JP4596168B2 - Photocoupler type analog signal transmission device - Google Patents

Description

  The present invention relates to an improvement in a photocoupler type analog signal transmission apparatus that transmits an analog signal voltage between different power supply voltage systems that need to be electrically insulated from each other.

  2. Description of the Related Art A two-power-source in-vehicle electronic circuit device equipped with a high voltage circuit system fed from a high voltage battery and a low voltage circuit system fed from a low voltage battery has been put into practical use. For example, in a two-power-source electronic circuit device mounted on a hybrid vehicle, the high-voltage circuit system converts electric power fed from a high-voltage battery of several hundred volts or more into AC power through a power control circuit such as an inverter, and a traveling motor The low voltage circuit system supplies power to the control device, AV device, and the like. The control circuit for controlling the switching element of the power control circuit of the high voltage circuit system is supplied with a constant power supply voltage from, for example, a low voltage battery through a transformer type electrically insulated power supply circuit. This type of in-vehicle electronic circuit device of the two power supply system detects the state of the power control circuit of the high voltage circuit system, transmits this state signal to the control circuit device belonging to the low voltage circuit system, and is monitored by the control circuit device In general, a control signal for controlling the power control circuit is formed. This type of in-vehicle electronic circuit device of the dual power supply system is described in Patent Document 1 filed by the present applicant.

  In this case, it is necessary to transmit the analog signal output from the sensor from the sensor on the high voltage circuit system side to the control circuit device on the low voltage circuit system side in an electrically insulated state, and a photocoupler is used for electrical insulation. Is normal. More specifically, the analog signal output from the sensor is converted to a PWM signal on the high voltage circuit side, then transmitted to the low voltage circuit side through a photocoupler, and converted again to an analog signal on the low voltage circuit system. Then, signal processing is performed in the control circuit device.

An analog-to-duty conversion circuit that converts an analog signal into a PWM signal, a photocoupler, and a duty-to-analog conversion circuit that converts a PWM signal back to an analog signal are used in this photocoupler-type analog signal transmission circuit. , A photocoupler, and a duty-analog conversion circuit are collectively referred to as a photocoupler type analog signal transmission device. A photocoupler type analog signal transmission device used in this kind of dual power-source vehicle-mounted electronic circuit device is described in Patent Document 1.
Japanese Patent Laid-Open No. 2001-257442

  However, in the above-described photocoupler type analog signal transmission device, it is actually necessary to transmit a large number of analog signals from the electronic circuit device on the high voltage circuit system side to the control device on the low voltage circuit system side. This is because the circuit configuration of the electronic circuit device on the high voltage circuit system side becomes complicated, and for the high-precision and safe control, many states of the electronic circuit device on the high voltage circuit system side are detected and transmitted. This is because it is necessary to do this. For example, even if it is limited to a three-phase inverter device for driving a traction motor, it has six power switching elements, and by simply monitoring the temperature of each power switching element, a six-channel photocoupler analog signal A transmission device is required. It is an analog signal to be transmitted such as the current and voltage of the travel motor. In addition, various motors other than the traveling motor exist as electronic circuit devices on the high voltage circuit system side.

  As a result, the output power required for the power supply circuit for supplying the power supply voltage to the photocoupler type analog signal transmission device increases, so that the power consumption and heat generation of the power supply circuit for supplying the photocoupler type analog signal transmission device increase. There is a problem that the circuit configuration is large and expensive. This problem is exacerbated by the fact that this photocoupler type analog signal transmission device needs to have high power supply voltage accuracy in order to handle analog signal voltages. The power consumption and circuit cost of a power supply circuit increase geometrically as its accuracy increases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a photocoupler type analog signal transmission device capable of simplifying a power supply circuit and reducing power loss.

