TWM328720U - Power supply circuit with safe and highly effective low-power-loss switch - Google Patents

Description

M328720 VIII. New Description: - [New Technology Area] This work reveals a class of safe, high-efficiency and low-power switching power supply circuits and technologies, including energy-saving control circuit with high-resistance starting resistor, light-load oscillation frequency control and minimum pulse width control. The main circuit current limiting circuit controlled by the input voltage is used, and the output voltage of the primary side control is abnormally protected, and the output constant voltage circuit is compensated by the line loss voltage. [Prior Art] A conventional switching power supply circuit mainly includes a first rectifying and juxtaposed circuit for rectifying an input voltage and excluding an alternating current component, and the rectifying and filtering circuit is connected to a primary side coil of the transformer. / The transformer includes the primary side coil, and a secondary side coil and a secondary coil are coupled to the primary side coil. A clamp is used to absorb the high voltage self-induced electromotive force generated by the secondary side coil, the clamp being located between the second end of the / secondary side coil and the input end of a first power switching unit. A second rectifying and filtering circuit is coupled to the secondary side coil of the transformer for rectifying the input pulse voltage to a constant value D c voltage. A control circuit is included for controlling the pulse width and frequency of the circuit. In the traditional switching power supply circuit, a large-capacity (rate) resistance starting resistor is often used, which is not only bulky but also increases the power.

Power consumption reduces efficiency and wastes energy. In the traditional self-excited ^^I source circuit, its operating frequency is subject to the transformer state (including the change of the input voltage and load of the eight-electrical input) and the feedback capacitance; due to the change of 5 = the uncertainty of the state and state, in the air At the time of loading, it is difficult to make the stabilizer + device special in the energy-saving intermittent operation mode. The primary current limiting device is used to find the 5 M328720 circuit. When the input AC voltage is different (110V/230V), the output current (or power) varies greatly. When the input AC voltage is high, the output current (or power) is large. 'The safety factor is reduced. The conventional circuit can make the voltage at the sampling end of the output voltage constant within the rated load range, but after the wire is added, a voltage drop occurs in the current wire resistance, resulting in a drop in the output voltage after passing the wire. [New content] Energy-saving into the A C (collective transformer dynamic resistance and dynamic resistance control. Power) is reduced by the pulse type. Safe high dynamic resistance voltage (the drain of the tube is connected to the auxiliary start. The small pulse width is rated to suppress the most working mode.

