Triangular wave generation circuit and power conversion device

Abstract

A triangular wave generation circuit (20) comprises: a current generation unit (21) that generates a prescribed charging current from a constant voltage power supply; a capacitor (22) that generates a triangular wave signal by accumulating the charging current generated by the current generation unit and discharging accumulated current; a charge / discharge control unit (23) that charges the capacitor with the charging current during a charging period, which is one of either the half-wave period of the positive voltage or the half-wave period of the negative voltage within an AC signal outputted in accordance with electricity generated by an electric generator, and discharges the charging current from the capacitor in a discharge period that is the other of the two periods; and an auxiliary charging unit (24) that, when an amplitude voltage of the AC signal outputted by the electric generator has reached or exceeded a threshold value, charges the capacitor with an auxiliary current that corresponds to the amplitude voltage, in addition to the charging current.

Description

Triangular wave generating circuit and power conversion device

[0001] The present invention relates to a triangular wave generating circuit and a power conversion device.

[0002] Conventionally, there is known a power conversion device that converts an AC signal output by a generator into DC power using a switching element such as a thyristor (see, for example, Patent Document 1). Such a power conversion device includes a triangular wave generating circuit that generates a triangular wave signal from a constant voltage using a half-wave output period of the AC signal, and controls energization of a switching element such as a thyristor using the triangular wave signal output by the triangular wave generating circuit to convert the AC signal into DC power.

[0003] Japanese Patent Application Publication No. 9-285127

[0004] However, as the rotation speed of the generator increases, the output peak value of the AC signal increases and the half-wave output period shortens, so in conventional triangular wave generating circuits, the peak voltage of the triangular wave signal decreases. As a result, in conventional triangular wave generating circuits, the peak voltage of the triangular wave signal fluctuates depending on the rotation speed of the generator, and the power conversion device may not be able to perform power conversion normally.

[0005] The present invention has been made to solve the above problems, and its object is to provide a triangular wave generating circuit and a power conversion device that can reduce the drop in peak voltage of a triangular wave signal when the rotation speed of the generator increases, thereby achieving stable power conversion.

[0006] In order to solve the above problems, one aspect of the present invention is a triangular wave generating circuit comprising: a current generating unit that generates a predetermined charging current from a constant voltage power supply; a capacitor that generates a triangular wave signal by charging the charging current generated by the current generating unit and discharging the charged current; a charge / discharge control unit that charges the capacitor with the charging current during a charging period, which is either a positive voltage half-wave period or a negative voltage half-wave period of an AC signal output by a generator in accordance with the power generated, and discharges the capacitor during a discharging period, which is the other period; and an auxiliary charging unit that, when the amplitude voltage of the AC signal output by the generator becomes equal to or greater than a threshold, charges the capacitor with an auxiliary current corresponding to the amplitude voltage in addition to the charging current.

[0007] In another aspect of the present invention, in the above-mentioned triangular wave generating circuit, the charge / discharge control unit may include a first transistor that discharges the current charged in the capacitor, and a second transistor that determines the charging period and the discharging period based on the AC signal, and brings the first transistor into a non-conducting state during the charging period and brings the first transistor into a conducting state during the discharging period.

[0008] In addition, according to one aspect of the present invention, in the above-described triangular wave generating circuit, the auxiliary charging unit may use a Zener diode to determine whether the amplitude voltage is equal to or greater than the threshold value.

[0009] In addition, one aspect of the present invention may be such that, in the above-mentioned triangular wave generating circuit, the current generating unit includes a resistive element that generates the predetermined charging current from the constant voltage power supply, and a diode that is connected in series with the resistive element and prevents backflow to the constant voltage power supply.

[0010] In addition, in one aspect of the present invention, in the above-described triangular wave generating circuit, the charging period may be a half-wave period of the positive voltage, and the discharging period may be a half-wave period of the negative voltage.

[0011] Another aspect of the present invention is a power conversion device including a switching element that rectifies the AC signal output by the generator and supplies the rectified AC signal to a load, and a gate control unit that controls the conduction timing of the switching element based on the triangular wave signal output by the triangular wave generating circuit described above.

[0012] In addition, one aspect of the present invention may be such that, in the power conversion device, the switching element is a thyristor, and the gate control unit generates a gate signal that fires the thyristor.

