Method for monitoring a power supply and circuit therefor

Abstract

The present invention provides a monitoring method and circuit for a power supply. It first obtains an auxiliary side voltage of a switching power supply and obtains a voltage divider of the auxiliary side voltage using a voltage divider circuit. Then, a first detection circuit and a second detection circuit detect the voltage divider and a detection current flowing into the detection circuit within a switching cycle, and generate a corresponding first detection signal and a second detection signal, which correspond to an ambient temperature and an output voltage of the switching power supply, respectively, thereby monitoring the power supply.

Description

Technical Field

[0001] This invention relates to a monitoring method and circuit thereof, and more particularly to a monitoring method and circuit thereof for a power supply. Background Technology

[0002] In existing switching power supply devices, a detection circuit is generally set up to detect the output voltage of the power supply device and provide different applications based on the detection results, such as over-temperature protection (OTP) and over-voltage protection (OVP).

[0003] However, to save on circuit costs, the aforementioned detection circuits typically integrate different detection methods to share circuit resources. For example, over-temperature protection and over-voltage protection can share a single voltage divider node and be implemented through time-sharing detection. This involves detecting the voltage divider node in one switching cycle to determine if the system temperature is too high, and then detecting the same voltage divider node in another switching cycle to determine if the output voltage is too high. However, time-sharing detection prevents the power supply device from accurately determining in real-time whether necessary over-temperature or over-voltage protection mechanisms need to be executed in each frequency cycle. Specifically, if an over-voltage situation occurs within a switching cycle, but the detection circuit is performing over-temperature detection in that cycle, it must delay for at least one switching cycle before attempting over-voltage protection, inevitably increasing the risk of damage to the power supply system.

[0004] Therefore, there is a need to improve the existing power supply monitoring technology that integrates over-temperature protection and over-voltage protection. Summary of the Invention

[0005] One objective of this invention is to provide a monitoring method and circuit for a power supply, wherein an auxiliary side voltage of a switching power supply is obtained through an auxiliary winding and a voltage divider is obtained through a voltage divider circuit, the voltage divider is detected by a first detection circuit and a detection current is detected by a second detection circuit, thereby enabling the execution of several detection modes within the same switching cycle to monitor the power supply.

[0006] One objective of this invention is to provide a power supply monitoring method and circuit, which further detects a reverse current flowing out through a third detection circuit.

[0007] To achieve the aforementioned objectives, the present invention provides a power supply monitoring method. First, an auxiliary winding senses the winding voltage of a switching power supply to obtain an auxiliary-side voltage. Then, a voltage divider circuit divides the auxiliary-side voltage to obtain a voltage divider. A first detection circuit detects the voltage divider during a switching cycle of the switching power supply and generates a first detection signal. A second detection circuit detects a detection current flowing into the second detection circuit during the switching cycle and generates a second detection signal. The first and second detection circuits operate during the switching cycle, and when the secondary side of the switching power supply discharges, respectively, so that the first and second detection signals correspond to an ambient temperature and an output voltage of the switching power supply, thereby monitoring the power supply.

[0008] The present invention provides an embodiment in which a third detection circuit detects a reverse current during the switching cycle and generates a third detection signal, wherein the third detection circuit operates during the switching cycle when the primary side of the switching power supply is charging, and the third detection signal corresponds to an input voltage of the switching power supply.

[0009] The present invention further provides a monitoring circuit for a power supply, which is applied to a switching power supply and obtains an auxiliary side voltage by sensing the winding voltage of an auxiliary winding included in the switching power supply. The monitoring circuit includes a voltage divider circuit, a first detection circuit, and a second detection circuit. The voltage divider circuit includes a first impedance and a second impedance. The second impedance includes a thermistor. The voltage divider circuit provides a voltage division for the auxiliary side voltage. The first detection circuit is coupled between the first impedance and the second impedance and detects the voltage division. The second detection circuit includes a switch coupled between the first impedance and the second impedance. Between the two impedances, the switch is closed or turned on during a switching cycle of the switching power supply when the secondary side of the switching power supply discharges. When the switch is closed, the first detection circuit detects the voltage divider and generates a first detection signal. When the switch is turned on, the second detection circuit is coupled to the voltage divider circuit to form a detection current flowing to the second detection circuit. The second detection circuit detects the detection current and generates a second detection signal. The first detection signal and the second detection signal correspond to an ambient temperature and an output voltage of the switching power supply, respectively, thereby being used to monitor the power supply. Attached Figure Description

[0010] Figure 1 This is a flowchart illustrating a power supply monitoring method according to an embodiment of the present invention.

