Pulse current output device

Abstract

The pulse current output device (1) includes a current limiting circuit (11) that limits a current input from an external power source by dynamically controlling the resistance value of a semiconductor element, capacitors (12, 15, 17) that store electric charge based on the current limited by the current limiting circuit, a pulse output control unit (18) that controls the pulse output time in accordance with a predetermined pulse output time ratio, and a pulse output switching circuit (19) that outputs the electric charge stored in the capacitor to the outside in accordance with the control from the pulse output control unit.

Description

[Technical field]

[0001] The present disclosure relates to a pulse current output device. [Background technology]

[0002] There is a need to capture images of fast-moving products, equipment, jigs, etc. for purposes such as visual inspection of products in factories, alignment control for positioning during product processing, and observation of the operation of high-speed mechanical devices. In particular, for visual inspection and alignment control, lighting fixtures that only illuminate the object to be photographed for a very short period of time, i.e., lighting fixtures that light up with a strobe, are sometimes used to obtain clear images without blur. In recent years, the use of LED lighting fixtures that use LEDs (Light Emitting Diodes) as a light source has been rapidly increasing due to their advantages such as long life and low power consumption.

[0003] When lighting an LED, the amount of current is generally controlled to control the amount of light. For example, the amount of current is controlled to match the specifications of the LED lighting fixture by combining a voltage control circuit that maintains a specified voltage with a current limiting resistor mounted on the LED side. When a voltage control circuit is combined with a current limiting resistor, the voltage and current are not proportional, so even a small voltage drop will cause a large decrease in the amount of current, and therefore the amount of light. For this reason, maintaining the output voltage is an important issue. In particular, to obtain clear images without blur, it is desirable to irradiate with a brighter amount of light in a shorter period of time, so maintaining the output voltage is even more important.

[0004] In addition, LED lighting fixtures that use strobe lighting have a duty ratio (lighting time ratio) that is determined by the product specifications. For example, even if a pulse current output device that outputs a pulse current of 2400 W is used, if the duty ratio is 1%, the required power capacity is about 24 W on average.

[0005] Patent Document 1 discloses an LED strobe lighting power supply device including a pulse current output device in which a capacitor for suppressing a voltage drop is provided between the positive and negative voltage input terminals of a constant voltage circuit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-220349 A Summary of the Invention [Problem to be solved by the invention]

[0007] The pulse current output device included in the LED strobe lighting power supply device described in Patent Document 1 requires a capacitor with a sufficiently large capacity as a capacitor for suppressing voltage drops, and a large charging current flows suddenly from the AC / DC converter when starting up and recharging after pulse output. To deal with this, a resistor is used to limit the current, but with current limiting by a resistor, the amount of current decreases when the AC / DC converter and the capacitor for suppressing voltage drops are close to the same potential, and there is also a loss due to the resistor, so the charging of the capacitor becomes slow. To shorten the charging time, a switching power supply with a power supply capacity larger than the required power supply capacity when averaged based on the duty ratio is required. As a result, the required power supply capacity increases and heat dissipation increases the size of the device using the pulse current output device, and the cost also increases.

[0008] The present disclosure has been made to solve the problems described above, and aims to reduce the required power supply capacity of a pulse current output device and to reduce the size and cost of an apparatus that uses a pulse current output device. [Means for solving the problem]

[0009] In order to achieve the above object, the pulse current output device according to the present disclosure includes a current limiting circuit, a capacitor, a pulse output control unit, and a pulse output switching circuit. , a step-up / step-down circuit, and a voltage monitoring circuitThe current limiting circuit limits a current input from an external power source by dynamically controlling a resistance value of a semiconductor element. The capacitor stores an electric charge based on the current limited by the current limiting circuit. The pulse output control unit controls the pulse output time in accordance with a predetermined ratio of the pulse output time. The pulse output switching circuit outputs the electric charge stored in the capacitor to the outside in accordance with the control from the pulse output control unit. The step-up / step-down circuit steps up and down the voltage. The voltage monitoring circuit controls the operation of the step-up / step-down circuit. The capacitor includes a first capacitor that stores the charge of the current limited by the current limiting circuit and a second capacitor that stores the charge stored in the first capacitor via the step-up / step-down circuit. The voltage monitoring circuit monitors the voltage of the first capacitor and controls the operation of the step-up / step-down circuit based on the voltage of the first capacitor. Effect of the Invention

