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
  • H02M1/00—Details of apparatus for conversion
  • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
  • H02M1/4208—Arrangements for improving power factor of AC input
  • H02M1/4225—Arrangements for improving power factor of AC input using a non-isolated boost converter
• • 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
  • H02M1/00—Details of apparatus for conversion
  • H02M1/0003—Details of control, feedback or regulation circuits
  • H02M1/0012—Control circuits using digital or numerical techniques
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
  • Y02B70/10—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

Definitions

• the present invention concerns a power supply comprising an electric converter, primarily for converting AC to DC, which converter comprises a self- induction, a rectifier element and a switch member controlled by a control cir- cuit, which controls the switch member on the basis of a reference and a measurement of a voltage at a given location in the power supply, a method for controlling a power supply, and the use of such a power supply for motor control.
• PFC circuits For the current supply of many electrical devices, mainly devices connected by one phase to the mains, circuits are used, which correct the power factor, the so-called PFC circuits.
• a substantially sine-shaped current can be drawn from the mains, that is, a current with a low content of harmonics, which today is required by standards.
• a power supply can be achieved, which is relatively independent of the —supply voltage, so that with one and the same power supply a unit can be realized, which can be connected directly to different supply voltages, for example 110 V or 240 V, without requiring a switch action.
• An example of such a PFC- circuit can be found in US-B1 -6,215,287, in which the PFC-circuit is based on a forward converter circuit in the form of a boost converter circuit.
• a transistor is ON -OFF controlled with a switch frequency that is substantially higher than the mains frequency, for example 50 to 100 times higher than the mains fre- quency, which is typically 50 Hz or 60 Hz.
• the transistor When the transistor is ON, the current flows from the mains through a rectifier bridge, a self-induction and the transistor, so that energy is stored in the self-induction.
• the transistor When the transistor is OFF, the current flows from the mains through the rectifier bridge, the self- induction, a rectifier element in the form of a diode and a load.
• the current in the self-induction decreases, while supplying its energy to the load.
• an inter- mediary circuit capacitor is normally used, which is connected in parallel with the load.
• the control of the transistor can, for example, be a pulse width modulation, as described in US-B1 -6,215,287.
• the pulse width modulation is typically controlled by a cascade control, that is, a control comprising two loops.
• One loop is a fast-controlling inner loop, which controls the current in the mains, for example, by controlling the current in the self-induction.
• This control can be made on the basis of a measuring resistor inserted at a suitable location in the circuit, for example between the rectifier bridge and the transistor emitter, or, as shown in DE-C1-33 13 124, in series with the self-induction. In this connection, it must be noted that it has no influence on the measurement that DE-C1-33 13 124 concerns a different type of forward converter.
• a not clearly defined detection device can be used, which measures on the phase or the 0-conductor on the mains side of the rectifier bridge.
• the second loop is a slow-regulating outer loop, which controls the output volt- age of the circuit, that is, in practice, the voltage across the load including the conductors to the load.
• the output signal from the outer control loop is multiplied by the instant value of the mains voltage, for example based on a measurement across the rectifier bridge output, and the result of this multiplication is used as a reference for the inner control loop.
• a PFC-circuit can typically comprise compensation for variations on mains voltage and load, and monitoring functions for overload and overvoltage.
• the inner control loop is fast-regulating, which, in this connection, means that it controls substantially faster than the mains frequency, but still slower than the switch frequency of the transistor.
• this control is a fast l-control.
• the outer control loop is slow, that is, substantially slower than the mains frequency. If this control is chosen too fast, it will equalise the ripple voltage, which will otherwise, due to the limited size of the intermediary circuit capacitor, inevitably occur on the output voltage. This would cause that the input current is not sine-shaped, but distorted, and thus contains exactly the harmonics, which are to be avoided by using the PFC- circuit.
• the task of the present invention is to provide a power supply as mentioned in the introduction, which is cost-effective, and o which does not suffer from the problems mentioned above with regard to stability and voltage overshoot.