[0011] Figure 2 This is a circuit diagram of the power supply unit according to the first embodiment of the present invention;

[0012] Figure 3A This is a schematic diagram of a monitoring circuit for detecting ambient temperature in a power supply according to the first embodiment of the present invention.

[0013] Figure 3B This is a circuit diagram of the monitoring circuit of the power supply in the first embodiment of the present invention for detecting the output voltage;

[0014] Figure 4 This is a signal schematic diagram of the first embodiment of the present invention;

[0015] Figure 5A This is a schematic diagram of an example circuit for detecting ambient temperature in the monitoring circuit of a power supply according to the first embodiment of the present invention.

[0016] Figure 5B This is a schematic diagram of an example circuit for detecting the output voltage in the monitoring circuit of the power supply of the first embodiment of the present invention.

[0017] Figure 6A This is a schematic diagram of another example circuit for detecting ambient temperature in the monitoring circuit of the power supply of the first embodiment of the present invention.

[0018] Figure 6B This is a schematic diagram of another example circuit for detecting the output voltage in the monitoring circuit of the power supply of the first embodiment of the present invention.

[0019] Figure 7 This is a flowchart illustrating a power supply monitoring method according to another embodiment of the present invention.

[0020] Figure 8A This is a circuit diagram of the monitoring circuit of the power supply in the second embodiment of the present invention for detecting ambient temperature;

[0021] Figure 8B This is a schematic diagram of the monitoring circuit for detecting the output voltage of the power supply in the second embodiment of the present invention.

[0022] Figure 8C This is a schematic diagram of the monitoring circuit for detecting input voltage in the power supply of the second embodiment of the present invention.

[0023] Figure 9 This is a signal schematic diagram of the second embodiment of the present invention;

[0024] Figure 10A This is a schematic diagram of an example circuit for detecting ambient temperature in the monitoring circuit of a power supply according to the second embodiment of the present invention.

[0025] Figure 10BThis is a schematic diagram of an example circuit for detecting the output voltage in the monitoring circuit of a power supply according to a second embodiment of the present invention; and

[0026] Figure 10C This is a schematic diagram of an example circuit for detecting input voltage in the monitoring circuit of a power supply according to the second embodiment of the present invention.

[0027] Figure 11A This is a schematic diagram of the voltage divider circuit of the monitoring circuit of the power supply in the second embodiment of the present invention. Figure 1 ;

[0028] Figure 11B This is a schematic diagram of the voltage divider circuit of the monitoring circuit of the power supply in the second embodiment of the present invention. Figure 2 .

[0029] [Figure Number Reference Guide]

[0030] 10 Switching power supplies

[0031] 12 Switching elements

[0032] 14 Buffer Units

[0033] 16 Control Unit

[0034] 162 First Detection Circuit

[0035] 1622 comparator

[0036] 1624 First Signal Processing Unit

[0037] 164 Second Detection Circuit

[0038] 1642 Output Comparator Circuit

[0039] 1644 Second Signal Processing Unit

[0040] 1646 switch

[0041] 166 Third Detection Circuit

[0042] 1662 Input Comparator Circuit

[0043] 1664 Third Signal Processing Unit

[0044] 1666 Switching Unit

[0045] 18 Feedback Control Unit

[0046] T Transformer

[0047] COMP comparator

[0048] DIV voltage divider circuit

[0049] N P Primary winding

[0050] N S Secondary winding

[0051] N A Auxiliary winding

[0052] D OUT rectifier diode

[0053] C OUT Output capacitor

[0054] D VCC bias diode

[0055] C VCC bias capacitor

[0056] I DET Detecting current

[0057] I ZUP Reverse current

[0058] IREF Reference Current Source

[0059] IREF1 First Reference Current Source

[0060] IREF2 Second Reference Current Source

[0061] M1 First Transistor

[0062] M2 Second Transistor

[0063] M3 Third Transistor

[0064] M4 fourth transistor

[0065] I M1 First current

[0066] I M2 Second current

[0067] I M3 Third current

[0068] I M4 Fourth current

[0069] OUT1 First comparison result

[0070] OUT2 Second comparison result

[0071] OUT3 Third comparison result

[0072] OP operational amplifier

[0073] OP1 First Operational Amplifier

[0074] OP2 Second Operational Amplifier

[0075] V IN Input voltage

[0076] V A_DIV partial pressure

[0077] V IN_REF Input reference signal

[0078] V OUT Output voltage

[0079] V OUT_REF Output reference signal

[0080] V TEMP_REF Temperature reference signal

[0081] VT1 First Detection Signal

[0082] VT2 Second Detection Signal

[0083] VCC bias

[0084] Z UP First impedance

[0085] Z NTC Second impedance

[0086] R1 is the first resistor.

