Ac/Dc Converter with Low Anharmonic Currents

• US 20080031021A1
• Filed: 04/21/2005
• Published: 02/07/2008
• Est. Priority Date: 05/11/2004
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Ros, Thierry, Taurand, Christophe
• Granted Patent: US 7,551,463 B2
• Time in Patent Office: Days
• US Class Current: 363/46
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• 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

This AC/DC converter is an isolated converter with switch-mode current regulation by means of a controlled switch (5). The controlled switch (5) is protected by a current limiting device (9, 7) obeying a peak current setpoint proportional to the instantaneous voltage from the power supply source (Vin). This allows the quality of the absorbed current to be improved and the risks of interference from the switch-mode power supply to be limited while at the same time satisfying the new demands on avionics power networks.

Claims

1. An AC/DC voltage converter with low anharmonic currents and using switch-mode regulation of a rectified current coming from a power supply source of alternating electric current (Vin), by means of at least one controlled switch (5) subjected, by a control device, to switching cycles with variable duty cycle adjusted in such a manner as to cancel an output voltage error detected by an error corrector (16) and to adhere to a limitation setpoint (I_pmax—

_peak) for the peak current generated by a peak current maximum setpoint generator (9) as a function of the instantaneous voltage from the power supply source (Vin), characterized in that the control device comprises an oscillator (10) equipped with a pulse-width modulator PWM (11) controlled by the error corrector (16) with a view to canceling an output voltage error, and a logic circuit (13, 13′

) inserted into the output of the pulse-width modulator PWM (11) ensuring the disabling of the controlled switch or switches (5) each time the instantaneous current flowing through the controlled switch or switches (5) exceeds the setpoint generated by the peak current maximum setpoint generator (9).

2. The converter as claimed in claim 1, characterized in that the peak current maximum setpoint generator (9) generates a peak current limitation setpoint (I_pmax—

_peak) which is a spline function, by parts, of the instantaneous voltage from the power supply source (V<sub>in—

inst</sub>) meeting the definition;

I<sub>pmax—

peak</sub>=k_iV<sub>in—

inst</sub>+b_i i integer varying from 1 to n

n being the number of parts of the spline function defined by successive ranges of variations of the instantaneous voltage V<sub>in—

inst</sub> from the power supply source, an i-th part corresponding to the range;

(V<sub>in—

inst</sub>)<sub>Max(i−

1)</sub>≦

V<sub>in—

inst</sub>≦

(V<sub>in—

inst</sub>)_Maxi

(V<sub>in—

inst</sub>)_Max0=0,

(V<sub>in—

inst</sub>)_Maxi being the value of a transition between the i_-th and (i+1)_-th parts and k_i and b_i being constants whose values depend on the part i in question.

3. The converter as claimed in claim 1, characterized in that it has a flyback topology and operates in discontinuous conduction mode.

4. The converter as claimed in claim 1, with an input circuit connected to the power supply source (V_in), containing the controlled switch (5), an output circuit galvanically isolated from the input circuit and a switch control device (7) having elements divided between the input and output circuits, characterized in that the switch control device (7) comprises, in the output circuit, at least one error correction circuit (16) integrating the difference between the output voltage (V_s) of the converter and a setpoint voltage (Vref), at the interface between the input and output circuits, a galvanic isolation component (15) transporting the output signal of the error correction circuit (16) toward the input circuit, to the input of a control signal generator circuit (10, 11) for the controlled switch (5).

5. The converter as claimed in claim 1, with an input circuit connected to the power supply source (V_in) containing the controlled switch (5), an output circuit galvanically isolated from the input circuit and a switch control device (7) having elements divided between the input and output circuits, characterized in that the switch control device (7) comprises, in the output circuit, at least one error correction circuit (16) integrating the difference between the output voltage (V_s) of the converter and a setpoint voltage (Vref), an oscillator (10, 11) with a variable duty cycle controlled by the error correction circuit (16) supplying, for the controlled switch (5), a control logic signal with two states one of which corresponds to a conduction command, the other to an off command, being pulse-width modulated and, at the interface between the input and output circuits, a galvanic isolation component (15′

) transporting toward the input circuit, to the controlled switch (5), the control logic signal.

