Level shifting circuit

Abstract

Provided is a level shift circuit capable of transmitting a signal even when a power supply of a secondary side circuit becomes smaller than or equal to GND. A level shift transistor of a first conductivity type performs level shifting of a signal from a primary side circuit to a secondary side circuit between the primary side circuit with a primary side reference potential as a reference and the secondary side circuit with a secondary side reference potential independent of the primary side reference potential. A diode is connected in forward direction between a first main electrode of the level shift transistor and the secondary side circuit. A capacitor is connected in parallel with the diode. An inverter inverts the signal, a control electrode of the level shift transistor is connected to a primary side power supply of the primary side circuit, a second main electrode is connected to an output of the inverter, the inverter operates between the primary side reference potential and the primary side power supply, and the diode is connected to a secondary side power supply of the secondary side circuit via a resistance element.

Description

Technical Field

[0001] This invention relates to a level shifting circuit that transmits a signal from a low-voltage side to a high-voltage side with a different reference potential. Background Technology

[0002] HVIC (High Voltage MOS Gate Driver IC) and other power device control ICs are high-voltage ICs that drive the gate of switching devices using input signals from a microcomputer or similar source. Examples of HVICs include those described in Patent Document 1. Figure 1 As shown, it has a high-potential-side gate drive circuit that drives the switching device on the high-voltage side (high potential side) and a low-potential-side gate drive circuit that drives the switching device on the low-voltage side (low potential side).

[0003] The high-potential-side gate drive circuit includes a high-voltage level shifting circuit that transmits signals from the low-voltage side to the high-voltage side, which has a different reference potential. The high-voltage level shifting circuit converts the voltage signal from the primary-side circuit, referenced to ground (GND), into a current signal via a high-voltage MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and transmits this current signal to the secondary-side circuit, referenced to a floating potential. The transmitted current signal is then recovered as a voltage signal through the secondary-side circuit.

[0004] More specifically, if a turn-on pulse synchronized with the rising edge of the high-potential side input signal is input to the high-potential side gate drive circuit, the gate potential of the high-voltage MOSFET in the high-voltage level shift circuit changes from GND to the power supply potential of the primary side circuit, and the gate-source interface becomes open, thus becoming the turn-on state. During the turn-on period, current flows from the power supply of the secondary side circuit to GND of the primary side circuit through the high-voltage MOSFET. This current is converted into a voltage signal by a resistor element placed in the secondary side circuit, thereby transmitting the current signal to the secondary side circuit. If a turn-off pulse synchronized with the falling edge of the high-potential side input signal is input, the gate potential of the high-voltage MOSFET in the high-voltage level shift circuit changes from the power supply potential of the primary side circuit to GND, and the gate-source interface becomes closed, thus becoming the turn-off state.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-196276

[0006] In the case of the existing high-voltage level shift circuit described above, if the power supply of the secondary side circuit becomes less than or equal to GND, the current flowing from the secondary side circuit to the primary side circuit of the transmission signal source will attenuate, which may result in the inability to transmit signals. Summary of the Invention

[0007] The present invention was proposed to solve the above-mentioned problems, and its purpose is to provide a level shifting circuit that can transmit signals even when the power supply of the secondary side circuit becomes less than or equal to GND.

[0008] The level shifting circuit of the present invention comprises: a first conductivity type level shifting transistor that levels a signal from the primary side circuit to the secondary side circuit between a primary side circuit with a primary side reference potential and a secondary side circuit with a secondary side reference potential independent of the primary side reference potential; a diode that is forward-biasedly connected between the first main electrode of the level shifting transistor and the secondary side circuit; a capacitor that is connected in parallel with the diode; and an inverter that inverts the signal. The control electrode of the level shifting transistor is connected to the primary side power supply of the primary side circuit, the second main electrode is connected to the output of the inverter, the inverter operates between the primary side reference potential and the primary side power supply, and the diode is connected to the secondary side power supply of the secondary side circuit via a resistive element.

[0009] The effects of the invention

[0010] According to the level shifting circuit of the present invention, when the secondary-side power supply is less than or equal to the primary-side reference potential, if the level shifting transistor is turned on, the potential of the electrode on the primary-side circuit side of the capacitor drops to the primary-side reference potential. At the instant the drop occurs, an attempt is made to maintain the potential of the two electrodes of the capacitor; therefore, the potential of the electrode on the secondary-side circuit side of the capacitor also drops. The voltage drop is applied to the resistive element, thus enabling signal transmission to the secondary-side circuit. Attached Figure Description

[0011] Figure 1 This is a diagram showing the structure of an HVIC assembled with the high-voltage level shifting circuit of the present invention.

