PWM output temperature sensing device and driver including same

Abstract

An apparatus includes a periodic exponential decay signal generation circuit and a pulse width modulation (PWM) generation circuit. The periodic exponential decay signal generation circuit is configured to generate a periodic exponential decay signal. In each period of the periodic exponentially attenuated signal, the periodic exponentially attenuated signal is continuously exponentially attenuated from a first reference voltage to a second reference voltage. The PWM generation circuit is configured to receive a temperature response of the thermistor and the periodic exponential decay signal, and to generate a PWM output temperature sensing signal indicative of a sensed temperature of the thermistor in accordance with the temperature response and the periodic exponential decay signal.

Description

TECHNICAL FIELD

[0001] The present invention relates to electronic circuits, and more particularly, but not exclusively, to a pulse width modulation ("PWM") output temperature sensing device for converting a temperature response of a thermistor into a PWM output, and a driver including the same. BACKGROUND

[0002] Thermistors are widely used for sensing temperature in automotive applications and industrial applications. Although thermistors have high sensitivity, their temperature response (e.g., voltage across the thermistor) is highly non-linear with respect to the sensed temperature. Various different solutions can be employed to convert the temperature response of a thermistor into a temperature value. One solution is to provide a digital PWM output signal having a duty cycle that carries temperature information. However, this solution can require an analog-to-digital conversion architecture (e.g., an analog-to-digital converter (ADC)) to convert the temperature response of the thermistor into a digital PWM output, and then a processor to linearize the digital PWM output to obtain a temperature according to the resistance-temperature relationship of the thermistor, which can increase the complexity and production cost of the circuit design. SUMMARY

[0003] Embodiments of the present invention provide a solution to the above problem.

[0004] In one embodiment, a temperature sensing device is provided, including a periodic exponentially decaying signal generation circuit and a pulse width modulation (PWM) generation circuit. The periodic exponentially decaying signal generation circuit is configured to generate a periodic exponentially decaying signal. In each cycle of the periodic exponentially decaying signal, the periodic exponentially decaying signal continuously exponentially decays from a first reference voltage to a second reference voltage. The first reference voltage is higher than the second reference voltage. The PWM generation circuit is configured to receive a temperature response of a thermistor and the periodic exponentially decaying signal, and generate a PWM output temperature sensing signal according to the temperature response and the periodic exponentially decaying signal, the PWM output temperature sensing signal being indicative of a temperature sensed by the thermistor.

[0005] In one embodiment, a driver for driving a power switching device is provided, including a temperature sensing input pin, a PWM output temperature sensing device, and a temperature sensing output pin. The temperature sensing input pin is coupled to a thermistor to receive a temperature response of the thermistor. The PWM output temperature sensing device is configured to be coupled to the temperature sensing input pin, and configured to generate a PWM output temperature sensing signal according to the temperature response, the PWM output temperature sensing signal being indicative of a temperature sensed by the thermistor. The temperature sensing output pin is configured to be coupled to the PWM output temperature sensing device, and configured to output the PWM output temperature sensing signal.

[0006] In one embodiment, a temperature sensing method is provided, comprising: generating a periodic exponentially decaying signal, wherein in each cycle of the periodic exponentially decaying signal, the periodic exponentially decaying signal continuously exponentially decays from a first reference voltage to a second reference voltage, wherein the first reference voltage is higher than the second reference voltage; receiving a temperature response of a thermistor and the periodic exponentially decaying signal, and generating a PWM output temperature sensing signal according to the temperature response and the periodic exponentially decaying signal to indicate a temperature sensed by the thermistor.

[0007] It should be understood that nothing in this section is intended to limit the scope of the embodiments of the present application. Other aspects of the application will become apparent to those skilled in the art upon reading the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0008] The following drawings are included to illustrate preferred embodiments of the application and are part of the disclosure. In the drawings:

[0009] Figure 1 A block diagram of a PWM output temperature sensing device 100 according to an embodiment of the present application is illustratively shown.

[0010] Figure 2 A substantially linear relationship between the duty cycle of the PWM output temperature sensing signal and temperature is illustratively shown.

[0011] Figure 3A A schematic circuit diagram of an exemplary PWM output temperature sensing device 300A according to an embodiment of the present application is shown.

[0012] Figure 3B A schematic circuit diagram of another exemplary PWM output temperature sensing device 300B according to another embodiment of the present application is shown.

[0013] Figure 4 A waveform diagram according to an embodiment of the present application is shown, which shows the waveforms of the RC output voltage V SW , the comparison signal CS, the charge / discharge control signal SCMD, and the PWM output temperature sensing signal.

[0014] Figure 5 A power converter 500 including a PWM output temperature sensing device 511 according to an embodiment of the present application is shown.

[0015] Figure 6 A flowchart of a temperature sensing method 600 according to an embodiment of the present application is shown.

[0016] In the drawings, like or corresponding elements are denoted by like or corresponding reference numerals. DETAILED DESCRIPTION

[0017] Various embodiments of the present application will now be described. In the following description, some specific details are included to provide a thorough understanding of the embodiments. One skilled in the relevant art, however, will recognize that the disclosure can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the disclosure.

[0018] Throughout the specification and claims, the phrases "in one embodiment," "in some embodiments," "in one implementation," and "in some implementations" include combinations and sub-combinations of various features and variations thereof, and changes and modifications thereof. These phrases do not necessarily refer to the same embodiment, although they can. A person of ordinary skill in the art will recognize that the meaning of these phrases are not necessarily limited to the specific terms, but are merely provided as illustrative examples of the terms. Note that when an element "is connected to" or "is coupled to" another element, it means that the element is directly connected or coupled to the other element, or indirectly connected or coupled to the other element via another element. Particular features, structures, or characteristics can be included in an integrated circuit, electronic circuit, combinational logic circuit, or other suitable component that provides the functionality. Also, it should be understood that the drawings provided herein are for explanation purposes only, and are not necessarily drawn to scale.

[0019] Figure 1 A block diagram of a PWM output temperature sensing device 100 according to embodiments of the present application is illustratively shown. As shown, the PWM output temperature sensing device 100 includes a periodic exponential decay signal generation circuit 110 and a PWM generation circuit 120. Figure 1

[0020] The PWM output temperature sensing device 100 is configured to receive a temperature response indicative of a sensed temperature from a non-linear temperature sensing circuit 130, and convert the temperature response into a PWM output temperature sensing signal whose duty cycle varies based on the sensed temperature.

[0021] The non-linear temperature sensing circuit 130 is configured to sense a temperature of an element (e.g., a power device in a power management IC), and provide a temperature response that carries information about the sensed temperature of the sensed element. The temperature response of the non-linear temperature sensing circuit 130 can follow a non-linear response curve in response to a linear change in temperature. The non-linear response curve can be approximated by an exponential or a logarithmic function.

[0022] ​In one embodiment, the nonlinear temperature sensing circuit 130 includes a thermistor (e.g., a negative temperature coefficient ("NTC") thermistor). Generally, the temperature response of a thermistor can be a function of the resistance value of the thermistor. For example, the nonlinear temperature sensing circuit 130 can have a constant current flowing through the thermistor, and the temperature response of the nonlinear temperature sensing circuit 130 includes a voltage across the thermistor. The voltage across the thermistor is linearly related to the resistance of the thermistor. In one embodiment, as shown in FIG. 1, the nonlinear temperature sensing circuit 130 is disposed outside of the PWM output temperature sensing device 100. In another embodiment, the nonlinear temperature sensing circuit 130 can be disposed inside of the PWM output temperature sensing device 100 to be part of the PWM output temperature sensing device 100. Figure 1

[0023] As is well known to those skilled in the art, the resistance of an NTC thermistor can be approximated by a "B model" that describes the resistance of the NTC thermistor using an exponential function as shown in the following relationship (1):

[0024]

[0025] where R NTC is the resistance value of the NTC thermistor at temperature T (in K), R 25 is the resistance value of the NTC thermistor at temperature T 25 , T 25 is a nominal temperature of 25 °C (in K), and B 25 / 100 is a material constant defined by 25 °C and 100 °C.

[0026] Rearranging relationship (1) to solve for temperature T gives:

[0027]

[0028] In practical application scenarios, for example, when the nonlinear temperature sensing circuit 130 is disposed to sense the temperature of an integrated circuit (e.g., a power management IC or a device therein as previously described), the temperature T of the sensed element is generally within a limited range (hereinafter referred to as a predetermined temperature range). For example, the predetermined temperature range includes the operating temperature range of the integrated circuit in which the PWM output temperature sensing device 100 is disposed. Within such a predetermined temperature range, the temperature T can be approximated by a Napierian logarithm function as shown in the following relationship (3):

[0029] T = k1ln(R NTC ) + k2 (3),

[0030] where k1 and k2 are constants.

[0031] ​The periodic exponentially decaying signal generation circuit 110 is configured to generate a periodic exponentially decaying signal. For example, the periodic exponentially decaying signal periodically decays from a first reference voltage to a second reference voltage lower than the first reference voltage, and the decay waveform in each cycle can be approximated by an exponential function. Details regarding the generation of such a periodic exponentially decaying signal will be referred to... Figure 3A , Figure 3B and Figure 4 To describe.

