Control unit of a switching converter operating in continuous-conduction and peak-current-control mode

• US 10,727,734 B2
• Filed: 03/09/2018
• Issued: 07/28/2020
• Est. Priority Date: 03/21/2017
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Gritti, Giovanni
• Primary Examiner(s): Rosario-Benitez, Gustavo A
• Application Number:
  US15/916,697
• Publication Number:
  US 20180278152A1
• Time in Patent Office: 872 Days
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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 unit for a switching converter has an inductor element coupled to an input and a switch element coupled to the inductor element and generates a command signal having a switching period to switch the switch element and determine a first time period in which an inductor current is flowing in the inductor element for storing energy and a second time period in which energy is transferred to a load. An input current is distorted relative to a sinusoid by a distortion factor caused by current ripple on the inductor current. The duration of the first time period is determined based on a comparison between a peak value of the inductor current and a current reference that is a function of an output voltage of said voltage converter. A reference modification stage modifies one of the current reference and sensed value of the inductor current to compensate for distortion introduced by the distortion factor on the input current.

Claims

1. A control unit configured to:

generate a command signal to control at least one switch element of a switching converter including a boost converter that includes the at least one switch element coupled to at least one inductor element, the at least one inductor element coupled to receive an inductor input voltage of the boost converter, the boost converter configured to provide an output voltage from an output of the boost converter, the command signal having a switching period that includes a first time period in which energy is being stored in said at least one inductor element, and a second time period in which stored energy is being transferred from the said at least one inductor element;

receive a sense signal having a value representative of an inductor current of the at least one inductor element, the command signal generated based on a comparison between the value and a reference signal that is a function of the inductor input voltage and the output voltage, and

the control unit having a first terminal for coupling to a node of the boost converter and including a reference modification stage configured to;

receive the command signal; and

generate, based on the command signal, an offset proportional to a current ripple of the inductor current, the control unit configured to introduce the offset to a current flowing through the boost converter via the first terminal, causing an input current to an input of the boost converter to correspond to a desired sinusoidal waveform.

2. The control unit according to claim 1, further comprising a comparator stage having a first comparison terminal configured to receive a first comparison voltage indicative of a peak value of the inductor current, and a second comparison terminal configured to receive the reference signal, said reference modification stage is configured to control said first comparison voltage to be a combination of a voltage across a sensing resistor in series with one of said at least one switch element through which said inductor current flows, and an offset voltage that satisfies the following equation:

3. The control unit according to claim 2, wherein said reference modification stage includes a first voltage-controlled current source having a first control input configured to receive a command voltage and being configured to output an optimization current, and including an optimization block configured to generate said command voltage having a value proportional to said inductor input voltage and to said first time period, wherein said optimization current generates said offset voltage across an optimization resistor.

4. The control unit according to claim 3, wherein said first voltage-controlled current source is configured to at least one of provide current to or draw current from the first terminal to generate a voltage at said first terminal that corresponds to said first comparison voltage.

5. The control unit according to claim 3, wherein the control unit includes a second terminal distinct from said first terminal, the control unit configured for connection of said sensing resistor to the first terminal, and configured for connection of the optimization resistor to the second terminal, and said first voltage-controlled current source has an output at said second terminal, the control unit further including a summing block having inputs coupled to said first terminal and to said second terminal and being configured to generate said first comparison voltage.

6. The control unit according to claim 3, wherein said optimization block further includes:

a second voltage-controlled current source having a second control input coupled to a second terminal of said control unit, the second terminal configured to receive a division of said inductor input voltage and the second voltage-controlled current source configured to output a charging current having a value that is a function of the inductor input voltage according to the following expression;

I_CH=g_maK_pV_IN

where g_ma is a transconductance of the second voltage-controlled current source and KP is a division factor of said division of the inductor input voltage;

a charging capacitor having a capacitance C_TR that is coupled to said second voltage-controlled current source and to be charged by said charging current during said first time period; and

a maintenance capacitor having a capacitance C_H, the maintenance configured to be selectively coupled to said charging capacitor and configured to maintain a value of a voltage across said charging capacitor at the end of said first time period to generate said command voltage of said first voltage-controlled current source.