[0012] Figure 2 This is a circuit diagram showing the structure of the high-voltage level shifting circuit according to Embodiment 1 of the present invention.

[0013] Figure 3 This is a circuit diagram showing the structure of the high-voltage level shifting circuit according to Embodiment 1 of the present invention.

[0014] Figure 4 This is a circuit diagram showing the structure of the high-voltage level shifting circuit according to Embodiment 2 of the present invention.

[0015] Figure 5This is a circuit diagram showing the structure of the high-voltage level shifting circuit according to Embodiment 2 of the present invention.

[0016] Figure 6 This is a circuit diagram illustrating the structure of the high-voltage level shifting circuit according to Embodiment 3 of the present invention.

[0017] Figure 7 This is a circuit diagram illustrating the structure of the high-voltage level shifting circuit according to Embodiment 3 of the present invention. Detailed Implementation

[0018] <HVIC Structure>

[0019] Figure 1 This diagram illustrates the structure of an HVIC 100 assembled with the high-voltage level shifting circuit of the present invention. The HVIC 100 includes a high-voltage side gate drive circuit 101 that drives a high-voltage side switching device Q1 and a low-voltage side gate drive circuit 102 that drives a low-voltage side switching device Q2. Both the high-voltage side switching device Q1 and the low-voltage side switching device Q2 are N-channel MOSFETs, and freewheeling diodes P1 and P2 are connected in reverse parallel, respectively. Furthermore, in... Figure 1 In the middle, the high-potential side switching device Q1 and the low-potential side switching device Q2 are MOSFETs, but IGBTs (Insulated Gate Bipolar Transistors) can also be used.

[0020] The structure of the high-potential side gate drive circuit 101 will be described below. The high-potential side gate drive circuit 101 includes an on pulse generation circuit 11, an off pulse generation circuit 12, a high-voltage level shift circuit 13, a high-voltage level shift circuit 14, a resistor element 19, a resistor element 20, a NOT gate 21, a NOT gate 22, a latch circuit 24, and an output circuit 25.

[0021] The high-potential side input signal HIN, input to the high-potential side gate drive circuit 101, is input to the turn-on pulse generation circuit 11 and the turn-off pulse generation circuit 12. The turn-on pulse generation circuit 11 generates a turn-on pulse whose timing is synchronized with the rising of the high-potential side input signal HIN. The turn-off pulse generation circuit 12 generates a turn-off pulse whose timing is synchronized with the falling of the high-potential side input signal HIN.

[0022] The output of the turn-on pulse generation circuit 11 is connected to the gate of the high-voltage MOSFET used for level shifting in the high-voltage level shifting circuit 13. The drain of this high-voltage MOSFET is fixed to the power supply of the secondary side circuit (referred to as the "secondary side power supply"), i.e., the high-potential side power supply voltage VB, via a resistor element 19, and is connected to the input terminal of the latch circuit 24 via a NOT gate 21. The source of the high-voltage MOSFET is connected to the reference potential of the primary side circuit (referred to as the "primary side reference potential"), i.e., the ground potential GND. Furthermore, the high-potential side power supply voltage VB is sometimes referred to as the high-potential side power supply VB, and the ground potential GND is simply referred to as GND.

[0023] The output of the pulse generation circuit 12 is disconnected from the gate of the high-voltage MOSFET used for level shifting in the high-voltage level shifting circuit 14. The drain of this high-voltage MOSFET is fixed to the high-potential power supply voltage VB via resistor element 20 and connected to the input terminal of the latch circuit 24 via NOT gate 22. The source of the high-voltage MOSFET is connected to ground potential GND. Furthermore, the specific structures of the high-voltage level shifting circuits 13 and 14 will be described later.

[0024] The latch circuit 24 is composed of an RS trigger circuit, etc., and latches the outputs from NOT gates 21 and 22 and outputs them to the output circuit 25.

[0025] The output circuit 25, based on the output of the latch circuit 24, will send data to the output terminal U. OUT The output voltage switches between the high-potential side power supply voltage VB, which serves as the reference potential for the secondary circuit (referred to as the "secondary-side reference potential"), and the high-potential side floating potential VS.

