KR20100125562A - Pwm input circuit of motor driver for fuel pump - Google Patents

Abstract

PURPOSE: A PWM input circuit of a motor driver for a fuel pump is provided to prevent confusion due to signal inversion and to enable the circuit to be easily designed since only the voltage level of a PWM signal from an ECU is converted and is output to an MCU without signal inversion by a photo coupler. CONSTITUTION: A PWM input circuit of a motor driver for a fuel pump comprises first to third resistors(R11~R13), a first node(N1), a first capacitor(C1), a second capacitor(C2) and first and second diodes(D11,D12). The first to third resistors divide a first voltage. The first node is formed between the first and second resistors and receives a PWM(Pulse Width Modulation) signal from an ECU. The first capacitor is connected to the first node. The second capacitor is connected to the third resistor in parallel. The first and second diodes are serially connected to a second voltage.

Description

PWM input circuit of a motor driving device for a fuel pump {PWM INPUT CIRCUIT OF MOTOR DRIVER FOR FUEL PUMP}

The present invention relates to a motor driving apparatus for a fuel pump, and more particularly to a pulse width modulation (PWM) signal for controlling a motor driving apparatus for a fuel pump. The present invention relates to a PWM input circuit of a motor driving apparatus for a fuel pump that receives an input from an ECU and outputs it to a micro controller unit (hereinafter referred to as an MCU).

In general, a vehicle that uses liquefied petroleum gas (Liquefied Petroleum Gas, hereinafter referred to as LPG) is used to supply LPG fuel stored in the fuel tank to the engine using a fuel pump. At this time, the amount of LPG fuel supplied to the engine is controlled by controlling the rotational speed of the fuel pump in consideration of the speed of the vehicle.

Recently, a liquefied petroleum injection (LPI) type engine that directly injects the LPG fuel into the engine in a liquid state has been used. This LPI engine can improve the engine output by 10 to 20% and reduce the emission of pollutants, compared to the existing engine that converts liquid LPG fuel into gaseous state and mixes it with air.

The motor that drives the fuel pump uses a brushless direct current motor (BLDC) to secure high efficiency, long life, and reliability, and in particular, uses a sensorless BLDC motor. It is common to use.

1 is a block diagram showing a configuration of a motor driving apparatus for a fuel pump according to the prior art, and FIG. 2 is a detailed circuit diagram showing a configuration of a PWM input circuit shown in FIG.

First, a configuration of a motor driving apparatus for a fuel pump according to the prior art will be described with reference to FIG. 1.

As shown in FIG. 1, the fuel pump motor driving apparatus 1 according to the related art includes a PWM input circuit 10, an MCU 20, an overvoltage protection unit 30, a motor controller 40, and a MOSFET driving circuit. 50 and the motor driver 60.

Here, the motor driving unit 60 is formed in a three-phase full bridge method to perform a switching role for transmitting a driving signal to the motor M driving the fuel pump. The motor driver 60 includes a P-channel MOSFET on a high side to which a driving signal for driving the motor M of a large vehicle using a driving power of 24V is input. A P-channel MOSFET is provided on a low side to which a driving signal for driving the motor M applied to a passenger vehicle using a driving power of 12V is input. The MOSFET driving circuit 50 may include a first MOSFET driving unit 51 for driving an N-channel MOSFET in response to the HIGH side signal, and a N-channel MOSFET for driving the N-channel MOSFET in accordance with the low side signal. And a voltage multiplier 55 for supplying power multiplied by 24V to the second MOSFET driver 53 and the first MOSFET drivers 51 and 53.

The motor controller 40 receives the current speed of the motor M measured by the motor driver 60 and transmits the current speed to the MCU 20.

Then, the MCU 20 calculates an error between the transmitted current speed and the target speed, and performs proportional integral control based on the calculated error. In addition, the MCU 20 outputs a control signal for the calculated error to the motor controller 40 so that the feedback signal is transmitted to the motor M. FIG.

Accordingly, the fuel pump motor driving apparatus 1 controls the error of the current speed and the target speed of the motor M to be minimized, and controls the fuel to be properly supplied to the engine according to the state of the vehicle.

The PWM input circuit 10 converts the 12V PWM signal output from the ECU of the vehicle into a 5V driving voltage level and inputs it to the MCU 20.

