Load driving device

Abstract

There is a problem that even if a large current is intentionally allowed to flow when the semiconductor element is turned on at high temperature, an overcurrent state is detected and the current is stopped. In the load driving device of the present invention, when the input voltage (Vin) reaches the threshold voltage (Vth), the overcurrent detection unit (4) detects the overcurrent and outputs the overcurrent detection signal (c) to the gate driving unit (3). On the other hand, when the temperature detection signal (a) and the current control signal (b) are input, the transistor (52) is turned on and the input voltage (Vin) of the overcurrent detection unit (4) becomes zero. Moreover, in this case, the input voltage (Vin) of the overcurrent detection unit (4) does not reach the threshold voltage (Vth). Therefore, the drive signal output from the gate driving unit (3) does not stop its output. Therefore, the drain current (Ids) can flow a large current.

Description

Technical Field

[0001] The invention relates to a load driving device. Background Art

[0002] In the load driving device, a semiconductor element is placed between electrodes, and current is supplied to the load by switching the semiconductor element. Moreover, overcurrent is detected by monitoring the potential difference between the electrodes of the semiconductor element. On the other hand, semiconductor elements such as SiC (silicon carbide) have the characteristic that the resistance value increases when turned on at high temperature, and the voltage between the electrodes increases significantly under large current.

[0003] Patent Document 1 discloses a load driving device that compares a drain-source voltage of a semiconductor element with a predetermined reference voltage to detect an overcurrent state.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-201593 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] The device described in Patent Document 1 has a problem that even if a large current is intentionally allowed to flow when the semiconductor element is turned on at high temperature, an overcurrent state is detected and the current flow is stopped.

[0009] Technical solutions adopted to solve technical problems

[0010] The load driving device involved in the present invention includes: a semiconductor element, which is arranged between electrodes through which current flows, and provides current when performing a conduction action and cuts off the current when performing a shutdown action; an overcurrent detection unit, which detects a situation where an input voltage based on the voltage between the electrodes is below a threshold voltage; and a voltage change circuit unit, which changes the input voltage based on the voltage between the electrodes, and the voltage change circuit changes the input voltage to below the threshold voltage based on a current control signal that allows a current above a specified value to flow through the semiconductor element and a temperature detection signal indicating that the temperature of the semiconductor element is above a specified value.

[0011] Effects of the Invention

[0012] According to the present invention, a large current can be intentionally caused to flow when a semiconductor element is turned on at a high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a circuit diagram of a load driving device.

[0014] Figure 2 This is a graph showing the resistance characteristics of a semiconductor element.

[0015] Figure 3 This is a graph showing an example of an increase in the voltage between electrodes due to temperature.

[0016] Figure 4 (A)~ Figure 4 (D) is a timing chart showing the operation of the load driving device when a large current is not allowed.

[0017] Figure 5 (A)~ Figure 5 (D) is a timing chart showing the operation of the load driving device when a large current is allowed. DETAILED DESCRIPTION

[0018] Figure 1 2 is a circuit diagram of the load driving device 100 .

[0019] The semiconductor element 1 is, for example, arranged between the positive electrode P and the negative electrode N. Moreover, the semiconductor element 1 provides current during the conduction operation and cuts off the current during the shutdown operation. The semiconductor element 1 is, for example, one of the semiconductor elements constituting the upper and lower arm series circuits of each phase of the UVW phase of a three-phase induction motor (MOTOR), and is equivalent to the upper arm of each phase or the lower arm of each phase. The upper and lower arm series circuits in the UVW phase constitute an inverter.

[0020] The temperature detection element 2 for detecting the temperature of the semiconductor element 1 is arranged near the semiconductor element 1. The temperature detection signal from the temperature detection element 2 is input to the control unit 10. When the detection signal from the temperature detection element 2 reaches a predetermined value, the control unit 10 outputs a temperature detection signal a.

