An over-temperature protection circuit and a power supply circuit

Abstract

The present invention discloses an over-temperature protection circuit and a power supply circuit. The over-temperature protection circuit includes: a charge and discharge circuit for generating a ramp signal; a comparison circuit that receives the ramp signal and a reference signal, compares the two, and outputs a first control signal; wherein, when the temperature reaches a first over-temperature protection point, the slope of the ramp signal is reduced by a first amplitude, and when the temperature reaches a second over-temperature protection point, the slope of the ramp signal is reduced by a second amplitude; the second over-temperature protection point is higher than the first over-temperature protection point, and the second amplitude is greater than the first amplitude; the first control signal is adjusted by reducing the slope of the ramp signal. By adopting the present invention, multiple over-temperature protection points are set, and different intensities of adjustment are performed at different over-temperature protection temperatures.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to an over-temperature protection circuit and a power supply circuit. Background Art

[0002] Over-temperature protection is an important protection function in circuit applications. An over-temperature protection circuit will be set in any occasion where over-temperature protection is required. The existing over-temperature protection circuits generally include a temperature sampling module and a preset over-temperature protection reference value. When the sampled circuit operating temperature reaches the over-temperature protection reference value, the over-temperature protection will be started or triggered, thereby generating an over-temperature protection signal or instruction. According to the over-temperature protection signal or instruction, current limiting or disconnection methods can be used for current limiting protection, and there are also other protection methods, and there are also multiple implementation circuits for the current limiting method.

[0003] In the prior art, the prior art cannot adjust the intensity of over-temperature protection. In the case of only one over-temperature protection point, it is impossible to distinguish the operating modes or protection methods at different temperatures, and thus it is impossible to adjust the over-temperature protection with different intensities according to different temperatures. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an over-temperature protection circuit and a power supply circuit that perform over-temperature protection with different intensities according to different temperature protections, so as to solve the technical problem that the over-temperature intensity in the prior art cannot be adjusted.

[0005] The technical solution of the present invention is to provide an over-temperature protection circuit with the following structure, including:

[0006] A charge and discharge circuit for generating a ramp signal;

[0007] A comparison circuit that receives the ramp signal and a reference signal, compares the two, and outputs a first control signal;

[0008] Wherein, when the temperature reaches the first over-temperature protection point, the slope of the ramp signal is reduced by a first amplitude, and when the temperature reaches the second over-temperature protection point, the slope of the ramp signal is reduced by a second amplitude; the second over-temperature protection point is higher than the first over-temperature protection point, and the second amplitude is greater than the first amplitude; the first control signal is adjusted by reducing the slope of the ramp signal.

[0009] Optionally, the charge and discharge circuit includes a constant current source, a first capacitor, and a first switch. The constant current source is connected to the first capacitor and charges the first capacitor. The first switch is connected in parallel with the first capacitor, and the charging and discharging of the charge and discharge circuit are controlled by the on / off of the first switch.

[0010] Optionally, the charge and discharge circuit further includes a first discharge current and a second discharge current. When the temperature reaches the first over-temperature protection point, the first discharge current is effective and the second discharge current is ineffective; when the temperature reaches the second over-temperature protection point, both the first discharge current and the second discharge current are effective.

[0011] 11. Optionally, the first current is generated by a first current generation circuit. The first current generation circuit receives a voltage value representing the actual temperature and a voltage value representing the first over-temperature protection point. After being processed by an operational amplifier, a first voltage is obtained. The first voltage is applied to a first resistor to obtain a first current, and the first current is mirrored to obtain the first discharge current; the second current is generated by a second current generation circuit. The second current generation circuit receives a voltage value representing the actual temperature and a voltage value representing the second over-temperature protection point. After being processed by an operational amplifier, a second voltage is obtained. The second voltage is applied to a second resistor to obtain a second current, and the second current is mirrored to obtain the second discharge current; the voltage value representing the second over-temperature protection point is greater than the voltage value representing the first over-temperature protection point.

[0012] Optionally, when the voltage value representing the actual temperature is less than the voltage value representing the first over-temperature protection point, both the first voltage and the second voltage are zero, and both the first current and the second current are zero, and no discharge current is generated; when the voltage value representing the actual temperature is greater than the voltage value representing the first over-temperature protection point and less than the voltage value representing the second over-temperature protection point, the second voltage is zero, and only the first current is generated to obtain the first discharge current; when the voltage value representing the actual temperature is greater than the voltage value representing the second over-temperature protection point, both the first voltage and the second voltage are not zero, the first current is generated to obtain the first discharge current, and the second current is generated to obtain the second discharge current.

