JPH033325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a relay drive device that drives a relay at around zero volts of an AC power source.

Conventional configurations and their problems In general, in relays with mechanical contacts, the power loss due to the contact resistance of the relay contacts is sufficiently smaller than the power loss due to the on-resistance of the semiconductor switching element, so it is difficult to pass large load currents. It also has the advantage of not requiring the use of a heat sink. However, arc discharge occurs between the contacts when the load current is switched on and off, resulting in significant deterioration of the contacts, making it difficult to switch on and off frequently and having poor reliability.

OBJECTS OF THE INVENTION An object of the present invention is to provide a relay drive device that can open and close relay contacts near zero volts of an AC power source in order to solve the above-mentioned problems.

Structure of the Invention The relay drive device of the present invention includes a power synchronization signal generation means for generating a signal synchronized with zero volts of an AC power supply, an opening/closing phase detection means for detecting the open/close phase of the relay contact, and the power synchronization signal generation means. time difference measuring means for inputting the power synchronization signal from the switch and the open/close signal from the open/close phase detecting means and measuring the time difference therebetween; and drive phase determining means for determining the drive phase of the relay contact based on the measurement signal from the time difference measuring means. and a relay drive means for driving the relay by an output signal from the control section, and the relay contacts are opened and closed near zero volts of the AC power source.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which 1 is an AC power supply, 2 is a DC power supply, 3 is a load, and 4 is a load 3.
5 is a power synchronization signal generating means for generating a signal synchronized with zero volts of the AC power supply 1, 6 is an open/close phase detecting means for detecting the open/close phase of the relay contact 4, and 7 is a control consisting of a microcomputer. Sections and 8 are relay driving means for driving the relays in response to output signals from the control section 7. The power synchronization signal generating means 5 is composed of a diode bridge 9, resistors 10 and 11, and a photocoupler 12, and the opening/closing phase detection means 6 is composed of a diode bridge 13, resistors 14 and 15, and a photocoupler 1.
The relay driving means 8 is composed of a relay coil 17, a transistor 18, a surge absorbing diode 19, and a resistor 20. The control unit 7 is composed of a CPU, RM, RAM, input/output ports, etc., and inputs the power synchronization signal from the power synchronization signal generation means 5 and the open/close signal from the open/close phase detection means 6 into the RM, and calculates the time difference between them. and drive phase determining means for determining the drive phase of the relay based on the measurement signal from the time difference measurement means. The flowchart, an example of which is shown in Figure 2, is shown in Figure 3.
The operation is explained in FIGS.

Next, the operation of the relay drive device configured as described above will be explained. As shown in the flowchart in Figure 2, when closing relay contact 4, when the falling edge of the power synchronization signal is input, measurement of time (phase) to is started (step 1), and in step 2 the measurement of the time (phase) to is started (step 1). To outputs a relay drive signal with a phase that matches the time ton stored in RAM. When the relay contact is closed, the falling edge of the open/close signal is input in step 3, and the measurement of time to is stopped. Compare this time to and the period T ₁ of the power synchronization signal, and only if they are not equal, calculate the difference between the time to and the period T ₁ to the above time.
ton and take that value as the new time ton
Store in RAM (step 4). That is, as shown in FIG. 3, when the relay drive signal b ₀ is output at a phase in which time ton has elapsed since the fall of the power supply synchronization signal a ₀ , the AC power supply voltage C ₀ applied to the load 3
When -d ₀ is near zero volts, the relay contact 4 is closed, and the time until the opening/closing signal e ₀ falls is equal to the period T ₁ of the power synchronization signal a ₀ . Time _t2 is the operating time of the relay and varies depending on the individual relay.

On the other hand, if the relay contact 4 is closed when the AC power supply is not near zero volts because the time ton is short, the power synchronization signal a ₀ , the relay drive signal b ₁ , and the load 3
The AC power supply voltage c ₁ − d ₁ applied to the switching signal e ₁
The relationship between time _t3 and period is shown in Figure 4.
The difference _t4 from _T1 is added to the time ton and stored in the RAM, returning to the state shown in FIG. When opening relay contact 4, as shown in the flowchart in Figure 2, when the rising edge of the power synchronization signal is input, measurement of time to is started (step 5), and the time t _p is
The output of the relay drive signal is stopped at a phase that matches the time toff stored in the RAM (step 6).
Next, when the rising edge of the opening/closing signal is input, measurement at time _t1 is started (step 7). When the rising edge of the opening/closing signal is input, the measurement at time t ₁ is stopped and the operation returns to step 7, and the falling edge of the opening/closing signal is not input, and time t ₁ changes to time T ₂ (Fig. 4, AC When the opening/closing signal in the vicinity of zero volts of the power supply exceeds the high time, the measurement at time t ₀ and time t ₁ is stopped and the process proceeds to step 9. This time in step 9
Compare the absolute value of the difference between t ₀ and time t 1 | t ₀ − _{t 1 |} with the period T ₃ that is twice the power synchronization signal, and only if they are not equal, the period T ₃ and the value | t ₀ − t ₁ | Add the difference to the time t _pff and store it in RAM. Figure 5 shows the power synchronization signal _a1 , relay drive signal _b2 , AC power supply voltage _c2 - _d2 applied to load 3, and open/close signal when the relay contact is open near zero volts of the AC power supply. Figure 6 shows the relationship between e ₂ and power synchronization signal a ₁ when the relay contact is opened at a phase that is not near zero volts of the AC power supply.
, the relationship between the relay drive signal _b3 , the AC power supply voltage _c3 - _d3 applied to the load 3, and the opening/closing signal _e3 . In the case of FIG. 6, the time _t7 is added to the time _tpff and stored in the RAM, and the state returns to the state of FIG. 5 next time.

Time t5 in FIGS. 5 and ₆ is the return time of the relay, and the value differs depending on each relay.

In this way, the relay drive device in the embodiment is
By repeating the operation shown in the flowchart in Figure 2, the relay drive phase (time ton and time toff) is
Determine so that the relay contacts open and close near zero volts of the AC power supply. Therefore, the voltage between the relay contacts when they open and close becomes almost zero, and the occurrence of arc discharge can be significantly reduced.

Effects of the Invention As is clear from the above description, according to the relay drive device of the present invention, since the relay contacts are opened and closed near zero volts of the AC power supply, arc discharge that occurs between the contacts when the load current is switched on and off is prevented. suppressed,
This has great industrial value, as the lifespan of the contacts can be significantly improved, variations in the lifespan can be reduced, reliability has been improved, and power duty control using relays has become possible.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a relay driving device showing one embodiment of the present invention, FIG. 2 is a flowchart of the operation of the same device, and FIGS. 3 to 6 are explanatory diagrams of the operation of the same device. DESCRIPTION OF SYMBOLS 1...AC power supply, 2...DC power supply, 3...Load, 4...Relay contact, 5...Power synchronization signal generation means, 6...Opening/closing phase detection means, 7...Control unit,
8... Relay driving means.

Claims (1)

[Claims] 1. A power synchronization signal generation means for generating a signal synchronized with zero volts of the AC power supply, an open/close phase detection means for detecting the open/close phase of the relay contact, and a power synchronization signal from the power supply synchronization signal generation means and the open/close phase detection. a control section having a time difference measuring means for inputting open/close signals from the means and measuring a time difference therebetween; and a drive phase determining means for determining a drive phase of the relay contact based on the measurement signal from the time difference measuring means; and a relay drive means for opening and closing the relay contacts at around zero volts of an AC power source according to an output signal from the section.