Over-voltage interrupt for a phase controlled regulator

• US 4,044,295 A
• Filed: 12/29/1976
• Issued: 08/23/1977
• Est. Priority Date: 12/29/1976
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Griess, Roy K., Ferraiolo, Frank A.
• Primary Examiner(s): Shoop, William M.
• Application Number:
  US05/755,285
• Time in Patent Office: 237 Days
• Field of Search: 321/5, 321/11, 321/14, 321/18
• US Class Current: 363/54
• CPC Class Codes: H02H 7/12 for static converters or rectifiers for discharge lamp power supplies using static converters H05B41/2851, H05B41/2921, H05B41/2981

Abstract

An over-voltage interrupt circuit is provided which senses the local output of the phase controlled regulator. A reference is generated which is utilized in a comparator as the over-voltage threshold. When the sensed regulator output is above this threshold setting an override signal is produced which overrides the condition of the on/off control. The comparator is arranged to have a lower reset threshold value than the setting threshold so that the on/off control is again switched in response to the sensed voltage dropping below the reset threshold level. If the over-voltage condition persists, the comparator continues to set and reset and, accordingly, the on/off control is continually switched off and on giving a limited average voltage output from the regulator. The on/off control operates through a walk-in circuit which controls the voltge during turn on and off to prevent over and undershoot voltage problems. The active capacitor is also turned off by an over-voltage condition recognized by the comparator and remains off as long as the over-voltage condition persists.

Claims

1. In a phase controlled regulator an over-voltage interrupt circuit comprising in combination:

a sensing means for sensing the outputs of the phase controlled regulator and for generating a voltage proportional to the voltage difference between the outputs;

a reference generator for generating a reference;

a comparator means having the reference connected thereto as one input for establishing an upper threshold and having positive feedback establishing a resetting threshold lower than said setting threshold;

an on/off controller means for controlling the on and off switching of said regulator;

a first switching means for providing an override signal to said on/off controller which turns said regulator off in response to a sensed output above said setting threshold and turns said regulator on in response to a sensed output below said resetting threshold, thereby providing output voltage off/on sequencing between said setting and resetting threshold values in response to an over-voltage.

2. In a phase controlled regulator an over-voltage interrupt circuit according to claim 1, wherein said sensing means for sensing the outputs of the phase controlled regulator and for generating a voltage proportional to the voltage difference between the outputs is a differential buffer circuit.

3. In a phase controlled regulator according to claim 1, wherein said comparator has an inverting (-) and non-inverting (+) terminal, the reference means generating a positive reference connected to said inverting terminal, the output of said sensing means being connected to the non-inverting terminal of said comparator so that the comparator changes output level when the output of said sensing means goes more positive than said reference level.

4. In a phase controlled regulator according to claim 3, wherein said comparator has a positive feedback from the output thereof to said non-inverting input to introduce a fixed positive offset such that the comparator will reset at the offset value lower than said reference.

5. In a phase controlled regulator according to claim 1, wherein said first switching means for providing an override signal to said on/off controller is a transistor which is saturated in response to an over-voltage condition sensed by said sensing means thereby providing an override signal to said on/off controller.

6. In a phase controlled regulator according to claim 1, wherein a second switching means is provided including a second and third transistor, a capacitor and a further comparator said second transistor saturating in response to said over-voltage condition to provide a discharge path for said capacitor, said further comparator responding to said capacitor discharge by changing its output to bias said third transistor to its conducting state causing the active capacitor to turn off.

7. In a phase controlled regulator according to claim 6, wherein the charging time of said capacitor is longer than the cycling time of the over-voltage interrupt circuit so that the capacitor does not reach the critical charge for changing said further comparator output while said regulator is responding to an over-voltage condition, thereby maintaining said third transistor in a non-conducting state and maintaining the active capacitor in the off condition.

8. In a phase controlled regulator according to claim 1, wherein a walk-in circuit is provided which operates in response to said override signal from said first switching means to provide a positive increase in error voltage to cause fast phase back of said regulator voltage.

9. In a phase controlled regulator according to claim 8, wherein said walk-in circuit operates in response to the removal of said override signal from said first switching means to provide said error voltage at the phase back level upon turn-on to provide a slow phasing forward by slowly decreasing said error voltage until the regulating level is reached thereby preventing voltage overshoot from the regulator.