JPH11275864A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit the output of which can be changed over across the polarities. SOLUTION: Switching elements Q1 and Q2 are push-pull connected to the primary side of a transformer T1 and a detecting output is inputted to a microcomputer IC1 from a secondary side of the transformer T1 through a rectifier circuit SW, an operational amplifier IC3, or an revrge-polatity voltage element diode D1. The microcomputer IC1 drives a timer IC2 to turn on a photocoupler PC1 or PC2 and either one of the switching elements Q1 and Q2, in accordance with the detecting output and a target value and the polarity (positive or negative) of the target value. The polarity of the output voltage of a power unit is set in accordance with the polarity of the target value, and the microcomputer IC1 sets the pulse width which resets the other switching element Q2 or Q1 by setting the operating pulse width of the turned-on switching element Q1 or Q2 from the detecting output and target value by performing proportionating- and-integrating operations. When the pulse width is set, a desired output voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply device,
More specifically, the present invention relates to a power supply device used in an electrophotographic device or the like capable of changing the output in both positive and negative polarities.

[0002]

2. Description of the Related Art Conventionally, a power supply having a positive polarity and a power supply having a negative polarity have been known as a power supply device capable of changing the output in both positive and negative polarities.
A device in which a load and a power supply output are switched by a relay, and a power supply having a positive polarity and a power supply having a negative polarity are connected in series (for example, Japanese Patent Publication No. 6-36668, Japanese Patent Publication No. 6-36668). JP-B-36669, JP-B-6-509
No. 35 gazette).

[0003]

However, since these devices use a plurality of power supply circuits, the number of components is increased, and there is a problem in miniaturization and cost reduction. Further, when the positive power supply and the negative power supply are connected in series, current flows to the power supply whose output is stopped, which causes a loss.

The present invention has been made in view of such circumstances, and a power supply circuit capable of changing from a positive polarity to a negative polarity is constituted by one circuit including one transformer, and is small in size, low in cost, and has low power efficiency. It is intended to provide a power supply device with good performance.

[0005]

According to a first aspect of the present invention, there is provided an electrode device capable of changing the output over both positive and negative poles, comprising a transformer having at least a primary winding and a secondary winding, and a pusher connected to the primary winding. A pull-connected switching element;
A rectifier circuit having a forward-direction switch element and a reverse-direction switch element connected to the secondary winding and connected in parallel; a smoothing circuit for smoothing an output of the rectifier circuit; and an output voltage of the power supply device. Or, an output detection circuit that detects an output current, a polarity conversion circuit that converts a detection voltage of the output detection circuit to positive polarity, a blocking circuit that blocks reverse polarity of the detection voltage, and a polarity conversion circuit or a blocking circuit. A control circuit for inputting an output voltage, a target value input circuit for inputting a target value of an output voltage or an output current of the power supply device, and a selection means for selecting a switch element for turning on the rectifier circuit according to the polarity of the target value. A microcomputer circuit that outputs an output according to the output voltage and the target value, and a switch connected to the primary winding on the side that supplies current to the switch element that is turned on by the output from the circuit. A switching element control circuit that controls a pulse width of the switching element and turns on a switching element on the other side of the switching element by a minimum constant pulse width required for resetting the transformer. An object of the present invention is to provide a small and low-cost power supply device with high power efficiency.

According to a second aspect of the present invention, there is provided a power supply device capable of changing an output across both positive and negative poles, comprising a transformer having at least a primary winding and a secondary winding, a switching element connected to the primary winding, A rectifier circuit having a forward-direction switch element and a reverse-direction switch element connected to the secondary winding and connected in parallel; a smoothing circuit for smoothing an output of the rectifier circuit; and an output voltage of the power supply device. An output detection circuit for detecting an output current, a polarity conversion circuit for converting a detection voltage of the output detection circuit to a positive polarity, a blocking circuit for blocking reverse polarity of the detection voltage, and an output of the polarity conversion circuit or the blocking circuit. A control circuit for inputting a voltage, a target value input circuit for inputting a target value of the output voltage or output current of the power supply device, and a means for turning on / off a switch element of the rectifier circuit according to the polarity of the target value. A microcomputer circuit that outputs an output corresponding to the output voltage and the target value, and the target value and the detection voltage determine the pulse width of a switching element connected to the primary winding by an output from the circuit. The present invention is characterized by having a switching element control circuit that performs control so as to be in agreement with each other, thereby providing a small-sized and low-cost power supply device with a simple configuration and high power efficiency.

