JPH01259756A - Power source device - Google Patents

Abstract

PURPOSE:To make a power source device small in size and low in price, by dividing the magnetic core of a transformer into a plural number and by providing a pair of primary and secondary windings tightly coupled to each magnetic core. CONSTITUTION:A power source device is composed of a drive circuit 1 of a switching transistor T1, a regulator circuit 2 of a power source for sequence control, etc. This transformer T1 is separated into a low-pressure winding section L1-L1' and a high-pressure winding section L2-L2'' by a gap 3-1. The flux of the magnetic core section wound around with windings L2-L2'' is fully damped with the gap 3-1. These windings L2-L2'' are tightly coupled; the winding L2' becomes high-pressure winding and the winding L2'' becomes high- pressure control winding. The power supply side of the primary windings L1 and L2 are connected in common to the rectification-smoothing output of a line input, while the other end is connected to Tr1 respectively, so that the conduction ratio is controlled by the drive circuit 1 and the output is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a power supply device, and particularly to a power supply device applicable to image forming apparatuses such as copying machines and printers.

[Background of the Invention] Conventionally, in a power supply device for a copying machine, a low-voltage power supply for sequence control, a power supply for exposure, and a high-voltage power supply for charging have been configured as independent power supply devices.

The high voltage power supply for charging has a stabilized low voltage power output (-4a
24V), 5~9KV with DC-DC inverter
is configured to boost the voltage to Such conventional devices require a large number of transformers and drive circuits, and suffer from reduced power efficiency.

From this point of view, attempts have been made to integrate a low voltage power source and a high voltage power source. However, when the transformer is integrated, high voltage output is generated as soon as the power is turned on, so it is difficult to control the high voltage according to the sequence signal.

[Purpose] The present invention has been made in view of the above points, and its purpose is to provide a power supply device that is smaller, less expensive, more efficient, and has further improved reliability. be.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, where l is a drive circuit for a switching transistor Tr1 of a power supply converter transformer T, and 2 is a regulator circuit for a sequence control power supply (24V inside the shell).

Converter transformer T, LI, LI at gap 3-1
' low voltage winding section and R21R2'.

It is separated into a high voltage winding portion L2''.L2' is a high voltage winding which is rectified and smoothed by a high voltage diode D1 and a high voltage capacitor C1, and is outputted as a high voltage to a high voltage terminal P5.

Now, when the power is turned on, the primary winding L1 is energized. L
, ' beams are tightly coupled and wound, so an output of approximately 26 to 29 V RMS can be obtained at both ends. After rectification by D2,
After being stabilized at 24V by the regulator circuit 2, it is supplied to the sequence control circuit via the output terminal P3°R4. At this time, Sl remains open, L2'
, R2", the magnetic flux of the magnetic core wound with the winding is the gap 3-
It is sufficiently attenuated by 1. The L, , L2', and L2'' windings are tightly coupled as shown in FIG. 3, with the L2' winding being a high voltage winding and the L2'' winding being a high voltage control winding.

During non-copying, TR2 is rendered conductive by the control signal to R6, so the induced voltage in the R2 winding becomes extremely small and the high voltage output becomes less than IKV. During copying, the sequence control circuit operates and switch S1 is turned on. At the same time, TR2 is opened, and by energizing the R2 winding, a preset high voltage is induced in the L2' winding, and the DC high voltage necessary for image formation is supplied to the charger via the terminal P5.

FIG. 2 shows a structural diagram of the actual winding of the transformer T1. i
The gap 3-1 shown in FIG. 1 is actually composed of gaps at portions A, B, and C.

The gap in section C is set sufficiently small compared to sections A and B to reduce the voltage induced in the L2' winding when S1 is cut off.

FIG. 5 shows details of the transformer drive circuit of the present invention.

The power supply sides of the primary windings ML+ and R2 are commonly connected to the rectified and smoothed output of the line input. The other ends are connected to switching transistors T, 21T, and 22, respectively. The energization ratio of each transistor is controlled by PWM circuits 21 and 22. The output of the secondary winding ' is stabilized at 5V and fed to the sequence control circuit. R2,
, R2□ at a predetermined ratio, and the error amplifier 27 compares the output with the output of the constant voltage element 29.

The comparison output is isolated by a photocoupler 26 and input to the PWM circuit 21 to stabilize +5V.

The output of the secondary winding L2' is fed to the charger, the load current is detected by R23, and the error amplifier 28 connects the terminal 21 to the charger.
is compared with the sequence control voltage connected to

The comparison output is isolated by a photocoupler 25 and input to the PWM circuit to stabilize the load current of the charger connected to R5.

FIG. 3 shows an example in which the primary winding is removed and only L is used, and the high voltage output is controlled only by the high voltage control winding L2''.

Also, in Figure 3, the load current of the charger is detected by resistor R4, and compared with the reference value by error amplifier 4, and in addition to the base of TR2, the collector current of TR2, that is, the current of high voltage control winding L2'' is calculated. The charger load current is stabilized by changing it.5
is an analog switch circuit which, by control input to 26, makes Tr□ conductive during non-copying, and switches the reference voltage so that the charging R current flowing through R4 or a predetermined current occurs during copying.

In FIG. 4, in the embodiment shown in FIG. 3, the output of the error amplifier 4 is added to the PWM circuit 7 and TR2 is controlled by switching to increase efficiency.

In the embodiment shown in FIG. 5, a common power supply for the primary winding is provided, and a plurality of switching transistors and PWM circuits for driving the switching transistors are provided, whereas in the embodiment shown in FIG. High voltage side switching transistor T122
It is also possible to delete L2 and make it common with T and 21, and connect the other end of L2 to a variable power supply output such as a series regulator or a switching regulator.

Regarding the embodiment shown in FIG. 5, the switching transistors of the primary windings L1 and L2 are made common, and are driven directly by the output of the oscillation circuit without going through the PWM circuit, and each power supply terminal is made independent, so that the switching transistors can be used as a series regulator or A method of controlling using a switching regulator or the like is also possible.

As is clear from the above embodiments, it is possible to feed both the low voltage power source and the high voltage power source from the same transformer.

Furthermore, the timing of high voltage output can be controlled by the sequence signal.

In the third and fourth embodiments, switching of the power supply on the primary side can be omitted, making it simpler.

Further, as shown in Examples 3 and 4, stabilization control of high voltage output becomes possible.

In the embodiments shown in FIGS. 5 and 6, it is possible to independently control not only on/off but also continuous output without using a mechanical switch such as a relay.

[Effects] As described above, according to the present invention, it is possible to supply high voltage and low voltage power from the same transformer, and it is also possible to independently perform on/off and stabilization control for each, resulting in miniaturization and low cost. In addition to improving efficiency and efficiency, it also becomes possible to further improve reliability.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a power supply device that is an embodiment of the present invention, and Figure 2 is a converter transformer T used in the embodiment of Figure 1.
FIG. 3 is a circuit diagram of a power supply device according to another embodiment of the present invention, and FIG. 4 is a circuit diagram of a power supply device according to yet another embodiment. FIG. 5 and FIG. 6 are diagrams showing the drive circuit. 1...Switching transistor drive circuit 2...Regulator 4...Error amplifier 7...PWM circuit T1...Converter transformer

Claims (1)

[Claims] (1) In a power supply device that extracts high-voltage and low-voltage power from multiple secondary windings of the same converter transformer, the magnetic core of the transformer is divided into multiple parts using caps, etc., and each of the divided magnetic cores is tightly coupled to each other. 1. A power supply device characterized in that a pair of secondary windings of a primary winding is provided, and separate switching circuits are connected to the primary sides of the pair of windings.