Booster circuit, method for operating booster circuit, voltage detection sensor, measurement device, and measurement method

Abstract

Provided are a booster circuit having input / output characteristics with high linearity, a method for operating the booster circuit, a voltage detection sensor in which the booster circuit is used, and a measurement device and a measurement method in which the voltage detection sensor is used.　This problem can be solved by a booster circuit (57a), etc., comprising a winding transformer (70), a main switch (71) connected to a primary winding (70a) of the winding transformer (70), a rectifying circuit (72) connected to a secondary winding (70b) of the winding transformer (70), and an auxiliary switch (78) connected in parallel to the primary winding (70a) or the secondary winding (70b) of the winding transformer (70).

Description

Boost circuit, method for operating boost circuit, voltage detection sensor, measuring device and measuring method

[0001] The present invention relates to a boost circuit, a method for operating the boost circuit, a voltage detection sensor including the boost circuit, a measuring device and a measuring method including the voltage detection sensor, and more particularly to a boost circuit including a wire-wound transformer.

[0002] Boost circuits, which are widely used as variable voltage generating circuits in non-contact voltage detection sensors, measurement signal sources, and the like, typically use piezoelectric transformers, such as those disclosed in Patent Document 1, in order to reduce their size. However, because piezoelectric transformers utilize the piezoelectric and electrostrictive effects of dielectrics, if the operating frequency deviates from the resonant frequency of the piezoelectric transformer, no output voltage (boosted voltage) is generated. This necessitates frequency control, which makes design difficult.

[0003] JP 2016-3989 A

[0004] Therefore, it is conceivable to use a wound-wire transformer, which has small changes in boost voltage even when the operating frequency fluctuates and is easy to control. FIG. 10( a) shows an example of a boost circuit including a wound-wire transformer. The boost circuit 57e is a flyback converter that generates a boost voltage V7 corresponding to the duty ratio of an input PWM signal V6. A constant voltage V0 is applied to a primary winding 70a of a wound-wire transformer 70 of the boost circuit 57e via a switch 71. The switch 71 is composed of a semiconductor switch such as a bipolar transistor or FET, and is controlled to open or close by the input PWM signal V6. A rectifier circuit 72 including a diode 73 and a capacitor 74 is connected to a secondary winding 70b of the wound-wire transformer 70, and the rectifier circuit 72 outputs a boost voltage V7.

[0005] The operating principle of the boost circuit 57e is as follows: First, when switch 71 is turned on, current flows through the primary winding 70a, and the magnetic flux generated magnetizes the core, storing energy. At this time, because the direction of diode 73 is reversed, no induced current flows through the secondary winding 70b. Next, when switch 71 is turned off, the energy stored in the core is released, and current flows through diode 73. The current is rectified and smoothed by diode 73 and capacitor 74 to generate an output voltage (boosted voltage V7).

[0006] The boost circuit 57e using the wound transformer 70 has the advantages that the boost voltage changes little even when the operating frequency (the frequency of the control signal of the switch 71) fluctuates, the circuit for generating the PWM signal V6 can be simplified, the input and output can be electrically isolated, and the magnitude of the boost can be set by the turns ratio of the transformer 70. On the other hand, it has the advantage that the boost voltage V7 does not change linearly with the duty ratio of the PWM signal V6. This point will be explained in detail below.

[0007] 10B shows an equivalent circuit of the boost circuit 57e. The secondary winding 70b of the boost circuit 57e has a parasitic capacitance 77, and the switch 71 has a parasitic diode 75 and a parasitic capacitance 76. Resonance between these parasitic capacitances 76 and 77 and the inductance of the transformer 70 impairs linearity.

[0008] The occurrence of resonance is shown in Figure 11(a). Figure 11(a) is a waveform diagram showing temporal changes in the voltage of PWM signal V6 and the voltage of signal V8 at terminal 71b of switch 71 on the wound transformer 70 side, with time on the horizontal axis and voltage on the vertical axis. When PWM signal V6 goes low at time t1, diode 73 connected to secondary winding 70b turns on. When the period during which diode 73 is on ends at time t2, parasitic diode 75 of switch 71 turns on. Then, when the period during which parasitic diode 75 is on ends at time t3, resonance occurs between parasitic capacitances 76 and 77 and the inductance of transformer 70, causing a ringing signal V8 to be generated at terminal 71b of switch 71 on the wound transformer 70 side. When this resonance occurs, PWM signal V6 goes high and switch 71 turns on (time t5), and the current supplied to primary winding 70a changes due to the ringing current. This impairs the linearity between the duty ratio of the PWM signal V6 and the boosted voltage V7.

