CN212231336U - Switching power supply, power adapter and charger - Google Patents
Switching power supply, power adapter and charger Download PDFInfo
- Publication number
- CN212231336U CN212231336U CN202020344433.XU CN202020344433U CN212231336U CN 212231336 U CN212231336 U CN 212231336U CN 202020344433 U CN202020344433 U CN 202020344433U CN 212231336 U CN212231336 U CN 212231336U
- Authority
- CN
- China
- Prior art keywords
- voltage
- power supply
- auxiliary
- current
- switching power
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Dc-Dc Converters (AREA)
Abstract
The utility model provides a switching power supply, a power adapter and a charger, wherein the switching power supply comprises a current type PWM control unit, a transformer, a direct current power supply circuit and a power compensation auxiliary circuit which are sequentially connected in series, and the current type PWM control unit comprises a current detection end; the input end of the direct current power supply circuit inputs a voltage related to the output voltage of the switching power supply; the output end of the power compensation auxiliary circuit is connected with the current detection end; when the current output voltage of the switching power supply is not greater than the threshold voltage, the power compensation auxiliary circuit generates output voltage so as to provide a compensation level for the current detection end; otherwise, the power compensation auxiliary circuit does not generate output voltage and does not provide compensation level for the current detection end; wherein the threshold voltage is within an output voltage range of the switching power supply. The utility model discloses even make and guarantee when exporting lower voltage that faults such as short circuit appear, output current also can not be too big, also can export rated maximum limit power when exporting higher voltage simultaneously.
Description
Technical Field
The utility model relates to a power field, concretely relates to switching power supply, power adapter and charger.
Background
Switching power supplies with transformers are widely used in electronic products, such as power adapters or chargers. In some cases, when the load of the switching power supply is overloaded or short-circuited, the output current of the switching power supply may exceed the rated range, thereby possibly causing a safety hazard.
To address the above safety issues, the International Electrotechnical Commission (IEC) specifies tests that a Limited Power Supply (LPS) needs to meet, for example, for a certain type of power supply: the output open-circuit voltage does not exceed 30Vdc, the output maximum short-circuit current cannot exceed 8A, and the output maximum power does not exceed 100 VA.
In the prior art, there are several ways to satisfy the LPS test, or to deal with the safety problem of the scenario corresponding to the LPS test:
(1) and a PTC resistor is connected in series on an output loop of the secondary winding of the switching power supply. However, the power loop series PTC resistor reduces the efficiency of the power converter, which makes the power converter unable to meet the six-level energy efficiency requirement.
(2) And a fuse is serially connected to an output loop of the secondary winding of the switching power supply. However, since the fuse is not recoverable after being fused, the reliability of the product is reduced, and the after-market quality of the power converter is affected.
(3) A two-stage overcurrent protection circuit is adopted. The current sampling resistor is connected in series with an output loop of a secondary winding of the switching power supply, and peripheral devices such as a comparator are additionally added to perform overcurrent protection of the second stage, but the overcurrent protection is not favorable for product miniaturization design, and meanwhile, the cost is increased.
In order to improve the safety and satisfy the LPS test, chinese patent document CN101783595B discloses a method for compensating the over-power of a flyback power supply, and the embodiments of the background art thereof respectively introduce the following two schemes: 1. as shown in fig. 3, power compensation for the PWM chip is achieved by introducing a compensation level from the input voltage of the primary winding of the transformer to the current detection pin CS of the PWM chip; but this power compensation continues. 2. As shown in fig. 4, when an increase in the output voltage Vout is detected, the power compensation circuit is turned on.
With the development of consumer electronics, 5G and large-capacity battery applications, the market demand for super fast-charging switching power supplies with high power density is increasing, such as fast-charging chargers or adapters with wide output voltage (5V-24V) and output power greater than 50W. However, this power compensation method is not suitable for these wide output range switching power supplies.
SUMMERY OF THE UTILITY MODEL
Based on the above current situation, the utility model discloses a main aim at provides a switching power supply, power adapter and charger for even fault such as short circuit appears when exporting lower voltage, output current can not too big yet, thereby improves the product security performance, also can export rated maximum limit power when exporting higher voltage simultaneously.
In order to achieve the above object, the utility model adopts the following technical scheme:
a switching power supply comprises a current type PWM control unit and a transformer, wherein the current type PWM control unit comprises a current detection end Is; the current detection end Is used for detecting the primary winding current of the transformer so as to control power transmission; the switching power supply further comprises a direct current supply circuit and a power compensation auxiliary circuit which are sequentially connected in series, wherein the input end of the direct current supply circuit Is connected with an auxiliary voltage output end, the auxiliary voltage output end outputs an auxiliary voltage Vi which Is related to the output voltage V0 of the switching power supply, and the output end of the power compensation auxiliary circuit Is connected with a current detection end Is; the power compensation auxiliary circuit comprises a P-type semiconductor switch tube, the direct current supply circuit respectively provides a second voltage VA and a first voltage VB to a current inflow end and a control end of the P-type semiconductor switch tube, and at least one of the second voltage VA and the first voltage VB is related to the current output voltage V0 of the switching power supply; the power compensation auxiliary circuit is used for judging the output voltage of the direct current supply circuit, when the current output voltage V0 of the switching power supply is not greater than a threshold voltage, the difference value between the second voltage VA and the first voltage VB is greater than the conduction voltage between the current inflow end and the control end of the P-type semiconductor switching tube, the P-type semiconductor switching tube is conducted, and the power compensation auxiliary circuit generates direct current voltage so as to provide a compensation level for the current detection end; when the current output voltage V0 of the switching power supply is greater than the threshold voltage, the difference between the second voltage VA and the first voltage VB is less than the conducting voltage between the current inflow end and the control end of the P-type semiconductor switching tube, the P-type semiconductor switching tube is turned off, the power compensation auxiliary circuit does not generate direct-current voltage, and therefore compensation level is not provided for the current detection end; wherein the threshold voltage is within an output voltage range of the switching power supply.
