz f)/(2Io L), and if the ON time of transistor Q1 is long, the output voltage will increase and the ON
If the time becomes shorter, the output voltage will decrease.

During these operations, when the secondary voltage of the flyback transformer FBT decreases and the voltage value detected by the voltage detector VR decreases, that voltage value is fed to the phase control circuit 10 and is output from the comparison voltage generation circuit 12. The output comparison voltage decreases. This increases the pulse width of the pulse signal output from the comparator 13, advances the conduction angle of the transistor Q1, and turns on the transistor Q1 at time 14/, which is before time t4. Therefore, O of transistor Q1
As the N time becomes longer, the output voltage of the power supply increases.

For this reason, the power supply voltage during the energy storage period for the flyback transformer FBT starting from time t5' increases, so the height of the flyback pulse increases, the secondary voltage of the transformer FBT increases, and the anode voltage increases. Stabilization will be achieved.

FIG. 5 is a block diagram showing another embodiment of the present invention. In this embodiment, the power supply circuit consists of a series circuit of a choke coil L and a transistor Q1 connected across a capacitor C2, and a collector of a transistor Q1.・It consists of a series circuit of a diode D4 and a capacitor C3 connected between the emitters, and as extracted and shown in Figure 6, the capacitor C2 is used as an input power supply, the transistor Q1 is used as a switching element, and the output is output from both ends of the capacitor C3. It has the same configuration as that in FIG. 1, except that it is a step-up switching power supply for obtaining voltage.

According to this configuration, the output voltage VO is as follows, and increases in proportion to the ON time of the transistor Q1.

〔Effect of the invention〕

According to this invention, the high voltage generation circuit is provided separately and independently from the horizontal output circuit, and the output transistor of the high voltage generation circuit and the switching element of the switching power supply are shared, so that the output voltage of the switching power supply is directly transmitted to the high voltage generation circuit. This eliminates the need for a stabilizing power supply circuit, a high-voltage regulator, etc. as in the past, and the circuit configuration can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the high voltage generation circuit according to the present invention, FIG. 2 is a block diagram of the power supply circuit shown in FIG. 1, and FIG. 3 is a block diagram showing an example of the phase control circuit shown in FIG. 1. 4 is a waveform diagram for explaining the operation of FIG. 1, FIG. 5 is a configuration diagram showing another embodiment of the present invention, and FIG. 6 is a configuration of the power supply circuit shown in FIG. 5. 7 are configuration diagrams showing a conventional high voltage generation circuit. 1...Horizontal drive circuit, lO...phase control circuit,
C2 to C4 -- Capacitor, D2 to D6... Diode, FBT... Flyback transformer, L... Choke coil, Ql... Output transistor, VR...
・Voltage detector.

Claims (1)

[Claims] A high voltage generation circuit that supplies a flyback pulse to a primary coil of a flyback transformer and a high voltage output obtained from a secondary coil to an anode electrode of a picture tube, and a DC voltage applied to this high voltage generation circuit. and a switching power supply that supplies a high voltage output, an output transistor that constitutes the high voltage generation circuit and a switching transistor that constitutes the switching power supply are configured with a common transistor, and the output transistor that configures the high voltage output from the secondary coil A high voltage generation circuit, characterized in that the on-time of the switching power supply is controlled to adjust the output of the switching power supply, thereby stabilizing the high voltage output.