[0087] R2 is the second resistor.

[0088] D1 diode

[0089] R NTC Thermistor

[0090] R ADJ Adjusting the resistance

[0091] SW switch control signal

[0092] T OVP Output voltage detection signal

[0093] Facebook feedback signal

[0094] T1, T2 Second switching cycle

[0095] T OFF Cutoff interval

[0096] T ON Conducting interval

[0097] T DIS Secondary side discharge time

[0098] T OD During output voltage detection

[0099] T IND During input voltage detection Detailed Implementation

[0100] To provide a better understanding of the structural features and effects achieved by the present invention, preferred embodiments and detailed descriptions are provided below:

[0101] To address the problems arising from the time-division multiplexing detection method required for over-temperature and over-voltage protection in existing technologies, this invention proposes a monitoring circuit and method for a power supply. Within the same switching cycle, a first detection circuit detects a voltage divider of an auxiliary side voltage, and a second detection circuit detects a detection current flowing into the second detection circuit, thereby performing several detection methods, such as over-temperature detection and over-voltage detection, within the same switching cycle.

[0102] The invention will be described in detail below by way of the drawings illustrating various embodiments thereof. However, the concept of the invention may be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein.

[0103] Please see Figure 1 This is a schematic flowchart illustrating the voltage monitoring method of the power supply in various embodiments of the present invention. To facilitate the explanation of the voltage monitoring methods in each embodiment, the relevant circuits used in the voltage monitoring methods of each embodiment will be described below.

[0104] Please see Figure 2 This is a circuit diagram of a power supply according to a first embodiment of the present invention. As shown in the figure, a switching power supply 10 of this embodiment includes an input voltage V. IN The system comprises a switching element 12, a buffer unit 14, a transformer T, a pulse width modulation (PWM) control unit 16, and a feedback control unit 18, wherein the transformer T includes a primary winding N. P Primary and secondary windings N S With an auxiliary winding N A The primary winding N P The input voltage V is coupled through the switching element 12. IN The primary winding N can also be coupled to the buffer unit 14 to absorb the input voltage V. IN Abnormal noise. The secondary winding N... S Through a rectifier diode D OUT With an output capacitor C OUTThe feedback control unit 18 is coupled to the feedback control unit 18 and outputs an output voltage V. OUT The auxiliary winding N A The winding coil senses the secondary winding N S The output voltage V OUT Therefore, an auxiliary side voltage V is obtained. A And through a bias diode D VCC With a bias capacitor C VCC A bias voltage VCC is provided to the PWM control unit 16. The PWM control unit 16 receives a feedback signal FB generated by the feedback control unit 18 and generates a switching control signal SW to the switching element 12, thereby controlling the switching element according to the input voltage VCC. IN The switching element 12 is controlled to turn on or off, thereby generating the output voltage V through the transformer T. OUT .

[0105] like Figures 2 to 3A As shown, in this embodiment, the PWM control unit 16 provides the monitoring function of the switching power supply 10, thus serving as a monitoring circuit. However, the monitoring circuit can also form an independent circuit block and does not necessarily need to be integrated into the PWM control unit 16. These differences do not affect the implementation of the present invention; therefore, in this embodiment, the integration of the monitoring circuit into the PWM control unit 16 is used as an example. The PWM control unit 16 includes a first detection circuit 162 and a second detection circuit 164, which are coupled to the voltage divider circuit DIV. The voltage divider circuit DIV includes a first impedance Z. UP With a second impedance Z NTC The first impedance Z UP With the second impedance Z NTC The difference is based on the auxiliary side voltage V. A This forms a partial voltage V. A_DIV In this embodiment, the auxiliary winding N A The winding coil senses the output voltage V OUT Therefore, the voltage divider circuit DIV is connected to the auxiliary winding N. A The obtained auxiliary side voltage V A At the first impedance Z UP With the second impedance Z NTC The voltage V is provided between them. A_DIV This allows the output voltage V to be fed back. OUT The state of the output voltage V. OUT During the rise, the auxiliary winding N A The sensed auxiliary side voltage V A and the partial pressure V A_DIV Both will increase accordingly. On the other hand, the second impedance ZNTC It includes a thermistor, which can have a negative temperature coefficient, therefore the second impedance Z NTC The overall impedance value will change with the ambient temperature, thus the voltage divider V A_DIV This corresponds to the ambient temperature. However, unlike existing technologies, this invention does not simply rely on time-division detection of this partial pressure V. A_DIV It is used for over-temperature detection and over-pressure detection.

[0106] Please refer to the following: Figure 3B and Figure 4 The PWM control unit 16 acquires the auxiliary side voltage V within one switching cycle of the switching element 12 (e.g., switching cycle T1 or switching cycle T2, taking the first switching cycle T1 as an example). A The voltage V is obtained by the voltage divider circuit DIV. A_DIV Subsequently, the first detection circuit 162 during a temperature detection period T TD Detecting the voltage divider V A_DIV And generate a first detection signal VT1; the second detection circuit 164 during an output voltage detection period T1 within the same switching cycle T1. OD Coupled to the first impedance Z UP With the second impedance Z NTC Between these points, a detection current I is formed that flows into the second detection circuit 164. DET The second detection circuit 164 is based on the detection current I DET A second detection signal VT2 is generated, causing the first detection circuit 162 and the second detection circuit 164 to operate during the switching cycle T1, respectively. This is because the auxiliary winding N needs to be activated at this time. A The winding coil senses the output voltage V OUT Therefore, during this temperature detection period T TD and the output voltage detection period T OD All are operated in a cutoff interval T when the switching element 12 is disconnected. OFF This is because during the conduction interval T of the switching element 12, ON In this state, the transformer T is in a state of charging the windings and will not have an output voltage V. OUT Therefore, the auxiliary winding N A Unable to sense the output voltage V OUT Moreover, during the temperature detection period T TD and the output voltage detection period T OD Preferably, the primary and secondary discharge times T of the switching power supply 10 are... DIS Internal action. Specifically, and as understood by those of ordinary skill in the art, within the cutoff interval T... OFF In the middle, the auxiliary side voltage VA Oscillations will occur after the winding completes its discharge (e.g.) Figure 4 As shown), therefore, the first detection circuit 162 and the second detection circuit 164 are preferably used when the winding is in the discharge process and the auxiliary side voltage V A The voltage value is in a steady state during the secondary side discharge time T. DIS Internal operation. In short, this embodiment of the invention causes the first detection circuit 162 and the second detection circuit 164 to operate within the same switching cycle T1, and during the discharge of the secondary side of the switching power supply 10. Therefore, the first detection signal VT1 and the second detection signal VT2 correspond to an ambient temperature and an output voltage V of the switching power supply 10. OUT Furthermore, it allows the ambient temperature to correspond to the first impedance Z. UP The impedance value and the second impedance Z NTC The proportion of the impedance value.

[0107] In this embodiment, the secondary side discharge time T DIS A temperature detection period T encompassing the first detection circuit 162 TD And a detection period T covering the output voltage of the second detection circuit 164 OD That is to say, each secondary side discharge time T DIS Including the temperature detection period T TD During the detection period T of the output voltage OD That is, the time T of each secondary side discharge. DIS Within this circuit, both the first detection circuit 162 and the second detection circuit 164 are activated. During the temperature detection period T... TD During the detection period T of the output voltage OD It can be continuous; or during the temperature detection period T TD During the detection period T of the output voltage OD There can also be a time interval between them. Furthermore, during this temperature detection period, T... TD It can be earlier than the output voltage detection period T OD (Not shown in the figure), or during the temperature detection period T TD It can be later than the output voltage detection period T OD .

[0108] See also Figure 3A and Figure 3B In this embodiment, the first detection circuit 162 is based on the voltage divider V. A_DIV With a temperature reference signal V TEMP_REF The ambient temperature is detected, thus generating the first detection signal VT1; the second detection circuit 164 in this embodiment generates the first detection signal VT1 based on the detection current I. DET With an output voltage reference signal VOUT_REF Detect the output voltage V OUT The input impedance of the second detection circuit 164 is preferably much smaller than the second impedance Z. NTC This causes almost all the current to flow through the first impedance Z when the second detection circuit 164 is coupled to the voltage divider circuit DIV. UP All currents flow into the second detection circuit 164 to form the detection current I. DET In this case, the detection current I DET The magnitude can reflect the auxiliary side voltage V A The magnitude of the voltage V can be used to determine the output voltage V. OUT The state. For example, it can be based on the secondary winding N. S With the auxiliary side winding N A The coil turns ratio is used to determine the output voltage V. OUT The voltage value status.

[0109] In particular, the first detection circuit 162 includes a comparator 1622 and a first signal processing unit 1624, with a positive input terminal of the comparator 1622 coupled to the temperature reference signal V. TEMP_REF And is coupled to the first impedance Z by a negative input terminal of the comparator 1622. UP With the second impedance Z NTC Between, therefore receive the voltage V. A_DIV This allows for comparison with the temperature reference signal V. TEMP_REF With this partial pressure V A_DIV This generates a first comparison result OUT1 and sends it to the first signal processing unit 1624, causing the first signal processing unit 1624 to generate the first detection signal VT1 based on the first comparison result OUT1. Wherein, if the second impedance Z... NTC If the thermistor has a negative temperature coefficient, then the second impedance Z NTC The overall impedance value decreases as the ambient temperature increases; therefore, assuming other conditions remain unchanged, the voltage drop V will remain constant. A_DIV It will also decrease as the ambient temperature rises. Therefore, by appropriately setting this temperature reference signal V... TEMP_REF The first detection circuit 162 can determine whether the ambient temperature exceeds a predetermined temperature value.