Consumption of switching power supply circuit, the circuit uses high resistance start control circuit, the circuit uses DC voltage connected to the high voltage of the mains after rectification and filtering) 戋 switch pole ... start resistance (greater than 5.2. Auxiliary low generated by the feedback winding The small resistance of the voltage, and the stable operation of the circuit during no-load and light load operation in the intermittent mode of operation, 4 to save energy and reduce the cost and the circuit uses light-loaded oscillation frequency. The circuit created by this circuit is empty and twisted. Baotou Mugong battle and light load (less than 20 〇 / 〇::: using the minimum pulse width control and frequency control technology = and the free shock of the feedback capacitor, and limited width, so that the circuit works stably in the energy-saving interval On the other hand, the loop current limiting circuit of the present invention, the circuit of the high main loop current limiting circuit is applied to the control loop, the voltage comparator), and the main circuit of the wheel voltage control is limited by the resistor voltage division method. The control element (triode,; voltage, so that the current of the main circuit decreases with the input voltage of the wheel 6 M328720 & A, the juice is reduced to reach the width (AC 8 5 - 2 R d ^ < b4V or DC120 - -370V ) Electricity ) Basically, ^ + changed 'saves the traditional circuit in the middle, improves the conversion efficiency of Ray % ^ Λμ $路, improves the productivity, and raises the reliability of the product with the product, so that the product is created once. The circuit controlled by the output voltage J of the side control uses an electronic switch circuit to control the current of the main circuit by the voltage change on the cow. The overload or short circuit causes the output voltage to be lower than the set value. The circuit is started to make the current of the main circuit smaller. Therefore, (or current), effective protection. This creation uses the line loss voltage compensation of the output constant output current to increase the voltage drop on the electrical line of the output voltage sampling end, so as to achieve the through voltage at the rated load The effect of the constant effect in the range. [Embodiment] The operation method of the preferred embodiment of the present case is as follows. a CMOS transistor or a BJT transistor (bipola transist 〇r). This will be initiated when the voltage of a gate control circuit reaches a certain level. The output power of the voltage range of the primary side of the transformer flowing through the power switch (or the voltage of the output current limiting device is adapted to the safety. Abnormal protection. When the optocoupler has different output voltage), the electronic output reduces the output power. Pressure circuit. With the transmission voltage, to compensate for the effect of the transmission after the wire and the details of the description of the creation of the diode, such as the junction switch, when the gate switch, and then the maximum current is negatively related to the input voltage of 7 M328720 The following is a description of the low power switching power supply circuit of the present application, and please refer to the block diagram of Figure 1. A first rectifying and filtering circuit RF 1 is used to rectify the input voltage and filter out the AC components. The rectifying and filtering circuit RF 1 is connected to the primary side coil N1 of the transformer. A transformer includes the primary side coil N 1, a secondary side coil N 3 and a feedback coil N 2 coupled to the primary side coil N1. A clamp C L is for absorbing the high-voltage self-induced electromotive force generated by the primary side coil, and the clamp C L is located between the primary side coil N 1 A terminal and the input terminal K 1 of the first power switching unit Q 1 . A second rectifying and filtering circuit R F 2 is coupled to the secondary side coil N 3 of the transformer for rectifying the input pulse voltage to a constant value D C voltage. A control circuit is configured to control a pulse width and a frequency of the circuit; the control circuit includes: a first power switching unit Q1 system bit between the output end of the clamp CL and the ground terminal PGND, and at the first power A resistor R1 is connected in series between the switch unit Q1 and the ground. A start control circuit A bit is between the transformer primary side coil N1A or N1B, the second end N1B of the feedback coil N3 and the gate G of the first power switch unit Q1 for actuating the start-up phase a first power switching unit Q1; the start control circuit A receives current from the primary side coil N 1 A or N 1 B of the transformer, and current from the second end N 1 B of the feedback coil N 3 , thus providing Sufficient current is supplied to the gate G of the first power switching unit Q1 to actuate the first power switching unit Q 1 at the start or restart; the second switching unit Q 2 is in the first Power switch 8 M328720 yuan single system control 第 first open this. And off the split end, one or two sources of the current electric coil. The line is taught to return to D to do this. From the FG source, the terminal is electrically connected to the 4 and the QA element road with a little pole connection. 3⁄4 is another ^ 1 system U controller wide Pulse-coupled light-loading light from the first end of the system from the source to the power system, the flow of the system, the control source, the current, the fourth, the first source, the current source, the current, the three, the R, the resistance, the single-unit Rate control width

The L U output converter is tuned to the light. The first end of the bit line is the one end of the K line end of the K line.

Pulse and load B light 1 IN rate of the frequency of the end of the second wave of the second wave L wide pulse -3 lightly this can be due to the LL pulse output ΙΜΊ wide and low drop rate frequency of the single element off rate 1 The first. The source of the power is saved by the wide section of the blessing of the J ^ pulse can be a single factor of aftlu, the rate of work 1 first in the connection 1.PC 叇 1 yuan single-coupled coupling open light three and the

At the end of the third period, the output is 1 U

And 2 R is blocked by the 3 Q yuan, which is connected to the 3 Q ί terminal.

