JP2022191924A - Power unit - Google Patents

Abstract

To provide a power unit with high safety which can arbitrarily control voltage and apply negative and positive current.SOLUTION: A power unit comprises: a first power supply unit 2 which outputs output voltage Vout1; and a second resonance-type power supply unit 3 which comprises an input capacitor Cin charged by DC voltage from the first power supply unit 2, converts the DC voltage of the input capacitor Cin into AC voltage with on/off operations of an Hi-side switching element 31 and a Low-side switching element 32 connected via a bridge to supply the voltage to a capacitive load CL, and regenerates an electric charge charged to the capacitive load CL to the input capacitor Cin as regenerative current Ire in fall of AC voltage. The first power supply unit 2 is constituted of current capacity smaller than that of the second power supply unit 3, and an excess current threshold I_oc1 at which the first power supply unit 2 starts excess current protection is set to a value lower than an excess current threshold I_oc2 at which the second power supply unit 3 starts the excess current protection.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply device for driving capacitive loads.

In recent years, dielectric elastomer actuators have been developed in various fields such as haptics as actuators with free forms. Dielectric elastomer actuators are inexpensive to manufacture and efficient actuators that convert electrical energy to mechanical energy.

A dielectric elastomer actuator is a capacitive load in a capacitor structure that produces a displacement in response to an applied voltage. Therefore, it is necessary to apply a voltage corresponding to the displacement to be generated. In other words, driving a capacitive load requires a power supply device capable of arbitrarily controlling the voltage and allowing positive and negative currents to flow. A power supply device having a bridge configuration as an output stage satisfies such conditions (see, for example, Patent Document 1).

Japanese translation of PCT publication No. 2003-524361

However, a power supply with a bridge configuration in the output stage is a high-power power supply (for example, the power supply of Patent Document 1 assumes a radio frequency band for processing materials by induction heating, dielectric heating, and plasma excitation). As it is, it is not suitable for driving a dielectric elastomer actuator. That is, dielectric elastomer actuators are expected to be used in applications such as devices that come into contact with the human body in the field of haptics and the like, and devices that grasp products. Safety is therefore an important consideration for power supplies that drive dielectric elastomer actuators.

The present invention has been made in view of such problems, and its object is to provide a highly safe power supply device capable of arbitrarily controlling the voltage and allowing positive and negative currents to flow. be.

In order to achieve the above objects, the power supply device according to the present invention is configured as follows.
A power supply device according to the present invention is a power supply device for driving a capacitive load, comprising: a first power supply unit for outputting a DC voltage; and an input capacitor charged by the DC voltage from the first power supply unit. The DC voltage of the input capacitor is converted into an AC voltage by the on/off operation of the connected switching element and supplied to the capacitive load, and the charge charged in the capacitive load when the AC voltage drops is transferred to the input capacitor. a regenerative resonance type second power supply unit, wherein the first power supply unit is configured with a current capacity smaller than that of the second power supply unit, and the first power supply unit starts overcurrent protection. The overcurrent threshold is set to a value lower than the overcurrent threshold at which the second power supply section starts overcurrent protection.

According to the power supply device of the present invention, even if the capacitive load is short-circuited or the second power supply section fails, the load current flowing through the capacitive load is automatically suppressed to a small value, ensuring safety. It works.

1 is a block diagram showing the configuration of an embodiment of a power supply device according to the present invention; FIG. 2 is a diagram showing overcurrent protection characteristics of a first current control section and a second current control section shown in FIG. 1; FIG. 2 is a waveform diagram when a sine wave is output by the second power supply section shown in FIG. 1; FIG. 2 is a waveform diagram when a sine wave is output by the second power supply section shown in FIG. 1; FIG. 2 is a diagram showing ON/OFF states of a Hi-side switching element and a Low-side switching element shown in FIG. 1 and current paths for charging and discharging a capacitive load; FIG. 2 is a waveform diagram when a sine wave is output by the second power supply section shown in FIG. 1; FIG. 2 is an equivalent circuit diagram when the capacitive load shown in FIG. 1 has a short-circuit failure; FIG.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the power supply device 1 of the present embodiment includes a first power supply section 2 and a second power supply section 3, and a capacitive load CL with a positive or negative half voltage and an arbitrary voltage (DC , sine wave, square wave, etc.).

