JPS5943905B2 - Control method for power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses four transistors to connect a DC power source to a DC-
The present invention relates to a method of controlling a power conversion device that performs DC conversion and DC-AC conversion.

In recent years, transistors have made remarkable progress, and large-capacity, high-speed transistors are now available at low cost.

Along with this, if we use transistors that can be easily turned off in place of the thyristors conventionally used in power conversion devices, 'for example, servo motor control, etc. can have faster response, and moreover, the transistors can be turned on and off. By controlling the
It is possible to obtain controlled equipment.

A method of controlling DC output or AC output from a DC power supply using ON-OFF control is pulse width modulation (hereinafter referred to as PWM), which controls the pulse width at ON or OFF.
control is known.

An object of the present invention is to provide a method for controlling a power converter using PWM control that has high speed response, small harmonic ripples in output current, and is inexpensive. The present invention will be explained below based on the drawings of the embodiments. FIG. 1 is a diagram showing the main circuit connection according to the present invention, and FIG. 2 shows the operating characteristics of the power conversion device according to the present invention. In FIG. 1, TR1 to TR4 are transistors, and D1 to D4 are diodes.

C is a capacitor inserted into a DC power supply, SHT is a shunt for current detection, and DM is a load, such as a servo motor (hereinafter referred to as motor DM). When the motor DM rotates in the forward direction, the transistors TRI and TR4 are energized, and when the motor DM is in the reverse direction, the transistors TR2 and TR3 are energized.
can be operated reversibly. Next, the operation mode of the power converter according to the present invention will be applied to the device shown in FIG. 1 and will be explained with reference to FIG.

In FIG. 2, FIG. 2A is a setting signal, and FIG. 2B is a motor current waveform. 2C-F shows the energization state of each transistor in FIG. 1; and FIG. 2G-J shows the energization state of each diode in FIG. 1. First, when a "+" signal is applied as a setting input signal, a time T occurs.

-t1, transistors TR1 and TR4 are both conductive and supply a "+" polarity signal to the motor DM. When the current value becomes +2 at time t1, only transistor TR4 becomes 0.
Make it FF. At this time, a flywheel current flows through DM→D3→TRl→SHT. Furthermore, when TRl and TR4 are made conductive again at time T2, the motor current increases, and the current value reaches +Ip at time T3. At this time, if only the transistor TRl is turned 0FF, DM→TR4→D2→S
A flywheel current flows through the HT. Note that this operation will be explained using the mode diagram of the PWM control operation shown in FIG.

In the figure, Figure 5a is 0N mode I, Figure 5b is 0F.
F mode U and FIG. 5c show the 0FF mode, respectively. First, as shown in FIG. 5a, in the 100N mode, the current 1 is passed through the motor D
Flows to M. In the subsequent 0FF mode, a flywheel current 12 flows through the transistor TRl, motor DM, and diode D3 as shown in FIG. 5b.
In the next PWM 0N mode, the current 11 is supplied from the power supply via the transistor TRl, the motor DM, and the transistor TR4 as shown in FIG. 5a, and in the subsequent 0FF mode, the transistor TR4 and Flywheel current 1 via diode D2 and motor DM
3 flows. Then it returns to I mode again. In this way, the PWMlhIl control operates in mode I every chopping cycle.
Repeat the cycle of ~. In this way, the input signal is "+"
At the time, current is supplied from the power supply to the motor M via transistors TRl and TR4, and the current value is a constant value +Ip.
When reaching , transistors TRl,
TR4 is turned 0FF to flow the flywheel current.

When the input signal is "-", the current is passed from the power supply to the motor M via transistors TR3 and TR2, and similarly the current value is -.
When the voltage reaches 1p, the transistor T
Turn R2 or TR3 to 0FF and DM→SHT→D1→T
A flywheel current is caused to flow through R3 or through DM→SHT-+TR2→D4. Further, when the polarity of the input signal at time TlO is reversed from "+" to "one", the transistors TRl and TR4 are immediately turned off.

At this time, the motor current flows as a charging current to the capacitor C via DM→D3→C→D2→SHT, and the time TlO−
Power is regenerated between Tll. FIG. 3 shows an embodiment of the servo motor 1 drive circuit implementing the energization mode shown in FIG. 2.
FIG. 4 shows waveforms of various parts of the circuit of FIG. 3. In Fig. 3, 1 is a PWMllll controlled transistor 0N-
A square wave oscillator that determines the 0FF total time, 2 a frequency divider that divides the output of the square wave oscillator 1 into 1/2, and 3 a current command polarity discriminator (hereinafter referred to as polarity discriminator) that detects the forward and reverse directions of the input current command. 4 is an inverter, 5 is an input signal 1
01 and current feedback signal (current detection signal) 102
The current feedback signal 102 is calculated as an absolute value by comparing
exceeds the input signal 101, the output 109 changes from “L” to “
This current comparator is configured with a comparator 5a, an inverter 5b1 AND circuit 5c, and a 5d1 OR circuit 5e.

6, 7 are flip-flops, 8-11 and 13-16
is an AND circuit, and 17 to 20 are transistor base drive circuits.

12 is a transistor TRl when the input signal polarity is inverted.
, TR4←→TR2, TR3 This is a delay circuit that provides a dead zone with respect to energization, and its interior is composed of resistors 12a, 12b1 capacitors 12c, 12d1 diodes 12e, 12f1 buffers 12g and 12h. Further, 21 is a delay circuit, which supplies the clock signal 10 to the flip-flops 6 and 7.
5' is corrected by the delay time of the frequency divider 2 and the AND circuits 8 to 11, which is a minute time of about 1 μS. The operation of the embodiment circuit according to the present invention will be explained using FIGS. 3 and 4.

The input signal 101 is "+" when the motor DM shown in FIG.
", and [-" when reversed. The output signal 103 of the polar gland 3 is connected as an input signal to the flip-flop 6, and the inverter 4 is connected as an input signal to the flip-flop 7.
The phase-inverted output signal 104 is connected to the polarity discriminator 3 via the polarity discriminator 180. Also, the block signals of the flip-flops 6 and 7 are used to connect the output 105 of the square wave oscillator 1 to the delay circuit 2.
1 via signal 105' is applied (signal 10
5' can be considered to have almost the same time as signal 105, so it will be explained below as signal 105). The set signal 110 of the flip-flop 6 is inputted to the output 106 of the frequency divider 2, the output 104 of the inverter 4, and the output signal 109 of the current comparator 5 via the AND circuit 8.

Further, the flip-flop 6 reset signal 111 is the output signal 106 of the frequency divider 2, the output signal 103 of the polar gland 3,
The output signal 109 of the current comparator 5 is then connected via an AND circuit 9. Similarly, the set signal 112 of flip-flop 7 is connected to the output signal 107 of frequency divider 2 (output signal 10
7 has a different polarity from the output signal 106), the output signal 103 of the polarity discriminator 3, and the output signal 109 of the current comparator 5.
are connected via an AND circuit 10, and the flip-flop 7 set signal 113 is connected to the output signal 10 of the frequency divider 2.
7. The output signal 104 of the inverter 4 and the output signal 109 of the current comparator 5 are connected via the AND circuit 11.

When a positive voltage is applied as the input signal 101, the output signal 103 of the polarity discriminator 3 becomes positive polarity (hereinafter referred to as "H"), and the output signal 104 of the inverter 4 becomes O (hereinafter referred to as "L").
).

Therefore, when the clock signal 105 changes from "L" to "H" at time t1 in FIG. 4, the output signal 116 of the flip-flop 6 becomes "H", the output signal 117 becomes "L", and the output signal 118 of the flip-flop 7 becomes "H". is "L", and the output signal 119 is "H". Also, the output signal 1 of the delay circuit 12
14 is "H" and the output signal 115 is "L", the output signal 120 of the AND circuit 13 is "H", and the AND circuit 1
The output signal 121 of the AND circuit 15 becomes "L", the output signal 123 of the AND circuit 16 becomes "H", and the output signal 121 of the AND circuit 15 becomes "L", and the output signal 123 of the AND circuit 16 becomes "H". TRl and TR4
An 0N signal is applied to.

At time T2, when the motor current exceeds the current command value, the output signal 109 of the current comparator 5 changes from "L" to "H". At this time, among the AND circuits 8 to 11, the output signal 111 of only the AND circuit 9 whose three input signals (signals 103, 106, and 109) are all "H" is "H", and the flip-flop 6 is inverted by the reset signal. , output signal 11
6 becomes "L" and the output signal 117 becomes "H".

At this time, since the flip-flop 7 does not change, only the transistor TRl in FIG. 1 becomes 0FF, and the transistor TR1 becomes 0FF.
4. Motor DM via diode D2 and shunt SHT
flywheel current flows.

After that, the current falls below the command value between time T2 and T3,
Even if the output of the current comparator 5 changes from "H" to "L" and the output signal 111 of the AND circuit 9 changes from "H" to "L", the flip-flop 6 remains unchanged and the motor DM continues to flow the flywheel current. Continue.