Preferably, the P-type semiconductor switch tube comprises a PNP triode or a P-channel field effect transistor; the current inflow end and the control end of the PNP triode are respectively an emitter and a base; the current inflow end and the control end of the P-channel field effect transistor are respectively a source electrode and a grid electrode.
Preferably, the power compensation auxiliary circuit further includes a resistance voltage division module, the resistance voltage division module includes a first resistor R1 and a second resistor R2, a collector of the PNP triode Is connected to the current detection end Is through the second resistor, and the current detection end Is connected to the sampling resistor Rs of the primary winding of the transformer through the first resistor; when the PNP transistor Q2 is turned on, the second voltage VA provides a compensation level to the current detection terminal by applying a voltage across the first and second resistors R1, R2.
Preferably, the transformer further comprises a first auxiliary winding and a second auxiliary winding, the first auxiliary winding for generating a first auxiliary voltage VL associated with the output voltage; a second auxiliary winding for generating a second auxiliary voltage VH associated with the output voltage, the first auxiliary voltage VL being less than the second auxiliary voltage VH; the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, and the first direct current power supply circuit is used for outputting a first voltage VB according to the input first auxiliary voltage VL; the second direct current supply circuit is used for outputting a second voltage VA according to the input second auxiliary voltage VH.
Preferably, the second dc power supply circuit includes a third resistor R3, an N-channel MOS transistor Q3, a first zener diode ZD1, and a capacitor C1, and the first dc power supply circuit includes a second zener diode ZD 2; the second auxiliary voltage VH is grounded through a third resistor R3 and a first zener diode ZD1, and the anode of the first zener diode ZD1 is grounded; the drain, the gate and the source of the N-channel MOS transistor Q3 are respectively connected to the second auxiliary voltage VH, the cathode of the first zener diode ZD1 and the emitter of the PNP triode Q2, wherein the emitter of the PNP triode Q2 outputs the second voltage VA; the first auxiliary voltage VL is connected to the base of the PNP transistor Q2 through the second zener diode ZD2, and the anode of the second zener diode ZD2 is connected to the first auxiliary voltage VL, wherein the voltage at the base of the PNP transistor Q2 is the first voltage VB.
Preferably, the second dc power supply circuit includes a voltage regulator chip, and the first dc power supply circuit includes a second voltage regulator diode ZD 2; the voltage stabilizing chip outputs a second voltage VA according to an input second auxiliary voltage VH, wherein the second voltage VA is a set voltage value or a voltage value associated with the second auxiliary voltage VH; the first auxiliary voltage VL is connected to the base of the PNP triode Q2 through the second zener diode ZD2, and the cathode of the second zener diode ZD2 is connected to the base of the PNP triode Q2, wherein the voltage at the base of the PNP triode Q2 is the first voltage VB.
Preferably, the transformer further comprises an auxiliary winding for generating an auxiliary voltage Vi associated with an output voltage of the switching power supply; the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, and the first direct current power supply circuit is used for outputting a first voltage VB according to the input auxiliary voltage Vi; and the second direct current supply circuit is used for outputting a second voltage VA according to the input auxiliary voltage Vi.
Preferably, the switching power supply further includes a third zener diode ZD3 and a fourth zener diode ZD 4;
the second voltage VA is connected to a power supply terminal VCC of the PWM control unit through the third zener diode ZD3, the first auxiliary voltage VL is connected to the power supply terminal VCC of the PWM control unit through the fourth zener diode ZD4, and cathodes of the third zener diode ZD3 and the fourth zener diode ZD4 are connected to the power supply terminal VCC of the PWM control unit; the regulated voltage value of the first zener diode ZD1 is determined by the power supply range of the power supply terminal VCC of the PWM control unit.
Preferably, the output voltage range of the switching power supply is 5-24V, or at least partially overlaps with the voltage range of 5-24V.
The utility model also provides a power adapter or charger, including arbitrary switching power supply.
