JP2019049929A - Electric power detection device and heating device - Google Patents

Abstract

To provide an electric power detection device possible to detect change of power with good response.SOLUTION: The device includes: a PWM switch (110) that performs PWM control that outputs input power from a power source with a predetermined duty ratio by being switched on and off; an RC circuit (120) consisting of a resistor R and a capacitor C and smoothing and outputting a fluctuation of the output of the PWM switch (110); a reset switch (130) for releasing a charge of the capacitor C at a predetermined timing; and a comparator (140) that compares a voltage output from the RC circuit (120) with a predetermined voltage threshold.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power detection device and a heating device.

  In Patent Document 1, a pair of IGBTs (Insulated Gate Bipolar Transistors) is provided in series with a heater, and a heater for vehicle heating that forcibly turns off the IGBTs when the temperature of the IGBT is equal to or higher than a predetermined temperature. A controller of the invention is disclosed.

JP, 2013-082377, A

  By the way, in the IGBT used for switching of the heater as described above, an abnormality may occur in on / off of the IGBT due to, for example, a surge voltage. If an abnormality occurs in on / off of the IGBT, an unexpected power may be input to the heater. On the other hand, although it is possible to provide a circuit that detects the voltage by smoothing the input power of the heater, in addition to an increase in cost, the response to detection of the voltage is low and it copes with rapid voltage fluctuations. could not.

  An object of the present invention is to provide a power detection device capable of detecting a power change in a responsive manner.

  According to an aspect of the present invention, a PWM switch is provided that performs PWM control for outputting input power from a power source at a predetermined duty ratio by being switched between on and off, and a resistor and a capacitor. An RC circuit in which the charge stored in the capacitor fluctuates according to the on time, a reset switch for releasing the charge of the capacitor in a predetermined cycle, and a comparator for comparing a voltage output from the RC circuit with a predetermined voltage threshold , And.

  Moreover, according to another aspect of the present invention, a heater that generates heat when power is supplied from a power source, and a heater connected in series with the heater are switched on and off to set the power to the heater to a predetermined level. Provided in at least one of a pair of switching elements performing PWM control outputting at a duty ratio, a control device controlling on / off of the switching elements, and a pair of switching elements, the output of the switching elements exceeds a predetermined voltage threshold A power detection device that determines whether or not the power detection device has a PWM switch that outputs input power from the power source at a predetermined duty ratio in conjunction with PWM control in the switching element; An RC circuit consisting of a capacitor, the charge stored in the capacitor varying according to the on time of the PWM switch, and The controller includes a reset switch for releasing charges at a predetermined cycle, and a comparator for comparing a voltage output from the RC circuit with a predetermined voltage threshold, and the control device determines that the voltage output from the RC circuit is predetermined as a result of comparison. Power supply to the heater is shut off when the voltage threshold of

  According to the above aspect, since the RC circuit uses a region where the output voltage varies with time, it is not necessary to increase the capacitance of the capacitor as compared to smoothing. In addition, by determining in a predetermined cycle, it is possible to improve responsiveness to changes in power.

FIG. 1 is a block diagram of a heating device according to an embodiment of the present invention. FIG. 2 is a block diagram of a power detection device according to an embodiment of the present invention. FIG. 3 is a time chart explaining the output voltage of the power detection device according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Hereinafter, with reference to the drawings, a heating device 100 according to an embodiment of the present invention will be described.

  FIG. 1 is a configuration diagram for explaining the overall configuration of a heating device 100 of the present embodiment.

  Heating apparatus 100 includes a heater 30 driven by power supplied from DC power supply 1 and IGBTs (Insulated Gate Bipolar Transistors) 10 and 20 as a pair of switching elements connected in series with heater 30. And.

  Heating device 100 is applied to a vehicle air conditioner (not shown) mounted on a vehicle such as EV (Electric Vehicle) or HEV (Hybrid Electric Vehicle). The vehicle air conditioner has a hot water tank 31 which heats the refrigerant by the heater 30 to execute the heating operation.

  The direct current power source 1 is a high power battery mounted on an EV or HEV. The output voltage of the DC power source 1 is a high voltage of 30 [V] or more, and here, for example, 350 [V]. The DC power supply 1 supplies power to the heater 30 through the supply line 5. The negative side of the heater 30 is connected to the ground 9.

  The heater 30 is a sheath heater which includes a heating wire inside a sheath and generates heat when power is supplied. The heater 30 is housed in the warm water tank 31 and heats the refrigerant flowing through the warm water tank 31.

  The IGBT 10 and the IGBT 20 are switched on and off in accordance with a command from the upper controller 3 to switch between supply and shutoff of power from the DC power supply 1 to the heater 30. The IGBT 10 and the IGBT 20 are switched on and off by PWM (Pulse Width Modulation) control.

