JP3198991B2 - Driving method of DC-AC inverter and temperature protection circuit of DC-AC inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a DC-AC inverter and a temperature protection circuit for the DC-AC inverter.

[0002]

2. Description of the Related Art FIG. 3 shows an electric circuit of a conventional DC-AC inverter. The H-bridge circuit 10 including the four first to fourth semiconductor switch elements SW1 to SW4 inputs a DC input voltage Vs applied to input terminals c and d via a smoothing electrolytic capacitor C1. And the first and fourth
Semiconductor switching elements SW1 and SW4, and second and third
By setting the semiconductor switching elements SW2 and SW3 to respective sets, and performing on / off control alternately for each set, the DC input voltage Vs is converted to an alternating current, and the AC voltage generated between the output terminals a and b is converted to a load. 11 is supplied.

[0003] First to fourth semiconductor switching elements SW1
SW4 are turned on / off in response to drive signals IS1 to IS4 from the switching control circuit 12. When the set of the first and fourth semiconductor switching elements SW1 and SW4 is turned on based on the drive signals IS1 and IS4 (the set of the second and third semiconductor switching elements SW2 and SW3 is turned off) Positive input terminal c → first semiconductor switching element SW1 → output terminal a → load 11 → output terminal b
A current flows through the path from the fourth semiconductor switching element SW4 to the negative input terminal d. The set of the second and third semiconductor switching elements SW2 and SW3 is the drive signal IS2 and IS3.
(The set of the first and fourth semiconductor switching elements SW1 and SW4 is off), the positive input terminal c → the third semiconductor switching element SW3 → the output terminal b → the load 11 → the output terminal. A current flows through a path from a to the second semiconductor switching element SW2 to the negative input terminal d.

In the DC-AC inverter, a breaker 13 (a fuse may be used instead of the breaker 13) is provided between a connection point between the third semiconductor switching element SW3 and the fourth semiconductor switching element SW4 and the output terminal b. It is connected. The breaker 13 cuts off the short-circuit current when the short-circuit current flows due to a short circuit or the like.

However, when the breaker 13 performs the shut-off operation, the user must perform a troublesome return operation. Further, when a fuse is used in place of the breaker 13, there is a problem that a new fuse must be replaced when the fuse is blown.

Further, the DC-AC inverter includes a current detecting resistor Rs between a connection point between the second semiconductor switching element SW2 and the fourth semiconductor switching element SW4 and the input terminal d.
Is connected. The current detection resistor Rs outputs a voltage between its terminals, that is, a voltage value relative to the load current to the switching control circuit 12 as a detection voltage SVs. The switching control circuit 12 detects the detection voltage SVs
Is greater than or equal to a predetermined reference value, that is, when an overcurrent flows through the load 11, the first to fourth semiconductor switching elements SW
Drive signals IS1 to IS4 for turning off SW1 to SW4
Is output. Then, damage to the first to fourth semiconductor switching elements SW1 to SW4 is prevented.

[0007]

However, when the switching control circuit 12 turns off the first to fourth semiconductor switching elements SW1 to SW4, the overcurrent disappears and the first to fourth semiconductor switching elements SW1 are immediately turned off. ~ S
W4 is driven again by the switching control circuit 12. By repeating such an operation, heat generated by the semiconductor switching elements SW1 to SW4 is accumulated. Then, the temperature of the semiconductor switching elements SW <b> 1 to SW <b> 4 itself increases due to the heat storage, and there is a possibility that the semiconductor switching elements SW <b> 1 to SW <b> 4 may be damaged due to heat.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and a method of driving a DC-AC inverter capable of preventing damage to a semiconductor switching element due to heat with a simple configuration. And a temperature protection circuit for the DC-AC inverter.

