JP2006280100A - Circuit and method for driving electrically insulated switching element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically insulated drive circuit wherein power is supplied through a pulse transformer, and information can be communicated regardless of the frequency of pulse operation by controlling the crest value of a pulse. <P>SOLUTION: A primary circuit ICα includes a supply voltage output section 2. A voltage corresponding to a control command signal CS is fed from the supply voltage output section 2 to a pulse transformer TR. The pulse transformer TR performs pulse operation according to a clock signal CLK. Therefore, the crest value of a pulse is changed according to the control command signal CS. The crest value of a secondary transformer output signal VT2 is detected by the comparison unit 3 and the crest value detection unit 4 provided in a secondary circuit ICβ. In the secondary circuit ICβ, therefore, decode operation is performed to extract the information of the control command signal CS contained in the secondary transformer output signal VT2. Switching of an upper arm element UA is controlled according to the decoded control command signal CS. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrically isolated switching element drive circuit and a drive method, and more particularly to an electrically isolated drive circuit capable of 100% on-duty in a pulse transformer type electrically isolated drive circuit. .

  In general, a DC-DC converter and various inverter circuits are driven based on a reference potential different from the reference potential of the input circuit system. In order to drive and control the switching element by a control circuit driven by a reference voltage different from the reference voltage of the switching element, an electrically insulating switching element driving circuit is generally used.

  As this electrically insulating switching element driving circuit, for example, a pulse transformer type switching element driving circuit that directly applies a secondary coil voltage of a pulse transformer to the gate electrode of the switching element is known. Further, the secondary coil voltage of the transformer is rectified to be a power supply voltage for a control electrode driving circuit (driving circuit) of the switching element, and a control signal transmitted by a photocoupler or the like is amplified by the driving circuit to switch the switching element. There is also known a transformer type switching element driving circuit which is applied to the control electrode.

  FIG. 8 is a basic circuit diagram of the pulse transformer type switching element driving circuit 200 disclosed in Patent Document 1. In FIG. The oscillation circuit 101 is a sine wave oscillator that oscillates at a predetermined frequency f1, and the oscillation circuit 102 is a sine wave oscillator that oscillates at a predetermined frequency f2. The pulse generating circuit 103 converts an external switching element drive command signal into a pulse signal. The primary capacitor 106, the core restaurant 107, and the secondary capacitor 108 constitute a resonance circuit having the oscillation frequency of the oscillation circuit 1 as a resonance frequency. When the oscillation circuit 102 is selected, the output voltage of the secondary coil of the core restaurant 107 is reduced by a predetermined ratio compared to when the oscillation circuit 101 is selected.

  When the oscillation circuit 101 is selected, the voltage sent from the detection circuit 110 to the comparator can exceed the output voltage of the voltage dividing circuit 111, but when the oscillation circuit 102 is selected, the detection circuit 110 transfers to the comparator. The voltage sent cannot exceed the output voltage of the voltage divider circuit 111. Therefore, the comparator 112 drives the MOS transistor 114 with a high-frequency pulse through the push-pull driver circuit 113 when the oscillation circuit 101 is selected, but the MOS transistor 114 remains off when the oscillation circuit 102 is selected. It becomes. However, even when the oscillation circuit 102 is selected, that is, when the cutoff of the MOS transistor 114 is selected, the drive circuit 200 maintains the operable state because the power supply voltage is applied. If 101 is selected, the MOS transistor 114 can be driven at high speed.

Other related techniques include DC-DC converters disclosed in Patent Documents 2 to 4.
JP 2004-274262 A JP-A-6-78526 JP 2004-194450 A JP 2003-299344 A

  However, in the conventional pulse transformer type switching element drive circuit, the frequency of the AC voltage applied to the core restaurant 107 is changed, and a control signal is transmitted to the drive circuit using a resonance circuit with a capacitor connected in series to the transformer. A method is specifically disclosed. However, there is no disclosure about a method for transmitting the control command signal by changing the amplitude of the AC voltage.

  An example of information transmission means using a transformer from the primary side to the secondary side is specifically disclosed. However, a method for transmitting information from the secondary side to the primary side using a transformer is not specifically described. Then, when information is transmitted from the secondary side to the primary side while maintaining insulation (for example, when an abnormality is detected by a sensor or the like provided on the secondary side, the abnormality occurrence signal is sent to the primary side or the CPU or the like. In the case of transmission), it is necessary to newly provide a mechanism such as a photocoupler. In this case, it is difficult to simplify, downsize, and reduce the cost of the mechanism of the electrically insulated drive circuit. In addition, when an element with low reliability such as a photocoupler is used, there is a problem because the reliability of the electrically insulated drive circuit cannot be improved.

  On the other hand, the photocoupler type switching element driving circuit has a problem because it requires a plurality of power supplies and the cost increases. In addition, the photocoupler has a complicated mechanism and has a problem of low reliability and durability.

  The present invention has been made to solve at least one of the above-mentioned problems of the prior art, and supplies power through a pulse transformer and controls the peak value of the pulse, thereby controlling the pulse operation frequency. An object of the present invention is to provide an electrically isolated drive circuit capable of transmitting information. It is another object of the present invention to provide an electrically isolated drive circuit that eliminates the limit of on-duty and is capable of 100% on-duty in a pulse transformer type electrically insulated drive circuit. It is another object of the present invention to provide an electrically isolated drive circuit capable of transmitting information from the secondary side to the primary side using a pulse transformer.

  In order to achieve the above object, an electrically isolated drive circuit according to claim 1 includes an oscillator that generates a predetermined frequency signal, a power supply voltage output unit that supplies two or more types of voltages according to input information, and a power supply voltage. A pulse transformer that is fed from an output unit and operates in a pulse manner according to a predetermined frequency signal; and a control unit that detects a peak value of an output signal on the secondary side of the pulse transformer and controls a switching element in accordance with the peak value. It is characterized by providing.

  The oscillator generates a predetermined frequency signal. The power supply voltage output unit supplies two or more types of voltages according to the input information. The pulse transformer is supplied with power from the power supply voltage output unit, and performs a pulse operation according to a predetermined frequency signal. Therefore, the pulse peak value is changed according to the supply voltage of the power supply voltage output unit. The control unit detects the peak value of the output signal on the secondary side of the pulse transformer, and controls the switching element according to the peak value.

  A control method for an electrically isolated drive circuit according to claim 20 is a method for controlling an electrically isolated drive circuit using a pulse transformer, wherein a peak value of a pulse transmitted to the pulse transformer at a predetermined frequency is input information. And a step of detecting a peak value of a pulse transmitted to the secondary side and controlling a switching element according to the peak value.

  Electric power is transmitted from the primary side to the secondary side by the pulse operation of the pulse transformer. At this time, the peak value of the output signal on the secondary side of the pulse transformer changes according to the change of the peak value of the input signal on the primary side of the pulse transformer. Thus, information can be transmitted from the primary side to the secondary side using the peak value simultaneously with power transmission via the pulse transformer. Here, when information transmission is performed using a pulse length, magnetic saturation occurs, so that it is difficult to transmit state information of a predetermined period or more. However, in the present invention, since information transmission is performed using the peak value of the pulse, information transmission can be performed even for a long state signal exceeding the pulse period regardless of the frequency of the pulse operation. Therefore, the on-duty of the switching element can be set to 100%.

