JPH02101965A - Power source equipment - Google Patents

Abstract

PURPOSE:To obtain a stabilized constant voltage by arranging a voltage regulating circuit at the output of a first winding in a converter transformer and lowering the outputs from a plurality of output windings during standby mode, then rectifying the output from a second winding and feeding through a switch circuit to a voltage regulating circuit. CONSTITUTION:A voltage regulating circuit 2 is arranged at the output of a first winding in a converter transformer T1 and the output from a plurality of output windings are lowered in the standby mode, while the output from the second high voltage winding in the first winding is rectified and fed through a switch circuit Tr2 to the voltage regulating circuit 2. By such an arrangement, switching can be made between the normal operation mode and standby mode.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power supply device for an information processing device, an image forming device, etc., and in particular, the present invention relates to a power supply device for an information processing device, an image forming device, etc. The present invention relates to a power supply device for this type of device.

(Prior Art) Conventionally, in image forming apparatuses, information processing apparatuses, etc. that use multiple different voltages, in which the difference in power consumption between normal operation mode and standby mode is relatively large, CPU When controlling to lower voltages other than low voltages, separate power supplies were used to control the voltages.In particular, for example in electrophotographic copying machines, high voltage and low voltage Since multiple voltage values were used, dedicated power supplies were used for both high voltage and low voltage.

[Problem to be solved by the invention] However, in the conventional example as described above, since multiple power supply devices are used, there are drawbacks such as an increase in the size and cost of the entire device. It has also been proposed to adopt a method of obtaining multiple voltage values from a transformer, but
When high voltage is used in an electrophotographic copying machine, etc., there is a problem in that it is extremely difficult to control low and high voltages.

The present invention was made to solve the problems of the conventional examples as described above, and it is possible to switch between normal operation mode and standby mode with a single converter transformer, and
The purpose of the present invention is to provide a power supply device of this type that can always supply a stable low voltage to a constant voltage circuit.

(Means for Solving the Problems) Therefore, in the present invention, the voltage used in the constant voltage circuit is obtained by rectifying and smoothing the output winding output of the converter transformer of the switching regulator, and then making the voltage constant in the constant voltage circuit.
Furthermore, when the output of each output winding is lowered in standby mode, the above purpose is achieved by controlling the output of the other output windings to be connected to the input of the constant voltage circuit after rectification and smoothing by a switch circuit. This is what we are trying to achieve.

[Effect]

With the configuration of the present invention as described above, the input voltage value of the constant voltage circuit is always ensured to be above a certain value, so even if each output voltage is lowered, a stable voltage can be supplied to the constant voltage circuit. becomes.

【Example〕

The present invention will be explained below based on examples.

(Structure) FIG. 1 shows a circuit configuration diagram of an embodiment of a power supply device for an information processing apparatus such as an electrophotographic copying machine according to the present invention. On the right side of the figure, D+ is a bridge diode for rectifying the commercial AC line input, C8 is a smoothing capacitor, and T
, is a converter transformer (flyback transformer) of a voltage co-mining type flyback regulator as a switching regulator, and T and I are power MOS FETs (metal oxide semiconductor field effect transistors) for driving this converter transformer T1. , C2 is a capacitor for resonating with the converter transformer T, to perform more effective voltage conversion, and C6 is a diode for protecting the FET T,l.

By switching the FET Trl, an output voltage is generated in each output winding of the converter transformer T.

C2, Ds, C4, Ds and C3°C4, cs, as
are diodes and capacitors for rectifying and smoothing the output of each winding. Output 1 is the charging of the copying machine,
Output 2 is a high voltage output for use in transfer, etc., and output 3 is a high voltage output for use in development, etc., and output 3 is a motor driven by output winding L2.

24V output for driving solenoids, output 4,
This is a 5v output for driving the CPU 3 etc. by the output winding Ll.

2 is a constant voltage circuit for making the 5V of output 4 a constant voltage;
R+, R2, and R3 are each resistor for dividing the output 3 (7) 24V voltage, and Tr3 is each resistor R,, R2
The transistor Tr4 for driving the photocoupler 4 compares the divided voltage with the Zener diode ZD and its own base-emitter voltage, and by short-circuiting the resistor R3, each resistor R, , R, , R, is a transistor for changing the voltage division ratio.

Reference numeral 1 denotes a PWM (pulse width modulation) circuit which performs PWM control using a signal from a photocoupler 4 in a primary control method and controls the overall output by driving FET T-+. The switching transistor TP2 is
A switching transistor (switch circuit) for switching the connection of the output of output 3 to the input of constant voltage circuit 2, R4
is a bias resistor for applying a bias to the base of the switching transistor T,2, T,6 is a transistor that turns on/off the switching transistor Tr2, and 3 is a CPU for controlling the device.

(motion) Next, the operation in the above configuration will be explained.

