JPS6013434A - Power source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device, and particularly to a power supply device effective for application to electronic image forming apparatuses that require a low-voltage power source and a high-voltage power source, such as electronic copying machines and electronic printers. It is.

Conventionally, in this type of electronic image forming apparatus.

A low-voltage power supply for sequence control first converts a commercial AC power supply into low-voltage DC through a low-voltage transformer and rectifier circuit, and supplies it to sequence control circuits, lamps, solenoids, etc., and at the same time converts the DC output to an inverter circuit. It was supplied to the primary side of the high-voltage transformer of the high-voltage power supply for feeding the charger. For this reason, the high-voltage output is multiplied by the conversion efficiency of the low-voltage power supply and the high-voltage power supply, resulting in a significant drop in energy efficiency.Also, the drive circuits for the low-voltage and high-voltage transformers are doubled, which increases the number of parts. This, in turn, caused an increase in the size and cost of the equipment.

The present invention has been proposed in view of the above, and aims to improve power conversion efficiency, obtain a highly reliable compact power supply device with a small number of parts, and achieve a compact size through high-density packaging while suppressing temperature rise and generating heat. The purpose is to prevent failure of circuit elements.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 is a commercial AC power supply connected to the input side of the rectifier circuit 2, and 3 is a low voltage inverter transformer 4 connected to the output side of the rectifier circuit 2. The control circuits W1 to W3 to control are the secondary windings of the low voltage inverter transformer 4 described in 1.

The control circuit 3 is a switching transistor oscillation circuit,
Including PWM (pulse width modulation) circuit, error amplifier, etc.
The rectified output of the rectifier circuit 7 which inputs the output of the secondary winding W3 is compared with a reference value, and the energization time of the low voltage inverter transformer 4 is controlled so that the rectified output becomes constant.

The rectified output of the rectifier circuit 6 which inputs the output of the secondary winding W2 is outputted to a terminal 12.13, and a sequence control circuit (not shown) connected to the terminal outputs a voltage of approximately 24V.
Supplies low voltage circuits such as lamps and solenoids.

The secondary winding W1 is connected to the primary winding of a high voltage inverter transformer 8 via an electrical or mechanical switch 5. The rectified output of the rectifier circuit 9 connected to the secondary side of the high-voltage inverter transformer 8 is kept at a constant voltage by the constant voltage characteristics of the control circuit 3 and the high-voltage inverter transformer itself, and this constant voltage is applied to the terminals 10.11. Supplied to a high voltage circuit such as a charger (not shown) connected to the

In this embodiment, a relay is used as the switch 5, which is opened and closed by a sequence control signal.

FIG. 2 is an external perspective view of an embodiment of the present invention, and FIG. 3 is a longitudinal sectional view thereof. In FIG. 2.3, a bobbin 18 around which a primary coil 17 of a low-voltage inverter transformer 4 is wound is fitted into one of insulating cylinders 15 and 16 erected on the surface of a substrate 14. A bobbin 2o around which secondary coils w1, W2, and W3 are wound is fitted onto the outside of the bobbin. Further, a bobbin 22 on which a primary coil 21 of a high-voltage inverter transformer 8 is wound is fitted into the other cylinder 16, and a bobbin 24 on which a secondary coil 23 is wound on the outside of the bobbin. There is. Lead terminals 4a and 8a of the transformer 4.8 are provided protruding from the back surface of the substrate 14. Secondary coil 23 of the above high voltage inverter transformer
Rectifiers 9a to 9d constituting the high voltage rectifier circuit 9 are connected to.

19 partitions a hole 25.26 into which the cylindrical body 15.16 fits, and a bobbin 18.20 of the low-voltage inverter transformer 4 and a bobbin 22.24 of the high-voltage inverter transformer 8 to increase insulation against social gatherings. Part 4 Part 27
As shown in Figure 3, each bobbin,
Cover the rectifier and other circuit elements connected to each of the above coils, such as switching transistors, electrolytic capacitors, etc.
An epoxy-based highly insulating and highly thermally conductive resin 28 is vacuum injected and dried and integrated. 29.3o is the cylinder body 15.
This is an iron core inserted and disposed within 16.

