JPH09130960A - Rush current interruption circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability and productivity of a circuit, and reduce the area of a printed board, by supplying a voltage to the whole control system by the control voltage of a low voltage breaking means, and controlling the first rush current of a commercial voltage. SOLUTION: A rectification part 22 converts a commercial AC voltage supplied by a commercial power supply switch 21 to a DC voltage. A smoothing capacitor 23 is charged by a DC voltage from the rectification part 22, and outputs a smoothed voltage (driving voltage). A low voltage breaking circuit part 40 extinguishes an excessive rush current supplied from the smoothing capacitor 23, and outputs a control voltage in normal operation. A power supply circuit part 45 supplies a voltage to the whole control system by the control voltage of a low voltage breaking circuit part 40. An NTC(negative temperature characteristics) element 35 prevents the first rush current of a commercial power supply. Thereby reliability and productivity of a circuit are improved, and the area of a printed board can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inrush current cutoff circuit for preventing inrush current generated at the initial stage of power-on and improving system reliability.

[0002]

2. Description of the Related Art Generally, in a BLDC motor control device for driving a washing machine, elements such as a rectifying diode, a capacitor and a switch are damaged or their life is shortened due to an excessive charging current of an instantaneous capacitor when the power is turned on. The problem occurs.

In order to solve this, the instantaneous charging current of the capacitor is lowered by the characteristic that the resistance becomes high at a low temperature in the initial stage of turning on the power, and the resistance loss becomes low by the characteristic that the resistance becomes low after the turning on of the power. Negative temperature characteristic (NTC)
Although the elements were connected and used, it was not possible to prevent the instantaneous charging current (rush current) generated when the power was turned off and then turned on again. However, recently, there is a tendency to provide a circuit for disconnecting the power supply circuit section and the power supply circuit at a low voltage in order to reduce the inrush current when the power is turned on again.

A conventional inrush current cutoff circuit will be described below with reference to the accompanying drawings. Figure 1 is a general washing machine drive BL
FIG. 2 is a block diagram of a DC motor control device, and FIG. 2 is a circuit diagram of a conventional inrush current prevention circuit. A general washing machine driving BLDC motor control device is as shown in FIG. 1, and includes a control circuit unit 16, a filter unit 1, an inrush current prevention unit 2, a rectification unit 3, a smoothing capacitor 4, an inverter unit 5, and a power supply circuit. Divided into part 7 and so on.

When a voltage is applied, the smoothing capacitor 4 is passed through the filter unit 1, the inrush current prevention unit 2 and the rectification unit 3.
To charge. The charging voltage of the smoothing capacitor 4 is converted into an AC voltage having a required voltage and frequency according to the control of the control circuit unit 16 via the inverter unit 5, and is supplied to the electric motor 6.
The control circuit unit 16 detects the rotation speed of the rotor of the electric motor 6 by the sensor unit 11 and transmits the signal to the microcomputer 12, and the microcomputer 12 modulates the phase signal and the PWM signal so as to match the position of the rotor. And the buffer circuit 14 process the signal to generate a gate signal, and the gate driving unit 10 generates and supplies a signal capable of directly driving the gate of the power switching element (triac) of the inverter unit 5. The AC voltage sensing unit 8 senses a power failure and detects the microcomputer 12
The overcurrent protection circuit unit 9 detects an overload signal and transmits it to the microcomputer 12 for overcurrent protection.
The microcomputer 12 controls the overload signal. Power circuit section 7
Is a display for displaying the process status and each status of the washing machine and an interface circuit 1 for the user to select a mode.
A command signal is inputted / outputted to / from the microcomputer 12 by 5 to receive the charging voltage of the smoothing capacitor and supply the voltage to the control circuit section 16.

As shown in FIG. 2, the conventional inrush current cutoff circuit includes a commercial power supply switch 21 for applying and cutting off a commercial power supply, and a rectifying section 22 for converting the commercial power supply switch 21 into a DC voltage. , A smoothing capacitor 2 that charges a voltage by the rectifying unit 22 and outputs a control voltage
3, a resistor 30, a capacitor 29, a diode, and an operational amplifier 31, and a voltage detection unit 28 that receives a control voltage of the smoothing capacitor 23 to generate a detection signal, and a triac drive IC. Drive unit 27 that outputs a gate signal by a temperature sensor, and a temperature sensitive element such as a PTC element (Positive Temperature Coefficient the
rmistor) 25, triac 26 and the like, and includes an inrush current cut-off section 24 which receives and drives the gate signal of the drive section 27.

