FR2640058A1 - Alternating, variable-ratio switched electronic regulator - Google Patents

Abstract

During the half period in which the phase is positive with respect to neutral, the transistor Q1 does the switching, the diode D2' being conducting. The diode D1 recovers the energy contained in L1, Q2' being conducting. During the half period in which the phase is negative with respect to neutral, Q1' does the switching, D2 being conducting, D1' recovers energy, Q2 being conducting. The electronic system P provides control of the transistors Q1 and Q1' at several tens of KHz for example, with a variable duty cycle depending on the information voltage Van and determining the alternating input/alternating output transformation ratio of the regulator. The electronic system P provides control of the transistors Q2 and Q2', in synchronism with the polarity of the input voltage. The inductor L1 and the capacitor C1 eliminate the high-frequency component resulting from the switching. The assembly behaves like a variable-ratio autotransformer, generating neither distortion nor phase shifting.

Description

We know, for use in direct current, the regulators known as "positive and lowerers", for example their traditional diagram is represented on plate 1. The transistor Q1 is made successively conductive or not according to the signals generated by the pilot P.

These signals can be of fixed frequency and variable duty cycle or of fixed control duration and variable frequency, which amounts to the same thing, but makes filtering more difficult. It is the first solution which is generally adopted.

The duty cycle can be controlled by the value of the Van voltage (O 10 v for example), this resulting from an open loop command, or from a comparison in the case of closed loop regulation.

When transistor Q1 is conductive, current flows through Q1,
The inductance L1 and the resistance of use Ri.

Let’s ignore the role of CI capacity for now.

During this phase the current is identical in Q1, L1, R1 and increasing to Ve-Vs the origin according to a slope equal to it
le is equal to Is.

At the end of this conduction phase, the inductance which has been receptive LIe
(polarity + at the input, - at the output) contains an energy2.

when Q 1 stops driving, the inductor becomes generative (polarity - to
input, + at output) diode D1 becomes conductive, seat of current
id.

During this phase, the current is identical in Di, L1 and Rt. It is decreasing at the origin according to a slope L / R, the current in the transistor
Q1 is zero.

Curve A (plate 1) represents the voltage at the output of QI (therefore at
the input of L1 or across D1) (n - VE as zero reference),
changing from a duty cycle of 9110 to 1/10 for example.

Curve B (plate 1) represents the voltage across R1 (Vms at
Vms' equal to 90% of Ve in the case of the 9/10 duty cycle and 10% of
Ve for the report 1/10
For an appropriate value of L1, the ripple of Vms may be weak and
become negligible by the implementation of Ct.

In the case of a 1/2 duty cycle, we will have:
Fr
Vs = 2
Vs 15 = R
Is the means = 2
Pe = Vex le = Vsx Is (with losses near Q-LI-Di) the assembly therefore presents itself as a true "autotransformer" for direct current, the efficiency of which is close to 1 regardless of the step-down ratio.

This very well-known and widely used system, using high "chopping" frequencies (several tens of KHz) is unidirectional and cannot be used as an alternative.

The present invention consists in a "symmetrization" of the diagram making it usable as an alternative subject to a synchronous "orientation" of certain components, of special arrangements and protections.

The diagram of the axis is shown in Plate 2.

The transistor Qi is replaced by two transistors C sposed in series "back to back", their "sources" being common and the pilot controlling them in parallel (Q1 and Q1 '). They each receive in reverse parallel a diode (D2 and D2 ').

The diode D1 is replaced by two diodes D1 and D1 ', arranged in series "back to back", their anodes being common. They each receive in reverse parallel a transistor (Q2 and Q2 ') controlled alternately by the synchronizer S.

For the convenience of the analysis of the operation, the alternative inputs N and PH have been identified for "neutral" and "phase", these two references being able to be inverted without drawback, it simply seems more logical that the neutral is the common point between entry and exit.

When the phase is positive and throughout the half-period Q2 'will be kept conductive, D1 ensuring the function of energy return diode.

During this same half-period, the current coming from the sector by Q1 (when ordered) and D2 'will cross L1 then R1, in the direction +
When Q1 is not controlled, the energy contained in LI will always flow in the direction +. By QT, D1, L1 and R1.

When the phase is negative and throughout the half-period, it is Q2 which will be kept conductive and D1 'which will perform the function of energy return diode.

During this same half-period, the current coming from the sector by Q1 '(when ordered) and D2, will cross L1 then R1 this time in the direction
For a constant value of the control voltage Van, the duty cycle will be constant throughout the sector period and the waveform obtained at the output will be identical to that of input, with an amplitude which will depend on the duty cycle chosen .

