KR102069068B1 - Power transforming apparatus, Method for controlling the same and Air conditioner including the power transforming apparatus - Google Patents

Abstract

The power converter of the present invention, the rectifier for rectifying the AC power source; A converter for boosting / stepping down or controlling the power factor of the DC voltage rectified by the rectifier; A power relay connected between the AC power source and the rectifier and switched by applying a PWM (pulse width modulation) signal; And a controller configured to apply and drive a PWM signal to the power relay, wherein the controller is configured to control the PWM after the power relay is switched on by an ON time signal of the PWM signal. The ON / OFF time of the PWM signal may be determined to maintain the switch ON state when the signal is an OFF time T2 signal.

Description

Power transforming apparatus, method for controlling the same and air conditioner including the power transforming apparatus}

The present invention relates to a power converter, a control method thereof, and an air conditioner including the power converter.

Generally, the compressor of an air conditioner uses a motor as a drive source. These motors are supplied with AC power from the power converter.

Such a power conversion device is generally known to include a rectifier, a power factor controller and an inverter.

First, the commercial voltage of the AC output from the commercial power supply is rectified by the rectifier. The rectified voltage is supplied to the inverter. In this case, the inverter generates AC power for driving the motor by using the voltage output from the rectifier.

In some cases, a DC-DC converter may be provided between the rectifier and the inverter to improve power factor.

In this case, the voltage output from the rectifier or the voltage output from the converter is charged in the DC-link capacitor, and the motor driving signal may be generated by the inverter using the charged voltage.

A power relay is connected between the AC power supply and the rectifier to control the ON / OFF of the power relay by a switching signal applied from the controller.

The relay is a kind of switching element that controls whether the high voltage / current is energized by applying a low voltage / current.

In general, in order to maintain the switch ON state, a predetermined DC power must be continuously supplied to a coil provided therein.

However, if a pulse width modulation (PWM) signal, in which the ON time and the OFF time are repeated, is applied to the power relay, the switch ON state can be maintained. Therefore, the power consumption can be reduced as much as the OFF time.

Korean Patent Publication No. 10-1068007 discloses a relay of an electronic control unit (ECU) of a vehicle for noise reduction.

Disclosed is a relay mounted on an automobile to open and close a circuit, comprising: a relay switch having a contact terminal on and off to open and close a circuit; An exciting coil configured to control the relay switch to an on / off state by controlling the contact terminal by exciting when an exciting voltage is applied to generate a magnetic force; A PWM driving signal unit for outputting a PWM signal; And a relay driving switch configured to receive and switch the PWM signal to transmit an excitation voltage to the excitation coil.

However, the disclosed invention adds a drive switch and an excitation coil, which makes the switching circuit complex and expensive. In addition, since the circuit is intended for noise reduction, it is difficult to apply to an electronic device that needs to maintain a continuous switching on state.

An object of the present invention is to provide a power conversion device and a control method for controlling the power relay by applying a PWM signal to the power relay to reduce the power consumption to maintain a switched on (ON) state.

Power conversion device of the present invention for achieving the above object, the rectifier for rectifying the AC power source; A converter for boosting / stepping down or controlling the power factor of the DC voltage rectified by the rectifier; A power relay connected between the AC power source and the rectifier and switched by applying a PWM (pulse width modulation) signal; And a controller configured to apply and drive a PWM signal to the power relay, wherein the controller is configured to control the PWM after the power relay is switched on by an ON time signal of the PWM signal. The ON / OFF time of the PWM signal may be determined to maintain the switch ON state when the signal is an OFF time T2 signal.

The power relay preferably includes a coil unit to which current is applied, and a switch unit to be turned on when a current of a predetermined value or more flows in the coil unit.

The control unit preferably increases the ON time T1 stepwise when the switch unit is not turned ON in the ON time T1 signal of the PWM signal.

The control unit preferably decreases the OFF time T2 stepwise when the switch unit is turned OFF in the OFF time T2 signal of the PWM signal.

The power converter includes a DC-link capacitor connected in parallel with the converter; And an inverter connected to the DC-link capacitor to output a three-phase alternating current.

