ELECTRONIC INTERFACE FOR POWER STEALING CIRCUIT
First Claim
1. An interface circuit for converting to high AC voltage use, a power-stealing circuit designed for switching a relatively low AC voltage for a load and for providing low voltage DC power for use by a separate load, said power-stealing circuit comprising:
- a) a first semiconductor switch of the type having a control terminal, said first semiconductor switch having first and second power terminals for connection in series with the load and conducting between the first and second power terminals responsive to a conduction signal at the control terminal;
b) a control circuit having first and second power terminals for connection across the first semiconductor switch power terminals, said control circuit having a switch terminal for receiving an on/off signal having first and second levels, and a switch control terminal providing the conduction signal to the first semiconductor switch for a period of time between successive zero crossings by the AC voltage responsive to the first level of the on/off signal, and having a low DC terminal providing low voltage DC power; and
c) a storage element storing the power available across the first semiconductor switch while the conduction signal is absent and while the first level of the on/off signal is present, and providing the stored power to the control circuit, wherein said interface circuit comprises a variable impedance element connected between the first semiconductor switch first power terminal and the control circuit first power terminal, said variable impedance element functioning to clip the voltage at the control circuit first power terminal.
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0 Petitions
Accused Products
Abstract
An interface circuit cooperates with an existing power-stealing circuit designed for use with low voltage AC power. The existing power-stealing circuit provides low voltage DC power for operating an auxiliary circuit and for switching power for an AC load. The existing power-stealing circuit has a semiconductor switch for switching power to the AC load, and a control circuit that when the load receives power, shuts off the semiconductor switch near the zero crossing points in the power voltage waveform and converts the voltage to DC for use by the auxiliary circuit. The interface circuit is interposed between the semiconductor switch and the control circuit of the power-stealing circuit, and reduces the high voltage AC power to the lower voltage for which the power-stealing circuit was designed. In a preferred embodiment, a power field effect transistor drops the voltage applied to the control circuit to a level compatible with the control circuit while the semiconductor switch is open and the load unpowered.
34 Citations
11 Claims
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1. An interface circuit for converting to high AC voltage use, a power-stealing circuit designed for switching a relatively low AC voltage for a load and for providing low voltage DC power for use by a separate load, said power-stealing circuit comprising:
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a) a first semiconductor switch of the type having a control terminal, said first semiconductor switch having first and second power terminals for connection in series with the load and conducting between the first and second power terminals responsive to a conduction signal at the control terminal;
b) a control circuit having first and second power terminals for connection across the first semiconductor switch power terminals, said control circuit having a switch terminal for receiving an on/off signal having first and second levels, and a switch control terminal providing the conduction signal to the first semiconductor switch for a period of time between successive zero crossings by the AC voltage responsive to the first level of the on/off signal, and having a low DC terminal providing low voltage DC power; and
c) a storage element storing the power available across the first semiconductor switch while the conduction signal is absent and while the first level of the on/off signal is present, and providing the stored power to the control circuit, wherein said interface circuit comprises a variable impedance element connected between the first semiconductor switch first power terminal and the control circuit first power terminal, said variable impedance element functioning to clip the voltage at the control circuit first power terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification