Series inverter for capacitor charging
AssigneeCandela Corporation
InventorGeorge L. Bees
Life of this patent
Estimating the term…
Abstract
A series inverter, high voltage capacitor charging circuit includes current sensors for sensing the current through each SCR in the circuit. The sensed current is used to vary the gating frequency of the SCRs and to preclude firing of an SCR until the other is in a stable off condition. The gating of each SCR is delayed by an amount of time determined by a control capacitor charging circuit. That charging circuit is inhibited as long as one of the SCRs is conducting and once the load voltage has reached a predetermined level. The time constant of that charging circuit can be changed as the desired level is approached.
Claims14
A laser firing circuit having a series inverter, high voltage capacitor charging circuit comprising electronic switches connected in a push pull configuration between a dc supply and a reactance load characterized by:
- means for sensing an electrical parameter of each electronic switch circuit the timing of which provides a direct indication of the resonant frequency of the circuit and of the timing of current flow through the electronic switches;
- gate control means responsive to the sensed electrical parameters for gating each electronic switch only after the other has settled to a stable off condition and for varying the gating frequency to closely follow the resonant frequency of the charging circuit as that frequency varies with the charge on the capacitor;
- and
- means for disabling the gate control means when the charged capacitor voltage reaches a predetermined level.
A series inverter load capacitor charging circuit comprising electronic switches connected in a push pull configuration between opposite junctions of a dc supply and a capacitor charging transformer in a common load circuit characterized by:
- a diode in parallel with each electronic switch to form a parallel circuit;
- individual inductors in series with responsive ones of the switch/diode parallel circuits between the common load circuit and opposite power supply junctions;
- means for sensing electric currents which pass through the common load circuit;
- gate control means responsive to the sensed electric currents for directly gating each electronic switch "on" a predetermined time after current flow through the other switch has dropped to zero, that predetermined time being about, but greater than, the time required for the other switch to settle to a stable off condition;
- and
- means for disabling the gate control means when the charged load capacitor voltage reaches a predetermined level.
In a laser firing circuit, a high voltage capacitor charging circuit comprising:
- a dc power source;
- a series inverter including silicon controlled rectifiers in series across the dc power source and an output transformer in a common load circuit connected between the silicon controlled rectifiers;
- means for sensing electric currents which pass through the common load circuit;
- gate control means responsive to the sensed currents for alternately gating the silicon controlled rectifiers, each rectifier being directly gated on a predetermined time after current flow through the other rectifier has dropped to zero, that predetermined time being about, but greater than, the time required for the other rectifier to settle to a stable off condition;
- means for increasing said predetermined time as the charged capacitor voltage approaches a predetermined level;
- and
- means for disabling the gate control means when the charged capacitor voltage reaches said predetermined level.
Dependencies are inferred from the claim text.