[0009] 11B shows the input / output characteristics of the boost circuit 57e, i.e., the relationship between the duty ratio of the input PWM signal V6 and the boosted voltage V7 when the operating frequency of the boost circuit 57e is changed from 16 kHz (f1) to 60 kHz (f6). As is clear from the figure, the linearity of the input / output characteristics is degraded at each operating frequency.

[0010] Deterioration in linearity not only leads to deterioration in the accuracy of the boosted voltage V7, but also, in the case where the boost circuit 57e forms part of a feedback system, if the feedback system cannot cancel out the nonlinearity of the boost circuit 57e, it can cause waveform distortion and partial oscillation, leading to the problem of instability in the feedback system.

[0011] Therefore, an object of the present invention is to provide a boost circuit having highly linear input / output characteristics, a method for operating the boost circuit, a voltage detection sensor including the boost circuit, and a measuring device and measuring method including the voltage detection sensor.

[0012] The above problem can be solved by a boost circuit including a wound transformer, a main switch connected to the primary winding of the wound transformer, a rectifier circuit connected to the secondary winding of the wound transformer, and an auxiliary switch connected in parallel with the primary winding or the secondary winding of the wound transformer. That is, the auxiliary switch connected in parallel with the primary winding or the secondary winding of the wound transformer shorts both terminals of the winding, thereby attenuating resonance and improving linearity.

[0013] The above problem can also be solved by a boost circuit including a wound transformer having a primary main winding, a secondary main winding, and an auxiliary winding provided on the primary or secondary side, a main switch connected to the primary main winding, a rectifier circuit connected to the secondary main winding, and an auxiliary switch connected in parallel with the auxiliary winding. That is, the resonance can be attenuated by shorting both terminals of the auxiliary winding using an auxiliary switch connected in parallel with the auxiliary winding that is magnetically coupled to the primary or secondary main winding, thereby making it possible to improve linearity.

[0014] Here, it is desirable that the auxiliary switch comprises a bipolar transistor, a MOS transistor, or a photoMOS relay, which allows the auxiliary switch to be configured with a simple circuit configuration.

[0015] The above problem can also be solved by a method for operating any of the above-mentioned boost circuits, the method including the steps of: controlling the opening and closing of a main switch by a main signal having a duty ratio corresponding to the boost voltage; turning on an auxiliary switch during a period when resonance occurs in the terminal voltage on the wound transformer side of the main switch; and turning off the auxiliary switch before or simultaneously with turning on the main switch. By turning on the auxiliary switch during the period when resonance occurs and shorting the windings, it is possible to attenuate the resonance and improve linearity.

[0016] Furthermore, the above-mentioned problems can be solved by a voltage detection sensor comprising: any one of the above-mentioned boost circuits; an integration circuit disposed opposite the object to be measured and configured to integrate a current flowing through the measurement signal detection unit in accordance with a potential difference between the object to be measured and a measurement signal detection unit to which a boosted voltage is applied to generate an integrated signal; a main signal generation circuit configured to generate a main signal having a duty ratio corresponding to the voltage of the integrated signal and controlling the opening and closing of a main switch; an auxiliary signal generation circuit configured to generate an auxiliary signal controlling the opening and closing of an auxiliary switch; and an output processing circuit configured to generate a voltage measurement signal based on the boosted voltage, wherein the boost circuit generates a boosted voltage in accordance with the duty ratio of the main signal. That is, by using a boost circuit including a wire-wound transformer and an auxiliary switch in a voltage detection sensor having a boost circuit in its feedback system, it is possible to provide a voltage detection sensor having improved stability of the feedback system and having high linearity between the voltage of the object to be measured detected by the measurement signal detection unit and the boosted voltage, and having high accuracy.

[0017] Here, it is desirable that the main signal generating circuit includes a comparator that compares the integrated signal with a carrier signal having a periodic triangular waveform, and the auxiliary signal generating circuit includes a comparator that compares the carrier signal with an auxiliary analog signal having a voltage corresponding to the period during which the auxiliary switch is on. That is, while the main signal and auxiliary signal are both PWM signals, by using a common carrier signal having a triangular waveform and generating the main signal and auxiliary signal through analog signal processing, it is possible to generate the main signal and auxiliary signal with a simple circuit configuration. Note that in this application, "triangular waveform" or "triangular wave" means a triangular waveform or wave, including a sawtooth waveform.

