High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

• US 5,418,707 A
• Filed: 04/13/1992
• Issued: 05/23/1995
• Est. Priority Date: 04/13/1992
• Status: Expired due to Fees

• Current Assignee: United States Enrichment Corporation (Centrus Energy Corp.)
• Original Assignee: United States Department of Energy
• Inventors: Lange, Arnold C., Shimer, Daniel W.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US07/867,639
• Time in Patent Office: 1,135 Days
• Field of Search: 363/65, 363/55, 363/40, 363/50, 363/79, 363/95, 363/132, 363/37, 361/71, 361/79, 361/93, 361/18, 307/43, 307/82
• US Class Current: 363/65
• CPC Class Codes: H01J 37/241 High voltage power supply or regulation circuits components H01J37/248
• CPC Class Codes: H02H 7/00 Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current

Abstract

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

Claims

1. A method for quickly shutting down a switch mode dc--dc converter whenever an incipient arc current is sensed, said switch mode dc--dc converter including a voltage regulator with at least one switching transistor, and said switch mode dc--dc converter including an inverter which comprises at least two parallel branches of at least two series connected switching transistors which are switched to generate alternating current through the primary winding of a transformer, said method comprising the steps of:

sensing the dc--dc converter output current and producing an output error voltage proportional to said sensed output current;

comparing said sensed output error voltage with a constant reference voltage to establish one of two logic states;

using said logic states for driving a timing means, having a first state and a second state, into the first state for producing a normal pattern of pulses to said switching transistors of said voltage regulator and of said inverter, wherein said first state produces a control signal having a variable duty cycle as a function of said error voltage, said variable duty cycle control signal being applied to said voltage regulator such that the on and off times of said voltage regulator maintain a regulated dc voltage output substantially constant under varying loads;

using said logic states for driving the timing means into the second state for producing the second state of said timing means, said second state of said timing means provided (a) for simultaneously disabling said switching transistors of said voltage regulator so that the output voltage of said voltage regulator is zero and (b) for enabling said switching transistor of said inverter so that the switching transistors of the inverter provide a short circuit across the primary winding of said transformer whenever an incipient arc current is sensed.

2. A control circuit for shutting down a switch mode dc--dc converter or the like whenever an arc current is sensed, comprising:

means for generating a controlled source of direct current on first and second output leads including a voltage regulator switching means wherein each switching means has an enable lead, a collector lead having a connection with a free wheeling diode and an inductor, and an emitter lead;

inverter means for generating high frequency square wave current through the primary winding of a transformer from said source of direct current including first and second parallel branches, each branch having at least two switching means connected in series, forming a bridge circuit for connecting said first and second output leads of said means for generating direct current through said transformer primary, wherein each switch means has an enable lead, a collector lead and an emitter lead;

control means for alternately enabling diagonal switch means in each of said parallel branches of said bridge circuit such that the on time of said alternately activated switch means produces a positive or negative current through the primary of said transformer means;

means for sensing incipient arc currents at the output of said supply;

control means responsive to said means for sensing incipient arc currents and for substantially simultaneously disabling said voltage regulator switching means to force the inductor current to flow in the free wheeling diode and for simultaneously enabling all of said inverter switching means in said parallel branches of said bridge circuit to produce a short circuit across the primary of said transformer means for a predetermined period of time when the incipient arc current is sensed.

3. A dc--dc converter for producing a controlled dc voltage under varying and arcing loads comprising:

a voltage regulator means for providing a pulsating voltage of controlled duty cycle from an unregulated dc input voltage, said voltage regulator means including a free wheeling diode and voltage regulator switching means having a control lead, a first lead connected to a first output terminal of the unregulated dc input and having a second lead connected to a first end of said free wheeling diode; and

wherein a second end of said free wheeling diode connects to a second output terminal of the unregulated dc input;

an inductor means for smoothing current connected to the common node of said voltage regulator switching means and said second end of said free wheeling diode;

an inverter network for producing a high frequency alternating current from said smoothed direct current, including a plurality of switch means arranged in a bridge configuration for generating square wave current of alternating polarity in the primary of a transformer, each switch means having a control lead for receiving enable or disable signals;

means for sensing incipient arc currents at the output of said power supply and for simultaneously applying a disable signal to said control leads of said voltage regulator switching means for disabling conduction of said switching means and for applying an enable signal to said control leads of said inverter network switch means for enabling conduction of said switch means and shorting out said transformer primary when an arc is sensed;

control means for producing an enable or disable signal on said control lead of said voltage regulator switching means and for regulating the output voltage of the said dc--dc converter by selectively varying the ratio of on time and off time of said voltage regulator switching means as a function of the difference between a desired dc--dc converter output voltage and a simulated output voltage.

4. A dc--dc converter as in claim 3 wherein said control means further includes a voltage feedback loop circuit comprising:

a voltage sense winding means inductively coupled to said primary winding and to the secondary winding of said transformer for producing an ac voltage proportional to the magnitude of the alternating square wave voltage pulses across said secondary winding;

an output simulator means for rectifying said ac voltage from said sense winding and for producing an output dc voltage proportional to the dc--dc converter output voltage;

means for producing an error voltage which is the difference between a reference voltage fixed to provide a desired output voltage and the dc voltage of said output simulator;

means for converting said error voltage into said enable signal having a variable duty cycle such that said enable signal has a variable ratio of the time during which the signal is true to the time during which the signal is false as a function of said error voltage;

means, responsive to said enable signal and connected to said enable leads of said voltage regulator switch means for regulating said dc voltage on the output of the dc--dc converter.

5. A high voltage dc--dc converter with dynamic voltage regulation and means for decoupling a power supply during load generated arcs comprising;

switching regulator means responsive to control signals for providing a source of pulsating voltage with controlled duty cycle from a rectified input voltage;

inductor means for filtering said pulsating voltage and creating a smooth direct current;

switching means for producing a high frequency alternating current from said smooth direct current;

step up transformer means including a primary winding for receiving said high frequency alternating current and a secondary winding for stepping up the voltage at said primary winding and for coupling said stepped up alternating voltage to an output rectifier and filter;

control means including output simulator means for producing an error voltage representative of the difference between the dc--dc converter output voltage from said output rectifier and filter and a desired voltage, and for producing a control signal having a variable duty cycle as a function of said error voltage, said control means applying said variable duty cycle control signal to said switching regulator means such that the on and off times of said switching regulator means maintain said regulated dc voltage output substantially constant under varying loads, and wherein said control means further includes current sensing means for sensing an incipient arc current on an output of said output rectifier and filter and for producing a second control signal to simultaneously turn off said switching regulator means and turn on said switching means for producing high frequency ac and thereby short circuit and isolate said transformer primary winding from said supply output and to short circuit said transformer primary winding.

6. An apparatus according to claim 5 wherein said switching regulator means, inductor means, switching means for producing high frequency ac, transformer means, and output rectifier and filter means each form a discrete circuit module and said high voltage power supply comprises a plurality of such circuit modules linked together with their inputs in parallel and their outputs in series.