The super-single of the carrier is super-single-line C, the side is normally open, and the other is three or two voltages. The electric power should be in the out-of-position. When the bit is lost, the value is small 2 / the fixed end is set to the low voltage of the electric current. Returning Q to the main element to make the order to open the short 3 rate or Q resistance ^6-1 to make the ER compensator pressure to stabilize the output of the output end of the second side of the second side As shown in FIG. 2, the third switching unit Q 3 in the present invention includes an electronic switch Q 3 and resistors R 1 1 and R 1 2 . The resistor R i i is connected to the second end of the photocoupler U1; the resistor R12 is connected to the ground terminal pGND. The control terminal of the electronic switch is at the junction of the resistors R 1 1 and r丨2; the start control circuit A includes a resistor R 5 A and _ | resistor 9 M328720 R 6, the resistor R 5 A is in the Between the second end N1 B of the primary side coil n 1 and the gate G of the first power switching element Q1, the resistor R 6 A is located at the second end N 2 B of the feedback coil N 2 and the The light load pulse width controller includes a resistor R8A and a capacitor C2 capacitor C1 and a resistor R9. The regulator R E includes a Ο P comparator c P and a B J T transistor T. The reference end of the comparator is the second end, and the input end is the third end. The output end is the first end, and when the voltage of the third end is higher than the second end, the output end outputs an apostrophe to actuate the 6th crystal τ. The input end of the optical combiner is a photodiode whose handle is connected to the output end. A resistor R7 is coupled between the input of the optocoupler and the ground. A resistor R 6 is coupled between the high voltage output of the second rectifying and chopper circuit r f 2 and the third terminal of the 〇P comparator CP. A resistor Rg is coupled between the third terminal of the OP comparator and the output of the regulator RE. The function of R5 and 糸 is used for partial pressure. A resistor R4 is coupled between the voltage output of the second rectifying and filtering circuit R F 2 and the input of the optocoupler U 1 . The resistor R 1 is connected between the output terminal K 2 of the first power switching unit q 1 and the ground terminal PGND , and the resistor R 2 is connected to the gate G of the second switching unit Q 2 and the output terminal κ of the first power switching unit q 1 . Between 2. The resistor R 3 is connected between the input terminal κ 1 of the second switching unit q 2 and the input terminal K1 of the third switching unit Q3. The capacitor C4 is connected between the second terminal N2B of the feedback coil N2 and the ground terminal PGND. The rectifier D 2 is connected between the input terminal N 2 A of the feedback coil n 2 and the ground terminal P G N D . 10 M328720 A resistor R 5 A is connected between the second terminal N 1 B of the primary side coil N1 and the gate G of the first power switching unit Q 1 . The resistor R 6 is connected between the gate G of the first power switching unit Q 1 and the second terminal N2B of the feedback coil N2. A resistor R7 and a capacitor C3 are connected in series between the gate G of the first power switching unit Q1 and the first terminal N2B of the feedback coil N2. A resistor R8 and a capacitor C2 are connected in series between the gate G of the second switching unit Q 2 and the first terminal N1A of the feedback coil N 2 . A resistor R9 and a capacitor C1 are connected in series between the gate G of the second switching unit Q 2 and the output terminal of the photocoupler U 1 . A resistor R2 and a resistor R3 are connected in series between the output terminal K 2 of the first power switching unit Q1 and the input terminal of the third switching unit. The resistor R 4 is connected in series between the second switch unit and the junction of the resistors R 2 and R 3 , and the diode D 1 is connected in series to the second end N 1 B of the primary side coil N1 and the capacitor C 1 and the resistor Between the junctions of R 9 . The resistor R 5 B is located between the first end N 1 A and the second end N 1 B of the primary side coil N1. Or as shown in FIG. 3, the resistor R 5 B is not connected, and the other resistor R 8 B is connected to the first end N 1 A of the primary side coil N 1 and the gate G of the second switching unit Q 2 . between. In the present creation, the first power switching unit Q1, the second switching unit Q2, the third switching unit Q3 is a CMOS (complementary-symmetric metal oxide semiconductor) transistor (or precisely a CMOS field effect transistor) or BJT transistor (bi ρ ο 1 ar junction transistor) ° 11 M328720 Description of the working principle of this creation: (1) Start the input AC voltage after rectification and filtering of the DC mains high power “ Η V + ” (Transformer Τ 1 Ν 1 Α ) 经 经 经 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初 初When the voltage is greater than its threshold, Q 1 generates a current and is strongly positively fed through Τ 1 (C 4 -> feedback winding N 2 - C 3 - R 7 ) its saturation conduction; when the main circuit (transformer primary winding Ν 1 - The current of Q 1 R1) generates a voltage on R1 that is large enough to cause Q 2 to conduct, the Q 1 - G network voltage is discharged, Q 1 is turned off, and N 2 induces a reverse voltage (N2A-, N2B+). R6, R7 charge C3 and charge C4 through D2 to establish auxiliary voltage, while sub-group N 3 To be the second voltage output by the rectifier filter. After the boost voltage is established, when the circuit is restarted, R 5 A and R 6 and the feed branches (N2 - R7 - C3) work together to generate the starting voltage, and the circuit works normally. R5B is another connection to the main start resistor. (2) Frequency and minimum pulse width control When the normal operation of the circuit is established, the voltage Vfl generated by the electrical coupler U1 is higher at no load and light load, and is given to R through R9 (Vfl — R9 — Cl — Q2 G) Charging to the value of Vfl. When saturation is turned on again, C1 discharges through D1 (Q2-G - C1 - Q1), and the discharge current of C 1 forcibly pulls down the voltage of Q 2 - G, and the direct discharge ends. The discharge time determines the minimum pulse width of the Q1 turn-on. -> The bypass of the auxiliary light: 1 ! 