[ PROBLEMS ] the present invention
By setting the threshold voltage, when the current output voltage V0 of the switching power supply Is not greater than the threshold voltage, the power compensation auxiliary circuit generates the output voltage, so as to provide a compensation level to the current detection terminal Is, the compensation level Is superposed with the voltage on the current sampling resistor, so that the level detected by the PWM control unit through the current detection terminal Is becomes larger, thereby reducing the duty ratio of the PWM signal at a certain smaller power below the maximum limit output power, and finally maintaining the power of the primary winding at the smaller power, i.e., maintaining the output power at a smaller power, and further maintaining the output current at a smaller value, thereby more easily meeting the requirements of LPS testing, or reducing the safety risk in practical application. In addition, since the power compensation auxiliary circuit stops providing the compensation level to the current detection end Is when the output voltage V0 Is greater than the threshold voltage, the actual output power of the switching power supply in the output voltage section Is not reduced (for example, the output of the switching power supply can reach its maximum limit output power), the charging efficiency Is improved, which Is particularly important for a fast charging power adapter, and the power consumption can be reduced and the energy efficiency of the switching power supply can be improved by stopping providing the compensation level. The P-type semiconductor switching tube (such as a PNP triode) is used as a device for comparing the magnitude between the output voltage V0 and the threshold voltage by comparing the magnitude between the first voltage VB and the second voltage VA, and is also used as a switch for controlling a power supply channel of the direct current power supply circuit to the power compensation auxiliary circuit, so that the circuit is simple in structure and relatively small in size and power consumption.
In some embodiments, the output voltage ripple is smaller and the audible noise is smaller than in a switching power supply that does not employ the power compensation auxiliary circuit of the present invention.
Other advantages of the present invention will be described in the detailed description, and those skilled in the art can understand the technical advantages brought by the technical features and technical solutions through the descriptions of the technical features and the technical solutions.
Drawings
Preferred embodiments according to the present invention will be described below with reference to the accompanying drawings. In the figure:
fig. 1 is a schematic diagram of a switching power supply according to a preferred embodiment of the present invention
Fig. 2 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 3 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 4 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 5 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 6 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 7 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 8 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 9 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
Fig. 10 is a schematic diagram of a switching power supply according to another preferred embodiment of the present invention
FIG. 11 is a waveform diagram of the output current and output voltage of the switching power supply not using the present invention
FIG. 12 shows the output voltage ripple of the switching power supply not using the present invention
Fig. 13 is a waveform diagram of output current and output voltage of an embodiment of the switching power supply of the present invention
Fig. 14 shows an output voltage ripple according to an embodiment of the present invention
Detailed Description
FIG. 1 is a schematic diagram of a switching power supply according to an embodiment of the present invention, which has a wide output voltage range, such as 2-30V, or 5-24V, or outputs a variable voltage (5V-9V/5V-11V/5V-12V/5V-15V/5V-20V), or its output voltage range Vmin-VmaxAt least partially overlapping with the voltage range of 5-24V, the switching power supply is particularly suitable for a fast charging power adapter or charger with high power density and wide output voltage.
The switching power supply includes a current-mode PWM control unit (e.g., a current-mode PWM control chip), a transformer T, a power switch Q1, a current sampling resistor Rs, a dc power supply circuit, a power compensation auxiliary circuit, a clamping circuit, a filter circuit, and a voltage feedback circuit (not shown in the figure). The rectified direct current voltage Vbulk (obtained by rectifying and filtering the alternating current) is input into a primary winding NP of the transformer T, a clamping circuit is connected with the primary winding in parallel to provide clamping protection, and a secondary winding NS outputs voltage V0 through a filtering circuit. The primary winding is grounded through a power switch tube Q1 and a current sampling resistor Rs which are connected in series. The current-mode PWM control unit further includes a voltage detection terminal (not shown in the figure) and a current detection terminal Is. The output voltage V0 is input to the voltage detection end through a voltage feedback signal obtained by the voltage feedback circuit, and the PWM control unit participates in generating a corresponding PWM control signal according to the voltage feedback signal, so that the output voltage is controlled and maintained at the voltage V0 required to be output. The current detection end Is used for detecting the primary winding current of the transformer T by detecting the voltage on the current sampling resistor Rs, and when the detected voltage Is greater than the set voltage, the duty ratio of a PWM signal for controlling the power switch tube Q1 Is reduced to control the primary winding current, namely the power of the primary winding, so that the power transmission of the transformer T Is controlled, and the output power Is also controlled.
The direct current power supply circuit, the power compensation auxiliary circuit and the current detection end Is are sequentially connected in series, the input end of the direct current power supply circuit Is connected with an auxiliary voltage output end, and the auxiliary voltage output end outputs an auxiliary voltage Vi related to the output voltage V0 of the switching power supply; the output end of the power compensation auxiliary circuit Is connected with the current detection end Is. As shown in fig. 3, the voltage Vi may be the output voltage VH or VL of the auxiliary winding.
In the output voltage range (V) of the switching power supplymin-Vmax) A preset threshold voltage greater than VminAnd is less than VmaxFor example, the threshold voltage may be approximately equal to Vmax/2。
Because the PWM control unit actually controls the output power by controlling the power of the primary winding, the PWM control unit only limits the maximum output power, and for a switching power supply with a wide output voltage, when the output voltage is at a small value, if the load is overloaded or short-circuited, the output current becomes very large and may exceed the range specified by the LPS test, or in practical applications, the large current may cause a safety hazard. For example, the output range of the switching power supply is 5-20V, the maximum limit power is 60W, when the output voltage is 5V, if the load is short-circuited, the output current can reach 12A at this time to trigger the power protection action of the PWM control unit to reduce the PWM duty ratio, but the current of 12A is greater than 8A required by the LPS test, so that the LPS test cannot be passed, or a great safety risk is brought to practical application. When the output voltage is 20V, even if the load is short-circuited, the power protection action of the PWM control unit is triggered once the maximum output current reaches 60W/20V to 3A, and the maximum current does not exceed the LPS test requirement, so that the risk in practical application is low. It can be seen that in such a switching power supply with a wide output voltage, when a small voltage is output, the output current more easily exceeds the safety range, and as long as the output current does not exceed the safety range when the small voltage is controlled, the output current at a high voltage does not exceed the safety range.
