JPS5850102B2 - transistor chopper device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a transistor chopper device.

Conventionally, methods for driving power transistors in this type of device include always supplying a base current capable of driving the maximum collector load current regardless of the increase or decrease of the load current, or
Alternatively, a Darlington connection was commonly made.

Therefore, in such a driving method, a large power loss is generated to supply the base current, and a Darlington connection generates a large collector loss, so it is particularly difficult to use a transistor chopper circuit at light load. This significantly reduced efficiency.

In order to improve this efficiency reduction, the collector current of the power transistor is detected by a current transformer, and a current proportional to the collector current is supplied as the base current of the power transistor, which can be used under a wide range of load conditions. A method for driving power transistors that maintains high efficiency has been proposed and has been applied to transistor inverters and transistor choppers.

However, when configuring a chopper device using such a driving method, the current transformer must detect direct current.

That is, since the current magnetic core is DC-excited, its magnetic reset must be performed periodically and with good timing, making this type of chopper device have a relatively complicated circuit configuration.

The present invention is particularly applicable to a transistor chopper device that controls a DC power source obtained by rectifying an AC power source, in which the collector current of a power transistor is detected and a current proportional to the collector current is supplied as the base current of the power transistor. At that time, by exciting the current transformer through its primary winding using the periodic voltage fluctuations of the AC power supply,
It is an object of the present invention to provide a transistor chopper device that does not require a special reset circuit for resetting a current transformer, has a simple circuit configuration, and is highly efficient.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are magnetization characteristic diagrams of the current transformer core and FIG. This is a time chart.

In FIG. 1G, VAC is an AC power supply, and D1 to D4 are diodes that constitute a full-wave rectifier circuit 10.

2 is a DC load, Vz is the voltage across this DC load, DI is a flywheel diode, TR is a transistor, CT
is a current transformer having a primary winding Np, a first secondary winding Ns1, and a second secondary winding Ns2.

Reference numeral 20 denotes a base current supply circuit that rectifies the current flowing through the secondary winding Ns, controls the current on and off, and supplies it as a base current to the transistor TRc.

CR2 is a silicon risk for ON and OFF, D5 and D6 are diodes, R is a current detection resistor, and CCU is a control device.

Next, the operation will be explained.

As an example, the DC load Z is a DC motor, and the control device C
A case will be described in which the motor current is controlled by the CU.

Positive half wave (shaded area) of the rectified voltage VDC waveform shown in Figure 3
During the period, the control unit CCU turns ON as shown in FIG.
When the pulse signal VG1 is given, Cyrisk CR1,
and transistor TR both try to conduct, and the load current Il is transferred from the AC power supply VAC to the primary winding Np of the current transformer CT.
, diode D1. The current tries to flow through the DC load Z, the collector of the transistor TR, the emitter, and the diode D4.

This load current Il induces an electromotive force in the primary winding Np of the current transformer CT, with the black dot (Fig. 1) indicating the winding direction as the positive pole, and similarly, in the secondary winding Ns 1 , Ns 2
Also, an electromotive force is induced with the sunspot as the positive pole.

The electromotive force generated in the second secondary winding Ns2 does not act because there is no current path, but the electromotive force generated in the first secondary winding Ns1 causes the current transformer CT magnetic core to become magnetically saturated. Since this is not the case, the equal ampere turn law should be satisfied (np/ns1
)×■l (where np is the number of turns of the primary winding Np, and nsl is the number of turns of the first secondary winding Ns1), the secondary winding current ■s1 is the resistor R, the thyristor CR1, It attempts to flow from the base of the transistor TR to the emitter and through the diode D6.

Note that the excitation current of the current transformer CT is assumed to be a negligible value.

In advance, the relationship between the current transformation ratio (ns/np) of the current transformer CT and the current amplification rate β of the transistor TR is expressed as ns/n
If p < β, the transistor TR will increase the primary winding current Il as described above due to the current feedback action of the current transformer CT.
The secondary winding current Is proportional to the transistor T
It continues to conduct due to the base current of R and supplies power to the DC load 2.

Next, when the OFF pulse signal VG2 shown in FIG. 3 is applied from the control unit CCU, the cyrisk CR2 becomes conductive.

The forward voltage drop when Cyrisk CR2 is on is lower than the voltage between the anode and cathode when it is off, that is, the sum of the voltage drops between the resistor R, Cyrisk CR1, and the base and emitter of transistor TR, so the base current is lower than the voltage drop between the anode and cathode when Cyrisk CR2 is turned on. CR2G is bypassed, the transistor TR is turned off, and the load current l is transferred to the flywheel diode D.
It is commutated to I.

At the same time as the load current is commutated, both the primary winding current and the secondary winding current of the current transformer CT become zero, so the si risk C
R2 turns off and prepares for the next operation.

While the transistor TR is conducting, the magnetic core of the current transformer CT is excited toward +0 m from the initial position 0 point shown in FIG.
Suppose that point a1 has been reached.

Next, in the negative half wave of the rectified voltage VDC waveform in Fig. 3,
When an ON pulse signal is given from the control device CCU, the transistor TR tries to conduct as in the above explanation, and the load current Il is transferred from the AC power supply VAC to the diode D3.
, the DC load Z, the collector to the emitter of the transistor TR, the diode D2, and the primary winding Np of the current transformer CT.

Therefore, contrary to the above, an electromotive force is induced in the primary winding NpG of the current transformer CT, and an electromotive force is induced in the secondary winding NpG with the black dot as the negative pole.
Similarly, an electromotive force is induced in s with the sunspot as the negative pole.

Due to the electromotive force generated in the second secondary winding Ns2 of the secondary winding Ns, a secondary current Is2 of a magnitude of (np/n52) Flows from the emitter to the diode D5, and the current transformation ratio (ns2/np) is ns2/np<β
If so, transistor TR continues to conduct.

In addition, when turning off the transistor TR, the operation is exactly the same as that described above, and the OFF pulse signal VG2 is turned off by the cyrisk C.
It is sufficient to apply the current to the gate of R2 and bypass the base current to Cyrisk CR2.

During this negative half-wave conduction period, the current transformer CT core is energized in the opposite direction to the aforementioned energization direction.

In other words, the moving direction of the magnetic core magnetic flux depends on the direction of the electromotive force induced in the winding, and the amount of movement is proportional to the time integral value of the electromotive force. It is assumed that the magnetic flux held at is moving in the direction of -Φm and reaches point b1.

The reason why point 0 is exceeded and point b1 is reached is because it is assumed that the DC motor 2 is accelerating and the energization rate has increased from the previous time.

Therefore, by repeating the above operation, the magnetic core of the current transformer CT is excited in opposite directions in each positive and negative half-wave, increasing the amount of magnetic flux movement and finally (time) point A2 and point b2 are reciprocated, and the magnetic core operates as a transistor chopper device without being saturated.

Further, impedance Z is indicated by a broken line in FIG.

is a case where a current flows through the primary winding Np when the transistor TR is off, such as when the power supply for a load such as the control unit CCU is supplied from the rectified voltage VDC, and the current value is equal to the excitation of the current transformer CT. This connection is made in order to allow an appropriate amount of secondary winding current to flow so that the magnetic core of the current transformer CT does not become saturated when the current is larger than the current.

As described above (according to the device of this embodiment, the transistor T
By driving R from the current feedback action of the current transformer CT and detecting the load current by the current transformer CT on the AC power supply side, high efficiency can be achieved, and the reset of the current transformer CT can be used to detect the load current. Since it also functions as a circuit, it has very excellent effects such as a simple circuit configuration.

FIG. 4 is an electric circuit diagram showing another embodiment of the present invention,
In order to full-wave rectify the AC output of the secondary winding Ns of the current transformer CT, a full-wave rectifier circuit is constructed using diodes D5 and D6 and a thyristor CR.
Each of the above thyristors CRI and CR2 is configured by the control unit CCU in synchronization with the AC power supply VAC.
It is configured to ignite and perform phase control.

That is, in the figure, when a positive half-wave voltage is applied from the AC power supply VAC, the control unit CCU gives an ON pulse signal to the Cyrisk CRI in order to obtain a predetermined firing angle.

Then, the transistor TR starts to conduct, and due to the current feedback action of the current transformer CT, its secondary winding Ns becomes sirisk CR.
1. A base current proportional to the load current is supplied to the transistor TR via the diode D5.

Therefore, the transistor TR continues to be conductive and turns off when the AC voltage VAC is near zero.

Next, when a negative half-wave voltage is applied, the control unit CCU gives the Cyrisk CR2G ON signal with a desired phase delay, and the current feedback action of the current transformer CT also causes the 2G signal to turn on.
The next winding Ns causes a base current to flow through the silicon risk CR2 and the diode D6, making the transistor TR conductive.

By performing this operation alternately, the transistor TR
can perform phase control efficiently.

FIG. 5 is an electric circuit diagram showing still another embodiment of the present invention, in which T is a transformer whose primary coil is connected to an AC power source VAC, and a two A full-wave rectifier circuit is constituted by the secondary winding and diodes DI and D2, and the primary winding of the current transformer CT is composed of the first and second primary windings Np 1 and Np 2, respectively. It is connected in series to each of the positive half-wave and negative half-wave rectifier paths in a full-wave rectifier circuit, and is energized by the positive and negative half-waves, respectively.

In this configuration, when the transformer T generates a positive voltage +V'AC, the diode D1 and the current transformer C
A load current I7 flows from the first primary winding Np 1 of T, the DC load Z, and the collector to the emitter of the transistor TR, and at this time, the first primary winding Np1 of the current transformer CT has a black dot as its positive pole. An electromotive force is generated, and the magnetic core flux of the current transformer CT moves in a direction determined by the direction of this electromotive force.

When a negative voltage V'AC is generated, a load current 4 is caused to flow from the collector of the diode D2, the second primary winding Np2 of the current transformer CT, the DC load Z, and the transistor TR to the emitter.

Therefore, an electromotive force with the black dot as a negative pole is generated in the second primary winding Np2, and the magnetic core flux of the current transformer CT fluctuates in the opposite direction to that described above.

Therefore, the number of turns of the first primary winding Np1 and the second primary winding Np2 are made equal, and this is set as the number of primary windings np, and 2
When the number of secondary windings is ns, current ratio ns / n p
If the relationship between the current amplification factor β of the transistor TR and the current amplification factor β of the transistor TR is set in the same manner as described in FIG. 1, the current transformer CT will not be saturated and will operate in the same manner as in FIG.

As described above, according to the present invention, it is possible to improve the efficiency of the device by setting the base current of the transistor that controls opening and closing of the load current path to a value corresponding to the load current using a current transformer.
The above current transformer utilizes the positive and negative half waves of AC power.
Since the current transformer is excited via the next winding, there is no need for a special reset circuit for magnetically resetting the current transformer, and the device can be simplified.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, FIG.
FIG. 3 is a magnetization characteristic diagram and a time chart diagram of a current transformer for explaining the operation of FIG. 1, respectively, and FIGS. 4 and 5 are electric circuit diagrams showing other different embodiments of the present invention. . VAC: AC power supply, 10: Rectifier circuit, 2: DC load, TR: Transistor, CT: Current transformer, Np...1
Next winding, Ns... Secondary winding, CRLCR2...
...Sirisk, 20...Base current supply means. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. An AC power source, a rectifier circuit that rectifies the output of this AC power source and converts it to DC, a series circuit of a load and a transistor connected in series to the DC side of this rectifier circuit, and an AC side of the rectifier circuit. A current transformer having a primary winding through which a current is passed through and a secondary winding through which a current approximately proportional to the current through the primary winding is conducted, the current transformer rectifying the current through the secondary winding. A transistor chopper device comprising a base current supply means for supplying a base current to the transistor by intermittent controlling the si-risk. 2. The rectifier circuit is constituted by a full-wave rectifier circuit, and the primary winding of the current transformer consists of a first and a second winding, and the first and second windings are configured by a full-wave rectifier circuit, respectively. 2. The transistor chopper device according to claim 1, wherein the transistor chopper device is connected in series to each circuit that conducts positive and negative waves of alternating current in a rectifier circuit.