JP3442143B2 - Power supply for air conditioner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for an air conditioner capable of outputting at least two types of DC voltages for a plurality of electric loads of the air conditioner. It is. 2. Description of the Related Art Conventionally, this type of power supply device has a DC variable voltage source and a DC constant voltage source, and the DC variable voltage source is used, for example, as a variable speed drive power source for an indoor fan. Is commonly used as an operating power supply for a control microprocessor (MPU), a switching element driving circuit, and the like. However, these two
Different DC voltages are conventionally obtained through separate DC power circuits connected to separate transformers. Adjustment of the rotational speed of a load connected to a DC variable voltage power supply, for example, an indoor fan, is performed through voltage control of a fan motor. The voltage adjustment width in this voltage control is considerably large because the variable speed range of the fan motor is wide, and is performed through pulse width modulation control. On the other hand, a load of a DC constant voltage used in a control circuit or the like is required to have little load fluctuation and to have a substantially constant voltage. Therefore, conventionally,
The DC variable voltage source and the DC constant voltage source were prepared separately and independently. Providing a variable voltage source and a constant voltage source separately as described above increases the number of components of the circuit and increases the size and cost. Accordingly, an object of the present invention is to provide a power supply device for an air conditioner that can stably supply a DC variable voltage and a DC constant voltage, and that can be configured at a small size and at low cost. . [0005] In order to achieve the above object, the present invention provides an air conditioner power supply device capable of outputting at least two kinds of DC voltages for a plurality of electric loads of an air conditioner. A switching transformer having a primary winding and a plurality of secondary windings, connected in series with the primary winding,
A first switching element for generating an AC voltage in the secondary winding by turning on / off a supplied DC current, and a first switching element for a predetermined repetition such that a predetermined output voltage is generated in the secondary winding. A first switching element drive circuit for performing on / off control with a frequency, and a first for converting an alternating voltage generated by a first secondary winding of the switching transformer into a direct current
Connected to the output side of the first DC converting means
Supply a variable DC voltage to the fan motor of the indoor blower
Buck DC to - a DC converter, step-down DC - second to control the output voltage of the DC converter according to the load condition
And a second DC converter for converting an AC voltage generated by a second secondary winding of a switching transformer into a DC, outputting a substantially constant DC constant voltage, and supplying the DC voltage as an operating power supply of a control circuit device. Means and output of the first secondary winding
Detects AC voltage load fluctuation and compensates for the load fluctuation
Signal to the first switching element drive circuit.
Output correction circuit . In the power supply unit for an air conditioner of the present invention, a DC variable voltage and a DC constant voltage are obtained through a first secondary winding and a second secondary winding of a common switching transformer, respectively. . By obtaining two voltages from different secondary windings of a common switching transformer, a stable
Various DC voltages can be supplied under a power supply device that can be configured to be smaller and cheaper. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a power supply device according to the present invention. AC power supply, eg 50Hz or 6
AC power is input from a 0 Hz commercial AC power supply to the rectifier circuit 4 via the noise removal line filter 2 and the inrush current prevention circuit 3, and the rectified DC power is input to the power supply device 10 according to the present invention. Is done. The internal configuration of the power supply 10 will be described below. The output DC voltage of the rectifier circuit 4 is connected to a switching element 12 having a snubber circuit 11 in the power supply device 10.
, And is converted to AC power by the ON / OFF of the switching element 12 and output. The switching element 12 is a switching element drive circuit 1 that operates by obtaining driving power from a third secondary winding (see FIG. 2) of a switching transformer 13.
4 driven. On the secondary side of the switching transformer 13, a first rectifying / smoothing circuit 15 for variable voltage and a second rectifying / smoothing circuit 16 for constant voltage are connected. A step-down chopper circuit, that is, a step-down DC-DC (DC-DC) converter 17 is connected to the output side of the first rectifying / smoothing circuit 15, and the DC-DC converter 17 outputs a DC variable voltage. This DC variable voltage is used, for example, for driving the indoor fan motor 18 at a variable speed. In some cases, the outdoor fan is also driven at a variable speed. In such a case, the outdoor fan motor can also be a load of the variable voltage power supply. The constant voltage circuit 19 is connected to the output side of the second rectifying / smoothing circuit 16.