[0010] According to the present disclosure, by providing a current limiting circuit that dynamically controls the resistance value of a semiconductor element, it is possible to charge a capacitor quickly within the limited current, reduce the required power supply capacity of a pulse current output device, and reduce the size and cost of an apparatus that uses the pulse current output device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a configuration example of a pulse current output device according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing an example of a current limiting circuit according to a first embodiment; [Diagram 3] FIG. 1 is a diagram showing an example in which an inductor is inserted into a current limiting circuit according to a first embodiment; [Figure 4] FIG. 13 is a diagram showing another example in which an inductor is inserted into the current limiting circuit according to the first embodiment; [Diagram 5] FIG. 13 is a graph comparing the inrush current suppression effect of the current limiting circuit according to the first embodiment; [Figure 6] FIG. 1 is a graph showing proactive control of current using the inductance of the current limiting circuit according to the first embodiment; [Figure 7] FIG. 1 is a graph showing a difference in operation between current limiting using the current limiting circuit according to the first embodiment and current limiting using a resistor; [Figure 8] FIG. 1 is a graph showing the relationship between the input capacitor voltage and the main capacitor voltage at start-up when there is and is not voltage monitoring according to the first embodiment; [Figure 9] FIG. 1 is a diagram showing an example of a voltage monitoring circuit according to a first embodiment; [Figure 10] FIG. 1 is a diagram showing an example of a high-speed voltage compensation circuit according to a first embodiment; [Figure 11] FIG. 1 is a graph showing a boost control operation by a boost capacitor of the high-speed voltage compensation circuit according to the first embodiment; [Figure 12] FIG. 1 is a diagram showing an example of a circuit that charges a boost capacitor in a high-speed voltage compensation circuit according to a first embodiment; [Figure 13] FIG. 1 is a diagram showing an example in which a Zener diode for protecting an operational amplifier is added to a circuit for charging a boost capacitor in a high-speed voltage compensation circuit according to a first embodiment; [Figure 14] FIG. 1 is a diagram showing an example in which a simple voltage compensation circuit is added as a bypass to a circuit that charges a boost capacitor in a high-speed voltage compensation circuit according to a first embodiment; [Figure 15] FIG. 1 is a graph showing a charging operation when a simple voltage compensation circuit is added as a bypass to a circuit that charges a boost capacitor in the high-speed voltage compensation circuit according to the first embodiment; [Figure 16] FIG. 1 is a diagram showing an example in which a charge pump circuit is added to a circuit that charges a boost capacitor in the high-speed voltage compensation circuit according to the first embodiment; [Figure 17] FIG. 13 is a diagram showing an example of the configuration of a pulse current output device provided with a plurality of LED channels according to a second embodiment. [Figure 18] FIG. 13 is a diagram showing another example of the configuration of a pulse current output device provided with a plurality of LED channels according to the second embodiment. [Figure 19] FIG. 13 is a graph showing changes in current and voltage when the LEDs of four channels of the pulse current output device according to the second embodiment are continuously turned on; [Figure 20] FIG. 13 is a diagram showing an example of a power supply circuit that uses a high-speed voltage compensation circuit according to a third embodiment and prevents a voltage drop when an inrush current occurs. [Figure 21] FIG. 13 is a diagram showing an example of a low-ripple power supply circuit using a high-speed voltage compensation circuit according to a third embodiment. [Figure 22]FIG. 13 is a diagram showing an example of a level shift circuit using a boost capacitor according to a fourth embodiment; [Figure 23] FIG. 13 is a graph showing high-speed high-voltage level shifting of a pulse signal in a level shift circuit according to a fourth embodiment; [Figure 24] FIG. 13 is a graph showing high-speed transmission between a low-side pulse signal and a high-side pulse signal in a level shift circuit according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a pulse current output device according to the present embodiment will be described in detail with reference to the drawings, in which the same or corresponding parts are given the same reference numerals.

[0013] (Embodiment 1) The configuration of the pulse current output device 1 according to the first embodiment will be described with reference to FIG. 1. The pulse current output device 1 includes a current limiting circuit 11 for limiting the current input to the power source, an input capacitor 12 for storing the charge of the current that has passed through the current limiting circuit 11, a voltage monitoring circuit 13 for monitoring the voltage of the input capacitor 12, a step-up / step-down circuit 14 for stepping up / down the voltage, a main capacitor 15 for storing the charge that has passed through the step-up / step-down circuit 14, a high-speed voltage compensation circuit 16 for compensating the voltage, an output capacitor 17 for storing the charge that has passed through the high-speed voltage compensation circuit 16, a pulse output control unit 18 for controlling the pulse output that lights up the external LED 2, and a pulse output switching circuit 19 for lighting up the external LED 2 using the charge stored in the output capacitor 17. The input capacitor 12 is an example of a first capacitor. The main capacitor 15 is an example of a second capacitor. The high-speed voltage compensation circuit 16 is an example of a voltage compensation circuit. The output capacitor 17 is an example of a third capacitor.

[0014] The current input from an external power source is limited by the current limiting circuit 11, and the charge is stored in the input capacitor 12. The charge stored in the input capacitor 12 is stored in the main capacitor 15 via the step-up / step-down circuit 14. At this time, the voltage monitoring circuit 13 monitors the voltage of the input capacitor 12, and if the voltage does not reach a predetermined voltage, the step-up / step-down operation of the step-up / step-down circuit 14 is stopped. The charge stored in the main capacitor 15 is stored in the output capacitor 17 via the high-speed voltage compensation circuit 16. The pulse output control unit 18 controls the pulse output switching circuit 19 in accordance with a predetermined duty ratio (lighting time ratio), so that the charge stored in the output capacitor 17 is output from the pulse output switching circuit 19, and the lighting of the external LED 2 is controlled. The duty ratio is an example of the ratio of the pulse output time.

[0015] In addition, the external power supply may be not only a DC power supply but also an AC power supply. When an AC power supply is used, a rectifier circuit is provided in front of the current limiting circuit 11, and the current that passes through the rectifier circuit passes through the current limiting circuit 11, and the charge is stored in the input capacitor 12.

[0016] Here, the current limiting circuit 11 will be described with reference to Figs. 2, 3 and 4. The current limiting circuit 11-1 shown in Fig. 2 is an example in which a minute voltage dropped by a shunt resistor 61 for measuring current is measured, and the resistance value of a P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) element 63 is changed so that the specified voltage is obtained by an operational amplifier 62, thereby controlling the current amount to be equal to or less than a certain amount. The P-channel MOSFET element 63 is an example of a semiconductor element. For example, if the specifications of the pulse current output device 1 are an output voltage of 48V, a maximum output current of 50A, and a duty ratio of 1%, the average power is 48V x 50A x 0.01 = 24W. If the input voltage is 24V, the required current amount is 24W / 24V = 1A, but in consideration of the conversion efficiency during boosting and various losses in the circuit, the current may be limited to, for example, twice as much, 2A. In this case, if the resistance value of the shunt resistor 61 is 0.1 Ω, the comparison voltage 64 of the operational amplifier 62 is designed so that the potential difference is 0.2 V. The circuit that controls the resistance value of the P-channel MOSFET element 63 including the operational amplifier 62 is an example of a first feedback circuit.

