JPH0155532B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a relay drive circuit that operates a relay using a transistor.The present invention relates to a relay drive circuit that operates a relay using a transistor.The relay is operated by applying a voltage higher than the operating voltage to the relay coil. By lowering the applied voltage below the operating voltage, the purpose is to suppress the rise in temperature of the relay coil and to allow the relay to operate stably even in the event of a momentary power outage. Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Figure 1, 1 is an AC power supply, 2 is a power transformer, 3 is a diode bridge, 4, 6 and 8
is a capacitor, 5 and 7 are resistors, 9 and 12
1 is a transistor, 10 is a control circuit, and 11 is a relay.

Next, the operation will be explained. An AC power source 1 is reduced in pressure by a power transformer 2 and rectified by a diode bridge 3. Then, it is smoothed by a capacitor 4 and becomes a direct current. Let this voltage be _V1 . Further, a voltage is generated at the emitter of the transistor 9 by the resistor 7 (resistance value is R ₇ ) and capacitor 8 (capacitance is C ₈ ). This voltage is V ₂
shall be. This voltage is supplied to the control circuit 10 and serves as a power source for the control circuit 10. Here, the control circuit 10
When no current is supplied to the base of the transistor 12 from the transistor 12, the collector current of the transistor 12 does not flow, and the capacitor 6 is charged with a voltage of V ₁ by the resistor 5. On the other hand, when a current is supplied from the control circuit 10 to the base of the transistor 12, the transistor 12 is turned on. Here, if the collector-emitter saturation voltage of the transistor 12 is very small and the resistance value of the coil of the relay 11 is R ₁₁ , then in the equilibrium state after the transistor 12 is turned on, the voltage across the relay 11 (this is V ₄
) is V ₄ =R ₁₁ V ₁ /R ₅ +R ₁₁ . In this case, V ₁ is set higher than the operating voltage of the relay 11, and after the transistor 12 is turned on and the relay operating time has elapsed, the voltage V ₄ across the relay 11 becomes higher than the operating voltage of the relay 11, and V ₄ is balanced. Relay 11 when
The resistance value of resistor 5 is set so that the voltage across V ₄ is less than the operating voltage of the relay and more than the holding voltage.
By setting R ₅ and the capacitance C ₆ of the capacitor 6, a voltage higher than the operating voltage is applied to the relay 11 until the relay 11 operates, and after operation, the relay can be maintained at a voltage lower than the operating voltage. However, if the voltage of the AC power supply 1 becomes zero due to a power outage while the control circuit 10 is supplying current to the base of the transistor 12, V ₁ , V ₂ , and V ₃ all become zero voltage. When the voltage of the AC power supply 1 is restored, the relay will not operate unless the transistor 12 is turned on after the voltage of the capacitor 6 becomes higher than the operating voltage of the relay 11 (see Figure 2, however, each waveform is G ). To achieve this, the time constant R ₅ ×C ₆ made up of the resistor 5 and capacitor 6 may be set to be faster than the time constant R ₇ ×C 8 made up of the resistor 7 and capacitor ₈ .

As is clear from the above description, according to the present invention, after the relay operates, the voltage applied to the relay coil can be lowered to the lowest voltage at which the relay can maintain its operating state, so the power consumption of the relay coil is reduced. This reduces the temperature rise of the relay coil, making it economical and improving the reliability of the relay, and the relay operates reliably even during a power outage.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of a relay drive circuit showing one embodiment of the present invention, and FIG. 2 is a signal waveform diagram of the main parts thereof. 4, 6, 8... Capacitor, 5, 7... Resistor,
9, 12...transistor, 10...control circuit,
11...Relay coil.

Claims (1)

[Claims] 1 Connect a series circuit of a first resistor and a second capacitor in parallel to a first capacitor that serves as a DC power supply,
A control circuit is connected in series to a first transistor driven by the charging voltage of the second capacitor,
A relay coil is connected in series to a second transistor driven by the output of this control circuit, a third capacitor is connected in parallel to this series circuit, and a third capacitor is connected in parallel to this series circuit.
is connected to the power supply via a second resistor, and the time constant determined by the first resistor and the second capacitor is changed to the time constant determined by the second resistor and the third capacitor. Relay drive circuit becomes larger.