The utility model discloses a solve above-mentioned problem, through setting up above-mentioned threshold voltage, when switching power supply current output voltage V0 Is not more than threshold voltage, power compensation auxiliary circuit produces direct current voltage, thereby provide the offset level to current detection end Is, the voltage stack on this offset level and the current sampling resistance Rs, make the level grow that PWM the control unit detected through current detection end Is, thereby reduce the duty cycle of PWM signal promptly when certain less power below the maximum limit output power, finally make primary winding's power maintain on this less power, be about to output and maintain on a less power, and then make output current maintain at less value, satisfy the demand that LPS tested more easily, perhaps reduce safe risk in practical application. In addition, when the output voltage V0 Is greater than the threshold voltage, the power compensation auxiliary circuit does not generate a dc voltage, so that the compensation level Is not supplied to the current detection terminal Is, and therefore, the actual output power of the switching power supply in this output voltage section Is not reduced (for example, the output of the switching power supply can reach its maximum limit output power of 60W, and when the output voltage V0 Is greater than the threshold voltage, the switching power supply can output 60W, but when the output voltage V0 Is less than the threshold voltage, the power that the switching power supply can output Is less than 60W), which improves the charging efficiency, which Is particularly important for a fast charging power adapter or charger, and in addition, stopping supplying the compensation level can reduce the power consumption and improve the energy efficiency of the switching power supply.
The magnitude of the compensation level may be
Wherein, VRSUnder the condition of no power compensation auxiliary circuit, the voltage V on the sampling resistor Rs when the switching power supply outputs the maximum limit output powerminIs the minimum value of the output voltage range of the switching power supply, ImaxIs the maximum limit output current.
For example, the output range is 5-20V, VRS＝1V，Pmax＝60W，ImaxWhen the ratio is 8A:
Vmin·Imax＝5v*8A＝40W，
the magnitude of the offset level may be taken to be 330 mV. In some embodiments, the magnitude of the offset level may be between 50mV and 700 mV.
Fig. 2 shows a more preferred embodiment of the switching power supply of the present invention. The power compensation auxiliary circuit comprises a PNP triode Q2 and a resistance voltage division module, the direct current supply circuit provides a second voltage VA and a first voltage VB to an emitter and a base of the PNP triode Q2 respectively according to an input voltage Vi, the input end of the resistance voltage division module Is connected with a collector of the PNP triode Q2, the output end of the resistance voltage division module Is connected with a current detection end Is, and at least one of the second voltage VA and the first voltage VB Is related to the current output voltage V0 of the switching power supply. When the current output voltage V0 of the switching power supply Is not greater than the threshold voltage, the difference between the second voltage VA and the first voltage VB Is greater than the conduction voltage between the emitter and the base of the PNP transistor Q2 (the conduction voltage Is usually about 0.7V), the PNP transistor Q2 Is turned on, the power compensation auxiliary circuit generates an output voltage, and thus, the compensation level Is provided to the current detection end Is through the resistance voltage dividing module; when the current output voltage V0 of the switching power supply is greater than the threshold voltage, the difference between the second voltage VA and the first voltage VB is less than the conduction voltage V between the emitter and the base of the PNP triode Q2EBThe PNP transistor Q2 Is turned off, and the power compensation auxiliary circuit does not generate an output voltage, thereby not providing a compensation level to the current detection terminal Is. The PNP triode Q2 is used as a device for comparing the magnitude between the output voltage V0 and the threshold voltage by comparing the magnitude between the first voltage VB and the second voltage VA, and is also used as a switch for controlling a power supply channel of the direct current power supply circuit to the power compensation auxiliary circuit, and the circuit is simple in structure and relatively small in size and power consumption.
In some embodiments, the second voltage VA is a fixed value, and the first voltage VB is a voltage positively correlated to the output voltage V0, such as a multiple of the output voltage V0;
in other embodiments, the first voltage VB is a fixed value and the second voltage VA is a voltage related to the output voltage V0.
Fig. 4 shows a more preferred embodiment of the switching power supply of the present invention. The power compensation auxiliary circuit further comprises a resistance voltage division module, the resistance voltage division module comprises a first resistor R1 and a second resistor R2, a collector of the PNP triode Q2 Is connected with a current detection end Is through the second resistor R2, and the current detection end Is connected with a sampling resistor Rs of a primary winding of the transformer T through the first resistor R1; when the PNP transistor Q2 Is turned on, the second voltage VA provides a compensation level to the current detection terminal Is by applying voltages to the first resistor R1 and the second resistor R2, the compensation level Is:
fig. 5 shows a more preferred embodiment of the switching power supply of the present invention. The transformer T further comprises a first auxiliary winding having a first auxiliary voltage output for generating a first auxiliary voltage VL (for example equal to V0) associated with the output voltage (the induced electromotive force generated on the first auxiliary winding generates the first auxiliary voltage VL via a first diode D1 and a capacitor C1); a second auxiliary winding having a second auxiliary voltage output terminal for generating a second auxiliary voltage VH associated with the output voltage, the first auxiliary voltage VL being less than the second auxiliary voltage VH (e.g., equal to 3V0 in magnitude) (the induced electromotive force generated on the second auxiliary winding generates the second auxiliary voltage VH via a second diode D2 and a capacitor C2); the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, wherein the first direct current power supply circuit is used for outputting a first voltage VB according to an input first auxiliary voltage VL; the second direct current supply circuit is used for outputting a second voltage VA according to the input second auxiliary voltage VH.
