Patent Abstract:
A level shift circuit does not affect delay time, regardless of the size of resistor resistance value. The level shift circuit includes first and second series circuits wherein first and second resistors and first and second switching elements are connected in series, rise detector circuits that compare the rise potentials of output signals of the first and second series circuits with a predetermined threshold value, and output first and second output signals, which are pulse outputs of a constant duration, when the threshold value is exceeded, and third and fourth switching elements connected in parallel to the first and second resistors respectively. The gate terminals of the third and fourth switching elements are connected to the rise detector circuits, and the third and fourth switching elements are turned on by the first and second output signals respectively.

Full Description:
TECHNICAL FIELD 
     The present invention relates to a malfunction prevention method, a delay time shortening method, a current consumption reduction method, and a circuit area reduction method for a level shift circuit typified by a half bridge power supply. 
     BACKGROUND ART 
     In a half bridge circuit, or the like, in which switching elements are connected in series and which is driven by a high potential power supply, a level shift circuit is used in order that a high potential side switching element is driven by a low potential signal. 
       FIG. 1  shows a configuration diagram of a half bridge circuit  100  using a heretofore known level shift circuit. The half bridge circuit  100  shown in  FIG. 1  is configured of an output circuit  110 , a high potential side drive circuit  120 , and a low potential side drive circuit  130 . The output circuit  110  is connected to the high potential side drive circuit  120  and low potential side drive circuit  130 . Also, synchronized signals are input from the exterior into each of the high potential side drive circuit  120  and low potential side drive circuit  130 . 
     The output circuit  110  is configured of a switching element XD 1 , a switching element XD 2 , a power source E, and a load L 1 . In the output circuit  110 , the switching element XD 1  is connected in series to the switching element XD 2 , to which the load L 1  is connected in parallel, and the high voltage power source E supplies power to the load L 1  via the switching element XD  1 . The switching element XD  1  is a high potential side switching element, and can be, for example, an n-channel or p-channel MOS transistor, a p-type or n-type IGBT (Insulated Gate Bipolar Transistor), or the like. The switching element XD 2  is a low potential side switching element, and can be, for example, an n-channel MOS transistor, an n-type IGBT, or the like. Hereafter, the switching element XD 1  and switching element XD 2  will be assumed to be n-channel MOS transistors. 
     The high potential side drive circuit  120  is configured of a level shift circuit, a high side driver  123 , and a power source E 1  (hereafter, the output voltage thereof will also be expressed as E 1 ). The level shift circuit is a portion of the high potential side drive circuit  120  excluding the high side driver  123  and power source E 1 , and is configured of a latch malfunction protection circuit  121 , a latch circuit  122 , a first series circuit  124 , a second series circuit  125 , feedback resistors R 3 , R 4 , R 5 , and R 6  (the resistance values thereof are also taken to be R 3 , R 4 , R 5 , and R 6  respectively), p-channel MOS transistors (hereafter expressed as PM)  1  and PM 2 , a diode D 1  and diode D 2 , and an inverter INV. 
     The first series circuit  124  is configured of a level shift resistor R 1  (the resistance value thereof is also taken to be R 1 ) and a high breakdown voltage n-channel MOSFET (hereafter expressed as HVN)  1  connected in series, and outputs a level shift output signal setdrn (hereafter expressed as a setdrn signal) to the latch malfunction protection circuit  121  via a first connection point Vsetb (the potential thereof is also taken to be Vsetb). Herein, the first series circuit  124  includes a first level shift output terminal (corresponding to the first connection point Vsetb) for outputting the setdrn signal to the latch malfunction protection circuit  121 , and the first level shift terminal is connected to the latch malfunction protection circuit  121 . 
     The second series circuit  125  is configured of a level shift resistor R 2  (the resistance value thereof is also taken to be R 2 ) and an HVN 2  connected in series, and outputs a level shift output signal resdrn (hereafter expressed as a resdrn signal) to the latch malfunction protection circuit  121  via the HVN 2  and a second connection point Vrstb (the potential thereof is also taken to be Vrstb). Herein, the second series circuit  125  includes a second level shift output terminal (corresponding to the second connection point Vrstb) for outputting the resdrn signal to the latch malfunction protection circuit  121 , and the second level shift terminal is connected to the latch malfunction protection circuit  121 . 
     The PM 1  is connected in parallel to the resistor R 1  configuring the first series circuit  124 . The PM 2  is connected in parallel to the resistor R 2  configuring the second series circuit  125 . 
     A connection point of the feedback resistors R 3  and R 5  is connected to the gate terminal of the PM 2 , and a connection point of the feedback resistors R 4  and R 6  is connected to the gate terminal of the PM 1 . A feedback circuit is configured of the inverter INV, the feedback resistors R 3 , R 4 , R 5 , and R 6 , the PM 1 , and the PM 2 . Also, regarding the resistance values of the level shift resistors R 1  and R 2  and the feedback resistors R 3 , R 4 , R 5 , and R 6 , it is taken that R 1 =R 2 , R 3 =R 4 , and R 5 =R 6 . 
     The setdrn signal and resdrn signal are input into the latch malfunction protection circuit  121 . The latch malfunction protection circuit  121  is a circuit that, when a false signal called dv/dt noise occurs because of source-to-drain parasitic capacitors Cds 1  and Cds 2  of the HVN 1  and HVN 2 , that is, when the potential Vsetb and the potential Vrstb are both at an L (low) level, outputs at a high impedance so that the latch circuit  122  is not affected. 
     The latch circuit  122  is connected to the latch malfunction protection circuit  121  and high side driver  123 . The latch circuit  122  is a circuit into which the output from the latch malfunction protection circuit  121  is input that stores and outputs the value of the input when the input is at an L or H level and, when the input is of a high impedance, holds and outputs the value stored immediately before the input reaches the high impedance. 
     The output terminal of the latch circuit  122  is connected via the feedback resistors R 4  and R 6  to the second connection point Vrstb, which is a connection point of the level shift resistor R 2  and HVN 2  configuring the second series circuit  125 . Also, by inverting the output of the latch circuit  122  using the inverter INV, an output the inverse of the output of the latch circuit  122  is obtained. The output terminal of the inverter INV that outputs the inverted output is connected via the feedback resistors R 3  and R 5  to the first connection point Vsetb, which is a connection point of the level shift resistor R 1  and HVN 1  configuring the first series circuit  124 . 
