A lapping machine of tension is an electrical circuit making it possible to obtain twice a output voltage equal to the tension of entry. The lapping machines of tension are thus multipliers of tension with for factor two. For that of the interruptory condensers and elements are used.
The simplest circuits are rectifiers having for a tension of alternate entry (AC) and exit a continuous tension (cd.) doubled. The commutating elements are diodes and are thus commutated naturally by the alternating voltage. Circuits DC ⁄ DC need commutating elements commandables, for example a transistor, in order to carry out the doubling of the tension.
Often the multipliers of tension of a higher nature are right extensions of the circuits lapping machine of tension with more stages. One speaks about setting in cascade. In this case, the comprehension of the associated lapping machine of tension is simpler than that of the whole of the assembly.
Circuit of Villard
The circuit of Villard is only made up of one condenser and a diode. It has as advantages its great simplicity and its low level of harmonics. It functions like a circuit clamp. The condenser is in charge on during alternation (half-period) negative to the maximum amplitude of the alternating voltage (Vpk). The output voltage is equal to the alternating voltage of entry to which the constant tension of the condenser is added. The circuit makes pass the component continues signal of zero in Vpk, its minimum becomes zero volt, by neglecting the tension of threshold of the diode, the maximum output voltage thus becomes 2*Vpk. The output voltage is certainly continuous, it strongly oscillates at the rate/rhythm of the alternating voltage of entry. To avoid these oscillations, the circuit should be made much more complex. It is the circuit generally employed, with that with reversed diode, to feed in negative tension the magnetron of a furnace microwaves.
Circuit of Greinacher
The assembly of Greinacher is definitely better than that of Villard for a very limited overcost. The harmonics are normally very weak, zero for the open circuit, dependant on the resistance of the load and the value of the capacities if not. Coarsely, it is about a circuit of Villard associated with a detector with peak. This last element makes it possible to limit the oscillations in the output voltage.
Quadruplor of tension
This circuit was invented in 1913 by Heinrich Greinacher in order to enable him to supply its ionometer between 200 and 300 V thanks to the network 110 V of the town of Zurich.
It puts then its circuit cascades about it in 1920 to carry out a more powerful multiplier of tension. The assembly cascades of Greinacher by error is sometimes named assembly cascades of Villard. In 1932, John Cockcroft and Ernest Walton redécouvrent the assembly in an independent way and use it for their particle accelerator, the assembly is sometimes thus called Cockcroft-Walton generator.
By assembling two assemblies of Greinacher in an opposed way, one obtains a quadruplor of tension. As in the case of a bridge, it is not possible to put at the ground at the same time the entries and the exits of this assembly.
Circuit of Delon
The circuit of Delon is an electric bridge being used to double the tension. This assembly was very current in the construction of cathode tube televisions, where it was used to provide the food very high voltage. Indeed, an electric transformer is at the same time expensive and dangerous within the framework of a use tension of 5 Kv domesticates beyond. Televisions black and white needed 10 Kv, that colors moreover, it was thus necessary to find another solution. A lapping machine of tension was installed after rolling up high voltage of the transformer or on the transformer fly-back.
The circuit is carried out thanks to two detecting circuits of peak and functions in a way similar to the assembly of Greinacher. Each half-circuit functions during an alternation. The output voltage is equal to twice the amplitude of the tension of entry, in other words equal to the amplitude peak with peak.
Circuit with commutated condensers
A chopper can be combined with the circuit of Villard. Thus, a continuous tension can be made alternate, doubled then rectified. The circuit is then more powerful if the switches are commutated simultaneously by an external clock. This type of gating circuit the name of circuit with commutated condensers. This approach is particularly useful in the case of applications with a battery of weak tension and where the integrated circuits require a tension higher than that of the battery. A clock being generally present in the integrated circuits, the overcost of such an assembly is often null.
The figure presents one of the assemblies to commutated condensers simplest. The two condensers are charged simultaneously with the same tension. The food is then stopped and the condensers connected in series. The output voltage east taken at the boundaries of the two series condensers, it is thus twice higher than the initial tension. Many elements can be used in order to carry out commutation, in practice however them.
Circuit lapping machine of tension out of pump of load
The condenser CP is initially charged with the tension with entry. The switches are commutated and the first series condenser with the source start to twice charge the condenser with C0 exit to the tension of entry. The total loading of the C0 condenser can take several periods, but in permanent mode the loads and discharges of CP must be with balance. They result in light oscillations. If the frequency is high, these oscillations are weaker and easier to filter. In the integrated circuits, the frequency of maximum clock is typically about a few hundred Khz.
Pump of load of Dickson
The pump of load of Dickson, or multiplier of Dickson, consists in placing in cascade of the whole of diodes and condensers with the terminal low tension of the condenser ordered by a clock. The circuit is a modification of the circuit in cascade of Greinacher, but the tension of entry is continuous, the variation coming from the clock, whereas for that of Greinacher the tension of entry is alternate. The multiplier of Dickson requires that the clock signals of two consecutive stages are in opposition of phase. However, the assembly out of lapping machine of tension being only on one floor, a clock is enough.
The multiplier of Dickson is frequently used for the integrated circuits, if the tension of the battery is insufficient. Its advantage is that all its components are in the same way standard, that simplifies the production with large scales. The MOSFET are the standard logical doors in the integrated circuits. The diodes of the Dickson assembly thus are often carried out thanks to connected MOSFET in an adequate way. Figure 8 presents this type of assembly.
Double of tension of Dickson using of the MOSFET cabled so as to function in diode
Many alternatives exist for the assembly of Dickson. The majority seek to reduce the effect of the voltage drop between the drain and the source of the transistor. If the tension of entry is weak, this voltage drop can indeed have a great influence. The multiplicative factor for the tension, which is theoretically two, can become much weaker, the tension being lost in the transistor. The use of a Schottky diode against the effect, this one having a very weak voltage drop on its terminals. For reasons of production, the originators of integrated circuits prefer to use despite everything the MOSFET and to increase the complexity of the circuit.
A circuit supplied with an alkaline pile of tension 1,5 V can be used as illustrative example. With a circuit lapping machine of ideal tension, the output voltage is worth 3,0 V. the voltage drop drain-source of a MOSFET connected in diode is worth a little more than the threshold of the tension of trigger is typically 0,9 V. If the voltage drop of the transistor of smoothing also added to the circuit is taken into account, this assembly does not manage to increase the tension without using several stages. A diode of Schottky on the other hand has a voltage drop of about 0,3 V. an assembly with this diode thus has as a output voltage 2,7 V, or 2,4 V after the diode of smoothing.
Circuit with cross commutated condensers
The circuit with cross commutated condensers are employed for the very weak tension of entry, for example for the apparatuses functioning using a pile whose tension can go down in lower part from the volt with time.
When the Φ1 clock is on a low level, the Q2 transistor is open. At the same time, the Φ2 clock is with an elevated level and firm the Q1 transistor. The C1 condenser is then charged by the tension with entry. When the Φ1 clock goes up the terminal in top in the diagram of C1 is carried to a tension equal to twice the tension of entry. at this moment, the S1 switch is closed, the output voltage then becomes equal to twice the entry. Q2 is then closed, the C2 capacity starts to charge like made C1 previously. The roles are then reversed during this second alternation. The exit thus sees always a tension equal to twice the tension of entry.
The losses are weak, because there are no MOSFET connected in diode and thus not the associated voltage drop. The frequency of the oscillations is also doubled, the circuit making up of two assemblies lapping machine, each one connected to a clock. If this last point is rather advantageous, the stray capacities have a greatter importance in assembly than in that of Dickson. They also cause losses.