JPH04251564A - Power supply unit - Google Patents

Abstract

PURPOSE:To provide a power unit, which does not require a transformer for input voltage detection, a photocoupler, etc., and capable of miniaturization, and cost reduction and is suitable for an electrophotographic copier, a printer, etc. CONSTITUTION:This is a switching type power unit, which rectifies and smoothes and outputs generated forward output by a converter transformer T11, which has a switching transistor Q11 on the primary side, a diode D13, which is equipped on the secondary winding n3, an inductor L11, and a capacitor C12, and the pulse width modulating circuit 2 controls the output voltage to be constant by detecting the input voltage of a converter transformer T11 from the output of the said secondary winding n3, and controlling the switching duty ratio of the switching transistor Q11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device suitable for electrophotographic copying machines, printers, and the like.

0002

[Prior Art] Conventionally, in electrophotographic copying machines or printers, the controller for sequence control was located on the secondary side isolated from the line input, so the DC motor and solenoid driven by low voltage were directly connected to the controller. Heater and AC controlled and driven by line input
Motors and other equipment were controlled after being insulated using transformers, photocouplers, etc.

In such a case, depending on the input voltage, the heater,
When trying to control an AC motor, etc., the input voltage is detected and the controller controls the controlled part according to the detection signal, but in order to detect the input voltage and isolate it, a transformer,
Control was performed after insulation using photocouplers, etc.

0004

However, in the conventional example described above, a transformer, a photocoupler, etc. are required to detect the input voltage, which causes problems such as an increase in the size of the device and an increase in cost.

The present invention was made to solve the problems of the prior art described above, and detects the input voltage from the secondary side of the power transformer, thereby reducing the size and cost by eliminating the need for a transformer, photocoupler, etc. The purpose of this invention is to provide a power supply device that can reduce power consumption.

[0006]

[Means for Solving the Problems] Therefore, the power supply device according to the present invention is a switching type power supply device, which
The above object is achieved by a configuration characterized by comprising a circuit for rectifying and smoothing the forward output connected to the secondary winding of the power transformer, and detecting the transformer input voltage by the circuit.

Furthermore, in the above configuration, a circuit for rectifying and smoothing the forward output connected to the secondary winding of the power transformer is provided separately from the rectifying and smoothing circuit for supplying power to the load connected to the secondary winding of the power transformer. It is also a voltage resonant flyback power supply device, which rectifies the forward output with a rectifier connected to the secondary winding of the flyback transformer and detects a zero-cross timing signal of the flyback voltage. The above object is achieved by a configuration characterized in that the power transformer has a plurality of secondary windings.

[0008]

[Operation] With the above configuration, the transformer input voltage can be detected by rectifying and smoothing the forward output using the rectifier and smoothing circuit connected to the secondary winding of the power transformer, and the load can be controlled according to the input voltage. becomes possible.

Furthermore, in addition to the rectifying and smoothing circuit for the load power supply connected to the secondary winding of the power transformer, the forward output is rectified and smoothed by a rectifying and smoothing circuit connected to the secondary winding to convert the transformer input voltage. Can be detected.

Further, in the voltage resonance type flyback power supply device, a zero-cross timing signal of the flyback voltage can be detected by a rectifying element that rectifies the forward output connected to the secondary winding of the flyback transformer.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The power supply device according to the present invention will be explained below by way of embodiments.

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention. In the figure, a controller 1 is a controller that controls the entire device in which the power supply device of this embodiment is mounted, and controls a heater, a motor, a solenoid, etc. (not shown). The power supply device of this embodiment constitutes a forward switching power supply, and the line input is rectified and smoothed by a bridge diode D11 and a capacitor C11. And the positive output is converter transformer T1
1, and the other end is the switching transistor Q11.
connected to the collector of

The emitter of switching transistor Q11 is connected to the negative electrode of bridge diode D11. With this configuration, switching of the switching transistor Q11 generates a voltage on the secondary side of the converter transformer T11 according to the turns ratio of the converter transformer T11.

Secondary winding n of converter transformer T11
3 is rectified by a diode D13 and smoothed by a capacitor C12 via an inductor L11. At this time, when the switching transistor Q11 is turned on, a voltage is generated in the secondary winding n3, and the diode D1
3 and the output via inductor L11. When the switching transistor Q11 is turned off, the magnetic energy stored in the inductor L11 supplies a voltage to the output via the diode D14.

In the above operation, pulse width modulation (hereinafter P
The circuit 2 (referred to as WM) detects the above output and controls the switching duty rate of the switching transistor Q11, thereby making it possible to control the output voltage at a constant voltage.

The second secondary winding n4 of the converter transformer T11 is rectified and smoothed by a diode D15 and a capacitor C13. The same output is converter transformer T11
Since the forward voltage generated in the line is rectified, it is possible to obtain an output proportional to the line input.
It is not affected by WM duty. Therefore, by connecting this voltage to the controller 1, control that takes the power supply voltage into consideration becomes possible.

In this way, the input voltage can be easily detected by using the conventional transformer even without a special circuit for detecting the input voltage.

(Other Embodiments) FIG. 2 shows a second embodiment according to the present invention.
FIG. 2 is a circuit block diagram showing an embodiment of the present invention. In the figure, the output terminal of the secondary winding n3 of the converter transformer T11 has diodes D13, D14 for supplying output to the load,
It is connected to a first rectifying and smoothing circuit including a capacitor C12 and an inductor L11, and a second rectifying and smoothing circuit including a diode D15 and a capacitor C13. Other than the above, the second embodiment is the same as the first embodiment, and the same or corresponding parts are indicated by the same reference numerals, and redundant explanation will be omitted.

