Improved hiiccup mode short-circuit protection circuit for BOOT converter

Abstract

The invention discloses an improved hiiccup mode short-circuit protection circuit for a BOOT converter, and relates to the technical field of switching power supplies, and the improved hiiccup mode short-circuit protection circuit is composed of a POWERSEL (power supply selection) module, a one-shot (single state) circuit, a PRECHARGE (pre-charging) module, a 1: 16 divider (sixteen frequency divider), a comp (comparator), a capacitor C1 and a discharge tube M1. According to the improved hiiccup mode short-circuit protection circuit for the BOOT converter, the pre-charging module is adopted to charge the load capacitor during each detection, the inductive current is limited, if a short circuit is removed, the load capacitor can be smoothly charged, and if the short circuit is not removed, next detection is waited, so that the problem of large current during detection is solved, overboot during restarting is eliminated, and the detection efficiency is improved. In the short-circuit period, a sleep mode and a detection mode are introduced, the short-circuit state is intermittently tested, at the moment, the converter works in a low-frequency clock, most modules are closed, only a few devices work, and therefore power consumption in the short-circuit period can be greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of switch power supplies, in particular to an improved hiccup mode short-circuit protection circuit for a BOOT converter. Background Art

[0002] Short-circuit protection mainly detects the short circuit of the circuit by detecting the abnormality of the output current or output voltage, thereby shutting down the relevant modules to achieve short-circuit protection. The pulse-by-pulse current limiting function of the switching power converter in the peak current mode cannot provide effective output short-circuit protection. In order to achieve safe operation of the system, when the controller detects an output short circuit, it shuts down the main switch tube, the system stops working for a period of time, and then the system restarts.

[0003] In the way of detecting current, short-circuit protection is performed by current limiting. This limiting technology shuts down the entire circuit system by detecting large current when a short circuit occurs, which has a certain protective effect on the system. However, the output current during the short circuit is still maintained at a large value, which leads to a large power consumption. Subsequently, a method was proposed to maintain a low output current and reduce the power consumption during the short circuit to a lower level, but it ignores the voltage overshoot caused by short circuit recovery. In addition, there is a short-circuit protection technology based on the hiccup mode, which intermittently tests whether the short circuit state is removed. When the output short circuit is eliminated, the system restarts; when the output short circuit still exists, the circuit continues to be shut down. In this mode, when the short circuit state is removed, the circuit will restart. If there is no voltage overshoot at the initial power-on startup, there will be no voltage overshoot at the restart, and it retains the necessary pre-charge and soft start process. Therefore, this effectively reduces the voltage overshoot after the short circuit recovery. However, the power consumption of the converter during the short circuit is still a problem. As Figure 1 As shown, there are two main types of hiccup mode short-circuit protection commonly used at present. One is to detect the feedback voltage signal V FB , one is to detect the error amplifier output signal V EA When it is lower than the reference voltage, it starts to enter the hiccup short-circuit protection mode.

[0004] Traditional short-circuit technology generally has three problems: large current at the moment of short circuit, high power consumption during short circuit, and overshoot during restart. Figure 2 shown.

[0005] There is a delay t from when a short circuit occurs to when the control signal turns off the power tube. delay , mainly including the generation time t1 and action time t2 of the identification signal, expressed as ; t1 generally refers to the comparator flip time, and t2 generally refers to the time it takes for the identification signal to pass through the DRIVER.delay In time, V OUT The power tube remains in switch mode and the converter continues to switch between T ON and T OFF Mode switching, at this time the inductor current keeps rising, and the rising slope k can be expressed as:

[0006] In t delay After time, the inductor current can be expressed as follows:

[0007] At this time, a large current is generated at the moment when a short circuit occurs.

[0008] The power consumption problem during a short circuit is that the circuit needs to open the circuit in the process of detecting whether the short circuit has been removed, which will cause a large inductor current and increase power consumption. At the same time, the overshoot during restart is also caused by the energy stored in the inductor during the detection period being transferred to the load capacitor. Summary of the invention

[0009] In view of the deficiencies of the prior art, the present invention provides an improved hiccup mode short-circuit protection circuit for a BOOT converter, which solves the problems raised in the above background technology.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions: an improved hiccup mode short-circuit protection circuit for a BOOT converter, the improved hiccup mode short-circuit protection circuit consisting of a POWER_SEL (power selection) module, a one-shot (single state) circuit, a PRE_CHARGE (pre-charge) module, a 1:16 divider (sixteen-frequency divider), a comp (comparator), a capacitor C1, and a discharge tube M1.

[0011] Optionally, the POWER_SEL module functions as a comparator that can quickly compare V CC With V OUT and assign the larger value to V INT , and at the same time generates an identification signal PG to switch the working mode of the converter.

[0012] Optionally, the reference current I ref Charging C1 generates V SS , the comp module is responsible for the reference voltage V ref2 With V SS The comparison is performed to generate the clock CKL1 during the short-circuit period.

[0013] Optionally, the CKL1 input 16 frequency divider generates SSA signal. The PRE_CHARGE module processes the SSA signal and the identification signal PG to generate a clock signal GP for controlling the power tube. The signal generated by the PG signal after passing through the single state circuit and CKL1 generate a signal PG2 for controlling the discharge tube M1 through an OR gate.

[0014] Optionally, the short circuit protection circuit detects V OUT The change of V OUT Drop to V CC When the output voltage is below 0.004 V, the converter determines that the output is short-circuited and enters the short-circuit protection state.

[0015] Optionally, during the short circuit period, the circuit has two operations, namely a sleep mode and a detection mode.

[0016] The present invention provides an improved hiccup mode short-circuit protection circuit for a BOOT converter, which has the following beneficial effects: The improved hiccup mode short-circuit protection circuit for BOOT converter uses a pre-charging module to charge the load capacitor each time it is detected. At this time, the inductor current is limited. If the short circuit is removed, it can be charged smoothly. If it is not removed, it waits for the next detection. This not only solves the high current during the detection period, but also eliminates the overshoot during restart. At the same time, a sleep mode and a detection mode are introduced during the short circuit period to intermittently test the short circuit state. At this time, the converter works under a low-frequency clock, most modules are turned off, and only a few devices are working, thereby greatly reducing the power consumption during the short circuit period. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 For the present invention (a) with V FB Hiccup short circuit protection technology for detection signal (b) with V EA This is a diagram of the hiccup short-circuit protection technology for the detection signal; Figure 2 This is a diagram showing the shortcomings of the conventional hiccup short-circuit protection technology of the present invention; Figure 3 This is a schematic diagram of the structure of the improved hiccup mode short-circuit protection circuit of the present invention; Figure 4 This is a related working waveform diagram of the improved hiccup mode short-circuit protection model of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] See also Figure 3 The present invention provides a technical solution: an improved hiccup mode short-circuit protection circuit for a BOOT converter, the improved hiccup mode short-circuit protection circuit is composed of a POWER_SEL (power selection) module, a one-shot (single state) circuit, a PRE_CHARGE (pre-charge) module, a 1:16 divider (sixteen frequency divider), a comp (comparator), a capacitor C1, and a discharge tube M1.

[0020] The inductor current is limited by the inductor's own characteristic of hindering current change. Therefore, the current cannot increase sharply after a short circuit. Increasing the inductance value can reduce the rising slope and reduce t delay The increase in current can be reduced. By calculation, we can get t delay Get the maximum value: but:

[0021] So t delay By setting it to an appropriate value, the overshoot current can be reduced and a large current can be avoided when a short circuit occurs.

[0022] The function of the POWER_SEL module is equivalent to a comparator, which can quickly compare V CC With V OUT and assign the larger value to V INT , and at the same time generates an identification signal PG to switch the working mode of the converter.

[0023] Reference current I ref Charging C1 generates V SS , the comp module is responsible for the reference voltage V ref2 With V SS The comparison is performed to generate the clock CKL1 during the short-circuit period.

