WO1992007414A1 - Buck-boost converter circuit - Google Patents

Buck-boost converter circuit

Info

Publication number
WO1992007414A1
WO1992007414A1 PCT/EP1991/001962 EP9101962W WO1992007414A1 WO 1992007414 A1 WO1992007414 A1 WO 1992007414A1 EP 9101962 W EP9101962 W EP 9101962W WO 1992007414 A1 WO1992007414 A1 WO 1992007414A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
connected
converter
switching
means
circuit
Prior art date
Application number
PCT/EP1991/001962
Other languages
French (fr)
Inventor
Giuseppe Cimador
Paolo Prestifilippo
Original Assignee
Italtel Società Italiana Telecomunicazioni S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00Conversion of dc power input into dc power output
    • H02M3/02Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00Conversion of dc power input into dc power output
    • H02M3/22Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M19/00Current supply arrangements for telephone systems
    • H04M19/001Current supply source at the exchanger providing current to substations
    • H04M19/008Using DC/DC converters

Abstract

Buck-boost converter circuit, supplied by a variable direct voltage (Vg) applied between two input terminals (A, B) to produce a constant output voltage on a load (R) connected between two output terminals (C, D). The buck-boost converter circuit includes a single conversion stage consisting of two flyback type converters, which according to the controlling duty cycle, can operate as boost or buck, either with negative or positive polarity on the load.

Description

BUCK-BOOST CONVERTER CIRCUIT

The present invention refers to a buck-boost converter circuit, that is a device allowing to obtain a constant output voltage on a user load R, starting from a battery variable voltage.

The subject of the invention can be employed for instance to generate the microphonic voltage which is sent to the user telephone lines.

Known devices of this kind, called also reversible boosters, show several troubles, such as for instance considerable overall'-.'dimensions, and- ..weight, * or high complexity, due to the presence of two separate stages.

In particular, according to the known technique, two cascade connected stages are used, having a limited total efficiency and of complex operation and control.

The scope of the present invention is to realize a single stage buck-boost converter, free from the above mentioned troubles and of limited weight and volume, high efficiency and of simple construction. These purposes are attained with the invention consisting of a buck-boost converter circuit suitable to produce a constant output voltage on a load connected between two output terminals, being the converter supplied by a direct voltage applied between two input terminals, characterized by the fact of including two branches connected in parallel between the input terminals, each branch including: a first inductor connected in series to the first bidirectional switching means, and a diode connected in parallel to said first bidirectional switching means, a second inductor connected in series to the second bidirectional switching means, and a diode connected in parallel to said second bidirectional switching means; and two meshes connected in series between them matching one common node and between one input terminal and one output terminal, each mesh including a third inductor connected in series to a first capacitor and to third bidirectional switching means, and a diode connected in parallel to said third bidirectional switching means; a fourth inductor connected in series to a second capacitor and to fourth bidirectional switching means, and a diode connected in parallel to said fourth bidirectional switching means; said common node being connected to a terminal of each capacitor, and by the fact.that the .first and third inductors are magnetically coupled between them and that said second and fourth inductors are magnetically coupled between them, said converter including also means able to generate pulse control signals having constant repetition frequency and variable duration depending on the load and on the direct voltage applied to the input terminals.

Further advantageous characteristics form the subject of dependent claims. The converter according to -the invention is applied, preferably but not limited to, powers lower than 1 kW.

The invention shall be now described more in detail making reference to a preferred but not limiting realization form, shown in the figures enclosed, where: figure 1 shows a general block diagram of a buck-boost converter circuit according to the invention, and figure 2 schematically outlines the driving circuit.

As shown in the general diagram of figure 1, the buck- boost converter circuit according to the invention includes two input terminals A, B, supplied by a direct voltage Vg, supplied by a battery and two output terminals C, D, supplying a load R.

