TWI464415B - Measurement system and method for power conversion efficiency - Google Patents

Measurement system and method for power conversion efficiency Download PDF

Info

Publication number
TWI464415B
TWI464415B TW098127335A TW98127335A TWI464415B TW I464415 B TWI464415 B TW I464415B TW 098127335 A TW098127335 A TW 098127335A TW 98127335 A TW98127335 A TW 98127335A TW I464415 B TWI464415 B TW I464415B
Authority
TW
Taiwan
Prior art keywords
measurement
electronic load
voltage regulator
current
output current
Prior art date
Application number
TW098127335A
Other languages
Chinese (zh)
Other versions
TW201105983A (en
Inventor
Ting Chung Wang
Original Assignee
Hon Hai Prec Ind Co Ltd
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
Application filed by Hon Hai Prec Ind Co Ltd filed Critical Hon Hai Prec Ind Co Ltd
Priority to TW098127335A priority Critical patent/TWI464415B/en
Publication of TW201105983A publication Critical patent/TW201105983A/en
Application granted granted Critical
Publication of TWI464415B publication Critical patent/TWI464415B/en

Links

Description

Power conversion efficiency measurement system and method

The present invention relates to a power conversion efficiency measurement system and method.

In order to ensure that the computer performs various functions during use, the tester must perform measurement and verification of various functions of the computer hardware after completing the computer hardware assembly, such as Voltage Regulator Device (VRD). The power conversion efficiency of the voltage conversion device is measured. The voltage regulator converts the higher DC voltage to a lower DC voltage to power different wafers on the motherboard, and the power conversion efficiency varies with the connected wafer. The power conversion efficiency of the voltage regulator is an important performance indicator to measure the operating state of the voltage regulator. Therefore, the power conversion efficiency of the voltage regulator needs to be measured before the computer motherboard is shipped to verify compliance.

At present, the measurement method of the power conversion efficiency of the voltage regulator is generally measured by the tester to measure the input power and output power of the voltage regulator, and the measurement results are recorded, and the measurement time of each voltage regulator is often long. It took several hours, and the testers were unable to leave the site during the measurement period, and a large amount of data was recorded. This manual measurement method takes a lot of time and effort, and is extremely error-prone and cannot be measured in a short time, so the measurement accuracy and efficiency are extremely low.

In view of the above, it is necessary to provide a power conversion efficiency measurement system and method, which can automatically measure the power conversion efficiency and improve the efficiency and accuracy of the measurement.

A power conversion efficiency measuring system includes a power source, a resistor, a voltmeter, an electronic load, and a measuring device, and the power source is connected to the voltage regulator through a parallel circuit of the resistor and the voltmeter, the voltage regulator And connecting the computer through the electronic load, the computer is further connected to the voltmeter, the computer comprises a processor and a memory, the processor is connected to the memory and executes instructions stored in the memory, the memory comprises a memory The measurement setting module is configured to preset the maximum output current and the number of measurement times of the voltage regulator, and calculate a target output current of the voltage regulator according to a preset calculation formula of the target output current; a load adjustment module for reading a current recorded on the electronic load flowing through the electronic load, and adjusting the electronic load such that a current of the electronic load is equal to a target output current of the voltage regulator; a computing module, The current flowing through the electronic load through the read complex array is multiplied by the input voltage of the electronic load to calculate each of the voltage regulators Outputting power, and reading the voltage across the resistor measured by the voltmeter, calculating the input power of each group of the voltage regulator according to the resistance value of the resistor and the output voltage of the power source, and the power conversion of the voltage regulator The efficiency is equal to the average of the ratio of the output power of all groups to the input power of all groups; and a judging module is used to determine whether the serial number of the measurement times exceeds the preset measurement number, and if not, the sequence number of the measurement times is set. For the next measurement.