Preferably, the apparatus further includes a noise filter connected between the power relay and the rectifier.

The air conditioner of the present invention includes a power conversion device as described above.

The control method of the power converter of the present invention is a control method of a power converter that rectifies and converts AC power to supply three-phase AC power, wherein a PWM (pulse width) is connected to a power relay connected between the AC power and the rectifier. Applying a modulation) signal; After the power relay is switched on by the ON time T1 signal of the PWM signal, the switch ON state is maintained when the PWM signal is an OFF time T2 signal. Determining a frequency of the PWM signal; And operating the power converter by applying the PWM signal determined in the frequency determining step to the power relay.

The determining of the frequency may include the ON time T1 until the switch is turned ON if the power relay is not turned ON in the ON time T1 signal of the PWM signal. It is preferable to include the step of increasing.

The determining of the frequency may include: turning off the power relay in the OFF time T2 signal of the PWM signal until the OFF time T2 is not switched off. It is preferable to further include the step of reducing step.

The PWM signal determined in the determining of the frequency may maintain the switch-on state of the power relay by maintaining the coil unit current of the power relay above a predetermined value.

According to the present invention described above, by applying a PWM signal as the DC power applied to the power relay, the power consumption for switching the relay can be reduced as much as the OFF time.

In addition, the ON state and the OFF time may be set so that the coil current does not fall below a predetermined value while applying a PWM signal to the power relay, thereby maintaining the ON state of the power relay.

In addition, since the control is performed by adjusting the ON / OFF time of the PWM signal without adding an element for switching control to the power relay control circuit, the existing power converter can be used as it is.

1 is a circuit diagram illustrating a power conversion apparatus according to an embodiment of the present invention.
2 is a graph illustrating changes in a PWM signal applied to a power relay, a relay signal, and a coil current.
3 is a flowchart illustrating a control method of a power conversion apparatus according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram illustrating a power conversion apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the power converter includes a rectifier 40 rectifying the AC power supply 10, a converter 50 for boosting / depressing a DC voltage rectified by the rectifier 40 or controlling a power factor, and the AC power supply. It may include a power relay 20 connected between the 10 and the rectifier 40, and a control unit 200 for driving by applying a PWM signal to the power relay 20.

The rectifier 40 converts the input AC power 10 into a DC power and outputs the rectified power to the converter 50. To this end, the rectifier 40 may be configured as a full-wave rectifier circuit using a bridge diode.

The converter 50 may use a DC-DC converter operating as a power factor control (PFC) unit. In addition, such a DC-DC converter may use a boost converter. In some cases, the converter 50 may be a concept including the rectifier 40. Hereinafter, the converter 50 will be described taking the case of using a boost converter as an example.

As described above, the converter 50 may perform a power factor improving operation in the process of boosting and smoothing the voltage signal rectified by the rectifier 40.

The power converter may further include a DC-link capacitor C1 connected in parallel with the converter 50, and an inverter 60 connected to the DC-link capacitor to output a three-phase AC current.

The converter 50 may include an inductor connected to the rectifier 40, a switching device connected to the inductor, and a diode connected between the switching device and the DC-link capacitor C1.

The boost converter 50 is a converter capable of obtaining an output voltage higher than an input voltage. When the switching element is turned on, the diode is cut off, energy is stored in the inductor, and the charge stored in the DC-link capacitor C1 is discharged. Generate an output voltage at the output.

In addition, when the switching element is cut off, the energy stored in the inductor is added to the output terminal when the switching element is turned on.

Here, the switching device may perform a switching operation by a separate PWM signal. That is, the PWM signal transmitted from the converter control unit is connected to a gate (gate) or base end of the switching element, thereby performing a switching operation by this PWM signal.

The converter controller may be configured to include a gate driver for transmitting a PWM signal to a gate terminal of the switching element, and a controller for transmitting a control signal to the gate driver.

Such a switching element may use a power transistor, for example, an insulated gate bipolar mode transistor (IGBT).

The IGBT is a switching device having a structure of a power MOSFET (metal oxide semi-conductor field effect transistor) and a bipolar transistor, and has a small driving power, and is capable of high speed switching, high breakdown voltage, and high current density.