  Further, the output voltage value of the power supply voltage output unit is two or more types, and the peak value is two or more types. Therefore, if the number of peak values is increased according to the number of types of signals to be transmitted, it is possible to increase information that can be transmitted. For example, when there are two kinds of peak values (binary signal), the on / off of the switching element can be controlled. Further, when the peak value is multivalued, multistage output can be controlled. For example, a plurality of switching elements such as for U, V, and W phases may be provided, and conduction of the phase switching elements corresponding to the peak value may be controlled.

  According to a second aspect of the present invention, in the electrically isolated drive circuit according to the first aspect, the control unit compares the output signal on the secondary side of the pulse transformer with a predetermined threshold value. And a peak value detection unit for detecting a peak value of the output signal of the comparison unit.

  The comparison unit compares the output signal on the secondary side of the pulse transformer with a predetermined threshold value. The predetermined threshold value is set to a value that can detect whether or not the peak value has changed. The peak value detection unit detects the peak value of the output signal of the comparison unit. Thereby, the decoding operation | movement which extracts the information contained in a peak value can be performed. Therefore, it is not influenced by the cycle of the pulse operation, and information can be transmitted to the secondary side even with a long state signal exceeding the pulse cycle.

  According to a third aspect of the present invention, in the electrically isolated drive circuit according to the second aspect of the present invention, the peak value detecting unit outputs a predetermined delay time to the output signal on the secondary side of the pulse transformer. And a flip-flop to which the output signal of the delay unit is input as a trigger signal and the output signal of the comparison unit is input as an input signal, and the output signal of the comparison unit is set according to the output signal of the delay unit. It is taken in.

  The delay unit gives a predetermined delay time to the output signal on the secondary side of the pulse transformer and outputs the result. In the flip-flop, the output signal of the delay unit is input as a trigger signal, and the output signal of the comparison unit is input as an input signal. The length of the predetermined delay time is set so that the pulse peak value of the output signal on the secondary side of the pulse transformer can be seen according to the rising or falling edge of the output signal of the delay unit. Then, according to the output signal of the delay unit, the output signal of the comparison unit is taken into the flip-flop. As a result, the peak value of the output signal on the secondary side of the pulse transformer can be detected. Therefore, it is possible to perform a decoding operation for extracting information from the peak value of the output signal on the secondary side of the pulse transformer.

  According to a fourth aspect of the present invention, in the electrically isolated drive circuit according to the first aspect, the power supply voltage output unit includes a regulator that receives the reference voltage and outputs a voltage corresponding to the input information. It is characterized by that.

  The regulator outputs a voltage corresponding to the input information with reference to the reference voltage. The power supply voltage output unit outputs a voltage corresponding to the input information from the reference voltage and the output voltage of the regulator. Therefore, the power supply voltage output unit can supply two or more types of voltages according to the input information. Thereby, the pulse peak value can be changed. In addition, by regulating the reference voltage, other voltages can be obtained, so that only one power source is supplied to the power source voltage output unit, the number of power sources can be reduced, and the cost can be reduced. Can do.

  Further, the electrically isolated drive circuit according to claim 5 is the electrically isolated drive circuit according to claim 4, wherein the power supply voltage output unit includes a regulator that steps down the input voltage, an output transistor that outputs the input voltage, and a regulator. And a first rectifier element having a forward direction from the regulator to the connection node. The first rectifier element is provided on a path from the output terminal to a connection node between the output terminal of the regulator and the output terminal of the output transistor. And

  The regulator steps down the input voltage. The output transistor outputs an input voltage. The output terminal of the regulator and the output terminal of the output transistor are connected in common at the connection node. The first rectifier element is provided on a path from the output terminal of the regulator to the output node with the direction from the regulator to the output node as a forward direction. Since the input voltage is higher than the output voltage of the regulator, backflow of current is prevented by the first rectifier element.

  As a result, with the configuration including one switch element (transistor), it is possible to switch the output of the power supply voltage output unit in two stages of the input voltage and the output voltage of the regulator. Therefore, the mechanism of the power supply voltage output unit can be simplified.

  Further, it is not necessary to stop the regulator during the period in which the output transistor is in the conductive state and the power supply voltage output unit outputs the input voltage. Therefore, when the output transistor is changed from the conductive state to the non-conductive state, the output voltage of the power supply voltage output unit can be quickly transitioned from the input voltage to the output voltage of the regulator.

  According to a sixth aspect of the present invention, there is provided an electrical insulation type drive circuit according to the first aspect, further comprising a power holding unit for holding power transmitted by the pulse transformer on the secondary side.

  The power holding unit is provided on the secondary side. Then, the power transmitted from the primary side to the secondary side is held by the pulse transformer and operates as a power source for the circuit on the secondary side. Accordingly, since the primary side can operate the power supply with respect to the secondary side circuit, it is not necessary to provide a separate power supply in the control circuit on the secondary side. Therefore, the number of power supplies can be reduced, and cost can be reduced.

  Moreover, as a structure of an electric power holding | maintenance part, it can be set as the structure provided with the 2nd rectifier connected to the secondary side of a pulse transformer, and the capacitor connected to this 2nd rectifier, for example.

  An electrical insulation type drive circuit according to claim 8 is the electrical insulation type drive circuit according to claim 1, wherein the electrical insulation type drive circuit is provided on the secondary side of the electrical insulation type drive circuit and detects an abnormality on the secondary side. An impedance detection unit that is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary side impedance via the pulse transformer, an output signal on the secondary side of the pulse transformer, and a predetermined threshold value. The comparator for comparison, the delay unit for giving a predetermined delay time to the output signal on the secondary side of the pulse transformer, and the output signal of the delay unit are input as trigger signals, and the output signal of the comparator is used as the input signal A switching state of the switching element is controlled by an output signal of the flip-flop, and when the abnormality detecting unit detects an abnormality, the flip-flop is controlled to be non-conductive. And, the impedance detection unit a change in the secondary impedance associated with non-conduction control state of the flip-flop and detecting.

  The abnormality detection unit is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side. Examples of the abnormality include overheating of the switching element. The impedance detection unit is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary side impedance via a pulse transformer. Changes in the secondary impedance can be detected by monitoring changes in the voltage value or current value on the primary side of the pulse transformer. The comparison unit compares the output signal on the secondary side of the pulse transformer with a predetermined threshold value. The predetermined threshold value is set to a value that can detect whether or not the peak value has changed. The delay unit gives a predetermined delay time to the output signal on the secondary side of the pulse transformer and outputs the result. The output signal of the delay unit is input to the flip-flop as a trigger signal, and the output signal of the comparison unit is input as an input signal. The conduction state of the switching element is controlled by the output signal of the flip-flop.

  The output signal of the delay unit is input to the flip-flop as a trigger signal, and the output signal of the comparison unit is input as an input signal. The conduction state of the switching element is controlled by the output signal of the flip-flop. The abnormality detection unit sets the flip-flop in a non-conduction control state when detecting the occurrence of an abnormality in the switching element. Thereby, the switching element is protected from an overheat / overcurrent state, and the switching element or the like is prevented from being destroyed. This also makes it possible to change the impedance on the secondary side in response to stopping the operation of the flip-flop for protecting the switching element. Therefore, it is possible to notify the primary side circuit of the abnormality occurrence information detected by the secondary side circuit via the pulse transformer by changing the impedance on the secondary side.

  An electrical insulation type drive circuit according to claim 9 is the electrical insulation type drive circuit according to claim 1, and is provided on the secondary side of the electrical insulation type drive circuit, and detects an abnormality on the secondary side. And an impedance detection unit which is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary impedance via a pulse transformer, and the secondary impedance on the secondary side of the electrically insulated drive circuit is changed. An impedance changing unit that includes at least one current consumption path connected to the secondary side of the pulse transformer, and at least one error detection transistor that controls conduction of the current consumption path. When the abnormality detection unit detects an abnormality, the impedance change unit turns on the error detection transistor according to the detected value and supplies current to the current consumption path. Change the secondary impedance to flow, the impedance detection unit a change in the secondary side impedance and detecting.

