JP2819863B2 - Motor drive element protection method - 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 protecting a motor driving element, and more particularly to a method for protecting a motor driving element for preventing overheating of the motor driving element due to an excessive current.

[0002]

2. Description of the Related Art Conventionally, in this kind of protection method for a motor driving element, in order to prevent the motor driving element from being burned out by an excessive current, a thermostat disposed on a heat sink disposed near the motor driving element is used. The case temperature of the motor driving element is detected and the gate of the motor driving element is turned off to protect the motor driving element.

FIG. 3 is a block diagram showing a configuration of a conventional protection method for a motor driving element.

In the case of FIG. 3, two motor driving elements T
The motors r1 and Tr2 receive the DC voltage E1 and output motor drive currents in opposite directions to drive the motor 2.

[0005] The motor driving elements Tr1 and Tr2 detect the case temperature of the motor driving elements Tr1 and Tr2 by a thermostat 9 disposed on a heat sink 8, and based on the detected temperature, the gate driver 7 causes the motor driving elements Tr1 and Tr2 to operate. Tr
1 and Tr2 were controlled to be in an off state.

[0006]

In the conventional method for protecting a motor driving element described above, the temperature of the heat sink near the motor driving element is detected, so that a time delay is caused with respect to the temperature inside the motor driving element. The resulting motor drive element cannot be completely protected from overheating, and this is addressed by setting the overheat detection temperature of the heat sink sufficiently low. Therefore, in order to obtain a predetermined driving current, there is a disadvantage that the rank of the motor driving element must be raised by one rank or more.

An object of the present invention is to provide a method for protecting a motor driving element which can avoid burning due to overheating without raising the rank of the motor driving element.

[0008]

According to the present invention, there is provided a method of protecting a motor driving element for protecting a motor driving element which is connected to a DC power supply and outputs a directional motor driving current, from overheating. Direction determining means for determining the flow direction of the motor drive current and switching the output destination in accordance with the determined direction; and transmitting as an output corresponding to the internal temperature of the motor drive element through the current value switched by the direction determining means. Filtering means for filtering such that the output of the filtering means is compared with a reference value corresponding to an allowable maximum temperature of the motor driving element, and when the output exceeds the reference value, the operation of the motor driving element is turned off. And a gate driving means.

Further, the system of the present invention has a configuration in which the filtering means is a filter having a time constant equal to a thermal time constant inside the motor driving element.

[0010]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

The embodiment shown in FIG. 1 is an example in which two motor driving elements are used. A current voltage E1 is applied to the motor driving elements Tr1 and Tr2, In addition to the motor 2, a current detector 1 and a direction discriminator 3 which constitute direction discriminating means directly related to the present invention, two primary filters 4a and 4b as filtering means, and two comparators which constitute gate driving means 5a and 5b, reference voltages E2a and E2b, an OR gate 6, and a gate driver 7.

Next, the operation of this embodiment will be described.

The DC voltage E1 is applied to the motor driving element Tr1.
And Tr2, and outputs the drive current of the motor 2.
The motor 2 is driven by on / off control of the motor driving element Tr1 and the driving element Tr2.

The detection output of the current detector 1 inserted into the drive line of the motor 2 is discriminated in the current direction by the direction discriminator 3, and in the case of the + direction, the current is flowing through the motor driving element Tr1. Judge and input to the primary filter 4a.
In the negative direction, it is determined that a current is flowing through the motor driving element Tr2, and the current is input to the primary filter 4b.

The outputs of the primary filters 4a and 4b are input to comparators 5a and 5b, respectively, and when they exceed a preset reference voltage E2a or E2b, they act on the gate drive unit 7 to drive the motor drive elements Tr1 and Tr2. The gate of Tr2 is turned off.

Here, if the filter time constants of the primary filters 4a and 4b are set to be equal to the thermal time constants inside the motor driving elements Tr1 and Tr2, the outputs of the primary filters 4a and 4b are used to output the motor driving. Elements Tr1, Tr2
Take a value corresponding to the internal temperature of the comparator 5a, 5b
The reference voltages E2a, E2b of the motor driving elements Tr1,
If it is set so as to correspond to the allowable maximum temperature of Tr2, it becomes possible to protect the motor driving elements Tr1 and Tr2 even at the time of an excessive current.

