Regulating controller for controlled self-oscillating converters using bipolar junction transistors

• US 9,647,567 B2
• Filed: 03/26/2011
• Issued: 05/09/2017
• Est. Priority Date: 03/26/2010
• Status: Active Grant

• Current Assignee: Redisem Ltd.
• Original Assignee: Jacques Russell
• Inventors: van der Duijn Schouten, Nicolaas, Coulson, David Robert, Jacques, Russell
• Primary Examiner(s): Behm, Harry
• Application Number:
  US13/637,636
• Publication Number:
  US 20130094248A1
• Time in Patent Office: 2,236 Days
• Field of Search: 363 22- 23
• CPC Class Codes: H01F 38/20 Instruments transformers
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/083 for the ignition at the zero crossing of the voltage or the current
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• 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 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/338 in a self-oscillating arrangement H02M3/337 takes precedence
• CPC Class Codes: H02M 3/3385 with automatic control of output voltage or current H02M3/33561 takes precedence
• CPC Class Codes: H02M 7/5383 in a self-oscillating arrangement H02M7/538 takes precedence
• CPC Class Codes: H03K 17/13 Modifications for switching at zero crossing generating an impulse at zero crossing H03K5/1536
• CPC Class Codes: H03K 17/133 in field-effect transistor switches
• 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

A power converter controller and methods for its operation are provided that can control a self-oscillating power converter that uses a Bipolar Junction Transistor (BJT) as a switch by manipulating the current flowing in a control winding. The controller is able to determine the optimum time to remove a short circuit applied to the control winding, as well as being able to determine the optimum time to pass current through the control winding. The controller can further draw power from the power converter using the control winding. The controller is capable of maintaining the midpoint voltage of the power converter in the case that the converter has more than one switch. The controller estimates the output power of the converter without requiring a connection to the secondary side of the converter transformer. The controller further controls entry and exit into a low-power mode in which converter oscillations are suppressed.

Claims

1. A method for controlling a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, whereby control over the power converter is achieved by controlling a control winding magnetically coupled to said drive winding, the method comprising:

selectively providing a short-circuit across the control winding;

monitoring the load winding current; and

removing the short-circuit after the load winding voltage has commutated and the load winding current drops below a first threshold value greater than zero.

2. The method according to claim 1, wherein said short-circuit is selectively applied when the load winding current drops below a second threshold value.

3. The method according to claim 1, wherein the load winding current is monitored by monitoring the voltage across a resistive element in series with the load winding.

4. The method according to claim 1, wherein the load winding current is monitored by reference to the current in the control winding.

5. A controller for a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, the controller comprising:

first and second control winding connections for connection to a control winding magnetically coupled to the load and drive windings;

a first switch coupled between the first and second control winding connections;

a current monitoring element for monitoring the current in the load winding; and

a switch controller for selectively closing said first switch to provide a short circuit across the first and second control winding connections, further adapted to open the switch when the load winding voltage has commutated and the current monitoring element determines that the current in the load winding has fallen below a first threshold greater than zero.

6. The controller according to claim 5, wherein said switch controller selectively closes said first switch when the current in the load winding drops below a second threshold value.

7. The controller according to claim 5, wherein the current monitoring element monitors the current in the load winding by reference to the voltage across a resistive element in series with the load winding.

8. The controller according to claim 5, wherein the current monitoring element monitors the current in the load winding by reference to the voltage across the first and second control winding connections.

9. A method of controlling a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, whereby control over the power converter is achieved by controlling a control winding, having first and second ends, magnetically coupled to said drive winding, the method comprising:

monitoring a current flowing in the load winding by measuring a voltage across a resistance in series with the load winding; and

entering a low power mode when the current flowing in the load winding falls beneath a threshold wherein during said low power mode a short circuit is applied across the control winding for inhibiting operation of the power converter, wherein the threshold is a function of a switching frequency of the power converter.

10. The method according to claim 9, wherein the low power mode is entered when the real portion of the current flowing in the load winding falls beneath said threshold.

11. A method of controlling a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, whereby control over the power converter is achieved by controlling a control winding, having first and second ends, magnetically coupled to said drive winding, the method comprising:

monitoring a current flowing in the load winding by measuring a voltage across a resistance in series with the load winding;

entering a low power mode when the current flowing in the load winding falls beneath a threshold wherein during said low power mode a short circuit is applied across the control winding for inhibiting operation of the power converter;

recording a second threshold value based on a switching frequency of the power converter on entering the low power mode;

monitoring a demanded switching frequency of the power converter; and

exiting the low power mode when the demanded switching frequency falls below a threshold value.

12. A controller for a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, the controller comprising:

first and second control winding connections for connection to a control winding magnetically coupled to the load and drive windings;

a first switch coupled between the first control winding connection and second control winding connection;

first and second current sensing resistor connections for connection to a current sensing resistor in series with the load winding;

a monitor coupled to the first and second current sensing resistor connections for monitoring the voltage across the current sensing resistor, adapted to determine when the current in the load winding falls beneath a threshold, wherein the threshold is a function of the switching frequency of the power converter; and

a switch controller adapted to enter a low power mode when the monitor determines that the current in the load winding has fallen beneath the threshold, wherein

when in said low power mode, the switch controller closes the first switch to apply a short circuit between the first and second control winding connections for suppressing power conversion in the power converter.

13. The controller according to claim 12, wherein the monitor is adapted to determine when the real portion of the current flowing in the load winding falls beneath the threshold.

14. A controller for a power converter, the power converter having a BJT as a switch, the base of the BJT being connected to a drive winding, said drive winding being magnetically coupled to a load winding which carries the power converter load current, the controller comprising:

first and second control winding connections for connection to a control winding magnetically coupled to the load and drive windings;

a first switch coupled between the first control winding connection and second control winding connection;

first and second current sensing resistor connections for connection to a current sensing resistor in series with the load winding;

a monitor coupled to the first and second current sensing resistor connections for monitoring the voltage across the current sensing resistor, adapted to determine when the current in the load winding falls beneath a threshold; and

a switch controller adapted to enter a low power mode when the monitor determines that the current in the load winding has fallen beneath the threshold, wherein when in said low power mode, the switch controller closes the first switch to apply a short circuit between the first and second control winding connections for suppressing power conversion in the power converter, and wherein the switch controller produces a control signal for controlling the switching frequency of the power converter;

the switch controller records a second threshold value based on the value of the control signal on entering the low power mode; and

the switch controller ends the low power mode when the control signal reaches the second threshold value.