[0013] According to the present invention, the triangular wave generating circuit includes a capacitor that generates a triangular wave signal by charging the capacitor with a charging current generated by a current generating unit from a constant-voltage power supply and discharging the charged current, and when the amplitude voltage of the AC signal output by the generator becomes equal to or greater than a threshold, the auxiliary charging unit charges the capacitor with an auxiliary current corresponding to the amplitude voltage by adding it to the charging current generated by the current generating unit from the constant-voltage power supply.As a result, even when the rotation speed of the generator increases and the half-wave output period of the AC signal becomes shorter, the triangular wave generating circuit of the present invention charges the capacitor with an auxiliary current corresponding to the amplitude voltage of the AC signal by adding it to the charging current.This makes it possible to reduce the decrease in the peak voltage of the triangular wave signal and achieve stable power conversion.

[0014] 1 is a block diagram showing an example of a power conversion device according to the present embodiment; FIG. 2 is a block diagram showing an example of a gate control unit in the present embodiment; FIG. 3 is a block diagram showing an example of a triangular wave generating circuit according to the present embodiment; FIG. 4 is a diagram explaining an example of operation when a generator rotates at low speed in the triangular wave generating circuit according to the present embodiment; FIG. 5 is a diagram explaining an example of operation when a capacitor of the triangular wave generating circuit according to the present embodiment is discharged; and FIG. 6 is a diagram explaining an example of the effect of the triangular wave generating circuit according to the present embodiment.

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A triangular wave generating circuit and a power conversion device according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] Fig. 1 is a block diagram showing an example of a power conversion device 100 according to this embodiment. As shown in Fig. 1, the power conversion device 100 converts AC power (AC voltage VA) generated by a generator 10 into DC power (DC voltage Vo) and supplies the DC power to a load RL. The power conversion device 100 includes a thyristor 101, resistors (102, 103), and a gate control unit 120.

[0017] The generator 10 is, for example, a single-phase magneto AC generator that generates electricity in response to the rotation of a rotor (not shown) and outputs an AC signal (for example, AC voltage VA) corresponding to the generated power. Here, the rotor is, for example, a crankshaft connected to the rotating shaft of an internal combustion engine (engine) of a motorcycle. The generator 10 supplies the AC signal (for example, AC voltage VA) corresponding to the generated power to the thyristor 101 via a power supply line.

[0018] The generator 10 has a coil 11 , and an AC voltage VA is output from one end of the coil 11 and supplied to a thyristor 101 .

[0019] The thyristor 101 is a switching element that rectifies an AC signal (e.g., AC voltage VA) output by the generator 10 and supplies the rectified signal to the load RL. The thyristor 101 has an anode terminal connected to a signal line for the AC voltage VA output by the generator 10, a cathode terminal connected to a signal line for DC power (DC voltage Vo) output by the power conversion device 100, and a gate terminal (control terminal) connected to a signal line for a control signal VSCR output by the gate control unit 120. The thyristor 101 outputs DC power (DC voltage Vo).

[0020] The resistors 102 and 103 are connected in series between the signal line of the DC voltage Vo and the ground line. A voltage VR obtained by dividing the DC voltage Vo by the resistance ratio of the resistors 102 and 103 is output to a node N1 between the resistors 102 and 103, and the voltage VR is supplied to the gate control unit 120.

[0021] The gate control unit 120 supplies a control signal VSCR to a gate terminal that controls the conduction of the thyristor 101 based on the voltage VR and the AC voltage VA so that the DC voltage Vo becomes a constant voltage. The gate control unit 120 includes a triangular wave generating circuit 20, which will be described later. The detailed configuration of the gate control unit 120 will now be described with reference to FIG. 2.

[0022] 2 is a block diagram showing an example of the gate control unit 120 in this embodiment. As shown in Fig. 2, the gate control unit 120 includes a voltage conversion circuit 121, a reference voltage generation circuit 122, a differential circuit 123, an amplifier circuit 124, a triangular wave generation circuit 20, a comparison circuit 125, a start circuit 131, and a limit voltage generation circuit 132.

[0023] The voltage conversion circuit 121 converts the voltage VR at the node N1 into an effective voltage VR' representing its effective value. The voltage conversion circuit 121 has an input terminal connected to the node N1, and supplies the converted effective voltage VR' to a first input terminal of the differential circuit 123. The effective voltage VR' corresponds to the output voltage Vo supplied to the load RL, and is treated as a detected value of the output voltage Vo.

[0024] The reference voltage generating circuit 122 generates a target voltage VT as a reference voltage for supplying power to the load RL. The reference voltage generating circuit 122 supplies the target voltage VT to a second input terminal of the differential circuit 123.