     The high side driver  123  is connected to the high potential side switching element XD 1  and latch circuit  122 , and outputs a signal HO in accordance with the output of the latch circuit  122 , thereby controlling the turning on and off of the switching element XD 1 . 
     The output terminal of the high side driver  123  is connected to the gate terminal of the switching element XD 1 . The latch malfunction protection circuit  121 , the latch circuit  122 , the high side driver  123 , and the low potential side power source terminal of the power source E 1  are connected to a connection point vs (hereafter, the potential thereof will also be expressed as vs) of the switching elements XD 1  and XD 2 . Also, the latch malfunction protection circuit  121 , latch circuit  122 , and high side driver  123  receive a supply of power from the power source E 1 . In the same way, although not shown, the low potential side power source terminal of the inverter INV is also connected to the connection point vs, and receives a supply of power from the power source E 1 . 
     One end of each of the first series circuit  124  and second series circuit  125  is connected to a power source line vb (hereafter, the potential thereof will also be expressed as vb) connected to the high potential side terminal of the power source E 1 , while the other end of each is connected to a ground potential (GND). A set signal, which is a signal input into the level shift circuit of the high potential side drive circuit  120 , is input into the gate of the HVN 1 , while a reset signal, which is a signal input into the level shift circuit of the high potential side drive circuit  120 , is input into the gate of the HVN 2 . 
     The anodes of the diodes D 1  and D 2  are connected to the connection point vs of the switching elements XD 1  and XD 2 , the cathode of the diode D 2  is connected to the first connection point Vsetb, and the cathode of the diode D 1  is connected to the second connection point Vrstb. The diodes D 1  and D 2  are for clamping the voltages Vsetb and Vrstb so that they do not drop to or below the potential vs, thus protecting the latch malfunction protection circuit  121  by ensuring that no overvoltage is input. 
     The feedback resistors R 5  and R 6  are connected to the vb potential or vs potential via a PMOS or NMOS of a CMOS circuit or logic inversion CMOS circuit (INV) used in the latch circuit  122 , but for the sake of simplicity, the PMOS and NMOS are not shown in the latch circuit  122 , and in the same way, will not be shown hereafter. 
     The low potential side drive circuit  130  is configured of a low side driver  131  that controls the turning on and off of the low potential side switching element XD 2 , and a power source E 2  (hereafter, the potential thereof will also be expressed as E 2 ) that supplies power to the low side driver  131 . 
     The low side driver  131  is supplied with power from the power source E 2 , amplifies a signal S input into the low side driver  131 , and inputs it into the gate terminal of the switching element XD 2 . According to this configuration, the switching element XD 2  is turned on (energized) when the signal S is at an H (high) level, and the switching element XD 2  is turned off (cut off) when the signal S is at an L (low) level. That is, the signal S is a signal that directly commands the turning on or off of the switching element XD 2 . 
     Of the set signal and reset signal input into the high potential side drive circuit  120 , the set signal is a signal that indicates the timing of the start of an on-state period (the end of an off-state period) of the switching element XD 1 , while the reset signal is a signal that indicates the timing of the start of an off-state period (the end of an on-state period) of the switching element XD 2 . 
     The switching elements XD 1  and XD 2  are turned on and off in a complementary way such that when one is in an on-state the other is in an off-state, except during a dead time to be described hereafter, with the potential vs of the connection point vs reaching the ground potential when the switching element XD 2  is in an on-state, and the potential vs of the connection point vs reaching the output voltage E of the power source E when the switching element XD 1  is in an on-state. Also, the load L 1  is a load that receives a supply of power from the half bridge circuit  100 , and is connected between the connection point vs and the ground potential. 
     In the kind of heretofore known half bridge circuit  100  shown in  FIG. 1 , it is often the case that there is a large difference in potential of in the region of several hundred volts between the low potential side power source voltage E 2  and high potential side power source voltage E 1 . Because of this, it may happen that the difference in potential occurs between wiring linking the high potential side circuit and low potential side circuit and a semiconductor forming an underlay of the wiring. In particular, when the wiring potential is a high voltage due to the high potential side circuit and a subsequent stage is a low potential side circuit region, voltage generation and the effect thereof are marked. When simply applying metal wiring of a semiconductor as the wiring linking the high potential side circuit and low potential side circuit, a high electric field is generated between the wiring and the semiconductor immediately below, and various problems occur in the level shift circuit. In order to solve the heretofore described kind of problem, it is possible to apply a wire bonding method in the level shift circuit. A wire bonding method is a method whereby the drain of the HVN 1  and the first connection point Vsetb, and the drain of the HVN 2  and the second connection point Vrstb, are connected by wiring in, for example,  FIG. 1 . As the wiring is point-to-point wiring distanced from the semiconductor when using a wire bonding method, it is possible to prevent a high electric field from being generated in the semiconductor region forming the underlay. 
     However, the application of a wire bonding method has a detrimental effect on the cost of the level shift circuit and on downsizing the product due to, for example, an increase in man-hours, the need for wiring space, and the like. Consequently, there is a demand for a level shift circuit that does not use a wire bonding method. The technologies shown in PTL 1 and PTL 2 (identified below) exist as level shift circuits that do not use a wire bonding method. 
