JP3474775B2 - Inverter control semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an intelligent power device used in a home inverter air conditioner, an inverter refrigerator, an industrial inverter pump system, etc., for detecting an overcurrent and protecting the inverter system. The present invention relates to an overcurrent protection circuit.

[0002]

2. Description of the Related Art FIG. 2 schematically shows an inverter system. The inverter system generally includes a power supply input section (converter section) 11 and a system control section (microcomputer) 1.
2 and an output unit (inverter unit) 13. An alternating current (AC) signal is input to the power supply input unit 11, and current is supplied from the output unit 13 to a load (for example, a three-phase motor). In order to protect the inverter output element from an overcurrent, the output unit 13 detects the output current of the inverter output element and limits the output current when the output current exceeds a predetermined value. Is provided.

FIG. 3 shows a main part of an output part of the three-phase inverter system shown in FIG. Inverter output element 21
Are composed of power devices such as IGBTs and FETs. The current flowing through the inverter output element 21 is converted into a voltage by the current detection shunt resistor (hereinafter, current detection resistor) 22. The gate driver 23 that drives the inverter output element 21 has an overcurrent protection circuit. The overcurrent protection circuit includes an overcurrent detection comparator 24 and a NOR (logical sum negation) circuit 26.

The reference voltage Vref from the power supply 25 is applied to the negative input terminal of the overcurrent detection comparator 24, and the voltage VS generated by the voltage drop of the current detection resistor 22 is applied to the positive input terminal. .

When a current (overcurrent) of a predetermined value or more flows through the current detection resistor 22, the voltage VS generated by the current detection resistor 22 becomes larger than the reference voltage Vref,
The output of the overcurrent detection comparator 24 becomes positive (“H”). At this time, all the outputs of the NOR circuit 26 are forcibly made negative (“L”), and the output current is cut off.

When the current flowing through the current detection resistor 22 is less than the predetermined value, the voltage VS generated by the current detection resistor 22 becomes smaller than the reference voltage Vref, and the output of the overcurrent detection comparator 24 becomes negative ( "L"). At this time, the output of the NOR circuit 26 has control inputs φ1 to φ1.
Plus (“H”) or minus (“L”) depending on φ6
Becomes

[0007]

As shown in FIG. 3, the inverter control semiconductor device includes an inverter output element 21.
Has an overcurrent protection circuit to protect the device from overcurrent. Then, the conventional overcurrent protection circuit directly detects the output current flowing through the inverter output element 21 by using the current detection resistor 22 connected to the main path of the output current.

However, since the output current flowing through the inverter output element 21 is usually as large as several tens to several hundreds of amperes, the wattage generated in the current detection resistor 22 also becomes as large as several tens of watts.

Therefore, there is a drawback that an expensive current detection resistor 22 that can withstand such a large wattage is required and that the efficiency of the system deteriorates due to the loss of power due to the use of the current detection resistor 22.

The present invention has been made in view of the above circumstances, and an object thereof is to detect an output current for protecting an inverter output element from an overcurrent in a semiconductor device for controlling an inverter, and to detect a main path of the output current. Without connecting a current detection resistor to, and control overcurrent protection I
It is to be performed accurately in C.

[0011]

In order to achieve the above object, a semiconductor device for inverter control according to the present invention controls the operation of a transistor which is integrated into one chip and has a sense terminal. A resistor for converting a sense current flowing through the sense terminal into a sense voltage, a comparator for comparing a reference voltage with the sense voltage, and a gate driver for controlling the operation of the transistor based on the comparison result of the comparator are provided.

The resistor for generating the reference voltage and the resistor for generating the sense voltage have substantially the same characteristics. The reference voltage has a characteristic of canceling variations in the sense current of the transistor due to environmental changes.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The semiconductor device for inverter control of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of a main part of a semiconductor device (control IC) for controlling an inverter according to an embodiment of the present invention.

In this example, an inverter control semiconductor device applied to a three-phase inverter system will be described.
The inverter output element 1 is composed of a power device (IGBT, FET, etc.) having a sense terminal. In the present invention, the current detection resistor is not connected to the main path through which the main current IM of the inverter output element 1 flows, and the inverter output element 1 is directly connected to the ground point.