[0009]

SUMMARY OF THE INVENTION The first aspect of the present invention converts the switching control of the plurality of semiconductor switching elements provided in the H-bridge circuit a DC input voltage to the exchange <br/> current voltage a method of driving a DC-AC inverter for supplying a load, at least one of the semiconductor switching of the plurality of semiconductor switching elements
The element is turned off by another semiconductor switching
It is earlier than the element, and the off timing is earlier
Detecting the temperature of the semiconductor switching element,
When the detected temperature reaches a predetermined temperature, the conversion operation of the H-bridge circuit is stopped.

According to a second aspect of the present invention, a plurality of semiconductor switching elements provided in the H- bridge circuit are controlled by a switching control circuit to switch a DC input voltage.
In the temperature protection circuit is converted into an AC voltage DC-AC inverter for supplying to the load, and of the double several semiconductor switching element, the over other semiconductor switching elements
One of semiconductor vinegar and less off timing is early
Detecting a temperature of the switching element, and its occasional temperature detecting means you outputting a temperature detection signal, and inputs the temperature detection signal, the temperature of the semiconductor switching elements off timing is early reaches a predetermined temperature A temperature determination circuit for outputting an operation stop command signal for turning off the plurality of semiconductor switching elements to the switching control circuit .

According to a third aspect of the present invention, in the temperature protection circuit for a DC-AC inverter according to the second aspect, the temperature detecting means is a thermistor, and the thermistor is provided on a package surface of the semiconductor switching element.

According to the first aspect of the invention, off- tie
Detection temperature sooner the semiconductor switching element timing is
When the predetermined temperature is reached, the conversion operation of the H-bridge circuit stops. Therefore, the semiconductor switching element does not generate any more heat and stops increasing in temperature. As a result, the semiconductor switching element is prevented from being damaged by heat.

According to the second aspect of the present invention, the temperature of the semiconductor switching element whose off timing is advanced by the temperature detecting means is detected and output to the temperature determining circuit.
When the detected temperature reaches a predetermined temperature, the temperature determination circuit outputs an operation stop command signal for turning off the plurality of semiconductor switching elements to the switching control circuit . Therefore, the semiconductor switching element does not generate any more heat and stops increasing in temperature. As a result, the semiconductor switching element is prevented from being damaged by heat.

According to the third aspect of the present invention, the temperature of the semiconductor switching element can be accurately detected by bonding the thermistor to the package surface of the semiconductor switching element.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. For convenience of description, the same reference numerals are used for the parts common to the DC-AC inverter shown in FIG. 3, and the detailed description is omitted, and different parts will be described.

In FIG. 1, the DC-AC inverter is
The DC input voltage Vs is input between the plus input terminal c and the minus input terminal d. The DC input voltage Vs is applied to the H bridge circuit 10. The H-bridge circuit 10 includes four semiconductor switching elements SW1 to SW4. One end of the first semiconductor switching element of the upper arm is connected to the plus input terminal c, and the other end is connected to the minus input terminal d via the second semiconductor switching element SW2 of the lower arm and the current detection resistor Rs. One end of the third semiconductor switching element SW3 of the upper arm is connected to the plus input terminal c, and the other end is connected to the minus input terminal d via the fourth semiconductor switching element SW4 of the lower arm and the current detection resistor Rs.

The first semiconductor switching element SW1 and the second
The connection point of the semiconductor switching element SW2 is connected to the output terminal a, and the connection point of the third semiconductor switching element SW3 and the fourth semiconductor switching element SW4 is connected to the output terminal b. The load 11 is connected between the output terminals a and b. First and fourth semiconductor switching elements S
W1 and SW4 and the second and third semiconductor switching elements S
The DC input voltage Vs is converted to an alternating current, and the alternating voltage generated between the output terminals a and b is supplied to the load 11 by performing the on / off control alternately for each set of W2 and SW3. Is done.

Further, a current detection resistor Rs is connected between a connection point between the second semiconductor switching element SW2 and the fourth semiconductor switching element SW4 and the input terminal d. The current detection resistor Rs uses a voltage between its terminals, that is, a voltage value relative to the load current as a detection voltage SVs as a switching control circuit 2.
1 is output.