Figure 4 shows a heat sink 31 attached to the outside of the case 19 with screws 3.
This is an example of installation in step 2. In this example, as shown in FIG. 5, the fin portion 33a of the switching transistor 33 (another element that generates a large amount of heat, such as an electrolytic capacitor) is brought into contact with the inner surface of the wall surface of the case 19 that is in close contact with the heat sink 31. The fin portion 33a is held by a holding plate 34 provided on the inner surface of the case, and the switching transistor 33 is connected to the heat sink 31 with very low thermal resistance. Therefore, switching transistor 3
The heat generated in step 3 is efficiently dissipated, eliminating failures caused by heat and improving reliability.

As detailed above, the present invention connects the secondary winding of the low-voltage inverter transformer and the primary winding of the high-voltage inverter transformer, so there is no need for any drive circuit on the primary side of the high-voltage inverter transformer. Therefore, switching and other losses in the drive circuit can be eliminated and power conversion can be made highly efficient.

Further, there is no noise caused by switching, heat generation due to switching loss, etc., and the number of parts is reduced, so reliability can be significantly improved, and miniaturization and cost reduction can be achieved.

In addition, a low-voltage inverter transformer and a high-voltage inverter transformer are housed in the same case, and the circuit elements connected to the transformer are brought into contact with the inner surface of the case, and a highly insulating and highly thermally conductive resin is injected into the interior of the case. Since it is filled and integrated as a whole, each member can be brought close to each other by shortening the insulation distance specified by safety regulations, and can be mounted at high density, making it possible to significantly downsize the power supply assembly. Further, since the case and the filled resin have high thermal conductivity, the heat of the circuit elements can be efficiently dissipated, and failures of the circuit elements can be prevented.

Note that the high-voltage inverter transformer 8 may have a plurality of secondary windings to supply power to a plurality of chargers having different charging voltages.

In the above embodiment, the control circuit 3 is composed of a switching transistor oscillation circuit, a PWM circuit, and an error amplifier, which implicitly indicates that it is a passive inverter.
By adding a feedback @ line input to the base of the switching transistor to the inverter transformer, it is possible to simplify the automatic inverter by removing the oscillation circuit.

The stabilized output of the low voltage inverter transformer 4 is connected to the secondary winding W.
It is also possible to use the rectified output of the secondary winding W2 instead of the rectified output of the secondary winding W2. Therefore, it is easily possible to stabilize the output of the secondary winding W1 or the output of the high voltage inverter transformer 8 itself.

In addition to the rectifiers 9a to 9d that constitute the high voltage rectifier circuit 9, circuit components that share a common ground with the input commercial power supply, which is called a primary circuit due to safety standards, are housed in the case 19, and are filled with high insulation. By integrating the parts with a material, the insulation distance can be shortened and the device can be made more compact.

The illustrated example shows the primary coil and 2 of the low voltage inverter transformer 4.
Although the next coils are wound on separate bobbins 18, 20, they may be on the same bobbin.

In addition, in the illustrated example, the shield plate that covers the case 19 from the front is used as a heat sink in order to shield unnecessary radiation noise from the coil of the high-voltage inverter transformer 8. A shield plate or heat sink may be provided only on the exposed surface. This heat sink may also be used as the power supply unit case or the frame of the main body.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the power supply device of the present invention, Fig. 2 is an external perspective view of the power supply device of the present invention, Fig. 3 is a vertical sectional view thereof, Fig. 4 is a side view with a heat sink attached, and Fig. 5 is its external perspective view. It is a sectional view of the main part. 4 is a low voltage inverter transformer, 8 is a high voltage inverter transformer, 19 is a case, 28 is a highly insulating and highly thermally conductive resin, 31 is a heat sink, and 33 is a switching transistor. Patent applicant Canon Co., Ltd. JP-A-Sho GO-13434 (4)

Claims (1)

[Claims] (1) A first transformer having a plurality of secondary windings and supplying low voltage output to a low voltage circuit; one of the secondary windings of the first transformer and the primary winding are connected to supply a high voltage to the high voltage circuit; and a second transformer that supplies an output, with both transformers housed in a highly thermally conductive case and a circuit element connected to the transformer in contact with the inner surface of the case. A power supply device characterized by being filled with an insulating and highly thermally conductive resin and integrally fixed as a whole.