TWI747713B - Heat detection circuit and heat detection method - Google Patents

Abstract

A heat detection circuit is provided. The heat detection circuit includes a thermistor, an oscillation circuit and a processing circuit. The thermistor is arranged adjacent to a power element. The oscillation circuit is coupled to the thermistor and generates a clock signal, wherein the oscillation circuit adjusts the frequency of the clock signal according to the resistance value of the thermistor. The processing circuit is configured to receive the clock signal to detect the frequency of the clock signal. The processing circuit is configured to search a comparison table according to the frequency value of the frequency to obtain temperature information corresponding to the frequency value. The comparison table includes a plurality of candidate frequency values and a plurality of corresponding candidate temperature information.

Description

Heat detection circuit and heat detection method

The present invention relates to a heat detection circuit, and more particularly to a heat detection circuit for detecting the temperature of a power device.

In recent years, environmental awareness has risen, making electric vehicles more and more popular, such as electric cars, electric cars, electric buses, etc. When the electric vehicle is running, the power transistor in the power module will have different frequency and magnitude current output according to the vehicle speed and load. Depending on the output current, the power transistor will generate different temperatures. When the aforementioned temperature exceeds a threshold, the power transistor will be damaged or even burned.

In order to avoid the aforementioned situation, those skilled in the art will usually install a detection circuit near the power transistor to monitor the temperature change of the power transistor. FIG. 1A shows a schematic circuit diagram of the detection circuit. As shown in Figure 1A, the detection circuit 100 includes a power supply voltage VDC, a resistor R, and a thermistor R _T. Resistor R and the thermistor R _T constituting the voltage dividing circuit 110, and the thermistor R _T is disposed near the power transistor (not shown) is. Since the resistance value of the thermistor R _T has the characteristic of changing with temperature, the divided voltage value V2 of the voltage divider circuit 110 will also change accordingly. By detecting the divided voltage value V2, the core temperature of the power transistor can be estimated, so that corresponding measures can be taken to protect the power transistor when the temperature rises, thereby ensuring driving safety.

However, the ripple component (represented by V1) in the power supply voltage VDC will affect the divided voltage value V2. FIG. 1B shows a waveform diagram of the divided voltage value V2 with time. The vertical axis of the aforementioned waveform diagram is the divided voltage value V2, and the horizontal axis is time t. The waveform W1 shows the change of the divided voltage value V2 excluding the influence of the ripple component V1, and the waveform W2 shows the change of the divided voltage value V2 actually affected by the ripple component V1. It can be seen from FIG. 1B that _{there is a non-negligible gap between the peak W P} and the trough W _{T of the} waveform W2, which may cause the actual temperature of the power transistor to be misjudged. In addition, the wire resistance of the pull wire will also affect the divided voltage value V2.

Therefore, it is necessary to propose a solution to avoid the problem that the actual temperature of the power transistor is misjudged due to the unstable power supply voltage and the existence of line resistance.

The present invention provides a thermal detection circuit, which can detect the temperature of a power element without being affected by the stability of the power supply voltage and the line resistance.

The heat detection circuit of the present invention includes a thermistor, an oscillation circuit and a processing circuit. The thermistor is arranged adjacent to a power element. The oscillation circuit is coupled to the thermistor and generates a clock signal. The oscillation circuit adjusts the frequency of the clock signal according to the resistance value of the thermistor. The processing circuit is used to receive the clock signal and detect the frequency of the clock signal, to search a comparison table according to the frequency value of the frequency to obtain the corresponding frequency The temperature information of the value. The comparison table includes multiple candidate frequency values and corresponding multiple candidate temperature information.

The heat detection method of the present invention is suitable for heat detection circuits. The thermal detection circuit includes a thermistor, an oscillation circuit, and a processing circuit. The thermistor is arranged adjacent to the power element, and the oscillation circuit is coupled to the thermistor. The aforementioned heat detection method includes: generating a clock signal by an oscillation circuit, and adjusting the frequency of the clock signal according to the resistance value of the thermistor by the oscillation circuit; and receiving and detecting the frequency of the clock signal by a processing circuit, and processing The circuit searches a comparison table according to the frequency value of the frequency to obtain the temperature information corresponding to the frequency value. The comparison table includes multiple candidate frequency values and corresponding multiple candidate temperature information.