     CITATION LIST 
     Patent Literatures 
     
         
         PTL 1: Japanese Patent No. 3,941,206 
         PTL 2: Japanese Patent No. 3,214,818 
       
    
     A high breakdown voltage IC having a device configuration wherein HVNs are embedded in a high breakdown voltage separation portion (hereafter referred to as an HVJT), and having parasitic resistors (R 1  in  FIG. 3  of PTL 1) configured in parallel with level shift resistors configuring a level shift circuit, and a technology for controlling the resistance value of the parasitic resistors used in the level shift circuit, are described in PTL 1.  FIG. 2  shows a configuration of the level shift circuit shown in PTL 1. The same reference signs are given to regions the same as in  FIG. 1 , and a detailed description will be omitted. As shown in  FIG. 2 , the level shift circuit shown in PTL 1 differs from the level shift circuit shown in  FIG. 1  in that it includes, in addition to level shift resistors LSR 1  and LSR 2 , parasitic resistors LSRp 1 , LSRp 2 , and LSRp 3 . A first series circuit of the parallel resistance of the level shift resistor LSR 1  and parasitic resistor LSRp 1  and the HVN 1 , and a second series circuit of the parallel resistance of the level shift resistor LSR 2  and parasitic resistor LSRp 2  and the HVN 2 , are configured in the level shift circuit shown in PTL 1. The resistance values of the parasitic resistor LSRp 1  configured in parallel with the level shift resistor LSR 1  and the parasitic resistor LSRp 2  configured in parallel with the resistor LSR 2  can be controlled in the level shift circuit shown in PTL 1. 
     A high voltage power integrated circuit having a device configuration, differing from that in PTL 1, wherein a level shift from a low potential signal to a high potential signal is made without using wire bonding, wherein a level shift operation is possible, and that does not have a metal crossover, is described in PTL 2. 
     The technologies described in PTL 1 and PTL 2 are both such that the circuit area is reduced by embedding the HVNs in the HVJT region, thereby realizing a high voltage breakdown IC. Also, the kinds of method shown in PTL 1 and PTL 2 that do not use a wire bonding method differ from the wire bonding method in terms of device structure in that parasitic resistors corresponding to the level shift resistors are added, and that a parasitic resistor is added between the two series circuits. 
     However, the technology described in PTL 1 is such that the first series circuit and second series circuit have the same circuit configuration and device configuration. Because of this, a malfunction occurs due to the drain potentials of the turn-on signal side HVN and turn-off signal side HVN both exceeding the threshold value of a logic circuit at a subsequent stage due to the effect of the current flowing into the parasitic capacitor Cds 1  of the HVN 1  and the parasitic capacitor Cds 2  of the HVN 2  when dV/dt noise occurs. When reducing the resistance value of the level shift resistors in order to avoid this malfunction, the current flowing through the level shift resistors increases when an HVN is turned on and dV/dt noise occurs, and current consumption increases. Also, when the resistance value of the level shift resistors is not reduced, it is necessary to strengthen a noise cancellation function such as a low-pass filter in order to prevent a malfunction caused by level shift output fluctuation due to the occurrence of dv/dt noise, and there is a problem in that delay time increases because of the effect of the noise cancellation function. 
     Also, the technology described in PTL 2 too, in the same way as the technology described in PTL 1, is such that the first series circuit and second series circuit have the same circuit configuration and device configuration, because of which there is the problem of malfunction when dV/dt noise occurs, or the like, the problem of power consumption increasing due to reducing the resistance value of the level shift resistors in order to avoid malfunction, and the problem of delay time increasing due to strengthening the noise cancellation function when the resistance value of the level shift resistors is not reduced. 
     Consideration will be given to a case of replacing the level shift resistors of the heretofore known level shift circuit with the parasitic resistors described in PTL 1 or PTL 2 in order to avoid wire bonding and reduce the circuit area.  FIG. 3  shows an example wherein the heretofore known level shift circuit shown in  FIG. 1  is configured using the HVN-embedded type of HVJT described in PTL 1. The same reference signs are given to regions the same as in  FIG. 1 , and a detailed description will be omitted. The main difference between a high potential side drive circuit  220  of a half bridge circuit  200  shown in  FIG. 3  and the high potential side drive circuit  120  of the half bridge circuit  100  shown in  FIG. 1  is the adoption of a configuration wherein the feedback resistors R 3  and R 4  are eliminated, the level shift resistor R 1  is replaced with a parasitic resistor Rpar 1  in the semiconductor substrate, the level shift resistor R 2  is replaced with a parasitic resistor Rpar 2  in the semiconductor substrate, and a parasitic resistor Rpar 3  is connected between a first series circuit  221  and second series circuit  222 . The first series circuit  221  is configured of the PM 1  or parasitic resistor Rpar 1  and the HVN 1 , while the second series circuit  222  is configured of the PM 2  or parasitic resistor Rpar 2  and the HVN 2 . By applying the device structure described in PTL 1, PTL 2, and the like in this way, it is possible to configure a level shift circuit without using wire bonding in the half bridge circuit  200  shown in  FIG. 3 . 
     The resistance value of the parasitic resistors varies depending on temperature, power source voltage, and the like.  FIG. 4  shows the temperature dependency of the parasitic resistor resistance value. As shown in  FIG. 4 , the parasitic resistor resistance value is 3 kΩ when the temperature is −50° C., while the resistance value is 10 kΩ when the temperature is 150° C.  FIG. 5  shows the power source voltage dependency of the parasitic resistor resistance value. As shown in  FIG. 5 , the parasitic resistor resistance value is 3 kΩ when the voltage between the vb and GND is 0V, while the resistance value is 30 kΩ when the voltage between the vb and GND is 800V. In this way, the resistance value of the parasitic resistors, which are resistors in the semiconductor substrate, has temperature dependency and power source voltage dependency. Because of this, the rise time of the setdrn signal and resdrn signal varies in accordance with the temperature and power source voltage conditions, which may affect the operation of the level shift circuit, as will be described hereafter. 
     Also, the resistance value of the parasitic resistor Rpar 3  provided between the first series circuit  221  and second series circuit  222  varies depending on the distance between the HVN 1  and HVN 2 .  FIG. 6  shows the dependency of the parasitic resistor Rpar 3  resistance value on the distance between the HVN 1  and HVN 2 . As shown in  FIG. 6 , the parasitic resistor Rpar 3  resistance value is 500 kΩ when the distance between the HVN 1  and HVN 2  is 1,000 μm. 
     In the level shift circuit shown in  FIG. 3 , the resistance value of the parasitic resistors Rpar 1  and Rpar 2  is regulated so as to be around 10 kΩ, while the resistance value of the parasitic resistor Rpar 3  is regulated so as to be around 500M. When the resistance value of the parasitic resistor Rpar 3  is on the high side, it is possible to reduce the effect when the level shift circuit carries out each operation. 