The photocoupler type analog signal transmission device of the present invention that solves the above-mentioned problems is a two-power-source vehicle-mounted type equipped with a high-voltage circuit system fed from a high-voltage battery and a low-voltage circuit system fed from a low-voltage battery. An analog signal voltage corresponding to the chip temperature of the switching element of the inverter device that is used as a part of the electronic circuit device and drives and controls the traveling motor that is the high voltage circuit system is output to the signal processing circuit of the low voltage circuit system A photocoupler type analog signal transmission device that converts the analog chip voltage into a possible analog signal voltage and outputs the chip temperature to the signal processing circuit , wherein the analog signal voltage corresponding to the photocoupler and the chip temperature is converted into a PWM signal voltage. An analog-to-duty conversion circuit for conversion and a PWM signal output from the analog-to-duty conversion circuit A driver circuit for driving the coupler, and Duty-analog converter circuit a PWM signal voltage is converted into an analog signal voltage, and outputs the converted analog signal voltage to the signal processing device as the chip temperature of the photo-coupler output, each A power supply circuit device for applying a power supply voltage to the circuit, wherein the power supply circuit device forms a power supply voltage to be applied to the Duty-Analog conversion circuit, and the first power supply circuit portion outputs The photocoupler is driven by forming a low-accuracy power supply voltage having a voltage fluctuation rate larger than the power supply voltage to be electrically insulated from the power supply voltage output by the first power supply circuit unit. And a second power supply circuit section applied to the driver circuit.

In a preferred aspect, the power supply circuit device includes a third power supply circuit unit that forms a power supply voltage to be applied to the analog-to- duty conversion circuit, and the second power supply circuit unit includes the third power supply circuit. For driving the photocoupler by forming a power supply voltage with a lower accuracy than the power supply voltage output from the power supply unit in a state electrically insulated from the power supply voltage output from the first power supply circuit unit . It is characterized by being applied to the driver circuit.

That is, the power supply circuit device of the photocoupler type analog signal transmission device according to the present invention is characterized in that a power supply voltage having an accuracy lower than that of the power supply voltage applied to the analog-to- duty conversion circuit is applied to the driver circuit for driving the photocoupler. It is said. In this way, it is possible to realize a photocoupler analog signal transmission device that can simplify the power supply circuit and reduce power loss.

  More specifically, among the analog-to-duty conversion circuit, the photo-coupler (including a driver circuit for driving the photo-coupler) and the duty-to-analog conversion circuit constituting the photo-coupler type analog signal transmission device, the photo-coupler is the light emission efficiency of the LED. Therefore, in order to drive at high speed, a large amount of power is consumed for high-speed charge / discharge of the parasitic capacitance. Generating such a large amount of power with high accuracy necessary for the analog-to-duty conversion circuit and the duty-to-analog conversion circuit leads to a significant increase in power loss and manufacturing cost of the power supply circuit device. In view of this problem, when the present inventor transmits a PWM signal through a photocoupler, fluctuations in the power supply voltage of the photocoupler (including a driver circuit for driving the photocoupler) cause a change in the amount of light, It was found that the duty change of the PWM signal is not essentially caused, that is, the power supply voltage of the photocoupler can be much lower than the power supply voltage accuracy required for the analog-duty conversion circuit and the duty-analog conversion circuit. I noticed.

  The present invention has been made based on this point of view. Among photocoupler-type analog signal transmission devices, a high-accuracy power supply voltage is applied to an analog-to-duty conversion circuit and / or a duty-to-analog conversion circuit as usual. The power supply voltage for supplying power to the photocoupler (and the driver circuit that drives the photocoupler) and the light receiving circuit portion of the photocoupler is much less accurate than the power supply voltage applied to the analog-to-duty conversion circuit and / or the duty-to-analog conversion circuit. A power supply voltage having a large voltage fluctuation rate is applied. Such a power supply voltage having a large voltage fluctuation rate can be used without making the rectified and smoothed voltage of the transformer type DCDC converter constant, for example, and the power loss due to significant simplification of circuit configuration and constant voltage It was possible to avoid and avoid.

