JPH01133472A - High voltage stabilized power source - Google Patents

Abstract

PURPOSE:To always obtain a constant high voltage output by arranging a transistor for a high voltage control at the low voltage side of the secondary side winding of a flyback transformer, and controlling the transistor based on the high voltage output. CONSTITUTION:The current flowing at the primary side winding of a flyback transformer 1 is switched with a switching transistor 2 and the high voltage is generated at the secondary side winding. A transistor 19 for a high voltage control is arranged at the low voltage side of the secondary side winding and the transistor 19 is controlled by the output of an error amplifier 16 to output the difference between the high-voltage voltage and a reference voltage 19.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Field of Industrial Application) The present invention relates to high voltage power supplies, and more particularly to high voltage stabilizing circuits thereof.

(Prior Art) A conventional circuit configuration for stabilizing high voltage will be explained with reference to FIG. 2.

In Figure 2, first, a flyback transformer (hereinafter referred to as FBT) for generating high voltage is connected to the primary side, and a switching transistor (hereinafter referred to as ST) to turn on/off the -side current is connected to the primary side. It is connected between one side of the winding and ground, and the drive power supply (10B) is connected to the other side of the negative winding.
) is connected, and by turning st■ on and off, a voltage of 5t (3 (TH: time of one cycle when St turns on and off, Tr: off time of st) is generated,
A high voltage is obtained by setting the number of secondary windings to be the number of primary windings multiplied by the output voltage/Vcp so as to obtain the required output voltage.

Furthermore, a high-voltage DC voltage is obtained by rectifying it with a diode.The high-voltage output is connected to a cathode ray tube or other load, and when this load fluctuates, the high-voltage output voltage also fluctuates, so that a constant voltage is always supplied to the load. Therefore, an attempt is made to make the high-voltage output voltage constant by detecting fluctuations in the high-voltage output voltage and amplifying the fluctuations (10B) to vary the voltage. First, the high voltage output voltage is converted to a differential amplifier (to)
In order to lower the input voltage to a value suitable for the input voltage, connect two voltage dividing resistors in series between the high voltage output and the ground, determine the ratio of the high voltage side voltage dividing resistor ■ and the earth side voltage dividing resistor ■, The voltage generated between the ground and the ground-side voltage dividing resistor 0 is used as the detection voltage for high voltage fluctuations at the negative amplification input terminal of the error amplifier (to).
The positive amplification input terminal (to) is input to the reference voltage (hereinafter v
The output (10) of (10B) is connected to the base of (11B) voltage control transistor (11), and the emitter is connected to (+B)r of FBT■. A voltage (Vcc) higher than the (10B) voltage by the voltage required for control is input to the collector connected to the input terminal. The operation of the conventional example will be explained below.

When the high voltage output voltage becomes lower than the set reference value, the voltage generated at the ground side voltage dividing resistor 0 becomes low, and this voltage is input to the negative amplification input terminal ■ of the error amplifier (A). It is compared with VF■ of the positive amplification input terminal ■. In this case, since the negative amplification input voltage is low with respect to VF■, the output voltage (10) of the error amplifier (to) becomes high (
10B) The base voltage of the control Tr (11) also increases, and the emitter voltage also increases, which is applied to the FBT ■ (10B)
When the voltage increases, the voltage (v
cp) increases, the high-voltage output voltage also increases, and an attempt is made to keep the output voltage constant. When the high-voltage output voltage is higher than the reference value, it operates in the opposite way and tries to keep the output voltage constant.

However, even when ideal operation is achieved with the configuration and operation of the prior art described above, problems still occur, and this will be discussed in the third section.
This will be explained using figures.

In Fig. 3(a), st■ is in a switching operation, and the energy stored in the primary winding of FBT■ during the on time (21) is transferred to vCP (23) during the off time (22).
This vCP is proportional to the voltage (10B) applied to FBT■ during the on-time (21) of st■.

In other words, when a pulse-like load (23) is applied to the high voltage output during the time when st is on as shown in Fig. 3(b), the st
During the ON time (21), the single pressure output (24) gradually decreases. At this time, the input voltage (10B) of FBT (1) has been increased, so the next time st (2) turns off (25), the high output voltage is high but the load (23) is zero.