     The half bridge circuit  200  shown in  FIG. 3  can change the potential at one end of the feedback resistors R 5  and R 6  to the vb potential or the vs potential in accordance with the latch circuit  122  output status by changing the connection status of the feedback resistors R 5  and R 6  in accordance with the latch circuit  122  output status.  FIG. 7  shows an equivalent circuit diagram of the level shift circuit shown in  FIG. 3  when an output HO of the high side driver  123  is at an L level, while  FIG. 8  shows an equivalent circuit diagram of the level shift circuit shown in  FIG. 3  when the output HO is at an H level. As shown in  FIG. 7 , when the output HO is at an L level, the parasitic resistor Rpar 1  and feedback resistor R 5  are in a condition wherein they are connected in parallel, while the parasitic resistor Rpar 2  and feedback resistor R 6  are in a condition wherein they are connected in series. Consequently, by the gate potential of the PM 1  becoming lower than the potential vb and the PM 1  ceasing to be in a cut off state, the impedance of the output terminal of the first series circuit  221  decreases, and by the gate potential of the PM 2  becoming the potential vb and the PM 1  becoming cut off, the impedance of the output terminal of the second series circuit  222  increases. As shown in  FIG. 8 , when the output HO is at an H level, the parasitic resistor Rpar 1  and feedback resistor R 5  are in a condition wherein they are connected in series, while the parasitic resistor Rpar 2  and feedback resistor R 6  are in a condition wherein they are connected in parallel. Consequently, by the gate potential of the PM 1  becoming the potential vb and the PM 1  becoming cut off, the impedance of the output terminal of the first series circuit  221  increases, and by the gate potential of the PM 2  becoming lower than the potential vb and the PM 1  ceasing to be in a cut off state, the impedance of the output terminal of the second series circuit  222  decreases. 
       FIG. 9  shows an operation time chart of the level shift circuit shown in  FIG. 3 . On the input pulse of the set signal switching to an H level at a time t 1 , the setdrn signal drops to the vs potential, and the latch output starts to rise to an H level. While the input pulse of the set signal is at an H level, the setdrn signal continues to be at the vs potential level. On the output of the latch circuit  122  switching from an L level to an H level at a time t 2 , the parallel/series condition of the feedback resistors R 5  and R 6  switches. On the input pulse of the set signal switching from an H level to an L level at a time t 3 , the setdrn signal rises. On the input pulse of the reset signal switching to an H level at a time t 4 , the resdrn signal drops to the vs potential, and the latch output starts to fall to an L level. While the input pulse of the reset signal is at an H level, the resdrn signal continues to be at the vs potential level. On the output of the latch circuit  122  switching from an H level to an L level at a time t 5 , the parallel/series condition of the feedback resistors R 5  and R 6  switches. On the input pulse of the reset signal switching from an H level to an L level at a time t 6 , the resdrn signal rises. 
     When the timing of the inversion (setting) of the output of the latch circuit  122  is earlier than the input pulse width of the set signal, the impedance of the output terminal of the first series circuit  221  when the setdrn signal starts to rise becomes high, as heretofore described, the time constant of a time constant circuit configured of this and the parasitic capacitor Cds 1  increases, and the rise of the setdrn signal is delayed. 
     Also, when utilizing the parasitic resistors Rpar 1  and Rpar 2  as level shift resistors, the rise time fluctuates due to the effect of temperature and power source voltage, as heretofore described. As shown in  FIG. 4  and  FIG. 5 , the resistance value of the parasitic resistors Rpar 1  and Rpar 2  increases when the temperature or voltage rises. When the resistance value of the parasitic resistors Rpar 1  and Rpar 2  increases, the delay in the rise of the setdrn signal and resdrn signal increases, but provided that the pulses of the set signal and reset signal are generated singly, there is no problem however long the rise of the setdrn signal and resdrn signal is delayed. However, when the resistance value of the parasitic resistors Rpar 1  and Rpar 2  is high, the pulse interval between the set signal and reset signal is short, the pulses of the set signal and reset signal are generated continuously, and the next pulse falls before the previous pulse has finished rising, both the setdrn signal and resdrn signal will be at an L level. As dV/dt noise is generated when both the setdrn signal and resdrn signal are at an L level, it is arranged, in order to combat the generation of dV/dt noise, that the latch malfunction protection circuit  121  does not transmit this state to a subsequent circuit. Consequently, as the subsequent pulse does not become effective until the previous pulse has finished rising, the delay time increases, as shown in  FIG. 9 , and responsiveness worsens. 
       FIG. 10  shows circuit simulation results for the half bridge circuit  200  shown in  FIG. 3  when the pulse interval between the set signal and reset signal is 0.5 μs.  FIG. 11  shows circuit simulation results for the half bridge circuit  200  shown in  FIG. 3  when the pulse interval between the set signal and reset signal is 0.2 μs. As shown in  FIG. 10 , when the pulse interval between the set signal and reset signal is 0.5 μs, the latch output waveform shown by the broken line when the parasitic resistor resistance value is 5 kΩ, and the latch output waveform shown by the solid line when the parasitic resistor resistance value is 35 kΩ, are the same. 
     However, as shown in  FIG. 11 , when comparing the output waveform when the parasitic resistor resistance value is 5 kΩ and the output waveform when the parasitic resistor resistance value is 35 kΩ when the pulse interval between the set signal and reset signal is 0.2 μs, it can be seen that a delay occurs in the latch output waveform when the parasitic resistor resistance value is 35 kΩ. 
     SUMMARY 
     The invention provides a level shift circuit that does not affect delay time, regardless of the size of parasitic resistor resistance value. 