The above-mentioned protection of the motor driving element will be described in more detail with reference to FIG.

Assume that the motor drive element conduction current flowing through the motor drive element is ITr. As shown in FIG. 2, I1 until time t1, I2 until time t2, and time t2 and t3.
Let us consider a case in which control is performed so as to be I4 between the time t4 and I3 when the time t3 is exceeded.

A comparison between the heat sink temperature TC indicated by the broken line and the temperature change of the motor driving element internal temperature Tj indicated by the alternate long and short dash line clearly shows that the motor driving element internal temperature Tj
The temperature change is sharper. This is based on the fact that the thermal time constant tH of the heat sink and the thermal time constant tTr inside the motor driving elements Tr1 and Tr2 generally have a relationship represented by the following equation (1). tTr << tH (1) In FIG. 2, when an excessive current indicated by I4 flows at times t2 and t3 of t3-t2 = tTr, the motor drive is performed even though the heat sink temperature TC does not exceed the set temperature T1. The element internal temperature Tj exceeds the allowable maximum temperature T2 and burns out.

Conventionally, in order to prevent the occurrence of such burnout, the overheat detection temperature of the heat sink 8 is set to a sufficiently low level, and therefore, in order to secure a predetermined motor drive current, the capacity of one rank is increased. As described above, the motor drive element is used.

On the other hand, in the present embodiment, the flow direction of the motor drive current, and thus the filter time constants of the two primary filters 4a and 4b arranged corresponding to the motor drive elements are determined by the motor drive elements Tr1 and Tr2. The output can be set to a value corresponding to the motor driving element internal temperature Tj in FIG. 2 by setting the thermal time constant equal to the internal thermal time constant. On the other hand, the reference voltage E2a which is the comparison reference voltage of the comparators 5a and 5b. , E2b are set to a value corresponding to the maximum allowable temperature T2 at which the burnout of the motor drive elements Tr1 and Tr2 can be avoided, and the motor drive elements Tr1 and Tr2 are controlled to protect against burnout due to excessive current. .

[0023]

As described above, according to the present invention, after the direction of the flowing current of the motor driving element is determined, the signal is passed through a primary filter having a time constant equal to the internal thermal time constant of the motor driving element, and the output of the primary filter is determined. If the value exceeds a predetermined allowable value, the gate of the motor driving element is turned off, thereby providing an effect of protecting the motor driving element from burning due to excessive current.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing motor driving elements Tr1 and Tr2 in FIG.
It is explanatory drawing of prevention of burnout.

FIG. 3 is a block diagram of a conventional method for protecting a motor driving element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current detector 2 Motor 3 Direction discriminator 4a, 4b Primary filter 5a, 5b Comparator 6 OR gate 7 Gate drive part 8 Heat sink 10 Thermostat E1 DC voltage E2a, E2b Reference voltage Tr1, Tr2 Motor drive element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-48-86023 (JP, A) JP-A-48-99636 (JP, A) JP-A-49-72644 (JP, A) JP-A 50-860 132414 (JP, A) JP-A-51-42942 (JP, A) JP-A-56-56187 (JP, A) JP-A-57-160325 (JP, A) JP-A-58-95991 (JP, A) JP-A-2-155875 (JP, A) JP-B-38-8689 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02H 6/00 H02H 7/08-7/097 H02K 11/00 H02P 3/00-3/26 H02P 7/04-7/34

Claims (2)

(57) [Claims] 1. A motor drive element protection method for protecting a motor drive element that is connected to a DC power supply and outputs a directional motor drive current, wherein the direction of the motor drive current is determined. Direction discriminating means for switching an output destination in accordance with the discriminated direction; filtering means for filtering so as to send out as an output corresponding to the internal temperature of the motor driving element through a current value switched by the direction discriminating means; Gate driving means for comparing the output of the filtering means with a reference value corresponding to the maximum allowable temperature of the motor driving element, and turning off the operation of the motor driving element when exceeding the reference value. A method for protecting a motor driving element, characterized in that: 2. A method according to claim 1, wherein said filtering means comprises a filter having a time constant equal to a thermal time constant inside said motor driving element.