  The abnormality detection unit is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side. The impedance detection unit is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary side impedance via a pulse transformer. The impedance changing unit includes a current consumption path and an error detection transistor. The impedance changing unit brings the error detection transistor into a conductive state according to the amount of change in the secondary side impedance. That is, by increasing the number of error detection transistors to be turned on and increasing the number of current consumption paths, it is possible to increase the rate of change in impedance on the secondary side of the electrically insulated drive circuit. Thus, a plurality of pieces of information detected by the secondary side circuit can be notified to the primary side circuit via the pulse transformer by changing the impedance on the secondary side in multiple stages. That is, it is possible to transmit a plurality of information from the secondary side to the primary side by changing the value of the current flowing through the pulse transformer in a plurality of stages.

  An electrical insulation type drive circuit according to claim 10 is the electrical insulation type drive circuit according to claim 1, wherein a plurality of input information is input to one oscillator, and a plurality of input information is provided corresponding to the plurality of input information. A power supply voltage output unit, a plurality of pulse transformers, and a plurality of control units are provided.

  A plurality of input information is input to one oscillator. Corresponding to a plurality of input information, a power supply voltage output unit, a pulse transformer, and a control unit are provided. This makes it possible to manage the operations of a plurality of power supply voltage output units, pulse transformers, and control units using a single oscillation signal generated by one oscillator. Therefore, it is possible to reduce the probability that a frequency shift or a phase shift occurs in the control unit or the like as compared with a case where a plurality of oscillators are operated. Then, it is possible to prevent the switching element from being broken due to occurrence of a short circuit or the like.

  An electrical insulation type drive circuit according to claim 11 is the electrical insulation type drive circuit according to claim 1, wherein a plurality of input information is inputted to one oscillator, and a plurality of power supplies are provided corresponding to the plurality of input information. A voltage output unit, a plurality of control units, and a pulse transformer are provided, and at least one of two or more types of voltages supplied from the plurality of power supply voltage output units is different from each other.

  A plurality of input information is input to one oscillator. A plurality of power supply voltage output units and control units are provided corresponding to a plurality of input information. One pulse transformer is provided. Thereby, the peak value of the pulse generated by one pulse transformer is set to a number corresponding to the number of types of input information. That is, a plurality of pieces of information can be included in the carrier wave as changes in the peak value. In each of the plurality of control units, an operation for detecting a peak value corresponding to a plurality of input information is performed. Therefore, the control unit can perform a decoding operation to extract a plurality of pieces of information included in the carrier wave by distinguishing a plurality of types of peak values. Thereby, since the number of transformers can be reduced, it is possible to reduce the weight, reduce the size, and reduce the price of the electrically insulated drive circuit.

  According to a twelfth aspect of the present invention, there is provided an electrically isolated drive circuit according to the first aspect, further comprising a pulse monitoring unit that monitors an output signal on the secondary side of the pulse transformer, the pulse monitor unit being a pulse transformer. When detecting that no pulse is detected from the output signal on the secondary side, the control unit turns off the switching element.

  The pulse monitoring unit monitors pulses in the output signal on the secondary side of the pulse transformer. Then, by detecting that no pulse is detected from the output signal on the secondary side of the pulse transformer, it is detected that an abnormality or the like has occurred on the primary side. As a result, when the pulse is interrupted due to an abnormality on the primary side or the like, it is possible to prevent the switching element from being kept in a conducting state and causing destruction or the like.

  The primary side circuit of the electrically isolated drive circuit according to claim 13 is an electrically isolated drive circuit that controls the switching element, and includes an oscillator that generates a predetermined frequency signal and two or more types according to input information. A power supply voltage output section for supplying a voltage, and outputs a voltage from the power supply voltage output section to a pulse transformer in accordance with a predetermined frequency signal.

  The power supply voltage output unit that generates the predetermined frequency signal from the oscillator supplies two or more types of voltages according to the input information. The voltage from the power supply voltage output unit is output to the pulse transformer according to the predetermined frequency signal. Thereby, a pulse having a plurality of types of peak values according to the input information is output, and information transmission can be performed using the pulse peak values.

  The primary side circuit of the electrically insulated drive circuit according to claim 14 is the primary circuit of the electrically insulated drive circuit according to claim 13, wherein the change in the secondary side impedance of the pulse transformer is transmitted via the pulse transformer. An impedance detection unit for detecting

  The impedance detection unit detects a change in the secondary side impedance via a pulse transformer. The impedance detection unit monitors physical quantities such as current values and voltage values. Examples of the impedance detection unit include a sense resistor and a pulse transformer auxiliary inductor. It is also possible to use current detection with a current transformer or voltage detection with a Hall element. Thereby, it is possible to detect that an abnormality or the like has occurred on the secondary side.

  The secondary side circuit of the electrically isolated drive circuit according to claim 15 is an electrically isolated drive circuit that controls the switching element, and detects a peak value of the output signal of the pulse transformer, and according to the peak value. A control unit for controlling the switching element is provided.

  The control unit detects the peak value of the output signal of the pulse transformer, and controls the switching element according to the peak value. Thereby, information transmission can be performed through the pulse transformer by using the peak value. In addition, since information transmission is performed using the peak value of the pulse, information transmission can be performed even for a long state signal exceeding the pulse period regardless of the frequency of the pulse operation.

  The secondary side circuit of the electrically isolated drive circuit according to claim 16 is the secondary side circuit of the electrically isolated drive circuit according to claim 15, further comprising: a power holding unit that holds power transmitted by the pulse transformer. It is characterized by providing.

  The power holding unit is provided in the secondary circuit. Then, it operates as a power source for the secondary circuit. As a result, it is not necessary to provide a separate power supply for the control circuit on the secondary side. Therefore, the number of power supplies can be reduced, and cost can be reduced.

  The secondary side circuit of the electrically isolated drive circuit according to claim 17 is the secondary side circuit of the electrically isolated drive circuit according to claim 15, wherein an abnormality detection unit for detecting an abnormality of the circuit, and a pulse transformer A comparison unit that compares the output signal with a predetermined threshold value, a delay unit that outputs a predetermined delay time on the secondary side of the pulse transformer, and an output signal of the delay unit are input as trigger signals. A flip-flop to which an output signal is input as an input signal, the conduction state of the switching element is controlled by the output signal of the flip-flop, and the abnormality detection unit sets the flip-flop to a non-conduction control state when detecting an abnormality. Features.

  The abnormality detection unit is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side. The comparison unit compares the output signal on the secondary side of the pulse transformer with a predetermined threshold value. The delay unit gives a predetermined delay time to the output signal on the secondary side of the pulse transformer and outputs the result. The output signal of the delay unit is input to the flip-flop as a trigger signal, and the output signal of the comparison unit is input as an input signal. The conduction state of the switching element is controlled by the output signal of the flip-flop. The abnormality detection unit sets the flip-flop in a non-conduction control state when detecting the occurrence of an abnormality in the switching element. Thereby, the switching element is protected from an overheat / overcurrent state, and the switching element or the like is prevented from being destroyed. This also makes it possible to change the impedance on the secondary side in response to stopping the operation of the flip-flop for protecting the switching element.