[0021] The gate driving unit 3 is powered by the power supply Vcc, and outputs a driving signal to the gate electrode of the semiconductor element 1 in response to a PWM signal or the like from the control unit 10. When the driving signal is input from the gate driving unit 3, the semiconductor element 1 performs a conduction operation. In addition, when an overcurrent detection signal c indicating that an overcurrent is detected is input from the overcurrent detection unit 4 described later, the gate driving unit 3 stops outputting the driving signal to the semiconductor element 1.

[0022] The voltage change circuit unit 5 includes a series circuit of resistors R1, R2, and R3 powered by a power supply Vcc. The connection point between the resistors R1 and R2 is connected to the positive electrode P side of the semiconductor element 1 via a diode D1 for preventing backflow. The terminal of the resistor R3 is connected to the negative electrode N side of the semiconductor element 1. In addition, the capacitor C1 is connected in parallel with the resistor R3, and the voltage of the circuit composed of the parallel circuit of the resistor R3 and the capacitor C1 is input to the overcurrent detection unit 4 as an input voltage Vin.

[0023] The values ​​of the resistors R1, R2, and R3 are set so that when the semiconductor element 1 is turned on, if the voltage Vds of the semiconductor element 1 rises and reaches a voltage at which no current flows in the forward direction of the diode D1, the input voltage Vin of the overcurrent detection unit 4 reaches the threshold voltage Vth. When the input voltage Vin reaches the threshold voltage Vth, the overcurrent detection unit 4 detects an overcurrent and outputs an overcurrent detection signal c to the gate drive unit 3.

[0024] In addition, the voltage changing circuit section 5 includes a voltage drop control section 50. The voltage drop control section 50 includes a light emitting diode D2, a light receiving diode D3, an operational amplifier 51, and a transistor 52. When a temperature detection signal a and a current control signal b described later are input from the control section 10 and an output signal from the AND gate circuit 6 exists, the light emitting diode D2 emits light.

[0025] The light-emitting diode D2 is received by the light-receiving diode D3, and the driving signal is input to the gate electrode of the transistor 52 via the operational amplifier 51. The collector and emitter of the transistor 52 are connected to the input side of the overcurrent detection unit 4. That is, when the temperature detection signal a and the current control signal b are input, the transistor 52 is turned on, and the input voltage Vin of the overcurrent detection unit 4 becomes zero. Therefore, in this case, the input voltage Vin of the overcurrent detection unit 4 does not reach the threshold voltage Vth. Although an example is shown in which the voltage change circuit unit 5 changes the input voltage Vin of the overcurrent detection unit 4 to zero, the input voltage Vin of the overcurrent detection unit 4 may be changed to be below the threshold voltage Vth.

[0026] The current control signal b is explained. The overvoltage protection of the inverter has a three-phase short-circuit mode. The so-called three-phase short-circuit means that when the motor rotates under the action of external force although the inverter stops working, in order to prevent the filter capacitor of the inverter from exceeding the withstand voltage due to the induced voltage of the motor, the semiconductor elements of the upper arm of each phase or the semiconductor elements of the lower arm of each phase are all in the on state, thereby short-circuiting the winding of the motor. In order to maintain the three-phase short circuit, it is necessary to increase the inter-electrode voltage between the drain and source of the semiconductor element 1, but when this embodiment is not applied, the overcurrent detection unit 4 activates the overcurrent protection, so that the inter-electrode voltage cannot be increased. In the event of a three-phase short circuit, an instruction s for indicating a three-phase short circuit is input from the upper control unit (not shown) to the control unit 10, and the control unit 10 receives the instruction and outputs the current control signal b.

[0027] Figure 2 It is a graph showing the resistance value characteristics of the semiconductor element 1 . Figure 2 The X-axis represents temperature, the Y-axis represents resistance value, and the Z-axis represents current value. Figure 2 As shown, the resistance value of the semiconductor element 1 tends to increase as the temperature increases and the current value increases.