[0025] The differential circuit 123 generates a differential voltage VD (=VR'-VT) between the effective voltage VR' and the target voltage VT. The differential circuit 123 supplies the generated differential voltage VD to the amplifier circuit .

[0026] The amplifier circuit 124 multiplies the differential voltage VD by a magnification coefficient (amplification degree) M (>0) and outputs a differential voltage VD′ obtained by amplifying the differential voltage VD by a factor of M. The amplifier circuit 124 supplies the generated differential voltage VD′ to a second input terminal b of the comparison circuit 125.

[0027] The triangular wave generating circuit 20 generates a triangular wave signal VB (triangular wave voltage) corresponding to each cycle of the AC voltage VA output from the coil 11 of the generator 10, and outputs the generated triangular wave signal VB to the comparison circuit 125. The triangular wave generating circuit 20 also supplies the triangular wave signal VB to a first input terminal a of the comparison circuit 125. The detailed configuration of the triangular wave generating circuit 20 will be described later with reference to FIG. 3.

[0028] The start circuit 131 monitors the AC voltage VA input to the triangular wave generating circuit 20, and at the timing when the input of the AC voltage VA starts, outputs a start signal ST to the limit voltage generating circuit 132. The start signal ST is a signal for generating the limit voltage VL.

[0029] The limit voltage generating circuit 132 outputs a limit voltage VL based on the start signal ST. The limit voltage generating circuit 132 supplies the generated limit voltage VL to the third input terminal of the comparison circuit 125.

[0030] The comparator circuit 125 compares the differential voltage VD' (a control signal that controls the output voltage Vo to coincide with the target voltage VT) input from the amplifier circuit 124 with the limit voltage VL (a signal that limits the increase in the output voltage Vo) input from the limit voltage generator circuit 132, and selects the signal with the higher voltage level between the voltage VD' and the limit voltage VL. The comparator circuit 125 further compares the selected voltage (the differential voltage VD' or the limit voltage VL) with the triangular wave voltage VB.

[0031] For example, when comparing the differential voltage VD' and the triangular wave voltage VB, the comparison circuit 125 detects the point where the differential voltage VD' and the triangular wave voltage VB coincide, i.e., the timing of the cross point where the differential voltage VD' and the triangular wave voltage VB intersect. At this timing, the comparison circuit 125 sets the pulse signal VSCR, which defines the conduction timing of the thyristor 101, to high level and outputs this pulse signal VSCR to the gate terminal of the thyristor 101. In this case, the pulse signal VSCR is maintained at high level in the section where the triangular wave voltage VB is greater than the differential voltage VD' (VB>VD'), and is at low level in other sections.

[0032] Similarly, when comparing the limit voltage VL and the triangular wave voltage VB, the comparison circuit 125 detects the point where the limit voltage VL and the triangular wave voltage VB coincide, i.e., the timing of the cross point where the limit voltage VL and the triangular wave voltage VB intersect. At this timing, the comparison circuit 125 sets the pulse signal VSCR, which defines the conduction timing of the thyristor 101, to high level and outputs this pulse signal VSCR to the gate terminal of the thyristor 101. In this case, the pulse signal VSCR is maintained at high level in the section where the triangular wave voltage VB is greater than the limit voltage VL (VB>VL), and is at low level in other sections.

[0033] The thyristor 101 is turned on when the pulse signal VSCR output from the comparison circuit 125 goes high. After that, when the pulse signal VSCR goes low and the AC voltage VA shifts to a negative voltage, the thyristor 101 goes into a reverse bias state and is turned off. That is, the thyristor 101 is in an on state in the section where the triangular wave voltage VB is higher than both the differential voltage VD' and the limit voltage VL, and is in an off state in other sections.

[0034] In this way, the gate control unit 120 controls the conduction state of the thyristor 101 based on the triangular wave voltage VB generated by the triangular wave generating circuit 20, the differential voltage VD' output from the amplifier circuit 124, and the limit voltage VL output from the limit voltage generating circuit 132. In other words, the gate control unit 120 generates a gate signal (pulse signal VSCR) that fires the thyristor 101.

[0035] Next, the triangular wave generating circuit 20 according to this embodiment will be described in detail with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the triangular wave generating circuit 20 according to this embodiment.

[0036] As shown in FIG. 3, the triangular wave generating circuit 20 includes a current generating section 21, a capacitor 22, a charge / discharge control section 23, and an auxiliary charging section 24.

