JP2005295761A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve power factor and to reduce power consumption during waiting in the power supply circuit of an air conditioner. <P>SOLUTION: A diode bridge 3 for converting AC primary voltage into DC high voltage, a plurality of smoothing capacitors 4 and 5, and a DC/DC converter 6 for converting the DC high voltage into DC low voltage constitute a power supply circuit. Secondary load level of the DC/DC converter 6 is detected and a smoothing capacitor selected based on the detection value is connected thus reducing the capacity of the capacitor and improving power factor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply circuit used for an air conditioner or the like, and more particularly to a power supply circuit that variably controls a smoothing capacitor capacity and aims to improve efficiency.

Conventionally, in this type of air conditioner power supply circuit, the AC voltage from the AC power source passes through a noise filter and is then rectified to a DC voltage by a diode bridge, and the DC voltage after rectification is smoothed by a smoothing capacitor, It is converted to a constant voltage value by a DC converter and output to each actuator or the like. (For example, see Patent Document 1)
As shown in FIG. 3, the AC power source 1, the noise filter 2, the diode bridge 3, the smoothing capacitor 4 capacitance C <b> 1, and the DC / DC converter 6 are included.
Japanese Utility Model Publication No. 2-131158

  Conventionally, air conditioners that perform indoor air conditioning include power supplies for controlling air conditioners, power supplies for driving various drive mechanisms (actuators, etc.) such as relays and stepping motors, and fan motors. A power supply for driving is required. For example, a DC voltage of 5V is required as a control system power supply, a DC voltage of 12V as a power system power supply, and a 0-40V variable DC voltage as a power supply for driving a fan motor. Therefore, the capacitor has a large capacity sufficient to supply the secondary side maximum output. What is required. However, when the air conditioner is on standby, there is no need for variable DC voltage, and only a constant voltage of 5 V is required to operate the control system circuit. It remains a large capacity to match the supply. This difference in capacity deteriorates the power factor, resulting in unnecessary power loss, and increases standby power consumption.

  In order to solve the above problems, a power supply circuit according to the present invention detects a secondary load level of a DC / DC converter and selects and connects the plurality of smoothing capacitors based on the detected value. With this configuration, the capacity of the smoothing capacitor can be switched between a large capacity and a low capacity according to the secondary load level of the DC / DC converter, thereby improving the power factor and reducing standby power consumption.

  The power supply circuit of the present invention can improve the power factor and consume power efficiently, and as a result, standby power consumption can be reduced.

  According to the first aspect of the present invention, switching means is provided in the smoothing capacitor constituting the power supply circuit, and the capacity of the smoothing capacitor can be varied and reduced by the switching means, thereby improving the power factor and reducing power consumption. .

  The second aspect of the invention makes it possible to act equivalently as an inductance by utilizing the properties of the common mode choke coil, improve the power factor, and reduce power consumption.

According to a third aspect of the present invention, the power supply circuit of the first or second aspect is mounted on an air conditioner, the capacity of the smoothing capacitor is reduced during standby of the air conditioner, power factor is improved, and standby power consumption is reduced. Can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a power supply circuit according to Embodiment 1 of the present invention.

  In FIG. 3 of the conventional example, two smoothing capacitors, a capacitor 4 capacitor C1 and a capacitor 2 capacitor C2, are connected in series, and a switching means 9 is provided between them to detect the secondary load level of the DC / DC converter 6. Based on the detection level information 7, the switching instruction means 8 for instructing switching is provided. Here, C1 = C2. The smoothing capacitor capacity at this time is C1 / 2. The operation and action of the control block configured as described above will be described below.

  When the air conditioner starts operation, it is necessary to supply a sufficient amount of secondary power to drive various drive mechanisms (actuators, etc.) and control system circuits. . On the other hand, when the air conditioner is on standby, only the operation of the control system circuit is required, and a capacitor having a low capacity is sufficient.

  From this, the secondary load level of the DC / DC converter 6 is detected, and when the detected secondary load level information 7 is larger than a predetermined value, the switching means 9 connects the terminals S1 and S3. Thus, the total capacity of the smoothing capacitor can be increased by using only the capacitor 4 capacity C1 as the smoothing capacitor.