  In a preferred aspect, the analog-to-duty conversion circuit detects a state of a high-voltage control circuit that controls an electric device fed from an in-vehicle high voltage battery, and the duty-to-analog conversion circuit is fed from an in-vehicle low voltage battery The analog signal voltage is output to the control circuit, the second power supply circuit unit is powered from the low voltage battery, and the first power circuit unit is powered from the low voltage battery. It is composed of a rectifying / smoothing circuit of the converter. In this way, since the driving power of the photocoupler can be supplied from the low voltage battery side, the step-down of the high voltage battery becomes unnecessary, and the output voltage of this transformer type DCDC converter is transferred to another electronic circuit on the high voltage battery side. Since it can be shared with the apparatus, the circuit configuration is simplified.

  A preferred embodiment of the apparatus of the present invention will be described below. However, the present invention is not limited to the following embodiments, and the technical idea of the present invention may be implemented in combination with other techniques.

(Overall circuit configuration)
The photocoupler type analog signal transmission apparatus of the present invention will be described with reference to the circuit diagram shown in FIG.

  This device is a photocoupler type analog signal transmission device used as a part of a vehicle-mounted electronic circuit device such as a vehicle DC-DC converter device or a motor control device, and converts the analog signal voltage into a PWM (pulse width modulation) signal. Analog-to-Duty conversion circuit 1 for converting, driver circuit 2 for amplifying the PWM signal output from analog-to-Duty conversion circuit 1, photocoupler 3, and duty-to-analog conversion for converting the PWM signal output from photocoupler 3 into an analog signal voltage A circuit 4, an electrically insulated power supply circuit 5, and constant voltage power supplies 6 and 7 are provided. Reference numeral 8 denotes a low-voltage battery for supplying driving power for each circuit, which supplies power to each partial circuit constituting the photocoupler type analog signal transmission device.

(Signal processing circuit configuration)
The analog-to-duty conversion circuit 1 is a known PWM signal generation circuit that forms a PWM signal voltage by comparing an analog signal voltage Va to be transmitted with an input triangular wave voltage. The analog signal voltage Va is a voltage corresponding to the chip temperature of a switching element of an inverter device that is fed from a high-voltage battery of several hundred volts and drives and controls a traveling motor. The analog duty voltage is detected from a thermistor type or diode type temperature detection circuit. Input to the conversion circuit 1.

  The driver circuit 2 intermittently drives the light emission of the photocoupler 3 based on the PWM signal voltage output from the analog-to-duty conversion circuit 1. An example of the driver circuit 2 is shown in FIG. The driver circuit 2 shown in FIG. 2 includes an operational amplifier amplifier circuit 21 and load resistors R1 and R2 connected in series with the LED of the photocoupler 3. The output terminal of the operational amplifier amplifier circuit 21 is connected to the load resistors R1 and R2. Connected to a point. The output stage of the operational amplifier amplifier circuit 21 has an open collector configuration, but is not limited thereto. Thereby, when the output voltage Vo of the operational amplifier amplifier circuit 21 is at a low level, power supply to the LED of the photocoupler 3 is stopped, and when the output voltage Vo of the operational amplifier amplifier circuit 21 is at a high level, the LED of the photocoupler 3 is stopped. Is turned on. The operational amplifier amplifier circuit 21 may have a voltage follower circuit configuration or a normal voltage amplifier circuit configuration. However, the current drive capability of the operational amplifier amplifier circuit 21 needs to be ensured to drive the LED of the photocoupler 3 at a sufficiently high speed. Of course, if the LED of the photocoupler 3 can be intermittently driven at a necessary speed according to the PWM signal voltage output from the analog-to-duty conversion circuit 1, the driver circuit 2 may be configured without using the operational amplifier amplifier circuit 21.

  The photocoupler 3 includes an LED, a photodiode that photoelectrically converts the light emission energy of the LED, and an open collector transistor that amplifies the output current of the photodiode. The R is the collector load resistance of the open collector transistor, and the output voltage of the photocoupler 3 is output from the collector of the open collector transistor to the duty-analog conversion circuit 4.

  The duty-analog conversion circuit 4 is a known circuit that converts an input PWM signal voltage into an analog signal voltage, and outputs the converted analog signal voltage to an external signal processing circuit such as an A / D converter.

  As a result, the chip temperature of the switching element (for example, IGBT) of the inverter device that drives and controls the traveling motor that is fed from a high-voltage battery of several hundred volts is detected as an analog signal voltage Va with reference to the reference potential of the switching element. After that, the analog signal voltage Va corresponding to the chip temperature can be converted into an analog signal voltage based on the low potential end (vehicle body potential) of the low voltage battery 8.

(Power circuit configuration)
The photocoupler type analog signal transmission device shown in FIG. 1 includes an electrically insulated power supply circuit 5 and constant voltage power supplies 6 and 7 as power supply circuits. The constant voltage power supply 7 is not essential and may be shared with the constant voltage power supply 6.

  The electric insulation type power supply circuit 5 is a transformer type electric insulation type power supply circuit, and includes an inverter circuit 51, a transformer 52, and secondary side power supply circuits 53 to 55. However, the secondary power supply circuits 54 and 55 are not essential and may be shared with the secondary power supply circuit 53.

  The inverter circuit 51 is supplied with DC power from the low-voltage battery 8 to generate an AC voltage having a predetermined frequency, and applies this AC voltage to the primary coil of the transformer 52. A plurality of secondary coils of the transformer 52 are provided in accordance with the voltage level required in the high voltage side circuit system. The first secondary coil outputs a first magnitude AC voltage to the secondary power circuit 53, and the second secondary coil outputs a second magnitude AC voltage to the secondary power circuit 54. The third secondary coil outputs the AC voltage having the third magnitude to the secondary power supply circuit 55.

  Each of the secondary power supply circuits 53 to 55 includes a rectifier circuit that rectifies the input AC voltage, a smoothing circuit that smoothes the rectified voltage, and a constant voltage circuit that converts the smoothed voltage to a constant voltage. However, the secondary side power supply circuits 53 to 55 can have a voltage fluctuation rate within the range of the voltage fluctuation rate allowed by the circuits fed from the secondary side power supply circuits 53 to 55. Therefore, if the allowable voltage fluctuation range is large, the secondary power supply circuits 53 to 55 can directly output the smoothed voltage smoothed by the smoothing circuit without the constant voltage circuit.

  In this embodiment, the secondary power supply circuit 53 applies a power supply voltage to the driver circuit 2, and the secondary power supply circuit 54 applies a power supply voltage to the analog-to-duty conversion circuit 1.

  The constant voltage power supply 6 is supplied with power from the low voltage battery 8 and applies a predetermined power supply voltage as a power supply voltage to the duty-analog conversion circuit 4. The constant voltage power supply 7 is supplied with power from the low voltage battery 8 and applies the predetermined power supply voltage to the photo. A power supply voltage is applied to the light receiving circuit unit 31 of the coupler 3. In FIG. 1, the photodiode of the light receiving circuit unit 31 is directly applied with the power supply voltage from the constant voltage power supply 7, and the open collector transistor of the light receiving circuit unit 31 is directly applied with the power supply voltage from the constant voltage power supply 7 through the collector load resistor R. However, the present invention is not limited to this.

(Setting of power supply voltage accuracy)
Next, the setting of the accuracy (voltage fluctuation rate) of each of the power supply voltages V1 to V4 that characterize this embodiment will be described. The power supply voltage V1 is a power supply voltage output from the secondary power supply circuit 54 to the analog-to-duty conversion circuit 1, and the power supply voltage V2 is a power supply voltage output from the secondary power supply circuit 53 to the driver circuit 2. The power supply voltage V3 is a power supply voltage output from the constant voltage power supply 7 to the light receiving circuit portion 31 of the photocoupler 3, and the power supply voltage V4 is a power supply voltage output from the constant voltage power supply 6 to the duty-analog conversion circuit 4.

  In the photocoupler analog signal transmission device of this embodiment, at least the accuracy of the power supply voltage V4 is set higher than the accuracy of the power supply voltage V2. Preferably, the accuracy of the power supply voltage V1 is set higher than the accuracy of the power supply voltage V2. Preferably, the accuracy of the power supply voltage V4 is set higher than the accuracy of the power supply voltage V3. Preferably, the accuracy of the power supply voltage V1 is set higher than the accuracy of the power supply voltage V3.

  That is, in the photocoupler analog signal transmission device of this embodiment, the accuracy of the power supply voltage of the driver circuit 2 for driving the photocoupler that requires a large power supply power due to the small power supply utilization efficiency of the photocoupler 3 is obtained. It is characterized in that it is lower than the accuracy of the power supply voltage of the analog-to-duty conversion circuit 1 and the duty-to-analog conversion circuit 4 which are analog circuits at the front and rear stages.

  In this way, in addition to the power supply circuit system of the analog-to-duty conversion circuit 1 and the duty-to-analog conversion circuit 4, it is necessary to separately provide a power supply circuit system for driving the photocoupler. Since the secondary side power supply circuit 53 is low in accuracy, the circuit configuration is simple and the power loss is small, so that the circuit configuration can be simplified and the power efficiency can be improved.

  More specifically, in the photocoupler type analog signal transmission device, the analog-to-duty conversion circuit 1 and the duty-to-analog conversion circuit 4 on both sides of the photocoupler 3 require a highly accurate power supply voltage in order to ensure the necessary analog signal accuracy. However, the required power itself is smaller than the power consumption of the photocoupler 3. On the other hand, the high-speed driving of the photocoupler 3 requires relatively large power consumption. Therefore, the driving power of the photocoupler 3 is supplied to the driver circuit 2 from a high-accuracy constant voltage power supply circuit for driving the analog-to-duty conversion circuit 1 or the duty-to-analog conversion circuit 4 having a large power loss and a complicated circuit configuration. This leads to an increase in the scale of this high-accuracy constant voltage power supply circuit, resulting in an increase in the required chip area and an increase in power loss.

  On the other hand, in this embodiment shown in FIG. 1, since the power supplied to the driver circuit 2 for driving the photocoupler 3 is supplied from the relatively low accuracy secondary power supply circuit 53, the power supply circuit system The power loss can be reduced and the circuit configuration can be simplified.

  In this embodiment, the secondary power supply circuit 53 omits the constant voltage circuit by smoothing the rectified power by the smoothing circuit and using it as the power supply voltage V2. The secondary side power supply circuit 54 makes the smoothed voltage constant by a switching regulator to obtain the power supply voltage V1. The constant voltage power supply 6 makes the voltage of the low voltage battery 8 constant by a switching regulator to obtain a power supply voltage V4. In this embodiment, the constant voltage power supply 7 is omitted, and the voltage of the low voltage battery 8 is directly applied to the resistor R.

(Description of on-board electronic circuit device of dual power supply system)
An example of a two-power-source in-vehicle electronic circuit device using the above-described photocoupler type analog signal transmission device will be described with reference to a block diagram shown in FIG.

  In FIG. 3, 100 is a high voltage battery, 101 is a three-phase inverter, 102 is a three-phase motor, 103 is a motor control circuit, and 104 is a low voltage side control circuit. Although not shown in FIG. 3, the high voltage side motor control circuit 103 and the low voltage side control circuit 104 are capable of digital communication through a photocoupler system (not shown).

  The high voltage battery 100 supplies power to the three-phase motor 102 through the three-phase inverter 101, and the motor control circuit 103 controls the three-phase inverter 101. The electrically isolated power supply circuit 5 including a transformer type DCDC converter has a secondary power supply circuit 55 that outputs a power supply voltage V5 to the motor control circuit 103. The duty-analog conversion circuit 4 outputs an analog signal voltage to the low voltage side control circuit 104. The power supply voltage of the low voltage side control circuit 104 is supplied from the constant voltage power supply 6, but may be supplied from the constant voltage power supply 7 with lower accuracy.

