JPH03235664A - Current detector of power supply apparatus - Google Patents

Abstract

PURPOSE:To reduce the size and the cost of a current transformer by detecting a high frequency current (high frequency modulated current) which is switched on and off by an inverter circuit. CONSTITUTION:If a current detecting voltage between the output terminals 71 and 72 of a current detector 27 provided in an inverter circuit 100 is inputted to a full-wave rectifying circuit 34 and a full-wave rectified output (absolute value) is obtained, a waveform corresponding to the full-wave rectified waveform of an AC input current i2 can be obtained. First and second currents Ia and Ib in the current detector 27 is switched on and off at a high frequency, for instance 50kHz. As a result, the current detector 27 can be used as a high frequency current transformer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current detection device for detecting an alternating current input current in a power supply device including a rectifier circuit and an inverter.

[Prior Art] A DC power supply for an inverter is generally composed of a rectifier circuit. When this rectifier circuit is connected to a commercial AC power source, the input voltage is a sine wave, but the input current is not necessarily a sine wave and the power factor is not 1.

In order to approximate the input current waveform of the rectifier circuit to a sine wave and bring the power factor close to 1, a reactor is connected to the input or output power line of the rectifier circuit, and a switching element of the inverter is connected between the power lines at a stage after the reactor. Controlling the input terminal waveform by shorting with
It is disclosed in Japanese Patent No. 557.

[Problems to be Solved by the Invention] Incidentally, in this type of device, it is necessary to detect an alternating current input current. In the above publication, a current transformer (CT) is used to detect the current at the input end of the rectifier circuit. Alternatively, it is also possible to connect a current detection resistor or a DC CT to the output line of the rectifier circuit to obtain a signal waveform corresponding to the input current.

However, in the conventional detection method using OCT, the current is detected at the commercial AC frequency stage, which makes the CT relatively large and expensive. Furthermore, when detecting with a current detection resistor, power loss occurs and efficiency decreases. It is also possible to detect the current using a Hall element or the like, but this would require a separate power source, which would also result in high costs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a low-cost, small-sized current detection device that can indirectly detect AC input current in a power supply device including a rectifier circuit and an inverter circuit.

[Means for Solving the Problems] The present invention for achieving the above object includes a power terminal for supplying a sine wave alternating current voltage, a rectifier circuit connected to the power terminal, and a pair of rectifier circuits. an inverter circuit connected between output terminals and having a switching element for flowing a current in a first direction and a switching element for flowing a current in a second direction opposite to the first direction; ,
A current detection device for detecting an AC input current of a power supply device comprising a magnetic core, first and second primary windings wound around the magnetic core, and a second primary winding wound around the magnetic core. the first primary winding is connected in series to the path through which the current in the first direction of the inverter circuit flows, and the second primary winding is Second
connected in series to a path through which a current in the direction flows, and the polarity of the first primary winding is determined such that the current in the first direction generates a magnetic flux in the first direction in the magnetic core, The polarity of the second primary winding is determined such that the current in the second direction generates a magnetic flux in a second direction opposite to the magnetic flux in the first direction in the magnetic core. and,
and an absolute value circuit for obtaining the absolute value of the output of the secondary winding of the current transformer.

In addition, in order to improve the waveform of the AC input current, as shown in FIG.
8, etc., a difference signal forming means between the current detection signal and the reference sine wave, consisting of an error amplifier 35, etc.;
A control circuit including a comparator 40, a sawtooth wave generating circuit 41, a control signal forming circuit 42, etc. can be provided.

[Function] In the present invention, since an intermittent high frequency current (high frequency modulated current) is detected in the inverter circuit, the current transformer becomes a high frequency current transformer, thereby achieving miniaturization and cost reduction.

According to claim 2, it is possible to improve the input current waveform.

[Embodiment] Next, a power supply device including an AC-DC-AC-DC conversion circuit according to an embodiment of the present invention will be described based on FIGS. 1 to 8.

