JP6679397B2 - Fuel pump drive circuit - Google Patents

Description

  The present invention relates to a fuel pump drive circuit that rectifies AC power supplied from an external commercial power source and drives a fuel pump with DC power smoothed by a capacitor.

  As the fuel pump drive circuit as described above, for example, there is known one that increases / decreases the amount of fuel discharged from the fuel pump by PWM controlling the DC power supplied to the fuel pump (see, for example, Patent Document 1).

  In such PWM control of the power supplied to the fuel pump, the voltage of the AC power supplied from the commercial power supply is monitored, and when the voltage drops, the duty ratio of the power supplied to the fuel pump is increased. The control is performed so that the fuel discharge amount does not change.

JP 2006-220327 A (Pages 5-7, FIG. 1)

  In the above conventional one, the fluctuation of the power supply voltage is taken in as the voltage of the rectified DC power, and when the power supply voltage changes due to the operating state of other loads, the duty ratio of the power supplied to the fuel pump is changed. . That is, it is necessary to increase the duty ratio when the voltage of the external power supply decreases.

  On the other hand, it is known that power source harmonics are superposed on AC power from an external power source. When the power supply harmonics are superimposed on the AC power, a phenomenon occurs in which the voltage of the DC power supply after rectification drops even if the voltage of the AC power of the external power supply has not dropped. Since the above-mentioned conventional drive circuit does not consider the influence of the power supply harmonics at all, if the phenomenon that the voltage after rectification drops occurs, it is assumed that the voltage of the external power supply decreases uniformly and the duty ratio is increased. However, if the voltage after rectification has dropped due to superimposition of power supply harmonics, the duty ratio will be increased more than necessary if control is performed on the assumption that power supply harmonics are not superposed. As a result, there arises a problem that the fuel discharge amount increases more than the set amount.

  Therefore, in view of the above problems, it is an object of the present invention to provide a fuel pump drive circuit capable of ensuring an appropriate fuel discharge amount in consideration of the influence of power source harmonics.

In order to solve the above problems, a fuel pump drive circuit according to the present invention is a fuel pump drive circuit that rectifies AC power supplied from an external commercial power source and drives the fuel pump with DC power smoothed by a capacitor, What detects the voltage fluctuation of the AC power and PWM-controls the DC power supplied to the fuel pump according to the change of the AC power, in which the AC power is branched and the voltage is lowered by a step-down transformer for voltage monitoring. The AC power for voltage monitoring is full-wave rectified to generate a pulsating current, the voltage smoothed by the capacitor is taken into the microcomputer, and the duty ratio of the PWM control supplied to the fuel pump is determined. A resistor is provided in the charging path, and the capacitor voltage when the capacitor is charged through this resistor and the capacitor voltage when this resistor is short-circuited By comparing the voltage of the capacitor while charging, determine the distortion rate by power supply harmonics are superimposed on the AC power from the external commercial power source, correcting the PWM control based on the strain rate It is characterized by

  In the present invention, since the distortion rate due to the power source harmonic can be detected, it is possible to perform appropriate control according to the distortion rate.

  As is apparent from the above description, the present invention can detect the distortion rate due to the power supply harmonics, so that the conventional control device could not properly control the fuel pump when affected by the power supply harmonics. Such a problem can be solved.

The figure which shows the structure of one embodiment of this invention. Diagram showing changes in detection voltage depending on distortion rate

  Referring to FIG. 1, reference numeral 1 denotes an external AC power supply, which receives AC power having an effective value of 100 V. The supplied AC power is full-wave rectified by the diode bridge 2, smoothed by the capacitor 3, and converted into DC power with a maximum value of 141 volts. The direct current power is supplied to the fuel pump 4 to supply the liquid fuel to the burner (not shown), but the supply amount of the fuel is controlled by increasing or decreasing the duty ratio of the pulse signal supplied to the switching element 41.

  This duty ratio is controlled by the microcomputer 5. The voltage of the AC power supplied from the AC power supply 1 may fluctuate depending on the operating conditions of other loads (not shown). Therefore, when the voltage from the AC power supply 1 decreases, the microcomputer 5 increases the duty ratio and When the voltage of the AC power supply 1 rises, the duty ratio is reduced so that the fuel supply amount is controlled to be constant even if the voltage of the AC power supply 1 changes.