6. The converter as claimed in claim 1, making use of an inductance (L_p), in switch-mode operation, supplied with current from the power supply source (Vin) via the controlled switch (5), characterized in that it comprises an input current harmonic reduction circuit formed by an oscillation damping circuit (14) connected across the terminals of the inductance (L_p).

7. The converter as claimed in claim 6, characterized in that the input current harmonic reduction circuit (14) is a dissipative circuit comprising a capacitor (70) placed in series with a resistor (71) across the terminals of the inductance (L_p).

8. The converter as claimed in claim 6, characterized in that the input current harmonic reduction circuit (14) is a non-dissipative switched circuit comprising an auxiliary controlled switch (100) placed in series with a flywheel diode (101) across the terminals of the inductance (L_p), allowing the inductance (L_p) to be short-circuited during the times where it is not supplied with current by the power supply source (Vin).

9. The converter as claimed in claim 2, characterized in that it comprises a current limitation setpoint generator (13) generating a peak current limitation setpoint proportional to the instantaneous voltage from the power supply source, with a progressive limitation of the gain (k_i≦

k_i+1) beyond the normal range of amplitude variation of the voltage from the power supply source (Vin).

10. The converter as claimed in claim 1, making use of the inductance (L_p), in switch-mode operation, of an isolation transformer (1) providing a galvanic isolation between input and output, characterized in that it comprises:

on the secondary side of the transformer (1),

an error corrector (16) delivering a setpoint which is a function of the difference presented by the output voltage (Vs) of the converter with respect to a voltage setpoint (Vref),

straddling the boundary separating the primary and secondary sides of the transformer (1),

a coupler (15) with galvanic isolation transmitting the output setpoint from the error corrector (16) to the primary side of the transformer, and

on the primary side of the transformer (1),

a rectifier circuit (2) supplying an unregulated DC electrical voltage,

a pulse-width modulated oscillator (10, 11) controlled by the setpoint produced by the error corrector (16) and transmitted by the coupler (15) supplying, to the controlled switch (5), a switching signal composed of pulses,

a current sensor (6) measuring the instantaneous current flowing through the controlled switch (5),

a peak current threshold crossing detector circuit (12) comparing the setpoint delivered by the peak current setpoint generator (13) with the instantaneous current measured by the current sensor (6), and

a pulse inhibitor circuit (134, 135) inserted between the pulse-width modulated oscillator (10, 11 FIG. 2) and the control of the controlled switch (5), triggered by the threshold crossing detector circuit (12) and reset by each pulse of the switching signal delivered by the pulse-width modulated oscillator (10, 11).

11. The converter as claimed in claim 1, making use of the inductance (L_p), in switch-mode operation, of an isolation transformer (1) providing a galvanic isolation between input and output, characterized in that it comprises:

on the secondary side of the transformer (1),

an error corrector (16) delivering a setpoint which is a function of the difference presented by the output voltage (Vs) of the converter with respect to a setpoint (Vref), and

an oscillator (10, 11), called main oscillator, with pulse-width modulation controlled by the setpoint output from the error corrector (16), supplying a switching signal,

straddling the boundary separating the primary and secondary sides of the transformer (1),

a galvanic isolation coupler (15′

) transmitting the signal from the main oscillator (10, 11) toward the control of the controlled switch (5),

on the primary side of the transformer (1),

a rectifier circuit (2) supplying an unregulated DC electrical voltage,

an oscillator (131), called auxiliary oscillator, supplied by the rectifier circuit (2) placed on the primary side of the transformer (1) and supplying periodic pulses driving the controlled switch (5) into conduction,

a routing circuit (132), with two inputs and one output, inserted behind the outputs of the auxiliary oscillator (131) and of the coupler (15′

), giving priority to the signal, when it exists, from the main oscillator (10, 11) transmitted by the coupler (15′

),

a current sensor (6) measuring the instantaneous current flowing through the controlled switch (5),

a peak current threshold crossing detector circuit (12) comparing the setpoint delivered by the peak current setpoint generator (13) with the instantaneous current measured by the current sensor (6), and

a pulse inhibitor circuit (134, 135) placed at the output of the routing circuit (132), triggered by the threshold crossing detector circuit (12) and reset by each pulse crossing the routing circuit (132).