JPS62221882A - Control circuit for ac power - Google Patents

Abstract

PURPOSE:To simplify and miniaturize a device and reduce the cost, by boosting power with the oscillation signal of an oscillating circuit in a power control section, and by using the output for the control signal of the switching elements of an inverter section. CONSTITUTION:The control circuit of AC power switches the operation of an inverter section consisting of switching elements Q1-Q6 on and off by the control signal of high potential. The circuit has a power control section for controlling the effective value of power fed to an AC load M, and executes PWM control 30 on oscillation signal from an oscillating circuit 32 built in. The control circuit is provided with a booster circuit 10, and by the booster circuit 10, the power of a specified multiplying factor is boosted with the oscillation signal from the oscillating circuit 32. Besides, the output of the booster circuit 10 is connected to the switching control terminals of the switching elements Q1-Q6 of the inverter section, and is used for the voltage of high potential.

Description

[Detailed Description of the Invention] [Industrial Application Field] -1 - The present invention converts DC power into AC power, and performs appropriate intermittent control when supplying the AC power to a load. This invention relates to an AC power control circuit that can make even the effective value variable.

[Prior Art] Conventionally, various inverter circuits have been proposed for driving various AC loads such as AC motors with DC power sources. For example, in order to control the speed of an electric motor with high efficiency, it is necessary to supply AC power of a desired frequency and effective value to the electric motor. According to the inverter circuit,
By changing the operating frequency, the frequency of AC power can be easily controlled, and by appropriately intermittent operation (so-called PWM control), even the effective value of AC power can be easily controlled.

'' - As is well known, a useful inverter circuit as described above is constructed by a bridge connection of high-speed switching elements, and these switching elements are selectively connected to 0N10F.
The inverter operation is performed by F control. In recent years, power MOSFETs have been used as switching elements with the aim of achieving even higher performance OL in inverter circuits.
Some devices have appeared that adopt F1MO8T (hereinafter referred to as F1MO8T). If an inverter circuit using this MO8T is applied to motor control, it is clear that it will have the following excellent features.

First, MO8T has an extremely high switching speed, which makes motor control more efficient, less noisy, and more compact.

Second, since the MO8T is a voltage control type switching element, power saving and simplification of the control circuit can be achieved.

Thirdly, since the current characteristics of MO3T accelerate the negative temperature coefficient, it is easy to increase the capacity by parallel connection.

Fourth, the diode built in between the drain and source of MO8T has extremely high performance and can therefore be used as a conventional flywheel diode.

etc.

[Problems to be Solved by the Invention] However, even the inverter circuit using MO8T as described above is not sufficient and has the following problems.

There are two types of MO8T: a P-MOS FET (hereinafter referred to as P-MOS king) that uses a P-type semiconductor as a channel and an N-MOS FFT (hereinafter referred to as N-MO8T) that uses an N-type semiconductor. If these two MO8Ts both have highly efficient operating performance and can be easily manufactured, a complementary configuration using both is possible, and the inverter circuit can be simplified and miniaturized.

However, as is well known, P-MO8T has disadvantages such as a large voltage drop compared to N-MO8T, so its utilization rate is low, and an inverter circuit is constructed using only N-MO8T. It is usual. This N-MO8T is
In order to enter the N-state, a gate voltage of several square meters is applied between the source and gate of N-MO8T.
When the drain of T is connected to the →- side of the DC power supply, its source potential will also be as high as the voltage of the DC power supply (1'l) (because the voltage drop between the drain and north is small) , in order to obtain the control voltage applied to the gate, a voltage source with a higher potential other than the DC power source is required.This is a factor that increases the number of components of the inverter circuit using If-MO8T. This was a factor that hindered the miniaturization and cost reduction of circuits.

The present invention was made in view of the above problems, and is based on N-MO8
To provide an excellent AC power control circuit that further simplifies, downsizes, and lowers the cost of a control circuit that configures an inverter circuit using T or the like and obtains AC power of a desired frequency and effective value. It is an object.

Means for Solving Problem E] The means configured by the present invention to solve the problem described in , is connected to an electric circuit of a controlled system, and has a potential higher than the potential of the controlled system by a predetermined value. an inverter section having a switching element that opens and closes the electric circuit of the controlled system when a potential control signal is applied; and an oscillation signal from an oscillation circuit having a predetermined oscillation frequency to intermittent operation of the inverter section; In an AC power control circuit comprising a power control section that controls AC power supplied to a load connected to an inverter section, a booster circuit that inputs an oscillation signal of an oscillation circuit in the power control section and boosts the voltage. An alternating current power control circuit, characterized in that the output of the booster circuit is appropriately used as a control signal for a switching element of the inverter section.

[Function] The AC power control circuit of the present invention uses a switching element, such as an NPN, which is connected to an electrical circuit of a controlled system and performs a switching operation when a control signal with a higher potential than the potential of the controlled system is applied. An inverter section is composed of transistors, ll-M08T, and the like. On the other hand, it also has a power control section that changes the effective value of the power supplied to the AC load by intermittent operation of the inverter section, and uses the so-called P W M III I
Execute II.

Furthermore, the AC power control circuit of the present invention includes the following booster circuit. The above-mentioned power control section requires an oscillation circuit as mentioned above in order to obtain the timing of PWM control due to its function, but the booster circuit inputs the oscillation signal from this oscillation circuit and boosts it at a predetermined rate. . There are various circuits including a so-called pumping circuit as a circuit for boosting the oscillation signal, and any of them may be used.

The output of the booster circuit that boosts this oscillation signal is connected to the switching control terminal of the switching element of the inverter section, and is used as a high potential power source.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, the present invention will be described in detail by giving examples.

[Example] Figure 1 shows how to reduce AC power consumption by using six N-MO3Ts (Ql to Q6) which exhibit excellent characteristics when used as a speed control circuit for AC motor M as described above. - It is an electric circuit diagram configuring the circuit. N-
3 with two MO8TQN (N=1 to 6) connected in series
The three sets (Ql, Q4, Q2, Q5, Q3, Q6) are connected in parallel to the DC power supply VDC, and power is supplied from the midpoint of these three sets to the three-phase electric 111M each phase input terminal. It is a normal three-phase bridge configuration. As is well known, N-MO8TQN is 5 to 6 [V] lower than its source potential.
The drain and source become conductive only when a potential higher than 1 is applied to the gate. Therefore, among N-MO8TQN, the lower element of the three-phase bridge whose source potential is at ground level, N-MO3TQ4. The gate terminals of Q5 and Q6 are pulled up to the + side line of the DC power supply VDC via resistors R4, R5, and R6. On the other hand, the upper elements of the three-phase bridge N-MO3TQ1, Q, 2. The source potential of Q3 is a high potential several meters [V] lower than the drain connected to the + side line of the DC power supply, and the voltage applied to the gate to make it conductive is obtained from the same DC power supply VDC. It is not possible. Therefore, in this embodiment, Tco1'L, etc. (7) N-MO8TQ1. Q2. Q3
The configuration is such that the gate terminal of the device is pulled up. N-MO8 whose terminals are pulled up as shown above
Since TQN is always in a conductive state as it is, each N-
The gate terminal of MO8TQN is also connected to the control terminal of a gate drive circuit 20 that takes switching timing to achieve the invert function. This gate drive circuit 200 type @ terminal is A-uncollector type output J
It is a terminal and can take two values: ground level or open. Therefore, when the control terminal of the gate drive circuit 20 is at ground level, N-MO8TQN is in a cut-off state,
N-MO8TQ only when the control terminal is open
N becomes conductive.

Note that the gate drive circuit 20 drives each N-MO8TQN to 0N.
The timing at which the 10FF is applied is the normal timing at which 3-0-phase AC having different phases by (2/3)π is applied to the electric motor M.

Three-phase bridge lower element N-MO8TQ4 of this embodiment. Q
5. The gate terminal of Q6 is further connected to an NPN type switching transistor Tr4. It is also grounded through Tr 5° and r6. Therefore, the switching transistor Tr4. Tr5. When a signal is input to the base of Tr 6, the control terminal of the gate drive circuit 20 is in an open state and N-MO8TQ4°Q5. Even when Q6 is in a conductive state, "'CN-MOS T
It is possible to change the Q 4 , Q 5 , and Q 6 laminates into a disconnected state. That is, switching transistor Tr4. Tr5. Tr6 is a control element of the PWM circuit 30, and enables three-phase AC PWM control in synchronization with the oscillation signal of the square wave oscillation circuit 32 when the gate circuit 34 passes the oscillation signal.

Note that the gate circuit 34 opens its gate only when the @high level signal is applied to the control terminal CP.

The output of the square wave oscillation circuit 32 of the PWM circuit 30 is also input to the booster circuit 10 in addition to the above-described PWM circuit control. Also, dut is used as a signal to the arm pressure circuit 10.
If you want a signal of y50%, for example, if you branch out, you can get d
This is a signal with a utility of 50%.

This booster circuit 10 is configured as a well-known pumping circuit, and when the output of the square wave oscillation circuit 32 is at a low level, the transistor Tr1 is turned off.

