JP2015163016A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To add a new function by adding a circuit to a second power supply circuit without exerting influence on current detection of a current detection circuit included in the second power supply circuit in a power supply device including a first power supply circuit for applying a DC voltage to a load and the second power supply circuit for applying a DC voltage with reverse polarity to polarity of an output voltage from the first power supply circuit to the load.SOLUTION: A power supply device includes a first power supply circuit 111 for applying a DC voltage to a load 30 and a second power supply circuit 121 for applying a DC voltage with reverse polarity to polarity of an output voltage from the first power supply circuit 111 to the load 30, in which a current detection circuit 33 for detecting a current to be supplied from the first power supply circuit 111 to the load 30 is provided on the ground potential side of a rectifying and smoothing circuit in the second power supply circuit 121. In such a configuration, an additional circuit is connected between a secondary coil Ns of a transformer T2 of the second power supply circuit 121 and the rectifying and smoothing circuit of the second power supply circuit 121.

Description

  The present invention relates to a power supply apparatus including a circuit that applies a positive and negative DC voltage to a load and detects a load supply current.

  For example, in an electrophotographic image forming apparatus using a photosensitive drum, generally, a recording sheet is set at a contact portion between a photosensitive drum on which a toner image is formed and a transfer roll, and a predetermined transfer voltage is applied to the transfer roll. Is applied, and the recording paper is given a charge having a polarity opposite to that of the toner, whereby the toner is transferred to the surface of the recording paper. As the transfer voltage applied to the transfer roller for transferring the toner image formed on the surface of the photosensitive drum to the recording paper, a high voltage of about several hundred volts to several kV is usually set. When the transfer roller is cleaned, a cleaning voltage having a polarity opposite to the transfer voltage is applied to the transfer roller during a non-transfer operation.

  Thus, for example, Patent Document 1 discloses a power supply apparatus that switches and outputs positive and negative high voltages. FIG. 3 is a circuit diagram of the power supply device disclosed in Patent Document 1. In FIG. This power supply device includes a first power supply circuit 110 that outputs a positive voltage to the load 20 and a second power supply circuit 120 that outputs a negative voltage to the load 20. The first power supply circuit 110 includes a primary side drive control circuit 101, a transformer 56, a diode 62, a capacitor 64, and a resistor 66. The second power supply circuit 120 includes a primary side drive control circuit 102, a transformer 82, diodes 88 and 92, a capacitor 90, and a resistor 94. In the second power supply circuit 120, the diode 88 and the capacitor 90 constitute a rectifying and smoothing circuit. A current detection circuit 98 is connected to the ground potential side of the rectifying / smoothing circuit. The current detection circuit 98 detects a current flowing from the first power supply circuit 110 to the load 20.

JP 2004-45731 A

  In the conventional power supply device as shown in FIG. 3, the current supplied from the first power supply circuit 110 to the load 20 is detected by the current detection circuit 98 provided on the low potential side of the second power supply circuit 120. Because of the configuration, another circuit cannot be provided in the rectifying / smoothing circuit portion of the second power supply circuit 120. For example, when a load circuit or the like that supplies a negative voltage output from the second power supply circuit 120 and is different from the load 20 is provided, the other load circuit becomes a path of a current flowing through the load 20. Therefore, the current of the load 20 cannot be detected correctly, and the first power supply circuit 110 cannot perform predetermined constant current control. Therefore, any new function cannot be added to the second power supply circuit 120.

  An object of the present invention is to provide a power supply device including a first power supply circuit that applies a DC voltage to a load, and a second power supply circuit that applies a DC voltage having a polarity opposite to the output voltage of the first power supply circuit to the load. Therefore, it is desirable to provide a power supply apparatus in which a circuit is added to the second power supply circuit and a new function is added without affecting the current detection of the current detection circuit provided in the second power supply circuit.

A power supply device of the present invention includes a first power supply circuit that applies a DC voltage to a load, and a second power supply circuit that applies a DC voltage having a polarity opposite to the output voltage of the first power supply circuit to the load,
The first power supply circuit and the second power supply circuit include a transformer having a primary coil and a secondary coil, a drive control circuit that is connected to the primary coil and allows a drive current to flow through the primary coil, and an output of the secondary coil A rectifying / smoothing circuit that rectifies and smoothes the voltage and outputs it to the load,
A current detection circuit for detecting a current supplied from the first power supply circuit to the load on the ground potential side of the rectifying and smoothing circuit of the second power supply circuit;
An additional circuit to which the voltage of the secondary coil of the transformer of the second power supply circuit is applied is connected between the secondary coil of the transformer of the second power supply circuit and the rectifying / smoothing circuit of the second power supply circuit. It is characterized by that.

  With the above configuration, the additional circuit is separated from the current path flowing through the current detection circuit, and the additional circuit does not affect the current detection of the current detection circuit. Therefore, a new function can be added by providing an additional circuit.

  The additional circuit is preferably composed of a rectifying / smoothing circuit that rectifies and smoothes the output voltage of the secondary coil of the transformer of the second power supply circuit, and a load circuit connected to the output of the rectifying and smoothing circuit. With this configuration, it is possible to separately output a DC voltage having the same polarity as the DC voltage output by the second power supply circuit or a DC voltage having a reverse polarity.

  According to the present invention, since the additional circuit does not affect the current detection of the current detection circuit, by providing the additional circuit, a new function that operates with the output of the second power supply circuit can be provided.

FIG. 1 is a circuit diagram of a power supply device according to the first embodiment. FIG. 2 is a circuit diagram of a power supply device according to the second embodiment. FIG. 3 is a circuit diagram of the power supply device disclosed in Patent Document 1. In FIG.

<< First Embodiment >>
FIG. 1 is a circuit diagram of a power supply device according to the first embodiment. The power supply device 201 includes a first power supply circuit 111 and a second power supply circuit 121. The first power supply circuit 111 uses the voltage input to the Vin (+) and Vin (−) terminals as an input power supply, applies a positive voltage to the load 30, and the second power supply circuit 121 uses the Vin (+), Vin A voltage input to the Vin (−) terminal is used as an input power source, and a negative voltage is applied to the load 30. The load 30 is, for example, a transfer roller in an electrophotographic image forming apparatus using a photosensitive drum.

  The first power supply circuit 111 includes a transformer T1 having a primary coil Np and a secondary coil Ns, a switching element Q1, a switching control circuit 31, a diode D1, a capacitor C1, and a resistor R1. The switching control circuit 31 switches the switching element Q1 to flow a driving current through the primary coil Np of the transformer T1. The switching element Q1 and the switching control circuit 31 are examples of the “drive control circuit” according to the present invention. The diode D1 and the capacitor C1 are examples of the “rectifying and smoothing circuit” according to the present invention.

  When the switching control circuit 31 of the first power supply circuit 111 switches the switching element Q1, a positive high voltage of, for example, several kV is applied to the load 30.

  The second power supply circuit 121 includes a transformer T2 having a primary coil Np and a secondary coil Ns, a switching element Q2, a switching control circuit 32, a diode D2, a capacitor C2, a resistor R2, a current detection circuit 33, and a voltage detection circuit 34. I have. The switching control circuit 32 causes the drive current to flow through the primary coil Np of the transformer T2 by switching the switching element Q2. The switching element Q2 and the switching control circuit 32 are examples of the “drive control circuit” according to the present invention. The diode D2 and the capacitor C2 are examples of the “rectifying and smoothing circuit” according to the present invention. The transformer T2 includes an auxiliary coil Na, and the voltage detection circuit 34 rectifies and smoothes the electromotive voltage of the auxiliary coil Na and outputs a proportional value of the negative voltage applied to the load 30 to the switching control circuit 32. When the switching control circuit 32 of the second power supply circuit 121 switches the switching element Q2, a negative high voltage of, for example, several hundred volts is applied to the load 30.

  The switching control circuit 31 of the first power supply circuit 111 performs PWM control of the switching element Q1 according to the output voltage of the current detection circuit 33 when the signal of the remote terminal RM1 is valid. Therefore, in this state, a positive voltage is applied to the load 30 and constant current control is performed. When the signal at the remote terminal RM1 is invalid, the switching element Q1 is kept off. Therefore, in this state, the output voltage of the first power supply circuit 111 becomes zero.

  The switching control circuit 32 of the second power supply circuit 121 performs PWM control of the switching element Q2 according to the output voltage of the voltage detection circuit 34 when the signal of the remote terminal RM2 is valid. Therefore, in this state, a negative constant voltage is applied to the load 30. When the signal at the remote terminal RM2 is invalid, the switching element Q2 is kept off. Therefore, in this state, the output voltage of the second power supply circuit 121 becomes zero.

  When the first power supply circuit 111 is operating and the second power supply circuit 121 is stopped, the output of the first power supply circuit 111 → the load 30 → the ground line → the current detection circuit 33 → the resistor R2 → the first power supply A load current flows through the path of the rectifying / smoothing circuit of the circuit. The current detection circuit 33 detects this current and outputs the proportional voltage to the switching control circuit 31. The current detection circuit 33 is, for example, a resistor that generates a drop voltage when current is applied.

  In the second power supply circuit 121, an additional circuit 91 is provided between the secondary coil Ns of the transformer T2 and the rectifying / smoothing circuit (diode D2 and capacitor C2) of the second power supply circuit 121. The additional circuit 91 includes a rectifying / smoothing circuit including a diode D3 and a capacitor C3, and a load 21 to which an output voltage of the rectifying / smoothing circuit is applied. Further, a rectifying / smoothing circuit including a diode D4 and a capacitor C4 and a load 22 to which an output voltage of the rectifying / smoothing circuit is applied are provided. A DC negative voltage is obtained by a rectifying / smoothing circuit including the diode D3 and the capacitor C3, and this is applied to the load 21. Further, a DC positive voltage is obtained by a rectifying / smoothing circuit including a diode D4 and a capacitor C4, and this is applied to the load 22.