Next, the PWM input circuit 10 of the conventional fuel pump motor driving apparatus will be described in detail with reference to FIG. 2.

As shown in Fig. 2, the conventional PWM input circuit 10 uses a photo coupler 11 to prevent noise from the digital circuit from affecting the analog circuit.

In detail, when the ECU outputs a PWM signal having a battery voltage level of 12V high, the first diode D1 blocks the PWM signal. Accordingly, the light emitting diode (hereinafter, referred to as 'LED') 12 of the photocoupler 11 receives the 12V voltage of the anode A terminal by the second resistor R2 at the cathode K terminal. Licensed. Since the transistor 13 of the photocoupler 11 has no signal input to the base B end, the transistor 13 is turned off. At this time, the MCU 20 receives a low signal, that is, 0V, by the third resistor R3 which is a pull-down resistor.

On the other hand, when the ECU outputs the PWM signal low, the first diode D1 becomes conductive. At this time, the LED 12 of the photo coupler 11 has a voltage at which the driving voltage VCC of 12V, which is the battery voltage level, is divided by the second and first resistors R2 and R1 at the cathode K, The voltage dropped by the forward reverse voltage is applied to the first diode D1. Thus, the LED 12 of the photo coupler 11 is turned on using the voltage applied to the cathode K end. Then, the transistor 13 of the photo coupler 11 is MCU as the collector (C) and the base (B) is turned on and conducting as the light emitted by the LED 12 is turned on the base (B) stage In step 20, the PWM signal converted to the voltage level of 5V is input to the MCU 20 at a high level.

As described above, the conventional PWM input circuit 10 has a photo coupler 11 when the voltage level 12V of the PWM signal output from the ECU and the voltage level 5V of the PWM signal input to the MCU 20 are different from each other. Convert the voltage level using. At this time, the photo coupler 11 inverts the PWM signal and transfers the PWM signal to the MCU 20.

However, the PWM input circuit of the conventional fuel pump motor driving apparatus as described above has the following problems.

When noise occurs in the digital circuit, the generated noise is transferred to the analog circuit to generate an overvoltage. The overvoltage generated as described above may cause burnout of the circuit unit, thereby increasing the maintenance cost of the circuit unit.

In order to solve this problem, the conventional PWM input circuit 10 as described above uses the photo coupler 11 to block the influence of noise generated in the digital circuit. However, since the photo coupler 11 inverts the PWM signal output from the ECU and inputs it to the MCU 20, there is a problem in that the circuit design may cause confusion due to the inversion of the input signal.

In addition, since the photocoupler 11 which is relatively expensive is used in the related art as described above, the manufacturing cost of the PWM input circuit 10 increases, and the use of semiconductor elements causes a problem of circuit unit burnout.

The present invention is to solve the problems as described above, the object of the present invention is to reduce the circuit manufacturing cost by using a device such as a relatively inexpensive resistance of the fuel pump motor driving apparatus that can prevent the burn out of the circuit unit It is to provide a PWM input circuit.

According to a feature of the present invention for achieving the above object, the present invention is a PWM input circuit for converting the first voltage to the level of the second voltage according to the PWM signal output from the ECU of the vehicle and outputs to the MCU, A first node formed between the first to third resistors for dividing the first voltage, the first and second resistors to receive a PWM signal from the ECU, a first capacitor coupled to the first node, and the first node And a second capacitor coupled in parallel to the three resistors, and first and second diodes coupled in series to the second voltage.

One end of the first capacitor is coupled to the first node, and the other end of the first capacitor is coupled to an analog ground terminal.

The present invention further includes a second node formed between the second resistor and the third resistor, one end of the second capacitor is coupled to the second node, and the other end of the second capacitor is coupled to an analog ground terminal. It is characterized by.

The first diode may be coupled to the second voltage, and the second diode may be coupled to a digital ground terminal.

When the second and third resistors are applied with a voltage whose voltage level is changed to the first node due to noise generated from the digital ground terminal, the second and third resistors divide the first voltage to obtain a voltage near the low through the second node. It is characterized by outputting.

When the PWM signal output from the ECU is not input, the first to third resistors divide the first voltage to output a high level PWM signal, and when the PWM signal is high level, the second and third resistors. Divides the first voltage to output a high level PWM signal through the second node, and when the PWM signal is low level, the first node goes low to output a low level PWM signal to the MCU. Characterized in that.

The first voltage is 12V, the second voltage is characterized in that 5V.

The first voltage is 24V, and the second voltage is 5V.

As described above, the present invention converts only the voltage level of the PWM signal output from the ECU and outputs it to the MCU without signal inversion by the photo coupler, so that the circuit can be easily designed by preventing confusion due to signal inversion during circuit design. have.

In addition, by applying circuit elements such as resistors and capacitors, and applying the digital ground terminal and the analog ground terminal separately, it is possible to prevent the noise generated in the digital circuit from affecting the analog circuit, thereby preventing damage to the circuit unit due to the noise. Can be. Accordingly, the present invention has the effect of reducing the cost required for the design and maintenance of the circuit unit.

Hereinafter, a PWM input circuit of a motor driving apparatus for a fuel pump according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a detailed circuit diagram of a PWM input circuit of a fuel pump motor driving apparatus according to a preferred embodiment of the present invention.

3, the PWM input circuit 10 of the fuel pump motor driving apparatus according to the present invention is the first to third resistors (R11, R12, R13), the first and second capacitors (C1, C2), And first and second diodes D11 and D12.

The first to third resistors R11, R12, and R13 are connected in series between a power supply line for supplying a battery voltage VCC of 12V and an analog ground terminal AGND to divide the battery voltage VCC. .

The first capacitor C1 is provided between the first node N1 formed between the first resistor R11 and the second resistor R12 and the analog ground terminal AGND. The first node N1 is a node that receives a PWM signal from the ECU. The second capacitor C2 is provided between the second node N2 formed between the second resistor R12 and the third resistor R13 and the analog ground terminal AGND. That is, the second capacitor C2 is coupled in parallel with the third resistor R13. The first and second capacitors C1 and C2 reduce noise and surge voltage flowing from the ECU side.

The first diode D11 is provided between the driving voltage supply line for supplying the driving voltage VDD and the third node N3, and the second diode D12 is connected to the third node N3 and the digital ground. It is provided between stages DGND, respectively. That is, the first diode D11 and the second diode D12 are coupled in series. The third node N3 is connected to the second node N2 and divided through the first to third resistors R11, R12, and R13 to convert the PWM signal into a voltage level of 5V. Output to (20). The first and second diodes D11 and D12 prevent burnout of the circuit unit due to an overvoltage reverse voltage applied from an analog circuit, that is, the ECU, due to noise generated in a digital circuit.

 In a digital circuit, noise is generated during the rapid conversion of the PWM signal, which is a digital signal, into a high / low state. Therefore, in the present embodiment, the analog ground terminal AGND and the digital ground terminal DGND are formed separately, thereby preventing the noise of the digital circuit from affecting the analog circuit, thereby preventing burnout of the circuit unit.

Hereinafter, the operation of the PWM input circuit of the motor driving apparatus for a fuel pump according to a preferred embodiment of the present invention having the configuration as described above.

In the present embodiment, a case in which a PWM signal is not output from the ECU to the first node N1 and a case where the PWM signal is output at a high / low level, respectively, will be described.

In all four cases, the battery voltage VCC as the first voltage and the driving voltage VDD as 5V as the second voltage are continuously supplied through the power supply line and the driving voltage supply line, respectively. It explains.

In addition, as the battery voltage VCC is divided by the first to third resistors R11, R12, and R13, the PWM signal output through the third node N3 to which the driving voltage VDD is applied is generated. It will be described as being converted to a voltage level of 5V and output to the MCU (20).

First, the case where the PWM signal is not output from the ECU will be described.

At this time, as the first to third resistors R11, R12, and R13 connected in series divide the battery voltage VCC, the PWM signal output to the MCU 20 through the third node N3 is 5V. It has a level and is input to the MCU 20 in a high level state.

Next, the case where the PWM signal is output at a high / low level will be described.

When the PWM signal of the high level is output, the PWM signal is in a high level state as the second and third resistors R12 and R13 divide the battery voltage VCC and the PWM signal of the high level. Is entered.