[0037] The current generator 21 generates a predetermined charging current from the constant voltage power supply Vcc to generate the triangular wave signal VB. The current generator 21 charges the capacitor 22 with the generated charging current to generate the triangular wave signal VB. The current generator 21 includes a resistor 211 (resistive element) and a diode 212.

[0038] Resistor 211 (resistive element) generates a predetermined charging current from constant voltage power supply Vcc. Resistor 211 is connected between the power line of constant voltage power supply Vcc and the anode terminal of diode 212. Resistor 211 has a predetermined resistance value and limits (sets) the current flowing from constant voltage power supply Vcc to capacitor 22 to a predetermined current value (predetermined charging current value), thereby generating the predetermined charging current.

[0039] The diode 212 is connected in series with the resistor 211 (resistance element) to prevent backflow to the constant voltage power supply Vcc. The diode 212 has an anode terminal connected to one end of the resistor 211 and a cathode terminal connected to the node N2.

[0040] The capacitor 22 is connected between the node N2 and the ground line. The capacitor 22 is charged with the charging current generated by the current generating unit 21 and discharges the charged current to generate the triangular wave signal VB. The triangular wave generating circuit 20 outputs the triangular wave signal VB from the node N2.

[0041] The charge / discharge control unit 23 charges the capacitor 22 with the charging current supplied from the current generating unit 21 and the auxiliary charging unit 24 during the charging period, which is either a positive voltage half-wave period or a negative voltage half-wave period of the AC signal (AC voltage VA) output by the generator 10 in accordance with the power generated, and discharges the capacitor 22 during the discharging period, which is the other period. That is, the charge / discharge control unit 23 charges and discharges the capacitor 22 during the charging period and discharging period, thereby outputting a triangular wave signal VB from the node N2.

[0042] Here, the charging period is, for example, a half-wave period of a positive voltage of the AC voltage VA, and the discharging period is a half-wave period of a negative voltage of the AC voltage VA. The charge / discharge control unit 23 includes a resistor 231, a resistor 232, a capacitor 233, a resistor 234, an NPN transistor 235, a resistor 236, an NPN transistor 237, and a resistor 238.

[0043] Resistors 231, 232, and capacitor 233 are connected in series between the signal line of AC voltage VA and the ground line. Resistor 231 is connected between the signal line of AC voltage VA and node N3, and resistor 232 is connected between node N3 and node N4. Node N3 is connected to auxiliary charging unit 24, which will be described later, and the voltage at node N3 is used to detect whether the amplitude voltage of AC voltage VA has reached or exceeded a threshold value.

[0044] The capacitor 233 is connected between the node N4 and the ground line. The node N4 is connected to the base terminal of the NPN transistor 235.

[0045] The resistor 234 is connected between the power supply line of the constant voltage power supply Vcc and the node N5. The resistor 234 limits (sets) the current flowing through the NPN transistor 235 and the base current of the NPN transistor 237.

[0046] The NPN transistor 235 (an example of a second transistor) has a collector terminal connected to the node N5, a base terminal connected to the node N4, and an emitter terminal connected to the ground line. The NPN transistor 235 determines whether it is a charging period or a discharging period based on the AC voltage VA, and turns the NPN transistor 237 off (non-conducting) during the charging period and turns the NPN transistor 237 on (conducting) during the discharging period.

[0047] When the AC voltage VA is in a half-wave period of a positive voltage, the node N4 goes high and the NPN transistor 235 is turned on. When the AC voltage VA is in a half-wave period of a negative voltage, the node N4 goes low and the NPN transistor 235 is turned off.

[0048] The resistor 236 is connected between the node N4 and the ground line and functions as a pull-down resistor that sets the base terminal of the NPN transistor 235 to the ground level.

[0049] The NPN transistor 237 (an example of a first transistor) has a collector terminal connected to node N6, a base terminal connected to node N5, and an emitter terminal connected to the ground line. When the AC voltage VA is in a half-wave period of a positive voltage, node N5 becomes low, so that the NPN transistor 237 is turned off. That is, the NPN transistor 237 is turned off during the charging period.

[0050] Furthermore, when the AC voltage VA is in a half-wave period of a negative voltage, the node N5 becomes high level, so that the NPN transistor 237 is turned on and discharges the current charged in the capacitor 22. That is, the NPN transistor 237 is turned on during the discharge period and discharges the current charged in the capacitor 22 via the resistor 238.

[0051] The resistor 238 is connected between the node N2 and the collector terminal of the NPN transistor 237, and limits (sets) the discharge current of the capacitor 22 that flows when the NPN transistor 237 is turned on to a predetermined value.

[0052] When the amplitude voltage of the AC voltage VA output by the generator 10 becomes equal to or greater than a threshold, the auxiliary charging unit 24 adds an auxiliary current according to the amplitude voltage of the AC voltage VA to the charging current generated by the current generating unit 21 to charge the capacitor 22. The auxiliary charging unit 24 includes a Zener diode 241, a resistor 242, and a diode 243.

[0053] The Zener diode 241 has an anode terminal connected to node N8, which is one end of the resistor 242, and a cathode terminal connected to node N3. The Zener diode 241 is turned on when the node N3, which corresponds to the amplitude voltage of the AC voltage VA, is equal to or greater than a threshold. The Zener diode 241 is turned off when the node N3, which corresponds to the amplitude voltage of the AC voltage VA, is less than the threshold. In other words, the auxiliary charging unit 24 uses the Zener diode 241 to determine whether the amplitude voltage of the AC voltage VA is equal to or greater than the threshold.

[0054] The resistor 242 is connected between the node N7 and the node N8, and limits (sets) the value of the auxiliary current that charges the capacitor 22 via the Zener diode 241 and the diode 243.

[0055] The diode 243 has an anode terminal connected to a node N7 which is one end of the resistor 242, and a cathode terminal connected to the node N2. The diode 243 prevents the auxiliary current that charges the capacitor 22 from flowing backward.

[0056] In this way, the auxiliary charging unit 24 uses the Zener diode 241 to determine whether the amplitude voltage of the AC voltage VA has reached or exceeded the threshold value, and when the amplitude voltage of the AC voltage VA has reached or exceeded the threshold value, the Zener diode 241 turns on, and the auxiliary current is added to the charging current to charge the capacitor 22.

[0057] Next, the operation of the triangular wave generating circuit 20 according to this embodiment will be described with reference to the drawings. Figure 4 is a diagram illustrating an example of the operation of the triangular wave generating circuit 20 according to this embodiment when the generator 10 is rotating at a low speed.

[0058] The example shown in Fig. 4 shows the state of the triangular wave generating circuit 20 during the charging period when the generator 10 is rotating at low speed. In Fig. 4, since the AC voltage VA is a positive voltage, first, a base current flows from the signal line of the AC voltage VA to the NPN transistor 235 via a path RT1 that passes through resistors 231 and 232 of the charge / discharge control unit 23, and the NPN transistor 235 turns on.

[0059] Next, when the NPN transistor 235 of the charge / discharge control unit 23 is turned on, a current flows from the power supply line of the constant voltage power supply Vcc through the resistor 234 of the charge / discharge control unit 23, the NPN transistor 235, and the path RT2 of the ground line, and the node N7 becomes low level, thereby turning off the NPN transistor 237 of the charge / discharge control unit 23.

[0060] Next, a charging current I1 flows from the power line of the constant voltage power supply Vcc to the capacitor 22 via a path RT3 including the resistor 211 and diode 212 of the current generating unit 21, charging the capacitor 22 and causing the voltage of the triangular wave signal VB to rise over time.

[0061] In the example shown in Figure 4, since the generator 10 is rotating at a low speed and the amplitude voltage of the AC voltage VA is less than the threshold voltage, the Zener diode 241 of the auxiliary charging unit 24 remains in the off state and no auxiliary current flows.

[0062] 5 is a diagram illustrating an example of the operation of the triangular wave generating circuit 20 according to this embodiment when the generator 10 is rotating at high speed. The example shown in FIG. 5 illustrates the state of the triangular wave generating circuit 20 during a charging period when the generator 10 is rotating at high speed.

[0063] 5 , current flows through paths RT1, RT2, and RT3, and the current generating unit 21 supplies a current I1 to the capacitor 22. Next, in the example shown in FIG. 5 , when the generator 10 is rotating at high speed, the amplitude voltage of the AC voltage VA becomes equal to or greater than the threshold voltage, so the Zener diode 241 of the auxiliary charging unit 24 is turned on. As a result, the auxiliary charging unit 24 additionally supplies an auxiliary current I2 to the capacitor 22 via path RT4, which includes the Zener diode 241, resistor 242, and diode 243. As a result, the charging current to the capacitor 22 becomes a current (I1 + I2), and the capacitor 22 is charged more quickly than in the case of low speed rotation shown in FIG. 4 .

[0064] Next, the operation of the triangular wave generating circuit 20 according to this embodiment when the capacitor 22 is discharged will be described with reference to Fig. 6. Fig. 6 is a diagram illustrating an example of the operation of the triangular wave generating circuit 20 according to this embodiment when the capacitor 22 is discharged.

[0065] The example shown in Fig. 6 shows the state of the triangular wave generating circuit 20 during the discharge period of the generator 10. In Fig. 6, since the AC voltage VA is a negative voltage, the base current does not flow through the above-mentioned path RT1, and the NPN transistor 235 is turned off.

[0066] Next, when the NPN transistor 235 of the charge / discharge control unit 23 is turned off, a base current flows from the power line of the constant voltage power supply Vcc through the resistor 234 of the charge / discharge control unit 23 to the NPN transistor 237 via the path RT5, and the NPN transistor 237 is turned on.

[0067] Next, when the NPN transistor 237 is turned on, a discharge current I3 flows from the capacitor 22 to the ground line via a path RT6 via the resistor 238 and the NPN transistor 237.

[0068] As a result, during the discharge period (the period when the AC voltage VA is negative), the triangular wave generating circuit 20 outputs a voltage equivalent to that of the ground line to the node N2. Note that the discharge current I3 is much larger than the charge current I1 generated by the current generating unit 21 (I3>>I1).

[0069] Next, the effect of the triangular wave generating circuit 20 according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram illustrating an example of the effect of the triangular wave generating circuit 20 according to this embodiment.

[0070] 7, waveforms W1 and W3 represent the voltage waveforms of the AC voltage VA, and waveforms W2 and W4 represent the voltage waveforms of the triangular wave signal VB output by the triangular wave generating circuit 20 according to this embodiment. The horizontal axis of each graph represents time.

[0071] Waveform W1 shows the voltage waveform of the AC voltage VA when the generator 10 is rotating at a low speed, and the period from time T1 to time T2 is the charging period of the triangular wave generating circuit 20, and the period from time T2 to time T3 is the discharging period of the triangular wave generating circuit 20.

[0072] During the charging period from time T1 to time T2, the AC voltage VA is less than the threshold voltage Vth, so the triangular wave generating circuit 20 enters the state shown in Figure 4 above, and the current I1 generated by the current generating unit 21 charges the capacitor 22, causing the triangular wave signal VB to rise (see waveform W2).

[0073] During the discharge period from time T2 to time T3, the triangular wave generating circuit 20 is in the state shown in Figure 6, and the capacitor 22 is discharged by the discharge current I3 (see waveform W2). As a result, the triangular wave generating circuit 20 outputs a triangular wave as shown in waveform W2.

[0074] In contrast, waveform W3 shows the voltage waveform of AC voltage VA when generator 10 is rotating at high speed, with the period from time T4 to time T6 being the charging period of triangular wave generating circuit 20 and the period from time T6 to time T7 being the discharging period of triangular wave generating circuit 20.

[0075] After time T5 during the charging period from time T4 to time T6, the AC voltage VA becomes equal to or greater than the threshold voltage Vth, causing the triangular wave generating circuit 20 to enter the state shown in FIG. 5 . The capacitor 22 is charged with a current (I1+I2) that is the sum of the current I1 generated by the current generating unit 21 and the current I2 (supplementary current) generated by the auxiliary charging unit 24, causing the triangular wave signal VB to rise (see waveform W4). In this case, the triangular wave signal VB of waveform W4 rises faster than the waveform W2 described above because it is replenished by the supplementary current generated by the auxiliary charging unit 24. Therefore, the triangular wave signal VB of waveform W4 rises to a level equivalent to that of the waveform W2 described above.

[0076] During the discharge period from time T6 to time T7, the triangular wave generating circuit 20 is in the state shown in Figure 6, and the capacitor 22 is discharged by the discharge current I3 (see waveform W4). As a result, the triangular wave generating circuit 20 outputs a triangular wave as shown in waveform W4.

[0077] Waveform W5 represents a triangular wave signal generated by a conventional triangular wave generating circuit that does not include the auxiliary charging unit 24 of this embodiment. When the generator 10 is rotating at high speed, the triangular wave signal VB of the triangular wave generating circuit 20 is higher than the triangular wave signal (waveform W5) generated by the conventional triangular wave generating circuit, as shown by waveform W4, and a triangular wave signal VB equivalent to that generated at low speed (equivalent to waveform W2) can be generated.