The assembly constitutes a true alternative autotransformer, in which the power taken from the network is equal to the power used by the load, whatever the step-down ratio (to the losses of the components).

In particular, when using the step-down device, the intensity supplied to the load will be greater than that absorbed by the network, which cannot be the case with regard to the variable angle series settings obtained using of transistors, Triac or Thyristors.

In addition, the system does not generate any distortion, the shape of the input current being identical to that of the current absorbed by the load.
The system works as is on resistive loads or with a cos very close to 1.

For highly reactive loads, you must order:
Q1 'permanently when the phase is positive, D2 ensuring the
return of reactive energy, and Q1 cutting.

Q1 permanently when the phase is negative, D2 'ensuring the
return of reactive energy and Qi 'cutting.

Points A and B follow the switching frequency with high dv / dt (around 300 v / lls on a 220 v sector).

This poses the problem of controlling galvanically isolated transistors Q1, Q1 ', Q2, Q2'.

Plate 3 shows a complete and experienced diagram, studied for a compensated asynchronous motor close to cos 1.

The control electronics are supplied for a small transformer with 3 12v insulated secondaries.

There are thus 3 15 v regulated sources (at the terminals of C2 - C9 - Ci 6 assigned to points A, O and B).

The transistors Qi - Q1 '- Q2 - Q2' are of the "HEXFET" field effect type.

A number of components complete the basic scheme:
L2 - L3 - L4 - L5 - L6 - C4, which prevent the return of the switching frequency to the network.

D23 - D24 - D27 - D28, which provide voltage protection of the transistors against switching overvoltages.

R12 and R13 which limit the switching currents, etc ...

The diodes D8 - D9 - D10 - D11 have been designed to eliminate the internal diodes in the HEX-FET, which are too slow.

The connections in "galvanic isolation" were obtained by using "optoelectronic" systems (light-emitting diode + phototransistor) CI1, Cl 2, Cl 3.

Of course, any other connection system (galvanic, by transformers, etc.) and the use in place of other semiconductors (bipolar transistors, Thyristors with controlled extinction, etc.) cannot go beyond the scope. of the invention.

Likewise, three identical systems can constitute a three-phase regulator.

A "modulation" of the duty cycle of the chopping frequency, during a sector period, can make it possible to modify the shape of the output wave, with numerous applications which would remain within the scope of the invention.

Claims (4)

 1. Bidirectional switching system intended to regulate or regulate an alternating voltage with a view to supplying a resistive, inductive or inductive and resistive load (RI) by means of an inductance circuit (LI), capacitance (cul), characterized in that it comprises - a first and a second transistors (Ql.Q'l) mounted head to tail, their  source electrode being common, in series with the charge by  through the inductance-capacitance circuit (LI, Cl), a diode (D2,  D'2) being mounted in reverse parallel on each transistor, the first  transistor (Ql) having its collector electrode intended to be connected to  the phase (PH) of the alternating voltage and the second transistor (Q'l)  being connected to the capacitance inductance circuit (LI, Cl), - a first and a second diode (Dl, Dtl) mounted head to tail, their  anode being common, the two diodes connecting the common point of the  second transistor (Q'l) and capacitance inductance circuit (LI, Cl) at  neutral (N) of the alternating voltage, each of the first and second  diodes (Dl, D'l) being connected in reverse parallel on a transistor (Q2)  respectively (Q'2) having their common source, - a pilot circuit (P) controlling the first and second transistors (Ql,  Q'1) made successively conductive at the switching frequency, - a synchronizing circuit (S) alternately controlling the transistors  (Q2) and (Q'2? In conduction in synchronism with the AC voltage.  2. System according to claim 1, characterized in that when the phase (PH) is positive, said transistor (Q'2) is kept conductive, said first diode (Dl) ensuring the return of energy, the current coming from the phase (PH) passing through said first transistor (QI) and the diode (D'2) then the inductance (him) and the load (Rl) when said first transistor (Ql) is conductive, and, when said first transistor (Ql ) is not conductive, the energy flowing through the transistor (Q'2) the first diode (Dl), then the inductance (Ll) and the load (Rl), whereas when the phase (PH) is negative, said transistor (Q2) is kept conductive, the second diode (D'l) providing energy return, the phase current (PH) passing through the second transistor (Q'l), the diode (D2) from the load (Rl) and inductance (Ll) in reverse.  3. System according to claim l or 2, characterized in that the first and second transistors (Ql, Q'l) and the transistors (Q2, Q'2) are constituted by power transistors, bipolar transistors, transistors field effect, thyristors.  4. Use of three identical systems according to one of claims l to 3, to constitute a three-phase system.