JPH02261052A - Electric power source device - Google Patents

Abstract

PURPOSE:To permit the setting of constant voltage mode and constant current mode freely and facilitate the control of the switching of the modes by a method wherein an output voltage detecting circuit and an output current detecting circuit are compared with predetermined reference values respectively and a DC-DC converter is controlled in accordance with the results of the comparisons. CONSTITUTION:A power source device is provided with an output voltage detecting circuit 6 and an output current detecting circuit 7 and the detecting output of the output voltage detecting circuit 6 is compared with a reference value for setting an overvoltage limiter and another reference value for setting a low-voltage limiter while the detecting output of the output current detecting circuit 7 is compared with the other reference value for setting a current. One of output variable DC-DC converter 1 is controlled in accordance with the results of respective comparisons while the other output fixed DC-DC converter 2 is controlled in accordance with a program incorporated previously. According to this method, switching control between constant voltage mode and constant current mode may be facilitated and proper constant voltage control as well as constant current control with respect to the load fluctuation of a wide range may be effected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention particularly relates to a high-voltage power supply device for a developing device, a charger, a static eliminator, a transfer device, etc. of an electrophotographic printer or a copying machine. .

(Conventional technology) Conventionally, it was common to use separate power supplies for constant voltage output type power supplies and constant current output type power supplies, and it was extremely difficult to switch and control both motes. In addition, in the case of a constant current output type power supply, the voltage may become overvoltage or too low due to wide variations in load impedance, causing leakage, and in electrophotographic copying machines, developing problems or charging may occur. This caused defects, transfer defects, static elimination defects, etc.

(Problems to be Solved by the Invention) In conventional power supplies, it is difficult to control switching between constant voltage mode and constant current mode as described above, and it is difficult to control the switching between constant voltage mode and constant current mode as described above. There was a problem in that control and constant current control could not be performed.

The present invention has been developed in view of these problems, and allows easy switching control between constant voltage mode and constant current mode, and provides appropriate constant voltage control and constant current control even over a wide range of load fluctuations. The aim is to obtain a power supply device that can perform

[Means to solve the problem]

The power supply device of the present invention is configured as follows.

(a) In a power supply device that obtains a variable positive and negative output by connecting two DC-D (converters) in series with different output polarities, the output voltage detection circuit is equipped with an output voltage detection circuit and an output current detection circuit. The detection output of the output current detection circuit is compared with the overvoltage limiter setting reference value and the low voltage limiter setting reference value, and the detection output of the output current detection circuit is compared with the current setting reference value.
The DC-DC converter is controlled according to the comparison results.

(b) In the power supply device of (a) above, one of the variable output DC-DC converters is controlled in accordance with the results of comparing the detected outputs of the output voltage detection circuit and the output current detection circuit with their respective reference values, and The other fixed output DC-DC converter is controlled according to the linked program.

(C) In the power supply device of (a) or (b) above, the detection input of the output current detection circuit is the terminal voltage of a current detection resistor connected between the ground and the secondary winding of the DC-DC converter. The detection input of the output voltage detection circuit was a voltage obtained by dividing the difference voltage between the output voltage and the terminal voltage of the current detection resistor.

(d) In any of the power supply devices (a) to (C) above,
A voltage limiting element was connected between the input side of the output current detection circuit and the ground or DC power supply.

[Effect]

In the power supply device of the present invention, the configuration (a) above allows easy switching between constant voltage mode and constant current mode, and limits for overvoltage and undervoltage are set, so appropriate control can be performed in each mode. be exposed.

Furthermore, by adopting the configurations (b), (c), and (d), errors in voltage detection can be corrected.

〔Example〕

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, 1 and 2 are two series-connected DC-DC converters with different output polarities, and one converter 1 is approximately O
~1.8KV variable output type, other converter 2
is of a type with a fixed output of approximately -700V, and variable positive and negative outputs of 500V to +1000V can be taken out from the output terminal P1. T I and T 2 are the drive transformers of each converter 1 and 2, and the -order winding N, ,
.

One end of NF2 is connected to a +VCc DC power supply, and the other end is connected to switching transistors Tr+ and Tr2, respectively.
Rectifier diodes D, D2 are installed in the secondary windings N□ and N82.
and smoothing capacitors C, C2 are connected). 3
．． 4 is a PWM circuit and an oscillation circuit for controlling the on/off state of the transistors T, T, 2, 5 is a load connected to the output terminal p, and 6 is an output voltage detection circuit. Operational amplifier 7 is an operational amplifier provided as an output current detection circuit, and the detection input of operational amplifier 7 for current detection is ground and DC-D.
This is the terminal voltage of a current detection resistor R2 connected between the secondary winding Ns2 of the C converter 2, and the detection input of the voltage detection operational amplifier 6 is the output voltage V to the load 5.

The difference voltage between the terminal voltage of the current detection resistor R1 and the resistor R
The voltage is divided by 2 and R3. 8 is an operational amplifier for inverting the output of the operational amplifier 7; 9. 0 is the input side child P2. The reference voltage for overvoltage limiter setting V1.P3. The reference voltage V2 for setting the low voltage limiter is an operational amplifier that is manually operated, and the comparators 11 and 12 are connected to each other.
Together, they constitute an overvoltage limiter circuit and a low voltage limiter circuit, and the detection output of the operational amplifier 6 is determined by comparators 11 and 12, respectively, to a reference value for overvoltage limiter setting (
voltage) and the reference value (voltage) for setting the low voltage limiter.

Reference numeral 13 denotes an operational amplifier provided as an error amplifier, which compares the detection output of the operational amplifier 7 with a constant current setting reference voltage V3 from the input terminal P4. 14 is comparator 11
The operational amplifier that amplifies the output of You may do so.

Next, the operation will be explained.

The output voltage vo and output current 1 given to the load 5 are:
It is detected by each detection circuit and compared with a reference value, and the DC-DC converter 1.2 is controlled according to the comparison result. At this time, an output current I flows through the load 5. is DC-
It is detected by the current detection resistor R1 inserted between the DC converter 2 and the ground, and the detected voltage Vfl is FE
It is detected with high impedance by the voltage follower of the operational amplifier 7. This detection voltage Vr
After l is compared with the reference voltage V3 by the operational amplifier 13,
The pulse width is controlled by the PWM circuit 3 to change the output of the DC-DC inverter 1.

On the other hand, the output voltage V applied to the load 5. is the resistance R2,
It is divided into a division ratio m by R3. Here, in order to avoid errors in the output current, resistors R2 and R3 are connected to the output terminal P.
1 and the ground, but between the output terminal P1 and the current detection point (A), the voltage VA at the connection point of resistors R2 and R3 is Vx = Vr++ (Vo Vr+)7
m. If m〉〉1, the above voltage vA is ■A=V
f1+v. It will be 7m. And this voltage vA is FET
It is detected with high human power impedance by the voltage follower of the human power operational amplifier 6.

Further, a part of the output voltage of the operational amplifier 7 for current detection is inverted by the operational amplifier 8, and -Vfl is obtained at the output of the operational amplifier 8. This output Vfl is the operational amplifier 9.
However, the reference voltage v1 for overvoltage limiter setting is manually applied to the operational amplifier 9 via the terminal P2, and the output of the operational amplifier 9 is Vr+-V2. Further, a reference voltage v2 for setting a low voltage limiter is manually applied to the operational amplifier 10 via a terminal P3, and the operational amplifier 10
Vr+V3 is obtained at the output. The outputs of these operational amplifiers 9 and 10 are respectively input to oven collector output type comparators 11 and 12, and the comparators 11 receive the output V of the operational amplifier 6. / m +
Compare V (1) with the outputs -V, +vr, of the operational amplifier 9. At this time, if V. Set the output of PWM circuit 3 to zero,
Cut off the output of the DC-DC converter 1. Also, Vo
When V is smaller than -V, the output of the comparator 11 is open and becomes 10 Vcc, making the output of the operational amplifier 14 the lowest level. Therefore, the PWM circuit 3
It becomes a constant current mode controlled by the output of the operational amplifier 13.

Also, the comparator 12 is the output ■ of the operational amplifier 6. /m
+Vf, and the output of the operational amplifier 10, -V2+V, are compared. At this time, if VO/m becomes smaller than -v2, the output of the comparator 12 becomes zero potential, the output of the operational amplifier 13 is set to the minimum, the pulse width of the output of the PWM circuit 3 is maximized, and the output of the DC-DC converter 1 is increase. Conversely, when vo/m is greater than -v2, the output of the comparator 12 is open, so it does not affect the operation of the operational amplifier 13.

FIG. 2 is a diagram showing the current/voltage characteristics of the output due to the above-mentioned control, and shows the case of four types of control modes: constant current modes A and B and constant voltage modes C and D. These modes are, for example, As shown in Table 1, each reference value V + , V 2 ,
V3 is set.

In constant voltage modes C and D, the reference voltage V for setting the overvoltage limiter is set to the constant voltage setting value, the reference voltage V2 for setting the low voltage limiter is set to be slightly lower than the constant voltage setting value, and the comparator 11 Make sure that only the In this mode, the load 5 connected to the output terminal P,
When the impedance of the operational amplifier 6 becomes smaller than a predetermined value, the detection voltage Vfl increases and the input V 6 /
The value of In + V (H) exceeds the human power tolerance range of the operational amplifier 6, causing an error in constant voltage detection. The value of human power vr+ is limited so that the input does not exceed the permissible range.Therefore, false detection will not occur.

In this way, constant voltage mode and constant current mode can be freely set in the positive and negative regions, and switching control between the two is easy, and appropriate constant voltage and constant current control can be performed even over a wide range of load fluctuations. be able to. Further, even if the load impedance is too small in the constant voltage mode and the voltage detection output exceeds the allowable range of the operational amplifier's manual power, there will be no erroneous detection as described above. Also, when the output is positive, the DC of the negative fixed output
- Since the DC converter 2 is cut off, the dynamic range of the positive variable output DC-DC converter 1 can be reduced.

FIG. 3 is a block diagram showing a second embodiment of the present invention. In this embodiment, one output variable DC-DC is selected according to the results of comparing the detection outputs of the output voltage detection circuit (op-amp 6) and output current detection circuit (op-amp 7) with respective setting reference voltages V, ~V3. The converter 1 is controlled, and the other DC-DC:r converter 2 with a fixed output is controlled according to a program pre-installed in a microcomputer. In the figure, 15 is a microcomputer for sequence control of a copying machine, etc., which has a built-in CPU, and a program written in -F is incorporated therein. 16 is a D/A converter that converts the digital output signal of the microcomputer 15 into an analog signal.

The microcomputer 15 inputs signals from various sensors and key switches (not shown) and performs sequence control of motors, solenoids, lamps, power supplies, etc. according to built-in programs. At this time, for example, a high level control voltage V4 is output to the terminal P5 except when resetting the microcomputer 15 and when outputting a negative voltage (mode D), and
Cut off the output of the C-DC converter 2. Note that this control voltage V4 may be output directly from the I10 port of the microcomputer 15 without going through the D/A converter 16.

Further, FIG. 4 is a circuit configuration diagram showing a third embodiment of the present invention. In the second embodiment, the control voltage V4 is output from the microcomputer 15 or the D/A converter 16, but in this embodiment, the control voltage V4 is output from the comparator 17 to the terminal P5, which compares the reference voltage V1 with a predetermined value. There is. In the second embodiment and the stud, the control voltage v4 drives the DC-DC converter 2 through the transistor T.
It is controlled via r3. That is, the output voltage V. When the value of the reference voltage v1 is set so that T becomes negative, the output of the comparator 17 becomes a low level, and the transistor T
13 is turned off. Thereby, the DC-DC converter 2 is operated by the oscillation circuit 4. Also, the output voltage vo
When the value of the reference voltage V1 is set so that V1 becomes positive, the output of the comparator 17 becomes high level, and the transistor Tr3 is turned on. As a result, the DC-DC converter 2 is cut off.

Here, the above-mentioned second. In the third embodiment, each setting reference voltage V, -V3 is set using the microcomputer 15.
Just set the value of according to the sequence timing,
Constant voltage mode and constant current mode can be freely selected and set.

FIG. 5 shows a general flow of control operations using the microcomputer 15.

When power-on control starts, each control mode of constant voltage and constant current is determined in step S1, and if it is constant voltage mode, the reference voltage for setting is output in step S2, and the above-mentioned control mode is output in step S3. Control voltage v4 is output. In addition, in the constant voltage mode, each setting reference voltage v2. V3 is output. These reference voltages are then compared with each detected voltage, and the DC-DC converters 1 and 2 are driven according to the comparison results.

〔Effect of the invention〕

As described above, according to the present invention, constant voltage mode and constant current mode can be freely set in the positive and negative regions, switching control is easy, and appropriate constant voltage control and constant current mode can be performed even in a wide range of load fluctuations. This has the effect of being able to perform constant current control. In addition, by connecting the voltage control element to the detection circuit, it is possible to eliminate false detection due to load impedance fluctuations during constant 'I' voltage mode, and the constant voltage mode and constant voltage mode can be easily selected by microcomputer control. The effect of being able to do this is obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between current and voltage in each output mode, and FIG. 3 is a configuration diagram showing a second embodiment of the present invention. FIG. 4 is a circuit configuration diagram showing a third embodiment of the present invention, and FIG. 5 is a flowchart showing a general flow of control operations by a microcomputer. 1... DC-DC converter with variable output 2...
...Fixed output DC-DC converter 5...
・Load 6...Operational amplifier (output voltage detection circuit) 7...
...Operational amplifier (output current detection circuit) 11.12.
・ ・ ・ ・ ・ ・ Comparator 13.14 ・ ・ ・ ・ ・ ・ ・ ・ Opier amplifier〉〉〉〉〉〉〉 ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０ ０

Claims (4)

[Claims] (1) In a power supply device that obtains a positive and negative variable output by connecting two DC-DC converters with different output polarities in series,
Equipped with an output voltage detection circuit and an output current detection circuit, the detection output of the output voltage detection circuit is compared with a reference value for overvoltage limiter setting and a reference value for undervoltage limiter setting, respectively, and the detection output of the output current detection circuit is used for current setting. A power supply device that compares the DC-DC converter with a reference value and controls the DC-DC converter according to the comparison results. (2) One variable output DC-DC converter is controlled according to the results of comparing the detected outputs of the output voltage detection circuit and the output current detection circuit with their respective reference values, and the other output fixed DC-DC converter is controlled according to a pre-installed program. - The power supply device according to claim 1, wherein the power supply device controls a DC converter. (3) The detection input of the output current detection circuit is ground and DC.
- The terminal voltage of the current detection resistor connected between the secondary winding of the DC converter, and the detection input of the output voltage detection circuit is the voltage difference between the output voltage and the terminal voltage of the current detection resistor. Claim 1 or 2 characterized in that the voltage is a voltage.
Power supply listed. (4) The power supply device according to any one of claims 1 to 3, characterized in that a voltage limiting element is connected between the input side of the output current detection circuit and ground or a DC power supply.