[0110] The second detection circuit 164 includes a switch 1646, an output comparison circuit 1642, and a second signal processing unit 1644. The switch 1646 can be controlled by an output voltage detection signal T. OVP The output comparator circuit 1642 is controlled to turn on or off. One end of the output voltage reference signal V is coupled to this circuit. OUT_REFThe other end of the output comparator circuit 1642 is coupled to the first impedance Z when the switch 1646 is turned on. UP With the second impedance Z NTC Between these, the detection current I is thus formed. DET The current flows into the second detection circuit 164, whereby the output comparison circuit 1642 compares the detected current I. DET With the output voltage reference signal V OUT_REF This generates a second comparison result OUT2 and sends it to the second signal processing unit 1644, causing the second signal processing unit 1644 to generate the second detection signal VT2 based on the second comparison result OUT2. As mentioned above, the detection current I... DET The magnitude of the output voltage V can be used to determine the value of the output voltage. OUT The magnitude of the output voltage reference signal V is determined by appropriately setting the output voltage reference signal V. OUT_REF The second detection circuit 164 can then determine the output voltage V. OUT Does it exceed a predetermined voltage value?

[0111] Furthermore, the PWM control unit 16 can control the switching power supply 10 to perform an over-temperature protection (OTP) based on the first detection signal VT1, and can control the switching power supply 10 to perform an output overvoltage protection (OVP) based on the second detection signal VT2. The over-temperature protection (OTP) and the output overvoltage protection (OVP) are general protection mechanisms for the switching power supply, and therefore will not be described in detail.

[0112] like Figure 5A and Figure 5B The diagram shown illustrates an example circuit of the second detection circuit 164 in the first embodiment of the present invention, with the switch 1646 both off and on. The output comparator circuit 1642 of the second detection circuit 164 includes an input impedance Z. DET With a comparator COMP, the input impedance Z DET The impedance value is less than the second impedance Z. NTC The impedance value, therefore, when the switch 1646 is turned on, the original current flowing through the second impedance Z... NTC The current is converted into the input impedance Z of the second detection circuit 164. DET The second detection circuit 164 can then detect the current I. DET With the input impedance Z DET The product of the output voltage reference signal V and the output voltage reference signal V OUT_REF Compare to detect the output voltage V OUT .

[0113] Furthermore, such as Figure 6A and Figure 6BThe diagram shown illustrates another example of the second detection circuit 164 in the first embodiment of the present invention, with the switch 1646 both turned off and on. Figures 6A to 6B The output comparator circuit 1642 includes the input impedance Z. DET A mapped impedance Z M An operational amplifier OP, a first transistor M1, a second transistor M2, and a reference current source IREF, wherein a positive input terminal of the operational amplifier OP is coupled to the mapped impedance Z. M And coupled to one of the drain terminals of the first transistor M1, and the negative input terminal of the operational amplifier OP is coupled to the input impedance Z. DET And coupled to the switch 1646, one output terminal of the operational amplifier OP is coupled to the gate terminals of the first transistor M1 and the second transistor M2, so when the switch 1646 is turned on, the detection current I is formed. DET The input impedance Z flows into the input impedance. DET The mapped impedance Z M The detected current I is mapped. DET A first current I is formed M1 The first current I is transmitted through a current mirror composed of the first transistor M1 and the second transistor M2. M1 Converted into a second current I M2 This is then compared with the reference current source IREF to detect the output voltage V. OUT In this example circuit, the reference current source IREF is essentially the aforementioned output voltage reference signal V. OUT_REF One way of doing it.

[0114] The following is a simple numerical example. Figure 6A and Figure 6B The characteristics of the example circuit shown are assumed to be the first current I. M1 For the detected current I DET K times, and assume that the second current I M2 For the first current I M1 If the value is a multiple of M, then the temperature reference signal V TEMP_REF The setting of the reference current source IREF can be referenced to the following formula:

[0115]

[0116]

[0117] Figures 5A to 5B and Figures 6A to 6BThe differences are also evident in the fact that the detection circuit 16 in the first embodiment of the present invention actually has a variety of different detailed circuit implementations, all of which can achieve the purpose of the present invention to perform several detection methods to monitor the switching power supply 10 within the same switching cycle.