[0018] The above-mentioned problems can be solved by a measuring device including the above-mentioned voltage detection sensor and a measuring main body that determines the voltage of the object to be measured based on the voltage measurement signal output from the voltage detection sensor. By using a highly linear and highly accurate voltage detection sensor, it is possible to provide a highly accurate measuring device.

[0019] Furthermore, the above-mentioned problem can also be solved by a method for measuring the voltage of an object to be measured using the above-mentioned measuring device, the method including the steps of capacitively coupling the object to a measurement signal detection unit of the measuring device, integrating a current flowing through the measurement signal detection unit, which is arranged opposite the object to be measured, in accordance with a potential difference between the object to be measured and the measurement signal detection unit to which a boosted voltage is applied, to generate an integrated signal, generating a main signal having a duty ratio corresponding to the voltage of the integrated signal, generating a boosted voltage corresponding to the duty ratio of the main signal using a boost circuit including a wire-wound transformer, and determining the voltage of the object to be measured based on the boosted voltage. In this case, the object to be measured is a conductor of a covered electric wire, and the capacitive coupling step preferably includes bringing the measurement signal detection unit close to the conductor of the covered electric wire via the insulating coating of the covered electric wire, and capacitively coupling the measurement signal detection unit to the conductor.

[0020] According to the present invention, it is possible to provide a boost circuit having highly linear input / output characteristics, a method for operating the boost circuit, a voltage detection sensor including the boost circuit, and a measuring device and measuring method including the voltage detection sensor.

[0021] FIG. 1 is a schematic configuration diagram of a boost circuit according to the present invention. FIG. 2 is a configuration example of an auxiliary switch. FIG. 3 is a flowchart of a method for operating a boost circuit according to the present invention. FIG. 4 is a waveform diagram (a) and an explanatory diagram (b) of linearity in a boost circuit according to the present invention. FIG. 5 is a schematic configuration diagram of a boost circuit according to the present invention. FIG. 6 is a schematic configuration diagram of a voltage detection sensor and a measurement device according to the present invention. FIG. 7 is a configuration example of a main signal generation circuit and an auxiliary signal generation circuit. FIG. 8 is a waveform diagram in a main signal generation circuit and an auxiliary signal generation circuit. FIG. 9 is a flowchart of a measurement method according to the present invention. FIG. 10 is a schematic configuration diagram of a boost circuit without an auxiliary switch. FIG. 11 is a waveform diagram (a) and an explanatory diagram (b) of linearity in a boost circuit without an auxiliary switch.

[0022] 1 shows a schematic configuration diagram of a boost circuit 57a according to an embodiment of the present invention. The boost circuit 57a is a flyback converter that receives a main signal V6 and an auxiliary signal V9 and generates a boosted voltage V7 according to the duty ratio of the main signal V6. The main signal V6 and the auxiliary signal V9 are PWM signals, which are binary signals having two states: a high level (a voltage that turns on the main switch 71 or the auxiliary switch 78) and a low level (a voltage that turns off the main switch 71 or the auxiliary switch 78).

[0023] The boost circuit 57a includes a wound-type transformer 70 having a primary main winding 70a, a secondary main winding 70b, and a primary auxiliary winding 70c provided on the primary side. A main switch 71 is connected to the primary main winding 70a, and a constant voltage V0 is applied via the main switch 71. The main switch 71 is composed of a bipolar transistor, a MOSFET, or the like, and is controlled to open and close by a main signal V6. An auxiliary switch 78 is connected in parallel between both terminals of the primary auxiliary winding 70c. The auxiliary switch 78 is controlled to open and close by an auxiliary signal V9. A rectifier circuit 72 is connected to the secondary main winding 70b, and outputs a boosted voltage V7 from the rectifier circuit 72. The rectifier circuit 72 includes a diode 73 and a capacitor 74. The anode of the diode 73 is connected to one end of the secondary main winding 70b of the wound-type transformer 70, and the cathode is connected to one end of the capacitor 74. The other end of the capacitor 74 is connected to the other end of the secondary main winding 70 b, and a boosted voltage V 7 is generated across the terminals of the capacitor 74 .

[0024] 2 shows an example of the configuration of the auxiliary switch 78. Fig. 2(a) shows an auxiliary switch 78a including a bipolar transistor 90a. A resistor 90b is connected to the base of the bipolar transistor 90a, and an auxiliary signal V9 is input via the resistor 90b. A resistor 90c is connected between the base and emitter of the bipolar transistor 90a. When the auxiliary signal V9 goes high, the collector and emitter of the bipolar transistor 90a are conductive (ON), and when the auxiliary signal V9 goes low, the collector and emitter of the bipolar transistor 90a are non-conductive (OFF).