     In order to solve the heretofore described problem, the invention according to a first aspect is a level shift circuit, characterized by including a first series circuit wherein a first resistor in a semiconductor substrate, a first switching element connected to an input terminal that inputs a first level shift input signal, and a first level shift output terminal for outputting a first level shift output signal are connected in series, a second series circuit wherein a second resistor in a semiconductor substrate, a second switching element connected to an input terminal that inputs a second level shift input signal, and a second level shift output terminal for outputting a second level shift output signal are connected in series, a rise detector circuit, connected to the first series circuit and second series circuit and into which are input the first level shift output signal and second level shift output signal output from the first series circuit and second series circuit respectively, that compares the rise potential of the first level shift output signal and second level shift output signal with a predetermined threshold value, and outputs a first output signal and second output signal, which are pulse outputs of a constant duration, when the threshold value is exceeded, a third switching element connected in parallel to the first resistor, wherein the source terminal of the third switching element is connected to a power source potential, the drain terminal of the third switching element is connected to the first level shift output terminal, and the gate terminal of the third switching element is connected to the rise detector circuit, and a fourth switching element connected in parallel to the second resistor, wherein the source terminal of the fourth switching element is connected to a power source potential, the drain terminal of the fourth switching element is connected to the second level shift output terminal, and the gate terminal of the fourth switching element is connected to the rise detector circuit, wherein the third switching element is turned on by the first output signal from the rise detector circuit, and the fourth switching element is turned on by the second output signal from the rise detector circuit. 
     The level shift circuit according to a second aspect is the level shift circuit according to the first aspect, characterized in that the first resistor and second resistor are parasitic resistors in the semiconductor substrate. 
     The level shift circuit according to a third aspect is the level shift circuit according to the first or second aspects, characterized by including a logic circuit that outputs a third output signal when either of the first output signal or second output signal is output from the rise detector circuit, wherein a dead time is provided for the input times of the first level shift input signal and second level shift input signal, the output pulse width of the rise detector circuit is equal to or less than the dead time, and the third switching element and fourth switching element are turned on when the third output signal is output. 
     The level shift circuit according to a fourth aspect is the level shift circuit according to any one of the first to third aspects, characterized by further including a latch malfunction protection circuit, into which the first level shift output signal and second level shift output signal are input, that outputs a high impedance signal when both the first level shift output signal and second level shift output signal are at an L level, and a latch circuit, into which an output from the latch malfunction protection circuit is input, that stores and outputs the value of the output from the latch malfunction protection circuit when the output is at an L or H level and, when the output from the latch malfunction protection circuit is of a high impedance, holds the value stored immediately before the input reaches the high impedance, and outputs the stored value together with an inverse signal of the stored value, wherein one output terminal of the latch circuit is connected via a first feedback resistor to the first level shift output terminal, and the other output terminal is connected via a second feedback resistor to the second level shift output terminal. 
     The level shift circuit according to a fifth aspect is the level shift circuit according to any one of the first to fourth aspects, characterized by further including a first feedback transistor connected in parallel to the first resistor and a second feedback transistor connected in parallel to the second resistor, wherein the gate of the first feedback transistor is connected to the second level shift output terminal, and the gate of the second feedback transistor is connected to the first level shift output terminal. 
     Advantageous Effects of Invention 
     According to the invention according to the first aspect, it is possible to reduce delay time to a minimum, even when using resistors with temperature characteristics and power source voltage characteristics as level shift resistors. Also, it is possible to shorten the pulse input interval between a set side pulse input and a reset side pulse input. 
     According to the invention according to the second aspect, it is possible to use parasitic resistors with temperature characteristics and power source voltage characteristics as level shift resistors. 
     According to the invention according to the third aspect, it is possible to prevent shoot-through current when the level shift circuit according to the first aspect is operating. 
     According to the invention according to the fourth and fifth aspects, it is possible to prevent malfunction caused by dV/dt noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a configuration diagram of a half bridge circuit using a heretofore known level shift circuit. 
         FIG. 2  shows a configuration diagram of the heretofore known level shift circuit. 
         FIG. 3  shows a circuit configuration diagram when level shift resistors in the heretofore known level shift circuit configuration are replaced with parasitic resistors. 
         FIG. 4  is a diagram showing the temperature dependency of parasitic resistor resistance value. 
         FIG. 5  is a diagram showing the voltage dependency of parasitic resistor resistance value. 
         FIG. 6  is a diagram showing the dependency of parasitic resistor resistance value on the distance between HVNs. 
         FIG. 7  shows an equivalent circuit diagram of the circuit configuration shown in  FIG. 3  when a feedback resistor R 5  and parasitic resistor Rpar 1  are in a condition in which they are connected in parallel, while a feedback resistor R 6  and parasitic resistor Rpar 2  are in a condition in which they are connected in series. 
         FIG. 8  shows an equivalent circuit diagram of the circuit configuration shown in  FIG. 3  when the feedback resistor R 5  and parasitic resistor Rpar 1  are in a condition in which they are connected in series, while the feedback resistor R 6  and parasitic resistor Rpar 2  are in a condition in which they are connected in parallel. 
         FIG. 9  shows an operation time chart of the level shift circuit shown in  FIG. 3 . 
         FIG. 10  is a diagram showing circuit simulation results for the half bridge circuit  200  shown in  FIG. 3  when the pulse interval between the set signal and reset signal is 0.5 μs. 
         FIG. 11  is a diagram showing circuit simulation results for the half bridge circuit  200  shown in  FIG. 3  when the pulse interval between the set signal and reset signal is 0.2 μs. 
         FIG. 12  shows a circuit configuration diagram according to Example 1 of the invention. 
         FIG. 13  shows an internal configuration diagram of a rise detector circuit. 
         FIG. 14  shows an operation time chart of the rise detector circuit shown in  FIG. 13 . 
         FIG. 15  is a diagram showing another circuit configuration of a rise detector circuit. 
         FIG. 16  shows an operation time chart of the rise detector circuit shown in  FIG. 15 . 
         FIG. 17  is a diagram showing the results of a circuit simulation when the pulse interval between a set signal and reset signal is 0.5 μs. 
         FIG. 18  is a diagram showing the results of a circuit simulation when the pulse interval between a set signal and reset signal is 0.2 μs. 
         FIG. 19  is a diagram showing a circuit configuration of a half bridge circuit  400  according to Example 2 of the invention. 
         FIG. 20  is a diagram showing a circuit configuration of a rise detector circuit for utilizing the circuit configuration according to Example 2. 
         FIG. 21  is a diagram showing the relationship between the pulse intervals of a set signal, reset signal, and gen signal and the output waveforms of a setdrn signal and resdrn signal. 
         FIG. 22  is a diagram showing circuit simulation results when the pulse interval between the set signal and reset signal is 0.5 μs. 