The first power supply unit 2 is a DC-DC converter that converts an input voltage Vin input to an input terminal Tin1 from a DC power supply E into a DC output voltage Vout1 and supplies the DC output voltage Vout1 to the second power supply unit 3 from an output terminal Tout1. Although the first power supply section 2 shown in FIG. 1 is configured by a flyback type switching power supply, other systems such as a forward type may be used.

The first power supply section 2 includes a transformer 21 , a switching element 22 , an output rectifying/smoothing circuit 23 , a first voltage control circuit 24 , a first current control circuit 25 and a driver 26 .

The transformer 21 has a primary winding and a secondary winding, and the polarity of the primary winding and the polarity of the secondary winding are set opposite to each other. A primary winding of the transformer 21 is connected between the positive terminal of the DC power supply E and the switching element 22 . As a result, the DC power source E is applied to the primary winding of the transformer 21 as the input voltage Vin.

The switching element 22 is composed of, for example, an N-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The switching element 22 may be an IGBT (Insulated Gate Bipolar Transistor) or a BJT (Bipolar Transistor). The drain of the switching element 22 is connected to the primary winding of the transformer 21, and the source of the switching element 22 is connected to the ground terminal. As a result, the input voltage Vin is output to the secondary winding of the transformer 21 during the off period by the ON/OFF operation of the switching element 22 connected through the primary winding of the transformer 21 .

The output rectifying/smoothing circuit 23 includes a rectifying diode D1 and an output capacitor Cout, and the output capacitor Cout is connected between both terminals of the secondary winding of the transformer 21 via the rectifying diode D1. As a result, the AC voltage induced in the secondary winding of the transformer 21 is rectified and smoothed by the output rectifying/smoothing circuit 23, and is output as a DC output voltage Vout1 via the resistor R1 and the reverse current prevention diode 4 to the second power supply section 3. supplied to

The resistor R1 is a current detection resistor that detects an output current Iout1 output from the first power supply section 2 (input current to the second power supply section 3), and a voltage across the resistor R1 is input to the first current control circuit 25. Note that the resistor R1 may be provided on the Low (low side) side.

The backflow prevention diode 4 is a diode for preventing backflow of charge from the second power supply section 3 to the first power supply section 2, and has an anode connected to the output terminal Tout2 of the second power supply section 3 and a cathode connected to the first power supply section. 2 input terminal Tin2.

The first voltage control circuit 24 is a circuit that generates a control signal for on/off controlling the switching element 22, and controls the output voltage Vout1 to a desired constant voltage by the control signal. A control signal generated by the first voltage control circuit 24 is input to the gate of the switching element 22 via the driver 26, and the switching element 22 is turned on and off based on the control signal.

The first current control circuit 25 monitors the output current Iout1 by the voltage across the resistor R1, and when the output current Iout1 rises and reaches the overcurrent threshold I_oc1, the switching element 22 is turned on and off via the driver 26. It has an overcurrent protection (OCP) function that limits the power supplied to the second power supply unit 3 .

The overcurrent protection characteristic of the first current control circuit 25 is not particularly limited, and may be the drooping characteristic indicated by the solid line in FIG. It may be a characteristic or a v-shaped characteristic indicated by a one-dot chain line in FIG. 2(a).

The second power supply unit 3 converts the output voltage Vout1 of the first power supply unit 2 into an arbitrary (sine wave, rectangular wave, triangular wave, direct current, etc.) output voltage Vout2 and supplies it to the capacitive load CL. is a resonant DC-AC converter. In addition, although the example which comprised the 2nd power supply part 3 shown in FIG. 1 by the half-bridge circuit is shown, the full-bridge circuit may be sufficient.