[0025] 2B shows the auxiliary switch 78b including a MOS transistor 91a. An auxiliary signal V9 is input to the gate of the MOS transistor 91a. A diode 91b is connected to the drain of the MOS transistor 91a for rectification. When the auxiliary signal V9 goes high, the drain-source of the MOS transistor 91a is conductive (ON), and when the auxiliary signal V9 goes low, the drain-source of the MOS transistor 91a is non-conductive (OFF).

[0026] 2(c) shows an auxiliary switch 78c equipped with a photoMOS relay 92. The photoMOS relay 92 is a semiconductor relay that uses an LED as the input element and a MOSFET as the output element, and is capable of providing electrical isolation between the input and output. When the auxiliary signal V9 applied to the input element of the photoMOS relay becomes high level, the output element becomes conductive (ON), and when the auxiliary signal V9 becomes low level, the output element becomes non-conductive (OFF).

[0027] As is clear from the above-described configuration example, it is possible to configure the auxiliary switch 78 with a simple circuit configuration. In particular, the auxiliary switch 78a including the bipolar transistor 90a shown in Fig. 2(a) does not require a diode for rectification, and therefore the auxiliary switch 78 can be configured with a very simple circuit.

[0028] Next, the operation of the boost circuit 57a, i.e., a method of operating the boost circuit according to an embodiment of the present invention, will be described with reference to the flowchart of Fig. 3 and the waveform diagram of Fig. 4(a). Fig. 4(a) is a waveform diagram, with time on the horizontal axis and voltage on the vertical axis, showing the temporal changes in the voltage of the main signal V6, auxiliary signal V9, and signal V8 at terminal 71b of main switch 71 on the wound transformer 70 side, in steps 31 to 34 of Fig. 3.

[0029] First, when the main switch 71 is turned on by a high-level main signal V6, current flows through the primary main winding 70a, and the magnetic flux generated magnetizes the core, storing energy (step 30). At this time, because the direction of the diode 73 is reversed, no induced current flows through the secondary main winding 70b. Next, at time t1, the main signal V6 goes low and the main switch 71 is turned off. The energy stored in the core is released, the diode 73 is turned on, and current flows through the diode 73. The current is rectified and smoothed by the diode 73 and capacitor 74, generating the boosted voltage V7 (step 31). After that, at time t2, when the period during which the diode 73 is on ends, the parasitic diode of the switch 71 is turned on.

[0030] When the period during which the parasitic diode of the main switch 71 is on ends at time t3, resonance occurs between the secondary main winding 70b, the parasitic capacitance of the main switch 71, and the inductance of the transformer 70, causing a ringing signal V8 to be generated at the terminal 71b of the main switch 71 on the wound transformer 70 side. During this resonance period, the auxiliary signal V9 transitions to high level to turn on the auxiliary switch 78, shorting both terminals of the primary auxiliary winding 70c and thereby damping the resonance (step 32). In Figure 4(a), the auxiliary switch 78 is turned on at time t4, and it can be seen that the resonance damps from time t4 onwards (the portion indicated by the solid circle).

[0031] Then, at time t5, the main signal V6 goes high, turning on the main switch 71, and simultaneously the auxiliary signal V9 goes low, turning off the auxiliary switch 78 (steps 33 and 34). This causes current to flow through the primary main winding 70a, and the generated magnetic flux magnetizes the core, storing energy. Thereafter, steps 31 to 34 are repeated to generate the boosted voltage V7 according to the duty ratio of the main signal V6.

[0032] Since the resonance is damped in step 32, no current flows through the transformer at step 34, and therefore energy corresponding to the duty ratio of the main signal V6 can be stored in the transformer 70. This improves the linearity between the duty ratio of the main signal V6 and the boosted voltage V7. Note that in the above flow, the timing at which the auxiliary switch 78 is turned off (step 33) and the timing at which the main switch 71 is turned on (step 34) are simultaneous, but the timing at which the auxiliary switch 78 is turned off may be any timing other than the timing at which the main switch 71 is turned on (step 34), as long as it is before the timing at which the main switch 71 is turned on (step 34).