According to a third aspect of the present invention, in the first or second aspect, the microcomputer circuit inputs an A / D conversion circuit for inputting a detection voltage at the time of positive output and a detection voltage at the time of negative output. It is characterized by having an A / D conversion circuit, thereby facilitating output control near OV and improving output accuracy.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the microcomputer circuit receives an A / D conversion circuit for inputting a detection voltage for a positive polarity and a detection voltage for a negative output. The present invention is characterized by having the same A / D conversion circuit, thereby further reducing the cost, size, and reliability of a power supply device that does not require output control near the OV.

According to a fifth aspect of the present invention, in the first or second aspect of the present invention, a diode and a switch element having the opposite polarity to the diode are connected in parallel.
This is to simplify the rectifier circuit.

According to a sixth aspect of the present invention, in the first or second aspect, a circuit in which a diode and a resistor are connected in series and a switch element having the opposite polarity to the diode are connected in parallel. It is intended to reduce the loss in the forward direction of the diode at the time of output of the polarity opposite to that of the diode, and to improve the efficiency.

According to a seventh aspect of the present invention, in the first or second aspect, a circuit in which a diode and a constant voltage element are connected in series and a switch element having the opposite polarity to the diode are connected in parallel, Accordingly, the loss in the forward direction of the diode at the time of the output of the polarity opposite to that of the diode is reduced, and the withstand voltage of the switch element is reduced, thereby improving the efficiency.

According to an eighth aspect of the present invention, in the first or second aspect, a circuit in which a switch circuit and a resistor are connected in series and a diode having a polarity opposite to that of the switch circuit are connected in parallel. In addition, the current flowing through the switch element is reduced to achieve low cost and high efficiency.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a high-voltage power supply for a transfer roller of an electrophotographic apparatus according to one embodiment of the present invention will be described.

The transfer roller of the electrophotographic apparatus is for transferring a toner image to paper, so that a high voltage of a positive polarity is applied at the time of transfer to paper, and unnecessary toner is not attached to the roller when transfer to paper is completed. A negative high voltage is applied. The applied voltage needs to be changed according to the temperature, humidity, and other conditions for both positive and negative voltages.

FIG. 1 is a circuit diagram of a power supply device for explaining an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a proportional integral (PI) calculation or the like from a target value of output voltage and a detected value of output voltage. The microcomputers IC1 and IC2 perform timer switching for switching the transistor with a predetermined pulse width according to the calculation result of the microcomputer IC1, and the operational amplifiers IC3 and P perform a polarity change.
C1 and PC2 are photocouplers, Q1 and Q2 are switching transistors, T1 is a transformer,
SW is a rectifier circuit. Microcomputer IC1, timer IC
2, a drive voltage Vc is applied, and a bias voltage Vd is applied to the operational amplifier IC3.

The power supply device shown in this circuit calculates a proportional integral (PI) in the microcomputer IC1 from a target value of the output voltage or the output current and a detected value thereof, sets a timer IC2 based on the result, and sets a predetermined pulse. It is a digitally controlled power supply device that switches transistors by width.
The details of this type of power supply are shown in
No. -10178.

In FIG. 1, a 24V power supply Va is connected to an intermediate terminal of a primary winding of a transformer T1, and collectors (drains) of transistors Q1 and Q2 are connected to both terminals, respectively. The base (gate) is connected to the timer output of the timer IC2. An appropriate base current (gate current) is obtained by the resistors R1, R2, R3, and R4. The operation of the timer IC2 is controlled by an instruction from the microcomputer IC1 as described later with reference to FIG.
1, a pulse width for driving Q2.

On the secondary side of the transformer T1, a photocoupler PC1 in the direction of the positive output and a photocoupler PC2 in the direction of the negative output are connected in parallel, and the output is intended to be output by a signal from the output port of the microcomputer IC1. The transistor corresponding to the polarity is turned on. The turned on transistor functions as a conventional diode, and the transformer T1
, A voltage is generated on the secondary side, rectified by the rectifier circuit SW, smoothed by the capacitor C1, and a DC output is obtained.

Now, let us look at when the photocoupler PC2 is ON. The output is negative, and the output current detection resistor R6
Is input to an A / D conversion circuit (not shown) of the microcomputer IC1 via the reverse voltage blocking diode D1. At this time, the primary winding transistor Q1
Is used for pulse width control, and the other transistor Q2 is turned on by a pulse of a very narrow width necessary for resetting the transformer.
Let it.

The pulse width of the transistor Q1 can be changed by the load connected to the output or the fluctuation of the input voltage, and also by the set value of the output. The pulse width for resetting is fixed to the minimum necessary, or the transistor Q1
Can be adjusted according to the pulse width.