  The IGBT 10 and the IGBT 20 are periodically switched on and off in cycles different from each other. The on state may be maintained after the IGBT 10 or the IGBT 20 is switched on without being switched periodically.

  The IGBT 10 is provided upstream of the heater 30, and the IGBT 20 is provided downstream of the heater 30. Since the IGBT 10 and the IGBT 20 are provided in series, power is supplied from the DC power supply 1 to the heater 30 only when both the IGBT 10 and the IGBT 20 are switched on.

  The IGBT 10 is provided with a driver circuit 11 that switches on and off through the control line 12, and a power detection device 13 that detects power supplied to the heater 30 through the IGBT 10.

  Similarly, the IGBT 20 is provided with a driver circuit 21 that switches on and off through the control line 22.

  The controller 3 is, for example, an electronic control unit (ECU) that controls a vehicle air conditioner. The controller 3 includes a CPU (central processing unit) that executes control of a vehicle air conditioner, a ROM (Read Only Memory) in which control programs and setting values required for processing operations of the CPU are stored, and various sensors. And RAM (Random Access Memory) for temporarily storing detected information. Connected to the controller 3 is a heater switch 4 which starts to be energized when the heater 30 is switched on.

  The heater switch 4 is switched on and off based on the driver's operation when the vehicle air conditioner is manual. The heater switch 4 is switched on and off based on a heating request of the vehicle air conditioner, when the vehicle air conditioner is an automatic type.

  The driver circuit 11 switches the IGBT 10 between on and off based on a command by PWM control from the controller 3. The driver circuit 11 is a gate drive circuit that switches the gate of the IGBT 10 on and off.

  Next, detection of power input to the heater 30 in the heating device 100 configured as described above will be described.

  The DC power supply 1 of the present embodiment is supplied by a vehicle-mounted high-power battery. The high-power battery is charged and discharged in accordance with the operation of the vehicle, so the output voltage fluctuates. As an example, fluctuation of about 200 [V] to 400 [V] occurs with respect to the rated voltage 350 [V] of the high-power battery.

  In particular, when the battery voltage is high, for example, when an abnormality occurs in the control of the controller 3 and the driver circuits 11 and 21 or when an ON signal is input to the IGBTs 10 and 20 more than necessary due to noise etc. Overpower may be input.

  In order to prevent the excessive power from being input to the heater 30, a detection device for detecting the excessive power may be provided, and a warning or a stop of energization may be performed when the predetermined power is exceeded. For example, an RC circuit is provided to smooth the output of PWM control of the IGBTs 10 and 20, and an average of voltage values input to the heater 30 is acquired by the output of the RC circuit, and the acquired voltage value does not exceed a predetermined threshold value Can be configured to detect the overpower to the heater 30.

  However, in such an RC circuit, in consideration of the stability and accuracy of the voltage value, it is necessary to set the time constant of the RC circuit to five times or more of the control period. However, in the case of such a configuration, it takes time for the voltage value to be stabilized, and the response is delayed even in the case of excessive power, so that the situation where the power increases rapidly can not be dealt with. Furthermore, since the capacitor of the RC circuit is required to have a capacitance and withstand voltage that are five times the time constant, there is a problem that the cost of the capacitor is increased.

  On the other hand, in the embodiment of the present invention, the following configuration is configured so that the power can be detected in a responsive manner without increasing the cost.

  FIG. 2 is a block diagram of the power detection device 13 according to the embodiment of this invention.

  The power detection circuit is configured to include the PWM interlock switch 110, the RC circuit 120, the reset switch 130, and the comparator 140.

  The PWM interlock switch 110 is configured of a switching element such as a transistor. The PWM interlocking switch 110 is switched on and off in accordance with a command from the driver circuit 11 to switch supply and interruption of the power input from the reference power supply 1 to the RC circuit 120 via the output circuit 111. . That is, the PWM interlocking switch 110 performs the same operation as the IGBT 10, and the on time is the same on time as the IGBT 10.

  The RC circuit 120 includes a resistor R connected in series to the output circuit 111 of the PWM interlock switch 110 and a capacitor C connected in parallel between the output circuit 111 and the ground 9. The RC circuit 120 outputs a predetermined response according to a time constant determined by the resistance value of the resistor R and the capacitance of the capacitor C. That is, in the RC circuit 120, the charge accumulated in the capacitor C fluctuates according to the on time of the PWM interlock switch 110, and the result is output to the comparator 140 via the output circuit 121. As for this time constant, as will be described later, it is only necessary to be able to determine voltage fluctuation during one cycle of PWM control.