9 outputs a DC constant voltage, for example, +5 V DC constant voltage. The DC constant voltage output from the constant voltage circuit 19 is MP
It is used as various operation power supplies in the control circuit including the U (microprocessor) 20. The output voltage of the first rectifying and smoothing circuit 15 is input to an output correction circuit 21 together with the constant voltage output from the constant voltage circuit 19, and the two are compared. As described above, the output secondary voltage of the switching transformer 13 is controlled by changing the duty ratio of the switching element 12 via the switching element drive circuit 14. A load state of a load (DC motor 18 for driving an indoor fan in the illustrated example) driven by a DC variable voltage output from the DC-DC converter 17, for example, the number of revolutions, is detected by a load state detecting device 22. , And its detection output is input to the MPU 20. The MPU 20 has a load state command value for internally setting the detected load state separately,
In the embodiment illustrated here, the output voltage of the DC-DC converter 17 is controlled via the switching element drive circuit 24 so as to compare with the rotational speed command value and make the deviation zero. Note that the rotation speed command value is changed by the air conditioning load. The MPU 20 further controls on / off of an outdoor unit main switch 25 provided between the AC power supply and the outdoor unit main circuit. The outdoor unit main circuit includes, in addition to an inverter for supplying power to the compressor / motor, an electric load such as an outdoor fan motor and a four-way valve operating solenoid. FIG. 2 shows a more detailed circuit connection of the power supply device 10 of FIG. This power supply device includes a switching transformer 13. The switching transformer 13 includes a primary winding 131, two sets of secondary windings 132 and 133, and a tertiary winding 134. DC current is intermittently supplied to the primary winding 131 from the rectifier circuit 4 via the switching element 12 (for example, a transistor). The snubber circuit 11 including a capacitor, a resistor, a diode, and the like is connected to the primary winding 131 in parallel. Switching element drive circuit 14
Operates as a driving power source from a tertiary winding 134 through a rectifying / smoothing circuit 30 including a diode, a capacitor, and a resistor, and changes the ON / OFF ratio, that is, the duty ratio of the switching element 12 at a predetermined repetition frequency Control. The rectifying and smoothing circuit 15 including a diode and a capacitor is connected to the first secondary winding 132. A step-down DC-DC comprising a switching element 171 and a smoothing circuit 172 is provided on the output side of the rectifying / smoothing circuit 15.
Converter 17 is connected. Switching element 171
Functions as a well-known chopper. The indoor fan motor 18 is driven by the variable DC output voltage of the step-down DC-DC converter 17, and the load state (for example, the number of revolutions) is detected by the load state detector 22. The load state detected by the load state detector 22 is input to the MPU 23, and the load state is compared with a set value in the MPU 20,
According to the comparison result, the switching element 171 is turned on and off.
The off ratio, that is, the duty ratio is controlled. More specifically, the MPU 23 detects the rotation speed of the indoor fan motor 18 based on the output of the load state detector 22 composed of a Hall element. The fan motor 18 is formed of a DC motor, and the number of rotations increases as the applied voltage increases, and decreases as the applied voltage decreases. Here, the MPU 23 detects the actual rotation speed of the fan motor 18 and compares the actual rotation speed with a commanded rotation speed determined according to the difference between the air conditioning load, that is, the actual room temperature and the set room temperature. As a result of the comparison, if the actual rotation speed is higher than the command rotation speed, the duty ratio of the switching element 171 is reduced to reduce the output of the step-down DC-DC converter 17 and reduce the rotation speed of the fan motor 18. . On the other hand, if the actual rotation speed is lower than the command rotation speed, the duty ratio of the switching element 171 is increased and the step-down DC-
The output of the DC converter 17 is increased and the fan motor 1
8 is increased. The second secondary winding 133 of the switching transformer 13 is provided with an intermediate tap. From the intermediate tap, a +5 V DC is passed through a rectifying / smoothing circuit 31 composed of a diode and a capacitor and a constant voltage circuit 19. A constant voltage is obtained, and a DC constant voltage of +12 V is obtained from the winding end terminal through another rectifying / smoothing circuit 32 also composed of a diode and a capacitor. The former +
The DC constant voltage of 5V is a fairly strict constant voltage, and the latter + 12V constant voltage is a fairly rough constant voltage. More specifically, the outdoor unit main switch 25 includes a switch contact 250, an operation coil 251 for operating the switch contact 250, a transistor 252 for controlling an operation current of the operation coil 251, and a base resistor 253 of the transistor.