[0032] The PWM generation circuit 120 is configured to receive a temperature response from the nonlinear temperature sensing circuit 130 and a periodically exponentially decaying signal from the periodically exponentially decaying signal generation circuit 110. The PWM generation circuit 120 is configured to convert the temperature response of the nonlinear temperature sensing circuit 130 into a PWM output temperature sensing signal based on the periodically exponentially decaying signal. The duty cycle of the PWM output temperature sensing signal varies with the temperature sensed by the nonlinear temperature sensing circuit 130, and the period of the PWM output temperature sensing signal is equal to the period of the periodically exponentially decaying signal. Figure 2 As shown, in response to linear temperature changes within a predetermined temperature range, the duty cycle of the PWM output temperature sensing signal approximately follows a linear response curve. This linear response curve can be approximated by a linear function.

[0033] Figure 3A A schematic circuit diagram of an exemplary PWM output temperature sensing device 300A according to an embodiment of this application is shown. The PWM output temperature sensing device 300A is... Figure 1 An embodiment of the PWM output temperature sensing device 100 shown.

[0034] like Figure 3A As shown, the PWM output temperature sensing device 300A includes a periodically exponentially decaying signal generation circuit 310A and a PWM generation circuit 320A. The periodically exponentially decaying signal generation circuit 310A and the PWM generation circuit 320A are respectively... Figure 1 The embodiments of the periodic exponential decay signal generation circuit 110 and the PWM generation circuit 120 shown are illustrated.

[0035] The periodic exponentially decaying signal generation circuit 310A includes a resistive-capacitive (RC) circuit 311A ​​and a charge / discharge control circuit 312A. The RC circuit 311A ​​includes components configured to provide an output voltage (also referred to as the RC output voltage) V. SW The output terminal (also known as the RC output terminal) is SW.

[0036] In one embodiment, the RC circuit 311A ​​includes at least a capacitor C1 and a resistor R1. In one embodiment, such as Figure 3AAs shown, capacitor C1 and resistor R1 are connected in parallel between the power supply V_MAX and the reference ground. In another embodiment, RC circuit 311A ​​may further (but not necessarily) include a reference power supply V connected in series with resistor R1. REF This provides additional design flexibility in applications where specific voltage requirements / limitations apply to the first and second reference voltages. For ease of description, the reference power supply V is omitted in the following description. REF .

[0037] Specifically, such as Figure 3A As shown, the RC circuit 311A ​​also includes a switch S1. Switch S1 can be alternately turned on and off under the control of the charging / discharging control circuit 312A, thereby alternately charging and discharging capacitor C1. For example, when switch S1 is on, the power supply PMAX charges capacitor C1 to the first reference voltage V. SWMAX When switch S1 is open, capacitor C1 discharges through resistor R1. Figure 3A In the embodiment shown, the RC output voltage V of the RC circuit 311A ​​is... SW It is equal to the voltage across capacitor C1.

[0038] Based on the characteristics of a capacitor, when capacitor C1 discharges, the voltage across capacitor C1 follows an exponential curve with respect to the discharge time. Therefore, by periodically charging and discharging the RC circuit 311A, while minimizing the charging time to a relatively short / negligible time, the output voltage V of the RC circuit 311A ​​can be increased. SW It can be approximated as a periodic curve that continuously decays exponentially from the first reference voltage to the second reference voltage.

[0039] The charging / discharging control circuit 312A converts the RC output voltage V SW With the second reference voltage V SWMIN The comparison is performed, and a comparison signal CS is provided at the output. Figure 3A In the illustrated embodiment, the comparison signal CS is used as the charge / discharge control signal SCMD to control the charging and discharging of capacitor C1 in the RC circuit 311A. For example, when the RC output voltage V SW Attenuation to below the second reference voltage V SWMIN When the comparator CMP1 changes the comparison signal CS to the first CS logic state (e.g., logic high), the switch S1 is turned on to connect the first power supply V_MAX to the capacitor C1 and the first input terminal (e.g., the inverting input terminal) of the comparator CMP1. The capacitor C1 is then charged to the first reference voltage V_MAX. SWMAXSince the first input of comparator CMP1 is connected to RC circuit 311A, after a short time, the comparison signal CS changes to the second CS logic state (e.g., logic low), turning off switch S1 and starting to discharge capacitor C1 again. The RC output voltage V... SW From the second reference voltage V SWMIN Rise to the first reference voltage V SWMAX There may be a rise delay. However, with capacitor C1 from the first reference voltage V SWMAX Discharge to the second reference voltage V SWMIN Compared to the discharge time, the rise delay is relatively small and can be ignored. Therefore, the RC output voltage V SW It can be approximated by a periodically exponentially decaying function, which periodically and continuously decays from the first reference voltage V. SWMAX Exponential decay to the second reference voltage V SWMIN .