         FIG. 23  is a diagram showing circuit simulation results when the pulse interval between the set signal and reset signal is 0.2 μs. 
         FIG. 24  is a diagram showing a circuit configuration of a half bridge circuit  500  according to Example 3 of the invention. 
         FIG. 25  is a diagram showing circuit simulation results when the pulse interval between the set signal and reset signal is 0.5 μs. 
         FIG. 26  is a diagram showing circuit simulation results when the pulse interval between the set signal and reset signal is 0.2 μs. 
     
    
    
     DETAILED DESCRIPTION 
     Example 1 
       FIG. 12  is a circuit configuration diagram according to Example 1 of the invention. The same reference signs are given to regions the same as in  FIG. 3 , and a detailed description will be omitted. As shown in  FIG. 12 , a half bridge circuit  300  according to Example 1 of the invention differs from a half bridge circuit  200  shown in  FIG. 3  in that the half-bridge circuit  300  further includes a PM 11 , a PM 21 , a first rise detector circuit  321 , and a second rise detector circuit  322 . The resistance values of parasitic resistors Rpar 1  and Rpar 2  in a high potential side drive circuit  320  of the half-bridge circuit  300  shown in  FIG. 12  can be controlled as described in PTL 1. As one example, the parasitic resistors Rpar 1  and Rpar 2  at a predetermined power source voltage and predetermined temperature conditions are taken to be of 10 kΩ, taking into consideration the temperature characteristics shown in  FIG. 4  and power source voltage characteristics shown in  FIG. 5 . The resistance value of a parasitic resistor Rpar 3  at a predetermined power source voltage and predetermined temperature, based on the dependency on the distance between HVN 1  and HVN 2  shown in  FIG. 6 , is taken to be the 500 kΩ when the distance between HVN 1  and HVN 2  is 1,000 μm. 
     The first rise detector circuit  321  is connected to a first series circuit  221  and the gate terminal of the PM 11 , detects a rise of a setdrn signal output from the first series circuit  221 , and inputs a set-gen signal into the gate terminal of the PM 11 . The second rise detector circuit  322  is connected to a second series circuit  222  and the gate terminal of the PM 21 , detects a rise of a resdrn signal output from the second series circuit  222 , and inputs a reset-gen signal into the gate terminal of the PM 21 . 
     The PM 11  is connected in parallel with the parasitic resistor Rpar 1  of the first series circuit  221 , while the PM 21  is connected in parallel with the parasitic resistor Rpar 2  of the second series circuit  222 . The gate terminal of the PM 11  is connected to the output terminal of the first rise detector circuit  321 , while the gate terminal of the PM 21  is connected to the output terminal of the second rise detector circuit  322 . 
       FIG. 13  is an internal configuration diagram of the first rise detector circuit  321  and second rise detector circuit  322 . As shown in  FIG. 13 , the first rise detector circuit  321  and second rise detector circuit  322  are configured of a delay circuit  330 , a comparator  325 , a PMOS gate signal connection terminal logic circuit  335 , and a threshold value voltage source E 3 . The first rise detector circuit  321  differs from the second rise detector circuit  322 , which inputs the resdrn signal and outputs the reset-gen signal, only in that it inputs the setdrn signal and outputs the set-gen signal. Hereafter, in order to describe the configuration of a rise detector circuit, a description will be given using the first rise detector circuit  321  as an example, but the same operation is carried out in the second rise detector circuit  322  too, except that the input signals and output signals differ, as heretofore described. 
     When the setdrn signal is input into the first rise detector circuit  321 , the setdrn signal is input into the comparator  325  and delay circuit  330 . The comparator  325  is such that the setdrn signal is input into one input terminal thereof while a threshold value voltage E 3  from the threshold value voltage source E 3  (the output voltage thereof is also taken to be E 3 ) is input into the other input terminal, and the comparator  325  compares the setdrn signal and threshold value voltage E 3 . The comparator  325  inputs a comparison signal CMO into the PMOS gate signal connection terminal logic circuit  335 , with the comparison signal CMO being at an H level when the signal level of the setdrn signal is higher than the threshold value voltage, and with the comparison signal CMO being at an L level when the signal level of the setdrn signal is lower than the threshold value voltage. 
     The delay circuit  330  delays the input setdrn signal, and inputs it into the PMOS gate signal connection terminal logic circuit  335  as a delay signal DLY. The delay circuit  330  is realized by, for example, a delay circuit using a method whereby the number of stages of a CMOS logic inverter is changed, a delay circuit wherein a resistive element and capacitive element are combined, a delay circuit using a method whereby the parameters of a resistive element and capacitive element are changed, or the like. The rise detector circuit may be configured so that, by the comparison signal CMO from the comparator  325  being input into the delay circuit  330 , the signal CMO rather than the setdrn signal is delayed. 
     The input terminal of the PMOS gate signal connection terminal logic circuit  335  into which the delay signal DLY is input is set to have a function of inverting and inputting the delay signal DLY, while the output terminal that outputs the set-gen signal has a function of inverting the logical product of the comparison signal CMO and the inverted delay signal DLY, and outputting the set-gen signal. That is, the comparison signal CMO and delay signal DLY are input into the PMOS gate signal connection terminal logic circuit  335 , the PMOS gate signal connection terminal logic circuit  335  sets the set-gen signal at an L level only when the comparison signal CMO is at an H level and the delay signal DLY is at an L level, sets the set-gen signal at an H level at all other times, and inputs the set-gen signal into the gate terminal of the PM 11 . In the same way, the second rise detector circuit  322  too, going through the same operation as in the case of the first rise detector circuit  321 , but with the resdrn signal as an input, inputs the reset-gen signal into the gate terminal of the PM 21 . 
       FIG. 14  shows an operation time chart of the rise detector circuit shown in  FIG. 13 . As shown in  FIG. 14 , on the setdrn signal or resdrn signal being switched from an H level to an L level at a time t 7 , the comparison signal CMO is also switched from an H level to an L level. The delay signal DLY is switched from an H level to an L level at a time t 8 . On the setdrn signal or resdrn signal starting to rise to an H level, the signal level becoming higher than the threshold value voltage E 3  at a time t 9 , and the comparison signal CMO being switched to an H level, the set-gen signal or reset-gen signal is switched from an H level to an L level. Then, as a PM 1  or PM 2  is turned on (energized), the set-gen signal or reset-gen signal rises swiftly, and the rise time is shortened. On the delay signal DLY switching to an H level at a time t 10 , the set-gen signal or reset-gen signal is also switched to an H level. 
       FIG. 15  shows another circuit configuration of a rise detector circuit. Hereafter, a description will be given using the first rise detector circuit  321  as an example. The first rise detector circuit  321  according to the other circuit configuration includes the delay circuit  330  and PMOS gate signal connection terminal logic circuit  335 . When the setdrn signal is input into the first rise detector circuit  321 , the setdrn signal is input into the delay circuit  330  and one input terminal of the PMOS gate signal connection terminal logic circuit  335 . The delay circuit  330  delays the input setdrn signal, and inputs it into the other input terminal of the PMOS gate signal connection terminal logic circuit  335  as the delay signal DLY. As the threshold value of the input terminals of the PMOS gate signal connection terminal logic circuit  335  is a potential intermediate between vb and vs, the PMOS gate signal connection terminal logic circuit  335  outputs the set-gen signal at an L level only when the signal level of the setdrn signal is higher than the threshold value and the delay signal DLY is at an L level, and outputs the set-gen signal at an H level at all other times. However, as the threshold value of the input terminals of the PMOS gate signal connection terminal logic circuit  335  is a potential intermediate between vb and vs, there is a drawback in that the time at which the output pulse of the first rise detector circuit  321  changes is delayed, but this drawback is eliminated by lowering the threshold value of the H level side input terminal of the PMOS gate signal connection terminal logic circuit  335 . 
       FIG. 16  shows an operation time chart of the rise detector circuit shown in  FIG. 15 . As shown in  FIG. 16 , the setdrn signal or resdrn signal is switched from an H level to an L level at the time t 7 . The delay signal DLY is switched from an H level to an L level at the time t 8 . On the setdrn signal or resdrn signal starting to rise to an H level, and the signal level becoming higher than the threshold value of the input terminals of the PMOS gate signal connection terminal logic circuit  335  at the time t 9 , the set-gen signal or reset-gen signal is switched from an H level to an L level. Then, as the PM 1  or PM 2  is turned on, the set-gen signal or reset-gen signal rises swiftly, and the rise time is shortened. On the delay signal DLY switching to an H level at the time t 10 , the set-gen signal or reset-gen signal is also switched to an H level. 
       FIG. 17  and  FIG. 18  show results of the level shift circuit according to Example 1 shown in  FIG. 12  being tested by circuit simulation.  FIG. 17  shows the results of a circuit simulation when the pulse interval between a set signal and reset signal is 0.5 μs. As shown in  FIG. 17 , even when comparing cases in which the resistance values of the parasitic resistors Rpar 1  and Rpar 2  are 5 kΩ and 35 kΩ, no delay occurs in latch output, which is the same as the simulation results of a heretofore known level shift circuit shown in  FIG. 10 .  FIG. 18  shows the results of a circuit simulation when the pulse interval between the set signal and reset signal is 0.2 μs. Despite the fact the a delay occurs in the latch output in the simulation results of a heretofore known level shift circuit shown in  FIG. 11 , no delay occurs in the latch output waveform shown in  FIG. 18 . 
     Example 2 
       FIG. 19  is a circuit configuration of a half bridge circuit  400  according to Example 2 of the invention. The basic circuit configuration of the half bridge circuit  400  is the same as that in Example 1. Example 2 differs from Example 1 in that the configuration is such that the first rise detector circuit  321  and second rise detector circuit  322  shown in Example 1 are eliminated, one rise detector circuit  421  is provided instead, the setdrn signal and resdrn signal output from the first series circuit  221  and second series circuit  222  are input into the rise detector circuit  421 , and one gen signal output from the rise detector circuit  421  is input into the PM 11  and PM 21 . 
       FIG. 20  shows a circuit configuration of the rise detector circuit  421  for utilizing the circuit configuration according to Example 2. As shown in  FIG. 20 , the rise detector circuit  421  of a high potential side drive circuit  420  includes the threshold value voltage source E 3 , a first comparator  435 , a first delay circuit  436 , a first logical circuit  437 , a second comparator  438 , a second delay circuit  439 , a second logical circuit  440 , and a PMOS gate signal connection terminal logic circuit  441 . 
     The first comparator  435  and first delay circuit  436  are connected to the first series circuit  221 , and the setdrn signal is input into each of them. The setdrn signal is input into one input terminal of the first comparator  435 , the threshold value voltage E 3  is input into the other input terminal, and the first comparator  435  compares the setdrn signal and threshold value voltage E 3 . The first comparator  435  inputs a comparison signal CMO into the first logic circuit  437 , with the comparison signal CMO being at an H level when the signal level of the setdrn signal is higher than the threshold value voltage E 3 , and with the comparison signal CMO being at an L level when the signal level of the setdrn signal is lower than the threshold value voltage E 3 . 
     The first delay circuit  436  delays the input setdrn signal, and outputs it to the first logic circuit  437  as a delay signal DLY. 
     The comparison signal CMO and delay signal DLY are input into the first logic circuit  437 . The input terminal into which the delay signal DLY is input is set to have a function of inverting and inputting the delay signal DLY from the first delay circuit  436 , while the output terminal of the first logic circuit  437  has a function of inverting the logical product of the comparison signal CMO from the first comparator  435  and the inverted delay signal DLY, and outputting a signal. 
     The second comparator  438  and second delay circuit  439  are connected to the second series circuit  222 , and the resdrn signal is input into each of them. The resdrn signal is input into one input terminal of the second comparator  438 , the threshold value voltage E 3  is input into the other input terminal, and the second comparator  438  compares the resdrn signal and threshold value voltage E 3 . The second comparator  438  inputs a comparison signal CMO into the second logic circuit  440 , with the comparison signal CMO being at an H level when the signal level of the resdrn signal is higher than the threshold value voltage E 3 , and with the comparison signal CMO being at an L level when the signal level of the resdrn signal is lower than the threshold value voltage E 3 . 