A power conversion efficiency measuring method includes the following steps: presetting a maximum output current of a voltage regulator and a number of measurement times, and calculating a target of the voltage regulator according to a preset calculation formula of a target output current Output current and set the serial number of the initial measurement times; Reading a current recorded on an electronic load flowing through the electronic load, and adjusting the electronic load such that a current of the electronic load is equal to a target output current of the voltage regulator corresponding to a serial number of the measurement times; The current flowing through the electronic load is multiplied by the input voltage of the electronic load to calculate the output power of each group of the voltage regulator, and the voltage across the resistor measured by a voltmeter is read, according to the resistance value of the resistor And the output voltage of the power source, calculating each group of input power of the voltage regulator; calculating a power conversion efficiency of the voltage regulator, the power conversion efficiency being equal to an average value of a ratio of all group output powers to all group input powers; And determining whether the serial number of the measurement times exceeds a preset measurement number. If not, setting the sequence number of the measurement times, and returning to the step of reading the current flowing through the electronic load recorded on an electronic load.

The power conversion efficiency measuring system and method of the present invention pre-sets the maximum output current and the number of measurement times of the voltage regulator through the measurement setting module, and calculates the target output current of the voltage regulator at each measurement; the reading flows through The current of the electronic load makes the current of the electronic load equal to the target output current of the voltage regulator corresponding to the serial number of the measurement times. Finally, the output power, input power and power conversion of each group of the voltage regulator are calculated through the read data. Efficiency; automatic measurement of power conversion efficiency can be achieved until all measurements are completed in sequence, thereby improving measurement efficiency and accuracy.

6‧‧‧Power Conversion Efficiency Measurement System

20‧‧ voltmeter

40‧‧‧Electronic load

52‧‧‧ processor

530‧‧‧Measurement setting module

534‧‧‧Computation Module

10‧‧‧Power supply

30‧‧‧Voltage regulator

50‧‧‧ computer

53‧‧‧ memory

532‧‧‧Load adjustment module

536‧‧‧Judgement module

1 is a block diagram of a preferred embodiment of a power conversion efficiency measurement system of the present invention coupled to a voltage regulator.

2 is a block diagram of the memory of FIG. 1.

3 is a flow chart of a preferred embodiment of the power conversion efficiency measurement method of the present invention.

Referring to FIG. 1 and FIG. 2 together, the power conversion efficiency measuring system 6 of the present invention can measure the power conversion efficiency of a voltage converting device such as a voltage regulator 30 at different output currents, and the preferred embodiment includes a The power source 10, a resistor R, a voltmeter 20, an electronic load 40, and a measuring device such as a computer 50. The power supply 10 is connected to the voltage regulator 30 through a parallel circuit of the resistor R and the voltmeter 20. The voltage regulator 30 is also connected to the computer 50 via an electronic load 40, and the computer 50 is also connected to the voltmeter 20. In the present embodiment, the resistor R is a precision resistor having a very small resistance value, and the electronic load 40 is a precision electronic load instrument capable of adjusting a load, which can provide voltage and current information such as an input voltage of the electronic load 40 and flow through the electron. The current of the load 40, and the electronic load 40 will completely convert the input electrical energy into thermal energy dissipation. The power supply 10 can output a DC voltage divided by the resistor R and then supply it to the voltage regulator 30. The voltage regulator 30 converts this DC voltage into another DC voltage output to the electronic load 40. The voltmeter 20 accurately measures the voltage across the resistor R. The computer 50 calculates the power conversion efficiency of the voltage regulator 30. In the present embodiment, the computer 50 is connected to the voltmeter 20 and the electronic load 40 via a USB (Universal Serial Bus) interface. In other embodiments, the computer 50 can also communicate with other interfaces such as RS232. The voltmeter 20 and the electronic load 40 are connected.

The computer 50 includes a processor 52 and a memory 53. The processor 52 is connected to the memory 53 and executes instructions stored in the memory 53. The memory 53 includes a measurement setting module 530, a load adjustment module 532, a calculation module 534, and a determination module 536.

The measurement setting module 530 is configured to preset the maximum output current Imax of the voltage regulator 30 (which is set according to the specification of the voltage regulator 30 product) and the number of measurements. Calculate the target output current of the voltage regulator 30 at the pth measurement according to the calculation formula Ip=Imax×(5×p-5)% (p=1, . . . , n) of the preset target output current Ip. And sequentially measured in increasing order of the number of measurement times. In other embodiments, the measurement may be performed sequentially in descending order of the number of measurement times. For example, if the maximum output current Imax of the voltage regulator 30 is 10 amps and the number of measurement times is set to 21 times, the equation Ip=Imax×(5×p-5)% (p=1, . . . , 21) is transmitted. The target output current Ip of each of the measurement voltage regulators 30 can be calculated to be 0 amps, 0.5 amps, 1 ampere, 1.5 amps, ..., 10 amps, respectively.

The load adjustment module 532 is configured to read the current flowing through the electronic load 40 recorded on the electronic load 40, and adjust the electronic load 40 such that the current of the electronic load 40 is equal to the target output current of the voltage regulator 30 during the current measurement. For example, if the current of the electronic load 40 is greater than the target output current of the voltage regulator 30 during the current measurement, the electronic load 40 is controlled to increase the impedance, and if the current of the electronic load 40 is less than the target output current of the current measuring voltage regulator 30, the control is performed. The electronic load 40 reduces the impedance until the current of the electronic load 40 is equal to the target output current of the voltage regulator 30. Since the voltage regulator 30 takes a period of time to reach the thermal balance, the measurement before the thermal balance is reached may cause the accuracy of the measurement to decrease. Therefore, the load adjustment module 532 is also used to set a preset time, for example, 3 minutes. The voltage regulator 30 can be brought to thermal equilibrium to increase the accuracy of the measurement.

The calculation module 534 is configured to read a current flowing through the electronic load 40 and an input voltage of the electronic load 40 recorded on the electronic load 40 of the complex array (eg, 30 groups) according to the current flowing through the electronic load 40 and the electronic load 40 The input voltages are multiplied to calculate the respective sets of output power of the voltage regulator 30, and simultaneously read the voltage across the measured resistance R of the voltmeter 20, based on the known resistance value of the resistor R and the output voltage of the power source 10, Power out Each set of input power of the voltage regulator 30, the power conversion efficiency of the voltage regulator 30 is equal to the average of the ratio of each set of output power to each set of input power. For example, assume that one of the currents flowing through the electronic load 40 is Iou=Ip, the input voltage of the electronic load 40 is Vou, the output power of the voltage regulator 30 is Pou, and the input power of the voltage regulator 30 is Pin, the power supply 10 The output voltage is V1, the input voltage of the voltage regulator 30 is Vin, the resistance of the resistor R is r, the current flowing through the resistor R is Iin, the power conversion efficiency of the voltage regulator 30 is Eff, and both V1 and r are known. , Pou=Vou×Iou, Iin=(V1-Vin)/r, Pin=Vin×Iin, Eff=Pou/Pin.

The determining module 536 is configured to determine whether the serial number of the measurement times is equal to a preset number of measurement times. If not, the sequence number of the measurement times is incremented by one to perform the next measurement. If so, it is determined that the measurement has been completed, and the electronic load 40 is controlled to set the load to zero, and the tester is informed in the display manner that the measurement has been completed. In other embodiments, after the measurement is completed, the determination module 536 may also need to control the electronic load 40 to set the load to zero and inform the tester that the measurement has been completed. In other embodiments, if the measurement is performed sequentially in descending order of the number of measurement times, the determination module 536 determines whether the serial number of the measurement times is equal to the sequence number 1 of the minimum measurement number, and if not, the quantity The sequence number of the number of measurements is decremented by 1 for the next measurement. If yes, it is determined that the measurement has been completed, and the electronic load 40 is controlled to set the load to zero, and the test result is displayed and the tester is informed that the measurement has been completed. The test result is the power conversion of the voltage regulator 30 when the different target output currents are different. effectiveness.

As shown in FIG. 3, the power conversion efficiency measurement method of the present invention can measure the power conversion efficiency of a voltage conversion device such as a voltage regulator 30 at different output currents. The preferred embodiment includes the following steps: In step S100, the measurement setting module 530 presets the maximum loss of the voltage regulator 30. The current Imax (such as 10 amps) and the number of measurements (such as 21 times) are calculated according to the preset target output current Ip Ip = Imax × (5 × p - 5)% (p = 1, ..., 21) The target output current Ip of the voltage regulator 30 at the time of the pth measurement is calculated, and the number of the initial measurement times is set to 1.