[0040] The charge / discharge control circuit 312A includes a comparator CMP1. The comparator CMP1 includes a first input (e.g., an inverting input), a second input (e.g., a non-inverting input), and an output. The first input is connected to the RC output SW of the RC circuit 311A ​​to receive the RC output voltage V. SW The second input terminal is connected to the second power supply V_MIN to receive the second reference voltage V. SWMIN In one embodiment, such as Figure 3A As shown, the second power supply V_MIN is disposed inside the charging / discharging control circuit 312A (and the PWM output temperature sensing device 300) to become part of the charging / discharging control circuit 312A (and the PWM output temperature sensing device 300). In another embodiment, the second power supply V_MIN may be disposed outside the PWM output temperature sensing device 300.

[0041] Figure 3A The periodic exponentially decaying signal generation circuit 310A shown is provided by way of example only, and the invention is not limited thereto. In other embodiments, the periodic exponentially decaying signal generation circuit 310A includes any circuit structure capable of providing a periodic exponentially decaying signal.

[0042] In one embodiment, for example, the first reference voltage V SWMAX Second reference voltage V SWMIN The duty cycle can be determined based on the temperature range of the thermistor, the constant current supplied to the thermistor, the rated voltage, and the duty cycle extreme values.

[0043] In one embodiment, the PWM generation circuit 320A includes a comparator CMP2. For example... Figure 3AAs shown, comparator CMP2 includes a first input terminal (e.g., a non-inverting input terminal), a second input terminal (e.g., an inverting input terminal), and an output terminal. The first input terminal is connected to RC circuit 311A ​​to receive the RC output voltage V. SW The second input terminal is connected to the nonlinear temperature sensing circuit 330A to receive the temperature response of the nonlinear temperature sensing circuit 330A. In one embodiment, such as Figure 3A As shown, the nonlinear temperature sensing circuit 330A includes a constant current source I_TSI and a thermistor R. NTC In this embodiment, the temperature response includes a thermistor R. NTC Voltage V across the terminals NTC Comparator CMP2 will convert the RC output voltage V SW With voltage V NTC The comparison is performed, and a PWM output temperature sensing signal is provided at the output terminal. For example, during each discharge process of capacitor C1, the RC output voltage V... SW (or the voltage across capacitor C1) from the first reference voltage V SWMAX Reduced to the second reference voltage V SWMIN When the RC output voltage V S W is higher than voltage V NTC When comparator CMP2 sets the PWM output temperature sensing signal to the first PWM logic state (e.g., logic high), and when the RC output voltage VSW becomes lower than the voltage V... NTC At this time, comparator CMP2 changes the PWM output temperature sensing signal to the second PWM logic state (e.g., logic low).

[0044] For an RC circuit, it is known that during discharge, the voltage across a capacitor (e.g., capacitor C1) is defined as a function of time:

[0045]

[0046] Among them, V SW (t) is the voltage across the capacitor (e.g., capacitor C1) at time t, V REF It is the reference voltage connected in series with a resistor (e.g., resistor R1) in an RC circuit, V SWMAX It is the initial voltage across the capacitor before discharge, and RC is the time constant of the RC circuit (e.g., RC circuit 311A).

[0047] It can be concluded that:

[0048] V sW (t=P)=V SWMIN (5), and

[0049] V sW (t=D·P)=VNTC (6),

[0050] Where P represents the RC output voltage V SW The period (which is also equal to the period of the PWM output temperature sensing signal), D represents the duty cycle of the PWM output temperature sensing signal.

[0051] It can be proven that the duty cycle D of the PWM output temperature sensing signal follows the following relationship:

[0052]

[0053] Therefore, the duty cycle of the PWM output temperature sensing signal is relative to the thermistor R. NTC voltage V NTC Follow the Napier logarithmic function. Return to the reference relation (3), where the temperature T can be approximated by a logarithmic function over a finite temperature range, and the relationship between the duty cycle of the PWM output temperature sensing signal and the temperature can be approximated by a linear function.

[0054] As mentioned earlier, the output voltage V from the RC circuit... SW Drops below the second reference voltage V SWMIN Time to RC output voltage V SW Rise back to the first reference voltage V SWMAX There may be a short rise time between the two time intervals. To further reduce the delay time, this invention further proposes another PWM output temperature sensing device, such as... Figure 3B As shown.

[0055] Figure 3B A schematic circuit diagram of another exemplary PWM output temperature sensing device 300B according to another embodiment of this application is shown.

