Apparatus for improving stability and dynamic response of half-bridge converter

• US 6,396,716 B1
• Filed: 09/20/2001
• Issued: 05/28/2002
• Est. Priority Date: 09/20/2001
• Status: Expired due to Term

• Current Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Original Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Inventors: Liu, Chui-Pong Joe, Pong, Man-Hay Bryan, Poon, Ngai-Kit Franki
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US09/960,435
• Time in Patent Office: 250 Days
• Field of Search: 363/16,17,56.01,56.02,97,98,131,132
• US Class Current: 363/17
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• 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

Typically, in a half-bridge converter A DC blocking capacitor and inductance on the primary side combines with the inductor and capacitor on the secondary side to produce complicated converter dynamic characteristics that make converter stabilization difficult. The disclosed system and methods enable converter stabilization by modulating, as a function of the voltage across the DC blocking capacitor, the feedback output error signal or the ramp signal for the PWM controller of the converter. The modulation removes the effect of the resonant circuit formed by the primary inductance and the DC blocking capacitor in the output voltage regulation loop. Further adjustment of the duty cycle of the power switches enables keeping the output voltage undisturbed by voltage variation across the DC blocking capacitor. Since, this inner compensation loop results in the voltage regulation feedback loop respond to only the output inductor-capacitor filter, the transfer function of this loop displays second order characteristics from the fourth order. Hence, stability issues are simplified to conventional second order compensation network whereby the converter can be optimized for fast transient response.

Claims

1. A power converter for DC to DC voltage conversion to generate a desired regulated output voltage, the power converter comprising:

input terminals for receiving power;

at least one switch coupled to the input terminals to generate a variable current in accordance with a duty cycle;

a magnetic component suitable for transforming the variable current to generate a transformed current;

an input capacitor coupled to magnetic component;

a rectifying circuit for rectifying the transformed current to generate a rectified current;

a filter for smoothing the rectified current at output terminals;

a feedback network generating an error signal reflecting deviation of a voltage at the output terminals from a desired reference; and

a controller receiving the error signal, sensing the voltage across the input capacitor and responsive to a ramp signal for generating driving signals to operate the at least one switch in accordance with the duty cycle whereby the power converter operates as a closed loop feedback system.

2. The power converter of claim 1 wherein the voltage across the input capacitor modulates the error signal in a modulator.

3. The power converter of claim 1 wherein the voltage across the input capacitor modulates the error signal in a modulator.

4. A power converter for DC to DC voltage conversion to generate a desired regulated output voltage, the power converter comprising:

input terminals for receiving power;

switches coupled to the input terminals to generate a variable current;

a magnetic component suitable for transforming the variable current to generate a transformed current;

an input capacitor coupled to magnetic component;

a rectifying circuit for rectifying the transformed current to generate a rectified current;

a filter for smoothing the rectified current;

output terminals coupled to the filter to provide the rectified current following smoothing;

a current source generating a current in response to a voltage across the input capacitor;

a current source capacitor coupled to the current source to be charged up by the current source;

at least one switch to discharge the current source capacitor periodically to generate a ramp signal;

a feedback network generating an error signal reflecting deviation for a voltage at the output terminals from a desired reference; and

a controller receiving the error signal and the ramp signal for generating driving signals to operate the switches in accordance with a duty cycle whereby the power converter operates as a closed loop feedback system.

5. A power converter for DC to DC voltage conversion to generate a desired regulated output voltage, the power converter comprising:

input terminals for receiving power;

switches coupled to the input terminals to generate a variable current in accordance with a duty cycle;

a magnetic component suitable for transforming the variable current to generate a transformed current;

an input capacitor coupled to magnetic component;

a rectifying circuit for rectifying the transformed current to generate a rectified current;

a filter for smoothing the rectified current;

output terminals coupled to the filter to provide the rectified current following smoothing;

a second magnetic component magnetically coupled to first magnetic component to provide a control signal related to the voltage across the input capacitor;

a feedback network generating an error signal reflecting deviation for a voltage at the output terminals from a desired reference; and

a controller receiving the error signal, the control signal and a ramp signal for generating driving signals to operate the switches in accordance with the duty cycle whereby the power converter operates as a closed loop feedback system.

6. The power converter of claim 5 further comprising a rectifier coupled to the second magnetic component to produce the signal related to the voltage across the input capacitor.

7. The power converter of claim 6 wherein the control signal modulates the error signal in a modulator.

8. The power converter of claim 6 wherein the voltage across the input capacitor modulates the ramp signal in a modulator.

9. The power converter of claim 6 further comprising a first resistor for sensing the output error signal.

10. The power converter of claim 9 further comprising a second resistor for sensing the signal related to the voltage across the input capacitor, the second resistor coupled to the first resistor to produce a signal proportional to the difference between the output error signal and the signal related to the voltage across the input capacitor.

11. The power converter of claim 10 further comprising means to couple the first and second resistor together to produce a signal proportional to the difference between the output error signal and the signal related to the voltage across the input capacitor.

12. A method for simplifying the regulation of the output voltage in a half-bridge DC-DC power converter, the method comprising the steps of providing a DC blocking capacitor on a primary side of a magnetic component;

sensing a voltage across the DC blocking capacitor as a control signal;

generating a modulated output error signal from at least one members chosen from the set consisting of the control signal, an output error signal and a ramp signal; and

determining a duty cycle to drive at least one switch in an input path for power input into the power converter in response to receiving the modulated output error signal at a PWM controller.