DC power supply device

Abstract

The standby power consumption is improved by reducing the charging and discharging current of the X capacitor in standby mode. [Solution] A DC power supply device comprising a diode bridge circuit (13) for rectifying an input AC voltage, a filter circuit (12) provided in front of the diode bridge circuit and equipped with an X capacitor and a coil, a current suppression element (TH1) for suppressing the inrush current flowing through the diode bridge circuit when AC input is applied, and a first switch means (RLY1) provided in parallel with the current suppression element and switched on and off by a control signal, wherein the X capacitor is composed of two or more capacitors connected in parallel, a second switch means (RLY2) is provided in series with any of the two or more capacitors, and the second switch means is configured to switch from on to off at the same time as the first switch means switches from on to off in response to a change in the control signal.

Description

Technical Field

[0001] The present invention relates to a DC power supply device provided with an AC filter, and particularly relates to a technique for reducing the charge and discharge current of an X capacitor constituting the AC filter in a standby state and improving standby power.

Background Art

[0002] A DC power supply device includes a diode bridge circuit that rectifies an AC power supply, and an isolated AC-DC converter of a switching power control system that converts the DC voltage rectified by the circuit with a voltage conversion transformer and outputs a DC voltage of a desired potential. In an isolated AC-DC converter, generally, an AC filter for the purpose of attenuating noise is mounted.

[0003] Normally, an X capacitor is used for the AC filter, and the capacitance of the X capacitor is generally adjusted according to the circuit system and output power. However, since the switching power supply generates more noise as the output power increases, the capacitance value of the X capacitor required for noise reduction also increases. Therefore, there is a technique for switching the capacitance value of the X capacitor according to the magnitude of the output load (for example, Patent Document 1).

[0004] Also, for example, when considering the case of applying a switching power supply to a power supply device for a copying machine, in the copying machine, in addition to the power supply for copying machine control and the motor drive (main power supply), there is a fixing unit equipped with a heater circuit for warming the toner. Therefore, since noise generated from the fixing unit may also leak into the main power supply side, it is necessary to increase the capacitance value of the X capacitor on the substrate side of the main power supply.

[0005] Incidentally, X capacitors constantly undergo charging and discharging due to the AC voltage, resulting in a small amount of power consumption. Since this power consumption is proportional to the capacitance value of the X capacitor, power supply boards with high output power will consume more power. In recent years, there has been a demand for reduced standby power consumption in electronic devices that have a standby state, such as office equipment like photocopiers with built-in power supply boards, home appliances with internet communication functions, and industrial equipment, and there is a demand for improved standby efficiency in power supply boards. Therefore, in power supply boards consisting of AC-DC converters, the losses in the X capacitor have become a matter of concern.

[0006] Furthermore, in power supply devices consisting of AC-DC converters, a resistor is provided between one terminal of the AC filter and the diode bridge circuit to prevent excessive inrush current from flowing from the AC power supply to the converter when the power is turned on. In addition, when the output power is large, the power loss in the resistor used to prevent inrush current also becomes large, so a relay (electromagnetic relay) may be provided in parallel with the resistor to reduce this power loss (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2010-4613 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the power supply device (AC-DC converter) described in Patent Document 1, which includes a resistor to prevent inrush current between one terminal of the AC filter and the diode bridge circuit, and a relay (switching means) in parallel with this resistor, there is a problem that power consumption occurs in the X capacitor (C1) and discharge resistors (R6~R10). In addition, there is a problem that the circuit becomes complex because it is necessary to provide two diode bridges (D1 and DD1~DD4).

[0009] The present invention has been made in view of the above-mentioned problems, and its objective is to improve standby power by reducing the charging and discharging current of the X capacitor in the standby state in a DC power supply device equipped with an element for preventing inrush current and a switching means provided in parallel with the element. [Means for solving the problem]

[0010] To achieve the above objective, the present invention A DC power supply device comprising: a diode bridge circuit for rectifying an input AC voltage; a filter circuit provided in front of the diode bridge circuit, comprising an X capacitor and a coil or line filter; a current suppression element for suppressing the inrush current flowing through the diode bridge circuit when the AC input is turned on; and a first switch means provided in parallel with the current suppression element and switched on and off by a control signal, wherein The aforementioned X capacitor is composed of two or more capacitors connected in parallel. A second switching means is provided in series with one of the two or more capacitors mentioned above. The second switching means is configured to switch from on to off simultaneously with the switching of the first switching means from on to off in response to a change in the control signal.