Fig. 6 shows a more preferred embodiment of the switching power supply of the present invention. The second direct current supply circuit comprises a third resistor R3, an N-channel MOS transistor Q3, a first zener diode ZD1 and a capacitor C3, and the first direct current supply circuit comprises a second zener diode ZD 2; the second auxiliary voltage VH is grounded through the third resistor R3 and the first zener diode ZD1, and the anode of the first zener diode ZD1 is grounded; the drain electrode, the grid electrode and the source electrode of the N-channel MOS tube Q3 are respectively connected with the second electrodeThe auxiliary voltage VH, the cathode of the first voltage stabilizing diode ZD1 and the emitter of the PNP triode Q2 are connected, wherein the emitter of the PNP triode Q2 outputs a second voltage VA; the first auxiliary voltage VL is connected to the base of the PNP transistor Q2 through the second zener diode ZD2, and the anode of the second zener diode ZD2 is connected to the first auxiliary voltage VL, wherein the voltage at the base of the PNP transistor Q2 is the first voltage VB. When VH is more than or equal to VZD1The first zener diode ZD1 is reverse breakdown, and the gate voltage of Q3 is clamped at VZD1And Q3 is turned on, VH starts to charge the capacitor C3 until the voltage of the capacitor C3 reaches VZD1Vth (the Vth is Q3 grid source electrode conduction threshold voltage), the Q3 tube is turned off, and the magnitude of the first voltage VA is maintained at VZD1-Vth. When VH < VZD1The first zener diode ZD1 cannot break down, the gate voltage of Q3 is maintained at VH, Q3 is kept on, and the magnitude of the first voltage VA is maintained at VH-Vth. When:
VA-VEB-VL≥VZD2when the temperature of the water is higher than the set temperature,
the PNP transistor Q2 is turned on, and is turned off otherwise, wherein VEBIs the conduction voltage, V, between the emitter and collector of the PNP transistor Q2ZD2Is the reverse breakdown voltage of the second zener diode ZD 2).
In one embodiment, if: VH-3V 0, VL-V0, and the reverse breakdown voltage of the first zener diode ZD1 is 16V;
(1) when VH is more than or equal to 16V (namely V0 is more than or equal to 16/3V is 5.3V),
the PNP transistor Q2 has the following relationship when turned on: VA-VB is more than or equal to 0.7,
and VA is 16-Vth and VB is VZD2+V0，
Namely: (16-Vth) - (V)ZD2+V0)≥0.7，
16-Vth-0.7-V0≥VZD2Therefore, V0 is not more than 15.3-Vth-VZD2，
That is, the threshold voltage is: 15.3-Vth-VZD2；
Such as setting VZD2At 5v, Vth is 2.5v, and the threshold voltage is 7.8v, i.e., when the output voltage is 5.3v-7.8v, power compensation is required, and when the output voltage is greater than 7.8v, power compensation is not required.
(2) When VH < 16V (i.e. V0 < 16/3V-5.3),
the PNP transistor Q2 is turned on according to the following relationship: VA-VB is more than or equal to 0.7,
and VA is 3V0-Vth and VB is VZD2+V0，
(3V0-Vth)-(VZD2+ V0) is not less than 0.7, namely: 2V0-Vth-0.7 is more than or equal to VZD2And therefore, the first and second electrodes are,
(Vth+0.7+VZD2)/2≤V0。
such as setting VZD2Is 5V, Vth is 2.5V, (Vth +0.7+ V)ZD2) Since the output voltage is 5v with a minimum value of 4.4 v/2, power compensation is required when the output voltage is 5v-5.3v, and the normal operation is not performed when the output voltage is less than 5 v.
In summary, when the output voltage is 5v-7.8v, power compensation is required; when the output voltage is more than 7.8v, power compensation is not needed. Therefore, the output voltage V0 is not greater than the threshold voltage (15.3-Vth-V)ZD2) When the PNP transistor Q2 is turned on, power compensation is required.
It can be seen that for a certain magnitude of VA, the magnitude of the designed threshold voltage determines how large the reverse breakdown voltage V is selectedZD2And second zener diode ZD 2.
Fig. 7 shows a more preferred embodiment of the switching power supply of the invention, which is substantially similar to that of fig. 6, the main differences including the difference of the second dc supply circuit, which includes the zener chip, and the first dc supply circuit including the second zener diode ZD 2; the voltage stabilizing chip outputs a stable second voltage VA according to the input second auxiliary voltage VH, wherein the second voltage VA is a set voltage value (for example, 15-17V); the first auxiliary voltage VL is connected to the base of the PNP transistor Q2 through the second zener diode ZD2, and the cathode of the second zener diode ZD2 is connected to the base of the PNP transistor Q2, wherein the voltage at the base of the PNP transistor Q2 is the first voltage VB.