(Problems to be Solved by the Invention) The high voltage stabilizing circuit of the prior art cannot control the high voltage output voltage while the 5tci is on, and further corrects the high voltage output voltage when the 5tci is turned off, so it is always on. - Involves a delay longer than the off time. For this reason, it is not possible to always obtain a constant high voltage output voltage, and a time delay always occurs in response to load fluctuations.

For example, in a CRT monitor, this causes screen curvature and distortion, making it impossible to obtain high-quality images.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a high-voltage stabilized power supply that can always obtain a constant high-voltage output voltage.

[Structure of the invention]

(Means for Solving the Problems) The present invention uses a flyback transformer to switch the current flowing through the primary winding, and the secondary winding boosts the voltage generated in the primary winding to create a high voltage voltage. In a high-voltage stabilized power supply that generates a constant high voltage, a transistor for high-voltage control is placed on the low-voltage side of the secondary winding, and the same voltage is applied to the base of the transistor using an error amplifier. A high-voltage stabilized power supply capable of obtaining an output voltage can be obtained.

(Function) The present invention varies the ground side potential of the secondary winding of the flyback transformer by the same voltage to maintain the high voltage output voltage at a constant voltage regardless of the on-off time of the switching transistor. By arranging a control transistor at the low-voltage side terminal of the transformer and connecting its base to an amplifier that is controlled at the same voltage as the high-voltage output voltage, it is possible to always obtain a high output with a constant voltage despite load fluctuations.

(Example) Next, an embodiment according to the present invention is shown in FIG. 1 and will be described.

In Figure 1, first connect 10B to one side of the primary winding of FBT■.
Supply voltage and connect st■ to the other side between ground 0
Next, a rectifier diode ■ is connected to the high voltage output side of the secondary winding of the FBT ■ to obtain direct current, which is supplied to the load. A voltage dividing resistor ■, 0 is connected in series between this output terminal and ground for the primary The output voltage at both ends of the ground side voltage dividing resistor (■) is used as the detection voltage, which is connected to the negative input terminal (17) of the error amplifier (16), and the positive input terminal (18) is connected to the reference voltage V, (19) Fix it with. Further, the low voltage side of the secondary winding of FBT (2) is connected to the emitter of a high voltage control transistor (19), and a voltage higher than the maximum value of the high voltage fluctuation is applied to the collector. The base is connected to the output terminal of the error amplifier (16).

The effect of the present invention is that when the high voltage output voltage decreases, a voltage proportional to the decrease is generated in the earth side voltage dividing resistor 0, and that voltage is input to the error amplifier (16).
The output of 16) is (reference voltage V, (19) - input voltage (
17)) In this case, the output becomes high and is input to the base of the high-voltage control transistor (19), which increases the potential on the low-voltage side of the secondary winding of FBT■, so the high-voltage output voltage also increases. Correction is attempted until the input voltage of the error amplifier (16) and the reference voltage V, (19) become equal.

Due to the above-mentioned action, the high voltage output can be kept constant regardless of the switching of st■, and real-time correction can be made even for load fluctuations.While conventional stabilizing circuits were far from ideal, the present invention According to the stabilization circuit, an ideal high voltage stable power source can be obtained. Regarding the power consumption of the control transistor, the conventional technology controls the primary side of the FBT, so there is coupling loss between the primary and secondary sides, which requires extra power, but with the present invention, the coupling loss is reduced. Since it is zero, power consumption may also be small.

〔Effect of the invention〕

According to the present invention, it is possible to always obtain a constant voltage output even when the load changes over time, and it is possible to obtain a highly stabilized high output voltage regardless of the operating state of the switching transistor.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a high-voltage stabilized power supply showing an embodiment of the present invention, Figure 2 is a circuit diagram of a conventional high-voltage stabilized power supply, and Figure 3 is a circuit diagram of a conventional high-voltage stabilized power supply.
Figures (a) and (b) are waveform diagrams for explaining problems with conventional high-voltage stabilized power supplies. Agent Patent Attorney Nori Chika Yudo Kikuo Takehana

Claims (1)

[Claims] 1) A method of switching the current flowing through the primary winding using a flyback transformer and boosting the voltage generated in the primary winding with the secondary winding to generate high voltage. A high-voltage stabilized power supply, characterized in that a transistor for high-voltage control is arranged on the low-voltage side of a secondary winding, and the same voltage is applied to the base of the transistor by an error amplifier. 2) The high voltage stabilized power supply according to claim 1, wherein the same voltage is applied to the base of the transistor by an error amplifier in an opposite phase to the high voltage fluctuation.