[0028] Figure 3 This is a graph showing an example of an increase in the voltage between electrodes due to temperature. Figure 3 The horizontal axis represents temperature, and the vertical axis represents the voltage between electrodes. Figure 3 As shown, the semiconductor element 1 such as SiC has the characteristic that the resistance value increases when it is turned on at high temperature, and the voltage between electrodes increases significantly under large current. For example, when the voltage between electrodes is the detection voltage V0, if the input voltage Vin of the overcurrent detection unit 4 becomes the threshold voltage Vth, when the temperature of the semiconductor element 1 rises to about 107°C, the overcurrent detection unit 4 will cause the overcurrent protection to operate if this embodiment is not applied.

[0029] In this embodiment, when a large current is intended to flow at high temperature, such as during a three-phase short circuit, the temperature detection signal a and the current control signal b are output to stop the unintended overcurrent protection by the overcurrent detection unit 4 .

[0030] Hereinafter, the operation of the load driving device 100 will be described.

[0031] Figure 4 (A)~ Figure 4 (D) is a timing chart showing the operation of the load driving device 100 when a large current is not allowed, that is, when the temperature detection signal a and the current control signal b are not output.

[0032] Figure 4 (A) shows the gate-source voltage Vgs (refer to Figure 1 ), Figure 4 (B) shows the drain current Ids (refer to Figure 1 ), Figure 4 (C) shows the drain-source voltage Vds (refer to Figure 1 ), Figure 4 (D) shows the input voltage Vin of the overcurrent detection unit 4 (see Figure 1 ).

[0033] The gate driving unit 3 outputs a driving signal to the gate electrode of the semiconductor element 1 in response to a PWM signal or the like from the control unit 10. Figure 4 As shown in (A), the drive signal is applied to the semiconductor element 1 as the gate-source voltage Vgs at time t1, and the semiconductor element 1 is turned on. Figure 4 As shown in (B), the drain current Ids starts to increase from time t1. Figure 4 As shown in (C), the drain-source voltage Vds drops at time t1 and then gradually rises. Figure 4 As shown in (D), the input voltage Vin of the overcurrent detection unit 4 increases as the drain-source voltage Vds rises. At time t2, when the input voltage Vin of the overcurrent detection unit 4 reaches the threshold voltage Vth, the overcurrent detection unit 4 detects this and sends an overcurrent detection signal c indicating the occurrence of overcurrent to the gate drive unit 3. When the drain-source voltage Vds becomes equal to the voltage Vdet across the resistors R3 and R4 and no forward current flows through the diode D1, the input voltage Vin of the overcurrent detection unit 4 becomes the threshold voltage Vth. Figure 4 As shown in (A), the gate driving unit 3 stops outputting the driving signal at time t3 in response to the overcurrent detection signal c.

[0034] When the output of the driving signal stops at time t3, the semiconductor element 1 is turned off. Figure 4 As shown in (B), the drain current Ids starts to decrease from time t3. Figure 4 As shown in (C), the drain-source voltage Vds rises. Since the semiconductor element 1 is cut off, Figure 4 As shown in (D), the input voltage Vin of the overcurrent detection unit 4 decreases.

[0035] Figure 5 (A)~ Figure 5 (D) is a timing chart showing the operation of the load driving device 100 when a large current is allowed, that is, when the temperature detection signal a and the current control signal b are output.

[0036] Figure 5 (A) shows the gate-source voltage Vgs (refer to Figure 1 ), Figure 5(B) shows the drain current Ids (refer to Figure 1 ), Figure 5 (C) shows the drain-source voltage Vds (refer to Figure 1 ), Figure 5 (D) shows the input voltage Vin of the overcurrent detection unit 4 (see Figure 1 ).