[0017] However, for example, at start-up, the control of the operational amplifier 62 may not be in time, and an inrush current may occur. The period of high current is extremely short compared to when the current is limited by a resistor as in the technology described in Patent Document 1, and the configuration of the current limiting circuit 11-1 may be acceptable depending on the power supply specifications, but in order to prevent this inrush current, as shown in Figure 3, an inductor 71 may be inserted in the current path of the current limiting circuit 11-1 to form a current limiting circuit 11-2, or as shown in Figure 4, an inductor 81 may be inserted in the current path of the current limiting circuit 11-1 to form a current limiting circuit 11-3.

[0018] FIG. 5 is a graph comparing the suppression effect of the inrush current in each of the configurations shown in FIG. 2, FIG. 3, and FIG. 4. Graph 91 is the current limited by the current limiting circuit 11-1 shown in FIG. 2, graph 92 is the current limited by the current limiting circuit 11-2 shown in FIG. 3, and graph 93 is the current limited by the current limiting circuit 11-3 shown in FIG. 4. As shown in graph 92, in the current limiting circuit 11-2, the inductance of the inductor 71 is used to suppress a sudden change in current, so that the inrush current can be slowed down more than in the current limiting circuit 11-1. As shown in graph 93, in the current limiting circuit 11-3, the inductance of the inductor 81 is used to feed back the potential difference of the induced electromotive force that occurs prior to the change in current to the operational amplifier 62, so that the operation of the operational amplifier 62 can be preceded. Since the potential difference for measuring the current is generally less than 1V, the potential difference of the induced electromotive force may be small, and an inductor of several μH has a sufficient effect.

[0019] 6 is a graph showing proactive current control using inductance in the current limiting circuit 11-3. The voltage caused by the inductance shown in graph 101 changes prior to the current change shown in graph 103. The voltage change is fed back to the operational amplifier 62, which starts control shown in graph 104 with a delay from the voltage change, and the necessary control is completed before the current change overshoots. As a result, it is possible to prevent inrush current, as shown in graph 93 of FIG. 5.

[0020] Returning to FIG. 4, in the current limiting circuit 11-3, the potential difference between the terminal 84a and the terminal 84b fed back to the operational amplifier 62 in a balanced state is the sum of the potential differences due to the shunt resistor 61 and the series resistance of the inductor 81 when the induced electromotive force of the inductor 81 becomes 0V. However, the series resistance of an inductor generally has a larger accuracy error than the shunt resistor used for current measurement. For this reason, to improve the accuracy of the current limiting, it is better to use an inductor whose series resistance is sufficiently smaller than the shunt resistor. For example, when using a shunt resistor of 0.1Ω, it is better to use an inductor with a series resistance of 0.02Ω. Generally, the accuracy error of the series resistance of an inductor is ±20%. For this reason, for example, when a shunt resistor of 0.1Ω±1% is combined with an inductor of 0.02Ω±20%, the total resistance falls within 0.12Ω±5%.

[0021] Here, the change in the voltage of the input capacitor 12 when the current limiting circuit 11-3 is used to limit the current is compared with the change in the voltage of the input capacitor 12 when the current limiting circuit 11-3 is used to limit the current. FIG. 7 is a graph showing the difference in operation between the current limiting circuit 11-3 and the current limiting circuit 11-3. The current graph 111 and the voltage graph 113 of the input capacitor 12 correspond to the current limiting circuit 11-3, and the current graph 112 and the voltage graph 114 of the input capacitor 12 correspond to the current limiting circuit 11-3. In the current limiting circuit 11-3, a large current flows at first, and the current value gradually drops. In accordance with this, the voltage of the input capacitor 12 rises and stagnates. In contrast, in the current limiting circuit 11-3, the current transitions in a rectangular waveform, and the voltage of the input capacitor 12 rises proportionally. In current limiting using current limiting circuit 11-3, the voltage of input capacitor 12 overshoots due to the inductance of inductor 81. However, since there is voltage boost / buck circuit 14 in the subsequent stage, the voltage accuracy of input capacitor 12 is not important. Conversely, the overshoot has the effect of making the operation of voltage boost / buck circuit 14 more efficient.

[0022] Generally, the step-up / step-down of the step-up / step-down circuit 14 can be performed using either a method using inductance such as an inductor or a transformer, or a charge pump method using a capacitor. Here, an example of step-up using an inductor or an isolated step-up / step-down using a transformer will be described. In particular, in the case of an isolated step-up / step-down using a transformer, the step-up and step-down functions differ between the input and output voltages, but generally, the operation of switching the output side capacitor to step up or maintain a specified voltage while transmitting power in an isolated manner by electromagnetic induction due to switching remains the same.

[0023] When the amount of current consumed by the step-up / step-down circuit exceeds a certain amount relative to the amount of current supplied by the power supply or current limiting circuit 11, the voltage of the input capacitor 12 drops, significantly reducing the step-up / step-down efficiency. For this reason, a voltage monitoring circuit 13 is provided to monitor the voltage of the input capacitor 12, and when the voltage falls below a certain voltage, the operation of the step-up / step-down circuit is stopped, and when the voltage exceeds the certain voltage, the operation of the step-up / step-down circuit is started.

[0024] FIG. 8 is a graph showing the relationship between the voltage of the input capacitor 12 and the voltage of the main capacitor 15 at the time of start-up in the cases with and without voltage monitoring. In the case without voltage monitoring, when the amount of current consumed by the step-up / step-down circuit exceeds a certain amount, the voltage of the input capacitor 12 shown in graph 121 drops significantly, and the voltage of the main capacitor 15 shown in graph 122 does not rise at all. In addition, the voltage difference between the power supply voltage and the voltage of the input capacitor 12 increases, and a huge loss calculated by multiplying the voltage difference by the amount of current occurs in the current limiting circuit 11. In response to this, the voltage of the input capacitor 12 shown in graph 123 is monitored so as not to drop in voltage, and when the voltage of the step-up / step-down circuit 14 is stopped operating when the voltage falls below a certain voltage, the voltage of the main capacitor 15 shown in graph 124 is quickly boosted to an appropriate voltage. In addition, by preventing the voltage of the power supply voltage from deviating from the voltage of the input capacitor 12, the loss occurring in the current limiting circuit 11 can be suppressed.

[0025] 9 is an example of the voltage monitoring circuit 13. The power supply voltage and the voltage of the input capacitor 12, which are respectively input to the input terminal 133 and the input terminal 134 of the comparator 132, are compared at a ratio based on voltage division, and if the voltage falls below a threshold, the operation of the step-up / step-down circuit 14 is stopped. For example, if the voltage of the input capacitor 12 is less than 95% of the power supply voltage, a signal for disabling the switching operation for step-up / step-down of the step-up / step-down circuit 14 is output from the output terminal 135 of the comparator 132, thereby stopping the consumption of charge in the input capacitor 12.

[0026] Next, the high-speed voltage compensation circuit 16 will be described with reference to Figs. 10 to 14. In the high-speed voltage compensation circuit 16-1 shown in Fig. 10, the main capacitor 15 charged by the step-up / step-down circuit 14 is connected to the drain terminal of the N-channel MOSFET element 142, and the output capacitor 17 for LED output is connected to the source terminal. In this embodiment, the main capacitor 15 is assumed to vary between 50V and 55V, and the output capacitor 17 is intended to be fixed at 48V. For this reason, the operational amplifier 144 compares the voltage of the output capacitor 17 with a reference voltage, and controls the resistance value of the N-channel MOSFET element 142 so that the output capacitor 17 becomes 48V. A boost capacitor 145 for boosting is inserted between the gate terminal of the N-channel MOSFET element 142 and the operational amplifier 144. That is, the boost capacitor 145 and the operational amplifier 144 are connected in series to the N-channel MOSFET element 142. The circuit that controls the resistance value of the N-channel MOSFET element 142 including the operational amplifier 144 is an example of a second feedback circuit. The operational amplifier 144 is on the low side of the low voltage, and the output capacitor 17 is on the high side of the high voltage. The low side and the high side share a ground voltage.

[0027] FIG. 11 is a graph showing the boost control operation by the boost capacitor 145. Graph 151 is the charging voltage of the boost capacitor 145, graph 152 is the voltage of the source terminal of the N-channel MOSFET element 142, graph 153 is the voltage applied to the gate terminal of the N-channel MOSFET element 142, and graph 154 is the output voltage of the operational amplifier 144. As shown in FIG. 11, the boost capacitor 145, which has a capacitance sufficiently large compared to the capacitance of the gate terminal, is charged to a constant voltage based on 48V, which is the designated voltage of the output capacitor 17. The boost capacitor 145 boosts the output voltage of the operational amplifier 144 to a voltage higher than the voltage of the source terminal of the N-channel MOSFET element 142 without delay, and applies it to the gate terminal of the N-channel MOSFET element 142. In other words, the constant voltage to which the boost capacitor 145 is charged is a voltage that can boost the output voltage of the operational amplifier 144 to a voltage higher than the voltage of the source terminal of the N-channel MOSFET element 142 without delay.

[0028] Generally, the lower the voltage range of a semiconductor element, the faster it can operate and the cheaper it is. In addition, for this purpose, the resistance value of the MOSFET element is used within a limited range, so a voltage applied to the gate terminal of the MOSFET element with a potential difference of 5V with respect to the voltage of the source terminal is sufficient. In other words, by providing the boost capacitor 145, the power supply voltage of the operational amplifier 144 is also sufficient at 5V. Therefore, the number of options for the operational amplifier 144 is increased, making it easy to select one with priority given to speed, and providing the boost capacitor 145 is an effective configuration for realizing a high-speed voltage compensation circuit. In addition, it is also advantageous that a high-speed, low-cost N-channel can be used by boosting the voltage to a voltage higher than the voltage of the source terminal of the MOSFET element.

[0029] The high-speed voltage compensation circuit 16-2 shown in FIG. 12 is an example including a circuit for charging the boost capacitor 145 in addition to the configuration of the high-speed voltage compensation circuit 16-1. By connecting a diode 146 between the connection part of the gate terminal of the N-channel MOSFET element 142 and the boost capacitor 145 and the connection part of the source terminal of the N-channel MOSFET element 142 and the output capacitor 17, the boost capacitor 145 is charged when the potential is lower than that of the source terminal of the N-channel MOSFET element 142. In the case of a switching element having an insulated gate terminal such as a MOSFET or an IGBT (Insulated Gate Bipolar Transistor), no current flows between the gate terminal and other terminals. In addition, when the gate terminal of the N-channel MOSFET element is at a higher potential than the source terminal of the N-channel MOSFET element, the charging voltage of the boost capacitor 145 is maintained due to the backflow prevention effect of the diode.

