JP5225921B2 - Inverter protection circuit - Google Patents

Description

  The present invention relates to an inverter protection circuit using an intelligent power module.

An intelligent power module (hereinafter referred to as “IPM”) is a power module that incorporates a power device drive circuit such as a power MOSFET for power control and an insulated gate bipolar transistor (IGBT) and a self-protection circuit. It is widely used as a useful tool for reducing the size and weight of devices, reducing development costs, and shortening the development period.
Conventionally, this IPM has a built-in short-circuit protection circuit and overload protection circuit, and there is an IPM that urgently stops the power supply of the IPM when short-circuited, and controls to eliminate the overload while operating the IPM when overloaded. It was.
JP 2003-88093 A

  However, in recent years, IPM specialized in function has been developed according to its application, and further reduction in size and weight has been demanded. In addition, since IPM configures a plurality of circuits on the same substrate, various protection circuits tend to be simplified. Recently, built-in protection circuits are limited to only short circuit protection or overload protection. There are also things.

  In this case, the IPM can only provide either a short-circuit protection function or an overload protection function, so it is necessary to compensate for the insufficient function as necessary. For example, the setting value of the short-circuit protection circuit built in the IPM is lowered. Thus, the protection circuit functions even during an overload, or a separate overload protection circuit is provided outside the IPM.

  However, if the setting value of the short-circuit protection circuit built in the IPM is lowered so that this protection circuit functions even in the event of an overload, a temporary overload that does not lead to an IPM breakage such as a transient overcurrent caused by the load. The protection circuit also functions for the load and performs the same operation (power supply OFF or output OFF) as when a short circuit occurs, and the inverter cannot be operated stably. On the other hand, if the function of this protection circuit is overload protection (control to eliminate overload while operating the IPM), even if the load is short-circuited, the overload protection operation is entered, so the IPM is urgently It cannot be stopped and the IPM will be damaged.

  For example, as shown in FIG. 3, a current transformer and a shunt resistor are interposed on the input side of the IPM, the current transformer is an overload detection sensor, and the shunt resistance is a short-circuit detection sensor. As shown in FIG. 4, two shunt resistors are connected in series between the converter and the IPM input side, and one resistor is used as an overload detection sensor, and the combined resistance of the two shunt resistors is used as a short circuit detection sensor. Things are common.

According to these protection circuits, short circuit protection by a protection circuit built in the IPM and overload protection by an overload protection circuit provided outside the IPM are possible.
However, these protection circuits increase the size of the circuit by using a current transformer and a plurality of shunt resistors, so that not only the effect of reducing the size and weight of the IPM is diminished, but also the problem of heat generation occurs. End up.

  The present invention provides an overload protection circuit provided outside an IPM that includes only a short circuit protection circuit, and an inverter protection circuit that enables short circuit protection and overload protection of an IPM without increasing the size of the circuit. It is to be an issue.

The inverter protection circuit according to the present invention is an inverter protection circuit in which an overload protection circuit is provided outside an intelligent power module having a built-in short circuit protection circuit, wherein current detection means is connected to the input side of the intelligent power module, and the current detection A short-circuit protection circuit built in the intelligent power module and set with a threshold for short-circuit determination; and an overload connected to the control means of the intelligent power module and having a value lower than the threshold for short-circuit determination An overload protection circuit having a comparison means having a threshold value for determination is branched and connected, and the detection value of the current detection means is compared with each threshold value to detect a short circuit state or an overload state. When the short circuit occurs, the short circuit protection circuit outputs a short circuit signal. It is configured to force.

As the short-circuit protection circuit, a known short-circuit protection circuit in which a threshold value for determining a short-circuit state is set can be used. The threshold value for short-circuit determination is set in advance in the IPM according to the current resistance performance of the IPM. Is set. The short-circuit protection circuit outputs a short-circuit signal to the drive circuit in the IPM when the detection value detected by the current detection means is larger than the threshold value for short-circuit determination.
As the current detecting means, a shunt resistor for detecting a circuit current is used.
As a comparison means for overload detection, a known means can be appropriately used. For example, a comparison operation circuit or a comparator can be used. It is also possible to use a function in the one-chip microcomputer for PWM generation that is an IPM control circuit. In this comparison means, a threshold value for determining an overload state is set in advance. As this overload determination threshold, a value lower than the short-circuit determination threshold can be arbitrarily set according to the performance of the IPM. The comparison means outputs an overload signal to the control means when the detection value detected by the current detection means is larger than the overload determination threshold. In addition, a transistor can be used as the comparison means, and in this case, the operating point of the transistor is used as a threshold value.
The control means is a control circuit for controlling ON / OFF of the power device in the IPM. For example, a one-chip microcomputer for generating PWM can be used.