[0033] 4(b) shows the input / output characteristics of the boost circuit 57a, i.e., the relationship between the duty ratio of the input main signal V6 and the boosted voltage V7 when the operating frequency of the boost circuit 57a (the frequency of the main signal V6) is changed to 16 kHz (f1), 20 kHz (f2), 30 kHz (f3), 40 kHz (f4), 50 kHz (f5), and 60 kHz (f6). It can be seen that, compared with the boost circuit 57e without an auxiliary switch shown in FIG. 11(b), a highly linear input / output characteristic is obtained at any operating frequency.

[0034] 5 shows other examples of booster circuits. Booster circuits 57b, 57c, and 57d shown in FIGS. 5(a) to 5(c) differ from booster circuit 57a in the connection position of the auxiliary switch 78. Any of the auxiliary switches 78 can be configured as shown in FIG. 2.

[0035] 5A, the wound transformer 70 does not have an auxiliary winding, and an auxiliary switch 78 is electrically connected in parallel with the primary winding 70a of the wound transformer 70. The configurations of the main switch 71 and rectifier circuit 72, the connection between these and the wound transformer 70, and the method of operating the boost circuit 57b are the same as those of the boost circuit 57a.

[0036] 5(b), the wound transformer 70 does not have an auxiliary winding, and an auxiliary switch 78 is electrically connected in parallel with the secondary winding 70b of the wound transformer 70. The configurations of the main switch 71 and rectifier circuit 72, the connection between these and the wound transformer 70, and the method of operating the boost circuit 57c are the same as those of the boost circuit 57a.

[0037] 5(c), a boost circuit 57d includes a wound transformer 70 having a primary main winding 70a, a secondary main winding 70b, and a secondary auxiliary winding 70d provided on the secondary side. An auxiliary switch 78 is connected in parallel with the secondary auxiliary winding 70d. The configurations of the main switch 71 and rectifier circuit 72, the connections between these and the wound transformer 70, and the method of operating the boost circuit 57d are the same as those of the boost circuit 57a.

[0038] 1 and 5 have in common the fact that the auxiliary switches 78 are connected to any one of the windings 70a, 70b, 70c, and 70d of the wound transformer 70, and short-circuit both terminals of the windings 70a, 70b, 70c, and 70d when the switches are turned on. Therefore, the boost circuits 57b, 57c, and 57d have the same effect as the boost circuit 57a, i.e., they reduce resonance and have highly linear input / output characteristics.

[0039] Next, a voltage detection sensor 42 and a measurement device 40 according to an embodiment of the present invention will be described with reference to the schematic diagram of Fig. 6. Fig. 6 is a schematic diagram showing the measurement device 40 capacitively coupled to a measurement target 43. The measurement target 43 is, for example, a coated electric wire having a conductor 43b that transmits AC power of 400 Vrms, 60 Hz, and an insulating coating 43a that covers the conductor 43b.

[0040] Measurement device 40 includes voltage detection sensor 42 and measurement main body 44 connected to voltage detection sensor 42. When measurement signal detection unit 50 of voltage detection sensor 42 is placed facing and close to measurement object 43, measurement signal detection unit 50 and measurement object 43 are capacitively coupled. Voltage detection sensor 42 generates voltage measurement signal VS from current I1 flowing through measurement signal detection unit 50 due to capacitive coupling. Measurement main body 44 receives voltage measurement signal VS and performs signal processing and information processing to determine voltage V1 of measurement object 43.

[0041] The voltage detection sensor 42 includes a measurement signal detection unit 50, an integration circuit 51 connected to the measurement signal detection unit 50 and a boost circuit 57, an amplitude limiting circuit 52 connected to the integration circuit 51, an insulation circuit 53 connected to the amplitude limiting circuit 52, a carrier signal generation circuit 55, a main signal generation circuit 56 connected to the insulation circuit 53 and the carrier signal generation circuit 55, an auxiliary signal generation circuit 59 connected to the carrier signal generation circuit 55, a boost circuit 57 connected to the main signal generation circuit 56 and the auxiliary signal generation circuit 59, and an output processing circuit 58 connected to the boost circuit 57. A feedback system including the integration circuit 51, the amplitude limiting circuit 52, the insulation circuit 53, the main signal generation circuit 56, and the boost circuit 57 is formed within the voltage detection sensor 42.

[0042] A boosted voltage V7 is applied to the measurement signal detection unit 50 via an integration circuit 51, and a current I1 is generated whose magnitude corresponds to the potential difference between the voltage V1 of the capacitively coupled measurement object 43 and the boosted voltage V7 (more precisely, whose magnitude corresponds to the potential difference and the coupling capacitance C0 between the measurement signal detection unit 50 and the measurement object 43).