  The microcomputer 5 includes an input port 51, and is configured to recognize the voltage of the AC power supply 1 based on the voltage input to the input port 51. Reference numeral 6 denotes a step-down transformer, which reduces the voltage of the AC power supply 1 to an appropriate voltage, performs full-wave rectification with a diode bridge 61, and smoothes it with a capacitor 62. Then, the charging voltage of the capacitor 62 is input to the input port 51 as an intermediate voltage between the two voltage dividing resistors 72 and 73.

  If the voltage of the AC power supply 1 increases, the voltage input to the input port 51 increases, and if the voltage of the AC power supply 1 decreases, the voltage input to the input port 51 decreases. In the conventional drive circuit, the duty ratio of the pulse signal supplied to the switching element 41 is increased / decreased by detecting the voltage of the AC power supply 1 with the configuration described above. However, with this configuration, it is not possible to consider the influence of power source harmonics superimposed on the AC power supplied by the AC power supply 1. That is, even if the voltage of the AC power supply 1 does not change, the voltage input to the input port 51 changes due to the superposition of power supply harmonics, and the duty ratio cannot be controlled appropriately.

  Therefore, in the present invention, a resistor 71 is separately provided in the path for charging the capacitor 62, and an opening / closing element 52 that can short-circuit the resistor 71 is provided. The microcomputer 5 can control the opening / closing state of the opening / closing element 52. I did it. With this configuration, the voltage (fixed value) in the state where the capacitor 62 is charged via the resistor 71 and the voltage in the conventional configuration in which the capacitor 62 is directly charged without passing through the resistor 71 (Variable value) can be input to the input port 51.

  The fixed value is almost unaffected by the distortion rate due to superposition of power source harmonics. On the other hand, when the strain rate increases, the fluctuation value decreases. For example, in a state where the voltage of the AC power supply 1 does not fluctuate at 100 V, the fixed value is MV and is constant without being influenced by the distortion rate, but the fluctuation value drops as the distortion rate increases, as indicated by MVH. .

  If the voltage of the AC power supply 1 rises, the fixed value becomes HV and the fluctuation value becomes HVH. Conversely, if the voltage of the AC power supply 1 drops, the fixed value becomes LV and the fluctuation value becomes LVH.

  Prior to operating the fuel pump 4, a fixed value is read first. When the voltage input to the input port 51 is V1 (point A) and the fluctuation value is V2 (point B), the distortion rate may be 10% from the voltage difference (V1-V2) between the two voltages. I understand. Then, while the fuel pump 4 is operating, the variable value is input to the microcomputer 5 to adjust the duty ratio for the operation of the fuel pump 4, but the state in which V2 is input is ignored by ignoring the influence of the distortion rate. Is not controlled as if it is input, but the duty ratio is adjusted assuming that V3, which is the voltage at the point C between V1 and V2 and obtained at a predetermined internal division ratio, is input. I chose

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the present invention.

1 AC power supply 3 Capacitor 4 Fuel pump 5 Microcomputer 41 Switching element 51 Input port 52 Switching element 62 Capacitor

Claims (1)

A fuel pump drive circuit that rectifies AC power supplied from an external commercial power source and drives a fuel pump with DC power smoothed by a capacitor. It detects voltage fluctuations in AC power and detects changes in the AC power. In the PWM control of the direct current power supplied to the fuel pump, the alternating current power is branched and the voltage monitor alternating current power whose voltage is lowered by the step-down transformer for voltage monitor is full-wave rectified to generate a pulsating flow. Then, the voltage smoothed by the capacitor is taken into the microcomputer and the duty ratio of the PWM control to be supplied to the fuel pump is determined, a resistor is provided in the path for charging this capacitor, and the capacitor is charged through this resistor. Compare the voltage of the capacitor in the state of charging and the voltage of the capacitor in the state of charging the capacitor with this resistor short-circuited, A fuel pump driving circuit, characterized in that calculated distortion rate by power supply harmonics are superimposed on the AC power from the commercial power supply, correcting the PWM control based on the strain rate.

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