[0030] In this case, by using a Zener diode for diode 146, it is possible to prevent the application of an overvoltage to the gate terminal of N-channel MOSFET element 142. For example, if the operating power supply for low-side operational amplifier 144 is 5V, a Zener diode with a Zener voltage of about 5.6V should be used to match the low-side voltage. Note that application of an overvoltage can also occur when, in addition to a surge, output capacitor 17 is discharged due to a power outage, making it impossible to maintain 48V. In this case, discharging boost capacitor 145 in accordance with the voltage drop of output capacitor 17 is a rational operation.

[0031] When charging the boost capacitor 145, the voltage at the output terminal of the operational amplifier 144 may be raised, and may exceed the allowable operating voltage of the operational amplifier 144. For this reason, in the high-speed voltage compensation circuit 16-3 shown in FIG. 13, in addition to the configuration of the high-speed voltage compensation circuit 16-2, a Zener diode 147 is connected to the output terminal of the operational amplifier 144 to protect the operational amplifier 144. For example, if the operating power supply of the operational amplifier 144 is 5V, it is advisable to use a Zener diode of about 5.6V, which is slightly higher than 5V. Note that, although a configuration in which a diode is used to clamp the operating power supply of the operational amplifier 144 may be used, it is simpler to use a Zener diode since there are cases in which the 5V power supply is raised.

[0032] 13, the output capacitor 17 must be charged before the boost capacitor 145 is charged, whereas the boost capacitor 145 must be charged in advance to charge the output capacitor 17 so that a higher voltage can be applied to the gate terminal of the N-channel MOSFET element 142 than to the source terminal. Therefore, in the high-speed voltage compensation circuit 16-4 shown in FIG. 14, in addition to the configuration of the high-speed voltage compensation circuit 16-3, a simple voltage compensation circuit 181 configured by connecting a PNP bipolar transistor 182 and an NPN bipolar transistor 183 to the output terminal of the same operational amplifier 144 is added as a bypass. The simple voltage compensation circuit 181 does not need to perform high-speed voltage compensation, and it is sufficient that the compensation speed is faster than the speed at which the main capacitor 15 is charged in the step-up / step-down circuit 14.

[0033] For example, if the specifications of the pulse current output device 1 are an output voltage of 48 V, a maximum output current of 50 A, and a duty ratio of 1%, the average current amount is 0.5 A. Therefore, the current amount required for voltage compensation is sufficient to be twice as much, that is, 1 A. Therefore, it is sufficient to select components and determine the resistance value for the PNP bipolar transistor 182 that can pass a current of 1 A.

[0034] Fig. 15 is a graph showing the charging operation of the high-speed voltage compensation circuit 16-4 shown in Fig. 14. Graph 191 is the output terminal voltage of the operational amplifier 144, graph 192 is the charging voltage of the boost capacitor 145, graph 193 is the gate terminal voltage of the N-channel MOSFET element 142, graph 194 is the voltage of the output capacitor 17, and graph 195 is the voltage of the main capacitor 15. When the voltage of the output capacitor 17 does not reach the designated voltage of 48V, the output terminal voltage of the operational amplifier 144 is output as the power supply voltage of 5V for the operational amplifier 144, and the output capacitor 17 is charged via the simple voltage compensation circuit 181. As shown in graph 192, the boost capacitor 145 is charged with a voltage obtained by subtracting the Zener voltage of the Zener diode from the voltage of the output capacitor 17. When the voltage of output capacitor 17 shown in graph 194 reaches the specified voltage of 48 V, simple voltage compensation circuit 181 stops its voltage compensation operation, so that the output terminal voltage of operational amplifier 144 shown in graph 191 drops to the ground voltage, and the voltage of boost capacitor 145 shown in graph 192 becomes close to the voltage of output capacitor 17 shown in graph 194, and charging of boost capacitor 145 is completed.

[0035] In the pulse current output device 1, there is a restriction on the continuous output time based on the amount of energy that can be stored in the main capacitor 15, and there is a state in which the pulse current output is not operated for a sufficiently long time at short intervals due to the specifications of the duty ratio. In this state, the boost capacitor is in a charging operation, so there is no problem, but if the output state continues, charging will not be possible and a voltage drop due to natural discharge of the boost capacitor 145 will become a problem. In this case, in addition to the method of charging using an isolated power supply, a voltage compensation circuit 16-5 may be configured more simply by providing a charge pump circuit 201 that utilizes repeated switching in addition to the configuration of the high-speed voltage compensation circuit 16-3, as shown in FIG. 16. This is a countermeasure against natural discharge, and since a sudden voltage change in the boost capacitor 145 affects the voltage compensation operation and is undesirable, it is preferable to use resistors 202 and 203 with a high resistance value of, for example, 100 KΩ or more in the charge pump circuit 201 so that charging can be performed with a small current.

[0036] According to the pulse current output device 1 of the first embodiment, by providing a current limiting circuit that dynamically controls the resistance value of the semiconductor element, it is possible to charge the capacitor quickly within the limited current, reduce the required power supply capacity of the pulse current output device, and reduce the size and cost of the device that uses the pulse current output device.

[0037] (Embodiment 2) In the second embodiment, a plurality of LEDs are connected and lighted at different timings. The configurations of the pulse current output device 1-1 and the pulse current output device 1-2 according to the second embodiment will be described with reference to Figs. 17 and 18, respectively. The pulse current output device 1-1 shown in Fig. 17 is an example of a configuration in which the circuit upstream of the output capacitor 17 and the pulse output control unit 18 are shared, and two channels are provided: a pulse output switching circuit 19-1 and an external LED 2-1, and a pulse output switching circuit 19-2 and an external LED 2-2. The pulse current output device 1-2 shown in Fig. 18 is an example of a configuration in which the circuit upstream of the main capacitor 15 and the pulse output control unit 18 are shared, and two channels are provided: a high-speed voltage compensation circuit 16-1, an output capacitor 17-1, a pulse output switching circuit 19-1, and an external LED 2-1, and a high-speed voltage compensation circuit 16-2, an output capacitor 17-2, a pulse output switching circuit 19-2, and an external LED 2-2. In Figs. 17 and 18, for the sake of convenience, the number of LED channels is shown as two, but it may be three or more.

[0038] The configuration in Figure 18 is preferable because a sudden change due to the start or end of pulse output may affect other channels, but the configuration in Figure 17 may be sufficient depending on product specifications such as the allowable brightness variation and lighting pattern restrictions.

[0039] 19 is a graph showing the change in voltage of main capacitor 15 when four channels of LEDs are continuously lit. Graphs 231 to 234 show the current flowing through the LEDs of each channel, graph 235 shows the voltage of output capacitor 17, and graph 236 shows the voltage of main capacitor 15.

[0040] Generally, the duty ratio is a setting for the lighting time ratio for each channel for the purpose of protecting the LED. The required storage capacity of the main capacitor 15 is the number of channels × the maximum output power of each channel × the maximum lighting time of each channel. However, in the case of a product intended to be lit strongly and briefly, it is rare to use the maximum lighting time specified in the specifications. For this reason, if the product is designed assuming continuous lighting for the maximum lighting time, there is a high possibility that the device size, materials, and costs will be wasted. In response to this, for example, data indicating the remaining amount of the main capacitor 15 is recorded and notified to the user every time the minimum value of the main capacitor 15 is updated, and if there is a rare shortage, the method of use is changed, so that the storage capacity of the main capacitor 15 does not need to be the number of channels × the maximum output power of each channel × the maximum lighting time of each channel, and the problem of the above-mentioned device size, materials, and costs being wasted can be solved.

[0041] Specifically, measures to change the usage method include shortening the lighting time or increasing the lighting interval to allow for charging time. If these measures are difficult, multiple pulse current output devices can be prepared. The data indicating the remaining charge of the main capacitor 15 is an example of voltage information.

[0042] In order to realize high-speed and flexible control, the pulse output control section 212 and the pulse output control section 222 are preferably programmable devices such as a field programmable gate array (FPGA) or a complex programmable logic device (CPLD). Since it is relatively easy for these devices to record data in an internal register and perform external communication, it is preferable to configure the device so that data indicating the remaining capacity of the main capacitor 15 is recorded in the pulse output control section 212 and the pulse output control section 222 via an AD converter and notified to the user. In this case, the pulse output control section 212 and the pulse output control section 222 are examples of a voltage information recording section. The voltage information recording section may be provided separately from the pulse output control section 212 and the pulse output control section 222.

[0043] According to pulse current output device 1-1 and pulse current output device 1-2 of embodiment 2, even when a plurality of LEDs are connected and turned on at different timings, by providing a current limiting circuit that dynamically controls the resistance value of the semiconductor element, it is possible to quickly charge the capacitor within the limited current, reduce the required power supply capacity of the pulse current output device, and reduce the size and cost of the device that uses the pulse current output device.

[0044] (Embodiment 3) A high-speed voltage compensation circuit is also useful for applications other than a pulse current output device. In the third embodiment, the high-speed voltage compensation circuit is used in a power supply. The configuration of a power supply circuit using the high-speed voltage compensation circuit according to the third embodiment will be described with reference to Figs. 20 and 21.

[0045] The power supply circuit shown in Fig. 20 uses a high-speed voltage compensation circuit to prevent a voltage drop when an inrush current occurs. An output capacitor 245 is charged to an appropriate voltage from the power supply input. In parallel, a voltage compensation capacitor 243 is charged to a voltage higher than the output capacitor 245 via a boost circuit 242 from the power supply input.

[0046] When the current consumption of the external circuit 246 can be covered by the supply current of the power supply input, the voltage of the output capacitor 245 is maintained, but when the current consumption cannot be covered by the supply current of the power supply input, such as in the case of an inrush current, the voltage of the output capacitor 245 drops. When the voltage of the output capacitor 245 drops, the high-speed voltage compensation circuit 244 operates to transfer charge from the voltage compensation capacitor 243 to the output capacitor 245, and performs voltage compensation so as to maintain the designated voltage of the output capacitor 245. At this time, it is preferable to configure the voltage compensation trigger to be lowered by, for example, 0.5 V. This makes it possible to prevent a voltage drop due to an inrush current of several μs to several ms, while reducing the capacity of the output capacitor 245 for voltage smoothing due to current fluctuations, and thus to reduce the size of the power supply device.

[0047] The power supply circuit shown in Fig. 21 is a low-ripple power supply circuit that uses a high-speed voltage compensation circuit. Fluctuations in the power supply input that are greater than the voltage compensation speed are removed by low-pass filter 252, and then electricity is stored in voltage compensation capacitor 253. When the amount of current changes due to external circuit 256, high-speed voltage compensation circuit 254 quickly compensates the voltage to maintain the voltage of output capacitor 255, making it possible to configure a low-cost power supply with almost no ripple even during output. Note that with this configuration, the natural discharge countermeasures shown in Fig. 16 are necessary.