[0056] and Figure 3A In comparison, apart from capacitor C1 and resistor R1, Figure 3B The RC circuit 311B shown also includes a capacitor C2 and a resistor R2, and the charge / discharge control circuit 312B also includes a latch. Figure 3B As shown, capacitor C2 and resistor R2 are also connected in parallel between the power supply PMAX and the reference ground. Capacitor C2 is the same as capacitor C1, and resistor R2 is the same as resistor R1.

[0057] While one capacitor (e.g., capacitor C1) is discharging, another capacitor (e.g., capacitor C2) can be charged to a first reference voltage V. SWMAXSpecifically, the RC circuit 311B also includes a switch S2 coupled between the first power supply V_MAX and the capacitor C2 and resistor R2 connected in parallel. Switches S1 and S2 are alternately turned on and off according to the charge / discharge control signal SCMD and its inverted signal SCMD' provided from the charge / discharge control circuit 312B. In one embodiment, the RC circuit 311B also includes a multiplexer switch S3, which can selectively connect the RC output terminal SW to one of the capacitors C1 and C2 to receive the voltage across that capacitor under the control of the charge / discharge control signal SCMD. In one example, when the RC output terminal SW is connected to capacitor C1, and when the voltage across capacitor C1 drops below the second reference voltage V_MAX... SWMrN At this time, comparator CMP1 changes the comparison signal CS from a second CS logic state (e.g., logic low) to a first CS logic state (e.g., logic high). Latch receives the comparison signal CS and generates / provides the charge / discharge control signal SCMD based on the comparison signal CS. In one embodiment, as... Figure 3B As shown, the latch LATCH is a D latch. In another embodiment, the latch LATCH is an RS latch. This disclosure is not limited thereto. In response to the comparison signal CS changing from a second CS logic state (e.g., logic low) to a first CS logic state (e.g., logic high), the latch LATCH changes the logic state of the charge / discharge control signal SCMD (e.g., from logic high to logic low or from logic low to logic high).

[0058] In response to the charging / discharging control signal SCMD changing to the first SCMD logic state (e.g., logic high), switch S1 is turned on, switch S2 is turned off, and switch S3 connects the RC output terminal SW to the lower port, for example, to capacitor C2. Then, the first reference voltage V is applied. SWMAX Remove capacitor C2 and connect it to capacitor C1 to charge capacitor C1 while capacitor C2 begins to discharge. In response to the charge / discharge control signal SCMD changing to the second SCMD logic state (e.g., logic low), switch S1 opens, switch S2 opens, and switch S3 connects the RC output terminal SW to the upper port, for example, to capacitor C1. Then, the first reference voltage V is... SWMAX Remove capacitor C1 and connect it to capacitor C2 to charge capacitor C2 while capacitor C1 begins to discharge. This achieves the effect of one capacitor charging while the other discharges. The RC output voltage V... SW Drops below the second reference voltage V SWMIN Time to RC output voltage V SW Rise back to the first reference voltage V SWMAX The time delay between events can be further reduced.

[0059] Figure 4 A waveform diagram according to an embodiment of this application is shown, illustrating the RC output voltage V. SW The waveforms of the comparison signal CS, the charging / discharging control signal SCMD, and the PWM output temperature sensing signal. Figure 4 Combining Figure 3B Describe it.

[0060] like Figure 4 As shown, the RC output voltage V at the RC output terminal SW of RC circuit 311B is... SW From the first reference voltage V SWMAX Periodically decays to the second reference voltage V SWMIN Thermistor R NTC voltage V NTC As time decreases, i.e., the thermistor R NTC The sensed temperature increases over time.

[0061] From time t0 to time t1, the RC output voltage V SW Higher than the second reference voltage V SWMIN When the charging / discharging control signal SCMD is low, switch S1 is open, switch S2 is open, and switch S3 connects the RC output terminal SW to the upper port, for example, to capacitor C1, and capacitor C1 is discharging. At time t1, the RC output voltage V... SW Attenuation to below the second reference voltage V SWMIN Comparator CMP1 sets the comparison signal CS to logic high. In response to CS becoming logic high, latch LATCH sets the charge / discharge control signal SCMD from logic low to logic high. In response to SCMD becoming logic high, switch S1 turns on, switch S2 turns off, and switch S3 connects the RC output SW to the lower port, for example, to capacitor C2. The first reference voltage V... SWMAX Remove capacitor C2 and connect it to capacitor C1 to charge capacitor C1; capacitor C2 begins to discharge. This is because capacitor C2 has already been pre-charged to the first reference voltage V. SWMAX Therefore, the RC output voltage V SW It will immediately rise back to the first reference voltage V. SWMAX At the RC output voltage V SW From the second reference voltage V SWMIN Increase to the first reference voltage V SWMAX Shortly thereafter, comparator CMP1 changes the comparison signal CS to logic low. Between time t1 and t2, the RC output voltage V... SW Higher than the thermistor R NTC voltage VNTC Furthermore, the PWM output temperature sensing signal remains at logic high. At time t2, the RC output voltage V... SW It becomes lower than the thermistor R NTC voltage V NTC Furthermore, the PWM generation circuit 320B changes the PWM output temperature sensing signal from logic high to logic low. At time t3, the RC output voltage V SW It becomes lower than the second reference voltage V SWMIN At this time, comparator CMP1 changes the comparison signal CS to logic high. In response to the comparison signal CS going high, latch LATCH sets the charge / discharge control signal SCMD from logic high to logic low, switch S1 opens, switch S2 opens, and switch S3 connects the RC output terminal SW to the high-side port, for example, to capacitor C1. This is because capacitor C1 has already been pre-charged to the first reference voltage V. SWMAX Therefore, the RC output voltage V SW It will immediately rise back to the first reference voltage V. SWMAX And start RC output voltage V SW A new cycle.