• a power supply comprising an electrical converter for converting AC to DC, said 5 converter comprising a self-induction, a rectifier element and a switch member controlled by a control circuit, which controls the switch member on the basis of a reference and a measurement of a voltage at a given location in the power supply, the power supply being characterised by comprising a filter with a first cut-off frequency for an increasing voltage and a second cut-off frequency, o which is different from the first cut-off frequency, for a decreasing voltage.
• the task is solved by a method for controlling a power supply comprising an electrical converter, primarily for converting AC to DC, the converter comprising a self-induction, a 5 rectifier element and a switch member controlled by a control circuit, and preferably a capacitor, said method comprising control of the switch member by means of the control circuit on the basis of a reference and a measurement of a voltage at a given location in the power supply, which method is characterised by a filtering of the signal in the control circuit by means of a filter with a o first cut-off frequency at an increasing voltage and a filtering of the signal in the control circuit by means of a filter with a second cut-off frequency, which is different from the first cut-off frequency, at a decreasing voltage.
• suitable cut-off frequencies it is thus achieved that the control of voltage increases is faster than that of voltage drops, so that the undesired voltage overshoots are reduced without causing the circuit to attempt removing the ripple voltage.
• the power supply is used as a motor control, meaning that the above-mentioned problems with regard to disconnection and low-frequent mixed frequencies are overcome.
• the power supply is made so that both the first cut-off frequency and the second cut-off frequency are fixed.
• the filter can be realized by means of simple components, for example, merely a diode, two resistors and a capaci- tor.
• the different time constants in the voltage measuring circuit are realized in the form of an RC-link comprising at least one capacitor and two parallel-connected resistors, a diode being connected in series with at least one of the parallel-connected resistors.
• the diode is part of a circuit for realising an ideal diode.
• the converter comprises a boost converter circuit, which is an inexpensive and simple way of realising the converter circuit.
• Fig. 1 a schematic view of a first embodiment of a power supply according to the invention
• Fig. 2 a schematic view of a partly digital, second embodiment of a power supply according to the invention
• Fig. 3 a flowchart schematically showing examples of the digital control in the embodiment according to Fig. 2
• Fig. 1 is a schematic view of a substantially analogue embodiment of the invention.
• the power supply circuit is supplied with single-phase AC from the inlets F and 0.
• a bridge rectifier D1-D4 rectifies the AC.
• the circuit comprises a pulse-width modulator 1 , which controls a transistor T1 to be conducting and blocking with a switch frequency that is substantially higher than the mains frequency, for example 50 to 100 times higher than the mains frequency, which is typically 50 Hz or 60 Hz.
• the transistor T1 is conductive, the current flows from the mains through the rectifier bridge D1-D4, a self-induction L1 and the transistor T1 , so that energy is stored in the self-induction L1.
• T1 is conductive, an intermediary circuit capacitor C1 , connected in parallel with the load 2, is inserted in the circuit.
• Control loops are used for controlling the pulse-width modulator 1.
• One loop is a fast-controlling inner loop, which controls the current in the mains, for example by controlling the current in the self-induction. This control takes place on the basis of current measuring derived from a voltage measuring over a measuring resistor R1 , which is inserted between the rectifier bridge D1-D4 and the emitter of the transistor T1.
• This current measuring in itself is known state of the art, and can of course be made at any suitable location in the circuit and in any manner known. For example, as mentioned above in connection with the state of the art.
• the voltage signal 3 corresponding to the voltage measurement is supplied to a subtraction node 4, where it is subtracted from the output signal 5 from a multiplication device 6.
• the resulting signal 7 is filtered in a low-pass filter 8, so that a filtered signal 9 is obtained, which controls the pulse-width modulator 1 , which again controls the transistor T1.
• the second loop is a slow regulating outer loop, which controls the output voltage of the circuit.
• this voltage is measured across the capacitor C1 , in the form of a voltage signal on the conductor 10.
• This signal is filtered through an RC-link comprising a capacitor C3 and two parallel-connected resistors R2 and R3, a diode D6 being arranged in series with the resistor R2.
• the output signal 11 from this RC-link is subtracted from a reference signal 13 in a subtraction node 12.
• the reference signal 13 indicates the nominal output voltage to be supplied by the circuit, for example the 110 V or 240 V mentioned in the introduction.
• the output signal 14 from the subtraction node 12 can be scaled in a scaling device 15 to obtain an output signal 16 from the outer control loop.
