JPS6285953A - Deflection high tension supply circuit of ink jet printer - Google Patents

Abstract

PURPOSE:To stabilize an output voltage of a deflection high-tension supply circuit under a simple circuit configuration by holding the input pulse of a buffer circuit provided on the input side of a piezoelectric transformer at a constant voltage level. CONSTITUTION:A transistor Tr is provided as a buffer. An input pulse Pf is accompanied by a voltage variation; however, this variation does not appear at A point because the transistor Tr performs a switching operation. However, it is common that the variation amounts to a few percent normally although the +DC voltage is stable. Therefore, unless a Zener diode ZD is provided, the variation appears at A point and is multiplied proportionately to the boosting of a piezoelectric transformer T. For this reason, the variation cannot be ignored. The Zener diode used should preferably be such as one for reference voltage with a temperature compensation. A voltage stabilized by the Zener diode is applied to the piezoelectric transformer T to assure satisfactory temperature characteristics of the transformer, so that a constant high tension is obtained in HV0.

Description

TECHNICAL FIELD The present invention relates to a high-voltage power supply circuit for deflection in a charge-controlled inkjet printer.

PRIOR ART FIG. 4 is a diagram showing an example of a conventional high voltage generation circuit. In the figure, IC is an integrated circuit for PWM control, RB is a base current limiting resistor of a drive transistor Tr, and Tr is a diagram showing an example of a conventional high voltage generation circuit.
l is a transistor for driving the transformer T1, Do
= Ca, Ra are snubber circuits for absorbing rebound voltage, T
1 is a step-up transformer, C1 to C4, D1 to D4 are quadruple voltage rectifying and smoothing circuits, R and u.

Rou' is an output voltage detection resistor, and as shown in the figure, the HVo was stabilized by feeding back the output voltage detected using a pulse width modulation type control IC, but the control IC is based on the standard The cost is high because it includes a voltage, oscillator, error amplifier, pre-driver, etc., and the number of external parts makes it complicated. Further, the detection resistor R1U has disadvantages such as having to use a high resistance of several tens of MΩ to several hundred MΩ, noise easily entering the feedback loop, and control becoming unstable.

Purpose The present invention was made in view of the above-mentioned circumstances.
In particular, this invention was made for the purpose of stabilizing the output voltage of a high voltage power supply circuit for deflection of an inkjet printer with a simple circuit configuration.

Structure In order to achieve the above object, the present invention includes a piezoelectric transformer,
A buffer circuit is provided on the input side of the piezoelectric transformer, and the input pulse of the buffer circuit is maintained at a constant voltage. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a configuration diagram for explaining an embodiment of a high voltage power supply circuit according to the present invention. In the figure, Tr, Tr.

is a transistor, ZD is a zener diode, T is a piezoelectric transformer, and the piezoelectric transformer T is, as shown in FIG.
It has a characteristic that the step-up ratio becomes maximum at a certain frequency fr, and when the load is changed at the same frequency, the characteristic shown in FIG. 3 is exhibited.

This material has good voltage resistance and temperature characteristics, for example,
Tohoku Metal Industry Co., Ltd.'s product name: Nepec X-6. N-6
1 material is suitable.

Usually, in an inkjet printer, a pulse signal is applied to a head unit to turn ink into particles. This signal is often a sine wave, but its signal source is a TTL level, 50% duty square wave. The present invention is based on the premise that this signal is used as the input pulse Pf.

Of course, aTr6, which may be provided with a separate oscillator, is a transistor for interface with the digital section. When the level of the pulse becomes high, the transistor Tr is turned on and the voltage at point A becomes zero, and when the level of the pulse becomes low, point A becomes high, but the voltage becomes equal to the voltage of the zener diode ZD. Since the impedance of the signal is high as it is, the transistor Tr is provided as a buffer. Although the input pulse Pf is accompanied by voltage fluctuations, this fluctuation does not occur at point A because the transistor Tr performs a switching operation. However, although the +DC power supply is stabilized,
It is normal for there to be a fluctuation of several percent, and Zener diode Z
Without D, the fluctuation would occur at point A, and since the fluctuation would be multiplied by the step-up ratio of the piezoelectric transformer T, it cannot be ignored. It is preferable to use a temperature-compensated Zener diode called a reference voltage type Zener diode ZD. Zener diode ZD
A voltage stabilized by is applied to the piezoelectric transformer T, and since the piezoelectric transformer T has good temperature characteristics, a constant high voltage can be obtained at HV. Diode D1. D also has a slight temperature characteristic, but since the output voltage is on the order of KV, it can be ignored. Furthermore, since the input pulse Pf is frequency-divided from the crystal oscillation circuit, it is not affected by the frequency fluctuations shown in FIG. 2.

Effects As is clear from the above explanation, according to the present invention, (a) feedback control is not performed, so stable control can be performed without fear of oscillation.

Furthermore, since there is no need to use a high resistance, control is stable.

(b) The circuit is simplified and can be extremely miniaturized.

(c) Significant cost reduction is possible.

There are advantages such as

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the high voltage power supply circuit according to the present invention, FIG. 2 is a diagram showing the relationship between the frequency and step-up ratio of the piezoelectric transformer, and FIG. 3 is the step-up ratio of the piezoelectric transformer. The characteristic diagram, FIG. 4, is a diagram showing an example of a conventional high voltage power supply circuit. Trr T r,...transistor, ZD...zener diode, T...piezoelectric transformer, D, D,...
diode.

Claims (2)

[Claims] (1) A high-voltage power supply circuit for deflection of an inkjet printer, comprising a piezoelectric transformer and a buffer circuit provided on the input side of the piezoelectric transformer, and maintaining the input pulse of the buffer circuit at a constant voltage. . (2) The high-voltage power supply circuit for deflection of an inkjet printer according to claim (1), characterized in that the input pulse is also used as an ink particle formation pulse signal number.