In step S102, the load adjustment module 532 adjusts the electronic load 40 such that the current of the electronic load 40 is equal to the target output current of the voltage regulator 30 corresponding to the serial number of the measurement times.

In step S104, the calculation module 534 reads the current Ioui (i=1, . . . , 30) flowing through the electronic load 40 and the input voltage Voui of the electronic load 40 recorded on the electronic load 40 in the complex array (such as 30 groups). (i=1, . . . , 30), and multiplying the current flowing through the electronic load 40 by the input voltage of the electronic load 40 by Ioui×Voui (i=1, . . . , 30) to calculate the voltage regulator Each group of 30 outputs power Poi (i = 1, ..., 30). At the same time, the voltage Vi (i=1, . . . , 30) across the measured resistance R of the voltmeter 20 is read, and the voltage adjustment is calculated according to the known resistance value r of the resistor R and the output voltage V1 of the power source 10. Each set of input power of the unit 30 is Pini = (V1 - Vi) 2 / r (i = 1, ..., 30). For example, if the resistance value of the resistor R is r = 0.1 ohm and the output voltage of the power source 10 is V1 = 12 volts, and the voltage across the set of measured resistors R is Vi = 6 volts, the input of the set of voltage regulators 30 Power Pini = (12-6) 2 / 0.1 = 360 watts.

Step S106, the calculation module 534 calculates the power conversion efficiency Eff of the voltage regulator 30, the power conversion efficiency Eff is equal to each set of output power Poi (i = 1, ..., 30) and each set of input power Pini The average of the ratios of (i = 1, ..., 30), that is, (p = 1, ..., 21), where p is the number of the number of measurements.

In step S108, the determining module 536 determines whether the serial number of the measurement times is equal to the preset number of measurement times. If not, step S110 is performed, and if yes, step S112 is performed.

In step S110, the determining module 536 increments the sequence number of the measurement times by one, and returns to step S102.

In step S112, the determining module 536 controls the electronic load 40 to set the load to zero, and displays the test result and informs the tester that the measurement has been completed. The test result is the power conversion efficiency of the voltage regulator 30 when the different target output currents.

The power conversion efficiency measuring system 6 and the power conversion efficiency measuring method of the present invention can automatically calculate the power conversion efficiency of the voltage regulator 30 at different target output currents through the computer 50, thereby improving the efficiency and accuracy of the measurement.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

6‧‧‧Power Conversion Efficiency Measurement System

20‧‧ voltmeter

40‧‧‧Electronic load

52‧‧‧ processor

10‧‧‧Power supply

30‧‧‧Voltage regulator

50‧‧‧ computer

53‧‧‧ memory

Claims (10)