The switching control circuit 21 turns on and off the first drive signal IS1 for turning on and off the first semiconductor switching element SW1, and turns on and off the second semiconductor switching element SW2.
A second drive signal IS2 for turning off, a third drive signal SW3 for turning on / off the third semiconductor switching element SW3, and a fourth drive signal for turning on / off the fourth semiconductor switching element SW4 are generated and output.

The switching control circuit 21 comprises first, fourth
When the drive signals IS1 and IS4 are at the H level, the second and third drive signals IS2 and IS3 are at the L level, and when the second and third drive signals IS2 and IS3 are at the H level, the first and fourth drive are performed. Each of the drive signals IS1 to IS4 is generated such that the signals IS1 and IS4 become L level. When the first and fourth drive signals IS1 and IS4 are at H level, the first and fourth semiconductor switching elements SW1 and SW4 are turned on. When the first and fourth drive signals IS1 and IS4 are at L level, the first and fourth drive signals IS1 and IS4 are at L level. 4th
The semiconductor switching elements SW1 and SW4 are turned off. When the second and third drive signals IS2 and IS3 are at H level, the second and third semiconductor switching elements SW2 and SW3 are turned on. When the second and third drive signals IS2 and IS3 are at L level, the second and third drive signals IS2 and IS3 are at L level. Third semiconductor switching elements SW2, SW3
Turns off.

The switching control circuit 21 determines the low level of the fourth drive signal IS4 for the first and fourth drive signals IS1 and IS4.
The fall to the level is caused to fall earlier than the fall of the first drive signal IS1 by a predetermined time.
The rise to the level is set to rise at the same time. Therefore, the fourth semiconductor switching element S of the lower arm
W4 is an upper arm first semiconductor switching element SW1
Turn off earlier. That is, the switching loss of the fourth semiconductor switching element SW4 of the lower arm is made larger than that of the first semiconductor switching element SW1 of the upper arm,
The heat generated by the semiconductor switching element SW4 is made to be more positive than that of the first semiconductor switching element SW1.

Further, the switching control circuit 21 applies the second drive signal IS2 to the second and third drive signals IS2 and IS3.
Is set to fall to the L level earlier than the fall of the third drive signal IS3 by a predetermined time, and to rise to the H level at the same time. Therefore, the second semiconductor switching element SW2 of the lower arm is turned off before the third semiconductor switching element SW3 of the upper arm. That is, the switching loss of the second semiconductor switching element SW2 of the lower arm is made larger than that of the third semiconductor switching element SW3 of the upper arm, and the heat generation of the second semiconductor switching element SW2 becomes more positive than that of the third semiconductor switching element SW3. Like that.

The switching control circuit 12 detects the detection voltage SV
s based on the first to fourth drive signals IS1 to IS
The duty ratio is set for 4 and output. That is, when the load current increases, the duty ratio is reduced in inverse proportion to the load current to suppress the increase in the load current. Conversely, when the load current decreases, the duty ratio is increased in inverse proportion thereto to suppress the decrease in the load current.

Thermistors 22a as temperature detecting means,
Reference numeral 22b denotes second and fourth semiconductor switching elements SW2 and SW4 of the lower arm, each having a large switching loss.
Detect the temperature of The thermistors 22a and 22b are shown in FIG.
As shown in FIG. 5, the respective temperatures of the second and fourth semiconductor switching elements SW2 and SW4 connected to the circuit board 23 are brought into contact with the package surface to detect the respective temperatures of the switching elements SW2 and SW4, and the temperature is detected as a temperature detection signal ST. Output to the temperature determination circuit 24.

The temperature judging circuit 24 generates the second and fourth semiconductor switching elements SW2, SW2 based on the temperature detection signal ST.
When any one of the switches SW4 reaches a predetermined reference temperature, it outputs an operation stop command signal SC. In the present embodiment, the reference temperatures are the semiconductor switching elements SW1 to SW4.
Is set to a value that is lower by 2 to 3 degrees than the maximum allowable temperature set to prevent heat damage.