1) When the copying machine or the like is in the normal operation mode, the CPU 3 turns on each transistor T r4 * T rl+.

Therefore, the Zener diode ZD and the transistor Tr
The emitter base voltage of 3 is V! Then, since the resistor R3 is short-circuited, the output 3 is turned on. At this time, all outputs are set so that the rated output is output. Furthermore, since the transistor T15 is on, the switching transistor Tr2 is turned off, so the diode D! is connected to the input of the constant voltage circuit 2. The output of , is input.

2) Next, when the copying machine or the like is in standby mode, each transistor Tr4. Tri performs control to turn off. As a result, the base of the transistors T, , 3 has a voltage P divided by each resistor R, , R, , R,
WM controlled. At this time, the voltage of output 3 is 6v~8■
Partial pressure ratio 1 so that it is about ! By setting , the output becomes a low consumption mode of about -. At this time, since the transistors T, 8 are off, the switching transistors T, 2 are turned on, and the input of the constant voltage circuit 2 is supplied with power from the output 3, even if the supply from the diode D6 is stopped. , it becomes possible to supply a stable constant voltage output to the output 4. In addition, since the input side of the constant voltage circuit 2 is also connected to the photocoupler 4, this photocoupler 4 can also transmit more stable signals.

(Second Embodiment) FIG. 2 shows a circuit configuration diagram of a second embodiment of the power supply device according to the present invention. Same as in FIG. 1 of the first embodiment (
Components (equivalent) are represented by the same reference numerals, and duplicate explanations will be omitted. In the figure, switching transistors T, 2
A Zener diode Z is connected between the base and ground of
D2 is connected, and the rest is substantially the same as the first embodiment. The Zener voltage of the Zener diode ZD is 7V to 8VP1 degree, and when the voltage supplied from the diode Ds becomes smaller than the voltage obtained by subtracting the pace emitter voltage of the switching transistor Tr2 from the Zener voltage of the Zener diode ZD2, the switching transistor Tr2 is turned on. In other words, even if there is no signal from the CPU 3, the input to the constant voltage circuit 2 is automatically switched, so even if the diode D5 is disconnected, it is possible to secure the output 4 at 5V.

(Third Embodiment) FIG. 3 shows a circuit configuration diagram of a third embodiment of the power supply device according to the present invention, and each reference numeral is the same as the note in the second embodiment.

Diodes D, D, D, are connected in series between the base of the switching transistor Tr2 and the output 4. The rest is substantially the same as the second embodiment. The voltage supplied by the diode Dr is the voltage of the output 4, that is, 5V, and the voltage supplied by each diode D7. When the forward voltage of DIS, D is added and becomes smaller than the voltage obtained by subtracting the pace emitter voltage of the switching transistors T, 2, the switching transistor Tr2 is turned on, and a voltage is supplied to the constant voltage circuit 2 from the output 3. At this time, since the forward current drop voltage has smaller variations than the Zener voltage, mode switching can be performed with more accurate voltage.

(Effects of the Invention) As explained above, according to the present invention, it is possible to switch between the normal operation mode and standby mode with a single converter transformer, and to supply stable low voltage. We were able to provide a power supply for processing equipment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a circuit diagram of a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a third embodiment of the present invention. It is. t--PWM circuit 2-----Constant voltage circuit 3----- CPU U 4.

Claims (6)

[Claims] (1) In a power supply device having a converter transformer with a plurality of output windings, a first
A constant voltage circuit is provided for rectifying and smoothing the output of the output windings and then making it a constant voltage. In the standby mode, the output of the plurality of output windings is lowered, and the output voltage is lowered from the first output winding. A power supply device characterized in that the output of the second high output winding is rectified and smoothed and then connected to the input of the constant voltage circuit by a switch circuit. (2) The converter transformer constitutes a voltage resonance type flyback regulator, and the first and second output windings are flyback outputs, and
Claim 1 characterized in that it has one or more high voltage outputs.
Power supply listed. (3) The power supply according to claim 1, wherein the switch circuit is driven by a CPU and configured to perform the connection control of the output of the second output winding at a timing when the standby mode is entered. Device. (4) The switch circuit includes a transistor and a Zener diode, and when the input of the constant voltage circuit becomes lower than the voltage set by the Zener diode, the transistor causes the output of the second output winding to change. The power supply device according to claim 1, characterized in that the power supply device is configured to perform connection control. (5) The switch circuit includes a transistor and a diode, and when the output of the constant voltage circuit becomes smaller than the voltage set by the diode, the transistor controls the output of the second output winding. The power supply device according to claim 1, characterized in that the power supply device is configured to perform. (6) The switching regulator is of a primary control type, and is PWM controlled using an output voltage signal generated on the secondary side by a photocoupler, and the photocoupler power source is obtained from the input of the constant voltage circuit. The power supply device according to claim 1, characterized in that it is configured as follows.