Tr2 is turned on, and capacitor C1 is charged to approximately the power supply voltage of DC power supply VDC through diode D1 with the polarity shown in the figure. Next, when the output of the square wave oscillation circuit 32 becomes HiQh level, the transistor Tr
1. Each of transistors Tr2 is inverted and transistors Tr1.
Capacitor C2 will be charged through capacitor C1 and diode D2. Therefore, capacitor C
2 has the opposite polarity as shown in the figure, so it is always charged at a voltage approximately twice the DC power supply voltage (slightly lower by the forward voltage drop of the diodes DI and D2), achieving the purpose of boosting and as described above. The upper element of the three-phase bridge N-MO8TQ1.
Q2. It becomes a voltage source that pulls up the gate of Q3. At this time, the current i that can be consumed from capacitor C2 is i = CX (VB - VF) expressed in frequency. N-M driven by capacitor C2
O8TQ1. Q2. Q3 is a voltage control type FET and consumes little power, so it provides a sufficient voltage source.

It is clear that the AC power control circuit of this embodiment configured as described above provides the following actions and effects.

First, the inverter circuit that performs DC-AC conversion is the same as that using the conventional N-MOST, and as described above, operates at low power consumption, high speed, and high efficiency.

Second, by providing the PWM circuit 30, it is possible to supply AC power commensurate with the mechanical load of the electric motor M.
Motor control efficiency can be further improved.

Furthermore, as a third point, the optimal N-
Although only the MO8T element is used, the high voltage for driving the gate is supplied from the booster circuit 10 that utilizes the oscillation signal of the PWM circuit 30. This eliminates the need for a separate power supply circuit, which conventionally increases the number of parts and increases costs when configuring this type of AC power control circuit, and further miniaturization and cost reduction can be achieved.

In the above embodiment, the PWM circuit 30 is replaced by a new switching element, a switching transistor Tr4. Tr
5. Although it is configured using Tr 6, the gate drive circuit 2
0 may be used to directly control 0N10FF of N-MO8TQN. Furthermore, the operating status of the PWM circuit 30 is determined by the control terminal CP input of the circuits 1 to 34, but as shown in FIG. Good too.

When this is done, the output to the booster circuit 10 is the result of comparison with the voltage E1 that is 1/2 times the maximum value of the triangular waveform, that is, a square wave with a duty ratio of 50%, as in the previous embodiment, and the switching Transistor Tr 4. Tr 5
．． If the reference voltage EV to be compared is made adjustable, the output to the switching transistor Tr 6 can produce a square wave with a desired duty ratio by adjusting EV as shown in the figure. Tr5. PWM control by Tr 6 can be freely controlled.

Above, the embodiment has been described in detail by illustrating the case of three-phase motor control, but it is of course applicable not only to three-phase but also to other multi-phase AC control, and even if the AC load is inductive. For example, the diode built into N-MO8TQN can be used as a flywheel diode, which is extremely useful.

[Effects of the Invention] As described above in detail with reference to the embodiments, the AC power control circuit of the present invention has high efficiency, high speed, and excellent switching characteristics; The inverter section is constructed using NPN, N-MO8T, etc., which require a high voltage source as described above, but the oscillation circuit of the power control section, which performs intermittent control such as PWM control, is skillfully used to This voltage is applied to control NPN, N-MO8T, etc.

Therefore, there is no need for a high current source, which was conventionally required as a separate power source for switching elements in addition to a DC power source.
The control circuit can be made smaller and the cost can be reduced to 1 or more.

[Brief explanation of drawings]

FIG. 1 is a schematic electrical circuit diagram of an AC power control circuit that is an embodiment of the present invention, and FIG. 2 is an explanatory diagram of another embodiment that provides PWM control timing in this embodiment. Q1~Q6...N-MO8T M...Motor 10...Boost circuit 20...Gate drive circuit 30...PWM circuit

Claims (1)

[Scope of Claims] A switching element that is connected to an electrical circuit of a controlled system and opens and closes the electrical circuit of the controlled system when a control signal having a potential higher than the potential of the controlled system by a predetermined value is applied. and a power control unit that controls AC power supplied to a load connected to the inverter unit by intermittent operation of the inverter unit based on an oscillation signal from an oscillation circuit having a predetermined oscillation frequency. An alternating current power control circuit comprising: a booster circuit that receives an oscillation signal from an oscillation circuit in the power control unit and boosts the voltage; the output of the booster circuit is appropriately used as a control signal for a switching element in the inverter unit. AC power control circuit.