[0026] <Implementation Method 1>

[0027] <Device Structure>

[0028] Figure 2 This is a circuit diagram illustrating the structure of the high-voltage level shifting circuit 131 according to Embodiment 1 of the present invention. Furthermore, hereinafter, with the level shifting transistor, i.e., the high-voltage MOSFET Q10, as the boundary, the side of the turn-on pulse generation circuit 11 is referred to as the primary side circuit, and the side of the NOT gate 21 is referred to as the secondary side circuit. Furthermore, the high-voltage level shifting circuit 131 is related to... Figure 1 The circuit corresponding to the high-voltage level shifting circuit 13 shown.

[0029] like Figure 2As shown, the structure is as follows: the gate of the high-voltage MOSFET Q10 in the high-voltage level shift circuit 131 is connected to the power supply of the primary side circuit (referred to as the "primary side power supply"), i.e., the low-potential side power supply VCC, and the turn-on pulse output from the turn-on pulse generation circuit 11 is supplied to the source via the inverter INV1. Furthermore, the voltage supplied from the low-potential side power supply VCC is sometimes referred to as the low-potential side power supply voltage VCC.

[0030] The inverter INV1 operates between the low-potential side power supply voltage VCC supplied from the low-potential side power supply VCC and GND.

[0031] The drain of the high-voltage MOSFET Q10 is connected to the cathode of the forward-biased diode D1. A capacitor C1 is connected in parallel with the forward-biased diode D1.

[0032] The anode of the forward diode D1 is connected to the high-potential side power supply VB via resistor element 19. Additionally, the anode of the forward diode D1 is also connected to the input of NOT gate 21. NOT gate 21 operates between the high-potential side power supply voltage VB and the high-potential side floating potential VS.

[0033] Figure 3 This is a circuit diagram showing the structure of the high-voltage level shifting circuit 141 in Embodiment 1. Furthermore, the high-voltage level shifting circuit 141 is related to... Figure 1 The circuit corresponding to the high-voltage level shifting circuit 14 shown.

[0034] The structure of the high-voltage level shift circuit 141 and Figure 2 The high-voltage level shifting circuit 131 shown is the same, except for the connection relationship between the primary and secondary side circuits. Specifically, it has the following structure: a cut-off pulse from the cut-off pulse generation circuit 12 is provided to the source of the high-voltage MOSFET Q10 in the high-voltage level shifting circuit 141 via an inverter INV1; and a high-potential-side power supply voltage VB is provided to the anode of the forward diode D1 via a resistor element 20. Furthermore, the anode of the forward diode D1 is also connected to the input of the NOT gate 22. The NOT gate 22 operates between the high-potential-side power supply voltage VB and the high-potential-side floating potential VS.

[0035] <Action>

[0036] The operation of the high-voltage level shift circuit 131 will be described below, but the operation of the high-voltage level shift circuit 141 is the same, so the operation description is omitted.

[0037] As an initial state, the signal supplied to the input of inverter INV1 is set to a low level, i.e., a voltage less than or equal to the threshold voltage of inverter INV1. Here, a voltage less than or equal to the threshold voltage of inverter INV1 refers to a voltage less than or equal to the threshold voltage of the N-channel MOSFET and higher than the threshold voltage of the P-channel MOSFET in the series connection of the P-channel and N-channel MOSFETs constituting inverter INV1. In this state, the P-channel MOSFET is turned on, the low-potential side supply voltage VCC is connected to the source of the high-voltage MOSFET Q10, the gate potential and source potential of the high-voltage MOSFET Q10 become equal to the low-potential side supply voltage VCC, and the high-voltage MOSFET Q10 is turned off.

[0038] Next, if a high-level signal is input to the inverter INV1, the P-channel MOSFET constituting the inverter INV1 will be turned off, the N-channel MOSFET will be turned on, and the source potential of the high-voltage MOSFET Q10 will drop to GND, turning the high-voltage MOSFET Q10 on. At this time, since the high-potential side power supply voltage VB is higher than GND, current flows from the high-potential side power supply VB to the high-voltage MOSFET Q10. Therefore, a voltage signal ΔV is generated in the resistor element 19, transmitting the signal to the secondary side circuit.

