TWI420790B - Controller for switching power supply - Google Patents

Description

Switching power supply controller

This case is related to the electric exchange power supply.

An exchange power supply generates an electrical output current to supply a load. One such power supply includes a transformer and a chopper. The chopper intercepts the primary current induced by the primary winding of the transformer. This induced output current flows through the secondary winding of the transformer to the load to power the load.

An switched power supply has an inductance that includes a coil. A current drawn by the carrier circuit of the chopper circuit from the coil, and an induced current is outputted by the power supply. The multifunction junction of the power supply has a multi-function voltage that is a function of the primary voltage that drives the coil. The first circuit suspends the chopping in response to a first induced voltage across the first threshold, the first induced voltage being a function of the multi-function voltage. The second circuit suspends the carrier in response to a second induced voltage across the second threshold, the second threshold being a function of the multi-function voltage.

The first circuit can be an overvoltage protection circuit that suspends the chopping in response to the overvoltage threshold of the first threshold exceeding the first threshold.

In another example, the first circuit can be an undervoltage protection circuit that suspends the chopping in response to the primary voltage drop being below an undervoltage threshold with respect to the first threshold. A shutdown circuit is configured to compensate for the multi-function voltage sufficient to cause the multi-function voltage to cross the first threshold to cause the first circuit to suspend the chop.

The second circuit can also be a burst mode circuit that suspends the chop when the output current of the power supply through the load exceeds the current threshold as a function of the multi-function voltage.

The apparatus shown in Figures 1A-1B has portions of the example of the elements cited in the scope of the patent application. The device is an exchange power supply 10. It includes a primary rectification/filtering circuit 11 that rectifies and filters the alternating current from the alternating current source 14. In order to obtain a DC supply voltage V _prim primary current I _prim, to drive the transformer primary winding W1 (or "coil") 20. The controller 26 intercepts the current I _prim induced via the primary winding W1. The resulting varying current I _prim induced via the primary winding W1 induces secondary and tertiary currents I _sec and I _tert to flow through the secondary and tertiary windings W2, W3 of the transformer. The induced secondary current I _sec supplies the load R _load and the tertiary current I _tert supplies the controller 26. The controller 26 has a multi-function junction 30. The voltage _Vmult supplied to this junction 30 affects the operating parameters of the six different functions of the controller 26. These functions are duty cycle control, primary current limit, over voltage protection, under voltage protection, burst mode, and external shutdown as explained below.

The primary rectification/filtering circuit 11 includes a full-wave rectifier including four diodes D1, D2, D3, and D4 to rectify the alternating current in full wave. The circuit 11 further includes a storage capacitor C1 for filtering and smoothing the primary voltage V _{prim of the} primary winding W1.

The secondary rectifying/filtering circuit 32 includes: a diode D5, an output V _{sec of the} secondary winding W2 of the half-wave rectifying transformer, to obtain an output voltage V _out applied to the load R _load ; and a storage capacitor C2 for filtering and Smooth V _out .

Similarly, the tertiary rectifying/filtering circuit 33 includes: a diode D6, an output V _{tert of the} tertiary winding W3 of the half-wave rectifying transformer to obtain a supply voltage V _cc of all components of the power supply controller 26; and a storage capacitor C3 to Filter and smooth V _cc .

The controller 26 has a ground rail Gnd1 that is isolated from the ground rail Gnd2 of the power supply output. For this reason, individual ground rails are labeled with different ground symbols 41, 42.

In this example, a portion of controller 26 is fabricated as an integrated circuit wafer with components sealed within a single package 51. The chip package 51 has pins for interposing components of the power supply 10 outside the package. These pins include a controller supply pin 53 tied to V _cc , a controller ground pin 54 connected to the controller ground Gnd1 , a drain pin 55 connected to the primary winding W1 , a multi-function pin 56 , and a The pin 57 is returned.

Multi-function pin 56 is tapped to a resistor divider 60 that extends from V _prim to Gnd1. The resistor divider 64 has an upper resistor R1 and a lower resistor R2. Therefore, the voltage V _mult at the multi-function pin is equal to V _prim R2/(R1+R2). This makes V _mult positively correlated (ie, its function, more specifically, proportional) to V _prim and can be adjusted by adjusting R1 and/or R2.

The feedback circuit 70 outputs a feedback voltage V _fb related to the load current I _load to the feedback pin 57. The feedback unit includes an optical coupler 62 having an LED transmission resistor R ₃ and a Zener diode Dz connected to Gnd1. As long as V _out sufficiently higher than the breakdown voltage of zener diode, the LED light intensity positively correlated V _out. Therefore, as the load current I _load decreases, V _out increases, which increases the light intensity of the LED. This increases the optocoupler phototransistor Tr1 62 is turned on while the feedback voltage V _fb raised to V _cc downwardly against the bias resistor R bias _4. Therefore, V _fb is positively related to the output voltage V _out supplied to the load R _load and inversely related to the load current I _load drawn for the _load .

In the transistor of this example, the field effect transistor (FET) has a ground pad S to which the source pad S is connected to the wafer, a pad junction 55 to which the drain pad D is connected to the wafer, and a gate connection. Face G. Pulling the gate G up, turning on the FET to discharge the primary current I _prim through the primary winding W1 to the controller ground Gnd1. This primary current I _prim is electrically driven - inductively opposite - in that it is generated by applying a potential difference between the coils W1. The FET gate G is pulled down to turn off the FET to stop the primary coil current I _prim flowing through the FET. This is in contrast to the secondary and tertiary currents I _sec and I _tert , which are induced to produce - as opposed to electrodynamic generation.

The gate G of the FET is connected to the output of the first AND gate A1 having four inputs 74. One of these inputs is driven by a secondary AND gate A2 having two inputs 75. The FET is turned on only when all inputs 74, 75 of AND gates A1 and A2 are high. Pulling any of the inputs 74, 75 of the AND gate low will turn off the FET. The AND gate inputs 74, 75 can be pulled low for any of the six circuits - specifically, the chopper circuit 81, the primary coil current limiting circuit 82, the overvoltage protection circuit 83, undervoltage protection as described below 84. The burst mode circuit 85 and the remote turn-off circuit 86.

A switch controller circuit 90 is configured to output a switch controller output 91 to switches S1, S2, and S3. If the FET is turned off by either or both of the chopper circuit 81 or the burst mode circuit 85, the switch control signal is high. This is done for the OR gate O1 with two OR inputs 94, 95. An OR input 94 is driven by the burst mode circuit 85 through the inverter Inv1. The other OR input 95 is driven by a third AND gate A3, and an AND input 96 of the AND gate A3 is coupled to the chopper circuit 81 via an inverter Inv2. The third AND gate A3 further has two other inputs 98 connected to the output of the overvoltage circuit 83 and the undervoltage circuit 84. Switches S1 and S2 are turned "on" by the switch controller output 91 going high. Conversely, switch controller output 91 goes high and switch S3 opens.

The chopper circuit 81 limits the maximum allowable duty cycle. The chopper circuit 81 includes a chopper comparator CR1 and a sawtooth generator Osc1 having a sawtooth output 104. Comparator CR1 has a positive input coupled to sawtooth output 104 and a negative input through switch S3 to multifunction pin 56. When the sawtooth wave 104 falls below the multi-function voltage _Vmult , the output of the comparator CR1 goes low, causing the output of the second AND gate A2 to go low, which causes the first AND gate A1 to pull the FET gate G low. This causes the FET to turn off.

Figure 2 shows the effect of V _mult on, the output signal 110 of the _chopper circuit comparator CR1. This shows that _Vmult is raised from the lower level 112 to the higher level 114, reducing the time 116 at which the comparator output 110 is high and increasing the time 118 to be low. This reduces the on time 112 of the FET and increases the off time 114. Therefore, the maximum value of the _chopper allows the duty cycle to be inversely proportional to V _mult . As shown in Figures 1A-1B, since _Vmult itself is related to _Vprim , R1, and R2, the duty cycle varies with _Vprim and can be adjusted by adjusting R1 and R2. However, the chopping frequency is equal to the frequency of the sawtooth wave and is not related to V _mult .

The cutoff system for the primary coil current I _{prim of the chopper} circuit 81 is effective for any AND gate input is a primary current limiting circuit 82, an overvoltage protection circuit 83, an undervoltage protection circuit 84, a burst mode circuit 85, and a remote end. Any one of the shutdown circuits 86 is pulled low to be suspended.

When the current I _prim flowing through the primary winding W1 exceeds the primary current limit, the primary current limiting circuit 82 in FIG. 1A-1B turns off the FET and remains FET off even after I _prim falls below the current threshold. Break until the next rise in the sawtooth wave. The current threshold is inversely related to the multi-function voltage V _mult .

The primary current limiting circuit 82 utilizes a square wave 120. The square wave 120 is generated by comparing the feedback voltage _Vfb with the sawtooth wave 104 in a manner similar to the manner in which the output 110 is generated by comparing _Vmult with the sawtooth wave 104. This square wave 120 is output to the Set input S of the flip-flop 122. The Reset pin R of the flip-flop 122 is connected to the output of the overcurrent comparator CR2. The positive input of the comparator is coupled to V _DD through a leading edge blanking circuit LEB that masks the inductive spike when the FET is turned off.

This causes circuit 81 to control the FET. In the absence of a fault condition, the on/off of the FET is controlled by the flip-flop output Q. V _{fb is} compared to sawtooth wave 104 to produce square wave 120. When square wave 120 is high, it indicates that the set input of the flip-flop is high, and the FET is turned on, and the primary current I _prim rises. When the current reaches the threshold, circuit 82 outputs a high signal to the flip-flop Reset input to turn off the FET.

Since the voltage between the FETs increases with increasing current, the voltage applied to the positive input of the overcurrent comparator CR2 is positively correlated, more specifically approximately proportional to the primary winding current I _prim . The negative output of comparator CR2 is coupled to the drain threshold voltage V _drnth , which is output by threshold voltage generator 130. The generator 130 includes a network of an op amplifier OP1, a voltage reference V _ref1 , and an interconnected resistor R5-R8 such that the drain threshold voltage V _drnth is equal to (V _ref1 /R5-V _mult /R7)×R6, wherein V _mult =V _prim R2/(R1+R2). As long as V _DD exceeds V _drnth , comparator CR2 drives the flip-flop Reset input R high, which drives the output of AND gate A2 low, which drives the output of AND gate A1 low, which turns off the FET.

This suspends the _chopping of the coil current I _prim as long as V _DD exceeds V _drnth . But V _DD is positively related to the primary coil current I _prim . And _V drnth negative correlation to V _mult, this equals V _{mult V prim R2 / (R1 + R2} ). Therefore, this circuit 82 suspends the chopping of the coil current I _prim after I _prim exceeds the primary current limit, which is negatively correlated with V _prim and can be adjusted by adjusting R1 and/or R2.

Typically, the intrinsic peak current limit is set to a constant for the internal circuitry in the rectifier. Once the drain current I _prim reaches the current limit threshold, the switching cycle should be terminated immediately. However, the fixed time delay ΔT is derived from the time until the threshold is reached until the FET is finally turned off. In this delay, the drain current I _prim continues to rise at a rate equal to the primary voltage V _prim divided by the inductance L _prim of the primary winding W1. Therefore, the actual current limit is the sum of the essential current limit threshold and the rise rate related component, which is the threshold current increase rate ΔI / Δt = V _prim / L _prim .

This is multiplied by a fixed time delay ΔT to obtain ΔT (ΔI/Δt). Therefore, the higher the DC input voltage, the higher the actual current limit rises to a higher level than the intrinsic current limit level of the low DC input voltage. This can result in a change in maximum output power P _o = L _prim I _p ² /2, where L _prim is the primary coil inductance and I _p is the peak current limit over the input line voltage range. V _mult can be used to adjust the fixed maximum output power over the entire input line voltage range. The true peak current limit is equal to (V _refl /R5-V _mult /R7)×R6+ΔTV _prim /L _prim , where V _mult =V _prim R2/(R1+R2). The higher the input voltage V _prim , the smaller (V _refl /R5-V _mult /R7)×R6 and the larger ΔTV _prim /L _prim . However, at the entire input line voltage, the true peak current limit (V _refl /R5-V _mult /R7) × R6 + ΔTV _prim /L _prim remains at a constant value.

The overvoltage protection circuit 83 turns off the FET when the primary voltage _Vprim that drives the primary winding W1 exceeds the overvoltage threshold. This circuit 83 includes an overvoltage comparator CR3 having a positive input coupled to the overvoltage threshold reference _Vref2 and a negative input transmissive switch S3 coupled to the multifunction voltage _Vmult .

Therefore, when V _mult exceeds V _ref2 , the output of the overvoltage comparator CR3 goes low, and the FET is turned off. This effectively suspends the chop as long as V _mult exceeds V _ref2 . Since V _{mult is} related to the function of V _prim , circuit 83 effectively suspends the chop when V _mult exceeds the effective overvoltage threshold associated with V _ref2 . More specifically, since V _mult =V _prim R2/(R1+R2), the effective overvoltage threshold is equal to V _ref2 (R1+R2)/R2. Therefore, the effective overvoltage threshold can be adjusted by adjusting R1 and/or R2. When switch S3 is turned off when OR gate O1 goes high, the negative input of comparator CR3 is separated from _Vmult , and the final voltage applied to the negative input of the comparator is maintained by voltage holding capacitor C4.

The undervoltage protection circuit 84 turns off the FET when the primary voltage _Vprim that drives the primary winding W1 is below the undervoltage threshold. The circuit 84 includes an undervoltage comparator CR4 having a negative input coupled to the undervoltage threshold _Vref3 and a positive input coupled to the multifunction voltage _Vmult via a third switch S3. Therefore, when V _{mult is} lower than V _ref3 , the output of the undervoltage comparator will go low to turn off the FET. This effectively suspends the chop as long as V _{mult is} lower than V _ref3 .

In the under-voltage protection circuit 84, since the line V _mult relates V _prim, so that when the effective temporary undervoltage limit V _mult below in relation to V _ref3, the suspension circuit 84 effectively cut-off wave. More specifically, since V _mult =V _prim R2/(R1+R2), the effective undervoltage threshold is equal to V _ref3 (R1+R2)/R2. Therefore, the effective undervoltage threshold can be adjusted by adjusting R1 and/or R2.

A feedback resistor (not shown) is applied between each positive input and its output by applying an input resistor (not shown) to each positive input and a feedback resistor (not shown) having a resistance value greater than the input resistance. The hysteresis can be applied to the outputs of the overvoltage and undervoltage comparators CR3, CR4. When the comparator output is high, this resistor configuration slightly boosts the comparator positive input, and when the comparator output is low to add hysteresis, the comparator positive input is slightly reduced.

When the output voltage V _out related to the V _fb exceeds the threshold voltage, the burst mode circuit 85 off FET. This occurs when the load R _load is attracted by the output current I _load drops below the threshold current. This increases the efficiency of the power supply 10 by increasing the length of time the FET is turned off and effectively suspending the secondary storage capacitor C2 without the need for a clipping in the supplemented period.

The burst mode circuit 85 includes a burst mode comparator CR5. This comparator CR5 has a negative input connected to _Vfb at the feedback pin 57. Further, a positive input is connected to V _mult and constant current source 140 through switches S1 and S2 (for example, IC chip PSSI2021SAY by NXP Semiconductors). Current source 140 conducts a fixed current I _ref from V _cc to the positive input of comparator CR5 and through resistors R2 through Gnd1. Therefore, when switches S1 and S2 are turned "OR gate high", the positive input voltage at the comparator is V _prim R2 / (R1 + R2) + I _ref R2, where I _ref R2 is equal to when the FET is off The fixed voltage at the time and when the FET is turned on, it is approximately zero. When the two switches S1 and S2 are turned off when the OR gate O1 goes low, the positive input of the comparator CR5 isolates V _mult and I _ref , and the final voltage applied to the comparator input is maintained by the voltage sustain capacitor C5.

When V _fb exceeds V _prim R2 / (R1 + R2) + I _ref R2 , the burst mode circuit 85 suspends the chop. This coincides with the output current I _load falling below the output current threshold. This is because V _fb is negatively related to I _load . The burst mode entry point is positively correlated with V _mult and I _ref R2 equal to V _prim R2/(R1+R2). Therefore, the output voltage threshold and output current threshold can be adjusted by adjusting R1 and/or R2.

The remote turn-off circuit 86 includes a transistor Tr2 that connects the multi-function pins 56 to Gnd1. This makes it possible to switch off the cutoff with switch S4, which can be outside the wafer housing 52, outside the controller 26 and outside of the power supply 10. In this example, switch S4 is a manually controlled mechanical switch, but can also be an electronically controlled switch. When the switch S4 is engaged, which is connected to the gate of the transistor Tr2 Vcc, which makes the discharge transistor Tr2 to V _mult Gnd1, which compensates for V _mult undervoltage below the threshold level V _ref3 of. This causes the undervoltage circuit 84 to turn off the FET. This effectively suspends the chopping as long as the external switch S4 is actuated. When the switch S4 is released, the bias resistor R9 pulls off the gate of the transistor Tr to turn off the transistor Tr and restart the chopping.

The overvoltage, undervoltage, and external shutdown circuits 83, 84, and 86 share a common characteristic that suspends the chopping based on a comparison of _Vmult with a reference value. This is different from the chopper, primary current limiting and burst mode circuits 81, 82 and 85, where _Vmult is the reference value and is used to compare with other induced voltages.

1A-1B illustrate an "isolated" type power supply, wherein the inductance is a transformer, wherein the primary winding W1 electrically isolates the secondary windings W2, W3. The controller 26 intercepts the current flowing through the primary coil W1 to generate an output current flowing through the secondary coils W2, W3 by the mutual inductance between the primary coil W1 and the secondary coils W2, W3.

Another type of power supply 210 is shown in Figures 3A-3B, wherein the components are labeled with the same component symbols as the corresponding components of Figures 1A-1B. This is "non-isolated", more specifically, a "boost" type power supply where the inductor contains only a single coil W4. In this type of power supply, the controller intercepts a primary current through coil W4 to induce an induced current flowing through the same coil W4 by self-inductance. The function of controller 26 for this non-isolated power supply 10' is the same as the "isolated" supply of Figures 1A-1B.

The illustrations used herein are intended to be illustrative of the invention, including the best mode, and are in The patentable scope of the invention is defined by the scope of the claims These other examples are within the scope of the present patent application, and may have elements that are different from those used in the scope of the patent application, or may use substantially equivalent elements in the scope of the patent application.

10. . . Switching power supply

11. . . Primary rectification filter circuit

14. . . Exchange source

20. . . transformer

26. . . Controller

30. . . Multi-functional joint

32. . . Secondary rectification/filter circuit

33. . . Triple rectification/filter circuit

41. . . Gnd1

42. . . Gnd2

51. . . Single package

52. . . Chip housing

53. . . Controller supply pin

54. . . Controller ground pin

55. . . Bungee pin

56. . . Multi-function pin

57. . . Feedback pin

60. . . Resistor divider

62. . . Optocoupler

70. . . Feedback circuit

74. . . Input

75. . . Input

81. . . Chopper circuit

82. . . Primary coil current limiting circuit

83. . . Overvoltage protection circuit

84. . . Undervoltage protection

85. . . Cluster mode circuit

86. . . Remote shutdown circuit

90. . . Switch controller circuit

91. . . Switch controller output

94. . . OR input

95. . . OR input

96. . . AND input

98. . . Input

104. . . Sawtooth output

110. . . output signal

112. . . Lower level

114. . . Higher level

120. . . Square wave

122. . . Positive and negative

130. . . Generator

140. . . Battery

210. . . Power Supplier

D1-D6. . . Dipole

C1-C5. . . Storage capacitor

W1. . . Primary winding

W2. . . Secondary winding

W3. . . Third winding

A1-A3. . . AND gate

CR1. . . Chop comparator

Osc1. . . Sawtooth generator

LEB. . . Leading edge masking circuit

CR2. . . Overcurrent comparator

CR3. . . Overvoltage comparator

CR4. . . Undervoltage comparator

CR5. . . Burst mode comparator

1A and 1B are two halves of an isolated power supply schematic

Figure 2 shows the waveform of the power supply.

3A and 3B are two halves of a schematic diagram of a non-isolated power supply.

10. . . Switching power supply

11. . . Primary rectification filter circuit

14. . . Exchange source

20. . . transformer

26. . . Controller

30. . . Multi-functional joint

32. . . Secondary rectification/filter circuit

33. . . Triple rectification/filter circuit

41. . . Gnd1

42. . . Gnd2

51. . . Single package

52. . . Chip housing

53. . . Controller supply pin

54. . . Controller ground pin

55. . . Bungee pin

56. . . Multi-function pin

57. . . Feedback pin

60. . . Resistor divider

62. . . Optocoupler

70. . . Feedback circuit

74. . . Input

75. . . Input

81. . . Chopper circuit

82. . . Primary coil current limiting circuit

83. . . Overvoltage protection circuit

84. . . Undervoltage protection

85. . . Cluster mode circuit

86. . . Remote shutdown circuit

90. . . Switch controller circuit

91. . . Switch controller output

94. . . OR input

95. . . OR input

96. . . AND input

98. . . Input

104. . . Sawtooth output

110. . . output signal

120. . . Square wave

122. . . Positive and negative

130. . . Generator

140. . . Battery

D1-D6. . . Dipole

C1-C5. . . Storage capacitor

W1. . . Primary winding

W2. . . Secondary winding

A1-A3. . . AND gate

CR1. . . Chop comparator

LEB. . . Leading edge masking circuit

CR2. . . Overcurrent comparator

CR3. . . Overvoltage comparator

CR4. . . Undervoltage comparator

CR5. . . Burst mode comparator

Claims (23)

An exchange power supply comprising: an inductor comprising a coil; a chopper circuit configured to intercept a primary current drawn from the coil for outputting an induced current of the inductor; a multi-functional junction having a multi-function voltage; Is a function of a primary voltage that drives the coil; the first circuit is configured to suspend the chopping in response to a first induced voltage across the first threshold, the first induced voltage being a function of the multi-function voltage; And a second circuit configured to suspend the chopping in response to a second induced voltage across the second threshold, the second threshold being a function of the multi-function voltage, wherein the second circuit is a burst mode circuit The burst mode circuit suspends the chopping when the output current of the power supply flowing through the load exceeds the current threshold as a function of the multi-function voltage. The switching power supply of claim 1, wherein the first circuit is an overvoltage protection circuit that suspends the chopping in response to the primary voltage exceeding an overvoltage threshold associated with the first threshold . The switching power supply of claim 1, wherein the first circuit is an undervoltage protection circuit that suspends the primary voltage drop in response to the undervoltage threshold associated with the first threshold. Cut off. The switching power supply of claim 3, further comprising a shutdown circuit configured to compensate for the multi-function voltage exceeding the first threshold to cause the first circuit to suspend the chop. The switching power supply of claim 4, wherein the shutdown circuit is controlled by a switch external to the power supply. The switching power supply device of claim 1, wherein the second circuit is a burst mode circuit, and the burst mode circuit suspends the cut when the output voltage of the power supply driving the load exceeds a voltage threshold Wave, the voltage threshold is a function of the second threshold, which is itself a function of the multi-function voltage. The switching power supply of claim 1, wherein the second circuit is a primary current limiting circuit, and the second induced voltage is a function of the primary current drawn through the coil, whereby the second circuit responds The cutoff is suspended when the primary current exceeds a primary current threshold associated with the multi-function voltage. The switching power supply of claim 7, wherein when the chop is suspended, the second circuit continues to suspend the chopping even after the primary current drops below the primary current threshold. Until the next clock cycle begins (onset). The switching power supply of claim 7, wherein the second induced voltage is a primary voltage derived from a junction between the chopper circuit and the coil. The switching power supply of claim 7, wherein the primary current threshold is negatively related to the multi-function voltage, the multi-function voltage system itself being positively correlated between the chopper circuit and the coil A voltage at the junction. An exchange power supply as described in claim 1 of the patent scope, The chopper circuit is configured to chop the primary current having a duty cycle as a function of the multi-function voltage. The switching power supply device of claim 11, wherein when the primary current is chopped by repeatedly turning on and blocking the primary current, the chopper circuit outputs and the multi-function voltage according to the waveform The waveform of the function is compared to determine when to turn on and when to block the primary current. The switching power supply of claim 1, wherein the multi-function voltage is tapped by a resistor divider extending from a higher voltage to a lower voltage. The switching power supply according to claim 13, wherein the higher voltage is a primary voltage for supplying the coil, and the lower voltage is a ground rail, and the chopper circuit discharges the primary current to the ground rail. . The switching power supply device of claim 1, further comprising a plurality of switches and a switch control circuit configured together to be in a first state to connect the multi-function junction to the first circuit, and Isolating the multi-function junction from the second circuit; and configuring together as a second state to connect the multi-function junction to the second circuit, and the multi-function junction and the first circuit Isolated. The switching power supply of claim 15, wherein the first circuit is an overvoltage protection circuit, the second circuit is a burst mode circuit, and the second state is based on the burst mode circuit. This primary current is interrupted. An exchange power supply as described in claim 1 of the patent scope, The inductor is a transformer, the coil is a primary coil of the transformer, and the induced current is output through a secondary coil of the transformer by mutual inductance between the primary and secondary coils. The switching power supply of claim 1, wherein the induced current is outputted by the coil itself by self-inductance. An exchange power supply, further comprising: an inductor including a coil; a chopper circuit configured to intercept a primary current drawn through the coil in a duty cycle, the duty cycle being related to the one of driving the coil a multi-function voltage of a voltage for the inductor to output an induced current; and a first circuit other than the chopper circuit configured to suspend the chopping in response to the first induced voltage crossing the first threshold One or both of the first induced voltage and the first threshold are functions of the multi-function voltage, wherein the second circuit is a burst mode circuit, and when the output current of the power supply flowing through the load exceeds The burst mode circuit suspends the cutoff when the current of the function voltage is thresholded. The switching power supply of claim 19, wherein the first induced voltage is a function of the multi-function voltage. The switching power supply of claim 19, wherein the first sensing threshold is a function of the multi-function voltage. The switching power supply device of claim 19, wherein when the primary current is chopped by repeatedly turning on and blocking the primary current, the chopper circuit outputs and the multi-function voltage according to the waveform. function The comparison of the thresholds, and decide when to turn on and when to block the primary current. A controller for exchanging a power supply, the power supply having an output junction configured to output an output current to the load and further having an inductance including a coil for extracting the change from the coil The current sense generates the output current, the controller comprises: a chopper circuit configured to intercept the primary current; the multi-function junction has a multi-function voltage, which is a function of a primary voltage for driving the coil, For the chopper circuit to intercept a primary current having a duty cycle, the duty cycle being a function of the multi-function voltage; the overvoltage protection circuit configured to suspend the intercept in response to the multi-function voltage exceeding an overvoltage threshold Wave; an undervoltage protection circuit configured to suspend the chopping in response to the multifunction voltage drop being below an undervoltage threshold; shutting down the circuit, configured to drop the multifunction voltage below the undervoltage threshold So that the undervoltage protection circuit suspends the chopping; the burst mode circuit is configured to suspend the chopping when the output current exceeds a current threshold that is a function of the multifunction voltage; a primary current limiting circuit suspending the chopping in response to the primary current exceeding a primary current threshold, the primary current threshold being related to the multi-function voltage, and even after the primary current drops below the primary current threshold , the intercept is still paused until the next clock cycle begins.