  When the short circuit signal is output, the control means operates the short circuit protection circuit in the IPM to turn off the power, and when the overload signal is output, the control means reduces the power input to the IPM. It is preferable that the IPM is controlled so as to be (Claim 2).

According to the present invention, the current detection means is connected to the input side of the IPM having a built-in short-circuit protection circuit, and this current detection means has a short-circuit protection built in the intelligent power module and set with a threshold for short-circuit discrimination. A circuit and an overload protection circuit having a comparison means connected to the control means of the intelligent power module and having a threshold value for determining an overload lower than the threshold value for short-circuit determination Connect, compare the detection value of the current detection means and each threshold value to determine a short-circuit state or an overload state, output a short-circuit signal to the short-circuit protection circuit at the time of a short circuit, and overload signal at the time of an overload Is provided for the short-circuit protection circuit in the case where an overload protection circuit is provided outside the IPM having only a short-circuit protection circuit. By using a detection value obtained by the flow detection means it can be short-circuited state without increasing the size of the circuit, none of the overload condition determination.
When the short circuit signal is output, the short circuit protection circuit operates to turn off the inverter output, and when the overload signal is output, the IPM is controlled so as to reduce the power input to the IPM. By doing so, it is possible to protect the IPM appropriately according to the short circuit state or the overload state, and to realize a stable operation of the IPM.

FIG. 1 is a block diagram showing an outline of the present invention.
A shunt resistor 3 serving as a current detecting means is connected between the input side of the IPM 1 and the rectifier 2.
The IPM 1 includes a switching element 11 for controlling power supplied to the load, a drive circuit 12 for driving the switching element 11, and a short-circuit protection circuit 13 for outputting a stop signal to the drive circuit 12 when short-circuited. The voltage Vc generated at both ends of the short circuit protection circuit 13 is input. In the short circuit protection circuit 13, a threshold value Vs for determining a short circuit state is preset according to the current resistance performance of the IPM.
The PWM control circuit 4 is connected to the drive circuit 12 of the IPM1, and the IPM1 is PWM-controlled. A comparison circuit 5 as a comparison means is interposed between the PWM control circuit 4 and the shunt resistor 3, and the voltage Vc generated at both ends of the shunt resistor 3 branches from the short-circuit protection circuit 13 and also to the comparison circuit 5. It is designed to be entered. In the comparison circuit 5, a threshold value Vo for determining an overload state is preset according to the performance of the IPM. This threshold value Vo is smaller than the threshold value Vs for determining the short-circuit state set in the short-circuit protection circuit 13.

During the operation of the IPM 1, the shunt resistor 3 functions as a current detection sensor, and the voltage Vc generated at both ends thereof is output to the short circuit protection circuit 13 and the comparison circuit 5. This voltage Vc is compared with the short-circuit determination threshold value Vs by the short-circuit protection circuit 13 and the overload determination threshold value Vo by the comparison circuit 5, respectively. When Vc> Vs, it is determined that the short-circuit state is detected. Ss is output to the drive circuit 12. When Vs ≧ Vc> Vo, it is determined that the load is overloaded, and the overload signal So is output to the PWM control circuit 4.
When the short circuit signal Ss is output to the drive circuit 12, the output of the inverter is turned off, the operation of the IPM 1 is urgently stopped, and the IPM 1 is protected from damage due to the short circuit. On the other hand, when the overload signal So is output to the PWM control circuit 4, the PWM control circuit 4 outputs a control signal with a reduced PWM duty ratio to the drive circuit 12 to control the IPM so that the overload is eliminated. .
Therefore, when an overload protection circuit is provided outside an IPM that has only a short circuit protection circuit, a short circuit can be achieved without increasing the size of the circuit using the detection value obtained by the current detection means provided for the short circuit protection circuit. Both the state and the overload state can be determined, and appropriate IPM protection can be performed according to the state.