[0039] On the other hand, when the high-potential side power supply voltage VB is less than or equal to GND, if the high-voltage MOSFET Q10 is turned on, the potential of the electrode on the primary side of capacitor C1 drops to GND. At the instant the drop occurs, an attempt is made to maintain the potential of both electrodes of capacitor C1, therefore, the potential of the electrode on the secondary side of capacitor C1 also drops. If the voltage of the drop is ΔV, a voltage ΔV is applied to resistor 19, thus transmitting a signal to the secondary side circuit. Then, the voltage ΔV gradually decreases according to the time constant of the RC circuit implemented by capacitor C1 and resistor 19, and the electrode on the secondary side of capacitor C1 rises to the high-potential side power supply voltage VB. At this time, a drain current transiently flows.

[0040] Additionally, if the high-potential side power supply voltage VB becomes less than or equal to GND, current may flow from the drain side of the high-voltage MOSFET Q10 to the back gate (GND), but the current is cut off by the diode D1.

[0041] Thus, with respect to the high-voltage level shifting circuit 131 of Embodiment 1, even when the high-potential side power supply voltage VB of the secondary side circuit drops to less than or equal to GND, a signal can still be transmitted to the secondary side circuit.

[0042] <Implementation Method 2>

[0043] <Device Structure>

[0044] Figure 4 This is a circuit diagram showing the structure of the high-voltage level shifting circuit 132 according to Embodiment 2 of the present invention. Furthermore, in Figure 4 In China, regarding the use Figure 2 The high-voltage level shifting circuit 132, which has the same structure as the previously described high-voltage level shifting circuit 131, is labeled with the same reference numerals, and repeated descriptions are omitted. Furthermore, the high-voltage level shifting circuit 132 is similar to... Figure 1 The circuit corresponding to the high-voltage level shifting circuit 13 shown.

[0045] like Figure 4 As shown, in the high-voltage level shifting circuit 132, a P-channel MOSFET Q11 is provided between the source of the high-voltage MOSFET Q10 and GND, and a low-potential side power supply voltage VCC is provided to the gate of the MOSFET Q11.

[0046] Figure 5 This is a circuit diagram showing the structure of the high-voltage level shifting circuit 142 in Embodiment 2. The structure of the high-voltage level shifting circuit 142 is similar to... Figure 4 The high-voltage level shifting circuit 132 shown is the same, and the connection relationship between it and the primary side circuit and the secondary side circuit is also the same. Figure 3 The high-voltage level shifting circuit 131 shown is the same.

[0047] <Action>

[0048] The operation of the high-voltage level shift circuit 132 will be explained below, but the operation of the high-voltage level shift circuit 142 is the same, so the operation of the high-voltage level shift circuit 142 will be omitted.

[0049] First, consider the case where the high-voltage level shifting circuit 131 is used, and the floating potential VS on the high-voltage side increases sharply, that is, the potential between the floating potential VS on the high-voltage side and GND increases sharply, resulting in a positive voltage change (+dv / dt).

[0050] At this time, a displacement current flows from the secondary side circuit to the primary side circuit. The displacement current behaves according to the state of the input to the high-voltage level shift circuit 131.

[0051] First, when a high-level signal is input to inverter INV1, the N-channel MOSFET that constitutes inverter INV1 is turned on, and the displacement current flows to GND through the N-channel MOSFET.

[0052] Next, when a low-level signal is input to inverter INV1, the N-channel MOSFET constituting inverter INV1 turns off, creating a high impedance between inverter INV1 and GND, making it difficult for current to flow to GND. Therefore, in terms of displacement current, current may flow from the drain side of the P-channel MOSFET to the back gate (GND) via the diode parasitic on the body of the P-channel MOSFET constituting inverter INV1.

[0053] On the other hand, the high-voltage level shifting circuit 132, such as Figure 4 As shown, a P-channel MOSFET Q11 is provided between the source of the high-voltage MOSFET Q10 and GND. When a low-level signal is input to the inverter INV1, MOSFET Q11 is in the off state.

[0054] On the other hand, the inverter INV1 becomes a high impedance to GND, making it difficult for current to flow to GND. However, if +dv / dt is generated at this time, displacement current can flow from the secondary side circuit to the primary side circuit. As a result, the potential on the source side of MOSFET Q11 rises, and the normally off MOSFET Q11 turns on, allowing the displacement current to flow to GND through MOSFET Q11.

[0055] Thus, the high-voltage level shifting circuit 132 of Embodiment 2 can release the displacement current generated when the floating potential VS on the high potential side increases sharply to the primary side reference potential, i.e., GND, regardless of the input state, and can suppress the occurrence of faults caused by displacement current.

[0056] Furthermore, in the high-voltage level shifting circuit 132, even when the high-potential side power supply voltage VB of the secondary side circuit drops to less than or equal to GND, a signal can still be transmitted to the secondary side circuit.

[0057] <Implementation Method 3>

[0058] <Device Structure>

[0059] Figure 6 This is a circuit diagram illustrating the structure of the high-voltage level shifting circuit 133 according to Embodiment 3 of the present invention. Furthermore, the high-voltage level shifting circuit 133 is related to... Figure 1 The circuit corresponding to the high-voltage level shifting circuit 13 shown.

[0060] like Figure 6As shown, the gate of the high-voltage MOSFET Q10 in the high-voltage level shifting circuit 133 is connected to the low-potential power supply VCC of the primary side circuit. A P-channel MOSFET Q16 is connected between the gate and source of the high-voltage MOSFET Q10. Alternatively, an N-channel MOSFET Q15 is connected between the source and GND of the high-voltage MOSFET Q10, the P-channel MOSFET Q16 is turned off, and MOSFET Q15 is turned on, thereby turning on the high-voltage MOSFET Q10.

[0061] This configuration provides the gate of MOSFET Q16 with a turn-on pulse output from the turn-on pulse generation circuit 11 via inverters INV2 and INV3 connected in series. Furthermore, although not shown in the diagram, inverters INV2 and INV3 operate between the low-potential side power supply voltage VCC and GND.

[0062] The drain of the high-voltage MOSFET Q10 is connected to the cathode of the forward-biased diode D1. A capacitor C1 is connected in parallel with the forward-biased diode D1.

[0063] The anode of the forward diode D1 is connected to the high-potential power supply VB via resistor 19. Additionally, the anode of the forward diode D1 is also connected to the input of NOT gate 21.

[0064] In addition, a P-channel MOSFET Q12, a resistor R1, and an N-channel MOSFET Q13 are connected in series between the low-potential power supply VCC and GND. The output of an inverter INV2 is connected to the gate of MOSFET Q12 and MOSFET Q13.

[0065] Additionally, an N-channel MOSFET Q14 is connected between the connection point between resistor R1 and MOSFET Q13 and GND. The gate of MOSFET Q14 and the gate of MOSFET Q15 are connected to the connection point between resistor R1 and MOSFET Q13. MOSFET Q15 forms the primary side of the current mirror circuit, while resistor R1 and MOSFET Q14 form the secondary side of the current mirror circuit.

[0066] Figure 7 This is a circuit diagram showing the structure of the high-voltage level shifting circuit 143 in Embodiment 3. Furthermore, the high-voltage level shifting circuit 143 is related to... Figure 1 The circuit corresponding to the high-voltage level shifting circuit 14 shown.

[0067] The structure of the high-voltage level shift circuit 143 and Figure 2The high-voltage level shifting circuit 133 shown is the same, except for the connection relationship between it and the primary and secondary side circuits. Specifically, it has the following structure: the gate of MOSFET Q16 in the high-voltage level shifting circuit 143 is supplied with a cut-off pulse output from the cut-off pulse generation circuit 12 via inverters INV2 and INV3 connected in series; the anode of the forward diode D1 is connected to the high-potential power supply VB via resistor 20. Furthermore, the anode of the forward diode D1 is also connected to the input of the NOT gate 22.

[0068] <Action>

[0069] The operation of the high-voltage level shift circuit 133 will be explained below, but the operation of the high-voltage level shift circuit 143 is the same, so the operation of the high-voltage level shift circuit 143 will be omitted.

[0070] As an initial state, it is set to provide a low-level signal to the input of inverter INV2, that is, a voltage less than or equal to the threshold voltage of inverter INV2. Here, the definition of the voltage less than or equal to the threshold voltage of inverter INV2 is the same as the definition of the voltage less than or equal to the threshold voltage of inverter INV1 described in Embodiment 1.

[0071] If a low-level signal is input to the inverter INV2, the inverter INV2 outputs a high-level signal. Due to the high-level signal output by the inverter INV2, MOSFET Q13 is turned on, but MOSFET Q12 is turned off, so the current mirror circuit does not operate. If the high-level signal output by the inverter INV2 is input to the inverter IV3, the inverter IV3 outputs a low-level signal, and MOSFET Q16 is turned on. However, MOSFET Q15 is not turned on, so the high-voltage MOSFET Q10 is in the off state.