1 » 1 to 12 M328720 When Q1 is turned off, Vfl charges the Cl again through R9, its The charging current raises the voltage of Q 2 - G, allowing Q 2 to continue to conduct, escaping the free oscillating voltage generated by the transformer and the feedback capacitor. This circuit suppresses the free oscillations caused by the transformer and the feedback capacitor and limits the minimum pulse width, allowing the circuit to operate stably in an energy-saving intermittent operation mode. At heavy loads, the voltage at V f 1 is low. When V f 1 is less than the tube voltage drop of D 1 + Q 1 , the circuit recovers from free oscillation controlled by the transformer and feedback capacitor. (3) Voltage-controlled current limiting When Q1 is saturated, the mains high voltage Η V + is applied to the primary winding Ν1 of the transformer. The transformer mutual inductance causes Ν2 to generate the voltage VI of Ν2Α +, Ν 2 Β -, VI: HV + = Ν2··Ν1. V 1 produces current I f 1 on R 8 ( (C 2 is only used for blocking), I f 1 = (HV + xN2 + Nl) + R8A, ie the higher HV + Ifl is, the Ifl is generated on R4 The voltage will also be higher; when the Q2 conduction voltage is constant (the temperature is constant), the voltage generated by the main circuit current on R1 (R 2 , R 3 voltage dividing point) will be limited, and the main circuit current will also be It will be smaller. With the transformer adjustment R 4 and R 8 A, the output power of the wide voltage range (in AC85--264V or DC120--370V) is basically constant, that is, the current is small when the voltage is high. R 8 B is another connection to this function. (4) In the output voltage abnormal protection circuit, Q3, R3, R11, and R12 form an electronic switch 13 M328720 circuit, the electric house signal (1) generated by the photoelectric surface combiner in, the secondary output voltage and load condition, when the output voltage is normal The electric dust on the Rll and R12 points is greater than (4) conduction ^ (3) Conducting R2, R3 dusting causes the main circuit current to increase in voltage, when the output voltage is abnormal (overload or short circuit makes the output electricity at the set value) ' Q 3 cut ± R 3 loses the voltage divider effect, and your current is pulled low, which reduces the output power (or current) and protects. (5) Line loss voltage compensation When we use SGND as the reference zero point, the voltage drop on the output power R17 is at the second rectified and filtered output 〇υτ—generating the voltage v V—the value is equal to the product voltage control of the output current and R17 The ground terminal (U 2 - 2 ) of the state U 2 is connected to the reference zero point SGND'. The voltage sampling pull-down resistor R16 is connected to V-, and the negative voltage of the output branch plus 'V- is numerically larger, so that the U2 is electrically tested. The voltage of the terminal (U 2 - 3 ) remains unchanged, the circuit must increase the voltage 'to compensate the current drop of the current output current on R 1 7 1 with the wire adjustment R 1 7 to compensate for the drop in the output current on the wire The effect of the output voltage after the wire is set at the rated negative circumference. , ντ, above, the humanized design of this case is quite equivalent to "water. Its specific improvement is existing, compared to the conventional technology. ', the advantages of the great break, the effect is indeed improved, easy to read The case has not been disclosed or disclosed in the domestic and foreign markets, and has been in compliance with the provisions of the Patent Law. L reflects the V f 1 t voltage, the voltage is low i R 1 to flow in the negative, potential The current-current voltage-parameter output J- 〇 voltage-loading model is obvious and non-literature 14 M328720 The detailed description above is a specific description of one of the possible implementations of this creation, but this embodiment is not intended to limit the scope of this creation. The equivalent implementation of this creative spirit should be included in the scope of the patent in this case. Example of the variant or change 15 M328720 [Simple diagram of the diagram] Figure 1 shows the block diagram of the creation. Figure 2 shows the creation The component architecture diagram. Figure 3 shows another component architecture diagram of the creation [main component symbol description] C1, C2, C3, C4 capacitor CL clamp D 1, D 2 diode RF 1 first rectification Filter circuit RF 2 Second rectification and filtering circuit N 1 Primary side coil N 2 One feedback coil N 3 Secondary side coil Q 1 Q 2 First power switching unit Second switching unit Q 3 Third switching unit LL Light carrier Wide controller K 1 input K 2 output R 1 1 voltage regulator R 1 , R 2 , R 3 , resistor R 4, R 5, R 6 , R 7 , R 8 , R 9 , R 1 1 , R 1 2, R 1 7 G gate CP 0 P comparator TBJT transistor 16 M328720 U 1 coupler U 2 voltage control device V f 1 voltage