The inverter output element 1 has a main current IM of 1
It has a sense terminal capable of outputting a minute current of / k times as the sense current IS. k = IM / IS (1) The sense terminal of the inverter output element 1 passes through the sense input terminal 2 of the inverter control semiconductor device (control IC) 10 and is connected to the resistor RS in the inverter control semiconductor device 10.
Connected to. Therefore, the sense current IS of the inverter output element 1 flows to the resistor RS via the sense input terminal 2.

A sense voltage VS is generated by the sense current IS and the resistor RS. VS = IS × RS (2) This sense voltage VS is input to one input terminal of the overcurrent detection comparator 3. The reference voltage V0 is input to the other input terminal of the overcurrent detection comparator 3.

The reference voltage V0 is generated by the current IR and the resistor R0. V0 = IR × R0 (3) Since the current IR is the current IRR folded by the current mirror circuit 8, the relationship of the following expression (4) is obtained.

IR = IRR (4) The current IRR is the power supply VR, the pnp bipolar transistor 4, the npn bipolar transistor 5 and the resistor 6.
Is generated by. Further, the current IRR flows through the terminal 7 to the overcurrent protection level determination resistor RR outside the inverter control semiconductor device 10.

VR = IRR × RR (5) That is, the reference voltage V0 is V0 = VR · (R0 / RR) (6) from the above equations (3) to (5).

Therefore, the overcurrent protection level IMth of the three-phase inverter control semiconductor device according to the present invention (a value recognized as an overcurrent) IMth can be calculated from the equations (1), (2) and (6) as follows: ) Can be expressed as

[0021]   VS = V0   IS × RS = VR ・ (R0 / RR)   (IM / k) × RS = VR · (R0 / RR)   IM = IMth   IMth = k · {R0 / (RS × RR)} · VR (7) However, IMth: main current protection level, k: ratio of sense current to main current (IM / IS), R0: resistance value of the resistor R0, RS: resistance value of the resistance RS, RR: resistance value of the resistor RR, VR: The voltage value of the power supply VR.

The comparator 3 and the resistor RS are provided for each phase of the three-phase inverter system. This is to protect the inverter output element corresponding to each phase. Further, the output signal of the comparator 3 is supplied to the gate driver 9 as a gate-off signal.

When an overcurrent is flowing (IM ≧ IMt
h), the voltage VS generated by the resistor RS is the reference voltage V0
Therefore, the comparator 3 puts the gate-off signal into the activated state (“H”) to put the inverter output element 1 into the off state.

On the other hand, when no overcurrent is flowing (IM <
IMth), since the voltage VS generated by the resistor RS becomes smaller than the reference voltage V0, the comparator 3
In order to maintain the on state of the inverter output element 1, the gate off signal is deactivated (“L”).

In this way, the output of the comparator 3 cuts off the inverter output element 1, or
A diagnostic signal can be output to the outside of the inverter controlling semiconductor device 10.

In the semiconductor device for controlling an inverter having the above structure, the present invention further takes the following measures. First, the power supply VR (V0) is made to have characteristics (including temperature characteristics) opposite to those of the inverter output element 1 (including temperature characteristics). That is, the ratio k between the sense current IS and the main current IM generally changes depending on the environmental conditions around the system (temperature change, etc.). If this is left as it is, the overcurrent cannot be detected accurately. Therefore, the power supply VR (V0) is provided with a characteristic that cancels out variations in the sense current IS of the inverter output element 1 due to changes in environmental conditions (variations in the ratio k between the sense current IS and the main current IM).

Secondly, the resistors R0 and RS have relative accuracy. That is, the resistor R0 and the resistor RS are formed in the same place, in the same direction, and in the same process in the chip so that the two resistors have substantially the same characteristics (including temperature characteristics). As a result, the comparison result in the comparator can always be made constant regardless of the environmental conditions, and the overcurrent can be detected with high accuracy.

Thirdly, the resistance R0 in each phase is provided with relative accuracy. That is, the resistance R0 in each phase is formed in the same place, in the same direction, and in the same process in the chip so that the characteristics (including the temperature characteristics) of each resistance corresponding to each phase are substantially the same. . As a result, overcurrent can be detected with high accuracy in each phase.