Based on the above, the present invention generates a clock signal by coupling the oscillation circuit to the thermistor, and uses the characteristic that the frequency of the clock signal varies with the resistance of the thermistor to read the frequency value of the aforementioned frequency. To estimate the surface temperature of the power element, so as to avoid the problem of misjudgment of temperature estimation due to the unstable power supply voltage or the influence of the line resistance.

100: Detection circuit

110: Voltage divider circuit

210: Power components

220: Oscillation circuit

230: processing circuit

240: Power Module

M1~M6: power transistor

C1~C3: Capacitance

G1~G4: Inverter

N1~N8: Node

OP: Operational amplifier

R, R1~R4: resistance

R _T , R _T1 , R _T2 , R _T3 : Thermistor

R _O : output resistance

S810, S820: steps

t: time

T: temperature

TA: Comparison table

T1: first temperature

T2: second temperature

t1, t2: time interval

VDC: power supply voltage

V1: ripple component

V2: divided voltage value

VB: Voltage

VDD: working voltage

V _O : Clock signal

W1~W6, W6’: Waveform

W _P : crest

W _T : trough

FIG. 1A shows a schematic circuit diagram of the detection circuit.

FIG. 1B shows a waveform diagram of the divided voltage value V2 with time.

FIG. 2 is a block diagram of the thermal detection circuit of the present invention.

FIG. 3 is a schematic circuit diagram of the power device 210 in FIG. 2.

FIG. 4A is a schematic circuit diagram of the oscillation circuit 220 according to the first embodiment of the present invention.

FIG. 4B is a schematic diagram showing the waveform of the _{clock signal V O in FIG. 4A changing with time.}

FIG. 5 is a schematic circuit diagram of the oscillation circuit 220 according to the second embodiment of the present invention.

FIG. 6 is a schematic circuit diagram of the oscillation circuit 220 according to the third embodiment of the present invention.

FIG. 7A is a schematic diagram showing the waveform of the _{clock signal V O varying with time at the first temperature.}

FIG. 7B is a schematic diagram showing the waveform of the _{clock signal V O changing with time at the second temperature.}

FIG. 7C is a schematic diagram of the waveform of the _{clock signal V O} affected by noise at the second temperature changing with time.

FIG. 8 is a flowchart showing the steps of the heat detection method of the present invention.

FIG. 2 is a block diagram of the thermal detection circuit of the present invention. As shown in Fig. 2, the thermal detection circuit includes an oscillation circuit 220, a processing circuit 230, and a thermistor R _T. The oscillating circuit 220 is coupled to the thermistor R _T , wherein the thermistor R _T is arranged near the power element 210 so that the resistance of the thermistor R _T changes with the temperature of the power element 210. FIG. 3 is a schematic circuit diagram of the power device 210 in FIG. 2. Please refer to FIG. 3. In this embodiment, the power element 210 is a power module with 6 power transistors M1 to M6. _{Among them, thermistors R T1} , R _T2 and R _T3 are respectively arranged near the power transistors M2, M4 and M6.

Please refer to FIG. 2 again. The oscillating circuit 220 is used to generate a clock signal. The frequency of the clock signal generated by the oscillating circuit 220 is affected by the resistance of the _{thermistor R T.} In other words, when the frequency of the oscillation circuit 220 may be adjusted based on the resistance of the thermistor R _T of clock signal. The processing circuit 230 is coupled to the oscillation circuit 220 to receive the clock signal generated by the oscillation circuit 220 and detect the frequency of the clock signal. The processing circuit 230 pre-established a comparison table TA, wherein the comparison table TA includes a plurality of candidate frequency values and corresponding candidate temperature information. The processing circuit 230 is also used for searching the comparison table TA according to the frequency value of the detected clock signal to obtain the temperature information corresponding to the aforementioned frequency value. The power module 240 is used to supply power to the oscillation circuit 220 and the processing circuit 230.

Briefly, the present invention may be acquired temperature of the power device 210 through the information detected by the frequency affected by the resistance of the thermistor R _T of clock signal. Compared with the method of measuring the divided voltage value adopted in the prior art, the present invention adopts a completely different technical method to estimate the temperature of the power device 210.

In this embodiment, the power element 210 is disposed in the power module, the oscillation circuit 220 may be a resistance capacitor oscillator (RC oscillator for short), and the processing circuit 230 is a digital signal processor (DSP). However, the present invention is not limited to this. In other embodiments, the processing circuit 230 may also be a microprocessor (Microprocessor), a central processing unit (CPU), or other programmable general-purpose or special-purpose microprocessor (Microprocessor), Programmable controller, Application Specific Integrated Circuits (ASIC), Programmable Logic Device (PLD) or other similar devices or a combination of these devices. In addition, in this embodiment, the thermistor R _T may be a thermistor with a positive temperature coefficient (PTC), that is, the resistance of the thermistor R _T will increase as the temperature rises. However, the present invention is not limited to this. In other embodiments, a thermistor R _T with a negative temperature coefficient (Negative Temperature Coefficient, NTC) may be used, that is, the resistance of the thermistor R _T will decrease as the temperature rises. .

A number of different implementation aspects of the oscillation circuit 220 will be described below with examples. FIG. 4A is a schematic circuit diagram of the oscillation circuit 220 according to the first embodiment of the present invention. Please refer to FIG. 4A. The oscillation circuit 220 includes a capacitor C1, a resistor R1, an inverter G1, an inverter G2, and a thermistor R _{T. The} oscillation circuit 220 also has nodes N1 to N3. The capacitor C1 is coupled between the node N1 and the node N2. One end of the resistor R1 is coupled to the node N1, and the other end of the resistor R1 is coupled to the input end of the inverter G1. The output terminal of the inverter G1 is coupled to the node N3. The thermistor R _T is coupled between the node N1 and the node N3. The input terminal of the inverter G2 is coupled to the node N3, and the output terminal of the inverter G2 is coupled to the node N2. The inverter G1 and the inverter G2 have the functions of oscillating and shaping the output waveform. The above-described elements constituting an RC oscillator, and a clock signal V _O may be read node N2.

FIG. 4B is a schematic diagram showing the waveform of the _{clock signal V O in FIG. 4A changing with time.} Please see Figure 4B, which has two waveforms. Waveform W3 is displayed as a triangular wave generated without shaping, and waveform W4 is displayed as a square wave after shaping. Please look at the waveform W3 first. The oscillating circuit 220 flips between the time interval t1 and the time interval t2. However, the waveform W3 forms a triangular wave due to no shaping process, and cannot be directly used by the processing circuit 230. Therefore, in the present invention, the triangular wave is shaped by setting the inverter G1 and the inverter G2 to generate a square wave that can be directly used by the processing circuit 230. Among them, the peak voltage of the waveform W3 is the voltage VB, and the peak voltage of the waveform W4 is the working voltage VDD.

FIG. 5 is a schematic circuit diagram of the oscillation circuit 220 according to the second embodiment of the present invention. See Figure 5, oscillation circuit 220 comprises a capacitor C2, inverter G3, the resistor R2, an inverter G4, a thermistor R _T, and an output resistance R _O, the oscillation circuit 220 and having a node N4 ~ N7. The capacitor C2 is coupled between the node N4 and a reference ground voltage. The input terminal of the inverter G3 is coupled to the node N4, and the output terminal of the inverter G3 is coupled to the node N5. The resistor R2 is coupled between the node N5 and the node N6. The thermistor R _T is coupled between the node N4 and the node N6. The input terminal of the inverter G4 is coupled to the node N5, and the output terminal of the inverter G4 is coupled to the node N7. One end of the output resistance R _O is coupled to node N7. The above-mentioned elements constitute an RC oscillator, and the clock signal V _O can be read from the other end of the output resistor R _O. Similar to the first embodiment, the inverter G3 and the inverter G4 of the second embodiment shown in FIG. 5 also have the functions of oscillating and shaping the output waveform.