  1. A power conversion efficiency measuring system includes a power source, a resistor, a voltmeter, an electronic load, and a measuring device, and the power source is connected to the voltage regulator through a parallel circuit of the resistor and the voltmeter, the voltage regulator The measuring device is further connected to the measuring device, the measuring device further comprises a voltage meter, the measuring device comprises a processor and a memory, the processor is connected to the memory and executes the instructions stored in the memory The memory includes: a measurement setting module, configured to preset a maximum output current of the voltage regulator, a number of measurement times, and a serial number of the initial measurement times, and calculate according to a preset calculation formula of the target output current a target output current of the voltage regulator at each measurement; a load adjustment module for reading a current recorded on the electronic load flowing through the electronic load, and adjusting the electronic load such that a current of the electronic load is equal to The number of measurement times corresponds to the target output current of the voltage regulator; a calculation module is configured to pass through the read complex array through the electronic load The flow is multiplied by the input voltage of the electronic load to calculate the output power of each group of the voltage regulator, and the voltage across the resistor is measured by the voltmeter, according to the resistance value of the resistor and the output voltage of the power supply. Calculating the input power of each group of the voltage regulator, the power conversion efficiency of the voltage regulator is equal to an average value of the ratio of the output power of all groups to the input power of all groups; and a determining module for determining the number of measurements Whether the serial number exceeds the preset measurement times. If not, set the serial number of the measurement times for the next measurement.
  2. The power conversion efficiency measuring system according to claim 1, wherein the target output current is calculated by Ip=Imax×(5×p-5)%, p is a serial number of the measurement times, and Imax is the The maximum output current of the voltage regulator, Ip is the target output current.
  3. The power conversion efficiency measuring system according to claim 1, wherein the load adjusting mode The group is also used to compare the current of the electronic load with the target output current of the voltage regulator during the current measurement, and if the current of the electronic load is greater than the target output current of the voltage regulator during the current measurement, the electronic load is controlled to increase. Impedance, if the current of the electronic load is less than the target output current of the voltage regulator, the electronic load is controlled to reduce the impedance.
  4. The power conversion efficiency measurement system of claim 1, wherein the determining module determines whether the serial number of the measurement times is equal to a preset amount if the measurement is sequentially performed in an increasing order of the number of measurement times. The number of measurements, if not, the number of measurements is incremented by one for the next measurement.
  5. The power conversion efficiency measurement system according to claim 1, wherein the determining module determines whether the serial number of the measurement times is equal to the smallest measurement if the measurement is sequentially performed in descending order of the serial number of the measurement times. The number of the number of times, if not, the number of the number of measurements is decremented by one to perform the next measurement.
  6. The power conversion efficiency measurement system according to claim 1, wherein if the serial number of the measurement times exceeds the preset measurement number, it is determined that the measurement has been completed, and the electronic load is controlled to set the load. Zero and display the test results.
  7. A power conversion efficiency measuring method includes the following steps: presetting a maximum output current of a voltage regulator and a number of measurement times, and calculating a target of the voltage regulator according to a preset calculation formula of a target output current Outputting a current, and setting a sequence number of initial measurement times; reading a current recorded on an electronic load flowing through the electronic load, and adjusting the electronic load such that the current of the electronic load is equal to the voltage adjustment corresponding to the serial number of the measurement times The target output current of the device; multiplying the current flowing through the electronic load through the read complex array by the input voltage of the electronic load to calculate the output power of each group of the voltage regulator, and reading a voltmeter for measurement The voltage across a resistor is calculated based on the resistance of the resistor and the output voltage of the power supply. The input power of each group of the regulator; calculating the power conversion efficiency of the voltage regulator, the power conversion efficiency being equal to an average value of the ratio of the output power of all the groups to the input power of all the groups; and determining whether the serial number of the measurement times exceeds the pre-predetermined The number of measurement times, if not, sets the sequence number of the measurement times, and returns to perform the step of reading the current flowing through the electronic load recorded on an electronic load.
  8. The frequency range test method as described in claim 7, wherein if the sequence number of the initial measurement times is set to 1, it is determined whether the sequence number of the measurement times exceeds a preset number of measurement times, and the steps are further included. : Determine whether the serial number of the measurement times is equal to the preset measurement number. If not, increase the sequence number of the measurement times by 1 to perform the next measurement.
  9. For example, the frequency range test method described in claim 7 wherein the target output current is calculated as Ip=Imax×(5×p-5)%, p is the serial number of the measurement times, and Imax is the voltage adjustment. The maximum output current of the device, Ip is the target output current.
  10. The frequency range test method of claim 7, wherein the step of determining whether the number of the measurement times exceeds a preset number of measurement steps further comprises the step of: if the number of measurement times exceeds a preset number If the number of measurements is measured, it is determined that the measurement has been completed, and the electronic load is controlled to set the load to zero, and the test result is displayed and the tester is informed that the measurement has been completed.
TW098127335A 2009-08-14 2009-08-14 Measurement system and method for power conversion efficiency TWI464415B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
TW098127335A TWI464415B (en) 2009-08-14 2009-08-14 Measurement system and method for power conversion efficiency

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
TW098127335A TWI464415B (en) 2009-08-14 2009-08-14 Measurement system and method for power conversion efficiency

Publications (2)

Publication Number Publication Date
TW201105983A TW201105983A (en) 2011-02-16
TWI464415B true TWI464415B (en) 2014-12-11