[0037] The gate driving unit 3 outputs a driving signal to the gate electrode of the semiconductor element 1 in response to a PWM signal or the like from the control unit 10. Figure 5 As shown in (A), the drive signal is applied to the semiconductor element 1 as the gate-source voltage Vgs at time t1, and the semiconductor element 1 is turned on. Figure 5 As shown in (B), the drain current Ids starts to increase from time t1. Figure 5 As shown in (C), the drain-source voltage Vds drops at time t1 and then gradually rises. Here, since the temperature detection signal a and the current control signal b are output from the control unit 10, the light emitting diode D2 emits light through the output signal from the AND gate circuit 6. The light is received by the light receiving diode D3, and the transistor 52 is turned on through the operational amplifier 51, as shown in FIG. Figure 5 As shown in (D), the input voltage Vin of the overcurrent detection unit 4 becomes zero.

[0038] Therefore, if Figure 5 As shown in (C), even if the drain-source voltage Vds rises to a value higher than the voltage Vdet at time t2, the overcurrent detection unit 4 does not detect the overcurrent. Therefore, the drive signal output from the gate drive unit 3 does not stop being output after time t3.

[0039] Therefore, if Figure 5 As shown in (B), a large current can flow through the drain current Ids. When the three-phase short circuit or the like is terminated, the output of the PWM signal or the like from the control unit 10 is stopped, and accordingly, the drive signal from the gate drive unit 3 is also stopped.

[0040] According to the above-described embodiment, the following effects can be obtained.

[0041] (1) The load driving device 100 includes: a semiconductor element 1, which is provided between electrodes through which current flows, and provides current when conducting and cuts off current when conducting; an overcurrent detection unit 4, which detects that an input voltage Vin based on the voltage between the electrodes is below a threshold voltage Vth; and a voltage change circuit unit 5, which changes the input voltage Vin based on the voltage between the electrodes, and changes the input voltage Vin to below the threshold voltage Vth based on a current control signal b that allows a current of a predetermined value or more to flow through the semiconductor element 1 and a temperature detection signal a that indicates that the temperature of the semiconductor element 1 is above a predetermined value. Thus, when the semiconductor element is conducting at high temperature, a large current can be intentionally allowed to flow.

[0042] The present invention is not limited to the above-described embodiments, and other embodiments that can be considered within the technical concept of the present invention are also included in the scope of the present invention as long as the characteristics of the present invention are not impaired.

[0043] Description of symbols

[0044] 1Semiconductor components

[0045] 2Temperature detection element

[0046] 3Gate drive unit

[0047] 4Overcurrent detection unit

[0048] 5 Voltage change circuit

[0049] 6 AND gate circuit

[0050] 10. Control Unit

[0051] 50 Voltage drop control unit

[0052] 51 Operational Amplifier

[0053] 52 transistors

[0054] 100 load drive device

[0055] aTemperature detection signal

[0056] bCurrent control signal

[0057] cOvercurrent detection signal

[0058] sThree-phase short circuit instruction

[0059] C1 capacitor

[0060] D1 diode

[0061] D2 LED

[0062] D3 light receiving diode

[0063] R1, R2, R3 resistors.

Claims

1. A load driving device, characterized in that: include: A semiconductor element, which is provided between electrodes through which current flows, supplies current when conducting, and cuts off current when shutting down; an overcurrent detection unit that detects that an input voltage based on the voltage between the electrodes is equal to or lower than a threshold voltage; as well as a voltage changing circuit unit that changes the input voltage based on the voltage between the electrodes, The voltage changing circuit changes the input voltage to be lower than the threshold voltage based on a current control signal that allows a current of a predetermined value or more to flow through the semiconductor element and a temperature detection signal indicating that a temperature of the semiconductor element is greater than a predetermined value.

2. The load driving device according to claim 1, characterized in that: The voltage changing circuit unit changes the input voltage to zero based on the current control signal and the temperature detection signal.

3. The load driving device according to claim 1 or 2, characterized in that: A control unit is included that outputs the current control signal when the three phases of the motor are short-circuited.

4. The load driving device according to claim 3, characterized in that: comprising a temperature detection element disposed near the semiconductor element, The control unit outputs the temperature detection signal when the temperature detected by the temperature detection element is equal to or higher than a predetermined value.

Images