[0078] As described above, the triangular wave generating circuit 20 according to this embodiment includes a current generating unit 21, a capacitor 22, a charge / discharge control unit 23, and an auxiliary charging unit 24. The current generating unit 21 generates a predetermined charging current from the constant-voltage power supply Vcc. The capacitor 22 generates a triangular wave signal VB by charging with the charging current generated by the current generating unit 21 and discharging the charged current. The charge / discharge control unit 23 charges the capacitor 22 with the charging current during a charging period, which is either a positive voltage half-wave period or a negative voltage half-wave period, of the AC signal (AC voltage VA) output by the generator 10 according to the power generated, and discharges the capacitor 22 during the other period, which is a discharging period. When the amplitude voltage of the AC signal (AC voltage VA) output by the generator 10 exceeds a threshold, the auxiliary charging unit 24 adds an auxiliary current according to the amplitude voltage to the charging current to charge the capacitor 22.

[0079] As a result, even when the rotation speed of the generator 10 increases and the half-wave output period of the AC signal (AC voltage VA) becomes shorter, the triangular wave generating circuit 20 according to this embodiment adds an auxiliary current corresponding to the amplitude voltage of the AC signal (AC voltage VA) to the charging current to charge the capacitor 22, thereby reducing the decrease in the peak voltage of the triangular wave signal VB (see FIG. 7 ), and achieving stable power conversion.

[0080] In this embodiment, the charge / discharge control unit 23 includes an NPN transistor 237 (first transistor) and an NPN transistor 235 (second transistor). The NPN transistor 237 (first transistor) discharges the current charged in the capacitor 22. The NPN transistor 235 (second transistor) determines the charge period and the discharge period based on the AC signal (AC voltage VA), and turns the NPN transistor 237 (first transistor) off (non-conductive) during the charge period and turns the NPN transistor 237 (first transistor) on during the discharge period.

[0081] As a result, the triangular wave generating circuit 20 according to this embodiment can appropriately determine the charging period and discharging period and generate an appropriate triangular wave signal VB using a simple configuration using an NPN transistor 237 (first transistor) and an NPN transistor 235 (second transistor).

[0082] Furthermore, in this embodiment, the auxiliary charging unit 24 determines whether the amplitude voltage of the AC voltage VA is equal to or greater than a threshold value using the Zener diode 241. As a result, the triangular wave generating circuit 20 according to this embodiment can appropriately determine whether the amplitude voltage of the AC voltage VA is equal to or greater than a threshold value with a simple configuration using the Zener diode 241, and can reduce a decrease in the peak voltage of the triangular wave signal VB.

[0083] In this embodiment, the current generating unit 21 includes a resistor 211 (resistive element) and a diode 212. The resistor 211 (resistive element) generates a predetermined charging current from the constant voltage power supply Vcc. The diode 212 is connected in series with the resistor 211 (resistive element) and prevents backflow to the constant voltage power supply.

[0084] As a result, the triangular wave generating circuit 20 according to this embodiment can appropriately generate a constant current charging current for generating a triangular wave with a simple configuration using a resistor 211 (resistive element) and a diode 212, and can reduce the decrease in peak voltage of the triangular wave signal VB.

[0085] In this embodiment, the charging period is a half-wave period of the positive voltage of the AC voltage VA, and the discharging period is a half-wave period of the negative voltage of the AC voltage VA. As a result, the triangular wave generating circuit 20 according to this embodiment can easily generate the triangular wave signal VB in the power conversion device 100, which turns on the switching element (e.g., the thyristor 101) during the half-wave period of the positive voltage.

[0086] The power conversion device 100 according to this embodiment also includes a switching element (e.g., a thyristor 101) and a gate control unit 120. The switching element (e.g., the thyristor 101) rectifies an AC signal (AC voltage VA) output by the generator 10 and supplies the rectified signal to the load unit RL. The gate control unit 120 controls the conduction timing of the switching element (e.g., the thyristor 101) based on the triangular wave signal VB output by the triangular wave generating circuit 20 described above.

[0087] As a result, the power conversion device 100 according to this embodiment has the same effect as the above-described triangular wave generating circuit 20, and can reduce the decrease in peak voltage of the triangular wave signal VB, thereby realizing stable power conversion.

[0088] In this embodiment, the switching element is a thyristor 101, and the gate control unit 120 generates a gate signal (control signal VSCR) that fires the thyristor 101. As a result, the power conversion device 100 according to this embodiment can achieve stable power conversion with a simple configuration using the thyristor 101.

[0089] The present invention is not limited to the above-described embodiment, and modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the generator 10 is a single-phase magneto AC generator, but the present invention is not limited to this, and may be a generator that outputs AC signals of multiple phases (e.g., three phases), or may be another generator.

[0090] Furthermore, in the above embodiment, an example has been described in which the charging period is a half-wave period of the positive voltage of the AC voltage VA and the discharging period is a half-wave period of the negative voltage of the AC voltage VA, but this is not limiting, and the charging period may be a half-wave period of the negative voltage of the AC voltage VA and the discharging period may be a half-wave period of the positive voltage of the AC voltage VA.

[0091] Furthermore, in the above embodiment, an example has been described in which the rise in the AC voltage VA due to high rotation of the generator 10 (the amplitude voltage of the AC voltage VA becoming equal to or greater than a threshold value) is detected using the Zener diode 241, but this is not limitative, and the rise in the AC voltage VA (the amplitude voltage of the AC voltage VA becoming equal to or greater than a threshold value) may be detected by other means.

[0092] In the above embodiment, an example has been described in which NPN transistors are used as the first transistor and the second transistor, but other types of transistors may also be used.

[0093] In the above embodiment, the processing of the gate control unit 120 and the charge / discharge control unit 23 of the triangular wave generating circuit 20 may be realized by software processing or by hardware processing such as an electronic circuit. That is, the gate control unit 120 and the charge / discharge control unit 23 may be realized by circuit means or by software processing that causes a CPU (Central Processing Unit) to execute a program.

[0094] In each of the above-described embodiments, some or all of the functions of the power conversion device 100 may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each of the above-described functions may be individually implemented as a processor, or some or all of the functions may be integrated into a processor.

[0095] Furthermore, the integrated circuit method is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used.

[0096] REFERENCE SIGNS LIST 10 Generator 11 Coil 20 Triangular wave generating circuit 21 Current generating section 22, 233 Capacitor 23 Charging / discharging control section 24 Auxiliary charging section 100 Power conversion device 101 Thyristor 102, 103, 211, 231, 232, 234, 236, 238, 242 Resistor 120 Gate control section 121 Voltage conversion circuit 122 Reference voltage generating circuit 123 Differential circuit 124 Amplifying circuit 125 Comparison circuit 131 Start circuit 132 Limit voltage generating circuit 212, 243 Diode 241 Zener diode 235, 237 NPN transistor RL Load section

Claims

1. A triangular wave generating circuit comprising: a current generating unit that generates a predetermined charging current from a constant voltage power supply; a capacitor that generates a triangular wave signal by charging the charging current generated by the current generating unit and discharging the charged current; a charge / discharge control unit that charges the capacitor with the charging current during a charging period, which is either a positive voltage half-wave period or a negative voltage half-wave period of an AC signal output by a generator in accordance with the power generated, and discharges the capacitor during a discharging period, which is the other period; and an auxiliary charging unit that, when the amplitude voltage of the AC signal output by the generator becomes equal to or greater than a threshold, charges the capacitor with an auxiliary current corresponding to the amplitude voltage in addition to the charging current.

2. The triangular wave generating circuit according to claim 1, wherein the charge / discharge control section comprises: a first transistor that discharges the current charged in the capacitor; and a second transistor that determines the charging period and the discharging period based on the AC signal, and brings the first transistor into a non-conducting state during the charging period and brings the first transistor into a conducting state during the discharging period.

3. The triangular wave generating circuit according to claim 1, wherein the auxiliary charging section uses a Zener diode to determine whether the amplitude voltage is equal to or greater than the threshold value.

4. The triangular wave generating circuit according to claim 1, wherein the current generating section comprises: a resistive element that generates the predetermined charging current from the constant voltage power supply; and a diode that is connected in series with the resistive element and prevents backflow to the constant voltage power supply.

5. The triangular wave generating circuit according to claim 1, wherein the charging period is a half-wave period of the positive voltage, and the discharging period is a half-wave period of the negative voltage.

6. A power conversion device comprising: a switching element that rectifies the AC signal output by the generator and supplies it to a load; and a gate control unit that controls the conduction timing of the switching element based on the triangular wave signal output by the triangular wave generating circuit described in any one of claims 1 to 5.

7. The power conversion device according to claim 6, wherein the switching element is a thyristor, and the gate control unit generates a gate signal that fires the thyristor.

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