JP3969880B2 - Control device with voltage doubler booster circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device including a voltage doubler booster circuit used in an air conditioner using a compressor in which, for example, an inverter controls the rotational speed of an electric motor.
[0002]
[Prior art]
In recent years, this type of air conditioner is configured to perform efficient operation throughout the year by variably controlling the rotation speed of an electric motor for driving a compressor using an inverter. In addition, in order to eliminate distortion of the input current, an electric motor drive device using a high power factor power converter that suppresses harmonics of the input current has been developed as disclosed in, for example, Japanese Patent Publication No. 7-89743. It is coming.
[0003]
[Problems to be solved by the invention]
In such an electric motor drive device for an air conditioner, an AC 200V power source is used. For this reason, a double voltage booster circuit is used for use with a normal household AC100V power supply. This voltage doubler booster circuit is configured by connecting two capacitors in series on the output side of a full-wave rectifier circuit connected to an AC 100V power supply, but the charging voltage to each capacitor varies depending on the individual capacitor capacity. Therefore, there is a difference between the positive and negative of the input current of the voltage doubler booster circuit.
[0004]
This is shown in FIG. That is, if there is an individual difference in the capacitance of each capacitor as described above, the input current in the period P2 to P3 is greater than the input current (indicated by A1) in the period P1 to P2 in one cycle P1 to P3 in FIG. (Indicated by A2, A2 is indicated by a broken line in P1 to P2) may be small.
[0005]
In such a situation, there are problems that even harmonics increase and DC component leakage occurs on the input side.
[0006]
The present invention has been made to solve the conventional technical problem, and provides a control device including a voltage doubler booster circuit capable of preventing the occurrence of DC component leakage on the input side with a simple configuration. Is.
[0007]
[Means for Solving the Problems]
The control device of the present invention includes a full voltage rectifier circuit that rectifies AC power, and a voltage doubler booster circuit that includes first and second capacitors connected to the output side of the full wave rectifier circuit. A switching element that substantially short-circuits the output of the full-wave rectifier circuit, a regulating element that prevents electric charge accumulated in each capacitor from being discharged through the switching element in the event of this short-circuit, and conduction of the switching element The control means detects the input current of the full-wave rectifier circuit so that the magnitude of the input current in the positive period is equal to the magnitude of the input current in the negative period. And adjusting the ON duty of the switch element.
[0008]
According to the present invention, in a control device comprising a full-wave rectifier circuit that rectifies AC power, and a voltage doubler booster circuit that includes first and second capacitors connected to the output side of the full-wave rectifier circuit. The switch element that substantially short-circuits the output of the full-wave rectifier circuit, the regulation element that prevents the electric charge accumulated in each capacitor from discharging through the switch element, and the conduction of the switch element are controlled The control means detects the input current of the full-wave rectifier circuit and switches so that the magnitude of the input current in the positive period is equal to the magnitude of the input current in the negative period. since so as to adjust the oN duty of the elements, it is possible to equalize the positive and negative magnitude of the input current by adjusting the switching signal of the switch elements, very inexpensive and easily input side straight In which it is possible to prevent the minute leakage.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a block diagram of an electric circuit of an air conditioner according to an embodiment to which the present invention is applied. In this figure, 1 is an AC (AC) 100V power supply (AC power), 2 is a full-wave rectifier (full-wave rectifier circuit) composed of diodes 2A, 2B, 2C, and 2D, and 3 is between the AC power supply 1 and the full-wave rectifier 2. Are connected to the output side of the full-wave rectifier 2, diodes 6 and 7 are capacitors connected downstream of the diodes 4 and 5, and 8 are capacitors 6 and 7 A smoothing capacitor connected to the subsequent stage, 9 is a switch element made of IGBT (or MOSFET or transistor) connected between the output side of the full-wave rectifier 2 and the diodes 4 and 5, and 11 is a general-purpose component constituting control means. A microcomputer, 13 is an inverter, and 14 is a DC brushless motor for driving a compressor.
[0010]
The capacitors 6 and 7 are connected to each other in series, and the capacitors 6 and 7 are connected to the connection point between the diodes 2B and 2D of the full-wave rectifier 2, thereby constituting a voltage doubler booster circuit. The input voltage from the AC power supply 1 is full-wave rectified by the full-wave rectifier 2 through the reactor 3 and converted into a rectified voltage. This rectified voltage is applied to the capacitors 6 and 7 via the diodes 4 and 5 to generate a boosted DC voltage.
[0011]
This DC voltage is smoothed by the capacitor 8 and supplied to the inverter 13 to become electric power for driving the electric motor 14. Further, in this case, the switching element 9 made of IGBT is provided in parallel with the diodes 4 and 5 and the capacitors 6 and 7, and substantially short-circuits the output of the full-wave rectifier 2 in the ON state.
[0012]
The diodes 4 and 5 prevent the electric charge accumulated in the capacitors 6, 7 and 8 from being discharged through the switch element 9 when the switch element 9 is turned on.
[0013]
Reference numeral 16 denotes a zero-cross detection circuit that generates a zero-cross signal from the input power of the previous stage of the reactor 3 and monitors an input current waveform. The output of the zero-cross detection circuit 16 is input to the PAM waveform generation circuit 17. The PAM waveform generation circuit 17 generates a switching drive signal whose ON duty changes under the control of the microcomputer 11.
[0014]
The output of the PAM waveform generation circuit 17 is connected to the gate of the switch element 9 through the gate block circuit 18, and the switch element 9 is ON / OFF driven by the switching drive signal.
[0015]
Reference numeral 19 denotes an overvoltage detection circuit connected to the subsequent stage of the diode 4, and 21 denotes an overcurrent detection circuit connected to the switch element 9. These outputs are input to the OR gate 22, and the output of the OR gate 22 is the gate. It is input to the block circuit 18.
[0016]
When an overvoltage is applied to the switch element 9 or an overcurrent flows, the gate block circuit 18 blocks the switching drive signal to the switch element 9 to protect the switch element 9.
[0017]
Next, the actual control operation of the microcomputer 11 will be described. The microcomputer 11 monitors the input current based on the output of the zero cross detection circuit 16. When the input current A2 in the negative period P2 to P3 is smaller than the input current A1 in the positive period P1 to P2 in one cycle P1 to P3 as shown in FIG. The ON duty of the switch element 9 is changed by controlling the switching drive signal applied to the switch element 9 so that the input current A3 in the positive period of P3 to P4 in the period matches the magnitude of A2.
[0018]
Thereafter, by repeating this, the microcomputer 11 equalizes the positive and negative of the input current, so that it is possible to prevent leakage of the DC component on the input side. In particular, since the positive and negative of the input current are made equal by adjusting the switching drive signal of the switch element 9, the circuit configuration becomes extremely inexpensive and easy.
[0019]
In the embodiment, the present invention is applied to an inverter-driven air conditioner. However, the present invention is not limited thereto, and the present invention is effective for various control devices using a voltage doubler booster circuit.
[0020]
【The invention's effect】
As described above in detail, according to the present invention, there is provided a voltage doubler booster circuit comprising a full-wave rectifier circuit for rectifying AC power and first and second capacitors connected to the output side of the full-wave rectifier circuit. A switch element that substantially short-circuits the output of the full-wave rectifier circuit, a regulating element that prevents electric charge accumulated in each capacitor from being discharged via the switch element, and a switch Control means for controlling the conduction of the element, the control means detects the input current of the full-wave rectifier circuit, the magnitude of the input current in the positive period and the magnitude of the input current in the negative period since so as to adjust the oN duty of the switching element to be equal, it is possible to equalize the positive and negative magnitude of the input current by adjusting the switching signal of the switching element, and very inexpensive In which it is possible to prevent the input side of the DC component leaked to easily.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electric circuit of a control device for an air conditioner as an embodiment to which the present invention is applied.
FIG. 2 is a diagram showing an input current waveform according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Full wave rectifier 3 Reactor 4, 5 Diode 6, 7 Capacitor 6 Switch element 11 Microcomputer 16 Zero cross detection circuit 17 PAM waveform generation circuit 13 Inverter 14 Electric motor

Claims (1)

In a control device comprising a full-wave rectifier circuit for rectifying AC power and a voltage doubler booster circuit composed of first and second capacitors connected to the output side of the full-wave rectifier circuit,
A switching element that substantially short-circuits the output of the full-wave rectifier circuit; a regulating element that prevents electric charges accumulated in the capacitors during the short-circuit from being discharged through the switching element; and Control means for controlling conduction, the control means detects an input current of the full-wave rectifier circuit, and the magnitude of the input current in the positive period is equal to the magnitude of the input current in the negative period controller having a voltage doubler circuit, characterized in that adjusting the ON-duty of the switching element so as.

Images