Hysteretic Control for Transformer Based Power Converters

• US 20170025961A1
• Filed: 03/18/2016
• Published: 01/26/2017
• Est. Priority Date: 07/23/2015
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Seeman, Michael D.
• Granted Patent: US 10,673,339 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33546 with automatic control of the output voltage or current H02M3/33561 takes precedence
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Hysteretic control for power converters. In an example arrangement, an apparatus includes a converter for converting an input voltage to an output voltage including a transformer; at least one primary side driver switch coupled to supply current from an input voltage terminal to the primary side of the transformer; at least one inductor coupled between the secondary side of the transformer and the output voltage terminal; at least one secondary side switch coupled between the inductor and a ground potential; and a hysteretic controller coupled to supply a first on-time signal to the at least one primary side switch and a second on-time signal to the at least one secondary side switch, the hysteretic controller configured for sensing the output voltage and having at least one current input coupled for sensing current flowing in the inductor and generating primary side driver switch on-time pulses to control the output voltage.

Claims

1. An apparatus, comprising:

a power converter for converting an input voltage to an output voltage, the power converter further comprising;

a transformer having a primary side and a secondary side coupled between an input voltage terminal and an output voltage terminal, respectively;

at least one primary side power switch coupled to supply current from the input voltage terminal to the primary side of the transformer;

at least one inductor coupled between the secondary side of the transformer and the output voltage terminal;

at least one secondary side switch coupled between a node coupled to the inductor and the secondary side of the transformer, and a ground potential; and

a hysteretic controller coupled to supply a first on-time signal to the at least one primary side switch and a second on-time signal to the at least one secondary side switch, the hysteretic controller having a feedback input coupled to the output voltage and configured for sensing the voltage at the output and having at least one current input coupled to the at least one inductor, and further configured for receiving a signal corresponding to the current flowing in the at least one inductor.

2. The apparatus of claim 1, wherein the power converter further comprises a half-bridge converter with a current doubler output.

3. The apparatus of claim 2, wherein the power converter further comprises:

a second primary side power switch coupled between the primary side of the transformer and a negative voltage input;

a second inductor coupled between the secondary side of the transformer and the output voltage terminal; and

a second secondary side switch coupled between a second node coupled to the second inductor and the secondary side of the transformer, and a terminal for receiving a ground potential;

wherein the hysteretic controller is further configured to supply on-time signals to the second primary side power switch and the second secondary side switch.

4. The apparatus of claim 3, wherein the power converter further comprises two alternating cycles and the at least one inductor and second inductor form a current doubler at the output voltage terminal.

5. The apparatus of claim 1, wherein the power converter further comprises an amplifier configured to compare the output voltage received to a reference voltage and to output an error signal, the hysteretic controller outputting the on-time signal to the at least one primary side power switch responsive to the error signal.

6. The apparatus of claim 5 wherein the power converter further comprises a compensator amplifier which amplifies and filters the error signal, and outputs a droop voltage signal.

7. The apparatus of claim 6, wherein the power converter further comprises a pulse sequencer to generate the at least one on-time signal to the at least one primary side driver switch responsive to a comparator that receives a voltage corresponding to summed current in the at least one inductor, and at least one of the error signal and droop voltage signal, and outputs an on-time pulse responsive to a comparison.

8. The apparatus of claim 1, wherein the at least one primary side power switch and the secondary side switch further comprise field effect transistors (FETs).

9. The apparatus of claim 8, wherein the FET transistors further comprise silicon MOSFET devices.

10. The apparatus of claim 1, wherein the at least one primary side power switch and the secondary side switch further comprise GaN devices.

11. The apparatus of claim 1, wherein the power converter further comprises a full-bridge converter with a current doubler output.

12. The apparatus of claim 11, wherein the full-bridge converter further comprises a second primary side driver switch coupled between the primary side of the transformer and a negative input voltage terminal, a third driver switch coupled between the input voltage terminal and the primary side of the transformer, and a fourth driver switch coupled between the primary side of the transformer and the negative input terminal.

13. The apparatus of claim 12, wherein the first, second, third, and fourth switches further comprise GaN transistors.

14. A half-bridge transformer-based power converter;

comprising;

a transformer having a primary side with a first terminal and a second terminal and a secondary side with a third terminal and a fourth terminal;

a first primary side driver transistor having a current conduction path coupled between a first voltage input terminal for receiving a positive input voltage and the first terminal of the primary side of the transformer, and having a gate terminal;

a second primary side driver transistor having a current conduction path coupled between a second voltage terminal for receiving a negative input voltage and the first terminal of the primary side of the transformer, and having a gate terminal;

a first secondary side driver transistor having a current conduction path between the first terminal of the secondary side of the transformer and a terminal for a ground potential, and having a gate terminal;

a second secondary side driver transistor having a current conduction path coupled between the second terminal of the secondary side of the transformer and the terminal for a ground potential, and having a gate terminal;

a first inductor coupled between the first terminal of the secondary side of the transformer and an output terminal for an output voltage;

a second inductor coupled between the second terminal of the secondary side of the transformer and the output terminal for an output voltage; and

a hysteretic controller coupled to the output voltage and having inputs for receiving sensed current signals for the first and second inductors, and having outputs for driving gate signals for each of the first and second primary side driver transistors, and for driving gate signals for each of the first and second secondary side transistors, configured to output on-time pulses on the gate terminals of the first and second primary side driver transistors to create an output voltage at the output voltage terminal.

15. The half-bridge power converter of claim 14, wherein the hysteretic controller further comprises a first amplifier for comparing the output voltage to a reference voltage and for outputting an error voltage.

16. The half-bridge power converter of claim 15, wherein the hysteretic controller further comprises a summer configured to add the sensed current signals and a second comparator comparing the sum of the sensed current signals to the error voltage, and configured to output a switch signal responsive to a comparison.

17. The half-bridge power converter of claim 14, wherein the first and second primary side driver transistors each comprise a GaN transistor.

18. The half-bridge power converter of claim 14, wherein the first and second primary side driver transistors each comprise a MOSFET.

19. A circuit for controlling driver transistors for a transformer based power converter, comprising:

a hysteretic controller integrated circuit having output signals for driving gate terminals of primary side driver transistors and secondary side driver transistors to form a voltage converter, the hysteretic controller circuit having an input for receiving a feedback output voltage, and having inputs for receiving signals corresponding to sensed inductor currents;

the hysteretic controller integrated circuit outputting a first gate signal to at least one primary side driver transistor having a current conduction path coupled between a terminal for receiving a positive input voltage and a terminal for coupling to the primary side of a transformer; and

the hysteretic controller integrated circuit outputting a second gate signal to at least one secondary side driver transistor having a current conduction path coupled between a terminal for coupling to the secondary side of the transformer and a terminal for a ground potential;

wherein the hysteretic controller integrated circuit is configured to output on-time pulses to the at least one primary side driver to control an output voltage using an approximately constant switching frequency.

20. The circuit of claim 19, wherein the hysteretic controller integrated circuit is adapted to provide gate signals to control a half-bridge isolated power converter.