FIG. 6 is a schematic circuit diagram of the oscillation circuit 220 according to the third embodiment of the present invention. As shown in FIG. 6, the oscillation circuit 220 includes an operational amplifier OP, a capacitor C3, a resistor R3, a thermistor R _T, and a resistor R4. The operational amplifier OP has an inverting input terminal, a non-inverting input terminal, and an output terminal. The capacitor C3 is coupled between the inverting input terminal of the operational amplifier OP and the reference ground voltage. The resistor R3 is coupled between the non-inverting input terminal of the operational amplifier OP and the reference ground voltage. The resistor R4 is coupled between the non-inverting input terminal of the operational amplifier OP and the output terminal (ie node N8) of the operational amplifier OP. Thermistor R _T is coupled to the inverting input terminal and output terminal of the operational amplifier OP of the operational amplifier OP (i.e., node N8) between. The above-described elements constituting an RC oscillator, and a clock signal V _O is read out by the node N8.

It should be noted that, for convenience of explanation, 4A, 5 and 6 in FIG thermistors R _T are shown in the oscillation circuit 220, but in fact the thermistor R _T is arranged in a power element (e.g., power Crystal) nearby, and can be coupled to other components of the oscillator circuit 220 through a cable. In addition, although FIGS. 4A, 5, and 6 are all double-ended RC oscillators, the present invention is not limited thereto. In other embodiments, a single-ended RC oscillator can also be used.

The following will observe the effect of the present invention from the waveform diagram. FIG. 7A is a schematic diagram showing the waveform of the _{clock signal V O varying with time at the first temperature.} FIG. 7B is a schematic diagram showing the waveform of the _{clock signal V O changing with time at the second temperature.} FIG. 7C is a schematic diagram of the waveform of the _{clock signal V O} affected by noise at the second temperature changing with time. In the waveform diagrams of FIGS. 7A to 7C, the vertical axis is the clock signal V _O (unit: V), and the horizontal axis is the time t (unit: ms). T represents the temperature of the power transistor, such as the first temperature T1 and the second temperature T2. In this embodiment, the first temperature T1 may be 85°C, and the second temperature T2 may be 25°C. It can be observed from the waveform W5 of FIG. 7A and the waveform W6 of FIG. 7B that as the temperature becomes lower, _{the frequency of the clock signal V O} will also become higher. FIG. 7C by the waveform W6 'can be observed, when the clock signal V _O affected by noise, the peaks and valleys of the clock signal V _O shape of FIG. 7B (V _O clock signal unaffected impact noise) shown in FIG. Different (see arrow). However, the clock signal frequency in FIG. 7C V _O remains the same as when the clock signal frequency V _O of FIG. 7B. In other words, _{the frequency of the clock signal V O} at the same temperature will not change due to the influence of noise. In addition, the noise here generally refers to the signal fluctuations caused by power supply ripples and line resistance changes mentioned in the prior art. Therefore, the present invention can _{perform a look-up table by detecting the frequency of the clock signal V O} without being affected by noise, so as to infer the temperature of the power element 210.

The content of the comparison table TA pre-established by the processing circuit 230 may be as shown in Table (1) below. The temperature information and the corresponding frequency value in Table (1) can be obtained through actual measurement. Specifically, by measuring the surface temperature of the power device and measuring _{the frequency value of the clock signal V O} at the aforementioned surface temperature, the values of each column of the table (1) can be obtained. The comparison table TA may be stored in the memory of the processing circuit 230 in advance. The aforementioned memory may be volatile memory such as random access memory (RAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and static random access memory (SRAM). The aforementioned memory may also be NAND flash memory, NOR flash memory, read-only memory (ROM), electrically erasable programmable ROM (EEPROM), erasable programmable ROM (EPROM), and Phase change random access memory (PCRAM) and other non-volatile memory. Alternatively, the aforementioned memory may also be a one-time programming non-volatile memory, such as a fuse memory (fuse).

Table I)

FIG. 8 is a flowchart showing the steps of the heat detection method of the present invention. The heat detection method of the present invention is suitable for the heat detection circuit shown in FIG. 2. Please refer to FIG. 2 and FIG. 8 at the same time. The thermal detection circuit includes the thermistor R _T , the oscillation circuit 220 and the processing circuit 230. Thermistor R _T are disposed adjacent to a power element 210, the oscillation circuit 220 and is coupled to the thermistor R _T. In step S810, generated by the oscillation circuit 220 when the clock signal, the frequency of the clock signal by the oscillation circuit 220 is adjusted based on the resistance value of the thermistor R _T. In step S820, the processing circuit 230 receives and detects the frequency of the clock signal, and the processing circuit 230 searches a comparison table according to the frequency value of the aforementioned frequency to obtain a temperature information corresponding to the frequency value.

In summary, the present invention couples the oscillation circuit to the thermistor to generate time Pulse signal, in which the frequency of the clock signal has the characteristic of changing with the resistance of the thermistor. In this way, the present invention can estimate the surface temperature of the power device by reading the frequency value of the aforementioned frequency. Compared with the prior art, the advantage of the present invention is that the aforementioned frequency value will not be affected by unstable power supply voltage or line resistance. Therefore, the present invention can obtain the surface temperature of the power element more accurately, avoid misjudgment of the surface temperature of the power element, and can take corresponding measures more immediately to prevent the power element from being damaged.

210: Power components

220: Oscillation circuit

230: processing circuit

240: Power Module

R _T : Thermistor

TA: Comparison table

Claims (4)

A heat detection circuit includes: a thermistor arranged adjacent to a power element; an oscillating circuit coupled to the thermistor to generate a clock signal, wherein the oscillating circuit is based on the resistance value of the thermistor To adjust a frequency of the clock signal, the oscillating circuit includes: a capacitor coupled between a first node and a second node; a resistor, one end of the resistor is coupled to the first node; A first inverter, an input end of the first inverter is coupled to the other end of the resistor, an output end of the first inverter is coupled to a third node; and a second inverter, An input end of the second inverter is coupled to the third node, an output end of the second inverter is coupled to the second node, and one end of the thermistor is coupled to the first node , The other end of the thermistor is coupled to the third node, and the clock signal is read from the second node; and a processing circuit for receiving the clock signal and detecting the clock signal Frequency, searching a comparison table according to a frequency value of the frequency to obtain a temperature information corresponding to the frequency value, wherein the comparison table includes a plurality of candidate frequency values and a plurality of corresponding candidate temperature information. A heat detection circuit includes: a thermistor, which is arranged adjacent to a power element; An oscillating circuit is coupled to the thermistor to generate a clock signal, wherein the oscillating circuit adjusts a frequency of the clock signal according to the resistance value of the thermistor, wherein the oscillating circuit includes: a capacitor coupled to Between a first node and a reference ground voltage; a first inverter, coupled between the first node and a second node; a first resistor, coupled between the second node and a first node Between three nodes; and a second inverter coupled between the second node and a fourth node, wherein one end of the thermistor is coupled to the first node, and the other of the thermistor One end is coupled to the third node, and the clock signal is read from the fourth node; and a processing circuit for receiving the clock signal, detecting the frequency of the clock signal, according to a frequency of the frequency The frequency value searches a comparison table to obtain a temperature information corresponding to the frequency value, wherein the comparison table includes a plurality of candidate frequency values and a plurality of corresponding candidate temperature information. A heat detection circuit includes: a thermistor arranged adjacent to a power element; an oscillating circuit coupled to the thermistor to generate a clock signal, wherein the oscillating circuit is based on the resistance value of the thermistor In order to adjust a frequency of the clock signal, the oscillating circuit includes: an operational amplifier having an inverting input terminal, a non-inverting input terminal and And an output terminal, wherein the thermistor is coupled between the inverting input terminal and the output terminal of the operational amplifier; a capacitor is coupled between the inverting input terminal of the operational amplifier and a reference ground voltage A first resistor, coupled between the non-inverting input terminal of the operational amplifier and the reference ground voltage; and a second resistor, coupled between the non-inverting input terminal and the output terminal of the operational amplifier Wherein, the clock signal is read out from the output terminal of the operational amplifier; and a processing circuit for receiving the clock signal, detecting the frequency of the clock signal, and pairing it according to a frequency value of the frequency A look-up table is performed to obtain temperature information corresponding to the frequency value, wherein the look-up table includes a plurality of candidate frequency values and a plurality of corresponding candidate temperature information. The thermal detection circuit according to any one of claims 1 to 3, wherein the processing circuit is a digital signal processor.

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