  The additional circuit 91 is separated from the current detection circuit 33 through the diode D2. Therefore, the current that flows when the positive voltage is applied from the first power supply circuit 111 to the load 30 does not flow to the loads 21 and 22. That is, in detecting the current flowing through the load 30, there is no substantial influence due to the provision of the additional circuit 91. Therefore, by providing the additional circuit between the rectifying / smoothing element of the current detection circuit and the output of the power supply circuit, a new function that operates with the output of the second power supply circuit can be provided.

  In this embodiment, two examples of the additional circuit connected to the output of the second power supply circuit, that is, the load, operate with a negative voltage and a positive voltage. However, the present invention is not limited to this. That is, only a load that operates at a negative voltage may be connected, or only a load that operates at a positive voltage may be connected. Two or more additional circuits may be connected.

<< Second Embodiment >>
FIG. 2 is a circuit diagram of a power supply device according to the second embodiment. The power supply device 202 includes a first power supply circuit 112 and a second power supply circuit 122. The first power supply circuit 112 applies a positive voltage to the load 30, and the second power supply circuit 122 applies a negative voltage to the load 30.

  The configuration of the first power supply circuit 112 is the same as that of the first power supply circuit 111 shown in FIG. The second power supply circuit 122 includes a transformer T2 having a primary coil Np and a secondary coil Ns, a switching element Q2, a switching control circuit 32, a diode D2, a capacitor C2, resistors R21 and R22, and a current detection circuit 33. . The switching control circuit 32 causes the drive current to flow through the primary coil Np of the transformer T2 by switching the switching element Q2. The switching element Q2 and the switching control circuit 32 are examples of the “drive control circuit” according to the present invention. The diode D2 and the capacitor C2 are examples of the “rectifying and smoothing circuit” according to the present invention. The resistors R21 and R22 output a proportional value of the negative voltage applied to the load 30 to the switching control circuit 32. The operation of the switching control circuit 32 is the same as that shown in FIG.

  In the second power supply circuit 122, an additional circuit 92 is provided between the secondary coil Ns of the transformer T2 and the rectifying / smoothing circuit (diode D2 and capacitor C2) of the second power supply circuit 122. The additional circuit 92 inputs an electromotive voltage of the secondary coil Ns of the transformer T2 and performs a predetermined circuit operation.

  The additional circuit 92 is separated from the current detection circuit 33 through the diode D2. Therefore, a current that flows when a positive voltage is applied from the first power supply circuit 111 to the load 30 does not flow to the additional circuit 92. That is, the detection of the current flowing through the load 30 is not affected by the provision of the additional circuit 92.

  In the above-described two embodiments, an example in which the rectifying / smoothing circuit is configured by a simple circuit using a single diode and a single capacitor has been shown. It may be a circuit or the like and can be similarly applied.

  Further, in the above-described two embodiments, an example in which one end of the secondary coil of the transformer is grounded is shown, but a transformer having a center tap may be used.

  In the above-described two embodiments, the current detected by the output current of the power supply circuit (first power supply circuit) that outputs a positive voltage is provided in the power supply circuit (second power supply circuit) that outputs a negative voltage. Although an example of detection by a circuit has been shown, this may be reversed. That is, the present invention can be similarly applied to a configuration in which an output current of a power supply circuit that outputs a negative voltage is detected by a current detection circuit provided in the power supply circuit that outputs a positive voltage.

  In the above-described two embodiments, an example in which one of the two power supply circuits performs constant current control and the other performs constant voltage control has been described. However, the same applies to the case where both perform constant current control. it can.

C1-C4 ... Capacitors D1-D4 ... Diode Np ... Primary coil Ns ... Secondary coil Na ... Auxiliary coils Q1, Q2 ... Switching elements R1, R2, R21, R22 ... Resistors RM1, RM2 ... Remote terminals T1, T2 ... Transformers 20, 21, 22, 30 ... load 31, 32 ... switching control circuit 33 ... current detection circuit 34 ... voltage detection circuit 91, 92 ... additional circuit 101, 102 ... primary side drive control circuit 110, 111, 112 ... first Power circuit 120, 121, 122 ... second power circuit 201, 202 ... power supply device

Claims (2)

A first power supply circuit that applies a DC voltage to the load; and a second power supply circuit that applies a DC voltage having a polarity opposite to the output voltage of the first power supply circuit to the load.
The first power supply circuit and the second power supply circuit include a transformer having a primary coil and a secondary coil, a drive control circuit connected to the primary coil and causing a drive current to flow through the primary coil, and the secondary A rectifying / smoothing circuit that rectifies and smoothes the output voltage of the coil and outputs the rectified voltage to the load,
In the power supply apparatus comprising a current detection circuit for detecting a current supplied from the first power supply circuit to the load on a ground potential side of the rectifying / smoothing circuit of the second power supply circuit,
An additional circuit to which the voltage of the secondary coil of the transformer of the second power circuit is applied is connected between the secondary coil of the transformer of the second power circuit and the rectifying / smoothing circuit of the second power circuit. A power supply device characterized by that.   The said additional circuit was comprised by the rectification smoothing circuit which rectifies and smooths the output voltage of the secondary coil of the transformer of a said 2nd power supply circuit, and the load circuit connected to the output of this rectification smoothing circuit. The power supply device described in 1.

Images