The transistor 252 is controlled by the MPU 20. The output correction circuit 21 includes a measuring voltage dividing resistor for dividing an output voltage of the rectifying / smoothing circuit 15 (a voltage corresponding to an output voltage of the first secondary winding 132 of the switching transformer 13), and a constant voltage. A voltage dividing circuit 211 composed of a reference voltage dividing resistor for dividing the output constant voltage of the circuit 19, a comparator 212 for comparing a measured voltage and a reference voltage output from the voltage dividing circuit 211, and electrically insulating the comparator output. A photocoupler 213 that transmits the signal to the switching element drive circuit 14. The photocoupler 2
Reference numeral 13 comprises a light emitting diode and a phototransistor. The switching element driving circuit 14 has an integrating circuit whose voltage rises in proportion to the on-time of the transistor of the photocoupler 213, and increases or decreases the duty ratio of the switching element 12 in inverse proportion to the output voltage of this integrating circuit. It is. That is, if the output voltage of the rectifying / smoothing circuit 15 increases, the comparator 212 turns off, the transistor of the photocoupler 213 turns on, and the output voltage of the integrating circuit increases. Accordingly, the duty ratio of the switching element 12 decreases, and as a result, the output voltage of the rectifying / smoothing circuit 15 decreases. On the other hand, when the output voltage of the rectifying and smoothing circuit 15 decreases, the comparator 212 turns on, the transistor of the photocoupler 213 turns off, the output voltage of the integrating circuit decreases, the duty ratio of the switching element 12 increases, and the rectifying and smoothing circuit increases. 15 output voltage rises. Thus, the output voltage of the rectifying / smoothing circuit 15 is controlled to a constant value determined by the reference voltage dividing resistor. The DC voltage of +12 V obtained as the output voltage of the rectifying / smoothing circuit 32 is used as a drive power source in the outdoor unit main switch 25 as described above.
The DC constant voltage of +5 V obtained through the rectifying / smoothing circuit 31 and the constant voltage circuit 19 is applied to other control circuit elements such as the MPU 20, the comparator 212, and the photocoupler 213.
Used as an operation power supply for the light emitting diode and the like. The operating power supply of the switching element drive circuit 14 is the third secondary winding 134 of the switching transformer 13 as described above.
Through the rectifying / smoothing circuit 30, and the operating power supply of the switching element driving circuit 24 is the switching transformer 1
3 from the second secondary winding 133 via the rectifying / smoothing circuit 31 and the constant voltage circuit 19. According to the embodiment described above, a power supply for an air conditioner capable of stably obtaining two types of DC voltages through a common switching transformer is provided at a relatively low cost and with a small number of parts. Can be configured. According to the present invention, the DC variable voltage and the DC constant voltage of the air conditioner are obtained from the same transformer, so that a small and inexpensive air conditioner capable of supplying stable power can be provided. Power supply device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a power supply device for an air conditioner of the present invention. FIG. 2 is a diagram showing a more detailed circuit connection example of the power supply device shown in FIG. 1; [Description of Signs] 4 Rectifier circuit 10 Power supply circuit 12 Switching element 13 Switching transformer 14 Switching element drive circuit 15 Rectification smoothing circuit 16 Rectification smoothing circuit 17 Step-down DC-DC converter 18 Fan motor 19 Constant voltage circuit 20 Microprocessor (MPU) Reference Signs List 21 output correction circuit 24 switching element drive circuit 25 main switch for outdoor unit 30 rectifying / smoothing circuit 31 rectifying / smoothing circuit 32 rectifying / smoothing circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F24F 11/02

Claims (1)

(57) Claims 1. A power supply device for an air conditioner capable of outputting at least two types of DC voltages for a plurality of electric loads of the air conditioner, comprising a primary winding and a plurality of power supplies. Switching with secondary winding of
And a transformer, connected in series with the primary winding to turn on / off the supplied DC current.
A first switching element that generates an AC voltage in the secondary winding by turning off, and a first switching element that is turned on at a predetermined repetition frequency so that a predetermined output voltage is generated in the secondary winding.・
A first switching element drive circuit for off-control, a first direct current converting means for converting the alternating voltage generated by the first secondary winding of the switching transformer into a direct current, and an output side of the first direct current converting means Connected to the indoor blower
A step-down DC-DC converter that supplies a variable DC voltage to the fan motor of the present invention, and the output voltage of the step-down DC-DC converter is changed to a load state.
A second switching element drive circuit that controls the AC voltage generated by the second secondary winding of the switching transformer to DC, and outputs a substantially constant DC constant voltage as an operating power supply for control circuit devices. A second DC converting means for supplying, and a load fluctuation of an output AC voltage of the first secondary winding is detected.
Then, a correction signal for compensating for the load fluctuation is sent to the first
A power supply device for an air conditioner, comprising: an output correction circuit that sends the signal to the switching element drive circuit .