  The reset switch 130 is formed of a switching element such as a transistor, and is connected between the output circuit 121 and the ground 9 in parallel with the capacitor C of the RC circuit 120. The reset switch 130 is turned on when the reset signal from the controller 3 is input, and connects between the output circuit 121 and the ground 9. When the output circuit 121 and the ground 9 are connected, the potential difference between the capacitor C and the ground 9 becomes substantially zero, and the charge stored in the capacitor C is discharged.

  The comparator 140 compares the output voltage of the output circuit 121 with the over power threshold signal 50 input from the controller 3. If the output voltage exceeds the voltage of the overpower threshold signal 50 as a result of comparison, the comparator 140 outputs an overpower signal from the output terminal 141. The output over power signal is input to the controller 3.

  The overpower threshold signal 50 input to the comparator 140 is a signal obtained by inverting and amplifying the reference power supply 1. The power input to the heater 30 is a value obtained by multiplying the ratio of the square of the DC power supply 1 and the on time. The on time to reach the overpower changes with the voltage of the DC power supply 1. That is, when the voltage of the reference power supply 1 is high, it is necessary to detect a short on-time. Since the output voltage of the output circuit 121 increases with the on time, the over power threshold signal 50 needs to be lowered.

  When an over power signal is input from the power detection device 13, the controller 3 determines that the IGBT 10 of the heating device 100 is over power, and executes the corresponding processing. For example, control is performed to stop the energization of power from the reference power source 1 to the heating device 100 or to shut off the security device (relay, fuse, etc.).

  Next, the operation of the power detection device 13 of the present embodiment will be described.

  In the present embodiment, the case where the IGBT 10 controls the heater 30 by PWM control and the IGBT 20 controls the heater 30 as a switch enabling energization in a state where the heater switch 4 is turned on will be described. .

  FIG. 3 is an explanatory view showing an output voltage of the power detection device 13.

  FIG. 3 shows the time change of the output voltage of the PWM interlocking switch 110 in the upper part, and the time change of the output voltage of the RC circuit 120 in the lower part, with time plotted on the horizontal axis.

  The controller 3 sends a command to always turn the IGBT 20 on to the driver circuit 21, and the driver circuit 21 transmits a gate signal to the IGBT 20 to put the IGBT 20 in the conductive state. Then, the controller 3 controls the driver circuit 11 to turn on and off the IGBT 10 and performs PWM control so as to supply desired power to the heater 30.

  In FIG. 3, each timing t0 to t7 is a cycle of PWM control for the IGBT 10, and one cycle is set to an interval of, for example, about 0.1 to 1 [s]. The duty ratio of the IGBT 10 is controlled by PWM control.

  In FIG. 3, at timings t0 to t1, t1 to t2, and t2 to t3, the time during which the IGBT 10 is turned on is set to, for example, 2/8, longer than the time when the IGBT 10 is turned on. Note that during the ON period, the ON signal is not continuously sent, but the PWM control repeats ON / OFF with a predetermined duty ratio. Similarly, during the off period, the on / off at a predetermined duty ratio is repeated by the PWM control instead of continuously sending the off signal.

  In the power detection device 13, the same signal as the gate signal to the IGBT 10 is input to the PWM interlock switch 110. That is, the change in the output voltage of the PWM interlock switch 110 shown in the upper part of FIG. 3 matches the change in the output voltage of the IGBT 10.

  Referring to the lower part of FIG. 3, in power detection device 13, the output of PWM interlock switch 110 is smoothed in RC circuit 120 and output to comparator 140.

  More specifically, the duty ratio of PWM control is set to 2/8 between timing t0 and t1. The output of the RC circuit 120 is zero at the timing t0, the capacitor C is charged by the output of the PWM interlock switch 110, and the output voltage of the RC circuit 120 gradually rises. Then, at a certain point in time, power for one cycle of PWM control is output to the output circuit 121 as a smoothed voltage.

  Next, when the next period of PWM control comes at timing t1, the controller 3 sends a reset signal to the reset switch 130. The reset switch 130 is turned on by the reset signal, the potential difference between the output circuit 121 and the ground 9 becomes substantially zero, and the charge stored in the capacitor C is discharged. After the charge stored in the capacitor C is discharged, the reset switch 130 is turned off again.

  As a result, at timing t1, the voltage output from the RC circuit 120 becomes zero again.

  In the next cycle of PWM control starting from timing t1, the capacitor C is charged again by the output of the PWM interlock switch 110, the output voltage of the RC circuit 120 gradually rises, and power for one cycle of the PWM control is again obtained. The smoothed voltage is output to the output circuit 121.

  Thereafter, the same operation is repeated for each cycle of PWM control.

  In the control cycle between the timing t3 and the timing t4, for example, the duty ratio of the PWM control is set to 5/8. Along with this, the charging time of the capacitor C also extends, but the power for one cycle of the PWM control is output to the output circuit 121 as a smoothed voltage.

  Next, in the control cycle between the timing t5 and the timing t6, for example, the duty ratio of the PWM control is set to 7/8. Along with this, the charging time of the capacitor C also extends, but the power for one cycle of the PWM control is output to the output circuit 121 as a smoothed voltage.

  At this time, when the voltage of the output circuit 121 exceeds the over power threshold signal 50 in the comparator 140, the comparator 140 outputs an over power signal from the output terminal 141. The output over power signal is input to the controller 3. The controller 3 determines that the IGBT 10 of the heating device 100 is overpower, and executes the corresponding processing.

  As described above, in the embodiment of the present invention, the PWM interlocking switch 110 that performs PWM control to output the input power from the power source with a predetermined duty ratio by being switched on and off, the resistor R and the capacitor C The RC circuit 120 in which the charge stored in the capacitor C varies according to the on time of the PWM interlock switch 110, the reset switch 130 for releasing the charge of the capacitor C at a predetermined timing, and the RC circuit 120 And a comparator 140 which compares the predetermined voltage with a predetermined voltage threshold (overpower threshold signal 50).

  The embodiment of the present invention has a simple circuit configuration because the voltage smoothed by the RC circuit 120 discharges the charge of the capacitor C at predetermined timings by the reset switch 130 with such a configuration. It is not necessary to increase the capacitance of the capacitor C for conversion, and the power detection device 13 with high responsiveness to changes in power can be configured while suppressing the cost by miniaturizing the capacitor C.

  Further, in the embodiment of the present invention, since the predetermined timing in the reset switch 130 is one cycle of the PWM control, it is not necessary to increase the capacitance and withstand voltage of the capacitor C, and the cost is reduced by downsizing the capacitor C. It is possible to configure the power detection device 13 which is responsive to changes in power while suppressing power.

  Further, in the embodiment of the present invention, the predetermined voltage threshold (over power threshold signal 50) in the comparator 140 is the voltage of the reference power supply 1 as input power (more specifically, it is inverted in positive and negative at the same voltage as the DC power supply 1). Since it is possible to determine that the DC power supply 1 is continuously input to the heater 30 as an overpower since the signal is used), the simple circuit configuration makes it possible to change the power without raising the cost. A responsive power detection device 13 can be configured.

  As mentioned above, although the embodiment of the present invention was described, the above-mentioned embodiment showed only a part of application example of the present invention, and in the meaning of limiting the technical scope of the present invention to the concrete composition of the above-mentioned embodiment. Absent.

1: DC power supply 3: Controller 4: Heater switch 11: Driver circuit 13: Power detection device 21: Driver circuit 30: Heater 100: Heating device 110: PWM interlock switch (PWM switch)
111: output circuit 120: RC circuit 121: output circuit 130: reset switch 140: comparator 141: output terminal C: capacitor R: resistor

Claims (4)

A PWM switch that performs PWM control that outputs input power from a power source at a predetermined duty ratio by being switched between on and off;
An RC circuit comprising a resistor and a capacitor, the charge stored in the capacitor varying according to the on time of the PWM switch;
A reset switch for releasing the charge of the capacitor at a predetermined timing;
A comparator that compares the voltage output from the RC circuit with a predetermined voltage threshold;
A power detection apparatus comprising: The power detection device according to claim 1,
The said predetermined timing in the said reset switch is 1 period of said PWM control, The electric power detection apparatus characterized by the above-mentioned. The power detection device according to claim 1 or 2, wherein
The power detection device according to claim 1, wherein the predetermined voltage threshold is a voltage of the input power. A heater that generates heat when power is supplied from a power source;
A pair of switching elements connected in series to the heater and performing PWM control to output electric power to the heater at a predetermined duty ratio by being switched on and off;
A control device that controls on and off of the switching element;
A power detection device provided in at least one of the pair of switching elements to determine whether an output of the switching elements exceeds a predetermined voltage threshold value;
Equipped with
The power detection device
A PWM switch that outputs input power from the power source at the predetermined duty ratio in conjunction with PWM control in the switching element;
An RC circuit comprising a resistor and a capacitor, the charge stored in the capacitor varying according to the on time of the PWM switch;
A reset switch for releasing the charge of the capacitor at a predetermined timing;
A comparator that compares the voltage output from the RC circuit with a predetermined voltage threshold;
Equipped with
The said control apparatus stops the supply of the electric power to the said heater, when the voltage which the said RC circuit outputs exceeds the said predetermined voltage threshold as a result of the said comparison.

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