On the other hand, when the low level PWM signal is output, as the first and second nodes N1 and N2 are in a low state, the PWM signal is input to the MCU 20 in a low level state.

That is, the PWM input circuit 10 of the present invention inputs to the MCU 20 in a high level state when a high level PWM signal is output from the ECU, and in a low level state when the PWM signal of a low level is output from the ECU. 20). As a result, the present invention can input the PWM signal in the same state as the signal output from the ECU to the MCU 20 without the signal inversion.

In addition, when noise and surge voltages are introduced from the ECU side, the first and second capacitors C1 and C2 reduce the noise and surge voltages that are introduced.

Finally, the case where noise is generated in the digital circuit will be described.

When noise occurs in the digital circuit, a voltage whose voltage level is shifted is applied to the first node N1 due to the generated noise. For example, when the reference value of the battery voltage is 12V, a voltage changed higher than the reference value, for example, a voltage of 13V or more is applied. At this time, as the second and third resistors R12 and R13 distribute the changed voltage and the first and second diodes D11 and D12 block the overvoltage reverse voltage, the third node N3 is at a low level. It is in a close state.

Accordingly, the PWM input circuit 10 of the present invention is provided with the analog ground terminal AGND and the digital ground terminal DGND separately, and prevents overvoltage reverse voltage of the first and second diodes D11 and D12. Accordingly, even when noise occurs in the digital ground terminal DGND, the PWM signal may be input to the MCU 20 in a low level state as before noise generation.

In the above embodiment, although the battery voltage of 12V has been described as an example as the first voltage, the present invention is not limited thereto, and the present invention may be applied to a case in which a large vehicle uses 24V as the first voltage.

The scope of the present invention is not limited to the embodiments described above, but is defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self evident.

1 is a block diagram showing the configuration of a motor driving apparatus for a fuel pump according to the prior art.

2 is a detailed circuit diagram showing the configuration of the PWM input circuit shown in FIG.

3 is a detailed circuit diagram showing a configuration of a PWM input circuit of a motor driving apparatus for a fuel pump according to a preferred embodiment of the present invention.

`` Explanation of symbols for main parts of drawings ''

1: Motor drive device for fuel pump 10: PWM input circuit

20: MCU 30: overvoltage protection

40: motor controller 50: MOSFET drive circuit

51: first MOSFET driver 53: second MOSFET driver

55: voltage multiplier 60: motor drive unit

Claims (8)

In the PWM input circuit for converting the first voltage to the level of the second voltage in accordance with the PWM signal output from the ECU of the vehicle and outputs to the MCU, First to third resistors for dividing the first voltage; A first node formed between the first and second resistors to receive a PWM signal from the ECU, A first capacitor coupled to the first node, A second capacitor coupled in parallel to the third resistor and And a first and a second diode coupled in series with the second voltage. The method of claim 1, One end of the first capacitor is coupled to the first node, The other end of the first capacitor PWM input circuit of the motor drive device for a fuel pump, characterized in that coupled to the analog ground end. 3. The method of claim 2, A second node formed between the second resistor and the third resistor; One end of the second capacitor is coupled to the second node, The other end of the second capacitor PWM input circuit of the motor driving device for a fuel pump, characterized in that coupled to the analog ground end. The method of claim 3, wherein The first diode is coupled to the second voltage, And the second diode is coupled to the digital ground terminal. The method of claim 4, wherein When the second and third resistors are applied with a voltage whose voltage level is changed to the first node due to noise generated from the digital ground terminal, the second and third resistors divide the first voltage to obtain a voltage near the low through the second node. PWM input circuit of a fuel pump motor drive device characterized in that the output. The method of claim 5, When the PWM signal output from the ECU is not input, the first to third resistors divide the first voltage to output a high level PWM signal, When the PWM signal is at a high level, the second and third resistors divide the first voltage and output a high level PWM signal through the second node. And the first node is in a low state when the PWM signal is at a low level, and outputs a low level PWM signal to the MCU. The method according to any one of claims 1 to 6, The first voltage is 12V, The PWM input circuit of the fuel pump motor drive device, characterized in that the second voltage is 5V. The method according to any one of claims 1 to 6, The first voltage is 24V, The PWM input circuit of the fuel pump motor drive device, characterized in that the second voltage is 5V.

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