[0043] The integration circuit 51 receives the boosted voltage V7 from the boost circuit 57 and applies the boosted voltage V7 to the measurement signal detection unit 50. It also converts the current I1 flowing through the measurement signal detection unit 50 into a current-voltage signal and integrates it to generate an integrated signal V2. The amplitude limiting circuit 52 is a voltage limiter circuit that limits the amplitude of the input signal. It receives the integrated signal V2 from the integration circuit 51 and generates an amplitude-limited integrated signal V3 when the voltage of the integrated signal V2 exceeds a predetermined amplitude. The isolation circuit 53 receives the amplitude-limited integrated signal V3 from the amplitude limiting circuit 52 and generates an integrated signal V4 that is electrically isolated from the integrated signal V3. The isolation circuit 53 can be configured, for example, with an isolation amplifier or a photocoupler.

[0044] Since amplitude limiting circuit 52 is a circuit for maintaining the stability of the feedback system, it is sufficient if it is provided on the transmission path of integrated signals V2, V3, and V4 between integrating circuit 51 and main signal generating circuit 56. However, from the viewpoint of suppressing the effects of excessive input, it is desirable to provide it on the transmission path as close as possible to the input of the feedback system, i.e., to integrating circuit 51. In particular, because the components that make up insulating circuit 53 are often vulnerable to excessive input, it is desirable to provide amplitude limiting circuit 52 on the transmission path of the integrated signal between integrating circuit 51 and insulating circuit 53. For this reason, measuring device 40 provides amplitude limiting circuit 52 between integrating circuit 51 and insulating circuit 53.

[0045] The main signal generating circuit 56 receives the integrated signal V4 and the carrier signal V5 generated by the carrier signal generating circuit 55, and generates a main signal V6 having a duty ratio corresponding to the voltage of the integrated signal V4. The boost circuit 57 is a flyback converter that receives the main signal V6 and the auxiliary signal V9 generated by the auxiliary signal generating circuit 59, and generates a boosted voltage V7 corresponding to the duty ratio of the main signal V6, and can be configured, for example, by the boost circuits 57a, 57b, 57c, and 57d shown in FIG. 1 or FIG. 5.

[0046] The output processing circuit 58 includes a voltage dividing circuit, a buffer circuit, etc., receives the boosted voltage V7, performs output signal processing such as voltage division and buffering, and generates a voltage measurement signal VS based on the boosted voltage V7.

[0047] Fig. 7 shows configuration examples of carrier signal generating circuit 55, main signal generating circuit 56, and auxiliary signal generating circuit 59, and Fig. 8 shows waveform diagrams of input and output signals of main signal generating circuit 56 and auxiliary signal generating circuit 59. In Fig. 8, the horizontal axis represents time and the vertical axis represents signal voltage, with the upper part of Fig. 8 showing waveforms of input signals (integrated signal V4, carrier signal V5, auxiliary analog signal V10) and the lower part of Fig. 8 showing waveforms of output signals (main signal V6, auxiliary signal V9).

[0048] The carrier signal generation circuit 55 generates a carrier signal V5 having a periodic triangular waveform, such as a sawtooth triangular wave with a steep drop and a gradual rise, as shown in signal V5 in FIG.

[0049] The main signal generating circuit 56 is composed of a comparator, and the carrier signal V5 is input to the inverting input of the comparator 56, and the integrated signal V4 is input to the non-inverting input. The comparator 56 compares the voltage of the integrated signal V4 with the voltage of the carrier signal V5. If the voltage of the carrier signal V5 is smaller than the voltage of the integrated signal V4, the comparator 56 generates a high-level main signal V6 (a voltage that turns on the main switch 71 of the voltage boost circuit 57). If the voltage of the carrier signal V5 is equal to or greater than the voltage of the integrated signal V4, the comparator 56 generates a low-level main signal V6 (a voltage that turns off the main switch 71 of the voltage boost circuit 57). In Fig. 8 , at time t1, the voltage of the carrier signal V5 becomes smaller than the voltage of the integrated signal V4, so the main signal V6 transitions to a high level. At time t2, the voltage of the carrier signal V5 becomes equal to or greater than the voltage of the integrated signal V4, so the main signal V6 transitions to a low level.