  The secondary side circuit of the electrically isolated drive circuit according to claim 18 is the secondary side circuit of the electrically isolated drive circuit according to claim 15, wherein an abnormality detection unit for detecting an abnormality of the circuit and an impedance of the circuit are provided. An impedance changing unit that changes the current consumption path, and the impedance changing unit includes at least one current consumption path connected to the pulse transformer, and at least one error detection transistor that controls conduction of the current consumption path. When the unit detects an abnormality, the impedance changing unit sets the error detection transistor in a conductive state according to the detected value, and causes a current to flow through the current consumption path.

  The abnormality detection unit is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side. The impedance changing unit includes a current consumption path and an error detection transistor. The impedance changing unit brings the error detection transistor into a conductive state in accordance with the amount of change in the impedance of the secondary circuit. Then, according to the increase in the number of current consumption paths, the change rate of the impedance on the secondary side of the electrically insulated drive circuit can be increased. As a result, a plurality of pieces of information detected by the secondary side circuit can be transmitted to other circuits by changing the impedance on the secondary side in multiple stages.

  The secondary side circuit of the electrically insulated drive circuit according to claim 19 is the secondary side circuit of the electrically insulated drive circuit according to claim 15, further comprising a pulse monitoring unit that monitors the output signal of the pulse transformer, When the pulse monitoring unit detects that no pulse is detected from the output signal of the pulse transformer, the control unit turns off the switching element.

  The pulse monitoring unit monitors pulses in the output signal of the pulse transformer. Then, by detecting that no pulse is detected from the output signal of the pulse transformer, it is detected that an abnormality or the like has occurred on the pulse output source circuit side. As a result, when the pulse is interrupted due to an abnormality on the pulse output side or the like, it is possible to prevent the switching element from being kept in a conductive state and causing destruction or the like.

  According to the present invention, there is provided an electrically insulated drive circuit capable of transmitting information regardless of the frequency of pulse operation by supplying power via a pulse transformer and controlling the peak value of the pulse. Is possible. Further, it is possible to provide an electrically insulated drive circuit capable of 100% on-duty in a pulse transformer type electrically insulated drive circuit. In addition, it is possible to provide an electrically insulated drive circuit that can transmit information from the secondary side to the primary side using a pulse transformer.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying an electrically insulated drive circuit according to the present invention will be described below in detail with reference to FIGS. A first embodiment is shown in FIGS. FIG. 1 is a circuit diagram of an electrically insulated drive circuit 10 according to the first embodiment. The electrically insulated drive circuit 10 includes a primary side circuit ICα, a secondary side circuit ICβ, and a pulse transformer TR. The primary side circuit ICα and the secondary side circuit ICβ are connected via a pulse transformer TR. The CPU 11 is connected to the primary circuit ICα. The CPU 11 outputs a control command signal CS for the upper arm element UA. The output terminal VO1 of the primary side circuit ICα is connected to the gate of the lower arm element DA of the half bridge section 20. The output terminal VO2 of the secondary side circuit ICβ is connected to the gate of the upper arm element UA of the half bridge section 20. In the present embodiment, the upper arm element UA and the lower arm element DA are IGBTs.

  The primary side circuit ICα includes a power supply voltage output unit 2, a dead time setting unit DT, an oscillator OSC, a first flip-flop FF1, and a driver circuit DRV. The power supply voltage output unit 2 includes a regulator REG, a transistor Q1, and a backflow prevention diode D1. The input voltage Vin is input to the terminal VI. A capacitor C1 is connected to the terminal TC1. The regulator REG performs an operation of stepping down the input voltage Vin to the step-down voltage V1.

  A control command signal CS is input from the CPU 11. The control command signal CS is input to the transistor Q1 via the inverter INV1 and the dead time setting unit DT. Further, the control command signal CS is input to the first flip-flop FF1 via the dead time setting unit DT. The output signal of the first flip-flop FF1 is input to the gate of the lower arm element DA via the driver circuit DRV and the output terminal VO1. The clock signal CLK output from the oscillator OSC is input to the first flip-flop FF1 and the gate of the transistor Q2.

  The transistor Q1 is a switch that selects a voltage output from the power supply voltage output unit 2 to the pulse transformer TR, and is turned on by a high-level control command signal / CSD. The transistor Q1 selects the input voltage Vin or the potential of the capacitor C1 according to the control command signal CS and supplies it to the pulse transformer TR.

  The secondary circuit ICβ includes a comparison unit 3, a peak value detection unit 4, a driver 5, an internal circuit power source 15, and diodes D2 and D3. The comparison unit 3 and the peak value detection unit 4 constitute a control unit 6. The comparison unit 3 includes a comparator COMP. The output voltage of the pulse transformer TR is divided by the resistance elements R1 and R2 and input to the inverting input terminal of the comparator COMP. Further, a reference potential e1 that determines a threshold potential is input to the non-inverting input terminal.

  The peak value detection unit 4 includes a second flip-flop FF2 and a delay unit DLY. The second flip-flop FF2 is a D flip-flop, and the output of the comparator COMP is input to the input terminal, and the output signal of the delay unit DLY is input to the clock terminal CK.

  Driver 5 includes transistors Q3 and Q4. The gates of the transistors Q3 and Q4 are connected in common and the output signal FO2 is input. The drain terminals of the transistors Q3 and Q4 are connected in common and connected to the output terminal VO2. The source terminal of the transistor Q3 is connected to the pulse transformer TR via the diode D3, and the source terminal of the transistor Q4 is grounded. The output of the driver 5 is input to the gate of the upper arm element UA via the output terminal VO2. The secondary transformer output signal VT2, which is the output of the secondary transformer of the pulse transformer TR, is input to the internal circuit power supply 15 and the capacitor C2 via the diode D2. The secondary-side transformer output signal VT2 is input to the capacitor C3 through the diode D3 and also input to the driver 5.

  The operation of the electrically insulated drive circuit 10 according to the first embodiment will be described with reference to the timing chart of the primary side circuit ICα (FIG. 2) and the timing chart of the secondary side circuit ICβ (FIG. 3). A voltage corresponding to the control command signal CS is applied to the primary transformer of the pulse transformer TR by the power supply voltage output unit 2. The transistor Q2 is switched at a predetermined frequency by the clock signal CLK of the oscillator OSC. Therefore, the pulse transformer TR performs a pulse operation according to the clock signal CLK. By the pulse operation, power is supplied from the primary side circuit ICα to the secondary side circuit ICβ. Therefore, the primary side circuit ICα serves as a power source for the secondary side circuit ICβ.

  When the control command signal CS output from the CPU 11 is at a low level, it commands the upper arm element UA of the half bridge section 20 to be in a conductive state and the lower arm element DA to be in a nonconductive state. On the other hand, when the control command signal CS is at a high level, the upper arm element UA is in a non-conductive state and the lower arm element DA is in a conductive state. In the period P1 (FIG. 2), the control command signal CS output from the CPU 11 is at a low level, and it is commanded to place the upper arm element UA in a conductive state. At this time, the control command signal / CS inverted to the high level by the inverter INV1 is input to the transistor Q1, and the transistor Q1 is turned on. Then, the input voltage Vin is output from the power supply voltage output unit 2. At this time, backflow of current is prevented by the diode D1. The peak value of the secondary transformer output signal VT2 is a peak value WH1 that is a peak value corresponding to the input voltage Vin (arrow Y0).

  A case will be described in which, when the control command signal CS is changed from the low level to the high level at the time T1, the upper arm element UA is instructed to be turned off. At this time, the control command signal / CS transits to a low level by the inverter INV1. The control command signal / CS is input to the dead time setting unit DT. The dead time setting unit DT outputs a control command signal / CSD, which is a signal in which the dead time time TT is not given to the control command signal / CS. Then, a low level control command signal / CSD is input to the power supply voltage output unit 2.

