Shared-bus current sharing parallel connected current-mode DC to DC converters

• US 6,009,000 A
• Filed: 02/05/1999
• Issued: 12/28/1999
• Est. Priority Date: 02/05/1999
• Status: Expired due to Term

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: Siri, Kasemsan
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US09/245,824
• Time in Patent Office: 326 Days
• Field of Search: 363/20, 363/21, 363/65, 363/71, 363/95, 363/97, 363/131
• US Class Current: 363/21.09
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence

Abstract

A power system consisting of parallel connected current-mode power converters combined with a voltage error signal on a shared-bus used in common for controlling all of the power stages for improved consistency, reliability, and performance in both transient and steady states. Near uniform current sharing is achievable without sacrificing the voltage regulation performance. The improved system offers faster settling time under step loads, consistent small signal characteristics and large signal responses regardless of mismatches of components values such as reference voltages, and reduced output impedance variations in magnitude and phase even during various modes of operation.

Claims

1. A power stage for converting an input voltage to an output voltage, the power stage comprising a converter and a control circuit wherein the converter is for receiving the input voltage and providing the output voltage and the control circuit is for controlling the converter,

the converter comprises:

a switching means for receiving the input voltage and conducting current in a first state and not conducting current in a second state for providing a switched power signal switching between the first and second states; and

a switch means for receiving a switching signal and for converting the switched power signal into the output voltage and for generating a switched current signal, and

the control circuit comprises;

a voltage error amplifier for providing a voltage error signal scaled to the difference between the output voltage and a voltage reference;

a voltage error diode for communicating the voltage error signal onto a shared-bus control line, the shared-bus control line is for receiving an external error signal, the voltage error diode is for translating the voltage error signal into a voltage control signal for controlling the switching signal, the voltage control signal is controlled by the voltage error signal or controlled by the external error signal; and

a driver means for receiving the voltage control signal and receiving the switched current signal for generating the switching signal for alternating driving the switch means being in the first and second states for switching the switching means.

2. The power stage of claim 1, wherein the voltage control signal is controlled by the voltage error signal when greater than the external error signal or controlled by the external error signal when greater than the voltage error signal.

3. The power stage of claim 1, wherein the voltage control signal is controlled by the voltage error signal when lesser than the external error signal or controlled by the external error signal when lesser than the voltage error signal.

4. The power stage of claim 1 wherein,

the converter is a DC to DC switching current mode converter,

the input voltage is a DC input voltage,

the output voltage is a DC output voltage,

the switching signal is a pulse width modulated switching signal,

the output voltage is regulated by the pulse width modulated switching signal, and

the switch means is also for rectifying the switched power signal into the DC output voltage.

5. A power stage for converting an input voltage to an output voltage, the power stage comprising a converter and a control circuit wherein the converter is for receiving the input voltage and providing the output voltage and the control circuit is for controlling the converter,

the converter comprises:

a transformer having a primary winding for receiving the input voltage and conducting current in a first state and for not conducting current in a second state, and having a secondary winding for providing a switched power signal;

a switch for receiving a transformer switching signal and for switching the primary of the transformer between the first and second states for transforming the input voltage signal into the switched power signal;

a current sensor for sensing the current through the primary winding and providing a switched current signal; and

a rectifier circuit for rectifying the switched power signal into the output signal, and

the control circuit comprises;

a voltage error amplifier for providing a voltage error signal scaled to the difference between the output voltage and a voltage reference;

a voltage error diode for communicating the voltage error signal onto a shared-bus control line, the shared-bus control line is for receiving an external error signal, the voltage error diode is for translating the voltage error signal into a voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal or controlled by the external error signal, and

a driver for receiving the voltage control signal and switched current signal for generating the transformer switching signal for alternating driving the switch being in the first and second states for switching the primary of the transformer to generate the switched power signal.

6. The power stage of claim 5 wherein, the voltage control signal is controlled by the voltage error signal when greater than the external error signal or controlled by the external error signal when greater than the voltage error signal.

7. The power stage of claim 5 wherein, the voltage control signal is controlled by the voltage error signal when lesser than the external error signal or controlled by the external error signal when lesser than the voltage error signal.

8. The power stage of claim 5 wherein,

the converter is a DC to DC switching current-mode converter,

the input voltage is a DC voltage,

the output voltage is a DC voltage,

the transformer switching signal is a pulse width modulated switching signal,

the output voltage is regulated by the pulse width modulated switching signal, and

the rectifier comprises a rectification diode and an output capacitor for generating and filtering the DC output voltage.

9. The power stage of claim 5 wherein the converter provides a current sense signal, the control circuit further comprising,

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference;

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal, the current error signal or the external error signal.

10. The power stage of claim 9 wherein the voltage control signal is controlled by the voltage error signal, the current error signal or the external error signal, whichever is greater.

11. The power stage of claim 9 wherein the voltage control signal is controlled by the voltage error signal, the current error signal or the external error signal, which ever is lesser.

12. The power stage of claim 5 wherein,

the converter further comprises:

a current sensing resistor for providing a current sense signal indicating current conducted to a load coupled to the output voltage; and

a current sensor for providing a current switching signal, and

the control circuit further comprising;

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference; and

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal, the external error signal or the current error signal.

13. The power stage of claim 5 wherein the converter provides a current sense signal, the control circuit further comprising,

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference;

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal, the current error signal or the external error signal, and

a blocking diode for blocking the voltage error signal and the external error signal from the control voltage signal when the current error signal is greater than the voltage error signal and the external error signal.

14. The power stage of claim 5 wherein the converter provides a current sense signal, the control circuit further comprising,

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference,

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal, the current error signal or the external error signal, and

a blocking diode for blocking the voltage error signal and the external error signal from the control voltage signal when the current error signal is lesser than the voltage error signal and the external error signal.

15. A power stage for converting an input voltage to an output voltage coupled to a load receiving load current, the power stage comprising,

a converter and a control circuit wherein the converter is for receiving the input voltage and providing an output voltage and the control circuit is for controlling the converter,

the converter comprises:

a transformer having a primary winding for receiving the input voltage and conducting current in a first state and for disconnecting the transformer from the input voltage in a second state, and having a secondary winding for providing a switched power signal;

a switch for receiving a transformer switching signal and for switching the primary of the transformer between the first and second states for transforming the input voltage signal into the switched power signal; and

a rectifier circuit for rectifying the switched power signal into the output voltage;

a sensing resistor for providing a current sense signal scaled to the load current; and

a current sensor for sensing the current in the primary winding and providing a switched current signal, and

the control circuit comprises;

a voltage error amplifier for providing a voltage error signal scaled to the difference between the output voltage and a voltage reference,

a voltage error diode for communicating the voltage error signal onto a shared-bus control line, the shared-bus control line for receiving an external error signal, the voltage error diode is for translating the voltage error signal into a voltage control signal for controlling the transformer switching signal;

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference;

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal when greater than the current error signal and the external error signal, controlled by the external error signal when greater than the voltage error signal and the current error signal, or controlled by the current error signal when greater than the voltage error signal and the external error signal;

a blocking diode for blocking the voltage error signal and the external error signal from the control voltage signal when the current error signal is greater than the voltage error signal and the external error signal; and

a driver for receiving the voltage control signal and the switched current signal for generating transformer switching signal for alternating driving the switch being in the first and second states for switching the primary of the transformer to generate the switched power signal.

16. The power stage of claim 15 wherein,

the voltage error diode has a cathode connected to the voltage error amplifier and has an anode connected to the shared-bus and to the blocking diode,

the blocking diode has a cathode connected to the shared-bus and the voltage error diode and has an anode connected to the current error diode,

the current error diode has a cathode connected to the current error amplifier and has an anode connected to the blocking diode,

the voltage error amplifier has a negative input connected to the output voltage and has a positive input connected to the voltage reference,

the current error amplifier has a negative input connected to the current sense signal and has a positive input connected to the current reference, and

the voltage control signal is controlled by the voltage error signal, or the current error signal, or the external error signal whichever one is lesser.

17. The power stage of claim 15 wherein,

the voltage error diode has an anode connected to the voltage error amplifier and has a cathode connected to the shared-bus and to the blocking diode,

the blocking diode has an anode connected to the shared-bus and the voltage error diode and has a cathode connected to the current error diode,

the current error diode has an anode connected to the current error amplifier and has a cathode connected to the blocking diode,

the voltage error amplifier has a positive input connected to the output voltage and has a negative input connected to the voltage reference,

the current error amplifier has a positive input connected to the current sense signal and has a negative input connected to the current reference, and

the voltage control signal is controlled by the voltage error signal, or the current error signal, or the external error signal whichever one is greater.

18. The power stage of claim 15 wherein,

the voltage error diode has an anode connected to the voltage error amplifier and has a cathode connected to the shared-bus and to the blocking diode,

the blocking diode has an anode connected to the shared-bus and the voltage error diode and has a cathode connected to the current error diode,

the current error diode has an anode connected to the current error amplifier and has a cathode connected to the blocking diode,

the voltage error amplifier has a positive input connected to the output voltage and has a negative input connected to the voltage reference,

the current error amplifier has a positive input connected to the current sense signal and has a negative input connected to the current reference, and

the voltage control signal is an algebraic difference between an offset reference and an error signal at the cathode of the blocking diode, and is controlled by the voltage error signal, or the current error signal, or the external error signal whichever one is greater.

19. A power system for supplying power to load, the power system comprises a plurality of parallel connected power stages, each of the plurality of power stages is for converting an input voltage to an output voltage coupled to a load, each of the plurality of power stages comprises a converter and a control circuit wherein the converter is for receiving the input voltage and providing the output voltage and the control circuit is for controlling the converter,

the converter comprises:

a transformer having a primary winding for receiving the input voltage and conducting current in a first state and for disconnecting the transformer from the input voltage in a second state, and having a secondary winding for providing a switched power signal;

a switch for receiving a transformer switching signal and for switching the primary of the transformer between the first and second states for transforming the input voltage signal into the switched power signal; and

a rectifier circuit for rectifying the switched power signal into the output voltage, and

the control circuit comprises;

a voltage error amplifier for providing a voltage error signal scaled to the difference between the output voltage and a voltage reference;

a voltage error diode for communicating the voltage error signal onto a shared-bus control line, the shared-bus control line for receiving an external error signal from the remaining converters of the plurality of power stages, the voltage error diode is for translating the voltage error signal into a voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal or controlled by the external error signal; and

a driver for receiving the voltage control signal for generating the transformer switching signal for alternating driving the switch between the first and second state for switching the primary of the transformer to generate the switched power signal.

20. The power system of claim 19 wherein each of the converters of the plurality of power stages provides a current sense signal, each of the control circuits further comprises,

a current error amplifier for providing a current error signal scaled to the difference between the current sense signal and a current reference, and

a current error diode for communicating the current error signal onto the voltage control line, the current error diode is for translating the current error signal into the voltage control signal for controlling the transformer switching signal, the voltage control signal is controlled by the voltage error signal, the external error signal or the current error signal.