[0050] The auxiliary signal generating circuit 59 is composed of a comparator, and the auxiliary analog signal V10 is input to the inverting input of the comparator 59, and the carrier signal V5 is input to the non-inverting input. The auxiliary analog signal V10 is a signal having a voltage corresponding to the period during which the auxiliary switch 78 of the voltage boost circuit 57 is on. The comparator 59 compares the voltage of the auxiliary analog signal V10 with the voltage of the carrier signal V5, and generates a high-level auxiliary signal V9 (a voltage that turns on the auxiliary switch 78 of the voltage boost circuit 57) when the voltage of the carrier signal V5 is greater than that of the auxiliary analog signal V10. However, when the voltage of the carrier signal V5 is equal to or less than the voltage of the auxiliary analog signal V10, the comparator 59 generates a low-level auxiliary signal V9 (a voltage that turns off the auxiliary switch 78 of the voltage boost circuit 57). In Figure 8, at time t3, the voltage of carrier signal V5 becomes greater than the voltage of auxiliary analog signal V10, so auxiliary signal V9 transitions to a high level, and at time t4, the voltage of carrier signal V5 becomes equal to or less than the voltage of auxiliary analog signal V10, so auxiliary signal V9 transitions to a low level.

[0051] Both the main signal V6 and the auxiliary signal V9 are PWM signals, and can be generated by analog signal processing using a common carrier signal V5. This makes it possible to generate the main signal V6 and the auxiliary signal V9 with a simple circuit configuration such as that shown in FIG. 7. In the above-described exemplary configuration, a sawtooth triangular wave with a steep decline and a gradual rise is used as the carrier signal V5 to simultaneously turn off the auxiliary switch 78 and turn on the main switch 71. However, by using a carrier signal V5 with a triangular wave that also declines gradually, the main signal V6 and the auxiliary signal V9 can be generated so that the main switch 71 turns on after the auxiliary switch 78 turns off.

[0052] Next, a measurement method according to an embodiment of the present invention will be described with reference to Fig. 9. First, the measurement signal detector 50 of the measurement device 40 is capacitively coupled to the measurement target 43 (step 80). For example, in the configuration shown in Fig. 6, to measure the voltage V1 of the conductor 43b of the insulated electric wire 43, the measurement signal detector 50 is clamped to the insulating coating 43a of the insulated electric wire 43, and the measurement signal detector 50 is brought close to the conductor 43b of the insulated electric wire 43 via the insulating coating 43a of the insulated electric wire 43, thereby capacitively coupling the measurement signal detector 50 to the conductor 43b.

[0053] Next, the integration circuit 51 integrates the current I1 flowing through the measurement signal detector 50 in accordance with the potential difference between the conductor 43b being measured and the measurement signal detector 50 to which the boosted voltage V7 is applied, to generate an integrated signal V2 (step 81).Then, the amplitude limiting circuit 52 limits the amplitude of the integrated signal V2 to within a predetermined voltage range, to generate an amplitude-limited integrated signal V3 (step 82).The amplitude-limited integrated signal V3 is then used by the isolation circuit 53 to generate an integrated signal V4 electrically isolated from the integrated signal V3 (step 83).

[0054] Next, the main signal generating circuit 56 generates the main signal V6 having a duty ratio corresponding to the voltage of the electrically separated integrated signal V4 (step 84). At this time, as described above, the carrier signal generating circuit 55 generates the carrier signal V5 having a periodic triangular waveform, and the comparator 56 compares the voltage of the integrated signal V4 with the voltage of the carrier signal V5 to generate the main signal V6.

[0055] Next, the boost circuit 57, which includes the wound transformer 70, generates a boosted voltage V7 corresponding to the duty ratio of the main signal V6 (step 85). As described above, the auxiliary signal V9, generated by the comparator 59 by comparing the voltage of the auxiliary analog signal V10 with the voltage of the carrier signal V5, is used to reduce resonance in the boost circuit 57. The output processing circuit 58 then generates a voltage measurement signal VS based on the boosted voltage V7 (step 86). Finally, the measurement main unit 44 determines the voltage V1 of the object to be measured 43 based on the voltage measurement signal VS (step 87).

[0056] As described above, in a boost circuit including a wound transformer, a method for operating the boost circuit, a voltage detection sensor including the boost circuit, and a measuring device and method including the voltage detection sensor, by shorting the terminals of the windings using an auxiliary switch connected in parallel to the windings of the wound transformer, it is possible to reduce resonance that occurs in the boost process and improve linearity, thereby providing a highly accurate boost circuit, a method for operating the boost circuit, a voltage detection sensor, a measuring device, and a measuring method.