In the above embodiment, the inverter controlling semiconductor device (control IC) is composed of bipolar transistors, but it may be composed of MOS transistors.

[0030]

As described above, according to the semiconductor device for inverter control of the present invention, by using the transistor having the sense terminal as the inverter output element,
It is not necessary to connect a current detection resistor, which is expensive and causes power loss, to the main path of the current. Further, by providing the overcurrent protection circuit inside the control IC, it is possible to contribute to downsizing and cost reduction of the system.

Further, in the present invention, the current detecting resistor for detecting the main current is eliminated, and instead, the resistor for detecting the sense current is provided in the control IC. However, I
The variation of the resistance value of the internal resistance formed in C is ± several tens%, and the temperature characteristic is several thousands ppm / ° C. That is, the overcurrent protection level also largely varies due to the variation in the resistance value of the internal resistance.

The variation of the overcurrent protection level is
This may result in erroneous detection of turning off the inverter output element in the normal current range, or a situation in which an overcurrent that reaches the breakdown point of the inverter output element is missed.

In the present invention, the resistors in the control IC (chip) are formed in the same place, in the same direction and in the same process, and the main resistance characteristics (including temperature characteristics) in the control IC are substantially the same. I am trying to become. Therefore, the comparison result in the comparator can always be made constant regardless of the environmental conditions, and the overcurrent can be detected with high accuracy.

Further, by making the power supply VR (V0) have a characteristic opposite to that of the inverter output element, variations in the sense current of the inverter output element due to changes in environmental conditions (variations in the ratio of the sense current and the main current). ) Can be canceled out, the overcurrent can be detected with higher accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an inverter control semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an inverter system.

FIG. 3 is a diagram showing a conventional inverter control semiconductor device.

[Explanation of symbols]

1, 21: Inverter output element, 2: Sense input terminal, 3,24: Overcurrent detection comparator, 4: pnp type bipolar transistor, 5: npn type bipolar transistor, 6,7: resistor, 8: current mirror circuit, 9 , 23: gate driver, 10: semiconductor device for inverter control, 11: power supply input part, 12: system control part, 13: output part, 22: current detection resistor, 25: power supply, 26: NOR circuit.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H03K 17/08

Claims (6)

(57) [Claims] 1. A one-chip integrated semiconductor device for controlling an inverter, which controls an operation of a transistor having a sense terminal, wherein a first resistor generates a reference voltage by a constant current.
When, a second resistor for converting the sense current flowing through the sense terminal of the transistor to the sense voltage, a comparator for comparing the reference voltage and the sense voltage, the operation of the transistor based on a comparison result of the comparator control And a gate driver for generating the reference voltage.
And the resistance that generates the sense voltage are substantially
An inverter control semiconductor device having the same characteristics as described above . 2. The inverter control semiconductor device according to claim 1, wherein the reference voltage has a characteristic of canceling out variations in the sense current of the transistor due to environmental changes. 3. A semiconductor device for inverter control, which is integrated into one chip for controlling the operation of a transistor having a sense terminal , wherein a first resistor for generating a reference voltage and a sense flowing to the sense terminal of the transistor are provided. comprising a second resistor for converting the current to a sense voltage, a comparator for comparing the reference voltage and the sense voltage, and a gate driver for controlling the operation of the transistor based on a comparison result of said comparator, said reference The voltage is
Resistance value of the external resistor outside the semiconductor device for inverter control
Generated by flowing a constant current based on
A semiconductor device for controlling an inverter, characterized in that: 4. The semiconductor device for controlling an inverter according to claim 3 , wherein the resistance generating the reference voltage and the resistance generating the sense voltage have substantially the same characteristics. 5. The inverter controlling semiconductor device according to claim 3 , wherein the reference voltage has a characteristic of canceling out variations in the sense current of the transistor due to environmental changes. 6. The reference voltage is a characteristic of the transistor.
5. It has a temperature characteristic opposite to
2. The semiconductor device for controlling an inverter according to 2 or 5.