As such, the converter controller may control the turn-on timing of the switching element in the converter 50. Accordingly, the converter control signal for the turn on timing of the switching element can be output.

To this end, the converter controller may receive an input voltage and an input current from the input voltage detector and the input current detector, respectively.

In some cases, the converter 50 and the converter controller may be omitted. That is, the output voltage passing through the rectifier 40 may be charged in the DC-link capacitor C1 or drive the inverter 60 without passing through the converter 50.

The inverter 60 may be driven by a driving signal applied by the inverter controller.

The inverter 60 outputs a three-phase alternating current, and this output current is supplied to the motor 70. Here, the motor 70 may be a compressor motor for driving the air conditioner. Hereinafter, the motor 70 is a compressor motor for driving the air conditioner, the power converter is described as an example of the motor driving device for driving such a compressor motor.

However, the motor 70 is not limited to the compressor motor, and may be used in various applications using a frequency variable AC voltage, for example, an AC motor such as a refrigerator, a washing machine, an electric car, an automobile, a cleaner, and the like.

The motor driving apparatus may further include a DC stage voltage detector and an output current detector. The motor drive device receives AC power from a system, converts power, and supplies the converted three-phase electric power to the motor 70.

The DC voltage detector detects a pulsating voltage of the DC-link capacitor C1. For such power supply detection, a resistive element, OP AMP, or the like can be used. The detected voltage of the DC-link capacitor C1 may be applied to the inverter controller as a discrete signal in the form of a pulse, and an inverter control signal is generated based on the DC voltage of the DC-link capacitor C1. Can be.

The inverter 60 includes a plurality of inverter switching elements, converts the smoothed DC power supply into a three-phase AC power source having a predetermined frequency by turning on / off an operation of the switching element Q1 of the converter 50, It can output to the motor 70.

Specifically, the inverter 60 is a pair of the upper switching element and the lower switching element which is connected in series with each other, respectively, a total of three pairs of the upper and lower switching elements may be connected in parallel to each other.

Like the converter 50, the switching element of the inverter 60 may use a power transistor, for example, an insulated gate bipolar mode transistor (IGBT).

The inverter controller may output an inverter control signal to the inverter 60 to control the switching operation of the inverter 60. The inverter control signal is a switching control signal of the pulse width modulation scheme PWM, and may be generated and output based on an output current flowing through the motor 70 and a DC-link voltage across the DC-link capacitor C1. The output current at this time can be detected from the output current detector, and the DC-link voltage can be detected from the DC-link voltage detector.

The inverter controller may be configured to include a gate driver for transmitting a PWM signal to a gate terminal of a switching element included in the inverter 60, and a controller for transmitting a control signal to the gate driver.

The controller for applying the control signal to the gate driver of the converter 50 and the controller for applying the control signal to the gate driver of the inverter 60 may be the same. That is, one controller may control the gate driver for driving the switching element included in the converter 50 and the gate driver for driving the switching element included in the inverter 60. In addition, the controller 200 controlling the power relay 20 may also control the gate driver driving the switching elements of the converter 50 and the inverter 60.

The output current detector may detect an output current flowing between the inverter 60 and the motor 70. That is, the current flowing through the motor 70 is detected. The output current detector may detect all the output currents of each phase, or may detect the output currents of the two phases using three-phase balance.

The output current detector may be located between the inverter 60 and the motor 70, and a current transformer (CT), a shunt resistor, or the like may be used for current detection.

Meanwhile, a noise filter 30 may be connected between the power relay 20 and the rectifier 40. The noise filter 30 is installed at the output terminal of the switching power supply circuit such as the power relay 20 to prevent the noise of the high frequency band from passing to the output side. That is, the filter is designed to have a low impedance to remove the high frequency noise signal, but the low frequency band signal is transmitted to the rectifier 40.

The noise filter installed at the input terminal of the load connected to the AC power source 10 is also referred to as a 'line filter'.

The power relay 20 may include a coil unit 22 that becomes a magnet when a current flows, and a switch unit 24 that is moved on and off by the coil unit 22.