Next, the operation of the conventional inrush current cutoff circuit thus constructed will be described. First, when commercial power is applied through the commercial power supply switch 21, it changes to a DC voltage via the rectifying unit 22, and this DC voltage becomes a smooth voltage via the smoothing capacitor 23. At this time, the generated current passes through the inrush current cutoff section 24. On the other hand, at the initial stage of voltage application, the PTC element 25 of the inrush current blocking unit 24 having a low resistance characteristic at low temperature operates to charge the smoothing capacitor 23 via the rectifying unit 22. When the charging of the smoothing capacitor 23 is completed, a control voltage is generated in the voltage detecting unit 28, the voltage charged in the capacitor 29 of the voltage detecting unit 28 and the voltage across the resistor 30 are compared by the operational amplifier 31, and the capacitor is compared. If the voltage charged in 29 is large, a detection signal is output to the drive unit 27. When the drive unit 27 receives the detection signal and outputs the gate signal to the triac 26 of the inrush current cutoff unit 24, the current path passing through the PTC element 25 is changed to the current path passing through the triac 26.

That is, when power is applied, a path is formed which passes through the PTC element 25 having a low resistance characteristic at low temperature, and after the power is applied, the generation time of the control voltage generated from the smoothing capacitor 23 and the capacitor 29 of the voltage detector 28. During the charging time, the temperature of the PTC element 25 rises and the resistance thereof rises, while the signal passing through the voltage detection unit 28 and the drive unit 27 conducts the triac 26 of the inrush current cutoff unit 24 and passes through the triac 26. Form a path.

[0009]

The conventional inrush current cutoff circuit described above has a complicated circuit, a high unit price due to the large number of parts, and a large printed circuit board (PCB) area. When the commercial power supply switch is turned off and then re-energized, the smoothing capacitor is not completely discharged, and the remaining voltage causes the triac of the inrush current cutoff unit to operate to prevent excessive current flowing at the initial stage when the power is turned on again. There was a disadvantage that it could not be cut off.

The present invention has been made to solve the above problems, and an object thereof is to improve the reliability of the circuit while sufficiently preventing an inrush current generated at the initial stage of power-on by using an element having an NTC characteristic. An object of the present invention is to provide an inrush current cutoff circuit which improves productivity and reduces the PCB area.

[0011]

In order to achieve the above object, the inrush current cutoff circuit of the present invention converts a commercial power supply switch and a commercial AC power supply supplied by the commercial power supply switch into a DC voltage. A rectifying unit, a smoothing unit that charges a DC voltage by the rectifying unit and outputs a smoothed voltage, and a low voltage cutoff unit that extinguishes an excessive inrush current supplied from the smoothing unit and outputs a control voltage during normal operation. And a power supply circuit section that supplies a voltage to the entire control system by the control voltage of the low-voltage cutoff means, and an element having a negative temperature characteristic that prevents the first inrush current of the commercial power supply. To do.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An inrush current cutoff circuit of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a circuit diagram of an inrush current cutoff circuit of the present invention, FIG. 4 is a graph showing temperature and resistance characteristics of the NTC element of the present invention, and FIG. 5 is a graph showing smoothing capacitor discharge characteristics of the present invention when power is cut off. Is.

As shown in FIG. 3, the inrush current cutoff circuit of the present invention includes a commercial power supply switch 21 for applying and cutting off a commercial power supply, and a rectifying unit for converting the commercial power supply switch 21 into a DC voltage. 22, a smoothing capacitor 23 that outputs a control voltage by charging the voltage from the rectifying unit 22, and first and second transistors 43 and 44,
It consists of LED42, Zener diode 41, etc.,
A low voltage cutoff circuit unit 40 configured to cut off a low voltage generated by the incomplete discharge of the smoothing capacitor 23 to completely discharge the smoothing capacitor 23 and output a driving voltage, and an RCC method. A power supply circuit unit 45 that supplies a drive voltage to a control circuit unit that controls the entire washing machine system by the output control voltage, and an NTC element 35 that controls an initial inrush current by a low resistance characteristic at high temperature and a high resistance characteristic at low temperature. Comprises.

Next, the operation of the inrush current cutoff circuit of the present invention thus constructed will be described. As shown in FIGS. 3 and 4, when commercial power is applied through the commercial power supply switch 21, the voltage is converted into a DC voltage via the rectifying unit 22, and this voltage is smoothed by the smoothing capacitor 23 (driving voltage).
become. The rush current generated at this time passes through the NTC element 35, and the characteristics of the NTC element 35 are shown in FIG.
As described above, since the low temperature 101 and the high temperature resistance 102 control an excessive initial inrush current, the temperature becomes high (101) and the resistance becomes low (102) due to the heat loss generated by the flowing current after the power is turned on, and the operation is performed. Be able to reduce the resistance loss at the time.

However, if the NTC element 35 has a large thermal time constant and a sufficient time for cooling the NTC element 35 is not secured when the power is turned on again, the temperature of the NTC element 35 becomes high and the resistance becomes low, resulting in an excessive rush. Current flows and damages peripheral elements.

By the way, the smoothing voltage (driving voltage) generated from the smoothing capacitor 23 is formed as an applied voltage to the low voltage cutoff circuit section 40, and the driving voltage (smoothing voltage) after the power is turned on is generated by the low voltage cutoff circuit section 40. Zener diode 41
Since it is higher than the Zener voltage of, the current flows through the A path to operate the first transistor 43 and the second transistor 44. At this time, the drive voltage is applied to supply the voltage to the power supply circuit section 45 and the control circuit section.

As shown in FIG. 5, when the power is cut off (T1)
When the driving voltage (smoothing voltage) generated from the smoothing capacitor 23 decreases to an appropriate voltage (zener voltage) or less, the LED (light emitting diode) 42 of the low voltage cutoff circuit unit 40 slowly and spontaneously discharges (103, 104). ),
A current flow to the B path is formed.

When the power is turned on again before the NTC element 35 cools down, the smoothing voltage (driving voltage) is maintained by allowing only the natural discharge of the smoothing capacitor 23 and holding the discharge time. The reduction is compensated by reducing the voltage difference (commercial power supply voltage-smoothing (driving) voltage). At this time, even if an excessive inrush current flows, the inrush current is prevented by compensating for the voltage difference reduction.

[0019]

As described above, in the inrush current cutoff circuit of the present invention, the circuit can be simply constructed and the inrush current can be sufficiently prevented, so that the reliability of the circuit is increased and the unit price is reduced. There are effects of saving, improving productivity and reducing the PCB area.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a general washing machine driving BLDC motor control device.

FIG. 2 is a circuit diagram showing a conventional inrush current cutoff circuit.

FIG. 3 is a circuit diagram of an inrush current cutoff circuit according to the present invention.

FIG. 4 is a graph showing temperature and resistance characteristics of a negative temperature characteristic (NTC) element of the present invention.

FIG. 5 is a graph showing a smoothing capacitor discharge characteristic when the power supply of the present invention is cut off.

[Explanation of symbols]

 21 Commercial Power Supply Switch 22 Rectifier 23 Smoothing Capacitor 40 Low Voltage Cutoff Circuit 35 Negative Temperature Characteristic (NTC) Element 41 Zener Diode 42 Light Emitting Diode 43 First Transistor 44 Second Transistor 45 Power Supply Circuit

Claims (2)

[Claims] 1. A commercial power supply switch, a rectifying unit for converting a commercial AC voltage supplied by the commercial power supply switch into a DC voltage, and a smoothing means for charging the DC voltage by the rectifying unit and outputting a smoothed voltage. And extinguishing the excessive inrush current supplied from the smoothing means,
Low voltage cutoff means for outputting a control voltage, a power supply circuit section for supplying a voltage to the entire control system by the control voltage of the low voltage cutoff means, and a negative temperature characteristic for preventing the first inrush current of the commercial power supply. An inrush current cutoff circuit comprising: an element having the same. 2. The low-voltage cutoff means includes a Zener diode that cuts off or flows a current according to the magnitude of a smoothed voltage with respect to the Zener voltage, first and second transistors operated by the Zener diode, and the Zener. The inrush current cutoff circuit according to claim 1, further comprising a light emitting diode that extends a discharge time with respect to a smoothed voltage charged when the diode is cut off.