JPH024973B2 - - Google Patents

Description

Detailed Description of the Invention When controlling a load with a large inrush current, the present invention inserts a certain kind of resistor in series with the load, suppresses the inrush current when the power is turned on, and then connects the resistor with a relay contact, etc. This relates to a relay delay circuit that applies full power to the load by short-circuiting both ends, satisfies product functionality, and prevents breakers and fuses in the home from being cut off by inrush current.

FIG. 1 shows an example of a conventional circuit. Power switch 2
When the power is turned on, the smoothing capacitor 7 on the secondary side starts charging via the power transformer 5. This charging speed is determined by the secondary coil resistance of the power transformer 5, the forward equivalent resistance value of the diode 6, and the capacitor 7.
It is determined by the capacity of Its charging characteristics are shown in FIG.
Immediately after the power switch 2 is turned on in FIG. 1, the inductive load 4 includes a series resistor 3, and as a result, the inrush current is limited. 1 and 2, after the power switch 2 is turned on, charging of the smoothing capacitor 7 begins over time, and as a result, the voltage across the relay coil 8 increases. When the operating voltage of relay coil 8 reaches point a, contact 9 is attracted and series resistor 3 is short-circuited. As a result, the power supply voltage itself is applied to the inductive load 4, and the original functions of the device are satisfied. The delay time from turning on the power switch 2 until the series resistor 3 is short-circuited is T ₁ + contact moving time.

T ₁ can be set by the capacitance of the smoothing capacitor 7. Next, when the power switch 2 is opened, the electric charge in the smoothing capacitor 7 is discharged through the relay coil 8. When the electric charge decreases to point b in FIG. 3, the relay coil 8 reaches the open circuit voltage and its contact 9 is opened. The delay time during this time is T ₂ + contact moving time. T ₂ is determined by the capacitance of the smoothing capacitor 7 and the resistance of the relay coil 8. T ₂ is generally T ₁
The longer it gets, the longer it gets proportionally. The problem with the conventional example is that while the relay coil 8 is energized, the power switch 2 is opened or the power supply 1 is interrupted and T ₂
When the power is applied again during this time, the contacts 9 of the relay coil 8 remain closed, so full power is suddenly applied to the inductive load 4, resulting in an inrush current and The breaker, fuse, etc. will shut it off. The present invention has been made to improve this problem in view of the above problems, and its configuration is to turn on the relay using a full-wave rectified power supply, and control the rise of the full-wave rectified power supply with a capacitor to delay the on-state. If the power supply stops due to a power outage, etc., immediately turn off the relay and
The charge in the capacitor is discharged in a circuit separate from the relay circuit so that it does not affect the off-time of the relay.
This is to prevent inrush current when the power is turned on again after the power is restored, and one embodiment of this will be explained below.

In FIGS. 3 and 4, reference numeral 1 denotes a power source, and when a power switch 2 is turned on, a voltage is generated on the secondary side of the transformer via a power transformer 5. However, at this time, since the capacitor 7 has zero charge, it is in a short-circuited state. Therefore, no voltage is generated in the relay coil 8, and its contacts 9 are in the "open" state. Therefore, since the load current of the inductive load 4 flows through the resistor 3, inrush current can be prevented.

As time passes, the capacitor 7 is charged by the secondary coil resistance of the power transformer 5, and as the charged liquid increases, the equivalent impedance of the capacitor increases, the secondary load current of the low voltage transformer decreases, and the low voltage transformer's secondary load current decreases. Due to regulation, the output voltage of the low-voltage transformer increases, and as a result, the voltage across the relay coil 8 (the full-wave rectified voltage by the full-wave rectifier circuit 10) increases. In FIG. 4, when the operating voltage of the relay coil 8 reaches point a, the relay coil 8 is turned on, its contacts 9 are closed, and the power supply voltage itself is applied to the inductive load 4, thereby satisfying the original function of the device.

The time during which inrush current is prevented after the power switch 2 is turned on is T ₁ + contact moving time. T ₁
can be varied by the capacitance of the capacitor 7.

Next, when the power switch 2 is turned off, the voltage across the relay coil 8 immediately becomes zero.
Its contact 9 opens. Since the charge in the capacitor 7 is prevented from flowing to the relay coil 8 side by the diode 6, it is instantly discharged through the resistor 11 without affecting the relay coil 8.
Therefore, the time from when the power switch 2 is turned off until the contact 9 opens is only the time during which the contact 9 moves.
Therefore, when the power is turned on again, contact 9 remains closed and no inrush current flows.

As described above, according to the present invention, inrush current to the inductive load can be prevented when the power is turned on or turned on again.
This can be achieved with a very simple circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a characteristic diagram thereof, and FIG. 3 is a circuit diagram showing an embodiment of the present invention.
FIG. 4 shows its characteristic diagram. 1...Power source, 2...Power switch, 3...Resistor, 4...Inductive load, 8...Relay coil, 9...
…contact.

Claims (1)

[Claims] 1. A power supply, a power switch, a relay contact, and a load connected in series, a low voltage transformer having a primary side connected between a connection point of the power switch and the relay contact, and a connection point of the power supply and the load; A diode bridge for full-wave rectification connected in parallel to the secondary side of the low voltage transformer, a coil of the relay connected in parallel to the diode bridge, a capacitor and a resistor connected in parallel to the diode bridge, and the capacitor. and a parallel circuit of resistors and a diode connected in series in the forward direction between the diode bridge.