Family

ID=44814183

Family Applications (1)

Application Number Title Priority Date Filing Date
TW098127335A TWI464415B (en) 2009-08-14 2009-08-14 Measurement system and method for power conversion efficiency

Country Status (1)

Country Link
TW (1) TWI464415B (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6323652B1 (en) * 1997-10-17 2001-11-27 Stephen D. Collier Electrical testing device
CN1885274A (en) * 2005-06-24 2006-12-27 鸿富锦精密工业(深圳)有限公司 CPU power estimating method
US20070211506A1 (en) * 2006-03-08 2007-09-13 Samsung Electronics Co., Ltd. Power converting apparatus, electronic apparatus comprising the same and power converting method
JP2008187833A (en) * 2007-01-30 2008-08-14 Fujitsu Ltd Electronic equipment and dc voltage conversion system
TW200839270A (en) * 2007-01-22 2008-10-01 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Circuit arrangement and method of measuring electrical quantities
TW200923377A (en) * 2007-11-19 2009-06-01 Inventec Corp Power measuring apparatus

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6323652B1 (en) * 1997-10-17 2001-11-27 Stephen D. Collier Electrical testing device
CN1885274A (en) * 2005-06-24 2006-12-27 鸿富锦精密工业(深圳)有限公司 CPU power estimating method
US20070211506A1 (en) * 2006-03-08 2007-09-13 Samsung Electronics Co., Ltd. Power converting apparatus, electronic apparatus comprising the same and power converting method
TW200839270A (en) * 2007-01-22 2008-10-01 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Circuit arrangement and method of measuring electrical quantities
JP2008187833A (en) * 2007-01-30 2008-08-14 Fujitsu Ltd Electronic equipment and dc voltage conversion system
TW200923377A (en) * 2007-11-19 2009-06-01 Inventec Corp Power measuring apparatus

Also Published As

Publication number Publication date
TW201105983A (en) 2011-02-16

Similar Documents

Publication Publication Date Title
US10203374B2 (en) System and method for sensing battery capacity
US7902828B2 (en) Method and apparatus for monitoring the condition of a battery by measuring its internal resistance
US7573237B2 (en) System and method for monitoring battery state
JP5132713B2 (en) Method and test bench for testing a hybrid drive system or partial components of the system
US7359809B2 (en) Electricity metering with a current transformer
US8073642B2 (en) System and method for compensating for potential and current transformers in energy meters
JP6040684B2 (en) Secondary battery state evaluation device, secondary battery state evaluation method, and secondary battery state evaluation program
EP2365348B1 (en) Monitoring apparatus for current transformer
US9696357B2 (en) Element resistance measurement in an electricity meter
KR100927541B1 (en) Apparatus and method for estimating battery's resistance characteristics based on open circuit voltage estimated by battery voltage variation pattern
US20040130329A1 (en) Method for testing a transformer and corresponding test device
US20020008523A1 (en) Apparatus and method for carrying out diagnostic tests on batteries and for rapidly charging batteries
CN102749520B (en) Multichannel high-precision thermal resistance breadboard based on extensions for instrumentation (PXI) bus
CN100501436C (en) Electric resistance loading system
US7285947B2 (en) Power metering using current-indicative signal
TWI247127B (en) Battery charging-discharging monitoring circuit and its method
CN201425621Y (en) Error checking system of high-voltage electric energy metering device
WO2017152479A1 (en) Method and apparatus for rapidly detecting remaining capacity and state of health of storage battery
TW200535951A (en) Method and apparatus of temperature compensation for integrated circuit chip using on-chip sensor and computation means
EP1619512B1 (en) Device and method for the determination of the internal resistance of a batterie
WO1990000740A1 (en) Adjustment circuit and method for solid-state electricity meter
US20060208754A1 (en) Method and apparatus for a reliability testing
CN102064597B (en) Energy storage device
KR20120135075A (en) State judging device, battery apparatus, state judging method
KR20060060830A (en) Control equipment of charge/discharge with balancing function of battery cell and method to establish condition of using of optimun battery module using the same

Legal Events

Date Code Title Description
MM4A Annulment or lapse of patent due to non-payment of fees