(Modification)
The power supply power of the constant voltage power supplies 6 and 7 may be supplied by rectifying the secondary voltage of the transformer 52. Further, the constant voltage power supplies 6 and 7 may be replaced by a rectifier circuit that rectifies the secondary voltage of the transformer 52. Also good.

  In addition, instead of configuring the secondary power supply circuit 54 with a switching regulator, the secondary power supply circuit 54 may be configured with a rectifier circuit that rectifies the secondary voltage of the transformer 52.

1 is a block circuit diagram showing a preferred embodiment of a photocoupler type analog signal transmission device of the present invention. FIG. 2 is a circuit diagram illustrating a circuit example of a driver circuit illustrated in FIG. 1. FIG. 2 is a block diagram showing a two-power-source vehicle-mounted electronic circuit device using the photocoupler analog signal transmission device shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Analog-DUTY conversion circuit 2 Driver circuit 3 Photocoupler 4 DUTY-Analog conversion circuit 5 Electrically insulated power supply circuit 6 Constant voltage power supply 7 Constant voltage power supply 8 Low voltage battery 21 Operational amplifier amplification circuit 31 Light receiving circuit part 51 Inverter circuit 52 Transformers 53-55 Secondary side power supply circuit 100 High voltage battery 101 Three phase inverter 102 Three phase motor 103 Motor control circuit 104 Low voltage side control circuit

Claims (3)

The high-voltage circuit system is used as part of a two-power-source vehicle-mounted electronic circuit device equipped with a high-voltage circuit system fed from a high-voltage battery and a low-voltage circuit system fed from a low-voltage battery . An analog signal voltage corresponding to a chip temperature of a switching element of an inverter device that drives and controls a traveling motor is converted into an analog signal voltage that can be output to a signal processing circuit of the low voltage circuit system, and the chip temperature is converted into the signal processing A photocoupler type analog signal transmission device that outputs to a circuit ,
A photocoupler,
An analog-to-duty conversion circuit for converting an analog signal voltage corresponding to the chip temperature into a PWM signal voltage;
A driver circuit for driving the photocoupler based on a PWM signal output from the analog-to-duty conversion circuit;
A duty-analog conversion circuit that converts the PWM signal voltage output from the photocoupler into an analog signal voltage, and outputs the converted analog signal voltage as the chip temperature to the signal processing device ;
A power supply circuit device for applying a power supply voltage to each circuit;
With
The power supply circuit device includes:
A first power supply circuit unit for forming a power supply voltage to be applied to the duty-analog conversion circuit;
A low-accuracy power supply voltage having a voltage fluctuation rate larger than the power supply voltage output from the first power supply circuit section is electrically insulated from the power supply voltage output from the first power supply circuit section. A second power supply circuit section formed and applied to the driver circuit for driving the photocoupler;
A photocoupler type analog signal transmission device comprising: In the photocoupler type analog signal transmission device according to claim 1,
The power supply circuit device includes:
A third power supply circuit unit for forming a power supply voltage to be applied to the analog-to-duty conversion circuit,
The second power supply circuit unit includes:
A power supply voltage having a lower accuracy than the power supply voltage output from the third power supply circuit unit is formed in a state of being electrically insulated from the power supply voltage output from the first power supply circuit unit. A photocoupler type analog signal transmission device applied to the driver circuit for driving a coupler. In the photocoupler type analog signal transmission device according to claim 1 or 2,
The analog-to-duty conversion circuit is
Detects the state of the high-voltage control circuit that controls the electrical equipment that is fed from the in-vehicle high-voltage battery,
The duty-analog converter circuit
The analog signal voltage is output to a control circuit that is powered from an in-vehicle low voltage battery,
The second power supply circuit unit is powered by the low voltage battery,
The first power supply circuit unit is a photocoupler type analog signal transmission device configured by a rectifying and smoothing circuit of a transformer type DCDC converter fed from the low voltage battery.

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