[AC-DC-AC-DCC conversion circuit diagram 1] For example, a 50Hz commercial AC power supply terminal 1.2 is equipped with a filter circuit 5 for improving the current waveform, that is, for removing harmonic components, consisting of a reactor 3, a capacitor 4, and a reactor 7. It is connected. A pair of AC input terminals of a rectifier circuit 12 consisting of four bridge-connected diodes 8.9.10.11 are connected via a filter circuit 5 to a power supply terminal 1.2. An inverter circuit 100 is connected between a pair of DC lines 13 and 14 connected to the DC output terminal of the rectifier circuit 12. This inverter circuit 100 includes first, second, third and fourth switches Ql, Q2
, QB, and Q4 are connected in a bridge manner to form an inverter switch circuit 15 and an output transformer 16. Each switch Q
l, Q2, QB, and Q4 are composed of FETs (field effect transistors), which are connected in parallel with diodes D1 and
D2, D3, and D4 are connected. Although not shown, there is a line between the pair of DC lines 13.14 to limit the sum of the power supply voltage of the power supply terminal 1.2 and the voltage of the reactor 3.7 from exceeding a predetermined value. A parallel circuit of a varistor and a capacitor is connected through a diode. The output transformer 16 has a primary winding 17 and a secondary winding 1.
8, one end of the primary winding 17 is connected between the first and second switches Ql and Q2, and the other end is connected between the third and fourth switches.
is connected between switches Q3 and Q4. An output rectifier circuit 23 consisting of diodes 19, 20, 21, 22 is connected to the secondary winding 18. Output rectifier circuit 23
A smoothing capacitor 24 is connected between the pair of output lines. A load circuit is connected between the DC output terminals 25 and 26 via, for example, an inverter.

The first to fourth switches Q1 to Q4 in the inverter switch circuit 15 are driven to convert direct current to alternating current, and are short-circuited to improve the input current waveform. Short-circuit control is performed by simultaneously turning on the first switch Q1 and the second switch Q2, and turning on the third switch Q3 and the fourth switch Q4 simultaneously. As a result, a pair of DC lines 1
3.14 or short-circuited.

A control circuit 101 for performing both inverter control and short circuit control of the inverter switch circuit 15 will be described. A current detector (current transformer) 27 for detecting a current corresponding to the current 12 on the output side of the capacitor 4 is provided in the inverter circuit 100 as shown in principle by a broken line. Further, an input voltage detection circuit 28 is connected to the commercial AC power supply terminal 1.2 to obtain a reference sine wave for comparison with the detected current. This input voltage detection circuit 28 consists of a transformer primary winding 29 and a secondary winding 30. Of course, the voltage detection circuit 28 may be configured with a voltage dividing resistor.

An output voltage detection circuit 31 is connected to the DC output terminals 25 and 26 to detect a DC output voltage corresponding to the output AC voltage of the inverter circuit 100.

This output voltage detection circuit 31 consists of voltage dividing resistors 32 and 33.

The current detector 27 is connected to one input terminal (inverting input terminal) of a first error amplifier 35 via a first full-wave rectifier circuit 34 serving as an absolute value circuit. The output line of the input voltage detection circuit 28 is connected to the other input terminal (non-inverting input terminal) of the first error amplifier 35 via a second full-wave rectifier circuit 36 and a coefficient circuit, ie, a multiplier 37. . 1st
The error amplifier 35 generates an output corresponding to the difference between the current 12 including a ripple component and the sinusoidal voltage.

Inverter switch circuit 1 to keep the output voltage constant
5, the output line of the output voltage detection circuit 31 is connected to one input terminal (inverting input) of a second error amplifier 38, and the other input terminal (inverting input) of this error amplifier 38 is
A reference voltage source 39 is connected to the inverting input. This second error amplifier 38 generates an output voltage corresponding to the difference between the detection voltage and the reference voltage, and sends it to the multiplier 37 . Multiplier 37
is the value obtained by multiplying the amplitude of the reference sine wave waveform (full-wave rectified waveform) given from the second full-wave rectifier circuit 36 by the output of the second error amplifier 38 to the non-inverting input terminal of the first error amplifier 35. give.