In parallel to terminals A and B two branches are connected, each one formed by an inductor and by a switching bidirectional element, schematically represented by a transistor, with a corresponding diode connected in parallel among the terminals of collator and emitter. In detail, the first branch includes a first inductor

LIA in series to a transistor Ql with diode Dl connected between collector and emitter, while the second branch includes a second inductor L2A in series to a transistor Q2 with diode D2 connected between collector and emitter.

The two transistors Ql and Q2 are of the NPN type and their bases are driven by pulse signals G and H, generated in one control unit CO (see figure 2) .

The circuit foresees also two meshes, formed by the connection in series of a third transistor Q3, a third inductor LIB, a capacitor Cl and by the connection in series of a fourth transistor Q4, a fourth inductor L2B, a capacitor C2, respectively. The two meshes are connected matching the common node Z to the two capacitors Cl and C2, while the other two terminals of capacitors are connected, to the input terminal A and to the output terminal C, respectively. Furthermore two diodes, diode D3 and D4 respectively, are connected between the terminals of collector and emitter of the two transistors Q3 and Q4. The two transistors Q3 and- Q4 are of NPN type and their bases too are driven by pulse signals L and M, generated by a control unit which shall be described hereafter.

As shown in figure 1, inductors LIA and LIB are magnetically coupled, e.g. through a common magnetic support (usually ferrite) , and inductors L2A and L2B, are they too magnetically coupled through an additional common magnetic support (usually ferrite) . Furthermore, always in fig. 1, winding directions of inductors are indicated in the conventional way with points matching one end of windings.

The scheme described can be considered as formed by two reversible flyback PWM type converters. The two elementary converters are identified by the following components:

1) Vg, Ql, Dl, LIA, LIB, Q3, D3, Cl

2) Vg, Q2, D2, L2A, L2B, Q4, D4, C2 The transfer static characteristic of a single flyback converter is given by:

Vout = Vg*D/(l-D) where D is the duty cycle, that is the time within the switching period for which the active element is kept conducting.

Calling Dl and D2 the work duty cycles of the first and of the second converter at a given moment, we have: VI - Vo = Vg*Dl/(l-Dl) (1) V2 - Vo = Vg*D2/(l-D2) (2) subtracting (2) from (If we obtain:

VI -V2 = Vg*(Dl/(l-Dl) -D2/(l-D2)) assuming also that D2 = 1 - Dl, we have:

VI -V2 = Vg* [(2*D1 - 1)/(Dl)*(1-D1) ] (3). Finally, for the voltage applied to the load R we obtain: VR = Vg-Vg* (2*D1-1)/(Dl)*(1-D1) (4)

It is evident, from (4) , that: for Dl = 0.5 we obtain VR = Vg for Dl > 0.5 we obtain VR < Vg for Dl < 0.5 we obtain VR > Vg so for Dl > 0.5 we have an operation as buck converter for Dl < 0.5 we have an operation as boost converter. The four transistors, or more in general active bidirectional switching devices, called Ql, Q2, Q3 and Q4 are driven through signals G, H, L, and M of the pulse type, in such a way that each one of them can assume two operation stages, and more particularly an open and a closed state. In the open state, the switching element shows a very high impedence, not allowing the current to pass through its terminals, typically the transistor results interdicted and there is no current circulation between the collector and emitter. In the closed state, the switching element has a very low impedence allowing the current to pass through its terminals, typically in the case of a transistor, this last is in a saturation state.

During operation, when the transistor Ql is closed, a current supplied by the source Vg passes through the inductor LIA which stores power under the magnetic form.

This power is then transferred to the capacitor Cl during the off time of transistor Ql. The diode D3 is a rectifier diode and is just employed to transfer the power stored in the magnetic field of LIA on capacitor Cl. Similarly, but shifted in time, during closure of transistor Q3 a current supplied by the source Vg circulates in inductor L2A storing power under the magnetic form. This power is then transferred to the capacitor C2 during the off time of transistor Q2. The diode D4 is a rectifier and is just employed to transfer the power stored in the magnetic field of L2A on capacitor C2. Furthermore this diode has also the function to offer a closure way to the direct current of load R.