[0013] Optionally, the first resistor and the second resistor are external resistors, and the magnitudes of the first discharge current and / or the second discharge current are adjusted by adjusting the resistance values of the first resistor and / or the second resistor.

[0014] Optionally, the first switch is turned off when the current in the power supply circuit is zero to charge the first capacitor; and is turned on when the ramp signal reaches the reference signal to discharge the first capacitor.

[0015] Optionally, the first control signal represents the time between the zero-crossing of the current in the power supply circuit and the conduction moment of its main switch tube in the next cycle. When over-temperature protection occurs, the time between the zero-crossing of the current in the power supply circuit and the conduction moment of its main switch tube in the next cycle is extended.

[0016] The present invention further provides a power supply circuit applying an over-temperature protection circuit. The power supply circuit includes a power stage circuit and a control circuit. The control circuit is connected to the power stage circuit, and the over-temperature protection circuit is connected to the control circuit. Alternatively, the over-temperature protection circuit is disposed within the control circuit and connected to other circuits as a part of the control circuit. When over-temperature protection occurs, the over-temperature protection circuit outputs a first control signal, and the control circuit controls the output current of the power stage circuit to decrease according to the first control signal.

[0017] Optionally, the control of reducing the output current of the power stage circuit is achieved by extending the time between the zero-crossing time of the current of the power supply circuit and the conduction time of the next cycle of its main switching transistor.

[0018] Adopting the present invention, compared with the prior art, has the following advantages: By adopting the present invention, multiple over-temperature protection points are set, and the first control signal is adjusted at different over-temperature protection points. Different intensities of over-temperature protection adjustment are controlled through the adjustment and change of the first control signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the structural schematic diagram of the over-temperature protection circuit of the present invention;

[0020] Figure 2 is the working waveform diagram of the present invention;

[0021] Figure 3 is the schematic diagram of the power supply circuit applying the over-temperature protection circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following describes the preferred embodiments of the present invention in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0023] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention. However, those skilled in the art can also fully understand the present invention without the description of these details.

[0024] In the following paragraphs, the present invention is described more specifically by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all in a relatively simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0025] Refer to Figure 1 shown, which schematically shows the structural principle of the over-temperature protection circuit of the present invention. The over-temperature protection circuit includes:

[0026] A charge and discharge circuit for generating a ramp signal V R ;

[0027] A comparison circuit that receives the ramp signal V R and the reference signal V REF , and after comparing the two, outputs a first control signal Vctrl1;

[0028] Among them, when the temperature T reaches the first over-temperature protection point T1, the slope of the ramp signal V R is reduced by a first amplitude. When the temperature T reaches the second over-temperature protection point T2, the slope of the ramp signal V R is reduced by a second amplitude; the second over-temperature protection point T2 is higher than the first over-temperature protection point T1, and the second amplitude is greater than the first amplitude; the first control signal Vctrl1 is adjusted by reducing the slope of the ramp signal. The comparison between the temperature T and the first over-temperature protection point T1 and the second over-temperature protection point T2 is all realized by an operational amplifier. The voltage VBE represents the temperature T, the voltage VT1 represents the first over-temperature protection point T1, and the voltage VT2 represents the second over-temperature protection point T2. The voltage VBE and the voltage VT1 are processed by an operational amplifier to obtain the voltage V1, and the voltage VBE and the voltage VT2 are processed by an operational amplifier to obtain the voltage V2. According to the principle of this circuit, the following relationships can be obtained:

[0029] 1. When T < T1 < T2, VBE > VT1 > VT2, at this time both V1 and V2 are 0, and over-temperature protection does not occur, then a very short fixed delay can be set, but not limited to this;

[0030] 2. When T1 < T < T2, VT1 > VBE > VT2, at this time V1 > 0, V2 = 0, and I1 shunts part of the current of I REF , resulting in an increase in the delay time; and the greater the voltage difference, the greater V1, and the longer the delay time;

[0031] 3. When T1 < T2 < T, VT1 > VT2 > VBE, at this time V1 > 0, V2 > 0, and both I1 and I2 will shunt part of the current of I REF , for the same temperature change, more current is shunted, and the change amount of the delay time is also greater.

[0032] The charge and discharge circuit includes a constant current source I REF , a first capacitor C1, and a first switch S1. The constant current source I REF is connected to the first capacitor C1 and charges the first capacitor C1. The first switch S1 is connected in parallel with the first capacitor C1, and the charging and discharging of the charge and discharge circuit are controlled by the on-off of the first switch S1.

[0033] The charge and discharge circuit further includes a first discharge current I1 and a second discharge current I2. When the temperature reaches the first over-temperature protection point, the first discharge current I1 is effective and the second discharge current I2 is ineffective; when the temperature reaches the second over-temperature protection point, both the first discharge current I1 and the second discharge current I2 are effective.

[0034] S1 is turned off when the zero-current signal arrives and is turned on when the drive signal arrives; comparator COMP1 flips when the voltage of the first capacitor C1 is greater than the reference voltage V REF and the flipped signal serves as the turn-on signal for the main power transistor of the power supply circuit.

[0035] In this embodiment, the slopes of the first segment (related to R1) and the second segment (related to R1 and R2) can be adjusted by externally setting resistors R1 and R2, and the setting is very flexible.

[0036] The first current is generated by a first current generation circuit. The first current generation circuit receives the voltage value VBE representing the actual temperature and the voltage value VT1 representing the first over-temperature protection point. After being processed by an operational amplifier, a first voltage V1 is obtained. The first voltage V1 is applied to the first resistor R1 to obtain a first current, and the first current is mirrored to obtain the first discharge current I1; the second current is generated by a second current generation circuit. The second current generation circuit receives the voltage value VBE representing the actual temperature and the voltage value VT2 representing the second over-temperature protection point. After being processed by an operational amplifier, a second voltage V2 is obtained. The second voltage is applied to the second resistor R2 to obtain a second current, and the second current is mirrored to obtain the second discharge current I2; the voltage value VT2 representing the second over-temperature protection point is greater than the voltage value VT1 representing the first over-temperature protection point.

[0037] When the voltage value VBE representing the actual temperature is less than the voltage value VT1 representing the first over-temperature protection point, both the first voltage V1 and the second voltage V2 are zero, and both the first current and the second current are zero, and no discharge current is generated; when the voltage value VBE representing the actual temperature is greater than the voltage value VT1 representing the first over-temperature protection point and less than the voltage value VT2 representing the second over-temperature protection point, the second voltage is zero, and only the first current is generated to obtain the first discharge current I1; when the voltage value VBE representing the actual temperature is greater than the voltage value VT2 representing the second over-temperature protection point, both the first voltage and the second voltage are not zero, the first current is generated to obtain the first discharge current I1, and the second current is generated to obtain the second discharge current I2.

[0038] The first resistor R1 and the second resistor R2 are external resistors, and by adjusting the resistance values of the first resistor or / and the second resistor, the magnitudes of the first discharge current or / and the second discharge current can be adjusted.

[0039] The first switch S1 is turned off when the current in the power supply circuit passes through zero, and charges the first capacitor C1; when the ramp signal V R reaches the reference signal V REF , it is turned on to discharge the first capacitor C1.

[0040] Reference Figure 2 As shown, partial waveforms of the present invention are illustrated. The first control signal Vctrl1 represents the time between the moment when the current in the power supply circuit passes through zero and the conduction moment of the next cycle of its main switch tube, that is, T DELAY . When over-temperature protection occurs, the time T DELAY between the moment when the current in the power supply circuit passes through zero and the conduction moment of the next cycle of its main switch tube is extended, where T ON is the conduction time of the main switch tube, and TOFF is the turn-off time of the main switch tube.

[0041] Reference Figure 3 As shown, the circuit structure of the power supply circuit is illustrated. The power supply circuit includes a power stage circuit and a control circuit. The control circuit is connected to the power stage circuit, and the over-temperature protection circuit is connected to the control circuit. Alternatively, the over-temperature protection circuit is disposed within the control circuit and connected to other circuits as part of the control circuit. When over-temperature protection occurs, the over-temperature protection circuit outputs an over-temperature protection adjustment signal, and the control circuit controls to reduce the output current of the power stage circuit according to the over-temperature protection adjustment signal. The reduction of the output current of the power stage circuit is achieved by reducing the output current reference of the power stage circuit, reducing the switching frequency of the power stage circuit, or extending the turn-off time of the main power switch tube in the power stage circuit. The power stage circuit can adopt various topological forms.

[0042] Although the embodiments are described and illustrated separately above, for some common technologies, in the view of those of ordinary skill in the art, substitutions and integrations can be made between the embodiments. For the content not clearly recorded in one of the embodiments, reference can be made to the other embodiment with records.

[0043] The above-described embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the above embodiments shall be included within the protection scope of the technical solution.

Claims

1. An over-temperature protection circuit, comprising: a charge and discharge circuit for generating a ramp signal; a comparison circuit that receives the ramp signal and a reference signal, compares the two, and outputs a first control signal; wherein, when the temperature reaches a first over-temperature protection point, the slope of the ramp signal is reduced by a first amplitude, and when the temperature reaches a second over-temperature protection point, the slope of the ramp signal is reduced by a second amplitude; the second over-temperature protection point is higher than the first over-temperature protection point, and the second amplitude is greater than the first amplitude; the first control signal is adjusted by reducing the slope of the ramp signal; wherein, the charge and discharge circuit includes a constant current source, a first capacitor, and a first switch. The constant current source is connected to the first capacitor and charges the first capacitor. The first switch is connected in parallel with the first capacitor, and the charging and discharging of the charge and discharge circuit are controlled by the on / off of the first switch. When the temperature reaches the first over-temperature protection point, a first discharge current for discharging the first capacitor is effective, and a second discharge current is ineffective; when the temperature reaches the second over-temperature protection point, both the first discharge current and the second discharge current for discharging the first capacitor are effective.

2. The over-temperature protection circuit according to claim 1, characterized in that a first current is generated by a first current generation circuit. The first current generation circuit receives a voltage value representing the actual temperature and a voltage value representing the first over-temperature protection point. After being processed by an operational amplifier, a first voltage is obtained. The first voltage is applied to a first resistor to obtain a first current, and the first current obtains the first discharge current through current mirroring; a second current is generated by a second current generation circuit. The second current generation circuit receives a voltage value representing the actual temperature and a voltage value representing the second over-temperature protection point. After being processed by an operational amplifier, a second voltage is obtained. The second voltage is applied to a second resistor to obtain a second current, and the second current obtains the second discharge current through current mirroring; the voltage value representing the second over-temperature protection point is greater than the voltage value representing the first over-temperature protection point.

3. The over-temperature protection circuit according to claim 2, characterized in that when the voltage value representing the actual temperature is less than the voltage value representing the first over-temperature protection point, both the first voltage and the second voltage are zero, and both the first discharge current and the second discharge current are also zero, and no discharge current is generated; when the voltage value representing the actual temperature is greater than the voltage value representing the first over-temperature protection point and less than the voltage value representing the second over-temperature protection point, the second voltage is zero, and only the first current is generated to obtain the first discharge current; when the voltage value representing the actual temperature is greater than the voltage value representing the second over-temperature protection point, both the first voltage and the second voltage are not zero, the first current is generated to obtain the first discharge current, and the second current is generated to obtain the second discharge current.

4. The over-temperature protection circuit according to claim 2, characterized in that: the first resistor and the second resistor are external resistors, and by adjusting the resistance values of the first resistor or / and the second resistor, the magnitude of the first discharge current or / and the second discharge current is adjusted.

5. The over-temperature protection circuit according to claim 1, characterized in that: The first switch is turned off when the current in the power supply circuit crosses zero, charging the first capacitor; and is turned on when the ramp signal reaches the reference signal, discharging the first capacitor.

6. The over-temperature protection circuit according to claim 1 or 2, characterized in that: The first control signal represents the time between the zero-crossing of the current in the power supply circuit and the conduction time of its main switch tube in the next cycle. When over-temperature protection occurs, the time between the zero-crossing of the current in the power supply circuit and the conduction time of its main switch tube in the next cycle is extended.

7. A power supply circuit applying an over-temperature protection circuit, the power supply circuit includes a power stage circuit and a control circuit, the control circuit is connected to the power stage circuit, the over-temperature protection circuit is connected to the control circuit, or the over-temperature protection circuit is disposed within the control circuit and is connected to other circuits as a part of the control circuit; when over-temperature protection occurs, the over-temperature protection circuit outputs a first control signal, and the control circuit controls to reduce the output current of the power stage circuit according to the first control signal, and the over-temperature protection circuit is the over-temperature protection circuit according to any one of claims 1-6.

8. The power supply circuit applying an over-temperature protection circuit according to claim 7, characterized in that: The control to reduce the output current of the power stage circuit is achieved by extending the time between the zero-crossing of the current in the power supply circuit and the conduction time of its main switch tube in the next cycle.

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