17

Claims (1)

M328720 IX. Patent application scope: A safe, efficient, low power switching power supply circuit comprising: A first rectifying and filtering circuit (RF 1 ) is used for rectifying the input AC current into a sinusoidal type DC current by full-wave rectification and filtering out the noise, and the rectifying and filtering circuit (RF 1 ) is connected a primary side coil (N 1 ) of the transformer; a transformer comprising the primary side coil (N 1 ), a secondary side coil (N 3 ) coupled to the primary side coil (N 1 ), and a feedback coil (N 2 ) ) is coupled to the primary side coil (N 1 ); a clamper (CL ) is used to remove the ringing or glancing of the DC current to obtain a stable DC current, and the clamper position is further the primary side coil (N) 1) between the second end and the input end (K 1 ) of the first power switching unit (Q 1 ); a second rectifying and filtering circuit (RF 2 ) is connected to the secondary side coil of the transformer (N 3 ) for rectifying the input pulsed DC current into a constant DC current; a control circuit is configured to control the frequency of the pulsed DC current at the output end; the control circuit includes a first power switching unit (Q 1 ) system bit between the output end of the clamper and the ground terminal PGND; And a resistor (R 1 ) is connected in series between the first power switch unit (Q 1 ) and the ground; a start control circuit A bit is in the clamp (CL), and the feedback coil (N 3 ) The second end (N 1 B ) and the gate (G ) of the first power switching unit (Q 1 ) are used to actuate the first power switching unit (Q 1 ) at the start-up; the starting control Circuit A receives current from the first end of the clamp (CL) and current from the second end (N 1 B ) of the feedback coil (N 3 ), thereby providing sufficient current to the first The gate (G) of the power switch unit (Q 1 ) is used to control the opening of the road unit when the first power is turned on 18 ο 72 8 2 3 Μ Bit system; element) single 1 i Q § C open rate single work * θβ start at the same point and connect -\gc AJ 1 first &lt;3* The reason is to make the current flow of a four-pole electric circuit, the dynamic coil system, the line control, the wide-ranging pulse, the self-source, the current system, the power supply system, the current control system, the first control system; It is a different part, the end of the 5th source of the τ&gt; yuan (1 single U port \_\ the first electric} Ϊ 2 by C through C a source end, the outflow end of the electric power of the second four of the dawn The source of the source of electricity, the third power pulse 1 β --43 — the light of the slave · ' ) stream 2 ε RC take the L interceptor open control ratio is wide 3) system B 1 control (N wide end rr two load light The X)/1 (one of the second side of the N-terminal end line 1) The U is (the position y &gt; the L-coupled TL·C-optic device (LL) is used to adjust the output wide-wave The oscillating frequency, so that the wavelength of the output pulse wave can be extended so that the frequency of the first power switching unit is lowered, thereby saving power; and /|\ - KC element and the three terminals of the single terminal are turned off. Single-ended afl of the inter-element - the opening and closing rate} U1 - (the first, the coupling of the horse in the light-to-single-opening rate) The 9th power-resistance is outputted by the 3Q element single-ended terminal to the J3I (K2); when the input voltage is changed, the output current and voltage at the second end of the transformer can still be maintained at a fixed value; a voltage regulator (R Ε ) at the output end of the first end of the secondary side coil, wherein a resistor (R 7 ) is used to adjust the voltage of the output coil of the secondary side coil. 2. As claimed in claim 1 A safe and efficient low-power switching power supply circuit, wherein the third switching unit comprises an electronic switch (Q 3 ) and resistors (R11) and (R12); the resistor (R11) is connected to the second end of the optical coupler (U1); R12) Connect the ground terminal PGND; electronic 19 2Q Υ 2 3Μ. Resistor ^H This is controlled at the meta-end. Close the opening point and 3 Such as road source 1CN electricity and coil power 1 system control encirclement Fan Qili this special in the middle, the item off 0W 5 consumption (R power resistance low power efficiency high including all-inclusive road AAA 6 R resistance ^ 6- end two The first line 1 Q side C the second piece 1 yuan is closed at the opening rate system function} a 5A the second R the W and the electric B Hai 1 word N pole} between