One input terminal (inverting input) of the voltage comparator 40 is connected to the output terminal of the first error amplifier 35 via a low-pass filter 43, and the other input terminal (non-inverting input) is connected to the sawtooth wave generation circuit 41. has been done. This comparator 40 outputs a comparison output of both human forces in a binary format.

A switch control signal forming circuit 42 connected to the output terminal of the comparator 40 controls the switch Q based on the output of the comparator 40.
1 to Q4 control signals are formed.

Although not shown, the output line of the control signal forming circuit 42 is connected to the control terminals (gates) of each of the switches Q1 to Q4.

As shown in FIG. 3, the control signal forming circuit 42 includes a rectangular wave generating circuit 50, a NOT circuit 51, a trigger pulse generating circuit 52, and a trigger type flip-flop 53. The rectangular wave generating circuit 50 generates a fixed rectangular wave pulse for controlling the on/off of the first switch Q1 shown in FIG. 2(B). NOT circuit 5 is square wave generation circuit 5
0 and the third switch Q3 shown in FIG.
Generates a square wave that controls the The rectangular wave generation circuit 50 is also connected to the sawtooth wave generation circuit 41.

The sawtooth wave generating circuit 41 generates the sawtooth wave A2 shown in FIG. 2(A) in synchronization with the output waveform of the rectangular wave generating circuit 50 shown in FIG. 2(B). That is, the sawtooth wave generating circuit 41 generates the sawtooth wave A2 in response to the leading and trailing edges of the pulse shown in FIG. 2(B).

The comparator 40 generates the comparison output shown in FIG. 4(A) based on the comparison between the signal A1 shown in FIG. 2(A) and the sawtooth wave A2. A trigger pulse generating circuit 52 connected to the comparator 40 generates the trigger pulse shown in FIG. 4(B) in response to the leading edge of the comparison output pulse shown in FIG. 4(A). The trigger input terminal T of the pulse flip-flop 53
(;Each time the trigger pulse shown in FIG. 4(B) is input from the trigger pulse generation circuit 52, the state of the output terminal of the flip-flop 53 changes, and the switch control signal shown in FIG. 4(C) is sent to the non-inverting output terminal. A switch control signal shown in FIG. 4(D) is applied from the inverting output terminal to the fourth switch Q4.

The constants of each part of the circuit shown in FIG. 1 are as follows.

The inductance values of reactors 3 and 7 are both 100μ
H (microhenry), the capacitance value of the capacitor 4 is 10 μF (microfarad), and the frequency of the sawtooth wave A2 in FIG. 2(A) generated from the sawtooth wave generation circuit 41 is 100 kHz.

[Current Detection Device] In the power supply device of FIG. 1, it is necessary to detect the AC input current 12. In this embodiment, this input current 12
is not detected directly, but is detected indirectly based on a current detector (high frequency current transformer) 27 provided in the inverter circuit 100. FIG. 5 shows the connection relationship between this current detector 27 and the inverter circuit 100, and FIG. 6 shows the AC input current 1
2, the output voltage of the current detector 27, and its absolute value, that is, the output of the full-wave rectifier circuit 34 in FIG.