Fig. 8 is a more preferred embodiment of the switching power supply of the present invention, which is substantially similar to the switching power supply of fig. 6, with the main differences including the differences between the auxiliary winding and the dc supply circuit. The transformer T further comprises an auxiliary winding for generating an auxiliary voltage Vi associated with the output voltage of the switching power supply; the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, wherein the first direct current power supply circuit is used for outputting a first voltage VB according to an input auxiliary voltage Vi; the second direct current supply circuit is used for outputting a second voltage VA according to the input auxiliary voltage Vi. For example, the second dc power supply circuit of the present embodiment may employ a voltage stabilizing chip to output the second voltage VA with a fixed voltage value, and the first dc power supply circuit may employ the first dc power supply circuit as shown in fig. 7.
Fig. 9 shows a more preferred embodiment of the switching power supply of the present invention, wherein the switching power supply further comprises a third zener diode ZD3, a fourth zener diode ZD4, and a fourth resistor R4; the second voltage VA is connected to a power supply terminal VCC of the PWM control unit through a third zener diode ZD3, the first auxiliary voltage VL is connected to the power supply terminal VCC through a fourth zener diode ZD4, cathodes of the third zener diode ZD3 and the fourth zener diode ZD4 are connected to the power supply terminal VCC of the PWM control unit, and a zener value of the first zener diode ZD1 is determined by a power supply range of the power supply terminal VCC of the PWM control unit. In addition, the first auxiliary voltage VL is grounded through a fourth resistor R4.
According to the embodiment of FIG. 6, when VH ≧ VZD1The voltage of the second voltage VA is maintained at VZD1Vth, when VH < VZD1The voltage of the second voltage VA is maintained at VH-Vth.
(1) When: when VA is greater than VL, VCC is VA-VZD3＝VZD1-Vth-VZD3，
It can be seen that the regulation value of the first zener diode ZD1 is determined by the supply range of the power supply terminal VCC of the PWM control unit, where VZD3The forward conduction voltage of the third zener diode ZD3 is usually about 0.7V;
(2) when: when VA is less than or equal to VL, VCC is VL-VZD4(VZD4Which is the forward conduction voltage of the fourth zener diode ZD4, typically around 0.7V).
Specific examples are as follows: when VH is 3V0, VL is V0, Vth is 2.5V,
(1) when V0 is 5V, VA is 15V-2.5V-12.5V, VL is 5V,
thus, VCC is VA-VZD3＝12.5V-0.7V＝11.8V；
(2) When V0 is 20V, VA is 16V-2.5V-13.5V, VL is 20V,
thus, VCC is VL-VZD4＝12V-0.7V＝11.3V。
Fig. 3 shows a more preferred embodiment of the switching power supply of the present invention, wherein the transformer T further comprises a first auxiliary winding and a second auxiliary winding; a first auxiliary winding having a first auxiliary voltage output for generating a first auxiliary voltage VL associated with the output voltage; the second auxiliary winding has a second auxiliary voltage output terminal for generating a second auxiliary voltage VH associated with the output voltage, the first auxiliary voltage VL being less than the second auxiliary voltage VH; the power compensation auxiliary circuit comprises a switch K, a comparator A1 and a level generation circuit; the direct current power supply circuit comprises a first direct current power supply circuit, a second direct current power supply circuit and a third direct current power supply circuit; the input end of the first direct current power supply circuit Is connected with the first auxiliary voltage output end or the second auxiliary voltage output end, and the output end of the first direct current power supply circuit, the switch K, the level generating circuit and the current detection end Is are sequentially connected; the input end of the third direct current supply circuit is connected with the first auxiliary voltage output end, and the output end of the third direct current supply circuit is connected with the first input end (for example, the inverting input end) of the comparator A1 to input the first auxiliary voltage VL; the input end of the second direct current supply circuit is connected with the second auxiliary voltage output end, and the output end of the second direct current supply circuit is connected with a second input end (for example, a non-inverting input end) of the comparator A1; the comparator A1 Is used for comparing the voltage output by the third DC power supply circuit with the voltage output by the second DC power supply circuit, so that when the current output voltage V0 of the switching power supply Is not greater than the threshold voltage, a control signal Is output to control the switch K to be switched on, the level generating circuit generates an output voltage, and a compensation level Is provided for the current detection end Is; when the current output voltage V0 of the switching power supply Is greater than the threshold voltage, the output control signal controls the switch K to be turned off, and the level generating circuit generates no output voltage, so that no compensation level Is provided to the current detection terminal Is. The second dc power supply circuit in fig. 6 may be used as the second dc power supply circuit, so that the voltage input to the non-inverting input terminal is the second voltage VA. The first dc power supply circuit may employ a resistor, so that the voltage input to the inverting input terminal is VL. The level generating circuit can adopt the resistance voltage dividing module in fig. 4.
