JP3158805B2 - Voltage converter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic induction means, wherein a current flowing through a magnetic induction means such as a reactor receiving a rectified AC voltage is intermittently switched by a switching means so that a power factor of an electric power taken from an AC power supply approaches one. The present invention relates to a so-called active filter type voltage converter circuit that extracts a DC output voltage from a power supply.

[0002]

2. Description of the Related Art It is well known that the above-mentioned voltage converter for converting a power supply voltage is widely used as a DC power supply for supplying a stable voltage to an electronic circuit or an electronic device in the form of a switching power supply or a stabilized power supply. However, the source of the supplied power is usually an AC commercial power supply, except for the case of very small power. You. That is, in a converter, the power factor of the power taken from the AC power supply is reduced due to the inductance of a magnetic induction means such as a reactor for voltage conversion or a transformer. The power factor is improved by controlling to have the same phase as the AC voltage. The outline of the circuit and operation of a conventional example of this type of voltage converter will be described below with reference to FIG.

FIG. 3 shows a so-called step-up type voltage converter. In this type of converter, a voltage Vr obtained by rectifying a commercial frequency AC voltage Va by a rectifier circuit 1 is supplied to a reactor 2, and a current flowing through the reactor 2 is interrupted at a high frequency by a switching transistor 3. Is taken out as an output voltage Vo via a diode 4 and smoothed and stabilized by a capacitor 5. An actual value vo of the output voltage Vo by the voltage dividing circuit 6 is supplied to an error amplifier circuit 7, and an error voltage indicating a difference from the set value vs.
Output ve. The multiplication circuit 8 calculates the error voltage ve and the rectified voltage Vr.
Then, a voltage error signal Se proportional to the error voltage ve and having the same pulsating waveform as the rectified voltage Vr is output by multiplication of the two.

A current flowing when the switching transistor 3 is turned on and its waveform are detected by a detection resistor 9, and this current waveform signal Sc and the above-described voltage error signal Se are supplied to a current error detection circuit 10 to represent a waveform difference between the two signals. Current error signal
S1 is output to the non-inverting input of the intermittent command circuit 30. The intermittent command circuit 20 is, for example, a single comparator circuit, and the high-frequency oscillation circuit 21
The on-off command Sw, which is a kind of PWM signal, is output to the switching transistor 3 by comparing it with, for example, a periodic signal S0 of a sawtooth wave which designates the intermittent cycle of the switching transistor 3 received from the switching transistor 3. At the duty ratio specified by the on / off command Sw.

As can be seen from the above circuit configuration and operation, in the voltage converter circuit of FIG. 3, the switching transistor 3 is turned on and off at a high frequency of about 100 kHz, for example, so as to correct the error voltage ve, and to control the AC voltage of 50-60 Hz. By controlling the duty ratio of the current flowing through the switching transistor 3 to match the current waveform signal Sc with the pulsating waveform of the voltage Vr obtained by rectifying the voltage Va, the power taken from the AC power supply while maintaining the output voltage Vo at a predetermined set value Can be controlled to approximately one.

When the voltage converter is of the step-up type as shown in FIG. 3, the magnetic energy accumulated in the reactor 2 during the ON period of the switching transistor 3 is taken out to the output voltage Vo during the OFF period. The power factor of the electric power taken by the input side can be accurately controlled by the active filter system almost without being affected by the state of the power supply. Similarly, a voltage converter using a flyback type transformer as a magnetic induction means instead of the reactor 2 is also advantageous for applying this active filter system.

[0007]

However, in the above-mentioned conventional circuit of the voltage converter of the active filter system, when an abnormality occurs on the load side, the circuit operation does not always become in a state conforming to or coping with it. There is a problem of insufficient handling of abnormal conditions. For example, if the load is cut off or suddenly becomes a light load, the output voltage Vo
Therefore, it is necessary to control the switching transistor 3 so that the current flowing through the reactor 2 is reduced to almost 0 in order to lower it. However, in the circuit of FIG. When the current waveform signal Sc is almost 0 due to an error, the operation becomes inaccurate. Therefore, the current of the reactor 2 is sufficiently reduced to reduce the output voltage.
It is difficult to limit Vo to a safe range.

In the circuit of FIG. 3, when the output voltage Vo is excessively large, the error voltage ve becomes extremely low, and the operation of the multiplying circuit 8 receiving the output voltage ve always has a slight offset error.
It is difficult to generate a voltage error signal Se that is exactly proportional to this low error voltage Ve. Of course, a high-precision class circuit can be used for the multiplication circuit 8 although it is expensive, but since the voltage error signal Se output from the circuit becomes almost zero,
Each of the current error detection circuits 10 is a low-level current waveform signal.
The operation must be performed based on Sc and the voltage error signal Se, which may result in unstable operation.

[0009] In addition to the load interruption, an abnormal condition in which the load is short-circuited may occur. In this case, the switching is performed so as to limit the current flowing through the load to a predetermined value or less when the output voltage Vo is extremely low. It is necessary to control the current intermittent operation of the transistor 3, and it is the same that the precise control is difficult due to the offset error in the operation of the current error detection circuit 10 and the multiplication circuit 8, although not as much as when the load is interrupted.

In view of the foregoing, an object of the present invention is to enable the circuit operation of an active filter type voltage converter to accurately cope with an abnormal state when an abnormality occurs on the load side.

[0011]

SUMMARY OF THE INVENTION According to the present invention, the above object is attained by providing an electric current flowing through a magnetic induction means for receiving a voltage obtained by rectifying an AC voltage as described in the opening paragraph, by interrupting the current through the magnetic induction means by a switching means. For a voltage converter circuit that extracts a DC output voltage, a current is calculated from a voltage error signal that is proportional to an error voltage indicating a deviation from a set value of the output voltage and has the same pulsating waveform as the rectified voltage and a waveform signal of a current flowing through the switching means. A current error detection circuit that issues an error signal; an intermittent command circuit that issues an on / off command based on the periodic signal that specifies the control cycle of the switching means and the current error signal described above; and when an abnormality occurs on the load side of the converter. An abnormality detection circuit that issues an abnormality signal is provided. Controls the waveform of the flowing current so that it has the same phase as the rectified voltage. If an abnormal signal occurs, it gives it to the intermittent command circuit in preference to the current error signal, and sends the ON / OFF command to the duty ratio specified by the abnormal signal. This is achieved by outputting

The magnetic induction means is, for example, a reactor or a flyback transformer, and the switching means may be a switching transistor as usual. Also, the abnormality detection circuit is configured to generate an abnormality signal when the output voltage exceeds a predetermined limit value, for example, when the abnormal state is load shedding, and when the abnormal state is a load short circuit, an excessive load current or It may be configured to detect an abnormal decrease in the output voltage and generate an abnormal signal. In the abnormality detection circuit for detecting the load rejection, it is advantageous to provide an abnormality detection transistor for receiving the above-mentioned error voltage at the base, and to generate an abnormality signal when the error voltage exceeds the base-emitter voltage.

Further, the intermittent command circuit may be a conventional two-input comparator for receiving a periodic signal and a current error signal. However, an inverting input for receiving the periodic signal and two non-inverting comparators for receiving the current error signal and the abnormal signal, respectively. It is advantageous to use a three-input comparator having an input for comparing the current error signal with the periodic signal at all times, but when receiving an abnormal signal, to compare it with the periodic signal prior to the current error signal. When the interrupting command circuit has two inputs, for example, when an abnormal signal is generated, the current error signal may be switched to the interrupt signal and supplied to the interrupting command circuit. For example, an abnormal signal when the load is interrupted and an abnormal signal when the load is short-circuited are generated separately. In this case, the current error signal may be switched to any one of the signals.

The circuit of the present invention is particularly applicable to a step-up type or polarity reversal type voltage converter using a reactor for magnetic induction means, or a voltage converter that is a stabilized power supply or a switching power supply using a flyback type transformer for magnetic induction means. Suitable.

[0015]

In the present invention, the problem of the conventional voltage converter circuit is that the operation of the current error detection circuit becomes inaccurate or unstable as described above when an abnormality such as load shedding occurs, and the switching means Focusing on the fact that a signal value designating it can be directly applied to the gating command circuit in order to make the gating intermittent with a desired duty ratio, an abnormality detection circuit is provided to provide an abnormality signal when the voltage converter is abnormal with the above specified signal value. The problem is solved by applying this abnormal signal directly to the gating command circuit without going through the current error detection circuit, thereby switching the switching means with the correct duty ratio most suitable for the specified abnormal condition. I do.

That is, by causing the current error detection circuit to generate a current error signal from the voltage error signal and the current waveform signal, and always causing the intermittent command circuit to generate an on / off command for the switching means from this and the periodic signal, the AC power supply is used. Although it operates as an active filter type voltage converter that controls the power factor of the electric power to be substantially equal to one, the present invention is different from the conventional one in that the abnormal condition is detected by an abnormality detection circuit and an abnormal signal is detected when an abnormality occurs. By giving the interrupting command circuit a higher priority than the current error signal, an ON / OFF command for interrupting the switching means is generated at an accurate duty ratio specified by the abnormal signal value independently of the operation of the current error detecting circuit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the circuit of the present invention is applied to a step-up type voltage converter, and FIG. 2 shows an embodiment in which the circuit of the present invention is applied to a voltage converter using a flyback type transformer. Since the same reference numerals are given to the portions corresponding to FIG. 3 in both drawings, the description of the overlapping portions will be omitted as appropriate. In each of the embodiments, the case where the abnormal state is load shedding will be described. However, even when the abnormal state is an overload or load short circuit, the configuration of the abnormality detecting circuit or the way of giving an abnormal signal value is only slightly changed. The circuit of the present invention can be easily applied within its gist.

AC voltage supplied to the voltage converter of FIG.
Va is a commercial frequency of 100 to 220 V, and its rectified voltage Vr is 140 to
The output voltage is 310 V because it is a step-up converter
Vo is usually in the range of 170 to 380 V, and the load receiving this is often a motor drive device or a plurality of stabilized power supplies. When the load is the former, the power it takes is highly variable, and in the latter case the converter functions as a constant-voltage rectifier, but recently a regulated power supply has been generated with the load to reduce power consumption. Since the vehicle tends to stop, it is easy to fall into an abnormal state with no load during operation.

The structure of the main circuit of the voltage converter shown in FIG. 1 is the same as that shown in FIG. 3. To operate this circuit in an active filter system, an error amplifier circuit 7, a multiplier circuit 8, a current detection resistor 9, and a current error detection circuit 10 are provided. It is the same to provide. The same applies to the use of a comparator for the intermittent command circuit 20, but
In the illustrated example, a three-input comparator having two non-inverting inputs in addition to an inverting input receiving the periodic signal S0 from the oscillation circuit 21 is used for this.

In addition to the above, in the voltage converter circuit of the present invention, an abnormality detection circuit 30 is provided, and in this embodiment, a single comparator is used in this circuit to limit the error voltage ve output from the error amplifier circuit 7 to a predetermined limit. Abnormality is detected by comparing with the value vl. When the converter load is cut off, the output voltage Vo and its actual value vo increase, and in the example shown in the figure, when the error voltage ve decreases and falls below the limit value vl, the abnormality detection circuit
30 emits a low level abnormal signal S2. The above-mentioned interrupted command circuit 20 receives the current error signal S1 from the current error detection circuit 10 at one non-inverting input, and receives the abnormal signal S2 from the abnormality detection circuit 30 at the other non-inverting input.

The circuit of the embodiment shown in FIG. 1 thus constructed always operates as an active filter type converter which makes the power factor of the electric power obtained from the AC voltage Va almost equal to one as in the conventional circuit. That is, the error amplifier circuit 7 generates an error voltage ve indicating the deviation of the actual value vo of the output voltage Vo from the set value vs, and the multiplier circuit 8 generates a voltage error having a pulsating waveform proportional to the error voltage ve and the same as the rectified voltage Vr. Make the signal Se,
A power error detection circuit 10 generates a current error signal S1 from a voltage error signal Se and a power waveform signal Sc obtained by detecting a current flowing through the switching means 3 by a detection resistor 9, and further generates a power error signal S1 and an oscillation circuit by an intermittent command circuit 20. 21 periodic signal
By generating an on / off command Sw based on SO and giving it to the switching means 3, the switching transistor 3
The power factor of the power is controlled to be approximately 1 so that the waveform of the current flowing through the rectifier voltage Vr, that is, the waveform of the current flowing from the AC voltage Va, is in phase with the rectified voltage Vr.

When an abnormality occurs on the load side of the voltage converter circuit of FIG. 1 and an abnormality signal S2 is generated from the abnormality detection circuit 30, two of the comparators used in the intermittent command circuit 20 in this embodiment are Since the lower signal value of the signals received by the non-inverting inputs of the respective signals always takes precedence, as described above, the abnormal signal S2 generated at a low level takes precedence over the current error signal S1, and this and the periodic signal An on / off command Sw is generated at a duty ratio specified by the signal value of the abnormal signal S2 from SO and output to the switching means 3. Abnormal signal
In this embodiment in which S2 is issued when the load is cut off, the low-level signal value of the abnormal signal S2 is set to the output voltage Vo in a no-load state generated by the intermittent switching means 3 receiving the on / off command Sw, for example, the abnormality detecting circuit 30. Is set to a value slightly higher than the voltage value corresponding to the detection limit value vl.

As described above, the voltage converter circuit shown in FIG. 1 switches between the normal operation as the active filter system and the operation at the time of an abnormality. It is particularly advantageous to operate the error amplifier circuit 7 such that the error voltage ve is biased, for example, so as to deviate from this range in the event of an abnormality. When the abnormal state is an overload or a load short circuit, the abnormality detecting circuit 30 detects the abnormal state from an abnormal increase in the load current or an abnormal decrease in the output voltage Vo, and the abnormal signal S2 is suitable for limiting the load current. It may be generated by a signal value.

Further, the circuit of the present invention can be configured so as to be able to cope with any abnormal state, for example, load interruption and load short circuit. For this purpose, for example, two abnormality detection circuits 20 are provided to detect an abnormal state, respectively.
The current error signal S1 always given to the non-inverting input may be switched to an abnormal signal that detects a load interruption or a load short circuit when an abnormality occurs, using an input comparator.

The voltage converter of the embodiment shown in FIG. 2 is a switching power supply using a flyback type transformer as the magnetic induction means 2, and the current flowing through the primary coil 2 a is interrupted by the switching means 3 as usual. ,
The voltage induced in the secondary coil 2b when the current is cut off is rectified by the diode 4 and the DC voltage smoothed and stabilized by the capacitor 5 is taken out as the output voltage Vo. The circuit of this embodiment also includes an error amplifier circuit 7, a multiplication circuit 8, a current detection resistor 9, and a current error detection circuit 10 to operate as an active filter type converter. FIG. 1 also shows the use of a three-input comparator for the intermittent command circuit 20.
This is the same as the embodiment.

However, in the embodiment of FIG. 2, unlike the previous embodiment, the abnormality detection circuit 30 is configured by combining two transistors 31 and 32, and applies the error voltage ve to the base of the transistor 31. The transistor 31 is normally turned on by the error voltage ve, and therefore the transistor 32 receiving its output at the base is off, but the output voltage Vo abnormally rises due to a load cutoff of the converter and the error voltage ve is increased. When the voltage between the base and the emitter of the transistor 31 is lower than about 0.7 V, the transistor 31 is turned off, and thus the transistor 32 is turned on to generate a low-level abnormal signal S2. The operation of the intermittent command circuit 20 receiving this is the same as that of the previous embodiment, and the signal value of the abnormal signal S2 specifying the duty ratio of the on / off command Sw to be output thereto is, for example, the base-emitter voltage of the transistor 32 and its emitter. Set by the resistor 33.

As can be seen from the above description, in the embodiment of FIG. 2, the abnormality detection circuit 30 is constituted by a simple transistor circuit, so that it is necessary to provide the comparator with the detection limit value vl as in the embodiment of FIG. As a result, the signal value of the abnormal signal S2 can be set accurately. The operation reference point is set so that the error amplifier circuit 7 in this embodiment outputs the error voltage ve in a range higher than the base-emitter voltage of the transistor 31, for example, 1 V or more while the output voltage Vo is normal. Is done.

[0028]

As described above, according to the present invention, the set value of the output voltage is applied to the voltage converter circuit which takes out the output voltage from the magnetic induction means while interrupting the current flowing through the magnetic induction means receiving the rectified voltage by the switching means. A current error detection circuit for generating a current error signal from a voltage error signal proportional to the error voltage indicating the deviation and having the same waveform as the rectified voltage and a waveform signal of the current flowing through the switching means;
An intermittent command circuit that issues an on / off command based on a current error signal and a periodic signal that specifies an intermittent cycle of the switching means, and an abnormality detection circuit that issues an abnormal signal when an abnormality occurs on the load side of the converter. Controls the waveform of the current flowing through the switching transistor to the same phase as the rectified voltage according to the current error signal by the intermittent command circuit. When an abnormal signal occurs, it gives it to the intermittent command circuit in preference to the current error signal. By outputting an on / off command to the switching means at a duty ratio specified by the signal value, the following effects can be achieved.

(A) When an abnormality occurs, the abnormality signal is directly supplied from the abnormality detection circuit to the intermittent command circuit without passing through a current error detection circuit or a multiplication circuit, which is likely to be unstable or uncertain. In the event of an abnormality such as interruption or short circuit, it is possible to limit the output voltage or the load current much more reliably than before. (b) Since the duty ratio of the on / off command for switching the switching means in an abnormal state is specified in the interrupting command circuit by the signal value of the abnormal signal, the current error detection circuit and the multiplying circuit may be troubled by inaccurate operation in the event of an error. Therefore, the switching means can be switched on and off at an accurate duty ratio most suitable for each abnormal state.

(C) By simply giving priority to the abnormal signal over the current error signal, the operation as an active filter system that constantly controls the power factor of the power taken from the AC power supply to approximately 1 and the switching means in the event of an abnormality. An operation of surely intermittently switching the state at the optimum duty ratio can be achieved. Note that the circuit of the present invention is particularly suitable for an active filter type step-up voltage converter that supplies DC voltage to a load such as a switching power supply that is frequently started and stopped, and reliably prevents an excessive increase in output voltage when a load is cut off. Meanwhile, the power factor of the power taken from the AC power supply during normal operation can be increased to minimize power consumption.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a step-up voltage converter circuit using a reactor as magnetic induction means.

FIG. 2 is a circuit diagram showing an embodiment in which the present invention is applied to a voltage converter circuit using a flyback type transformer as magnetic induction means.

FIG. 3 is a circuit diagram of a conventional step-up type voltage converter circuit.

[Explanation of symbols]

 2 Magnetic induction means 3 Switching means 10 Current error detection circuit 20 Intermittent command circuit 30 Abnormality detection circuit Sc Current waveform signal Se Voltage error signal Sw On / off command S0 Period signal S1 Current error signal S2 Abnormal signal Va AC voltage Vo Output voltage Vr Rectification voltage ve Error voltage vo Actual value of output voltage vl Detection limit value of abnormality detection circuit vs. set value for output voltage

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M ^7/ 00-7/40 H02M 3/00-3/44

Claims (3)

(57) [Claims] 1. A converter circuit for taking out a DC output voltage from a magnetic induction means while interrupting a current flowing through a magnetic induction means receiving a voltage obtained by rectifying an AC voltage by a switching means, wherein a deviation from a set value of the output voltage is provided. A current error detection circuit for generating a current error signal from a voltage error signal proportional to the error voltage and having the same pulsating waveform as the rectified voltage and a waveform signal of a current flowing through the switching means, and a cycle for designating a control cycle of the switching means An intermittent command circuit that issues an on / off command based on the signal and the current error signal;
An abnormality detection circuit that issues an abnormality signal when an abnormality occurs on the load side of the converter, and always makes the waveform of the current flowing through the switching transistor in phase with the rectified voltage according to the current error signal by the intermittent command circuit. So that when an abnormal signal is generated, the signal is given to the intermittent command circuit in preference to the current error signal, and an on / off command is output to the switching means at a duty ratio specified by the abnormal signal. Voltage converter circuit. 2. The circuit according to claim 1, further comprising a three-input comparator having an inverting input for receiving a periodic signal and a non-inverting input for receiving a current error signal and an abnormal signal, respectively. A voltage converter circuit that gives priority to the current error signal when the voltage error occurs. 3. The circuit according to claim 1, further comprising an abnormality detecting transistor provided in the abnormality detecting circuit for receiving the error voltage as a base, and generating an abnormal signal when the error voltage exceeds the base-emitter voltage. A voltage converter circuit characterized in that: