Power converter with zero-voltage switching control

Patent metadata

Field	Value
Publication number	US-9979271-B2
Application number	US-201715434453-A
Country	US
Kind code	B2
Filing date	Feb 16, 2017
Priority date	Feb 17, 2016
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

In a power converter, switch-off of the synchronous rectification switch while the auxiliary switch is on causes the first capacitance of the main switch and the second capacitance of the synchronous rectification switch to resonate with the inductance of the second magnetic component. A parameter obtainer detects a voltage across a selected one of the main switch and the synchronous rectification switch, and obtains a parameter indicative of a corresponding one of rising and falling waveforms of the voltage across the selected switch while the selected switch is switched. A controller controls a switching control signal for the auxiliary switch to adjust switch-on timing of the auxiliary switch as a function of the parameter obtained by the parameter obtainer.

First claim

The invention claimed is:

1. A power converter comprising:
a switching circuit comprising a main switch with a first capacitance, a synchronous rectification switch with a second capacitance, and a first magnetic component, the switching circuit being configured to convert an input voltage to a predetermined output voltage according to complementary switching of the main switch and the synchronous rectification switch;
an auxiliary switching circuit comprising an auxiliary switch and a second magnetic component with an inductance,
the auxiliary switching circuit being configured such that switch-off of the synchronous rectification switch while the auxiliary switch is on causes the first capacitance of the main switch and the second capacitance of the synchronous rectification switch to resonate with the inductance of the second magnetic component;
a parameter obtainer configured to:
detect a voltage across a selected one of the main switch and the synchronous rectification switch; and
obtain a parameter indicative of a corresponding one of rising and falling waveforms of the voltage across the selected switch while the selected switch is switched; and

a controller configured to:
output a switching control signal to each of the main switch, the synchronous rectification switch, and the auxiliary switch to control switching of the corresponding one of the main switch, the synchronous rectification switch, and the auxiliary switch;
perform a comparison of the parameter indicative of the corresponding one of rising and falling waveforms of the voltage across the selected switch with a target parameter indicative of a corresponding one of target rising and falling waveforms; and
control, as a function of a result of the comparison, the switching control signal for the auxiliary switch to adjust switch-on timing of the auxiliary switch.

2. The power converter according to claim 1 , wherein:
the main switch has the first capacitance connected in parallel thereto;
the synchronous rectification switch is connected in series to the main switch to form a series switch unit, and has the second capacitance connected in parallel thereto;
the first magnetic component comprises a main inductor that has opposing first and second ends, the first end being connected to a connection point between the main switch and the synchronous rectification switch; and
the auxiliary switching circuit is connected to the first end of the first magnetic component, and further comprises an auxiliary rectification element,
the second magnetic component comprising an auxiliary inductor having the inductance.

3. The power converter according to claim 2 , wherein:
the switching circuit is configured such that:
the series switch unit has opposing high- and low-side terminals,
a first current is supplied from a power source to the main inductor when the main switch is on, and
a second current is supplied from the main inductor to an electrical load;

the power converter further comprises:
a first smoothing capacitor connected between the high- and low-side terminals of the series switch unit, and
a second smoothing capacitor connected across the second end of the main inductor and the low-side terminal of the series switch circuit;

the parameter obtainer comprises a transition-time signal obtainer configured to:
perform a comparison of the voltage across the selected switch with a predetermined threshold voltage, and
obtain, based on a result of the comparison and the switching control signal to the selected switch, a transition-time signal indicative of transition time,

the transition time representing one of:
a first period from a start of rising of the voltage across the synchronous rectification switch up to a predetermined first level when the selected switch is the synchronous rectification switch, and
a second period from a start of falling of the voltage across the main switch down to a predetermined second level when the selected switch is the main switch; and
the controller is configured to:
generate the switching control signals to the respective main switch and synchronous rectification switch based on the input voltage supplied from the power source, a target voltage or a target current for the electrical load, and the predetermined output voltage or an output current to the electrical load; and
generate the switching control signal to the auxiliary switch as a function of:
the transition time based on the transition time signal, and
predetermined target transition time for the transition time.

4. The power converter according to claim 3 , wherein:
the controller is configured to:
calculate a voltage deviation between the target voltage and an actual output voltage or a current deviation between the target current and an actual output current,
generate the switching control signals for the respective main switch and the synchronous rectification switch such that the actual output voltage matches with the target voltage or the actual output current matches with the target current,
calculate a time deviation between the predetermined target transition time and the transition time, and
generate the switching control signal for the auxiliary switch such that the transition time matches with the predetermined target transition time.

5. The power converter according to claim 3 , wherein, when loss of the power converter changes while the transition time varies, the controller is configured to determine a value of the predetermined target transition time such that a change amount of the loss of the power converter within a predetermined range of the transition time is lower than a predetermined amount,
the determined value of the predetermined target transition time being within the predetermined range of the transition time.

6. The power converter according to claim 5 , wherein the predetermined range of the transition time is defined from an eighth part of a resonance period to four-thirteenths of the resonance period inclusive, the resonance period being defined based on:
the inductance of the auxiliary inductor,
the first capacitance connected in parallel to the main switch, and
the second capacitance connected in parallel to the synchronous rectification switch.

7. The power converter according to claim 3 , wherein the controller is configured to determine a fourth part of a resonance period as the predetermined target transition time, the resonance period being defined based on:
the inductance of the auxiliary inductor,
the first capacitance connected in parallel to the main switch, and
the second capacitance connected in parallel to the synchronous rectification switch.

8. The power converter according to claim 2 , wherein the series switch unit comprised of the main switch and the synchronous rectification switch connected in series to each other, the first magnetic component, and the auxiliary switching circuit constitute a step-down converter for stepping down the input voltage to obtain the predetermined output voltage.

9. The power converter according to claim 2 , wherein the series switch unit comprised of the main switch and the synchronous rectification switch connected in series to each other, the first magnetic component, and the auxiliary switching circuit constitute a step-up converter for stepping up the input voltage to obtain the predetermined output voltage.

10. The power converter according to claim 1 , further comprising:
a capacitor connected between first and second ends of the first magnetic component in parallel to the auxiliary switching circuit.

11. The power converter according to claim 1 , wherein:
the first magnetic compone

Assignees

• Denso Corp
• National Univ Corp Oita Univ
• National Univ Corporation Oita Univerty

Inventors

• Takahashi Masaya
• Yamaguchi Nobuhisa
• Nishijima Kimihiro

Classifications

• H02M3/158

  including plural semiconductor devices as final control devices for a single load · CPC title

• H02M1/083 Primary

  for the ignition at the zero crossing of the voltage or the current · CPC title

• H02M3/1588

  comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence) · CPC title

• H02M2001/0058

  Electricity · mapped topic

• Y02B70/1466

  Cross-Sectional Technologies · mapped topic