CN102237789A - Control method and controller - Google Patents

Abstract

A method for controlling output energy of a power supply and a related controller. The power supply includes a switch and an inductor. When the switch is turned on, the stored energy of the inductive component is increased. The inductive current flowing through the inductive component is detected to generate a current detection signal. A limit signal is provided to substantially limit a peak value of the inductor current. And updating the limit signal according to the peak value and an inductor average current corresponding to the current detection signal, so that the peak value and the inductor average current approach a preset relation along with a switching period. The predetermined relationship makes the output energy outputted by the power supply in a switching period approximately a constant value.

Description

Control method and controller

technical field

The present invention relates to a switch mode power supply (Switched-mode power supply, SMPS), more specifically, relates to a kind of can provide over current protection (over current protection, OCP or overload protection, OVP) switching power supply.

Background technique

As a power management device, a power supply is used to convert power to provide power to electronic devices or components. Sometimes the power management device is implemented with a switching power supply, because its energy conversion efficiency is good, and the required inductance components are relatively small, which is suitable for most modern electronic devices or components. Switching power supplies need to have many protection mechanisms to prevent themselves or the outside world from being damaged under incorrect or inappropriate conditions. Some existing protections include over voltage protection (OVP), over temperature protection (OTP), OCP, OLP, etc. Among them, the overcurrent protection generally means that the maximum output current is limited; the overload protection generally means that the maximum output power is limited.

Figure 1 shows a booster circuit (booster) with overcurrent/load protection. The booster circuit (booster) 10 is only used as an example of over-current/load protection, and the over-current/load protection can also be applied to SMPS of other architectures.

A switch 14 in a booster circuit (booster) 10 controls the current flowing through the inductor 12 . When the gate control signal GATE turns on the switch 14, the inductor 12 increases the energy stored therein. When the gate control signal GATE turns off the switch 14 , the energy stored in the inductor 12 is released to the load through the diode 16 to charge the load capacitor 20 . The detection resistor 22 detects the inductor current flowing through the inductor 12 when the switch 14 is turned on. The voltage value of the detection signal V _CS- on the terminal CS will reflect the magnitude of the inductor current, and the controller 18 will generate the gate signal GATE accordingly.

FIG. 2 shows an existing controller 18a, which can be applied to FIG. 1 . When the controller 18 a turns on the switch 14 in FIG. 1 , the voltage value of the detection signal V _CS- increases with the turn-on time. The comparator 36 makes the peak value of the detection signal V _CS approximately not larger than the limit signal V _CS-LIMIT . Once the detection signal V _CS- is higher than the limit signal V _CS-LIMIT , the comparator 36 will make the gate controller 34 close the switch 14 . This achieves overcurrent/load protection. However, due to the signal propagation delay, the peak value of the detection signal V _CS will be slightly larger than the limit signal V _CS-LIMIT , and this difference will increase as the voltage of the input power V- _IN increases. If the limit signal V _CS-LIMIT is a fixed value, it means that the over-current/load protection provided in Figure 2, the maximum output current or maximum output power limited by it will follow the voltage of the input power supply V- _IN And change. The OCP/OLP achieved by such a result is often difficult to meet the system specifications.

Moreover, even if the peak value of the detection signal V _CS is accurately locked at a certain value, the maximum output current/power defined by OCP/OLP will often follow the inductor 12 operating in a continuous conduction mode (continuous conduction mode, CCM) or discontinuous conduction mode (discontinuous conduction mode, DCM).

Therefore, the circuit for overcurrent/load protection needs to be specially designed so that the maximum output current/power when triggered is about a certain value and does not change with the operation mode or input power voltage.

Contents of the invention

An embodiment of the present invention provides a control method suitable for a power supply, which includes a switch and an inductance component. When the switch is turned on, the energy storage of the inductance component increases. A current detection signal is generated by detecting the inductor current flowing through the inductor component. A peak value of the current detection signal is compared with a limit signal to generate an adjustment value. Comparing the current detection signal with the limit signal, when the current detection signal, the limit signal and the adjustment value are about a specific relationship, close the switch so that the next peak value of the current detection signal is approximately equal to the limit signal , roughly eliminating the effect of signal delay.

The embodiment of the present invention also provides a method for controlling the output energy of a power supply. The power supply includes a switch and an inductor. When the switch is turned on, the energy storage of the inductance component increases. The inductor current flowing through the inductor component is detected to generate a current detection signal. A limit signal is provided for roughly limiting a peak value of the inductor current. The limit signal is updated according to the peak value and an inductor average current corresponding to the current detection signal, so that the peak value and the inductor average current are close to a preset relationship with the switching cycle. The preset relationship makes the output energy output by the power supply in a switching cycle approximately a certain value.

An embodiment of the present invention also provides a controller suitable for a power supply, which includes a switch and an inductance component. The controller includes a peak limiter and a regulator. The peak limiter receives a limit signal and a current detection signal, and is used for roughly limiting a peak value of the inductor current flowing through the inductor component. The current detection signal corresponds to the inductor current. The adjuster is used for updating the limit signal, so that the peak value and an inductor average current corresponding to the current detection signal approach a preset relationship with each other as the switching cycle progresses. The predetermined relationship makes the power transmitted by the inductance component in a switching period approximately a certain value.

Description of drawings

Figure 1 shows a boost circuit with overcurrent/load protection.

Figure 2 shows an existing controller.

The solid line in Figure 3 shows the relationship between V _CS-PEAK and V _CS-AVG .

Figure 4 shows a controller implemented in accordance with the present invention.

Figure 5A and Figure 5B show two kinds of signal delay compensators.

Figure 6 shows the average current comparator, updater, and clamper.

FIG. 7 shows the relationship between the limit signal V _CS-LIMIT and the expected inductor average current signal V _CS-AVG-EXP , and its simplified results.

Figure 8 shows a converter.

Fig. 9 shows another controller implemented according to the present invention.

Figure 10 illustrates a peak detector.

Figure 11 shows a simplified relationship between V _CS-PEAK and V _CS-AVG .

FIG. 12 is a converter implementing the relationship of FIG. 11. FIG.

Description of reference symbols

10 Boost circuit

12 Inductance

14 switch

16 Diodes

18, 18a, 18b, 18c controller

20 Load Capacitance

22 Sense resistor

34 Door control controller

32 Other signal processors

36 Comparator

51, 51a, 51b Signal delay compensator

52, 52a Average current comparator

54, 54a Updater

56, 56a, 57, 57a converter

59, 59a clamper

61, 61a Peak detector

362, 364 Current Source

366 Capacitance

502, 504 Comparator

506, 507 Current Mirror

508 Capacitance

CS Endpoint

GATE Gating signal

I _con constant current

I _R , I _L current source

L straight line

V-- _bias capacitor voltage

V _BIAS1 voltage drop

V _CS- detection signal

V _CS-AVG-EXP expected inductor average current signal

V _CS-AVG-REAL average current

V _CS-HIGHER Higher current detection signal

V _CS-LIMIT limit signal

V _{CS-LIMIT-BOTTOM} lower limit

V _{CS-LIMIT-LOWER} lower limit signal

V _CS-LIMIT-TOP upper limit

V _CS-PEAK peak value

V- _IN input power supply

_V output voltage

R _B , R _BIAS1 , R ₁ , R ₂ resistors

Detailed ways

In this specification, the same symbols are used to refer to the same or similar devices/components, and those skilled in the art can implement them with the same or similar methods/structures based on the disclosure/teaching of the present invention, so no further restate.

An embodiment of the present invention provides an SMPS, the highest output current/power when the OCP/OLP is triggered does not vary substantially with the input voltage and operating mode.

Please refer to the booster circuit (booster) 10 in FIG. 1 . The output power P delivered by the inductor 12 to the load capacitor 20 can be expressed by the following formula (1):

P＝1/2*L*(I _CS-PEAK ² -I _CS-INI ² )*f _SW ----(1)

Among them, L is the inductance value _of the inductor 12; I _CS-PEAK is the peak value of the inductor current flowing through the inductor 12, which is also the peak value of the current flowing through the switch 14; The initial value of the inductor current at 12 is also the initial value of the current flowing through the switch 14 ; and, f _SW is the switching frequency of the switch 14 . In DCM operation, I _CS-INI will be 0; in DCM operation, I _CS-INI will be greater than 0.

When the OLP is triggered, because the highest output power P _OLP needs to be a certain value, it means that the right half of the formula (1) needs to be a constant value. When the OCP is triggered, it is assumed that the output power supply V _OUT is still maintained at a constant voltage, and the maximum output current C _OCP needs to be a certain value, so the right half of the formula (1) still needs to be a constant value.

Assuming that the switching frequency f _SW of the booster circuit (booster) 10 is constant, when the OLP/OCP is triggered, the following formula (2) can be deduced from formula (1).

I _CS-PEAK ² -I _CS-INI ² ＝4*I _CS-AVG *(I _CS-PEAK -I _CS-AVG )＝K ₁ ---(2)

Wherein, I _CS-AVG is 1/2*( _ICS-PEAK + _ICS-INI ), which can also be regarded as the average current value of the inductor flowing through the switch 14 when the switch 14 is turned on; and, K ₁ is a constant .

Formula (2) can be sorted into the following formula (3).

V _CS-PEAK ＝V _CS-AVG +K/V _CS-AVG ---(3)

Wherein, K is a constant; V _CS-PEAK and V _CS-AVG are the voltage values when the detection signal V _CS corresponds to the inductor current I _CS-PEAK and I _CS-AVG , respectively. In other words, when OCP/OLP occurs, as long as V _CS-PEAK and V _CS-AVG meet the conditions of formula (3), the maximum current/power defined by OCP/OLP will be approximately a constant value.

The solid line in Figure 3 shows the relationship between V _CS-PEAK and V _CS-AVG in formula (3); the two dashed lines show V _CS-PEAK = V _CS-AVG and V _CS-PEAK = K/V respectively _CS-AVG . For example, if the booster circuit (booster) 10 is designed to operate in DCM, and V _CS-PEAK is 0.9V, OCP/OLP should be triggered, which means that V _CS-AVG is 0.45V, and K should be 0.45 *0.45V ² . The curve in Figure 3, that is, the relationship between V _CS-PEAK and V _CS-AVG when OCP/OLP is triggered, can be clearly defined.

Therefore, as long as you know the V _CS-PEAK and V _CS-AVG of the current switching cycle, and substitute them into the formula (3) for calculation, you can know that the current output current/power is greater than the maximum current/power defined by OCP/OLP is still small, and then update the limit signal V _CS-LIMIT . In this way, after several switching cycles, the output current/power in each switching cycle will be approximately a fixed value, which is the highest current/power defined by OCP/OLP.

Fig. 4 shows a controller 18b implemented according to the present invention, which can be applied to the boost circuit 10 in Fig. 1, and can also be applied to other types of SMPS. The gate controller 34 receives signals from other signal processors 32 and the signal delay compensator 51 to drive the switch 14 . The signal delay compensator 51 can roughly compensate the influence of signal delay, so that the peak value V _CS-PEAK of the detection signal V _CS is almost completely equal to the limit signal V _CS-LIMIT . Therefore, the limit signal V _CS-LIMIT can be regarded as the peak value V _CS-PEAK of the detection signal V _CS in the current switching cycle. The converter 56 is roughly based on a relationship between V _CS-PEAK and V _CS-AVG (which can be simplified from the solid line in FIG. 3 ), and takes the limit signal V _CS-LIMIT as input, and then outputs the expected average current signal of the inductor V _CS-AVG-EXP . The average current comparator 52 compares the average current V _CS-AVG-REAL corresponding to the detection signal V _CS (when the switch 14 is turned on) with the expected inductor average current signal V _CS-AVG-EXP . The output of the average current comparator 52 causes the updater 54 to update the limit signal V _CS-LIMIT . A clamp 59 is used to limit the highest value and the lowest value of the limit signal V _CS-LIMIT .

It can be found from FIG. 4 that the converter 56 , the average current comparator 52 , and the updater 54 roughly constitute a close loop. During this cycle, after several switching cycles, the relationship between V _CS-PEAK and V _CS-AVG will approach the solid line or the relative line segment in Figure 3, so that the highest value defined by OCP/OLP The current/power becomes a fixed value.

The signal delay compensator 51, the converter 56, the average current comparator 52, and the updater 54 can be regarded as an adjuster, which updates the limit signal V _CS-LIMIT so that the peak value V _CS-PEAK and the detection signal V _CS are The corresponding average currents V _CS-AVG-REAL approach the preset relationship in FIG. 3 as the switching cycle progresses.

For example, when the expected inductor average current signal V _CS-AVG-EXP is lower than the average current V _CS-AVG-REAL , the limit signal V _CS-LIMIT is increased during the next switching cycle. Therefore, in the next switching cycle, the average inductor current signal V _CS-AVG-EXP is expected to approach the average current V _CS-AVG-REAL .

FIG. 5A and FIG. 5B show two kinds of signal delay compensators 51a and 51b, each of which is applicable to FIG. 4 . In FIG. 5A , the signal delay compensator 51 a mainly includes comparators 502 and 504 , a capacitor 508 , current sources I _R and _IL , and resistors _RB and R _BIAS1 . If the peak value V _CS-PEAK of the detection signal V _CS is greater than the limit signal V _CS-LIMIT , the comparator 504 causes the current source I _R to charge the capacitor 508 to pull up the capacitor voltage V-- _bias . On the contrary, if the peak value V _CS-PEAK of the detection signal V _CS is always smaller than the limit signal V _CS-LIMIT , the comparator 504 will discharge the current source _IL to the capacitor 508 and pull down the capacitor voltage V-- _bias . The current of the current source _IL must be much smaller than the current of the current source I _R. The capacitor voltage V-- _bias is converted by the resistor and the current mirror 506 and 507, and a voltage drop V _BIAS1 will be generated on the resistor R _BIAS1 , thereby providing a lower limit signal V _CS-LIMIT- lower than the limit signal V _{CS-LIMIT- LOWER} . When the detection signal V _CS is greater than the lower limit signal V _{CS-LIMIT-LOWER} , the signal from the comparator 502 turns off the switch 14 . It can be seen from the deduction that after several switching cycles, the capacitor voltage V-- _bias will be approximately maintained at a constant value, so that the comparator 502 will send a signal earlier when the detection signal V _CS is equal to the lower limit signal V _{CS-LIMIT-LOWER} , Finally, the peak value V _CS-PEAK of the detection signal V _CS is equal to the limit signal V _CS-LIMIT . The current source I _L may be omitted, and the capacitor 508 may use its own leakage or junction leakage to make the capacitor voltage V-- _bias drop very slowly.

The signal delay compensator 51b in FIG. 5B can also make the peak value V _CS-PEAK of the detection signal V _CS equal to the limit signal V _CS-LIMIT . Unlike the lower limit signal V _{CS-LIMIT-LOWER} in FIG. 5A , the higher current detection signal V _CS-HIGHER is generated in FIG. 5B . Other circuit structures or operating principles in FIG. 5B are the same or similar to those in FIG. 5A , which can be deduced from FIG. 5A .

FIG. 6 shows average current comparator 52a, updater 54a, and clamper 59a, applicable to FIG. 4 .

From the variation of the output voltage V _M of the average current comparator 52a, it can be seen that the average current V _CS-AVG-REAL (average of the detection signal V _CS ) is greater or smaller than the expected inductor average current signal V _CS-AVG-EXP . When the detection signal V _CS is greater than the expected inductor average current signal V _CS-AVG-EXP , the current source 362 provides a constant current I _con to charge the capacitor 366; when the detection signal V _CS is smaller than the expected inductor average current signal V _CS-AVG-EXP , the current source 364 provides a constant current I _con to discharge the capacitor 366 . Because the detection signal V _CS increases linearly, when the gate control signal GATE turns on the switch 14, if the average current V _CS-AVG-REAL is greater than the expected inductor average current signal V _CS-AVG-EXP , the output voltage V _M will be rise. On the contrary, if the average current V _CS-AVG-REAL is relatively small, the output voltage V _M will drop.

When the switch 14 is turned off by the gating signal GATE, the updater 54a updates the limit signal V _CS-LIMIT according to the output voltage V _M . To avoid excessively high or low voltage, the clamp 59a uses two diodes to make the voltage of the limit signal V _CS-LIMIT between the upper limit V _CS-LIMIT-TOP and the lower limit V _{CS-LIMIT-BOTTOM} .

The left half of Figure 7 shows the relationship between the limit signal V _CS-LIMIT and the expected inductor average current signal V _CS-AVG-EXP when OCP/OLP is triggered, that is, the relationship between V _CS-PEAK and V _CS-AVG in Figure 3 relation; the right half shows its simplified result. Because the relationship between V _CS-PEAK and V _CS-AVG in Figure 3 is a curve, it may be more complicated when it is implemented with a circuit, so one or more line segments (linesegment) can be used to segment the linear curve (piecewise linear curve) approximate representation. One of the simplest ways is to use a straight line to represent the upper half of the curve, as shown by the straight line L in the right half of FIG. 7 . As for the lower half of the curve, since it does not happen in practice, it can be omitted and not implemented. The straight line L in the right half of Fig. 7 can be implemented with various circuits. For example, as shown in FIG. 8 , a simple operational amplifier and resistors R ₁ and R ₂ can realize the straight line L as a converter 56 a for the controller 18 b in FIG. 4 .

FIG. 9 shows another controller 18c implemented according to the present invention, which can be applied to the boost circuit 10 in FIG. 1, and can also be applied to other types of SMPS.

The signal delay compensator 51 in FIG. 4 is not shown in FIG. 9, but is replaced by a comparator 36, so that the peak value V _CS-PEAK of the detection signal V _CS is not greater than the limit signal V _CS-LIMIT . As mentioned before, in such an architecture, due to the signal delay, the peak value V _CS-PEAK is very close to but slightly larger than the limit signal V _CS-LIMIT . In FIG. 9, a peak detector 61 is used to detect the peak value V _CS-PEAK . The converter 57 is roughly based on a relationship between V _CS-PEAK and V _CS-AVG (which can be simplified from the solid line in FIG. 3 ), and takes the peak value of V _CS-PEAK as an input, and then outputs an expected inductor average current signal V _CS-AVG-EXP .

A closed loop is also implied from FIG. 9, consisting roughly of peak detector 61, converter 57, average current comparator 52, updater 54, comparator 36, gating controller 34, switch 14, and sense resistor 22. constituted. During this cycle, after several switching cycles, the relationship between V _CS-PEAK and V _CS-AVG will approach the solid line or the relative line segment in Figure 3, so that the highest value defined by OCP/OLP The current/power becomes a fixed value.

The peak detector 61, the converter 57, the average current comparator 52, and the updater 54 can be regarded as another regulator, which updates the limit signal V _CS-LIMIT so that the peak value V _CS-PEAK and the detection signal V _CS are The corresponding average currents V _CS-AVG-REAL approach the preset relationship in FIG. 3 as the switching cycle progresses.

FIG. 10 exemplifies a peak detector 61a, where the capacitor can record the peak value V _CS-PEAK . Figure 11 shows a simplified relationship between V _CS-PEAK and V _CS-AVG , which can make the maximum current/power defined by OCP/OLP approximately a fixed value. FIG. 12 is a converter 57a for realizing the relationship of FIG. 11, which can be applied in FIG. 9. FIG.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (10)

1. a control method is applicable to a power supply unit, and it includes a switch and an Inductive component, and this method includes:

Open this switch, so that this Inductive component increases energy storage;

The flow through inductive current of this Inductive component of detection is to produce a current detection signal;

A peak value of this current detection signal relatively and one limits signal, to produce an adjusted value; And

Relatively this current detection signal and this limit signal, when this current detection signal, this qualification signal and this adjusted value are approximately a particular kind of relationship, close this switch, so that next peak value of this current detection signal, approximate this qualification signal greatly, roughly the erasure signal delayed impact.

2. control method as claimed in claim 1 includes:

When this peak value of this current detection signal limits signal greater than this, one electric capacity is charged with one first electric current;

When this peak value of this current detection signal limits signal less than this, to this capacitor discharge, wherein this second electric current is less than this first electric current with one second electric current; And

With the voltage of this electric capacity, convert this adjusted value to.

3. control method as claimed in claim 1 includes:

Should limit signal and reduce this adjusted value, to produce low signal that limits; And

Relatively this current detection signal with should lowly limit signal, when this current detection signal is low when limiting signal more than or equal to this, close this switch.

4. control method as claimed in claim 1 includes:

This current detection signal has been increased this adjusted value, to produce a high current detection signal; And

Relatively this high current detection signal and this qualification signal when this high current detection signal limits signal more than or equal to this, are closed this switch.

5. the output control of energy method of a power supply unit, this power supply unit includes a switch and an Inductive component, and this method includes:

Open this switch, so that this Inductive component increases energy storage;

The flow through inductive current of this Inductive component of detection is to produce a current detection signal;

Provide one to limit signal, in order to roughly to limit a peak value of this inductive current; And

According to this peak value and the pairing inductance average current of this current detection signal, upgrade this qualification signal, so that this peak value and this inductance average current are along with switch periods, and near a preset relation, this preset relation is exported this power supply unit in a switch periods this output energy is approximately certain value.

6. control method as claimed in claim 5 includes:

Make this peak value of this current detection signal, equal this qualification signal; And

Limit signal according to this current detection signal and this, upgrade this qualification signal.

7. control method as claimed in claim 6 comprises:

Limit signal according to this, produce an expection inductance average current signal; And

According to this expection inductance average current signal and this current detection signal, upgrade this qualification signal.

8. the output control of energy method of a power supply unit includes:

This power supply unit includes a switch and an Inductive component, and this method includes:

Open this switch, so that this Inductive component increases energy storage;

The flow through inductive current of this Inductive component of detection is to produce a current detection signal;

Provide one to limit signal, in order to roughly to limit a peak value of this inductive current; And

One closed circulation is provided, controls this qualification signal, make the pairing inductance average current of this peak value and this current detection signal, approach a preset relation each other, the power that this preset relation makes this Inductive component transmit in a switch periods is approximately certain value.

9. a controller is applicable to a power supply unit, and it includes a switch and an Inductive component, and this controller includes;

One peak value delimiter receives one and limits a signal and a current detection signal, and in order to the flow through peak value of inductive current of this Inductive component of restriction roughly, wherein this current detection signal is to should inductive current; And

One adjuster is in order to upgrade this qualification signal, so that the pairing inductance average current of this peak value and this current detection signal, carrying out along with switch periods, approach a preset relation each other, the power that this preset relation makes this Inductive component transmit in a switch periods is approximately certain value.

10. controller as claimed in claim 9, wherein, this peak value delimiter includes a comparator, it has two inputs, receives this qualification signal and this current detection signal respectively, and, this adjuster includes a peak detector, notes down this peak value of this inductive current.

Images