JPH07219657A - Series control type constant voltage circuit - Google Patents

Abstract

PURPOSE:To stabilize the output voltage against load variation and reduce a screen flicker by supplying the bias of a voltage control drive circuit by a peak detector. CONSTITUTION:A voltage which is divided by bias resistors 10 and 11 with a voltage having its peak rectified by the diode 20 and capacitor 21 of the peak detector 9 is smoothed by a capacitor 12 and applied. Consequently, the base voltage of a drive transistor(TR) 13 is stabilized, the output voltage of the voltage control drive circuit 4 becomes stable, and the output voltage of the output voltage control circuit 3 does not vary. Therefore, when an AC input voltage drops, the output voltage is prevented from varying owing to the load variation. Consequently, the output voltage can be stabilized against the load variation and the screen flicker is reducible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage circuit of a television receiver, and in particular, when the input voltage drops and goes out of the error detection control range, the output voltage fluctuates due to load fluctuations such as audio output. The present invention relates to a constant voltage circuit that prevents screen shake.

[0002]

2. Description of the Related Art The smoothing capacitor on the input side is made large to suppress the fluctuation of the output voltage, but the effect is not sufficient and it is difficult to obtain a large sound output from the series control type power supply circuit. .

[0003]

SUMMARY OF THE INVENTION In a constant voltage circuit of a television receiver, it is intended to reduce the fluctuation of the power supply output due to the load fluctuation, especially when the input voltage drops and the error detection control range is out of the control range. .

[0004]

A bias of a voltage control drive circuit is supplied by a peak detector.

[0005]

[Operation] The ripple of the output voltage due to the load change can be reduced outside the control range.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a conventional series control type power supply circuit, FIG. 2 is a conventional example, FIG. 3 is a block diagram of a series control type power supply circuit of the present invention, and FIG. 4 is an embodiment of the present invention.
FIG. 5 shows the waveform after rectification.

First, a conventional serial control type power supply circuit is shown in FIG.
This will be described with reference to FIGS.

In FIG. 1, 1 is a rectifier circuit for rectifying an AC input voltage, 2 is a smoothing capacitor, 3 is an output voltage control circuit, 4 is a voltage control drive circuit, 5 is an error detection circuit,
Reference numeral 6 is a reference voltage circuit, 7 is a smoothing capacitor, and 8 is a load circuit.

Next, in FIG. 2, the voltage control drive circuit 4 comprises bias resistors 10 and 11 for dividing the input voltage, a capacitor 12 and a drive transistor 13, and the error detection circuit 5 is a bias resistor 1 for dividing the output voltage.
4, 15 and the amplifying transistor 16 and the resistor 17, and the reference voltage circuit 6 includes the resistor 18 and the Zener diode 19.

In FIG. 2, the AC input voltage decreases, the output voltage of the output voltage control circuit 3 decreases, and the base voltage of the amplifying transistor 16 of the error detection circuit 5 becomes the reference voltage circuit 6.
When the error detection circuit does not operate because the amplifying transistor 16 is cut off below the Zener voltage of, the bias for dividing the input voltage of the drive transistor 13 of the voltage control drive circuit 4 changes the voltage determined by the resistors 10 and 11 to the capacitor 12 Will be added smoothly.

In this case, when the load current changes due to the load change of the load circuit 8, the voltage waveform of the rectifier circuit 1 is as shown in FIG.
The rectified peak voltage does not change, and the smoothed voltage changes like the dotted line.

At this time, the base voltage of the drive transistor 13 also changes, and the voltage control drive circuit 4
The output voltage of the output voltage control circuit 3 changes and the output voltage of the output voltage control circuit 3 changes.

As described above, in the conventional circuit, it is understood that when the AC input voltage drops, the output voltage fluctuates due to the load fluctuation.

Next, the present invention will be described with reference to the embodiments shown in FIGS.

FIG. 3 shows a configuration in which the bias of the voltage control drive circuit 4 of FIG. 1 is further added by a peak detector 9.

In FIG. 4, the peak detector 9 is a diode 20,
There is a configuration including a capacitor 21 and being added to the voltage control drive circuit 4.

In FIG. 4, the AC input voltage drops, the output voltage of the output voltage control circuit 3 drops, and the base voltage of the amplifying transistor 16 of the error detection circuit 5 becomes the reference voltage circuit 6.
When the amplifying transistor 16 is cut off and the error detection circuit does not operate, the bias of the drive transistor 13 of the voltage control drive circuit 4 is as shown in FIG. By utilizing the fact that it does not change, the voltage divided by the bias resistors 10 and 11 by the voltage obtained by rectifying the peak voltage by the diode 20 and the capacitor 21 of the peak detector 9 is smoothed by the capacitor 12 and added to the drive transistor. 13 is stable, the output voltage of the voltage control drive circuit 4 is stable, and the output voltage control circuit 3 is stable.
Output voltage does not change.

As described above, in the circuit of this embodiment, A
When the C input voltage drops, the output voltage is prevented from fluctuating due to load fluctuations.

[0019]

According to the present invention, there is an effect that the output voltage can be stabilized against a load change and the screen fluctuation can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a block diagram of a conventional series control type power supply circuit.

FIG. 2 is a diagram showing a conventional example.

FIG. 3 is a diagram showing a block diagram of a series control type power supply circuit of the present invention.

FIG. 4 is a diagram showing an example of the present invention.

FIG. 5 is a diagram showing a waveform after rectification.

[Explanation of symbols]

 1 ... Rectifier circuit for rectifying AC input voltage, 2 ... Smoothing capacitor, 3 ... Output voltage control circuit, 4 ... Voltage control drive circuit, 5 ... Error detection circuit, 6 ... Reference voltage circuit, 7 ... Smoothing capacitor, 8 ... Load circuit, 9 ... Peak detector.

Claims (1)

[Claims] 1. A serial control type constant voltage circuit comprising an output voltage control circuit, a voltage control drive circuit, and an error detection circuit for comparing a reference voltage and an output voltage, wherein the bias of the voltage control drive circuit is supplied by a peak detector. Series control type constant voltage circuit characterized by.