At time T3, the clock signal 105 goes low again →
When it goes high, the flip-flop 6 outputs the output signal 116.
becomes [H], the output signal 117 becomes "L", the output signals 120, 123 of AND circuits 13, 16 both become "H", and the transistors TR1, TR4 in FIG. 1 become conductive.
A current is applied to motor DM. Then, at time T4, the current exceeds the command value, and the output signal 109 of the current comparator 5 becomes "L".
"→"H", all of the input signals 107, 103, 109 of the AND circuits 8 to 11 become "H", and the output signal 112 of only the AND circuit 10 becomes "H", and the flip-flop 7 receives the set signal. Therefore, the output signal 118 is “
"H", the output signal 119 becomes "L", and the output signal 12
0 remains "H" and the output signal 123 changes from "H" to "L", only the transistor TR4 in FIG. 1 becomes 0FF, and the transistor TRl, diode D3, and shunt S in FIG.
A flywheel current flows through the HTl motor DM.

At time T5, the clock signal 105 becomes "L" again →
When the level becomes "H", the flip-flop 7 is inverted, the output 118 becomes "L", the output 119 becomes "H", transistors TR1 and TR4 in FIG. 1 are both conductive, and a current is applied to the motor DM. Further, at times T and O, when the polarity of the current command 101 is reversed, the output signal 114 immediately changes from [H] to "L" via the delay circuit 12, and the AND circuit 13~
All of the output signals of 16 become "L", transistors TRl and TR4 in FIG. Output signal 1 of circuit 12
15 changes from "L" to "H", and at time Tll, the output signal 117 of flip-flop 6 and flip-flop 7
When the output signals of both are "H", AND circuit 1
4, 15, the transistors TR2 and TR3 shown in FIG. 1 are made conductive via the base drive circuits 18 and 19, and a reverse current is applied to the motor DM.

The following modes are the same as the normal rotation mode described above, so the explanation will be omitted.

As explained above, according to the present invention, when energizing in a certain direction,
When the transistor is 0FF, the flywheel current flows, so the motor current is "current supply - flywheel current"
When the transistor is 0FF, the current ripple can be reduced compared to the regeneration method that regenerates the current from the motor to the power supply via the diode.By increasing the output frequency of the oscillator, the ripple can be further reduced. Instead, the two transistors that flow the flywheel current are operated alternately, which has the effect of averaging the losses of the transistors and diodes.

Also, when switching between forward and reverse, the current-carrying transistor is quickly turned off.
F, the motor current is regenerated to the power supply, and the motor current can be brought to zero at an early time.Furthermore, since the reverse side transistor is made conductive after a delay time, the positive and
It is possible to switch the energization of the reverse transistor.

Although the present invention has been described as a servo motor and a drive circuit, if the current manual command is input as a sine wave, the power converter output current becomes a sine wave, and it is clear that the device according to the present invention can be employed as an inverter device.

Also gate turn-off thyristor GTO transistor
It is also clear that the method can also be applied to those using .

[Brief explanation of the drawing]

Fig. 1 is a main circuit connection diagram of the power conversion device according to the present invention, Fig. 2 is a diagram showing the operating characteristics of each part of the device shown in Fig. 1, and Fig. 3 is an implementation of the servo motor 1 drive circuit implementing the energization mode shown in Fig. 2. FIG. 4 is a characteristic diagram showing waveforms of various parts of the circuit of FIG. 3, and FIG. 5 is a mode diagram of PWM control operation. TRl~TR4...Transistor, D1~D4
・・・・・・Diode, SHT・・・Shunt,
DM...Load, C...Capacitor, 1
...Square wave oscillator, 2 ... Frequency divider, 3
...Current command polarity discriminator, 4...Inverter, 5...Current comparator, 6,7...
・Flip-flop, 8-11, 13-16...
・AND circuit, 12, 21...Delay circuit, 17
~20...Transistor base 1 drive circuit.

Claims (1)

[Scope of Claims] 1. In a PWM type power conversion device in which a transistor and a diode are connected in anti-parallel to a DC current and brittle connected, when supplying a load current, first the two transistors are made conductive in the PWM on mode, and then one of the transistors is made conductive and one is cut off in a PWM off mode;
Continuing, the two transistors are made conductive in the on mode,
In the next chopper off mode, the transistor in the conduction/cutoff mode is replaced with the transistor in the previous off mode, and the PW
In the M-off mode, one of the two transistors is alternately made conductive in every PWM chopping cycle to cause a flywheel current to flow through the transistor and the diode to the load, and when the polarity is reversed, the transistor is cut off. A method for controlling a power conversion device, characterized in that the flywheel current is regenerated to the power source via the diode. 2. It is characterized by comprising an oscillator and a comparator that receives an input signal and a current detection signal as inputs, and the oscillator output signal causes two transistors to conduct, and the comparator output signal causes the two transistors to be cut off. A method for controlling a power conversion device according to claim 1.