[0118] Please see Figure 7 This is a schematic flowchart illustrating a voltage monitoring method for a power supply according to another embodiment of the present invention. To facilitate the explanation of the voltage monitoring methods in each embodiment, the relevant circuits used in the voltage monitoring methods of each embodiment will be described below.

[0119] like Figures 8A to 8C The diagram shown is a circuit schematic of a power supply according to a second embodiment of the present invention. The difference from the previous embodiment is... Figures 8A to 8C Furthermore, a third detection circuit 166 is used to detect a reverse current I during the switching cycle T1. ZUP Used to detect the input voltage V of the switching power supply 10 IN The third detection circuit 166 includes an input comparison circuit 1662, a third signal processing unit 1664, and a switching unit 1666. One end of the input comparison circuit 1662 is coupled to the switching unit 1666, and the other end of the input comparison circuit 1662 is coupled to an input reference signal V. IN_REF The switching unit 1666 can be turned on or off by the switching control signal SW of the switching element 12. When the switching unit 1666 is turned on, the third detection circuit 166 is coupled to the voltage divider circuit DIV. The third detection circuit 166 detects an input voltage during the same switching cycle T1 of the first detection circuit 162 and the second detection circuit 164. IND Coupled to the first impedance Z UP With the second impedance Z NTC Between these, a reverse current I is formed by the third detection circuit 166 flowing to the voltage divider circuit DIV. ZUP During the input voltage detection period T IND It operates within a conduction range T when the switching element 12 is turned on. ON This is because in the conduction interval T ON In this process, the transformer T is in a state of charging the windings, and the auxiliary winding N will be charged. A The upper-induced negative auxiliary side voltage V is generated A Therefore, in this embodiment, the switch control signal SW can be used to control the switch unit 1666 of the third detection circuit 166.

[0120] Further as Figure 8CAs shown, the switching unit 1666 is turned on (high potential) by the switching control signal SW, therefore the input comparator circuit 1662 is coupled to the first impedance Z. UP With the second impedance Z NTC Between, because at this time the auxiliary side voltage V A Since it is a negative voltage, a reverse current I will be generated. ZUP Flow through the first impedance Z UP At this time, as Figure 9 As shown, the enable signal period of the switch control signal SW corresponds to an input voltage detection period T of the third detection circuit 166. IND At this time, the input comparator circuit 1662 compares the reverse current I. ZUP With an input voltage reference signal V IN_REF This generates a third comparison result OUT3, which is sent to the third signal processing unit 1664, causing the third signal processing unit 1664 to generate a third detection signal VT3 based on the third comparison result OUT3. Reverse current I ZUP The magnitude of the input voltage V can be used to determine the input voltage. IN The magnitude of the input voltage reference signal V is determined by appropriately setting the input voltage reference signal V. IN_REF The third detection circuit 166 can then determine the input voltage V. IN Does it exceed a predetermined voltage value?

[0121] Furthermore, such as Figures 10A to 10C As shown, in the second embodiment of the present invention, an exemplary circuit of the second detection circuit 164 and the third detection circuit 166 is shown in a circuit diagram of the switches 1646 and 1666 being turned off and on. The input comparator circuit 1662 of the third detection circuit 166 includes a current mirror composed of a third transistor M3 and a fourth transistor M4. The switching unit 166 includes a second operational amplifier OP2, wherein the second operational amplifier OP2 has a positive input terminal coupled to ground, that is, the second operational amplifier OP2 is only activated when the voltage divider V... A_DIV The third detection circuit 166 is coupled to the voltage divider circuit DIV only when the value is 0 or less than 0. A negative input terminal of the second operational amplifier OP2 is coupled to the first impedance Z. UP With the second impedance Z NTC Between them, and one output terminal of the second operational amplifier OP2 is coupled to the gate terminals of the third transistor M3 and the fourth transistor M4 of the input comparator circuit 1662, the second operational amplifier OP2 is equivalent to controlling whether the input comparator circuit 1662 and the voltage divider circuit DIV are turned on or off, which is equivalent to the effect of turning on the switching unit 1666 when the switching control signal SW of the switching element 12 is enabled (high potential) as described in the second embodiment. The auxiliary side voltage V AThat is, under negative voltage conditions, because the third transistor M3 and the fourth transistor M4 are turned on, current flows from the third transistor M3 to the first impedance Z. U The reverse current I of P ZUP Forming a third current I M3 Furthermore, through the current mirror conversion formed by the third transistor M3 and the fourth transistor M4, a fourth current I is output from the fourth transistor M4. M4 Therefore, the third signal processing unit 1664, based on the fourth current I, M4 And a second reference current source IREF2, which generates a current corresponding to the input voltage V. IN The third detection signal VT3. Because the third detection circuit 166 detects the primary winding N of the switching power supply 10 during this switching cycle... P During charging, the third detection signal VT3 corresponds to the input voltage V of the switching power supply 10. IN This allows for the detection of the input voltage V of the switching power supply 10. IN The remaining connections and signal operations are equivalent to... Figures 6A to 6B Therefore, the description will not be repeated in this embodiment.

[0122] In addition to controlling the switching power supply 10 to perform over-temperature protection based on the first detection signal VT1 and the switching power supply 10 to perform output over-voltage protection based on the second detection signal VT2, the PWM control unit 16 can also control the switching power supply 10 to perform under-voltage protection (Brown Out), a minimum startup voltage setting, or an input voltage switching based on the third detection signal VT3.

[0123] It should be noted that the power supply monitoring method and circuit of the second embodiment of the present invention perform at least three detection modes within the same switching cycle of the switching element 12, which will cause the temperature reference signal V to... TEMP_REF First reference current source IREF1 (outputs reference signal V) OUT_REF ), second reference current source IREF2 (input reference signal V) IN_REF Once these three parameters are set, subsequent individual adjustments may require changing the primary winding N of the transformer. P Secondary winding N S Or auxiliary winding N A The number of coil turns. For this, please refer to... Figure 11A As shown, the second embodiment of the present invention redesigns the first impedance Z of the voltage divider circuit DIV. UP , so that the first impedance Z UPIt includes a first resistor R1 and a second resistor R2, and the second resistor R2 is subjected to the aforementioned reverse current I. ZUP When the circuit is short-circuited (taking a diode D1 short-circuited as an example), that is, when the aforementioned detection current I is short-circuited... DET With reverse current I ZUP When the current flows, let the first impedance Z UP They have different equivalent impedance values. This avoids the need to change the number of turns in the transformer T's coil when individually adjusting the above three parameters. Similarly, please refer to... Figure 11B As shown, the second embodiment of the present invention redesigns the first impedance Z of the voltage divider circuit DIV by another method. UP , so that the first impedance Z UP It includes a first resistor R1 and a second resistor R2, and the second resistor R2 is in the aforementioned detection current I DET If a diode D1 is short-circuited during operation (for example, if a diode D1 is short-circuited), the same current detection I can be detected as described above. DET With reverse current I ZUP When the current flows, let the first impedance Z UP Different equivalent impedance values ​​are used to avoid the aforementioned problems, thereby significantly improving the practicality of the power supply's monitoring circuit. Furthermore, as shown in Figures 11A and 11B, this second impedance Z... NTC It may include a thermistor R NTC and an adjusting resistor R ADJ In order to facilitate the adjustment of the second impedance Z NTC The overall impedance value.

[0124] In summary, the present invention provides a monitoring method and circuit for a power supply, which obtains an auxiliary side voltage of a switching power supply through an auxiliary winding and obtains a voltage division of the auxiliary side voltage through a voltage divider circuit, and performs several detection methods to monitor the power supply within the same switching cycle. This effectively solves the problems arising from the use of time-division detection for the detection methods required for over-temperature protection and over-voltage protection in the prior art.

[0125] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent variations and modifications made in accordance with the shape, structure, features and spirit described in the claims of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method of monitoring a power supply, characterized by, It includes: An auxiliary winding senses the winding voltage of a switching power supply to obtain an auxiliary side voltage. A voltage divider circuit is used to obtain a voltage divider of the auxiliary side voltage. The voltage divider circuit includes a first impedance and a second impedance, and the second impedance includes a thermistor. During one switching cycle of the switching power supply, a first detection circuit detects the voltage divider and generates a first detection signal. as well as During the switching cycle, a second detection circuit is coupled between the first impedance and the second impedance to form a detection current flowing to the second detection circuit and generate a second detection signal. The first detection circuit and the second detection circuit are activated during the switching cycle when the secondary side of the switching power supply is discharged, so that the first detection signal and the second detection signal correspond to an ambient temperature and an output voltage of the switching power supply. The impedance value of an input impedance of the second detection circuit is less than the impedance value of the second impedance, so that the output voltage corresponds to the product of the detection current and the input impedance.

2. The monitoring method of a power supply as claimed in claim 1, wherein, in, The first detection circuit detects the ambient temperature based on the voltage divider and a temperature reference signal, and the second detection circuit detects the output voltage based on the detection current and an output voltage reference signal.

3. The monitoring method of a power supply as claimed in claim 2, wherein, in, The ambient temperature corresponds to the ratio of the impedance value of the first impedance to the impedance value of the second impedance.

4. The method of claim 1, wherein the step of determining the power supply status comprises the steps of: determining whether the power supply is in a standby mode; and determining whether the power supply is in a normal mode. It also includes: A control unit controls the power supply to perform an over-temperature protection based on the first detection signal, and the control unit controls the power supply to perform an output over-voltage protection based on the second detection signal.

5. The method of claim 1, wherein the step of determining the power supply status comprises the step of: determining the power supply status based on the voltage level of the power supply. It also includes: During the switching cycle, a third detection circuit detects a reverse current flowing to the voltage divider circuit and generates a third detection signal. The third detection circuit operates during the switching cycle when the primary side of the switching power supply is charging, and the third detection signal corresponds to an input voltage of the switching power supply.

6. The power supply monitoring method of claim 5, wherein, in, The third detection circuit detects the input voltage based on the reverse current and an input voltage reference signal.

7. The monitoring method of a power supply as claimed in claim 5, wherein, in, The third detection circuit only supplies the reverse current when the voltage divider is negative.

8. The method of claim 5, wherein the step of determining the power supply status comprises the step of: determining the power supply status based on the voltage level and the current level. It also includes: A control unit controls the power supply to perform an over-temperature protection based on the first detection signal, the control unit controls the power supply to perform an output over-voltage protection based on the second detection signal, and the control unit controls the power supply to perform an under-voltage protection or a minimum start-up voltage setting based on the third detection signal.

9. A monitoring circuit for a power supply, characterized by For a switching power supply, the switching power supply includes an auxiliary winding to sense its winding voltage to obtain an auxiliary side voltage, and the monitoring circuit of the power supply includes: A voltage divider circuit is coupled to the auxiliary winding. The voltage divider circuit includes a first impedance and a second impedance, and the second impedance includes a thermistor. A first detection circuit is coupled between the first impedance and the second impedance; and A second detection circuit includes a switch coupled between the first impedance and the second impedance; During a switching cycle of the switching power supply, when the secondary side of the switching power supply is discharging, the second detection circuit is either turned off or turned on. When the switch is off, the first detection circuit detects a voltage divider of the auxiliary side voltage and generates a first detection signal. When the switch is on, the second detection circuit is coupled to the voltage divider circuit to form a detection current flowing to the second detection circuit. The second detection circuit detects the detection current and generates a second detection signal. The first detection signal and the second detection signal correspond to an ambient temperature and an output voltage of the switching power supply. The impedance value of an input impedance of the second detection circuit is less than the impedance value of the second impedance, so that the output voltage corresponds to the product of the detection current and the input impedance.

10. The monitoring circuit of a power supply of claim 9, wherein, in, The first detection circuit includes a voltage comparison circuit to detect the ambient temperature based on the voltage divider and a temperature reference signal.

11. The monitoring circuit of a power supply of claim 9, wherein, in, The second detection circuit includes a current comparison circuit to detect the output voltage based on the detected current and an output voltage reference signal.

12. The monitoring circuit of a power supply of claim 11, wherein, in, The impedance value of one input impedance of the second detection circuit is less than the impedance value of the second impedance, so that the output voltage corresponds to the product of the detection current and the input impedance.

13. The monitoring circuit of a power supply of claim 10, wherein, in, The ambient temperature corresponds to the ratio of the impedance value of the first impedance to the impedance value of the second impedance.

14. The monitoring circuit of a power supply of claim 9, wherein, It also includes: A control unit is coupled to the first detection circuit and the second detection circuit respectively. The control unit controls the power supply to perform an over-temperature protection based on the first detection signal and controls the power supply to perform an output over-voltage protection based on the second detection signal.

15. The monitoring circuit of a power supply of claim 9, wherein, It also includes: A third detection circuit is coupled between the first impedance and the second impedance; During the switching cycle, when the primary side of the switching power supply is being charged, the third detection circuit supplies a reverse current to the voltage divider circuit to detect the reverse current and generate a third detection signal, which corresponds to an input voltage of the switching power supply.

16. The monitoring circuit of a power supply of claim 15, wherein, in, The third detection circuit includes a current comparison circuit to detect the output voltage based on the reverse current and an input voltage reference signal.

17. The monitoring circuit for a power supply of claim 15, wherein, in, The third detection circuit only supplies the reverse current when the voltage divider is negative.

18. The monitoring circuit for a power supply of claim 15, wherein, It also includes: A control unit is coupled to the first detection circuit and the second detection circuit respectively. The control unit controls the power supply to perform an over-temperature protection based on the first detection signal, controls the power supply to perform an output over-voltage protection based on the second detection signal, and controls the power supply to perform an under-voltage protection or a minimum start-up voltage setting based on the third detection signal.

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