  In the power supply voltage output unit 2, the input voltage Vin is stepped down to the step-down voltage V1 by the regulator REG, and the step-down voltage V1 is held in the capacitor C1. At time T1, when a low-level control command signal / CSD is input to the transistor Q1, the transistor Q1 is turned off. Therefore, the output voltage of the power supply voltage output unit 2 decreases from the input voltage Vin to the step-down voltage V1 held in the capacitor C1.

  As a result, the power supply voltage output unit 2 can switch the output of the power supply voltage output unit 2 in two stages of the input voltage Vin and the step-down voltage V1 with a configuration including one switch element (transistor Q1). Therefore, the mechanism of the power supply voltage output unit 2 can be simplified. Further, it is not necessary to stop the regulator REG during the period in which the transistor Q1 is in the conductive state and the power supply voltage output unit 2 outputs the input voltage Vin. Therefore, when the transistor Q1 is changed from the conductive state to the nonconductive state, the output voltage of the power supply voltage output unit 2 can be quickly transitioned from the input voltage Vin to the step-down voltage V1.

  As the output voltage of the power supply voltage output unit 2 decreases, the peak value of the primary-side transformer input signal VT1 decreases. As the peak value of the primary transformer input signal VT1 decreases, the peak value of the secondary transformer output signal VT2 changes from the peak value WH1 corresponding to the input voltage Vin to the peak value WH2 corresponding to the step-down voltage V1. Decrease (arrow Y1).

  The operation on the secondary side circuit ICβ side will be described. The voltage value of secondary transformer output signal VT2 is divided by resistance elements R1 and R2. Then, the divided divided voltage DV is input to the comparator COMP. At time T1, as the peak value of the secondary transformer output signal VT2 decreases from the peak value WH1 to WH2, the peak value of the divided voltage DV also decreases from the peak value WH1D to WH2D (FIG. 3, region). A10). Since the value of the peak value WH2D is equal to or lower than the reference potential e1, the comparison signal CV output from the comparator COMP is quantized to “0” (arrow Y9).

  The secondary transformer output signal VT2 is input to the delay unit DLY. In the delay unit DLY, a delay time LT is given to the secondary transformer output signal VT2. The delayed clock signal DC output from the delay unit DLY is input to the clock terminal CK of the second flip-flop FF2. As shown in FIG. 3, the length of the delay time LT is set so that the rising edge of the delayed clock signal DC is at a timing at which the pulse peak value of the comparison signal CV can be seen. Therefore, when the comparison signal CV becomes zero (arrow Y9), the second flip-flop FF2 takes in the low-level comparison signal CV and outputs the low-level output signal FO2 in accordance with the rising edge of the delayed clock signal DC. (Arrow Y10). That is, the second flip-flop FF2 detects the peak value of the comparison signal CV, thereby performing a decoding operation for extracting information on the control command signal CS included in the secondary transformer output signal VT2 that is a carrier wave. Therefore, the output signal FO2 can be extracted without being influenced by the frequency of the secondary transformer output signal VT2.

  The low-level output signal FO2 is input to the driver 5. Transistor Q3 is turned off and transistor Q4 is turned on. Therefore, the output voltage VO2 of the driver 5 becomes low level, and the upper arm element UA is rendered non-conductive.

  Next, the switching operation of the lower arm element DA will be described. At time T1 (FIG. 2), the control command signal CS is changed from the low level to the high level, thereby instructing the lower arm element DA to be in a conductive state. The control command signal CS is input to the dead time setting unit DT. The dead time setting unit DT adds the dead time time TT to the input control command signal CS, and outputs the signal after the addition as the control command signal CSD. Therefore, at time T2, the control command signal CSD that has transitioned to the high level is input to the first flip-flop FF1, and the output signal FO1 of the first flip-flop FF1 transitions to the high level (arrow Y2). The high-level output signal FO1 is input to the gate of the lower arm element DA via the driver circuit DRV, and the lower arm element DA is turned on.

  Next, at time T3 (FIG. 2), the control command signal CS is changed from the high level to the low level, so that the upper arm element UA is in a conductive state and the lower arm element DA is in a nonconductive state. Further, the control command signal / CS transits to a high level. Then, the control command signal CSD transitioned to the low level is input to the first flip-flop FF1. Then, the output signal FO1 of the first flip-flop FF1 transitions to a low level (arrow Y3). The low-level output signal FO1 is input to the gate of the lower arm element DA via the driver circuit DRV, and the lower arm element DA is turned off.

  The low level control command signal CS is inverted by the inverter INV1 to the high level control command signal / CS, and then input to the dead time setting unit DT. After the lower arm element DA is turned off (time T3), after the dead time TT has elapsed (time T4), the dead time setting unit DT outputs the control command signal / CSD that has transitioned to the high level. Is done. The transistor Q1 is turned on by the high level control command signal / CSD. Then, the output voltage of the power supply voltage output unit 2 rises from the step-down voltage V1 to the input voltage Vin, and the peak value of the primary-side transformer input signal VT1 also rises. Therefore, the peak value of the secondary transformer output signal VT2 increases from the peak value WH2 corresponding to the step-down voltage V1 to the peak value WH1 corresponding to the input voltage Vin (arrow Y4).

  At time T4, as the peak value of the secondary transformer output signal VT2 increases from the peak value WH2 to WH1, the peak value of the divided voltage DV also increases from the peak value WH2D to WH1D (FIG. 3, region). A11). Since the value of the peak value WH1D is equal to or higher than the reference potential e1, the comparison signal CV output from the comparator COMP is quantized to “1” (arrow Y11). When the comparison signal CV becomes “1”, the second flip-flop FF2 takes in the high-level comparison signal CV and outputs the high-level output signal FO2 in accordance with the rising edge of the delayed clock signal DC ( Arrow Y12). When the high-level output signal FO2 is input to the driver 5, the transistor Q3 is turned on and the transistor Q4 is turned off. Therefore, the output voltage VO2 of the driver 5 becomes high level, and the upper arm element UA is brought into conduction.

  As described above in detail, the electrically isolated drive circuit 10 according to the first embodiment changes the output voltage value of the power supply voltage output unit 2 in accordance with the control command signal CS, so that the input / output signal of the pulse transformer is changed. The peak value can be changed. Therefore, it is possible to transmit information along with power supply from the primary side to the secondary side via the pulse transformer TR. Here, in an electrically insulated drive circuit using a normal pulse transformer, when information transmission is performed using a pulse length, magnetic saturation occurs, so it is difficult to transmit state information of a predetermined period or more. is there. However, in this embodiment, since information transmission is performed using the pulse peak value, information transmission can be performed even for a long state signal exceeding the pulse period regardless of the frequency of the pulse operation. .

  That is, the on / off state signal of the upper arm element UA can be transmitted from the primary side circuit ICα to the secondary side circuit ICβ through the pulse transformer TR by the pulse peak value. Therefore, regardless of the pulse operation cycle of the pulse transformer TR, an on-duty of 100% is possible with respect to the on-command time commanded by the control command signal CS. Therefore, it is possible to eliminate the on-duty limit in the pulse transformer type electrically insulated drive circuit. In particular, when performing control such that the period of the switching time is longer than the pulse period, such as when the motor is driven by a square wave, the electrically isolated drive circuit according to the present invention is effective.

  Further, the peak value of the comparison signal CV includes information on the control command signal CS. The peak value detection unit 4 can detect the peak value (amplitude) of the comparison signal CV. Therefore, the peak value detection unit 4 can perform a decoding operation for extracting information of the control command signal CS included in the peak value. Thereby, the control command signal CS can be transmitted to the secondary side regardless of the cycle of the pulse operation of the pulse transformer TR.

  Also, the secondary side circuit ICβ includes a power holding unit (capacitors C2 and C3, internal circuit power supply 15) that holds the power transmitted by the pulse transformer TR. The internal circuit power supply 15 is an operating power supply for the secondary circuit ICβ. The capacitor C3 is a power source for the driver 5. Thereby, since the primary side circuit ICα plays the role of the power source with respect to the secondary side circuit ICβ, it is not necessary to separately provide a new power source in the secondary side circuit ICβ. Therefore, the number of power supplies can be reduced, and cost can be reduced.

  The dead time setting unit DT sets the dead time time TT. In the switching control between the lower arm element DA and the upper arm element UA, one element is always turned off, and the other element is turned on after the dead time TT has elapsed. Therefore, the presence of the dead time TT prevents the upper arm element UA and the lower arm element DA from being conducted simultaneously. As a result, it is possible to prevent a situation in which a short circuit occurs in the half bridge portion 20 and the switching element is destroyed.

  A second embodiment will be described with reference to FIG. FIG. 4 is a circuit diagram of an electrically insulated drive circuit 10a according to the second embodiment. The electrically insulated drive circuit 10a includes a mechanism for detecting an abnormality occurrence in the upper arm portion on the secondary side circuit ICβ side and transmitting abnormality occurrence information from the secondary side circuit ICβ to the primary side circuit ICα side. Circuit.

  The electrically insulated drive circuit 10a includes a temperature sensor 40, a protection circuit 41, a resistor RG, an impedance detector 42, and a sense resistor RS in addition to the electrically insulated drive circuit 10 according to the first embodiment. The resistor RG is connected between the gate terminal and the emitter terminal of the upper arm element UA. The temperature sensor 40 is a sensor for detecting the occurrence of an abnormality in the upper arm element UA or the like of the half bridge unit 20. Needless to say, the abnormality detection sensor is not limited to the temperature sensor, and various sensors such as a current sensor and a voltage sensor can be used. The temperature sensor 40 is connected to the protection circuit 41. The output terminal of the protection circuit 41 is connected to the reset terminal RST of the second flip-flop FF2. The abnormality notification signal ABS output from the protection circuit 41 is input to the second flip-flop FF2. The sense resistor RS is connected to the transistor Q2, and the impedance detector 42 is connected to both ends of the sense resistor RS. The detection signal DET output from the impedance detection unit 42 is input to the CPU 11. Since other configurations are the same as those of the electrically insulated drive circuit 10 according to the first embodiment, the description thereof is omitted here.

  A case where an abnormality occurs in the upper arm element UA during the operation of the electrically insulated drive circuit 10a and the abnormality is detected by the temperature sensor 40 will be described. In response to the abnormality detection by the temperature sensor 40, the abnormality notification signal ABS is output from the protection circuit 41 to the second flip-flop FF2. When the abnormality notification signal ABS is input, the second flip-flop FF2 is reset and the output signal FO2 is fixed at a low level. Therefore, the upper arm element UA is maintained in the non-conductive state during the period in which the temperature sensor 40 detects an abnormality. Thereby, the occurrence of an overcurrent / overheat state of the half bridge portion 20 can be prevented, and the upper arm element UA and the like can be prevented from being destroyed.

  As the upper arm element UA is maintained in the non-conducting state, for example, the current does not flow through the resistor RG, so that the impedance of the secondary side circuit ICβ increases, so that the sense resistor RS of the primary side circuit ICα is reduced. The flowing current I1 decreases, and the amount of decrease is detected by the impedance detector 42. When the reduction amount of the current I1 reaches a predetermined amount, the impedance detection unit 42 determines that an abnormality is detected in the secondary side circuit ICβ and the switching operation of the half bridge unit 20 is stopped. And the impedance detection part 42 outputs the detection signal DET to CPU11, and notifies that to CPU11.

  As described above in detail, the electrical insulation type drive circuit 10a according to the second embodiment changes the information detected by the secondary side circuit ICβ through the pulse transformer TR by changing the impedance on the secondary side. It is possible to notify the primary side circuit ICα. Moreover, according to the abnormality detection of a half bridge part, the impedance of a secondary side can be changed according to stopping the operation | movement of a half bridge part for protection of a switching element. That is, it is possible to transmit information from the secondary side to the primary side using the current value flowing through the pulse transformer TR. Therefore, it is not necessary to additionally provide a mechanism for transmitting information while maintaining insulation from the secondary side to the primary side, such as a photocoupler. Therefore, the mechanism of the electrically insulated drive circuit 10a can be simplified, reduced in size, and reduced in cost. Further, it is not necessary to use a low-reliability element such as a photocoupler, and the reliability can be improved.

  In the second embodiment, the resistor RG is added so that the impedance change becomes large when the upper arm element UA is stopped. However, for example, even if there is no resistor RG, it is only necessary to detect an impedance change corresponding to the electric capacity of the upper arm element UA when the upper arm element UA is stopped, or an impedance change caused by other parts of the secondary side circuit ICβ. For example, when the upper arm element UA is a bipolar transistor, the impedance change is large even without the resistor RG, and the impedance change can be easily detected. That is, a configuration that intentionally causes a large impedance change when the upper arm element UA is stopped may be added, or may not be added.

  A third embodiment will be described with reference to FIG. FIG. 5 is a circuit diagram of an electrically insulated drive circuit 10b according to the third embodiment. The electrically insulated drive circuit 10b is a circuit provided with a mechanism for detecting the occurrence of a plurality of abnormalities in the upper arm portion and transmitting information on the occurrence of a plurality of abnormalities to the CPU 11.

  The electrically isolated drive circuit 10b deletes the resistor RG from the electrically isolated drive circuit 10a according to the second embodiment, and replaces the protection circuit 41 with a protection circuit 41a, transistors Q10 and Q11, and resistance elements R10 and R11. Is provided. Resistance elements R10 and R11 form a path for current consumption. One of resistance elements R10 is connected to pulse transformer TR, and the other is connected to transistor Q10. One of resistance elements R11 is connected to pulse transformer TR, and the other is connected to transistor Q11. Since other configurations are the same as those of the electrically insulated drive circuit 10a according to the second embodiment, the description thereof is omitted here.

  A case where an abnormality is detected by the temperature sensor 40 during the operation of the electrically insulated drive circuit 10b will be described. When the temperature detected by the temperature sensor 40 is the first level (warning required level), the abnormality notification signal ABS1 is output from the protection circuit 41a to the transistor Q10, and the transistor Q10 is turned on. Then, the impedance of the secondary side circuit ICβ decreases according to the amount of current consumed by the resistance element R10, and thus the current I1 detected by the primary side sense resistor RS increases according to the abnormality notification signal ABS1. . The increase in the current I1 is detected by the impedance detector 42. Then, the detection signal DET1 corresponding to the abnormality notification signal ABS1 is output from the impedance detection unit 42 to the CPU 11. As a result, the CPU 11 detects that the protection circuit 41a has issued a warning and takes measures such as notifying the outside.

  When the temperature detected by the temperature sensor 40 is the second level (required operation stop level), the abnormality notification signals ABS1 and ABS2 are output from the protection circuit 41a to the transistor Q10, and the transistors Q10 and Q11 are turned on. State. As a result, the amount of current consumed increases as compared with the case where only the resistance element R10 is conductive, so that the impedance of the secondary side circuit ICβ is further reduced. Therefore, the current I1 detected by the primary side sense resistor RS further increases. Then, a detection signal DET2 corresponding to the abnormality notification signal ABS2 is output from the impedance detection unit 42 to the CPU 11. As a result, the CPU 11 detects that the protection circuit 41a issues a stop signal, and outputs a control command signal CS for maintaining the upper arm element UA in a non-conductive state.

  As described above in detail, the electrically isolated drive circuit 10b according to the third embodiment changes a plurality of pieces of information detected by the secondary-side circuit ICβ by changing the secondary-side impedance in multiple stages. It is possible to notify the primary side circuit ICα via TR. That is, it is possible to change the value of the current flowing through the pulse transformer TR in a plurality of stages and transmit information of a plurality of levels from the secondary side to the primary side.

  In the impedance detection unit 42, the correlation between the amount of change in the current amount and the content of the abnormality notification signal ABS notified to the CPU 11 can be determined according to the design specification of the electrically insulated drive circuit 10a.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications can be made without departing from the spirit of the present invention. When driving a bridge circuit of a multiphase motor using the electrically insulated drive circuit according to the present invention, a plurality of sets of primary side circuits ICα and secondary side circuits ICβ are provided according to the number of phases, A pulse (carrier wave) generated by an oscillator OSC provided in the primary circuit ICα may be used. However, it is more preferable that the primary side circuit ICα is shared and the carrier wave generated from one oscillator OSC is shared by the plurality of secondary side circuits ICβ. This will be described below.

  An example of driving a bridge circuit of a three-phase motor is shown in FIG. The first upper arm driver 51, the second upper arm driver 52, and the third upper arm driver 53 correspond to the secondary side circuit ICβ, and are connected to the W, U, and V phase half bridges 54 to 56, respectively. The master driver 50 corresponds to the primary side circuit ICα and is provided in common for the three upper arm drivers 51 to 53. Control command signals CS1 to CS3, which are signals for controlling the half bridges 54 to 56 of each phase and have a phase shift of 120 ° with respect to each other, are input to the master driver 50. The master driver 50 includes one oscillator OSC (not shown), and the pulse transformers TR1 to TR3 perform a pulse operation based on a clock signal output from the oscillator OSC.

  As a result, it is possible to manage the driving of the three-phase upper arm driver and the three lower arm drivers by using a single clock signal generated in the master driver 50. Then, it is possible to reduce the probability of occurrence of a frequency shift or a phase shift compared to the case where three sets of the primary side circuit ICα and the secondary side circuit ICβ are operated. Therefore, it is possible to prevent the half bridge circuit from being broken due to occurrence of a short circuit or the like. Further, the dead time time margin can be reduced, and the dead time time itself can be shortened. Therefore, motor noise and pulsation due to dead time can be reduced, and on-duty can be improved. Needless to say, the master driver 50 is not limited to a three-phase motor, and can be applied to a multi-phase motor such as a two-phase, six-phase, and nine-phase motor.

  Further, in the present embodiment, the information transmitted through the transformer is binary information on half-bridge on / off, but is not limited thereto. It goes without saying that multi-value information can be transmitted by changing the peak value according to the number of information. For example, in FIG. 1, a case where a three-phase motor is driven will be described. Assume that the CPU 11 receives control command signals CS1 to CS3 for three phases whose phases are shifted by 120 °. The primary circuit ICα is assumed to include three power supply voltage output units 2. Each of the power supply voltage output units 2 outputs step-down voltages V1 to V3 according to the control command signals CS1 to CS3.

  Further, three half bridge portions 20 are provided for the U, V, and W phases. The secondary side circuit ICβ is provided with three comparison units 3, peak value detection units 4, and three drivers 5 corresponding to the half bridge unit 20. Each of the output terminals of the driver 5 is connected to the upper arm element UA of the U, V, W phase half bridge. Further, reference potentials e1 to e3 are applied to the reference voltages of the comparison unit 3 provided in the secondary side circuit ICβ according to the step-down voltages V1 to V3. Therefore, the comparison unit 3 performs an operation of detecting a peak value according to the step-down voltages V1 to V3.

  The operation will be described. The voltages output from the three power supply voltage output units 2 and input to the primary-side transformer of the primary-side circuit ICα are four voltage values, that is, the input voltage Vin and the step-down voltages V1 to V3. Therefore, the peak values of the pulses generated by the pulse transformer TR are four types of peak values corresponding to the input voltage. That is, four types of information can be included in the carrier wave. The three comparison units 3 perform operations for detecting peak values according to the step-down voltages V1 to V3, respectively. Therefore, the secondary side circuit ICβ can distinguish the four types of peak values of the secondary side transformer output signal VT2, and performs a decoding operation for extracting information on the four types of control command signals included in the secondary side transformer output signal VT2. It can be carried out. As a result, the U, V, and W phase control command signals CS1 to CS3 having a phase shift of 120 ° can be transmitted to the secondary side circuit ICβ with one transformer. Thereby, since the number of transformers can be reduced, it is possible to reduce the weight, reduce the size, and reduce the price of the electrically insulated drive circuit.

  In the second embodiment and the third embodiment, the sense resistor RS and the impedance detector 42 are used as a mechanism for detecting a change in the impedance of the secondary circuit ICβ by the primary circuit ICα. I can't. The current may be monitored by an auxiliary inductor provided in the pulse transformer TR. Needless to say, the physical quantity monitored by the primary circuit ICα is not limited to the current value, but may be a voltage value or the like. It is also possible to use current detection with a current transformer or voltage detection with a Hall element.

  Further, when the pulse of the pulse transformer stops, the upper arm element UA may be stopped. The electrically insulated drive circuit 10c shown in FIG. 7 has a configuration in which a pulse monitoring unit 61 is added to the configuration of FIG. The pulse monitoring unit 61 monitors a pulse generated by the pulse transformer TR, and outputs a signal to the protection circuit 41 when the pulse is interrupted. The protection circuit 41 outputs the abnormality notification signal ABS to the reset terminal RST of the second flip-flop FF2. Therefore, the upper arm element UA can be maintained in a non-conductive state. With this configuration, it is possible to prevent the upper arm element UA from continuing the conduction state when the pulse is interrupted due to an abnormality of the primary side circuit ICα.

  In this embodiment, the delay unit DLY simply gives the delay time LT to the secondary transformer output signal VT2, and the delayed clock signal DC (FIG. 3) has no change in waveform or the like. However, the present invention is not limited to this configuration, and the waveform may be changed. The delayed clock signal DC is established as a clock signal for the second flip-flop FF2 if it has the same frequency as the secondary transformer output signal VT2 and is given the delay time LT to the secondary transformer output signal VT2. Then, the information of the control command signal CS included in the secondary transformer output signal VT2 can be extracted.

  The clock signal CLK is an example of a predetermined frequency signal, the diode D1 is an example of a first rectifier, the diodes D2 and D3 are examples of a second rectifier, the protection circuit 41 is an example of an impedance changing unit, a sense resistor RS and an impedance detector The unit 42 is an example of an impedance detection unit, the transistors Q10 and Q11 are examples of error detection transistors, and the resistance elements R10 and R11 are examples of current consumption paths.

1 is a circuit diagram of an electrically insulated drive circuit 10 according to a first embodiment. It is a timing chart of the primary side circuit ICα. It is a timing chart of secondary side circuit ICβ. It is a circuit diagram of the electrically insulated drive circuit 10a which concerns on 2nd Embodiment. It is a circuit diagram of the electrically insulated drive circuit 10b which concerns on 3rd Embodiment. 2 is a circuit diagram of an electrically isolated drive circuit using a master driver 50. FIG. It is a circuit diagram of the electrically insulated drive circuit 10b which concerns on 3rd Embodiment. FIG. 6 is a basic circuit diagram of a conventional pulse transformer type switching element driving circuit 200.

Explanation of symbols

2 power supply voltage output unit 3 comparison unit 4 peak value detection unit 5 driver 6 control unit 10, 10a, 10b electrically insulated drive circuit 11 CPU
15 Internal circuit power supply 20 Half bridge unit 42 Impedance detection unit 61 Pulse monitoring unit ICα Primary side circuit ICβ Secondary side circuit CS Control command signal DLY Delay unit DRV Driver circuit DT Dead time setting unit FF1 First flip-flop FF2 Second Flip-flop REG Regulator TR Pulse transformer TT Dead time UA Upper arm elements WH1, WH2, WH1D, WH2D Peak value

Claims (20)

An oscillator for generating a predetermined frequency signal;
A power supply voltage output unit for supplying two or more kinds of voltages according to input information;
A pulse transformer that is fed from the power supply voltage output unit and operates in pulse according to the predetermined frequency signal;
And a controller that detects a peak value of an output signal on the secondary side of the pulse transformer and controls a switching element in accordance with the peak value. The controller is
A comparator for comparing the output signal on the secondary side of the pulse transformer with a predetermined threshold;
The electrical insulation type drive circuit according to claim 1, further comprising: a peak value detection unit that detects a peak value of the output signal of the comparison unit. The peak value detector is
A delay unit for giving a predetermined delay time to the output signal on the secondary side of the pulse transformer and outputting the delay signal;
An output signal of the delay unit is input as a trigger signal, and an output signal of the comparison unit is provided as a flip-flop.
3. The electrically isolated drive circuit according to claim 2, wherein an output signal of the comparison unit is captured according to an output signal of the delay unit. The power supply voltage output unit is
The electrically insulated drive circuit according to claim 1, further comprising a regulator that receives a reference voltage and outputs a voltage corresponding to the input information. The power supply voltage output unit is
The regulator for stepping down the input voltage;
An output transistor for outputting the input voltage;
A first rectifying element provided on a path from an output terminal of the regulator to a connection node between the output terminal of the regulator and an output terminal of the output transistor, and having a forward direction from the regulator to the connection node; The electrically insulated drive circuit according to claim 4, further comprising:   The electrically insulated drive circuit according to claim 1, further comprising a power holding unit that holds power transmitted by the pulse transformer on a secondary side. The power holding unit is
A second rectifying element connected to the secondary side of the pulse transformer;
The electrically insulated drive circuit according to claim 6, further comprising: a capacitor connected to the second rectifier element. An abnormality detection unit that is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side;
An impedance detection unit that is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary side impedance via the pulse transformer;
A comparator for comparing the output signal on the secondary side of the pulse transformer with a predetermined threshold;
A delay unit for giving a predetermined delay time to the output signal on the secondary side of the pulse transformer and outputting the delay signal;
An output signal of the delay unit is input as a trigger signal, and an output signal of the comparison unit is provided as a flip-flop.
The conduction state of the switching element is controlled by the output signal of the flip-flop,
When the abnormality detection unit detects an abnormality, the flip-flop is brought into a non-conductive control state,
The electrically insulated drive circuit according to claim 1, wherein the impedance detection unit detects a change in the secondary side impedance associated with a non-conduction control state of the flip-flop. An abnormality detection unit that is provided on the secondary side of the electrically insulated drive circuit and detects an abnormality on the secondary side;
An impedance detection unit that is provided on the primary side of the electrically insulated drive circuit and detects a change in the secondary side impedance via the pulse transformer;
An impedance changing unit for changing a secondary side impedance on the secondary side of the electrically insulated drive circuit,
The impedance changing unit is
At least one current consumption path connected to the secondary side of the pulse transformer;
And at least one error detection transistor that controls conduction of the current consumption path,
When the abnormality detection unit detects an abnormality, the impedance change unit changes the secondary side impedance by causing the error detection transistor to be in a conductive state according to the detected value and passing a current through the current consumption path.
The electrically insulated drive circuit according to claim 1, wherein the impedance detector detects a change in the secondary impedance. A plurality of the input information is input to the one oscillator,
2. The electrically isolated drive circuit according to claim 1, further comprising a plurality of power supply voltage output units, a plurality of pulse transformers, and a plurality of control units corresponding to the plurality of input information. A plurality of the input information is input to the one oscillator,
A plurality of power supply voltage output units corresponding to the plurality of input information, a plurality of control units, and one pulse transformer,
The electrically insulated drive circuit according to claim 1, wherein at least one of two or more types of voltages supplied from the plurality of power supply voltage output units is different from each other. A pulse monitoring unit for monitoring an output signal on the secondary side of the pulse transformer;
2. The electrically isolated drive according to claim 1, wherein when the pulse monitoring unit detects that no pulse is detected from an output signal on the secondary side of the pulse transformer, the control unit turns off the switching element. 3. circuit. An electrically isolated drive circuit for controlling a switching element,
An oscillator for generating a predetermined frequency signal;
A power supply voltage output unit that supplies two or more types of voltages according to input information,
A primary side circuit of an electrically insulated drive circuit, wherein a voltage from the power supply voltage output unit is output to a pulse transformer in accordance with the predetermined frequency signal.   The primary side circuit of the electrically insulated drive circuit according to claim 13, further comprising an impedance detection unit that detects a change in the secondary side impedance of the pulse transformer via the pulse transformer. An electrically isolated drive circuit for controlling a switching element,
A secondary circuit of an electrically insulated drive circuit, comprising a control unit that detects a peak value of an output signal of a pulse transformer and controls a switching element in accordance with the peak value.   The secondary side circuit of the electrically insulated drive circuit according to claim 15, further comprising a power holding unit that holds power transmitted by the pulse transformer. An anomaly detector that detects an anomaly in the circuit;
A comparator for comparing the output signal of the pulse transformer with a predetermined threshold;
A delay unit that outputs a predetermined delay time to the secondary side of the pulse transformer;
An output signal of the delay unit is input as a trigger signal, and an output signal of the comparison unit is provided as a flip-flop.
The conduction state of the switching element is controlled by the output signal of the flip-flop,
The secondary side circuit of the electrically insulated drive circuit according to claim 15, wherein the abnormality detection unit sets the flip-flop to a non-conductive control state when an abnormality is detected. An anomaly detector that detects an anomaly in the circuit;
An impedance changing unit for changing the impedance of the circuit,
The impedance changing unit is
At least one current consumption path connected to the pulse transformer;
And at least one error detection transistor that controls conduction of the current consumption path,
16. The electricity according to claim 15, wherein when the abnormality detecting unit detects an abnormality, the impedance changing unit causes the error detecting transistor to be in a conductive state according to the detected value and causes a current to flow through the current consumption path. Secondary side circuit of isolated drive circuit. A pulse monitoring unit for monitoring the output signal of the pulse transformer;
16. The secondary of the electrically insulated drive circuit according to claim 15, wherein when the pulse monitoring unit detects that no pulse is detected from the output signal of the pulse transformer, the control unit turns off the switching element. Side circuit. A method for controlling an electrically isolated drive circuit using a pulse transformer,
Changing a peak value of a pulse transmitted to the pulse transformer at a predetermined frequency according to input information;
And a step of detecting a peak value of the pulse transmitted to the secondary side and controlling the switching element in accordance with the peak value.

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