Fig. 10 is a more preferred embodiment of the switching power supply of the present invention, which is substantially the same as the switching power supply of fig. 4, with the main difference that PNP transistor Q2 is replaced by P-channel fet Q4. As shown in fig. 10, the power compensation auxiliary circuit includes a P-channel fet Q4, and the dc power supply circuit provides a second voltage VA and a first voltage VB to the source and the gate of the P-channel fet Q4, respectively, at least one of the second voltage VA and the first voltage VB being related to the current output voltage V0 of the switching power supply; when the current output voltage V0 of the switching power supply is not greater than the threshold voltage, the difference between the second voltage VA and the first voltage VB is greater than the conduction voltage between the source and the gate of the P-channel field effect transistor Q4, the P-channel field effect transistor Q4 is turned on, and the power compensation auxiliary circuit generates an output voltage, thereby providing a compensation level for the current detection terminal; when the current output voltage V0 of the switching power supply is greater than the threshold voltage, the difference between the second voltage VA and the first voltage VB is smaller than the turn-on voltage between the source and the gate of the pfet Q4, the pfet Q4 is turned off, and the power compensation auxiliary circuit does not generate an output voltage, thereby not providing a compensation level to the current detection terminal.
Fig. 11 is a waveform diagram of the output current and the output voltage of the switching power supply of the present invention, and the curve 2 and the curve 1 in the diagram are respectively the output current and the output voltage of the switching power supply, so that it can be seen that the output current reaches 9.54A at most to enter the current-limiting protection, and the requirement of LPS test is not satisfied and is less than 8A. Fig. 12 shows the output voltage ripple of the switching power supply not using the present invention, and it can be seen from the figure that the output voltage ripple reaches 184 mV.
Fig. 13 is a waveform diagram of the output current and the output voltage of an embodiment of the switching power supply of the present invention, and in the diagram, the curve 2 and the curve 1 are respectively the output current and the output voltage of the switching power supply, and it can be seen that the output current reaches 6.6A, i.e. enters the current limiting protection, and conforms to the rule that the LPS test requirement is less than 8A. Fig. 14 is adopted the utility model discloses switching power supply's output voltage ripple can be seen from the picture that the output voltage ripple is only 124mV, and is visible, the utility model discloses the output voltage ripple can also be reduced.
It will be appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.
It will be understood that the above-described embodiments are illustrative only and not restrictive, and that various obvious and equivalent modifications and substitutions may be made in the details described herein by those skilled in the art without departing from the basic principles of the invention.
Claims (10)
1. A switching power supply comprises a current mode PWM control unit and a transformer, wherein the current mode PWM control unit comprises a current detection end; the current detection end is used for detecting the primary winding current of the transformer so as to control power transmission; it is characterized in that the preparation method is characterized in that,
the switching power supply also comprises a direct current power supply circuit and a power compensation auxiliary circuit which are sequentially connected in series, wherein the input end of the direct current power supply circuit is connected with an auxiliary voltage output end, the auxiliary voltage output end outputs an auxiliary voltage related to the output voltage of the switching power supply, and the output end of the power compensation auxiliary circuit is connected with a current detection end;
the power compensation auxiliary circuit comprises a P-type semiconductor switch tube, the direct current supply circuit respectively provides a second voltage and a first voltage for a current inflow end and a control end of the P-type semiconductor switch tube, and at least one of the second voltage and the first voltage is related to the current output voltage of the switching power supply;
the power compensation auxiliary circuit is used for judging the output voltage of the direct current power supply circuit, when the current output voltage of the switching power supply is not greater than a threshold voltage, the difference value between the second voltage and the first voltage is greater than the conduction voltage between the current inflow end and the control end of the P-type semiconductor switching tube, the P-type semiconductor switching tube is conducted, and the power compensation auxiliary circuit generates direct current voltage so as to provide a compensation level for the current detection end;
when the current output voltage of the switching power supply is greater than the threshold voltage, the difference value between the second voltage and the first voltage is smaller than the conduction voltage between the current inflow end and the control end of the P-type semiconductor switching tube, the P-type semiconductor switching tube is turned off, the power compensation auxiliary circuit does not generate direct-current voltage, and therefore compensation level is not provided for the current detection end;
wherein the threshold voltage is within an output voltage range of the switching power supply.
2. The switching power supply according to claim 1,
the P-type semiconductor switch tube comprises a PNP triode or a P-channel field effect tube;
the current inflow end and the control end of the PNP triode are respectively an emitter and a base;
the current inflow end and the control end of the P-channel field effect transistor are respectively a source electrode and a grid electrode.
3. The switching power supply according to claim 2,
the power compensation auxiliary circuit further comprises a resistance voltage division module, the resistance voltage division module comprises a first resistor and a second resistor, a collector of the PNP triode is connected with the current detection end through the second resistor, and the current detection end is connected with a sampling resistor of a primary winding of the transformer through the first resistor;
when the PNP triode is conducted, the second voltage provides a compensation level for the current detection end by applying voltage to the first resistor and the second resistor.
4. The switching power supply according to claim 2,
the transformer further comprises a first auxiliary winding and a second auxiliary winding, the first auxiliary winding for generating a first auxiliary voltage associated with the output voltage; a second auxiliary winding for generating a second auxiliary voltage associated with the output voltage, the first auxiliary voltage being less than the second auxiliary voltage;
the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, and the first direct current power supply circuit is used for outputting a first voltage according to the input first auxiliary voltage; the second direct current supply circuit is used for outputting a second voltage according to the input second auxiliary voltage.
5. The switching power supply according to claim 4,
the second direct current power supply circuit comprises a third resistor, an N-channel MOS (metal oxide semiconductor) tube, a first voltage stabilizing diode and a capacitor, and the first direct current power supply circuit comprises a second voltage stabilizing diode;
the second auxiliary voltage is grounded through a third resistor and a first voltage stabilizing diode, and the anode of the first voltage stabilizing diode is grounded; the drain electrode, the grid electrode and the source electrode of the N-channel MOS tube are respectively connected with the second auxiliary voltage, the cathode of the first voltage stabilizing diode and the emitting electrode of the PNP triode, wherein the emitting electrode of the PNP triode outputs the second voltage;
the first auxiliary voltage is connected with the base of the PNP triode through the second voltage-stabilizing diode, the anode of the second voltage-stabilizing diode is connected with the first auxiliary voltage, and the voltage of the base of the PNP triode is the first voltage.
6. The switching power supply according to claim 4,
the second direct current power supply circuit comprises a voltage stabilizing chip, and the first direct current power supply circuit comprises a second voltage stabilizing diode;
the voltage stabilizing chip outputs a second voltage according to an input second auxiliary voltage, wherein the second voltage is a set voltage value or a voltage value related to the second auxiliary voltage;
the first auxiliary voltage is connected with the base of the PNP triode through the second voltage-stabilizing diode, the cathode of the second voltage-stabilizing diode is connected with the base of the PNP triode, and the voltage of the base of the PNP triode is the first voltage.
7. The switching power supply according to claim 1,
the transformer further comprises an auxiliary winding for generating an auxiliary voltage associated with an output voltage of the switching power supply;
the direct current power supply circuit comprises a first direct current power supply circuit and a second direct current power supply circuit, and the first direct current power supply circuit is used for outputting a first voltage according to the input auxiliary voltage; the second direct current supply circuit is used for outputting a second voltage according to the input auxiliary voltage.
8. The switching power supply according to claim 5,
the switching power supply further comprises a third voltage-stabilizing diode and a fourth voltage-stabilizing diode;
the second voltage is connected with the power supply end of the PWM control unit through the third zener diode, the first auxiliary voltage is connected with the power supply end of the PWM control unit through the fourth zener diode, and cathodes of the third zener diode and the fourth zener diode are connected with the power supply end of the PWM control unit;
the regulated voltage value of the first voltage regulator diode is determined by the power supply range of the power supply terminal of the PWM control unit.
9. The switching power supply according to any one of claims 1 to 8,
the output voltage range of the switching power supply is 5-24V, or at least partially overlaps with the voltage range of 5-24V.
10. A power adapter or charger, comprising a switching power supply according to any one of claims 1-9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020344433.XU CN212231336U (en) | 2020-03-18 | 2020-03-18 | Switching power supply, power adapter and charger |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020344433.XU CN212231336U (en) | 2020-03-18 | 2020-03-18 | Switching power supply, power adapter and charger |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN212231336U true CN212231336U (en) | 2020-12-25 |
Family
ID=73903025
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020344433.XU Active CN212231336U (en) | 2020-03-18 | 2020-03-18 | Switching power supply, power adapter and charger |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN212231336U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111884512A (en) * | 2020-03-18 | 2020-11-03 | 深圳市航嘉驰源电气股份有限公司 | Switching power supply, power adapter and charger |
-
2020
- 2020-03-18 CN CN202020344433.XU patent/CN212231336U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111884512A (en) * | 2020-03-18 | 2020-11-03 | 深圳市航嘉驰源电气股份有限公司 | Switching power supply, power adapter and charger |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP3972107A1 (en) | Switching power supply, power supply adapter, and charger | |
| CN104660022B (en) | The system and method that overcurrent protection is provided for supply convertor | |
| US7339359B2 (en) | Terminal for multiple functions in a power supply | |
| CN109905042B (en) | Power supply equipment and power supply circuit thereof | |
| CN105245112B (en) | A kind of adaptive high-accuracy and constant current circuit and Switching Power Supply | |
| US20080291709A1 (en) | Switching power supply apparatus | |
| JP2012196109A (en) | Control circuit of switching power supply device, and switching power supply device | |
| CN213846230U (en) | Overcurrent protection circuit | |
| US10886845B2 (en) | Detection method, detection circuit, controller and switching power supply | |
| CN217445265U (en) | Current limit control circuit | |
| CN212231336U (en) | Switching power supply, power adapter and charger | |
| TWI729807B (en) | Flyback power converter and active clamp snubber and overcharging protection circuit thereof | |
| WO2018163413A1 (en) | Electronic circuit breaker | |
| JP2011200034A (en) | Switching power supply apparatus | |
| US11716029B2 (en) | Power supply circuit for switching mode power supply and control method thereof | |
| CN113206494B (en) | Input voltage detection circuit and charger | |
| CN113726175B (en) | Conversion device, controller and power supply control method thereof | |
| CN216290693U (en) | Conversion device and controller | |
| CN107994763B (en) | Switching power supply, control circuit thereof and starting system of controller | |
| CN213817222U (en) | Overvoltage protection circuit, switching power supply and electrical equipment | |
| CN216530712U (en) | Redundant power supply control circuit of low-voltage direct-current power equipment | |
| CN217282714U (en) | Direct current motor driving power supply based on PSR technology | |
| CN220605552U (en) | Switching power supply and vehicle | |
| US20240128882A1 (en) | Power converter apparatus protected against input voltage of opposite polarity with small heat and loss | |
| CN214900684U (en) | Flyback AC-DC voltage conversion circuit and control chip thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |