Dual Voltage Relay Driver Circuit for Low-Voltage Unlatching
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Solution Overview
Problem
Latching relays in climate control systems often fail to unlatch during low-voltage conditions, as the available voltage is insufficient to reverse the latching process, leading to operational issues.
Innovation Solution
A dual voltage level circuit for driving latching relays, where a lower voltage is used to unlatch the relay compared to the voltage required for latching, utilizing relay drivers with switches and transistors to selectively connect the coil to different current paths for latching and unlatching, ensuring the relay can be unlatched even under low voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage is used to latch the relay, then the relay can be reliably latched, but the relay cannot be unlatched under low voltage conditions
Solution Approach 1:
The patent applies inversion by using opposite polarity voltages to control relay state transitions. A positive voltage (+V) is applied to latch the relay, while a negative voltage (-V) is applied to unlatch it. This bidirectional voltage approach allows the relay to be reliably latched during normal operation while enabling unlatching even when voltage magnitude is reduced, as the polarity reversal provides a distinct control mechanism independent of voltage level.
Solution Approach 2:
The patent changes the voltage parameter from unidirectional to bidirectional by introducing polarity reversal. The control circuit switches between positive and negative voltage polarities to control the coil current direction, thereby controlling the magnetic field polarity. This parameter change enables the relay to distinguish between latching and unlatching commands through polarity rather than just voltage magnitude, solving the contradiction between reliable latching and low-voltage unlatching capability.
2Reliability
If a high current is applied to the coil for latching, then the relay switches reliably, but excessive energy is consumed during operation
Solution Approach 1:
The patent employs periodic pulsed voltage application rather than continuous voltage to control the relay. The control circuit applies voltage pulses of appropriate duration and polarity to achieve reliable state transitions. This periodic action reduces average power consumption while maintaining reliable switching, as the coil is energized only during the pulse duration rather than continuously.
Solution Approach 2:
The patent optimizes the voltage and current parameters by using polarity-reversed pulses with controlled duration. The circuit applies minimal necessary current for the required time to achieve reliable switching, then immediately reverses polarity for unlatching. This parameter optimization reduces energy consumption while maintaining reliable operation by avoiding excessive or prolonged current application.
3Stability of the object's composition
If the relay is designed to latch with high voltage, then stable operation is achieved, but the relay becomes stuck in latched state during voltage fluctuations
Solution Approach 1:
The patent uses polarity reversal as the primary control mechanism rather than relying solely on voltage magnitude. By applying a negative voltage pulse to unlatch the relay, the system can reliably reverse the magnetic field and release the latch even when the available voltage is reduced during fluctuations. The polarity distinction provides a robust control signal that is less sensitive to voltage magnitude variations.
Solution Approach 2:
The control circuit is designed to proactively apply the unlatching voltage pulse when voltage fluctuations are detected or when normal operation is no longer needed. This preliminary action prevents the relay from remaining stuck in the latched state during voltage drops, as the control system actively manages the transition rather than passively relying on voltage conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable operation of latching relays by allowing unlatching at lower voltage levels than latching, preventing relays from becoming stuck in the latched state due to low voltage, which is beneficial for battery-powered devices and other applications where voltage fluctuations occur.
Implementation Method 1
A first relay driver has first and second switches selectively switchable to connect a first end of the coil with (a) a first current path between the first switch and a relay voltage input or (b) a second current path between the second switch and a ground connection
Data Source
AI summary
A driving circuit includes a relay driver for selectively connecting a relay coil with (a) a first current path between the relay driver and a relay voltage input or (b) a second current path between the relay driver and a ground connection. Another relay driver selectively connects the coil with (a) a third current path between the other relay driver and the relay voltage input or (b) a fourth current path between the other relay driver and the ground connection. The relay drivers may connect the coil between the second and third current paths for latching the relay, and between the first and fourth current paths for unlatching the relay. The driving circuit applies signals of opposite polarity and different magnitudes through the coil to latch and unlatch the relay. The signal for unlatching can be of lower voltage than the signal for latching the relay.