In the circuit of this embodiment shown in FIG.
The output of the rectifying and smoothing circuit is PWM as in the first embodiment.
Constant voltage control is performed by circuit 2. The output of the second rectifying and smoothing circuit is not influenced by the PWM circuit 2 and outputs a voltage proportional to the input voltage.

[0020] Since the input voltage can be detected from the output from the conventional output winding without particularly providing a secondary winding for detecting the input voltage, there is no need to increase the size of the transformer.

FIG. 3 is a circuit block diagram showing a third embodiment of the present invention. This embodiment constitutes a voltage resonance type flyback switching power supply, and is particularly suitable for electrophotographic copying machines.

In the figure, T31 is a flyback transformer, and the positive polarity of the output obtained by rectifying and smoothing the line input by a bridge diode D31 and a capacitor C31 is applied to the primary winding n1. The other end is transistor Q31
The collector of the diode D32 is connected to the negative electrode side of the bridge diode D31 via the diode D32 and the capacitor C32. T32 is a pulse transformer and is driven by the controller 5. The output of pulse transformer T32 is rectified by diode D34 and drives transistor Q31. With the above configuration, the output of the controller 5 is caused by switching the transistor Q31 and the flyback transformer T3.
The output can be supplied to the secondary side of 1.

The secondary winding n2 of the flyback transformer T31 generates high voltage, and the diode D33 and capacitor C
33, the signal is rectified and smoothed and output, and applied to a charger transfer device. Also, the secondary winding n2 of the flyback transformer T31
The other end is connected to a high voltage control circuit 3, and the circuit 3 controls the output. The secondary winding n3 is a fluorescent light drive output, and is connected to the fluorescent light control circuit 4 via an inductor L31 and a lamp P.
is applied to Secondary winding n4 generates a developing bias. The signal is rectified and smoothed by a diode D31 and a capacitor C36, and applied to the DC bias control circuit 6 via a resistor R32, and then connected to a transformer T33, the end of which is supplied to a developing load. Note that the transformer T33 is driven by the AC bias application circuit 7.

The secondary winding n5 is a low voltage output, and the flyback output is connected to diodes D35, D37 and capacitor C.
It is rectified and smoothed by 34 and used as a DC24V power supply, and 5
The V regulator 8 supplies each load as a 5V DC power source. Also, the forward output is diode D36,
The signal is rectified and smoothed by D38 and capacitor C35 and input to the controller 5.

Further, the forward output is rectified by the diode D39 and inputted to the controller 5. The controller 5 performs low voltage control of the secondary side output by detecting the low voltage flyback output and performing PWM control. Further, the forward output can detect the line input voltage without being affected by PWM control, and the signal from the diode D39 can detect the zero cross of the flyback voltage, thereby enabling efficient voltage conversion.

[0026]

As explained above, according to the present invention, the transformer input voltage is detected from the secondary side by rectifying and smoothing the forward output using the rectifying and smoothing circuit connected to the secondary winding of the power transformer. This makes it possible to control the load in accordance with the input voltage. Furthermore, by using the output winding to the load for input voltage detection, the input voltage can be detected without requiring a new winding.

That is, unlike conventional power supply devices, it is possible to provide a power supply device that does not require a transformer, a photocoupler, etc. for input voltage detection, and can be downsized and cost-reduced.

Furthermore, in addition to the rectifying and smoothing circuit for the load power supply connected to the secondary winding of the power transformer, the forward output is rectified and smoothed by a rectifying and smoothing circuit connected to the secondary winding to convert the transformer input voltage. In addition, a plurality of secondary windings can be provided to enable various outputs.

In the voltage resonance type flyback power supply device, both the input voltage and the switching zero-cross timing signal can be detected from the secondary winding for output from the flyback transformer to the load.

[Brief explanation of the drawing]

[Fig. 1] Block diagram of a first embodiment according to the present invention

[Figure 2
]Circuit block diagram of a second embodiment according to the present invention

[Figure 3
]Circuit block diagram of a third embodiment according to the present invention

[Explanation of symbols]

1,5 Controller 2 PWM circuit 3 High voltage control circuit C13, D15 Capacitor and diode C35, D36, D38 forming a rectifying and smoothing circuit Capacitor and diode D11, D31 forming a rectifying and smoothing circuit Bridge diode D39 Rectifier for zero-cross timing signal detection Element diode T11 Converter transformer T31 Flyback transformer

Claims (4)

[Claims] 1. A switching power supply device, comprising a circuit for rectifying and smoothing a forward output connected to a secondary winding of a power transformer, and detecting a transformer input voltage by the circuit. Device. 2. The power supply transformer has a rectifying and smoothing circuit for supplying power to the load connected to the secondary winding of the power transformer, and a circuit for rectifying and smoothing the forward output connected to the secondary winding. The power supply device according to claim 1. 3. A voltage resonant flyback power supply device, wherein a forward output is rectified by a rectifying element connected to a secondary winding of a flyback transformer, and a zero-cross timing signal of a flyback voltage is detected. The power supply device according to claim 1 or 2. 4. The power supply device according to claim 1, wherein the power transformer has a plurality of secondary windings.