As described above, in the first embodiment, the effective current value is reduced by switching the smoothing capacitor capacity according to the secondary load level, and the power and voltage consumed by the converter are constant. Power factor can be improved from 1) and (Formula 2), power loss can be reduced, and standby power consumption of the air conditioner can be reduced.
P = Eicos θ (Formula 1)
cos θ = R / √ (R ² + (ωL−1 / ωC) ² ) (Formula 2)
Next, P is the power after high-voltage DC voltage conversion, E is the effective voltage value, I is the effective current value, L is the inductance, C is the capacitor capacity, R is the resistance, and cos θ is the power factor.

Next, a detailed description of standby power consumption reduction will be given. For example, in FIG. 1, when the standby power consumption (input voltage) Pin of the air conditioner is 0.8 W and the power factor is 35%, The electric power P after the high-voltage DC voltage conversion is obtained as 0.28 W from the following (Equation 3). If this power factor is improved to 70% according to the present invention, standby power consumption Pin is 0.4 W from (Equation 3), and standby power consumption can be reduced.
Pin = P · cos θ (Formula 3)
Here, Pin indicates standby power consumption of the air conditioner, and P indicates power after high-voltage DC voltage conversion.

(Embodiment 2)
FIG. 2 is a control block diagram of the power supply circuit according to the second embodiment of the present invention. The circuit configuration and operation of the power supply circuit according to the second embodiment are basically the same as those of the first embodiment.

As in the first embodiment, when the plurality of smoothing capacitors are switched by the switching means, a space and cost for arranging the plurality of smoothing capacitors are generated. Therefore, in the present embodiment, as shown in FIG. 2, the noise filter for noise reduction of the switching power supply that converts the full-wave rectified DC voltage into a low voltage is used as the detection level information of the secondary load level of the DC / DC converter 6. 7 so that the noise filter 10 and the noise filter 11 can be switched by the switching means 14.

  The noise filter 10 includes a symmetric common mode choke coil 12, and the noise filter 11 includes an asymmetric common mode choke coil 13. An ideal common mode choke coil works to counteract the magnetic flux with each other and is equivalent to not working on the circuit. Therefore, when the coil is viewed from the center, the magnetic flux that cannot be canceled out is increased by making the coil asymmetrical, and the normal mode choke component is equivalently increased, which can act as a primary circuit inductance.

  As in the first embodiment, when the secondary load level information 7 is smaller than a predetermined value, the switching means 9 connects the terminal S3 and the terminal S4, and the noise is composed of an asymmetrical common mode choke coil. By selecting the filter 13 and increasing the inductance, from (Equation 2), the power factor is improved, the power loss is reduced, the power consumption of the air conditioner is further reduced, and it is smaller than the smoothing capacitor and is inexpensive. By using the noise filter, it is possible to reduce the size and cost of the substrate.

  As described above, since the power supply circuit according to the present invention can reduce standby power consumption, the power supply circuit is provided with a remote control and is aimed at improving the efficiency of electronic and electrical equipment that consumes a large amount of power as equipment. It can be adapted to other uses.

Block diagram of a power supply circuit in Embodiment 1 of the present invention Block diagram of a power supply circuit in Embodiment 2 of the present invention Block diagram of a conventional power circuit

Explanation of symbols

1 AC voltage 2 Noise filter 3 Diode bridge 4 Capacitor capacity C1
5 Capacitor capacity C2
6 DC / DC converter 7 Secondary load level information 8 Switching instruction means 9 Switching means 10 Noise filter 11 Noise filter 12 Common mode choke coil (symmetrical)
13 Common mode choke coil (asymmetric type)
14 Switching means

Claims (3)

A power supply circuit is configured by a diode bridge that converts an AC primary power source into a high-voltage DC voltage, a plurality of smoothing capacitors, and a DC / DC converter that converts the high-voltage DC voltage into a low-voltage current voltage, and the secondary of the DC / DC converter A power supply circuit that detects a side load level and reduces the capacitance by switching the plurality of smoothing capacitors by a switching means based on the detected value. A plurality of noise filters composed of a common mode choke coil are provided between an AC primary power supply and a diode bridge, a secondary load level of the DC / DC converter is detected, and based on the detected value, the plurality of noise filters Is switched to a noise filter composed of an asymmetric common mode choke coil by a switching means. An air conditioner equipped with the power supply circuit according to claim 1 or 2.

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