Passive drive control circuit for AC current
First Claim
1. A silicon controlled rectifier drive circuit for an in-line thermostat comprising:
- a first silicon controlled rectifier (SCR) having a cathode connected to a first line, an anode connected to a second line, and a gate connected to a source of a first field effect transistor (FET);
a first capacitor having a first end connected to a drain of the first FET and a second end connected to a drain of a second FET;
a second SCR having a cathode connected to the second line, an anode connected to the first line, and a gate connected to a source of a third FET;
a second capacitor having a first end connected to a drain of the third FET and a second end connected to a drain of a fourth FET;
a first diode having an anode connected to the first line and a cathode connected to the source of the first FET; and
a second diode having an anode connected to the second line and a cathode connected to the source of the second FET.
3 Assignments
0 Petitions
Accused Products
Abstract
A circuit that may control current to a load without generating a large amount of electromagnetic interference on main lines of an AC power supply for the load and circuit. Control may be effected with silicon controlled rectifiers (SCRs). For instance, the circuit may implement passive triggering using a capacitor between the anode and the gate of an SCR. By using a sufficiently large capacitor, gate current may be applied during a zero crossing of a waveform of the AC power supply in a passive manner without a need to store energy prior to the zero crossing. The circuit may synchronize SCR triggering with a voltage variation in a clean manner, that is, without generating electromagnetic interference. The circuit may be used with an in-line thermostat. However, the circuit may be used in other ways.
71 Citations
20 Claims
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1. A silicon controlled rectifier drive circuit for an in-line thermostat comprising:
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a first silicon controlled rectifier (SCR) having a cathode connected to a first line, an anode connected to a second line, and a gate connected to a source of a first field effect transistor (FET); a first capacitor having a first end connected to a drain of the first FET and a second end connected to a drain of a second FET; a second SCR having a cathode connected to the second line, an anode connected to the first line, and a gate connected to a source of a third FET; a second capacitor having a first end connected to a drain of the third FET and a second end connected to a drain of a fourth FET; a first diode having an anode connected to the first line and a cathode connected to the source of the first FET; and a second diode having an anode connected to the second line and a cathode connected to the source of the second FET. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A silicon controlled rectifier (SCR) passive drive system comprising:
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a first SCR having a cathode connected to an anode of a first diode, an anode connected to a first terminal of a first switch, and having a gate connected to a first terminal of a second switch and a cathode of the first diode; a second SCR having a cathode connected to an anode of a second diode, the first terminal of the first switch, an anode connected to a first terminal of a third switch and the cathode of the first SCR, and having a gate connected to a first terminal of a fourth switch and a cathode of the second diode; a first capacitor having a first end connected to a second terminal of the first switch and a second end connected to a second terminal of the second switch; and a second capacitor having a first end connected to a second terminal of the third switch and a second end connected to a second terminal of the fourth switch; and wherein each switch comprises a control terminal. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A heating control system comprising:
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a passive drive mechanism; and a trigger signal generator connected to the passive drive mechanism; and wherein; the passive drive mechanism comprises; a first switch having a first terminal, a second terminal connectable to a load, and a control terminal connected to a first output of the trigger signal generator; a capacitor having a first end connected to the first terminal of the first switch and having a second end; a second switch having a first terminal, a second terminal connected to the second end of the capacitor, and a control terminal connected to the trigger signal generator; an SCR having a first terminal connected to the second terminal of the first switch, a second terminal, and a control terminal connected to the first terminal of the second switch; and a diode having a first terminal connected to the second terminal of the SCR, and a second terminal connected to the first terminal of the second switch. - View Dependent Claims (18, 19, 20)
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Specification