The current detector 27 includes a magnetic core 60, first and second primary windings 61, 62, a secondary winding (output winding) 63, and an output resistor 64. One terminal 65 of the first primary winding 61
is connected to the first switching element Q1, and the other terminal 66 is connected to the upper end of the primary winding 17 of the transformer 16 and the second switching element Q2. One terminal 67 of the second primary winding 62 is connected to the third switching element Q3, and the other terminal 68 is connected to the primary winding 1 of the transformer 16.
7 and the fourth switching element Q4. Further, the first primary winding 61 passes through the first switching element Q1 and moves 1is1 in the direction shown by the arrow in FIG.
The magnetic core 60 is wound so that a magnetic flux in a first direction shown by an arrow 69 is generated in the magnetic core 60 when a current Ia flows therethrough. When the current 1b flows through the third switching element Q3 in the direction shown by the arrow, the second primary winding 62 is connected to the magnetic flux shown by the arrow 70 in the opposite direction to the magnetic flux in the first direction shown by the arrow 69. The magnetic core 60 is wound so that magnetic flux in two directions is generated in the magnetic core 60. In FIG. 6, the first switching element Q1 is turned on from tO to t2 and from t4 to t6, and the first current 1a flows, and from t2 to t4 and from t6 to t8, the third switching element Q3 is turned on. , a second electric current filb flows. In addition,
The current waveforms in FIGS. 6A and 6C correspond to the current waveform Fl in FIG. 2F. Since the first current 1a and the second current 1b do not flow simultaneously, the current detection voltage Vc shown in FIG. 6(B) is applied to the output terminals 71 and 72 of the secondary winding 63.
t can be obtained. That is, the positive current detection voltage VCt is obtained during the periods tO to t2 and t4 to t6 when the first current 1a is flowing, and the current detection voltage VCt in the positive direction is obtained during the periods t2 to t4 and tB to t8 when the second current 1b is flowing. is the reverse current detection voltage Vc
t is obtained. When the current detection voltage Vct of the output terminals 71 and 72 of the current detector 27 is inputted to the full-wave rectifier circuit 34 shown in FIG. 1 to obtain the full-wave rectified output (absolute value),
) waveform F1 can be obtained. This waveform F1 corresponds to a full-wave rectified waveform of the AC input current 12.

First and second currents 1a in current detector 27.

Ib is interrupted at a high frequency (50k) (z). As a result, the current detector 27 can be configured as a high-frequency CT, achieving significant size reduction and cost reduction.

That is, compared to commercial frequency CT, the high frequency CT of this embodiment
The diameter of the magnetic core is about 378 mm, and the cost is 1/10
It becomes below.

[Conversion Operation] Next, the operation of the circuit shown in FIG. 1 will be explained. In the circuit of FIG. 1, 50H is connected between the output lines 13 and 14 of the rectifier circuit 12.
A capacitor for smoothing the full-wave rectified waveform of the AC power supply voltage z is not connected.

Therefore, the inverter switch circuit 15 has a power supply terminal 1
．． A voltage obtained by full-wave rectification of the sum of the AC power supply voltage No. 2 and the voltage based on the energy stored in the reactors 3 and 7 by the rectifier circuit 12 is applied. Inverter switch circuit 15
When the switches Q1 to Q4 are controlled on and off, the currents on the input side and output side of the rectifier circuit 12 change accordingly.

The on/off frequency of the switches Q1 to Q4 of the inverter switch circuit 15 is 50 kHz, and the input terminals 1.
Since the current 12 flowing through the actuator in Fig. 1 is sufficiently higher than the power supply frequency (50Hz) of switch Q1~
Corresponding to the on/off control of Q4, an approximate sine wave containing high frequency ripples is generated as shown in FIG. However, since the capacitor 4 is provided, the harmonic components are removed, and the input current 11 becomes an approximate sine wave including no pull as shown in FIG.

When operating the circuit shown in FIG. 1, the sawtooth wave generation circuit 41 generates a sawtooth wave A2 shown in FIG.
The control signal for the first switch Q1 in Figure (B) and the control signal for the first switch Q1 in Figure 2 (
The control signals of the third switch Q3 in C) are generated in a fixed manner in synchronization with each other. In addition, the control signals of the first and third switches Ql and Q3 in FIGS. 2B and 2C have a phase difference of more than 180 degrees.
) and apply these to the second and fourth switches Q2 and Q4.

The control signals in FIGS. 2(D) and (E) are applied to the first error amplifier 3.
5 and comparator 40.

The current detection signal F1 including the ripple shown in FIG. 2(F) is input to one input terminal of the error amplifier 35, and the reference sine wave F2 shown in FIG. 2(F) is input from the multiplier 37 to the other input terminal.
When input, a signal A1 containing information on the input current 12 and information on the output voltage is obtained at the output stage of the low-pass filter 43 connected to the output terminal of the error amplifier 35. As shown in FIG. 2(A), the signal AI and the sawtooth wave generation circuit 41
When the sawtooth wave A2 of FIG. 2(A) obtained from the signal AI is compared by the comparator 40, the output of the comparator 40 changes every time the sawtooth wave A2 crosses the signal AI.

That is, the sawtooth wave A2 is higher than the signal Al (from t1 to
During periods such as t2, t3 and t4, the output of the comparator 40 becomes high level, and the waveform shown in FIG. 4(A) is obtained. Based on the output of the comparator 40, the control signal forming circuit 42 controls the second and fourth switches Q2 and Q4 shown in FIGS. form a control signal. That is, in response to the inversion of the output of the comparator 40 at tl, the control signal of the second switch Q2 is returned to a low level;
Conversely, the control signal of the fourth switch Q4 is inverted to high level. At time t3, when the output of the comparator 40 changes to high level again, the control signal of the second switch Q2 is changed to high level 1, and the control signal of the fourth switch Q4 is changed to low level. The time points t2, t4, etc. at which the sawtooth wave A2 crosses the level of the signal A1 from high to low are independent of the control signals of the second and fourth switches Q2, Q4.

During to-tl, t4-t5 periods in FIG.
short-circuited. As a result, the current i2 flowing through the reactor 7 increases as shown from t0 to t1 in FIG. In the period t1 to t2, the second switch Q2 is turned off, so the short circuit is released, and the first switch Q1, the primary winding 17 of the output transformer 16, and the fourth transistor Q
4 is formed, so the current 12 decreases. At this time, the AC power supply voltage and reactors 3 and 7
The sum of the voltages is input to the rectifier circuit 12. Therefore, the input voltage of the inverter circuit 100 is higher than the voltage obtained by rectifying the AC power supply voltage by the voltage of the reactor.

When the switch Q3 and the fourth switch Q4 from t2 to t3 are simultaneously turned on, a short circuit is formed again, and the current i2 increases again. However, at t8 the fourth switch Q
4 is turned off, the third switch Q3 and the primary winding 17
and the second switch Q2 is formed, and the current 12 decreases again. The AC power supply voltage changes with a sine wave,
Since this is given to the error amplifier 35 as a reference, the current 12 also changes along the sinusoidal voltage. t0 to tl when the inverter switch circuit 15 does not generate an output voltage;
Even during periods t2 to t3, t4 to t5, etc., current flows through the reactors 3 and 7 because short circuits are formed by the switches Q1 to Q4. Therefore, the input current 1
2 is controlled, and this waveform can be approximated to a sine wave.

Since the reference sine wave for comparison with the current detection signal F1 in the first error amplifier 35 is formed based on the voltage of the power supply terminal 1.2, the input voltage and the input current are in phase and the power factor is 1. It can also be done.

When the detected value of the DC output voltage detection circuit 31 changes, the second
The output level of the error amplifier 38 changes, the output level of the multiplier 37, that is, the amplitude of the reference sine wave changes, and the output level of the first error amplifier 35 changes, and the short circuit time width α, that is, the output voltage of the inverter changes. The width changes and the voltage is adjusted.

[Modifications] The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(1) As shown in FIG. 9, the reactor 7 may be moved to the output side of the rectifier circuit 12. That is, the harmonic component removal filter 5 may be divided into a first portion 5a consisting of the reactor 3 and the capacitor 4 and a second portion 5b consisting of the reactor 7.

(2) As shown in Figure 10, two reactors 3.7
The entire filter 5 consisting of the capacitor 4 and the capacitor 4 may be connected to the output line 13, ], 4 of the rectifier circuit 12.

(3) As shown in Figure 11, the DC line 13 and
Even if a current detector 27 is connected between the third switching elements Ql and Q3, the same effect as in FIG. 5 can be obtained.

(4) As shown in FIG. 12, even if a current detector 27 is connected between the second and fourth switching elements Q2 and Q4 and the DC line 14, the same effect as in FIG. 5 can be obtained. I can do it.

(5) The present invention can also be applied to a device in which the output stage rectifier circuit 60 is omitted.

[Effects of the Invention] As is clear from the above, according to the present invention of claims 1 and 2, it is possible to reduce the size and cost of the current detection device.

[Brief explanation of drawings]

1 is a circuit diagram showing a power supply device according to an embodiment of the present invention, FIG. 2 is a voltage waveform diagram of each part of FIG. 1, FIG. 3 is a block diagram showing the control signal forming circuit of FIG. 1, Figure 4 is a voltage waveform diagram of each part in Figure 3. Figure 5 is a circuit diagram showing the relationship between the inverter circuit and current detector in Figure 1 in detail. Figure 6 explains the principle of the current detector in Figure 5. Figure 7 is a waveform diagram of the input terminal in Figure 1, Figure 8 is a waveform diagram that basically shows the current at the stage after the filter in Figure 1, Figures 9 and 10 are FIGS. 11 and 12 are circuit diagrams showing modified examples of the power supply device, respectively. FIGS. 11 and 12 are circuit diagrams showing modified examples of the connection of the current detector, respectively. 7... Reactor, 12... Rectifier circuit, 15... Inverter switch circuit, 16... Transformer, 27...
・Current detector, 34...Full wave rectifier circuit, Q1~Q4・
...first to fourth switching elements. Agent Nori Takano Figure 2 Figure 5 L - JLJ Figure 11

Claims (1)

[Scope of Claims] [1] A power supply terminal for supplying a sine wave AC voltage, a rectifier circuit connected to the power supply terminal, and a first
a switching element for causing a current to flow in the direction of
an inverter circuit having a switching element for flowing a current in a second direction opposite to the direction of the current detecting device for detecting an AC input current of a power supply device, comprising: a magnetic core; It consists of first and second primary windings wound around the magnetic core, and a secondary winding wound around the magnetic core, and the first primary winding is the first primary winding of the inverter circuit. is connected in series to a path through which a current flows in the direction of the second
A secondary winding is connected in series with a path through which a current in the second direction of the inverter circuit flows, and the polarity of the first primary winding is such that the current in the first direction causes the magnetic core to have a first polarity.
is determined to generate a magnetic flux in the direction of the second one.
a current transformer in which the polarity of the next winding is determined such that the current in the second direction generates a magnetic flux in a second direction opposite to the magnetic flux in the first direction in the magnetic core; and an absolute value circuit for obtaining the absolute value of the output of the secondary winding of the device. [2] Furthermore, a reactor connected in series to an AC or DC power line between the power supply terminal and the inverter circuit, and a reference sine wave generating means for generating a reference sine wave synchronized with the AC voltage; a difference signal generating means coupled to the current detecting device and the reference sine wave generating means, for generating a difference signal corresponding to a difference between a signal corresponding to the current detected by the current detecting device and the reference sine wave; , coupled to the switching element of the inverter circuit and the difference signal generating means, having a signal section for converting a DC voltage into an AC voltage in the inverter circuit, and converting the waveform of the input current of the rectifier circuit into the reference sine wave. forming a control signal having a signal section for controlling the switching element to short-circuit the pair of output terminals of the rectifier circuit based on the switching element of the inverter circuit in order to approximate the above, and supplying the control signal to the switching element; The power supply device according to claim 1, further comprising a control circuit.