7. The control unit according to claim 6, wherein said optimization resistor has a resistance value R_S given by the following expression:

8. The control unit according to claim 7, wherein said reference signal has a value equal to the product of a division of said inductor input voltage and a second comparison voltage, and wherein the control unit includes an error amplifier that generates said second comparison voltage as the difference between a division of the output voltage of said boost converter and a voltage reference.

9. The control unit according to claim 8, further including:

a set/reset latch having a reset input coupled to an output of the comparator stage, a set input coupled to a timer stage that generates a set signal based on the determination of a duration of the second time period, and a latch output that supplies the command signal; and

a drive unit coupled to the set/reset latch and configured to transform the command signal into a drive voltage configured to control switching of the at least one switch element.

18. The control unit according to claim 1, wherein the reference modification stage is configured to compensate for a distortion, of the input current of the boost converter in relation to the desired sinusoidal waveform, introduced by a distortion factor caused by the current ripple on said inductor current.

19. The control unit according to claim 1, wherein the offset is a current offset added to the inductor current via the first terminal.

20. The control unit according to claim 1, wherein the reference modification stage is coupled to receive a voltage proportional to the inductor input voltage and includes an active source that generates the offset using the voltage.

21. The control unit according to claim 1, wherein the control unit is configured for connection of the first terminal to the node of the boost converter on a ground return side of the at least one switching element.

10. A switching converter, comprising:

boost converter circuitry including;

a switch element coupled to an inductor element, the inductor element coupled to an input of the boost converter circuitry to receive an inductor input voltage, and the switch element configured to transition between a first switching state and a second state based on a command signal received by the switch element; and

an output configured to be coupled to a load and coupled to the inductor element; and

a control unit having at least a first terminal coupled to a node of the boost converter circuitry, the control unit configured to;

sense a first value of the inductor current in the inductor;

compare the first value with a second value of a reference signal that is a function of the inductor input voltage and the output voltage;

generate, based on a result of comparison of the first value with the second value, a command signal having a switching period that includes a first time period in which energy is stored in the inductor element and that includes a second time period in which stored energy is transferred from the inductor element; and

generate, based on the command signal, an offset signal proportional to a current ripple of the inductor element, the offset signal introduced via the first terminal to a current flowing through the boost converter circuitry and modifying an input current to the input of the boost converter circuitry to correspond to a desired sinusoidal waveform.

11. The switching converter of claim 10, wherein the boost converter circuitry is configured to operate in continuous-conduction mode and with peak-current mode control.

12. The switching converter according to claim 10, wherein the control unit further comprises a reference modification stage configured to control a current flowing through the node to compensate for a distortion of the input current relative to the desired sinusoidal waveform of the input current, the distortion being caused by the current ripple on the inductor current.

13. The switching converter of claim 10, further comprising:

an input stage coupled to a power source configured to supply an input voltage; and

an output stage configured to supply a regulated magnitude to the load as a function of the output voltage,

wherein the control unit is configured to control a power factor correction in a power absorption from the power source.

14. A method, comprising:

generating a command signal having a switching period to control switching of a switch element contained in a boost switching converter including an inductive element coupled to the switch element, the inductive element coupled to receive an inductor input voltage;

determining, in the switching period, a first time period in which energy is being stored in the inductive element;

determining, in the switching period, a second time period in which energy is being transferred from the inductive element;

receiving a reference signal based on an inductor input voltage and an output voltage of the boost switching converter;

sensing a value of an inductor current through the inductive element, the command signal generated based on a comparison between the value of the inductor current through the inductive element and a value of the reference signal; and

introducing, based on the command signal, an offset to a current flowing through a node of the boost switching converter, the offset being proportional to a current ripple of the inductor current and causing an input current of the boost switching converter to correspond to a desired sinusoidal waveform.

15. The method of claim 14, further comprising:

generating a current sense voltage across a sensing resistor in response to the inductor current flowing through the sensing resistor,

wherein introducing the offset to the current includes generating an offset voltage given by the equation;

16. The method of claim 15, wherein generating the offset voltage comprises generating the offset voltage having a polarity that is opposite of a polarity of the current sense voltage.

17. The method of claim 14, wherein introducing the offset to the current flowing through the node of the switching converter includes:

generating a charging current based upon the inductor input voltage;

charging a capacitor with the charging current to generate a charging voltage across the capacitor;

sampling the charging voltage to provide a command voltage; and

generating an optimization current based on the command voltage, the optimization current introduced to the current flowing through the node of the switching converter to modify the input current.