In this embodiment, the comparison circuit 5 is connected to the outside of the PWM control circuit 4. However, when a one-chip microcomputer is used as the PWM control circuit 4, the comparison circuit is utilized by using a comparison operation function in the microcomputer. It is also possible to configure the control circuit and the control circuit integrally.
In addition, a transistor can be used instead of the comparison circuit 5 as a comparison means. In this case, the operating point of the transistor is used as a threshold value. That is, the current detected by the shunt resistor 3 is used as a base current, and this detected current is used so as to obtain a base current in which the collector-emitter is turned ON during overload based on the hfe (current amplification factor) of the transistor. The transistor can be operated as a comparison means by adjusting with a resistor or the like.

  In addition, the use of a heating element such as a shunt resistor is suppressed as much as possible, and it is not necessary to use a large part such as a current transformer. Therefore, as a power source for a concrete vibrator used at a concrete placing site, a concrete vibrator is used. It becomes possible to reduce the size so that it can be built in the switch case.

A plurality of comparison means of the present invention can be used as shown in FIG.
Three comparison circuits 51, 52, 53 are interposed in parallel between the PWM control circuit 4 and the shunt resistor 3, and the voltage Vc generated at both ends of the shunt resistor 3 branches off from the short-circuit protection circuit 13. It is also inputted to the comparison circuits 51, 52, 53. In each comparison circuit, a threshold value for determining an overload state is preset according to the performance of the IPM. This threshold value is different for each comparison circuit. The comparison circuit 51 has a threshold value Vo1, the comparison circuit 52 has a threshold value Vo2, and the comparison circuit 53 has a threshold value Vo3. Is set. Each threshold value has a relationship of Vo1 <Vo2 <Vo3, and Vo3 is smaller than a short-circuit state determination threshold value Vs set in the short-circuit protection circuit 13. Other configurations are the same as in the case of using only one comparison means.
In this embodiment, three threshold values for determining the overload condition are provided, so that fine output adjustment can be made according to the overload condition. That is, the voltage Vc generated at both ends of the shunt resistor 3 is compared with the overload determination thresholds Vo1, Vo2, and Vo3 by the comparison circuits 51, 52, and 53, respectively. When Vo1 <Vc ≦ Vo2, the comparison circuit 51 When the load signal So1 is Vo2 <Vc ≦ Vo3, the overload signal So2 is output from the comparison circuit 52 to the PWM control circuit 4, and when the load signal So1 is Vo3 <Vc ≦ Vs, the overload signal So3 is output from the comparison circuit 53. The PWM control circuit 4 outputs a control signal for properly canceling the overload state to the drive circuit in accordance with the overload signals So1 to So3, thereby controlling the inverter. As a result, detailed inverter output control according to the level of the overload state is possible. Other operations are the same as when only one comparison means is used.

  The present invention relates to an inverter protection circuit using an intelligent power module, and has industrial applicability.

The block diagram which shows the outline | summary of the Example of this invention The block diagram which shows the outline | summary of the Example which used multiple comparison means Conventional configuration example when an overload protection circuit is provided outside the IPM Conventional configuration example of another aspect

1 Intelligent Power Module (IPM)
DESCRIPTION OF SYMBOLS 11 Switching element 12 Drive circuit 13 Short circuit protection circuit 2 Rectifier 3 Shunt resistor 4 Control circuit 5 Comparison circuit 51, 52, 53 Comparison circuit

Claims (2)

In the inverter protection circuit with an overload protection circuit outside the intelligent power module with built-in short circuit protection circuit,
Current detection means is connected to the input side of the intelligent power module,
The current detection means includes
A short circuit protection circuit built in the intelligent power module and set with a threshold for short circuit discrimination;
An overload protection circuit having a comparison means connected to the control means of the intelligent power module and set with a threshold for determining an overload having a value lower than the threshold for determining a short circuit ;
Is branched and connected,
The detection value of the current detection means and each threshold value are compared to determine a short-circuit state or an overload state,
The short-circuit protection circuit outputs a short-circuit signal at the time of a short circuit, and the comparison means outputs an overload signal at the time of overload.
Inverter protection circuit. When the short circuit signal is output, the control unit operates the short circuit protection circuit to turn off the output, and when the overload signal is output, the control unit reduces the power input to the intelligent power module. 2. The inverter protection circuit according to claim 1, wherein the intelligent power module is controlled.

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