JPS63310374A - Power source device - Google Patents

Abstract

PURPOSE:To reduce cost of power source device, by biasing AC voltage induced in secondary winding of a booster transformer with DC voltage obtained by rectifying/smoothing the aforementioned AC voltage. CONSTITUTION:A DC power source Vp connected to primary winding N1 of a booster transformer T is connected/interrupted by means of an inverter drive circuit 1 through a switching element Q1 so as to feed power to a load 3 through a rectifier diode D1 at the secondary winding N2 side of the transformer T and an output terminal HV. The load 3 is connected through a smoothing capacitor C1 and an output terminal G. When AC voltage VAC induced in the secondary winding N2 has a polarity shown by an arrow 1, the capacitor C1 is charged through the diode D1 and DC voltage VDC is produced. When the polarity is inverted as shown by an arrow 2, combined voltage of AC voltage VAC and DC voltage VDC is fed to the load 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates primarily to a power supply device used in an electrophotographic apparatus, and more particularly to a bias power supply that supplies a DC biased AC voltage to a developing sleeve, a toner removal roller, and the like.

[Prior art]

In an electrophotographic apparatus, a developing device and a cleaning device use an alternating current voltage with a direct current bias.

For example, in a developing device, an AC voltage is applied between a grounded photoreceptor and a developing sleeve, and the DC bias sets the potential of the toner relative to the surface potential of the photoreceptor, and the AC voltage improves the mobility of the toner. I am getting good images.

The power supply device used for such applications had the configuration shown in FIG. This biases the AC voltage generated by the power supply ACP with the DC voltage generated by the power supply DCP.
Although it has the advantage of being able to independently control the AC and DC components, it has the disadvantage of requiring two power sources, making the configuration complex and expensive.

In the figure, 1.2 is the inverter drive circuit, 3 is the load, Q,
~Q, is a switching transistor, T.

, T8 are transformers, and , are diodes.

〔the purpose〕

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a TFL device with a simple configuration and at low cost that supplies an AC voltage with a DC component superimposed thereon to a load.

〔composition〕

To this end, the present invention is characterized in that the AC voltage induced in the secondary @ line of the step-up transformer is biased with a DC voltage obtained by rectifying and smoothing the AC voltage, and the DC biased AC voltage is supplied to the load. That is.

Hereinafter, each embodiment of the present invention will be described based on the drawings. still,
Components similar to those in FIG. 2 are given the same reference numerals.

FIG. 1 shows a first embodiment, +a) is a circuit diagram, and (b) is a waveform diagram thereof.

The configuration will be explained in (a). The DC power supply V is a power supply for driving the power supply device. The step-up transformer T has a primary t
! ! N, and a secondary winding N3 are provided, one end of the primary winding Nl is connected to a DC power source (2), and the other end is connected to a DC power source VP via a switch element (transistor) QI. The inverter drive circuit 1 generates a conduction signal for the switch element Q.

2nd m! One end of mN□ is connected to the load 3 via the output terminal HV.
The other end is connected to a load via a smoothing capacitor CI and an output terminal G.

A rectifying diode D between the output terminal G and HV.

is connected.

With such a configuration, when the inverter drive circuit 1 is started, the switching element Q is intermittently turned on, an exciting current flows through the primary S line NI, and an alternating current voltage vAe is induced in the secondary winding N2. When AC voltage VAC has the polarity shown by arrow 1, capacitor C3 is charged via diode D1, and output terminals G and 2
A DC voltage VaC is generated between 1HNz and 1HNz. When the polarity is reversed (arrow 2), the AC voltage VaC and the DC voltage ■. , is supplied to the load.

The waveform of the output voltage V during steady state is shown in FIG.

The DC voltage VDC is the AC voltage V induced in the secondary winding N2.
Since it is approximately 1/2 of aC, the output voltage Vl is the DC voltage V
The waveform is centered around IIC and has an amplitude of VaC, and when viewed from the output terminal G, the AC voltage ■ becomes the DC voltage V (IC
The waveform is DC biased.

Next, FIG. 3 shows another embodiment.

The difference from the first embodiment shown in FIG. 1 is that the DC bias voltage is controlled at a constant voltage and can be switched to a plurality of set values.

The configuration will be explained with reference to the drawings.

In addition to primary and secondary windings jli and Nz, the step-up transformer T is provided with a tertiary winding N that generates a conduction signal for a transistor Q, which is a switching element.

One end of the tertiary winding N3 is connected to the base of the transistor Q through a parallel circuit of a resistor R6, a transistor Q2 that controls the output voltage 1, a diode D3, and a capacitor C8. The tertiary is L'A N *The other end is the power supply V,
Connect to the low pressure side of the

A starting resistor R5 is connected between the base of the transistor Q and the voltage RVP. Secondary winding N.

The capacitors CI, C! and diode D+, DZ
A voltage doubler circuit consisting of is connected. The output terminal HV is connected to the high voltage side of the secondary winding N through a current limiting resistor R9, and the output terminal G is connected to the low voltage side of the power supply vP. Resistor R7 and R・ connected across capacitor C2
The midpoint of the series circuit is connected to one input terminal of an output control amplifier C0NT. The other input terminal of the amplifier C0NT is connected to the midpoint of a series circuit of reference voltage resistors R1 and R1. Furthermore, a switch SWt and a resistor RI, which are output voltage switching circuits, and a series circuit of a switch SW2 and a resistor R2 are connected in parallel with the resistor R1.

In such a configuration, when the power supply (2) is input, a starting current flows through the starting resistor Rs to the base of the transistor Q, and the transistor Q begins to conduct. Along with this 1
Current flows through NIA N I, energizing the step-up transformer T, and the secondary winding N! and a voltage is induced in the tertiary S line N. The voltage induced in the tertiary winding N3 is positively fed back to the base of the transistor Q via the diode D5, the transistor Q2, etc., and the transistor Q is suddenly turned on. After that, when a certain point is reached, the current amplification factor hfe becomes insufficient with respect to the collector current, and the transistor Q shifts to the off state, but becomes conductive again and repeats the above operation.

As a result, an alternating current voltage VaC is generated in the secondary winding N. This AC voltage VAC is converted into a DC voltage by a voltage doubler rectifier circuit consisting of a diode DIldz, capacitors C+, and Cx, and a DC voltage V is applied across the capacitor C1. C
occurs.

Therefore, an AC voltage vAc is output between the output terminals HV and G, and an AC voltage (2) biased with a DC voltage VIC obtained by rectifying and smoothing the AC voltage vAc is output.

Next, the DC voltage V! In order to control the IC at constant voltage, a resistor R? is connected in parallel with the capacitor CI. The DC voltage (■) is detected by the voltage divider circuit of R6 and R6. This detection signal is compared with a reference voltage created by a voltage dividing circuit of resistors R3 and R4 in an output control amplifier C0NT, and a voltage corresponding to the difference between the two is input to the base of the transistor Q. Transistor Q2 controls the base current supplied to transistor Q1 by the voltage induced in the tertiary winding. As a result, the collector current of the transistor Ql that excites the step-up transformer T is controlled, and constant voltage control is performed to maintain the DC voltages v, c, which are obtained by rectifying and smoothing the voltage VaC induced in the secondary winding N, at a predetermined value.

Next, by turning on or off the switches SWI and SW2, the reference voltage of the amplifier CON T for output control can be varied, and the DC voltage Vlle can be switched to the value shown in FIG. 4. Oni 1 switch S
When both WI and SW2 are off, the DC voltage VIIC is OV.
(output off), and when only switch SWI of Arashi 2 is on, Vl (v) is output, when only switch SW2 of Arashi 3 is on, Vl +60 (v) is output, and switch S
When both WI and SW2 are on, Vl+120(v) is output.

Next, a third embodiment is shown in FIG.

The difference from the previous embodiment is that the ratio of AC components included in the output voltage V is reduced.

This will be explained below with reference to the drawings. A diode D, DR1 and a capacitor C are connected to both ends of the secondary winding N2 of the step-up transformer T.
T-C! A voltage doubler circuit consisting of a secondary winding N
A DC voltage VDC obtained by rectifying and smoothing the AC voltage vac' induced across the capacitor C1 is generated across the capacitor C1. The secondary winding HNt is provided with an intermediate tap a, and an alternating current voltage vAc is induced between it and the anode side of the diode D1 of the voltage doubler circuit, and the alternating current voltage ■^C biased with direct current voltage V1+C is connected to the resistor RQ. It is output between output terminals HV and G via.

This output voltage (3) has the waveform shown in FIG. 6, and since the AC voltage VaC is taken out from the intermediate tap a, the AC voltage VaC with respect to the DC voltage VOC is
is getting smaller. This ratio can be set to any value by changing the position of the intermediate tap a.

In addition, DC voltage ■. As in the previous embodiment, the detection signal from the midpoint between the resistors R7 and R6 connected in parallel to the capacitor CI is fed back to the inverter drive circuit on the primary side to perform constant voltage control. .

Further, FIG. 7 shows a fourth embodiment.

This embodiment differs from the previous embodiment in that the DC bias is of negative polarity and that the inverter is driven by a push-pull method and the voltage supplied to the primary winding Nl is controlled by a DC/DC converter. .

This will be explained below with reference to the drawings. The secondary side of the step-up transformer 10 is the same as the embodiment shown in FIG. 3 except that the polarities of the diodes D1 and D2 of the voltage doubler circuit are reversed.

On the primary side, transistors Q8 and Q are connected to both ends of a primary winding N1 provided with an intermediate tap, and their bases are connected to an oscillator (DRIV) 4, respectively.

Volume 1! A transistor Ql is connected between the intermediate tap of i N + and the voltage RVP, and its base is connected to the output control circuit C0NT. A variable reference voltage source (2) is connected to one input of the output control circuit C0NT, and a DC voltage (2) is connected to the other input via a resistor (R1). ,
Detection signal is input.

With this configuration, when the voltage RVp is applied, voltage is supplied to the primary winding NI via the transistor Q, and the voltage is supplied from the oscillation 34 to the transistor Q.

and Q3 alternately i i! ! (When No. 3 is supplied and the transistors Q8 and Q are alternately connected four times, the step-up transformer T is energized and a voltage VAC which crosses the secondary winding N2) is induced.

The AC voltage vAc is rectified and smoothed by a voltage doubler circuit,
An AC voltage which is selectively DC-biased is outputted to output terminals HV and Gπi via a resistor R9.

The negative polarity signal outputted from the midpoint between resistors R1 and R1) is biased to positive polarity by resistor R0 and resistor R1)1, and is input to the output control circuit C, ON'l''.

And the output side? ITi! The transistor Q is compared with the reference voltage V at the L path C0NT so that the output signal becomes a predetermined value.
, and the DC voltage vnc is kept at a constant voltage value. Therefore, by varying the reference voltage (3), the DC voltage v1 can be set to any value.

In this Xff5 example, the step-up transformer is a push-pull type, and the positive and negative oscillations are rIJ magnetized equally, so the distortion of the AC component included in the output voltage V, compared to the embodiments shown in Figs. This has the advantage of reducing the amount of

〔effect〕

The present invention is as described above, and according to the present invention, the AC voltage induced in the secondary winding of the step-up transformer is biased with the DC voltage obtained by rectifying and smoothing the AC voltage, so that one system With the power supply circuit of i! ! Accordingly, it is possible to provide an inexpensive power supply device that can supply a current-biased AC voltage to a load.

[Brief explanation of drawings]

FIG. 1 shows the first embodiment, and (a) is its circuit diagram;
+(b) is the waveform diagram, Figure 2 is the circuit diagram related to the conventional example,
FIG. 3 is a circuit diagram according to the second embodiment, FIG. 4 is a diagram for explaining the value of DC voltage by switching the switch, FIG. 5 is a circuit diagram according to the third embodiment □, FIG. 6 is a waveform diagram thereof, and FIG. 7 is a circuit diagram according to the fourth embodiment. T...Step-up transformer, VOC...DC bias,■
AC: AC voltage, ■3: DC biased output voltage. Figure 1 (a) (b) Figure 2 Figure 3 Figure 4ffl Figure 5

Claims (3)

[Claims] (1) The AC voltage induced in the secondary winding of the step-up transformer is
A power supply device characterized in that the AC voltage is biased with a rectified and smoothed DC voltage, and the DC biased AC voltage is supplied to a load. (2) The power supply device according to claim 1, wherein the DC-biased AC voltage is an AC voltage that alternates based on a rectified and smoothed DC voltage. (3) A means for detecting a DC voltage is provided, and the AC voltage induced in the secondary winding of the step-up transformer is controlled so that the detected value becomes a predetermined value. The power supply device described in (1).