A DC voltage of 15V may be applied to the coil unit 22 of the power relay 20. When an alternating voltage signal is applied to the coil unit 22, the current flowing through the coil unit 22 gradually increases, and when the voltage exceeds the predetermined value, the switch unit 24 is turned on.

The DC voltage applied to the power relay 20 may be applied as a PWM (pulse width modulation) signal from the controller 200. The PWM signal is a square wave signal in which an ON time T1 signal and an OFF time T2 signal are repeated, and the controller 200 has an ON time T1 at both ends of the power relay 20. It applies a PWM signal with a voltage of 15V.

The ON time T1 and the OFF time T2 of the PWM signal applied from the control unit 200 are not predetermined, but while detecting ON / OFF of the power relay 20. It can be determined and changed while operating the power converter. The control unit 200 controls the ON time T1 and the OFF time T2 of the PWM signal in detail later.

Meanwhile, the rectifier 40, the converter 50, the DC-link capacitor C1, and the inverter 60 eventually output three-phase AC power, and separately from the AC power supply 10, the second rectifier ( 140, the second capacitor C2 and the switched mode power supply 150 may be connected in parallel.

Thus, the rectifier 40 and the DC-link capacitor C1 are referred to as the first rectifier 110 and the first DC-link capacitor C1 and are distinguished from the second rectifier 140 and the second capacitor C2. can do.

The charge capacity of the first DC-link capacitor C1 is much greater than that of the second capacitor C2, so that the first DC-link voltage across the first DC-link capacitor C1 is connected across the second capacitor C2. It can be discharged for much longer on discharge than the second DC-link voltage being applied.

Accordingly, the AC voltage output from the inverter 60 is about 100 to 400V, while the DC voltage output from the SMPS 150 is about 5 to 20V.

The DC voltage output from the SMPS 150 may be supplied to a microcomputer or LED display of a controller driven by low voltage power. In FIG. 1, the load 2 170 may be an LED display receiving DC 15V, and the load 3 180 may be a microcomputer receiving DC 5V.

The control unit 200 is also supplied with a DC voltage output from the SMPS 150, usually 5V DC power may be supplied to the microcomputer of the control unit 200.

As shown in FIG. 1, the DC voltage output from the SMPS 150 may output various DC voltages different from each other. For example, various DC voltages may be output depending on a transformer included in the SMPS 150 as well as 5V or 15V, such as 12V, 18V, or 24V.

In a preferred embodiment of the present invention, the control unit 200 may receive a 15V DC voltage from the output terminal of the SMPS 150 and apply a 15V PWM signal to the power relay 20.

The controller 200 is switched on when the power relay 20 is switched off by the ON time T1 signal of the PWM signal and then the OFF time T2 signal of the PWM signal. Determines the ON / OFF time of the PWM signal to maintain the state.

2 is a graph illustrating changes in a PWM signal applied to a power relay, a relay signal, and a coil current according to the present invention, and FIG. 3 is a flowchart illustrating a control method of the power converter according to an embodiment of the present invention.

When the PWM signal is applied by the controller 200 (S10), while the first ON time T1 signal is applied (S20), the current flowing through the coil unit 22 gradually increases (S30). Then, the switch unit 24 may be turned on at a predetermined time.

The controller 200 determines in real time whether the switch of the power relay 20 is turned on (S40).

If the switch unit 24 is not turned on by the first ON time signal T1, the ON time T1 is increased until it is turned on (S45). That is, the ON time T1 is increased by a predetermined time ΔT to detect whether the switch unit 24 is ON, and if it is not ON, the T1 is increased by ΔT again to switch ON ( ON) is repeated.

Next, after the switch unit 24 is turned on by the first ON time T1 signal, when the OFF time T2 signal of the PWM signal is applied (S50), the coil unit The current flowing in 22 gradually decreases (S60). Then, when the current falls below a predetermined value, the switch section 24 is turned off.

The control unit 200 determines in real time whether the switch of the power relay 20 is OFF (S70).

When the switch section 24 is OFF, the OFF time T2 is reduced by ΔT and set to a new OFF time T2 (S75).

Next, the ON time T1 signal of the PWM signal set above is applied again (S20), the coil unit 22 current is increased (S30), and the switch unit 24 of the power relay 20 is turned on. (ON) (S40).

Next, the OFF time T2 signal of the PWM signal set above is applied again (S50), the current of the coil unit 22 is lowered (S60), and the switch unit 24 of the power relay 20 is turned off. It is determined again whether or not (OFF) (S70).

If the switch unit 24 is turned OFF even at this set OFF time T2, the OFF time T2 is decreased again by ΔT and the PWM signal of the next cycle is repeated.

If the switch unit 24 is not turned off at the set OFF time T2, that is, if the switch unit 24 is kept ON, the set OFF time T2 is set. ) And the frequency of the PWM signal is determined from the ON time T1 determined above (S80).

Subsequently, by applying the PWM signal to the power relay 20 in accordance with the ON / OFF time of the PWM signal thus determined, it is possible to stably control the relay ON / OFF (S90).

Meanwhile, in FIG. 2, the OFF time T2 is started at a time elapsed by ΔT after the relay is turned ON at the first ON time T1.

In the above description, the ON time T1 is increased until the switch is ON, and the OFF time T2 is set by decreasing the switch until the switch is not OFF.

Alternatively, the ON time T1 may be further increased in advance after the switch is turned on so that the current of the coil unit 22 decreases at the OFF time T2 so as not to fall below a predetermined value. Can be. In other words, even if the ON time T1 is further increased in advance so that the OFF time T2 is not reduced, the current of the coil unit 22 does not fall below the predetermined value at the OFF time T2. The switch can be kept ON.

According to the present invention, by applying a PWM signal as the DC power applied to the power relay, the power consumption for switching the relay can be reduced as much as the OFF time.

In addition, the ON state and the OFF time may be set so that the coil current does not fall below a predetermined value while applying a PWM signal to the power relay, thereby maintaining the ON state of the power relay.

In addition, since the control is performed by adjusting the ON / OFF time of the PWM signal without adding an element for switching control to the power relay control circuit, the existing power converter can be used as it is.

Although the preferred embodiment of the present invention has been described above, the scope of the present invention is not limited only to this specific embodiment, and those skilled in the art are appropriately within the scope of the claims of the present invention. Changes will be possible.

10: AC power source 20: power relay
30: first noise filter 40: first rectifier
50: converter 60: inverter
70: three-phase motor 130: second noise filter
140: second rectifier 150: SMPS
170: load 2 180: load 3
200: control unit

Claims (11)

Rectifier for rectifying AC power;
A converter for boosting / stepping down or controlling the power factor of the DC voltage rectified by the rectifier;
A power connected between the AC power source and the rectifier, and a PWM (pulse width modulation) signal is applied and switched, and a coil unit to which a current is applied and a switch unit to be turned on when a current of a predetermined value or more flows in the coil unit. relay; And
A control unit directly connected to the coil part of the power relay to drive the PWM by applying a PWM signal to the power relay,
The controller determines in real time whether the switch unit of the power relay is ON, and after the power relay is switched on by the ON time signal T1 of the PWM signal, the PWM signal The ON / OFF time of the PWM signal is determined so that the coil part current does not fall below a predetermined value when the OFF time T2 signal of the signal is maintained, so that the switch ON state is maintained.
The control unit increases the ON time T1 by a predetermined amount when the switch unit is not ON in the ON time T1 signal of the PWM signal,
The control unit decreases the OFF time T2 stepwise by the predetermined magnitude when the switch unit is OFF in the OFF time T2 signal of the PWM signal,
If the switch unit is not turned OFF at the set OFF time T2, the frequency of the PWM signal is determined from the set OFF time T2 and the ON time T1 at this time.
And applying the PWM signal having the determined frequency to the power relay for driving. delete delete delete The method of claim 1,
A DC-link capacitor connected in parallel with the converter; And
And an inverter connected to the DC-link capacitor to output a three-phase alternating current. The method of claim 5,
And a noise filter connected between the power relay and the rectifier. An air conditioner comprising the power conversion device according to any one of claims 1 to 5. delete delete delete delete

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