• output signal 16 from the outer control loop is multiplied by a signal representing the curve shape of the mains voltage, for example as shown on the basis of a measuring across the output of the rectifier bridge D1-D4, and the result of this multiplication, which is sup- plied as the output signal 5 from the multiplication device 6, is used as reference for the inner control loop.
• the RC-link which comprises a capacitor C3 and two parallel-connected re- sistors R2 and R3, a diode 6 being arranged in series with the resistor R2, serves the purpose of providing two different time constants, one for increasing voltage on conductor 10 and one for decreasing voltage on conductor 10, that is, it provides a low-pass filter with two different cut-off frequencies, depending on whether the control circuit must control an increasing or a decreas- ing output voltage for the circuit.
• a diode D6 is connected in series with one of the two parallel-connected resistors R2 and R3, in the present case R2. If the voltage on the conductor 10 increases, the diode 6 will conduct, and a charging current will run through both parallel-connected resistors R2 and R3 to the capacitor C3. If, on the other hand, the voltage on the conductor 10 drops, the diode D6 will block, so that the capacitor is only discharged through the resistor R3. As the total resistance of the parallel connection of the resistors R2 and R3 is lower than the resistance of R3 alone, the capacitor of the RC-link will thus see a lower time constant for increasing voltage than for decreasing voltage on the conductor 10.
• the values of the resistors R2 and R3 have been chosen so that R3 is in the range of 100 times larger than R2, which ensures a sufficient differ- ence between the two time constants.
• the compensation of the circuit for increasing voltages is faster than that for decreasing voltages, which mainly causes that the damaging and thus unwanted overvoltages can be regulated away faster.
• this provides the desired filtering with two substantially fixed cut-off frequencies.
• it is advantageous to use an ideal diode coupling with an operation amplifier 17, as shown in Fig. 1.
• the two different time constants can also be achieved by using two oppositely polarised diodes arranged in series with the respective resistors R2 and R3. This means that in series with the resistor R3 is inserted a diode, whose polarisation is opposite to that of the diode D6, which is arranged in series with R2 in Fig. 1.
• Fig. 2 shows a second embodiment of the invention, in which the control circuit is digitally implemented in, for example, a microprocessor or a digital signal processor, as suggested with a dotted line.
• the control circuit comprises a multiplexer 21 , which combines the output voltage signal 10, the voltage-measuring signal 3 and the signal representing the curve shape of the mains voltage to a common signal 22.
• This signal 22 is supplied to an analogue/digital converter 23, in which it is converted to a digital signal 24 for use with a calculating unit 25.
• the calculating unit 25 calculates a signal 29, which controls the pulse-width modulator 1 , which again controls the transistor T1.
• Fig. 3 shows an example of a control algorithm, which can be used by the calculating unit 25.
• This algorithm can be stored in a memory 26 in connection with or integrated in the microprocessor or the digital signal processor.
• This memory can be RAM, ROM or, in principle, any suitable memory medium.
• the algorithm which is iterative, starts in a step 100. Then, in a step 101 , the calculating unit 23 awaits the next pulse-width modulated pulse and then, in step 102, reads a UDC, which is a variable representing the actual output voltage on the conductor 10. In the step 103, the calculating unit then compares with the voltage value represented by the variable UDCI, which the pulse-width modulator is presently set to supply. If the measured value, repre- sented by the variable UDC is larger than UDCI, a new value for UDCI is calculated in the step 104.
• the new value for UDCI is calculated in the step 105.
• the calculation of the new UDCI can take place in any of the steps 104 or 105, as both calculations will con- tinue to give the same value of UDCI, namely equal to UDC-
• the new value of UDCI is sent to a step 106 as control signal for the pulse-width modulator 1 , which controls the transistor T1.
• the calculation of the new value of UD C I takes place in the two steps 104 and 105 with two different weightings x and y, so that UDCI approaches UDC with two different speeds, depending on whether UDCI is larger than UDC or not.
• converter circuits than the described forward-converter of the boost type can be used, for example SEPIC-converters (Single Ended Primary inductance Converter), and also that other modulation forms than the described pulse-width modulation can be used.
• SEPIC-converters Single Ended Primary inductance Converter

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Rectifiers (AREA)
• Inverter Devices (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=28459425

Family Applications (1)

Country Status (3)

Cited By (18)

Citations (3)

• 2002
  • 2002-07-04 DK DK200201048A patent/DK174716B1/da not_active IP Right Cessation
• 2003
  • 2003-07-02 WO PCT/DK2003/000458 patent/WO2004006416A1/en not_active Application Discontinuation
  • 2003-07-02 AU AU2003243927A patent/AU2003243927A1/en not_active Abandoned

Patent Citations (3)

Also Published As

Similar Documents

Legal Events