CONTROL LOGIC FOR SWITCHING RECTIFIER SYSTEMS

• US 3,764,885 A
• Filed: 08/18/1971
• Issued: 10/09/1973
• Est. Priority Date: 08/19/1970
• Status: Expired due to Term

• Current Assignee: Arne Buxbaum, Horst Kahlen
• Original Assignee: Arne Buxbaum, Horst Kahlen
• Inventors: Buxbaum, Arne, Kahlen, Horst
• Primary Examiner(s): Beha, Jr., William H.
• Application Number:
  US05/172,720
• Time in Patent Office: 783 Days
• Field of Search: 321/13,27R 318/257
• US Class Current: 363/54
• CPC Class Codes: H02M 7/1623 with control circuit
• CPC Class Codes: H02M 7/757 using semiconductor devices only
• CPC Class Codes: H02P 7/293 using phase control H02P7/295 takes precedence

Abstract

In a switching logic for a current controller of the type employing two groups of controlled rectifiers connected in parallel opposition and each arranged for delivering current in a respectively different direction, the logic functions are performed by operational amplifiers or comparators operating as switching elements.

Claims

1. For use in controlling current converters composed of two groups of controlled rectifiers arranged in a circuit which is free of circulating current and includes current means for producing output signals dependent upon the desired value and the actual value of the current in the circuit, a switching logic having inputs coupled to the output of said current means and an output coupled to the two groups of controlled rectifiers for selectively blocking or releasing triggering pulses to the two converter groups in response to the signals applied to said logic inputs and which are dependent on the desired value and the actual value of the current in the circuit, the improvement wherein said logic comprises:

a plurality of operational amplifiers connected to operate as switches for processing the input signals to said logic; and

a first switching transistor connected between the output and the input of a first of said operational amplifiers so as to form a regenerative feedback branch of said first amplifier for causing said amplifier to operate as a storage element when said switching transistor is conductive and as a signal comparator when said switching transistor is nonconductive so as to enable the polarity of the desired current value to be determined.

2. Switching logic as defined in claim 1 wherein there is a second operational amplifier coupled to the output of said current means for receiving a signal representative of the actual current value and for producing an output indicating whether the actual current value is above or below a predetermined current level, the output of said second amplifier being connected for controlling the conductive state of said switching transistor.

3. Switching logic as defined in claim 2 wherein said first amplifier is arranged to be switched from storage to comparator operation when the actual current value falls below a selected current limit which lies below the limit of continuous current.

4. Switching logic as defined in claim 1 further comprising means for determining the conduction time of each rectifier of a group, said means being connected to said switching transistor for controlling its state.

5. Switching logic as defined in claim 4 wherein said means control said transistor to switch said first amplifier from its storage to its comparator operation when the rectifier conduction time falls below a settable time which is shorter than the minimum conduction time for causing a group of rectifiers to produce a continuous current.

6. Switching logic as defined in claim 1 wherein said switching transistor is a field effect transistor.

7. Switching logic as defined in claim 1 wherein there are third and fourth operational amplifiers each having a direct input, an inverting input and an output connected for controlling the delivery of conduction control pulses to a respective group of controlled rectifiers, the output of said first amplifier is connected to the direct input of said third amplifier and to the inverting input of said fourth amplifier, and the other input of each of said third and fourth amplifiers is connected to ground, whereby pulses are delivered to only a respective one of the rectifier groups depending on the polarity of the output of said first amplifier.

8. Switching logic as defined in claim 7 further comprising:

a diode connected in series with the direct input of said third amplifier, a diode connected in series with the inverting input of said fourth amplifier, and a pair of RC arrangements each connected to a respective diode, said diodes and RC members serving to provide a time delay in the release of the triggering pulses to the converter group controlled by each of said third and fourth amplifiers.

9. Switching logic as defined in claim 8 further comprising means connected for switching said first amplifier to its storage function during each such time delay.

10. Switching logic as defined in claim 1 further comprising:

a further feedback connected operational amplifier for producing a signal representing the desired current values and having a predetermined polarity and delivering such signal to a current controller;

a second switching transistor and an input resistor connected in series with the inverting input of said further amplifier;

a second input resistor connected to the direct input of said further amplifier;

a third switching transistor connected between the direct input of said further amplifier and ground; and

means connected for placing both of said second and third transistors in the same state, which state is determined by the polarity of the output signal produced by said first amplifier and occurs in such a manner that said further amplifier operates as a noninverting unity gain amplifier when said third and fourth switching transistors are nonconductive and as an inverting unity gain amplifier when said third and fourth switching transistors are conductive.

11. Switching logic as defined in claim 10 wherein said third and fourth switching transistors are field effect transistors.

12. Switching logic as defined in claim 1 for use with a speed-controlled converter having a speed controller and provided with an underlying current control, wherein the output voltage of the speed controller is fed to said first amplifier as the desired current value.