Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS 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
  • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
  • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
  • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
  • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
  • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters

Definitions

• the present invention relates in general to electronic control circuits and specifically to an electronic circuit for controlling a vibration pump.
• Pumps of this type are utilised in various branches of the art and, in particular, in machines for dispensing drinks, for example coffee, tea, chocolate etc.
• Such pumps are normally made in such a way as to be able to operate from an alternating supply, usually about 220 volts (mains voltage) .
• the present invention therefore seeks to provide means allowing a vibration pump to be supplied, in an almost direct manner, from a DC supply, above all a DC supply of low voltage (12, 24 or 48 volts) .
• the present invention in its preferred embodiment, is based on the idea of allowing the operation of a normal vibration pump by supplying it with DC through an oscillator and a power supply circuit operating with HEX-FET, that is to say with a transistor able to deliver very high currents.
• Figure 1 illustrates, in the form of a block diagram, the general configuration of apparatus incorporating a circuit according to the invention
• Figure 2 illustrates in more detail the structure of the circuit according to the invention.
• FIG. 1 diagram reproduces, purely by way of example, the structure of the control circuit for an electric vibration pump 1 intended to allow delivery of water under pressure into apparatus for preparing and dispensing drinks such as coffee, tea or chocolate.
• this possible application is • not to be interpreted in a limitative sense.
• the pump 1 is controlled through a power supply circuit 2 the structure of which will be illustrated better with reference to the diagram of Figure 2.
• the circuit 2 is in turn controlled by an oscillator circuit 3 subject to control logic 4 (for example a micro processor) .
• Various input/output lines lead to the micro processor 4 and are connected to various other circuit modules.
• the reference numeral 5 indicates a voltage stabiliser circuit, in turn connected to the general supply source of the device, represented by a battery 6 able to deliver a voltage of 12, 24 or 48 volts (depending on the type of vehicle on which the device is mounted) .
• the circuit 5 and the battery 6 are also connected to a module 7 for controlling the temperature to which the water utilised for the preparation of the drinks is heated: this water is received in a boiler (not illustrated) which has an associated heating resistor 8 controlled by the circuit 7.
• the reference numeral 9 indicates a sensor connected to a water level indicating float in the boiler, whilst the reference numeral 10 indicates an operating push button intended to be actuated by the user to stop delivery of the drink once it has reached the desired level.
• a further sensor switch 11 is sensitive to the introduction into the machine of a capsule containing powder material for the preparation of the drink.
• the switch 11 could be simply constituted by another actuating switch intended to be activated by theteil.
• the reference numeral 12 indicates a solenoid valve for controlling the delivery of water
• the reference 13 indicates a warning lamp for indicating the level of water, intended in particular to indicate when this level falls below a minimum acceptable value.
• the logic 4 commands activation of the pump 1: to this end the logic 4, via the resistance 107, will pull the base of the NPN transistor 105 down to earth, which transistor, no longer being in conduction, will allow pulses generated by the oscillator stage 3 to reach the bases of the transistors 14a and 14b via the resistor 106.
• the oscillator circuit 3 is constituted by a stage comprising two bistable circuits such as two Schmitt triggers 100a, 100b (each constituted, for example, by one sixth of a CMOS integrated circuit 40106) connected in cascade as illustrated in Figure 2, with the output of the downstream trigger 100b (constituting the output of the oscillator) fed back to the input of the upstream trigger 100a through a capacitor 101 (typical value 0.1 ⁇ F) .
• bistable circuits such as two Schmitt triggers 100a, 100b (each constituted, for example, by one sixth of a CMOS integrated circuit 40106) connected in cascade as illustrated in Figure 2, with the output of the downstream trigger 100b (constituting the output of the oscillator) fed back to the input of the upstream trigger 100a through a capacitor 101 (typical value 0.1 ⁇ F) .
• a resistor unit 102, 103 connected to the terminal of the capacitor 101 opposite that connected to the output of the downstream trigger 100b so as to form an RC unit the time constant of which regulates the feedback action to the input of the oscillator 3 so as to cause selective variation of the oscillation frequency.
• the resistor 102 can have a resistance value of 82 K Ohm, and the resistor 103 may be a multiturn 50 K Ohm potentiometer.
• the oscillator 3 is able to produce at its output a square wave signal with a frequency of the order of, for example, 50-100 Hz adjustable (by acting on the potentiometer 103) to achieve a precise adaptation to the mechanical characteristics of the pump 1 so as to obtain the maximum output pressure (10-13 atmospheres) .
• the oscillation frequency of the circuit 3 and therefore the control frequency of the power circuit 2 be a frequency corresponding to the mains frequency (typically 50 Hz) for which the pump 1 has been originally arranged to operate.
• the pump 1 is in fact a normal vibration pump intended to be supplied by connection to the electrical mains.
• the power circuit 2 receives, via the resistor 106 (10 K Ohm) , the output signal from the oscillator circuit 3 at its input stage comprising the two transistors 14a and 14b connected in a complementary symmetrical arrangement (push-pull) .
• the transistor 14a comprises an NPN transistor the collector of which is connected to the DC voltage.
• This latter is constituted usually by the battery voltage Vb (when this latter is 12 volts) or the battery voltage stepped down by a voltage divider or the like, if the battery voltage is of higher value (24-48 volts).
• the emitter of the transistor 14a is connected to the emitter of the transistor 14b, which is a PNP type transistor the collector of which is connected to the circuit earth.
• the output signal from the oscillator is passed to the bases of the two transistors 14a, 14b which are connected together.
• Respective diodes 15a and 15b serve as protection for the two transistors 14a, 14b.
• the signal present at the emitters of the two transistors 14a, 14b (which emitters are connected together) is transferred through a power resistor 16 (for example a % watt resistor with a resistance value of the order of 10 Ohm) to the gate electrode of the component 17 having HEX FET characteristics the source electrode of which is connected to earth M, whilst the drain electrode is connected to one of the terminals of the pump 1, the
• the component 17 is usually constituted by an N-channel power FET of the enhancement mode type such as, for example, IRFP150 able to deliver currents of the order of 40 amps.
• a polarisation resistor 18 typically 10 K Ohm
• a diode 19 of FAST type for example a By 329
• the FAST diode 19 protects the transistor 17 from strong reverse currents due to inductive load.
• a capacitor 20 which, in the example, is0.47 ⁇ F having a working voltage of 250 volts and which acts as a filter.
• the arrangement described is such that the transistor 17 is alternatively conductive and non-conductive (that is to say switched off and saturated) by the output signal from the input stage constituted by the two transistors 14a, 14b.
• the transistor 17 behaves as a sort of switch connected in series with the pump 1 between the battery voltage V and earth with the capacity of selectively allowing currents of high intensity through the pump 1, according to whether the transistor 17 itself is in conduction or switched off.
• the voltage control arrangement normally provided for the pump 1 (excitation voltages of high value typically the 220 volts of the mains network, or the alternating 24 volts possibly taken from a transformer with 220 volt primary winding and a 24 volt secondary winding, both of adequate power) is on the other hand replaced in the arrangement according to invention with a DC control (high current values by comparison with moderate voltage values, such as the DC voltage values of a battery) .

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Dc-Dc Converters (AREA)
• Tea And Coffee (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

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Cited By (2)

Citations (3)

• 1992
  • 1992-04-09 IT ITTO920326A patent/IT1259532B/it active IP Right Grant
• 1993
  • 1993-04-06 WO PCT/EP1993/000843 patent/WO1993021684A1/en active Application Filing

Patent Citations (3)

Non-Patent Citations (5)

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