[0057] The above has described the boost circuit of the present invention, the method for operating the boost circuit, the voltage detection sensor including the boost circuit, and the measuring device and measuring method including the voltage detection sensor, but the present invention is not limited to the above-described embodiments and includes all aspects included in the concept of the present invention and the scope of the claims.

[0058] 40 Measuring device 42 Voltage detection sensor 43 Measurement object (coated electric wire) 43a Insulating coating 43b Conductor 44 Measuring body 50 Measurement signal detection section 51 Integration circuit 52 Amplitude limiting circuit 53 Isolation circuit 55 Carrier signal generating circuit 56 Main signal generating circuit (comparator) 57, 57a, 57b, 57c, 57d, 57e Boost circuit 58 Output processing circuit 59 Auxiliary signal generating circuit (comparator) 70 Wound transformer 70a Primary winding, primary main winding 70b Secondary winding, secondary main winding 70c Primary auxiliary winding 70d Secondary auxiliary winding 71 Main switch 71a, 71b Terminal 72 Rectifier circuit 73 Diode 74 Capacitor 75 Parasitic diode 76, 77 Parasitic capacitance 78, 78a, 78b, 78c auxiliary switch 90a bipolar transistor 90b, 90c resistor 91a MOS transistor 91b diode 92 photoMOS relay

Claims

1. A boost circuit comprising: a wound transformer; a main switch connected to a primary winding of the wound transformer; a rectifier circuit connected to a secondary winding of the wound transformer; and an auxiliary switch connected in parallel with the primary winding or the secondary winding of the wound transformer.

2. A boost circuit comprising: a wound transformer having a primary main winding, a secondary main winding, and an auxiliary winding provided on the primary or secondary side; a main switch connected to the primary main winding; a rectifier circuit connected to the secondary main winding; and an auxiliary switch connected in parallel with the auxiliary winding.

3. The boost circuit according to claim 1 or 2, wherein the auxiliary switch comprises a bipolar transistor, a MOS transistor, or a photoMOS relay.

4. A method for operating the boost circuit of claim 1 or 2, comprising the steps of: controlling the opening and closing of the main switch by a main signal having a duty ratio corresponding to the boost voltage; turning on the auxiliary switch during a period when resonance occurs in the terminal voltage on the wound transformer side of the main switch; and turning off the auxiliary switch before or simultaneously with the main switch being turned on.

5. A voltage detection sensor comprising: a boost circuit as defined in claim 1 or 2; an integration circuit arranged opposite to an object to be measured, which generates an integrated signal by integrating a current flowing through the measurement signal detection section in accordance with a potential difference between the object to be measured and a measurement signal detection section to which a boosted voltage is applied; a main signal generation circuit which generates a main signal having a duty ratio in accordance with the voltage of the integrated signal and which controls the opening and closing of the main switch; an auxiliary signal generation circuit which generates an auxiliary signal in accordance with the opening and closing of the auxiliary switch; and an output processing circuit which generates a voltage measurement signal based on the boosted voltage, wherein the boost circuit generates the boosted voltage in accordance with the duty ratio of the main signal.

6. The voltage detection sensor according to claim 5, wherein the main signal generating circuit comprises a comparator that compares the integrated signal with a carrier signal having a periodic triangular waveform, and the auxiliary signal generating circuit comprises a comparator that compares the carrier signal with an auxiliary analog signal having a voltage corresponding to the period during which the auxiliary switch is on.

7. A measuring device comprising: a voltage detection sensor according to claim 6; and a measurement main body that determines the voltage of the object to be measured based on a voltage measurement signal output from the voltage detection sensor.

8. A method for measuring the voltage of an object to be measured using the measuring device of claim 7, comprising the steps of: capacitively coupling the object to be measured with a measurement signal detection unit of the measuring device; integrating a current flowing through the measurement signal detection unit, which is disposed opposite the object to be measured, in accordance with the potential difference between the object to be measured and the measurement signal detection unit to which the boosted voltage is applied, to generate an integrated signal; generating a main signal having a duty ratio in accordance with the voltage of the integrated signal; generating the boosted voltage in accordance with the duty ratio of the main signal using a boost circuit equipped with a wire-wound transformer; and determining the voltage of the object to be measured based on the boosted voltage.

9. The method according to claim 8, wherein the measurement object is a conductor of a coated electric wire, and the step of capacitively coupling includes a step of bringing the measurement signal detection unit close to the conductor of the coated electric wire via the insulating coating of the coated electric wire, and capacitively coupling the measurement signal detection unit and the conductor.

Images