CURRENT CONVERTER WITH CURRENT CONTROL ON THE PRIMARY WINDING SIDE AND COMPENSATION OF THE PROPAGATION DELAY

• US 20160336861A1
• Filed: 11/23/2015
• Published: 11/17/2016
• Est. Priority Date: 05/13/2015
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Gritti, Giovanni
• Granted Patent: US 9,954,445 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 1/0016 Control circuits providing compensation of output voltage deviations using feedforward of disturbance parameters
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• 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 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• 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 control circuit controls a switch of a switching current converter receiving an input quantity, with a transformer having a primary winding and a sensor element generating a sensing signal correlated to a current in the primary winding. The control circuit has a comparator stage configured to compare a reference signal with a comparison signal correlated to the sensing signal and generate an opening signal for the switch. The comparator stage has a comparator element and a delay-compensation circuit. The delay-compensation circuit is configured to generate a compensation signal correlated to the input quantity and to a propagation delay with respect to the opening signal. The comparator element generates the opening signal with an advance correlated to the input quantity and to the propagation delay.

Claims

1. A control circuit for controlling a switch of a switching current converter configured to receive an input quantity and includes a transformer having a primary winding, and a sensor element configured to generate a sensing signal correlated to a current in the primary winding, the control circuit comprising:

a comparator stage configured to compare a reference signal with a comparison signal correlated to the sensing signal and to generate an opening signal for opening the switch, the switch being configured to switch with a propagation delay with respect to the opening signal, the comparator stage including;

a delay-compensation circuit configured to generate a compensation signal correlated to the input quantity and to the propagation delay, and

a comparator element configured to receive the reference signal, the sensing signal, and the compensation signal and to generate the opening signal with an advance correlated to the input quantity and to the propagation delay.

2. The circuit according to claim 1, wherein the comparator stage comprises:

a delay estimation block configured to generate a delay estimation signal having a parameter correlated to the propagation delay, and

a current source block configured so that the compensation signal is correlated to a product of the delay estimation signal parameter and a control signal correlated to the input quantity.

3. The circuit according to claim 2, wherein the comparator stage is configured to detect an auxiliary current flowing in an auxiliary winding of the transformer and proportional to the input quantity, and to generate the control signal proportionally to the auxiliary current.

4. The circuit according to claim 3, wherein the delay estimation block comprises a switching circuit configured to be activated by the opening signal and deactivated upon detection of a reduction of the auxiliary current.

5. The circuit according to claim 4, wherein the switching circuit comprises:

an estimation comparator configured to compare an instantaneous value of the auxiliary current with a delayed value of the auxiliary current, and

a latch logic element coupled to an output of the estimation comparator and configured to receive the opening signal.

6. The circuit according to claim 2, wherein the current source block comprises:

a switch configured to be controlled by the delay estimation signal; and

a memory element configured to receive the control signal through the switch.

7. The circuit according to claim 6, wherein:

the current source block comprises a charge generator;

the memory element comprises a capacitive element;

the switch is configured to connect the capacitive element to the charge generator for a time controlled by the delay estimation signal; and

the capacitive element is configured to be discharged with a delay with respect to a turning-on signal for the switch.

8. The circuit according to claim 7, comprising:

a zero current detector configured to detect a zero current in an auxiliary winding of the transformer and generate the turning-on signal for the switch,

a delay element, and

a switch element configured to couple the capacitive element to a reference potential line and receive the turning-on signal through the delay element.

9. The circuit according to claim 1, further comprising a reference generator stage configured to generate the reference signal correlated to the input quantity.

10. The circuit according to claim 1, wherein the comparator element has a first input configured to receive the reference signal and a second input configured to receive the sensing signal and a signal correlated to the compensation signal.

11. A switching power supply, comprising:

input terminals configured to receive an input quantity;

a transformer having a primary winding coupled to the input terminals and configured to be passed by a primary current;

a switch coupled to the primary winding;

a sensor element configured to generate a sensing signal correlated to a current in the primary winding; and

a control circuit including;

a comparator stage configured to compare a reference signal with a comparison signal correlated to the sensing signal and to generate an opening signal for the switch, the switch being configured to switch with a propagation delay with respect to the opening signal, the comparator stage including;

a delay compensation circuit configured to generate a compensation signal correlated to the input quantity and to the propagation delay, and

a comparator element configured to receive the reference signal, the sensing signal, and the compensation signal and to generate the opening signal with an advance correlated to the input quantity and to the propagation delay.

12. The switching power supply according to claim 11, wherein the comparator stage comprises:

a delay estimation block configured to generate a delay estimation signal having a parameter correlated to the propagation delay, and

a current source block configured so that the compensation signal is correlated to a product of the delay estimation signal parameter and a control signal correlated to the input quantity.

13. The switching power supply according to claim 12, wherein the comparator stage is configured to detect an auxiliary current flowing in an auxiliary winding of the transformer and proportional to the input quantity, and to generate the control signal proportionally to the auxiliary current.

14. The switching power supply according to claim 13, wherein the delay estimation block comprises a switching circuit configured to be activated by the opening signal and deactivated upon detection of a reduction of the auxiliary current.

15. The switching power supply according to claim 14, wherein the switching circuit comprises:

an estimation comparator configured to compare an instantaneous value of the auxiliary current with a delayed value of the auxiliary current, and

a latch logic element coupled to an output of the estimation comparator and configured to receive the opening signal.

16. A control method, comprising:

controlling a switch of a switching current converter including a transformer having a primary winding, the controlling including;

receiving an input quantity;

comparing a reference signal with a comparison signal correlated with a current in the primary winding;

generating an opening signal for the switch;

detecting switching of the switch with a propagation delay with respect to the opening signal;

generating a compensation signal correlated to the input quantity and to the propagation delay; and

advancing the opening signal by a time correlated to the input quantity and to the propagation delay.

17. The method according to claim 16, comprising generating a delay estimation signal having a parameter correlated to the propagation delay and generating a control signal correlated to the input quantity, wherein the compensation signal is correlated to the product between the parameter of the delay estimation signal and the control signal.

18. The method according to claim 17, comprising detecting an auxiliary current flowing in an auxiliary winding coupled to the primary winding of the transformer and proportional to the input quantity, and generating the control signal correlated to the auxiliary current.

19. The method according to claim 18, wherein generating a delay estimation signal comprises generating a first switching edge of the delay estimation signal upon receiving the opening signal and generating a second switching edge of the estimation signal upon detection of a reduction of the auxiliary current.

20. A method according to claim 17, wherein the parameter of the delay estimation signal is a pulse width, and the compensation signal comprises charging a memory element with the control signal for a time correlated to the pulse width.