Next, the case where the photocoupler PC1 is ON will be described. The output is positive, and the output current detection resistor R6
, A negative voltage is obtained. The voltage is made positive by an operational amplifier IC3 and then input to an A / D conversion circuit (not shown) of the microcomputer IC1. The resistors R7 and R8 are for determining the ratio (magnification) at the time of conversion, and here, R7 = R8. Resistor R9 is for protection, resistor R10, capacitor C
2. Similarly, R11 and C3 are simple filter circuits.

In this mode, the transistor Q2 is used for pulse width control, and the other transistor Q1 is used for resetting the transformer. The method of use is the same as described above.

Here, the switching element can replace the photocoupler with a transistor. Further, which of the switching elements and which of the switching elements are combined is determined by the winding structure of the transformer, and a combination in which a current flows in the secondary winding when a current flows in the primary winding.

The power supply device described above is a push-pull type switching power supply, and can easily control the output when each switching element is ON.

FIG. 2 is a circuit diagram of a power supply unit for explaining another embodiment of the present invention. In the figure, the same components as those of FIG. .

In this embodiment, in order to simplify the circuit configuration, one switching element is used, one A / D conversion circuit is used, and one switch element of the rectification circuit SW is a diode D1. The transformer has the simplest configuration without an intermediate terminal, and the primary winding is a transistor Q1.
, And an output is obtained on the secondary winding. The basic operation of the power supply device is the same as that of FIG.

In FIG. 2, first, the case where the photocoupler PC2 of the rectifier circuit is off will be described. A positive high voltage V1 rectified by the diode D2 and smoothed by the capacitor C1 is obtained. This voltage controls the pulse width of the transistor Q1 so that this voltage becomes a predetermined value from the output current detection result and the target value as in the former case.

Next, the case where the photocoupler PC2 is ON will be described. The output V1 is output. If the negative voltage obtained from the current flowing through the secondary winding when the transistor Q1 is OFF is -V2, then Vo =
V1 + V2. Therefore, if the flyback method is used so that a high voltage can be obtained when the transistor Q1 is ON, and if −V2 = 2 KV and V1 = 1 KV, the output voltage Vo = −1 KV is obtained as a result. Here, in the case of the single-pole forward method, the direction of the switch element is selected so that a high voltage can be obtained at the time of forward.

In FIG. 1, the positive and negative polarity components of the output detection result are input to separate A / D conversion circuits, but here, wire connection is performed, and the target value of which polarity is being output now is determined. And a proportional integral (PI) calculation is performed.

Here, the rectifier circuit may be constituted by a photocoupler or a transistor in both directions as in FIG. Further, similarly to FIG. 1, the signals can be input to separate A / D conversion circuits.

FIGS. 5 to 8 are configuration diagrams of a rectifier circuit applied to the power supply device of the present invention, in which one of the switch elements connected in parallel has a diode.

In FIG. 3, a resistor R is connected in series with the diode D2.
12 is connected to reduce the loss due to the voltage component generated on the diode side when the transistor Q3 is ON. In FIG. 4, a constant voltage element ZD1 is connected in series with the diode D2 to reduce the loss due to the voltage component generated on the diode side when the transistor Q3 is ON, and to limit the voltage applied to the transistor when the transistor Q3 is OFF. . FIG.
Now, connect the resistor R12 in series with the transistor Q3,
The current flowing through the transistor Q3 is limited.

Next, a method of deciding which of the switch elements connected in parallel of the rectifier circuit to turn on and a method of controlling the switching elements in the control method of the circuit configuration of FIG. 1 will be described.

FIG. 6 is a flowchart for determining whether to output a positive voltage or a negative voltage from the target value of the output voltage, and to determine which one of the switch elements of the rectifier circuit is to be turned ON in accordance with the determination. When you start setting the value (S
1) If the target value is positive (YES in S2), the photocoupler PC1 in FIG. 1 is turned on (S3); if negative (NO in S2), PC2 is used.
Is turned on (S4) to control the switch element (S5).

FIG. 7 is a flowchart of the control method shown in FIG. 1 in which a proportional integral (PI) is calculated from a target value and a detected value, and a timer is controlled based on the result.

From the target value, the proportional integral calculation is started from the detected value (S11), and as a result PW is obtained (S12). Depending on whether the target value is positive or negative (S13), if the target value is positive (YES in S13), the PW is set in the timer T1 (S1).
4) The data C corresponding to the pulse width required for resetting the transformer is set in the other timer T2 (S1).
4 '), if the target value is negative (NO in S13), the PW is set in the timer T2 (S15), and the timer T1 is set.
Is set to data C (S15 '), and the switching element is driven (S16).