The transistor Q3 is used with its closure to store power on inductor LIB to recover -it to the battery whenever the loading conditions and the battery rate impose a negative power on the converter Q3 belongs to. The diode Dl represents the rectifier diode for these operation conditions for the recovering of power in the battery. Furthermore the transistor Q3 has the primary function to cause the closure of the direct current going to the load R.

Similarly, the transistor Q4 is used with its closure to store power on inductor L2B to recover it to the battery whenever the loading conditions and the battery rate impose a negative power on the converter Q4 belongs to. The diode D2 represents the rectifier diode for these operation conditions for the recovering of power in the battery.

Making reference to figure 2, it is now described the circuit generating the control pulses G, H, L, M which are sent to the four switches Q1-Q4. These pulses have a constant or fix repetition frequency in all operation conditions, called conversion frequency. On the contrary, duration results variable, that is the transition moment from a state to the subsequent one, and this variable duration is called duty cycle.

Modulation pulses are obtained by comparison of a voltage signal Vml, called modulating signal, and of a triangular shaped signal R, called carrier, this last having a much higher (in the range of 50-100 kHz in applications for low powers) frequency than that of the first signal. As shown in fig. 2, the modulating signal Vml is obtained by the difference, in an error amplifier Al, between a reference signal Vr and the output voltage V present on load R. These voltages are taken through resistances Rl and R2, and the output of the operational amplifier Al is connected to the inverting input through a compensation network CM. The negative feedback so obtained is used to obtain a regulated output voltage.

In particular driving signals of Ql and Q3 are obtained comparing the modulating signal Vml and the ramp R to the input of a irst comparator CP1. Aninverting driver DR1, that is a circuit inverting.the signal coming out from CP1 and brings it to the required power level for the control of transistor Ql, is connected to the output of a comparator CP1. Pulses L are obtained from G ones (that it at DR1 output) through an non-inverting optocoupler 0P1 followed by another inverting driver DR3.

Driving signals for Q2 and Q4 are obtained by comparing a signal Vm2 (obtained from Vml through a phase shifter SF by 180°) with the ramp R in a second comparator CP2. The output of comparator CP2 drives the transistor Q2 (signal H) through an inverting driver DR2, while pulses M for Q4 are obtained from the previous ones at DR2 output through a non-inverting optocoupler 0P2 followed by another inverting driver DR4.

The buck-boost converter circuit according to the invention does not employ two cascade connected stages, but a single conversion stage which according to the controlling duty cycle can act as boost or buck converter circuit. Reduced overall dimensions compared to conventional buck-boost convert circuit of equal power are thus obtained thanks also to the very high conversion efficiency due to the fact that it handles only a small portion of the power to transfer on the load.

It also has a high operation reliability, having the output power determined by the dimensioning of active and passive components present in the circuit.

Furthermore it foresees a limited number of active elements, with an ensuing reduction of production costs and does not require the use of complementary couple semiconductors. Finally, being the active elements referred in groups of two to the same potential, a considerable driving simplification is obtained.

Claims

CLAIMS 1. Buck-boost converter circuit suitable to produce a constant output voltage on a load (R) connected between two output terminals (C,D) , the converter being supplied by a direct voltage (Vg) applied between two input terminals (A, B) , characterized by the fact of including two branches connected in parallel between the input terminals (A,B) , each branch including:
- a first inductor (LIA) connected in series to the first bidirectional switching means (Ql) , and a diode (Dl) connected in parallel to said first bidirectional switching means (Ql) ;
- a second inductor (L2A) connected in series to the second bidirectional switching means (Q2) , and a diode (D2) connected in parallel to said second bidirectional switching means (Q2) ; and two meshes connected in series between them matching one common node (Z) and between one input terminal (A) and one output terminal (C) , each mesh including - a third inductor (LIB) connected in series to a first capacitor (Cl) and to third bidirectional switching means (Q3) , and a diode -(D3) connected in parallel to said third bidirectional switching means (Q3) ;
- a fourth inductor (L2B) connected in series to a second capacitor (C2) and to fourth bidirectional switching means (Q4) , and a diode (D4) connected in parallel to said fourth bidirectional switching means (Q4) ; and said common node (Z) being connected to a terminal of each capacitor (Cl, C2) , and by the fact that said first and third inductors
(LIA, LIB) are magnetically coupled between them and that said second and fourth inductors (L2A, L2B) are magnetically coupled between them, said converter including also means (CO) to generate pulse control signals having constant repetition frequency and duration varying according to the load and on the direct voltage (Vg) applied to the input terminals.
2. Buck-boost converter circuit according to claim 1, characterized by the fact that said bidirectional switching means are made of transistors (Q1-Q4) controlled on the base electrode by said pulse control signals and that said diodes (D1-D4) are connected between the terminals of collector and emitter of said transistors (Q1-Q4) .
3. Buck-boost converter circuit according to claim 2, characterized by the fact that said control signals applied to the first and third switching means (Ql, Q3) are negative logic between them.
4. Buck-boost converter circuit according to claim 3, characterized by the fact that said control signals applied to the first and third switching means (Q2, Q4) are negative logic between them.
5. Buck-boost converter circuit according to claim 3, characterized by the fact that said means (CO) to generate the pulse control signals for the first and third switching means include a first comparator (CPl) supplied at one input by a modulating signal (Vml) , and at the other input by a ramp signal (R) having frequency much higher than the modulating signal (Vml), and a first inverting driver (DR1) connected to the output of said first comparator (CPl) .
6. Buck-boost converter circuit according to claim 4, characterized by the fact that said means (CO) to generate the pulse control signals for the second and fourth switching means include a second comparator (CP2) supplied at one input by a modulating signal (Vml) phase shifted by 180°, and at the other input by a ramp signal (R) having frequency much higher than the modulating signal, and a second inverting driver (DR2) connected to the output of said second comparator (CP2) .
7. Buck-boost converter circuit according to claims 5 or 6, characterized by the fact to foresee a non inverting optocoupler (OP1, 0P2) connected to the output of each one of said first and second inverting drivers (DR1, DR2) .
8. Buck-boost converter circuit according to claim 7, characterized by the fact to include an error amplifier (Al) supplied at one input by a reference signal (Vr) and by the output voltage (V) present on the load (R) , the output of the error amplifier (Al) being also connected to said input through a compensation network (CM) .
PCT/EP1991/001962 1990-10-19 1991-10-12 Buck-boost converter circuit WO1992007414A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
IT21806A/90 1990-10-19
IT2180690 1990-10-19

Publications (1)

Publication Number Publication Date
WO1992007414A1 true true WO1992007414A1 (en) 1992-04-30

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ID=11187104

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1991/001962 WO1992007414A1 (en) 1990-10-19 1991-10-12 Buck-boost converter circuit

Country Status (1)

Country Link
WO (1) WO1992007414A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2090078A (en) * 1977-09-28 1982-06-30 California Inst Of Techn D.c.-to-d.c. Switching Converter
EP0087593A2 (en) * 1982-02-25 1983-09-07 Siemens Aktiengesellschaft Circuit arrangement for telecommunication installations, especially for telephone exchange installations, with direct voltage converters
EP0252557A1 (en) * 1986-07-08 1988-01-13 Philips Electronics N.V. DC-supply arrangement for a telecommunication line

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2090078A (en) * 1977-09-28 1982-06-30 California Inst Of Techn D.c.-to-d.c. Switching Converter
EP0087593A2 (en) * 1982-02-25 1983-09-07 Siemens Aktiengesellschaft Circuit arrangement for telecommunication installations, especially for telephone exchange installations, with direct voltage converters
EP0252557A1 (en) * 1986-07-08 1988-01-13 Philips Electronics N.V. DC-supply arrangement for a telecommunication line

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