[0062] from Figure 4 As can be seen from this, with the thermistor R NTC voltage V NTC As the voltage decreases, the duty cycle of the PWM output temperature sensing signal increases. Based on the relationship between voltage and the temperature sensed by the thermistor, it can be known that the duty cycle of the PWM output temperature sensing signal increases with increasing temperature.

[0063] The PWM output temperature sensing device according to embodiments of the present invention can provide a PWM output temperature sensing signal with a duty cycle linearly related to temperature using a relatively simple circuit structure. Compared with the above-described ADC solution (where the analog temperature response is converted into a digital PWM signal by an ADC converter), the system complexity can be significantly reduced. Furthermore, since the duty cycle of the PWM output temperature sensing signal provided by the PWM output temperature sensing device according to embodiments of the present invention is substantially linear with respect to temperature, it can be directly used to indicate the temperature value of a thermistor without further linearization processing.

[0064] Temperature is crucial for integrated circuit (IC) chips. IC chips typically require temperature information, such as the temperature sensed by a thermistor, to perform control operations. This is not only to prevent damage or malfunction caused by overheating, but also to keep the IC chip within a specified operating temperature range to ensure optimal performance.

[0065] Figure 5A power converter 500 including a PWM output temperature sensing device 511 is shown according to an embodiment of this application. The PWM output temperature sensing device 511 is an embodiment of the PWM output temperature sensing devices 100, 300A, or 300B described above. It should be understood that... Figure 5 The power converter 500 shown is provided as an example only, and the PWM output temperature sensing device according to the invention can be applied to any suitable integrated circuit that requires control based on temperature information.

[0066] like Figure 5 As shown, the power converter 500 includes a driver 510, a power switching device 520, and a thermistor R. NTc . refer to Figure 5 In one embodiment, the driver 510 and the power switch 520 are integrated on different ICs. In another embodiment, the driver 510 and the power switch 520 are integrated on the same IC. Thermistor R NTC It is arranged on the same IC as the power switch device 520 and close to the power switch device 520 to sense the temperature of the power switch device 520.

[0067] In one embodiment, driver 510 is adapted to drive power switching device 520. In one embodiment, such as Figure 5 As shown, the driver 510 includes a first input pin 501, a first output pin 502, a temperature sensing input pin 503, a temperature sensing output pin 504, a PWM output temperature sensing device 511, a driving circuit 512, and a constant current source I_TSI. The circuit structure of the driver 510 is not limited to... Figure 5 The example shown.

[0068] The first input pin 501 is configured to receive a switch control signal PWM1. The drive circuit 512 is configured to generate a drive signal DRV based on the switch control signal PWM1 received through the first input pin 501. The first output pin 502 is coupled to the control terminal of the power switching device 520. The drive signal DRV is output to the control terminal of the power switching device 520 through the first output pin 502. Thermistor R NTC Coupled to a constant current source I_TSI to receive a constant current from the constant current source I_TSI. Figure 5 The constant current source I_TSI shown is located inside the driver IC 510. It should be understood that the constant current source I_TSI can also be located outside the driver IC 510. Thermistor R NTC Temperature response (e.g., thermistor R) NTC The voltage across the two ends is transmitted to the PWM output temperature sensing device 511 through the temperature sensing input pin 503. The PWM output temperature sensing device 511 determines the voltage based on the thermistor R. NTCThe temperature response generates a PWM output temperature sensing signal PWM2. The PWM output temperature sensing signal PWM2 includes signals generated by the thermistor R. NTC The sensed temperature information is related to the temperature. In one embodiment, within a predetermined temperature range, the duty cycle of the PWM output temperature sensing signal PWM2 substantially follows a linear response curve, which is responsive to the thermistor R. NTC The response curve changes linearly with the sensed temperature (i.e., the temperature of the power switching device 520). In one embodiment, this linear response curve can be approximated by a linear function.