the gate 2 (the end of the resistance of the end of the second The first and the second round of the incoming line of the transfer of the element in the closed rate} work A - 0 \jy οβ A 0W 8 consumption (R power resistance low power one high including all-inclusive device control 1 wide The pulse-carrying capacity of the light-weight electric power of the special school} Please C2 Shen, C such as Lurong 4 source and electricity and resistance 1 and T-Η C / IV 5. If the patent application scope 1 is safe, efficient and low-power The switching power supply circuit, wherein the voltage regulator (RE) comprises a ΟP comparator (CP) and a BJT transistor; the reference end of the comparator is the second end, and the input end is the third end. The output end is the first At the end, when the voltage of the third terminal is higher than the second terminal, the output terminal outputs a signal to actuate the transistor (T). A safe, high-efficiency, low-power switching power supply circuit, wherein the input end of the optical coupler is a photodiode coupled to the output end. 7. A safe, high-efficiency, low-power switching power supply circuit as claimed in claim 1 One of the resistors (R7) is connected between the input end of the optocoupler and the grounding terminal. 8. A safe high-efficiency low-power switching power supply circuit according to claim 1, wherein a resistor (R 6 ) is connected to the second Rectification and filtering 20 The high voltage output of the M328720 circuit (RF2) and the 〇P comparator (between the C terminal; a resistor (r 5 ) is connected between the third terminal of the 〇P comparator and the output of the voltage regulator (RE); The functions of R 5 ) and (R 6 ) are used for 'dividing; a resistor (R 4 ) is connected to the second rectifying and wave, the high voltage output of the circuit (RF2) and the light are combined! §( U1) is between the wheel and the creep. 9 · A safe, high-efficiency, low-power switching power supply circuit as claimed in claim 1, wherein the resistor (R 1 ) is connected to the output of the first power switching unit (Q1) (K2) And the ground terminal PGND, the resistor is connected between the gate (G) of the second switching unit (Q 2 ) and the output terminal (K 2 ) of the first power switching unit (Q 1 ); the resistor (R 3 ) is connected to Between the input terminal (K 1 ) of the second switching unit (Q 2 ) and the input terminal (κ 1 ) of the third switching unit (Q 3 ), the capacitor (C 4 ) is connected to the feedback coil (N 2 ) Between the two terminals (n 2 B ) and the ground terminal PGND, the rectifier (D2) is connected between the input terminal (N2A) of the feedback coil (N2) and the ground terminal PGND. A safe high-efficiency low-power switching power supply circuit further includes a resistor (R7) and a capacitor (C3) connected in series with the gate (G) of the first power switching unit (Q 1 ) and the feedback coil (N2) Between the first end (N2B); a resistor (R8) and a capacitor (C 2 ) connected in series to the gate (g) of the second switching unit (Q 2 ) and the feedback coil (N2) One end (N1A); a resistor (R9) and a capacitor (C 1 ) are connected in series to the gate (g) of the second switching unit (Q 2 ) and the output end of the photocoupler (U 1 ) a resistor (R 2 ) and a resistor (R 3 ) are connected in series between the output terminal (K 2 ) of the first power switching unit (Q 1 ) and the input terminal of the third switching unit; 4) 21 connected in series with the second switching unit and the resistors (r 2 ) and (R 3 ) Between the M328720, the diode (D 1 ) is connected in series between the primary side coil (N 1 ) (N 1 B ) and the junction of the capacitor (C 1 ) and the resistor (R 9 ). 11. A safe, high-efficiency, low-power switching power supply circuit as claimed in claim 1, further comprising a resistor (R 5 B ) at a first end (N1A) and a second end of the primary side coil '(N1) Between (N1B). 12. The safe, high-efficiency, low-power switching power supply circuit of claim 1 includes a resistor (R 8 B ) at a first end (N 1 A ) of the primary side coil (N 1 ) and the first Between the gates (G) of the two switching units (Q 2 ). 13. The safe high-efficiency low-power switching power supply circuit of claim 1, wherein the first power switching unit (Q 1 ), the second switching unit (Q 2 ), and the third switching unit (Q 3 ) are C Μ 0 S transistor. 14. The safe high-efficiency low-power switching power supply circuit of claim 1, wherein the first power switching unit (Q 1 ), the second switching unit (Q 2 ), and the third switching unit (Q 3 ) are BJ Τ transistor. twenty two