The operation stop command signal SC from the temperature determination circuit 24 is output to the switching control circuit 21. The switching control circuit 21 outputs an operation stop command signal SC.
In response to the first to fourth semiconductor switching elements SW1 to SW1.
First to fourth drive signals IS1 to IS4 for turning off SW4
IS4 is all set to L level. This is because the detection voltage S
This is performed by disabling the duty control of the first to fourth drive signals IS1 to IS4 based on Vs.

Next, the operation of the DC-AC inverter configured as described above will be described. Now, when the temperatures of the second and fourth semiconductor switching elements SW2 and SW4 are lower than the reference temperature, the switching control circuit 21 detects the detection voltage SVs
, And outputs the first to fourth drive signals IS1 to IS4. The first to fourth drive signals I
The first to fourth semiconductor switching elements SW1 to SW4 are turned on / off in response to S1 to IS4, convert the DC input voltage Vs to an AC voltage, and supply the AC voltage to the load 11. The duty is set according to the load current at that time, and the load 11
Control the AC power supplied to the

When the overcurrent state continues, the second or fourth
When the temperature of the semiconductor switching elements SW2 and SW4 rises and reaches the reference temperature, the temperature determination circuit 24 outputs an operation stop command signal SC to the switching control circuit 21 based on the temperature detection signal ST from the thermistors 22a and 22b. In response to the operation stop command signal SC, the switching control circuit 21 switches the first to fourth semiconductor switching elements SW1
To SW4 are turned off. The first to fourth semiconductor switching elements SW1 to SW4 are turned off. Heating of each of the semiconductor switching elements SW1 to SW4 is stopped based on this off. Eventually, when the temperature of the semiconductor switching elements SW2 and SW4 falls below the reference temperature, the temperature determination circuit 24 stops outputting the operation stop command signal SC. Based on the disappearance of the operation stop command signal, the switching control circuit 21 again outputs the first to fourth drive signals IS1 to IS based on the detection voltage SVs.
4 to output an AC voltage to the load 11 by converting the DC input voltage Vs into an AC voltage.

As described above, according to the present embodiment, when the temperature of the second or fourth semiconductor switching element SW2, SW4 rises above the reference temperature, all of the first to fourth semiconductor switching elements SW1 to SW4 are turned off. To stop further temperature rise. Therefore, the semiconductor switching elements SW1 to SW4 are prevented from being damaged by heat.

In this embodiment, the thermistor 22a,
22b is connected to the second and fourth semiconductor switching elements SW2,
It was brought into contact with the surface of the SW4 package. Therefore, since the temperatures of the semiconductor switching elements SW2 and SW4 are directly detected, accurate temperature detection can be performed.

Further, in this embodiment, the H bridge circuit 1
0 and the second and fourth semiconductor switching elements S of the lower arm
The temperatures of W2 and SW4 were detected by the thermistors 22a and 22b. That is, the second and fourth semiconductor switching elements SW1 and SW3 of the lower arm are compared with the second and fourth semiconductor switching elements SW1 and SW3 of the lower arm.
The switching loss of the semiconductor switching elements SW2 and SW4 is positively increased to increase the heat generation temperature. Therefore, without providing a thermistor for all of the semiconductor switching elements SW1 to SW4, it is possible to surely prevent the semiconductor switching elements SW1 to SW4 from being thermally destroyed.

Further, the semiconductor switching elements SW2,
When the ambient temperature has risen above the reference temperature in a state where SW4 has not risen to the reference temperature, the thermistors 22a and 22b detect this ambient temperature. Therefore, even if the ambient temperature rises abnormally, each of the semiconductor switching elements SW1 to SW4 is turned off beforehand.
The AC conversion operation of the C-AC inverter can be stopped.

The present embodiment is not limited to the above-described embodiment, but may be implemented as follows. In the above embodiment, the thermistors 22a and 22b are connected to the second and fourth semiconductor switching elements SW2 and SW of the lower arm.
4, the first to fourth semiconductor switching elements SW
A thermistor may be provided for all of the switches 1 to SW4. Further, the operation may be performed by providing a thermistor for one semiconductor switching element. In this case, the number of thermistors can be reduced.

In the above embodiment, the first to fourth semiconductor switching elements SW1 to SW4 are not particularly limited. However, as long as the ON / OFF control is performed by the driving IS1 to IS4, for example, a MOS transistor, It may be embodied by a bipolar transistor or the like.

In the above embodiment, the DC-AC inverter is a single-phase AC inverter, but may be applied to a three-phase AC inverter. Technical ideas other than the technical ideas described in the claims, which are found from the above embodiments, will be described below together with the effects.

In a method of driving a DC-AC inverter for controlling a plurality of semiconductor switching elements provided in an H-bridge circuit to convert a DC input voltage into an AC voltage and supplying the AC voltage to a load, a plurality of semiconductor switching elements are provided. At least one of the semiconductor switching elements is turned off earlier than other semiconductor switching elements to increase the switching loss, and the temperature of the semiconductor switching element having the increased switching loss is detected, and the detected temperature is predetermined. When the temperature is reached, the H
DC- that stops the conversion operation of the bridge circuit
Driving method of AC inverter.

Accordingly, it is not necessary to provide a thermistor for all of the semiconductor switching elements, and it is possible to reliably prevent all of the semiconductor switching elements from being thermally damaged.

[0038]

According to the first and second aspects of the present invention,
It has an excellent effect of preventing a semiconductor switching element from being destroyed by heat.

According to the invention set forth in claim 3, according to claim 2
In addition to the advantageous effects of the invention, there is an excellent effect that the temperature of the switching element can be accurately detected.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a DC-AC inverter embodying the present invention.

FIG. 2 is an explanatory diagram illustrating attachment of a thermistor.

FIG. 3 is an electric circuit diagram of a conventional DC-AC inverter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... H bridge circuit, 11 ... Load, 21 ... Switching control circuit, 22a, 22b ... Thermistor as a temperature detecting means, 24 ... Temperature determination circuit, SW1-SW4 ... First
~ 4th semiconductor switching element, ST ... temperature detection signal,
SC: operation stop command signal, IS1 to IS4 ... first to fourth
Drive signal, Vs: DC input voltage.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 1/00 H02M 7/48

Claims (3)

(57) [Claims] 1. A straight inlet by switching control of the plurality of semiconductor switching elements provided in the H-bridge circuit
DC-AC that converts a power voltage into an AC voltage and supplies it to a load
In the method of driving an inverter, at least one of the semiconductor switching elements of the plurality of semiconductor switching elements, the Ofutai
Is faster than other semiconductor switching devices
And the semiconductor switch whose off timing is advanced
The temperature of the switching element is detected and the detected temperature
A method for driving a DC-AC inverter, wherein the conversion operation of the H-bridge circuit is stopped when the inverter reaches the voltage. Wherein the H-bridge circuit a plurality of semiconductor switching elements of the switching control circuit at a temperature protection circuit DC-AC inverter for supplying a load by converting a DC input voltage into an AC voltage by the switching control provided in in, among the multiple several semiconductor switching element, another semiconductor scan
Also detects the temperature of the one semiconductor switching elements and <br/> fewer its off timing is earlier than the switching element, and its occasional temperature detecting means you outputting a temperature detection signal, the temperature detection signal Enter and turn off timing earlier
Temperature of the semiconductor switching element reaches the predetermined temperature
Then, a temperature determination circuit for outputting an operation stop command signal for turning off the plurality of semiconductor switching elements to the switching control circuit, the temperature protection circuit for a DC-AC inverter. 3. The DC-AC according to claim 2, wherein the temperature detecting means is a thermistor, and the thermistor is provided on a package surface of the semiconductor switching element.
Inverter temperature protection circuit .