[0069] In one embodiment, the PWM output temperature sensing signal PWM2 is also transmitted to the control circuit (not shown) of the power converter 500 via the temperature sensing output pin 504, so that the control circuit can use the signal to perform control of the power switching device 520 accordingly.

[0070] Figure 6 A flowchart of a temperature sensing method 600 according to an embodiment of the present invention is shown. Method 600 is performed by any one of the aforementioned PWM output temperature sensing devices 100, 300A, 300B, and 511. As previously described, each of the PWM output temperature sensing devices 100, 300A, 300B, and 511 includes a periodically exponentially decaying signal generation circuit (e.g., 110, 310A, or 310B) and a PWM generation circuit (e.g., 120, 320A, or 320B).

[0071] In block 610, an exponential decay signal generation circuit generates a periodic exponential decay signal, wherein in each period of the periodic exponential decay signal, the periodic exponential decay signal continuously and exponentially decays from a first reference voltage to a second reference voltage.

[0072] In block 620, the PWM generation circuit receives the temperature response and periodically exponentially decaying signal from the thermistor.

[0073] In block 630, the PWM generation circuit generates a PWM output temperature sensing signal based on the temperature response and the periodically exponentially decaying signal to indicate the temperature sensed by the thermistor.

[0074] In one embodiment, within a predefined temperature range, the duty cycle of the PWM output temperature sensing signal is substantially linearly related to the temperature sensed by the thermistor.

[0075] although Figure 6 The flowchart illustrates the sequential actions. It will be apparent to those skilled in the art that these actions can be performed in any order.

[0076] As previously stated, the circuit structure of the PWM output temperature sensing device according to embodiments of the present invention is much simpler than existing ADC solutions. Therefore, when implementing the PWM output temperature sensing device on an IC (e.g., driver IC 510), significant silicon area and power consumption can be saved, and system complexity can be reduced. Furthermore, since the duty cycle of the PWM output temperature sensing signal provided by the PWM output temperature sensing device according to embodiments of the present invention is linear, discrete components at the PCB level are not required to linearize the digital PWM signal provided by a conventional ADC.

[0077] The specific embodiments and accompanying drawings described above are merely common examples of the present invention. Obviously, various additions, modifications, and substitutions can be made without departing from the spirit and scope of the invention as defined in the claims. Those skilled in the art should understand that the present invention can be varied in form, structure, layout, proportion, materials, elements, components, and other aspects in practical applications according to specific environments and working requirements, without departing from the inventive principles. Therefore, the embodiments disclosed herein are for illustrative purposes only and not for limitation. The scope of the present invention is defined by the appended claims and their legal equivalents, and is not limited to the preceding description.

Claims

1. A temperature sensing device comprising: a periodic exponentially decaying signal generation circuit configured to generate a periodic exponentially decaying signal, wherein in each cycle of the periodic exponentially decaying signal, the periodic exponentially decaying signal continuously exponentially decays from a first reference voltage to a second reference voltage, wherein the first reference voltage is higher than the second reference voltage; and a pulse width modulation (PWM) generation circuit configured to receive a temperature response of a thermistor and the periodic exponentially decaying signal, and generate a PWM output temperature sensing signal according to the temperature response and the periodic exponentially decaying signal, the PWM output temperature sensing signal being indicative of a temperature sensed by the thermistor. The PWM generation circuit is configured to compare the periodic exponentially decaying signal with the temperature response, and provide the PWM output temperature sensing signal.

2. The apparatus of claim 1, wherein, The PWM generation circuit comprises a first comparator, and wherein the first comparator has a first input configured to receive the periodic exponentially decaying signal, a second input configured to receive the temperature response, and an output configured to provide the PWM output temperature sensing signal.

3. The apparatus of claim 2, wherein, The periodic exponentially decaying signal generation circuit comprises:

4. The apparatus of claim 1, wherein, a resistor-capacitor (RC) circuit comprising a first capacitor and a first resistor connected in parallel between a first power supply and a reference ground; an RC output configured to provide an output voltage of the RC circuit; and a charge / discharge control circuit configured to control charging and discharging of the first capacitor in the RC circuit. The charge / discharge control circuit is configured to compare the output voltage on the RC output with the second reference voltage, and according to a comparison result of the output voltage on the RC output with the second reference voltage, provide a charge / discharge control signal to control charging and discharging of the first capacitor in the RC circuit, thereby providing the periodic exponentially decaying signal on the RC output.

5. The apparatus of claim 4, wherein, The RC output is connected to the first capacitor and the first resistor connected in parallel to receive a voltage across the first capacitor, wherein when the output voltage on the RC output becomes lower than the second reference voltage, the charge / discharge control circuit controls charging of the first capacitor to the first reference voltage, and when the output voltage on the RC output increases from the second reference voltage to the first reference voltage, the charge / discharge control circuit controls discharging of the first capacitor.

6. The apparatus of claim 4, wherein, ​ 7. The apparatus of claim 4, the RC output coupled to the first capacitor and the first resistor connected in parallel to receive a voltage across the first capacitor, wherein, The RC circuit further includes a first switch coupled between the first power source and a first capacitor and a first resistor connected in parallel, and wherein when the output voltage on the RC output becomes lower than the second reference voltage, the charge / discharge control circuit provides a charge / discharge control signal to turn on the first switch to connect the first power source to the first capacitor to charge the first capacitor to the first reference voltage, and when the output voltage on the RC output becomes higher than the first reference voltage, the charge / discharge control circuit provides the charge / discharge control signal to turn off the first switch to disconnect the first power source from the first capacitor and to discharge the first capacitor.

8. The apparatus of claim 4, wherein, The RC circuit further includes a second capacitor and a second resistor connected in parallel between the first power source and the reference ground, and wherein the charge / discharge control circuit is configured to control charging and discharging of the first capacitor and the second capacitor, and wherein when one of the first capacitor and the second capacitor is discharging, the other of the first capacitor and the second capacitor is charging to the first reference voltage.

9. The apparatus of claim 8, wherein, The RC output is connected to one of the first capacitor and the second capacitor to receive a voltage across the one capacitor, and wherein when the output voltage on the RC output becomes lower than the second reference voltage, the charge / discharge control circuit provides a charge / discharge control signal to connect the RC output to the other of the first capacitor and the second capacitor to receive a voltage across the other capacitor.

10. The apparatus of claim 8, wherein, The RC circuit further includes a first switch coupled between the first power source and a first capacitor and a first resistor connected in parallel, a second switch coupled between the first power source and a second capacitor and a second resistor connected in parallel, and a multiplexer switch to selectively connect the RC output to one of the first capacitor and the second capacitor.

11. The apparatus of claim 1, wherein, A duty cycle of the PWM output temperature sense signal is linearly related to a sensed temperature within a predetermined temperature range.

12. The apparatus of claim 1, wherein, The thermistor is a negative temperature coefficient (NTC) thermistor.

13. The apparatus of claim 1, wherein, The temperature response of the thermistor includes a voltage across the thermistor.

14. A driver for driving a power switching device, comprising: a temperature sense input pin configured to be coupled to a thermistor to receive a temperature response of the thermistor, a PWM output temperature sense device configured to be coupled to the temperature sense input pin and to generate a PWM output temperature sense signal indicative of a temperature sensed by the thermistor from the temperature response, wherein a duty cycle of the PWM output temperature sense signal is linearly related to the sensed temperature within a predetermined temperature range; and a temperature sense output pin configured to be coupled to the PWM output temperature sense device and configured to output the PWM output temperature sense signal.

15. The driver of claim 14, wherein, The PWM output temperature sensing device includes: a periodic exponentially decaying signal generation circuit configured to generate a periodic exponentially decaying signal, wherein in each cycle of the periodic exponentially decaying signal, the periodic exponentially decaying signal continuously exponentially decays from a first reference voltage to a second reference voltage, wherein the first reference voltage is higher than the second reference voltage; and a pulse width modulation (PWM) generation circuit configured to receive a temperature response of a thermistor and the periodic exponentially decaying signal, and generate the PWM output temperature sensing signal according to the temperature response and the periodic exponentially decaying signal to indicate a temperature sensed by the thermistor.

16. The driver of claim 15, wherein, The PWM generation circuit is configured to compare the periodic exponentially decaying signal with the temperature response, and provide the PWM output temperature sensing signal.

17. The driver of claim 15, wherein, The periodic exponentially decaying signal generation circuit includes: a resistor-capacitor (RC) circuit including a first capacitor and a first resistor connected in parallel between a first power supply and a reference ground, and an RC output configured to provide an output voltage of the RC circuit.

18. A temperature sensing method, comprising: generating a periodic exponentially decaying signal, wherein in each cycle of the periodic exponentially decaying signal, the periodic exponentially decaying signal continuously exponentially decays from a first reference voltage to a second reference voltage; receiving a temperature response of a thermistor and the periodic exponentially decaying signal, and generating a PWM output temperature sensing signal according to the temperature response and the periodic exponentially decaying signal to indicate a temperature sensed by the thermistor.

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