[0011] With a DC power supply having the above configuration, when transitioning to a standby state, a control signal switches off a switch means provided in series with one of the capacitors constituting the X capacitor. This disconnects some of the capacitors in the X capacitor from the circuit during the standby state, thereby reducing the charging and discharging current of the X capacitor during the standby state and improving standby power. [Effects of the Invention]

[0012] According to the present invention, in a DC power supply device equipped with an element for preventing inrush current and a switching means provided in parallel with the element, the X capacitor is composed of multiple elements, and in the standby state, a part of the X capacitor is disconnected from the circuit, thereby reducing the charging and discharging current of the X capacitor in the standby state and improving standby power. [Brief explanation of the drawing]

[0013] [Figure 1] This is a circuit diagram showing a first embodiment of a DC power supply device to which the present invention is applied. [Figure 2] This is a circuit diagram showing a second embodiment of a DC power supply device to which the present invention is applied. [Figure 3] (A) is an equivalent circuit diagram of a single-contact type relay that constitutes the DC power supply device of the embodiment, and (B) is an equivalent circuit diagram of a two-contact type relay. [Figure 4] (A) is an equivalent circuit diagram of a cement resistor with a thermal fuse, which is an example of a resistive element that functions as a current suppression element, and (B) is an equivalent circuit diagram of a triac, which is an alternative element to a relay. [Figure 5] This is a circuit diagram showing a third embodiment of a DC power supply device to which the present invention is applied. [Modes for carrying out the invention]

[0014] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Some AC filters use one X capacitor, but in the AC filter of the DC power supply device of the present invention, a plurality of X capacitors are provided separately, and a switch is connected in series with any one of the X capacitors, and the switch is turned off during standby to disconnect the corresponding X capacitor from the circuit, so that charge and discharge of electric charge do not occur in some of the X capacitors, and the standby power is improved. Hereinafter, specific embodiments thereof will be described.

[0015] (First Embodiment) FIG. 1 is a circuit configuration diagram showing a first embodiment of a DC power supply device to which the present invention is applied. As shown in FIG. 1, the DC power supply device 10 of the present embodiment includes an AC power line filter circuit (hereinafter referred to as an AC filter) 12 for removing normal mode noise, which is composed of X capacitors C1 and C2 connected between a pair of AC terminals to which an AC voltage (AC) from an AC power supply 11 is input, a common mode choke coil L1, etc., and a diode bridge circuit 13 for rectifying the AC voltage (AC). Further, a resistor R1 for discharging the X capacitor C1 when the AC power supply is cut off is provided between the AC input terminals.

[0016] Although not particularly limited, in the DC power supply device 10 of the present embodiment, a current fuse F1 for preventing an excessive current from flowing is connected between one terminal of the AC input and the AC filter 12. Further, Y capacitors C4 and C5 for removing common mode noise are provided in front of the diode bridge circuit 13 together with the common mode choke coil L1, and a smoothing capacitor C6 for smoothing the pulsating current after rectification is provided at the rear stage. The Y capacitors C4 and C5 are provided in a series form in this embodiment, and the intermediate node is connected to the ground point. Then, a switching power supply type converter 14 having a transformer is provided at the rear stage of the diode bridge circuit 13, and the voltage converted by the converter 14 is configured to be supplied to the load 15.

[0017] Furthermore, in the DC power supply device 10 of the present embodiment, a thermistor TH1 is connected between the AC filter 12 and the diode bridge circuit 13 to prevent an inrush current from flowing into the smoothing capacitor C6 when the power is turned on. Also, when the output power is large, the loss in the thermistor TH1 also increases. Therefore, a relay RLY1 is provided corresponding to the thermistor TH1. The contact S1 of this relay RLY1 is connected in parallel with the thermistor TH1. The relay RLY1 is configured to turn on the contact S1 in the normal operating state to bypass the current and prevent current from flowing through the thermistor TH1.

[0018] Separate from the relay RLY1 described above, a second relay RLY2 is provided. The contact S2 of the second relay RLY2 is directly connected to the X capacitor C2, and the contact S2 is turned on and off synchronously with the contact S1. Specifically, when shifting from the normal operating state to the standby state, the contact S1 of the first relay RLY1 becomes off, and when shifting from the standby state to the power-on state, current flows through the thermistor TH1 to exhibit the function of preventing an inrush current. The relay RLY1 and the thermistor TH1 have the function of preventing an inrush current when the AC power is turned on. On the other hand, when shifting from the normal operating state to the standby state, the contact S2 of the second relay RLY2 becomes off, disconnecting the X capacitor C2 from the circuit. As a result, in the standby state, the X capacitor C2 is not charged and discharged by the AC input. Therefore, the standby power in the AC filter 12 is improved.

[0019] On the other hand, the X capacitor C1 remains connected to the circuit even when shifting to the standby state, so it is charged and discharged. Here, in the standby state, since the output power of the power supply device is in the minimum state, noise can be dealt with only by the X capacitor C1. Therefore, even if the X capacitor C2 is opened by the relay RLY2, there is no problem with the noise prevention function of the AC filter 12.

[0020] The relays RLY1 and RLY2 are of the normally open type, which are off (de-energized) in standby mode, and their coils are energized when normal operation begins, causing contacts S1 and S2 to become conductive. The power supply voltage for relays RLY1 and RLY2 is supplied from converter 14, and an on / off switch SW1 is provided in the power supply path. Instead of using two single-contact type relays RLY1 and RLY2, as shown in Figure 3(A), a single two-contact type relay, as shown in Figure 3(B), may be used. Switch SW1 can be made of semiconductor elements such as transistors and FETs (field-effect transistors).

[0021] Furthermore, the ON / OFF control signal ON / OFF for switch SW1 is generated according to the operating state of the main function (load 15) output from the control device 16 of the equipment (actual set) on which the DC power supply is installed, and is configured to be supplied via the photocoupler (PC) 17. Specifically, switch SW1 is turned off by the ON / OFF control signal when the operation of the load 15 is paused (standby), de-energizing relays RLY1 and RLY2 and opening contacts S1 and S2. Also, SW1 is turned on when the operation of the main function (load 15) starts or standby is released, and is controlled to energize relays RLY1 and RLY2 and close contacts S1 and S2.

[0022] Furthermore, in the embodiment shown in Figure 1, a series circuit of the second X capacitor C2 and contact S2 is provided after the coil L1, but the series circuit of C2 and S2 may also be provided in parallel with the first X capacitor C1 before the coil L1. Also, the thermistor TH1 may be provided at the positions indicated by the symbols P1 and P2 before the coil L1, or it may be provided at any position on the wire side where the fuse F1 is placed. Furthermore, although the embodiment shown in Figure 1 describes a configuration with two X capacitors C1 and C2, it is also possible to provide three or more X capacitors and connect the relay contacts in series with multiple of these capacitors. In addition, the control device 16 may be configured to switch the number of X capacitors that are left open during standby according to the magnitude of the output power required by the load.

[0023] (Second Embodiment) Next, a second embodiment of the DC power supply device according to the present invention will be described with reference to Figure 2. In the DC power supply device of the second embodiment, as shown in Figure 2, X capacitors C1 and C2 (C2 > C1) are provided before the common mode choke coil L1, and the contact S2 of relay RLY2 is connected in series with the second X capacitor C2. In addition, a third X capacitor C3, which constitutes the AC filter 12, is connected after the coil L1. Similar to the first embodiment, instead of providing two relays RLY1 and RLY2, one two-contact type relay with two contacts may be used.

[0024] Furthermore, in the DC power supply device of this embodiment, a power factor correction circuit 18 is provided after the diode bridge circuit 13, and a converter 14A that steps down the voltage output from the power factor correction circuit 18, for example 300-400V, to a DC voltage of 5V and a converter 14B that steps down the voltage to a DC voltage of 24V are connected thereafter. The DC voltage generated by converter 14A is supplied to the load 15A, and the DC voltage generated by converter 14B is supplied to the load 15B. In addition, instead of the resistor R1 for discharging the X capacitors C1 and C3 in Figure 1, a circuit consisting of diodes D6 and D7 with their anode terminals connected to the AC input terminals and a cathode-side resistor R2 is provided between the AC input terminals and the converter 14A, so that the converter 14A can quickly discharge the X capacitors C1 and C3.

[0025] Furthermore, in the DC power supply device of this embodiment, the 24V DC voltage generated by the converter 14B is applied to the coils of relays RLY1 and RLY2 via switch SW1. In addition, the 5V DC voltage generated by the converter 14A is supplied as a power supply voltage to the control device 16, which is composed of a microprocessor or the like that generates on / off control signals for switch SW1, which is in series with the coils of relays RLY1 and RLY2. Note that converters 14A and 14B are switching power supply type converters equipped with transformers, similar to converter 14 in the first embodiment.

[0026] In this embodiment of the DC power supply, when the system transitions from normal operation to standby (converter 14B stops operating), the contact S2 of relay RLY2 is turned off, and the X capacitor C2 is disconnected from the circuit. As a result, in standby mode, the X capacitor C2 is no longer charged or discharged by the AC input, improving the standby power consumption of the AC filter 12. Furthermore, since C2 > C1, even greater improvements in standby power consumption are possible. Furthermore, even if C2 > C1, in standby mode, the noise that is originally coming in (noise leaking in from converter 14A) is small, so the noise level can be kept low with C1 alone. On the other hand, when the converter 14B starts operating after waking from standby mode, switch SW1 is turned on and contact S2 conducts, so the X capacitor C2 is connected, which can reduce the relatively large noise coming in from converter 14B.

[0027] When the DC power supply in this embodiment is a power supply unit mounted on a copier, converter 14A mainly generates the power supply voltage for the control unit (loads 15A and 16), and converter 14B mainly generates the power supply voltage for the motor unit (load 15B) that drives the rotating part. The control unit (copier control unit) 16 is programmed to output an ON / OFF control signal that turns off switch SW1 when transitioning to a standby mode that pauses the operation of the copier.

[0028] In a power supply divided into converter 14A and converter 14B, as in the above-mentioned copier, the noise generated increases in proportion to the output power, so the X capacitor also needs to be set to a large value, and without relay RLY2, the power wasted in the AC filter 12 in standby mode becomes large. In the DC power supply device of this embodiment, the X capacitor C2 is disconnected from the circuit in standby mode, so the power consumption of the AC filter 12 in standby mode can be reduced. In the circuit shown in Figure 2, the power factor correction circuit 18 and the X capacitor C3 may be omitted. Also, the series circuit of the X capacitor C2 and contact S2 may be provided after the coil L1, as in the embodiment of Figure 1. The thermistor TH1 is not limited to the position shown in Figure 2, and may also be placed before the coil L1.

[0029] (Third embodiment) Next, a third embodiment of the DC power supply device according to the present invention will be described with reference to Figure 5. As shown in Figure 5, the DC power supply of the third embodiment is configured to supply a separate output voltage (approximately 12-20V) generated in addition to the 5V output voltage generated by converter 14A to converter 14B with a 24V output via switch SW, and to use this as the power supply voltage to operate the ICs that make up converter 14B. Similar to the above embodiment, switch SW transmits and controls the ON / OFF signal output from control unit 16 via photocoupler 17. On the other hand, the 24V output voltage of converter 14B is wired to be directly supplied to relays RLY1 and RLY2.

[0030] Here, the ON / OFF signal of the switch SW matches or is used interchangeably with the signal that controls the operation of the converter 14B output from the control unit 16. Therefore, in the DC power supply of this embodiment, when the switch SW is OFF, the operation of the 24V output converter 14B is stopped, and since there is no output voltage from the converter 14B, no power supply voltage is supplied for the relays, and relays RLY1 and RLY2 are also turned OFF. When the switch SW is turned ON, the converter 14B starts up and outputs a voltage of 24V, so 24V is supplied to the coil side of relays RLY1 and RLY2, and the relays can be driven.

[0031] Although the present inventor's invention has been described in detail above based on embodiments, the present invention is not limited to the above embodiments. For example, in the above embodiment, the power supply voltage for the relay is supplied from the secondary side of the converter 14, but the power supply voltage for the relay may also be supplied from the primary side of the converter 14.

[0032] Furthermore, although a thermistor TH1 is provided as a current suppression element in the above embodiment, a resistive element (for example, a cement resistor with a thermal fuse as shown in Figure 4(A)) may be used instead of the thermistor TH1, and a relay may be provided in parallel with the resistive element. Furthermore, in the above embodiment, relays RLY1 and RLY2 are of the normally open type, but depending on the equipment or system to which they are applied, relays with normally closed contacts may be used. Alternatively, instead of relays, semiconductor elements such as triacs, thyristors, or transistors, as shown in Figure 4(B), may be used. [Explanation of symbols]

[0033] 11…AC power supply, 12…AC filter (filter circuit), 13…Diode bridge circuit (rectifier circuit), 14…Converter, 15…Load, 16…Control device, 17…Photocoupler, 18…Power factor correction circuit, C1, C2…X capacitors, TH1…Thermistor (current suppression element), RLY1, RLY2…Relay (switching mechanism), S1, S2…Relay contacts, SW1…Switching element

Claims

1. A DC power supply device comprising: a diode bridge circuit for rectifying an input AC voltage; a filter circuit provided in front of the diode bridge circuit, comprising an X capacitor and a coil or line filter; a current suppression element for suppressing the inrush current flowing through the diode bridge circuit when AC input is applied; and a first switch means provided in parallel with the current suppression element and switched on and off by a control signal, wherein The aforementioned X capacitor is composed of two or more capacitors connected in parallel. A second switching means is provided in series with one of the two or more capacitors mentioned above. The DC power supply device is characterized in that the second switching means is configured to switch from on to off simultaneously with the switching of the first switching means from on to off in response to a change in the control signal.

2. The first and second switching means are relays each equipped with a coil and contacts, The DC power supply device according to claim 1, characterized in that the relay is configured such that the contacts are made conductive or non-conductive by a control signal supplied from an external control device.

3. The first and second switching means are the first and second contacts of a relay having a coil and two contacts, The DC power supply device according to claim 1, characterized in that the relay is configured to be made conductive or non-conductive by a control signal supplied from an external control device.

4. The first switching means and the second switching means each consist of a semiconductor element, The DC power supply device according to claim 1, characterized in that the semiconductor element is configured to be made conductive or non-conductive by a control signal supplied from an external control device.

5. A first converter for voltage conversion that outputs a DC voltage is provided downstream of the aforementioned diode bridge circuit. A DC voltage converted by the first converter is applied to one terminal of the coil of the relay via a switching element. The DC power supply device according to claim 2, characterized in that the control device is configured to be supplied with a DC voltage converted by the first converter.

6. A first converter for voltage conversion that outputs a first DC voltage and a second converter that outputs a second DC voltage higher than the first DC voltage are provided downstream of the diode bridge circuit. A DC voltage converted by the second converter is applied to one terminal of the coil of the relay via a switching element. The DC power supply device according to claim 2, characterized in that the control device is configured to be supplied with a DC voltage converted by the first converter.

7. A first converter for voltage conversion that outputs a first DC voltage and a second converter that outputs a second DC voltage higher than the first DC voltage are provided downstream of the diode bridge circuit. The second converter is configured to receive the DC voltage converted by the first converter via a switching element as the voltage to drive the second converter. A DC voltage converted by the second converter is applied to one terminal of the coil of the relay. The DC power supply device according to claim 2, characterized in that the control device is configured to be supplied with a DC voltage converted by the first converter.

8. The DC power supply device according to any one of 5 to 7, characterized in that the control device outputs a control signal that turns the switch element off or on to open the contacts of the relay when in standby mode, which pauses the operation of a load that operates in response to the output voltage of the first converter.

Images