[0048] According to the power supply circuit of the third embodiment, the size of the power supply device that prevents a voltage drop when an inrush current occurs can be reduced by using a high-speed voltage compensation circuit. In addition, the cost of the low-ripple power supply device can be reduced by using a high-speed voltage compensation circuit.

[0049] (Embodiment 4) The boost capacitor, which boosts the input voltage without delay, is also useful for purposes other than the pulse current output device. In the fourth embodiment, the boost capacitor is used in a level shift circuit for a pulse signal. The configuration of the level shift circuit using the boost capacitor according to the fourth embodiment will be described with reference to FIG.

[0050] The level shift circuit shown in FIG. 22 shifts the level of a 3.3V pulse signal to a 48V pulse signal at high speed. A low-side pulse signal 261 is inverted by an inverter circuit 262, boosted by a boost capacitor 263 charged to a constant voltage based on the difference between the low-side voltage and the high-side voltage, and the voltage is applied to the gate terminal of a high-side P-channel MOSFET 266 without delay, thereby enabling high-speed level shifting. The P-channel MOSFET 266 is an example of a semiconductor element having an insulated gate terminal. In other words, the constant voltage to which the boost capacitor 263 is charged is a voltage that can boost the low-side pulse signal 261 to the high-side voltage without delay. The low side and the high side share a ground voltage.

[0051] Generally, a cause of a decrease in transmission speed when the voltage is increased is the Miller effect that occurs when voltage is amplified, which is due to the voltage difference between the terminals of a semiconductor switching element. However, by using boost capacitor 263, voltage amplification by a semiconductor switching element is no longer necessary, making it possible to minimize the decrease in transmission speed.

[0052] 22, by providing Zener diode 264 and Zener diode 265, charging is performed when low-side pulse signal 261 is HI, that is, when the low-side voltage is inverted by inversion circuit 262 and is 0 V. The charging voltage of boost capacitor 263 is adjusted by the Zener voltage of Zener diode 264.

[0053] 23 is a graph showing a high-speed high-voltage level shift of a pulse signal using a boost capacitor. Graph 271 is a low-side pulse signal, graph 272 is a low-side power supply voltage, graph 273 is a pulse signal voltage obtained by inverting the low-side pulse signal and the low-side power supply voltage by the inverter circuit 262, graph 274 is a boosted pulse signal voltage, and graph 275 is a high-side power supply voltage. The low-side pulse signal and the pulse voltage obtained by inverting the low-side power supply voltage by the inverter circuit 262 shown in graph 273 are boosted to the high-side voltage without delay as shown in graph 274. Due to the difference between the high-side power supply voltage shown in graph 275 and the boosted pulse signal voltage shown in graph 274, a negative voltage is applied to the gate terminal of the P-channel MOSFET 266, and the drain-source of the P-channel MOSFET 266 becomes conductive.

[0054] As a result, as shown in FIG. 24, both the rising and falling edges of a low-side pulse signal shown by graph 281 and a high-side pulse signal shown by graph 282 can be transmitted at high speed.

[0055] According to the level shift circuit of the fourth embodiment, in a circuit that transmits a low-side signal to the high-side, a boost capacitor is provided that boosts the voltage of the control signal of the low-side circuit to the high-side voltage. This eliminates voltage constraints in the low-side circuit, makes it possible to select a high-speed device from low-cost options, and eliminates the need for voltage amplification using a semiconductor switching element, thereby minimizing the decrease in transmission speed, and enables low-cost, high-speed transmission to be achieved even with a high voltage.

[0056] In the above-mentioned first embodiment, the pulse current output device 1 includes the current limiting circuit 11, the input capacitor 12, the voltage monitoring circuit 13, the step-up / step-down circuit 14, the main capacitor 15, the high-speed voltage compensation circuit 16, the output capacitor 17, the pulse output control unit 18, and the pulse output switching circuit 19, but is not limited thereto. The pulse current output device 1 may include at least the current limiting circuit 11 that limits the current input to the power source, the main capacitor 15 that stores the charge of the current that has passed through the current limiting circuit 11, the pulse output control unit 18 that controls the pulse output that lights the external LED 2, and the pulse output switching circuit 19 that lights the external LED 2 using the charge stored in the main capacitor 15. In this configuration, the main capacitor 15 is an example of the first capacitor. The pulse current output device 1 may also be configured to include a current limiting circuit 11 that limits the current input to the power source, an input capacitor 12 that stores the charge of the current that has passed through the current limiting circuit 11, a voltage monitoring circuit 13 that monitors the voltage of the input capacitor 12, a step-up / step-down circuit 14 that raises / lowers the voltage, a main capacitor 15 that stores the charge that has passed through the step-up / step-down circuit 14, a pulse output control unit 18 that controls the pulse output that lights up the external LED 2, and a pulse output switching circuit 19 that lights up the external LED 2 using the charge stored in the main capacitor 15. In this configuration, the main capacitor 15 is an example of a second capacitor. Alternatively, the pulse current output device 1 may be configured to include a current limiting circuit 11 that limits the current input to the power source, a main capacitor 15 that stores the charge of the current that has passed through the current limiting circuit 11, a high-speed voltage compensation circuit 16 that compensates for the voltage, an output capacitor 17 that stores the charge that has passed through the high-speed voltage compensation circuit 16, a pulse output control unit 18 that controls the pulse output that lights up the external LED 2, and a pulse output switching circuit 19 that lights up the external LED 2 using the charge stored in the output capacitor 17. In this configuration, the main capacitor 15 is an example of the first capacitor. Also, the number of LED channels may be multiple by combining each configuration with the second embodiment.

[0057] In addition, various embodiments and modifications of the present disclosure are possible without departing from the broad spirit and scope of the present disclosure. The above-described embodiments are for explaining the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the disclosure equivalent thereto are considered to be within the scope of the present disclosure. [Explanation of symbols]

[0058] 1,1-1,1-2 Pulse current output device, 2,2-1,2-2 LED, 11,11-1,11-2,11-3 Current limiting circuit, 12 Input capacitor, 13 Voltage monitoring circuit, 14 Step-up / step-down circuit, 15 Main capacitor, 16,16-1,16-2,16-3,16-4,16-5,244,254 High-speed voltage compensation circuit, 17,17-1,17-2,245,255 Output capacitor, 18,212,222 Pulse output control section, 19,19-1,19-2 Pulse output switching circuit, 61 Shunt resistor, 62 Operational amplifier, 63 P-channel MOSFET element, 64 Comparison voltage, 71,81 Inductor, 84a,84b terminals, 91-93, 101, 103, 104, 111-114, 121-124, 151-154, 191-195, 231-236, 271-275, 281, 282 graph, 132 comparator, 133, 134 input terminals, 135 output terminals, 142 N-channel MOSFET element, 144 operational amplifier, 145 boost capacitor, 146 diode, 147 Zener diode, 181 voltage compensation circuit, 182 PNP bipolar transistor, 183 NPN bipolar transistor, 201 charge pump circuit, 202, 203 resistor, 242 boost circuit, 243, 253 voltage compensation capacitor, 246, 256 external circuit, 252 low-pass filter, 261 pulse signal, 262 inverting circuit, 263 Boost capacitor, 264,265 Zener diode, 266 P-channel MOSFET.

Claims

1. A current limiting circuit that limits current input from an external power source by dynamically controlling the resistance value of a semiconductor element; a capacitor that stores an electric charge based on the current limited by the current limiting circuit; a pulse output control unit that controls the pulse output time in accordance with a predetermined pulse output time ratio; a pulse output switching circuit that outputs the charge stored in the capacitor to the outside in accordance with control from the pulse output control unit; a step-up / step-down circuit that steps up or down a voltage; a voltage monitoring circuit that controls the operation of the step-up / step-down circuit; Equipped with the capacitor includes a first capacitor that stores charge of the current limited by the current limiting circuit and a second capacitor that stores the charge stored in the first capacitor via the step-up / step-down circuit; The voltage monitoring circuit a voltage of the first capacitor is monitored, and an operation of the step-up / step-down circuit is controlled based on the voltage of the first capacitor; Pulse current output device.

2. A current limiting circuit that limits the current input from an external power source by dynamically controlling the resistance value of a semiconductor element; a capacitor that stores an electric charge based on the current limited by the current limiting circuit; a pulse output control unit that controls the pulse output time in accordance with a predetermined pulse output time ratio; a pulse output switching circuit that outputs the charge stored in the capacitor to the outside in accordance with control from the pulse output control unit; a voltage compensation circuit for performing voltage compensation; Equipped with the capacitor includes a first capacitor that stores charge of the current limited by the current limiting circuit and a third capacitor that stores the charge stored in the first capacitor via the voltage compensation circuit; the voltage compensation circuit performs voltage compensation for the third capacitor. Pulse current output device.

3. a voltage compensation circuit for performing voltage compensation; the capacitor further includes a third capacitor that stores the charge stored in the second capacitor via the voltage compensation circuit; the voltage compensation circuit performs voltage compensation for the third capacitor.

2. The pulse current output device according to claim 1.

4. a plurality of the pulse output switching circuits; a voltage information recording unit that records voltage information related to the voltage of the capacitor that stores the charge input to the voltage compensation circuit; 4. The pulse current output device according to claim 2 or 3.

5. A current limiting circuit that limits a current input from an external power source by dynamically controlling the resistance value of a semiconductor element; a capacitor that stores an electric charge based on the current limited by the current limiting circuit; a pulse output control unit that controls the pulse output time in accordance with a predetermined pulse output time ratio; a pulse output switching circuit that outputs the charge stored in the capacitor to the outside in accordance with control from the pulse output control unit; Equipped with The current limiting circuit The resistance value of the semiconductor element is changed by the first feedback circuit so that the specified voltage is obtained, thereby limiting the current amount to a certain amount or less, and limiting the current to the required current amount calculated based on the maximum value of the ratio of the pulse output time. Pulse current output device.

6. The current limiting circuit An inductor is inserted in the current path, and the inductance of the inductor reduces the inrush current.

6. The pulse current output device according to claim 5.

7. The first feedback circuit comprises: A potential difference generated by the inductance of the inductor is fed back.

7. The pulse current output device according to claim 6.

8. The voltage compensation circuit a second feedback circuit changes a resistance value of a switching element having an insulated gate terminal connected to the first capacitor and the third capacitor so that the third capacitor has a designated voltage, thereby performing voltage compensation for the third capacitor; 3. The pulse current output device according to claim 2.

9. The voltage compensation circuit a second feedback circuit changes a resistance value of a switching element having an insulated gate terminal connected to the second capacitor and the third capacitor so that the third capacitor has a designated voltage, thereby performing voltage compensation for the third capacitor; 4. The pulse current output device according to claim 3.

10. The voltage compensation circuit a boost capacitor charged to a constant voltage based on a designated voltage of the third capacitor is inserted between the insulated gate terminal of the switching element and the second feedback circuit; 9. The pulse current output device according to claim 8.

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