     The second delay circuit  439  delays the input resdrn signal, and outputs it to the second logic circuit  440  as a delay signal DLY. 
     The comparison signal CMO and delay signal DLY are input into the second logic circuit  440 . The input terminal into which the delay signal DLY is input is set to have a function of inverting and inputting the delay signal DLY from the second delay circuit  439 , while the output terminal of the second logic circuit  440  has a function of inverting the logical product of the comparison signal CMO from the second comparator  438  and the inverted delay signal DLY, and outputting a signal. 
     The PMOS gate signal connection terminal logic circuit  441  inputs a gen signal into the PM 11  and PM 21 , with the gen signal being at an L level in a case in which an output when the comparison signal CMO of the first comparator  435  is at an H level and the delay signal DLY of the second delay circuit  436  is at an L level is input from the first logic circuit  437 , and in a case in which an output when the comparison signal CMO of the second comparator  438  is at an H level and the delay signal DLY of the second delay circuit  439  is at an L level is input from the second logic circuit  440 , and with the gen signal being at an H level in all other cases. 
     When applying the rise detector circuit shown in  FIG. 20 , a temporal restriction (a dead time DT) is provided for the set signal and reset signal. 
       FIG. 21  shows the relationship between the pulse intervals of the set signal, reset signal, and gen signal and the output waveforms of the setdrn signal and resdrn signal. As shown in  FIG. 21 , on the set signal being switched from an L level to an H level at a time t a , the setdrn signal is switched to an L level. On the set signal being switched from an H level to an L level at a time t b , the setdrn signal starts to rise to an H level, and on the signal level of the setdrn signal becoming higher than the threshold value voltage E 3  at a time t c , the gen signal is switched from an H level to an L level. On the delay signal DLY of the first delay circuit switching to an H level at a time t d , the set-gen signal or reset-gen signal is also switched to an H level. On the reset signal being switched from an L level to an H level at a time t e , the resdrn signal is switched to an L level. On the reset signal being switched from an H level to an L level at a time t f , the resdrn signal starts to rise to an H level, and on the signal level of the resdrn signal becoming higher than the threshold value voltage E 3  at a time t g , the gen signal is switched from an H level to an L level. On the delay signal DLY of the first delay circuit switching to an H level at a time t h , the gen signal is also switched to an H level. 
     A dead time period DT is provided for the set signal and reset signal so that the pulses of the two are not superimposed. That is, unless the dead time period DT has elapsed since the fall of one of the set signal or reset signal, the other signal is not raised. Further, a pulse width PW of the gen signal of the rise detector circuit  421  is regulated so as to be equal to or less than DT. The pulse width PW of the gen signal can be regulated by the delay circuit shown in  FIG. 20 . It is assumed that the output amplitude of the gen signal is of a voltage level such that a turning on and off of the PM 11  and PM 21  is possible. 
       FIG. 22  and  FIG. 23  show circuit simulation results for the level shift circuit of  FIG. 19 .  FIG. 22  is the test results when the pulse interval between the set signal and reset signal is 0.5 μs, while  FIG. 23  is the test results when the pulse interval between the set signal and reset signal is 0.2 μs. As shown in  FIG. 22  and  FIG. 23 , no delay in latch output due to a difference in parasitic resistance occurs, even when the pulse intervals differ. 
     There is an advantage in applying the rise detector circuit  421  shown in  FIG. 20  in that, even when a rise of the setdrn signal or resdrn signal is detected, the PM 11  and PM 21  are turned on, the set-gen signal or reset-gen signal rises swiftly, and the rise time is shortened. Owing to a relative operation of the parasitic resistors Rpar 1  and Rpar 2  and feedback resistors R 5  and R 6 , there is no change in an operation whereby one series circuit is connected in parallel while the other series circuit is connected in series, because of which a relationship between the impedances of the first series circuit  221  and second series circuit  222  wherein one is low while the other is high is maintained, and a relationship such that no malfunction occurs is maintained. 
     Example 3 
       FIG. 24  shows a circuit configuration of a half bridge circuit  500  according to Example 3 of the invention. The same reference signs are given to regions the same as in  FIG. 19 , and a detailed description will be omitted. A high potential side drive circuit  520  of the half bridge circuit  500  shown in  FIG. 24  is such that a first series circuit  521  is configured using a series circuit of the parasitic resistor Rpar 1  and a parasitic resistor Rpar 4 , while a second series circuit  522  is configured using a series circuit of the parasitic resistor Rpar 2  and a parasitic resistor Rpar 5 . The PM 11  and PM 21  are connected in parallel to the parasitic resistor Rpar 1  and parasitic resistor Rpar 2  respectively. The source terminal of the PM 1  is connected to a power source line Vb, while the drain terminal is connected to a first connection point Vsetb, and the gate terminal is connected via a second connection point Vrstb and the feedback resistor R 6  to the output terminal of a latch circuit  122 . The source terminal of the PM 2  is connected to the power source line Vb, while the drain terminal is connected to the second connection point Vrstb, and the gate terminal is connected via the first connection point Vsetb and the feedback resistor R 5  to the output terminal of an inverter INV. 
       FIG. 25  and  FIG. 26  show circuit simulation results for the level shift circuit shown in  FIG. 24 .  FIG. 25  is the test results when the pulse interval between the set signal and reset signal is 0.5 μs, while  FIG. 26  is the test results when the pulse interval between the set signal and reset signal is 0.2 μs. As shown in  FIG. 25  and  FIG. 26 , no delay in latch output due to a difference in parasitic resistance occurs, even when the pulse intervals differ. 
     INDUSTRIAL APPLICABILITY 
     In the description thus far, the Rpar 1 , Rpar 2 , Rpar 4 , and Rpar 5  have been adopted as parasitic resistors in a semiconductor substrate but, the invention not being limited to parasitic resistance, the normal resistance in a semiconductor substrate may be applied instead of the parasitic resistors Rpar 1 , Rpar 2  and Rpar 4 . Even when these resistors have properties in accordance with  FIGS. 4 to 6 , the effect thereof can be suppressed by the invention.

Technology Classification (CPC): 7