Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/003—Measuring mean values of current or voltage during a given time interval
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
  • G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass

Definitions

• the present invention relates to the technical field of power switching power supplies, also called chopper circuits, used for example for the supply of electric heating elements or electric motors DC.
• a circuit, called chopper, power switching power supply is designed to cyclically deliver a voltage and / or an electric current during a fraction, variable duration, each cycle or period of its operation.
• the regime of such a chopper is defined by its period T and its duty cycle which belongs to the interval] 0; 1 [.
• the supply current is, on the one hand, non-zero during an "on" phase of duration aT and, on the other hand, zero during an "off" phase of duration (1 - a) T.
• modulating the value of the duty cycle it is then possible to vary the average power supply power of the load connected to the chopper circuit.
• Such a chopper circuit finds many applications, particularly in electric heating applications where the modulation of the duty cycle makes it possible to regulate the average heating power delivered by an electric heating element.
• an operational amplifier can be chosen whose offset voltage, the lowest possible, is compatible with the voltage values that it is desired to measure.
• operational amplifiers with very low offset voltage are relatively expensive.
• the invention relates to a method for measuring an output quantity, current or voltage, of a circuit, called chopper, power switching power supply, of period T and duty cycle ratio belonging to at the interval] 0; 1, so that at each period the supply current is, on the one hand, non-zero during an "on" phase of duration aT and, on the other hand, zero during an off phase of duration (1 -a) T.
• this measuring method comprises the following steps:
• the measurements G on and G 0 ff are carried out during the "on" and "off" phases of the same period.
• the measurements G on and G 0 ff are performed at a frequency greater than the switching frequency of the power supply.
• the measurements G on and G 0 ff are each carried out during the phase respectively "on” and "off" of two consecutive periods.
• the measured or measured magnitude may be the output voltage or the output current of the chopper supply circuit.
• the evaluated quantity is the output current and the measured images correspond to an amplified value of the voltage across a measurement resistor in which the output current flows.
• a correction component is added to the evaluated quantity.
• the measured images then correspond to an amplified value of the sum, on the one hand, of the voltage at the terminal of a measurement resistor in which the output current flows. and, on the other hand, a constant value correction voltage.
• the implementation of such a correction component makes it possible to compensate the offset due to amplification defects.
• the correction voltage is a positive DC voltage, which makes it possible to compensate for the negative value shifts.
• the invention also relates to a device for measuring a voltage or current output quantity, a circuit, said chopper, power switching power supply, period T and duty cycle a belonging to the interval] 0 ; 1, so that at each period the supply current is normally, on the one hand, non-zero during an "on" phase of duration aT and, on the other hand, zero during an "off" phase of duration (1-a) T.
• this measuring device comprises:
• a unit of measurement of the amplified voltage at the output of the amplification circuit, which is adapted to:
• the measuring device comprises a circuit for adding a correction voltage to the voltage representative of the quantity measured at the input of the amplification circuit.
• the correction voltage is a positive DC voltage.
• the measurement unit is adapted to perform the measurements G on and G 0 en during the "on" and "off" phases of the same period.
• the measurement unit is adapted to perform measurements G on and G 0 ff at a frequency greater than the switching frequency of the power supply.
• the measurement unit is adapted to calculate the difference ⁇ at a frequency lower than the switching frequency of the power supply.
• the measurement unit is adapted to perform measurements G on and G 0 ff during "on" and "off" phases of two different periods.
• the device is adapted to measure the output current of the chopper circuit and comprises a measurement resistor in which the output current flows, the amplification circuit being adapted to amplify the voltage across the terminals. the measuring resistance.
• the invention is implemented in the context of controlling and regulating the operation of an electric heating element 1 used for heating a passenger compartment of the vehicle.
• the heating element 1 is supplied by a power switching power supply circuit also called chopper H.
• This power supply circuit H has an operating period T and a duty cycle can vary in the interval] 0; 1 [.
• the supply circuit H is controlled by a control unit UC which modulates the value of the duty cycle a as a function of the desired heating power at the level of the heating element 1.
• a measurement resistor S also called a "shunt" which is connected in series with the heating element 1.
• the measurement of the voltage U across the latter makes it possible to evaluate the value of the output current Is delivered to the heating element 1.
• the invention therefore proposes to implement a measurement device 2 which will amplify the voltage U by means of an amplification circuit 3 and then evaluate this voltage by means of a measurement unit UM.
• the amplification circuit 3 comprises an operational amplifier 4 whose inverting input (-) is connected via a resistor R1 to a first terminal of the measurement resistor S.
• the circuit of FIG. amplification 3 also includes a counteraction line 5 which connects, by a resistor R2, the inverting input (-) to the output 6 of the operational amplifier 4.
• the non-inverting input (+) of the operational amplifier is further connected to the second terminal of the resistor measurement S through a resistor R3 and to the ground by a resistor R4.
• the amplification circuit 3 comprises a circuit 7 for adding a correction voltage which is formed of a resistor R5 of which one terminal is connected to the non-inverting input (+) while the other is fed by a constant correction voltage Vc of constant value.
• the supply circuit, the measurement resistor, the amplification circuit and the measurement unit can be made in the form of a single integrated circuit or in the form of discrete components associated with each other. others or in the form of a combination of integrated circuits and discrete components.
• R345 R3 // R4 // R5 is the resistance equivalent to the three resistors R3, R4, R5 in parallel,
• Offset is the offset voltage, called offset, between the inverting input (-) and the non-inverting input (+) of the operational amplifier 4.
• Offset offset voltage preferably chosen to be greater than the maximum value likely to be met for the absolute value of the Offset offset voltage.
• the measurement unit UM is then adapted to measure, on the one hand, the value G on of the output voltage Vs during each "on” phase and the value G 0 ff of the output voltage Vs during each "off” phase. ".
• the unit of measure UM is preferably adapted to have a sampling period less than the period T hash of the supply circuit.
• the sampling period may for example be less than or equal to 1 / 10th of the hash period T.
• the value G 0 ff corresponds to the error induced by the Offset offset attention.
• the unit of measurement calculates or evaluates from AG the value of the output current.
• This evaluation of the output current can then be used by the control unit UC to control the duty cycle a of the supply circuit H so as to regulate the available power level of the heating element 1, to ensure that the output current does not exceed a value the permissible value for the electrical wiring or to identify any malfunction of the supply circuit.
• the output current of the supply circuit is evaluated; however, the invention could also be used to evaluate the output voltage of the supply circuit during each "on" phase.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Current Or Voltage (AREA)
• Dc-Dc Converters (AREA)

Applications Claiming Priority (2)

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Citations (1)

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• 2010
  • 2010-11-09 FR FR1004379A patent/FR2967260B1/fr active Active
• 2011
  • 2011-11-09 EP EP11781530.8A patent/EP2638406A1/fr not_active Withdrawn
  • 2011-11-09 US US13/883,876 patent/US9429596B2/en active Active
  • 2011-11-09 CN CN201180064122.1A patent/CN103492887B/zh active Active
  • 2011-11-09 JP JP2013538176A patent/JP5989654B2/ja active Active
  • 2011-11-09 WO PCT/EP2011/069714 patent/WO2012062789A1/fr active Application Filing

Patent Citations (1)

Non-Patent Citations (2)

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