US 5,668,706 A · Load driving circuit

Abstract

This invention relates to a load driving circuit having a fail-safe breaking mechanism for breaking a primary power source when a failure occurs. This invention also relates to a load driving circuit capable of saving electricity in driving an inductive load and reducing a delay in stopping the load. The breaking mechanism for braking the primary power source has no contact. The load driving circuit includes a power supply circuit involving a semiconductor switching element that turns ON and OFF the supply of power to the load. There is arranged a detector for detecting a failure in the semiconductor switching element. When detecting a failure, the detector provides an output signal to activate the breaking mechanism. To drive the inductive load, the power supply circuit may have two power supply sources. In response to a load driving instruction signal, the two power supply sources together apply a high voltage to the load. After a predetermined period, one of the power supply sources is stopped, and during a steady-state operation of the load, the remaining power source applies a low voltage to the load. The load driving instruction signal may be used to provide a pulse width modulated output, which is used to supply power to the load through a transformer. During a steady-state operation of the load, this arrangement supplies a voltage lower than an operation start voltage to the load, to thereby reduce power consumption and a delay in stopping the load.

Claims9

Dependent claims

A load driving circuit for controlling the supply of power to a load by directly turning ON and OFF a switching element, which is connected in series with a power supply circuit of the load, according to a load driving instruction signal, comprising a switching power source having an input end electromagnetically coupled with a commercial primary AC power source through a first transformer and an output end electromagnetically coupled with the power supply circuit of the load through a second transformer, to supply a load driving current from the commercial AC power source to the power supply circuit of the load, a semiconductor switching element serving as the switching element, connected in series with the load in the power supply circuit of the load, to close the power supply circuit in response to the load driving instruction signal so that the current from the switching power source is supplied to the load;

semiconductor switching element status detection means for detecting an ON/OFF status of the semiconductor switching element and generating a low-level output of logical value 0 if the switching element is ON, as well as if the detection means itself is out of order, and a high-level output of logical value 1 if the switching element is OFF;
and power source stoppage decision means for receiving an output of the semiconductor switching element status detection means and the load driving instruction signal, and if the load driving instruction signal is absent and the output of the detection means is at low level, determining that the switching element is abnormal and providing a low-level output to stop the power supplying operation of the switching power source.

A load driving circuit for driving an inductive load that shows hysteresis that an operation stop voltage of the load is lower than an operation start voltage of the load, the load driving circuit rectifying an AC signal prepared from a load driving AC instruction signal and supplying the rectified signal to the load to thereby drive the load, the load driving circuit comprising first output supply means for supplying a first rectified output to the load in response to the load driving instruction signal, the level of the first rectified output being higher than the operation stop voltage and lower than the operation start voltage;

and second output supply means for supplying a second rectified output only for a predetermined period in response to the-load driving instruction signal, the second rectified output overlapping the first rectified output and being supplied to the load, the level of the overlapping first and second rectified outputs being higher than the operation start voltage of the load.

Dependencies are inferred from the claim text.

Load driving circuit

Life of this patent

Load driving circuit

Life of this patent

Abstract

Claims9