A TOP COURT has rejected key elements of one of Philips Lighting’s patents on LEDs as ‘unpatentable’.
The United States Court of Appeals for the Federal Circuit declared that swopping the order of two basic circuit elements in an LED driver circuit could be discovered by ‘a person of skill’ and therefore was not novel. It upheld an earlier ruling of a lower court and found against Philips Lighting, which had appealed the earlier decision.
US luminaire maker WAC Lighting challenged US Patent Number 6013988, which describes a circuit arrangement for a signalling light, such as a traffic light, that uses LEDs rather than an incandescent lamp. Typically, a signalling light in a traffic light is regulated by a control unit having a solid-state relay. The control unit conducts status tests of the relay and of the signalling light at the connection terminals to make sure that multiple traffic lights – such as red and green – are not illuminated at the same time.
Using LEDs causes problems for the status tests because solid-state relays conduct current even in the ‘off’ state, resulting in leakage current. For LEDs, leakage current from a solid-state relay results in a relatively high voltage at the connection terminals and produces incorrect status test results.
The solution described in the patent is the addition of a self-regulating current-conducting network, which allows for the retrofitting of LEDs in existing traffic light systems without producing status-test problems. ]
The argument turned on the sequence of the addition of this network. In essence, the Federal Circuit confirmed that Philips Lighting was not entitled to patent what ultimately amounted to swapping the order of two basic circuit elements in an LED driver circuit.
Although Patent 6013988 has been cited in previous patent disputes, this was the first time a challenger was successful in defeating it.
- Read the judgement in full HERE.
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