Although the example in which the output current is detected and controlled has been described above, it is also possible to detect and control the output voltage. Further, although the description has been given of the example of the high voltage power supply for the transfer roller of the electrophotographic apparatus, the present invention can be applied to all applications of the DC power supply in which the output voltage needs to be changed from positive to negative.

[0038]

According to the first aspect of the present invention, there is provided an electrode device capable of changing the output over both positive and negative poles, comprising a transformer having at least a primary winding and a secondary winding, and a push-pull connection to the primary winding. Switching element, a rectifier circuit connected to the secondary winding, and provided with a forward switch element and a reverse switch element connected in parallel, a smoothing circuit for smoothing the output of the rectifier circuit, An output detection circuit that detects an output voltage or an output current of the power supply device, a polarity conversion circuit that converts a detection voltage of the output detection circuit into a positive polarity, a blocking circuit that prevents reverse polarity of the detection voltage, and the polarity. A control circuit that inputs the output voltage of the conversion circuit or the blocking circuit, a target value input circuit that inputs a target value of the output voltage or output current of the power supply device, and the rectifier circuit turns on according to the polarity of the target value. A microcomputer circuit having selection means for selecting a switch element and outputting an output corresponding to the output voltage and the target value; and the primary winding on a side for supplying a current to the switch element to be turned on by an output from the circuit. A switching element control circuit that controls the pulse width of the switching element connected to the switching element and turns on the switching element on the other side of the switching element by a minimum constant pulse width required for resetting the transformer. It is possible to control elements and switch elements of rectifier circuits and switch elements of rectifier circuits and their combinations arbitrarily, and it is possible to obtain both positive and negative output voltages by simply providing switch elements of different polarities in parallel with the rectifier circuit. In addition to the above, the power supply device can be reduced in size, cost, reliability and function.

According to the second aspect of the present invention, there is provided a power supply device capable of changing the output over both positive and negative poles, comprising a transformer having at least a primary winding and a secondary winding, and a switching element connected to the primary winding. A rectifier circuit connected to the secondary winding and having a forward switch element and a reverse switch element connected in parallel, a smoothing circuit for smoothing an output of the rectifier circuit, An output detection circuit for detecting an output voltage or an output current, a polarity conversion circuit for converting a detection voltage of the output detection circuit to positive polarity, a blocking circuit for blocking reverse polarity of the detection voltage, and the polarity conversion circuit or the blocking circuit A control circuit for inputting an output voltage of the power supply, a target value input circuit for inputting a target value of the output voltage or output current of the power supply device, and a switching element of the rectifier circuit according to the polarity of the target value. A microcomputer circuit for outputting an output according to the output voltage and the target value, and detecting the pulse width of a switching element connected to the primary winding based on the output from the circuit as the target value and the detection value. Since it has a switching element control circuit that controls the voltage to match, it is possible to control the switching element and the switching element of the rectifier circuit arbitrarily. Output voltage, the power supply voltage can be reduced,
Cost reduction, high reliability, and high functionality can be achieved.

According to the invention of claim 3, according to claim 1 or 2,
In addition to the effect of the invention, the microcomputer circuit has an A / D conversion circuit that inputs a detection voltage at the time of positive output and an A / D conversion circuit that inputs a detection voltage at the time of negative output.
Output control near the OV can be facilitated and output control can be improved.

According to the invention of claim 4, claim 1 or 2
In addition to the effect of the invention, the microcomputer circuit has an A / D conversion circuit for inputting a detection voltage at the time of positive polarity and the same A / D conversion circuit for inputting a detection voltage at the time of negative output. In addition, it is possible to further reduce the cost, reduce the size, and increase the reliability of the power supply device that does not need to control the output near the OV.

According to the invention of claim 5, claim 1 or 2
In addition to the effects of the invention, the rectifier circuit can be simplified because the diode and the switch element having the opposite polarity to the diode are connected in parallel.

According to the invention of claim 6, claim 1 or 2
In addition to the effect of the invention, the circuit in which the diode and the resistor are connected in series and the switch element having the opposite polarity to the diode are connected in parallel, so that the loss in the forward direction of the diode at the time of the output of the polarity opposite to the diode is reduced. It is possible to achieve a reduction in efficiency and an increase in efficiency.

According to the invention of claim 7, claim 1 or 2
In addition to the effect of the invention of the present invention, since a circuit in which a diode and a constant voltage element are connected in series and a switch element having the opposite polarity to the diode are connected in parallel, the diode in the forward direction at the time of output of the opposite polarity to the diode is connected. The loss can be reduced and the withstand voltage of the switch element can be reduced, so that higher efficiency can be achieved.

According to the invention of claim 8, claim 1 or 2
In addition to the effects of the invention, a circuit in which a switch circuit and a resistor are connected in series and a diode having a polarity opposite to that of the switch circuit are connected in parallel, so that the current flowing through the switch element is reduced, thereby reducing costs and increasing efficiency. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply device according to one embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a power supply device according to another embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a rectifier circuit applied to the power supply device of the present invention.

FIG. 4 is a circuit configuration diagram of a rectifier circuit applied to the power supply device of the present invention.

FIG. 5 is a circuit configuration diagram of a rectifier circuit applied to the power supply device of the present invention.

FIG. 6 is a flowchart for determining which of the switch elements of the rectifier circuit applied to the power supply device of the present invention is turned on.

FIG. 7 is a flowchart showing a method for controlling a timer used in the power supply device of the present invention.

[Explanation of symbols]

1: microcomputer IC1, 2: timer IC2, 3: operational amplifier IC3, D1: reverse polarity blocking diode, PC1, P
C2: Photocoupler, Q1, Q2: Switching transistor, SW: Rectifier circuit power supply, T1: Transformer.

Claims (8)

[Claims] 1. An electrode device capable of changing output over both positive and negative poles, comprising: a transformer having at least a primary winding and a secondary winding; a switching element push-pull-connected to the primary winding; A rectifier circuit having a forward switch element and a reverse switch element connected to a winding and connected in parallel, a smoothing circuit for smoothing an output of the rectifier circuit, and an output voltage or output current of the power supply device An output detection circuit, a polarity conversion circuit for converting the detection voltage of the output detection circuit to positive polarity, a blocking circuit for blocking the reverse polarity of the detection voltage, and an output voltage of the polarity conversion circuit or blocking circuit. A control circuit to input, a target value input circuit to input a target value of an output voltage or an output current of the power supply device, and a selection to select a switch element to turn on the rectifier circuit according to the polarity of the target value. A microcomputer circuit having means for outputting an output corresponding to the output voltage and the target value, and a switching element connected to the primary winding on a side for supplying a current to the switch element to be turned on by an output from the circuit. A switching element control circuit for controlling the pulse width of the switching element and turning on the switching element on the other side of the switching element by a minimum constant pulse width required for resetting the transformer. 2. A power supply device capable of varying output over both positive and negative poles, comprising: a transformer having at least a primary winding and a secondary winding; a switching element connected to the primary winding; and a secondary winding. A rectifier circuit having a forward-direction switch element and a reverse-direction switch element connected in parallel, a smoothing circuit for smoothing the output of the rectifier circuit, and detecting an output voltage or output current of the power supply device. Output detection circuit, a polarity conversion circuit for converting the detection voltage of the output detection circuit to a positive polarity, a blocking circuit for blocking the reverse polarity of the detection voltage, and a control for inputting the output voltage of the polarity conversion circuit or the blocking circuit. A target value input circuit for inputting a target value of a circuit and an output voltage or an output current of the power supply device, and means for turning on and off a switch element of the rectifier circuit according to the polarity of the target value; A microcomputer circuit for outputting an output corresponding to the voltage and the target value, and controlling a pulse width of a switching element connected to the primary winding based on an output from the circuit so that the target value matches the detection voltage. A power supply device comprising a switching element control circuit. 3. The microcomputer circuit according to claim 1, further comprising an A / D conversion circuit for inputting a detection voltage at the time of positive output and an A / D conversion circuit for inputting a detection voltage at the time of negative output. 3. The power supply device according to 1 or 2. 4. The microcomputer circuit has an A / D conversion circuit for inputting a detection voltage at the time of positive polarity and an A / D conversion circuit for receiving a detection voltage at the time of negative output. The power supply device according to claim 1. 5. The power supply device according to claim 1, wherein the rectifier circuit includes a diode and a switch element having a polarity opposite to the diode connected in parallel. 6. The power supply device according to claim 1, wherein the rectifier circuit includes a circuit in which a diode and a resistor are connected in series and a switch element having the opposite polarity to the diode is connected in parallel. 7. The power supply according to claim 1, wherein the rectifier circuit includes a circuit in which a diode and a constant voltage element are connected in series and a switch element having a polarity opposite to that of the diode is connected in parallel. apparatus. 8. The rectifier circuit according to claim 1, wherein a circuit in which a switch circuit and a resistor are connected in series and a diode having a polarity opposite to that of the switch circuit are connected in parallel.
Or the power supply device according to 2.