[0024] CKL1 inputs a 16-frequency divider to generate the SSA signal. The PRE_CHARGE module processes the SSA signal and the identification signal PG to generate the clock signal GP for controlling the power tube. The signal generated by the PG signal after passing through the single-state circuit and CKL1 generate the signal PG2 for controlling the discharge tube M1 through an OR gate.

[0025] The short circuit protection circuit detects V OUT The change of VOUT Drop to V CC When the output voltage is below 0.004 V, the converter determines that the output is short-circuited and enters the short-circuit protection state.

[0026] During the short circuit period, this circuit has two operations, namely sleep mode and detection mode; Since M1 is initially kept off, V SS At high potential, CLK1 is low. OUT Lower than V CC When PG becomes low, M1 turns on and discharges the charge on C1 to ground. At this time, V SS At this stage, the converter shuts down most modules, and only a few devices are working. The reference current I ref Keep charging C1. When V SS Exceed V ref2 After that, CLK1 goes high, turning M1 on again and V SS Drops to 0, and repeats this cycle to obtain the converter's operating clock CLK1 during the short circuit period. The pre-charge module does not start to detect whether the short circuit is removed every time CLK1 is high, but divides CLK1 by 16 to obtain the signal SSA. Only when SSA is high will the pre-charge module work to charge the load capacitor, which is called the detection mode. When SSA is low, the converter is in sleep mode. At this time, even if the short circuit state of the converter output is removed, the converter will not restart until SSA is high. The added sleep mode greatly reduces the power consumption during the short circuit, and the inductor current in the detection mode is also limited by the pre-charge module, and the current will not be very large. Figure 4 The waveforms of the improved hiccup mode short-circuit protection circuit show the working process during the short-circuit period. OUT The preset value is 5V. The high level of SSA is two cycles of CLK1, 2T, which is equivalent to two times of soft start voltage from low to high, which is enough for the normal restart of the converter. When an output short circuit occurs, the circuit system will shut down most of the circuit modules and at the same time SS Discharge to zero. V SS During this period, it will be continuously charged and discharged, showing a sawtooth wave. Only when the output short circuit is released, V OUT Only with V SS increases with the increase of .

[0027] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An improved hiccup mode short-circuit protection circuit for BOOT converter, Features: The improved hiccup mode short-circuit protection circuit is composed of a POWER_SEL (power selection) module, a one-shot (single state) circuit, a PRE_CHARGE (pre-charge) module, a 1:16 divider (sixteen frequency divider), a comp (comparator), a capacitor C1, and a discharge tube M1.

2. The improved hiccup mode short-circuit protection circuit for BOOT converter according to claim 1, Features: The POWER_SEL module functions as a comparator, which can quickly compare V CC With V OUT and assign the larger value to V INT , and at the same time generates an identification signal PG to switch the working mode of the converter.

3. The improved hiccup mode short-circuit protection circuit for BOOT converter according to claim 1, Features: The reference current I ref Charging C1 generates V SS , the comp module is responsible for the reference voltage V ref2 With V SS The comparison is performed to generate the clock CKL1 during the short-circuit period.

4. The improved hiccup mode short-circuit protection circuit for BOOT converter according to claim 1, Features: The CKL1 input 16 frequency divider generates SSA signal, and the PRE_CHARGE module processes the SSA signal and the identification signal PG to generate the clock signal GP for controlling the power tube. The signal generated by the PG signal after passing through the single state circuit and CKL1 generate the signal PG2 for controlling the discharge tube M1 through the OR gate.

5. The improved hiccup mode short-circuit protection circuit for BOOT converter according to claim 1, Features: The short circuit protection circuit detects V OUT The change of V OUT Drop to V CC When the output voltage is below 0.004 V, the converter determines that the output is short-circuited and enters the short-circuit protection state.

6. The improved hiccup mode short-circuit protection circuit for BOOT converter according to claim 1, Features: During the short circuit period, the circuit has two operations, namely, a sleep mode and a detection mode.

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