[0072] Next, if a high-level signal is input to the input of inverter INV2, inverter INV2 outputs a low-level signal. The low-level signal output by inverter INV2 turns on MOSFET Q12, but turns off MOSFET Q13. If the low-level signal output by inverter INV2 is input to inverter IV3, inverter IV3 outputs a high-level signal, turning off MOSFET Q16, and disconnecting the connection between the low-potential power supply VCC and the source of the high-voltage MOSFET Q10.

[0073] Here, assuming MOSFETs Q14 and Q15 have equivalent capabilities, the drain current of MOSFET Q14 is the same as that of MOSFET Q15. Since the drain current of MOSFET Q15 is the drain current of the high-voltage MOSFET Q10, it is equal to the drain current of MOSFET Q14, i.e., the current flowing through resistor R1. That is, it can limit the drain current of the high-voltage MOSFET Q10 when a high-level signal is input to the input of inverter INV2.

[0074] Thus, the high-voltage level shifting circuit 133 of embodiment 3 has a current mirror circuit, which can limit the drain current of the high-voltage MOSFET Q10 and limit the overcurrent flowing through the high-voltage MOSFET Q10.

[0075] Furthermore, in the high-voltage level shifting circuit 133, even when the high-potential side power supply voltage VB of the secondary side circuit drops to less than or equal to GND, a signal can still be transmitted to the secondary side circuit.

[0076] Furthermore, the present invention allows for free combination of various embodiments within its scope, or appropriate modification or omission of various embodiments.

[0077] Explanation of the label

[0078] C1 capacitor, D1 diode, GND ground potential, IV1, IV2, IV3 inverters, Q10 high-voltage MOSFET, Q11, Q12, Q13, Q14, Q15, Q16 MOSFET, VB high-potential side power supply, VCC low-potential side power supply, VS high-potential side floating potential.

Claims

1. A level shifting circuit, comprising: A level-shifting transistor of the first conductivity type shifts a signal from the primary side circuit to the secondary side circuit between a primary side circuit with a primary side reference potential and a secondary side circuit with a secondary side reference potential independent of the primary side reference potential. A diode, which is forward-biasedly connected between the first main electrode of the level-shifting transistor and the secondary side circuit; A capacitor connected in parallel with the diode; as well as An inverter, which inverts the signal. The control electrode of the level shift transistor is connected to the primary-side power supply of the primary-side circuit, and the second main electrode is connected to the output of the inverter. The inverter operates between the primary-side reference potential and the primary-side power supply. The diode is connected to the secondary power supply of the secondary circuit via a resistor.

2. The level shifting circuit according to claim 1, wherein, It also includes: a transistor of a second conductivity type connected between the second main electrode of the level shift transistor and the primary side reference potential, wherein the control electrode of the transistor of the second conductivity type is connected to the primary side power supply.

3. A level shifting circuit, comprising: A level-shifting transistor of the first conductivity type shifts a signal from the primary side circuit to the secondary side circuit between a primary side circuit with a primary side reference potential and a secondary side circuit with a secondary side reference potential independent of the primary side reference potential. A diode, which is forward-biasedly connected between the first main electrode of the level-shifting transistor and the secondary side circuit; A capacitor connected in parallel with the diode; The first transistor of the second conductivity type is connected between the control electrode of the level shift transistor and the second main electrode; The current mirror circuit has its primary side connected to the second main electrode of the level shift transistor, and its secondary side connected between the primary side power supply and the primary side reference potential of the primary side circuit via the second transistor of the second conductivity type. The third transistor of the first conductivity type is connected between the secondary side and the primary side reference potential of the current mirror circuit; The first inverter inverts the signal; and The second inverter inverts the output of the first inverter. The control electrode of the level shift transistor is connected to the primary-side power supply. The control electrode of the first transistor is connected to the output of the second inverter. The control electrodes of the second and third transistors are each connected to the output of the first inverter. The diode is connected to the secondary power supply of the secondary circuit via a resistor.

4. The level shifting circuit according to claim 3, wherein, The primary side of the current mirror circuit has a fourth transistor of a first conductivity type connected between the second main electrode of the level shift transistor and the primary side reference potential. The secondary side of the current mirror circuit has a first resistive element and a fifth transistor of a first conductivity type, which are sequentially arranged between the second transistor and the primary side reference potential. The control electrodes of the fourth and fifth transistors are commonly connected to the connection point between the first resistive element and the third transistor.

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