The second power supply unit 3 includes an input capacitor Cin, a Hi (high side) side switching element 31, a Low (low side) side switching element 32, a reactor L1, a second voltage control circuit 33, and a second current control circuit. 34 and a Hi/Low (high side/low side) driver 35 .

The input capacitor Cin is composed of, for example, an electrolytic capacitor, and has a positive terminal connected to an input terminal Tin2 (cathode of the backflow prevention diode 4) to which the output voltage Vout1 from the first power supply section 2 is input, and a negative terminal thereof. side terminal is connected to the ground terminal. It is preferable that the capacitance of the input capacitor Cin is sufficiently large with respect to the capacitance of the capacitive load CL.

The Hi-side switching element 31 and the Low-side switching element 32 are composed of, for example, N-type MOSFETs. The Hi-side switching element 31 and the Low-side switching element 32 may be IGBTs (Insulated Gate Bipolar Transistors) or BJTs (Bipolar Transistors). A series circuit (half bridge circuit) of the Hi-side switching element 31 and the Low-side switching element 32 is connected between the positive terminal of the input capacitor Cin and the ground terminal. The drain of the Hi-side switching element 31 is connected to the positive terminal of the input capacitor Cin, the source of the Hi-side switching element 31 is connected to the drain of the Low-side switching element 32, and the source of the Low-side switching element 32 is connected to , is connected to the ground terminal.

Diodes DH and DL are connected between the drain and source of the Hi-side switching element 31 and the Low-side switching element 32, respectively. The diodes DH and DL have their cathodes connected to their drains and their anodes connected to their sources. Note that when the Hi-side switching element 31 and the Low-side switching element 32 are composed of, for example, N-type MOSFETs as in the present embodiment, the diodes DH and DL are connected to the Hi-side switching element 31 and the Low-side switching element 32. can be a parasitic diode of

A connection point X between the Hi-side switching element 31 and the Low-side switching element 32 is connected to the output terminal Tout2 via a reactor L1 and a resistor R2. A capacitive load CL is connected between the output terminal Tout2 and the ground terminal.

The resistor R2 is a current detection resistor that detects the output current Iout2 output from the second power supply section 3, and the voltage across the resistor R2 is input to the second current control circuit . Note that the resistor R2 may be provided on the Low side.

The second voltage control circuit 33 is a circuit that generates a control signal for on/off controlling the Hi-side switching element 31 and the Low-side switching element 32, and controls the output voltage Vout2 to an arbitrary voltage by the control signal. A control signal generated by the second voltage control circuit 33 is input to the gates of the Hi-side switching element 31 and the Low-side switching element 32 via the Hi/Low driver 35, and based on the control signal, the Hi-side switching element 31 and The low-side switching element 32 is turned on and off.

The second current control circuit 34 monitors the output current Iout2 based on the voltage across the resistor R2. It has an overcurrent protection (OCP) function that controls the on/off of the element 32 to limit the power supplied to the capacitive load CL.

The overcurrent threshold I_oc1 at which the first current control circuit 25 starts overcurrent protection is set to a lower value than the overcurrent threshold I_oc2 at which the second current control circuit 34 starts overcurrent protection, as shown in FIG. ing.

The overcurrent protection characteristics of the second current control circuit 34 are not particularly limited, and may be the drooping characteristics indicated by the solid line in FIG. It may also be a character characteristic or a v-character characteristic indicated by a one-dot chain line in FIG. 2(b).

In the second power supply unit 3, an LC filter circuit is configured with a reactor L1, an input capacitor Cin, and a capacitive load CL, and as shown in FIG. , and a desired output voltage Vout2 is output by controlling the duty ratio. Note that the output voltage Vout2 shown in FIG. 3 has a waveform when a sine wave is output.

As shown in FIGS. 4 and 5, the ON/OFF operations of the Hi-side switching element 31 and the Low-side switching element 32 are performed during a dead time period (period T1 , T3). 4 shows, from top to bottom, the ON/OFF state of the Hi-side switching element 31, the ON-OFF state of the Low-side switching element 32, the drain current of the Hi-side switching element 31, the drain current of the Low-side switching element 32, and the reactor current of the reactor L1. showing. FIG. 5 shows the ON/OFF states of the Hi-side switching element 31 and the Low-side switching element 32 during periods T1 to T4b shown in FIG. 4, and current paths for charging and discharging the capacitive load CL.

In the second power supply unit 3, when the voltage of the capacitive load CL is to be lowered (at the time of voltage drop) during periods T1 and T2a shown in FIGS. The extracted charge is regenerated in the input capacitor Cin as regenerated current Ire. That is, the second power supply section 3 can reuse unnecessary charges.

In the power supply device 1 of the present embodiment, the backflow prevention diode 4 prevents charge from flowing back from the second power supply section 3 to the first power supply section 2 . Therefore, an increase in the output voltage Vout1 of the first power supply section 2 due to the regenerated energy of the regenerated current Ire is prevented. As a result, the switching operation of the first power supply unit 2 is not stopped as the output voltage Vout1 rises, so dynamic regulation is improved.

The relationship between the input current to the second power supply unit 3, that is, the output current Iout1 of the first power supply unit 2, the output current Iout2 of the second power supply unit 3, and the regenerated current Ire is
Iout1=Iout2−Ire (Formula 1)
is represented by

In the case of the capacitive load CL, if there is no loss in the circuit, all the charges charged in the capacitive load CL are regenerated and returned to the input capacitor Cin, so there is no loss between the input capacitor Cin and the capacitive load CL. It can exchange electric charges. In this case, the current supply capability required of the first power supply unit 2 is to charge the input capacitor Cin of the second power supply unit 3 first, and thereafter the output current Iout1 of the first power supply unit 2 becomes zero. Become.

In practice, there is energy consumption in the resistance component of the circuit and the capacitive load CL, so that the output current Iout2>regenerative current Ire, it is necessary to supply the current even after charging the input capacitor Cin. However, since the charge charged in the capacitive load CL is reused by the regenerative current Ire, as shown in FIG. The current Iout1 can be a small current. 6 shows waveforms when a sine wave is output, where (a) is the output voltage Vout2 of the second power supply unit 3, (b) is the output current Iout2 of the second power supply unit 3, and (c) is the second power supply unit 3 (the output current Iout1 of the first power supply unit 2) are respectively shown.

Therefore, the first power supply section 2 can be configured with a current capacity smaller than that of the second power supply section 3 . Since the first power supply unit 2 may have a smaller current capacity than the second power supply unit 3, as described above, the overcurrent threshold I_oc1 at which the first power supply unit 2 starts overcurrent protection is 3 is set to a value lower than the overcurrent threshold I_oc2 that initiates overcurrent protection. As a result, safety is ensured even when the capacitive load CL is short-circuited or when the second power supply section 3 fails.

FIG. 7 shows an equivalent circuit when the capacitive load CL is short-circuited, and the resistance component RL is connected in parallel to the capacitive load CL. The value of the resistance component RL, which is negligibly large under normal conditions, becomes negligibly small at the time of a short-circuit failure. And the resistive component RL=0Ω is the perfect short circuit fault condition.

When the capacitive load CL has a short-circuit failure, part of the charge to be regenerated is consumed by the resistance component RL, and the regenerated current Ire is reduced. As the resistance component RL becomes smaller, the ratio of the regenerated current Ire to the output current Iout2 becomes smaller. Therefore, considering the above (Equation 1), the input current to the second power supply section 3, that is, the output current Iout1 of the first power supply section 2 and the output current Iout2 of the second power supply section 3 are almost equal.

Here, the first power supply unit 2 has a smaller current capacity than the second power supply unit 3, and the overcurrent threshold I_oc1 of the first power supply unit 2 is lower than the overcurrent threshold I_oc2 of the second power supply unit 3. is set to Therefore, the output current Iout1 of the first power supply unit 2 is limited to the output current Iout1 of the first power supply unit 2, and even if the capacitive load CL is short-circuited or the second power supply unit 3 fails, the capacitive load The load current flowing through CL is automatically suppressed to a small value near I_oc1 to ensure safety.

As described above, in the present embodiment, the power supply device 1 that drives the capacitive load CL includes the first power supply unit 2 that outputs the output voltage Vout1 (DC voltage) and the power supply from the first power supply unit 2. An input capacitor Cin charged by a DC voltage is provided, and the DC voltage of the input capacitor Cin is converted into an AC voltage by the ON/OFF operation of the Hi-side switching element 31 and the Low-side switching element 32 which are bridge-connected, and supplied to the capacitive load CL. and a resonance-type second power supply unit 3 that regenerates the electric charge charged in the capacitive load CL when the AC voltage drops to the input capacitor Cin as a regenerative current Ire. The overcurrent threshold I_oc1 at which the first power supply unit 2 starts overcurrent protection is higher than the overcurrent threshold I_oc2 at which the second power supply unit 3 starts overcurrent protection. set to a low value.
With this configuration, even if the capacitive load CL is short-circuited or the second power supply unit 3 fails, the load current flowing through the capacitive load CL is automatically suppressed to a small value near I_oc1, ensuring safety. It is possible to provide a highly safe power supply device capable of arbitrarily controlling the voltage and allowing positive and negative currents to flow.
Safety can be further improved by latch-detecting that the capacitive load CL has a short-circuit failure and that Iout2 has flowed more than a predetermined current Ith, and turning off the switching element 22 of the first power supply unit 2 .
In addition, it latch-detects that the capacitive load CL has a short-circuit failure and Iout2 has flowed more than a predetermined current Ith, and the Hi (high side) side switching element 31 of the second power supply section 3 is turned off to switch to the Low (low side) side. By turning on the switching element 32, the safety can be further improved.

Furthermore, in the present embodiment, a backflow prevention diode 4 is provided to prevent backflow of charge from the second power supply section 3 to the first power supply section 2 .
With this configuration, the switching operation of the first power supply unit 2 is not stopped as the output voltage Vout1 rises, so dynamic regulation is improved.

It should be noted that the present invention is not limited to the above-described embodiments, and it is obvious that each embodiment can be modified as appropriate within the scope of the technical idea of the present invention. Further, the number, position, shape, etc. of the constituent members are not limited to those of the above-described embodiment, and the number, position, shape, etc. can be set to be suitable for carrying out the present invention. The same constituent elements are denoted by the same reference numerals in each figure.

1 Power supply device 2 First power supply unit 3 Second power supply unit 4 Backflow prevention diode 21 Transformer 22 Switching element 23 Output rectification smoothing circuit 24 First voltage control circuit 25 First current control circuit 26 Driver 31 Hi side switching element 32 Low side switching Element 33 Second voltage control circuit 34 Second current control circuit 35 Hi/Low driver CL Capacitive load Cin Input capacitor Cout Output capacitor D1: Rectifier diode DH, DL Diode E DC power supply L1 Reactor R1, R2 Resistor

Claims (2)

A power supply device for driving a capacitive load,
a first power supply that outputs a DC voltage;
An input capacitor is provided that is charged by the DC voltage from the first power supply unit, and the DC voltage of the input capacitor is converted into an AC voltage by on/off operation of the bridge-connected switching elements and supplied to the capacitive load, a resonance type second power supply unit that regenerates the charge charged in the capacitive load to the input capacitor when the AC voltage drops,
The first power supply section is configured with a current capacity smaller than that of the second power supply section, and
A power supply device, wherein an overcurrent threshold at which the first power supply unit starts overcurrent protection is set to a lower value than an overcurrent threshold at which the second power supply unit starts overcurrent protection. 2. The power supply device according to claim 1, further comprising a backflow prevention diode for preventing backflow of charge from said second power supply unit to said first power supply unit.

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